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尾巨桉树干木质部液流密度径向变化特征

周翠鸣1,黄玉清1**,顾大形1,任世奇2,张德楠1,曾丹娟1   

  1. (1广西喀斯特植物保育与恢复生态学重点实验室, 广西壮族自治区中国科学院广西植物研究所, 广西桂林 541006; 2广西林业科学研究院, 南宁 530002, 广西吴圩森林生态系统定位观测研究站, 南宁 530225)
  • 出版日期:2015-08-10 发布日期:2015-08-10

Radial variation of xylem sap flow density in trunks of Eucalyptus urophylla×Eucalyptus grandis.

ZHOU Cui-ming1, HUANG Yu-qing1**, GU Da-xing1, REN Shi-qi2, ZHANG De-nan1, ZENG Dan-juan1   

  1. (1Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Academy of Sciences, Guilin 541006, Guangxi, China; 2Guangxi Forestry Research Institute, Nanning 530002, China; 3Wuxu Forest Ecosystem Observation and Research Station in Guangxi, Nanning 530225, China)
  • Online:2015-08-10 Published:2015-08-10

摘要: 目前尾巨桉(Eucalyptus urophylla × Eucalyptus grandis)在中国南部大面积种植,尤其是在广西。其水分利用效率对森林的可持续发展以及水资源管理越来越受到关注。在不了解树干液流径向变化的前提下,将最外层边材液流测定值推广到整树或者林分尺度会产生很大的误差。为了准确测定整树耗水,采用热消散探针法(TDP)研究了南宁七坡林场4年生尾巨桉树干液流的径向变化特征。结果表明:各个深度有相似的日变化规律,0~20 mm深液流占有很大比例,随季节有所变化,20~40 mm深液流保持相对稳定;通过对0~20 mm和20~40 mm两个边材深度的日平均液流密度进行曲线回归分析,两者存在显著的幂指数相关关系(R2>0.90,P=0.00);同时分析了不同深度的径向分布格局,发现尾巨桉属于4大液流径向分布格局之一的递减型,且递减程度比较陡峭;白天和夜间的径向变化规律不一样,白天液流密度径向变化较明显,夜间则表现稳定。本文的发现有助于通过更精确地计算季节性液流密度来准确估算混种桉树的水分利用效率,对土地管理有重要的意义。

关键词: 粗木质残体 , 养分, 高山森林, 林窗, 苔藓

Abstract: Largescale plantations of Eucalyptus urophylla × Eucalyptus grandis have been recently developed in southern China, especially in Guangxi Province. For sustainable forest and water resource management of these plantations, attention is increasingly paid to their water use efficiency. Sap flow measurement provides a powerful tool for quantifying plant water use, and it is widely employed to estimate the ecological and hydrological outcomes of plant growth. However, a potential error might occur if one applies the sap flow measurements of the outermost layer of these trees to the entire trunk or an entire plantation without considering the radial distribution of xylem sap flow density. Hence, we determined the radial distribution of xylem sap flow density in trunks of 4-year-old E. urophylla × E. grandis using the Granier thermal dissipation probe (TDP) method at the Qipo Forest Farm, Guangxi Province. We found that despite similar diurnal variation of sap flow at different depths of the trunk, sap flow at the 0-20 mm depth constituted bulk of the flow, which changed with seasons, while that of the 20-40 mm depth remain relatively stable. The curve regression analysis showed a significant exponential correlation in daily mean sap flow density (R2>0.90, P=0.00) between the 0-20 and 20-40 mm depths. Radial distribution pattern of sap flow of, E. urophylla × E. grandis showed a declining pattern with steep slope. The mean monthly sap flow density showed significant changes in the daytime, but it was relatively stable at night. Our findings will be helpful in accurately assessing the water use efficiency of this widely planted Eucalyptus hybrid by more precise calculation of its seasonal sap flow density, having significant implications for land management.

Key words: gap, bryophyte, alpine forest., coarse woody debris, nutrient