天山北坡天山云杉的种群结构特征和空间分布格局

从径级结构、静态生命表、存活曲线和个体空间分布格局等方面研究新疆天山北坡天山云杉的种群结构特征与空间分布规律。研究结果表明:1)种群年龄结构中幼苗幼树(Ⅰ级)比例最大(82.11%),中树(Ⅲ-Ⅵ级)和大树(Ⅶ-Ⅹ级)比例次之,小树(Ⅱ级)比例最小(0.26%)的规律;2)种群死亡率在Ⅰ径级最高(99.70%),随着径级的增加,死亡率呈现"高-低-高"模式,种群生命期望呈现"低-高-低"的模式;3)天山云杉种群的存活曲线接近于DeeveyⅢ型,即Ⅰ径级存活指数最高(6.91),Ⅱ径级(1.16)急剧下降,Ⅱ-Ⅴ径级逐渐上升,随后逐渐下降;4)种群格局随取样尺度由25-400m2增加,聚集强度逐渐降低,其中,在取样规模为25和150m2尺度上聚集分布强度较大;5)随着种群年龄增加,分布格局由聚集型向随机型过渡,聚集强度减弱。幼苗幼树在取样规模为25和150m2尺度上聚集分布强度较大;中树在50m2和150m2尺度上较大;而小树和大树聚集强度不受取样面积影响。因此,天山北坡的天山云杉天然林应适当间伐以促进更新,种群更新的最适林隙面积为25m2。

Structure characteristics and spatial distribution of Picea schrenkiana population on the northern slopes of the Tianshan Mountain

Based on the life table,DBH(diameter at breast height) class structure,survivorship curve and spatial distribution of Picea schrenkiana on the northern slopes of the Tianshan Mountain,China were studied.The results were as follows: 1) The DBH class structure of the population indicated that most individuals were assembled in the seedling stage(DBH classⅠ,82.11%),young(DBH class Ⅲ-Ⅵ) and mature(DBH class Ⅶ-Ⅹ) were the next,and sapling ones(DBH classⅡ,0.26%) were the least.2) The mortality rate of the seedlings was the highest(99.70%).With DBH class increasing,mortality displayed "high-low-high" mode,while the expectancy life of population displayed "low-high-low" mode.3) The survivorship curve of population generally matched a Deevey Type Ⅲ.The survivorship index was the highest in DBH classⅠ(6.91),and it fell sharply in DBH classⅠ(1.16).The survivorship index increased between DBH class Ⅱ to Ⅴ,it would decrease when the DBH class was over Ⅴ.4) With sampling plot dimension increasing from 25m2 to 400m2,the spatial distribution transformed from clumped or random to clump distribution.Especially,the patchiness intensities in 25m2 and 150m2 plot were greater than others.5) As population became older,their distribution transformed from the clumped into a random distribution pattern.While their clumped intensities came down.The patchiness intensities of seedling were greater in 25m2 and 150m2;ones of young were greater in 50m2 and 150m2;while there were no effect of the sample area on patchiness intensities.Therefore,the P.schrenkiana forest reach thinning period due to difficult regeneration on the northern slopes of the Tianshan Mountain.Under natural circumstances,the 25m2 at the highest clumped intensity of seedling was the optimal area for the population regeneration.