A multiple-scale analysis of plant species richness, vegetation, landscape heterogeneity, and spectral diversity along an arctic river

Arctic landscapes are the subject of intensive ecological study in light of (1) the circumpolar nature of the biome, (2) the pristine nature of the ecosystem, and (3) the pace of land use and projected climate change in high latitudes. Riparian areas are plant diversity hotspots, harboring over 75% of the regional floras in some arctic areas. Understanding the patterns and environmental controls of plant distributions and diversity within riparian and upland areas is important if we are to predict changes in ecosystem patterns and processes.; This study examines the relationships in the Hood River valley of plant species richness, the environment, community composition, the structure of plant diversity (i.e., the relationships of {dollar}alpha, beta,{dollar} and {dollar}gamma{dollar} diversity), and patterns of remotely-sensed spectral heterogeneity from the plot level (10 m{dollar}sp2){dollar} to regional scales (10,000 km{dollar}sp2).{dollar} The goals of this research are to (1) understand patterns of species richness at a variety of scales, (2) describe and map plant communities and vegetation, (3) use remote sensing to estimate species richness, and (4) map biodiversity hotspots.; The vascular flora for the area includes 210 species. Species richness increases along the river to the coast and variation is positively correlated with environmental heterogeneity. The most significant component of this heterogeneity is an increase in the range of soil pH.; Twenty-four plant community types are described using the Braun-Blanquet approach. An increase in site species richness is correlated with an increase in the number of communities {dollar}(rsp2=0.323, P=0.0173){dollar} and {dollar}beta{dollar} diversity {dollar}(rsp2=0.388, P=0.0075),{dollar} rather than an increase in the {dollar}alpha{dollar} diversity of individual communities {dollar}(rsp2=0.018, P=0.6045).{dollar} Moisture and pH controlled most of the differences in composition between communities. Patterns of species richness differed among vascular, bryophyte, and lichen species. Vascular plant {dollar}alpha{dollar} diversity had a peak in richness at pH 6.5 {dollar}(rsp2=0.214, P<0.0001).{dollar}; A map of the vegetation of the region was derived from a supervised classification of Landsat TM data. Estimates of plant species richness were derived using variation in the normalized difference of vegetation index (NDVI) and weighted abundance of mapped vegetation types. Together, these explain 86% of the variance in species richness of sample areas (adj. {dollar}rsp2=0.861, P<0.0001).{dollar} Species richness hotspots in the region are concentrated along riparian corridors.