Subalpine Fir Forest Research Articles

Soil biochemical dynamics at three elevations during the soil thawing period, Eastern Tibetan Plateau: Nutrient availabilities, microbial properties and enzyme activities

Studies during last decade have established that soil microbial biomass, enzyme activity and nutrient pools in some cold regions often keep relatively high level in winter and drop rapidly when soil temperatures approach and exceed 0°C during winter-spring transitional period. However, the inconsistent results were observed in different ecosystems due to various temperature dynamics. Based on previous observations on nutrient dynamics, soil microbial biomass, enzyme activity and soluble carbon and nitrogen were investigated in the highly humified soils of subalpine and alpine fir (Abies faxoniana) forests along an altitude gradient in the Eastern Qinghai–Tibet Plateau every 10 days from 5 March until 25 April, 2009, including the winter-spring transitional period. Soil temperature significantly changed during the soil thawing period with frequent soil temperature fluctuations around 0°C. Microbial biomass sharply increased as soil thawing proceeded until an obvious peak when soil temperatures rise to 0°C. Thereafter, microbial biomass declined during the thawing period when soil temperatures exceeded 0°C. Likewise, the rapid crashed in the soluble organic nutrient pools occurred shortly before or coincident with the microbial biomass dropped as soil temperature fluctuated close to 0°C. Meanwhile, the sudden decline in enzyme activity occurred just before the soluble organic nutrient pools collapsed. Additionally, the dynamic patterns of microbial biomass, enzyme activity and soluble organic substrate varied with altitudes due to different temperature fluctuations. The results indicate that the release of nutrients as microbial biomass decline might represent an important pulse of carbon and nutrients pools for vegetation growth in the early stage of growing season. Key words: Subalpine and alpine forest, temperature dynamics, soil microbial biomass, soil enzyme activity, soluble organic substrate, soil thawing period.

Seasonal variations in leaf δ13C and nitrogen associated with foliage turnover and carbon gain for a wet subalpine fir forest in the Gongga Mountains, eastern Tibetan Plateau

AbstractIt is still unclear to what extent variations in foliar δ13C and nitrogen can be used to detect seasonal changes in canopy productivity. We hypothesize that in a wet and cloudy fir forest, seasonally higher litterfall and lower leaf area index (LAI) are correlated with higher mass‐based leaf nitrogen (Nmass) and net primary productivity (NPP), while foliar δ13C may change with specific leaf area (SLA), area‐based leaf nitrogen (Narea), and/or starch concentration. In order to test our hypotheses, stand‐level litterfall and the means of δ13C, Nmass, Narea, SLA, and starch concentration of canopy needles for a wet and cloudy Abies fabri forest in the Gongga Mountains were monthly measured during the growing season. Seasonal estimates of LAI were obtained from our previous work. A conceptual model was used to predict seasonal NPP of the fir forest. Seasonal mean δ13C and Nmass and climatic variables were used as inputs. The δ13C across 1–7‐year‐old needles increased from May to September associated with decreasing SLA and increasing Narea. There were no significant differences in seasonal starch concentration. With increasing litterfall and decreasing LAI, seasonal mean Nmass increased, while the δ13C varied little. The simulated NPP increased with increasing litterfall and related traits of Nmass and Narea. Our data generally supported the hypotheses. The results also suggest that in the forest with relatively moist and cloudy environment, the largest fraction of annual carbon gain may occur in the early part of the growing season when higher litterfall results in higher Nmass of canopy leaves.

Age structure and regeneration of subalpine fir (Abies fargesii) forests across an altitudinal range in the Qinling Mountains, China

Age structure and regeneration dynamics of subalpine fir (Abies fargesii) forest were studied across the altitudinal range in both the north and south aspects of the Qinling Mountains, China. Ages of individual fir trees were determined based on the number of rings counted from cores and the number of years to reach coring height estimated using age–height regression. Fir age structure and regeneration dynamics were similar in both the north and south aspects. A unimodal population age structure was found at the low- and mid-elevations in both aspects, indicating that environmental factors might play an important role in shaping A. fargesii age structure and regeneration at those sites. There was a recruitment pulse during the time period 1830–1890 at each altitudinal site, but no stem recruitment occurred at the low- and mid-elevations in the last century, which might be attributed to the intensive cover of understory bamboo. Fir trees were, however, persistently recruited at the upper limits during the last 150 years, and the fir tree density at the upper limits was significantly higher than that at the lower limits in both aspects. The fir population at the upper limits showed a significant increase in recruitment and stem density relative to the fir population at the low- and mid-elevations in the last century. We propose that the differences in recruitment might promote variations in stand structure and regeneration dynamics of the subalpine fir forests along the altitudinal gradient in the Qinling Mountains, China.

