Belowground plant trait contributions to grassland ecosystem function across aridity gradients
Understanding of plant responses to aridification is critical to management of grasslands worldwide. Typically, ecosystem responses to environmental change are studied using aboveground plant traits and responses without much consideration of belowground plant traits. Belowground traits can include fine roots, belowground organs like tubers and rhizomes, and their associated buds used for resprouting. Abrupt shifts in aboveground plant communities across aridity gradients have been predicted. We further connected these predicted plant community shifts across aridity gradients to belowground plant traits in temperate grasslands to provide the groundwork for a more mechanistic belowground understanding behind shifts in ecosystem functioning due to environmental change.
Based on our literature review, seasonal regeneration decreasingly relies on recruitment from the belowground bud bank and increasingly relies on regeneration from seeds across an increasing aridity gradient. This leads to greater inter-annual variability in biomass production. Other belowground traits, such as bud bearing organs and fine root distribution in the soil, also shift along the aridity gradient. As aridification begins, plants would become more conservative in their belowground traits producing lower amounts of belowground litter. Increasing aridification would lead to the loss of rhizomatous plants from the community and a prevalence of deep rooting plants leading to changes in soil resource utilization and increasing susceptibility to soil erosion. Under extreme aridification, perennial plants, except those with bulbs, would be lost from the community and replaced by annuals which produce low amounts of litter and use only ephemeral water resources in the upper soil layers. Using these concepts will provide a basis for further work with belowground traits and aridification.