Differences in Biological Structure and Organic Matter Cycling Between Constructed and Natural Tidal Marshes

Download or read book Differences in Biological Structure and Organic Matter Cycling Between Constructed and Natural Tidal Marshes written by Erin Smyth and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Coastal wetlands, including tidal marshes, impart a wide variety of ecosystem services, including organic matter (OM) production and carbon (C) storage. However, approximately 25% to 50% of the world's vegetated coastal habitat has been destroyed in the past 50 years, representing a massive loss of C-sink capacity. Wetland restoration presents an opportunity to recover this ecosystem function, but significant temporal lags in the restoration of OM production, decomposition, and storage have been recorded for many constructed marshes. The cycling of OM is regulated, in part, by above- and belowground production. It also is regulated by litter decomposition, a microbially-mediated process, yet microbial biomass and community composition often differ between natural and constructed marshes. Decomposition is also controlled by plant litter quality, but little is known about how litter quality differs between constructed and natural marshes. These potential differences in biological structure and ecosystem function between constructed and natural marshes warrant further exploration, as they may have important consequences for OM accumulation and C storage. In this study, I asked: (1) Do constructed marshes and naturally occurring tidal marshes differ in their biological structure, including above- and belowground plant biomass and fungal biomass? and (2) What factors are driving differences in OM decomposition and soil organic matter (SOM) pools between constructed and natural marshes? To answer these questions, I quantified decomposition rates of Juncus roemerianus shoot tissue in one natural and two constructed tidal marshes along the Alabama Gulf Coast. In addition to mass loss, I measured litter quality (C, N, P, lignin), fungal biomass, above- and belowground biomass, and SOM in all three marshes. While shoot litter quality was similar, above- and belowground biomass, fungal biomass on shoot litter, aboveground decomposition rates, and SOM were all greater in the natural marsh than in the constructed marshes. Soil organic C pools in the pine savannas and natural marshes were roughly two and ten times, respectively, of those in the constructed marshes. These results suggest that, while some aspects of biological structure are similar among sites, rates of OM processing and C-storage potential in these constructed marshes have not yet reached functional equivalency with the natural marsh 33 years after their creation, nor are they comparable to the OM stored in the forests from which they were constructed. Even so, estimates of C accumulation rates over the 33-year period since creation are similar to those reported for other coastal wetlands, making marsh construction a potentially beneficial strategy to recover ecosystem services in the long term.