ALBERT

Description: We investigated yellow birch ( Betula alleghaniensis Britt.) growth patterns and disturbance frequency before and after the advent of selection harvesting at the Ford Forestry Center in the Upper Peninsula of Michigan, USA, through the use of tree-ring analysis. Based on the boundary-line release detection procedure, 88% of the trees in our sample (n = 67) displayed evidence of at least one moderate or major release. Prior to active forest management, releases were infrequent, and trees that originated during that period had growth histories consistent with establishment after large-scale disturbances (i.e., large canopy gaps, 〉200 m2). Conversely, tree cohorts that recruited to the canopy more recently displayed a growth pattern suggestive of periodic small gap expansion. Given the declining representation of yellow birch in these forests, the latter strategy, although probably sufficient to prevent extirpation, is unlikely to ensure a sustainable and harvestable population of this and other midtolerants in managed uneven-aged forests. Our results highlight the importance of considering the cumulative influence of infrequent disturbances and chance events on the maintenance of tree species diversity.

Description: In this paper, we consider a tactical transportation planning problem in forestry to decide the destination of logs. This problem is generally solved by finding the flow between a set of supply points and demand points. It can be formulated as a linear programming problem involving direct flows between supply and demand points. However, better solutions can be found by using additional flow variables representing flow in potential backhaul routes. However, the number of such variables is often very large. In this article, we provide the basis for backhaul flow planning in forestry. This includes defining the underlying operations research models for both the flow problem and the subproblem to find backhaul routes. The size of the problem in terms of the number of variables increases rapidly with the number of supplies and demands and we describe a column generation approach for its solution. We report on some case studies and industrial systems where the approach has been used.

Description: A modified logistic function was used for modeling specific-gravity profiles obtained from X-ray densitometry analysis in 675 loblolly pine ( Pinus taeda L.) trees in four regeneration trials. Trees were 21 or 22 years old at the time of the study. The function was used for demarcating corewood, transitional, and outerwood zones. Site and silvicultural effects were incorporated into the model. Heteroscedasticity and within-group correlation were accounted for by specifying the variance and serial-correlation structure, respectively. The estimated transition zone was located between rings 5 and 15, and the outerwood demarcation point varied from rings 12 to 15. No effects of treatments on the demarcation points were observed; however, site preparation and fertilization affected the lower asymptotes of the curves in all sites. A geographical trend for the demarcation point was observed, with the northern site requiring more time to reach a plateau in specific gravity compared with the southern sites. The diameter of the juvenile core was increased as a result of the treatments. However, the amount of corewood was not statistically affected, ranging from 55% in the north to 75% in the south, except at one site where fertilization decreased the percentage of corewood.

Description: The effects of 20th century spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks on forest dynamics was examined in the southern and northern parts of the mixedwood forest zone in central Quebec, Canada. In each region, three study areas were placed in unmanaged stands that had not burned for more than 200 years. Disturbance impacts and forest succession were evaluated using aerial photographs and dendrochronology. Spruce budworm outbreaks occurred around 1910, 1950, and 1980 in both regions. The 1910 outbreak seemed to have limited impact in both regions, and the 1950 outbreak caused heavy mortality in conifer stands (mostly of balsam fir, Abies balsamea (L.) Mill.) in the southern region. The 1980 outbreak caused major mortality in the northern region, but had little impact in the southern region. Successive spruce budworm outbreaks led to a massive invasion by hardwood species in the last century in the southern region but not in the northern region. The reason for such contrasting dynamics between regions is unknown, but we hypothesize that differences in disturbance intensities, influenced by climate, played a major role. Results from this study emphasize that generalizations about the effect of spruce budworm outbreaks on forest dynamics cannot be derived from observations made during a single outbreak or at a single location.

Description: We surveyed and wounded forest-grown sugar maple ( Acer saccharum Marsh.) trees in a long-term, replicated Ca manipulation study at the Hubbard Brook Experimental Forest in New Hampshire, USA. Plots received applications of Ca (to boost Ca availability above depleted ambient levels) or Al (to compete with Ca uptake and further reduce Ca availability). We found significantly greater total foliar and membrane-associated Ca in foliage of trees in plots fertilized with Ca when compared with trees from Al-addition and control plots (P = 0.005). Coinciding with foliar Ca differences, trees exhibited a significant difference in crown vigor and in percent branch dieback among treatments (P 〈 0.05), with a trend towards improved canopy health as Ca levels increased. Annual basal area increment growth for the years following treatment initiation (1998–2004) was significantly greater in trees subjected to Ca addition compared with trees in control and Al treatments. Treatment-related improvements in growth were particularly evident after overstory release following a 1998 ice storm. The amount of wound closure was also greatest for trees in Ca-addition plots relative to Al-addition and control plots (P = 0.041). These findings support evidence that ambient Ca depletion is an important limiting factor regarding sugar maple health and highlight the influence of Ca on wound closure and growth following release from competition.

Description: We assessed canopy openness (%) in an old-growth beech–maple forest immediately before and in the 3 years following a severe ice storm. We estimated canopy openness using hemispherical photographs taken at a height of 0.6 m above the soil surface in 101 permanent plots. Mean canopy openness increased from a prestorm value of 7.7% to 16.6% in the summer immediately following the storm. However, the mean canopy openness returned to prestorm levels within 3 years. The changes in canopy openness immediately after the storm were significantly influenced by canopy openness prior to the storm and also by species composition; plots with lower canopy openness prior to the storm and plots that consisted of more shade-tolerant species had greater canopy damage. While canopy gaps are often considered to promote the establishment of shade-intolerant species in the deciduous forests of eastern North America, gaps created by ice storms at our study site may not persist long enough to promote the establishment of these species.

Description: Plant polyphenolics are receiving increased attention for their influences on belowground processes. Tannins are of particular interest because of their predominance in natural systems, their wide variation in both quality and quantity, and their protein-binding abilities. Current theory holds that simple phenolics increase microbial activity by acting as carbon substrates, while larger tannins decrease microbial activity by binding with organic nitrogen such as proteins. Here, we present results from a simple microcosm experiment that demonstrates that the influence of condensed tannins on soil respiration depends on the availability of additional carbon substrates. We purified tannins from trembling aspen ( Populus tremuloides Michx.) and crossed three levels of tannin additions with three levels of cellulose additions in laboratory microcosms. Soil respiration was measured over 36 days. In the absence of cellulose, high amounts of condensed tannins increased cumulative soil respiration. In the presence of abundant cellulose, condensed tannins decreased cumulative soil respiration. The positive and negative effects of purified tannins on soil respiration are time dependent, such that initial respiration is likely tannin induced, while later respiration is cellulose induced and tannin limited.

Description: This paper aims to assess the influence of canopy cover on lichen growth in boreal forests along a regional forest gradient. Biomass and area gain, and some acclimation traits, were assessed in the old-forest lichens Lobaria pulmonaria (L.) Hoffm., Pseudocyphellaria crocata (L.) Vain., and Usnea longissima Ach. transplanted 110 days in three successional Norway spruce ( Picea abies (L.) Karst.) forest stands (clearcut, young, and old forest) repeated along a rainfall gradient (continental, suboceanic, and Atlantic zones) in Scandinavia. Lichen growth peaked in Atlantic rainforests with mean dry matter (DM) gain up to 36%–38%. The alectorioid lichen U. longissima showed the widest range of growth responses and no signs of chlorophyll degradation. Its highest DM gain consistently occurred in clearcuts, whereas the DM gain was close to zero in the shadiest young forest. The two foliose lichens L. pulmonaria and P. crocata exhibited maximal growth rates in old forests, but apparently growth was limited by low light even in old forests. Their DM gain was reduced in the most sun-exposed clearcuts due to chlorophyll degradation and was relatively high under closed young canopies, suggesting a better adaptation to shade. The lichen responses show that a high frequency and dominance of young and dense fast-growing forest stands at a landscape level are not compatible with large populations of these old-forest lichens and that a lack of lichens under an industrial forestry regime may not necessarily be determined by low dispersal efficiency only.

Description: The forwarding of logs at harvest areas once the harvesting is done is planned manually by experienced operators. To improve their efficiency and simplify the planning we have developed and tested a decision support system at a major Swedish forest company. The system is based on a combination of a geographic information system (GIS), global positioning system (GPS), and optimization routines to solve the underlying vehicle routing problem. The routes for the forwarders are found by using a repeated matching algorithm. The solution time is short, and it is possible to find routes dynamically in a real-time environment. The geographic information required is found by using a GPS together with data obtained from the bucking software in the harvesters. To show the routes and location of the forwarder, we make use of a GIS that is connected to the GPS. We report on a study with savings in the distance travelled of 8% and numerical tests on the solution methodology. We also compare the proposed solution method with some well-known routing methods.

Description: In forests historically maintained by frequent fire, reintroducing fire after decades of exclusion often causes widespread overstory mortality. To better understand this phenomenon, we subjected 16 fire-excluded (ca. 40 years since fire) 10 ha longleaf pine ( Pinus palustris Mill.) stands to one of four replicated burning treatments based on volumetric duff moisture content (VDMC): wet (115% VDMC); moist (85% VDMC); dry (55% VDMC); and a no-burn control. During the first 2 years postfire, overstory pines in the dry burns suffered the greatest mortality (mean 20.5%); pine mortality in the wet and moist treatments did not differ from the control treatment. Duff reduction was greatest in the dry burns (mean 46.5%), with minimal reduction in the moist and wet burns (14.5% and 5%, respectively). Nested logistic regression using trees from all treatments revealed that the best predictors of individual pine mortality were duff consumption and crown scorch (P 〈 0.001; R2 = 0.34). Crown scorch was significant only in dry burns, whereas duff consumption was significant across all treatments. Duff consumption was related to moisture content in lower duff (Oa; R2 = 0.78, P 〈 0.001). Restoring fire to long-unburned forests will require development of burn prescriptions that include the effects of duff consumption, an often overlooked fire effect.

Description: Locating a log landing is an important task in forest operations planning. Several methods have been developed to find an optimal landing location and compute a mean skidding distance, but they simplify harvest unit attributes and do not simultaneously consider multiple design factors influencing optimal landing locations. In this study, we introduce a computerized model developed to determine the optimal landing location for ground-based timber harvesting. Using raster-based GIS data, the model finds skid trails from stump to each of candidate landings and selects the best landing location that minimizes total skidding and spur road costs. The model is applied to several hypothetical harvest units with different terrain and harvest volume attributes to analyze the effects of design factors influencing optimal landing locations. Unit boundary shapes, volume distribution, the presence of obstacles, terrain conditions, and spur road construction are considered as influencing design factors.

Description: Forest litter and soil may contain 〉10 × 106 individual nematodes·m–2 and, regionally, 〉400 species. Root-feeding nematodes may be pathogenic to young plants; microbial-feeding nematodes may increase turnover of the microbial pool; predacious and omnivorous nematodes represent higher trophic levels. The spatial distribution and abundance of nematode species in forests reflect soil type, soil fertility, climate, canopy and understorey plant species, litter depth, forest age, and management. Nematodes may be important in forest nurseries; they occur throughout the rooting depth of forest trees; hyphal-feeding species may influence mycorrhizae; and insect-vectored Bursaphelenchus species are a quarantine risk. Nematode populations interact with those of other soil animals (e.g., mites, tardigrades, enchytraeids, and protozoa). The diversity and abundance of the nematode assemblage make nematodes a useful indicator of soil condition and soil processes. Information available from forest systems suggests that, as long as physical disturbance is minimized and remaining trees or herb layer moderate the microclimate, logging and other forestry operations have only transitory effects on nematode populations. Extreme disturbance, such as bulldozing and slash-and-burn management, can significantly reduce nematode abundance and diversity. In contrast, management that enhances growth of understorey or herb layer can stimulate nematode populations. Each of these changes can be related to changes in food resource availability and environmental conditions, such as soil temperature and moisture. Although details of soil nematode contributions to nutrient processes in forest soils are sparse, that their populations are maintained through cycles of moderate management practices suggest that their beneficial contributions will also be maintained.

Description: Two midmontane moist evergreen broad-leaved forests on the Ailao Mountains, Yunnan, and one on Mount Emei, Sichuan, southwestern China were studied to characterize the forest structure and dynamics as manifested in size, age, canopy gaps, regeneration modes, and the survival of seedlings. The most dominant canopy trees were species of Lithocarpus and Castanopsis of Fagaceae along with species of Machilus of Lauraceae and of Schima of Theaceae. The vertical structures of the forests were multilayered. All the canopy species had multimodal-shaped size and age distributions. In each forest of the study sites, the mean size of a canopy gap, caused mainly by the death of canopy trees, was smaller than 65 m2. No surviving seedlings of Fagaceae species were found in understories having bamboo with a coverage greater than 25% in any quadrat of the three forests. The poor seedling bank in the study forests is apparently due to the presence of bamboo in the understory. The tree regeneration may be synchronously related to the bamboo flowering event (interval approximately 55–60 years).

