Topographic and climatic controls on soil environments and net primary production in a rugged temperate hardwood forest in Korea

Eight years (1994–2001) of field data and a biogeochemical process model, BIOME-BGC, were used to examine effects of local topography and inter-annual climatic variability on soil physical (i.e., soil moisture and temperature) and biogeochemical (i.e., organic matter content, soil respiration, and leaf litter production) variables in a temperate hardwood forest in Korea. The field data were collected from adjacent south-facing (S) and north-facing (N) slopes, respectively, to examine effects of local topography, and were utilized to validate predictability according to BIOME-BGC which was applied to model unmeasured hydro-ecological processes [i.e., evapotranspiration, net primary production (NPP), and net ecosystem exchange of carbon]. Our field-data analyses indicated that soil-related variables including soil temperature, water content, organic matter, soil respiration, and floor leaf litter store significantly differed between the S and N slopes, while leaf litter production did not differ as significantly as the soil-related variables. The BIOME-BGC predictions showed good agreement with the mean field data aggregated across the slopes. Our simulation results and field observations indicated that the inter-annual variations of leaf litter production and maximum leaf area index were best explained by precipitation, both at a 1-year lag, while variation in annual NPP was well correlated with precipitation without a temporal lag. Our results imply that: (1) local topography needs to be explicitly considered in ecosystem studies as a forcing function generating spatial heterogeneity in soil physical and biogeochemical variables within a rugged landscape, and (2) water limits vegetation productivity in our study forest, in spite of a relatively high annual precipitation rate (1,579 mm year^–1).     

Ecological impacts of a widespread frost event following early spring leaf‐out

In the spring of 2010, temperatures averaged ~3 °C above the long‐term mean (March–May) across the northeastern United States. However, in mid‐to‐late spring, much of this region experienced a severe frost event. The spring of 2010 therefore provides a case study on how future spring temperature extremes may affect northeastern forest ecosystems. We assessed the response of three northern hardwood tree species (sugar maple, American beech, yellow birch) to these anomalous temperature patterns using several different data sources and addressed four main questions: (1) Along an elevational gradient, how was each species affected by the late spring frost? (2) How did differences in phenological growth strategy influence their response? (3) How did the late spring frost affect ecosystem productivity within the study domain? (4) What are the potential long‐term impacts of spring frost events on forest community ecology? Our results show that all species exhibited early leaf development triggered by the warm spring. However, yellow birch and American beech have more conservative growth strategies and were largely unaffected by the late spring frost. In contrast, sugar maples responded strongly to warmer temperatures and experienced widespread frost damage that resulted in leaf loss and delayed canopy development. Late spring frost events may therefore provide a competitive advantage for yellow birch and American beech at the expense of sugar maple. Results from satellite remote sensing confirm that frost damage was widespread throughout the region at higher elevations (>500 m). The frost event is estimated to have reduced gross ecosystem productivity by 70–153 g C m^?2, or 7–14% of the annual gross productivity (1061 ± 82 g C m^?2) across 8753 km² of high‐elevation forest. We conclude that frost events following leaf out, which are expected to become more common with climate change, may influence both forest composition and ecosystem productivity.     

High Foliar and Soil Nitrogen Concentrations in Central Appalachian Forests

Regional topography and climate variation yield differences in ecosystem attributes that make spatially scaled estimates of forest productivity challenging. Foliar nitrogen is a primary indicator of forest ecosystem productivity and is used in regional estimates of terrestrial productivity, but this characteristic has not been well described in the Central Appalachian region. Here we describe foliar and soil N variation among species and elevations at two spatial scales in the Central Appalachian region: (1) across the Elklick watershed in the Fernow Experimental Forest and (2) across the state of West Virginia. We found higher foliar N concentrations at both scales than those previously reported for other temperate forest regions. Canopy and soil nitrogen concentrations were also much greater in the Fernow than generally observed across West Virginia. Soil N concentrations in the Fernow were two times greater than those observed across West Virginia. Species-related differences were observed at both spatial scales, but were not always consistent. Canopy N ranges are generally consistent across elevations throughout the state of West Virginia, but should be scaled according to species-related elevation effects for studies that estimate productivity differences in response to harvest or changing species composition. The incongruence of foliar and soil N concentrations at the Fernow Experimental Forest are not explained by elevation or species composition, but are likely a consequence of greater historical N and H⁺ deposition relative to the surrounding West Virginia region.     

