林冠干扰作为鳞毛蕨（Dryopteris filix-mas （L.） Schott）天山云杉（Picea schrenkiana Fisch. et Mey.）林动态自维持的重要因素,在整个林分的动态发展过程中发挥着重要作用.通过对西天山国家级自然保护区内1hm^2典型的鳞毛蕨天山云杉纯林中林冠空隙特征及其形成木和边界木结构的研究,结果表明：在西天山国家级自然保护区实验区46林班内的1hm^2临时标准地中,共调查到17个林冠空隙,林冠空隙干扰返回间隔期为763年.扩展空隙面积在20～280m^2之间变化,冠空隙面积在0～180m^2之间变动.大多数林冠空隙形状变异较大,不同程度地偏离圆形,且均在20～100年之间形成,拥有多株形成木,边界木多由近熟木和成熟木组成.
Disturbance acting as a universal characteristic of all forest goes with survival and development of forest. In forest community, gap disturbance drives forest circular transformation. This function makes forest become a mosaic consisting of different stage patches, improves spatial heterogeneity of forest and alters validity of forestry resources. Finally, disturbance enforces structural stability of community and influences dynamic of forest. In a word, gap disturbance plays a driving role in dynamics development of forest because it maintains forest cycle. In gap disturbance, gap acting as the most intuitionist token, becomes unaffectedly the basis of the research about gap disturbance mechanism. In this paper, characteristics of gap, structure of gap maker and framework of gap border are studied in a 1-hm^2 Picea schrenkiana -Dryopteris filix-mas temporary plot in the Western Tianshan National Nature Reserve. The nature reserve（43°03＇ -43°15＇N,82°51＇ -83°06＇E）is located in the western section of the central Tianshan Mountains, its south -north length and east -west width are 28 km and 14 km respectively, and its area is 31 217 km^2 ,in which the areas of woodlands and shrubbery lands are 11 701 km^2 and 380 km^2 respectively, and the forest coverage is 39%. The results show that there are 17 gaps in the study region. The return interval of gap disturbance is 763 a. The area of expanded gaps range from 20 to 280 m^2, the area of canopy gaps vary from 0 to 180 m^2. Shape of all gaps varies greatly, shape index of most expanded gaps and canopy gaps are seldom close to 1. Most of gaps are formed by many gaps makers, and all of gaps are formed in 20 - 100 a. What＇ s more, most of gap borders are adolescent trees and mature trees.
Arid Land Geography
Picea schrenkiana Fisch. et Mey.