ABSTRACT Aim For improved predictions of the redistribution of species under climate change, there is a need to better understand how interactions among multiple abiotic drivers affect species distributions. We examined whether occupancy patterns of forest plant species change consistently along geographic and macroclimatic gradients. We further tested whether these changes co‐vary with species’ edaphic niche widths—specifically, whether niche widths contract as occupancy declines. Finally, we assessed ehether changes in occupancy and niche widths depend on species’ climatic and edaphic niche optima. Location Sweden. Time Period 2004–2013. Major Taxa Studied Vascular plants. Methods We used data from the National Forest Inventory on soil (pH and C:N‐ratio), and on occurrence of plant species from ca . 7000 inventory plots located along a climatic gradient (MAT −3 to +8°C). We modelled the probability of occurrence, as well as the edaphic pH and C:N‐ratio niche widths, along this gradient, using Generalized Additive Mixed Models. We then examined whether species’ occupancy and niche widths vary along the climatic gradient and whether this variation can be explained by climatic and edaphic niche optima quantified by ecological and climatic indicator values. Results The probability of occurrence and niche widths of most species either increased or decreased along the temperature gradient. Generally, species that decreased in occurrence and edaphic niche widths towards colder climate had their niche optima in warmer climate and vice versa . Indicators related to the climatic niche of the species generally explained a much larger proportion of the variation in species occurrence and edaphic niche width than soil‐related indicator values. Main Conclusions The results highlight that climate not only drives species’ redistributions directly, but also indirectly through modulating how plants interact with their soil environments, that is, their edaphic niches—an often‐overlooked mechanism important for understanding species responses to climate change.
Hedwall et al. (Fri,) studied this question.