Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily—and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have… More

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Humans have altered the global and regional cycles of nitrogen more than any other element. Alteration of N cycling patterns and processes in forests is one potentially negative outcome of accelerated N deposition worldwide. To assess potential impacts of N deposition on temperate forests, a series of chronic nitrogen additions in two contrasting forest types… More

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Abandonment and reforestation of agricultural lands has been a major influence on the landscape of eastern North America. Cultivation and soil amendments can dramatically alter soil nutrient pools and cycling, yet few studies have examined the long-term (>50 yr) influence of pasturing and cultivation on soil processes in the forests that develop after abandonment. Twelve… More

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We examine the atmospheric budget of CO2 at temperate continental sites in the Northern Hemisphere. On a monthly time scale both surface exchange and atmospheric transport are important in determining the rate of change of CO2 mixing ratio at these sites. Vertical differences between the atmospheric boundary layer and free troposphere over the continent are… More

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Future climate change is expected to affect ecosystem-atmosphere CO2 exchange, particularly through the influence of temperature. To date, however, few studies have shown that differences in the response of net ecosystem CO2 exchange (NEE) to temperature among ecosystems can be explained by differences in the photosynthetic and respiratory processes that compose NEE. Using a new… More

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Carbon (C) exchange of a ∼200-year-old eastern hemlock (Tsuga canadensis L.) forest in central Massachusetts, USA, was estimated from mid-October 2000 through October 2001 based on eddy covariance measurements and statistical modeling from microclimatic data. Measurements were made in 68% of the hours during the year of study, with > 50% coverage in all months… More

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