荆条对太行山南麓裸岩立地的水分生理生态适应机制研究

In this project, pioneer shrub Vitex negundo var heterophyiia settled at shrub stages of community succession in bare rock site of south Taihang mountain will be selected as study material. Three different succession processes of the shrub, i.e. scattered V. negundo and V. negundo clump at bared rock site as well as V. negundo dominated shrub land will be studied. The stable water and carbon isotope technique will be adopted to study seasonal pattern of the water use strategies such as water sources, relative absorbing quantity and water use efficiency of V. negundo at the 3 succession processes. The growth status, water parameters, stomatal regulation and leaf morphological and anatomical structures will also be studied to understand the adaptation strategies of V. negundo in water eco-physiological characters and leaf anatomical structures to the barren site conditions. Microclimate will be monitored and soil profile traits as well as soil nutrition will also be investigated to help understand site environment of the 3 succession processes. Finally, the dendrochronology technique combining with measurements of ring-wood stable carbon and oxygen isotope will be used to study the annual change of water use and growth status of V. negundo. All the works are expected to determine the adaptation mechanism of V. negundo in water use, eco-physiological and anatomical characters and growth status to the barren and drought condition of the naked rock site. The above research is significant to reveal drought tolerance mechanism of V. negundo, as well as water use and manipulation mechanism in adaptation of extreme site condition. The proposed work will provide theoretical ideas for the selection of drought-tolerate tree species, revegetation and ecological construction at south Taihang Mountain of north China as well as continuous development and utilization of V. negundo.

本项目以太行山南麓裸岩立地群落演替的灌木阶段中定居的先锋灌木荆条为研究对象，分别在雨季、旱季以及降雨前后，采用稳定水碳同位素技术结合水分生理生态特性和解剖结构等研究方法，选择该立地的散生荆条和荆条灌丛以及荆条灌木林地作为荆条的3个演替进程，对各个进程的荆条的生长状况、水分参数、气孔调节和叶片形态解剖特性以及不同季节的水分利用来源和相对吸收量、水分利用效率等水分利用策略进行研究，同时对不同演替进程的小气候和土壤性状、养分等立地环境进行观测和研究，最后通过树木年轮学方法和年轮碳氧同位素测定研究其生长过程中的水分利用、生长状况的年际变化，探索荆条的水分生理生态特性、解剖结构和生长状况对太行山南麓裸岩石坡上的干旱贫瘠立地条件的适应机制及改善作用。对揭示荆条的耐旱机理、在极端立地条件下的水分利用和调控机制具有重要意义，为荆条的后续开发利用及太行山南麓节水抗旱树种选择、植被恢复和生态建设提供理论依据。

以太行山南麓裸岩立地群落演替的灌木阶段中定居的先锋灌木荆条为研究对象，采用稳定水碳同位素技术结合水分生理生态特性和解剖结构等研究方法，选择该立地的散生荆条和荆条灌丛以及荆条灌木林地作为荆条的3个演替进程，对各个进程荆条的生长状况、水分参数、气孔调节和叶片形态解剖特性以及不同季节的水分利用来源和相对吸收量、水分利用效率等水分利用策略进行研究，同时对不同演替进程的小气候和土壤性状、养分等立地环境进行观测和研究，最后通过树木年轮学方法和年轮碳氧同位素测定研究其生长过程中的水分利用、生长状况的年际变化，结果表明，不同演替阶段荆条的土壤厚度和土壤含水量均为单株<灌丛<林分；降雨后土壤含水量提高的幅度为荆条单株>灌丛>林分，恢复至雨前土壤含水量的时间则表现为单株<灌丛<林分；裸岩立地裸土的总N、P、K、有效氮磷钾和有机质等各个养分含量都最低，总K含量和可溶性K含量随着演替进程的发展而增加。荆条林分的叶片N含量在2016年夏季低于荆条单株和灌丛，叶片P、K含量在2015年和2016年的夏季高于荆条灌木和单株。随着演替进程的发展，土层越来越厚，保水能力越来越强、养分含量越高，荆条的叶片和树轮δ13C越来越低，耗水量越来越多，对土壤水的利用比例越高。单株和灌丛阶段荆条均是在极端干旱过后（分别在1981年和1997年的370mm和217mm），降雨突然增多的年份开始萌发并生长的。表明荆条需要遇到合适的水分条件才能在裸岩立地上萌发和生存，过了幼苗阶段后，荆条的抗旱性逐渐增强并继续在恶劣的立地条件下生长和存活。