ALBERT

Beschreibung: The pine-wood nematode, Bursaphelenchusxylophilus (Steiner and Buhrer), was most commonly extracted from Cerambycidae emerging from nematode-infested pines in Minnesota and Wisconsin during 1981 and 1982. The greatest number of nematodes were extracted from Monochamusscutellatus (Say) and Monochamuscarolinensis (Olivier). Low numbers of B. xylophilus were found in some buprestids but no nematodes were found in the curulionid and scolytid beetles examined. Two species of Cerambycidae, Monochamusmannorator (Kiby.) and M. scutellatus were associated with B. xylophilus from balsam fir in Minnesota. Bursaphelenchusxylophilus from insects associated with balsam fir were morphologically different from insects associated with pine. Dauer larvae of B. xylophilus were concentrated in the thoracic segments of M. scutellatus and Monochamusmutator (Lec.) examined. Bursaphelenchusxylophilus was transmitted to twigs during maturation feeding and to logs during oviposition by M. carolinensis, M. mutator, and M. scutellatus.

Beschreibung: Alnusrubra Bong, dominates the first 65 – 80 years of a sere that is initiated naturally on the terraces of the Hoh River. Stands of 14, 24, and 65 years were studied to determine to what extent the Alnus stage enriched the nitrogen inventory of the site. Bare sandbars deposited by the river had a mean of 783 kg/ha nitrogen. Alnus communities caused an increase in the nitrogen inventory so that, by 65 years, total community nitrogen was 4659 kg/ha, soils held 3594 kg/ha N in the upper 45 cm, and Alnus trees held 942 kg/ha N. The nitrogen contents of the soil, Alnus wood, bark, and branches, grasses, total aboveground biomass, total belowground biomass, and sticks less than 1 cm diameter all showed significant increases from 14 to 65 years. The A. rubra stage is an important link in the nutrient inventory between unvegetated, recently deposited sandbars and the climax coniferous forests dominated by Tsugaheterophylla (Raf.) Sarg. and Piceasitchensis (Bong.) Carr.

Beschreibung: The effects of different intensities of forest management on forest floor organic matter and nitrogen dynamics in northern hardwoods were simulated with a computer model built from the extensive data base of the Hubbard Brook Ecosystem Study. Three cutting intensities and three rotation lengths were tested. In all cases, both nitrogen availability and forest floor organic matter declined for 15–30 years following cutting and required 60–80 years to recover to precut levels. Rotation length had a much greater effect on the forest floor than harvesting intensity with short-rotation (30-year) complete forest harvesting causing the greatest reduction in both biomass and nitrogen availability. Average forest floor biomass under this treatment was reduced to roughly one-half of that under clear-cutting (90-year rotation).

Beschreibung: Soils on 53 burned sites in the upper peninsula of Michigan were examined for fire-induced water repellency. The development of water repellency was found to be fire related with over 40% of the burned soils showing at least some water-repellent properties. Most water-repellent layers occurred in the upper 5 cm of mineral soil and were related to burn intensity. Laboratory burning experiments with 10 hardwood and conifer litters showed that white pine, red pine, and quaking aspen litter produced water repellency in underlying mineral soil. Repellency was also found on unburned sites, particularly under aspen. Water-repellent soils were widely distributed, but their nonwettable properties generally decreased rapidly over time. Fire-induced water repellency does not appear to present a major long-term management problem on most soils in this region. However, on certain burned sites, water repellency may influence seedling survival and subsequent stand establishment.

Beschreibung: Root elongation of greenhouse-grown Alaskan taiga tree seedlings increased with increasing root temperature in all six species examined and was most temperature sensitive in warm-adapted aspen (Populustremuloides Michx.). Root elongation was slower in fine than large roots and in black spruce (Piceamariana (Mill.) B.S.P.) was less temperature sensitive in fine than in large roots. Root elongation in the laboratory was slowest in black spruce, which has an inherently slow growth rate, and most rapid in poplar (Populusbalsamifera L.) and aspen, which grow more rapidly. In contrast, field root elongation rates tended to be highest in black spruce from cold wet sites, suggesting that site factors other than soil temperature (e.g., moisture) predominated over genetic differences among species in determining field root elongation rates. The seasonal pattern of root elongation was closely correlated with soil temperature and reached maximum rates in July for all tree species (except aspen medium-sized roots). Most roots of each species were in the top 20 cm of soil. However, root growth penetrated to greater depth in warm compared with cold sites. Root biomass in a 130-year black spruce forest (1230 g/m2) comprised only 15% of total tree biomass. Root biomass of 25-year aspen and 60-year poplar sites (517 and 5385 g/m2, respectively) comprised a greater proportion (57% in poplar) of total tree biomass than in spruce.

