Tree species composition affects litter eco‐hydrological function in Pinus massoniana conifer‐broadleaf mixed forest stands in southwest China

Abstract

Although changes in tree species composition profoundly affect the structure, function, and processes of mixed forest ecosystems, there is limited knowledge on the effects of these changes on the hydrological functions of the litter layer in Pinus massoniana conifer‐broadleaf mixed forests in subtropical mountains. Here, we investigated three typical P. massoniana forest stands in southwest China: P. massoniana‐Liquidambar formosana conifer‐deciduous broadleaf mixed forest (Pm + Lf), P. massoniana‐Castanopsis eyrei conifer‐evergreen broadleaf mixed forest (Pm + Ce), and P. massoniana plantation (Pm), and conducted field investigations (litter composition and mass) and indoor immersion experiments to analyse the litter water‐holding capacity (LWHC) of forest stands in their natural state and with artificial ratios combining mixed (needle‐leaf and broad‐leaf) litters. The total litter mass did not significantly differ among the three forest stands (p > 0.05), but significant differences were observed in the needle‐leaf (0.67–2.92 t hm−2), broad‐leaf (0.32–1.89 t hm−2) and bark (0.11–0.34 t hm−2) masses in the undecomposed layer. The LWHC of different stand types was in the order of Pm + Lf > Pm + Ce > Pm. The maximum water‐holding capacity of different artificial ratios of mixed litters was positively proportional to the broad‐leaf mass and inversely proportional to the needle‐leaf mass, and the P. massoniana‐L. formosana mixed litter had a higher maximum water‐holding capacity than the P. massoniana‐C. eyrei mixed litter. The LWHC of mixed forests is mainly influenced by stand structure (tree composition) and litter characteristics, and is positively correlated with leaf area, thickness, dry matter content, and surface roughness. This study revealed that the LWHC can be significantly affected by different P. massoniana stands in subtropical mountains. This study will aid the sustainable and ecological management of forest in subtropical mountains, and P. massoniana plantations should be gradually converted into mixed conifer‐broadleaf forests with greater LWHC and buffering capacity.