Small-mammal response to group-selection silvicultural systems in Engelmann spruce – subalpine fir forests 14 years postharvest

Concerns about the impacts of clear-cut harvesting on ecosystem components in subalpine forests have generated a variety of alternative silvicultural systems in high-elevation forests in western North America. We examined responses of forest-floor small mammals, 14 years posttreatment, in four replicate units, uncut forest, a 1.0 ha group-selection cut, a large (>30 ha) clearcut, and the edge between the group-selection cut and uncut forest, in the Engelmann Spruce ( Picea engelmannii Parry ex Engelm.) – Subalpine Fir ( Abies lasiocarpa (Hook.) Nutt.) biogeoclimatic zone in south-central British Columbia, Canada. Populations of small mammals were livetrapped during five sessions from June to September 2006. The mean abundance of southern red-backed voles ( Myodes gapperi Vigors) was significantly lower on large clearcuts than in uncut old-growth forests, with intermediate numbers in 1 ha cuts. The opposite trend was found for dusky shrews ( Sorex monticolus Merriam), while there was no significant difference in mean abundance of deer mice ( Peromyscus maniculatus Wagner) among treatments. Trappability, proportion of adult females breeding, and rate of survival of red-backed voles and deer mice were similar among treatments. Our results suggest that group-selection silviculture conducted in subalpine forests may have fewer negative impacts on the small-mammal community than large clearcuts.

Dendroecological study of a subalpine fir (Abies fargesii) forest in the Qinling Mountains, China

Dendroecological techniques were used to investigate the stand dynamics and the disturbance history of the subalpine fir forest in the Qinling Mountains of Shaanxi Province, China. The results indicated that 68% of the fir trees experienced 1–2 release events for a total of 10–29 (an average of 15.8) years, and 1–2 suppression events for a total of 10–27 (an average of 13.4) years before they reached canopy. Large number of Abies fargesii and Betula albo-sinensis recruitment coincided temporally with larger increases in the ring-width index from the 1830s to 1880s, suggesting occurrence of a major stand-wide disturbance during this time period. Few seedlings and saplings were found in the forest, and there was a dramatic decline in recruitment after 1890, probably because of the intensive cover of understory umbrella bamboo (Fargesia spathacea). Radial growth analyses indicated frequent canopy opening resulting from small-scale disturbances in the forest. Thus, the subalpine fir forest experienced frequent small-scale disturbances and infrequent large-scale disturbances in its developmental history, and these disturbances coupled with the understory umbrella bamboo might have influenced tree growth and species recruitment.

Habitat Fragmentation and the Persistence of Lynx Populations in Washington State

Abstract Lynx (Lynx canadensis) occur in the northern counties of Washington state, USA; however, current distribution and status of lynx in Washington is poorly understood. During winters 2002–2004 we snow-tracked lynx for 155 km within a 211-km2 area in northern Washington, to develop a model of lynx–habitat relationships that we could use to assess their potential distribution and status in the state. We recorded movements and behaviors of lynx with a Global Positioning System and overlaid digitized lynx trails on various habitat layers using a Geographic Information System. Based on univariate analyses, lynx preferred Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) forests, with moderate canopy and understory cover, and elevations ranging from 1,525 m to 1,829 m but avoided Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) forests, openings, recent burns, open canopy and understory cover, and steep slopes. A map of suitable lynx habitat based on a logis...

