Comparison Studies on Water Transport and Nutrient Acquisition of Trees with Different Mycorrhiza Types in Subtropical Forest

Abstract:

To reveal the mechanisms of changing trend of mycorrhizal tree dominance under the environmental influence of increasing seasonal drought and nitrogen deposition in the lower subtropical monsoon evergreen broad-leaved forest, the hydraulic traits and nutrient traits of three ectomycorrhizal (EM), including Engelhardtia roxburghiana, Castanopsis chinensis and C. fissa, and three arbuscular mycorrhizal (AM) dominant trees, including Aporusa yunnanensis, Syzygium levinei and Craibiodendron scleranthum var. kwangtungense, were measured. The results showed that the leaf water potential at which 50% and 88% hydraulic conductance are lost (P₅₀ and P₈₈) and leaf turgor loss point (Ψ_tlp) of EM trees were lower than those of AM trees, while the sapwood specific hydraulic conductivity (K_S), leaf specific hydraulic conductivity (K_L), photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE) of EM trees were higher than those of AM trees. The results suggested that EM trees have stronger drought resistance ability and higher water and nutrient use efficiency compared with AM trees. This might be the physiological mechanism of increasing dominance of EM trees while decreasing dominance of AM trees under the background of increasing drought and nitrogen deposition.