Abstract
Little is known of how hurricane-induced deposition of canopy material onto tropical forest floors influences the soil microbial communities involved in decomposition of these materials. In this study, to identify how soil bacterial and fungal communities might change after a hurricane, and their possible roles in the C and N cycles, soils were collected from five 2000 m2 permanent plots in Lowland, Upland and Riparian primary forests in Costa Rica 3 months before and 7 months after Hurricane Otto damaged the forests. The soil Water, inorganic N and Biomass C increased and total organic C decreased Post-Hurricane, all of which best predicted the changes in the Post-Hurricane soil microbial communities. Post-Hurricane soils from all forest types showed significant changes in community composition of total bacteria, total fungi, and five functional groups of microbes (i.e., degrading/lignin degrading, NH4+-producing, and ammonium oxidizing bacteria, and the complex C degrading/wood rot/lignin degrading and ectomycorrhizal fungi), along with a decrease in richness in genera of all groups. As well, the mean proportion of DNA sequences (MPS) of all five functional groups increased. There were also significant changes in the MPS values of 7 different fungal and 7 different bacterial genera that were part of these functional groups. This is the first evidence that hurricane-induced deposition of canopy material is stimulating changes in the soil microbial communities after the hurricane, involving changes in specific taxonomic and functional group genera, and reduction in the community richness while selecting for dominant genera possibly better suited to process the canopy material. These changes may represent examples of taxonomic switching of functionally redundant microbial genera in response to dramatic changes in resource input. It is possible that differences in these microbial communities and genera may serve as indicators of disturbed and recovering regional soil ecosystems, and should be evaluated in the future.
Highlights
The occurrence of tropical hurricanes are thought to likely be increasing in frequency in the future [1, 2]
The % Water, Biomass C, Biomass C/total organic C (TOC), NH4+ and NO3- were significantly greater, and the total N mass (TN) significantly less in the Post-compared to the Pre-Hurricane soils of all three forest habitats, and the TOC levels were significantly less in the Upland and Riparian Forest Postcompared to Pre-Hurricane samples (S1 Table)
We provide evidence to confirm our predictions that there would be post-hurricane increases in the soil water, inorganic N, Biomass C, and Biomass C/TOC, and increases in the mean proportion of DNA sequences (MPS) values, and changes in the community composition of the general soil bacterial and fungal communities, the specific bacterial groups associated with the N cycle, and the bacterial and fungal groups associated with decomposition of more complex forms of organic C, 7 months after Hurricane Otto hit these jungle sites
Summary
The occurrence of tropical hurricanes are thought to likely be increasing in frequency in the future [1, 2]. Hurricanes cause rapid deposition of significantly large amounts of leaf litter and woody debris from the canopy to the forest floor [4,5,6,7], which results in short to long-term changes to the forest structure and forest ecological processes [4] These processes are critical to forest recovery, and are associated with both the rapid increase in the carbon (C) components and nitrogen (N) nutrients [8,9,10,11] and the subsequent influences to the soil microbiota involved in the dynamic processes of the C and N cycles [12, 13]. Increasing our understanding of these biota would be beneficial in assessing the impacts that land disturbances, including hurricanes, have had on tropical soils, and the efficacy of different restoration practices used in ecosystem recovery
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