Spatial Effect Analysis on Individual Aboveground Biomass of Eucalyptus Plantation

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.