放牧牦牛行为及其对高寒草地土壤特性的影响研究进展

放牧牦牛是对高寒天然草地的一种重要的利用方式,牦牛通过采食牧草、践踏土壤和排泄粪尿等行为可能对草地生态系统产生不容忽视的直接或间接影响。通过归纳分析放牧牦牛行为及其生态环境效应的有关研究成果,系统论述了牦牛采食牧草、践踏土壤和排泄粪尿3种主要行为的表现特性及其对草地土壤理化和生物学性质的影响效应和作用机制,阐明了高寒草地土壤碳氮养分、植被生物量及微生物群落等对牦牛践踏和粪尿排泄物返还的响应特征及差异性。指出牦牛采食、践踏和粪尿排泄是影响草地物质循环和能量转换的重要环节。未被消化利用的牧草养分通过粪尿排泄返还到草地土壤中,被认为是对养分匮缺的天然草地的一种重要的施肥措施,也是维持土壤养分平衡和植被生产力的重要保障。而畜蹄践踏相对于采食和排泄行为而言具有作用时间长、直接作用的草地组分多且效果持久的特点。因此,系统阐释牦牛采食特征、践踏过程和粪尿返还对土壤物理结构、主要养分动态和植被生长的影响效应,能够为加深关于放牧牦牛行为对高寒草地土壤-植被系统养分生物地球化学循环的作用过程和影响机制的认知奠定重要的理论基础,进而可为优化牦牛放牧模式、维持脆弱高寒草地生态系统可持续发展和加强青藏高原国家生态安全屏障建设等提供有益参考。

Research progress on yak grazing behavior and its influence on the soil properties of alpine grassland

Yak grazing is an important means of utilization of natural grassland in alpine ecosystems, and the herbage consumption, soil treading, and dung and urine excretion during grazing inevitably generate direct or indirect influences on grassland ecosystems. This paper reviews the basic characteristics of the 3 main impacts of grazing, foraging, trampling, and dung and urine deposition. Using this framework, research results relating to the behavioral ecology of grazing yaks are summarized and analyzed, and the influences and functional mechanisms of the animal behavioral processes on soil physicochemical and biological properties are explored. Through this approach, the impacts of grazing on soil carbon (C) and nitrogen (N) status, vegetation biomass and microbial communities in the alpine grassland were clarified. Results showed that foraging, trampling and excretion of dung and urine are important components of grassland C and N cycling and energy conversion. Forage nutrients not digested and utilized by grazing animals are returned to the soil as dung and urine, and this nutrient return is an important source of fertilization in the fragile natural grassland, and ensures the maintenance of soil nutrient balance and vegetation productivity. Compared to the influence of foraging behavior and excreta return, treading impacts emerge more slowly, but have a more permanent effect. Therefore, it is important to systematically elucidate the separate effects of herbage consumption, treading, and dung and urine deposition on the soil physical structure, nutrient dynamics, and herbage accumulation rate, in order to gain a comprehensive theoretical understanding the functional processes and mechanisms of yak grazing and how they influence the alpine grassland nutrient biogeochemical cycling in soil-vegetation systems. Such understanding could be helpful for providing scientific guidance for optimizing yak grazing patterns, maintaining the sustainable development of fragile ecosystems, and enhancing the construction of national ecological security safeguards on the Qinghai-Tibetan Plateau.