ALBERT

Beschreibung: Trees and their environment were studied in floodplain forests in the glaciated region of northern Missouri. Ordination of tree vegetation samples by detrended correspondence analysis indicated a primary vegetation continuum of decreasing Acersaccharinum L. and increasing Caryalaciniosa (Michx. f.) Loud with several other species associated with secondary vegetation gradients, TWINSPAN classification of tree vegetation identified three groups of plots that were dominated by A. saccharinum in varying degrees of association with other species, most importantly Populusdeltoides Bartr. and Ulmusamericana L.; two groups dominated by species of Carya and Ulmus; and two groups where dominance was more broadly distributed among lowland Quercus spp., U. americana, Aesculusglabra Willd., Fraxinuspennsylvanica Marsh., Platanusoccidentalis L., and Betulanigra L. Importance of A. saccharinum was greatest in plots where the leading dominants were young, while Quercus and Carya spp. were more common in plots with older leading dominants, suggesting that the predominant environmental influence on vegetation composition was frequency and severity of disturbance associated with flooding. Plots with younger dominant trees had lower species richness and diversity than plots with older dominants. Higher soil pH and slough location were also positively correlated with A. saccharinum importance, and Acernegundo L. was more frequent in sloughs. Analysis of overstory and understory relationships indicated that A. saccharinum is likely to remain important in the immediate future in many forests currently dominated by this species because of its abundance in subcanopy positions. Potential canopy trees of F. pennsylvanica, C. laciniosa, Caryacordiformis (Wangenh.) K. Koch, and Celtisoccidentalis L. may, in the absence of major flooding disturbance, cause long-term shifts in composition in some of these forests. While Ulmus spp. are abundant in the understory, they are unlikely to become important canopy species because of disease.

Beschreibung: On the rocky shores and islands of Lake Duparquet, in the southwestern Quebec boreal forest, Thujaoccidentalis L. reaches ages in excess of 800 years. Annual ring widths from 38 trees were used to develop an 802-year chronology (1186–1987) standardized by polynomial regressions. Excellent cross dating, correlation with a shorter chronology located 14 km inland, and 33.6% common variance in a chronology subsample all point to the existence of a climatic signal. After autoregressive modeling to obtain a serially random residual chronology, correlation and response functions were used to identify the growth–climate relationship. The resulting model reduced 19.2% of the chronology variance. Precipitation in June as well as low temperature in June or July seemed to have a positive influence on growth. Likewise, a drought index was closely related to growth, indicating that the chronology could be used to estimate past drought conditions. Moisture deficits are thus inferred for the 13th century as well as during the Little Ice Age (17th century to late 19th century). Since the end of the latter period, precipitation seems to have followed an upward trend.

Beschreibung: Change in the health of sugar maple (Acersaccharum Marsh.) and associated northern hardwoods was evaluated for 3 years (1988–1990) in seven states and four provinces. Generally, levels of crown dieback and crown transparency (a measure of foliage density) in 165 stands decreased during this period. In 1990, less than 7% of all dominant–codominant sugar maples (n = 7317) exhibited crown dieback ≥ 20%. Significantly (p = 0.05) fewer of these maples were classified as having high crown transparency (≥ 30%) in 1990 compared with 1988. Crowns of maples that received moderate (31–60%) or heavy (〉 60%) pear thrips (Taeniothripsinconsequens (Uzel)) damage for 1 year recovered the following year. Crowns of maples exposed to severe drought in 1988 (Wisconsin) continued to show the effects (high transparency) of this stress in 1990. A majority (69–71%) of the dominant–codominant sugar maples with high (≥ 20%) crown dieback had bole and (or) root damage. Of those maples with crown dieback ≥ 50%, 86% had bole and (or) root damage. The condition of sugar maple in operating sugar bushes and undisturbed stands was similar. The condition of sugar maple crowns was similar in locations presumably exposed to low, medium, and high levels of sulfate deposition.

Beschreibung: A simple conceptual model is proposed concerning how leaf area efficiency (stemwood growth per unit leaf area) changes with leaf area for trees within a stand. Greater leaf area is generally associated with (i) improved light environment due to greater height and (ii) a lower ratio of photosynthetic to nonphotosynthetic tissue. Greater height and improved light environment result in higher photosynthetic production, which should increase leaf area efficiency. A lower ratio of photosynthetic to nonphotosynthetic tissue suggests that the ratio of respiration to photosynthesis increases, which should decrease leaf area efficiency. In relatively small trees, the influence of increased height (associated with greater leaf area) should more than offset the influence of the increased respiration:photosynthesis ratio; as a result, leaf area efficiency should increase with leaf area. In large trees, further increases in leaf area are associated with minimal increases in height, and leaf area efficiency should decline as the respiration:photosynthesis ratio increases. Predictions from this conceptual model were examined with data from stands of subalpine fir (Abieslasiocarpa (Hook.) Nutt.).

Beschreibung: Red spruce (Picearubens Sarg.), black spruce (Piceamariana (Mill.) B.S.P.), and balsam fir (Abiesbalsamea (L.) Mill.) seedlings were root inoculated with tomato mosaic virus, potted, and maintained in a cold frame. The virus was detected by enzyme-linked immunosorbent assay in root extracts of several inoculated seedlings of each species 6–12 months postinoculation, and in root extracts of approximately 35–40% of both inoculated and noninoculated seedlings of each species 12–18 months postinoculation. Virus spread apparently occurred from the roots of infected to noninfected seedlings within the cold frame. The presence of virus in root extracts was confirmed by immunoelectron microscopy. The virus was not detected in the needles of any seedling at any time by either enzyme-linked immunosorbent assay or immunoelectron microscopy. A transitory needle chlorosis was observed in approximately 14% of the inoculated black spruce and 30% of the inoculated red spruce seedlings, but tomato mosaic virus was not detected in all plants with symptoms.

Beschreibung: Rising atmospheric carbon dioxide concentrations may have important consequences for forest ecosystems. We studied above- and below-ground growth and leaf gas exchange responses of Populusgrandidentata Michx. to elevated CO2 under natural forest conditions over the course of a growing season. Recently emerged P. grandidentata seedlings were grown in native, nutrient-poor soils at ambient and twice ambient (707 μbar (1 bar = 100 kPa)) CO2 partial pressure for 70 days in open-top chambers in northern lower Michigan. Total leaf area and shoot and root dry weight all increased in high CO2 grown plants. Photosynthetic light and CO2 response characteristics were measured 28, 45, and 68 days after exposure to elevated CO2. In ambient grown plants, light saturated assimilation rates increased from day 28 to day 45 and then declined at day 68 (15 September). This late-season decline, typical of senescing Populus leaves, was due both to a decrease in the initial slope of the net CO2 assimilation versus intercellular CO2 partial pressure relationship and to decreased CO2 saturated assimilation rates. Specific leaf nitrogen (mg N•(cm2 leaf area)−1) did not change during this period, although leaf carbon content and leaf weight (mg•cm−2) both increased. In ambient grown plants stomatal conductance also declined at day 68. In contrast, plants grown at elevated CO2 showed no late-season decline in photosynthetic capacity or changes in leaf weight, suggesting a delay in senescence with long-term exposure to high CO2. High CO2 grown plants also maintained photosynthetic sensitivity to increasing Ci throughout the exposure period, while ambient CO2 grown plants were insensitive to Ci above 400 μbar on day 68. These results indicate the potential for direct CO2 fertilization of P. grandidentata in the field and provide evidence for a new mechanism by which elevated atmospheric CO2 could influence seasonal carbon gain.

Beschreibung: Attraction of scolytids and other bark- and wood-dwelling beetles to volatile constituents of Norway spruce (Piceaabies (L.) Karst.) was studied in field experiments in central Sweden. The volatiles were released from chips of newly cut spruce stems as well as from stems stored over winter. These host materials were kept in cylinders covered on both ends with fine nylon mesh. Attracted insects were caught in barrier traps. The composition of volatile constituents of wood samples was determined using gas chromatography. Hylurgopspalliatus (Gyll.), Hylastescunicularius Er., Ipstypographus (L.) (Scolytidae), and Glischrochilusquadripunctatus (L.) (Nitidulidae) were particularly attracted to stored spruce wood. Trypodendronlineatum (Oliv.) (Scolytidae) and Pityophagusferrugineus (L.) (Nitidulidae) were only attracted to stored wood. There were indications that Tomicuspiniperda (L.) and Hylastesbrunneus Er. (Scolytidae) preferred fresh wood. Chemical analyses revealed that during storage ethanol and acetaldehyde increased considerably in two out of the five examined tree stems.

