ALBERT

Description: Morphological plasticity in terms of asymmetric display of crowns was compared between Piceaabies (L.) Karst. and Betulamaximowicziana Regel. To evaluate crown asymmetry in relation to local environment, a model that predicts crown asymmetry from topography and configuration of neighbors was applied to data derived from a mixed forest in Hokkaido, northern Japan. Betulamaximowicziana had greater crown asymmetry than P. abies in absolute value. However, observed crown asymmetry of both species was determined by local environment to similar degrees. Some other differences were found between the two species. Crowns of P. abies were more influenced by neighbors than topography, while crowns of B. maximowicziana were more influenced by topography than neighbors. Crowns of P. abies were influenced mainly by larger neighbors, while crowns of B. maximowicziana were influenced by large and by relatively small neighbors.

Description: The rates of nutrient release were investigated during the Castanopsiskawakamii (Hayata) leaf, branch, and bark litter decomposition processes over a 360-day period within five different size classes of forest gaps that comprise a gap size gradient. Five different size classes of gaps were gap 1, under the closed canopy of pure C. kawakamii vegetation; gap 2, small gaps with a diameter of less than 5 m; gap 3, small to intermediate gaps with a diameter of 5–15 m; gap 4, intermediate to large gaps with a diameter of 15–30 m; gap 5, large gaps with a diameter of bigger than 30 m. After 360 days, decomposing plant litter under canopy condition or small gaps lost weight more rapidly than those in large gaps. Loss of K was highest among all nutrients measured for all three types of litter in all five size classes of gaps. Net immobilization of N and P occurred for all three types of litter in the first 2 or 4 months. Litter residue concentrations of N and P then declined until the end of this study, decreasing to 47% and 70%, respectively, of initial amounts. Loss of Ca and Mg averaged 60 and 40%, respectively, during the period of this study; loss of S averaged 50% and was continuous. Loss of nutrients measured were highest in leaves, intermediate in bark, and lowest in branches under the same size class of gaps, and were highest in gaps 1 and 2, intermediate in gap 3, and lowest in gaps 4 and 5 for the same type of litter. Cellulose and lignin components showed the similar patterns of mass loss as nutrients with highest in gaps 1 and 2, intermediate in gap 3, lowest in gaps 4 and 5 (P ≤ 0.001). Annual decomposition rate was correlated to the microclimatic factors for all types of litter within five different gap size conditions. Soil moisture content was the best predictor of annual decay rate (R2 = 0.922, P ≤ 0.001) among the microclimatic factors. The results indicated that small scale of natural disturbance do not influence the nutrient dynamics during plant litter decomposition; however, rates of nutrient release are strongly inhibited with the increase of scales of disturbance. In this study, gap size of 15 m in diameter is critical in determining the rates of nutrient release from plant litter decomposition processes.

Description: Six old-growth, late postfire Scots pine (Pinussylvestris L.) dominated forest stands of the Vaccinium–Cladina type were selected along a latitudinal gradient in northern Sweden. In two of the stands, Scots pine seedlings that had naturally regenerated during the last 40 years were surveyed in relation to field- and bottom-layer vegetation. The most abundant forest floor species, viz. Cladina spp., occupied 41% of the ground cover and dominated the microhabitat of Scots pine seedlings

Description: In northern Patagonia, Argentina, we examined the influences of climatic variation and inter-site variation in substrate stability on the dendroecological effects of earthquakes. In association with the great earthquake in 1960 centered off the coast of nearby Valdivia, Chile, extensive tree mortality occurred in northern Patagonia in Nothofagusdombeyi–Austrocedruschilensis stands on unstable debris fans. To examine the effects of the 1960 and earlier earthquakes on tree growth, we developed tree-ring chronologies from samples of the surviving A. chilensis on unstable debris fan sites and at adjacent nonfan sites of more stable substrates. For controlling the effects of regional climatic variation, we also produced a tree-ring chronology from this species in a more distant and undisturbed stand. Strong variations in tree-growth patterns on fan sites were associated with the historically documented major seismic events of south central Chile that occurred in 1737, 1751, 1837, and 1960. Tree-ring chronologies from nonfan sites (i.e., sites of greater substrate stability) showed much less response to these earthquakes. On the fan sites, strong growth suppressions were associated with the former three earthquakes, whereas strong releases followed the 1960 earthquake. The difference in response is explained by the occurrence of the 1960 earthquake during a period of drought, which in combination with the violent shaking of the ground, resulted in extensive tree mortality followed by growth releases of the survivors. However, severe droughts in the absence of earthquakes also can produce tree mortality and subsequent release of the survivors. Consequently, the synergistic effects of climatic variation and earthquake events must be carefully considered in developing records of both climatic variation and earthquakes.

