杂种落叶松人工幼龄林林分枯损规律及枯损模型

根据2003—2015年黑龙江省江山娇实验林场杂种落叶松人工林48块固定样地复测数据,在对不同初植密度(Dp)等级(SD1(Dp2 000株/hm~2)、SD2(2 000≤Dp3 000株/hm~2)、SD3(3 000≤Dp4 000株/hm~2)、SD4(Dp≥4 000株/hm~2))林分的总体枯损趋势以及不同密度等级的株数、蓄积和径阶枯损分布规律分析的基础上,假定相对枯损率同林分年龄呈常数、幂指数、指数关系,利用差分模型结合拟合优度比较得出基础模型,并以初植密度等级作为哑变量构建了林分枯损(存活木株数)模型。结果表明:杂种落叶松林分枯损总体趋势分为3个阶段(林龄7~11 a为阶段1,林龄≥11~15 a为阶段2,林龄≥15~19 a为阶段3),枯损强度呈现强-弱-强的变化趋势,林分密度越大,株数枯损、蓄积枯损强度越大。杂种落叶松直径分布呈单峰山状曲线,且近似于正态分布,径阶枯损分布主要集中在2~12径阶。建议杂种落叶松造林初植密度小于4 000株/hm~2,在林分年龄为15 a时,对林分进行抚育间伐。杂种落叶松人工林林分相对枯损率同林龄的指数函数显著相关,将林分初植密度作为哑变量能明显提高林分枯损模型的拟合效果(R2a由0.77~0.93提高到0.97),该模型适用于预测不同初植密度幼龄林的存活木株数。

Mortality of Stand Trees for Hybrid Larch Young Plantation in Heilongjiang

With the re-measured data of hybrid larch plantations of 48 permanent sample plots from 2003 to 2015 of Jiangshanjiao Experimental Forest Farm in Heilongjiang Province,we studied the mortality trend and mortality rules for the tree number,volume and mortality distribution of diameter in different initial density levels including SD1 (＜2 000 tree/hm2),SD2 (2 000-3 000 tree/hm2),SD3 (3 000-4 000 tree/hm2),and SD4 (＞4 000 tree/hm2).The relative mortality rate was assumed constant,power,and exponential relationship with stand age,and the basic model was got through the difference equation and goodness of fit comparison.Adding stand density level as the dummy variable into the basic equation,the stand mortality model (survival function) was developed.The mortality trend of hybrid larch plantation can be divided into three stages:7-11,11-15,and 15-19 a.The mortality trend showed strong-weak-strong,and mortality increased with higher density nunber.The diameter distribution of hybrid larch was a single peak curve,near to the normal distribution and the diameter class distribution of the mortality was centralized in 2-12.The best initial planting density of hybrid larch was less than 4 000 tree/hm2,and the tbrest should be thinning in 15 a.The stand relative mortality rate was proportional to the exponential function of stand age.Adding initial density level as the dummy variable,the fitting index of stand mortality model was significantly increased with the goodness-of-fit (adjust Ra2) of 0.97 (advanced from 0.77-0.93),and the model was suitable to predict unit-area tree survival over time for hybrid larch plantation.