Increases in thermophilus plants in an arid alpine community in response to experimental warming

Meagan F Oldfather,David D Ackerly

doi:10.1080/15230430.2019.1618148

Meagan F Oldfather, David D Ackerly

Open Access

https://doi.org/10.1080/15230430.2019.1618148

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Abstract

ABSTRACTA warming climate has been shown to drive thermophilization—shifts in species abundance toward those adapted to warm and dry conditions. The community dynamics shaping this process have been proposed to vary between temperature-limited alpine plant communities and those that are both temperature and moisture limited. In nine sites across the xeric alpine zone in the White Mountains, California, USA, we experimentally increased summertime temperature and precipitation for three seasons and quantified community responses with a climatic niche analysis. We asked if thermophilization occurred in response to experimental heating, and if this effect was ameliorated by experimental watering. Under experimentally warmer conditions, we found no change in the mean community-weighted climatic niche (CCN); however, thermophilization of this community was observed based on a shift in the seventy-fifth percentile of the CCN and an increase in the proportional abundance of the hottest, driest adapted species. In addition, total vegetation abundance increased and species richness decreased with heating. Experimental watering did not ameliorate these effects of heating. Together, these results suggest that warming in arid alpine areas may result in less diverse plant communities dominated by hot, dry associated species, although short-term responses may be limited because of community lags.

Highlights

Climatic niche values for the species found across these sites ranged widely (CWD = 176 mm–710 mm) and the most abundant species were widely distributed across the range of Climatic water deficit (CWD) species means (Table 1, Figure 2)
We examined the effects of experimental warming and watering on xeric alpine plant communities across a mountain range
Thermophilization of this community was supported by two lines of evidence: (1) an increase in the seventy-fifth percentile CCN, indicating an increase of hot, dry adapted species within each site (Figure 4b), and (2) a positive interaction between experimental heating and Δniche, demonstrating that species with higher climatic niche values relative to their community increased in proportional abundance and species with lower climatic niche values relative to their community decreased in proportional abundance (Figure 5)

Summary

Introduction

Mountain systems provide important early indicators of plant community responses to changing climate (Körner 2003; Grabherr, Gottfried, and Pauli 2010; Rixen and Wipf 2017; Steinbauer et al 2018); climate warming is more pronounced at higher elevations (Pepin et al 2015), and exposure to climate change is exacerbated in xeric mountain ranges because of shifts from snow-dominated to rain-dominated precipitation (McCullough et al 2016). The topographic complexity of mountains creates a variety of potentially suitable microrefugia that may allow alpine species to persist at local scales (Scherrer and Körner 2011; Spasojevic et al 2013; Winkler et al 2016b; Graae et al 2018).

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