Analysis On Reasons Of Wind-throw Poplar Trees In River Slope Area

Populus is one of the important tree species of river protection forest in China,which is of great significance to river protection and river ecology.Taking the shelterbelts along Benghe River in Feixian County,Shandong Province as the research object,this paper did an investigation about the wind-throw status of the stands suffering long-term flooding outdoors,analysis characteristics of the above-ground e.g.tree height,DBH,canopy characteristics,and root distribution characteristics etc.and primary root characteristics,and the characteristics of biomass allocation to find out the key characteristics of Populus L in order to provide the theoretical support for river-land shelter-forest management.The results of our study are illustrated as follows.1 The trees lodging 0-60 ° which is called serious situation accounted for 39.84%of the total while the number of trees wind-throw 31-60 ° took up about 4.69%.It indicates that the trees are likely to lead to two extremes.2 In the ground features,the angle of the trees was significantly affected by the crown,crown tree height ratio,and first branching angle,but not affected by tree height,DBH,crown volume,branch height,first branch length and first branch base diameter.The larger the tree crown is,the higher the crown/tree height ratio is.The ratio is related to the friction between the trees.3 In the underground features,the angle of the trees is significantly affected by the root depth and weight,instead of the root width,primary root angle,and root length and root diameter.With the increase of standing angle,the root depth and root weight become the largest at the range of 31-60 ° in standing trees.4 In the biomass allocation,the trees stand angle was significantly affected by root shoot ratio,root biomass ratio,stem biomass ratio,branch biomass ratio and leaf biomass ratio.With the increase of stand angle,the root shoot ratio and root biomass ratio increased first and then decreased,which became.the highest at the range of 31-60 °.The stem biomass ratio decreased first and then increased,and the shoot biomass ratio decreased gradually.Besides,foliage biomass increased.This indicates that the biomass allocation has a significant response to tree wind-throw,but trees cannot adjust by themselves when the stand angle exceeds 31-60 °.Through the investigation and analysis of Populus wind-throw,it was found that the wind-throw was affected by aboveground features,underground features and biomass allocation.The large crown can reduce the degree of wind-throwed through the friction between trees.The increase of root depth and weight is beneficial to the erect of trees,and the biomass allocation can respond obviously when the angle of standing trees is less than 31-60 °.Moreover,if the degree of wind-throwed is larger than 31-60°,trees would not adapt to lodging by themselves.