The Spatial-temporal Dynamics Analysis of Landscape Pattern and Process in Watershed Scale:a Case Study of 1977-2000 in Siletz Basin, Oregon

Abstract

在集水区尺度利用景观生态学的原理进行分析和管理是现代生态学与地理科学的一个重要课题.在人口增长和经济发展的压力下,集水区的格局和过程己受到人类活动越来越强烈地干扰.赛勒支盆地是一个典型的美国太平洋西北部沿海地区的集水区,本文以此为例,研宄了美国俄勒冈州中部集水区尺度的景观格局和过程在人类活动干扰下的时空动态.通过卫星遥感影像的应用,我们对1977年到2000年间赛勒支盆地土地覆盖的变化进行了检测.我们用陆地资源卫星1977年的多光谱影像(MSS), 1988年的专题影像(TM)' 2000年的增强专题影像(ETM+)高精度地定量分析了森林演替系列(如,演替后期的老针叶林和成熟针叶林,演替前期的年轻针叶林,以及更新的幼林）和其它土地覆盖类型的变化.景观的空间格局通过多种格局指数,例如,缀块指数、缀块形状复杂性指数、以及连接指数等进行了分析.同时,基于美国太平洋西北部主要森林类型和其它土地覆盖类型碳通量和碳贮量的空间数据库和文献资料,我们对 1977-2000年赛勒支盆地中的碳库及其在人类活动干扰下的变化作了测定.研宄结果揭示出,因为森林皆伐,老针叶林和成熟针叶林在1977-2000年间显著地减少,分别由占整个盆地土地覆盖面积的23%和12%, 减少为12%和7%;与此相反,年轻针叶林和无林地则分别从24%和5%增加为43%和14%.同时,因为采伐等干扰,留存的老针叶林和成熟针叶林空间分布格局的破碎度也迅速增加.集水区的碳收支在 1977-2000期间发生了巨大的变化.在收获干扰的压力下,在1977-2000年间,整个集水区的生态系统碳贮量从 17640797t 减少到 13405720t;净生态系统生产力(Net Ecosystem Production, NEP)由每年 100462tC 减少为每年76800tC.;The landscape ecology applied in the analysis and management of watershed is an important issue in modem ecology and geography. Because the population growth and economic development, the pattern and process of watershed influenced strongly by human activity. In this paper, we discussed the spatial-temporal dynamics of landscape pattern and process in watershed scale in central Oregon. Siletz basin is a typical watershed in US Pacific Northwest. The land cover change of Siletz basin between 1977 to 2000 was determined through the satellite remote sensed data application. We used the Landsat MSS of 1977, Landsat TM of 1988 and Landsat ETM+ of 2000 imagery to quantified the forest succession serial (e.g. late serial old and mature conifer forests, early serial young conifer and regeneration forests) and other land covers with high accuracy. The spatial pattern of landscape was analyzed through the multiple pattern metrics, for example, patchiness indices, patch shape complexity indices, and connectivity indices. Based on the spatial databases and literature data, we parameterized the carbon fluxes and stocks information for the forest types and other lands in the US Pacific Northwest, and estimated the carbon fluxes and stock pools and the dynamics from 1977 to 2000 as the anthropogenic disturbance. We revealed the changes of land cover are significant from 1977 to 2000. The old conifer and mature conifer forests decreased quickly as the clearcut logging. In 1977-2000 periods, the percentage of old conifer and mature conifer area in entire Siletz basin from 23% and 12% decreased to 12% and 7%, respectively. In contrast, the young conifer forest and non-forest land from 24% and 5% increased to 43% and 14%, respectively. The fragmentation of old and mature conifer forest spatial pattern increased quickly as the harvest disturbance between 1977 and 2000. Carbon budget also was found changed significantly between 1977 and 2000. The ecosystem carbon pool decreased from 17640797t to 13405720 t, Net Ecosystem Production (NEP), an indicator of carbon sink and source, we found the pool of NEP had been changed from 100462 t/a to 76800 t/a between 1977 and 2000 as the land cover alternated by harvest disturbance.