Habitat Conditions Associated With Lynx Hunting Behavior During Winter in Northern Washington

Effectively managing habitat for threatened populations of Canada lynx (Lynx canadensis) requires knowledge of habitat conditions that provide for the ecological needs of lynx. We snow-tracked lynx to identify habitat conditions associated with hunting behavior and predation during winters of 2002–2003 and 2003–2004 in the northern Cascade Range in Washington state, USA. We recorded number and success of predation attempts, prey species killed, and trail sinuosity on 149 km of lynx trails. Lynx killed snowshoe hares (Lepus americanus), red squirrels (Tamiasciurus hudsonicus), and cricetids more than expected in Englemann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) forests, where snowshoe hare densities were highest. Lynx killed prey less than expected in Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) forests and forest openings. We used the sinuosity of lynx trails as an index of quality of habitat hunted. Lynx trails that included predation attempts were more sinuous than trail segments without predation attempts. Lynx trails had greater sinuosity in forest stands with high hare densities dominated by Engelmann spruce and subalpine fir than in stands with low hare densities dominated by Douglas-fir and ponderosa pine or in forest openings. We encourage forest managers to maintain or create sufficient understory cover to support high densities of snowshoe hares as foraging habitat for lynx.

Holocene vegetation and fire regimes in subalpine and mixed conifer forests, southern Rocky Mountains, USA

Our understanding of the present forest structure of western North America hinges on our ability to determine antecedent forest conditions. Sedimentary records from lakes and bogs in the southern Rocky Mountains of Colorado and New Mexico provide information on the relationships between climate and vegetation change, and fire history since deglaciation. We present a new pollen record from Hunters Lake (Colorado) as an example of a high-elevation vegetation history from the southern Rockies. We then present a series of six sedimentary records from ~2600 to 3500-m elevation, including sites presently at the alpine–subalpine boundary, within the Picea engelmannii–Abies lasiocarpa forest and within the mixed conifer forest, to determine the history of fire in high-elevation forests there. High Artemisia and low but increasing percentages of Picea and Pinus suggest vegetation prior to 13 500 calendar years before present (cal yr BP) was tundra or steppe, with open spruce woodland to ~11 900 cal yr BP. Subalpine forest (Picea engelmannii, Abies lasiocarpa) existed around the lake for the remainder of the Holocene. At lower elevations, Pinus ponderosa and/or contorta expanded 11 900 to 10 200 cal yr BP; mixed conifer forest expanded ~8600 to 4700 cal yr BP; and Pinus edulis expanded after ~4700 cal yr BP. Sediments from lake sites near the alpine–subalpine transition contained five times less charcoal than those entirely within subalpine forests, and 40 times less than bog sites within mixed conifer forest. Higher fire episode frequencies occurred between ~12 000 and 9000 cal yr BP (associated with the initiation or expansion of south-west monsoon and abundant lightning, and significant biomass during vegetation turnover) and at ~2000–1000 cal yr BP (related to periodic droughts during the long-term trend towards wetter conditions and greater biomass). Fire episode frequencies for subalpine–alpine transition and subalpine sites were on average 5 to 10 fire events/1000 years over the Holocene, corresponding to one fire event every ~100 to 200 years. (5) Our Holocene-length sedimentary charcoal records provide additional evidence for the anomalous nature of the 20th-century fire regime, where fires were largely suppressed as a national policy.

Effects of simulated elevated concentration of atmospheric CO 2 and temperature on soil enzyme activity in the subalpine fir forest

Little is known about the responses of the activities of soil enzymes that are related to mass cycle to simulated climate change. Therefore, 72 intact soil columns from the primary fir ( Abies faxoniana Rehder & E. H. Wilson) forest were parked in environment-controlled chambers with the CK (outside ambient CO 2 concentration and temperature), EC (elevated concentration CO 2 with (347.1 ± 22.1) μmol·mol −1), ET (elevated temperature with (2.4 ± 0.4)°C), and ECT (elevated CO 2 concentration with (352.8 ± 27.6) μmol·mol −1 and temperature with (2.2 ± 0.5)°C) treatments, and the activities of invertase, urease, nitrate reductase and acid phosphatase, which are related to the cycles of carbon, nitrogen and phosphorus in mineral soil (MS) and organic layer (OL) were measured simultaneously to understand the responses of these enzymes to climate change. Significant monthly variations on the activities of the studied enzymes were found in both OL and MS with the highest enzyme activities in summer, which were of ecological significance for soil nutrient availability and tree nutrition in the subalpine forest ecosystem. Different monthly patterns of enzyme activities were attributed to enzyme sources and soil layer. EC treatment had influenced slightly on the activities of the studied enzymes resulting from the higher CO 2 concentration in soil atmosphere and no indirect effect from the EC owing to a lack of trees planted on soils. ET treatment increased enzyme activities in comparison with the CK treatment because ET was beneficial to microbial growth and propagation. The increments of the enzyme activities in OL were higher than those in MS, implying that OL is more sensitive to climate change. ECT treatment sharply increased enzyme activities in comparison with the EC and CK, but there was no significant difference between ET and ECT, which was also attributed to no indirect effect by EC treatment owing to trees not planted on soils, implying that the increment of enzyme activities resulted from the temperature effect. However, further studies on indirect effect and complex effect on soil enzyme activity caused by EC, ET and ECT are needed to understand the soil enzyme responses to the climate change.

