Depth‐related response of soil enzymes to cyanobacteria‐dominated crusts along a precipitation gradient

Abstract

This study aimed to elucidate the ecological role of cyanobacteria-dominated crusts on soil enzymes activities along a precipitation gradient. Results showed that proteins and polysaccharides contents of cyanobacterial-dominated crusts changed significantly among nine sample sites. Meanwhile, proteins and polysaccharides displayed a downward trend with increasing thickness and decreased with increasing mean annual temperature, while these two first increased, and then decreased with increasing chlorophyll a. The pronounced variations of polysaccharides and proteins could be explained by the shift in cyanobacteria species composition due to the discrepancy of succession stage at the regional scale. Activities of soil enzymes decreased with depth and varied significantly among sample sites. Redundancy analysis showed that soil enzymes activities in 0-2 cm were mainly explained by microbial biomass, polysaccharides, and soil organic carbon, and those in 2-5 cm were mainly influenced by microbial biomass and climate, while those in 5-10 cm were mainly affected by climate. The results highlighted the intrinsic involvement of microbes in shallower soil (0-5 cm) after the establishment of crusts and proved the effect of polysaccharides on surface soil (0-2 cm) enzymes activities. The strengthened effect of climate on soil enzymes activities in depths manifested the water availability and temperature would restrict soil microbial activity. Therefore, we concluded that the response of soil enzymes activities beneath the cyanobacteria-dominated crusts is depth related. Overall, our findings will provide a better knowledge of cyanobacteria-dominated crusts properties at the regional scale, and its effects on soil enzymes activities can replenish the understanding of cyanobacteria-dominated crusts on biogeochemical processes. K E Y W O R D Sarid and semiarid ecosystem, cyanobacteria-dominated crusts, microbial biomass, polysaccharides, soil enzymes activities | INTRODUCTIONSoil enzymes are derived from living and dead microbes, soil organisms, plant roots and residues, and pivotal in mediating and catalyzing soil functions, for example, organic matter decomposition and nutrient cycling, which closely link with life processes of microorganisms in soils (Dick, 1994). Due to the widely acknowledged sensitivities to naturally or anthropogenically induced soil disturbances and the advantages of easy to be measured, soil enzymes activities have been often considered as a reliable measurement of soil performance to different vegetation, soil physicochemical properties, microbial community, and succession

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“…In this study, different soil enzyme activities were found to vary greatly in different regions and at different soil depths. With the increase in soil depth, the activities of soil URE, SUC, and ALP showed a downward trend, which is consistent with the findings of Zhang's study [40], while the changes in soil CAT activity were not significant (Figure 3). The soil enzyme activities in the coal mining subsidence area were significantly lower than those in the non-subsidence area at some soil layers, which is consistent with the findings of Ma's study on the northwestern arid and semi-arid mining area [41].…”

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