Although cooler, wetter springs increase grass production compared to 1978, hotter summers mean greens turn brown faster – and plants have a harder time resuming production in the fall
PICTURE: THE INTERMOUNTAIN BUNCHGRASS PRAIRIE IN THE NATIONAL BISON RANGE, MONTANA, USA IN ONE OF THE STUDY AREAS. Show more CREDIT: GARY BELOVSKY
Over 40 years of surveillance, an endangered hump grass prairie has grown hotter, drier, and more prone to fire annually – but dramatic seasonal changes (not annual climate trends) appear to be causing the largest changes in crop production, composition, and summer age. Gary Belovsky and Jennifer Slade from the University of Notre Dame, Indiana, will present these results on December 23 in the open access journal PLOS ONE.
The mid-mountain bunchgrass prairie is one of the most endangered ecosystems in North America, now covering less than 1 percent of the area it once was. Over the past century, hump grass prairies have become warmer and drier, and man-made climate change is expected to continue this trend and have potential impacts on heap grass ecosystems. However, bunchgrass is often overlooked in grassland studies.
To better understand the effects of climate change on the bunchgrass prairie, Belovsky and Slade spent 40 years studying the National Bison Range, a bunchgrass prairie in Montana. They made repeated observations of plant growth and production, the abundance of different plant species, and the availability of nitrogen (an important nutrient for plants), and created a comprehensive schedule for changes to the ecosystem.
As the study progressed, annual temperatures and rainfall increased on the prairie, making it more susceptible to fire. Surprisingly, the researchers found that annual primary above-ground production – the amount of plant material produced each year – increased by 110 percent, which was associated with increased rainfall and cooler temperatures during the important growing season from late May to June. However, this was associated with a change in plant composition, with an increase in 108 percent of invasive species, preference for more drought-tolerant species overall, and a 65 percent decrease in the number of Dicot non-grass plants over the 40-year study period.
The researchers also found that other ecosystem changes followed seasonal climate trends rather than annual trends. For example, summer temperatures were higher than expected based on annual trends, which fueled summer senescence – the annual "tan" of green plant material.
These results show the importance of considering local and seasonal changes in predicting the effects of climate change on a given ecosystem. The authors report that the Intermountain Bunchgrass prairie could turn into a different type of grassland previously unknown.
Dr. Belovsky adds, "Predicting the effects of climate change on crop production based on the expected average annual temperature increase and decreased rainfall may not be appropriate because seasonal climate changes may be more important and may not match average annual expectations."
Quote: Belovsky GE, Slade JB (2020) Climate Change and Primary Production: Forty Years in a Grassland Plains. PLoS ONE 15 (12): e0243496. https://doi.org/10.1371/journal.pone.0243496
Funding: Funding to the 1st author GEB: National Science Foundation: NSF – http://www.nsf.gov NSF DEB-78-02069, NSF BSR-83-07352, NSF DEB-93-17984, NSF DEB-97 -07564, NSF DEB-04-15390, NSF DEB-09-18306, NSF DEB-1456511 National Geographic Society Grant for Fiscal Year 79 – https://www.nationalgeographic.org; University of Michigan Rackham Graduate School – https://rackham.umich.edu/; Vice President, University of Michigan Research Fellowship – https://www.research.umich.edu; USDA / GHIPM (1989-1994) – http://www.ars.usda.gov (GHIPM program ended in 1994); Utah State University Agricultural Experimental Station (1992-1996) – https://uaes.usu.edu/; USDA / ARS and USDA-CSREES / NRICGP (00-35101-9267) – http://www.csrees.usda.gov/ Funders had no role in study design, data collection and analysis, decision to publish, or preparation from the manuscript.
Competing interests: The authors have stated that there are no competing interests.
Use this URL in your report to get access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0243496