Effect Of Neighborhood Competition On Biomass Partitioning And Growth Of Fraxinus Mandshurica In Northeast China

Northeast China ash tree(Fraxinus mandshurica)is a kind of precious tree specie species of forest in northeast of China.It is one of the three-hardwood in the northeast.Biomass allocation of northeast China ash tree(Fraxinus mandshurica)always effects on forest ecosystem carbon cycling in a certain extent.In this study,we use Northeast China ash tree(Fraxinus mandshurica)to research the above-and belowground biomass allocation patterns of and to analyze aboveground competition influences on biomass partitioning in a natural secondary mixed forest in the Administration Bureau for Jiaohe Forestry Experimental Area,Jilin Province,northeast China.The results show that:(1)The biomass allocation of stem,root,branch and leaf were 46.55%-71.91%,19.35%-24.38%,6.19%-27.7%and 1.30%-2.56%.And the mean value of proportion of different biomass components showed an order of stem(57.54±6.04)>root(23.35±1.16)>branch(17.33±5.25)>leaf(1.77±0.29).The root/shoot ratio for ranged from 0.24-0.32 with the average value of 0.28.(2)Stem diameter at breast showed a significantly negative exponential correlation with aboveground competition intensity(P<0.001).Breast-height diameter decreased with increasing competition intensity,whereas,there was no significant relationship(P>0.05)between competition intensity and tree height.The ratio of tree height to breast-height diameter showed a significant linear relationship with competition intensity(P<0.001).Under the consistent breast-height diameter circumstance,tree height increased with increasing competition intensity.(3)There was a significant relationship between competition intensity(P<0.001).With increasing competition intensity,the relative proportion of stem and leaf biomass increased while that of branch and root biomass decreased.(4)Total biomass and aboveground biomass showed a significantly negative exponential correlation with aboveground competition intensity(P<0.001).(5)The average root to shoot ratio value was 0.28.This ratio was showed a significant linear relationship with competition intensity(P<0.001).(6)When the competition intensity in 3<HgCi scope of 4 or less,The DBH growth,the annual rate of height growth and the basal area of individual annual rate of growth in northeast China ash peaked at the same time,1.944%,0.255%and 0.642%,respectively.The surrounding trees should be properly intermediate cutting when DBH of Fraxinus mandshurica individual in the range of 10 to 15cm,in order to maintain the annual growth rate of DBH at the highest level.(7)Under different competition intensity,the annual rate of height growth>DBH growth rate>the volume of individual annual rate of growth>the basal area of individual annual rate of growth.Conclusions:Thus,competition should not be disregarded in biomass studies.In order to obtain more space and nutrition,plant follows optimized distribution theory in its growth process and allocates more resources to competitive organs in order to increase its competitiveness and productivity.The high competition intensity will restrain the growth of the diameter,but it will promote the increase of the basal area and the volume.