Beschreibung: The patterns of translocation of carbon in different-age tissues of four common moss species in a black spruce (Piceamariana (Mill.) B.S.P.) dominated forest near Fairbanks, Alaska, were studied by 14C labelling and carbohydrate analysis. A simple, in-vial combustion technique was developed for combustion of small (

Beschreibung: The aboveground biomass of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) and annual production over 7 years was studied in relation to thinning and nitrogen fertilization. Biomass yield of both treatments increased during the first 3–4 years then decreased for fertilization but not with thinning. Treatments doubled biomass production of individual trees over the study period when applied separately and quadrupled it when combined. Annual biomass production per unit of foliage (E) increased during the first 3–4 years, but was at or below control level after 7 years. The increased E accounted for 20, 37, and 27% of the stemwood dry matter response to thinning, fertilization and the combined treatments, respectively; the remainder was attributed to an increase in foliage biomass. Thinning, but not fertilization, influenced distribution of radial growth along the stem, increasing growth only below the top one-third of the stem. This pattern was related to crown development.

Beschreibung: A review is presented of the shortcomings of most existing taper equations which predict diameter along the stem as a function of tree height and diameter at breast height. A new computerized system is developed that has many desirable features for tree profile prediction. This new system consists of two mathematical functions, one describing the upper bole and the other describing the lower bole. The two functions are linked together at the inflection point and are continuous at that point. Tests of this model on 32 species age and locality groupings of British Columbia species show that although there is still a slight bias near ground level, the prediction of diameter inside bark is almost perfect over most of the length of the trees.

Beschreibung: A nonlinear analytical model is developed to describe the relationship between average plant size (weight or volume) and stand density in single-aged, monospecific plant populations. The model gives estimates of the slope and intercept of the −3/2 power rule asymptote, the nature of the size–density trajectory, and such features as relative density at crown closure and the effects of soil type or site index. The model is tested by growing red alder (Alnusrubra Bong.) seedlings under greenhouse and lath house conditions at three initial spacings (8 × 8, 4 × 4, and 2 × 2 cm) and two soil types (river loam and alder forest soil) for 525 growth days. There are seven harvests, starting at crown closure. All size–density trajectories tend consistently towards the same single asymptote irrespective of initial spacing, soil type, or age. The asymptote slope and intercept are 1.46 and ca. 94 kg tree−1•m−2. The crown closure line is parallel to the asymptote at a relative density of 4.6 × 10−3. The model also adequately describes the size–density trajectories for 20–50-year-old red pines (Pinusresinosa Ait.) growing at six initial spacings. The asymptote slope and intercept are 1.6 and ca. 87 × 103 m3•tree−1•ha−1, respectively.

Beschreibung: Seedlings of four coniferous species, Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), white spruce (Piceaglauca (Moench) Voss), and lodgepole pine (Pinuscontorta Dougl.), were grown for 4 months from germination and then exposed to soil drying. Rates of photosynthesis were measured for all species and rates of dark respiration and transpiration were measured for Douglas-fir and hemlock. In a study of survival, seedlings were exposed to various durations of soil drying and the plant water potential was determined before the plants were rewatered; seedling survival was subsequently recorded.Rates of photosynthesis declined for Douglas-fir, hemlock, spruce, and pine when the plant water potential decreased from −10.0, −10.7, −12.4, and −6.6 bars (1 bar = 100 kPa), respectively, and became zero with potentials of −53.9, −39.7, −28.6, and −22.4 bars. When grown together in the same pot and exposed to soil drought, hemlock had a consistently lower potential than Douglas-fir, and spruce had a lower potential than pine. Hemlock could survive potentials of −40 to −60 bars, whereas seedlings of the other species survived potentials to −110 bars.

Beschreibung: Temporal and spatial dynamics of organic matter and mineral elements were studied in an aspen woodland floor in southwestern Alberta, Canada. The average depths of the layers comprising the organic horizon were as follows: L, 0–2 cm; F, 2–4 cm; H, 4–7 cm; and Ah, 7–8 cm. The average annual amounts of organic matter in the soil layers were the following: L, 10.3 × 103 kg ha−1 (range 8.0–16.4); F, 18.2 × 103 kg ha−1 (13.2–24.5); H, 31.5 × 103 kg ha−1 (24.0–40.4); and Ah, 4.2 × 103 kg ha−1 (3.8–5.0); the total weight of soil organic matter was 64.2 × 103 kg ha−1 (49.0–86.3). The H layer accounted for 50% of the soil organic matter; total soil organic matter, to a depth of 8 cm, constituted about 0.30 of the total living above-ground plant biomass. There were no evident statistically significant seasonal fluctuations of organic matter in any of the organic layers; the turnover rate of the soil organic matter was 0.08 year−1 and the mean residence time was 12.5 years.The concentrations of Ca, Mg, P, and N generally decreased with profile depth, while K, Fe, Mn, and Na increased in concentration. Zinc concentrations showed no obvious trend but it did appear that Zn might be concentrated in the F and Ah layers. The orders of abundance of elements in the soil layers were as follows: L,  Ca 〉 N 〉 K 〉 Mg 〉 P 〉 Fe 〉 Zn 〉 Mn 〉 Na 〉 Cu; F, Ca 〉 N 〉 Mg 〉 K 〉 Fe 〉 P 〉 Zn 〉 Mn 〉 Na 〉 Cu; H, Ca 〉 N 〉 Fe 〉 K 〉 Mg 〉 P〉 Na 〉 Mn 〉 Zn 〉 Cu; Ah, Fe 〉 N 〉 K 〉 Ca 〉 Na 〉 Mg 〉 P 〉 Mn 〉 Zn 〉 Cu; total, Ca 〉 N 〉 Fe 〉 K 〉 Mg 〉 Na 〉 P 〉 Mn 〉 Zn 〉 Cu. Maximum weights of Ca, N, Mg, and P were found in the H layer, whereas K, Fe, Zn, Mn, Na, and Cu were most abundant in the Ah. There was some indication that the amounts of some elements fluctuated positively or negatively with rainfall and (or) soil moisture levels. Based on limited input data for the elements, turnover times were calculated and compared with literature values.

