Precipitation regimes impacts dryland multifunctionality: A cascade of historical precipitation regimes via species replacement in multitrophic microbiota

Aim: The pervasive impacts of climate change on the biodiversity and
functionality in arid ecosystems are increasingly evident in the
Anthropocene. Although soil microbes are anticipated to be sensitive to
changes in precipitation regimes, the mechanisms through which
multifaceted precipitation variances impair the current delivery of
multiple functions by multitrophic microbiota remain largely unexplored.
Here, we examined the direct effects of historical precipitation regimes
on the multifunctionality and their indirect impacts mediated by soil
microorganisms in drylands. Location: Northwestern China. Time period:
Precipitation records (1979-2016); Field investigation in 2020. Major taxa
studied: Multitrophic microbiota in biocrusts. Methods: We evaluated a
38-year daily precipitation across the arid regions to quantify its
multifaceted characteristics, including mean amount, frequency, and
variability. The community structures of heterotrophic bacteria,
eukaryotic fungi, and photoautotrophic cyanobacteria were determined
through amplicon sequencing, aimed to measure taxonomic and phylogenetic
α-diversity, as well as spatial turnover in soil microbiota. We explored
the interactive linkages between precipitation impacts and diversity
effects on soil multifunctionality. Results: We found that α-richness
exerted positive functional influences, but phylogenetic dissimilarity was
a more important predictor in photoautotrophs. Species replacement, as a
component of β-diversity, consistently enhanced the multifunctional
dissimilarity and asynchrony of biocrusts. The legacy effect of historical
precipitation variability, rather than annual precipitation, emerged as a
primary driver on a convergence of less beneficial species, thereby
promoting the variance in soil functioning. Importantly, the findings
illuminated a cascading effect of precipitation regimes regulated by
multifaceted diversity, which potentially magnifies their influences on
vulnerable arid habitats. Main conclusions: Our study highlighted the
importance of precipitation variability and the indirect climate impact
via soil microbiota. It contributes to a deeper understanding of the
real-world consequences of altered precipitation on drylands, providing
valuable insights for more accurate modeling of global change.