新疆杨树干液流的径向变化及时滞特征

Abstract

PDF HTML阅读 XML下载 导出引用 引用提醒 新疆杨树干液流的径向变化及时滞特征 DOI: 10.5846/stxb201401060046 作者: 作者单位: 中国林业科学研究院荒漠化研究所,中国林业科学研究院荒漠化研究所,中国林业科学研究院荒漠化研究所,甘肃省治沙研究所,中国林业科学研究院荒漠化研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31070628); 中央级公益性科研院所基本科研业务费专项资金项目(CAFYBB2012024) Radial pattern and time lag of sap flow in Populus alba var. pyramidalis Author: Affiliation: Institute of Desertification Studies, Chinese Academy of Forestry,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用热扩散技术, 对绿洲农田防护林新疆杨(Populus alba L.var. pyramidalis)大树边材5个深度处(1、2、3、5 cm 和8 cm)的液流速率(Js)开展了连续两年的监测, 结果表明:(1)以标准长度2 cm的探针测得的液流速率(Js-2)为参照, 形成层下1、3、5、8 cm处的液流速率(Js-1, Js-3, Js-5, Js-8)与Js-2间具有显著的相关性, 回归系数分别为0.24-0.27、1.18-1.61、0.81-1.64和0.38-0.75, 液流速率最大的位点在形成层下3-5 cm处, 液流速率最小的位点在最外侧(1 cm)或最内侧(8 cm)处, 径向差异明显。边材不同深处的液流传输具有较一致的日变化过程。(2)在同步观测的5项气象要素中, 大气水汽压亏缺(VPD)和太阳辐射(Ra)与Js的回归系数均较大, 是驱动液流进程的主导气象要素。大气蒸发潜力(ET0)集合了多种气象要素的信息, 具有与Ra一致的日变化进程(启动、峰值时刻相同), 可作为分析液流昼、夜过程的综合气象变量。(3)新疆杨边材中五个深度处Js的峰值时刻基本相同(Js-1的峰值较其它层次提前4-123 min), 均明显滞后于Ra(时滞)并提前于VPD, 在7月份的晴天, ET0、Js和VPD峰值出现的时刻分别大致在12:30、14:00和15:00。新疆杨时滞的大小存在有规律的季节变化, 从6到10月份, Js与ET0峰值的时滞(ΔJ-E)逐渐增加, 变化在70-110 min(2011)、70-128 min(2012)之间, 但VPD与Js峰值的时滞(ΔJ-V)逐渐降低, 变化在73-20 min(2011)、63-8 min(2012)之间, 这表明在生长季的早期, 热量因子(Ra)对新疆杨液流变化的驱动较强, 而在生长季的末期, 大气水汽因子VPD的驱动效应更突出。 Abstract:Scientists have widely used sap flow measurements to estimate tree transpiration and to understand the physiological and environmental factors affecting the sap flow. However, the assumption of a uniform profile of sap flux may lead to a large bias when estimating whole-tree sap flow from measurements made with a single sensor in the outer part of the xylem sapwood. In this study, the sap flow velocities (Js) were measured at five depths (1 cm, 2 cm, 3 cm, 5 cm, and 8 cm) along a radial xylem transect of three larger trees of Populus alba L. var. pyramidalis Bunge, a popular tree species often planted in farmland shelterbelts of oasis in northern China. Measurements were made with five pairs of Granier thermal dissipation probes (TDP) for each tree over two consecutive growing seasons (in 2011 and 2012) to determine the radial sap flow pattern. The results showed that: (1) Js varies with depth in the descending order from 3 cm to 2 cm, 5 cm, 8 cm, and 1 cm. Js at depths of 1 cm (Js-1), 3 cm (Js-3), 5 cm (Js-5) and 8 cm (Js-8 ) were significantly and linearly correlated with that at 2 cm depth (Js-2), and their intercept coefficients were 0.24-0.27, 1.18-1.61, 0.81-1.64, and 0.38-0.75, respectively. The greatest Js appeared at depths of 3 to 5 cm under the cambium and the lowest appeared at depths of 1 cm or 8 cm; thus, the conventional 2-cm-long probe cannot reach the peak point of sap flow. Significant differences in Js were observed along the radial sapwood despite their similar diurnal course. (2) The atmospheric vapor pressure deficit (VPD) and solar radiation (Ra), two factors expressing the level of atmospheric vapor and heat, respectively, were the most important among the five meteorological factors controlling Js. The influence of Ra and VPD on Js in the outer and inner xylem during the growing season were similar for P. alba. However, accurately differentiating their respective contributions to sap flow proved to be difficult because of the interaction between them. The atmospheric potential evapotranspiration (ET0), which is a good indicator of the effects from meteorological variables, showed nearly similar diurnal pattern to Ra and was closely correlated with Js. (3) The diurnal course of Js for each depth displayed a near-normal curve with a peak at noon on typical sunny days. Js at depths of 2 cm to 8 cm peaked simultaneously. As an exception, the peak time of Js-1 appeared 4 min to 123 min ahead of the others. The peak times of all Js lagged behind Ra and were ahead of VPD. In July, P. alba exhibited vigorous physiological activities. The peak time of ET0, Js, and VPD on typical sunny days in July appeared at 12:30, 14:00 and 15:00, respectively. However, the time lag varied with season. The time lag between Js and ET0 (ΔJ-E) increased gradually from June to October with the amplitude of 70-110 min in 2011 and 70-128 min in 2012, indicating that solar radiation affected Js more strongly during the early growing season than later in the season. In contrast, the time lag between Js and VPD (ΔJ-V) decreased from June to October and varied in the range of 20-73 min in 2011 and 8-62 min in 2012, indicating that VPD affected Js more strongly in the late growing season than early in the season. 参考文献 相似文献 引证文献