Beschreibung: The history of spruce budworm (Choristoneurafumiferana (Clem.)) outbreaks for the past 200 to 300 years, for nine regions in eastern Canada, indicates that outbreaks have occurred more frequently in the 20th century than previously. Regionally, 21 outbreaks took place in the past 80 years compared with 9 in the preceding 100 years. Earlier infestations were restricted to specific regions, but in the 20th century they have coalesced and increased in size, the outbreaks of 1910, 1940, and 1970 having covered 10, 25, and 55 million ha respectively. Reasons for the increase in frequency, extent, and severity of outbreaks appear mostly attributable to changes caused by man, in the forest ecosystem. Clear-cutting of pulpwood stands, fire protection, and use of pesticides against budworm favor fir–spruce stands, rendering the forest more prone to budworm attack. The manner and degree to which each of these practices has altered forest composition is discussed. In the future, most of these practices are expected to continue and their effects could intensify, especially in regions of recent application. Other practices, including large-scale planting of white spruce, could further increase the susceptibility of forest stands. Forest management, aimed at reducing the occurrence of extensive fir–spruce stands, has been advocated as a long-term solution to the budworm problem. The implementation of this measure at a time when man's actions result in the proliferation of fir presents a most serious challenge to forest managers.

Beschreibung: Flooding of soil for 45 days severely inhibited growth of 115-day-old Pinusbanksiana Lamb, and P. resinosa Ait. seedlings, with significant effects apparent within 15 days after initiation of flooding. Both species adapted poorly to flooding of soil but P. banksiana was more adversely affected than P. resinosa as shown by earlier and more drastic reduction of growth in the former species. In both species flooding decreased the rate of height growth, production of secondary needles, dry weight increment, and relative growth rates of various plant parts. Root growth of both species was reduced more than shoot growth. The reduction in dry weight increment of root systems of both species reflected arrested branching and elongation of roots as well as decay of roots, mainly the very small nonwoody roots. Flooding slightly stimulated ethylene production by submerged stems.

Beschreibung: The presence of ectomycorrhizal and vesicular–arbuscular (VA) mycorrhizal fungi in soils from five sites in a mixed conifer zone in southwest Oregon, each consisting of a 1- to 1.5-year-old clear-cut adjacent to an undisturbed forest stand, was determined by bioassay with Pseudotsugamenziesii (Mirb.) Franco, Pinusponderosa Dougl. ex P. Laws & C. Laws, and Trifoliumsubterraneum L. 'Mt. Barker' as hosts grown at root zone temperatures ranging from 7.5 to 35 °C. Maximum formation of both ectomycorrhizae and VA mycorrhizae occurred at 18.5–24 °C in soils from all sites, and there were no significant qualitative or quantitative differences between disturbed (clear-cut) or undisturbed (forest) soils. Mycorrhiza formation was moderate even at the lowest temperature tested (7.5 °C) but was greatly reduced or prevented at or above 29.5 °C. Treatment of soil at 35 °C for 1 week did not appear to adversely affect viability of ectomycorrhizal fungus propagules, but young mycorrhizae subjected to the same treatment appeared to be severely injured. Thus the ability of native mycorrhizal fungi to grow at low soil temperatures is especially important as they may contribute to the survival of seedlings outplanted into climatic zones characterized by warm, dry summers following cool, wet winters and springs.

Beschreibung: Damage caused by the white-spotted sawyer, Monochamusscutellatus (Say), to felled white spruce, Piceaglauca (Moench) Voss, in northern Alberta was studied to provide data for improving a damage assessment technique. Numbers, density, and size of larval entrance holes, length of larval galleries, and diameter of adult exit holes were examined on three 122-cm-long log sections cut near the butt, middle, and top of each of 30 trees. Information on larval development and survival and adult emergence was also obtained.Size of larval entrance and adult exit holes and gallery length decreased from the butt to top of the tree, numbers of entrance holes were similar at the three stem positions, and density of entrance holes increased from butt to top on both south and north aspects. The density of entrance holes around the logs showed two maxima, while the mean density was approximated slightly above midlevel on south and north aspects. Larval galleries extended to an average maximum depth of 7.5 cm into the wood. About 25% of adults emerged 1 year after oviposition, the rest emerged after 2 years. Mortality of M. scutellatus within the logs averaged 71%. The results are discussed in relation to sampling problems for damage assessment in felled and standing fire-killed trees.