Forest Fires and Old-Growth Forest Abundance in Wet, Cold, Engelmann Spruce – Subalpine Fir Forests of British Columbia, Canada

The amounts of old-growth forest present under current and pre-harvesting era disturbance regimes in the dominant higher elevation (900–2300 m) forests in eastern British Columbia (B.C.) – wet cold Engelmann spruce (Picea engelmannii Parry ex Engelm.) - subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forests (ESSFwc), and one important group of ESSFwc forests, the Northern Monashee (ESSFwc2) biogeoclimatic variant – were quantified using a GIS forest age database, with the assumption that oldgrowth forests were forests >140 years old. This was done in order to inform natural disturbance based management in this part of British Columbia. Database constraints restricted the analysis to the post 1800 period only and resulted in estimation of a range of old growth for any time period. The oldest trees in old-growth forests do not necessarily indicate when the forests were last disturbed by fire, as 14C dating of charcoal indicated that, for two of five 210- to 320-year old stands sampled, the most recent fire event probably occurred over 1000 years ago. The amount of old growth in both ESSFwc and ESSFwc2 forests, since 1800, decreased to a minimum in the mid to late 1800s, then increased. In the case of the ESSFwc2, this increase occurred until the 1960s before the amount of old growth decreased again. Amounts of old growth in 2003 (58–59% of the forested area) were within the pre-harvesting era range of 30–60% in ESSFwc2 forests, but may be above the range of 20–50% in ESSFwc forests. Old-growth forests have dominated most subalpine landscapes in eastern B.C. for at least the last several decades. If management of ESSFwc forests is to emulate historical disturbance regimes, greater protection of old-growth ESSFwc forests than at present will be necessary.

A hierarchical analysis of stand structure, composition, and burn patterns as indicators of stand age in an Engelmann spruce – subalpine fir forest

We studied the relationship between observed fire effects and stand age in a recently burned subalpine Engelmann spruce ( Picea engelmannii Parry ex. Engelm.) – subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) forest in New Mexico. We installed a network of variable-radius plots to assess stand structure, and cored 379 trees to measure the spatial patterns of the stand ages with respect to fire boundaries. We found that pre-fire stand age and stand mortality were not significantly related at either of two spatial scales (p ≤ 0.33 and p ≤ 0.26). We also found that stand structure and stand composition were poor indicators of stand age. The random effects terms of a linear mixed-effects model revealed substantial heterogeneity in stand structure and composition with respect to age at fine spatial scales. Discussions of the factors contributing to stand-replacing fires in subalpine Engelmann spruce – subalpine fir forests might be improved by focusing on traits that are more reliably linked to fuel characteristics, rather than on the age of the stands.

Arboreal forage lichen response to partial cutting of high elevation mountain caribou range in the Quesnel Higland of east-central British Columbia

