黄土丘陵区油松天然次生林林窗特征与更新动态

研究了黄土丘陵区油松天然次生林林窗的形状、大小结构、分布、形成木特征及其更新状况.结果表明:在油松天然次生林中,林冠林窗(CG)和扩展林窗(EG)面积均呈以小林窗为主的偏态分布.CG平均面积为31.15 m2,以20~40 m2林窗的数量比和面积比最大,分别为38.24%和30.50%;EG平均面积为58.04 m2,以30~60 m2的数量比和面积比最大,分别为36.77%和27.79%,且CG的平均面积占EG平均面积的53.67%;林窗形状多呈椭圆形,高度多在14~16 m;林窗形成年龄以10~20年为主,占33.82%.林窗中基折和枯立木分别占形成木总数的47.66%和23.44%.林窗形成的主要因素是人为间伐或盗伐,树木衰老等引起的抗性下降、干旱、病虫害等也是导致树木死亡的原因之一;每个林窗中平均有1.89个形成木,其中以2株形成木的林窗最多.林窗形成木主要是油松,其次为山杨、白桦和辽东栎等.形成木的径级呈明显的偏态分布,以10~20 cm和21~30 cm径级最为普遍,分别占总数的25.0%和45.31%,与林窗面积偏态分布吻合;林窗内林木的更新状况好于林下,且油松幼苗不存在断层,而油松林下幼苗在年...

Taking the secondary natural Pinus tabulaeformis forest in hilly loess region as research object,the shape,size structure,distribution,gap-maker features,and renewal dynamics of gaps were investigated.The results showed that the areas of canopy gap(CG) and extended gap(EG) appeared to have a skewed and small gap-dominated distribution.The CGs had an average area of 31.15 m 2,and those with an area of 20-40 m2 made up the highest proportions in number and area,accounting for 38.24% and 30.50%,respectively;wh...