Should Northern mixed-grass prairie be rested from grazing after spring wildfires?

Steers grazing in northern mixed grass prairie in Wyoming (Photo Credit JD Scasta)

Montana researchers published a paper addressing this controversial question in the journal Agriculture, Ecosystems & Environment this year.  Specifically, this line of research is addressing the current federal policy in the US that requires that rangelands be deferred from grazing for 2 growing seasons after wildfires to allow for recovery.  Researchers setup a study to see if spring wildfire changed productivity and species composition of a northern mixed-grass prairie site after the 2013 Pautre wildfire that occurred in northwestern South Dakota.  The project used grazing exclosures for the first and second growing seasons after the fire to determine if grazing or the deferrment of grazing changed the vegetation.  It turns out that ecological site was more important that grazing or grazing deferrment in determining vegetation productivity or species composition.  There was no different in total forage biomass in grazed versus ungrazed areas and loamy sites produced more forage than sandy sites.  Finally, the species composition was explained by the ecological site and not the grazing or grazing exclusion treatments.  The authors concluded that “Results do not support the notion that a two growing season rest period following fire is required in the northern mixed-grass prairie.

Cattle response to prescribed fires in mesic sagebrush

Researchers in Idaho recently published a paper titled “Prescribed Fire Effects on Activity and Movement of Cattle in Mesic Sagebrush Steppe” in the journal Rangeland Ecology and Management.  In this study they tracked mature cows with GPS collars before prescribed burning (2 years) and after prescribed burning (5 years).  The site was mesic sagebrush steppe.  The effect of the fire on cattle behavior was an increase in foraging activity budgets, duration of foraging bouts, number of foraging bouts, and length of paths relative to prefire paths or cattle in unburned sites.  The prescribed burning did not seem to influence the steepness of cattle foraging paths.  Authors concluded that “Prescribed fire in mesic sagebrush steppe can be used to create opportunities for cattle to improve foraging efficiency by altering their activity budgets and movement path characteristics. Any consequent improvements in foraging efficiency could, in turn, promote increased rates of weight gain, better body condition, enhanced reproductive success, and ultimately, more pounds of beef for market.”

Check it out: http://www.sciencedirect.com/science/article/pii/S1550742416301117

Citation: [Clark, P. E., Nielson, R. M., Lee, J., Ko, K., Johnson, D. E., Ganskopp, D. C., … & Hardegree, S. P. (2017). Prescribed Fire Effects on Activity and Movement of Cattle in Mesic Sagebrush Steppe. Rangeland Ecology & Management.]

How will a changing climate impact snowpack and fire potential in the West?

2016 NW Wyoming wildfire
2016 NW Wyoming wildfire (Photo Credit: JD Scasta)

Researchers from 3 universities (University of Washington, University of Idaho, and University of California – Los Angeles) recently published a paper in the journal Climate Change.  The study assessed 10 climate scenarios for snow, soil moisture and fuel moisture across the western US.  These researches found that mountain snowpack is forecasted to decline, that spring melt is predicted to start earlier in the year, and the general snow season will get shorter.  In terms of wildfire, these cumulative changes due to warming will reduce summer moisture across western mountain environments through warmer and drier summers.  The dead fuel moisture in these types of locations is expected to decrease up to 25%.  This will lead to an increase in flammability in forests that typically have a lot of fuel but are typically moist and considered to be flammability-limited.

Check it out:  https://link.springer.com/article/10.1007/s10584-017-1899-y

Citation [Gergel, D. R., Nijssen, B., Abatzoglou, J. T., Lettenmaier, D. P., & Stumbaugh, M. R. (2017). Effects of climate change on snowpack and fire potential in the western USA. Climatic Change, 141(2), 287-299.]

If precipitation and forage production becomes more variable, what is the impact on cow-calf enterprises?

Researchers from the University of Wyoming and the USDA Agricultural Research Service recently published a modeling paper that predicts the effects of increasing precipitation variability on cow-calf enterprises in southeastern Wyoming.  Precipitation variation was related to forage production and economic data at the ranch-level across a 35 year period.  This study is important because forecasts indicate the precipitation may become more variable, or in other words, the wet years might be wetter and the dry years might be drier.  One of the model parameters was increasing spring precipitation variation by 10%, 20%, 30%, 40%, and 50% increases.  To put that in perspective, if currently the average, minimum, and maximum of available forage is 439 kg/ha, 214 kg/ha, and 649 kg/ha respectively then a 20% increase in variation will yield an average, minimum, and maximum of available forage of 433 kg/ha, 146 kg/ha, and 676 kg/ha and a 50% increase in variation will yield an average, minimum, and maximum of available forage of 419 kg/ha, 27 kg/ha, and 713 kg/ha.  Thus, the average is not that different but the extremes are more extreme.  As one might expect, variation in profitability also increases as precipitation and forage production variation increases.  The scary part to me though is the final conclusion by the authors, “that the positive benefits of wet years do not overcome the negative impacts of the dry years given relationships among precipitation, forage production, and calf gains used in our model“.  Authors also suggest that maintaining lower herd numbers could be a mitigation strategy to deal with greater variability and ranches need to continue to think about how to diversity their operation and income sources.

cattle and sage grouse in Wyoming

Cattle and sage grouse in Wyoming (photo by J.D. Scasta)

Here is the link:

http://ac.els-cdn.com/S1550742416300458/1-s2.0-S1550742416300458-main.pdf?_tid=d82b7a5c-adb2-11e6-9b48-00000aab0f01&acdnat=1479489612_7d98328c3a8ab0ee735effb72aa0cdc2

[Hamilton, T. W., Ritten, J. P., Bastian, C. T., Derner, J. D., & Tanaka, J. A. (2016). Economic Impacts of Increasing Seasonal Precipitation Variation on Southeast Wyoming Cow-Calf Enterprises. Rangeland Ecology & Management.]

New open access ‘Rangelands’ journal issue with 11 science papers available

I recently served as a co-coordinator of a special issue of the journal ‘Rangelands’ is titled “Drought on Rangelands: Effects and Solutions”.  The really cool part of this special issue is that all of the articles are open access and freely available to everyone.  These papers include scientists from across the United States and address the following topics:

  • Advancing Knowledge for Proactive Drought Planning and Enhancing Adaptive Management for Drought on Rangelands
  • Assessing Drought Vulnerability Using a Socioecological Framework
  • Where Do Seasonal Climate Predictions Belong in the Drought Management Toolbox?
  • New Tools for Assessing Drought Conditions for Rangeland Management
  • Evaluating New SMAP Soil Moisture for Drought Monitoring in the Rangelands of the US High Plains
  • Rangeland Responses to Predicted Increases in Drought Extremity
  • Droughts and Wildfires in Western U.S. Rangelands
  • Drought Mitigation for Grazing Operations: Matching the Animal to the Environment
  • Adaptive Management for Drought on Rangelands
  • “In Every Rancher’s Mind”: Effects of Drought on Ranch Planning and Practice
  • Coping With Drought on California Rangelands

Check out all of the articles at: http://www.sciencedirect.com/science/journal/01900528

Rangelands Journal website
Rangelands Journal website