毛乌素沙地天然臭柏径向生长特性研究

为了研究天然臭柏种群的径向生长发育规律，根据群落的更新进程，将毛乌素沙地的天然臭柏群落划分为4个发育阶段，采用样地调查法，调查各个发育阶段的地径和匍匐茎长度，采集地径及距地径20 cm处的树盘；用WinDENDRO-TM年轮图像分析系统测定年龄及年轮宽度，分析毛乌素沙地不同发育阶段天然臭柏的径向生长特性。结果表明:臭柏在30年内径向连年生长曲线呈不稳定的波动变化，变异系数为48.61%；在前10年生长缓慢，年平均生长量仅为0.2 mm；13～20年为臭柏径向生长的速生期，年生长量均大于1.0 mm，最大可达1.8 mm；之后随着年龄的增大，年径向生长量呈下降趋势，年平均生长量在0.34～0,73 mm之间。发育阶段Ⅰ、Ⅱ、Ⅲ、Ⅳ中，臭柏的年龄范围依次为1～19年、3～22年、15～72年、34～122年，平均年轮宽度分别为0.58、0.68、0.49和0.37 mm。在生长初期的Ⅰ、Ⅱ发育阶段，臭柏地径与年龄之间呈对数函数关系；进入成熟期，即Ⅲ、Ⅳ发育阶段后，地径与年龄之间呈线性相关关系。4个发育阶段中以成、过熟的个体为主体的Ⅲ、Ⅳ发育阶段的臭柏平均年轮宽度减小为速生期的一半。 

Radial growth characteristics of natural population of Sabina vulgaris in Mu Us sandy land

In order to study radial growth rules of Sabina vulgaris population，the natural population of S. vulgaris is divided into four developmental stages (Ⅰ，Ⅱ，Ⅲ and Ⅳ) based on the regeneration process of community in Mu Us sandy land. Through investigation method of sample plot，the diameter at ground and length of stolon were investigated and tree disks at ground and 20 cm above ground were collected. Using the WinDENDRO-TM analysis system of tree-ring image，the authors measured the age and tree-ring width. The results show that the annual radial growth curve of S. vulgaris presents unstable fluctuation and the variation coefficient is 48.61% when tree age is below 30 years. In the first 10 years of growth stage，S. vulgaris grew slowly and annual radial increment was only 0.2 mm. The radial fast-growth stage of S. vulgaris was from 13 years to 20 years，annual radial increment was over 1.0 mm，and the maximum value was 1.8 mm. After this stage，annual radial increment declined with the increased ages，the values were from 0.34 to 0.73 mm. The age ranges of S. vulgaris were 1-19 years，3-22 years，15-72 years and 34-122 years，and the average tree-ring widths of S. vulgaris were 0.58，0.68，0.49 and 0.37 mm in four developmental stages, respectively. There exists the exponential relationship between diameters and ages at the early growth stages. Diameters are correlated linearly with ages in the mature stages. The main body of developmental stages Ⅲ and Ⅳ are mature and old individuals，in which average tree-ring widths are the half of fast-growth stages.