Hierarchical Organization of Ecosystems at Multiple Spatial Scales on the Yukon-Kuskokwim Delta, Alaska, U.S.A.
Hierarchical Organization of Ecosystems at Multiple Spatial Scales on the Yukon-Kuskokwim Delta, Alaska, U.S.A.
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美国阿拉斯加育空-库斯科奎姆三角洲多空间尺度生态系统的层次组织
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发表时间：
2000
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通讯作者：
M. Jorgenson
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作者：
M. Jorgenson
1994年至1998年，我在阿拉斯加育空-库斯科维姆三角洲的哈森湾附近进行了一次生态陆地调查，以评估海平面上升对该地区沿海生态系统的潜在影响。三个景观组成部分的独立分类将该地区的生态特征归类为10个地貌单元(例如潮滩、废弃的洪水平原覆盖沉积)、9个地表形态(例如堤坝、盆地)和18个植物群落(例如苔草稀有植物-柳树)。然后，我利用这些景观成分之间的等级关系，得出了三个组织级别的生态系统分类，其中包括10个生态系统(基于地貌)、11个生态系统(基于地表形态和地貌)和27个生态类型(主要基于植被)。各层次生态系统的性质和分布受到地貌过程的强烈影响。活动的泛滥平原，洪水和沉积频繁，具有以禾本科和杂草为主的微咸水生态型。不活跃的泛滥平原很少发生洪水和沉积，具有略微微咸水的生态型，物种和生长形式广泛多样。相比之下，废弃的泛滥平原没有洪水和泥沙沉积，但受到永久冻土堆积的强烈影响，其生态型以常绿灌木、苔藓和地衣为主，这些灌木、苔藓和地衣不耐盐，但耐受酸性、营养不良的条件。具有相似植被的生态型通常具有相似的环境特性，包括地表高度、土壤形态、沉积、有机质积累、融化深度、水深、pH和电导率。当相似的生态型基于地貌相似性被聚集到生态系统中时，生态特性的差异增加。
I conducted an ecological land survey near Hazen Bay, on the Yukon-Kuskokwim Delta of Alaska during 1994–1998 in order to assess potential effects of sea-level rise on coastal ecosystems in this region. Independent classification of three landscape components grouped ecological characteristics of the area into 10 geomorphic units (e.g., tidal flats, abandoned floodplain cover deposits), 9 surface forms (e.g., levees, basins), and 18 plant associations (e.g., Carex rariflora–Salix fuscescens). I then used hierarchical associations among these landscape components to derive an ecosystem classification at three levels of organization that included 10 ecosections (based on geomorphology), 11 ecoseries (based on surface forms and geomorphology), and 27 ecotypes (primarily based on vegetation). The nature and distribution of ecosystems at all levels showed a strong influence from geomorphic processes. The active floodplain, with frequent flooding and sedimentation, had brackish ecotypes that were dominated by graminoids and forbs. The inactive floodplain, where flooding and sedimentation were infrequent, had slightly brackish ecotypes with a wide diversity of species and growth forms. In contrast, the abandoned floodplain, which lacked flooding and sediment deposition, but was strongly affected by permafrost aggradation, had ecotypes that were dominated by evergreen shrubs, mosses, and lichens that were intolerant to salts, but tolerated acidic, nutrient-poor conditions. Ecotypes with similar vegetation generally had similar environmental properties, including surface elevation, soil morphology, sedimentation, organic matter accumulation, thaw depths, water depths, pH, and electrical conductivity. When similar ecotypes were aggregated into ecosections based on geomorphic similarities, differences in ecological properties increased.