Effects of thinning retention density on litter and soil water retention characteristics of Chinese fir plantation

Taking Chinese fir plantation with 11−year thinning retention density of 1200, 1800 and 2500 trees·hm⁻² in northern Guangdong as the research object, the differences of litter and soil water retention characteristics of different Chinese fir plantation after thinning for 2 years and the influencing factors were analyzed, and the water retention performance of stands with different thinning retention density was explored. The results show that: Higher retention density was conducive to litter accumulation, and the litter inventory and thickness of 2500·trees/hm² Chinese fir forest increased by 7.96%～30.87% and 4.90%～24.92% compared with the other two density stands. The soil maximum water holding capacity and effective storage capacity of 1800 trees/hm² stands were the largest in different retention densities of Chinese fir forests, and were significantly greater than 1200 trees/hm² stands. The soil saturation water holding capacity and capillary water holding capacity of 1800/hm² stands were the largest in the 3 kinds of preserved density Chinese fir forests, which increased by 6.5% to 24.95% compared with the other 2 kinds of preserved density stands. The soil non−capillary water capacity increased with the increase of retention density, which was 2500 trees·hm⁻²(45.50 t/hm²) > 1800 ·hm⁻²(32.21 t/hm²) > trees/hm²(23.76 t/hm²). The results of correlation analysis showed that litter water capacity was significantly correlated with litter thickness and existing stock, soil pH value, organic carbon content, non−capillary porosity, and non−capillary water capacity. The soil moisture content is significantly correlated with total porosity, capillary porosity, and non−capillary porosity, soil bulk density, soil organic matter content, canopy density and leaf area index. The results of coordinate comprehensive evaluation showed that the comprehensive water holding capacity of litter and soil was 1800 trees/hm² > 2500 trees/hm² > 1200 trees/hm² in the stands with different retention densities. In conclusion, 1800 trees/hm² stands had the best litter and soil water retention capacity among the 3 different retention density stands.