Response of Ecosystem Phenology to Anomalous Spring Warmth in the Northeastern United States in 2010

Surface air temperatures were anomalously warm throughout much of the Northern Hemisphere in the spring of 2010. In the northeastern United States, temperatures in the spring of 2010 were among the warmest on record and were consistent with model-based projections of climate change decades from now in this region. The spring of 2010 therefore provides a unique opportunity to explore how the phenology of northeastern temperate forests will change in response to future warming. In this paper, we present results from an analysis of ground-based and satellite-derived measurements of northeastern hardwood forest phenology and air temperatures in 2010. Our study region includes the northern third of the eastern temperate forest ecoregion and embedded higher elevation zones extending from Pennsylvania to Canada, and is bounded by land areas between 38 and 48 degrees north and 65 and 90 degrees west. Data used for the analysis include daily near surface air temperatures collected at National Weather Service Cooperative Weather Service sites distributed throughout the region, time series of satellite derived vegetation indices from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS), data collected from webcams using the PhenoCam Network, and observations of plant phenology collected at field sites located within the study region. Our results show pronounced and unprecedented changes in the spring phenology of forests through the region caused by anomalously warm spring temperatures in 2010. Both satellite-based and ground measurements show onset of spring leaf development that is 10-15 days early relative to climatic average conditions. Results from this analysis provide insight into the sensitivity of temperate forest ecosystems to climate change, which in turn has significant implications for ecosystem function, composition, and regional biosphere-atmosphere interactions.