Diversity of canopy and understorey spiders in north-temperate hardwood forests

1 We characterized and compared diversity patterns of canopy and understorey spiders (Arachnida: Araneae) on sugar maple ( Acer saccharum Marsh.) and American beech ( Fagus grandifolia Ehrh.) in hardwood forests of southern Québec, Canada.
2 We sampled canopies of 45 sugar maple and 45 American beech trees and associated understorey saplings in mature protected forests near Montréal. Samples were obtained by beating the crown foliage at various heights and by beating saplings around each tree.
3 Eighty-two species were identified from 13 669 individuals. Forty-eight species and 3860 individuals and 72 species and 9809 individuals were collected from the canopy and the understorey, respectively.
4 Multivariate analyses (NMDS ordination and NPMANOVA) showed the composition of canopy and understorey assemblages differed significantly, and canopy assemblages differed between tree species. Rank-abundance distribution models fitted to the canopy and understorey data indicated that different mechanisms structure the assemblages in both habitats. Three abundant spider species were significantly more common in the canopy; ten species were collected significantly more often in the understorey.
5 The forest canopy was shown to be an important reservoir for spider diversity in north-temperate forests.     

Plant recruitment bottlenecks in temperate forest fragments: seed limitation and insect herbivory

Numerous studies have documented declines in plant diversity in response to habitat loss in fragmented landscapes. However, determining the mechanisms that lead to species loss is challenging using solely a correlative approach. Here we link correlative assessments of plant community composition with seed additions for a focal species to test the hypothesis that distributions of forests plants within a fragmented landscape are limited by seed dispersal. Woody plant species richness of fragments declined as fragments (n=26) became more isolated by agricultural fields. We predicted that if these isolation effects were driven by poor dispersal rather than other effects associated with habitat loss, then plants should vary in their response to isolation in relation to their seed size (i.e., stronger effects for plants with larger seeds). As predicted under this dispersal limitation hypothesis, sensitivity of bird-dispersed shrubs to isolation was related to their seed mass, with species with heavy seeds (e.g., Lindera benzoin) exhibiting stronger declines in presence across isolation gradients than species with light seeds. Seed addition experiments were performed for Lindera benzoin in two high isolation forest fragments (nearest neighbor mean distance=803 m) where Lindera was naturally absent, and two low isolation fragments (nearest neighbor mean distance=218 m) with naturally occurring Lindera populations. Seed addition and control plots (n=50 1 m² plots per fragment) were monitored for 13 censuses over 3 years. Across all four fragments, seed additions resulted in significant increases in Lindera seedling recruitment with no differences in final seedling establishment among fragments. However, insect herbivory was higher on Lindera seedlings in high isolation compared to low isolation fragments and was negatively correlated with seedling survival over some years. Consistent with prior work, our results confirm that seed dispersal plays a significant role in affecting plant diversity in fragmented landscapes. However, results also suggest the need for a better understanding of how additional processes, such as herbivory, may be altered as habitat is lost and what effects such changes have for forest plants.     

帽儿山天然次生林20个阔叶树种细根形态

 细根在森林生态系统C分配和养分循环过程中发挥着重要作用。细根形态不但影响养分和水分的吸收, 而且与细根寿命和周转有密切关系。因此, 研究森林树种的细根形态对了解根系结构与功能、预测寿命与周转具有重要理论意义。该文根据细根分枝等级划分方法, 研究了东北帽儿山天然次生林20个阔叶树种1～5级根直径、根长和比根长等形态指标。结果表明, 20个树种中, 除5个树种1级根直径略大于2级和比根长略小于2级根外, 其余15个树种均表现为1级根直径和根长最小、比根长最高, 随着根序增加, 直径和根长增加, 而比根长降低。20个阔叶树种前3级根的累积根长均占前5级根总根长的80%以上。9个内生菌根侵染的树种的平均直径、根长和比根长均大于11个外生菌根侵染的树种。     

Differences in residual lignin properties between Betula verrucosa and Eucalyptus urograndis kraft pulps

By comparing the ultrastructural features of two oxygen delignified hardwood kraft pulps (Eucalyptus urograndis and Betula verrucosa), we have demonstrated a marked difference in their residual lignin properties. In this study, properties such as crystallinity and crystal size of cellulose, molecular weights, carboxyl group contents, and carbohydrate compositions of the two kraft pulps were compared. The examined pulps were in our observations relatively similar. A significant difference, however, was observed in the size exclusion chromatography measurements, which indirectly suggested that a significant portion of residual lignin in eucalyptus pulp was associated with cellulose. Birch pulp, in contrast, exhibited a more conventional tendency for hardwood pulps: lignin mainly associated with hemicelluloses.     

