Meta-Analysis Reveals Consistent Bacterial Responses to Land Use Change Across the Tropics

Ian A B Petersen,Brendan J M Bohannan,Kyle M Meyer

doi:10.3389/fevo.2019.00391

Ian A B Petersen, Brendan J M Bohannan + Show 1 more

Open Access

https://doi.org/10.3389/fevo.2019.00391

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Abstract

Bacterial communities are a major component of global diversity and are intimately involved in most terrestrial biogeochemical processes. Despite their importance, we know far less about the response of bacteria to human-induced environmental change than we do about other organisms. Understanding the response of organisms to land use change is especially pressing for tropical rainforests, which are being altered at a higher rate than any other ecosystem. Here, we conduct a meta-analysis of studies performed in each of the major tropical rainforest regions to ask whether there are consistent responses of belowground bacterial communities to the conversion of tropical rainforest to agriculture. Remarkably, we find common responses despite wide variation across studies in the types of agriculture practiced and the research methodology used to study land use change. These responses include changes in the relative abundance of phyla, most notably decreases in Acidobacteria (-1.94±1.1 fold (average±95%CI)) and Proteobacteria (-1.38±1.0 fold) and increases in Actinobacteria (1.55±1.1 fold), Chloroflexi (3.47±1.2 fold) and Firmicutes (6.6±1.3 fold). We also find that alpha diversity (at the scale of single soil cores) consistently increases (1.17±1.0-fold) with ecosystem conversion. These consistent responses suggest that, while there is great diversity in agricultural practices across the tropics, common features such as the use of slash-and-burn tactics have the potential to alter bacterial community composition and diversity belowground.

Highlights

Deforestation of the world’s remaining tropical rainforests is occurring at a rapid rate and it is important to understand how the loss of tropical forest will change belowground bacterial communities
While studies using pre- generation sequencing approaches [such as denaturing gradient gel electrophoresis (DGGE), terminal restriction length polymorphism, phospholipid fatty acids (PLFA), or Sanger sequencing of amplicon clone libraries] provide valuable insights, they were not included in our metaanalysis because of the incommensurability and/or uncertainty of taxonomic affiliation (e.g., DGGE, tRFLP, PLFA) or low sampling depth, which limits their utility in the quantitative meta-analyses used here
We found that pH consistently increased with land use change across the studies we surveyed, and others have observed that pH can be correlated with bacterial richness (Fierer and Jackson, 2006; Lauber et al, 2009)

Summary

Introduction

Deforestation of the world’s remaining tropical rainforests is occurring at a rapid rate and it is important to understand how the loss of tropical forest will change belowground bacterial communities. When ecosystems undergo conversion, such as from forest to agriculture, biogeochemical cycles are often profoundly altered (Neill et al, 1997, 2005; DeFries et al, 1999; Verchot et al, 2000) and the diversity of plant and animal communities can decrease, along with changes in species composition (Perfecto and Snelling, 1995; Banks et al, 2009; Bernard et al, 2009; Gardner et al, 2009; Gibson et al, 2011; Newbold et al, 2015). While there is great diversity in agricultural characteristics across the tropics, consistent patterns in bacterial response should emerge if community change is driven by common aspects of ecosystem conversion, such as slash-and-burn tactics

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