Soil microbes contribute to absorption bias of NH4+-N associated with rapid growth and distribution of woody bamboos in laterite plateau of Southwest China

Red soil is generally of poor structure, low contents of organic carbon and soil nutrient elements. Hundreds of woody bamboo species grow on the red soil in southern China, and woody bamboos are one of taxa with the most rapid grow speed among seed plant. The interaction between soil microbes and plants has a significant effect on soil microbial community and function, as well as plant adaptability. However, there is rare research report on the relationship between soil type and distribution of woody bamboos, and the effect of micro-ecological factors, especially soil microorganisms, on ecological adaption and rapid growth of woody bamboos remains unclear. In this study, Dendrocalamus sinicus, endemic to Yunnan laterite plateau of Southwest China and the strongest woody bamboo in the world, was investigated for the topic. 16S rRNA and ITS rRNA genes of rhizosphere microorganisms were sequenced, and soil chemical properties were determined in the bending, straight and introduced straight type of D. sinicus during two key growth periods. The result showed that each type of D. sinicus preferred to absorb ammonia nitrogen (NH4+-N) rather than nitrate nitrogen (NO3--N). Compared to dormancy period of underground rhizome (in May), each type of D. sinicus required more NH4+-N during the shooting period (in August). The bacterial genera Bradyrhizobium and Paenibacillus, and the fungal genus Trichoderma were significantly correlated with soil NH4+-N content, which may contribute to increasing soil available nitrogen. The SOC, AP, AK, and NH4+-N contents of the introduced straight type were significantly lower than those of the straight type (p < 0.05). Inadequate nutrient will affect the diameter at the breast height (DBH) of introduced straight type. The microbial taxa (e.g., the nitrogen fixation, ureolysis) with increasing availability nutrients may contribute to the shooting of the introduced straight type in August. Our results suggested that woody bamboos in red soil had an absorption bias of NH4+-N during rapid growth stage and introduced cultivation. The soil available nutrients and mutually beneficial bacteria (especially nitrogen-fixing microbes) decreased beyond the native geographical range of D. sinicus, and further reduced the DBH of D. sinicus.