Weathering of calcareous bedrocks is strongly affected by the activity of soil microorganisms

Eduardo Vazquez,Marie Spohn,Giovanni Pastore,Alfons R Weig

doi:10.1016/j.geoderma.2021.115408

Abstract

Phosphorus (P) availability in calcareous forest soils is commonly low compared to siliceous soils. The main reason for this is that phosphate ions tend to precipitate with calcium (Ca). Weathering of calcareous rocks and the potential of microorganisms to dissolve calcareous parent material is not fully understood. Therefore, we examined microbial carbonate dissolution and the abundance of phosphorus-solubilizing bacteria in temperate forest soils with contrasting calcareous parent materials. We incubated soil extracts with weathered parent materials (i.e., dolomite and limestone) from two calcareous forest soils differing in P content and determined the rates of P and Ca solubilization. In addition, we determined the abundance of phosphorus-solubilizing bacteria (PSB). We found that the net Ca solubilization rate ranged from 8.8 to 511.1 nmol m−2 d−1 across both soils and depths. Calcium dissolution rates were negatively related to pH and positively related to the concentration of organic acids. The gross P solubilization rates were on average 63.6% higher from dolomite (P-poor soil) than from limestone (P-rich soil). The abundance of soil PSB ranged from 3.8 % at the limestone site (P-rich soil) to 24.4 % at the dolomite site (P-poor soil). The higher abundance of PSB in the soil derived from dolomite is in line with the high Ca and P solubilization rates at this site, indicating that PSB abundance is related to rock weathering rates from calcareous soils. Pseudomonadales and Enterobacteriales were by far the two most abundant bacterial orders in the PSB community of both soils and soil depths. In conclusion, this study shows, first, that weathering of calcareous bedrocks is strongly affected by the activity of soil microorganisms, and second, that there is likely a selective pressure in P-poor soils towards a higher abundance of PSB.

Highlights

Weathering of bedrock is the result of physico-chemical and bio logical processes that render nutrients available for uptake by organisms (Arvin et al, 2017; Finlay et al, 2019; Zaharescu et al, 2019; Wan et al, 2019)
We found that the total amounts of the three measured organic acids were higher in solution with dolomite than with limestone (p < 0.05) (Fig. 2). 2-keto-D-gluconic acid prevailed at the limestone soil, whereas D-glu conic and lactic acid dominated at the dolomite soil (Fig. 2)
We found that the weathering of calcareous rocks was strongly affected by the activity of soil microorganisms

Summary

Introduction

Weathering of bedrock is the result of physico-chemical and bio logical processes that render nutrients available for uptake by organisms (Arvin et al, 2017; Finlay et al, 2019; Zaharescu et al, 2019; Wan et al, 2019). The dissolved P concentrations in the soil liquid phase is generally very low (Plante, 2007). The reason for this is that phosphate ions become quickly unavailable through (i) adsorption to soil colloids and (ii) precipitation with cations, depending on the pH conditions of the soil (Lindsay, 1979; Hinsinger, 2001). In alkaline and calcareous soils, P availability is mainly reduced by precipitation of phosphate with calcium (Ca) and magnesium (Mg) ions (Dreybrodt et al, 1996; Kaufmann and Dreybrodt, 2007)

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