Monitoring climate impacts on annual forage production across U.S. semi-arid grasslands

Authors: PODEBRADSKA, MARKETA - University Of Nebraska; WYLIE, BRUCE - Us Geological Survey; BATHKE, DEBORAH - University Of Nebraska; BAYISSA, YARED - Texas A&M University; DAHAL, DEVENDRA - Us Geological Survey; Derner, Justin; Fay, Philip; HAYES, MICHAEL - University Of Nebraska; Wagle, Pradeep

Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2021
Publication Date: 12/21/2021
Citation: Podebradska, M., Wylie, B.K., Bathke, D.J., Bayissa, Y.A., Dahal, D., Derner, J.D., Fay, P.A., Hayes, M.J., Wagle, P. 2021. Monitoring climate impacts on annual forage production across U.S. semi-arid grasslands. Remote Sensing. 14(1). Article 4. https://doi.org/10.3390/rs14010004.
DOI: https://doi.org/10.3390/rs14010004

Interpretive Summary: Assessing within and across grazing season impacts of climate on forage production across semiarid rangelands in the western United States remains challenging for land managers. Increasing understating of this connection between seasonal climate and resulting forage production would be highly advantageous for producers to more effectively implement adaptive management at the ranch level to match forage availability with animal demand. Here, we evaluated a proxy model for forage production that reflects climatic influences while minimizing impacts of management and disturbances, based on 19 years of data at a site in the Nebraska Sandhills. This model was extended to, and compared with, ground-observed biomass datasets collected at several semiarid rangeland sites. The model predicted the forage production with good agreement, illustrating that it can be used in semiarid rangelands in the Great Plains for within season forage production assessments. This information, combined with seasonal climate predictions and experiential knowledge by land managers and producers, can be used to inform adaptive decision making by livestock producers and land managers at the ranch scale to more effectively match animal demand to forage availability.

Technical Abstract: The ecosystem performance approach, used in a previously published case study focusing on the Nebraska Sandhills, proved to minimize impacts of non-climatic factors (e.g., overgrazing, fire, pests) on the remotely-sensed signal of seasonal vegetation greenness resulting in a better attribution of its changes to climate variability. The current study validates the applicability of this approach for assessment of seasonal and interannual climate impacts on forage production in the western United States semi-arid grasslands. Using a piecewise regression tree model, we developed the Expected Ecosystem Performance (EEP), a proxy for annual forage production that reflects climatic influences while minimizing impacts of management and disturbances. The EEP model establishes relationships between seasonal climate, site-specific growth potential, and long-term growth variability to capture changes in the growing season greenness measured by time-integrated Normalized Difference Vegetation Index (NDVI) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS). The resulting nineteen years of EEP were converted to expected biomass (EB, kg ha-1 yr-1) using a newly-developed relationship with the Soil Survey Geographic Database range production data (R2 = 0.7). Results were compared to ground-observed biomass datasets collected by the U.S. Department of Agriculture and University of Nebraska-Lincoln (R2 = 0.67). This study illustrated that this approach is transferable to other semi-arid and arid grasslands and can be used for creating timely, post-season forage production assessments. When combined with seasonal climate predictions, it can provide within-season estimates of annual forage production that can serve as a basis for more informed adaptive decision making by livestock producers and land managers.