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A range of environmental factors regulate tree growth; however, climate is generally thought to most strongly influence year-to-year variability in growth. Numerous dendrochronological (tree-ring) studies have identified climate factors that influence year-to-year variability in growth for given tree species and location. However, traditional dendrochronology methods have limitations that prevent them from adequately assessing stand-level (as opposed to species-level) growth. We argue that stand-level growth analyses provide a more meaningful assessment of forest response to climate fluctuations, as well as the management options that may be employed to sustain forest productivity. Working in a mature, mixed-species stand at the Howland Research Forest of central Maine, USA, we used two alternatives to traditional dendrochronological analyses by (1) selecting trees for coring using a stratified (by size and species), random sampling method that ensures a representative sample of the stand, and (2) converting ring widths to biomass increments, which once summed, produced a representation of stand-level growth, while maintaining species identities or canopy position if needed. We then tested the relative influence of seasonal climate variables on year-to-year variability in the biomass increment using generalized least squares regression, while accounting for temporal autocorrelation. Our results indicate that stand-level growth responded most strongly to previous summer and current spring climate variables, resulting from a combination of individualistic climate responses occurring at the species- and canopy-position level. Our climate models were better fit to stand-level biomass increment than to species-level or canopy-position summaries. The relative growth responses (i.e., percent change) predicted from the most influential climate variables indicate stand-level growth varies less from to year-to-year than species-level or canopy-position growth responses. By assessing stand-level growth response to climate, we provide an alternative perspective on climate-growth relationships of forests, improving our understanding of forest growth dynamics under a fluctuating climate.

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Understanding the movement and storage of carbon in forests and other natural systems has long been a central goal of ecology (Gosz et al., 1978;Whittaker et al., 1974). This understanding is complicated today by rapid changes in the climate, biochemical environment, and disturbance regime in which ecosystems operate. At the same time, natural systems can play prominent roles in absorbing atmospheric CO 2 and thus reducing the impacts of present and past emissions (Pan et al., 2011).

Worldwide, forest plants and fungi that are harvested for their nontimber products are critical for the health of the ecosystems and the well-being of people who benefit from the harvest. This document provides an analysis of the volumes and values of nontimber forest products in the United States. It presents estimates of the annual harvest for a number of product categories over five regions for the United States. Data for the analysis comes from records of harvest permits and contracts issued by the U.S. National Forests and Bureau of Land Management, other Federal agencies, as well as several industry sources. The data illustrate that nontimber forest products represent significant contributions to the country's economy. The total value of the receipts from the issuance of permits and contracts to harvest nontimber forest products from Federal lands was estimated at $8.4 million in 2013. Estimated wholesale value of these products in that year was over $950 million. Total wholesale value, adjusted for trade, including firewood, posts and poles, and Christmas trees, was estimated at over $1 billion in 2013. There are challenges with reporting the full value of these products, but the framework to do so is improving.