Beschreibung: The prevalence of individual-tree growth decline was determined for red spruce (Picearubens Sarg.) populations at three locations in the southern Appalachians: Mount Rogers National Recreation Area, the Black Mountains, and Great Smoky Mountain National Park. An index of annual stemwood volume increment (AVI) was computed from dendrochronological data and a site-specific DBH–height regression equation. Individual-tree AVI time series were analyzed to identify changes in 20-year periodic mean AVI and AVI trend. The proportion of red spruce that exhibited decreasing mean AVI or negative AVI trend was determined for the most recent 20-year period, and this was compared with the estimated historical prevalence of these indications of growth decline. Also, the prevalence of growth decline was compared among subpopulations that differed with regard to various tree, stand, and site characteristics. Of 263 red spruce sampled, 25% exhibited a decrease in mean AVI during the period 1967–1986, 8% exhibited a negative AVI trend without a reduction in mean AVI, and 17% exhibited a reduction in the slope of the AVI curve. The proportion of trees that exhibited decreasing or slowed growth after 1967 was substantially greater among trees growing at 1980 m than in populations at lower elevations; no relationship was found between elevation and growth decline below 1980 m. No difference was found in prevalence of growth decline between subpopulations that differed with regard to age, DBH, competitive status, stand density, slope aspect, or site exposure. The prevalence of individual-tree growth decline for the most recent 20-year period did not exceed estimated levels for historical periods of decline in the Great Smoky Mountains population.

Beschreibung: In a routine determination of jack pine (Pinusbanksiana Lamb.) tree ages, several rings were overlooked or were difficult to count. Sections of the wood, when examined at higher magnification, revealed an unusually high proportion of "light rings." Light rings are characterized by having a small number of latewood cells whose walls are not as thick as those of latewood cells found in normal rings. Under low magnification, bands of these light rings may be interpreted as a single annual ring. Light rings may thus be a source of error in determining tree ages for forest productivity studies, particularly in older stands that have been affected by defoliators and root disease.

Beschreibung: A base-age invariant site index equation for jack pine based on the Chapman–Richards function was produced that satisfied nine criteria of preferred behavior for site index equations. A difference form of the Chapman–Richards equation produced the best behavior; height equalled site index at base age, and the shape of the curves reflected the data. The data structure used to fit the difference equation was all possible differences rather than the conventional nonoverlapping sequential intervals because this improved the behavior of the model. Height-prediction equations typically use height at base age (site index) as a predictor variable. As site index is measured with error, the equation will be biased. This bias will be evident in the predicted height at base age and in the shape of the curves. Base-age invariant equations predict height and site index with the same equation and thus diminish the effect of stochastic predictor variables. The equation performed comparably to a previously published equation with a specific base age of 50 years.

Beschreibung: Height and diameter growth, stem volume production, leaf phenology and leaf number, and number of branches of Populustrichocarpa Torr. & Gray, Populusdeltoides Bartr., and their F1 hybrids (P. trichocarpa × P. deltoides) were studied for 4 years in a research plantation in western Washington, United States. Twelve clones (three of each species and six of the hybrids) grew under a short-rotation silviculture regime in monoclonal plots at spacings of 1 × 1 m (10 000 stems/ha). Clones represented a north-south gradient within the geographic distribution of both the two North American poplar species and the parentage of the hybrid material. The results support earlier work by contributing additional evidence for the superiority of the hybrids. However, the relative hybrid superiority in these monoclonal plots was less pronounced than that found earlier in field trials with single-tree plots because of heightened intraclonal competition. After 4 years, mean estimated stem volume of the hybrids was 1.5 times that of P. trichocarpa and 2.3 times that of P. deltoides. Total tree height of the hybrids was 1.1 times that off. trichocarpa and 1.3 times that off. deltoides. Clonal variation was the dominant theme in height and diameter growth, stem volume productivity, time of bud break and bud set, tree mortality, and number of branches. Populustrichocarpa had the highest number of sylleptic branches, P. deltoides had the lowest, and hybrids were intermediate. Significant clone by replicate interactions were observed in height, diameter, and volume growth. Phenological traits, such as the dates of bud break and bud set, and the length of growing period only partly explained the observed differences in growth between the P. trichocarpa × P. deltoides hybrids and the parental species.

Beschreibung: Nitrogen transformations were examined in two pairs of adjacent, 55-year-old forests dominated by conifers (primarily Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco)) and by conifers and nitrogen-fixing red alder (Alnusrubra Bong.). Nitrogen availability was examined in aerobic and anaerobic incubations in the laboratory, and with resin-core and buried-bag incubations in the field. Rates of nitrogen mineralization and immobilization were examined in the field incubations using [15N]ammonium. Net nitrogen mineralization in a year-long series of resin-core incubations of forest floor plus 0–0.15 m depth soil was about 9 kmol•ha−1•year−1 for the two alder–conifer stands, but almost nil in the conifer stand at the low-productivity Wind River site, and 2.1 kmol•ha−1•year−1 in the conifer stand at the high-productivity Cascade Head site. The 15N pool dilution experiment showed that buried-bag incubations demonstrated more differences among stands than did resin cores; resin cores typically gave greater rates than buried bags. Previous estimates of nitrogen budgets were coupled with net mineralization estimates to examine how well the estimated fluxes balanced at an ecosystem scale. This tabulation of the complete nitrogen cycles showed substantial discrepancies, prompting caution in interpretation of some of the differences among the stands.

Beschreibung: The variable-form taper function was tested on a data set of 5074 trees, consisting of jack pine (Pinusbanksiana Lamb.), lodgepole pine {Pinuscontorta Dougl.), white spruce (Piceaglauca (Moench) Voss), and trembling aspen (Populustremuloides Michx.), from Alberta. When compared with the results of tests performed on the same data using the variable-exponent function and the segmented polynomial model, the variable-form model was found to be superior (based on residual mean squares) for estimating both upper stem diameter ratios and total stem volumes. The two pine species could be combined and a single taper function used without significant loss of accuracy. Stem form in two of the volume sampling regions was significantly different from that in other regions of the province, but this may have been because the samples were not representative of the two regions. The variable-form function gave accurate and unbiased estimates of both merchantable height and merchantable volume.

Beschreibung: Boreal forests contain large quantities of soil carbon, prompting concern that climatic warming may stimulate decomposition and accentuate increasing atmospheric CO2 concentrations. While soil warming increases decomposition rates, the accompanying increase in nutrient mineralization may promote tree growth in these nutrient-poor soils and thereby compensate for the increased carbon loss during decomposition. We used a model of production and decomposition to test this hypothesis. In black spruce (Piceamariana (Mill.) B.S.P.), white spruce (Piceaglauca (Moench) Voss), and paper birch (Betulapapyrifera Marsh.) forests, decomposition increased with the soil warming caused by a 5 °C increase in air temperature. However, increased nitrogen mineralization promoted tree growth, offsetting the increased carbon loss during decomposition. In the black spruce forest, increased tree production was maintained for the 25 years of simulation. Whether this can be maintained indefinitely is unknown. In the birch forest, tree production decreased to prewarming levels after about 10 years. Our analyses examined only the consequences of belowground feedbacks that affect ecosystem carbon uptake with climatic warming. These analyses highlight the importance of interactions among net primary production, decomposition, and nitrogen mineralization in determining the response of forest ecosystems to climatic change.

Beschreibung: Concepts and procedures are presented for the analysis of progeny trials that incorporate clonal replication as a means to resolve variance arising from nonadditive gene effects. Components of variance from the linear model may be expressed in terms of expected covariances among relatives, and these, in turn, may be used to derive approximations of additive, dominance, and epistatic components of genetic variance. In addition to the usual assumptions applied to conventional progeny trials, the use of this expanded genetic model in the analysis of tests with clonal replicates assumes that the greatest portion of the total epistasis is due to interactions involving groups of more than two or three loci. If this assumption is not satisfied, estimates of additive and dominance variance, including those from trials without clonal replicates, will be contaminated by a large fraction of epistasis, and total epistasis will be underestimated by a corresponding amount. Heritability and gain formulae for alternative selection and deployment schemes are developed and illustrate the use of genetic parameters in the comparison of seedling and clonal reforestation strategies.

Beschreibung: Identical pair crosses, including reciprocals, in Pinussylvestris L. (Scots pine) were made on ramets of the same clones in three clonal archives (seed orchards) in Sweden: Sävar (64°N), Röskär (59.5°N), and Degeberga (56°N). The offspring were used to test the hypothesis that the parental environment could affect the performance of the progeny (aftereffects). Growth and freezing tests were performed in the controlled conditions of the Stockholm Phytotron. Parental environment affected seed weight: the heaviest seeds came from Röskär and the lightest seeds, from Degeberga. Height development was affected in the two growth periods tested: seeds from Sävar produced the shortest plants and seeds from Röskär, the tallest plants. There was an effect on the autumn frost hardiness in the first growth period that disappeared after the second growth period. The most hardy progenies came from Sävar. The aftereffects of the parental environment were less than the maternal effects on seed weight and also less than the effects of full-sib families on growth and autumn frost hardiness. Small but mostly significant reciprocal effects were found for height and height increment during the second growth period. There was a significant reciprocal effect for seed weight. Seed weight differences could explain only a small part of the effects on growth and none of the effects on hardiness.

