不同长度热消散探针测定粉单竹(Bambusa chungii)液流的差异分析和原位验证  

Difference of measured sap flows of Bambusa chungii using thermal dissipation probes at different lengths and their in situ validation

作　　者：赵平[1] 梅婷婷[1] 朱丽薇[1] 牛俊峰[1] 倪广艳[1] 

机构地区：[1]中国科学院华南植物园,广州510650

出　　处：《生态学杂志》2014年第5期1420-1428,共9页Chinese Journal of Ecology

基　　金：国家自然科学基金项目(31170673;41030638和41275169);广东省自然科学基金项目(S2012020010933)资助

摘　　要：由于竹壁较薄,测定液流时安装常规长度(20 mm)的TDP探针易穿破竹壁。与木材的热传导不同,暴露于竹腔内的部分上探针的热量以辐射形式消散,加之竹壁水分传导分子的分布不均匀,导致液流密度的测定值不准确。因此,不少学者主张选用较短的探针,然而,对于改短探针的应用缺乏必要的户外原位验证。本文分析自制的5、8和10 mm的TDP探针原位测定粉单竹液流的适用性和理论依据。结果表明:新建立的液流密度公式与Granier原始经验公式的参数α值的差异较大,主要原因是竹腔的储热效应导致上探针周围温度偏高,竹秆水分含量较低,热消散系数(h0)较小,上探针周围的热量囤积致使上下探针的温差较大;此外,探针的安装方式也影响液流密度的测定结果,是导致相同长度探针测定粉单竹液流密度值明显差别的重要因子。本文通过分析探针周围介质的h0的变化,较合理地解释了这些差异的原因。Thin bamboo wall may easily be penetrated through when installing the common type TDP sensor of 20 mm long for sap flow measurement. Differing with the case of thermal conduc- tion in wood, the part of the upper probe penetrating into the bamboo cavity dissipates heat in a way of radiation. Hence, the dissipation, together with those unevenly distributed water-conduc- ting units within the bamboo wall, may result in measurement inaccuracy of sap flux density and shorter probes have been recommended in general. However, lacking of in situ validation of shor- ter probes limits their applications for accurate sap flow measurements. In this study, sap flow of Bambusa chungii was simultaneously monitored using self-made 5, 8 and 10 mm long TDPs in the field for testing their applicability as well as providing technical supports after theoretical analy- ses. Experimental results indicated that the difference between the fitted equation for calculating sap flux density that was established for B. chtmgii and the empirical one that was originally pro- posed by Granier was mainly due to the significant deviation of the parameter a. Such a discrep- ancy may be preliminarily resulted from the heat accumulating effect in the bamboo cavity that causes higher temperature in the area around the upper probe as well as the lower thermal diffu- sion coefficient （h0 ） of bamboo wall that, with a low water content, may also hoard heat and thus generate larger temperature difference between upper and lower probes. In addition, the way to insert probes into the bamboo wall also affected the measurement and might be another impor- tant factor leading to significant variation in monitored sap flux density of B. chungii even with TDPs at the same length. Further analyses on h0 of surrounding media of TDP provided reasona- ble explanation for these discrepancies.

关 键 词：粉单竹 热消散探针 液流密度、热消散系数 

分 类 号：S795[农业科学—林木遗传育种]