Hierarchical subdivision of Arctic tundra based on vegetation response to climate, parent material and topography

Current land-cover classifications used for global modelling portray Arctic tundra as one or two classes. This is insufficient for analysis of climate -vegetation interactions. This paper presents a simple three-level vegetati on-map legend system useful for modelling at global, regional, and landscap e scales. At the highest level (global scale: 10(7)-10(8) km(2)) the Tundra Zone is divided into four subzones based on vegetation response to tempera ture along the latitudinal temperature gradient from north to south: (1) Cu shion-forb, (2) Prostrate Dwarf-shrub, (3) Erect Dwarf-shrub, and (4) Low S hrub subzones. The boundaries follow a modification of Yurtsev's phytogeogr aphic subzones. Parent material and topography are also major consideration s at global, regional, and landscape scales. Soil pH is a key variable for many ecosystem responses, and a division into acidic (pH 5.5 or less) and n onacidic soils is used. A conceptual mesotopographic gradient is used to ch aracterize the influence of soil-moisture and snow regimes. The example leg end framework focuses on the Northern Alaska floristic subprovince, and cou ld be expanded to other floristic provinces using local expert knowledge an d available literature. Dominant plant functional types within each habitat type within the four subzones are also presented. Modellers could include or ignore different levels of resolution depending on the purpose of the mo del. The approach resolves conflicts in terminology that have previously be en encountered between the Russian, North American, and Fennoscandian appro aches to Arctic zonation.