Abstract
BackgroundGlobal warming can cause variation in plant functional traits due to phenotypic plasticity or rapid microevolutionary change. Seed mass represents a fundamental axis of trait variation in plants, from an individual to a community scale. Here, we hypothesize that long-term warming can shift the mean seed mass of species.MethodsWe tested our hypothesis in plots that had been warmed over 18 years in alpine meadow communities with a history of light grazing (LG) and heavy grazing (HG) on the Qinghai-Tibet plateau. In this study, seeds were collected during the growing season of 2015.ResultsWe found that warming increased the mean seed mass of 4 (n = 19) species in the LG meadow and 6 (n = 20) species in the HG meadow, while decreasing the mean seed mass of 6 species in the LG and HG meadows, respectively. For 7 species, grazing history modified the effect of warming on seed mass. Therefore, we concluded that long-term warming can shift the mean seed mass at the species level. However, the direction of this variation is species-specific. Our study suggests that mean seed mass of alpine plant species appears to decrease in warmer (less stressful) habitats based on life-history theory, but it also suggests there may be an underlying trade-off in which mean seed mass may increase due to greater thermal energy inputs into seed development. Furthermore, the physical and biotic environment modulating this trade-off result in complex patterns of variation in mean seed mass of alpine plant species facing global warming.
Highlights
Global warming induces variation in plant functional traits (Nicotra et al, 2010; Anderegg, 2015; Bjorkman et al, 2018)
We found that warming significantly increased the mean seed mass of Euphrasia pectinata, Gentiana aristata, Lomatogonium carinthiacum, and Stipa aliena (4 of 19 species), while decreasing the mean seed mass of Deschampsia caespitosa, Draba eriopoda, Elymus nutans, Pedicularis kansuensis, Potentilla nivea, and Taraxacum mongolicum (6 of 19 species) in the light grazing (LG) site (Fig. 2A)
We found that warming increased the mean seed mass of 4 of species in the LG meadow and 6 of species in the heavy grazing (HG) meadow, which support hypothesis I
Summary
Global warming induces variation in plant functional traits (Nicotra et al, 2010; Anderegg, 2015; Bjorkman et al, 2018). Experimental warming resulted in taller plants and larger leaves in Arctic tundra (Hudson, Henry & Cornwell, 2011; Bjorkman et al, 2018). Such temperature-driven changes in plant traits may reflect either phenotypic variation or rapid microevolutionary change (Thompson, 2013; Merilä & Hendry, 2014). Long-term warming results in species-specific shifts in seed mass in alpine communities. We hypothesize that long-term warming can shift the mean seed mass of species. The physical and biotic environment modulating this trade-off result in complex patterns of variation in mean seed mass of alpine plant species facing global warming
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