Description: We compared prefire and postfire organic-layer depths in boreal forest types (14 fires) across Canada, and examined tree recruitment as a function of depth. There was extensive within-stand variation in depth, much of it due to clustering of thinner organic layers around boles. There were no significant differences in postfire organic-layer depth among sites with different prefire forest species composition, but sites in the eastern boreal region had thicker postfire organic layers than those in the western boreal region. Mean organic-layer depth was much greater in intact stands than after fires; overall, fire reduced organic-layer depth by 60%, largely because of increases in the area of thin (

Description: We compared understory vegetation composition and richness in aspen-dominated boreal mixedwood forest stands in Alberta, Canada, that had been burned by wildfire with those that burned and were subsequently salvage logged. Stands were examined at early and midsuccessional (2 and 34 years after disturbance(s), respectively) developmental stages. In comparison with wildfire stands, understory communities of early successional salvage-logged stands were characterized by greater species richness, weedy species presence, higher shrub abundance, and lower abundances of fire-specialist seed bank species. In constrained ordination, the understory community of early successional wildfire stands was related to greater canopy cover, sapling density, and moss depth, whereas that of salvage-logged stands was related to greater light, volume of downed deadwood, and litter and organic matter. Longer term effects of salvage logging on the understory community were minimal and, instead, reflected the influence of forest canopy redevelopment. In midsuccessional stands, understory composition was related to conifer density, litter cover, soil moisture, organic layer depth, tall shrub density, and bryophyte-covered microsite cover. Postfire salvage logging can have substantial short-term effects on the postfire understory plant community; in the longer term, effects will depend to a large extent on the influence of harvesting and subsequent management on canopy redevelopment.

Description: This paper has three main objectives: (i) to investigate whether the four-quadrant approach introduced by     J.S. Maini reveals a useful typology for grouping countries by gross domestic product (GDP) and forest cover per capita, (ii) to determine if the framework can enhance our understanding of the relationship between forest cover and GDP per capita, and (iii) to investigate why countries in the four-quadrant world occupy different quadrants and to determine the principal factors affecting country movement across and within the individual quadrants. The examination reveals that countries can be classified into four broad categories and that GDP and forest cover per capita have a low but consistent level of negative association. After regressing economic, institutional, social capital, and other variables on a country’s occupancy and movement in the four-quadrant world, the results suggest that countries in each quadrant share different characteristics and that factors underlying country movement vary according to the quadrant being observed. Overall, countries with less corruption and higher education are likely to experience increases in both forest cover and GDP per capita, while countries exporting a significant proportion of forest products have a reduced probability of increasing both variables.

Description: In the winter of 1998–1999, two partial harvesting treatments that removed 33% (1/3) and 61% (2/3) of stand basal area were applied to even-aged trembling aspen ( Populus tremuloides Michx.) stands and compared with unharvested control stands. Stands in the 1/3 treatment were low thinned, while stands in the 2/3 removal were crown thinned. Coarse woody debris dynamics were assessed during the following 6 years by means of permanent sampling plots and downed wood inventories. Between 1999 and 2004, tree mortality was, respectively, 18%, 17%, and 32% in control stands and 1/3 and 2/3 harvesting treatments. Although total snag density was similar between controls and partial cutting treatments, total snag basal area was significantly higher in controls in 2004. Between 1999 and 2004, net change in aspen snag density was positive for controls and negative for both partial cutting treatments. Partial cutting also exacerbated mortality of small-diameter white birch ( Betula papyrifera Marsh.). Downed wood volume increased by 35 m3·ha–1 in controls and by 25 m3·ha–1 in the 2/3 harvesting treatment, while it decreased by 7 m3·ha–1 in the 1/3 harvesting treatment. Coarse woody debris goals can be established in silviculture prescriptions; type, timing, and intensity of partial cutting are crucial to the outcome.

Description: This work proposes a novel approach to describing intraring wood density characteristics as functions of annual weather events. This approach was tested using three different maritime pine clonal experiments, in which X-ray microdensitometry has revealed conspicuous within-ring patterns affecting most of the trees in 1996. This pattern has been interpreted as the variation of tree response to weather-controlled changes of water balance during the 1996 growing season. The level of tree response was estimated using an original norm of reaction obtained from the microdensity profiles. A 1996 site drought index profile was synchronized with the 1996 microdensity profile by pairing conspicuous points of abrupt change in both profiles (breakpoints). Regression of density breakpoints on drought breakpoints describes the norm of reaction of radial increment to water availability, and the plasticity of radial increment to changes in soil moisture is described by the slope of the regression. The slope showed moderate levels of genetic control that depended on the site and could potentially be used as criteria for the evaluation of tree adaptation to weather.

Description: Fuel distribution in the southern Appalachian Mountain region was measured in over 1000 study plots that were stratified by topographic position (aspect and slope position) and disturbance history. Few fuel differences occurred among topographic positions for undisturbed plots, indicating that fuel accumulation is no greater on highly productive sites than on less productive sites. Litter was slightly higher on undisturbed upper slopes (4.2 t/ha) than on lower slopes (3.7 t/ha) but woody fuels showed no significant differences. Rhododendron ( Rhododendron spp.) and mountain laurel ( Kalmia latifolia L.) were less common than expected, occurring on 25% and 42% of sampled plots, respectively. Disturbance history and type played a greater role in determining fuel loads than did topographic position. Disturbances had occurred on 30% of sample plots within the past 10 years and were most common on exposed slopes. Litter was significantly lower in burned plots (3.5 t/ha vs. 4.0 t/ha in undisturbed plots). One-hour fuels (1.0 t/ha) were significantly higher on beetle-killed plots than on undisturbed plots (0.7 t/ha) while larger woody fuels tended to be greater in plots subjected to beetle attack, fire, and wind.

Description: The Earth’s temperature has increased 0.6 °C over the last 100 years, and further climate change is predicted to potentially raise it by 3.5 °C over the next century. More than half of the global annual net primary production of biomass is estimated to occur in the tropics, especially tropical evergreen forest. In temperate forests, increasing temperature may extend the non-frost growing season, and thus increase the CO2 sequestration rate, but some authors have also suggested a negative impact of warming in tropical forests from decreased photosynthetic activity. Using the PL model (Ricker and del Río 2004), we forecast growth of two Mexican tree species after climate warming. The model predicts the high-mountain species Pinus hartwegii Lindl. to decrease its expected relative growth throughout its lifetime by 10.6% as a consequence of a 0.6 °C temperature increase; in contrast, the tropical rainforest species Diospyros digyna Jacq. is predicted to increase its expected relative growth throughout its lifetime by 25.4%. The key factor appears to be the expected relationship between temperature and precipitation, rather than temperature alone. While one cannot expect a universal response across sites, some standing tropical rainforests such as those at Los Tuxtlas in Mexico may constitute a carbon sink in a changing climate.

Description: Basic density (BD), fibre length (FL), fibre width (FW), and fibre wall thickness (FWT) were investigated in 46 Norway spruce ( Picea abies (L.) Karst.) trees from five different stands in eastern Norway. From each tree, wood samples were collected in different radial and longitudinal positions. Random coefficient mixed models were used to investigate variation within as well as among trees, both within and among stands. The R2 with random effects included, describing the best possible (individual) fit of the observed data to the models, were 0.90 for BD, 0.99 for FL, 0.88 for FW, and 0.91 for FWT. With only fixed effects, the best model explained 56% of the total variation for BD, 94.5% for FL, 61% for FW, and 63% for FWT. A common model for all trees, without tree and site information, predicted FL well but BD, FW, and FWT poorly. Adding site index, breast height diameter, and tree height to the models reduced the residual variance considerably for FW, FWT, and particularly BD, whereas only a minor improvement was gained for FL. The latter type of models might be easier to use for industrial purposes. Although information about ring width gave further improvements, ring width measurements are time consuming and difficult to perform in the forest and in industrial environments.

Description: A variety of competing hypotheses have been described to explain yield decline in Chinese-fir ( Cunninghamia lanceolata (Lamb.) Hook.) plantations. The difficulty in implementing field experiments suggests ecosystem modeling as a viable option for examining alternative hypotheses. We present a conceptual model of Chinese-fir yield decline and explore its merits using the ecosystem-based FORECAST model. Model results suggest that yield decline is caused primarily by a decline in soil fertility, largely as a consequence of slash burning in conjunction with short rotations. However, as tree leaf area declines, there is a transition (over subsequent rotations) from seed rain based competition to bud bank based competition, increasing the competitive impact of minor vegetation on tree growth. Short rotations increase understory survival between rotations and may cause a gradual shift from tree dominance to shrub/herb dominance over subsequent rotations. These effects are most evident on nutrient-poor sites, but understory competition poses a significant yield decline risk on good sites as well. We conclude that sustainable production in Chinese-fir plantations requires the avoidance of activities that compromise soil fertility and increase understory competition. The risk and severity of yield decline would be reduced by increasing rotation lengths and avoiding plantations on infertile sites.

Description: Forest management prescriptions increasingly incorporate snag and downed dead wood (DDW) guidelines. This study utilizes permanent inventory plots to determine dead wood dynamics in 33 balsam fir ( Abies balsamea (L.) Mill.) – spruce ( Picea spp.) (BFSP) and 17 spruce – balsam fir (SPBF) stands in New Brunswick, Canada. Stands were declining, unmanaged, and had a history of recurrent spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks and aerial insecticide spraying. Fixed-area sampling matched remnants of 1165 dead trees and 864 corresponding pieces of DDW to plot trees that died over the last 15–18 years with known year and cause of death. Declining BFSP stands had the highest accumulation of dead wood (196 m3/ha) compared with SPBF and nondeclining BFSP (122 m3/ha and 77 m3/ha, respectively). Dead wood dynamics were influenced by cause of death, as a function of differences in tree height at death affecting snag decay, fragmentation, and fall. One-half of all dead trees never made a significant contribution to the snag population (25% uprooted and 25% stem breakage), and attrition resulted in only 50% of snags standing with a mean height of 6 m 15–20 years after death. This study will be of direct value to those managing or modeling dead wood dynamics in similar forests.

Description: The influence of climatic factors on tree-ring width and the formation of double rings was studied in Quercus ilex L. growing in a coppice stand left unmanaged for 22 years. Ten trees were felled and discs were taken every 30 cm from bole and dominant branches. Dendrometer bands were installed on 10 nearby trees and the data recorded were used to confirm the accuracy of our tree-ring identification. They were also used to relate the seasonal radial growth pattern to double-ring formation. Double rings were frequent and occurred consistently along the stem. Two types of double rings could be recognized according to their width: type I, with the extra growth band accounting for approximately 50% of the tree ring; and type II, with a narrow extra growth band. Type I double rings were formed when approximately 1/2 of the growing-season precipitation occurred during the second growth period of the season and after the summer drought. Type II double rings occurred when approximately 1/3 of the precipitation in the growing season occurred after the summer drought. The formation of double rings was triggered by rainfall in summer and the extra growth-band width was related to summer and autumn environmental conditions. Double rings in Q. ilex can potentially be used in dendroclimatological studies, as they are formed in response to climatic conditions within the growing season.

Description: We evaluated agreement in the location and occurrence of 20th century fires recorded in digital fire atlases with those inferred from fire scars that we collected systematically at one site in Idaho and from existing fire-scar reconstructions at four sites in Washington. Fire perimeters were similar for two of three 20th century fires in Idaho (1924 and 1986). Overall spatial agreement was best in 1924 (producer’s accuracy = 94% and 68% and user’s accuracy = 90% and 70% for the 1924 and 1986 fires, respectively). In 1924, fire extent from the atlas was greater than for fire scars, but the reverse was true for 1986. In 1986, fire extent interpreted from the delta normalized burn ratio derived from pre- and post-fire satellite imagery was similar to that inferred from the fire-scar record (producer’s accuracy = 92%, user’s accuracy = 88%). In contrast, agreement between fire-scar and fire-atlas records was poor at the Washington sites. Fire atlases are the most readily available source of information on the extent of late 20th century fires and the only source for the early 20th century. While fire atlases capture broad patterns useful at the regional scale, they should be field validated and used with caution at the local scale.

