模拟岩溶水分供应分层的干旱胁迫对青冈栎光合特性和生长的影响

Effects of drought stress on the photosynthesis and growth of Cyclobalanopsis glauca seedlings:A study with simulated hierarchical karst water supply

根据喀斯特地质特点,建立水分供应分层模拟柱(土壤层-岩石层-岩溶水层),并设置不同土壤水分梯度:重度干旱、中度干旱、水分适宜和水分饱和(相当于土壤田间持水量的30%～40%、50%～60%、70%～80%和90%～100%),研究2年生青冈栎(Cyclobal-anopsis glauca)苗木在模拟喀斯特生境下地经生长量、枝条生长量、光合曲线特征以及光合参数变化。结果表明:土壤干旱胁迫能显著降低青冈栎地径和枝条生长量,但在岩溶层有水的条件下,地径生长量不受土壤干旱胁迫影响;青冈栎的光合作用-光响应曲线符合非直角双曲线函数模型,不同处理光响应曲线的变化趋势基本一致;最大净光合速率和表观量子效率均表现为水分饱和>水分适宜>中度干旱>重度干旱;土壤干旱胁迫使青冈栎光饱和点降低、光补偿点升高,但岩溶水层有水时情况发生改变。

Based on the geological characteristics of karst environment, a simulated hierarchical columniation of water supply （soil layerepikarst layerrock layer） was built up, and a gradient of soil moisture content （severe drought, medium drought, suitable soil moisture, and saturated soil moisture corresponding to 30%-40%, 50%-60%, 70%-80%, and 90%-100% of field moisture capacity, respectively） was installed to investigate the photosynthesis and growth of 2-year-old Cyclobalanopsis glauca seedlings under the simulated karst environment. The results showed that soil drought stress decreased the growth of the seedlings basal diameter and branch significantly （P〈0.01）, but had less effects on the basal diameter growth when the water in epikarst layer was available. The photosynthesis-light response curve of the seedlings fitted the nonrectangular hyperbola model well, meaning an agreement between the model and the actual response of the seedlings photosynthesis, and the light response curve under different soil moisture conditions had the similar variation trend. The maximum net photosynthetic rate （Pmax） and the apparent quantum yield （AQY） of the seedlings under different soil moisture conditions were in the order of saturated soil moisture 〉 suitable soil moisture 〉 medium drought 〉 severe drought. Soil drought stress decreased the light saturation point （LSP） and increased the light compensation point （LCP）, but the LSP and LCP changed irregularly when the water in epikarst layer was available.