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Ecologists have long been intrigued by the ways co-occurring species divide limiting resources. Such resource partitioning, or niche differentiation, may promote species diversity by reducing competition. Although resource partitioning is an important determinant of species diversity and composition in animal communities, its importance in structuring plant(More)
Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2), is important to primary production, water quality, and the chemistry and physics of the atmosphere at ecosystem, landscape, regional, and global scales. Unfortunately, this process is very(More)
Ammonia-oxidizing bacteria (AOB) play an important role in nitrogen cycling in estuaries, but little is known about AOB diversity, distribution and activity in relation to the chemical and physical changes encountered in estuary systems. Although estuarine salinity gradients are well recognized to influence microbial community structure, few studies have(More)
Plant species collected from tundra ecosystems located along a north-south transect from central Alaska to the north coast of Alaska showed large and consistent differences in 15N natural abundances. Foliar δ15N values varied by about 10% among species within each of two moist tussock tundra sites. Differences in 15N contents among species or plant groups(More)
Abundance of ammonia-oxidizing Archaea (AOA) was found to be always greater than that of ammonia-oxidizing Bacteria along an estuarine salinity gradient, and AOA abundance was highest at intermediate salinity. However, AOA abundance did not correlate with potential nitrification rates. This lack of correlation may be due to methodological limitations or(More)
The relationship between ammonia-oxidizing bacteria (AOB) and potential nitrification rates was examined along a salinity gradient in a New England estuary in spring and late summer over 3 years. Ammonia-oxidizing bacteria abundance was estimated by measuring gene copies of the ammonia monooxygenase catalytic subunit (amoA) using real-time polymerase chain(More)
Dynamic transformations of iron occur seasonally at Great Sippewissett Marsh, Massachusetts. Small changes in the dissolved iron concentration in porewater represent only a small fraction of the iron involved in transformation reactions during the year. During the growing season, salt marsh grasses oxidize the sediment, and a large percentage of sedimentary(More)