Beschreibung: The frost hardiness of 15- to 25-year-old Scots pine (Pinussylvestris L.) and Norway spruce (Piceaabies (L.) Karst.) growing under central Finnish conditions was followed during 1985–1987. Shoots were subjected to artificial frost in the laboratory. Frost hardiness was assessed by the impedance method and by visual scoring. Frost hardiness varied during the years from −3.5 °C to lower than −40 °C. The rate of dehardening increased after about mid-April in both tree species when the daily mean temperature increased by several degrees above 0 °C. The maximum rate of dehardening varied slightly from year to year. In both species the frost hardiness of the previous year's shoot decreased during shoot elongation. This phenomenon was more prominent in pine than in spruce. Shoots were most susceptible to frost damage at the time when shoot elongation was ceasing. The onset and development of hardiness in autumn varied from year to year, especially in spruce. Some difference in hardening was found between the current and the previous year's shoots. The rate of hardening increased typically around mid-September in both species, when the mean daily temperatures decreased to within the range of 5–10 °C.

Beschreibung: Biomass and nutrient dynamics were examined in a subalpine Piceaengelmannii Parry–Abieslasiocarpa (Hook.) Nutt. forest within Loch Vale watershed in north central Colorado by quantifying annual above- and below-ground production, biomass, nutrient pools, and internal nutrient transfers. Subalpine forest covers only 6% of the watershed, and the values reported here refer only to the forested area. Total ecosystem biomass was 42 kg•m−2, of which 30% was soil organic matter, 33% was detrital biomass (including deadwood and forest floor), and 36% was living biomass. Total forest biomass (not including soil organic matter) was 28.9 kg•m−2, of which root biomass was 11%. Net primary production was 520 g•m−2•year−1, of which fine root production was about 27% and foliar production was 30%. Much more N was recycled via fine root turnover than via aboveground litter fall (1.6 versus 0.9 g•m−2•year−1), whereas four times more Ca was returned via litter fall than via fine roots. Compared with other temperate coniferous forests, this subalpine forest had low production. Nutrient resorption contributed between 35 and 38% of the annual requirements of N, P, and K, but only 9% of Ca and 12% of Mg. Although a higher percentage of annual N requirement was met by resorption, this forest used N less efficiently than a similar forest in southwestern Alberta.

Beschreibung: Height-growth patterns of black spruce (Piceamariana (Mill.) B.S.P.) in the boreal forest were studied in layer-origin stands released by clear-cutting in the first half of this century. Most stems responded to release brought about by clear-cutting of the main stand. Initially, small stems responded more rapidly and more strongly, but their height-growth rate culminated between 20 and 30 years following release, the same period when height-growth rate culminated for the taller, older stems. After the culmination period, growth rates were independent of height at the time of release. Consequently, the taller stems at time of release were able to maintain their dominant position. Height growth over the recent years indicates that this position could be maintained in the years to come, and even indefinitely. It seems that second-growth black spruce stands behave like even-aged stands despite their uneven-aged structure. Consequently, years since release and stem height are more accurate measures of stem effective age than total age. Moreover, the taller stems in the understory, which are usually considerably older, should be considered to be as valuable as smaller regeneration when a stand is cut.

Beschreibung: Analysis was performed on 112 stems of black spruce (Piceamariana (Mill.) BSP) from the Réserve faunique des Laurentides to compare the growth in height, DBH, and volume of layers released by clear-cutting to the growth of individuals of comparable age originating from seeds after fire. The sampled stands originated from fires and clear-cuttings that occurred between 1894 and 1941. Stem analysis also permitted the calculation of specific volume increment, which corresponds to the annual volume increment divided by the surface of the cambium. Results show that height, DBH, and volume measured 60 years after clear-cutting were better correlated to the height of the advanced growth at the moment of release (Ho) than to the number of years of suppression. The mean annual increments in height and DBH of released layers were positively related to height at the year of logging when the height was less than 2 m. When layers were taller, mean annual increments in height and DBH were negatively related to initial height. These relationships were however variable, since for two-thirds of the stand's life, the periodic annual increments in height and diameter did not differ significantly (α = 0.05) between small (Ho  2 m). The superiority of taller layers is consequently due to greater heights before release. Volume growth rate of layers was positively related to initial height until approximately 60 years after clear-cutting. However, no differences in specific volume increment could be associated with initial height. Therefore, the relationship between initial height and volume increment can be attributed to the difference of cambial area between small, medium, and large second-growth spruces. Black spruce originating from seeds had greater height, DBH, and specific volume increments than second-growth trees, until about 50 years after stand origin. Thereafter, growth rates are comparable. Consequently, after 40 years, stands originating from seeds are comparable in height, volume, and DBH to layers that reached between 1 and 2 m in height after clear-cutting. Neither drainage class nor point density had a significant effect on the sampled black spruces. Stem analysis also revealed an important growth reduction that can be associated with the last spruce budworm (Choristoneurafumiferana Clem.) outbreak in the Réserve faunique des Laurentides. We can deduce from the results of this study that the performance of second-growth stands compared with fire-origin stands will mainly depend on the density of the advanced growth and its height structure.

Beschreibung: Two-year-old Sitka spruce (Piceasitchensis (Bong.) Cam), Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), and Japanese larch (Larixleptolepis (Sieb. & Zucc.) Gord.) were cold-stored at 1 °C for 1 to 6 months. In April at the end of the cold storage period, root growth potential and electrolyte leakage from the fine roots were assessed and related to plant survival and height growth. After cold storage, seedlings were planted on a second-rotation, cultivated site. In two experiments planted in 1989 and 1990, fine-root electrolyte leakage was closely correlated with survival and height growth. Fine-root leakage has also practical advantages over other available methods of assessing plant vitality after cold storage.

Beschreibung: Nitrogen (N) mineralization potential and net N mineralization insitu were measured monthly over 7 months for the forest floor horizons (Oi, Oe, Oa) and mineral soil (0–15 cm) of a pine stand and the mineral soil (0–15 cm) of a maple stand in Massachusetts, United States. In all cases, N mineralization potential per unit organic matter (anaerobic laboratory incubation) varied significantly by sampling month but was unrelated to the seasonal pattern for net N mineralization (buried-bag method). The organic horizons in the pine stand exhibited the most variable N mineralization potential, with the Oe horizon having more than a fourfold seasonal range. For the pine stand the Oe horizon also had the highest N mineralization potential (per unit organic matter) and the highest net N mineralization insitu (per unit area). In general, temporal and depth-wise variability should be considered when sites are assessed with respect to the pool of mineralizable N.

Beschreibung: Ninety hectares in a treed fen in north central Alberta were drained to improve growth of stagnant black spruce (Piceamariana (Mill.) B.S.P.) and tamarack (Larixlaricina (Du Roi) K. Koch) stands. Installation of 30-, 40-, 50-, and 60-m ditch spacings resulted in a lowering of the average water table by 79, 66, 56, and 73 cm, respectively. The results and the groundwater level criteria used (drainage norm, 40 cm; flood duration limit, 14 days) indicated that the 50-m ditch spacing was hydrologically the most appropriate one for this area. Given the relatively high hydraulic conductivity of the area, it is believed the 30-m spacing was too narrow and resulted in an excessively low average water table. The 60-m spacing was also overeffective, but in this case, overeffectiveness was attributed more to "edge effects" i.e., to site factors such as the proximity to uplands and the small size of upstream source areas, than to the distance between ditches. The results illustrate the importance, for ditch network design purposes, of taking into account hydrologic conditions both within and well beyond the boundaries of an area proposed to be drained. Peat subsidence after drainage appeared to be related to the average drop in water table level and amounted to about 5 cm•a−1.

Beschreibung: A litter-bag technique was used to measure decay rates and assess changes in organic and inorganic constituents of ponderosa pine (Pinusponderosa Laws.) needle litter during decomposition over a 2-year period in old- and young-growth forests in the Sierra Nevada of California. Rates of mass loss were among the lowest reported for temperate and boreal forests, with annual decomposition constants of about 0.08 and 0.18 year−1 for the old- and young-growth forests, respectively. Apparently, the temporal separation of warm temperatures and moist conditions found in Mediterranean-type climates severely limits decomposition in these coniferous forests. In the old-growth forest, comparison of estimates of tree nutrient uptake with net releases of nutrients from fine litter during their 1st year of decomposition suggests that recent litter fall potentially acts as a significant source of P, Mg, and K for tree uptake in this forest; in contrast, recently fallen litter acts as a net sink for N, S, and Ca. Despite initially lower indices of litter quality for litter originating from the old–growth relative to the young–growth forest, no significant difference in decomposition rates of these two litter age-classes was found when placed at either site. This result does not support the hypothesis that decreases in decomposition rates during forest development are driven by decreases in the quality of litter fall.

