Twenty Years of Ecosystem Research on Temperate Forest Succession at the Blandy Experiment Farm in Northwestern Virginia

Abstract:

Secondary succession resulting from land-use conversion is widespread across ecosystems globally. Whereas conceptual models describe the trajectories of vegetation dynamics, and carbon and nutrient cycling, throughout the process of secondary succession, empirical data are limited with regard to testing these models, largely given the timeframes necessary to observe ecosystem changes. Here we review findings from twenty years of ecosystem succession research within a temperate forest system, using “space-for-time” chronosequences of post-cultivation recovery, at the Blandy Experimental Farm (BEF) field station in northwestern Virginia. The BEF has two separate chronosequences of three fields each (early, middle, and late succession) that developed following years of agricultural use. Data collected since 2000 across numerous doctoral dissertations, masters theses, and undergraduate projects include (but are not limited to) vegetation composition, leaf area index (LAI), normalized difference vegetation index (NDVI); CO₂, water, and energy exchanges (flux tower); soil carbon and nitrogen, soil respiration, nitrogen mineralization and nitrification rates; and micrometeorology (e.g. soil temperature and moisture). Collectively, our findings indicate that 1) Community-level properties, such as LAI and NDVI can recover rather rapidly (order of 10 years), whereas soil C and N are close to their prior values after 30+ years; however, distance from the nearest forest edge is a dominant controlling factor, 2) Ecosystem carbon source peaked in the first two years following agricultural abandonment and switched from a source to a sink sometime between 5 and 19 years; dynamics of soil respiration are driven by opposing controls of decreasing soil temperatures and increasing soil organic matter and roots throughout succession, 3) Whereas total soil N has not increased significantly during succession, both soil C:N ratio and foliar N have increased; N mineralization and nitrification rates have not changed significantly with succession, however, they appear to be more spatially variable in late succession. These studies conducted at the BEF over a twenty-year period have added to our knowledge, and provided data to evaluate conceptual models, of succession in temperate forest ecosystems.