Search for: All records

The expansion of many wetland species is a function of both clonal propagation and sexual reproduction. The production of ramets through clonal propagation enables plants to move and occupy space near parent ramets, while seeds produced by sexual reproduction enable species to disperse and colonize open or disturbed sites both near and far from parents. The balance between clonal propagation and sexual reproduction is known to vary with plant density but few studies have focused on reproductive allocation with density changes in response to global climate change.Schoenoplectus americanusis a widespread clonal wetland species in North America and a dominant species in Chesapeake Bay brackish tidal wetlands. Long-term experiments on responses ofS.americanusto global change provided the opportunity to compare the two modes of propagation under different treatments. Seed production increased with increasing shoot density, supporting the hypothesis that factors causing increased clonal reproduction (e.g., higher shoot density) stimulate sexual reproduction and dispersal of genets. The increase in allocation to sexual reproduction was mainly the result of an increase in the number of ramets that flowered and not an increase in the number of seeds per reproductive shoot, or the ratio between the number of flowers produced per inflorescence and the number of flowers that developed into seeds. Seed production increased in response to increasing temperatures and decreased or did not change in response to increased CO₂or nitrogen. Results from this comparative study demonstrate that plant responses to global change treatments affect resource allocation and can alter the ability of species to produce seeds.

 

Abstract. Climate warming perturbs ecosystem carbon (C) cycling, causing both positiveand negative feedbacks on greenhouse gas emissions. In 2016, we began atidal marsh field experiment in two vegetation communities to investigatethe mechanisms by which whole-ecosystem warming alters C gain, viaplant-driven sequestration in soils, and C loss, primarily via methane(CH4) emissions. Here, we report the results from the first 4 years.As expected, warming of 5.1 ∘C more than doubled CH4emissions in both plant communities. We propose this was caused by acombination of four mechanisms: (i) a decrease in the proportion of CH4consumed by CH4 oxidation, (ii) more C substrates available formethanogenesis, (iii) reduced competition between methanogens and sulfate-reducing bacteria, and (iv) indirect effects of plant traits. Plotsdominated by Spartina patens consistently emitted more CH4 than plots dominated bySchoenoplectus americanus, indicating key differences in the roles these common wetland plants playin affecting anaerobic soil biogeochemistry and suggesting that plantcomposition can modulate coastal wetland responses to climate change. 

Coastal marshes are globally important, carbon dense ecosystems simultaneously maintained and threatened by sea‐level rise. Warming temperatures may increase wetland plant productivity and organic matter accumulation, but temperature‐modulated feedbacks between productivity and decomposition make it difficult to assess how wetlands and their thick, organic‐rich soils will respond to climate warming. Here, we actively increased aboveground plant‐surface and belowground soil temperatures in two marsh plant communities, and found that a moderate amount of warming (1.7°C above ambient temperatures) consistently maximized root growth, marsh elevation gain, and belowground carbon accumulation. Marsh elevation loss observed at higher temperatures was associated with increased carbon mineralization and increased microtopographic heterogeneity, a potential early warning signal of marsh drowning. Maximized elevation and belowground carbon accumulation for moderate warming scenarios uniquely suggest linkages between metabolic theory of individuals and landscape‐scale ecosystem resilience and function, but our work indicates nonpermanent benefits as global temperatures continue to rise.