摘要
2005年6—10月在宁夏六盘山南侧的西峡林场,选择比较均匀的坡面（坡度45°）,布设了20m×20m的华北落叶松固定标准地,应用热扩散茎流计连续测定13株树木的树干液流。结果表明：不同径级树木的树干日液流量存在较大差异,在6—7月,其值变化在11.27～24.46kg·d^-1,变异系数CV为0.298（n=5）;在8—10月,其值变化在5.01～22.25kg·d^-1,变异系数CV为0.454（n=13）。方差分析表明,胸径和液流密度是2个显著影响树干日液流量变异的因子,前者主要通过决定树干边材面积来控制树干液流量大小,它可以解释变异方差的56.9%;树干液流密度可以解释变异方差的34.7%。相关性分析表明,树干液流密度与与林木个体的生长指标（树高、胸径、冠幅和边材面积）无显著相关关系,但与林木的空间指标——树冠重叠度呈显著线性负相关（r=-0.668）,即树干液流密度随树冠重叠度增加而降低,说明树干液流密度主要受其林木所处的空间位置及周围树木遮荫影响而发生变化。最后,利用树干液流密度与树冠重叠度之间的关系,提出基于林木空间差异估计华北落叶松林分蒸腾量的方法,并与常用的基于边材面积的尺度转换方法进行对比。结果表明,2种方法估计的林分日蒸腾量的数值变化趋势基本相同,但基于林木空间差异的方法估计的华北落叶松林分平均日蒸腾量为1.15mm·d^-1,而基于边材面积的方法的估计值为1.32mm·d^-1,前者低于后者13.13%,说明不考虑林木空间特征可能会导致林分日蒸腾量估计值偏大。
Sap flow of 13 trees of Larix principis-rupprechtii was measured with the thermal dissipation probe between June and October in 2005. Those trees were randomly selected from a 20 m × 20 m plot, wihch is located on a slope with a gradient of 45° in the Xixia forestry station along the south side of Liupan Mountains, Ningxia. There was a large variation in daily sap flow among the individual trees ranged from 11.27 kg·d^-1 to 24.46 kg·d^-1 , with a variation coefficient of 0. 298 from June to July （ n = 5） ; and ranged from 5.01 kg·d^-1 to 22.25 kg·d^-1 , with a variation coefficient of 0.454 from August to October （ n = 13）. Analysis of variation indicated that diameter at breast height （DBH） and sap flux density （SFD） were two main factors that significantly affected the variation of daily sap flow. DBH and SFD were able to respectively explain 56.9% and 34.7% of the total variation of daily sap flow. The relation between sap flow and DBH may be well interpreted by the close relationship between DBH and sapwood area. Regression analysis showed that SFD was not correlated with DBH, tree height, crown area and sapwood area, however it was significantly and negatively correlated with the canopy overlapping（ r = -0.668）. This result suggested that SFD was strongly influenced bv the spatial position of trees and their shading condition bv surrounding trees. At last. a new
method used for estimating the stand transpiration was proposed based on the relationship between SFD and the canopy overlapping which is characterized by the spatial position difference of individual trees. The change pattern of the daily stand transpiration estimated by the method was basically similar to that estimated by the traditional method of sapwood area. The new method produced an estimation of stand transpiration of 1,15 mm·d^-1, which was 13.13 % lower than the value of 1.32 mm·d^-1 estimated by the traditional method. It was concluded that the stand transpiration could be over-estimated without considering the difference of spatial characters of individual trees.
出处
《林业科学》
EI
CAS
CSCD
北大核心
2008年第1期34-40,共7页
Scientia Silvae Sinicae
基金
国家重点基础研究发展规划项目(2002CB111501)
国家自然科学基金项目(30671677)
国家科技部林业科技支撑计划专题(2006BAD03A1803)
国家林业局引进国际先进技术项目(2003-4-43)
科技部社会公益研究专项(2004DIB3J102)
国家林业局森林生态环境重点试验室联合资助
关键词
华北落叶松
人工林
树干液流
个体差异
蒸腾
尺度上推
树冠重叠度
Larix principis-rupprechtii
plantation
sap flow
variation of individual trees
transpiration
scaling up
canopyoverlapping