Beschreibung: Stem analysis was used to compare the height, diameter at breast height, and volume growth of seven merchantable black spruce (Piceamariana (Mill.) B.S.P.) stands regenerated after harvesting from advance growth of layer origin with the growth of three merchantable black spruce stands regenerated after fire from seed. The year of harvesting in the second-growth stands was precisely determined using synchronous growth release after logging, scars left by the logging operation, and historical records. The year of the fires in seed-origin stands was determined using fire scars and historical records. Fire-origin stands showed typical even-aged structure, and logged, second-growth stands showed an uneven-aged structure associated with an asymmetric curve. When compared with seed-origin stands, layer-origin stands showed a significantly greater total height 30 years after the stand origin because of the initial height of the layers. However, annual height increments were similar between the two origin types at 30 years. The mean diameter increment at 30 years was significantly higher in the second-growth stands. The mean annual specific volume increment values for the entire period of growth were slightly higher for the fire-origin stands. Layers that were small at the time of logging (2 m). There was a significant negative correlation between the height, diameter, and age of the layers at the time of logging and both the mean specific volume increment and the mean annual height increment 30 years after logging. In the second-growth stands, the number of merchantable trees and volume increment increased gradually because of the uneven structure of the stands. In contrast, in the seed-origin stands, the trees attained merchantable size at around 30 years after the fire, and the merchantable volume rose rapidly after this. The layer-origin populations had a significant advantage over the seed-origin populations because of the initial height and diameter of the layers at the time of logging. All seven layer-origin stands achieved, or were predicted to achieve, higher merchantable volumes than the seed-origin stands at 40 years. Our results indicate that the second-growth stands growing on mesic sites have the potential to produce merchantable forests comparable to the yield tables available for black spruce provided that the number of stems per hectare is adequate.

Beschreibung: In remote subarctic North America, instrumental records are very short and sparsely distributed. Yet a long-term understanding of subarctic climate is critical to studies of global change. Annual tree-ring width and maximum latewood density are complementary, high-resolution parameters with different environmental and physiological controls that can be used to assess recent centuries of climatic change. In this paper we present a comparison of the different temperature information inferred from these parameters for white spruce (Piceaglauca (Moench) Voss), a dominant North American latitudinal tree line species. Ring-width and maximum latewood density chronologies (with a common period from 1720–1977) are shown for five sites along a widely spaced transect of the forest–tundra transition in northern Canada. The positive temperature response of maximum latewood density to year to year local temperatures is more consistent and covers a longer portion of the growing season than does that of ring width. Unlike density, the ring-width data show a preference for cold spring conditions. Some, but not all, of the ring-width and density series display increases during the recent century's large-scale climatic warming trend. It is concluded that both types of parameters are necessary for understanding changes in climate and forest dynamics at the northern tree line.

Beschreibung: A parameter recovery procedure for the Weibull distribution function, based on diameter percentiles, was modified to incorporate the effects of interfering vegetation in young Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco var. menziesii) plantations. The applicability of the system was tested by using data from sites in the Coast Ranges of Oregon and Washington and in the Siskiyou Mountains of southwestern Oregon. Four percentiles (0, 25th, 50th, 95th) of the cumulative probability distribution were predicted as functions of quadratic mean diameter and age. In the Siskiyou study, cover and total vegetation control affected quadratic mean diameter and all four percentiles; intensity of the vegetation treatments affected the 0 and 25th percentiles, and the interaction between intensity and timing of treatment affected quadratic mean diameter. In the Coast Ranges study, only quadratic mean diameter was affected by cover of woody vegetation, while quadratic mean diameter and the 25th percentile were significantly affected by total vegetation control. The predicted distributions showed decreasing variance with increasing cover, particularly in the Siskiyou Mountains. In the Coast Ranges study, the coefficient of variation increased with increasing cover, indicating that the variance of stem diameters was affected by average size. On xeric sites in the Siskiyou Mountains, high diameter variability in plots with total vegetation control suggests that interspecific competition may inhibit the expression of microsite variation.

Beschreibung: Landscape ecosystems of a 60-ha area, representative of the pine–mixed hardwood forest of the Changbai Shan Preserve in Jilin Province of northeastern China, were identified, described, and contrasted. Site–species relationships and successional trends were examined together with a comparison of these ecosystems and species with those of northern hardwood forests of eastern North America. Ecosystem components of physiography, soil, and vegetation were used to distinguish two major ecosystem types. The more widespread ecosystem 1 differed from ecosystem 2 in having a flatter topography and more moist and nutrient-rich soil. The overstory of ecosystem 1 was dominated by Tiliaamurensis Rupr., Pinuskoraiensis Sieb. & Zucc, Quercusmongolica Fisch. & Turcz., and Fraxinusmandshurica L., whereas that of ecosystem 2 was dominated primarily by Pinuskoraiensis and Quercusmongolica. Understory species and ground-cover vegetation also reflected the difference in physiography and soil between the two ecosystem types. Six Acer species were recorded; they occurred primarily in the subdominant overstory and the understory of both ecosystems. Without catastrophic disturbance, succession favors the more shade tolerant species in all layers. Pinus and Quercus are rare in the ground cover and understory. Acermono Maxim, is much less dominant than its North American counterpart, Acersaccharum Marsh., in their respective mesic ecosystems in the Changbai Shan forest and forests of western upper Michigan. Fagus and Tsuga, characteristic dominants of northern hardwood forests of eastern North America, are absent. The establishment ecology of Pinuskoraiensis, a five-needled pine with wingless seeds, in the mixed hardwood forest is discussed.

Beschreibung: This study examines the condition of fine-root systems of healthy and declining sugar maples (Acersaccharum Marsh.) at two sites in Central Ontario, one moderately declining and the other severely declining. Roots are frequently sensitive indicators of soil nutrition, thus ingrowth cores (soil transplants) were used to assess the effect of bulk surface (F-layered Ah horizon) soils collected from beneath healthy or declining trees on fine-root chemistry and growth. Soil at each site was collected from healthy and declining trees and reciprocally transplanted (buried) in mesh bags, and roots were allowed to grow into the soil cores for 8 weeks. In addition to transplants of untreated soils, additional transplants of "healthy" and "decline" soils treated by either (i) steam sterilization to remove pathogens or (ii) fertilization with superphosphate were made. Root dry weight of healthy and declining trees was reduced 25–70% in untreated decline soils compared with healthy soils (p ≤ 0.007). This was consistent with lower Ca, Mg, Mn, and Fe in the soil solution of declining trees at the severely declining site and a lower Mn concentration and Ca/Al and Mg/Al ratios in the soil solution at the moderately declining site. Compared with roots of healthy trees, roots of declining trees had significantly lower Ca concentrations for both stands, and in addition, significantly lower concentrations of P, Mg, S, K, Mn, Al, Fe, and Zn in the more severely declining stand. The experimental soil transplants established that lower nutrient concentrations in soils from declining trees are reflected in the chemistry of roots growing in them. On the whole, the fertilizer treatment significantly increased root growth and the steam sterilization treatment had no effect on root growth. While this study shows that reduced nutrient availability in the rooting substrate is an important factor in decline, it is not known how recently this nutrient depletion has occurred, nor what is the cause. Although other mechanisms may be involved, reduced nutrient availability in the rooting substrate is consistent with the speculation that deposition of acidic salt solutions of sulphate and nitrate to these forest soils has caused accelerated soil base cation leaching losses that are reflected in nutritional deficiencies and growth decline.

Beschreibung: Piceamariana (Mill.) B.S.P. seedlings were grown in containers under three levels of N–P–K fertilization. They were inoculated with one of three levels of mycelial slurry of either an isolate of Laccariabicolor (Maire) Orton or of Laccarialongipes G.M. Mueller. Seedlings were grown for 16 weeks in a glasshouse before planting on two different sites (organic and mineral soil) in northern Minnesota. Persistence of the two fungi was monitored over a 2.5-year period. Dikaryotic-monokaryotic pairings indicated that trees on the mineral soil site, inoculated with L. bicolor, remained colonized by that isolate for the entire test period. Controls and L. longipes treated seedlings on the same mineral soil site became colonized by indigenous isolates of L. bicolor. The half-strength fertilizer treatment produced significantly taller seedlings.

Beschreibung: Indoor and outdoor experiments demonstrated that allelopathy is an important factor explaining seed regeneration failures of Scots pine (Pinussilvestris L.) in forest floor vegetation dominated by the dwarf shrub Empetrumhermaphroditum Hagerup. Scanning electron micrograph views of the leaf surfaces of E. hermaphroditum reveal secretory glands that are shown to be involved in the release of water-soluble phytotoxic substances. Bioassays indicate that low doses and short exposure times of seeds to leachates have strong negative effects on germination and early root development. Activated carbon can eliminate the inhibitory effects of leachates and litter. This technique demonstrates the occurrence of allelopathic interference by E. hermaphroditum on seed germination of both Scots pine and aspen (Populustremula L.). In a field experiment the allelopathic effects by E. hermaphroditum are strong during early spring when germination and growth initiate and ground ice still is present. Extracts passed through soils collected from an E. hermaphroditum site were detoxified, while those passed through sterilized soil were not. Therefore, microorganisms may detoxify the allelochemicals under some environmental conditions.

