Location: Southwest Watershed ResearchTitle: Evaluating the effect of rainfall variability on vegetation establishment in a semidesert grassland Author
|Scott, Russell - Russ|
Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2013
Publication Date: 8/24/2013
Citation: Fehmi, J., Nie, G., Scott, R.L., Mathias, A. 2013. Evaluating the effect of rainfall variability on vegetation establishment in a semidesert grassland . Environmental Monitoring and Assessment. 186:395-406. DOI: 10.1007/s10661-013-3384-z. Interpretive Summary: Of the operations required for rangeland improvement and reclamation in arid regions, reestablishing vegetation entails the most uncertainty due to unpredictable rainfall for seed germination and seedling establishment. To determine how often grass reseeding operations may be successful in rangelands, we combined a computer simulation model and field data to predict grass establishment success for two sites in southern Arizona. Vegetation establishment had an annual failure rate of 32%. In the worst 10-year span in the historical rainfall record, six of ten planting years would have failed. In the best 10-year span, only one of ten was projected to fail. To improve future operations, “one-shot” reseeding operations should be discouraged along with a multiyear approach to improve reestablishment success.
Technical Abstract: Of the operations required for reclamation in arid and semi-arid regions, establishing vegetation entails the most uncertainty due to reliance on unpredictable rainfall for seed germination and seedling establishment. The frequency of successful vegetation establishment was estimated based on a land surface model driven by hourly atmospheric forcing data, 7 years of eddy-flux data, and 31 years of rainfall data at two adjacent sites in southern Arizona, USA. Two scenarios differing in the required imbibition time for successful germination were evaluated—2 or 3 days availability of sufficient surface moisture. Establishment success was assumed to occur if plants could germinate and if the drying front in the soil did not overtake the growth of seminal roots. Based on our results, vegetation establishment could be expected to fail in 32 % of years. In the worst 10-year span, six of ten plantings would have failed. In the best 10-year span, only one of ten was projected to fail. Across all assessments, at most 3 years in a row failed and 6 years in a row were successful. Funding for reclamation seeding must be available to allow reseeding the following year if sufficient amount and timing of rainfall does not occur.