Dynamics of Soil Bacterial and Fungal Communities During the Secondary Succession Following Swidden Agriculture IN Lowland Forests.

Qiang Lin,Jaroslav Kukla,Petr Baldrian,Petr Heděnec,Jan Frouz,Ruma Umari,Vojtech Novotny,Lingjuan Li,Lenka Meszárošová

doi:10.3389/fmicb.2021.676251

Abstract

Elucidating dynamics of soil microbial communities after disturbance is crucial for understanding ecosystem restoration and sustainability. However, despite the widespread practice of swidden agriculture in tropical forests, knowledge about microbial community succession in this system is limited. Here, amplicon sequencing was used to investigate effects of soil ages (spanning at least 60 years) after disturbance, geographic distance (from 0.1 to 10 km) and edaphic property gradients (soil pH, conductivity, C, N, P, Ca, Mg, and K), on soil bacterial and fungal communities along a chronosequence of sites representing the spontaneous succession following swidden agriculture in lowland forests in Papua New Guinea. During succession, bacterial communities (OTU level) as well as its abundant (OTU with relative abundance > 0.5%) and rare (<0.05%) subcommunities, showed less variation but more stage-dependent patterns than those of fungi. Fungal community dynamics were significantly associated only with geographic distance, whereas bacterial community dynamics were significantly associated with edaphic factors and geographic distance. During succession, more OTUs were consistently abundant (n = 12) or rare (n = 653) for bacteria than fungi (abundant = 6, rare = 5), indicating bacteria were more tolerant than fungi to environmental gradients. Rare taxa showed higher successional dynamics than abundant taxa, and rare bacteria (mainly from Actinobacteria, Proteobacteria, Acidobacteria, and Verrucomicrobia) largely accounted for bacterial community development and niche differentiation during succession.

Highlights

Slash-and-burn is a widespread agricultural technique in tropical forests (Whitfeld et al, 2014; Kukla et al, 2018)
Neither bacterial nor fungal community dynamics were significantly correlated with plant richness (Supplementary Table 2)
The successional dynamics of bacterial communities were more affected by their rare subcommunities than by abundant or intermediate subcommunities, whereas the successional dynamics of fungal communities were most affected by their abundant subcommunities (Supplementary Table 3)

Summary

Introduction

Slash-and-burn is a widespread agricultural technique in tropical forests (Whitfeld et al, 2014; Kukla et al, 2018) This technique has been reported to result in extensive soil degradation (Are et al, 2009) and loss of soil organic matter (Ogle et al, 2005; Huon et al, 2013), probably related to the extensive mechanical removal of vegetation, the disturbance of soil surface, and the fire effects. In contrast to these reports, swidden agriculture in rainforests in Papua New Guinea, including slash-and-burn, is extremely sustainable (for several millennia) and has little effects on soil characteristics (Kukla et al, 2018). Dynamics of soil microbial community composition are of particular interest, because a recent study finds that nether fungal nor bacterial biomass significantly change across successional stages in this ecosystem (Kukla et al, 2018)

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