Group selection silvicultural systems have been recommended for managing mountain caribou (Rangifer tarandus caribou) habitat in high elevation Engelmann spruce – subalpine fir forests in east-central British Columbia. We measured the response of arboreal lichen (a key winter forage) to harvesting of 30% of the forested area using three partial cutting treatments, which created small (0.03 ha), medium (0.13 ha), and large (1.0 ha) openings, and a no-harvest treatment. Treatments were replicated on four sites, and monitored over a ten year post-harvest period. The short-term loss of lichen associated with removal of approximately one third of the trees was partially offset by a significant (P=0.01) increase in lichen abundance on trees in the caribou feeding zone (up to 4.5 m) in the three partial cutting treatments relative to trees in the uncut forest. Differences among treatments in the change in lichen composition, as measured by the percentage of Alectoria sarmentosa and Bryoria spp., were marginally significant (P=0.10). The partial cutting treatments showing a greater likelihood of shifting towards more Bryoria spp. than no-harvest treatment (P=0.04). In the year of harvest (1993), larger trees were found to hold more lichen than smaller trees (P=0.04), and live trees supported more lichen than dead trees (P=0.01), but lichen loading was similar among tree species (P=0.51). Tree fall rates were similar among treatments, based on the ten year average (0.6–0.8% of sample trees per year). The results indicate that caribou foraging habitat is maintained in the residual forest when group selection systems that remove only 30% of the trees are applied. Information on the distribution of lichen is useful for developing stand level prescriptions. Providing lichen bearing habitat meets just one of the needs of caribou. A comprehensive approach that considers all factors and their interactions is essential to maintain and recover the threatened mountain caribou.

Arboreal forage lichens in partial cuts – a synthesis of research results from British Columbia, Canada

The mountain ecotype of the woodland caribou (Rangifer tarandus caribou) is highly dependent on the arboreal hair lichens Bryoria spp. and Alectoria sarmentosa during winter. In parts of British Columbia, partial-cutting silvicultural systems have been used in an effort to provide continuously usable winter habitat for mountain caribou, while allowing some timber removal. We reviewed available information about the changes in hair lichens after partial cutting in Engelmann spruce (Picea engelmannii) – subalpine fir (Abies lasiocarpa) forests of British Columbian and Idaho. Generally, abundance of Bryoria spp. in the lower canopy of individual residual trees increases with increased exposure after partial cutting, until the new regeneration begins to shelter the lower canopy of the residuals. Heavy basal area removal, however, results in low lichen availability at the stand level for many years. Abundance of Bryoria on the regeneration is low, and appears to be limited largely by the structure of the young trees, not by lichen dispersal, although dispersal capability may be limiting in Alectoria. Both distributional and physiological data suggest that Bryoria is intolerant of prolonged wetting, and that increased ventilation, rather than increased light, accounts for enhanced Bryoria abundance in the partial cuts. Alectoria sarmentosa reaches its physiological optimum in the lower canopy of unharvested stands; its growth rates are somewhat reduced in the more exposed environment of partial cuts. Both genera are capable of rapid growth: over a 7-year period, individual thalli of A. sarmentosa and Bryoria spp. (excluding those with a net biomass loss due to fragmentation) in an unlogged stand more than tripled their biomass. Calculated growth rates, as well as dispersal potential, are influenced by fragmentation. Bryoria produces more abundant, but smaller, fragments than Alectoria, and fragmentation in both genera increases in partial cuts. In subalpine mountain caribou habitat, partial-cutting prescriptions that enhance exposure of residual trees while keeping basal area removal low will maintain forage best. Regeneration management should focus on maintaining ventilation in the lower canopy of the residual stand.

The influence of variable snowpacks on habitat use by mountain caribou

Mountain caribou (Rangifer tarandus caribou) in southeastern British Columbia subsist for most of the winter on arboreal hair lichen, mostly Bryoria spp. Foraging occurs mainly in old subalpine fir (Abies lasiocarpa) forests near treeline. Here, the lower limit of Bryoria in the canopy is dictated by snowpack depth because hair lichens die when buried in snow. Bryoria is often beyond the reach of caribou in early winter, prompting caribou to move downslope to where lichen occurs lower in the canopy and other foraging modes are possible. Snowpacks are normally deep enough by late winter that caribou can reach Bryoria where it is most abundant, at high elevations. Extending this to inter-annual comparisons, Bryoria should be less accessible during late winter of low-snow years following normal winters, or of normal to low-snow years after deep-snow winters. We hypothesized that when maximum snowpack in late winter is low relative to the deepest of the previous 5 years, mountain caribou will use lower elevations to facilitate foraging (“lichen-snow-caribou” or LSC hypothesis). We tested this with late-winter data from 13 subpopulations. In the dry climatic region generally and for minor snowfall differences in wet and very wet regions, caribou did not shift downslope or in fact were at higher elevations during relatively low-snow years, possibly reflecting the ease of locomotion. The LSC hypothesis was supported within wet and very wet regions when snowpacks were about 1 m or more lower than in recent years. Elevation declined by 300 m (median) to 600 m (25th percentile) for snowpack differences of at least 1.5 m. Greater use of lodgepole pine and western hemlock stands sometimes also occurred. Management strategies emphasizing subalpine fir stands near treeline should be re-examined to ensure protection of a broader range of winter habitats used by caribou under variable snowpack conditions.

