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枯立木(standing dead tree)是森林的重要结构组成部分.对枯立木空间格局与其影响因子等进行探讨,有助于揭示森林树木死亡机理及森林群落动态规律.本研究将弄岗喀斯特季节性雨林15 hm2样地内胸径大于1 cm的枯立木划分为不同胸径等级,并在不同空间尺度上统计了枯立木多度、空间相邻因子、地形因子及群落类型因子等数据,用零膨胀负二项模型(zero-inflated negative binomial models)解决了多度数据的非正态性且零值过多等统计问题,分析了该森林枯立木多度的空间分布规律及影响因子.结果表明:(ⅰ)弄岗15 hm2样地内胸径大于1 cm的枯立木有2254株,平均胸径6.21 cm,最大胸径61.86 cm;胸径分布呈反“J”型,无明显断层;小径级枯立木在海拔较高地区分布较多,大径级枯立木在海拔较低地区分布较多;(ⅱ)小径级枯立木呈聚集型空间格局,大径级枯立木趋向于随机型空间格局;枯立木多度存在多尺度的空间自相关结构;(ⅲ)随着径级增大,枯立木多度与凹凸度、空间相邻因子的相关性逐渐减弱,与坡度、海拔的相关性逐渐增强;随着单位取样尺度增大,枯立木多度与凹凸度、海拔、坡度、群落类型因子的相关性逐渐减弱,与空间相邻因子相关性逐渐增强.研究表明,喀斯特森林中枯立木分布格局由多尺度的空间结构所构成,不同空间尺度、地形条件、群落类型等对枯立木的径级结构及数量组成有显著影响,而枯立木结构的空间异质性将会影响森林光资源及木质残体储量等的空间动态,进而影响群落物种组成.
Standing dead tree is an important structural component of the forest.It is helpful to reveal the mechanism of death of forest trees and the dynamics of forest community by discussing the spatial pattern and influential factors of the standing tree.This study studied the effects of seasonal changes in the seasonal dynamics of the Nonggang Karst seasonal rainforest Fifteen hm2 plots were divided into DBH with DBH> 1 cm, and statistics of the spatial heterozygosity, spatial adjacent factors, topographical factors and community type factors were performed on different spatial scales. (Zero-inflated negative binomial models) solve the statistical problems of non-normality and zero-value of multi-degree data and analyze the spatial distribution rules and influencing factors of the degree of forest deadwood.The results show that: (i) In the 15 hm2 plots of Nonggang, there were 2254 dead woods with a DBH greater than 1 cm. The average DBH was 6.21 cm and the maximum DBH was 61.86 cm. The DBH distribution was inverted “J” with no obvious faults. Large-scale distribution of large-size stand-up wood in the lower elevations; (ii) Small diameter-class stand-up wood in an aggregated spatial pattern, large-diameter stand-up wood tends to a random pattern of space; Degree of spatial autocorrelation; (iii) With the increase of diameter, the correlation between the spatial and the spatial adjacent factors gradually declines with the increase of the degree and the degree of ascending and descending, and the correlation with the slope and elevation gradually increases. With the increase of the diameter, The sampling scale of unit increased, the relativity of the degree of ascending and descending, elevation, slope and community type factor gradually decreased and the correlation with space adjacent factor gradually increased.The research shows that the distribution pattern of dead wood in karst forest is controlled by multi-scale Of the spatial structure, different spatial scales, topographical conditions and community types have significant effects on the diameter-class structure and the quantity and composition of dead wood, while the spatial heterogeneity of dead trees will affect the forest light resources and wood residue reserves And other spatial dynamics, which in turn affect the community species composition.