Regime shifts from grasslands to shrublands in arid and semiarid ecosystems are thought to be irreversible, similar to state changes in other systems. We analyze long-term data from the Jornada Basin LTER site to determine if a directional change in climate provides an opportunity to reverse this conversion in the Chihuahuan Desert. We compare historical dynamics based on 140 years of landscape change (1858-1998) with 18 years (1990-2007) of detailed ecosystem responses under a variable climate to predict future responses under either a directional increase or decrease in rainfall.

It is currently clear that both soil nutrient availability and consumers influence plant communities and that these factors may interact in interesting ways. However, the relative strengths of these factors and their interactions in terrestrial systems are still unclear. My goal is to generalize the relative impacts of nutrient availability and consumer control and their interactive effects on grassland communities across the precipitation gradient of the Great Plains, from shortgrass steppe through tallgrass prairie.

Patterns of phenology for plants and animals control ecosystem processes, determine land surface properties, control biosphere-atmosphere interactions, and affect food production, health, conservation, and recreation. Although phenological data and models have applications related to scientific research, education and outreach, agriculture, tourism and recreation, human health, and natural resource conservation and management, until recently there was no coordinated effort to understand phenology at the national scale.

The barrier islands of the Virginia Coast Reserve LTER site provide an opportunity to study interisland variability of dune plant communities. Our research focused on the variation in biomass and diversity of communities among islands and dune positions. Grassy dunes of young, intermediate and old age were sampled on Smith, Hog, and Parramore Islands. Above- and belowground biomass were obtained from harvest plots and roots were extracted from cores. Data were also collected on depth to groundwater and total soil nitrogen.

The goal of this workgroup is to continue discussions initiated at an EcoTrends working group meeting held in April 2009. The goal of the group is to develop synthetic products based on the long term ANPP and species richness datasets in the EcoTrends database as well as other sources of information. The ANPP and richness data and figures in EcoTrends consist of simple temporal trends over time. Theory predicts a hump-shaped relationship between species richness and ANPP over space, and a positive relationship between species richness and NPP within a site, up to some asymptotic value.

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.

Phenology is a critical aspect of nearly all ecological phenomena and processes. We propose a brain storming workgroup to take the next step in coordinating phenology monitoring and research across the LTER Network. The inspiration for this working group proposal has its roots in the 2006 ASM working group, the 2007 Sevilleta Workshop and the 2007 AGU Fall Meeting (see working group material). The paper by Henebry et al. 2007, "A White Paper on Phenology across LTER",  provides overview, background, and potential starting points for this session.