Abstract
Soil communities dominated by lichens and mosses (biocrusts) play key roles in maintaining ecosystem structure and functioning in drylands worldwide. However, few studies have explicitly evaluated how climate change-induced impacts on biocrusts affect associated soil microbial communities. We report results from a field experiment conducted in a semiarid Pinus halepensis plantation, where we setup an experiment with two factors: cover of biocrusts (low [<15%] versus high [>50%]), and warming (control versus a ∼2°C temperature increase). Warming reduced the richness and cover (∼45%) of high biocrust cover areas 53 months after the onset of the experiment. This treatment did not change the ratios between the major microbial groups, as measured by phospholipid fatty acid analysis. Warming increased the physiological stress of the Gram negative bacterial community, as indicated by the cy17:0/16:1ω7 ratio. This response was modulated by the initial biocrust cover, as the increase in this ratio with warming was higher in areas with low cover. Our findings suggest that biocrusts can slow down the negative effects of warming on the physiological status of the Gram negative bacterial community. However, as warming will likely reduce the cover and diversity of biocrusts, these positive effects will be reduced under climate change.
Highlights
Climate change is fostering major shifts in the composition and diversity of biota in terrestrial ecosystems worldwide (Visser and Both, 2005; Rosenzweig et al, 2007; Peñuelas et al, 2013; Buitenwerf et al, 2015)
The decline in the cover and richness of biocrusts observed was exacerbated by warming, which promoted a significant reduction in the cover and richness of well-developed biocrust communities, an effect that was mainly due to the response of their constituent lichens
This finding is consistent with other investigations of warming effects on biocrust-dominated grasslands and shrublands (Escolar et al, 2012; Maestre et al, 2013), and with those of Belnap et al (2006), who reported that a 6◦C increase in maximum summer temperatures over 8 years substantially reduced the cover of biocrust-forming lichens in the Colorado Plateau
Summary
Climate change is fostering major shifts in the composition and diversity of biota in terrestrial ecosystems worldwide (Visser and Both, 2005; Rosenzweig et al, 2007; Peñuelas et al, 2013; Buitenwerf et al, 2015). Large uncertainties exist about how climate change-induced alterations in the composition and diversity of biotic communities will directly impact ecosystem functioning (Hartley et al, 2012; Zhou et al, 2012; Maestre et al, 2013; Delgado-Baquerizo et al, 2014). This is true for terrestrial microbial communities in arid, semi-arid and dry-subhumid environments (drylands), as we are only starting to understand the role that. Reductions in the abundance of other biocrust-associated cyanobacteria with changes in rainfall patterns have been reported (Johnson et al, 2012)
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