Description: The seasonal flight of Hylurgus ligniperda (Fabr.) and Hylastes ater (Paykull) and the effect of log placement in Pinus radiata D. Don plantations on colonization by these species in Chile are described. Seasonal flight activity was monitored with α-pinene and ethanol-baited traps at three sites and colonization synchrony with trap logs. In two experiments with individual logs and log decks, data were recorded on adults found under the logs, attacks on the bark surface, and adults beneath the bark of logs in three storage treatments: individual logs and log decks (1) touching the soil; (2) elevated above the soil; and (3) touching other logs (individual logs) or logs separated with spacers (log decks). Each treatment was replicated in a plantation and a clearcut. At San José (region IX) and Peña Blanca (region VIII), H. ligniperda flew primarily in spring and H. ater flew in spring and fall. At Brasil (region VIII), H. ligniperda and H. ater flew primarily in summer through fall. The flight of H. ligniperda was more synchronized with colonization of logs than was that of H. ater. The mean number of attacks was significantly higher on individual logs and log decks stored on the soil than on those elevated above the soil, and significantly higher in the clearcut than in the plantation. Mean numbers of adults beneath the bark did not vary significantly among individual-log treatments, but were significantly lower in the log decks separated by spacers. Logging during nondispersal periods (June–August in regions VIII–X) and storing log decks above the soil could reduce beetle colonization of newly cut logs. With this information, management of recently cut logs (harvesting, transport, and storage operations) could be scheduled and executed so as to reduce the risk of these species being introduced into log-importing countries.

Description: Using a long-term silvicultural experiment, we (i) investigated how epiphyte and arthropod communities were affected by height on the stem, bark texture, and stem diameter of red maple ( Acer rubrum L.) trees, (ii) examined how harvest gaps influenced epiphyte and arthropod communities on red maple boles, and (iii) explored whether these effects influenced the relationship between the epiphyte and arthropod communities. Arthropod and epiphyte assemblages dwelling on the bark of red maple trees located in undisturbed forest and harvest gaps varied with height. Bryophytes, Cladonia spp., and cyanolichens were most abundant near the base of the tree, while noncyano, foliose lichens and fruticose lichens were most abundant 4–6 m above the ground. Acari, Araneae, and Collembola were most abundant near the base of the tree, while Diptera were most abundant above 2 m. A previously undocumented assemblage of dipterans (flies), primarily in the suborder Nematocera, was found. Gap harvesting reduced the abundance of bryophytes, Collembola (springtails), Araneae (spiders), and total arthropods on the bark of red maple. Canonical correlation analysis revealed a positive association between bryophytes, Collembola, and Araneae. A strong correlation between Collembola and Araneae suggested a possible trophic interaction that may be affected by gap harvesting through a reduction in bryophyte abundance.

Description: Fungal foliar endophytes (hereinafter endophytes) were isolated on malt agar from black spruce ( Picea mariana (Mill.) BSP) needles from the Quebec boreal forest during 2 successive years to study their distribution along a latitudinal transect. Twenty sites were sampled in 2002, 8 of which were sampled again in 2003, in an area located between 47°N and 54°N in the province of Quebec. The endophytes were named whenever possible, using homologies of ITS rDNA sequences from GenBank. In 2002, 232 morphotypes were classified in 40 operational taxonomic units (OTUs), and in 2003, 93 morphotypes were classified in 16 OTUs, for a total of 44 OTUs. Isolation frequencies of the most common endophyte species were 28% for Lophodermium piceae (Fuchel) Höhn., 17% for Darkera parca Whitney, Reid & Piroz, and 9% for Dwayaangam colodena Sokolski & Bérubé. Of the 44 OTUs identified, 18 were unique to P. mariana and found on one site only, possibly constituting rare endemic species. There was some evidence that needles colonized with rare endophyte species were more abundant in the western and southern regions than in the northern region. This supports our hypothesis that as the diversity of tree species surrounding the P. mariana decrease from the southern region to the northern region, the diversity of endophytes also decreases.

Description: The evergreen sclerophyllous broadleaf forests composed of alpine oaks in the Hengduan Mountains of southwest China are mainly distributed at altitudes of 1700–4800 m. Gas exchange and related leaf traits of Quercus guyavifolia H. Lév. and Quercus pannosa Hand.-Mazz. were measured at eight sites along an altitudinal gradient to understand their physiological adaptabilities. Both Q. guyavifolia and Q. pannosa showed a significant midday depression in the photosynthesis rate (PN) due to a high vapor pressure deficit and high temperature around noon. The optimum temperature for photosynthesis for the two oak species ranged from 17 to 23 °C depending on altitude. When the temperature exceeded 25 °C, PN decreased sharply. However, PN was not depressed by high irradiance. As altitude increased, the leaf dry mass per unit area of the two oaks increased but the chlorophyll content decreased, while the maximum values of daily mean photosynthesis rate (Pd), maximum photosynthesis rate (Pmax), Pd/Pmax, water-use efficiency, and photosynthetic nitrogen use efficiency occurred at altitudes of 3240–3610 m. Although the photosynthetic capacities of the two oaks were higher in August than in May, altitudinal trends did not change with season. The altitudinal range from 3240 to 3610 m would be optimal for the growth and development of these two alpine oaks in the Hengduan Mountains.

Description: Dendrochronology climate reconstruction studies often sample dominant, open-grown trees to reduce competition effects and isolate annual climate influences on radial increment growth. However, there has been no examination of how species respond as stand densities increase or which species in mixed-conifer forests provide a better record of past climate. We sampled 579 trees representing five upper montane mixed-conifer species at the Teakettle Experimental Forest in California’s southern Sierra Nevada to determine species-specific responses to annual climatic fluctuations. Using the Kalman filter, we examined the affect of local stand density on growth response and whether the growth–climate relationship improved with a time lag. The Kalman filter iteratively calculates error for predicted versus actual radial growth and accounts for this variation in the corrector equation. Under current high-density conditions, shade-tolerant white fir ( Abies concolor (Gord. & Glend.) Lindl.) provided the best model for climate reconstruction. Shade-intolerant Jeffrey pine ( Pinus jeffreyi Grev. & Balf.) had a lagged response to annual climatic fluctuations, possibly because its roots may tap water reserves in granitic bedrock fissures. Open-grown trees provided more accurate records of climate. Changes in forest density in this forest may have resulted in changes in species-specific response to annual climatic fluctuations.

Description: Impacts of elevated tropospheric ozone and soil nitrogen amendment on two native European aspen ( Populus tremula L.) and eight hybrid aspen (P. tremula L. × Populus tremuloides Michx.) clones were studied in a free-air ozone exposure system. Potted saplings were exposed to ambient (ca. 20 ppb) or 1.5× ambient ozone and two levels of soil nitrogen (39 and 78 kg N·ha–1·year–1 in the first year, 60 and 140 kg N·ha–1·year–1 in the second year for low-nitrogen and high-nitrogen treatments, respectively) over two growing seasons. The plants were measured for photosynthesis, chlorophyll fluorescence, and biomass accumulation. Ozone decreased leaf-level net photosynthesis (Asat) in particular early in the growing season and maximum quantum yield of photosystem II (Fv/Fm) at the end of the growing season. Nitrogen amendment increased the growth of all plant parts and mitigated the adverse ozone effects. There were significant differences in ozone responses among the clones, and we were able to cluster the clones into sensitivity groups based on their growth responses. The most ozone-tolerant genotypes were hybrid aspen clones, indicating that populations that have already experienced selection for ozone-tolerant genotypes should be used to cross-breed with ozone-sensitive populations to achieve tolerance of a climate with increasing tropospheric ozone concentrations.

Description: Real option theory has for some decades been used in forest economics to analyse problems that involve irreversible and stochastic decisions. One of these problems is when to harvest a stand and with what species to regenerate. This problem is analysed here, assuming that the value development of both the present and the next stand is stochastic and that the regeneration species must be chosen. The latter decision is assumed asymmetric, as natural regeneration can be exchanged for a planted regeneration but not vice versa. Consequently, the decision can be postponed for some time if natural regeneration is foreseen, making a species change possible if favoured by the value development or if regeneration of the present species proves unsuccessful. This is an extension of the traditional two-option problem, by involving several stochastic elements that are nested in another option problem: when to harvest a stand. Thus the decision on when to harvest a stand depends on its present value as well as on the value of the future stand, both values evolving stochastically. The problem is formulated as a sequential two-option problem and solved numerically.

Description: Until recently, natural dynamics of mixedwood stands have been largely ignored, resulting in the transformation of many North American mixedwoods into conifer- or hardwood-dominated stand types. The goal of this study was to examine canopy gap dynamics in balsam fir ( Abies balsamea (L.) Mill.) – yellow birch ( Betula alleghaniensis Britt.) mixedwoods to better understand possible mechanisms for species coexistence. Gap proportion in 12 study stands varied between 9% and 30% of the total stand area, while gap size varied from 20 to 2100 m2. Balsam fir mortality was the primary cause of gap formation. Balsam fir and mountain maple ( Acer spicatum Lamb.) dominated the tree and shrub regeneration layers, respectively. Shrub competition slows the natural filling of gaps by tree species. Our results indicate that yellow birch is most abundant in gaps over 800 m2 and balsam fir in those under 200 m2. Transition models showed that the greater longevity of yellow birch than balsam fir ensured its maintenance as a dominant. Dominant species coexistence thus results from divergent use of available resources through time and space. Forest management should maintain variability in harvest timing and size because the use of one gap size or a single rotation age will lead to an imbalance in species proportion relative to natural stands.

Description: An extensive survey of spruce growth forms was conducted in frost hollows of the Parc national des Grands-Jardins located in the highlands of the Charlevoix region (Quebec). Frost hollows studied were situated within lichen woodlands, which are a favourable environment for the formation of cold air masses. The mean number of frosts recorded 1 m aboveground during the growing seasons of 1997–2002 indicates that there is no frost-free period in frost hollows. Based on the records of minimum temperature in two frost hollows, the critical threshold for frost-ring formation is a nocturnal temperature below 0 °C for 6.4 h with a climax at around –5.7 °C, i.e., at a cooling rate of 1.78 °C/h under the freezing point for at least 3.2 h. Frequent and severe nocturnal frosts slow down the colonization of black spruce in frost hollows, and are at the origin of the inverted tree line that surrounds frost hollows. Mean stem height of black spruce in frost hollows is 1.97 m ± 2.15. A comparative analysis of aerial photographs between 1950 and 1996 showed a 34% reduction in frost hollow area due to the progressive colonization of black spruce. Massive tree establishment occurred in frost hollows between 1970 and 1980 because of the reduced frequency of freezing temperatures during the growing season.

Description: We measured soil seed banks in 102 plots within a 110 000 ha Arizona Pinus ponderosa landscape, determined seed-bank responses to fire cues and tree canopy types (open or densely treed patches), compared seed-bank composition among ecosystem types, and assessed the utility of seed banks for ecological restoration. Liquid smoke was associated with increased community-level emergence from seed banks in greenhouse experiments, whereas heating to 100 °C had minimal effect and charred P. ponderosa wood decreased emergence. We detected 103 species in seed-bank samples and 280 species in aboveground vegetation. Erigeron divergens was the commonest seed-bank species; with the exception of Gnaphalium exilifolium , species detected in seed banks also occurred above ground. Although a dry, sandy-textured black-cinder ecosystem exhibited the greatest seed density, seed-bank composition was more ecosystem-specific than was seed density. Native graminoids (e.g., Carex geophila and Muhlenbergia montana ) were common in seed banks, whereas perennial forbs were sparse, particularly under dense tree canopies. Our results suggest that (i) smoke may increase emergence from seed banks in these forests, (ii) seed banks can assist establishment of major graminoids but not forbs during ecological restoration, and (iii) seed-bank composition is partly ecosystem-specific across the landscape.

Description: Increases in the emission of greenhouse gases, particularly during the second half of the 20th century, have been associated with climate warming at the global scale. High latitude areas have been reported to be particularly sensitive to such changes, with significant impacts on plant phenology. The objectives of the present study were to (i) estimate changes in the flowering dates of 18 spring-flowering herbaceous plant species typical of the deciduous forests of eastern North America in three areas of eastern Canada (Gatineau–Ottawa, Montréal, and Québec) from 1900 to 2000 and (ii) associate these changes with those of annual and spring local temperatures. My results show a 2–6 days advance in flowering date over 100 years, depending on the region considered (corresponding to a ~2–3 days advance per 1 °C); these values are somewhat lower than those published in other studies, but still support the increasing body of literature on the effects of climate warming on plant phenology. Shifts in flowering phenology were particularly evident for Montréal, a large metropolitan region; this suggests that global climate warming, and its effects on plant phenology, may be exacerbated by local conditions, particularly those associated with large urban areas. Furthermore, species-specific responses to climate warming, as those presented here, might lead to significant changes in community composition and ecosystem functions.

