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BELOWGROUND NITROGEN UPTAKE AND ALLOCATION BY SPARTINA ALTERNIFLORA AND DISTICHLIS SPICATA
Citation:
Moore, N., C. Kanaskie, T. Hill, AND A. Oczkowski. BELOWGROUND NITROGEN UPTAKE AND ALLOCATION BY SPARTINA ALTERNIFLORA AND DISTICHLIS SPICATA. New England Estuarine Research Society (NEERS) Fall Meeting, Block Island, RI, October 20 - 22, 2016.
Impact/Purpose:
Our study of belowground nitrogen cycling lends new insight into how uptake could change as environmental changes shift vegetation communities on the marsh platform.
Description:
Anthropogenic nitrogen inputs coupled with rising sea level complicate predictions of marsh stability. As marsh stability is a function of its vegetation, it is important to understand the mechanisms that drive community dynamics. Many studies have examined aboveground dynamics and nutrient cycling, but few have studied the belowground uptake and allocation of nitrogen. Literature suggests that D. spicata may dominate the marsh platform in nutrient-rich conditions, though the mechanism driving the vegetation shift is unclear. Our study examines belowground nutrient uptake and allocation underlying these patterns. To determine whether D. spicata is a more efficient scavenger of nutrients than S. alterniflora we performed a 15N pulse-chase experiment. Tracer was added to mesocosms growing D. spicata and S. alterniflora in monoculture. After the initial pulse, a subset of pots were sacrificed weekly and partitioned into detailed depth intervals for 15N analysis of several belowground pools: live coarse and fine roots, live rhizomes, dead organic matter, and bulk sediment. Comparisons between D. spicata and S. alterniflora uptake and allocation can explain mechanisms of competitive advantage and predictions of D. spicata dominance. Additionally, we used denitrification enzyme assays (DEA) and greenhouse gas slurries to quantify denitrification rates and potentials. Initial results suggest that the vegetation types support similar N-relevant microbial communities. This implies that even if platform vegetation shifts as predicted, changes in nitrogen cycling and ecosystem functioning would be minimal. Our study of belowground nitrogen cycling lends new insight into how uptake could change as environmental changes shift vegetation communities on the marsh platform.