Open AccessEffects of topographic variability on the scaling of plant species richness in gradient dominated landscapes
Author(s) -
Hofer Gabriela,
Wagner Helene H.,
Herzog Felix,
Edwards Peter J.
Publication year - 2008
Publication title -
ecography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.973
H-Index - 128
eISSN - 1600-0587
pISSN - 0906-7590
DOI - 10.1111/j.2007.0906-7590.05246.x
Subject(s) - microsite , species richness , ecology , gamma diversity , abiotic component , habitat , alpha diversity , beta diversity , nestedness , niche , macroecology , geography , biodiversity , spatial heterogeneity , physical geography , biology , seedling , horticulture
It is commonly assumed that variation in abiotic site conditions influences the number of niches, which in turn affects the potential species richness in an area. Based on theoretical considerations, abiotic variation is often used as an estimator of species richness at broad scales, while at finer landscape scales the diversity of habitat types is used. However, habitat estimators assume the landscape to be composed of discrete, homogeneous patches with sharp boundaries, and such a concept is hard to apply in gradient‐dominated landscapes. The aim of this study was therefore to investigate the influence of topographic variability (TV) on species richness at the landscape level (gamma (γ) diversity) and on its components (alpha (α) and beta (β) diversity) at microsite and habitat group levels. Using floristic data from 12 “landscapes” of 1 km 2 we investigated the influence on diversity components of two simple and one complex measures of TV. While the standard deviation (SD) of altitude explained a high proportion of the variation in γ diversity (linear regression model, R 2 =0.63), the complex measure, SD of solar radiation explained it even better (R 2 =0.82). There were strong effects of TV on α and β diversity components at the microsite level, but only marginal increases of the diversity components at the habitat level. Further analyses revealed that the missing increase of the habitat level components was caused by differences between habitat groups and that only grassland diversity components increased significantly with TV. We conclude that TV at a landscape scale has strong effects on niche or microsite diversity and is an appropriate estimator of relative species richness in landscapes that are topographically heterogeneous and gradient dominated.