Soil multifunctionality and drought resistance are determined by plant structural traits in restoring grassland

Abstract

It is increasingly recognized that belowground responses to vegetation change are closely linked to plant functional traits. However, our understanding is limited concerning the relative importance of different plant traits for soil functions and of the mechanisms by which traits influence soil properties in the real world. Here we test the hypothesis that taller species, or those with complex rooting structures, are associated with high rates of nutrient and carbon (C) cycling in grassland. We further hypothesized that communities dominated by species with deeper roots may be more resilient to drought. These hypotheses were tested in a 3-yr grassland restoration experiment on degraded ex-arable land in southern England. We sowed three trait-based plant functional groups, assembled using database derived values of plant traits, and their combinations into bare soil. This formed a range of plant trait syndromes onto which we superimposed a simulated drought 2 yr after initial establishment. We found strong evidence that community weighted mean (CWM) of plant height is negatively associated with soil nitrogen cycling and availability and soil multifunctionality. We propose that this was due to an exploitative resource capture strategy that was inappropriate in shallow chalk soils. Further, complexity of root architecture was positively related to soil multifunctionality throughout the season, with fine fibrous roots being associated with greater rates of nutrient cycling. Drought resistance of soil functions including ecosystem respiration, mineralization, and nitrification were positively related to functional divergence of rooting depth, indicating that, in shallow chalk soils, a range of water capture strategies is necessary to maintain functions. Finally, after 3 yr of the experiment, we did not detect any links between the plant traits and microbial communities, supporting the finding that traits based on plant structure and resource foraging capacity are the main variables driving soil function in the early years of grassland conversion. We suggest that screening recently restored grassland communities for potential soil multifunctionality and drought resilience may be possible based on rooting architecture and plant height. These results indicate that informed assembly of plant communities based on plant traits could aid in the restoration of functioning in degraded soil.

Effects of climate warming on Sphagnum photosynthesis in peatlands depend on peat moisture and species‐specific anatomical traits

“…Despite identical desiccation in warmed plots, S. medium maintained a more stable water content, and then photosynthesis, thanks to its anatomical traits favouring water‐holding (Figure S4). This indicates that species having structural characteristics that strengthen their resistance to drought may determine community productivity in extreme drought periods (Fry et al, ; Matias, Luis Quero, Zamora, & Castro, ) but not necessarily the community assemblage in the near future. Indeed, although S. fallax was less resistant to drought than S. medium , we found that its photosynthesis fully recovered from extreme desiccation (20% of maximum capitulum water content; Figure S3) after a rewetting equivalent to 85% of capitulum water content.…”

“…Despite identical desiccation in warmed plots, S. medium maintained a more stable water content, and then photosynthesis, thanks to its anatomical traits favouring water-holding ( Figure S4). This indicates that species having structural characteristics that strengthen their resistance to drought may determine community productivity in extreme drought periods (Fry et al, 2018;Matias, Luis Quero, Zamora, & Castro, 2012) but not necessarily the community assemblage in the near future.…”

Soil microbial community responses to climate extremes: resistance, resilience and transitions to alternative states

“…R. Soc. B 375: 20190112 soil functioning [105], which underlies the importance of coupling plant and belowground measurements for a mechanistic understanding of ecosystem stability. A major challenge is therefore to quantify the relative roles of the various indirect and direct ways through which plants operate as an extrinsic factor controlling intrinsic attributes of microbial communities that confer resistance and resilience (figure 4), and to identify the consequences for ecosystem function and feedbacks to plant community dynamics.…”

Positive effects of crop diversity on productivity driven by changes in soil microbial composition

“…Numerous studies demonstrated a strong link between soil microbes and plants (Wardle et al ., 2004; Fry et al ., 2018). First, direct specific linkages between a plant species and a particular type of microbe, such as symbiotic interactions, might occur (Wubs & Bezemer, 2016).…”