Rhizosphere effects refer to the impact of living roots on soil C decomposition and nutrient mineralization. This plant-soil interaction not only increases nutrient availability to plants but also affects C and nutrient cycling profoundly. However, it is difficult to predict the interspecific variation of rhizosphere effects because its mechanism remains little known. In this study, we focused on two alternative strategies of plant nutrient acquisition, namely acquiring nutrient from bulk soils and increasing nutrient availability in the rhizosphere by rhizosphere effects. Plants may have different reliance on rhizosphere effects due to the nutrient availability in its corresponding bulk soils. We used 14 woody species grown in the Xishuangbanna Tropical Botanical Garden (XTBG) and measured microbial biomass, extracellular enzyme activity, C and N mineralization rates of the corresponding bulk and rhizosphere soils. We hypothesized that (1) species of slow bulk-soil nutrient cycling relies on strong rhizosphere effects; and alternatively (2) a fast bulk-soil nutrient cycling favors microbial activity and enhances rhizosphere effects.
Results/Conclusions
We found no dependence of rhizosphere microbial biomass C and N on its corresponding bulk soils. However, the rhizosphere effect of four extracellular enzyme activities, namely BG, NAG, AP and PPO exhibited negative dependence on its corresponding bulk soils. In line with this, the rhizosphere effects of C and N mineralization rates also exhibited negative dependence on the corresponding bulk soils. Our results suggested that species of slow bulk-soil nutrient cycling rely more on rhizosphere effects.