2.1 Study area
Our study area is located on the southwest mountain of Sichuan Province (Fig. 1), which experienced heavy deforestation starting in the 1950s and is the site of implementation of NFP and GGP. The forest area has recovered rapidly. By 2019, the forest coverage rate has reached 40% in Sichuan province (Cui H., and Liu M., 2020), exceeding the world average (30%). The forest types contain subtropical evergreen broad-leaved forest, deciduous broad-leaved forest, coniferous broad-leaved mixed forest and cold temperate coniferous forest (Sichuan Vegetation Cooperation Group, 1980). The climate is sub-humid subtropical climate. The study area represents the ‘ecological protective screen’ for the upstream Yangtze River catchment that has a great national significance for water, soil and biodiversity conservation.