基于竹树种间非对称性竞争的增铵促进毛竹扩张机制研究

毛竹在竞争中战胜本地树木，是决定竹子成功扩张的关键。毛竹扩张伴随着“增铵抑硝”的土壤氮矿化过程，而NH4+/NO3-增加会显著促进毛竹生长并引起毛竹与树木间不对称性竞争关系。本研究拟1）采用原位15N同位素试验，分析扩张过程中毛竹和主要树种各形态N吸收能力和体内N:P对土壤N转化及种间竞争的响应。2）开展温室模拟及控制竞争试验，动态监测毛竹和树木幼苗表型可塑性、细根生长和功能性状、15N吸收速率、体内N、P含量等的变化规律，分析各种植物N形态吸收策略与NH4+、NO3-利用效率、N：P、以及根系相对生长速率、N、P吸收量和相对竞争能力与其个体大小的关系。原位和控制实验相结合，从NH4+吸收能力与利用效率和地下根系竞争方式对N形态响应等角度，探明增NH4+促进竹树间大小不对称性竞争的作用机制。研究结果可为土壤N营养调控毛竹扩张机制提供理论依据，为竹子扩张防控提供科学指导。

Critical to the successful expansion of bamboo is overcoming and replacing native trees in competition. Enhanced ammonification rates but reduced nitrification rates following bamboo invasion of broad-leaved forests have been reported, and we found that the increased NH4+/NO3- significantly promoted bamboo’s growth and caused asymmetric competition between bamboo and tree species. In this study, 1) Organic and inorganic nitrogen uptake, ecological stoichiometry of N and P of bamboo and 8 dominant tree species to soil N transformation and inter-species competition in bamboo, bamboo-tree mixed forest and secondary evergreen broad-leaved forest forests were investigated by brief 15N exposures of labeled intact tree roots using field hydroponic experiments. 2) Greenhouse control competition experiments were conducted, to monitor growth dynamic, morphological plasticity, fine root growth and function characteristics, 15N absorption rate of bamboo and tree seedlings, analyse N uptake strategy of various plants, N use efficiency of NH4+ and NO3-, N, P concentration and ecological stoichiometry of N and P, and the relationship of root relative growth rate, N, P accumulation and relative competitive ability of bamboo and tree species relative to its size.By the combination of in-situ experiment and control experiment, the above-ground and underground competition effects and correlation analysis, to uncover the mechanism of asymmetric competition between bamboo and tree species driven by increasing NH4+ from the perspectives of NH4+ absorption capacity and utilization efficiency and response of underground root competition to N forms. The results can provide a theoretical basis for the regulation of soil N nutrition on bamboo expansion and scientific guidance for the prevention and control of bamboo expansion.