Description: Caribou Poker Creeks Research Watershed is a boreal forest watershed in Interior Alaska that is susceptible to regional warming and permafrost thaw. We measured seasonal foliar N concentrations of the black spruce understory shrubs, Vaccinium uliginosum L., Vaccinium vitis-idaea L., and Ledum palustre L. on north- and south-facing sides of the watershed. We predicted that the shrubs would respond to small-scale changes in active layer and soil climate, and we expected similar responses according to growth strategy (evergreen or deciduous). Overall, foliar N in shrubs was higher on warmer, drier soils with deep active layers: +7.9% N in V. uliginosum, +11.1% N in V. vitis-idaea, and +9.4% N in L. palustre. Each shrub had species-specific foliar N patterns that could not be categorized by growth strategy and were not well explained by soil climate or active layer. Leaf mineral nutrition is influenced by multiple processes, and foliar N was best explained by the combination of environmental variables operating at the study site. For Caribou Poker Creeks Research Watershed, we can expect increased N status of the black spruce understory along with continued climate warming, but changes cannot be predicted based on growth strategy.

Description: Down woody debris (DWD) plays a vital role in forest ecosystem structure and function. Although volume is likely the most common metric used to characterize DWD, an evaluation of the formulae used for volume estimation on individual DWD pieces has received little attention. We determined actual volume of 155 diverse DWD pieces (types, species, lengths, and diameters) by detailed field measurements. By comparing the actual and calculated volumes from six commonly used formulae, we assessed their bias, precision, and accuracy. Based on observed DWD forms, we developed a new formula, namely the “conic−paraboloid”, which was included in the assessment. Among the formulae that require length and two end diameter measurements, the conic−paraboloid had the lowest bias, highest precision, and hence greatest accuracy. Newton’s and the centroid formulae had higher accuracy yet require more field measurements. Smalian’s, conical frustum, and average-of-ends formulae had poor performance relative to the others. Accuracy of all formulae decreased with increasing piece length. Thus, partitioning pieces into two, three, and four sections for additional measurement improved accuracy. As decay advances, pieces become progressively more elliptical in cross section. Using the cross-sectional area derived from only the long axis of the ellipse leads to substantial volume overestimates for well-decayed DWD.

Description: Rising societal demands for forest resources along with existing natural disturbance regimes suggest that sustainable forest management will increasingly depend on better understanding the cumulative effects of natural and anthropogenic disturbances. In North America, for example, there is increasing economic pressure to salvage log burned forests, although the ecological consequences of combining fire and harvesting on the same sites are unclear. We examined the short-term (2 year) responses of boreal forest ground beetles (Coleoptera: Carabidae) to the individual and combined effects of wildfire, harvesting, and herbicide. Ground beetle responses to wildfire and forestry-related disturbances differed strongly and suggested that, although some species may appear to benefit from disturbance combinations (e.g., Sericoda quadripunctata (DeGeer)), these effects are detrimental to others (e.g., Sericoda bembidioides Kirby). Species compositional variability was significantly reduced by disturbance combinations suggesting that multiple disturbances may lead to a simplification of this entire assemblage. In addition, ground beetle responses were correlated with changes in several key habitat parameters such as amount of woody debris, exposed ground, and plant species richness suggesting avenues for future study. Overall, however, our results suggest that efforts to avoid compounding disturbances on any site should be considered when developing current and future forest management guidelines.

Description: The complex fluxes between standing and harvested carbon stocks, and the linkage between harvested biomass and fossil fuel substitution, call for a holistic, system-wide analysis in a life-cycle perspective to evaluate the impacts of forest management and forest product use on carbon balances. We have analysed the net carbon emission under alternative forest management strategies and product uses, considering the carbon fluxes and stocks associated with tree biomass, soils, and forest products. Simulations were made using three Norway spruce ( Picea abies (L.) Karst.) forest management regimes (traditional, intensive management, and intensive fertilization), three slash management practices (no removal, removal, and removal with stumps), two forest product uses (construction material and biofuel), and two reference fossil fuels (coal and natural gas). The greatest reduction of net carbon emission occurred when the forest was fertilized, slash and stumps were harvested, wood was used as construction material, and the reference fossil fuel was coal. The lowest reduction occurred with a traditional forest management, forest residues retained on site, and harvested biomass was used as biofuel to replace natural gas. Product use had the greatest impact on net carbon emission, whereas forest management regime, reference fossil fuel, and forest residue usage as biofuel were less significant.

Description: We investigated three primary causes of old-growth forest pedodiversity imposed by top-down trophic interactions, including pit and mound topography from past tree fall events, current canopy gaps from tree falls, and the influence of individual tree species on soil properties and processes. In this paper, we discuss the effects of pits, mounds, gaps, and individual tree species on pedodiversity in a single soil map unit in an old-growth northern hardwood forest. Pits and level areas had significantly greater soil organic matter, cation-exchange capacity, and exchangeable K and Ca contents than mounds. Gap subplots had significantly less cation-exchange capacity, K, Mg, and Ca compared with level areas within the contiguous forest. Base cations (K, Mg, and Ca) were significantly greater under sugar maple ( Acer saccharum Marsh.) compared with eastern hemlock ( Tsuga canadensis (L.) Carr.). Extractable P was significantly greater under yellow birch ( Betula alleghaniensis Britt.) compared with eastern hemlock. We quantified pedodiversity in an old-growth northern hardwood forest stand and single soil map unit using principal components analyses, ArcGIS, and biodiversity indices. Our results suggest that pedodiversity should be considered in soil survey and forest management.

Description: European aspen ( Populus tremula L.) is a keystone species for biodiversity in boreal forests. However, large aspen have largely been removed from managed forests, whereas regeneration and the long-term persistence of mature trees in protected areas are matters of concern. We recorded the numbers of mature (≥20 cm diameter) aspen in old-growth and managed forests in eastern Finland, based on a large-scale inventory (11 400 ha, 36 000 living and dead trees). In addition, saplings and small aspen trees were surveyed on thirty-six 1 ha sample plots. The average volumes of mature living and dead aspen were 4.0 and 1.3 m3/ha in continuous old-growth forests and 0.2 and 0.6 m3/ha in managed forests, respectively. These results indicate that large aspen trees in managed forests are a legacy of the past, when forest landscapes were less intensively managed. We conclude that the long-term persistence of aspen in protected areas can only be secured by means of restoration measures that create gaps large enough for regeneration to occur. More emphasis should be given to sparing aspen during thinning and to retaining mature aspen during regeneration cutting in managed forests.

Description: We examined the effects of group selection with legacy-tree retention on ground-layer or understory diversity and composition in an uneven-aged northern hardwood forest in the Upper Peninsula of Michigan. We sampled 20 reference plots in the surrounding forest matrix and 49 openings with radii of 0.5 (n = 16), 0.75 (n = 17), and 1.0 (n = 16) times mean canopy tree height (22 m). Resultant opening areas were 321 ± 16 (mean ± SEs), 697 ± 21, and 1256 ± 39 m2, respectively. Each opening contained a centrally located legacy tree. Two years after harvesting, ground-layer diversity was significantly higher in openings than on reference plots (p 〈 0.05) because of an influx of early seral, wetland, and weedy exotic species. The importance of aggressive ruderals (i.e., Carex ormostachya Wieg. and Rubus idaeus subsp. strigosus (Michx.) Focke) increased significantly (p 〈 0.001) with increasing opening area. Although the importance and cover of several late-seral species were lower in openings compared with the forest matrix, few species found in the matrix were wholly absent from the openings. These results suggest that ground-layer plant communities in managed northern hardwood forests may display a high degree of resilience to intermediate-intensity disturbances.

Description: We examined mortality of Abies concolor (Gord. & Glend.) Lindl. (white fir) and Pinus lambertiana Dougl. (sugar pine) by developing logistic models using three growth indices obtained from tree rings: average growth, growth trend, and count of abrupt growth declines. For P. lambertiana, models with average growth, growth trend, and count of abrupt declines improved overall prediction (78.6% dead trees correctly classified, 83.7% live trees correctly classified) compared with a model with average recent growth alone (69.6% dead trees correctly classified, 67.3% live trees correctly classified). For A. concolor, counts of abrupt declines and longer time intervals improved overall classification (trees with DBH ≥20 cm: 78.9% dead trees correctly classified and 76.7% live trees correctly classified vs. 64.9% dead trees correctly classified and 77.9% live trees correctly classified; trees with DBH 

Description: A mixed integer programming model that aims at supporting the tactical wood procurement decisions of a multifacility company is presented. This model allows for wood exchanges between companies. Furthermore, the material flow through the supply chain is driven by both a demand to satisfy ("pull" strategy) and a market mechanism ("push" strategy), enabling the planner to take into consideration both wood freshness and the notion of quality linked to the age of harvested wood into log, chips, and end-product demands. An inability to consider alternative plans for implementation, and the difficulty of assessing the performance of these plans in an uncertain environment, are two shortcomings of the manual planning process. A planning process, based on human planner – decision support system interactions that allows a company to overcome these shortcomings is therefore presented. The process combines Monte Carlo methods and an anticipation mechanism that will, in the long term, enable the company to take into account equipment transportation costs. The proposed planning process leads to a multicriteria decision-making problem where the human planner has to select a plan to implement from a set of candidate plans. A hypothetical test case shows that it is possible to manage the wood flow from stump to end market in such a way as to preserve freshness and extract higher value from the logs processed in the mills. The test case also shows that the proposed planning process achieves an average profitability increase of 8.8% compared with an approach based on a deterministic model using average parameter values. Finally, a sensitivity analysis reveals that the accuracy of standing inventory on harvest blocks and the anticipated market conditions are the most important parameters to consider in selecting a good wood procurement plan.

Description: Dendroecological techniques were applied to reconstruct stand-replacing fire history in upper montane forests in northern New Mexico and southern Colorado. Fourteen stand-replacing fires were dated to 8 unique fire years (1842–1901) using four lines of evidence at each of 12 sites within the upper Rio Grande Basin. The four lines of evidence were (i) quaking aspen ( Populus tremuloides Michx.) inner-ring dates, (ii) fire-killed conifer bark-ring dates, (iii) tree-ring width changes or other morphological indicators of injury, and (iv) fire scars. The annual precision of dating allowed the identification of synchronous stand-replacing fire years among the sites, and co-occurrence with regional surface fire events previously reconstructed from a network of fire scar collections in lower elevation pine forests across the southwestern United States. Nearly all of the synchronous stand-replacing and surface fire years coincided with severe droughts, because climate variability created regional conditions where stand-replacing fires and surface fires burned across ecosystems. Reconstructed stand-replacing fires that predate substantial Anglo-American settlement in this region provide direct evidence that stand-replacing fires were a feature of high-elevation forests before extensive and intensive land-use practices (e.g., logging, railroad, and mining) began in the late 19th century.

Description: The effects of depth, size, location, and season of artificial logging damage on increment and decay of Norway spruce ( Picea abies (L.) Karst.) and Scots pine ( Pinus sylvestris L.) trees were studied in long-term experiments in central Finland. Damage types applied were root damage, root collar damage, increment borer hole, and stem damage. In root collar and stem damages, two sizes (100 or 400 cm2) and depths (shallow or deep) were applied. Five to 20 years after damaging, the damages did not result in a decrease in radial, height, or volume increment. In Norway spruce, the frequency of decay in the root collar and stem damages was high. From large and deep damages, decay spread faster than from smaller and shallow ones. In Scots pine, a lower proportion of trees were decayed compared with Norway spruce. Increment coring resulted in decay in most of the trees, but the decay spread slowly. The effect of compass direction or the month of damaging was negligible. The most common decay fungus in Norway spruce was Stereum sanguinolentum (Alb. & Schwein. Fr.:) Fr. In Scots pine, only nondecay fungi were isolated. In general, logging damages decreased sawlog production through the rejection of butt logs containing decay or discoloration.

Description: To determine scale-specific effects of disturbance type, soil, and topography on regenerating plant species, we compared regeneration in 10- and 50-year-old clearcuts and burns in southeastern Labrador. Data were analyzed at three scales of resolution: subplot (5 m2), plot (398 m2), and site (3.89 ha). The influence of topography and edaphic factors, and the variance explained by these environmental variables, increased with scale. Disturbance type and year were important across all three scales, but soil and topography were most important at the site scale. Regeneration was more abundant within clearcuts, notably black spruce ( Picea mariana (Mill.) BSP) and balsam fir ( Abies balsamea (L.) Mill.). Disturbance type had a greater influence on plant species composition than disturbance age as plant communities remained dissimilar within 50 years after disturbance. Because regeneration is often low after fire in southeastern Labrador, it may be undesirable for forest harvesting to mimic the effects of fire at the scales we evaluated.

