Phenological events are integrative and sensitive indicators of ecosystem processes that respond to climate, water and nutrient availability, disturbance, and environmental change. The seasonality of ecosystem processes, including biogeochemical fluxes, can similarly be decomposed to identify key transition points and phase durations, which can be determined with high accuracy, and are specific to the processes… More

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A long-standing goal of ecology has been to understand the cycling of carbon in forests. This has taken on new urgency with the need to address a rapidly changing climate. Forests serve as long-term stores for atmospheric CO2, but their continued ability to take up new carbon is dependent on future changes in climate and… More

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Net primary productivity (NPP) and net ecosystem production (NEP) are often used interchangeably, as their difference, heterotrophic respiration (soil heterotrophic CO2 efflux, RSH = NPP−NEP), is assumed a near-fixed fraction of NPP. Here, we show, using a range-wide replicated experimental study in loblolly pine (Pinus taeda) plantations that RSH responds differently than NPP to fertilization… More

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Many secondary deciduous forests of eastern North America are approaching a transition in which maturing early successional tree species are declining, resulting in an uncertain future for this century-long carbon (C) sink. We initiated the Forest Accelerated Succession Experiment (FASET) at the University of Michigan Biological Station to examine the patterns and mechanisms underlying forest… More

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Knowing how evapotranspiration (ET) is mediated by abiotic and biotic pathways is essential to understanding how water affects ecosystem productivity. Recent studies have investigated the average transpiration fraction (T/ET) across sites and biomes, but the temporal variability of the partitioning and its controls are less understood. Here, we examine how water availability may regulate the… More

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Whether annual evapotranspiration of native ecosystems is increasing or decreasing with time as CO2 concentrations are rising, the climate is warming and rainfall experiences booms and busts, remains an unanswered question in the field of global change biology. To answer this question, we measured evapotranspiration and carbon dioxide exchange over and under an oak savanna… More

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How, where, and why carbon (C) moves into and out of an ecosystem through time are long‐standing questions in biogeochemistry. Here, we bring together hundreds of thousands of C‐cycle observations at the Harvard Forest in central Massachusetts, USA, a mid‐latitude landscape dominated by 80–120‐yr‐old closed‐canopy forests. These data answered four questions: (1) where and how… More

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Methane flux from freshwater mineral-soil (FWMS) wetlands and its variability among sites is largely modulated by plant-mediated transport. However, plant-mediated transport processes are rarely resolved in land surface models and are poorly parametrized for plants commonly found in FWMS wetlands. Here, relationships between methane flux and CO2 uptake, as well as plant conductance of methane… More

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We test the relationship between canopy photosynthesis and reflected near-infrared radiation from vegetation across a range of functional (photosynthetic pathway and capacity) and structural conditions (leaf area index, fraction of green and dead leaves, canopy height, reproductive stage, and leaf angle inclination), weather conditions, and years using a network of field sites from across central… More

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Wetlands store large C stocks and play important roles in biogeochemical C cycling. However, the effects of environmental and anthropogenic pressures on C dynamics in lower coastal plain forested wetlands in southern U.S. are not well understood. We established four eddy flux stations in two post-harvest and newly-planted loblolly pine (YP2–6, 2–6 yrs old; YP2–8,… More

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