Understanding how plant species and communities respond to precipitation can provide increased predictive power for inter-annual variation and directional trends in the provisioning of ecosystem services such as forage production and quality, biogeochemical cycling, and biodiversity, as well as reducing risks for managers. In a US shortgrass prairie, we collected data describing plant abundance, functional traits, and aboveground net primary productivity (ANPP) to identify “response traits” indicative of species- and community-responsiveness to annual precipitation (i.e., precipitation sensitivity), and “effect traits” exhibiting spatial relationships between community-weighted trait values and ANPP. We address the following questions: (1) How does precipitation sensitivity vary across a priori functional groups (forbs, graminoids, shrubs/subshrubs) and life forms (annuals, perennials)? (2) Which traits are associated with species-level precipitation sensitivity? (3) Do functional groups and life forms differ in which traits explain precipitation sensitivity? and (4) Are traits that vary in response to annual precipitation (response traits) the same as those related to spatial variation in primary productivity (effect traits)?
Results/Conclusions
Across 32 plant species, we explained 68% of the variation in species-level sensitivity to temporal fluctuations of annual precipitation using leaf dry matter content (LDMC), specific leaf area (SLA), and leaf osmotic potential (OP) – LDMC and OP were negatively and SLA positively related to precipitation sensitivity. Most trait-precipitation sensitivity relationships were consistent across functional groups and life forms. Yet for annual species, plant height was negatively related to precipitation sensitivity, and we found no relationship between plant height and precipitation sensitivity for perennial species. As effect traits, SLA and LDMC were negatively related to ANPP across the grassland, and these linkages were independent from abiotic factors. These findings demonstrate that this semiarid grassland experiences substantial shifts towards traits that confer rapid resource acquisition and growth, and away from traits that confer stress resistance in wet years, and vice versa in dry years. They suggest that chronic changes in precipitation regimes are also likely to shift community traits, and these trait shifts may lead to emergent effects on ANPP. This highlights the need to incorporate understanding of plant community dynamics if we are to accurately predict year-to-year variation and directional trends of ecosystem services and mitigate risks for land managers.