Abstract
The high diversity of tree species has traditionally been considered an important controller of belowground processes in tropical rainforests. However, soil water availability and resources are also primary regulators of soil bacteria in many ecosystems. Separating the effects of these biotic and abiotic factors in the tropics is challenging because of their high spatial and temporal heterogeneity. To determine the drivers of tropical soil bacteria, we examined tree species effects using experimental tree monocultures and secondary forests at La Selva Biological Station in Costa Rica. A randomized block design captured spatial variation and we sampled at four dates across two years to assess temporal variation. We measured bacteria richness, phylogenetic diversity, community composition, biomass, and functional potential. All bacteria parameters varied significantly across dates. In addition, bacteria richness and phylogenetic diversity were affected by the interaction of vegetation type and date, whereas bacteria community composition was affected by the interaction of vegetation type and block. Shifts in bacteria community richness and composition were unrelated to shifts in enzyme function, suggesting physiological overlap among taxa. Based on the observed temporal and spatial heterogeneity, our understanding of tropical soil bacteria will benefit from additional work to determine the optimal temporal and spatial scales for sampling. Understanding spatial and temporal variation will facilitate prediction of how tropical soil microbes will respond to future environmental change.
Highlights
Soil microbial communities in tropical ecosystems typically are assumed to track plant species and plant diversity [1,2,3,4,5]
There is evidence that tropical soil microbial biomass positively tracks plant richness [3] and community composition of both bacteria [4] and fungi [6] shift when tropical plant diversity is reduced by land use change
We addressed how soil bacteria were affected by tree species and abiotic factors in a wet Neotropical rainforest by sampling soils in experimental monoculture plots of four native trees (Hyeronima alchorneoides, Pentaclethra macroloba, Virola koschnyi, Vochysia guatemalensis) at La Selva Biological Station in Costa Rica [25]
Summary
Soil microbial communities in tropical ecosystems typically are assumed to track plant species and plant diversity [1,2,3,4,5]. There is evidence that tropical soil microbial biomass positively tracks plant richness [3] and community composition of both bacteria [4] and fungi [6] shift when tropical plant diversity is reduced by land use change. Limited soil resources in tropical soils [7] may mean that soil microorganisms rely more on plants for carbon and nutrients via rhizosphere exudation or litter production, which varies among plant species [8,9,10]. In the most comprehensive observational survey to PLOS ONE | DOI:10.1371/journal.pone.0159131. In the most comprehensive observational survey to PLOS ONE | DOI:10.1371/journal.pone.0159131 July 8, 2016
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