Relationship between effective solar radiation and sap flow process during an entire growing season in Western Mountains of Beijing

In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity （SFV） of Platycladus orientalis and Pinus tabulaeformis, effective solar radiation （ESR） and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe （TDP） system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5-3 hours later than those of solar radiation and there were small differences between Platycladus orientalis and Pinus tabulaeformis. But peak times and stopping times of sap flow varied considerably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalis and Pinus tabulaeformis were about 0-3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR （sunrise effect）. Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized.

树木边材液流传输研究述评

结合作者的研究工作进展,对当前国内外有关树边材木水分传输机理的研究概况进行了述评,分析了树木水分传输驱动力的构成要素及内聚力学说对树木边材水分传输连续体合理解释,探讨了稳态流模型和非稳态模型在描述树木水分传输方面的效果,介绍了树木组织水容的概念及其在调控树木水分传输过程中的作用和意义,介绍了当前国内外导管空穴化和木质部栓塞研究概况、树木边材导管空穴化的发生机制及检测方法、树木输导组织栓塞对水分传输的影响及栓塞脆弱性评价等。

基于热消散探针法的植物水分运输的研究进展

液流是分析树木耗水特性、研究树木水分传输机制的重要途径之一,热消散探针法已广泛用于树干液流变化的监测。热消散探针法是目前研究不同时空尺度上植物蒸腾耗水特性较为灵活、可靠、经济的一种方法。但由于物种特性的差异,可能造成试验过程中出现测量值与实际值相比偏低的状况。此外,相当一部分植物依赖树干储存水进行蒸腾,因此木材含水量的波动很可能会导致蒸腾作用测定的误差。对热消散探针法的工作原理、优势和局限以及使用时需要注意的问题进行了综述,并回顾了基于热消散探针法开展的植物水分运输研究以及针对该方法进行的校正与改进方面的相关成果。

风沙静电场对植物茎秆液流传输过程影响的理论分析

风沙流对植物生理过程具有非常重要的影响,但是对其影响机理目前并无相关理论模型给予解释。本文基于植物茎秆的刚性导管模型讨论了风沙静电场对植物茎流速率的影响。结果表明:随着外部电场增强,茎流速率指数增加,即外部电场越强,水分输运速度越快;植物茎秆导管半径越大,水分输运速度越快,且电场的影响越明显。本文结果在一定程度上解释了风沙流胁迫对植物的影响远大于净风影响的实验结果,可为沙化地区的植被保护提供一定的帮助。