Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA, United States of America.
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, United States of America.
PLoS One. 2024 Oct 1;19(10):e0311230. doi: 10.1371/journal.pone.0311230. eCollection 2024.
Processes modifying newly deposited litter substrates should affect fine fuels in fire-managed tidal marsh ecosystems. Differences in chemical composition and dynamics of litter should arise from fire histories that generate pyrodiverse plant communities, tropical cyclones that deposit wrack as litter, tidal inundation that introduces and alters sediments and microbes, and interactions among these different processes. The resulting diversity and dynamics of available litter compounds should affect microbial (fungal and bacterial) communities and their roles in litter substrate dynamics and ecosystem responses over time. We experimentally examined effects of differences in litter types produced by different fire regimes and litter loads (simulating wrack deposition) on microbial community composition and changes over time. We established replicated plots at similar elevations within frequent tidal-inundation zones of a coastal brackish Louisiana marsh. Plots were located within blocks with different prescribed fire regimes. We deployed different measured loads of new sterilized litter collected from zones in which plots were established, then re-measured litter masses at subsequent collection times. We used DNA sequencing to characterize microbial communities, indicator families, and inferred ecosystem functions in litter subsamples. Differences in fire regimes had large, similar effects on fungal and bacterial indicator families and community compositions and were associated with alternate trajectories of community development over time. Both microbial and plant community compositional patterns were associated with fire regimes, but in dissimilar ways. Differences in litter loads introduced differences in sediment accumulation associated with tidal inundation that may have affected microbial communities. Our study further suggests that fire regimes and tropical cyclones, in the context of frequent tidal inundation, may interactively generate substrate heterogeneities and alter microbial community composition, potentially modifying fine fuels and hence subsequent fires. Understanding microbial community compositional and functional responses to fire regimes and tropical cyclones should be useful in management of coastal marsh ecosystems.
新沉积的凋落物基质的过程会影响管理潮汐沼泽生态系统中的细可燃物。凋落物的化学成分和动态差异应源自产生多样植物群落的火灾历史、作为凋落物沉积的碎屑、引入并改变沉积物和微生物的潮汐淹没以及这些不同过程之间的相互作用。可用凋落物化合物的多样性和动态性应影响微生物（真菌和细菌）群落及其在凋落物基质动态和随时间推移的生态系统响应中的作用。我们通过实验研究了不同火灾制度和凋落物负荷（模拟碎屑沉积）产生的凋落物类型差异对微生物群落组成和随时间变化的影响。我们在路易斯安那州沿海咸水沼泽的频繁潮汐淹没区的类似海拔高度建立了重复的地块。地块位于具有不同规定火灾制度的块内。我们部署了从地块中建立的区域收集的不同测量负载的新消毒凋落物，然后在随后的收集时间重新测量凋落物质量。我们使用 DNA 测序来描述凋落物样本中的微生物群落、指示家族和推断的生态系统功能。火灾制度的差异对真菌和细菌指示家族和群落组成有较大的相似影响，并与随时间推移的群落发展的替代轨迹有关。微生物和植物群落组成模式都与火灾制度有关，但方式不同。凋落物负荷的差异引入了与潮汐淹没相关的沉积物积累差异，这可能影响了微生物群落。我们的研究进一步表明，在频繁的潮汐淹没背景下，火灾制度和热带气旋可能会相互作用产生基质异质性并改变微生物群落组成，从而可能改变细可燃物，进而影响随后的火灾。了解微生物群落对火灾制度和热带气旋的组成和功能响应，对于沿海沼泽生态系统的管理应该是有用的。
