College of Agriculture & Natural Resources
Permanent URI for this communityhttp://hdl.handle.net/1903/1598
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Browse
3 results
Search Results
Item DISTRIBUTION AND VARIABILITY OF CARBON STOCKS IN MID-ATLANTIC TIDAL MARSH SOILS(2022) Kim, Jordan; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tidal marsh wetlands have the capacity to store disproportionately large quantities of Cdespite their small areal extent. Good estimations of this “blue C” are now more critical than ever due to implications for the global C cycle and climate change, especially since C storage in tidal marshes has historically been understudied. In this study, we set out to measure, more accurately estimate, and conceptually model the C stocks in representative tidal marshes of the Mid-Atlantic region. We found that C storage differs significantly in marshes formed among various pedogeomorphic settings due to differences in pedogenic processes and soil morphology. Further, we have demonstrated that the mean C densities of particular soil materials can be used in conjunction with soil morphological descriptions to reliably estimate the C stocks in the absence of laboratory data. Finally, we augmented existing concepts of tidal marshes in the region by incorporating newly gained understandings of the spatial changes in morphology and C stocks across marshes within different pedogeomorphic settings.Item Assessing Wetland Restoration on the Delmarva Peninsula using Vegetation Characteristics(2015) McFarland, Eliza Katherine; Baldwin, Andrew H; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With wetland restoration, post-restoration monitoring is essential for determining developmental trajectories, particularly when comparing to natural reference systems. As part of the Mid-Atlantic Conservation Effects Assessment Project, 15 depressional wetlands on the Delmarva Peninsula of Maryland and Delaware were surveyed for above-ground vegetation and seed bank community composition, annual biomass production, and vegetation carbon content (10 restorations from prior-converted cropland (aged 5-31 years), and 5 natural forested depressions). Within each wetland, hydrologic zones (emergent, transition, upland) were also denoted and sampled. Restored wetlands showed more seed bank community similarity to natural wetlands than above-ground vegetation communities. Restorations also produced more annual herbaceous biomass than natural systems, and lower annual leaf litter biomass. After this period of post-restoration development, restored wetlands do not perform vegetation-related functions identical to their natural counterparts; however, these restorations are performing important vegetation-based functions that require yet more time to truly develop.Item Urea Hydrolysis in Soil Profile Toposequences: Mechanisms Relevant to Nitrogen Transport and Water Quality(2014) Fisher, Kristin A.; James, Bruce R.; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urea has been linked to harmful algal blooms in surface waters, but numerous studies of its hydrolysis in agricultural soils have concluded that urea does not persist long enough to be transported to surface waters. This paradox in the published literature may be explained by our lack of knowledge regarding the soil chemical conditions that affect microbial urease activity in surface and subsurface horizons of soil profiles that lie between agricultural fields and surface waters, particularly in sandy Coastal Plain regions. Laboratory studies were conducted to determine the most influential soil chemical characteristics predicting rates of urea hydrolysis in six Maryland soils. Soils were sampled from both the A and B horizons of toposequences consisting of an agricultural field, a grassed field border, and a transitional zone adjacent to surface waters. A pH-adjustment experiment identified soil C and N as important predictors of urea hydrolysis. Analysis of microbial community composition and ureC genes across a toposequence found the greatest abundance of bacteria, fungi, and ureC genes in riparian A horizon soils, despite inhibitory conditions of low pH, low field-sampled moisture content, and high extractable metal concentrations. The high carbon content of A horizon riparian soils likely mediated these toxic characteristics. Of particular note was the significant correlation between ureC genes and rate of urea hydrolysis (r2 = 0.82), indicating that the presence of this gene may be useful as a biomarker for predicting rates of urea hydrolysis in other soils. An investigation into the effects of added C revealed that diverse soil C compounds influenced urea hydrolysis differently. In a 24 hr incubation, ascorbic and gallic acid acted as pro- and antioxidants with both enhancement and inhibition of hydrolysis, depending upon concentration, whereas benzoic and cinnamic acids likely enhanced hydrolysis as a result of being metabolized by soil microorganisms. A better understanding of the mechanisms controlling urea hydrolysis in diverse soils will help researchers and policymakers formulate defensible recommendations related to urea fertilizer and animal waste application so that urea-N can be efficiently used by crops and urea movement across the landscape and into surface waters can be minimized.