The temperate forests of eastern North America support high biodiversity and critical ecosystem functions while providing natural resources and cultural benefits to an expanding human population. The region is shaped by a legacy of landscape change: major shifts in climate, vegetation and disturbance at millennial time scales; extensive deforestation for agriculture in the 17th – 19th centuries; and abandonment of farmlands, natural reforestation and increasing urbanization through the mid-21st century.

Tropical environments are changing fast due to deforestation and regrowth, urbanization, climate change, and other forces. The consequences are immense for the whole array of ecosystem services people require. The Luquillo Long-Term Ecological Research Program (LUQ) is tackling these issues in Puerto Rico. LUQ began in 1988 and focused on natural disturbances (hurricanes, landslides, droughts, floods) and ecosystem response. That work revealed patterns of resistance and resilience to cycles of natural disturbance.

In addition to seed deposition of both native and invasive plant species, birds may pollinate flowers, provide nutrient inputs, and deliver mutualistic or pathogenic microbes. Birds therefore may drive community assembly and succession, and play an especially significant role in the frequently-disturbed environments of barrier islands, where repopulation following storm and overwash events is critical to long-term species persistence.

Rusty crayfish (Orconectes rusticus) are invasive in the upper Midwest United States. They often reach high densities and negatively affect native crayfish species, aquatic macrophytes, benthic invertebrates, and some fish populations. However, in some lakes rusty crayfish do not achieve high densities and do not negatively affect native biota. We conducted a whole-lake experiment designed to remove rusty crayfish from Sparkling Lake, a part of the North Temperate Lakes LTER site in Vilas County, Wisconsin.

Understanding how biotic and abiotic factors combine to affect species interactions is an important challenge in ecology. Because the effects of biotic and abiotic factors on species interactions are often studied separately, it can be difficult to predict potential non-linear and indirect interactions among factors. We manipulated three key biotic and abiotic factors (temperature, food quality, predation) in field experiments in continental grassland using a plant – grasshopper – spider food chain.

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.”

The 2007 Regional report by the Intergovernmental Panel on Climate Change predicted that the central grassland region of North America is very likely to warm substantially during the twenty first century. Modelers are less certain about changes in the timing and amount of precipitation in the region. Our research examines how changes in plant available water will affect critical biological processes in the central grassland region of North America, specifically comparing a site at the Shortgrass Steppe LTER to a site on the mixed grass prairie near Hays, KS.

In tallgrass prairie, annual tiller recruitment occurs primarily from belowground meristems (bud bank) rather than from seed. Therefore, in this system bud banks regulate plant population and community dynamics to a greater extent than seed banks. Current models predict greater variability in precipitation, with larger events and longer dry spells between events for northeastern Kansas. We hypothesize that bud banks mediate plant community response to changing precipitation patterns by differential release of meristems from dormancy and changing the production of new meristems.

Soil microbes are key drivers of ecosystem processes, yet their role in regulating landscape-scale vegetation change is not known. Comprehensive studies of treeline position have noted that ectomycorrhizal fungi may be an important factor delineating the boundary between forest and tundra. Yet, these critical plant-fungal symbioses are sensitive to wildfires. Fire is the primary landscape-scale disturbance in the boreal forest and increasingly important in tundra.

Human activities have increased the amount of available nitrogen (N) globally. Increased N-availability can change plant community structure and function, and lead to diversity loss. Species traits associated with differential resource limitation may predict how plant communities will respond to N-enrichment across ecosystems. We focused on specific leaf area (SLA), leaf area per unit leaf mass, as a candidate trait because it is correlated with high relative growth rates, photosynthetic rates, and leaf N-concentrations.