Description: The relationships between site index and measures of soil, understory vegetation, and foliar nutrients were examined using data from 102 white spruce (Piceaglauca (Moench) Voss) stands in the Sub-boreal Spruce zone of British Columbia. Compared with soil physical properties (adjusted.R2 = 0.54), soil nutrient properties (adjusted.R2 = 0.29) were poor predictors of white spruce site index. The best soil model, using depth of major rooting zone, total nitrogen, and slope as predictors, explained 60% of the total variance in site index. The best understory vegetation model, using frequencies of soil-moisture and nitrogen indicator species groups as predictors, explained 53% of the total variance in site index. The best foliar nutrient model, using foliar phosphorus and sulphur as predictors, explained 64% of the total variance in site index. Adding variables from understory vegetation, foliar nutrients, or both into the best soil model significantly improved site index prediction. The resultant models explained up to 83% of the total variance in site index. When stands were stratified according to groundwater influence, regression models developed for three delineated strata were significantly improved compared with unstratified models. Based on practical consideration, four regression models were considered for predicting white spruce site index. Independent testing indicated that the stratified model, which used only soil variables as predictors, predicted white spruce site index with 79% of the estimate errors within 2 m in the study area.

Description: Experiments were conducted using black spruce (Piceamariana (Mill.) B.S.P.) seedlings to evaluate diurnal variability in heat tolerance of roots and shoots and in levels of root heat shock proteins (HSPs). Shoot heat tolerance was significantly lower in the morning than in the afternoon. Similarly, root systems exposed to high temperatures in the morning suffered significantly more damage than those exposed in the afternoon. Root HSPs were identified using an antibody specific for the constitutive HSP73 and inducible HSP72. Both the constitutive levels of root HSPs and the levels of root HSPs following heat shock varied diurnally, and in different patterns for different protein fractions. The levels of soluble and nuclear root HSP72/73 were enhanced by heat shock, both in the morning and afternoon. In comparison, HSP levels in the root mitochondrial protein fractions increased after heat shock in the morning, but decreased after heat shock in the afternoon. HSPs in the root microsomal protein fraction declined following both morning and afternoon heat shock. The higher afternoon levels of root heat tolerance were associated with the greater constitutive levels of HSP73 in the mitochondrial and microsomal root protein fractions in the afternoon. To examine the effects of the shoot on diurnal variation in root system heat tolerance, root heat damage was compared between seedlings with intact shoots versus seedlings with shoots excised either 4–6 h prior to, or immediately before, heat treatment. Regardless of time of day, root systems died when shoots were excised and root systems were treated with high temperatures. In contrast, shoot excision or root heating alone resulted in no root mortality.

Description: The self-thinning rule describes in overcrowded even-aged plant monocultures a consistent relationship of mean mass to the approximately −3/2 power of plant density. Recent analyses revealed cases of statistically significant departures of the exponent from −3/2, confirming earlier suggestions. Shade tolerance, crown structure, and stand conditions have been suggested to influence variation in the self-thinning exponent; however, quantitative relationships of the species' traits to thinning exponent have been unclear. I examined patterns of crown fractal dimension, a quantitative measure of crown structure, and their relationship to the self-thinning exponent in four tree species, Nothofagussolandri var. cliffortioides (Hook. f.) Poole, Pinusbanksiana Lamb., Pinusdensiflora Sieb. et Zucc., and Cryptomeriajaponica (Linn. fil.) D. Don. Only stands at maximum crowding were used for analysis. Crown fractal dimension of monocultures is hypothesized to be a factor determining the species-specific variation in the self-thinning exponent of tree populations and is inversely proportional to the thinning exponent. Species-specific change in foliage packing through development of overcrowded populations is suggested to be closely related to variation in crown fractal dimension and the self-thinning exponent. Implications to possible effects of leaf shape and structural characteristics of crowns to crown fractal dimensions are discussed.

