岩石边坡基质-植被系统的养分循环

基质-植被系统是岩石边坡植被护坡工程的主要功能构件，其养分循环状况决定了系统的稳定发展.该文以狗芽根为建植植物，利用模拟边坡的观测试验，对岩石边坡基质 植被系统的养分循环过程进行了研究.结果显示:基质中养分贮量平均占整个系统的98％以上，是系统营养元素的主要贮藏库，各种营养元素总贮量的顺序为KNPCaMg，生物亚系统营养元素总贮量的顺序为KNCaMgP；坡面植被建植2年左右，植被死体的生物量积累可达动态平衡，是系统养分循环得以实现的基础；系统养分元素的生物循环遵循KNCaMgP的顺序，坡面植被对基质养分的吸收以N、Ca、Mg的利用率较高，且各养分元素的年归还量均大于年存留量，坡面植被具有养分高速循环利用特征；由于基质良好的稳定特性及植被层的覆盖作用，系统的养分年输入量大于年输出量（径流输出），说明其处于良好的养分积累状态，基质（不包括枯落物及死根）的养分年输入量（K除外）也大于年输出量，K元素虽然处于亏损状态，但年亏损额不大，要维持坡面植被的稳定持续发展，不需要外源补给，表明经人工合理配置后，养分不是工程后期管理的主要因子. 

Nutrient cycling in substrate-vegetation systems of rock slopes

A substrate-vegetation system is the primary functional component of eco-engineering for rock slope protection(EERSP).Its stable development relies on the state of nutrient cycling.In this study,Cynodon Rich is selected as the trial plant to study the process of nutrient cycling in a substrate-vegetation system of rock slopes with observation tests simulating rock slopes.The results show that nutrient accumulations in the substrate,which is the main accumulation storage of nutrients,occupy 98% of the system.The total nutrient accumulations in the system are in the following order: K>N>P>Ca>Mg and that in the bio-subsystem are in the order of K>N>Ca>Mg>P;two years after the establishment of vegetation on slopes,biomass accumulation from decayed material reaches homeostasis,which is the basis of nutrient cycling of systems;biocycles of nutrient elements in the system are in the following order: K>N>Ca>Mg>P.The nutrient utilization efficiencies of N,Ca and Mg are higher than those of K and P when absorbing nutrients from substrates.The annual returns of each nutrient element are all greater than that of annual retentions,which indicates that slope vegetation has the characteristic of quick cyclic nutrient utilization.Due to favorable and stable characteristics of the substrate and the vegetation cover,the annual input of nutrients in the system is greater than the annual output of nutrients(runoff),which implies a favorable state of nutrient accumulation.The annual input(except K) of nutrients in the substrate(the litter layer is not included) is also greater than the annual output of nutrients.The annual deficit of K is small but persistent.It is,therefore,not necessary,to supply nutrients from external sources to maintain a stable development of vegetation on slopes.It is shown that the nutrient supply is not a major factor,after appropriate artificial deployment,during the later stages of engineering management.