从C、N、P化学计量特征分析雷竹氮素克隆整合分株年龄效应

Effect of Ramet Age on Nitrogen Clonal Integration of Phyllostachys violascens Based on Stoichiometric Characteristics of C, N and P

[目的]研究雷竹不同年龄分株叶片C、N、P化学计量特征对氮素克隆整合的响应机制,探讨雷竹林施肥的适宜立竹年龄,为雷竹林精准化、减量化施肥提供参考。[方法]以1年生和2年生雷竹分株组成的克隆整合单元为研究对象,通过给不同年龄分株竹腔注射15NH415NO3的方法,设置3个氮素添加水平(低浓度N,4.07 mol·L^-1;中浓度N,8.13 mol·L^-1;高浓度N,12.20 mol·L^-1),测定各处理1年生、2年生立竹叶片在时间梯度上的C、N、P含量,分析雷竹不同年龄分株间氮素整合方向及传输效率等差异。[结果]雷竹克隆分株间存在强烈的氮素传导功能,1年生立竹会部分传输氮素至2年生立竹,而2年生立竹会将氮素大量传输至1年生立竹,即2年生立竹的氮素传导能力显著强于1年生立竹,同时具有一定的时间效应和氮素浓度效应,氮素浓度过低或过高均会减弱分株间氮素传输能力,试验的中浓度N是整合功能显著变化的"拐点"。1年生、2年生立竹氮素处理均能提高相连分株叶片N、P养分利用效率,且随氮素处理浓度增大及处理时间延长而减弱,但都能维持相对稳定的N/P,并使立竹叶片C、N、P含量及其化学计量比关系产生适应性调节作用。[结论]雷竹氮素克隆整合存在明显的分株年龄效应,宜选择2年生立竹进行株穴法施肥,可以大幅度提高肥料利用率,显著减少肥料的使用量。

[Objective] To study the response mechanism of carbon(C), nitrogen(N) and phosphorus(P) stoichiometric characteristics of different age ramets of Phyllostachys violascens to nitrogen clonal integration, and to explore the suitable age of bamboo for fertilization, so as to provide references for precise and reduced fertilization in Ph. violascens forest. [Method] The clonal integration unit consisting of 1-year-old and 2-year-old ramets of Ph. violascens was studied. Three nitrogen addition levels(4.07 mol N·L^-1;8.13 mol N·L^-1;12.20 mol N·L^-1) were set up by injecting 15NH415NO3 into the bamboo cavity of different age ramets. The contents of C, N and P in leaves of 1-2-year-old bamboo were measured on time gradient, and the differences of N integration direction and transmission efficiency among ramets of different ages were discussed. [Result] Clonal ramets of Ph. violascens showed strong N conduction function. 1-year-old bamboo partly transmitted N to 2-year-old bamboo, while 2-year-old bamboo transferred N to 1-year-old bamboo as much as possible. Therefore, the N transmission capacity of 2-year-old bamboo was significantly stronger than that of 1-year-old bamboo. In addition, it showed time effect and N concentration effect to some extent. Low or high N concentration weakened the N transmission capacity. The middle N concentration in the experiment showed an "inflection point" of significant changes in the integration function. Nitrogen treatment of 1-year-old and 2-year-old bamboo could improve the nutrient utilization efficiency of N and P in the leaves of connected ramets, and weakened with the increase of N concentration and treatment time, but both of them could maintain relatively stable N/P and regulate the contents of C, N and P in leaves and their stoichiometric ratios adaptively.[Conclusion] Nitrogen clonal integration of Ph. violascens has obvious ramet age effect. It is advisable to select 2-year-old bamboo for plant-hole fertilization, which can greatly improve the fertilizer utilization rate and significantly reduce the amount of fertilizer used.