Beschreibung: Assessment of tree health requires accurate estimates of crown condition and identification of specific biotic and abiotic agents that may affect crowns, stems, or roots. ForestHealth, an expert advisory system written in C language for the Macintosh™ platform, provides a diagnostic module and two training modules. The diagnostic module provides guidance in identifying foliar symptoms and the common insects, diseases, and abiotic disorders found on leaves of: sugar maple (Acersaccharum Marsh.), red maple (Acerrubrum L.), black cherry (Prunusserotina Ehrh.), northern red oak (Quercusrubra L.), and white oak (Quercusalba L.). Graphical user interfaces are central to both training modules. The Foliar Severity routine trains users to categorize injury (percent leaf area) on single leaves using a modified Horsfall–Barratt scale. The Crown Dieback routine displays different types and degrees of crown injury that users must identify and classify. Each crown is unique, generated in "real time" using tree–branch parameters selected by the user. Since the crowns are created on a three-dimensional basis, multiple views are possible. Written output from training sessions or periodic checks provide quantitative information for quality assurance and quality control. ForestHealth provides diagnostic assistance, training, quality assurance and quality control data, and standardization for research or survey projects involving forest health.

Beschreibung: Four species of chestnut trees and four kinds of hybrids were inoculated with two virulent strains of the chestnut blight fungus (Cryphonectriaparasitica (Murr.) Barr). Rate of canker expansion was measured over 114 days (June–September), and rate change was used as a quantitative assessment of individual tree resistance. Cankers on two typical American chestnut trees (Castaneadentata (Marsh.) Borkh.) expanded at a rate of 1 mm/day. Expansion rates on Chinese chestnut (Castaneamollissima Blume) ranged from 0.2 to 0.6 mm/day, and the rates on two Japanese chestnut trees (Castaneacrenata Siebold & Zucc.) were 0.08 to 0.2 mm/day. Our single Henry chestnut (Castaneahenryi (Skan) Reh. & Wilson) tree allowed rates of 0.3 and 0.8 mm/day. Most rates on American–Chinese and Japanese–American hybrids were from intermediate between rates on Asian and American trees to near the rates on American trees. However, a first-generation backcross of Chinese–American × American only allowed expansion rates of 0.3 and 0.4 mm/day, similar to the lowest rates on Asian trees.

Beschreibung: Fifty-nine mixed oak stands in the Ridge and Valley Province of central Pennsylvania were sampled to evaluate the potential for oak replacement by later successional species or oak stability across a diverse landscape. Using species importance, stands were separated into four groups along detrended correspondence analysis axes 1 and 2. Betulalenta L.–Quercusprinus L.–Quercusrubra L. and Q. prinus–Q. rubra groups occurred on sandstone-based Inceptisols and Ultisols on ridges, whereas mixed–Quercus and Quercusalba L. groups were representative of limestone-based Alfisols on valley floors. Quercus species dominated the overstory of all groups; however, the understories mainly comprised shade-adapted Acerrubrum L., Acerpensylvanicum L., and (or) B. lenta on the xeric ridges and A. rubrum and Prunusserotina Ehrh. in the mesic valleys. The presettlement forests consisted of Quercus, Pinus, and Castaneadentata (Marsh.) Borkh. on the ridges and Quercus, Pinus, and Carya in the valleys. Comparisons between presettlement and present-day forests indicate that Pinusstrobus L. and C. dentata have declined dramatically, whereas Quercus species have increased. Changes in disturbance patterns following European settlement (e.g., the charcoal iron industry) initially favored Quercus expansion, followed later by increases in Acer, Prunus, and Betula. Under existing conditions where large-scale disturbances from fire or logging are minimal, Quercus species are expected to decline slowly in importance, being replaced by Acer, Prunus, and (or) Betula species regardless of site moisture relations. Thus, mixed oak forests do not appear to represent a prominent edaphic climax in the region, despite the long history of oak domination.

Beschreibung: Plagiotropism (angle departure from orthotropic growth) was measured on 360 Norway spruce (Piceaabies (L.) Karst.) clones propagated in 2 subsequent years. The clones were members of 20 full-sib families (18 clones per family) from a provenance hybrid factorial cross involving 10 parents of Norwegian (N) and 10 parents of east-European (EE) origin. The clones from the EE × EE crosses showed an average of 17° and 20° in plagiotropism, those from the N × N group showed 3° and 7° in plagiotropism, while the hybrids (EE × N and N × EE) showed 8° and 13° in plagiotropism in 1988 and 1989, respectively. A large family variation was found in the EE × EE and the hybrid groups (11 and 8.5% of total variation, respectively), but variation was small (3.5%) in the N × N group. The clonal component accounted for 10, 12, and 8.5% of total variation in EE × EE, hybrids, and N × N, respectively. Among the plagiotropic clones, some were heterogeneous with a large within-clone variation and others were homogeneous. The year × family and year × clone components were rather large in EE × EE (5 and 9% of total variation, respectively) but smaller in the hybrids and smallest in N × N. The clones with best growth were not among those with the worst plagiotropic growth. The clonal material is ideal for use in future studies on the genetic and physiological regulation of maturation.

Beschreibung: Spatial patterns of denitrification and temporal variation in the factors controlling this process were studied in three forested ecosystems in northern Lower Michigan. Two forest stands were randomly located within each of two well-drained upland forests (sugar maple–red oak/Maianthemum and sugar maple–basswood/Osmorhiza ecosystems) and one swamp ecosystem (silver maple–red maple/Osmunda ecosystem). Potential N mineralization, nitrification, and microbial respiration were measured in each forest stand using a 33-week laboratory incubation. Factors controlling denitrification were investigated in each ecosystem by treating soil samples with factorial combinations of NO3−, C, and Ar (anaerobic conditions). We also investigated the separate production of N2 and N2O during denitrification, and the factors controlling these fluxes, in a different experiment. Seasonal patterns of denitrification were quantified using an intact soil core method. Potential nitrification and microbial respiration were consistently highest in the swamp forest and lowest in the sugar maple–red oak/Maianthemum ecosystem (582 vs. 3 μg NO3−-N•g−1 and 5275 vs. 1254 μg CO2-C•g−1, respectively). Nitrate availability was the most important factor controlling denitrification in the swamp ecosystem, whereas increased soil water content resulted in the greatest response in the upland forests. Although NO3− significantly increased denitrification in the upland ecosystems, water additions elicited an even greater response. In addition, N2O production in the upland forests accounted for 70 to 90% of the total gaseous N loss; N2O accounted for only 25% of this loss in the swamp forest. Mean denitrification (intact soil cores) in the sugar maple–red oak/Maianthemum ecosystem (12 μg N2O-N•m−2•d−1) was significantly lower than rates measured in the sugar maple–bass-wood/Osmorhiza and silver maple–red maple/Osmunda ecosystems (24 and 39 μg N2O-N•m−2•d−1, respectively). Denitrification reached a maximum during June and July in the sugar maple–basswood/Osmorhiza ecosystem, whereas peaks occurred in May and September in the silver maple–red maple/Osmunda ecosystem. Denitrification in the sugar maple–red oak/Maianthemum forest was variable throughout the year and consistently low. Although variability was high, results suggest that denitrification and the factors controlling this process can be predicted using the spatial distribution of ecosystems.

Beschreibung: Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinuscontorta Dougl.), and white spruce (Piceaglauca (Moench) Voss) seedlings, each represented by two seed lots, were grown in Styroblock containers in a greenhouse and plastic shelter house from February 1989 to January 1990. The seedlings were exposed to two nitrogen (N) treatments and three potassium (K) treatments arranged factorially within three drought treatments. After winter storage, seedlings from a complete set of treatments were planted into hygric, mesic, and xeric sand beds during 12–14 March. Increasing nursery drought stress increased survival of Douglas-fir and lodgepole pine after planting, and high N treatment level increased survival of lodgepole pine and white spruce. Under xeric conditions, combined nursery drought and high N treatments increased survival of lodgepole pine by 33%, indicating the importance of nursery cultural regime for stock quality. Increase in nursery drought decreased seedling size relatively little, but increase in N increased seedling size one season after planting. A positive relationship between shoot/root ratio and survival in lodgepole pine and white spruce indicated that increase in N increased both shoot growth and drought resistance over the N range investigated. Only Douglas-fir showed an interaction between drought and N treatment and a small response in both survival and dry weight to K. Root growth capacity, measured at the time of planting, showed an approximate doubling in all species due to high N treatment, and was also increased in white spruce by drought stress. Survival and root growth capacity were poorly correlated, but dry-weight growth in sand beds was well correlated with root growth capacity. Shoot dry weight and percent N in shoots measured after nursery growth were correlated with root growth capacity. Manipulation of root growth capacity by changing nursery treatment was apparently possible without altering resistance to drought stress after planting.

