Study On Spatial Structure Characteristics Of Different Forest Types In Lin’an

At present,most forest spatial structure studies take large fixed sample plots or a small number of temporary sample plots in typical areas as the object to study the spatial structure characteristics of a typical forest type,yet few comparative studies on the spatial structure characteristics of various forest types at regional scale.Based on the 367 sample plots data of national forest inventory,in Lin’an District,Hangzhou City,Zhejiang Province in 2004,this study investigated the different forests of natural coniferous forest,natural broad-leaved forest,natural coniferous and broad-leaved mixed forest,coniferous plantation,broad-leaved plantation and coniferous and broad-leaved mixed plantation from three aspects,namely spatial distribution pattern,species mixing degree and tree competition,combining with the spatial analysis of GIS technology.The spatial structure characteristics of forest types were compared to provide accurate decision-making basis for improving forest management level in Lin’an.The main results and conclusions are as follows:(1)Comparative analysis of spatial distribution patterns of different forest types.At the individual level,62.7% of the trees were of aggregation distribution and 37.3% of them were evenly distributed.Among them,more than 70% of the trees in coniferous and broad-leaved mixed plantation and natural coniferous and broad-leaved mixed forests were aggregated;more than 60% of the trees in artificial and natural broad-leaved forests were aggregated;55.57% of the trees in coniferous plantation were aggregated and 44.43% were evenly distributed.At stand level,84.74% in Linan District were of aggregation distribution and 15.26% were evenly distributed.The aggregation distribution of coniferous and broad-leaved mixed forest and natural coniferous and broad-leaved mixed forest was of aggregation distribution as a whole;the aggregation distribution of natural coniferous forest and natural broad-leaved forest accounted for more than 90%;the aggregation distribution of coniferous plantation and broad-leaved plantation accounted for 73.45% and 65.22%,respectively;the aggregation degree of natural forest was stronger than that of plantations.(2)Minglings of different forest types in Lin’an District were compared.The results showed that at the individual level,the order of mingling of plantation and natural forest from low to high was coniferous forest,broad-leaved forest and coniferous-broadleaved mixed forest.In natural coniferous forests,there was obvious homologous aggregation of Cunninghamia lanceolata and Pinus massoniana as the zero and low mingling of individual trees were up to 71.9%,while the Cunninghamia lanceolata of the zero mingling in the coniferous plantations accounted for 91.14%.The Juglans regia forests were cultivated as the pure plantation which led to a high percentage,namely 95.56%,in the zero mingling of the individuals.At the stand level,there was no extremely strong mixed phenomenon in each forest type.The coniferous and broad-leaved mixed forests in natural and planted forests had higher stand mingling than coniferous and broad-leaved forests,and the range of mingling was more concentrated reflecting the relatively high degree of tree species isolation.In the broad-leaved forest,stands of zero mingling were all pure walnut forest.In the coniferous plantation,the low mingling of stand was dominated by Cunninghamia lanceolata pure forest.In the mixed coniferous and broadleaved plantations,stands in middle mingling were with the highest percentage of 80%,mainly composed of Pinus taiwanensis,Pinus massoniana,Cunninghamia lanceolate and other soft broadleaved species.(3)Comparative analysis of competition index of different forest types.At the level of single tree,the total competition index,intraspecific competition index and interspecific competition index of individual trees of different forest types were the largest at DBH of 5~10 cm.The average competition index of single tree decreased with the increase of DBH,and the competition pressure was alleviated as the DBH was larger than 30 cm.The competition of forests in Lin’an region mainly came from intraspecific competition.The intraspecific competition of natural forests accounted for more than 50% of the total competition index,and the intraspecific competition of plantations accounted for more than 60% of the total competition index.The relationship between the total competition index,intraspecific competition index,interspecific competition index across average DBH classes and the DBH was subject to logarithmic function.At stand level,there were significant differences in total competition index,intraspecific competition index and interspecific competition index among different forest types.The average total competition order was natural broad-leaved forest >natural coniferous and broad-leaved mixed forest >coniferous plantation >natural coniferous forest >coniferous and broad-leaved mixed plantation > broad-leaved plantation.The average intraspecific competition order was: coniferous forest plantation> natural broad-leaved forest >natural coniferous forest > natural mixed coniferous and broad-leaved forest > mixed coniferous and broad-leaved plantation > broad-leaved plantation.The average competition order among different forest types was natural coniferous and broad-leaved mixed forest >coniferous and broad-leaved mixed plantation > natural broad-leaved forest >natural coniferous forest > coniferous plantation > broad-leaved plantation.The average total competition index,intraspecific competition index and interspecific competition index of broad-leaved plantation were the smallest.The economic tree species Carya cathayensis was the dominant tree species in this forest type,which indicated that the management measures of artificial control of low planting density effectively reduced the competition intensity of the stand for increasing the yield of Carya cathayensis.