Description: Previous research on chronosequences of even-aged northern hardwood stands has suggested that forest clearing is accompanied by large losses of nitrogen from the forest floor. The timing of the losses and the fate of a large fraction of the lost nitrogen are unclear. The purpose of this investigation was to study these questions through direct measurement of soil nitrogen concentrations and pools through time on an experimental catchment cleared in a whole-tree harvest in 1983–1984. Nitrogen losses from the forest floor at the site, the Hubbard Brook Experimental Forest, New Hampshire, were lower than predictions based on previous research. The mean forest floor nitrogen pool was 17% lower 8 years after clear-cutting of the site (P = 0.18). Predictions based on chronosequence studies suggest that 25–40% of the forest floor nitrogen would be lost after 8 years. Mechanical disturbance during logging may play a role in limiting short-term nitrogen losses. The steep midsection of the catchment experienced the greatest losses of nitrogen and carbon, while pools in the relatively flat spruce-fir zone at the upper elevations were unchanged. Carbon was preferentially lost from soil organic matter, relative to nitrogen, resulting in significant decreases in the C/N and C/organic matter ratios in the soil. The N/organic matter ratio was generally unchanged. Nitrogen losses can be limited after clear-cutting by minimizing organic matter losses and promoting rapid regrowth.

Description: Effect of aluminum (Al) on the growth, anatomy, and nutrient content of eastern white pine (Pinusstrobus L.) was determined by growing newly germinated seedlings for 12 weeks in sand irrigated with nutrient solution (pH 3.8) containing 0, 12.5, 25, 50, 75, or 100 mg/L of Al. To determine the influence of mycorrhizal infection on Al toxicity, half of the seedlings were inoculated with the ectomycorrhizal fungus Pisolithustinctorius (Pers.) Coker & Couch. Across Al concentrations, shoot growth (height, needle length, biomass) but not root growth (lateral root length, biomass) was significantly greater in ectomycorrhizal (ECT) than nonmycorrhizal (NM) seedlings. Aluminum significantly decreased shoot and root growth in ECT and NM seedlings but had less effect on growth in ECT seedlings. Foliar symptoms of Al toxicity (chlorosis, tip necrosis) were more pronounced in NM than in ECT seedlings. Cellular and ultrastructural injury to needles and root meristematic tissues was observed at lower concentrations of Al in NM seedlings than in ECT seedlings. Amelioration of Al toxicity by mycorrhizal colonization appeared to result from enhanced uptake of nutrients, especially P, rather than to reduced uptake of Al.

Description: Ecotone vegetation may be especially sensitive to climate change. In particular, the invasion of subalpine meadows by tree seedlings has been well documented. However, there has been no systematic analysis of tree regeneration across the environmental heterogeneity of the alpine forest–tundra ecotone (FTE). Also, the position of the FTE may be relictual from more favorable climates of the past and therefore unresponsive to changing climate. To assess the environmental controls on FTE tree regeneration, to determine whether the ecotone might be relictual, and to determine whether tree invasion of nonforested FTE areas is occurring, we measured tree regeneration in various environments within the FTE of Rocky Mountain National Park, Colorado. Generally, seedling establishment appears to be controlled by patterns of soil moisture. Little seedling establishment was observed in krummholz openings, except for high seedling densities in willow wetlands. Tree seedling invasion of tundra is rare. Therefore, the upper limits of the FTE in Rocky Mountain National Park may be relictual from more favorable climates of the past. Abundant seedling establishment in patch forest openings suggests that patch forest may be poised to change to closed forest.