Abstract
AbstractAlthough the importance of edaphic factors and habitat structure for plant growth and survival is known, both are often neglected in favor of climatic drivers when investigating the spatial patterns of plant species and diversity. Yet, especially in mountain ecosystems with complex topography, missing edaphic and habitat components may be detrimental for a sound understanding of biodiversity distribution. Here, we compare the relative importance of climate, soil and land cover variables when predicting the distributions of 2,616 vascular plant species in the European Alps, representing approximately two‐thirds of all European flora. Using presence‐only data, we built point‐process models (PPMs) to relate species observations to different combinations of covariates. We evaluated the PPMs through block cross‐validations and assessed the independent contributions of climate, soil, and land cover covariates to predict plant species distributions using an innovative predictive partitioning approach. We found climate to be the most influential driver of spatial patterns in plant species with a relative influence of ~58.5% across all species, with decreasing importance from low to high elevations. Soil (~20.1%) and land cover (~21.4%), overall, were less influential than climate, but increased in importance along the elevation gradient. Furthermore, land cover showed strong local effects in lowlands, while the contribution of soil stabilized at mid‐elevations. The decreasing influence of climate with elevation is explained by increasing endemism, and the fact that climate becomes more homogeneous as habitat diversity declines at higher altitudes. In contrast, soil predictors were found to follow the opposite trend. Additionally, at low elevations, human‐mediated land cover effects appear to reduce the importance of climate predictors. We conclude that soil and land cover are, like climate, principal drivers of plant species distribution in the European Alps. While disentangling their effects remains a challenge, future studies can benefit markedly by including soil and land cover effects when predicting species distributions.
Highlights
Understanding how environmental factors influence plant species distributions and diversity has been a longstanding challenge in ecology (de Candolle 1820, MacArthur 1965, von Humboldt and Bonpland 2010)
Having disentangled the results of the relative influence along elevation bands (Fig. 4a), we found that the contribution of climate remained highest across all elevation bands, it declined with elevation
Our analyses demonstrate that other drivers besides climate need to be considered when modeling species distributions, especially in topographically heterogeneous regions
Summary
Understanding how environmental factors influence plant species distributions and diversity has been a longstanding challenge in ecology (de Candolle 1820, MacArthur 1965, von Humboldt and Bonpland 2010). It is recognized that climate has direct effects on plants’ growth and physiology (Woodward 1987, Ko€rner 2003), which explains the imprint of past climate changes on extinctions, distributions, and speciation (Comes and Kadereit 1998, Mittelbach et al 2007, Smycka et al 2017). Given these direct effects, and the ever-increasing availability of high-resolution climatic. Soil plays an important ecophysiological role for plants through the provisioning of nutrients and water, and its small-scale influence on plant distribution, in terms of variations in chemical and physical soil properties and bedrock types, is well documented (Ko€rner 2003, Coudun and Gegout 2005, Coudun et al 2006, Piedallu et al 2011, Bertrand et al 2012, Dubuis et al 2013, Scherrer and Guisan 2019)
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