Effects of Saltwater Pulses on Soil Microbial Enzymes and Organic Matter Breakdown in Freshwater and Brackish Coastal Wetlands (original) (raw)
Related papers
Biogeochemistry, 2011
The impact of salt-water intrusion on microbial organic carbon (C) mineralization in tidal freshwater marsh (TFM) soils was investigated in a year-long laboratory experiment in which intact soils were exposed to a simulated tidal cycle of freshwater or dilute salt-water. Gas fluxes [carbon dioxide (CO2) and methane (CH4)], rates of microbial processes (sulfate reduction and methanogenesis), and porewater and solid phase biogeochemistry were measured throughout the experiment. Flux rates of CO2 and, surprisingly, CH4 increased significantly following salt-water intrusion, and remained elevated relative to freshwater cores for 6 and 5 months, respectively. Following salt-water intrusion, rates of sulfate reduction increased significantly and remained higher than rates in the freshwater controls throughout the experiment. Rates of acetoclastic methanogenesis were higher than rates of hydrogenotrophic methanogenesis, but the rates did not differ by salinity treatment. Soil organic C content decreased significantly in soils experiencing salt-water intrusion. Estimates of total organic C mineralized in freshwater and salt-water amended soils over the 1-year experiment using gas flux measurements (18.2 and 24.9 mol C m−2, respectively) were similar to estimates obtained from microbial rates (37.8 and 56.2 mol C m−2, respectively), and to losses in soil organic C content (0 and 44.1 mol C m−2, respectively). These findings indicate that salt-water intrusion stimulates microbial decomposition, accelerates the loss of organic C from TFM soils, and may put TFMs at risk of permanent inundation.
2009
Soil microbial activity and diversity are affected by organic sources applied to improve soil quality and fluctuate seasonally. We investigated the effects of municipal compost (MC), poultry litter (PL), and cover crops of spring oats and red clover (RC) on soil enzyme activities, and soil bacterial community-level physiological profiling (CLPP) in a Mexico silt loam in North Central Missouri, USA. Temporal patterns of these parameters were observed by periodic five soil sampling from spring to fall over a two year period. MC increased soil dehydrogenase (DH) activity consistently beginning about three months after MC application; fluorescein diacetate (FDA) hydrolytic activity significantly began to increase by the September of the first year but fluctuated during the following period. DH activity responded more directly to the amount or properties of organic residues in soils while FDA hydrolysis and CLPP were generally influenced by composition of organic sources, and enzyme acti...
2011
MICROBIAL COMMUNITY FUNCTION IN FRESHWATER WETLAND SOILS: USING EXTRACELLULAR ENZYME ANALYSIS TO STUDY THE EFFECT OF MOISTURE AND VEGETATION By Aaron J. Porter, M.S. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Studies at Virginia Commonwealth University Virginia Commonwealth University, 2011 Major Director: Rima B. Franklin, Assistant Professor, VCU Department of Biology Differences in microbial community function via extracellular enzyme activity (EEA) were investigated to determine the effects of hydrology and plant-soil-microbe interactions in a young non-tidal freshwater riparian wetland. This was accomplished by establishing three plots along a moisture gradient at the VCU Rice Center; within each, five subplots were undisturbed while another five were cleared of all above-ground plant biomass each week for two years. Every eight weeks, soil cores (top 10 cm) were analyzed for pH, redox, carbon to nitrogen r...