Despite substantial changes in climate, sea-ice and glacier extent, and vegetation in much of the Arctic, the area near Toolik Lake, Alaska has experienced no significant trends of increasing temperature, altered precipitation, or increasing active-layer thaw depth. There has been, however, a near doubling of alkalinity in Toolik Lake since 1975 and increases in alkalinity in many lakes of all depths and sizes in the surrounding area. Lake monitoring indicates that in-lake processes such as sulfate or nitrate reduction cannot account for these alkalinity increases.

Much is known about the spatial and temporal distribution of macro-organisms and their activity rates. However, little is known about the spatial variability of microbial communities in lakes. In this study, we examined the spatial variability in both bacterial community composition and activity rates in Toolik Lake, Alaska. Community composition was characterized using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified rDNA, and activity rates were measured by uptake rates of 14C-leucine.

Increased woody plant cover in grasslands is a global phenomenon and a critical threat to conservation of grasslands and their biodiversity. Changes in land management, such as reduced fire frequency, can increase woody plant abundance, while other factors such as increased CO₂ concentration, N deposition, and habitat fragmentation might be contributing factors.

Climate change, insect defoliation, and management practices alter species composition and hence plant water use and catchment water yield.

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.

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.

Seagrass meadows are declining worldwide as a result of nutrient over-enrichment, warming water temperatures, and anthropogenic disturbances. In many areas, restoration projects are attempting to the reverse the trend with varying success. In the Virginia coastal lagoons, seagrasses (Zostera marina) were lost in the 1930’s due to a large hurricane impacting meadows already weakened by the wasting disease. A large-scale restoration effort has been underway since the early 2000’s and has resulted in >1000 acres of seagrass coverage.

The objective of this work was to compare estimates of microbial and biogeochemical processes obtained from year round versus field season only data. We also aimed to capture the response of soils to simultaneous warming and nitrogen fertilization in both winter and summer months. Our research took place at the chronic Soil Warming and Nitrogen Fertilization experiment at the Harvard Forest Long Term Ecological Research site. The experiment includes four treatments in a completely randomized design: control, +heat, +N, and +heat +N.

Long-term data from the Hubbard Brook Experimental Forest show that air temperature has increased by 1-1.5 °C over the last half century. While more variable, annual precipitation has also increased by 19-26% during the same period. These changes in climate influence streamflow, which provides an integrated climate signal that incorporates physical (snowpack, evaporation) and biological (evapotranspiration) responses. Unlike the western United States, water is generally abundant in the Northeast.

This poster outlines molecular analyses of soil fungi within the Bonanza Creek LTER over the last six years. We examined community structure in three studies in mixed upland, black spruce, and white spruce forests. While fungal diversity is extremely high, and we were unable to saturate diversity in one quarter gram of soil with 5000 clone sequences, we were nevertheless able to saturate diversity across the 12 black spruce sites after combing over 2000 soil cores and 30,000 clone sequences.