Disturbance Characteristics Of Gap In Second Forest In The Greater Xing’an Mountains South

This study selected gap in second forest in the Greater Xing’an Mountains South as the research object,based on lager and permanent plots of Inner Mongolia Shaihangwula Forest Ecosystem National Research Station,used the method of field investigation,has analyzed border tree,gap maker and seedlings regeneration in different slope(high slope,medium slope and low slope)and different forest gap area(large,medium and small),has revealed the short-term effects of second forest gap disturbance on forest dynamics in the Greater Xing’an Mountains South.The main results are as follows:1.The average area was 134m2,mainly distributed between 50～170m2.Species of border tree included Betula platyphylla,Quercus mongolica,B.dahurica,Populus davidiana and Tilia mongolica.The number of birch bones was the largest,accounting for 72%.Type of gap makers included standing death(27%),stem breakage(58%)and dry basis broken(15%)and the number of stem breakage was the largest.The type and time of gap maker had obvious differences in tree species.Seedlings regeneration of forest gap mainly included Quercus mongolica(79%),Populus davidiana(14%)and Betula platyphylla(2%).The number of seedlings regeneration of Quercus mongolica was the largest.2.Slope conditions affect the gap area,border trees,gap makers and seedlings regeneration in the Greater Xing’an Mountains South.There were a large number of large gaps on the high slope,the number of small gaps in the low slope.Slope conditions significantly affected tree height and DBH of the border trees(P<0.05).The gap makerss of high and medium slope were mainly stem breakage,but standing death and stem breakage in low slope.Gaps in high and medium slope inhibited the number of seedlings,but promoted high growth and horizontal growth of seedlings.3.Gap area affected the border trees,gap makers and seedlings regeneration in the Greater Xing’an Mountains South.Gap area significantly affected tree height and DBH of the border trees in high and low slope(P<0.05),and DBH of gap makers in low slope(P<0.05),and DBH of gap makers in small gap were smallest(11.11±7.23cm).4.Birch death was mostly in the near future,while Mongolia was more in the long-term death in second forest in the Greater Xing’an Mountains South.Birch choosed to keep the tree high and the larger diameter of the border trees in medium and low slope.So Forest gap changed the species composition in second forest in the Greater Xing’an Mountains South.Seedlings regeneration of forest gap were mainly Mongolia and there was only a very small number of birch seedlings.White Seedlings regeneration of birch could not be added in time.Suggesting that forest species will change in the future.