Beschreibung: Decay caused by some common wood-destroying fungi in several associated tree hosts of the Intermountain forests of western Montana was evaluated as a potential environment for the fixation of dinitrogen. Differences in the rates of fixation were demonstrated between various decay stages, tree species, decay fungi, and brown and white rots. Advanced brown-rotted wood was a more favorable system for nitrogen fixation than wood partially brown rotted. Also, brown-rotted substrates proved to be more favorable than did white rotted, particularly Pseudotsugamenziesii (Mirb.) Franco wood decayed by Fomitopsispinicola (Swartz ex Fr.) Karst. Data demonstrate that a nitrogenase function coexists naturally with decay fungi in woody substrates and that appreciable and significant amounts of nitrogen are fixed in these substrates.

Beschreibung: Reduced levels of root activity were associated with winter injury to shoots of 1-year-old black spruce (Piceamariana (Mill.) B.S.P.) container seedlings.

Beschreibung: Lateral buds were formed on Piceasitchensis (Bong.) Carr. leaders in April–May before the leaders emerged from the winter buds. At that time, the lateral buds seemed to be evenly (not randomly) dispersed over the cone-shaped surfaces of the parent leader buds. This observation was confirmed and extended by defining the positions of lateral buds on fully extended leaders of P. sitchensis, P. abies (L.) Karst., P. omorika (Pancic) Purkyne, and Larixdecidua Mill. and 'theoretically' telescoping the leaders to their probable shapes in April–May by using computer simulations. It was concluded that the centres of cell division which preceded lateral bud formation were positioned by inhibition–competition mechanisms. This explained why (a) the numbers of lateral buds were related to the sizes of the parent shoots, (b) lateral branches were dispersed with equal expectation in all compass directions, with minimal mutual shading, and (c) a variety of staggered and whorled branch arrangements could occur on leaders of different trees, as long as each whorl was associated with a branchless zone.

Beschreibung: Techniques are described for field and laboratory extraction of small quantities of sugar maple (Acersaccharum Marsh.) xylem sap when pressure in the xylem is less than atmospheric. Accurate estimates of sap sugar concentration can be made with a hand refractometer most of the year. There is, however, appreciable within-tree variation in sap sugar concentration at any given time and within short periods of time.

Beschreibung: Armillariamellea isolations from the roots of dead and dying conifer saplings increased by 40% when o-phenylphenol (OPP) was added to malt agar compared with isolations on malt agar alone; they were similar on the two media from the roots of larger, healthy trees. This is attributed largely to the inhibiting effect of the additive on fast-growing Hyphomycetes and other fungi which are far more abundant in the roots of dead or dying saplings than in the roots of healthy older trees. Decay-causing Basidiomycetes other than A. mellea were isolated less frequently, whereas bacteria and yeasts were isolated more frequently, when OPP was added to the malt agar medium. This suggests that the additive must be used with discretion.

Beschreibung: Three methods were compared for total sulphur analysis of tree foliage: magnesium nitrate ashing followed by turbidimetry, sodium hypobromite (NaOBr) oxidation followed by colorimetry, and an instrumental method using the Fisher S analyser, model 475. The latter method was found to be substantially better than the other methods with respect to accuracy and speed of analysis, and of satisfactory precision (average coefficient of variation (CV) was 2.5%). Dry ashing resulted in good precision (CV = 1.9%) but only recovered 76% of the reported total S in the United States National Bureau of Standards (NBS) orchard leaf standard. The NaOBr method recovered 88% of reported S from the NBS standard but showed poorer precision (CV = 4.5%). The Fisher analyser had the lowest operating cost per sample, largely owing to lower labour costs.

Beschreibung: Dry matter production by Sitka spruce seedlings (Piceasitchensis (Bong.) Carr) outside the period of shoot extension was determined in southern Scotland by harvesting plants from a nursery on 13 occasions between late September and mid-May. Air and soil temperature and incoming radiation were measured in an attempt to relate weight changes to climatic variables. Dry weight of the plants apparently doubled between late September and mid-April but subsequently changed little. Most dry weight increase occurred during October, late March, and April but there was also a slight increase in weight in midwinter. The relative increase in weight was similar in roots and shoots until mid-January but thereafter was proportionally much greater in shoots than in roots and was associated with a marked increase in needle weight. Lack of weight increase in late spring was attributed to the respiratory demands of bud expansion. Dry matter changes in the 12 harvest intervals was not related to mean daily temperature, incoming radiation, or photoperiod, but when averaged over periods of 1 month a much closer relationship was evident.

