| In order to explore the growth characteristics and benefit features of the main tree species stand in the Liuliping Forest Farm of Xinglong County,Chengde City,the three typical stands of the Chinese pine pure forest,the Quercus mongolica pure forest and the mixed forest of Chinese pine and Quercus mongolica,which in Liuliping Forest Farm,Xinglong County,Chengde City,Hebei Province,are selected as research objects.The stand structure,growth regularity and biodiversity characteristics of different stands are systematically studied by means of investigated method of standard block and steam analysis.The main results are as follows.（1）The diameter distribution characteristic of three stands all have a single-peak mountain-like distribution,as the forest diameters to grow,the number of strains is decreasing.While there are significant differences among the three stands.The Chinese pine pure forest has the largest number of trees in the 30cm diameter class of DBH structure,among which the number of forest trees with the diameter of 24-34cm accounts for the largest percentage,with the cumulative percentage reaching 63.7%;the Quercus mongolica pure forest has the largest number of trees in the 20cm diameter class,wherein the number of forest trees with the diameter of 12-26cm accounts for the largest percentage,with the cumulative percentage reaching 66.29%;the mixed forest has the largest number of trees in the 28cm diameter class,wherein the number of forest trees with the diameter of14-28cm accounts for the largest percentage,with the cumulative percentage reaching56.41%.The distribution law of the three types of stand diameters is consistent with the Weibull distribution.The tree height distribution characteristic of three stands all have a single-peak mountain-like distribution,while there are significant differences among the three stands.The Chinese pine pure forest has the largest forest trees in the 18m height class,among which the number of forest trees at the height class of 14-19m accounts for the largest percentage,with the cumulative percentage reaching 77.63%;the Quercus mongolica pure forest has the largest forest trees at the 13m height class,among which the number of forest trees at the height class of 8-14m accounts for the largest percentage,with the cumulative percentage reaching 65.59%;the mixed forests have the highest number of forest trees at the height class of 12m,among which the number of forest trees at the height class of 9-15m accounts for the largest percentage,with the cumulative percentage reaching 57.27%.While the tree height structure is more consistent with the normal distribution.（2）In the pure forest and mixed forest environment,the growth trend and regularity of Chinese pine and Quercus mongolica show roughly the same pattern.The growth of each index is obvious in the early growth stage,and the difference is significant in the late growth stage,and the mixed forest has higher difference significantly than the pure forest.Different tree species have different nodes in the time of difference and the time of change.The differences in growth characteristics of different indicators are also different.The DBH growth and volume growth show a degree of consistency,with poor tree height growth regularity.（3）The dominant species of the herb layer of the three stands are all Carex,and in the shrub layer,the undergrowth dominant species of the above-mentioned two pure forests are Rhododendron,and the undergrowth dominant species of the mixed forest is the raspberry.The species richness,Shannon diversity and Simpson dominance of the three stands are as follows:herb layer>bush layer,wherein mixed forest of Chinese pine and Quercus mongolica has the highest species diversity,Chinese pine pure forest has the lowest species diversity,which is herb layer>bush layer.The Pielou evenness index is as follows:mixed forest of Chinese pine and Quercus mongolica（0.648284458）>Quercus mongolica pure forest（0.583147983）>Chinese pine pure forest（0.487958334）,which is characterized by:herb layer>.shrub layer（4）The pair of species of the positive correlation of the undergrowth herb layer of the Chinese pine pure forest is less than that of the negative correlation.The probability of occurrence of a negative correlation pair of species is greater than that of a positive correlation pair of species.The pair of species of the positive correlation of the undergrowth herb layer of Quercus mongolica is 7 pairs less than that of the negative correlation,which is 2.16%lower.The probability of occurrence of a negative correlation pair of species is slightly more than that of positive correlation.The pair of species of the positive correlation of the undergrowth herb layer of Chinese pine-Quercus mongolica is151 pairs more than that of the negative correlation,which is 28.6%higher.The probability of occurrence of a positive correlation pair of species is greater than that of the negative correlation,and the community is in a relatively stable state.There is insignificant positive correlation between the overall interspecific associations of herb communities of the three stand types,and the overall association variance ratio（VR）of the stand types is>1.The W values are all within the chi-square threshold(x20.9545,x20.0545). |
