旱化成龄柠条补偿生长与土壤水分的平衡调节机制

The soil generally become more drought for the compemsative growth of mature peashrub after stump, therefore, the risk for productivity management will be increased. To futher increase the transforming and using effectivity of little precipitation events, it may be potential and effective pathway to improve compensative growth and remain soil water environment stable. However, there are some defects for the utilization of little precipitation events for deep-root shrubs, including the complexity of response mechanism and shortcomes in rainfall harvesting. In the program, we will study the dynamics of compensative growth and soil water environment and their relationship, the transformation and utilization of little precipitation events in the shrub-soil system and the dynamics of functional modulars, and so on, based on the little precipitation events and functional modulars(branch and fine root), for the drought and mature peashrub in desert steppe, through field control tests and indoor simulate ones. The relationship between branch architecture and stemflow, and that between soil water availabilities and fine roots distribution and dynamics will be analysed, to enucleate the utilization of little precipitation events and restricting factors and mechanism. At the end, the balancing mechanism and regulation pathway through functional modulars between compensative growth and soil water environment will be analysed based on little precipitation events. The theory to improve compensative growth and remain the stability of soil water environment at the same time will be explored.

旱化成龄柠条平茬后的补偿生长通常会加剧土壤旱化。从水源拓展的角度，进一步提高小降水事件的转化利用是改善柠条补偿生长并维持土壤水分环境相对稳定的一条潜在途径，但是深根性灌木对小降水的利用存在响应机制复杂、相对富集能力不足等问题。据此，本项目以荒漠草原旱化成龄人工柠条为对象，从小降水事件和枝、细根等功能构件入手，采用田间控制与室内模拟实验相结合的方法，分别开展补偿生长与土壤水分环境动态及其关系格局、小降水事件在灌丛-土壤系统的转化利用与功能构件动态等方面的控制模拟实验研究，分析枝系构型与灌丛茎流集水、土壤水分有效性与细根分布动态间的相互关系，阐明柠条对小降水事件的相对利用程度及其制约因素和作用机制，综合分析基于小降水事件的补偿生长与土壤水分环境平衡关系的功能构件调节机制与途径，探究有效改善旱化成龄柠条补偿生长并维持土壤水分环境相对稳定的理论依据。

从水源拓展的角度，进一步提高小降水事件的转化利用是改善柠条补偿生长与种群质量，并维持土壤水分环境相对稳定的一条潜在途径。本项目以荒漠草原旱化成龄人工柠条为对象，从小降水事件和枝、细根等功能构件入手，分别开展了补偿生长与土壤水分环境动态及其关系格局、小降水事件在灌丛-土壤系统的转化利用与功能构件动态等方面的研究。初步研究结果表明，由于水资源的总量约束，补偿生长对种群质量（个体生长）和土壤水分环境的改善只是一个短期可逆过程，土壤干旱（特别是水文过程的浅层化）将长期制约现有生长格局下柠条种群的更新或维持。在这样一个格局下，成龄柠条一是通过灌丛开放度的提高和枝叶的稀疏化，降低了冠层截留损失，提高了穿透雨比例，潜在增强了小降水直接补充土壤水的有效性，这是一种被动的构件水文适应机制；二是通过浅层根系发生量与逆向分布的调整，增强了对小降水转化的浅层土壤水的即时利用，配合深层根系的保留，形成了一种近乎通吃的水分利用策略，这是一种主动的构件水文适应机制。在现有生长格局和利用管理背景下，成龄柠条种群质量（包括补偿更新）与土壤水分环境的低质量稳定性格局可能会维持较长的时间，柠条暂时不会快速退出这个半自然的人工灌草复合系统。