Beschreibung: Descriptive records of wildfires since the earliest writings and quantitative provincial fire records since 1915 have been used to produce a synthesis of fire history for the Province of Nova Scotia, Canada. Large annual burns were common up to the mid-1930's. Annual burns totalling over 15 000 ha occurred in each of the years 1918, 1920, 1921, 1930, 1934, 1944, and 1947, and annual burns totalling over 30 000 ha occurred in each of the years 1920 and 1921. Lightning has accounted for 1% of the number of fires (three per year). Thirty percent of the fires have occurred in the month of May; however, fires have been recorded for all months. Fire rotation periods for the province as a whole were 1000 or 2500 years, using the mean annual burn or median annual burn, respectively, for all burns in the years 1915 to 1975. In contrast, calculations of burned areas on maps produced at the turn of the century gave presuppression fire rotation periods of just over 200 years. Vegetation types have had widely varying fire rotation periods. The vegetation of Cape Breton Island has been subjected to almost no fires over 20 ha, whereas the vegetation type with the shortest fire rotation period (in the interior of western Nova Scotia) has been subjected to fire rotation periods as low as 65 years at the turn of the century, to about 2000 years for the years 1958 to 1975. A summary of fire rotation periods for the Boreal, Great Lakes – St. Lawrence, and Acadian Forest Regions found in the literature is presented for comparison with the Nova Scotia data, and more detailed comparisons are made between the fire rotation periods of the similar vegetation types in New Brunswick and Nova Scotia.

Beschreibung: Some theory and observations are presented on the factors governing the start and spread of crown fire in conifer forests. Crown fires are classified in three ways according to the degree of dependence of the crown phase of the fire on the ground surface phase. The crown fuel is pictured as a layer of uniform bulk density and height above ground. Simple criteria are presented for the initiation of crown combustion and for the minimum rates of spread and heat transfer into the crown combustion zone at which the crown fire will spread. The theory is partially supported by some observations in four kinds of conifer forest.

Beschreibung: Oleoresin viscosity, flow (rate, duration, and total amount), and rate of crystallization were determined for Pinuselliottii Engelm., Pinuspalustris Mill., Pinustaeda L., and Pinusechinata Mill, in central Louisiana, U.S.A. Physical properties of the oleoresin and tree morphological characteristics (diameter at breast height, growth rate, height, crown ratio, and age) were not strongly related in either of the four species. Pinuselliottii oleoresin was extremenly viscous, crystallized very slowly, and flowed at a slow rate over a long period, and total yield was moderate. Pinuspalustris oleoresin was of moderately high viscosity and very high yield and had a high rate of flow. Pinustaeda and Pinusechinata oleoresin had, on the average, low viscosity, a moderate to low total yield, a short duration of flow, and rapid rate of crystallization. A discriminant function analysis revealed that 19% of the Pinustaeda and 6% of the Pinusechinata trees had oleoresin properties more similar to Pinuspalustris and Pinuselliottii than to the means for their own species. This information is being used to assess tree susceptibility to attack by Dendroctonusfrontalis Zimm.

Beschreibung: This paper describes the variation in the drying rate of jack pine (Pinusbanksiana Lamb.) litter with external conditions. Temperature, relative humidity (RH), and wind were varied separately. Drying runs were carried out in a cabinet with controlled temperature and humidity and also in the open laboratory. Most runs followed the exponential pattern, and the drying rates were measured in terms of the slope of the semilog graph of free moisture content versus time. The logarithm of this slope was found to be inversely proportional to the reciprocal of absolute temperature. The drying rate varied with 100 – RH at high RH but increased only slightly below 60% RH owing to the limiting effect of the wax and resin content on the rate of internal diffusion. Drying in wind proceeded in two stages, the first faster than the second. Wind was important at low speeds, and the drying rate increased but little above 2 km/h. These principles were used in the design of the drying equations of the Fine Fuel Moisture Code of the Canadian Forest Fire Weather Index.

Beschreibung: Previous studies of budworm impact on balsam fir stands have correlated the probability of tree damage and mortality with only a few broad stand characteristics. Improved predictability may be obtainable from a model incorporating foliage production of fir, budworm feeding rate, and tree vulnerability. Some data are presented on the first two variables with comments on further research requirement.

Beschreibung: Copper, nickel, and cobalt solutions were added to a variety of substrates to test the effects of these metals on the germination and radicle elongation of two deciduous and five coniferous woody species native to eastern North America. For species grown on filter paper, germination was little affected by metal concentrations of up to 100 ppm. Filter-paper tests showed that radicle elongation was reduced by 25% at concentrations that ranged from 1 to 5 ppm for Betulapapyrifera Marsh, to as much as 50 to 100 ppm for Pinusstrobus L. Concentrations causing similar effects on mineral and organic soil substrates were, respectively, 10 and 100 times greater than those for filter paper. For all species, toxicity followed the pattern Ni 〉 Cu 〉 Co for filter paper and [Formula: see text] for mineral and organic soils. Deciduous species were more readily damaged by these metals than were coniferous species.

Beschreibung: New methods of simulating aggregated distribution of point spatial patterns have been developed. These methods aggregate points to a degree specified by Pielou's index of nonrandomness by reversing its sampling procedure. Included are a review of previous methods of simulating aggregation, a full description of the present approach, and examples of simulations with varying density levels.