Description: Spatial patterns, rates, and temporal variation of standing-tree mortality were studied in unmanaged boreal old-growth forests of northeastern Quebec. The study was carried out by sampling living and dead trees within 15 transects (400 m long, 40 m wide). The transects lay in stands that were classified according to their species composition in three types: dominated by black spruce, Picea mariana (Mill.) BSP; mixed P. mariana and balsam fir, Abies balsamea (L.) Mill.; and dominated by A. balsamea. Spatial patterns were analysed using Ripley's K function. The year of death was cross-dated using 190 sample discs extracted from dead standing A. balsamea and P. mariana to assess the rates and temporal variation of mortality. The spatial patterns of standing dead trees in P. mariana stands were predominantly clustered. The spatial patterns of large dead trees (〉19 cm diameter at breast height (1.3 m height; DBH)) in mixed and A. balsamea-dominated stands were mainly random, with few stands showing clustered patterns. Small dead trees (9–19 cm DBH) in these stands were generally more clustered than larger trees. Tree mortality varied from year to year, though some mortality was observed in all the studied stand types for almost every year. Standing trees that had recently died accounted for 62%, 48%, and 51% of overall mortality in P. mariana-dominated, mixed, and A. balsamea-dominated stands, respectively. The results of this study indicate that mortality of standing trees outside of episodic mortality events (such as insect outbreaks) is an important process in the creation of structural complexity and habitat diversity in these stands.

Description: A survey of limber pine ( Pinus flexilis James) to determine the geographic distribution, incidence, and severity of white pine blister rust (WPBR) throughout 13 study areas in central and southeastern Wyoming and northern Colorado was conducted from 2002 to 2004. The majority (81.1%) of the 18 719 surveyed limber pines 〉1.37 m tall were classified as healthy, 13.5% were declining or dying from various causes, and 5.4% were dead. WPBR was present on 278 (55%) of the 504 survey plots. Incidence of the disease ranged from 0% to 100% and averaged 15.5% over all the plots and 28.0% on the infested plots. Likelihood of infection by WPBR was significantly greater for limber pines in larger diameter classes. Incidence was negatively correlated with elevation and positively correlated with geographic position, with more northerly and easterly plots having higher incidences of WPBR. Incidence varied by slope position and did not vary by aspect, slope configuration, or degree of canopy closure. The current level of infestation in central and southeastern Wyoming and northern Colorado has been attained within the past two to four decades. With time, the pathogen may spread to currently uninfested white pine populations and intensify throughout its current distribution impacting valuable ecosystems.

Description: The paper presents an econometric analysis of spatial integration of the United States and Canadian newsprint markets as reflected in newsprint prices. It applies the Johansen multivariate cointegration procedure to test the law of one price for five regional markets (British Columbia, Ontario, Quebec, US east, and US west) of newsprint using monthly data for 1988–2004. Preliminary data analysis shows that all price series are nonstationary I(1) processes. The hypothesis that the law of one price holds for all five regional newsprint markets simultaneously was not supported by the Johansen multivariate test. The law of one price was also tested for national markets, and it was found to hold between US west and US east newsprint prices. The results suggested that there is a single newsprint market in the United States, whereas there are several distinct newsprint markets in Canada.

Description: Crown depth, tree spacing, and stand density have major effects on wood quality and fibre characteristics of trees. Lodgepole pine ( Pinus contorta Doug. ex Loud.) trees from a mixture of plantation and fire origin stands were employed to determine how crown ratio, a surrogate for stand density, affected mature wood production. In total, 104 trees were sampled, ranging from 24 to 110 years of age, from stands in western Alberta and interior British Columbia, Canada. Samples taken along the bole were measured for wood density, which was subject to segmented regression analysis to identify the transition point from juvenile to mature wood production. On average, the lodgepole pine trees were 31 (±17 SD) years old before mature wood production began. A mixed-effects model, in which combination of fixed effects (tree age, height of the sample disc relative to crown base, and crown length) and random effects (site, trees nested in sites, and discs nested in both trees and sites) proved to be the best predictor of years of mature wood production along the bole. The transition from juvenile to mature wood was shown to be below the crown base in trees 

Description: Eastern hemlock ( Tsuga canadensis (L.) Carr.) is a coniferous evergreen species found across the northeastern United States that is currently threatened by the exotic pest hemlock woolly adelgid (HWA; Adelges tsugae Annand). As HWA kills eastern hemlock trees, black birch ( Betula lenta L.) has been found to be a dominant replacement species in the region. Seasonal changes in water use by eastern hemlock and black birch were investigated utilizing whole-tree transpiration measurement techniques. Annual evapotranspiration in an eastern hemlock and deciduous stand was also estimated. During the peak growing season, daily rates of transpiration were 1.6 times greater in black birch. Cumulative transpiration in black birch exceeded hemlock transpiration by 77 mm from June until October. During the dormant season, evapotranspiration rates were higher in the hemlock stand; however, estimated annual evapotranspiration was 327 mm in eastern hemlock compared with 417 mm in the deciduous stand. Our results suggest that a transition from a hemlock-dominated to a black birch-dominated stand will alter the annual water balance with the greatest impact occurring during the peak growing season. Late in the growing season, flow may be unsustainable in streams that normally have light or moderate flow because ofincreased water use by black birch.

Description: The aims of this microcosm-based study were to characterize Scots pine ectomycorrhizal (EcM) inoculum potential in humus (O) and underlying eluvial (E) and illuvial (B) mineral podzol soil horizons and to compare the inoculum potential 1 and 4 years following clear-cut logging. The specific horizons were collected from a Scots pine control uncut stand, the adjacent interface zone (3–10 m from the forest edge), and the adjoining clear-cut area. The highest Simpson's reciprocal diversity indices (SRDI) of ectomycorrhizal morphotypes and polymerase chain reaction – internal transcribed spacer – restriction fragment length polymorphism (PCR-(ITS)-RFLP) taxa were detected in the humus and E horizon. The B horizon supported the lowest SRDI, but the community consisted of mycorrhizas representing active rhizomorph-forming species. Identified RFLP taxa, confirmed via ITS sequence analysis, highlighted horizon specificity for some genera and species. With respect to clear-cutting impacts, the most dominant ectomycorrhizal morphotypes detected and diversity indices were the same irrespective of the sampling time, which strongly indicates that inoculum potential is maintained up to four growth seasons after the clearcut. No forest treatment dependent differences in Scots pine seedling biomass were detected, but, compared with humus, significantly reduced biomass was recorded in deeper mineral soil horizons. The data are discussed in relation with recent vertical profile studies and forest silvicultural practices.

Description: The aim of the study was an integrated monitoring of Scots pine ( Pinus sylvestris L.) bait seedling performance and ectomycorrhizal fungal community dynamics in a Scots pine dominated stand one growing season before and over four seasons after forest clear-cut logging. The effects of planting location and time were assessed in relation to subsequent seedling performance and ectomycorrhizal diversity. Application of advanced regeneration, where seedlings were planted one growing season before the clear-cut event, resulted in increased seedling growth in the clear-cut area over the subsequent 4 years. However, counterparts planted in the interface zone in 1997, between the future uncut stand and the clear-cut area, exhibited poorer growth compared with those planted after clear-cut harvesting. The interface zone was generally richest in ectomycorrhizal diversity, and this was confirmed using complementary morphotyping and rDNA-based identification methods. Large numbers of ectomycorrhizal types were present on Scots pine seedling roots and instead of detecting dramatic changes in total number of types, species composition changes could be better related to changes in exploratory types of ectomycorrhizas with a trend towards less rhizomorphic types in the clear-cut treatment compared with the control forest. Changes in the community structure are presumably influenced by changing environmental conditions in the site.

Description: Mating system pattern (selfing or outcrossing and correlated matings levels) comparisons between two interior spruce seed orchard designs (clonal-row and random) managed under intensive crown and pollen management were conducted. Crown manipulation consisted of tree topping and branch pruning, while pollen management involved multiple supplemental mass-pollination applications during peak seed-cone reproductive receptivity and pollen agitation using helicopters. Significant differences between orchards’ multilocus outcrossing rate estimates were observed, and both estimates significantly departed from complete outcrossing (t = 1.0). Clonal arrangements in the clonal-row design permitted higher chances for selfing (t = 0.948) in comparison with those of the random design (t = 0.989). Intensive pollen management, while effective, still produced a minor component of selfing. Both orchard designs produced similar individual tree's outcrossing rate trends with the majority showing high outcrossing, while few individuals showed high selfing propensity. Estimates of correlated mating varied substantially between the two seed orchard designs with 9.3% and 4.3% for the clonal-row and random seed orchards, respectively. While small but significant differences in the genetic quality of the seed crops were observed between the two orchard designs, the establishment of clonal-row seed orchards should be given serious considerations specifically under committed pollen and crown management. The ease of crop and orchard management in the clonal-row design outweighs the observed differences in the seed crop genetic quality. A slight modification to the clonal-row design is proposed and is expected to reduce the observed minor genetic quality differences between the two orchard designs.

Description: The profit from tree breeding is dependent on the amount of money invested and how these resources are spent, particularly in the testing of selection candidates. Simulations of within-family selection were used to find the optimum balance among the number of candidates, progenies per candidate, and test sites for a given investment level and to compare the profit from progeny testing and phenotypic selection. The simulations were based on genetic parameters estimated from 66 Pinus sylvestris L. progeny trials in southern Sweden and on compilations of breeding costs. For progeny testing the optimum number of candidates and test sites increased with increasing investment level, whereas the number of progenies per candidate and site decreased and stabilized at ca. 10 individuals. The maximum annual profit for the phenotypic selection was higher and occurred at a lower investment level than for progeny testing. Among the two alternatives of progeny testing studied, the intensive alternative with practices to stimulate early flowering showed a higher maximum annual profit than the base alternative.

Description: A factorial trial was established to examine the effects of planting density and fertilization on the growth of western redcedar ( Thuja plicata Donn ex D. Don) and western hemlock ( Tsuga heterophylla (Raf.) Sarg.) on nutrient-poor (CH) sites and nutrient-medium (HA) sites. Two levels of NPK fertilization were crossed with three levels of planting density (500, 1500, and 2500 stems/ha). Fifteen years after establishment and 10 years after the last fertilizer application, height, individual stem volume increment, stand volume, 5 year periodic annual increment (PAI), and 5 year periodic height increment were all increased by fertilization. Fertilization of CH sites increased annual stand volume increment by 753%–2552% and 122%–209% for hemlock and cedar, respectively; fertilization of HA sites increased PAI by 94%–264%. Volume growth response to fertilization was greater on HA than on CH sites. Increasing stand density reduced height growth on CH sites but not on HA sites. These results suggest that competition for nutrients can be a significant growth-limiting factor even before canopy closure occurs and that treatment of ericaceous sites may not be justified by productivity increases.

Description: We undertook a retrospective study of aspen age structure in the winter range of Jasper National Park to assess potential trophic cascades in wolf–elk–aspen systems. We compiled historical wolf ( Canis lupus Linnaeus, 1758) and elk ( Cervus elaphus Linnaeus, 1758) population data and, in 2005, sampled 42 trembling aspen ( Populus tremuloides Michx.) stands within the Palisades site along the Athabasca Valley near Jasper townsite and another 30 stands within the Willow Creek site in a relatively remote portion of the park. Results indicated that aspen recruitment (suckers or seedlings growing into tall saplings and trees) occurred at both sites in the early 1900s but decreased in the 1940s as elk numbers were reaching a maximum. Wolves were largely eliminated from the park in the mid-1900s, and aspen recruitment during that time ceased at both sites, apparently because of heavy browsing by elk. With recovery of wolf populations in the late 1960s and increasing predation risk, elk use of the Willow Creek site declined, and aspen recruitment resumed. However, at the Palisades site, an area of relatively low predation risk due to human use and developments, renewed aspen recruitment has not occurred. Results indicate that historical wolf or ungulate control programs and human developments influenced trophic cascades involving wolves, elk, and aspen in these winter ranges.

Description: Presettlement land survey records provide baseline data on forest characteristics prior to major European settlement, but questions regarding surveyor bias and methodological consistency have limited confidence in quantitative analyses of this important data source. We propose new correction factors, calculated from bearings, distances, and species of bearing trees, to account for the effects of (i) inconsistency in quadrant configuration, (ii) bearing angle bias, and (iii) species bias on forest density and species composition estimated from presettlement land survey records. Computer simulations confirmed accuracy in random and nonuniform density forests, with moderate bias in very clustered and dispersed forests. A case study of township and quarter-section corners surveyed by the Holland Land Company in western New York demonstrates the potential magnitude of errors caused by surveyor inconsistency/bias in estimation of density and relative species frequency. The influence of nonuniform density, clustering, and dispersal on plotless density estimators remains an important obstacle to quantitative analysis of Presettlement land survey records. However, by accounting for uncertainties regarding surveyor methodology, the proposed correction factors add confidence to conclusions made regarding presettlement forest structure and composition.

