Microbial communities associated with distance- and density-dependent seedling mortality in a tropical rainforest
The high levels of diversity within tropical rainforest communities has been linked to non-random patterns of seedling mortality with several studies implicating pathogenic plant–microbe interactions in driving mortality processes. Despite the proposed importance of microorganisms in maintaining rainforest diversity, few studies have investigated soil community dynamics in relation to non-random mortality processes. A mechanistic understanding of microbial processes that help create rainforest diversity is critical for the conservation of these ecosystems. This study investigated microbial community dynamics that may underpin distance- and density-dependent mortality in the long-term forest dynamics plot, Davies Creek, in tropical Far North Queensland using community fingerprinting. We hypothesized that: (1) microbial involvement in distance-dependent seedling mortality would result in an increase in community similarity or the presence of predictor OTUs in conspecific adult tree rhizospheres, relative to physically nearby heterospecifics; (2) on average, plant species identified as having a history of distance dependent seedling mortality would exhibit more similar microbial communities among their conspecific individuals, than those that did not; and (3) dense patches of conspecific seedlings would promote the assembly of distinct soil microbial communities, which may be involved in density-dependent seedling mortality. We found no evidence of rhizosphere community similarity amongst adult plant rhizospheres. However, the presence of densely germinating seedlings altered the soil communities relative to seedling-sparse soils, enriching different OTUs depending on the patch location.
KeywordsJanzen–Connell Rainforest diversity Soil pathogens Tropical
This research was supported by the La Trobe University Securing Food water and Environment Research Focus Area. A.E.F. and J.L.W also received supported from the Defense Science Institute, Office of Naval Research Global (Award No N626909-13–1-N259) AOARD (award FA2386-14–1-4032) and the Australian Research Council Linkage Grants (LP140100459). P.T.G. is also supported by the Long-Term Ecological Research Network.
Experimental designs were conceived by JLW, PTG and AEF. Integration of long-term plant demographic data into microbial community sampling designs was carried out by KEH and PTG. Sample collection was carried out by JLW, PTG and AEF. Soil DNA extraction, Data QC, bioinformatics analysis, trait-based analysis and statistical tests of ARISA and rRNA were performed by JLW. Soil physico-chemical analyses were carried out by CC JV and JLW. Manuscript was drafted by JLW and JLW, KEH, PTG, AEF, CC and JV contributed to the revision and copy-editing of the final manuscript.
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