Moisture Distribution Changes and Wetwood Behavior in Subalpine Fir Wood during Drying Using High X-Ray Energy Industrial CT Scanner

In some species, such as subalpine fir (Abies lasiocarpa [Hook] Nutt), the water content of the confined zones in heartwood is as high as or greater than that of sapwood. Such wet zones of heartwood are referred to as “wetpocket” or “wetwood.” Wood products from subalpine fir forests are adversely affected by the wetwood-associated problems, particularly during the drying process. The objectives of the study were as follows: (1) to investigate feasibility of a high X-ray energy industrial computed tomography (ICT) scanner for imaging wetwood; and (2) to determine changes of the 2-D and 3-D moisture profiles (from core to shell) at different drying times. Although medical CT scanning has been used for attaining signal intensity profiles of typical wood at different drying times, the technology has not, to date, been used for the study of wetwood phenomenon. This study presents, for the first time, results from the ICT imaging of the wetwood phenomenon. The results indicate that the ICT imaging system provides a powerful technique for imaging wetwood at different drying times. In addition, the results show that during the initial phase of drying, almost flat moisture profiles were observed in all wood types except for the wetwood, which showed a relatively higher moisture profile. A much slower (sluggish) drying development pattern at each increment from core to shell was found within the wetwood zone than normal wood regions along the width, thickness, and length of the board.

Performance of planted Engelmann spruce and subalpine fir seedlings in British Columbia's southern mountains

We compared survival and growth of planted seedlings of Engelmann spruce and subalpine fir across a range of harvest opening sizes (> 10 ha, 1 ha, 0.2 ha, 0.1 ha, 0.03 ha and individual tree selection) from three silvicultural systems trials in high-elevation spruce – subalpine fir forests in south-central British Columbia. Climatic patterns and growing season air and soil temperatures were similar across sites. Seedling survival decreased with opening size. Local site climates, influenced by aspect and moisture and air drainage, were more influential than elevation. Seedling growth was best in large openings and similar in opening sizes from 1 ha to 0.1 ha. Smaller openings created by group selection and individual tree selection methods were not favourable for successful planting at elevations close to timberline. The two species had similar absolute and relative growth rates but spruce responded more strongly to better growing environments. Key words: planted seedlings, Engelmann spruce, Picea engelmannii Parry ex Engelm., subalpine fir, Abies lasiocarpa (Hook.) Nutt., opening size, elevation effects, silvicultural systems, British Columbia, mountain forests

The significance of precipitation and substrate chemistry for epiphytic lichen diversity in spruce-fir forests of the Salish Mountains, northwestern Montana

The relevance of chemical site factors for the abundance of epiphytic lichens was studied in Picea engelmannii- Abies lasiocarpa forests of the Salish Mountains, northwestern Montana, USA. The Salish Mountains are an area with relatively low atmospheric pollutant load and low precipitation. Canonical correspondence analysis (CCA) suggests that cover of several lichen species was limited by high Mn concentrations of bark or by high ratios of Mn to Ca, Mg and Fe. Mn in the bark is known primarily to derive from the soil. An effect of Mn concentration or Mn/Ca and Mn/Mg ratios was not found on A. lasiocarpa. This suggests that A. lasiocarpa deposits Mn in the bark in a physiologically inactive form as already known from A. balsamea. Precipitation chemistry was apparently less relevant for epiphytic lichen distribution in the Salish Mountains, as no correlations between element concentrations in stemflow and cover values were found and as amounts of stemflow were small. However, precipitation in the study year was less than average. The lacking significance of precipitation chemistry is probably the cause why epiphytic lichen vegetation differed less between living and dead trees in the Salish Mountains than in highly polluted coniferous forests studied by our group in Germany; in Germany, the difference between living and dead trees was attributed to reduced interception of pollutants from the atmosphere by trees with reduced crown surface. The result of the present study that small-scale variation of epiphytic lichen abundance is only partly explainable by chemical parameters gives rise to the assumption that microclimate (e.g., moisture), which has not been systematically explored, could be an important site factor for epiphytic lichens in the Salish Mountains. Furthermore, tree age was identified by CCA as a relevant site factor for lichens on P. engelmannii.

