The objectives of this long-term study are: (1) to assess the effects of directional and prolonged changes in precipitation amount and variability on population, community and ecosystem processes; (2) to elucidate the mechanisms behind those changes, and finally (3) to predict the future state of drylands functioning under novel climate conditions.
To address these objectives, we build upon two extant experiments located in a Desert Grassland at the Jornada LTER (NM): (a) manipulation of rainfall amount (80% reduced PPT, ambient, 80% increased), and (b) manipulation of rainfall variability (control, enhanced variability by 50% and 80%). Long-term manipulations of precipitation amount will be accomplished using rainout shelters coupled with irrigation systems. Manipulations of precipitation variability is conducted by flipping drought and irrigation treatments from year to year in the same plots. Response variables monitored during the last 10 years will continue to be measured; aboveground net primary production by species, plant species cover, richness, diversity, composition and belowground productivity are measured annually to disentangle endogenous mechanisms at population, community and ecosystem levels.