Beschreibung: The photosynthetic capacity of different needle age-classes of black spruce (Piceamariana (Mill) B.S.P.) was studied using 14C labelling on whole branches at a site near Fairbanks, Alaska. Black spruce had highest photosynthetic rates in the 1-year-old tissue with the four most current age-classes showing similar high rates before declining with age. Older needles were found to maintain 40% of maximum photosynthetic rates after 13 seasons. Highest level of nitrogen was found in current needles with the first eight age-classes maintaining high levels before declining to 70% of maximum values in the oldest needles. Phosphorus levels were much higher in current tissue with a gradual decline after the 1-year-old tissue to a value of 55% of maximum values in the oldest tissue. Nutrient use efficiency was found to be highest in the 1-year-old tissue and declined with needle age. The loss of nutrient use efficiency may be due to the use of older tissue as aboveground nutrient stores, a decline in the efficiency of the photosynthetic apparatus of the needles, or an increase in the leaf specific weight. Black spruce has adapted to the low nutrient availability with low photosynthetic rates and low nutrient contents. Greater longevity of the needles would maximize the photosynthetic return per unit nitrogen invested in the needles.

Beschreibung: Twenty-four specimens of six boreal tree species were excavated: eight Pinusbanksiana Lamb., five Populustremuloides Michx., four Piceaglauca (Moench) Voss, three Piceamariana (Mill.) B.S.P., two Abiesbalsamea (L.) Mills., and two Lara laricina (Du Roi) K. Koch. Root systems were described, and percent biomass determined for above- and below-ground components for half these specimens. Tree ages ranged from 3 to 120 years. Horizontally spreading lateral roots dominated the root systems of all species and occurred within 3– 15 cm of the ground surface. Nutrient and moisture absorption appear to be the principal functions of lateral roots. Maximum vertical root growth occurred near the tree stump as: tap-, heart, sinker, and oblique lateral roots. Vertical root morphology is influenced by site conditions. In addition to providing mechanical support, sinker and taproots may be important adaptations for deep-water utilization on xeric sites. Our data suggest that roots may be important in boreal succession processes through two related mechanisms: (i) nutrient and water deprivation occurring through preemptive growth of tree roots from climax species over roots of serai species, and through interception by mosses; and (ii) niche partitioning occurring below ground between serai and climax, and among climax tree species, by vertical separation of the root systems.

Beschreibung: The impact of Hurricane David on the forests of Dominica was measured 40 days after the hurricane struck the island on August 29, 1979, with winds averaging 92 km/h which lasted 10.2 h. Sixteen 0.1-ha plots were studied. They were located on a variety of slope and exposure conditions, representing three life zones and 11 plant associations. Measurements included tree diameter at breast height (dbh), total height, wood volume, and percent canopy closure of stand. Species and damage conditions were noted. The hurricane caused severe damage, particularly to forests on the southern half of the island. Forty-two percent of the standing timber volume in the study areas was damaged at an average intensity of 27 m3/ha. About 5.1 × I06 timber trees were damaged in an area of 246 km2. "Complex" vegetation was more resistant to hurricane damage than "simpler" vegetation. The climax Dacryodesexcelsa Vahl associations suffered the least hurricane damage, while the palm brake suffered the most damage. Only one species (Richeriagrandis Vahl) exhibited significantly higher hurricane damage. Trees in larger diameter classes tended to uproot with more frequency than smaller diameter trees, which tended to snap and break. Regrowth of seedlings and saplings was rapid on wet areas of the damaged sites. We found more species on regenerating plots than on the undisturbed forest plots. The damage caused by Hurricane David is the most extensive reported to date anywhere, and damage to vegetation by hurricanes appears to be more extensive than damage by earthquakes and landslides. Owing to their high frequencies in the Caribbean, hurricanes induce cyclic plant successions.

Beschreibung: An index was developed that takes into account the combined influence of air and soil temperatures, light, and the availability of soil moisture upon photosynthesis by a unit area of fully exposed foliage of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco). The index is derived from a summation of daily estimates of carbon assimilation (milligrams CO2 assimilation per decimeter per day) for an entire year. In a comparison of forest environments in western Oregon the index was correlated to a measure of forest productivity (r2 = 0.99). Furthermore, it suggests that much of the annual carbon fixation occurs during the mild winters characteristic of the region. The ability to assess the effects of frost, soil drought, and other variables separately was valuable in explaining differences between coastal, valley, and mountainous sites.

Beschreibung: A probabilistic two-step method of analysis is described that overcomes the problems associated with using a single model to analyze data drawn from a two-state system. The two steps of the analysis are (i) to determine the probability that an observation with given characteristics falls in each of the two states of the system and (ii) to estimate the response of the dependent variable in each of the two states as a function of characteristics of observations. Estimating cull volume in standing trees provides an example. This analysis results in two component models that more closely describe the process of interest than is possible with any single model. Statistically sound approximations to confidence intervals and tests of hypotheses for the parameters of each of the component models may be computed.

Beschreibung: The effects of fertilization and thinning of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) on the distribution of area increment along the bole were assessed using radial growth measurements 6 and 9 years after treatment. Within treatments, the average area increment per tree was linearly related to diameter at breast height, and this relationship was used to evaluate the effects of treatment on growth rate. Fertilization had the greatest effect on average area increment, and for a particular fertilization regime, thinning increased the response. Thinning modified the distribution of growth over the bole of all trees and increased butt flare, especially in smaller trees. The effect declined from the 4- to 6-year measurement period to the 7-to 9-year measurement period. Fertilization had no consistent effect on growth distribution. The regression methods used in this study provided a more sensitive measure of form changes than previous methods, were independent of size distribution, and facilitated extrapolations and evaluation of temporal trend.

