六盘山南坡华北落叶松(Larix principis-rupprechtii)树干直径生长及其对气象因子的响应

The growth in stem diameter of Larix principis-rupprechtii and its response to meteorological factors in the south of Liupan Mountain

2005年6~9月份在宁夏六盘山南侧的西峡林场,应用带状树木径向变化记录仪(Dendrom eter)研究了5株华北落叶松树干的直径生长过程,结果表明,在无雨或小雨(日降雨量<10mm)天气下,树干直径变化呈现出明显的日周期性,可将其划分为3个阶段:收缩阶段、膨胀阶段和生长阶段;在连续降雨(日降雨量≥10mm)及随后的几个晴天中,树干直径变化并不表现出完整的日周期性。基于Deslauriers等人的方法,提出了树干直径日生长量估计的修正公式,并计算了华北落叶松树干直径日生长量和累积生长量,结果表明,各样木树干直径日生长量的季节变化趋势一致,即表现为前快后慢的季节变化格局,6~7月份为快速生长期,其日均生长量在27.0~44.2μm之间;8~9月份为缓慢生长期,其日均生长量在10μm以下;各测定样木的树干直径日生长量具有明显的个体差异,这主要与林木个体大小及其所处林分中的微环境条件差异有关;整个观测期内的树干直径累积生长过程可以较好地用幂函数描述。主分量分析和偏相关分析表明,影响树干径向生长的气象因子可划分为3类,其中日降雨量、日最低气温、日平均太阳辐射和日平均空气饱和差是影响树干径向生长的主要因子。

The growth pattern in stem diameter of five sample trees of Larix principis- dendrometer from June to September in 2005 in the south of Liupan Mountain, Ningxia. The results indicated that in the days with daily rainfall 〈 10mm, the daily fluctuation of stem diameter presented a periodical cycle and it could be divided into three phases： shrinking phase, expansion phase and growth phase. However, daily fluctuation of stem diameter presented a different pattern at in the days with daily rainfall I〉 10mm and followed clear days. Based on the method defined by Deslauriers et al. for estimating daily growth of stem diameter, a modified method was presented to calculate daily and cumulative growth of stem diameter, and the results showed that seasonal pattern of daily growth were similar among five sample trees. During June and July period, stem grows quickly with an average growth rate in stem diameter at 27.0 --44. 21j^na per day. Relatively, It grows slowly during August and September period, with a mean Both daily and cumulative stem growth were significantly different among sample trees, growth rate at 10 i.~m per day. which could attributed to the difference in tree domain and their positions in the stand. The pattern of cumulative growth could be fitted by the power function satisfactorily. Principle Component Analysis and Partial Correlation Analysis indicated that the meteorological factors could be classified into three groups, and daily precipitation, minimum daily temperature, average daily solar radiation and average daily vapor pressure deficit were four significant factors to determine daily stem growth.