*2.1. Study Area*

This study was conducted in Linshan Township, Yanting County (105◦45 E, 31◦27 N), located in the hilly area of the central Sichuan Basin, China. This region has typical low hill landforms with elevations of 400 m to 650 m. The climate is a subtropical monsoon climate, and the mean annual temperature and precipitation during 2008–2019 were 17.3 ◦C and 826 mm, respectively. This region is rich in purple shale that is easily weathered, and the soils are primarily purple soils. The aboveground vegetation is dominated by cypress plantations which were planted at a density of 4000–6000 plants/hm<sup>2</sup> in the 1970s. However, due to the high initial planting density and lack of necessary management, the ecological functioning of the plantation was in a degraded state, and the stand structure urgently needed adjustment.
