Abstract
Climate change can influence soil microorganisms directly by altering their growth and activity but also indirectly via effects on the vegetation, which modifies the availability of resources. Direct impacts of climate change on soil microorganisms can occur rapidly, whereas indirect effects mediated by shifts in plant community composition are not immediately apparent and likely to increase over time. We used molecular fingerprinting of bacterial and fungal communities in the soil to investigate the effects of 17 years of temperature and rainfall manipulations in a species‐rich grassland near Buxton, UK. We compared shifts in microbial community structure to changes in plant species composition and key plant traits across 78 microsites within plots subjected to winter heating, rainfall supplementation, or summer drought. We observed marked shifts in soil fungal and bacterial community structure in response to chronic summer drought. Importantly, although dominant microbial taxa were largely unaffected by drought, there were substantial changes in the abundances of subordinate fungal and bacterial taxa. In contrast to short‐term studies that report high resistance of soil fungi to drought, we observed substantial losses of fungal taxa in the summer drought treatments. There was moderate concordance between soil microbial communities and plant species composition within microsites. Vector fitting of community‐weighted mean plant traits to ordinations of soil bacterial and fungal communities showed that shifts in soil microbial community structure were related to plant traits representing the quality of resources available to soil microorganisms: the construction cost of leaf material, foliar carbon‐to‐nitrogen ratios, and leaf dry matter content. Thus, our study provides evidence that climate change could affect soil microbial communities indirectly via changes in plant inputs and highlights the importance of considering long‐term climate change effects, especially in nutrient‐poor systems with slow‐growing vegetation.
Highlights
The extremely high diversity of soil microorganisms makes it difficult to establish links between individual microbial taxa and specific functions (Allison & Martiny, 2008)
This was unexpected because fungi are widely regarded as drought-tolerant (Harris, 1981; Schimel et al, 2007) and previous studies have reported high resistance of soil fungi to drought treatments (De Vries et al, 2012a; Fuchslueger, Bahn, Fritz, Hasibeder, & Richter, 2014; Yuste et al, 2011)
We propose two possible explanations for this apparent discrepancy: 1. Changes in the abundances of fungal taxa may be more important and more readily apparent in grasslands such as Buxton, because fungal decomposers are more important in systems with low soil fertility and slow-growing perennial plant species (De Vries et al, 2012b)
Summary
The extremely high diversity of soil microorganisms makes it difficult to establish links between individual microbial taxa and specific functions (Allison & Martiny, 2008). Plant growth is strongly influenced by the soil microbial community because plant nutrient requirements are largely met by the breakdown and mineralization of organic matter, which requires the combined activities of many different microorganisms (Burns et al, 2013). This reciprocal exchange of resources between plants and soil microbial communities underpins ecosystem function, succession, and recovery from disturbance (Reynolds et al 2003) and is central to ecosystem responses to global change
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