Landscape patterns of understory composition and richness across a moisture and nitrogen mineralization gradient in Ohio (U.S.A.) Quercus forests

摘要: This study quantified relationships of understory vascular plant species composition and richness along environmental gradients over a broad spatial scale in second-growth oak forests eastern North America. Species frequencies were recorded 108 25 x m plots four sites extending 70 km southern Ohio, U.S.A. The stratified into three long-term soil moisture classes with GIS-derived integrated index (IMI). In addition to the IMI, data matrix included eight overstory variables. Canonical correspondence analysis (CCA) indicated that variations most strongly related topographic predicted (IMI), N mineralization rate, nitrification pH. addition, floristic variation at regional was correlated texture, nitrification, pH, PO14, resulting from differences parent material complexes among sites. averaged 65 species/plot, increased fertility. Stepwise regression positively Nmineralization rate inversely tree basal area. Greater on fertile largely result increasing forb richness. Forb per quadrat (2 m2) rate. Conversely, individuals greatest xeric, less-fertile plots. Our results describe general, broad-scale species-environment occurred both (long-term status fertility) (geomorphological sites). Strong richness-N correlations indicate an important link between below-ground processes above-ground iodiversity. Because availability strong correlate vegetation patterns broad-scale, our suggest rates atmospheric deposition region could have major impact dynamics.