Beschreibung: Bark temperatures were recorded on five lodgepole pine (Pinuscontorta Dougl. ex Loud.) in stands of different growing stock levels in Colorado and Wyoming. Mean bark temperatures were significantly different among growing stock levels. Temperatures in the partially cut growing stock levels were significantly warmer than in uncut controls during diurnal hours, but temperatures were cooler during nocturnal hours. Bark temperatures correlated with ambient air temperature. Equations were developed for predicting north- and south-side bark temperatures for partially cut stands of three growing stock levels and an uncut control from air temperatures. Bark temperature patterns in lodgepole and ponderosa pine (Pinusponderosa Laws.) stands are compared. The relationship between growing stock level and mountain pine beetle (Dendroctonusponderosae Hopk.) infestation is discussed from the standpoint of bark temperatures.

Beschreibung: Twenty nonlinear height–diameter functions were fitted and evaluated for major Alberta species based on a data set consisting of 13 489 felled trees for 16 different species. All functions were fitted using weighted nonlinear least squares regression (wi = 1/DBHi) because of the problem of unequal error variance. The examination and comparison of the weighted mean squared errors, the asymptotic t-statistics for the parameters, and the plots of studentized residuals against the predicted height show that many concave and sigmoidal functions can be used to describe the height–diameter relationships. The sigmoidal functions such as the Weibull-type function, the modified logistic function, the Chapman–Richards function, and the Schnute function generally gave the most satisfactory results.

Beschreibung: Total ecosystem carbon in the soil and vegetation was measured for a range of aspen (Populustremuloides Michx.) ecosystems, including a chronosequence on the same soil ranging in age from 0 to 80 years. Soil carbon stayed relatively constant throughout the stand's life and was not affected by timber harvesting. Changes in ecosystem carbon closely paralleled the changes in standing biomass. Aspen grown on 40-year rotations on good soils will sequester several times as much carbon per year as old-growth forests.

Beschreibung: Root and needle cold hardiness were compared in seedlings of subalpine conifers to determine if differences existed among species originating from either cold continental climates or mild maritime climates. Abiesamabilis (Dougl.) Carr. and Tsugamertensiana (Bong.) Carr. are exclusively distributed in maritime environments, while Abieslasiocarpa (Hook.) Nutt. and Pinuscontorta Dougl. are more generally distributed in both continental and maritime environments. Because of the differing winter soil conditions of these two climatic types, special emphasis was placed on root cold hardiness. Cold hardiness for root samples, as measured by a decrease in the electrolyte leakage, was much greater for A. amabilis and A. lasiocarpa than for P. contorta and T. mertensiana (−11.4, −11.5, −7.5, and −7.5 °C, respectively). Thus, subalpine conifer species distribution was not found to be influenced by root cold hardiness. Root cold hardiness of field-grown seedlings paralleled changes in soil temperature through February. Under constant temperature conditions (3 °C) the maximum cold hardiness achieved in 6 weeks was not subsequently maintained in A. amabilis and A. lasiocarpa. Injury in unhardened roots was coincident with bulk freezing, whereas hardened roots were able to tolerate bulk freezing. Needles had more than three times the level of cold hardiness of roots when measured in December, All species except P. contorta reached needle cold hardiness levels below −40 °C.

Beschreibung: The capture of pine engravers, Ipspini (Say), in ipdienol-baited, multiple-funnel traps in British Columbia was significantly reduced when devices releasing ipsenol or verbenone were placed in the traps. These results suggest that ipsenol and verbenone are synomones released by Ipslatidens (LeC.) and the mountain pine beetle, Dendroctonusponderosae Hopk., respectively. When verbenone and ipsenol were released together from five stations 2 m apart on felled trees, at 50 and 1.5 mg per day per tree, respectively, there was a 66.7% reduction in the number of logs attacked and a 98.8% reduction in attack density. The same treatment caused a 74.1% reduction in attack density on standing trees surrounded by a 4 × 4 grid of 16 release devices at 5- m centres. The antiaggregant composition of verbenone plus ipsenol has considerable operational potential for use in precommercial thinnings and in areas where standing pines are of high value; e.g., in rural subdivisions, shelterbelts, and recreational forests.

Beschreibung: Height–diameter relationships are an important component in yield estimation, stand description, and damage appraisals. A nonlinear exponential function used extensively in the northwest United States was chosen for bald cypress (Taxodiumdistichum (L.) Rich.). Homogeneity and normality of residuals were examined, and the function as well as the mean and individual prediction confidence bands were plotted. The inclusion of stand basal area as an additional independent variable provided a better fit to the data. The paper is concluded with a section on construction and use of simple and joint confidence intervals about the mean and individual predictions from the nonlinear regression.

Beschreibung: Logs, forest floor, and mineral soil were sampled and measured, and snags were measured, in a 450-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stand on the H.J. Andrews Experimental Forest, Oregon. Logs, some still identifiable after 300 years on the forest floor, contained large amounts of organic matter (222 Mg/ha), C (100 Mg/ha), water (559–10 700 L/log), N (183 kg/ha), and Ca (141 kg/ha), and smaller amounts of P (5.5 kg/ha), K (22 kg/ha), Mg (14 kg/ha), and Na (3.7 kg/ha). Logs and snags covered about 17% of the forest floor and had an all-sided area index of 0.69 m2/m2. Through mineralization, C, N, and K were lost through time; Ca and Mg increased; and P and Na increased then decreased, showing no net change. Also through mineralization, cellulose and hot acid detergent soluble fraction decreased more rapidly than lignin. Lignin was apparently not lost until the later stages of decay, when N was also lost in significant amounts. This parallels the shift from initial dominance by white rots that degraded cellulose and lignin to later dominance by brown rots that preferentially degraded cellulose. Lignin and cellulose were eventually lost at more similar rates in later decay stages. This may have been due in part to a close association between the remaining cellulose and lignin in later decay stages. Lignin was a better predictor of the onset of N release than was the C:N ratio.

Beschreibung: Seedlings of four birch species were examined to evaluate the presence and extent of phylogenetic constraints on the response of species to global CO2 change. The species differ in their habitat preferences and their successional status. Seedlings were grown for 3 months at near ambient (380 μL•L−1) and double (690 μL•L−1) CO2 concentrations in glasshouses. We found the following: (i) yellow birch (Betulaalleghaniensis Britton) was the only species whose survival differed among CO2 treatments. Survival was slightly increased by elevated CO2. (ii) All growth parameters considered in all four species were significantly stimulated by enriched CO2 conditions, but the magnitude of response was different among species. The most shade-intolerant, fast-growing species (grey birch; Betulapopulifolia Marsh.) took greater advantage of the elevated CO2 resource than the more shade-tolerant, later successional species (e.g., yellow birch). (iii) Patterns of allocation, shoot architecture, and leaf nitrogen content were affected differently by CO2 concentrations for the different species, (iv) The presence and identity of a neighbor did not influence the magnitude or pattern of response to CO2 in birches of a given community. Our results suggest that congeneric species might be more similar in their response to global CO2 in comparison to unrelated species of the same ecosystem that had been studied by others, despite the fact that these closely related birch species differ in their habitat preferences and successional status.

Beschreibung: A study was carried out to quantify the diurnal variation of soil respiration in fallow and barley fields and to assess the impact of atmospheric CO2 concentration (C) and crop photosynthesis on soil respiration rates under field conditions. Soil respiration rate was measured twice a day (06:00 and 13:00 h EST) for 69 consecutive days at Ottawa, Ontario, Canada, during the 1990 growing season. Measurements were taken on fallow and under a barley (Hordeum vulgare L. ’Léger’) crop using a dynamic closed chamber system. Crop net photosynthesis was obtained by substracting soil respiration from the vertical CO2 fluxes above the crop which was obtained using the eddy correlation technique. Afternoon soil respiration averaged 22 and 17% more than that in the morning on fallow and barley soils, respectively. No correlation was found between atmospheric CO2 concentration and morning respiration rates. The two daily respiration measurements on fallow soil could be fit to the same function of soil temperature despite important differences in C at the time of measurement. These results indicate that soil temperature might account for the differences in R between morning and afternoon, and that the effect of C need not be considered for the modelling of the soil respiration diurnal cycle. Respiration in soil under barley was 25% lower than in fallow soil. Soil under barley was estimated to have at least 199 g C m−2 more than fallow soil at the time of harvest due to the lower soil respiration and to the input of carbon by barley root residues. High correlations were obtained between crop photosynthesis and soil respiration rates during vegetative and reproductive periods, confirming that the biotic plant component is an important factor controlling soil respiration rates in cropped fields. Key words: Root respiration, chamber measurements, CO2 flux, crop net photosynthesis, greenhouse gas, soil organic matter.