Description: The Forest Inventory and Analysis (FIA) program of the USDA Forest Service alters plot locations before releasing data to the public to ensure landowner confidentiality and sample integrity, but using data with altered plot locations in conjunction with other spatially explicit data layers produces analytical results with unknown amounts of error. We calculated the potential error from using altered location data in combination with other data layers that varied in mean map unit size. The incidence of errors associated with the use of altered plot locations exhibited a strong inverse relationship to the mean map unit size of the other data sets used in the analyses. For a 30 m × 30 m resolution land cover map, plot misclassification rates ranged from 32% to 66%, whereas only 1%–10% of plots were misclassified for ecological subsection data (mean polygon size 9067 km2). Housing density data derived from the US Decennial Census (mean polygon size = 5.7 km2) represented an intermediate condition, with 5%–70% of data points misclassified when altered plot locations were used. These analyses demonstrate the impacts of altering FIA plot locations and represent an important step toward making the FIA database more helpful to a broad variety of end users.

Description: We evaluated soil conditions of rehabilitated log landings in the Interior Douglas-fir biogeoclimatic zone of British Columbia during the first 3 years after treatment and the growth of lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) on these log landings over 8 years. Rehabilitation treatments included combinations of tillage and the addition of either stockpiled topsoil or one of three organic amendments: hog fuel, sort-yard waste, and a wood waste – biosolids compost. The woody amendments were either applied as a surface mulch or incorporated into the soil after tillage. Tillage and addition of wood waste reduced soil bulk density and increased carbon content. Daytime soil temperatures in summer were lower under a hog fuel mulch than for the other treatments. The plots receiving hog fuel also had higher soil moisture content. One year after treatment, soil mechanical resistance for untreated soils, and those that were simply tilled, exceeded 2500 kPa for much of the growing season. Plots receiving wood waste had lower mechanical resistance. Use of wood waste in rehabilitation improved soil conditions and contributed to improved survival rates for planted lodgepole pine seedlings. Height growth after 8 years was not significantly affected by the treatments.

Description: To evaluate changes in surface water chemistry, peat, and the plant community in logged peatlands, we compared plots in 1–4 year old (class I) and 9–12 year old (class II) clearcuts with plots in wooded controls. Indicator species were significantly different between wooded and clear-cut plots but not between clear-cut plot age classes. Surface waters in class I clearcuts had significantly higher temperature and nutrients compared with controls, and this was attributed to warming of the soil, which resulted in faster decomposition and greater nutrient availability. Hummocks, important peatland plant microhabitats, were reduced in height in all clearcuts because of compaction and abrasion. These abiotic changes caused a shift in the plant community. Total plant diversity was approximately 30% higher on clearcuts and consisted primarily of herbs, particularly grasses. However, bryophyte and lichen diversity and cover was greatest in wooded controls. Picea mariana (Mill.) BSP regeneration was not compromised by clear-cutting and was greater in class II clearcuts. Greater diversity and cover of Salix species in class II clearcuts suggests stable shrub community formation, which may be persistent and may slow succession. The use of appropriate equipment to minimize site disturbances while the ground is frozen may reduce long-term shifts in the plant community.

Description: We examined the response of growth efficiency (GE), leaf area index (LAI), and resin flow (RF) to stand density manipulations in ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) forests of northern Arizona, USA. The study used a 40 year stand density experiment including seven replicated basal area (BA) treatments ranging from 7 to 45 m2·ha–1. Results were extended to the larger region using published and unpublished datasets on ponderosa pine RF. GE was quantified using basal area increment (BAI), stemwood production (NPPs), or volume increment (VI) per leaf area (Al) or sapwood area (As). GE per Al was positively correlated with BA, regardless of numerator (BAI/Al, NPPs/Al, and VI/Al; r2 = 0.84, 0.95, and 0.96, respectively). GE per As exhibited variable responses to BA. Understory LAI increased with decreasing BA; however, total (understory plus overstory) LAI was not correlated with BA, GE, or RF. Opposite of the original research on this subject, resin flow was negatively related to GE per Al because Al/As ratios decline with increasing BA. BAI, and to a lesser degree BA, predicted RF better than growth efficiency, suggesting that the simplest measurement with the fewest assumptions (BAI) is also the best approach for predicting RF.

Description: A new dendroecological method is developed to differentiate growth responses to fine-scale disturbance from regional-scale environmental variation. In spruce–fir forests of central British Columbia, release from suppression in response to overhead canopy tree mortality was calibrated as 〉60% change in radial growth (%CRG, adjacent 15 year periods compared) using gap-maker–gap-filler pairs with known years of mortality and response. Many release events, attributed to regional-scale environmental variation (e.g., bark beetle outbreaks), were counted. Species-specific regional-scale chronologies were subtracted from standardized gap-filler series producing residuals and 1 was added to all residual indices. Percent divergence (%DIV) values were calculated as the percent change in residuals (adjacent 15 year periods compared). A %DIV criterion was set at 〉15% increase in the residual series. The %CRG and %DIV criteria were applied to an independent data set of ring-width series, determining the date(s) of release for each tree. %CRG and %DIV criteria were used in a complementary approach to differentiate (i) release due to fine-scale canopy gaps, (ii) no response to a gap and regional-scale environmental variation, (iii) release due to regional-scale environmental variation, and (iv) response to a fine-scale canopy gap but not detected by the %CRG criterion.

Description: During periods of resource stress, such as drought, allocating limited photosynthate between growth and defense is a crucial component of tree survival. Our objectives were to describe the seasonal dynamics of physiology, growth, and resin defense of southwestern ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) which undergoes regular seasonal drought. We measured leaf-level net photosynthetic rate, leaf water potential, resin flow after phloem wounding, and growth in 24 consecutive months in 2002 and 2003. Precipitation was below average in both years, and 2002 was an extreme drought. In both years, the highest resin flow occurred when tree water stress was highest and photosynthesis was low. Belowground growth was highest in August in both years. Aboveground growth occurred primarily between May and August and was greater in 2003 than in 2002. Temporal variation in resin flow was positively related to temporal variation in needle and radial growth but was not related to temporal variation in root nor shoot growth. Thus, trade-offs in carbon allocation between resin and growth were weak. We discuss these results in the context of water stress in trees, current hypotheses of carbon allocation in plants, and the historical lack of pine bark beetle epidemics in northern Arizona.

Description: This study investigated aboveground pools and fluxes of biomass, carbon (C), and nitrogen (N) in the overstory and understory of a southern Appalachian red spruce ( Picea rubens Sarg.) – Fraser fir ( Abies fraseri (Pursh) Poir.) forest, following adelgid-induced fir mortality and spruce windthrow. Using fifty 20 m × 20 m plots, stratified by elevation (1700–1900 m), we estimated standing biomass and fluxes of all growth forms from periodic stand inventories (1998–2003), vegetation surveys, and existing or derived allometric equations. Total C and N pools and fluxes were calculated from plant- and tissue-specific C and N concentrations. Total aboveground biomass attained predisturbance values, ranging from 313 Mg·ha–1at the lower elevations to 204 Mg·ha–1at the upper elevations. Overstory biomass production (5650 kg·ha–1·year–1) and N uptake (11–15 kg·ha–1·year–1) exceeded earlier reported values, indicating forest recovery. Woody understory accounted for 3% of aboveground biomass, 10% of annual productivity, and 19% of total N uptake (∼7 kg·ha–1·year–1). Herbaceous vegetation, which comprised only 1% of total biomass, took up 18–21 kg N·ha–1annually, 〉50% of total ecosystem N uptake (37 kg·ha–1·year–1). This suggests that N-rich understory vegetation plays an important role in N cycling.

Description: The effect of canopy phenology on major ion fluxes beneath a mature European beech ( Fagus sylvatica L.) tree is examined. Annual and seasonal ion fluxes to the forest floor were significantly higher than the incoming wet-only deposition for all ions measured other than H+. The annual throughfall to wet deposition ratio generally ranged from 2.1 to 4.8. Stemflow contributed 9%–19% of the ion input to the forest floor, except for H+. Throughfall enrichment of K+, Ca2+, Mg2+, and NO3– was significantly higher in the leafed than in the leafless season, in contrast to Na+, NH4+, and H+. The temporal pattern of ion enrichment indicated canopy release of K+, Ca2+, and Mg2+ throughout the leafed season, of Na+, Cl–, and NH4+ from emerging leaves, and of Cl– and SO42– from senescing leaves. The contribution of canopy leaching to annual net throughfall and stemflow was estimated at 96% (K+), 54% (Ca2+), 40% (Mg2+), 12% (Cl–), and 7% (Na+, SO42–). Dry deposition accounted for 58%–75% of the total deposition onto the canopy. The throughfall enrichment during the leafless season indicated high particulate and gaseous dry deposition onto the woody canopy as well as K+ release from European beech branches.

Description: We present an overview of the Fuel Characteristic Classification System (FCCS), a tool that enables land managers, regulators, and scientists to create and catalogue fuelbeds and to classify those fuelbeds for their capacity to support fire and consume fuels. The fuelbed characteristics and fire classification from this tool will provide inputs for current and future sophisticated models for the quantification of fire behavior, fire effects, and carbon accounting and enable assessment of fuel treatment effectiveness. The system was designed from requirements provided by land managers, scientists, and policy makers gathered through six regional workshops. The FCCS contains a set of fuelbeds representing the United States, which were compiled from scientific literature, fuels photo series, fuels data sets, and expert opinion. The system enables modification and enhancement of these fuelbeds to represent a particular scale of interest. The FCCS then reports assigned and calculated fuel characteristics for each existing fuelbed stratum including the canopy, shrubs, nonwoody, woody, litter–lichen–moss, and duff. Finally, the system classifies each fuelbed by calculating fire potentials that provide an index of the intrinsic capacity of each fuelbed to support surface fire behavior, support crown fire, and provide fuels for flaming, smoldering, and residual consumption. The FCCS outputs are being used in a national wildland fire emissions inventory and in the development of fuelbed, fire hazard, and treatment effectiveness maps on several national forests. Although the FCCS was built for the United States, the conceptual framework is applicable worldwide.

Description: Wildfires and prescribed burns constitute widespread and potentially destructive disturbances in forest ecosystems. Fire-related effects on aboveground ecosystem components are well established, and it is known that fire can have both a direct and an indirect influence on the edaphic environment, but the effects of fire on soil-dwelling fungi are poorly understood. We review the disparate literature relating to fire effects on soil fungi, with emphasis on forest environments. A variety of effects have been reported, including altered fungal community structure along with increased or decreased mycorrhizal colonization of roots. Such effects, along with their duration, appear to be site- and (or) fire-specific, but are likely to be greater in the upper soil horizons. Where repeated burning occurs, the effects on soil fungal communities appear to be more pronounced with more frequent burning. Although fire may effect structural changes in soil fungal communities, the functional significance of such changes at the ecosystem level remains difficult to assess.

Description: This study presents an optimization method based on cellular automaton (CA) for solving spatial forest planning problems. The CA maximizes stand-level and neighbourhood objectives locally, i.e., separately for different stands or raster cells. Global objectives are dealt with by adding a global part to the objective function and gradually increasing its weight until the global targets are met to a required degree. The method was tested in an area that consisted of 2500 (50 × 50) hexagons 1 ha in size. The CA was used with both parallel and sequential state-updating rules. The method was compared with linear programming (LP) in four nonspatial forest planning problems where net present value (NPV) was maximized subject to harvest constraints. The CA solutions were within 99.6% of the LP solutions in three problems and 97.9% in the fourth problem. The CA was compared with simulated annealing (SA) in three spatial problems where a multiobjective utility function was maximized subject to periodical harvest and ending volume constraints. The nonspatial goal was the NPV and the spatial goals were old forest and cutting area aggregation as well as dispersion of regeneration cuttings. The CA produced higher objective function values than SA in all problems. Especially, the spatial objective variables were better in the CA solutions, whereas differences in NPV were small. There were no major differences in the performance of the parallel and sequential cell state-updating modes of the CA.

