天山野苹果林立地条件和林分结构对苹果小吉丁种群数量的影响

Effects of Forest Conditions and Stand Structure on the Quantity of Agrilus mali Mats in Tianshan Wild Apple Forest

【目的】研究苹果小吉丁Agrilus mali Matsumura自然种群在天山野苹果林的发生及其与影响因子之间的关系。【方法】基于17块天山野苹果林标准地,以苹果小吉丁为研究对象,研究天山野苹果林生态系统中海拔、坡度、坡位、坡向等立地因子和林分郁闭度、林分密度、野苹果比例、树种丰富度等林分因子对苹果小吉丁种群影响效应等,构建预测模型。【结果】海拔>1400 m的林分内平均虫口数量最低,仅为0.49头/m样枝,1250~1299 m平均虫口数量最高,达到1.26头/m样枝。随着样地坡度的增加,苹果小吉丁种群数量逐渐降低,缓坡(6°≤坡度≤15°)林分的平均虫口数量最高,达到1.24头/m样枝,显著高于陡坡(26°≤坡度≤35°)的0.39头/m样枝(P<0.05)。林分郁闭度为0~0.29的林分虫口数量最高,达到1.44头/m样枝,显著高于郁闭度为0.30~0.49和0.50~0.79的林分(P<0.05)。林分密度<0.11的稀疏林分平均虫口数量最高,为1.5头/m样枝。海拔和坡度偏相关系数绝对值较大,分别为0.598和0.542,是苹果小吉丁虫口数量的关键影响因子,两者与平均虫口数量的关系达到显著水平(PX 1=0.031;PX 3=0.047;均小于0.05)。由海拔(X 1)、坡度(X 4)与苹果小吉丁虫口数量(Y)建立的多元回归模型为:Y=5.541-0.003X 1-0.033X 4。经F检验该线性回归预测模型达到显著水平(F=12.021,df=2,16,P=0.001)。将预测值与实测值进行比较,平均差异度为0.193;对实测值与预测值进行独立样本T检验,两者之间无显著差异。【结论】海拔和坡度是影响苹果小吉丁种群数量的关键因子,其次为坡位,而林分郁闭度、林分密度、坡向、野苹果比例和树种丰富度对苹果小吉丁种群数量的影响作用稍弱,均为非主要因子。

【Objective】To understand the occurrence of natural quantity of Agrilus mali Matsumura in Tianshan wild apple forest and its relationship with influencing factors.【Methods】This study was based on 17 standard plots of wild apple trees in Tianshan Mountains,taking Agrilus mali Matsumura as the object of study to study the effects of site factors such as altitude,gradient,slope position and aspect,forest stand factors such as stand canopy,stand density,wild apples ratio and tree species richness on the quantity of Agrilus mali Matsumura,and to build the prediction mode.【Results】The results showed that:The average quantity of insect in stands with an altitude higher than 1,400 m was the lowest,only 0.49/m sample branch,the average insect quantity was the highest in the range of 1,250-1,299 m,up to 1.26/m sample branch.With the increase of the gradient of the sample land,the quantity of Agrilus mali Matsumura was decreasing,the average insect quantity in the gentle slope stands(6°≤gradient≤15°)was the highest,up to 1.24/m branches,which was significantly higher than the 0.39/m sample branches on the steep slope(26°≤gradient≤35°).The highest number of insect quantity was found in stands with canopy density of 0-0.29,up to 1.44/m branches,it was significantly higher than stand density of 0.30-0.49 and 0.50-0.79(P<0.05).The average number of insect quantity in sparse stands with stand density lower than 0.11 was the highest,which was 1.5/m sample branches.Partial correlation analysis showed that the absolute value of partial correlation coefficient between elevation and slope was larger,was 0.598 and 0.542,it was the key influencing factor of the quantity of Agrilus mali Matsumura.T test results showed that the relationship between them and the average quantity reached a significant level(PX 1=0.031;PX 3=0.047;<0.05).The multiple regression model:Y=5.541-0.003X 1-0.033X 4 was established based on altitude(X 1),slope position(X 4)and number of quantity(Y).F test shows that the linear regression prediction model reaches a significant level(F=12.021,df=2,16,P=0.001).The predicted value was compared with the measured value and the average difference was 0.193.The measured value and the predicted value were tested by T,the results showed that there was no significant difference.【Conclusion】Altitude and gradient are the key factors that affect the amount of Agrilus mali Matsumura,slope position is the second,the effects of stand canopy,stand density,slope direction,wild apple ratio and tree species richness on the number of Agrilus mali Matsumura population are weak,and they are non-major factors.