Beschreibung: An in-situ constant head well permeameter (CHWP) method employing three or more ponded heads per well was used to establish relationships between field-saturated hydraulic conductivity (Kfs), matric flux potential [Formula: see text], the alpha parameter (α*), soil texture, and soil structure. The relationships were then used to evaluate a single-head CHWP technique which employs representative mean α* values in the determination of Kfs and [Formula: see text]. The measurements were made at several depths on four soils which ranged in texture from loamy sand to silty clay, and in structure from single grain to strong, fine subangular blocky. The Kfs and [Formula: see text] results obtained from the multiple-head CHWP measurements were found to be highly variable within and between soils, yielding within-soil ranges as high as 3.5 orders of magnitude and standard deviation factors (SDF) as high as 5.1. The geometric mean (GM) Kfs and [Formula: see text] values were also highly variable between soils, but they were controlled primarily by soil structure rather than by soil texture or other factors. The α* values, on the other hand, were relatively consistent both within and between soils, yielding an overall SDF of only 1.2 and an overall GM of 11 m−1. Use of α* = 11 m−1 in the single-head CHWP technique yielded Kfs and [Formula: see text] values which were usually accurate to within a factor of 2, and often accurate to within ±25%. These levels of accuracy are within acceptable limits for a field method, considering the many potential sources of error and the extreme range and variability of Kfs and [Formula: see text] normally encountered in the field. Key words: Constant head well permeameter, hydraulic conductivity, matric flux potential, alpha parameter, soil texture, soil structure, single-head analysis

Beschreibung: Soil contamination is no longer restricted to isolated incidents and locations; it is a general and contentious problem. However, the problem is complex, starting with the very definition of what level and type of contamination is unacceptable. A myriad of regulatory and de facto guidelines have emerged, and they are extremely fragmented, inconsistent and incomplete. This review attempts to summarize the historical development of assessment and remediation guidelines, to highlight the unique difficulties of the problem, and then to discuss the scientific information that exists and that is needed to improve guidelines. There is an unlimited scope for research on this subject. Key words: Contaminant, cleanup, toxicity, pathways, risk, hazard assessment

Beschreibung: Field trials were conducted on three cryic soils in southcentral Alaska to determine the local suitability of the Mehlich 3 extractant. Mehlich 3 extractable B, Cu, Fe, Mn and Zn, DTPA-TEA extractable Cu, Fe, Mn and Zn, and hot water extractable B were measured on soils from factorial experiments with variable rates of B, Cu, Mn, and Zn. Additional soil samples from two B rate and liming studies in central Alaska were included in extractable B comparisons. Forage rape, broccoli, and potato tissue samples were collected from the factorial studies to determine relationships between soil- and plant-available micronutrients. Crop yields were not affected by micronutrient applications Neither Mehlich 3 nor DTPA-TEA extractant predicted plant-available Cu or Fe. Coefficients of determination between soil and plant tissue B were comparable for extraction by Mehlich 3 or hot water and ranged from 0.11 to 0.82 Neither the Mn nor Zn tests accounted for more than 39% of the observed tissue nutrient concentration variation. The inclusion of soil PH and organic matter slightly improved estimates of available B, Mn, and Zn. Mehlich 3 extractable Fe was poorly related to DTPA-TEA extractable Fe. Copper extracted with Mehlich 3 was related to that extracted with DTPA-TEA (r2 = 0.73); the inclusion of soil pH improved the relationship (r2 = 0.84). Mehlich 3 extractable Mn and Zn were closely related to DTPA-TEA extractable levels (r2 = 0.91 and 0.94, respectively). The correlation between Mehlich 3 and hot water B (r2 = 0.57) was significantly improved by including soil organic matter content (r2 = 0.71). Key words: Micronutrients, extractant, Mehlich 3, DTPA, hot water

Beschreibung: The objective of this study was to develop a method to describe aggregate stability-energy relationships using ultrasonic dispersion and to examine the role played by carbohydrate in soil aggregation. Aggregate size fractions (ASF) from three soils were sonified, and dispersed clay and solubilized carbohydrate measured at energy levels ranging from 0 to 1000 kJ L−1. Study soils included an Orthic Black, Orthic Dark Gray, and Orthic Gray Luvisol, representing the change from a prairie ecosystem to an aspen-forest ecosystem. Ultrasonic dispersion of aggregated clay resulted in characteristic "stability curves" for each ASF which obeyed a first-order decay curve and provided two parameters describing the release of clay from soil aggregates with increasing levels of applied energy: the "stability constant" k and the E1/2 value, which are analogous to a first-order rate constant and half-life, respectively. E1/2 values ranged from 51 to 502 kJ L−1.These values were smallest for the Ae horizon of the Orthic Gray Luvisol and greatest for the macroaggregates of the Ahe horizon of the Orthic Dark Gray. Carbohydrates solubilized upon aggregate destruction generally constituted a minor proportion (10%) of the total ASF carbohydrate, indicating that most of the carbohydrate was strongly adsorbed to surfaces. The development of a stability-energy relationship for aggregates provides a means to study the role of binding agents, such as carbohydrate, in the aggregation process. Key words: Aggregates, ultrasonic dispersion, clay, carbohydrate

Beschreibung: Urea (U) fertilizer solutions applied on soil surface lose nitrogen through ammonia (NH3) volatilization, and such losses may be influenced by tillage practices and by the presence of crop residues. Ammonia measurements in corn (Zea mays L.) fields were initiated and continued for 9 d in July 1988 and 1989 to assess the effects of three tillage practices used in corn production (conventional, CT; reduced, RT; and zero tillage, ZT) and urea-ammonium nitrate (UAN) formulations on the volatilization of NH3 from UAN solutions. The UAN formulations were 33% U — 67% ammonium nitrate (AN) and 50% U — 50% AN. These UAN formulations indicate proportion, as percentage, of total N derived from U and AN, respectively. The experiments were conducted on two agricultural soils of Quebec [Macdonald sandy loam (Humic Gleysol), and St. Benoit sandy loam (Eutric Brunisol)]. Cumulative NH3 losses over 9 d ranged from 0.8 to 9.5% of applied N. On both soils, NH3 losses from 50–50 UAN were higher than the 33–67 UAN by 13.5, 14.6 and 23.9% on CT, RT, and ZT, respectively. Reduced NH3 loss with CT was attributed in part to lower crop residues than with ZT treatments. In a separate experiment to evaluate the effect of plant residues on NH3 loss, chopped timothy hay (Phleum pratense L.) was used to provide a greater surface cover and a uniform spreading of residues. Hay straw surface-applied to a conventionally tilled St. Benoit soil had to reach a threshold level somewhere between 750 and 1500 kg ha−1 to increase N losses compared to no added hay treatment. Key words: UAN solution, ammonia volatilization, tillage, hay straw

Beschreibung: A chronosequence of sandy soils was investigated on four terraces near Lake Michigan to assess rates of podzolization and changes in soil properties with age. The terraces ranged in age from 3000 to 10 000 BP. Each surface was systematically sampled to determine the modal profile, which was then described and sampled. Quantities of OC, Fe, and Al in the B horizons of modal soils increased with soil age. Silt content of surface horizons also increased with age, possibly due to eolian input or physical weathering. For weighted profile and B horizon Al and Fe averages and a variety of soil development indices, a single logarithmic model generally gave the highest statistical significance of the three chronofunction models used. All pedons sampled failed to classify as Podzols, but the oldest two met the criteria for the Spodosol order. Thus, more than 4000, but less than 10 000, years are required for the development of a spodic horizon in Michigan. Key words: Soil chronosequence, Podzol development, soil genesis, modal profile

Beschreibung: A variant of solid-state 13C CPMAS NMR demonstrated the presence of carbon in spatially distinct domains within three de-ashed samples of humin from a forest soil profile under Douglas-fir near Victoria, British Columbia. Differences in 1H T1 values indicated incomplete spin diffusion in the solid state and separation of organic matter in domains with dimensions of tens of nanometres or more. These relaxation differences were used to separate subspectra of carbons associated with the slower- and faster-relaxing protons. The former were dominated by methylene chains, while the latter contained more aromatic and O-alkyl carbon. Most of the organic matter appears to remain associated with iron even after extensive de-ashing with HCl/HF, but the aromatic and carbohydrate structures appear to be more closely associated with iron than methylene groups in long chains. This NMR technique offers a novel approach to probing the structure of insoluble soil organic matter. Key words: Humin, CPMAS NMR, relaxation, iron, forest soil, Brunisol

Beschreibung: The relationships between the slope of three kinetic equations (Elovich, first-order and parabolic diffusion) and commonly measured soil chemical properties were investigated. Twenty-six horizons covering a variety of vegetation types, parent materials and topographic positions were sampled in 18 soil profiles of southern Quebec. A miscible displacement technique in which soils were leached with a 250 μmol SO4 L−1 solution (pH = 4.40) was used to determine time-dependent sulfate sorption. The sum of crystalline plus amorphous inorganic Fe (dithionite-pyrophosphate extraction) was the soil property most closely related to the slope parameters of the Elovich (r = 0.797) and of the parabolic (r = 0.808) equations. Amorphous Al (r = − 0.546) and soil pH measured in CaCl2 (r = − 0.588) were most strongly correlated to ln − k′a. Organic carbon was not directly related to sulfate sorption as an individual variable but it improved the multiple regression equations used to estimate 1/β and K0 for the 26 horizons. The Elovich equation was found to give the best representation (average R2 = 0.978) of sulfate sorption kinetics. Good results were also obtained using the first-order equation (average r2 = 0.976) although a marked deviation of experimental data from linearity was observed at high surface coverage. The relatively close relationship between predicted and calculated values confirmed the potential of equations based upon commonly measured soil properties to estimate the slope parameter of kinetic equations describing sulfate sorption by Podzolic soils. Key words: Podzols, sulfate, sorption, kinetics, sesquioxides