Relationships between vessel element anatomy and physiological as well as morphological traits of leaves in <Emphasis Type="Italic">Fagus crenata</Emphasis> seedlings originating from different provenances

We attempted to observe differences in vessel element anatomy, and physiological and morphological traits of leaves in Fagus crenata seedlings originated from seven different provenances grown under the uniform environmental conditions. We also investigated the relationships between the anatomical characteristics of the vessel elements and physiological plus morphological traits of leaves in Fagus crenata seedlings. To carry out the experiments, Fagus crenata samples were prepared from Chichibu Research Forest of Tokyo University. For anatomical studies of the vessel elements, vessel number per mm², average vessel area, and the percentage of vessel area from the pith to the bark side were measured. We also measured transpiration rate, stomatal conductance, leaf area, leaf thickness, leaf dry mass per unit leaf area and leaf density for foliar studies. The anatomical characteristics of the vessel elements as well as the physiological and morphological traits of leaves were noticeably different among provenances. In addition, we found significant correlations between the foliar characteristics not only with vessel number per mm², but also with vessel area percentage and sum of the (vessel area)², theoretical hydraulic conductivity, from the pith to the bark side. Therefore, we concluded that variations in physiological and morphological traits of leaves in response to provenance variation were in correspondence with vessel number per mm² as a parameter that determines the total vessel area and consequent water hydraulic conductance in Fagus crenata as a diffuse porous hardwood.     

Bioenergy production and forest landscape change in the southeastern United States

Production of woody biomass for bioenergy, whether wood pellets or liquid biofuels, has the potential to cause substantial landscape change and concomitant effects on forest ecosystems, but the landscape effects of alternative production scenarios have not been fully assessed. We simulated landscape change from 2010 to 2050 under five scenarios of woody biomass production for wood pellets and liquid biofuels in North Carolina, in the southeastern United States, a region that is a substantial producer of wood biomass for bioenergy and contains high biodiversity. Modeled scenarios varied biomass feedstocks, incorporating harvest of ‘conventional’ forests, which include naturally regenerating as well as planted forests that exist on the landscape even without bioenergy production, as well as purpose‐grown woody crops grown on marginal lands. Results reveal trade‐offs among scenarios in terms of overall forest area and the characteristics of the remaining forest in 2050. Meeting demand for biomass from conventional forests resulted in more total forest land compared with a baseline, business‐as‐usual scenario. However, the remaining forest was composed of more intensively managed forest and less of the bottomland hardwood and longleaf pine habitats that support biodiversity. Converting marginal forest to purpose‐grown crops reduced forest area, but the remaining forest contained more of the critical habitats for biodiversity. Conversion of marginal agricultural lands to purpose‐grown crops resulted in smaller differences from the baseline scenario in terms of forest area and the characteristics of remaining forest habitats. Each scenario affected the dominant type of land‐use change in some regions, especially in the coastal plain that harbors high levels of biodiversity. Our results demonstrate the complex landscape effects of alternative bioenergy scenarios, highlight that the regions most likely to be affected by bioenergy production are also critical for biodiversity, and point to the challenges associated with evaluating bioenergy sustainability.     

A demographic study of deer browsing impacts on Trillium grandiflorum

When white-tailed deer populations reach high densities, they have negative and often dramatic effects on forest herb populations. However, it is not clear how deer affect the demographic processes of plant populations. We examined how the structure and dynamics of Trillium grandiflorum (Michx.) Salisb. populations are affected by deer browsing in the Upper Great Lakes region by sampling populations from nine study sites in a forested landscape in 1998 and 1999. We constructed a stage-based matrix population model for the regional population. Our model indicated that the long-term growth rate of the population to be –3.56% per year ( = 0.965). Mortality rates were highest for seeds (97.5%) followed by seedlings (29.1%), and lower for all remaining stage classes (4.9 to 8.5%). The observed stage distribution significantly differed from the stable stage distribution, and the damping ratio ( = 1.103) indicated the population would not reach its stable stage distribution anytime soon. In the absence of deer browsing, the long-term growth rate would improve to between –3.46% and –1.61% per year. A moderate drought during the study could account for the negative population growth rate, but deer browsing accelerates the rate of decline. Population growth is most sensitive to the proportion of plants remaining in the nonflowering stage, and deer browsing reduces this proportion. Browsing damage was relatively low in this study (5.4% of stems in 1998, 11.5% in 1999) compared to another study of browsing impacts on T. grandiflorum, indicating deer could have far more severe demographic consequences in populations subject to higher levels of browsing.