基于克里金插值法的湖南省慈利县森林碳储量专题图研究

基于2014年湖南省慈利县森林资源二类调查的结果，利用生物量换算因子连续函数法以及不同森林类型的碳含量，求得慈利县森林碳储量，并利用地统计学中普通克里金（Kriging）插值的方法，基于最优的半变异函数绘制湖南省慈利县森林碳密度分布专题图。结果表明，在6种常用的半变异函数中，指数模型作为半变异函数的预测精度较高，决定系数（R²）为0.756，残差平方和（SSR）为0.000 7，很好地反映了研究区森林碳密度的空间结构特征，结果显示慈利县的中北部、西南部和东部的碳密度较高，大于18.84 t·hm^-2，其余地方的碳密度较低，小于15.77 t·hm^-2。插值结果显示，碳密度在11.19~14.33 t·hm^-2的面积最大，达到慈利县总面积的22%；其次为18.84~21.98 t·hm^-2，达到全县总面积的16.35%；碳密度在14.33~15.77 t·hm^-2以及17.40~18.84 t·hm^-2的面积较少，分别占到全县总面积的13.54%和11.58%；碳密度大于28.83 t·hm^-2的面积最少，仅占1.76%。可见慈利县主要林分的碳密度还是处于较低水平，林分质量差，不能有效地发挥森林固碳功能，需要开展科学经营改善林分结构与树种组成，实现固碳能力的提升。研究湖南省慈利县森林植被碳储量、碳密度及其地理空间区域分布特征，为慈利县森林碳汇经营、林业碳汇核算和政府科学决策提供科学依据。

Development of Thematic Map of Forest Carbon Storage Based on Kriging Interpolation Method in Cili County,Hunan Province

In this study,we investigated forest carbon storage,forest carbon density and their geographic spatial distributions in Cili County,Hunan Province,with the objective of providing scientific basis for forest carbon sink management,forestry carbon sink accounting and government decision-making.Based on the forest resource and planning inventory in Cili in 2014,we first calculated the forest carbon storage of the county by using the variable biomass expansion factor function method based on carbon content of different forest types.By using the ordinary Kriging interpolation method,the thematic map of forest carbon density distribution in the county was produced based on the optimal semi-variation.Among the six kinds of semi-variation functions in common use,the exponential model exhibited higher prediction accuracy as a semi-variation function,with the determination coefficient(R²)of 0.756 and the sum of squares of residuals(SSR)of 0.0007,and hence could well represent the spatial structure characteristics of forest carbon density in the study area.Our results showed that the carbon density in the north-central,southwestern,and eastern parts the county was relatively high,above 18.84 t·hm^-1,while the carbon density in other places was relatively low,below 15.77 t·hm^-1.The interpolation results indicated that the carbon density was the largest in the range of 11.19-14.33 t·hm^-1,which represented 22%of the total area of the county,followed by the range of 18.84-21.98 t·hm^-1,which accounted for 16.35%of the total.The carbon densities in the range of 14.33-15.77 t·hm^-1 and 17.40-18.84 t·hm^-1 were low,accounting for 13.54%and 11.58%of the total,respectively.The area with carbon density greater than 28.83 t·hm^-1 was the least,accounting for only 1.76%.It can be concluded that the forest carbon density in Cili County is still at a low level.Meanwhile,the quality of the stands is also poor,which hinders forest carbon sequestration ability.Therefore,it is necessary to carry out scientific management to improve forest structure and species composition,so as to enhance the carbon sequestration capacity.