西藏不同种源大果圆柏群落特征差异性研究

A Study of community characteristics difference of Juniperus tibetica from different provenances in Xizang

本研究以西藏大果圆柏自然分布区内的15个天然群落作为调查样地,运用单因素显著性方差分析及Pearson相关性分析方法,探究不同种源大果圆柏群落特征的差异性及与其生境环境因子的相关性,揭示地理-气候因子对大果圆柏生长的影响。研究结果表明:(1)不同种源大果圆柏天然群落郁闭度、树高、胸径、南北冠幅、东西冠幅、结实层、枝条生长及比叶重均存在显著性差异(p<0.05),部分种源间差异未达到显著性水平,其中郁闭度、冠幅、比叶重种源间的差异最大。郁闭度的变动范围较大,为0.16~0.82,其中那曲比如县羊秀种源的郁闭度最大,察雅县王卡种源最小且与其他重要差异极显著;树高变幅范围为2.17~6.8 m,中亦种源的树高最小,察雅县王卡种源的树高最大;胸径的变化幅度为3.65~39.98 cm,其中索县亚拉种源的胸径最小,浪卡子种源的胸径最大;比叶重的变动范围为439.85~732.33 g·m^(-2),其中浪卡子的比叶重伟大,亚拉种源的比叶重最小。(2)不同种群特征指标对经纬度、海拔及气候因子的响应强度不同,郁闭度、物种丰富度、枝条生长及比叶重受气候因素影响较大,树木生长形态指标受海拔影响较大。郁闭度与纬度呈显著正相关(R=0.333),物种丰富度与年均温呈极显著负相关(R=-0.423),与无霜期呈显著正相关(R=0.356);树高、冠幅与年均降水量呈显著负相关(R=-0.211、-0.201、-0.345),树高、胸径、冠幅、结实层与海拔均呈显著正相关(R=0.179、0.197、0.238、0.237、0.180);主枝当年生长量、侧枝基径与年均降水量呈显著正相关(R=0.441,0.210),与无霜期呈显著负相关(R=-0.296、-0.308);侧枝当年生长量与年日照时长呈显著正相关(R=0.165)。

In this study,15 natural communities in the natural distribution area of Juniperus tibetica in Xizang were taken as sample sites,and univariate significant analysis of variance and Pearson correlation analysis were used to explore the differences in community characteristics of different provenances and the correlation with habitat environmental factors,so as to reveal the effects of geo-climatic factors on the growth of Juniperus tibetica.The results showed that:(1)There were significant differences in canopy closure,tree height,DBH,crown width in north and south,crown width in east and west,fruit bearing layer,branch growth and specific leaf weight among different provenances(p<0.05).The differences among some provenances were not significant,among which the differences in canopy closure,crown width and specific leaf weight were the largest.The canopy density varied widely,ranging from 0.16~0.82.The canopy density of Yangxiu provenance in Naqu Biru County was the largest,and that of Wangka provenance in Chaya County was the smallest,which was significantly different from other important provenances.The tree height ranged from 2.17~6.8m,the tree height of Zhongyi provenance was the smallest,and the tree height of the Wangka provenances of Chaya County was the largest.The DBH variation range was 3.65~39.98 cm.The DBH of the Suoxian Yala provenances was the smallest,and that of the Langkazi provenances was the largest.The variation of specific leaf weight ranged from 439.85~732.33 g·m^(-2),in which the specific leaf weight of Langkazi seeds was the greatest,and that of Yala seeds was the least.(2)The response intensity of different population characteristics to latitude and longitude,altitude and climate factors was different.Canopy density,species richness,branch growth and specific leaf weight were significantly affected by climate factors,and tree growth form indexes were significantly affected by altitude.Canopy density was positively correlated with latitude(R=0.333),species richness was negatively correlated with average annual temperature(R=-0.423),and was positively correlated with frost-free period(R=0.356).Tree height and canopy width were negatively correlated with average annual precipitation(R=-0.211,-0.201,-0.345),while tree height,DBH,canopy width and bearing layer were positively correlated with altitude(R=0.179,0.197,0.238,0.237,0.180).The annual growth of main branch and base diameter of lateral branch were positively correlated with annual precipitation(R=0.441,0.210),and negatively correlated with frost-free period(R=-0.296,-0.308).There was a significant positive correlation between lateral growth and annual sunshine duration(R=0.165).