地下水埋深及水质对塔克拉玛干沙拐枣气体交换特性的影响

Effect of Groundwater Depth and Quality on Gas Exchange Characteristics of Calligonum taklimakanensis

塔克拉玛干沙漠地下水储量丰富,但因埋深和水质的限制,植物可有效利用的水资源十分有限。通过分析沙漠特有灌木塔克拉玛干沙拐枣(Calligonum taklimakanensis B.R.Pan & G.M.Shen)气体交换特性对地下水埋深和水质变化的响应,探讨了地下水对天然植物分布及生长的影响。结果显示,有天然植被分布的区域地下水埋深一般较浅,土壤水分供应充足;但受地下水矿化度、总硬度、总碱度、全盐含量及各离子含量比例的区域间差异影响,不同区域的塔克拉玛干沙拐枣气体交换特性各不相同。地下水总碱度大小是影响塔克拉玛干沙拐枣光合特性最主要的因素,总碱度增加时,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)及潜在最大净光合速率(Pmax)、光补偿点(LCP)和光饱和点(LSP)分别从14.9±0.39μmolCO2·m-2·s-1、6.79±0.21mmol·m-2·s-1、0.192±0.013mmol·m-2·s-1、21.4±1.1μmolCO2·m-2·s-1、175.5±3.5μmol·m-2·s-1、1805±31.2μmol·m-2·s-1降为11.7±0.5μmolCO2·m-2·s-1、5.79±0.18mmol·m-2·s-1、0.130±0.009mmol·m-2·s-1、16.3±2.5μmolCO2·m-2·s-1、78.1±15.8μmol·m-2·s-1、1564±55.6μmol·m-2·s-1。研究结果还表明,较浅的地下水埋深是沙漠腹地天然生植物生存繁衍的必要条件,塔克拉玛干沙拐枣天然分布区的适宜地下水埋深应在1.5～2.5m的范围内;塔克拉玛干沙拐枣也具有很强的盐碱耐受能力,在矿化度高达16g·L-1的环境中依然能正常存活生长。

Groundwater resource is abundant in the Taklimakan Desert, but the water which can be used effectively by plants is very limited due to restriction of groundwater depth and quality. The objective of this paper is to discuss the effect of groundwater depth and quality on the distribution and growth of natural vegetations through measuring the responses of gas exchange characteristics of endemic shrubs Calligonum taklimakanensis B.R. Pan G.M. Shen. In those regions where natural vegetation distributed groundwater depth is shallow and soil moisture is adequate for plant growth. The gas exchange characteristics of the C. taklimakanensis are various in different regions because of regional differences of salinity, total hardness, total alkalinity, total salt content and proportion of ions content in the groundwater. The total alkalinity of groundwater is the key factor that affected photosynthetic characteristics of C. taklimakanensis. With the increase of total alkalinity, the net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductance （Gs）, maximal net photosynthetic rate （Pmax）, light compensation point （LCP） and the light saturation point （LSP） of C . taklimakanensis decreased from 14.9±0.38 molCO2·m-2·s-1, 6.79±0.21 mmol·m-2·s-1, 0.192±0.013 mmol·m-2·s-1, 21.4±1.1 molCO2·m-2·s-1, 175.5±3.5 mol m-2·s-1, 1 805±31.2 mol·m-2·s-1 to 11.7±0.5 molCO2·m-2·s-1, 5.79±0.18 mmol·m-2·s-1, 0.130±0.009 mmol·m-2·s-1,16.3±2.5 molCO2·m-2·s-1, 78.1±15.8 mol·m-2·s-1, 1 564±55.6 mol·m-2·s-1, respectively. Moreover, the shallow buried depth of groundwater is the necessary condition for the distribution and survive of natural desert plants, and the appropriate groundwater level of natural C. taklimakanensis is about a range from 1.5 m to 2.5 m. C. taklimakanensis has so stronger salt and alkali tolerance that it still be able to survive under the salinity of 16 g·L-1.