Collaborative Research: Long-term Studies of Forest Dynamics: Analysis of Seedling and Sapling Populations

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Disturbance is nearly ubiquitous in ecological systems. Consequently, succession, the process of recovery from disturbance, is responsible for much variation in ecosystem structure and function. The primary objective of this research is to understand the process of succession, and the investigators assert that most successional changes in community-level properties and processes can best be understood as resulting from population processes. Although permanent plots are commonly used to examine the dynamics of mature trees, seedling and sapling dynamics remain virtually unstudied, simply because appropriate data have not been available. With the support of the National Science Foundation Long-term Research in Environmental Biology (LTREB) program, the investigators have collected seedling and sapling data from permanent plots in numerous types and ages of forests with observations ranging up to 13 years. Consequently the investigators are uniquely positioned to examine the dynamics of seedlings and saplings as related to succession and site characteristics. The LTREB dataset will be used to address questions related to the dynamics of seedlings and samplings such as the following: (1) How do seedling and sapling establishment, growth, and survival vary with succession and site conditions? (2) Is seedling-seedling competition significant? We suspect that competition with canopy trees controls seedling dynamics, except in canopy gaps, but if seedling interactions are important they will need to be added to forest simulation models. (3) Do canopy trees differentially inhibit conspecific seedlings and saplings? This is a popular hypothesis, largely untested in temperate forest. (4) Can year-to-year climatic variation explain co- existence of similar tree species? Again, this a popular but untested hypothesis. (5) Does seedling vigor change during succession in a fashion consistent with existing models of changing canopy-derived competition (see Peet and Christensen 1987)? This research will provide a unique perspective on successional patterns from a population standpoint.