How will anticipated changes in climate interact with grassland plant community composition and diversity to affect the performance of seedlings? We ask this question for two reasons. 1) If plant species are to track spatial shifts in the locations of suitable climatic conditions, plant species must invade communities by means of seedling establishment; more diverse plant communities have been shown to be less invasible, but it is not known how warming will interact with diversity to affect invasion.

Ecosystems worldwide are faced with climate change. In the northeastern United States, climate change is coupled with nitrogen deposition from air pollution. The objective of this study is to determine how soil warming and nitrogen deposition influence species richness, diversity, and abundance of vegetation in a northeastern forest. Our study site is the chronic Soil Warming and Nitrogen Fertilization experiment at the Harvard Forest Long Term Ecological Research site.

A field experiment has been initiated in August 2008 to determine if the vegetation of a coastal marsh is in synchrony with hydrologic conditions that have developed with rising sea-level. The hypothesis being tested is that plant community structure will persist in existing zones of vegetation in the face of sea-level rise unless disturbance provides opportunities for species change under more frequent tidal inundation.

Twenty year record of vegetation change from long-term plots in Alaskan tundra
William A. Gould¹, Joel A. Mercado Diaz^1,2, Jess K. Zimmerman²
1. USDA Forest Service, International Institute of Tropical Forestry, Río Piedras PR,
2. University of Puerto Rico, Río Piedras, PR

This session is intended both for social and biophysical scientists who want to help develop a proposal for the kind of “multi-site, highly collaborative and integrated research initiative” envisioned by the LTER planning group. The focus will be on what the LTER planning process calls the “centerpiece” of the group's conceptual framework, as well as one of “Grand Challenges” to be addressed at the network level – “the dynamics of coupled human-natural ecosystems.”

Plant phenology - the seasonal timing of growth, reproduction, and senescence - can be measured from the scale of individuals to biomes. Understanding the timing of plant canopy development and how it is related to climatic variables is an important step in our understanding of how grassland ecosystems are being altered by a changing climate. In this poster we compare 2 years of plant canopy development in a dry year (2002) and an average precipitation year (2005).

LiDAR (Light Detection and Ranging) has become an important tool for investigating the structure of the earth's surface and vegetation. It permits high vertical and special resolution characterization of ground and vegetation surface heights and structure across large areas. LiDAR has been used to characterize vegetation cover, biomass, leaf area, and basal area for live and dead vegetation. Software is now readily available for 3-D visualization of canopy surfaces.

Species diversity is expected to promote stability in ecosystem functions such as productivity. One mechanism that may contribute to stability is compensatory dynamics. Compensatory dynamics, which occur when an increase in density (biomass) of one species is associated with a decrease in another, are indicated by negative species covariances. These may be driven by competition or negatively correlated species responses to environmental drivers.