Plant production forecasts across geographical and ecological sites in sagebrush-steppe plant communities

Authors: Schantz, Merilynn; Hardegree, Stuart; Sheley, Roger; Bates, Jonathan - Jon; JAMES, JEREMY - California Polytechnic State University; ABATZOGLOU, JOHN - University Of California; Davies, Kirk

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Climate directly affects plant production across rangeland ecosystems. Forecasts of rangeland plant production could provide valuable management information pertaining to livestock stocking rates, restoration planning, wildfire fuel loads, and wildlife management. In a retrospective study that encompassed 50,000 km2 area in southeastern Oregon, we evaluated the ability to produce plant production forecasts across 45 intact late-seral sagebrush steppe sites over a 10-year time period. We found that plant production models and forecasts were able to identify key functional group responses to precipitation and temperature inputs; that climate and plant production forecasts could be used to produce significant monthly plant production forecasts; and that forecasts of total plant production by ecological site groupings were significantly better than those that forecast from geographical site groupings.

Technical Abstract: Climate directly affects plant production across rangeland ecosystems. Forecasts of rangeland plant production could provide valuable management information pertaining to livestock stocking rates, restoration planning, wildfire fuel loads, and wildlife management. In the sagebrush steppe ecoregion, plant production is dependent upon climate but also varies by geographic location and the ecological site or dominant plant community. In this study, we combined retrospective seasonal climate forecasts and plant production models and compared these to plant production models driven by observed weather data across both geographical and ecological sites. This study was conducted in 45 intact late-seral sagebrush steppe sites over a 10-year time period across a 50,000 km2 area in southeastern Oregon. Research sites were sorted into five geographical groupings and into five ecological site groupings. We used hindcasts as a proxy for forecasted climate conditions to test these models and have referred to modeled hindcasts as forecasts throughout. The objectives of this study were to 1) model plant functional group responses to actual and forecasted climate across time and space; 2) Determine plant production forecast skill for lead times of up to 7 months; and 3) Differentiate plant production model and forecast skill among both geographical site groupings and ecological site groupings. We found that plant production models and forecasts were able to identify key functional group responses to precipitation and temperature inputs. We also determined that climate forecasts and plant production forecasts yielded significant production forecasts for lead-times of up to 7-months for all site and functional groupings. We, furthermore, identified that forecasts of total plant production by ecological site groupings were significantly better than those that forecast from geographical site groupings. Forecasting by ecological site should, furthermore, lead to better rangeland management as it matches management inputs with inherent site conditions.