Epiphytic lichen diversity on dead and dying conifers under different levels of atmospheric pollution

Based on literature data, epiphytic lichen abundance was comparably studied in montane woodlands on healthy versus dead or dying conifers of Europe and North America in areas with different levels of atmospheric pollution. Study sites comprised Picea abies forests in the Harz Mountains and in the northern Alps, Germany, Picea rubens– Abies balsamea forests on Whiteface Mountain, Adirondacks, New York, U.S.A. and Picea engelmannii– Abies lasiocarpa forests in the Salish Mountains, Montana, U.S.A. Detrended correspondence analysis showed that epiphytic lichen vegetation differed more between healthy and dead or dying trees at high- versus low-polluted sites. This is attributed to greater differences in chemical habitat conditions between trees of different vitality in highly polluted areas. Based on these results, a hypothetical model of relative importance of site factors for small-scale variation of epiphytic lichen abundance versus atmospheric pollutant load is discussed.

Effects of Snow Avalanche Disturbance on Regeneration of Subalpine Abies mariesii Forest, Northern Japan

We examined the effects of snow avalanche on stand structure and the subsequent regeneration of subalpine Abies mariesii Mast forest in northern Japan, and discussed whether gap formation after avalanche disturbance leads to immediate seedling establishment or not. Tree size and age, tree-ring chronology, and seedling density were compared between, on, and around a relatively large avalanche path, which was created in the mid-1980s within Hachimantai National Park. On the avalanche path, only smaller and younger trees (height <5 m, 50–100 yr old) escaped the mechanical damage of avalanche by leaning into the remaining snowpack, and old canopy trees were mostly killed by stem breakage. Tree size structure of the avalanche path, including both living and dead individuals, was relatively similar to that of nearby undisturbed forest, indicating that a mature stand (>ca. 200 yr old) had been previously developed on the avalanche slope without large-scale disturbances in the past. Most of the surviving, younger trees showed abrupt growth release during the few years (1987–1989) after the avalanche event. However, densities of both post-avalanche (<15 yr old) and pre-avalanche (≥15 yr old) seedlings were much lower on the avalanche path than in the nearby forest, especially at microsites covered with dense dwarf bamboo (Sasa kurilensis) shrub. The pre-avalanche seedlings on the avalanche path sharply increased annual height growth rates after the mid-1980s avalanche, but such positive growth response did not continue longer than 6 to 7 yr. These findings suggested that gap formation following the infrequent, large-scale avalanche disturbance did not necessarily lead to immediate seedling recruitment and/or further growth release of pre-avalanche seedlings. The constraint of seedling establishment was primarily explained by the lack of potential seed supply, and shading effect of the dwarf bamboo bush. Consequently, post-avalanche regeneration of the subalpine fir forest was likely to depend on the smaller individuals (2–5 m in height) that were able to avoid both the mechanical damage of avalanche and mortality from shading by the dwarf bamboo.

Analytical methods for defining stand–clearcut edge effects demonstrated for N mineralization

Edge effects are becoming an important forest management consideration, but information regarding the influence of edges on N cycling variables has not been well documented. In addition, the quantification of edge effects can benefit from the application of complementary spatial analysis methods. Forest floor N mineralization and environmental variables were intensively measured 5 years after harvest along transects crossing the north and south edges of a 1-ha clearcut, in a high-elevation Engelmann spruce – subalpine fir forest. Wavelet analysis and depth-of-edge influence (DEI) methods were used to locate and measure the spatial extent of edge effects on N mineralization. Then variance partitioning (partial redundancy analysis) was used to examine the influence of edges on N mineralization relative to the influence of other environmental factors. Initial NO3-N content and net nitrification markedly increased in the opening within 2–6 m of each edge. Net ammonification did not exhibit obvious edge-related spatial patterns. Spatial patterns of nitrification appeared to be more closely related to spatial changes in substrate quality than to soil temperature and moisture. Results of the wavelet and DEI analyses provided quantification of locations and functional extents of edge effects.