桉树人工林单木地上生物量空间效应分析

Spatial Effect Analysis on Individual Aboveground Biomass of Eucalyptus Plantation

  • 摘要: 以桉树人工林皆伐样地调查数据为研究对象,记录样地内林木的空间位置坐标,并实测每株林木的木材、树皮、树枝、树叶的生物量,采用Ripley's K函数描述林木地上部分各维度生物量的空间分布模式,通过全局和局部Moran's I描述其空间自相关特征,基于组内方差定量描述各维度生物量的空间异质性变化。结果表明:桉树人工林单木地上生物量变化具有尺度效应,即在不同的距离尺度下表现出不同的聚集或离散特征,除树叶生物量在18.5~21.5 m范围内呈现显著聚集分布外,其余均未表现出显著的聚集分布特征;桉树人工林地上各维度生物量的最佳距离带宽均为12.5 m,且各维度均存在一定的空间自相关,全局Moran's I范围在0.0160~0.0289;各维度局部空间自相关变化趋势相对一致,各维度均有近15%的林木有显著空间自相关;随着距离尺度的增加,桉树人工林各维度生物量空间异质性均逐渐增大,且在距离大于5 m后逐渐平稳,所有生物量维度中树叶生物量的空间变异程度最大。因此,桉树人工林各维度单木生物量存在一定程度的空间自相关和空间异质性,且各维度间差异不大。

     

    Abstract: Taking the clear-cutting plot survey data of Eucalyptus plantation as the research object, the location coordinates of each tree in the plot were recorded, and the biomass of wood, bark, branch and foliage for each tree was measured. Then, the spatial distribution patterns were described for the wood, bark, stem, branches, foliage, crown and aboveground biomass using Ripley's K function, the spatial auto-correlation characteristics were analyzed by both global and local Moran's I, and the spatial heterogeneity of each biomass component was quantitatively described using the intra-variance index. The results showed that the aboveground biomass of Eucalyptus plantations had scale effect, and it showed the different aggregation or dispersion characteristics at different distance scales. Except for the foliage biomass shows a significant aggregation distribution if the distance is in the range of 18.5–21.5 m, and spatial distribution characteristics of the others are insignificant aggregation. Moreover, the optimal distance bandwidth for all biomass components of Eucalyptus plantation are 12.5 m, and spatial auto-correlation could be found in each component at a certain content, and the global Moran's I from 0.0160 to 0.0289. Meanwhile, the local spatial auto-correlation change of all biomass components are similar relatively, and nearly 15% of the trees in each component have a significant spatial auto-correlation. The spatial heterogeneity of all biomass components increase gradually with the increases of the distance, and the spatial variation would be stable if the distance is greater than 5 m, the spatial variation of foliage biomass is the largest one in all biomass components. In sum, there is spatial auto-correlation and spatial heterogeneity in the individual aboveground biomass in the Eucalyptus plantation at a certain degree, and the differences among the different biomass components are not significant.

     

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