Montane Temperate-Boreal Forests Retain the Leaf Economic Spectrum Despite Intraspecific Variability

Trait-based analyses provide powerful tools for developing a generalizable, physiologically grounded understanding of how forest communities are responding to ongoing environmental changes. Key challenges lie in (1) selecting traits that best characterize the ecological performance of species in the community and (2) determining the degree and importance of intraspecific variability in those traits. Recent studies suggest that globally evident trait correlations (trait dimensions), such as the leaf economic spectrum, may be weak or absent at local scales. Moreover, trait-based analyses that utilize a mean value to represent a species may be misleading. Mean trait values are particularly problematic if species trait value rankings change along environmental gradients, resulting in species trait crossover. To assess how plant traits (1) covary at local spatial scales, (2) vary across the dominant environmental gradients, and (3) can be partitioned within and across taxa, we collected data on 9 traits for 13 tree species spanning the montane temperate—boreal forest ecotones of New York and northern New England. The primary dimension of the trait ordination was the leaf economic spectrum, with trait variability among species largely driven by differences between deciduous angiosperms and evergreen gymnosperms. A second dimension was related to variability in nitrogen to phosphorous levels and stem specific density. Levels of intraspecific trait variability differed considerably among traits, and was related to variation in light, climate, and tree developmental stage. However, trait rankings across species were generally conserved across these gradients and there was little evidence of species crossover. The persistence of the leaf economics spectrum in both temperate and high-elevation conifer forests suggests that ecological strategies of tree species are associated with trade-offs between resource acquisition and tolerance, and may be quantified with relatively few traits. Furthermore, the assumption that species may be represented with a single trait value may be warranted for some trait-based analyses provided traits were measured under similar light levels and climate conditions

Effects of eastern hemlock removal on nutrient cycling and forest ecosystem processes at the MacLeish Field Station, Whately, MA

The loss of foundation species as a result of environmental change or exotic species invasions can alter community composition and ecosystem function. The spread of hemlock woolly adelgid (Adelges tsugae) in eastern North America that threatens the survival of eastern hemlock (Tsuga canadensis), a foundation species, and has also motivated pre-emptive logging efforts. In the northeastern United States, ecological succession following hemlock loss will eventually produce a deciduous hardwood forest, a change in forest type that might produce significant changes in ecosystem processes, such as nutrient cycling and decomposition. Comparisons between mature deciduous forests and mature hemlock forests have been used to predict future structure and function of forests affected by hemlock removal. Consequently, little is known about nutrient cycling in the several decade span of intermediate stages in forest succession, especially in early-successional forests dominated by black birch (Betula lenta) that replace mature hemlock forest in the northeastern United States. This study used a paired-plot design to compare throughfall chemistry, litterfall, litter decomposition, and soil chemistry in adjacent mature hemlock forest and young black birch forest patches from which hemlocks were logged in the late 1980s at the MacLeish Field Station in Whately, MA to investigate effects of hemlock removal after twenty years. Deposition of most ions in throughfall was greater in the hemlock forest than black birch forests (p \u3c 0.05), implying that canopy structure and tree physiology have a strong influence on throughfall, more so that foliar chemistry alone. Decomposition rates of black birch and hemlock litter did not differ between forest types (p \u3e 0.05), suggesting that changes in microclimate may not influence decomposition rates as much as changes in litter type would. Net nitrification rates and cation exchange capacity of the young black birch forest did not differ from the mature hemlock forests, whereas net nitrification rates and base saturation were higher in a mature deciduous reference plot. These results suggest that the early-successional forests that have replaced hemlock at this site do not yet resemble mature deciduous forests in terms of nutrient cycling characteristics, which suggests that it may take many decades before nutrient cycling in regrowth forests resembles that in deciduous forests

Changes in mass, carbon, nitrogen and phosphorus in logs decomposing for 30 years in three Rocky Mountain coniferous forests

Estimates of decomposition rates of coarse woody debris (CWD) and fluxes of nutrients therein are essential components of C and nutrient budget models. In a 30-year field experiment, we periodically measured mass remaining and nutrient concentrations in log segments of pine, spruce and fir in natural, mature coniferous forests in Alberta, Canada. The predicted turnover times (t95; years) were 43-44 years for pine, 42-60 years for spruce and 38-46 years for fir. Extrapolating from best-fit models, we predict that decomposition of these logs would be complete within 50 â 60 years. C:N declined for most of the decomposition period and ratios of the three species converged atThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Improving uncertainty in forest carbon accounting for REDD+ mitigation efforts

Reductions in atmospheric concentrations of greenhouse gases are urgently needed to avoid the most catastrophic consequences of warming. Reducing deforestation and forest degradation presents a climate change mitigation opportunity critical to meeting Paris Agreement goals. One strategy for decreasing carbon emissions from forests is to provide developing countries with results-based financial incentives for reducing deforestation: nearly two billion dollars are currently committed to finance such programs, referred to as REDD+ (Reducing Emissions from Deforestation and forest Degradation, conservation, sustainable management of forests, and enhancement of forest carbon stocks). Countries participating in these programs must document the uncertainty in their estimates of emissions and emission reductions, and payments are reduced if uncertainties are high. Our examination of documentation submitted to date to the United Nations Framework Convention on Climate Change (UNFCCC) and the Forest Carbon Partnership Facility (FCPF) reveals that uncertainties are commonly underestimated, both by omitting important sources of uncertainty and by incorrectly combining uncertainties. Here, we offer recommendations for addressing common problems in estimating uncertainty in emissions and emission reductions. Better uncertainty estimates will enable countries to improve forest carbon accounting, contribute to better informed forest management, and support efforts to track global greenhouse gas emissions. It will also strengthen confidence in markets for climate mitigation efforts. Demand by companies for nature-based carbon credits is growing and if such credits are used for offsets, in exchange for fossil fuel emissions, it is essential that they represent accurately quantified emissions reductions.ISSN:1748-9326ISSN:1748-931