Abstract
Soils are crucial in regulating ecosystem processes, such as nutrient cycling, and supporting plant growth. To a large extent, these functions are carried out by highly diverse and dynamic soil microbiomes that are in turn governed by numerous environmental factors including weathering profile and vegetation. In this study, we investigate geophysical and vegetation effects on the microbial communities of iron-rich lateritic soils in the highly weathered landscapes of Western Australia (WA). The study site was a lateritic hillslope in southwestern Australia, where gradual erosion of the duricrust has resulted in the exposure of the different weathering zones. High-throughput amplicon sequencing of the 16S rRNA gene was used to investigate soil bacterial community diversity, composition and functioning. We predicted that shifts in the microbial community would reflect variations in certain edaphic properties associated with the different layers of the lateritic profile and vegetation cover. Our results supported this hypothesis, with electrical conductivity, pH and clay content having the strongest correlation with beta diversity, and many of the differentially abundant taxa belonging to the phyla Actinobacteria and Proteobacteria. Soil water repellence, which is associated with Eucalyptus vegetation, also affected beta diversity. This enhanced understanding of the natural system could help to improve future crop management in WA since the physicochemical properties of the agricultural soils in this region are inherited from laterites via the weathering and pedogenesis processes.
Highlights
Soils provide a variety of essential ecosystem services which support life above- and below-ground (Smith et al, 2015; Adhikari and Hartemink, 2016)
T140 vegetation was dominated by Eucalyptus, whilst on T210 it shifted from a mixture of spring oats and Eucalyptus in the plateau and upper sections, to wheat and native grasses in the lower slope sections (Supplementary Table S2)
Our study indicates the strong influence that weathering history, vegetation cover and their associated influences on soil physicochemical attributes can exert on the soil microbial community
Summary
Soils provide a variety of essential ecosystem services which support life above- and below-ground (Smith et al, 2015; Adhikari and Hartemink, 2016). They form part of the Earth’s critical zone (CZ), which spans from the canopy to the bedrock, incorporating a complex network of biogeochemical processes and cycles that sustain terrestrial life (Brantley et al, 2007). Laterites are ancient weathered profiles that are typically formed under tropical climates (Volkoff, 1998) and comprise five horizons underneath the topsoil: ferricrete, mottled zone, pallid zone, saprolite, and (parent) bedrock (Figure 1A). The saprolite (isovolumetric weathering product) layer may contain some haematite, gibbsite and goethite (Girard et al, 1997; Théveniaut and Freyssinet, 1999)
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