Effects of soil particle size on enzyme activities and the amount of soil microorganism in rhizosphere of Caragana korshinskii in desert steppe

Caragana korshinskiiis the main afforestation tree species in desert steppe, it is important to study the relationship between microorganisms and enzymes in rhizosphere soil and soil particle size composition. Soil types affect enzyme activities and the amount of microorganism in rhizosphere soil, soil particle size in different soil types is different,however, little is known about how soil particle size affect on enzyme activities and the amount of soil microorganism in rhizosphere ofCaragana korshinskiiplanted in desert steppe. In this study, soil enzyme activities and the amount of soil microorganism in rhizosphere and non-rhizosphere soil in three soil types were analyzed, as well as soil particle size of sierozem, red clay soils, and aeolian sandy soils in Yanchi country of Ningxia. The results showed that the amount of bacteria in rhizosphere soil was significantly higher than that in non-rhizosphere soil, and the amount of fungi increased with the increase of fine sand grains in three soil types. The activities of sucrase, alkaline phosphatase, and catalase in rhizosphere and non-rhizosphere soil presented the tendency of sierozem > red clay soils > aeolian sand soils. The urease activity in red clay soils of rhizosphere was significantly higher than that in sierozem and aeolian sand soils. The amount offungi and actinomycetes decreased gradually, while the amount of bacteria increased firstly and then decreased. The amount of bacteria and fungi were more abundant than bulk soil. With the increasing of fine sand content, the amount of fungi and actinomycetes gradually decreased while the amount of bacteria increased and then decreased. Soil enzyme activity inrhizosphere exceeded bulk except catalase. With the increasing of fine sand content, soil enzyme activity gradually decreased. There was no significant correlation between soil particle size and the amount of soil microorganism and soilenzyme activity presented a positive correlation with clay and silt sand but it negatively correlated with fine sand and medium sand, rhizosphere soil has higher enzyme activity and could provide more nutrients for plants and microorganisms.