Rangeland responses to climate change
Bork,E.W., J.F.Cahill, S.X.Chang, H.Proctor, S.Wilson, B.Shore, B.Attaeian, S.White, S.Nyanumba and J. Newton. 2009. Alberta Sustainable Resource Development
Abstract
Canada contains 22 M ha of land dedicated to range and forage production. This land supports 4
M cow/calf pairs, and overgrazing in some areas has resulted in many areas being in less than 'good'
condition. Improving rangeland condition provides direct economic benefits and since native
rangelands typically store more carbon than cropland and tame pasture, this also leads to increased
carbon storage. A healthy rangeland stores equivalent carbon mass per ha as forested ecosystems, and
because this carbon is primarily belowground, it is at a lower risk of release during fires. Unfortunately,
we have a limited understanding of the belowground processes that drive rangeland dynamics, and a
general lack of information on how increased temperature and/or altered precipitation patterns will
impact the sustainability of these systems, particularly under sustained grazing. Moreover, sound
fundamental information on the nature of climate-grazing interactions within rangelands has the
potential to (1) improve carbon storage, (2) enhance native biodiversity and ecosystem functioning, and
(3) provide positive economic returns.
To mitigate the potential impacts of climate change on the biodiversity and sustainable
production of Canada's rangelands, it is essential to gain a mechanistic understanding of the links
between temperature, precipitation, soil chemistry, microbial and invertebrate diversity and activity,
primary production, and the dominant land use of livestock grazing. In this study, we are conducting
replicated field experiments at several locations of Alberta, Saskatchewan, and Manitoba from 2006 to
2009. At each location, we will establish plots subjected to a variety of treatments, including
combinations of defoliation and ambient warming (ambient or 2C using open-top greenhouses), and in
the main study, precipitation (ambient, -70% using rainout shelters, 70% using watering) treatments as
well for three growing seasons. We will measure primary productivity and range health, with a
particular emphasis linking above and belowground dynamics. Using technology such as mini-
rhizotrons (root periscope cameras) will allow for enhanced accuracy in estimating primary productivity
and carbon flow. We will also measure changes in microbial and invertebrate communities, litter
decomposition, and carbon and nitrogen cycling. We anticipate that changes in plant growth resulting
from changed climatic conditions and management practices will have cascading effects on ecosystem
resilience. From these data, we will identify a set of management recommendations for this sector of the
agricultural community on how to alter grazing regimes to mitigate the varied impacts of future climate
change.
