LTREB Renewal: Long-term ecosystem responses to directional changes in precipitation amount and variability in an arid grassland

Rainfall plays an important role in dryland environments. Climate is changing fast and significantly. A drier and more variable climate is expected, which could affect dryland environments. Predicting the effects of a new climate on the functioning of ecosystems is the most pressing objective of ecology. Understanding, the way ecosystems will function under these novel conditions is necessary to develop management strategies that generate optimal societal outcomes. Drylands are very important because they cover 40% of the terrestrial surface and provide invaluable goods and services. These goods and services range from forage production to recreation. This project will continue two unique long-term experiments, where researchers separately manipulated rain amount and variability in a desert grassland in New Mexico for 16 years. Results from the first 5 years of this project yielded unexpected results. Drought had indirect effects on the composition of plant species that offset the direct effects of drought. The continuation of the project will determine how these different responses occurred. Broader impacts include directly contributing to increasing participation of the public. This project will collaborate with Asombro Institute for Science Education by building a new demonstration project at the 960-acre Chihuahuan Desert Nature Park. Asombro is a non-profit organization that provides award-winning science education to more than 22,000 children and 4,500 adults annually in southern New Mexico and western Texas. This proposal is guided by two hypotheses about dryland responses to changes in amount and variability of precipitation. (1) Endogenous Mechanisms: Biogeochemical and demographic phenomena mediate abrupt or continuous changes in populations, communities and ecosystem processes. (2) Exogenous Phenomena: El Niño events at 3-4-year periods interact with changes in low-frequency Pacific Decadal Oscillation (PDO) and Atlantic Multi-Decadal Oscillation (AMO). These climate events interact with internal mechanisms. Jointly, they affect system resistance, and lead to changes in species composition and ecosystem processes. After 16 years, the ecosystem seems to be at crossroads regarding soil organic nitrogen forms. This condition may result in a new N-water limitation. The project will continue two unique long-term precipitation-manipulation experiments that separately manipulated precipitation amount and variability in a desert grassland in New Mexico for 16 years. The long-term manipulations of precipitation amount are accomplished using rainout shelters coupled with irrigation systems. This project will directly contribute to increasing participation of students. This project will collaborate with Asombro Institute for Science Education by building a new demonstration project at the 960-acre Chihuahuan Desert Nature Park. Asombro is a non-profit organization that provides award-winning science education to more than 22,000 children and 4,500 adults annually in southern New Mexico and western Texas. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.