黄龙山白皮松林林隙特征

Gap Characteristics in Pinus bungeana Forest in Huanglong Mountain,Shaanxi Province

对黄龙山白皮松林林隙的一般特征和干扰状况进行了研究。结果表明,白皮松林林隙形成的主要方式是人工砍伐,其次枯立、干基折断和干中折断也是较重要的形成方式,大多数林隙是由多种死亡方式混合而成的。林隙的线状密度为13.2个·km-1。扩展林隙大小分布为:A1(扩展林隙面积)≤200 m2的小林隙约占调查总数的57.89%,A1>800 m2的最大林隙占2.63%,扩展林隙的面积级越大,林隙的个数就越少;而林冠空隙大小分布并不遵循此规律,林冠空隙个数在450 m2<A2(冠空隙面积)≤600 m2时达到最小值,且所占面积比例最小,A2≤150 m2的小林隙约占调查总数的57.90%,且所占面积比例仅次于A2>600 m2的林隙。在白皮松林中,大多数林隙是由1～5株形成木形成的,其中由单株形成木形成的林隙最多,每个林隙的林隙形成木平均为2.05株;林隙形成木的腐烂等级以B级为主;组成林隙形成木的树种主要有4种,大多是由白皮松和侧柏形成的。d(胸径)<20 cm和h(树高)<5 m的形成木较容易形成林隙;而d>60 cm,h>15 m的树种不容易形成林隙。

A survey was conducted to study the gap characteristics and disturbance regime in Pinus bungeana forest in Huanglong Mountain. Results show that the most important manner of gap formation is the artificial felling, and the second important manner is the standing dead tree. The breakage at trunk base or its middle section is also an important manner of gap formation. Most gaps are formed by a combined manner. The linear gap density in the forest was 13.2 gaps per kilometer. Small gap （ extended gap area less than or equal to 200 m2 ） and large gaps （ extended gap area greater than 800 m2 ） accounted for 57.89% and 2.63% of the total forest gaps respectively. The number of forest gaps decreased as the extended gap area increased. However, the number of canopy gap reached its minimum value when canopy gap area ranged from 450 to 600 m2 , and the area ratio was also the lowest. Small canopy gap （ canopy gap area less than or equal to 150 m2 ） made up 57.9% of the total, and the area ranked second only to that of large canopy gap （ canopy gap area greater than 600 m2 ）. Most forest gaps were formed with 1-5 gap-makers, and the gap-makers per gap numbered 2.05 on average. The decaying level of gap-makers mostly belonged to B class. Gap-makers in the forest were consisted of four species, and the major gap-makers were Pinus bungeana and Platycladus orientalis. The probability of making gaps was the greatest when the big trees in the canopy layer got diameter grade less than 20 cm and height less than 5 m. And the gap makers with diameter grade greater than 60 cm and height creater than 15 m were hard to be seen in the gaps.