卧龙自然保护区人为活动对景观结构的影响

Human impacts on landscape structure in Wolong Natural Reserve

利用遥感景观制图 ,在确定不同人为影响发生源的显著影响范围后 ,分析了卧龙自然保护区人为活动对景观结构的影响。结果表明 ,在水电站、居民点和道路三种人为影响发生源中 ,水电站的修建对周围景观结构的一次性改造效果最显著 ,居民点属中等强度的持续性影响类型 ,道路的影响程度最小。人为活动使人为影响景观典型地段 ( 2 0 0 m缓冲区 )的林地覆盖率减小 1 5 %～ 4 0 % ,灌丛和裸地面积比重增加 1 5 %～ 5 0 %。在居民点和水电站周围 ,景观结构变化证明人为影响作用呈明显的梯度衰减 ,6 0 0 m半径缓冲区范围内为典型人为影响区域 ,6 0 0～ 1 2 0 0 m区间为人为影响景观与自然景观的过渡区域 ,其余地区属自然因素控制的自然景观。与水电站和居民点相比 ,道路两侧景观结构的梯度变化特征不甚明显 。

Influences of human activities on landscape structure and human-induced ecological degradation in protected areas have been given considerable attention in landscape ecological studies. We use methods of quantitative analysis to precisely assess human impacts on landscape structure in Wolong Natural Reserve, China. Based on the landscape map compiled with satellite remotely sensed data (TM data) from 1997, four aspects of analysis were carried out using the buffer zone method: 1) A t test is utilized to understand internal differences within human-impacted areas and to reasonably define different kinds of human-impacted areas. 2) Landscape variations are compared for different areas, such as the entire study area, the natural landscape, the human impacted-landscape, hydropower station buffer zones, residential area buffer zones, and road buffer zones, to assess the impact of human activities on landscape structure. 3) According to comparison analysis of landscape structures among the buffer zones of different human-impacted areas, gradient characteristics of human impact on landscape structure are assessed. 4) Under the same conditions, landscape structure within buffer zones of various human-impacted areas and the natural landscape are compared to assess human-induced variation of landscape structure. Types of human impact sources considered include 10 hydropower stations, 47 residential areas, and 400 km of roads. Ten buffer zones were set up within a 2000m distance around all human impact sources. Comparative study on the different sources of human impact: T-test results show that the impact of roads can be neglected; human activities related to roads have insignificant impact on the structure of surrounding landscape as compared with the impacts of residential areas and hydropower stations. The impact of residential areas is superior only when buffer zones of roads and residential areas overlap. When hydropower stations are considered, the landscape structure of the overlapping zones resembles that of hydropower station buffer zones. Impact of residential areas lies somewhere between that of road and hydropower stations, and the existence of hydropower stations has the greatest impact on the structure of the surrounding landscape. Comparative study of overall landscape structure: The current forest coverage of Wolong Nature Reserve (area with available data) is approximately 62%; shrubbery and grassland coverage is 17%; and non-vegetated land (bare land and ice and snow covered land) accounts for 20%. Except for conifer forest, bare land, and ice and snow covered land, the combined area of all other types of human-impacted landscape is greater than that of natural landscape. In buffer zones of residential areas and hydropower stations, the proportion of broadleaf forest is higher and is obviously distributed at lower altitude. In buffer zones of roads, the proportion of conifers, grassland, and bare land is the highest, indicating that the center of the areas independently impacted by roads is at high altitude. Analysis of landscape change over distance in human-impacted areas: In buffer zones of hydropower stations and residential areas, both the coverage of the 3 main types of forest and overall forest coverage increase as the distance of buffer zones increases, meaning that the impact of hydropower stations and residential areas declines with distance. In contrast, in buffer zones of roads, overall forest coverage is always approximately 60% and starts to decrease only in very distant buffer zones due to increase in altitude. This shows that the impact of roads is far less than that of residential areas and hydropower stations. Human impact is most intensive within 600m radius of residential areas and hydropower stations. That 600~1200m is the transitional area between human-impacted and natural landscape, and buffer zones beyond 1200m are dominated by natural landscape. The difference between the structures of human-impacted landscape and natural landscape: Forest coverage in buffer zones of various hum