Beschreibung: Distribution of N, P, K, Ca, and Mg in the tree, understory, forest floor, and mineral soil horizons was determined for two series of postfire forest stands in northeastern New Brunswick. Twelve pure jack pine stands (Pinusbanksiana Lamb.) and 11 mixed hardwood stands aged 7–57 years were examined. Regression equations relating aboveground tree nutrient content to diameter for eight tree species were calculated. The jack pine stands demonstrated variable stand density, but adjustment to normal stocking produced a sigmoid nutrient accumulation pattern in the tree layer during the 60-year period. Nutrient accumulation in the tree layer of both series of stands closely approximated biomass accumulation. Understory nutrients formed a significant fraction of the total aboveground pool, particularly in the younger stands. Organic and mineral soil horizon nutrients were found to be highly variable for both series of stands; this was postulated to be a result of the fire origin of the stands, with varying fire intensity and postfire conditions resulting in different nutrient losses from the site.

Beschreibung: Organic content of the forest floor decreases for several years after clear-cutting, and then slowly recovers. Thickness, bulk density, organic matter, and nitrogen content of forest floors were measured for 13 northern hardwood stands in the White Mountains of New Hampshire. Stands ranged from 1 to about 100 years in age. Forest-floor thickness varied significantly with stand age, but bulk density, organic fraction, and nitrogen fraction were independent of age. Total organic content of the forest floor agreed very well with data from Covington's (W. W. Covington 1981. Ecology, 62: 41–48) study of the same area. Both studies indicated that mature forest floors have about 80 Mg organic matter•ha−1 and 1.9 Mg nitrogen•ha−1. Within 10 or 15 years after cutting, the organic matter content of the floor decreases to 50 Mg•ha−1, and its nitrogen content to 1.1 Mg•ha−1. The question whether the decrease is rapid and the minimum broad and flat, or if the decrease is gradual and the minimum sharp, cannot be answered. The subsequent increase to levels reached in mature forest requires about 50 years. Some of the initial decrease in organic matter and nitrogen content of the forest floor may be caused by organic decomposition and nitrogen leaching, but mechanical and chemical mixing of floor into mineral soil, during and after the harvest operation, may also be important. The difference is vital with respect to maintenance of long-term productivity.

Beschreibung: A variety of evergreen and deciduous forests in the taiga of interior Alaska were studied over a 5-year period to examine how the chemical quality of forest-floor organic matter affected its rate of decomposition and mineral cycling within and outside the tree vegetation. Litterbag and respiration studies were used to monitor decomposition. Natural forest-floor substrates and others altered by addition of N, P, and K fertilizer and glucose as a carbon source were studied in the laboratory and field for rates of weight loss and O2 consumption. Forest floors differing in C/N ratios, including those deficient in N, were used to measure substrate quality influences on seedling growth, nutrient content, and tannin content. Microbial (bacteria and fungi) biomass was measured across a range of forest types along with pH, base saturation total pool sizes of N and P, and annual mineralization of organic matter per square metre. Under identical moisture and temperature conditions average respiration rates in evergreen forest-floor L, F, and H substrates were 1.8, 2.8, and 2.0 times less than in the corresponding deciduous forest horizons, respectively. Birch L and F horizons had respiration rates 11.5 times higher than the corresponding black spruce layers. Weight losses in birch L, F, and H horizons were 6, 3, and 2 times higher, respectively, than in the corresponding black spruce substrates. Substrates had a quality-dependent decay rate which did not change when they were relocated within or between sites indicating that measured field climatic differences were not as influential on decay rates as substrate quality components. Fungal biomass was significantly correlated with the quantity of organic matter in all sites (n = 15, r = 0.62) but correlations were better for deciduous (n = 9, r = 0.89), and evergreen (n = 6, r = 0.82) forests separately. Strong correlations exist also between grams of organic matter decayed per square metre per year and fungal biomass (n = 13, r = 0.86), and fungal biomass and grams of N and P mineralized per square metre per year (n = 14, r = 0.95) and (n = 11, r = 0.94, respectively). Seedlings on mineral-deficient substrates produced more tannins than the controls, and seedlings on substrates with widening C/N ratios had successively less tissue with lower N content, and proportionally more roots. Nitrogen content of litter fall in increasingly nitrogen-poor forest floors was correspondingly lower. Nitrogen content of litter fall on N rich forest floors and N fertilized forest floors was proportionately higher. Nitrogen withdrawal in leaves at senescence was inversely correlated with grams N mineralized per square metre per year in forest floors. Fertilization did not influence microbial processes in the field, though lab studies indicated a negative influence of NH4, P, and K on microbial respiration. Glucose added in the laboratory and field markedly increased forest-floor microbial respiration. In vitro glucose-induced increases in respiration were not influenced by addition of ammonium nitrate and were significantly depressed by addition of P and K. In the field, fertilization had no effect on either glucose-induced respiration or microbial biomass.