Description: A tree-ring reconstruction of forest tent caterpillar ( Malacosoma disstria Hubner) outbreaks was conducted in the Duck Mountain Provincial Forest. Trembling aspen ( Populus tremuloides Michx.), balsam poplar ( Populus balsamifera L.), and paper birch ( Betula papyrifera Marsh.) tree-ring chronologies were used to identify periods of outbreaks from approximately 1800 to 2002. The impacts of the major forest tent caterpillar outbreaks of the 20th century were compared among four stand types and two age classes. The presence of white rings and growth suppression were used to identify three important outbreak periods, 1939–1948, 1961–1965, and 1982–1985, with another large-scale outbreak suspected during the 1870s. A roughly 20-year interval was observed between major outbreaks. Few differences were found between stand types, except during the 1960s, when mixed stands with jack pine ( Pinus banksiana Lamb.) registered more growth suppression and white rings. In general, the outbreak signal in the younger sites was variable. The importance of utilizing white rings and growth suppression data together is discussed. The major outbreaks of the 20th century generally started in the north of the Duck Mountain Provincial Forest. The technique was successful at identifying forest tent caterpillar outbreaks during the 20th and late 19th centuries, when no historical surveys were available.

Description: The pinewood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, is listed as a quarantine pest in the legislation of more than 40 countries. Rapid and accurate detection of the pinewood nematode in coniferous chips, sawn wood, and logs is critical in preventing the introduction of the nematode and forms the basis for quarantine regulations. The traditional but laborious Baermann-funnel sampling technique delays the detection of pinewood nematode. We applied the chemotactic response of pinewood nematode to its insect vector, Monochamus alternatus Hope, to develop a novel and rapid sampling method. A trap tube, baited with a blend of attractant terpenes (α-pinene, β-pinene, and longifolene, 1:2.7:1.1) is shown to effectively capture third-stage dispersal juveniles of pinewood nematode from infested wood under laboratory and field conditions. Nematodes were first isolated after a 2 h trapping period, and the number of nematodes recovered increased with the duration of trapping. This chemical attraction technique is simple, effective, and rapid and should assist greatly in the detection of pinewood nematode at both ports-of-entry and forest habitats.

Description: A field study was conducted in a high-elevation spruce–fir ( Picea rubens Sarg. – Abies fraseri (Pursh.) Poir) forest in the Great Smoky Mountains National Park to assess the effect of temperature on soil C storage and dynamics. In eight plots along an elevation gradient (1500–1900 m), we measured soil temperature, forest floor and mineral soil C, litter decomposition, soil respiration, and forest floor mean residence time. Mean annual soil temperature and annual degree-days above 5 °C were inversely correlated with elevation. Total soil C (166–241 Mg·ha–1) showed no trend with elevation, while forest floor C accumulation (16.3–35.9 Mg·ha–1) decreased significantly with elevation. Carbon dynamics did not follow a consistent elevation pattern; however, the cooler upper elevations showed the lowest C turnover as indicated by the lowest needle decomposition rate (k = 0.0231·year–1) and the longest mean residence time of forest floor C (22 years). Mean annual CO2efflux from the soil (1020–1830 kg C·ha–1·year–1) was negatively correlated with mean annual soil temperatures and annual degree-days above 5 °C. This gradient study offers useful insights into C release patterns under future warming scenarios, and suggests that the highest elevation may be most susceptible to global warming.

Description: An ecosystem management model was used to project total aboveground and belowground production in hybrid poplar plantations for two sites in Saskatchewan that were previously in agricultural production and that differed in their soil organic matter and nitrogen content (categorized as poor and rich sites). Stemwood production (the primary measure of treatment response) was always negatively affected by the competition that resulted when weeds were abundant; the effect was more severe on the poor than on the rich site. Stemwood biomass was greater when weed competition was low, but peak production declined over successive rotations on both sites, regardless of whether fertilizer was used. Fertilization always enhanced stemwood production but less so on the rich than on the poor site. A single fertilizer application in the second or seventh year after plantation establishment resulted in consistently higher stemwood production than midrotation fertilization (year 12). Fertilization was more beneficial to stemwood production when weed competition was high than when it was low. Low weed competition in conjunction with early fertilization produced the highest stemwood production. The simulations indicate that the relative benefit of a given management regime cannot be considered independently of the site nutrient status and the particular rotation.

Description: Red spruce ( Picea rubens Sarg.) forests are an ecologically and economically important forest type in eastern Canada. We quantified the carbon (C) stocks of natural red spruce dominated stands in central Nova Scotia. Twenty-four stands over a 140 year chronosequence were sampled. Within each stand, major C pools including above- and below-ground tree biomass, shrub and herb vegetation, dead organic matter, and upper (0–10 cm) mineral soil were measured. A nonlinear four-parameter logistic function was fitted to the total site C stock data to describe the change in total ecosystem C storage over time. Total site C storage increased throughout stand development in a general sigmoidal pattern, increasing from 94.4 Mg C·ha–1 in the youngest age-class to a maximum of 247.0 Mg C·ha–1 in the 81- to 100-year-old age-class, then decreasing in the oldest age-classes. Carbon pools of live vegetation, standing dead trees, and downed woody debris displayed recognizable changes in C storage throughout stand development, conforming to some of the fundamental ideas on forest stand dynamics. Overall, above- and below-ground tree biomass had the greatest influence on total site C storage dynamics. These results are likely to be integrated into further forest management plans and generalized in other contexts to evaluate carbon stocks at the regional scale.

Description: Fluctuations in the abundance of Lepidoptera are common but inadequately understood. Here we show that caterpillar abundance in the White Mountains of New Hampshire has fluctuated by 〉20-fold from 1986 to 2005. We report tests of three possible causes: (i) extreme winter cold; (ii) long, warm summers; and (iii) interannual variation in tree growth, which tends to correlate with phytochemistry. Caterpillar fluctuations from summers t to t + 1 were uncorrelated or negatively correlated with minimum air temperature during the intervening winter (does not support the first cause), but were positively correlated with thermal sum during summer t (r = 0.49–0.56) (supports the second cause). There was limited interannual variation in the radial growth of two dominant tree species ( Acer saccharum Marsh. and Betula alleghaniensis Britt.) and no correlation with caterpillar fluctuations (refutes the third cause). Thermal sum might influence caterpillar fluctuations through direct effects on insect development, indirect effects on susceptibility to natural enemies, and (or) indirect effects on plant-insect interactions; the mechanisms are of particular interest because thermal sums have been increasing since local records began in 1957 (r = 0.41–0.45). In hardwoods forests of the northeastern United States, there is some broad-scale driver related to summer temperatures that generates fluctuations in caterpillar abundance, which influences herbivory as well as higher level consumers, such as insectivorous birds.

Description: A nonlinear mixed-effects model approach was used to model dominant height and site index for Eucalyptus globulus Labill. plantations in southeastern Australia. Mixed effects were considered initially for all three parameters of a modified Chapman–Richards model. Inclusion of random effects improved fitting and accounted for the within-plot heteroscedasticity. To correct for within-plot autocorrelation, a power autocorrelation model allowing for irregular intervals for remeasurements was found to be most appropriate. Additional fertilizer application at age 1 year and a number of environmental variables were related to the fixed-effects parameters, but these were not statistically significant, whereas mean annual rainfall and average daily maximum temperature in July (winter) greatly reduced the residual variability among plots. The resulting nonlinear mixed-effects model combines dominant height and site index prediction into a single model and predicts polymorphic height growth rates on different sites. The model can be used to predict population-mean dominant heights and site indices for different growing conditions of E. globulus plantations using existing information of annual rainfall and daily maximum temperature. When prior measures of dominant heights at several ages are available for a plot, specific random effects can be estimated and localized predictions of dominant height or site index can be obtained.

Description: Coarse wood provides important ecosystem structure and function such as water and nutrient storage and critical habitat for the conservation of a variety of organisms, including ectomycorrhizal (EM) fungi. The chemistry and EM communities were compared in coarse wood samples collected from two advanced decay stages of logs in 12 paired young and old-growth stands in the Oregon Cascade Range. Average total C and nonpolar extractives were higher in young stands (15–55 years) (mean = 53.38%, 95% CI of 52.48–54.27 and mean = 8.54%, 95% CI of 6.92–10.16, respectively) compared with old-growth stands (200–500 years) (mean = 51.22%, 95% CI of 49.67–52.77 and mean = 6.75%, 95% CI of 5.88–7.62, respectively). Averages for total and extractable P were higher in old-growth stands (mean = 0.03%, 95% CI of 0.02–0.04 and mean = 82.91, 95% CI of 52.24–113.57, respectively) compared with young stands (mean = 0.02%, 95% CI of 0.02–0.02 and mean = 56.17, 95% CI of 45.84–66.50, respectively). Average pH and total N were highest in logs in the most advanced decay stage (mean = 4.17, 95% CI of 3.97–4.38 and mean = 0.35%, 95% CI of 0.29–0.40, respectively). No differences between log decay class or stand age were detected for water-soluble extractives, hemicellulose plus cellulose (or acid-hydrolyzable fraction), or acid-unhydrolyzable residue. Observed differences in average wood property values between decay stages and between young and old-growth stands were small and, although statistically significant, may not reflect an important difference in EM fungal habitat. EM communities were similar between young and old-growth stands and between logs in decay classes 4 and 5. Results suggest that down wood in advanced decay stages provides similar habitat for EM fungi in both old-growth and young, managed stands.

Description: Dead wood dependent (saproxylic) insects have been identified as vulnerable to the effects of modern forestry practices. We examined the effects of variable retention harvesting on saproxylic beetle assemblages. Variable retention of living green trees seeks to leave more forest structure on the landscape with the goal of maintaining ecosystem function and biodiversity. Ninety flight-intercept traps were divided between recently dead natural snags and snags killed by girdling in three replicated forest stands with 10%, 20%, 50%, and 75% residual structure and in uncut control stands. Beetles were collected and identified during the second and third summers post harvest and grouped for analyses as (i) wood- and bark-borers, (ii) fungivores, and (iii) predators. Harvesting intensity explained a relatively small amount of the variability in the beetle assemblages. However, all groups responded strongly to coarse woody debris variables and especially to snag decay class during the third postharvest summer, suggesting that factors associated with coarse woody debris quality and quantity determine the initial responses and successional trajectories of saproxylic beetle assemblages. The main effects of variable retention on saproxylic assemblages are expected to be mediated through differences in amount of coarse woody debris expected to materialize with the death and decay of green trees left as residual elements.

Description: A total of 1640 increment cores from 343 radiata pine ( Pinus radiata D. Don) families were sampled at two second-generation progeny trials, aged 6 and 7 years, for a detailed genetic study of juvenile wood quality traits. Density, microfibril angle (MFA), and modulus of elasticity (MOE) were determined from pith to bark using SilviScan® technology. Heritability was greatest for area-weighted density at the two sites (0.63 and 0.77, respectively), and the lowest for growth traits (

Description: Volume growth has typically been used as a selection trait of prime importance in forest tree breeding. Less attention has been given to the genetic or phenotypic relationships between the growth or yield and wood density traits. In the above context, we aimed to investigate the phenotypic relationships among different growth, yield, and wood density traits of 20 Norway spruce ( Picea abies (L.) Karst.) clones grown in southeastern Finland, in order to identify whether a high growth rate was associated with low wood density in any of the clones. Compared with growth or yield traits, the wood density traits showed lower phenotypic variations. The phenotypic correlations between growth, yield, and wood density traits were, on average, from moderate to high, suggesting that selection for one trait would simultaneously affect the other traits. Compared with volume production, selection based on stem mass could be more profitable if a clonal stand is managed for pulpwood rather than mechanical wood processing and vice versa; whereas selection for overall wood density alone would reduce both the stem volume and stem mass. However, by compromising the gain or loss in wood density and stem volume, clones with high stem volume and a relatively high wood density could be found.

Description: Patterns of host use by herbivore pests can have serious consequences for natural and managed ecosystems but are often poorly understood. Here, we provide the first quantification of large differential impacts of the southern pine beetle, Dendroctonus frontalis Zimmermann, on loblolly pine, Pinus taeda L., and longleaf pine, Pinus palustris P. Mill., and evaluate putative mechanisms for the disparity. Spatially extensive survey data from recent epidemics indicate that, per square kilometre, stands of loblolly versus longleaf pine in four forests (380–1273 km2) sustained 3–18 times more local infestations and 3–116 times more tree mortality. Differences were not attributable to size or age structure of pine stands. Using pheromone-baited traps, we found no differences in the abundance of dispersing D. frontalis or its predator Thanasimus dubius Fabricius between loblolly and longleaf stands. Trapping triggered numerous attacks on trees, but the pine species did not differ in the probability of attack initiation or in the surface area of bark attacked by growing aggregations. We found no evidence for postaggregation mechanisms of discrimination or differential success on the two hosts, suggesting that early colonizers discriminate between host species before a pheromone plume is present.

