Abstract:
Changes in abiotic factors along altitudinal and latitudinal gradients cause powerful
environmental gradients. The topography of alpine areas generates environmental
gradients over short distances, and alpine areas are expected to experience greater
temperature increase compared to the global average. In this study, we investigate
alpha, beta, and gamma diversity, as well as community structure, of vascular plant
communities along altitudinal gradients at three latitudes in the Swedish mountains.
Species richness and evenness decreased with altitude, but the patterns within the
altitudinal gradient varied between sites, including a sudden decrease at high altitude,
a monotonic decrease, and a unimodal pattern. However, we did not observe a decline in beta diversity with altitude at all sites, and plant communities at all sites were
spatially nested according to some other factors than altitude, such as the availability
of water or microtopographic position. Moreover, the observed diversity patterns
did not follow the latitudinal gradient. We observed a spatial modularity according
to altitude, which was consistent across sites. Our results suggest strong influences
of site-specific factors on plant community composition and that such factors partly
may override effects from altitudinal and latitudinal environmental variation. Spatial
variation of the observed vascular plant communities appears to have been caused
by a combination of processes at multiple spatial scales.
