Get reliable rangeland science

Drought by definition is any annual reduction of rainfall greater than 25%. Historically, drought occurred in the Northern Mixed Grass Prairie, in one out of five years. Spring and summer drought occurs at the same frequency, but is more sporadic. The objective of this study was to simulate a 50% spring or summer drought using 3.3 x 2.2 m stationary rainout shelters to examine vegetation resistance and resilience. In South Dakota's Mixed Grass Prairie, rainout shelters were placed in high-diversity/high-productivity and low-diversity/low-productivity areas on three separate ranches. Treatments within each study area include a 1-yr spring drought, 1-yr summer drought, 2-yr spring drought, 2-yr summer drought, ambient precipitation, and 100% of the 30 year average precipitation (“control”). During the first year (2014), rainout shelters were placed on the 2-yr spring and summer treatments. Supplemental water was added, based on the 30-year average, to the 1-yr spring and summer treatments and “control”. In the second year of the study (2015), rainout shelters will be placed on all the replicates of both the 1-yr and 2-yr spring and summer droughts while “control” will continue to be the reference point. Spring drought was implemented from April 1st to June 30th and summer drought was from June 1st to August 31st. Biomass clippings (by species) and species composition were measured after the first frost event for all replicates and treatments. We hypothesize that sites with high-productivity/high-diversity will be more resistant and resilient than low/diversity/low productivity sites to the effects of drought due to species diversity. In addition, spring drought should have a greater impact than summer drought due to higher proportion of C3 species in the Northern Mixed Grass Prairie. These data can serve as baseline data for ranchers preparing drought management plans.