Fine root traits in adult trees of evergreen and deciduous taxa from low and high elevation in the Alps

Based on evidence for herbaceous plants we expected that trees become more efficient in terms of soil exploration by roots and, thus, produce longer and finer roots (higher specific root length, SRL) with increasing elevation. We tested this hypothesis in situ by excavating roots of eight tree taxa, all belonging to genera found frequently in both lowland and high elevation sites. Across three treeline, one montane and four lowland sites from elevations ranging from 320 masl to 2,235 masl, no elevational differences were found in SRL for both broadleaved and conifer tree species. Irrespective of the elevation preference of a species, SRL of evergreen conifers was significantly lower than that of deciduous species. However, there is an increase in total root length for a given 3rd order root diameter with elevation in the broadleaved taxa. Our findings clearly demonstrate that a high SRL is not an essential attribute of trees growing in a cold high elevation climate in temperate regions, but there is some indication that fine roots get longer as elevation increases.