Effects of intensive management practices on rhizosphere soil properties, root growth, and nutrient uptake in Moso bamboo plantations in subtropical China

Abstract

Understanding rhizosphere processes in relation to the aboveground productivity of bamboo stands may shed new light on the optimization of management practices and the ecological functions of belowground components in forest ecosystems. In this paper, Moso bamboo stands under intensive management with high-intensity (deep plowing plus biennial fertilization, T1) and low-intensity (deep plowing plus quadrennial fertilization, T2) practices were compared with those managed conventionally (no-tillage plus no fertilization, CK) to evaluate the impacts of intensive management strategies on the content and forms of soil C, N, and P, their associated microbial biomasses, abundances, and enzyme activities,and their relationships withbamboo root growth, nutrient uptake, and aboveground biomass. Bulk and rhizosphere soil samples from four adjacent extensively–intensively managed Moso bamboo plantation pairs were collected from a subtropical region in Zhejiang Province, China. The results show that compared with CK, intensive management practices, including T1 and T2, significantly decrease the total organic C, labile soil organic C pools including readily oxidizable C, free particulate organic C, and hot-water-extractable organic C, total N, water-soluble organic N, NH4+-N, NO3−-N, total P, organic P, and inorganic P content in the rhizosphere, but increase the content of water-soluble organic N, NH4+-N, and NO3−-N, as well as organic P and inorganic P, in the bulk soil surrounding the plant roots. Furthermore, microbial biomass C, microbial biomass N, bacterial and fungal abundances, and enzymes activities (urease, peroxidase, catalase, polyphenol oxidase, and β-glucosidase) involved in C and N metabolism were significantly decreased in the rhizosphere while acid phosphatase activity was enhanced. These changes were inferred from changes in the active C, N, and inorganic P fractions. Contrastingly, root growth traits, including biomass, length, diameter, and volume, increased continuously in response to the greater soil nutrient heterogeneity in the root zone caused by intensive management, thereby promoting root N, P, and K uptake and increasing the aboveground biomass. In conclusion, intensive management practices significantly promoted root development, growth, and biomass production in bamboo stands, but had notable negative effects on rhizosphere nutrient pools and biological properties, with potential impacts on soil functioning including in soil C sequestration and nutrient cycling.