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Divergent responses of soil microorganisms to throughfall exclusion across tropical forest soils driven by soil fertility and climate history
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  • Stephany Soledad Chacon,
  • Daniela Cusack,
  • Aizah Khurram,
  • Markus Bill,
  • Lee Dietterich,
  • Nicholas Bouskill
Stephany Soledad Chacon
Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720

Corresponding Author:[email protected]

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Daniela Cusack
Department of Ecosystem Science and Sustainability
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Aizah Khurram
Climate and Ecosystem Sciences Division
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Markus Bill
Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720
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Lee Dietterich
Department of Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO, 80523
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Nicholas Bouskill
1Climate aEcosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720
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Abstract

Model projections predict tropical forests will experience longer periods of drought and more intense precipitation cycles under a changing climate. Such transitions have implications for structure-function relationships within microbial communities. We examine how chronic drying might reshape prokaryotic and fungal communities across four lowland forests in Panama with a wide variation in mean annual precipitation and soil fertility. Four sites were established across a 1000 mm span in mean annual precipitation (2335 to 3300 mm). We expected microbial communities at sites with lower MAP to be less sensitive to chronic drying than sites with higher MAP; while fungal communities to be more resistant to disturbance than prokaryotes. At each location, partial throughfall exclusion structures were established over 10 x 10 m plots to reduce direct precipitation input. After the first nine months of throughfall exclusion, prokaryotic communities showed no change in composition. However, 18 months of throughfall exclusion resulted in markedly divergent prokaryotic community responses, reflecting MAP and soil fertility. We observed the emergence of a “drought microbiome” within infertile sites, whereby the community structure of the experimental drying plots at the lower MAP sites diverged from their respective control sites and converged towards overlapping assemblages. Furthermore, taxa increasing in relative abundance under throughfall exclusion at the highest MAP became more similar to taxa characteristic of the control plots at the lowest MAP site, suggesting a shift toward communities with life-history traits selected 1