Yan Cheng-Zheng, Zheng Wen-Ge, Jia Jian-Bo, Yan Wen-de, Wang Zhong-Cheng, Jia Guo-Dong
College of Life Science and Technology, Central South University of Forestry and Technology, Changsha 410004, China.
Beijing General Station of Soil and Water Conservation, Beijing 100036, China.
Ying Yong Sheng Tai Xue Bao. 2020 Dec;31(12):4017-4026. doi: 10.13287/j.1001-9332.202012.010.
A water-controlled experiment with four treatments (no rain, half raining, natural raining and double raining) was carried out in a forest. The factors including soil water content (SWC), precipitation, sap flow density (), leaf area index (LAI), vapor pressure deficit (VPD) were monitored during August 2016 to August 2017. We further analyzed the response of canopy stomatal conductance () to changes of SWC. The results showed that the SWC of plots (half, natural and double raining) showed a positive correlation with precipitation, and the range of SWC was 4.9%-16.0%, 7.2%-22.9%, 7.4%-29.6%, respectively. The SWC in the plot with no rain decreased by 50% from August to October. The daily reached a peak of 166.64 mmol·m·s at 14:00 in July, which was significantly higher than other months. A bimodal phenomenon occurred. The daily reached a peak of 54.1 mmol·m·s at 12:00 in January. Under the three rain plots, diurnal variation of and SWC showed a negative quadratic correlation. The SWC corresponding to the peak of was 8.5%, 12.5% and 18.5%, respectively, close to the annual average SWC. Sensitivity () of to VPD /reference canopy stomatal conductance () was more than or equal to 0.6 in different water-controlled plots, indicating that soil water condition was more suitable for water demand of . When SWC was between 3.7% and 7.5%, the and increased rapidly, indicating that stomata had better regulation ability, and that plant stomata was more sensitive to VPD. When SWC increased to 11%, SWC alteration did not affect the response sensitivity of and to VPD. There might be a SWC threshold value for the adaptation of . By closing or reducing stomatal aperture, leaf water potential decreased, could adapt to excessive VPD and avoid excessive transpiration, which was more effective in regulating transpiration.
在一片森林中进行了一项有四种处理方式（无雨、半雨、自然降雨和双倍降雨）的水分控制实验。在2016年8月至2017年8月期间，对包括土壤含水量（SWC）、降水量、液流密度（）、叶面积指数（LAI）、水汽压差（VPD）等因素进行了监测。我们进一步分析了冠层气孔导度（）对SWC变化的响应。结果表明，各试验区（半雨、自然降雨和双倍降雨）的SWC与降水量呈正相关，SWC范围分别为4.9%-16.0%、7.2%-22.9%、7.4%-29.6%。无雨试验区的SWC在8月至10月间下降了50%。7月14:00时，日 达到峰值166.64 mmol·m·s，显著高于其他月份，出现双峰现象。1月12:00时，日 达到峰值54.1 mmol·m·s。在三种降雨试验区下， 和SWC的日变化呈负二次相关。 峰值对应的SWC分别为8.5%、12.5%和18.5%，接近年平均SWC。在不同水分控制试验区， 对VPD/参考冠层气孔导度（）的敏感性（）大于或等于0.6，表明土壤水分条件更适合 的水分需求。当SWC在3.7%至7.5%之间时， 和 迅速增加，表明气孔具有较好的调节能力，且植物气孔对VPD更敏感。当SWC增加到11%时，SWC的变化不影响 和 对VPD的响应敏感性。 适应可能存在一个SWC阈值。通过关闭或减小气孔孔径，叶片水势降低， 可以适应过高的VPD并避免过度蒸腾，这在调节蒸腾方面更有效。