Description: An earlier study indicated that cereal straw may be removed after harvest without affecting crop production, soil organic matter and microbial biomass. Further measurements of early indicators of changes in soil organic matter, viz., the light fraction and mineralizable C and N, confirm that straw removal is superior to straw incorporation with moldboard ploughing, and comparable to straw incorporation by disking, in C and N retention and turnover. Key words: Carbon, light fraction, mineralization, nitrogen, straw management

Description: We quantified the dynamics of the tree stratum at Hubbard Brook Experimental Forest (HBEF), New Hampshire, to examine why live biomass reached a plateau in about 1980. Total aboveground biomass increased from 209 Mg·ha–1 in 1981 to 216 Mg·ha–1 in 2001. From 1991 to 2001, in-growth of ≥10 cm diameter at breast height (DBH) trees averaged 4.7 trees·ha–1·year –1 with a corresponding in-growth biomass of 0.29 Mg·ha–1·year–1. Mortality of trees ≥10 cm DBH averaged 5.3 trees·ha–1·year–1 (1.12% of trees·year–1). Dying trees represented 2.24 Mg·ha–1·year–1 of aboveground biomass from 1991 to 2001. The biomass pools of standing dead, snags, and coarse woody debris in this forest currently are near steady state with residence times of 7.5, 15, and 6.2 years, respectively. The plateau in live biomass was mostly associated with lower wood production. Aboveground net primary productivity was estimated at 6.53 Mg·ha–1·year–1 (3.28 Mg·ha–1·year–1 for aboveground woody tissues and 3.25 Mg·ha–1·year–1 for leaf production), considerably lower than published estimates for the 1956–1965 period at the HBEF. Net ecosystem productivity in this young, second-growth forest is near zero, indicating that it may not be a sink for carbon.

Description: Both the size and the density of gaps affect seedling growth, but these two parameters have a reciprocal relationship at a given gap ratio. The objective of the present study was to clarify the appropriate gap mosaic coarseness required to facilitate the growth of Quercus gilva Blume seedlings in Cryptomeria japonica D. Don plantations. The spatial heterogeneity of the photosynthetic photon flux density on the forest floor was predicted using mimicked hemispherical diagrams under five levels of gap mosaic coarseness ranging from the finest gap mosaic with a gap size of 25 m2 and a gap density of 100·ha–1 to the coarsest mosaic of 400 m2 and 6.25·ha–1. Photosynthetic potentials (PP) were calculated by combining the predicted photosynthetic photon flux density and photosynthetic relationships of Q. gilva and two nontree major competitors ( Mallotus japonicus (Thunb.) Muell. Arg. and Miscanthus sinensis Anderss.). The coarser gap mosaic formed a more heterogeneous and bimodal PP frequency and resulted in a wider site in which the three species had high growth potential without considering competition among species. However, an intermediate mosaic with a gap width to mean canopy height ratio of 0.7 formed the widest realized niche in which Q. gilva would show good growth with a relative PP 〉 70%, whereas the competitor species would be suppressed with a relative PP 〈 70%.

Description: Resource sustainability requires a thorough understanding of the influence of forest management programs on the conservation of genetic diversity in tree populations. To observe how differences in forest structure affect the genetic structure of eastern white pine ( Pinus strobus L.), we evaluated six eastern white pine sites across the 234 000 acre (1 acre = 0.4046856 ha) Menominee Indian Reservation in northeastern Wisconsin (45°00′N, 88°45′W). The six sites sampled for nuclear and chloroplast DNA microsatellite markers were of contrasting densities and managed by different management systems: shelterwood, pine release, plantation, and old growth. Three of the sites had natural regeneration, which was also sampled. Mean values of spatial genetic autocorrelation were positive in all mature populations and variable; the strongest spatial structuring of genes occurred in the least disturbed old-growth site (I – E(I) = 0.031). Genetic structuring at the historical old-growth site fit the isolation-by-distance model for a neighborhood size of 130 individuals. Significant inbreeding occurred in five populations, but the seedling or sapling populations as a group (f = 0.088) are significantly less inbred than the local mature populations (f = 0.197). The increase in heterozygosity between generations was attributed to harvesting having reduced the spatial genetic structure of the mature trees.

Description: Understory growth dynamics of northern conifer species were studied in four stands managed under multiaged silvicultural systems in eastern Maine. Height growth of Picea rubens Sarg., Abies balsamea (L.) Mill., and Tsuga canadensis (L.) Carr. saplings between 0.5 and 6.0 m in height was related to the proportion open sky (POS), using sapling height as a covariate. Height growth of T. canadensis equaled A. balsamea and exceeded P. rubens under very low light levels (POS 〈 0.1) but is much less responsive to both increasing POS and taller heights, reaching 50% of its maximum height growth at a POS of only 0.09. Abies balsamea outgrew P. rubens under similar dark conditions; at higher light levels (POS 〉 0.10), both species grew similarly. Evidently, no feasible overstory manipulation of light alone can promote more rapid height development of P. rubens saplings over A. balsamea. A nonlinear light-prediction model using stand basal area is linked with height-growth prediction equations to quantify sapling development from 0.5 to 6 m. Depending on overstory density, P. rubens requires a height advantage of 0.14–0.33 m over a 0.5 m tall A. balsamea to reach a height of 6 m over the same time period.

Description: The objective of this study was to assess the effects of fine-scale canopy disturbances induced by selection harvesting and its associated practices (artificial planting and machinery skidding) on the successful regeneration of tree species in a northern Japanese mixed forest. We set up 163 plots in a 6.7 ha permanent study stand where trees have been partially harvested at approximately 10-year intervals since 1974. The regeneration of trees (4324 stems·ha–1) occurred more frequently under closed canopies than under canopy gaps, except for a typical shade-intolerant species, Betula ermanii Cham. In particular, small canopy openings that tend to close quickly displayed higher understory tree regeneration densities likely due to the suppression of competition from dwarf bamboos. The surface soil disturbances that occurred during planting and harvesting even further enhanced understory regeneration. The results shown here should be generalized carefully because we have investigated only one stand. Nevertheless, our findings clearly indicated that the creation of small canopy gaps associated with site preparation that contains soil disturbances should be examined in management practices to maintain the community structure in this type of mixed forest.

Description: The Fuel Characteristic Classification System (FCCS) is a systematic catalog of inherent physical properties of wildland fuelbeds that allows land managers, policy makers, and scientists to build and calculate fuel characteristics with complete or incomplete information. The FCCS is equipped with a set of equations to calculate the potential of any real-world or simulated fuelbed to spread fire across the surface and in the crowns, and consume fuels. FCCS fire potentials are a set of relative values that rate the intrinsic physical capacity of a wildland fuelbed to release energy and to spread, crown, consume, and smolder under known or benchmark weather and fuel moisture conditions. The FCCS reports eight component fire potentials for every fuelbed, arranged in three categories: surface fire behaviour (reaction intensity, spread rate, and flame length), crown fire potential (torching and active crown fire), and available fuel potential (flaming, smouldering, and residual smouldering). FCCS fire potentials may be used to classify or compare fuelbeds that differ because of location, structure, passage of time, or management action, based on expected fire behavior or effect outcomes. As a classification tool, they are offered as an objective alternative to categorizing bulk properties of fuelbeds or stylized model inputs.

Description: The effects of two operational nursery fertilization regimes on the growth and nutrient dynamics of Douglas-fir ( Pseudotsuga menziesii var. glauca (Beissn.) Franco) seedlings after planting were compared. Seedlings were grown in a nursery with nutrients added at a constant rate (conventional fertilization) or at a rate that increased exponentially by 2%·day–1 (exponential fertilization) and planted near Barriere and Victoria, British Columbia. At the time of planting, half of the conventionally fertilized seedlings were planted with slow-release fertilizer packets. Growth and nutrient allocation was observed for 2 years following planting. Although the exponential fertilization regime provided 25% more N in the nursery compared with the conventional fertilization regime, exponentially fertilized seedlings were smaller at the time of planting, did not differ significantly in foliar N concentration, and showed no lasting benefits in growth or nutrient allocation. Two years after planting, there were no significant differences between the conventional and exponential fertilization regimes in seedling height, root collar diameter, total dry mass, or whole-plant N concentration. Seedlings fertilized at the time of planting had greater height and dry mass on the Barriere site but not on the dry Victoria site and whole-plant N concentrations did not differ 2 years after planting.

Description: Restoration attempts to reintroduce American chestnut trees to the eastern deciduous forest by means of a disease-resistant Chinese–American hybrid seed are in progress. Knowing the light conditions required for optimum seedling performance is necessary to maximize the success of reintroduction. American chestnut ( Castanea dentata (Marsh.) Borkh.) seedlings were planted in two replicate forests in Vinton County, Ohio, in areas that had been thinned (more available light) and in control areas (intact canopy, less available light). The photosynthetic capacity of 12 seedlings per treatment was assessed using an infrared gas-exchange analyzer. Seedlings in the thinned treatment reached light-saturating rates of photosynthesis at an irradiance level approximately 33% higher than did the seedlings in the control treatment. Seedlings grown in the thinned treatment had a significantly greater maximum rate of photosynthesis (Amax), dark respiration rate (Rd), and daily carbon gain per seedling than seedlings grown in the control treatment. The light compensation point (LCP), quantum efficiency (ϕ), leaf mass per area (LMA), and leaf nitrogen concentration per unit leaf area (Narea) were not significantly different between treatments. American chestnut seedlings in the thinned treatment clearly maximize leaf-level photosynthetic capacity. These results will aid land managers in planning reintroduction trials by providing information on the light conditions required for maximum seedling success.

Description: We present a modification of an earlier presented method using prior auxiliary information in the layout of survey strips. The idea is to imitate a skilled surveyor who purposively seeks the species of interest. Yet, the method “unrestricted guided transect sampling” (UGTS) is a probability sampling method. In comparison with a strip survey using no auxiliary information, UGTS gave 11%–64% lower standard errors for estimates of species population size in three simulated forest types. In a test in six stands where European aspen ( Populus tremula L.) and an epiphytic moss ( Orthotrichum speciosum Nees) had been mapped, UGTS gave a small improvement in some stands but considerably higher standard errors in other stands with kNN estimates of volume of deciduous trees derived from satellite images as covariate values. With covariates values simulated from aspen basal area, UGTS gave 8%–75% lower standard error than a strip survey using no auxiliary information. The study shows a gain in precision by using auxiliary information both in the design and in estimation when surveying sparse species but also that the correlation between the covariate and the variable of interest has to be relatively strong to make the method worthwhile.

Description: Phospholipid fatty acid profiles were used to evaluate microbial community composition in different soil layers of sugi ( Cryptomeria japonica (L.f.) D. Don) plantations and seminatural secondary forests in southeastern Kyushu, Japan. These forests had previously been utilized as meadows or coppices. Principal components analysis and canonical correspondence analysis of the phospholipid fatty acid data demonstrated differences in microbial community structure between current vegetation (sugi plantations or seminatural forests) in the FH layer. In contrast, differences between the previous land-use types (meadows or coppices) were detected through variation in the soil microbial community structure in the upper part of the A layer (0–5 cm). However, in the deeper part of the A layer (5–10 cm), the influence of the previous land-use history on soil microbial community structure was weak and the influence of the current vegetation could be detected. In the 0–5 cm part of the A layer, the organic matter was correlated with the microbial community structure. However, it cannot be assumed that these soil chemical characteristics were the principal factors responsible for separation of the microbial communities based on previous land-use history because the difference in chemical characteristics between the sites was small.

Description: Limber pine ( Pinus flexilis James) stands along the eastern escarpment of the Sierra Nevada, California, experienced significant mortality from 1985 to 1995 during a period of sustained low precipitation and high temperature. The stands differ from old-growth limber pine forests in being dense, young, more even-aged, and located in warmer, drier microclimates. Tree growth showed high interannual variability. Relative to live trees, dead trees over their lifetimes had higher series sensitivity, grew more variably, and had lower growth. Although droughts recurred during the 20th century, tree mortality occurred only in the late 1980s. Significant correlations and interactions of growth and mortality dates with temperature and precipitation indicate that conditions of warmth plus sustained drought increased the likelihood of mortality in the 1985–1995 interval. This resembles a global-change-type drought, where warming combined with drought was an initial stress, trees were further weakened by dwarf mistletoe ( Arceuthobium cyanocarpum (A. Nels. ex Rydb.) A. Nels.), and proximally killed by mountain pine beetle ( Dendroctonus ponderosae Hopkins). However, the thinning effect of the drought-related mortality appears to have promoted resilience and improved near-term health of these stands, which suffered no additional mortality in the subsequent 1999–2004 drought.