Beschreibung: An old, merchantable, low-site class black spruce (Piceamariana (Mill.) B.S.P.) stand growing on a Lithic Humo-Ferric Podzol overlying a granite bedrock, and a younger but merchantable low-site class jack pine (Pinusbanksiana Lamb.) stand growing on a Ferro-Humic Podzol overlying a deep coarse sand near Baie Comeau, P.Q., were analysed for stand biomass and macronutrient contents of both stand and soil. The magnitude of the depletions of macronutrients from the site, in full-tree and tree-length methods of logging, are compared with their available and total quantities in the soil. The range of values from the literature for nutrient inputs are presented and discussed in relation to logging losses. The results suggest that full-tree logging in the dry jack pine stand could cause a severe loss of potentially mineralizable N supply; P, K, and Mg deficiency problems owing to export are not apparent, but a Ca balance problem is apparent. The implication is that full-tree logging should be avoided on such sites.

Beschreibung: Seven units (about 2 ha each) of black spruce – feather moss forest were experimentally burned over a range of fuel moisture conditions during the summer of 1978. Surface woody fuels were sparse and the principal carrier fuel was the forest floor (largely mosses and their decomposition products). Forest floors after burning comprised a small-scale mosaic of unburned, scorched, lightly burned, moderately burned, and heavily burned (organic materials entirely consumed) conditions. Percentage of the unit area in the moderately and heavily burned condition ranged from 11.2 to 77.2% and percent decrease in forest-floor thickness varied from 27.4 to 63.1% in the seven units. Forest-floor consumption was most closely correlated with the moisture content of lower moss (01 horizon) and lower duff layers (022 horizon) at the time of burning. For the first 3 years after fire, biomass production was greater on heavily burned than on lightly burned sites (58 vs. 37 g/m2 on an annual basis). Heavily burned sites were completely dominated by the invading species Epilobiumangustifolium L., Ceratodonpurpureus (Hedw.) Brid., and Marchantiapolymorpha L., whereas lightly burned plots were occupied by sprouting species such as Calamagrostiscanadensis (Michx.) Beauv., Vacciniumuliginosum L., and Ledumgroenlandicum Oeder. Soil pH and amounts of total P and available P in the forest floor increased significantly as a result of burning; and in all cases, increases reached a maximum in moderately and heavily burned areas. Total N in the forest floor increased significantly in moderately burned, but decreased slightly in heavily burned areas. Total N and total P showed smaller increases in the surface mineral soil as a result of burning. Supplies of available P in the mineral soil increased almost 4-fold in moderately burned and over 16-fold in heavily burned areas.

Beschreibung: Straw was added over snow to smother ground vegetation (straw experiment) in sample plots in a 45-year-old jack pine (Pinusbanksiana Lamb.) stand in Quebec. Sample plots in the same stand were fertilized six times with N, P, and K in a 10-year period to maintain four foliar N regimes (optimum nutrition experiment). Smothering of ground vegetation with straw improved N nutrition and produced a sustained increase in tree growth. Sustained growth increases were obtained by repeated applications of 56 kg N/ha associated with 1.4% N foliar concentrations in current foliage. Gross volume increments of about 3 m3 • ha−1 • year−1 were sustained with these low applications. Repeated heavy N applications killed trees and reduced growth. Repeated additions of P and K with N did not produce appreciable differences in response from additions of N alone. Increment cores showed the annual development in growth as increasing over most of the 10-year period for low repeated N additions, and as increased and stable over the same period for the straw addition.

Beschreibung: Radial stem wood sections of fertilized (at age 14 years) and unfertilized loblolly pine (Pinustaecla L.) trees were analyzed 5 and 9 years after treatment to establish if xylem nitrogen (N) can be used for a diagnostic nitrogen test. The percentage of xylem nitrogen in wood formed since fertilization was greater in fertilized than in unfertilized trees. The 2 years of wood growth near the cambium had a higher percent N than older wood, but differences between treatments were less pronounced than in older wood. Concentrations of N for fertilized and unfertilized trees were nearly constant for 2- to 9-year-old wood indicating that a sampling technique to determine the N status of loblolly pine could be developed by increment coring.

Beschreibung: Allometric regressions for estimating red maple (Acerrubrum L.) biomass did not differ by stand age and site index. Significant differences were found only in terms of error variance, not in terms of regression slope or intercept. These trends suggest a single predictive model is valid for regional estimates. More attention should be given to regional sampling procedures and predictive relations that are valid for a wide range of stand and site conditions in developing weight tables and conducting biomass inventories.

Beschreibung: In 4 different years' experiments with loblolly (Pinustaeda L.), slash (Pinuselliottiielliottii Engelm.), and longleaf (Pinuspalustris Mill.) pine, timing of gibberellin A4/7 (GA4/7) treatments was critical for optimal promotion of pollen conebuds. Two or three biweekly treatments given at strategic times were equivalent to six given from May to August. July to August applications best promoted pollen conebuds. Using the cationic surfactant Aromox C/12, aqueous foliar sprays of 200 mg/L of GA4/7 were more effective than ethanolic topical bud treatments for pollen conebud induction in slash pine. Addition of naphthaleneacetic acid enhanced the GA4/7 effect in loblolly pine but diminished it in slash and longleaf pine.