Soil microbial community response to drying and rewetting stress: does historical precipitation regime matter?

Abstract

Climate models project that precipitation patterns will likely intensify in the future, resulting in increased duration of droughts and increased frequency of large soil rewetting events, which are stressful to the microorganisms that drive soil biogeochemical cycling. Historical conditions can affect contemporary microbial responses to environmental factors through the persistence of abiotic changes or through the selection of a more tolerant microbial community. We examined how a history of intensified rainfall would alter microbial functional response to drying and rewetting events, whether this historical legacy was mediated through altered microbial community composition, and how long community and functional legacies persisted under similar conditions. We collected soils from a long-term field manipulation (Rainfall Manipulation Plot Study) in Kansas, USA, where rainfall variability was experimentally amplified. We measured respiration, microbial biomass, fungal:bacterial ratios and bacterial community composition after collecting soils from the field experiment, and after subjecting them to a series of drying-rewetting pulses in the lab. Although rainfall history affected respiration and microbial biomass, the differences between field treatments did not persist throughout our 115-day drying-rewetting incubation. However, soils accustomed to more extreme rainfall did change less in response to lab moisture pulses. In contrast, bacterial community composition did not differ between rainfall manipulation treatments, but became more dissimilar in response to drying-rewetting pulses depending on their previous field conditions. Our results suggest that environmental history can affect contemporary rates of biogeochemical processes both through changes in abiotic drivers and through changes in microbial community structure. However, the extremity of the disturbance and the mechanism through which historical legacies occur may influence how long they persist, which determines the importance of these effects for biogeochemical cycling.

Increasing aridity reduces soil microbial diversity and abundance in global drylands

“…qPCR reactions were performed in triplicate by using 96-well plates on an ABI 7300 Real-Time PCR (Applied Biosystems). The bacterial 16S-rRNA genes and fungal ITS were amplified with the Eub 338-Eub 518 and ITS 1-5.8S primer sets (40). After qPCR analyses, the extracted DNA samples were frozen and shipped to the Next Generation Genome Sequencing Facility of Western Sydney University, where they were defrosted and analyzed by using the Illumina MiSeq platform (41) and the 341F/805R (bacteria) and FITS7/ITS4 (fungi) primer sets (42,43).…”

Dispersal-Based Microbial Community Assembly Decreases Biogeochemical Function

“…The cumulative impacts of ecological processes through time and how they relate to ecosystem-level processes is an emerging research frontier in ecosystem science [2,44,52,68,69]. We reveal how dispersal-based community assembly can decrease adaptation to local environments and, in turn, decrease biogeochemical function.…”

Impacts of drying–wetting cycles on rhizosphere respiration and soil organic matter decomposition

“…2C). Two possible mechanisms may explain this decline in soil C mineralization by dryingewetting in the sunflower treatment: (1) after 3 moderate and 8 severe dryingewetting cycles, the flush of soil C mineralization after wetting was not much higher compared with the constantly-moist soil, because frequent drying and wetting diminished the wetting flushes due to limitation of accessible soil organic mater pool (Xiang et al, 2008;Evans and Wallenstein, 2012); and (2) dryinge wetting significantly reduced sunflower shoot (32%) and root biomass (52%), which likely led to lower plant C inputs to the soil (rhizodeposition), less microbial biomass and activity (Table 2), and smaller rhizosphere priming effect (discussed in more detail in 4.3 section). Moreover, we found similar C mineralization in soils planted with soybean between a constantly-moist treatment and a moderate dryingewetting treatment.…”

“…Surface soils often undergo gradual drying by evapotranspiration followed by rapid wetting as a result of precipitation or irrigation. These dryingewetting cycles can influence soil aggregation (Denef et al, 2001;Cosentino et al, 2006), microbial activity and community structure (Gordon et al, 2008;Tiemann and Billings, 2011;Evans and Wallenstein, 2012), and C and N mineralization (Birch, 1958;Fierer and Schimel, 2003;Borken and Matzner, 2009). In the coming decades, many soils will likely be subjected to more frequent and intense dryingewetting cycles (Huntington, 2006), which can impact SOM decomposition and its feedback to climate change.…”