南亚热带森林2种菌根类型树木水分传导和养分利用策略的对比研究

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

摘要:

为揭示南亚热带季风常绿阔叶林在季节性干旱加剧和氮沉降增加等环境影响下，菌根树木优势度变化趋势机理，对3种优势EM树木黄杞（Engelhardtia roxburghiana）、锥（Castanopsis chinensis）、黧蒴锥（C. fissa）和3种优势AM树木云南银柴（Aporusa yunnanensis）、山蒲桃（Syzygium levinei）、广东金叶子（Craibiodendron scleranthum var. kwangtungense）的水力性状和养分性状进行了研究。结果表明，EM树木叶片导水率下降50%和88%时的水势（P₅₀、P₈₈）和膨压丧失点（Ψ_tlp）均低于AM树木，边材比导水率（K_S）、叶片比导水率（K_L）、光合氮利用效率（PNUE）和光合磷利用效率（PPUE）均高于AM树木。可见，EM树木比AM树木具有更强的抗旱能力以及更高的导水效率和养分利用效率，这可能是在干旱加剧和氮沉降增加背景下EM树木优势度增加而AM树木优势度减少的生理机制。

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.