黄土丘陵沟壑区典型小流域生态系统服务权衡与协同关系研究

Ecosystem service tradeoffs and synergies in typical small watersheds of the hilly and gully region of the Loess Plateau

黄土高原植被恢复状况制约生态系统服务的提升,本研究依托中国科学院水利部水土保持研究所安塞国家科学野外观测站的基础土壤、植被、气象和水文等数据,在黄土丘陵沟壑区选取纸坊沟和坊塌2个典型小流域,通过购买1998、2008和2018年遥感影像,采用InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)模型对生态服务(碳储量、土壤保持量、生境质量和产水量)进行评估,探究植被恢复过程中生态系统服务的协同效应和权衡关系。通过对比得知:随着植被的恢复,坊塌和纸坊沟各生态服务(碳储量、土壤保持量、生境质量和产水量)均得到了大幅度的提升,其中2008—2018年增加幅度较小,而1998—2008年增加幅度较大,主要原因在于该阶段(1998—2008年)是退耕还林还草的初始10年,林地及草地面积增长较多,而后10年为退耕的延续阶段,退耕面积增长减缓。从1998—2018年,受自然因素和人为因素的影响,坊塌和纸坊沟流域生态系统服务表现出协同和权衡关系。对于坊塌流域,2008年生态系统服务主要表现为协同关系,1998、2018年以权衡关系为主;对于纸坊沟流域,1998年生态系统服务主要表现为协同关系,2008和2018年以权衡关系为主。相同生态系统服务在不同年份有所差别,土地利用类型相同生态系统服务也可能不同。综合来看,2个典型小流域的碳储量、产水量和土壤保持量均以协同关系为主,伴随区域的权衡关系;主要是由于在植被恢复过程中,生态系统服务在时空上增加的幅度不同;因此,在黄土丘陵沟壑区的植被恢复过程中,应综合考虑生态系统服务的协同与权衡,因地制宜的划分和制定合适的保护策略。

Vegetation restoration on the Loess Plateau affects the improvement of ecosystem services. Based on the National Field Observation and Research Station of Farmland Ecosystem in Ansai, Shaanxi Province, the two typical small watersheds(Zhifanggou and Fangta) were selected. We used rainfall data, remote sensing interpretation data, social and economic data from 1998 to 2018 to assess four ecosystem service(including soil conservation, carbon storage, water conservation and habitat quality) and to explore the tradeoff and synergy relationships of these ecosystem service. The results showed that vegetation restoration promoted ecosystem services functions(soil conservation, carbon storage, water yield and habitat quality) in the two typical small watersheds, with a slight increase from 2008 to 2018, but a large increase from 1998 to 2008. The forestland and grassland were largely distributed during the initial 10 years from 1998 to 2008, while farmland was largely distributed in the subsequent 10 years from 2008 to 2018. In addition, there was a synergistic and tradeoff relationships of ecosystem services among the two typical small watersheds, which was dominant with the synergistic relationship, due to the influence of natural factors and human factors. Concretely, in 1998, ecosystem service functions exhibited synergy in Zhifanggou, and exhibited tradeoff in 2008 and 2018. In Fangta, ecosystem service functions exhibited tradeoff in 1998 and 2018, while exhibited synergy in 2008. There was a difference in ecosystem service function in different land use types and different areas. In total, water yield, carbon storage and soil conservation showed the synergy relationship. The main reason was that ecosystem services increased differently in time and space in the process of vegetation restoration. Thus, it is necessary to divide and develop appropriate protection strategies according to their trade-offs and synergies relationships among ecosystem service functions.