Beschreibung: Leached soils (Alfisols) with either an argillic horizon or a fragipan were encountered close to each other on the marly-limestone and sandstone plateaus of Haute–Saône (France). Soils have formed under periglacial conditions during the Riss in a similar climatic environment. Because the soils occurring today are in the same geomorphic and topographic position, the objectives of the investigations were to study the influence of other pedogenic factors, such as parent materials and underlying rock type. The soil mantle, above the bedrock, is from one and a half to several meters thick. Four types of materials were identified through the pedons studied: sands, clays, clay-loams, loams. Their location being directly above either a rhetian sandstone or a sinemurian marly-limestone, sandy or clayey materials were accumulated as insoluble residue of the underlying rocks. Related to particle size distribution and mineralogy, the clay loamy materials were identified as eolian dusts. The loamy materials were also eolian deposits, but they were reworked and transported with sandy particles from sandstone of other high landscape positions. The surficial materials, encountered in all the sites studied, were texturally and mineralogically similar, which suggested that the parent materials were not the main factor controlling the formation of argillic horizons or fragipans. On the other hand, the effect of rock type has been established. Our data suggest: (1) significant relationships between the internal drainage of soil and the underlying geological substrata (type, joints and fracture planes, permeability, effect on hydrology), (2) rock effect on formation of an argillic or a fragipan horizon. In the case where meteoric waters can move through fractured rocks, soils can undergo drying and wetting cycles and clays swell and shrink. These processes induce favorable effects on genesis of soil structure, particularly of Bt structure. In the case of low-porosity and low-permeability rocks, soils dry from the surface downward and dessication cycles accomplish a vertical cleavage and polygonal cracking. We have concluded that the rock effect is a major factor involved in the development of leached soils with an argillic horizon or a fragipan. A major advantage of the rock factor hypothesis is that the formation of fragipans is possible in periglacial areas and far from glaciated regions, as proposed by the literature. Key words: Fragipans, argillic horizon, pedogenetic factors, rock effect, Alfisols

Beschreibung: Water and N fertility are major limitations to cereal production in southwestern Saskatchewan. Both factors interact to determine grain yield and thus water use efficiency. A 9-yr study to assess the effects of snow management and fertilizer N on yields of spring wheat (Triticum aestivum L.) grown annually under zero-tillage provided an opportunity to quantify water use efficiency and relate this to apparent water used by the crop (WU), years of cropping (Yr) assumed to be 10 or fewer, soil test N (SN), and rate of fertilizer N (FN). The results showed that the estimated initial yield point (IYP) (available water required to produce the first unit of grain) and the yield increase per unit of water used beyond IYP increased with available N. Within the range of available N encountered in this study, IYP ranged between 60 and about 100 mm, values similar to those reported in the literature. However, because IYP is obtained by extrapolation, these values are regarded as first approximations. The yield increase per unit of WU increased with FN, varying between 10 and 14.4 kg ha−1 mm−1 (avg. 12.7) when a simple linear regression model was used to relate yield to WU. When a more accurate multiple regression equation that related yield to WU, SN, FN, and time and placement of fertilizer N was used, the marginal increase in yield per unit increase in available water (∂y/∂WU) ranged between 5 and 23 kg ha−1 mm−1 for assumed combinations of SN ranging between 0 and 50 kg ha−1 and FN ranging between 0 and 100 kg ha−1. The multiple regression model is superior to linear models because it allows the separation of available soil and fertilizer N effects. Key words: Water use efficiency, initial yield point, regression, N fertilizer, soil N

Beschreibung: Southern Alberta growers often burn fields of seed alfalfa (Medicago sp.) prior to initiation of growth in the spring as a part of an Integrated Pest Management Programme. An 8-yr study compared the effects of (a) fall-burned every year, (b) spring-burned, prior to growth, every year, (c) spring-burned, prior to growth, every other year, and (d) zero burned, on various chemical properties of the upper 50 mm of soil. Burning led to highly significant increases in carbohydrates, total N, NO3-N, and extractable K over the 8 yr. Increases were also highly significant for NH4-N under the fall-burned every year regime. Spring-burning, prior to growth, every other year, led to the least accumulations of measured parameters. Although pest insects were controlled and pedigreed alfalfa seed production was increased under the various burn treatments examined within the conditions of the experiment, changes in certain soil chemical properties identified the need to monitor subsequent crop behavior once the alfalfa fields have been ploughed. Key words: Fire, prescribed burning, pest management, seed alfalfa

Beschreibung: The importance of soil microflora and fauna in the breakdown of organic matter and nutrient release for plant growth is well recognized. However, the use of pesticides can affect soil bioactivity in a variety of ways. A long-term incubation laboratory experiment was performed to study the impact of the herbicide atrazine (commercial formulation) on soil respiration and arginine ammonification. The incubation time was lower than the half-life time for atrazine: this allows the presence of significant amounts of residual atrazine in soil throughout the incubation period. Atrazine induced a marked stimulation of cumulative CO2 evolution and the results were analyzed to fit a first-order degradation model for soil organic carbon. In the presence of various atrazine application rates (from 1 to 5 times the agricultural rate), the soil mineralizable carbon content was found to be 1.7 and 1.4 times higher than that of untreated soil. During the incubation, a marked temporal variability occurred in the arginine ammonification rate. Atrazine induced a decrease in ammonification rate, in comparison to the one obtained for the untreated soil. The ammonification rate varied little for atrazine applications greater than three times the agricultural rate, and for incubation times greater than 40 d. The characterization of the relation between the soil CO2 production rate (for 1 or 2 wk) and the ammonification rate (for 3 h) was obtained as a function of incubation time intervals by applying linear regression functions. Results showed that these variables are not significantly related. Key words: Bioactivity, atrazine, respiration, arginine ammonification, agricultural soil

Beschreibung: Cation speciation in soil extracts from a catenary sequence of salt-affected soils was studied to understand the chemical evolution of Solonetzic soils in a closed basin. Major changes in cation speciation were found to occur at each phase of soil development. The proportion of thermodynamically active cations was greater in the extracts from the more leached profiles. Saturation indices suggested that the extracts achieved equilibrium with calcite and gypsum, when present in the soil, within 24 h. Accumulations and/or losses of gypsum and calcite from saline layers indicate that there are ongoing changes in their stability. The ratio of Ca2+/Mg2+ suggested a possible equilibrium with Mg-bearing calcites; conditions existed in certain horizons for the formation of this group of minerals. Correlations between exchangeable sodium ratios and sodium adsorption ratios calculated using cation concentration and activity were similar; however, using activities to determine the exchange constants resulted in significant differences.Key words: Cation speciation, saturation indices, cation adsorption, exchange selectivity constants, Solonetzic soils

Beschreibung: Field experiments were conducted with alfalfa (Medicago sativa L. ’Peace’) planted on a Black Solod (Landry CL) with pH 5.8 in 3 consecutive years. The same experiment was conducted at two adjacent sites in each year. The population of Rhizobium meliloti in the soil was modified at one site by applying and incorporating a suspension of an indigenous isolate to increase the size to 105 g−1. The other site was on unamended soil with a normal indigenous population of less than 102 g−1. Granular inoculant was applied with the seed or below the seed, or, granular or liquid inoculant was applied beside the row after stand establishment. The soil-placed inoculant treatments were compared with an uninoculated control and a standard seed-applied inoculation treatment. All inoculants were prepared with Rhizobium meliloti NRG-61 which had been selected for low-pH tolerance. Root weight, shoot weight, nodule weight, nodule numbers and strain occupancy of nodules were measured in September of the establishment year and again the following June. Granular inoculant applied with or below the seed resulted in greater nodule weights, nodule numbers and percent nodule occupancy at both sites. Granular inoculant applied with or below the seed was more effective at the site with the normal indigenous population of R. meliloti than at the site with the modified population. When granular inoculants were applied, nodule weights were lower on the site with the modified indigenous population than on the soil with the normal indigenous population. Granular inoculants resulted in significant yield increases over the standard seed-applied inoculant only at the site with the normal indigenous population. There were no substantial differences between the sites in the proportion of nodules occupied by the inoculant strain. These results show that strain occupancy measurements do not necessarily reflect the beneficial effect of inoculation. Key words: Enzyme-linked immunosorbent assay (ELISA), granular inoculant, Rhizobium inoculant, seed inoculant, soil inoculant