multi-year lags between forest browning and soil respiration at high northern latitudes多年滞后之间的森林布朗宁和土壤呼吸在北半球高纬度.pdfVIP

Multi-Year Lags between Forest Browning and Soil Respiration at High Northern Latitudes 1 2 1 Ben Bond-Lamberty *, Andrew G. Bunn , Allison M. Thomson 1 Pacific Northwest National Laboratory, Joint Global Change Research Institute at the University of Maryland–College Park, College Park, Maryland, United States of America, 2 Department of Environmental Sciences, Huxley College, Western Washington University, Bellingham, Washington, United States of America Abstract High-latitude northern ecosystems are experiencing rapid climate changes, and represent a large potential climate feedback because of their high soil carbon densities and shifting disturbance regimes. A significant carbon flow from these ecosystems is soil respiration (RS, the flow of carbon dioxide, generated by plant roots and soil fauna, from the soil surface to atmosphere), and any change in the high-latitude carbon cycle might thus be reflected in RS observed in the field. This study used two variants of a machine-learning algorithm and least squares regression to examine how remotely-sensed canopy greenness (NDVI), climate, and other variables are coupled to annual RS based on 105 observations from 64 circumpolar sites in a global database. The addition of NDVI roughly doubled model performance, with the best-performing models explaining ,62% of observed RS variability. We show that early-summer NDVI from previous years is generally the best single predictor of RS, and is better than current-year temperature or moisture. This implies significant temporal lags between these variables, with multi-year carbon pools exerting large-scale effects. Areas of decreasing RS are spatially correlated with