Decreases in organic C reserves in soils can reduce the catabolic diversity of soil microbial communities
2000
Degens, B.P. | Schipper, L.A. | Sparling, G.P. | Vojvodic-Vukovic, M.
An understanding of the main factors influencing microbial diversity in soils is necessary to predict the effects of current land-use trends on terrestrial diversity. We used microbial catabolic evenness as a measure of one component of soil microbial diversity. Catabolic evenness was assessed by measuring the short-term respiration responses of soil to a range of simple organic compounds. Differences in catabolic evenness between pasture and other land-uses on matched soils were related to differences in organic C pools (total organic C, microbial biomass C, and potentially mineralizable C). This approach enabled comparison of land-use effects on organic C pools in relation to catabolic evenness without the effects of soil type. In general, microbial catabolic evenness was greatest in soils under pasture and indigenous vegetation (range: 19.7-23.3), and least in soils under cereal/maize/horticultural cropping (range: 16.4-19.6). Soils under mixed cropping land-uses had catabolic evenness that ranged between these extremes (range: 17.7-20.5), but under pine forestry there was no characteristic level of evenness (range: 15.1-22.3). Catabolic evenness correlated poorly with the absolute values of soil organic C pools (r2 < 0.36). However, across a range of paired comparisons between pasture and other land-uses, greater differences in microbial catabolic evenness corresponded with greater differences in organic C (r2 = 0.76) and , to a lesser degree, with differences in microbial biomass C(r2 < 0.45) or potentially mineralizable C (r2 < 0.13). Therefore, land-uses that deplete organic C stocks in soils may cause declines in the catabolic diversity of soil microbial communities. Although the implications of this for microbial processes are unknown, maintenance of soil organic C may be important for preservation of microbial diversity.
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