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Fungal communities are primary decomposers of detritus, including coarse woody debris (CWD). We investigated the succession of fungal decomposer communities in CWD through different stages of decay in the wide-ranging and early successional tree species Populus grandidentata (bigtooth aspen). We compared shifts in fungal communities over time with concurrent changes in substrate chemistry and in bacterial community composition, the latter deriving from an earlier study of the same system. We found that fungal communities were highly dynamic during the stages of CWD decay, rapidly colonizing standing dead trees and gradually changing in composition until the late stages of decomposed wood were integrated into soil organic matter. Fungal communities were most similar to neighboring stages of decay, with fungal diversity, abundance, and enzyme activity positively related to percent nitrogen, irrespective of decay class. In contrast to other studies, we found that species diversity remained unchanged across decay classes. Differences in enzyme profiles across CWD decay stages mirrored changes in carbon recalcitrance, as B-D-xylosidase, peroxidase, and Leucyl aminopeptidase activity increased as decomposition progressed. Finally, fungal and bacterial gene abundances were stable and increased, respectively, with the extent of CWD decay, suggesting that fungal-driven decomposition was associated with shifting community composition and associated enzyme functions rather than fungal quantities. 

Low elevation coastal zones (LECZ) are extensive throughout the southeastern United States. LECZ communities are threatened by inundation from sea level rise, storm surge, wetland degradation, land subsidence, and hydrological flooding. Communication among scientists, stakeholders, policy makers and minority and poor residents must improve. We must predict processes spanning the ecological, physical, social, and health sciences. Communities need to address linkages of (1) human and socioeconomic vulnerabilities; (2) public health and safety; (3) economic concerns; (4) land loss; (5) wetland threats; and (6) coastal inundation. Essential capabilities must include a network to assemble and distribute data and model code to assess risk and its causes, support adaptive management, and improve the resiliency of communities. Better communication of information and understanding among residents and officials is essential. Here we review recent background literature on these matters and offer recommendations for integrating natural and social sciences. We advocate for a cyber-network of scientists, modelers, engineers, educators, and stakeholders from academia, federal state and local agencies, non-governmental organizations, residents, and the private sector. Our vision is to enhance future resilience of LECZ communities by offering approaches to mitigate hazards to human health, safety and welfare and reduce impacts to coastal residents and industries. 

Abstract Sea level rise and changes in precipitation can cause saltwater intrusion into historically freshwater wetlands, leading to shifts in microbial metabolism that alter greenhouse gas emissions and soil carbon sequestration. Saltwater intrusion modifies soil physicochemistry and can immediately affect microbial metabolism, but further alterations to biogeochemical processing can occur over time as microbial communities adapt to the changed environmental conditions. To assess temporal changes in microbial community composition and biogeochemical activity due to saltwater intrusion, soil cores were transplanted from a tidal freshwater marsh to a downstream mesohaline marsh and periodically sampled over 1 year. This experimental saltwater intrusion produced immediate changes in carbon mineralization rates, whereas shifts in the community composition developed more gradually. Salinity affected the composition of the prokaryotic community but did not exert a strong influence on the community composition of fungi. After only 1 week of saltwater exposure, carbon dioxide production doubled and methane production decreased by three orders of magnitude. By 1 month, carbon dioxide production in the transplant was comparable to the saltwater controls. Over time, we observed a partial recovery in methane production which strongly correlated with an increase in the relative abundance of three orders of hydrogenotrophic methanogens. Taken together, our results suggest that ecosystem responses to saltwater intrusion are dynamic over time as complex interactions develop between microbial communities and the soil organic carbon pool. The gradual changes in microbial community structure we observed suggest that previously freshwater wetlands may not experience an equilibration of ecosystem function until long after initial saltwater intrusion. Our results suggest that during this transitional period, likely lasting years to decades, these ecosystems may exhibit enhanced greenhouse gas production through greater soil respiration and continued methanogenesis.