Richness of plant communities plays a larger role than climate in determining responses of species richness to climate change

Abstract

Experimental warming in situ suggests that warming could lead to a loss of biodiversity. However, species that remain in situ and experience climate change will interact with species tracking climate change, which could also affect patterns of biodiversity. The relative contribution of species gains and losses to net changes in species richness is still unclear. We use transplanted plant communities to test the hypothesis that both the change in climate and ecological communities tracking climate change will influence how species richness responds to climate change. Three intact alpine plant communities were reciprocally transplanted to create scenarios in which species experienced warmer and wetter conditions (transferred to lower elevations) and cooler and drier conditions (transferred to higher elevations) over 10 years on the Tibetan Plateau. Communities transplanted into the same elevation as controls represent species tracking climate change. Transferring to lower elevations generally caused a net increase in richness and a higher rate of gains relative to the control plots; the magnitude of this effect depended on the specific elevation. Transferring to higher elevations lead to either net increases or decreases in richness and gains, depending on elevation. Species gains predicted much more variation in changes in species richness (50%) than did species loss (9%). Species richness at the receptor site and the donor site were both important predictors of variation in species richness, and the abiotic environment did not explain additional variation. Changes in cover of dominant plant species in response to transfers did not predict changes in species richness, species gain or species loss. Our results suggest that species gains from species tracking climate change at the receptor sites, rather than species loss from the donor sites, predicted changes in species richness. Synthesis. Warming experiments with physical barriers to dispersal may overestimate the negative effect of warming on plant diversity by not accounting for species gains. Our study highlights the importance of biotic factors in addition to the abiotic environment, when considering how climate change will affect plant diversity.

Community diversity outweighs effect of warming on plant colonization

“…Using a unique experiment that allowed us to isolate direct abiotic effects of environmental change (Pathway A, Figure ) from indirect biotic effects (Pathway B), we show that direct effects of warming on species colonization are dwarfed by effects of community diversity. Combined with findings from studies that consider Pathway C (Alexander, Diez, & Levine, ; Bansal & Sheley, ; Catford, Morris, Vesk, Gippel, & Downes, ; Kraft et al, ; Wang et al, ), this set of results suggests that environmental change mostly facilitates species colonization indirectly, by altering biotic interactions with resident species (Pathways B or C), rather than by directly facilitating colonization based on colonists’ abiotic tolerances alone (Pathway A).…”

“…Milder winters can increase survival and extend growing seasons, enabling larger populations and greater reproductive output of species that do well under warming (Hellmann, Byers, Bierwagen, & Dukes, ), compounding the advantages that warming‐favoured species might experience. Had warming occurred at landscape or regional scales, species migration may have changed the composition of seed pools in the different warming treatments, potentially increasing the importance of Pathway A by increasing the pool of species that could colonize (Merow et al, ; Wang et al, )—either with range‐expanding natives or exotic species with spreading populations (Auffret & Thomas, ). Introduction of exotic species that are not yet naturalized in the region would likely have similar effects (Haeuser et al, ).…”

Precipitation Alters the Effects of Temperature on the Ecosystem Multifunctionality in Alpine Meadows

“…To examine the effects of climate change on the EMF in alpine meadows, we performed a reciprocal transplantation experiment along an altitudinal gradient of the Nyaiqentanglha Mountains on the central Tibetan Plateau. We simulated warming treatment expected under future climate change and cooling treatment usually occurred over temperature anomalies events through transplanting meadow blocks to lower and higher altitudes (Zhao et al, 2018 ; Wang et al, 2019a , b ). Previous studies have provided basic ecological information along the altitudinal gradient of the Nyaiqentanglha Mountains including plant phenology (Li et al, 2016a , 2020 ), species distribution (Li et al, 2013 ; Wang et al, 2013 ) and carbon dynamics (Zhao et al, 2016 , 2018 ).…”

Changes in Community Composition Induced by Experimental Warming in an Alpine Meadow: Beyond Plant Functional Type

“…First, the temperature increase in our experiment is smaller than that in other studies. Greater temperature increases often induce more pronounced changes in plant species diversity (Wang et al, 2019). Second, our experimental chambers are much larger than those used in previous studies.…”