Rapid soil fungal community response to intensive management in a bamboo forest developed from rice paddies

Abstract

Although heavy winter mulch and high rate fertilizer application are commonly practiced in intensively managed bamboo (Phyllostachys praecox) plantations, little is known about the effects of these practices on soil microbial activities. Therefore a field study was conducted to investigate the long term intensive management on the development and composition of soil fungal communities. Fungal biomass (fungal phospholipid fatty acid marker), fungal DNA (18S rDNA real-time qPCR) and fungal community composition (culture-independent methods: DGGE, cloning and sequencing) were determined across a bamboo plantation that included seven stand age-classes (1, 4, 6, 8, 10, 12 and 20 years old). Although soil microbial PLFA biomass and fungal DNA abundance were unaffected during the first two years of intensive management, all increased significantly after three years of intensive management. The total microbial PLFA and bacterial PLFA increase linearly (P < 0.001) with increasing stand age, while soil fungal PLFA and 18S gene abundance increase was best described using a quadratic equation (P < 0.01). The fungal/bacterial ratio generally remained constant, but did increase for the 8 and 12 year stand soils. Sequencing of commonly-occurring bands revealed that the majority of the soil fungi were species of either Sordariomycetes or Chytridiomycetes. Cluster analysis by Ward's method revealed rapid short-term change in fungal communities that returned to its original composition within one to two years when the soils were not disturbed. This indicated a robust original fungal community that was resilient to transient perturbations resulting from intensive land management when allowed breaks from nutrient loading and soil disturbance. Redundancy analysis indicated that soil chemical characteristics, such as pH, Ntot and Corg, could account for 12.7%, 12.1% and 10.3% of the variance in soil fungal community composition, respectively. Stand age contributed to 12.6% of the variance of soil fungal community.