title: Life stage, not climate change, explains observed tree range shifts.
abstract: Ongoing climate change is expected to shift tree species distribution and therefore affect forest biodiversity and ecosystem services. To assess and project tree distributional shifts, researchers may compare the distribution of juvenile and adult trees under the assumption that differences between tree life stages reflect distributional shifts triggered by climate change. However, the distribution of tree life stages could differ within the lifespan of trees, therefore, we hypothesize that currently observed distributional differences could represent shifts over ontogeny as opposed to climatically driven changes. Here, we test this hypothesis with data from 1435 plots resurveyed after more than three decades across the Western Carpathians. We compared seedling, sapling and adult distribution of 12 tree species along elevation, temperature and precipitation gradients. We analyzed (i) temporal shifts between the surveys and (ii) distributional differences between tree life stages within both surveys. Despite climate warming, tree species distribution of any life stage did not shift directionally upward along elevation between the surveys. Temporal elevational shifts were species specific and an order of magnitude lower than differences among tree life stages within the surveys. Our results show that the observed range shifts among tree life stages are more consistent with ontogenetic differences in the species' environmental requirements than with responses to recent climate change. The distribution of seedlings substantially differed from saplings and adults, while the distribution of saplings did not differ from adults, indicating a critical transition between seedling and sapling tree life stages. Future research has to take ontogenetic differences among life stages into account as we found that distributional differences recently observed worldwide may not reflect climate change but rather the different environmental requirements of tree life stages.
authors.affiliation: Faculty of Forestry, Technical University in Zvolen, T.G. Masaryka 24, SK-960 53, Zvolen, Slovak Republic.|Forest Research Institute Zvolen, National Forest Centre, T.G. Masaryka 22, SK-960 52, Zvolen, Slovak Republic.
authors.forename: František
authors.initials: F
authors.lastname: Máliš
authors.affiliation: Department of Vegetation Ecology, Institute of Botany, The Czech Academy of Sciences, Lidická 25/27, CZ-602 00, Brno, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Kopecký
authors.affiliation: Department of GIS and Remote Sensing, Institute of Botany, The Czech Academy of Sciences, Zámek 1, CZ-252 43, Průhonice, Czech Republic.
authors.forename: Petr
authors.initials: P
authors.lastname: Petřík
authors.affiliation: Forest Research Institute Zvolen, National Forest Centre, T.G. Masaryka 22, SK-960 52, Zvolen, Slovak Republic.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vladovič
authors.affiliation: Faculty of Forestry, Technical University in Zvolen, T.G. Masaryka 24, SK-960 53, Zvolen, Slovak Republic.
authors.forename: Ján
authors.initials: J
authors.lastname: Merganič
authors.affiliation: Faculty of Forestry, Technical University in Zvolen, T.G. Masaryka 24, SK-960 53, Zvolen, Slovak Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Vida
mesh_terms: D000531:Altitude; D057231:Climate Change; D065928:Forests; D063148:Plant Dispersal; D018154:Slovakia; D013045:Species Specificity; D013997:Time Factors; D014197:Trees / Q000254:growth & development / Q000502:physiology*
keywords: elevational range shift; realized niche; semipermanent plots; temperate forests; tree life stages; tree ontogeny; vegetation resurvey