Effects Of Spatial Structure On DBH Increment Of Natural Spruce-fir Forest

In order to explore the correlation between the spatial structure and DBH increment of natural spruce-fir forests in Changbai Mountain,3 typical plots of natural spruce-fir forest(4(Abies nephrolepis):2(Picea jezoensis))were set in Jin'gouling forest farm in Wangqing County of Jilin province to calculate mingling,neighborhood pattern,neighbourhood comparison,crowding and competition index at the stand and individual levels and discuss the distribution of spatial structure.Then,the effect of the different spatial structure of Abies nephrolepis and Picea jezoensis on the DBH increment was analyzed combined with the mean values of the mean DBH increment of Picea jezoensis and Abies nephrolepis in the latest 5 years,in addition,the relationship between the the competition index based on intersection angle and the diameter at breast height of Picea jezoensis and Abies nephrolepis in plots was simulated by power function,and the relationship between the competition intensity and DBH was analyzed.The main research conclusions are as follows:(1)Plot 1 was random distribution,Abies nephrolepis,Picea jezoensis and Betula platyphylla in plot 1 were also random distribution,and Pinus koraiensis,Tilia amurensis,Betula costata and Larix gmelinii were aggregated distribution;plot 2 was also random distribution,Picea jezoensis,Abies nephrolepis and Pinus koraiensis in plot 2 were also random distribution,and Larix gmelinii,Tilia amurensis,Betula costata were aggregated distribution;plot 3 was aggregated distribution,and all species were aggregated distribution except for Syringa reticulata.(2)Plot 1 was high-intensive mixture,Picea jezoensis and Abies nephrolepis reached between medium-intensive mixture and high-intensive mixture.Pinus koraiesi,Tilia amurensis,Betula platyphylla,Betula costata,Larix gmelinii reached between high-intensive mixture and ultra-intensive mixture;plot 2 was between high-intensive mixture and medium-intensive mixture,Pinus koraiensi,Betula costata and Picea jezoensis reached between high-intensive mixture and ultra-intensive mixture,Tilia amurensis,Abies nephrolepis and Larix gmelinii reached between medium-intensive mixture and high-intensive mixture;plot 3 was generally between high-intensive mixture and ultra-intensive mixture,Tilia amurensis,Picea jezoensis and Betula platyphylla of plot 3 also reached between high-intensive mixture and ultra-intensive mixture,and Syringa reticulata,Abies nephrolepis,Larix gmelinii and Acer mono were between medium-intensive mixture and high-intensive mixture.(3)Plot 1 was between medium and subinferiority,and Abies nephrolepis,Pinus koraiensis,Betula costata and Larix gmelinii were medium,Picea jezoensis,Tilia amurensis and Betula platyphylla were subinferiority;plot 2 was medium,Betula costata and Larix gmelinii were between medium and subdominant,and Abies nephrolepis and Picea jezoensis were medium,Tilia amurensis and Pinus koraiens is were subinferiority;plot 3 was between medium and subinferiority,Betula platyphylla,Tilia amurensis,Abies nephrolepis,Larix gmelinii,Acer mono were between medium and subinferiority,Syringa reticulata was medium,and Picea jezoensis was subdominant.(4)The average crowding of plot 1 was 0.683,and it was between medium-intensive dense andhigh-intensive dense,Betula costata,Tilia amurensis and Betula platyphylla were around 0.75,Abies nephrolepis,Picea jezoensis and Pinus koraiensis were around 0.7,and Larix gmelinii was around 0.45;and the average crowding of plot 2 was 0.818,it was between high-intensive dense and ultra-intensive dense,Betula costata,Tilia amurensis and Abies nephrolepis were around 0.9,Pinus koraiensis and Picea jezoensis were around 0.8,Larix gmelinii was lowest with 0.713;The average crowding of plot 3 was 0.935,also was between high-intensive dense and ultra-intensive dense,and average crowding of all species were above 0.9.(5)The overall spatial structure of plot 1 was the best,the plot 3 was the worst;the Picea jezoensis spatial structure in plot 2 was the best,the Picea jezoensis spatial structure in plot 1 was the worst;the Abies nephrolepis spatial structure in plot 1 was the best,and the spatial structure of Abies nephrolepis in plot 2 was the worst;the spatial index of spatial structure in 3 plots were all distributed in the range of 0.3-0.5,which was at a lower level.(6)The random distribution of Abies nephrolepis and Picea jezoensis had the largest DBH increment,and with the increase of mingling of Picea jezoensis and Abies nephrolepis,the DBH increment of Picea jezoensis and Abies nephrolepis showed an increasing trend,and with the increase of neighbourhood comparison and crowding,the DBH increment of Picea jezoensis and Abies nephrolepis showed a decreasing trend.(7)The competition indexes based on intersection angle were decreased with the increase of DBH by power function of Picea jezoensis and Abies nephrolepis,the biggest change was in the 5-20 cm stage of the DBH,Therefore,this stage requires certain thinning to reduce consumption by competition.