侧柏幼树不同生长阶段对水分的敏感性与蒸腾效率

通过旱棚人工控水,对不同生长阶段谐变供水条件下,供水量与供水方式对侧柏幼树蒸腾耗水、水分利用效率的影响、幼树不同生长阶段对水分的敏感性等问题进行了研究。结果表明,幼树总耗水量随年均土壤供水能力和幼树各生长阶段供水模式的不同而变化。在平均有效水供给能力较低或单一阶段土壤相对含水率不超过87.84 %时,幼树蒸腾耗水量随中后期——生长盛期和生长后期供水量的增加而增大;相反,在平均有效水供给能力较高或单一阶段土壤相对含水率超过87.84 %时,幼树蒸腾耗水量则随着中前期——生长前期和生长盛期供水量的增加而增大。在年均土壤供水能力基本相同时,不同生长阶段供水量的分配对侧柏幼树蒸腾耗水有较大影响。综合分析表明,生长盛期供水对蒸腾耗水的贡献最大,生长后期次之,生长前期最小。侧柏幼树不同生长阶段对水分的敏感性,以生长盛期和生长前期最大,生长后期较低。但生长后期适度减少水分供应,具有一定的促长作用。使侧柏幼树达到最佳水分利用效率的土壤供水水平为:生长前期土壤相对含水率75 .96 % ,生长盛期73.76 % ,生长后期6 9.5 2 %。并建立了侧柏幼树的时间水分生产函数

Sensitivity of Platycladus orientalis young tree to water stress and its transpiration efficiency at different growth stages during annual growth period

Using the artificial water control technique in the shed of free-rain and periodically- changing water supply at different growth stages during annual growth period, we examined the sensitivity of young trees to water stress and the relationships between transpiration water-consumption, transpiration efficiency and soil water supply for Platycladus orientalis. The results showed that the transpiration water-consumption was affected by the average amount and procedure of water supply at different growth stages over the annual growth period. Transpiration water-consumption of Platycladus orientalis increased with increasing water supply either at the fast growing and late growth stages when the annual water supply was low or relative soil moisture was no more than 87.84% at any growth stage, or at the early growth stage and fast growing stage when the annual water supply was high or relative soil moisture was more than 87.84% at any single growth stage. The apportionment of water supply among growth stages had a big impact on the transpiration water-consumption, showing the highest sensitivity of Platycladus orientalis to soil water stress at the fast growing stage and the lowest at the late growth stage. However, maintaining relative lower soil moisture at the late growth stage can improve the youngling's growth. The optimum relative soil moisture for WUE was 75.96% at the early growth stage, 73.76% at the fast growing stage, and 69.52% at the late growth stage. A dated water production functions for Platycladus orientalis were put forward for the first time.