Responses of Soil Microbial Community and Enzyme Activities to Shrub Species Artemisia gmelinii in Relation to Varying Rainfall in a Semiarid Land, SW China

Abstract

Widely distributed shrubs in drylands can locally alter soil physicochemical properties, which distinguish soil under plant canopy from soil outside the canopy. In the present study, we used a dominant shrub species Artemisia gmelinii in a semiarid land, SW China, to investigate the consequences of “shrub resource islands” for soil microbial communities and enzymatic activities. Such investigation was made at four sites that differed in rates of rainfall to examine how the consequences were altered by variation in the local climate. The results showed that A. gmelinii enhanced fungal abundance but did not influence bacterial abundance, resulting in higher total microbial abundance and fungal-to-bacterial ratio in under-canopy soil compared to outside-canopy soil. Microbial community composition also differed between the two soils, but this difference only occurred at sites of low rainfall. Redundancy analysis revealed that such composition was attributed to variation in soil water content, bulk density, and total phosphorus as a result of shrub canopy and varying rates of rainfall. Activities of hydrolytic enzymes (β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, alkaline phosphatase, and leucine aminopeptidase) were higher in under-canopy soil than in outside-canopy soil, among which C-acquisition enzyme, β-1,4-glucosidase, and P-acquisition enzyme, alkaline phosphatase, were also higher in the soil of high rainfall. The overall pattern of enzyme activities did not show differences between under- and outside-canopy soils, but it separated the sites of high rate from that of low rates of rainfall. This pattern was primarily driven by variation in soil physicochemical properties rather than variation in soil microbial community, suggesting that the distribution pattern of enzyme activities may be more sensitive to variation in rainfall than to shrub canopy. In conclusion, our study shows that shrub species A. gmelinii can shift the soil microbial community to be fungal-dominant and increase hydrolytic enzyme activities, and such effect may depend on local climatic variation, for example, rainfall changes in the semiarid land. The findings of this study highlight the important roles of shrub vegetation in soil biological functions and the sensitivity of such roles to climatic variation in semiarid ecosystems.

Effects of Variation in Tamarix chinensis Plantations on Soil Microbial Community Composition in the Middle Yellow River Floodplain

“…AMF PLFAs increased with shrub patch size, which is consistent with the results of previous studies [ 20 , 29 ]. Significant positive correlations between the soil salt content and AMF PLFAs suggest that islands of salinity provide substrates that promote the growth of AMF by the colonization of spores [ 56 ].…”

“…Previous studies demonstrated that the fertile island of shrub enriched soil available nutrients under their canopy, such as SOM, N, and P, supplying more substrates for soil microbes [ 7 , 20 , 42 , 43 ]. Here, our results found shrub patch size had a positive effect on soil nutrient status.…”

“…T. chinensis generated a “fertile island effect” that could promote the accumulation of soil nutrients, and it tended to increase in strength with shrub patch size [ 20 ]. The soil organic matter was 20.61%, 56.43%, and 80.33% higher in the small, medium, and large patch size, respectively, in inside-canopy soils than in outside-canopy soils.…”

“…Soil microorganisms, which have an intricate relationship with soil physicochemical properties, are sensitive to shrub patch size and sampling location [ 7 , 9 , 20 ]. Previous studies have shown that the growth of vegetated patches has a neutral [ 49 ], promotion [ 20 ], or inhibition [ 50 ] effect on soil microbial activities. The results of our study showed that the growth of vegetated patches has a positive effect on soil microbial communities.…”

“…Moreover, shrub patch size has a significant effect on soil organic carbon, total nitrogen, and soil microbial biomass [ 15 , 19 ]. The fungal abundance and biomass of Artemisia gmelinii are higher in inside-canopy soils than in outside-canopy soils due to the increased SOC input in semiarid land [ 20 ]. The ability of shrubs to alter the accumulation of nutrients has been demonstrated in desert-wash shrub communities, shrub-dominated semi-desert ecosystems, semi-arid savanna, and alpine ecosystems [ 21 , 22 , 23 , 24 ].…”