Evaluation of restoration effect in degraded alpine meadow under different regulation measures

Abstract: Alpine meadow mainly locates in the Qinghai-Tibetan Plateau and other high altitude areas, and plays a vital role in maintaining the balance of the global ecosystem. Recently, the extensive degradation of alpine meadow has been caused by the global climate change and the interference of human activities, which has made these areas extremely important for further study. People have applied a few measures to restore the degraded grassland, however there was no quantitative mean that could evaluate the effectiveness of ecological restoration measures synthetically. For the scientific assessment of the effects of different ecological regulation measures on the degraded alpine meadow ecosystems, this research was conducted in Maqu alpine meadow in Gansu Province, northwestern China from May 2010 to December 2012. The VOR (vigor, organization, resilience) and CVOR (condition, vigor, organization, resilience) ecosystem health evaluation models were utilized to evaluate the health condition of the degraded grassland ecosystem after restoration, and the restoration measures included enclosure, ripping, organic material addition, reseeding and comprehensive measure, and the grazing was taken as the control. We implemented enclosure and slicing of the pasture vertically and horizontally with the plough as ripping, implemented enclosure, scarifying and fertilization in the pasture with sheep manure of 22.5 t/hm2 as organic material addition, and implemented enclosure and reseeding with Elymus nutans of 15 kg/hm2 as reseeding. And for grazing treatment we used the grazing pressure of about 2-2.5 yak/hm2. As for comprehensive measure, we combined the treatment of enclosure with the treatments of ripping, organic material addition and reseeding. For the calculation of evaluation model, we determined soil organic carbon content and gauged above-ground biomass, Shannon-Wiener species diversity index, biomass of functional groups and economic groups of all the grass under different regulation measures to further compute condition index (C), vigor index (V), organization index (O), and resilience index (R). We expected to find which ecological regulation measure was the most effective and contrasted 2 models to check the applicability. The results showed the CVOR health evaluation index was relatively more comprehensive than the VOR health evaluation index considering the importance of basic condition, which could more objectively reflect the additional specific soil nutrient status (organic or inorganic), and more quantitatively manifest the effects of restoration measures of grassland ecosystem, contributing to the specific formulation and the implementation of specific engineering management measures. According to the 2 models, the VOR index evaluation calculation results showed the effects of organic material input and comprehensive measure on recovery and rehabilitation of degraded grassland were more obvious than others, their health values rose by 5%-9% year by year simultaneously, and the value of grazing was lower than other measures significantly (P<0.05). The CVOR index evaluation calculation results showed the effect of comprehensive ecological restoration measure was superior to other single treatment measure and its value reached 0.917 that was significantly higher than others (P<0.05), while grazing led alpine meadow ecosystem to health "warning" level and its value went down to 0.572, which was lower than other measures significantly (P<0.05). The results manifested that the implementation of comprehensive measure in local degraded areas can achieve the purpose of saving the grassland ecosystem health comprehensively and quickly. But in practice due to the comprehensive measure cost is high, for selecting the optimum ecological recovery measure, it requires specific consideration of each measure's dual benefits of economy and ecology so as to adjust the measures to local conditions.