Impact of Agricultural Practices on Bacterial Carbon Use Efficiency
Z. M. Lee and T. M. Schmidt
Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI

Iron (Fe) is abundant among trace elements in forest ecosystems and important in the development and function of soils. We constructed a biogeochemical budget for Fe to better understand the behavior of Fe and its role in the development of Spodosols (podsolization). Fluxes of reduced (ferrous, Fe(II)) and oxidized (ferric, Fe(III)) iron draining through the soil profile were calculated.

Many ecosystems, including grassland, forest, alpine, and desert, have shown responses to N enrichment. These responses vary considerably but include changes in soil respiration rates, enzyme activities, and microbial community structure. Surprisingly, little work has examined the effects of N enrichment on soil communities and processes in agricultural systems despite the high rates of N applied in most crop production systems.

With recent shifts in public attitudes across the United States concerning the problem of global climate change, momentum is building for aggressive action to mitigate greenhouse gas emissions. At the same time, the ongoing economic recession presents challenges for financing an aggressive climate change abatement campaign; hence, it is imperative that cost-effective strategies for reducing greenhouse gas emissions be identified and pursued. To accomplish this, policy instruments will need to be tailored to a complex range of local and regional conditions.

Macroalgae and phytoplankton support highly productive coastal marine ecosystems. Research based on stable isotope analyses has supported the idea that macroalgal detritus, especially that of giant kelp Macrocystis, is a major source of dietary carbon to benthic suspension feeders.

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.

The PAL study area encompasses a 200 x 500 km region extending from the nearshore coastal zone heavily influenced by seasonal sea ice cover to the open Southern Ocean, and from a northern area where sea ice cover is now limited to only the colder winters, to the south where perennial sea ice cover persists into summer months. In this region, primary production is dominated by unicellular phytoplankton and limited by light availability to the October-April period. The region is characterized by spring phytoplankton blooms that have declined by up to 90% in the northern region since 1978.

Biologically-mediated carbon export transports carbon from the sunlit surface layers into the ocean's interior where it can be sequestered for centuries.  It is a process mediated primarily by plankton ecology, particularly the phytoplankton that fix inorganic carbon and zooplankton that either rerespire it or repackage it into larger particles.  On a cruise in the CCE, we tracked parcels of water for four-day "cycles" during which we measured carbon flux and biological rates while measuring net changes to the plankton community.  These experimental cycles provided

The structure of zooplankton communities has a significant impact on vertical flux of organic material and cycling of elements in the sea, thus climate-induced changes in zooplankton abundance and species composition have the potential to dramatically affect biogeochemical cycles. The West Antarctic Peninsula (WAP) is one of the most rapidly warming regions on Earth, with documented changes in temporal and spatial distribution of the zooplankton community, and in annual peak organic particle export as measured by sediment traps.

The Luquillo Long Term Ecological Research Program (LUQ) focuses on understanding factors driving long-term change in tropical forest ecosystems in the Luquillo Mountains. To increase our understanding of biotic and abiotic controls on ecosystems, we extended our work from the tabonuco forest to a range of forest types occurring along a climatic and forest gradient in the Luquillo Mountains.