Large wood drives physical and ecological processes in river systems, but the relative roles of continuous individual tree mortality versus episodes of mass mortality in wood recruitment are not well understood. Here, the 2016 Chimney Tops 2 wildfire, a rare severe wildfire in the eastern United States, was used as a case study for examining the role of mass tree mortality in wood loads of streams in Great Smoky Mountains National Park (GSMNP), Tennessee. Wood surveys were conducted on four reaches in two drainage systems affected by the fire to ascertain the total frequency and volume of burned and unburned wood pieces and jams. Relative to unburned wood, the Chimney Tops 2 fire resulted in a major influx of burned wood to the study reaches, with large percentages of individual pieces (average of 47% by frequency, 48% by volume) and jams (average of 72% by frequency, 93% by volume) exhibiting burn marks. Burned wood pieces had a larger diameter than unburned pieces (p = .065). Results suggest that rare mass‐mortality events like the Chimney Tops 2 wildfire could play a major role in wood dynamics of mountain streams in humid forested regions.
Large wood (LW) has important physical and ecological functions in streams. Riparian vegetation is extensively removed during urban expansion, and urban streams may experience enhanced fluvial transport of LW due to flashy hydrology. In this study, LW loads were assessed for three reaches on North Buffalo Creek, an urban stream located in Greensboro, North Carolina, United States. These three reaches have similar hydrology but different riparian vegetation densities. We measured the frequencies and sizes of both in-channel LW and riparian vegetation across the three reaches. Our results showed that the recently reforested reach had greater LW volume (22.5 m 3 /km) compared to the unmanaged forested site (16 m 3 /km) and the site with low riparian vegetation density (4.78 m 3 /km). The difference in LW frequency among reaches was statistically significant (p ¼ :05). However, the difference in the volume of individual pieces was not significantly different across reaches (p ¼ :84Þ, indicating that a similar size of wood is recruited across the three sites. Our findings also showed that there is a positive relationship between riparian vegetation frequency and in-channel LW frequency, which are significantly related as a power function. Spatial lag models (integrating upstream riparian trees) did not show better results compared to a non-lagged model, suggesting that storage and recruitment were predominantly local and that the LW distribution at our reaches is limited by recruitment rather than dominated by fluvial transport. Our findings suggested that a fully forested watershed is not needed to provide some of the benefits of wood to urban streams.
Despite the fact that it is one of the most sacred and holy rivers in the world, the Ganges River is paradoxically among the most polluted. Over the past decade, researchers have described various mechanisms and actions for improving the pollution problem within the Ganges watershed. The aim of this policy-centric systematic review is to summarize these recommendations to make them more accessible for concerned citizen groups and planners while also critically appraising their findings. Using the Reporting standards for Systematic Evidence Syntheses (ROSES) framework, our findings indicate that there are a wide range of potential solutions for mitigating pollution in the river system that originate from 37 peer-reviewed sources that encompass field studies, modeling analyses, and review articles. While we find that there are many actionable and thoughtprovoking recommendations for improving water quality and pollution mitigation given by authors studying the Ganges, there are also areas for improvement. Notably, there is a heavy focus on state-centric planning in the basin with only a few examples of policies that have been tailored toward encouraging communitybased solutions. This lack of community-based planning may relate to the fact that there is also a missing social dimension to policy recommendations in the Ganges watershed, where most of the articles that we reviewed were published in natural science journals and were not interdisciplinary in nature. Better reporting standards for recommendations arising from reviews and a greater focus on the interrelations between different components of the Ganges system may also yield novel and more trustworthy policy findings for practitioners.
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