Forest Investment Account (FIA) - Forest Science Program
FIA Project Y092208

    Managing the interacting effects of grazing and global climate change in BC interior rangelands
Project lead: Fraser, Lauchlan (Thompson Rivers University)
Contributing Authors: Fraser, Lauchlan H.; Carlyle, Cameron N.; Turkington, Roy; Greenall, Amber; Friedman, Cynthia Ross
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Global climate change has been an ongoing phenomena for approximately 100 years (19, 2). However, it is anticipated that global warming will continue at a more rapid pace due to increases in greenhouse gas emissions in the atmosphere (20, 2). The most affected area is projected to be in the northern arctic (16, 5), but an increase of at least to two degrees is forecast for areas of British Columbia by 2100 (9).

Plants have already been shown to have responded to global climate change, with some terrestrial plant populations extending their ranges toward the poles or to higher elevations (17). Furthermore, the phenologies of some plants have shifted with leaf expansion and flowering occurring earlier in the spring (17, 18).

Grasslands in British Columbia are a rare ecosystem and are habitat for many of BCs endangered plants and animals. Grasslands also support much of BCs cattle industry. However, grasslands are threatened by tree encroachment, over-grazing, agricultural conversion and urban development. Global climate change has the potential to interact with the above disturbances (15), but the consequences of these interactions for grassland ecosystems in the southern interior have not been investigated. The interacting effects of disturbance caused by grazing and climate-change, a biological stress on plant communities, will not likely be uniform across grasslands. Variation of response is expected across the landscape and by species, furthermore the response of a species may depend on the environment it is in.

Coarse-filters, such as temperature, precipitation, the level of primary productivity, and elevation gradient, can assist in managing rangelands more appropriately at the landscape level for the maintenance of biodiversity, optimization of primary forage production, protection of sensitive individual species, and control of non-native invasive plants.

The effect of climate change (precipitation and temperature) on grasslands can be addressed with a factorial field experiment. Climate-change models predict that the interior of British Columbia will experience increased temperatures and altered precipitation patterns (drier summers, wetter winters) (9). Open-top-chambers (OTCs) and rain-shades have been used successfully for small scale temperature manipulations (13). Clipping of vegetation allows for a controlled disturbance of the plant community that can approximate the effects of grazing. Twelve treatment combinations will be tested: 2 temperature treatments (increased by 2-3 degrees Celsius and ambient); 3 watering treatments (water addition, rainshades and ambient); and 2 clipping treatments (clipped at 7.5 cm stubble height or not clipped). All twelve treatments will be replicated 6 times and then repeated at three points along a natural productivity gradient.

Strong predictions can be made to gauge the response of vegetation change to these manipulations based on existing ecological theory (6, 11, 22). Species richness displays an empirically supported hump-shaped relationship to productivity, such that species richness is maximal at intermediate levels of productivity. Similarly, the intermediate disturbance hypothesis also predicts species richness to be maximal at intermediate levels of disturbance (defined as partial or total physical destruction of plants).

The existing theory leads to four testable hypotheses:
1) Low productivity grasslands will be more resistant (i.e. less reduction in biomass and species richness) to climate change induced stress than high productivity grasslands.
2) Slow growing, stress tolerant species, typical of low productivity environments, will be least affected by changes in temperature, rainfall and disturbance.
3) In response to increased temperature and reduced precipitation, more stressful conditions, there will be a reduction in the intensity of competition in high productivity grasslands. On the other hand reduced stress will increase the intensity of competition by the addition of resources.
4) Species richness will decline when disturbance and stress are relatively high, but species richness will increase when the relative strength of either is reduced, and decrease when both are reduced because competitive dominance is possible under low stress low disturbance conditions.

This experiment will aid managers in understanding the general response of grasslands to stress and disturbance and to incorporate climate change into their long-term management plans.

*Numbers in parentheses are references, which are listed in uploaded file.
Related projects:  FSP_Y081208FSP_Y103208


Annals of Botany article (0.2Mb)
Executive summary (0.2Mb)
Presentation of Grasslands (6.2Mb)
Climate Change Poster (4.9Mb)
Presentation - IPC talk (2.7Mb)
Article in Link Magazine, Spring 2009

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Updated August 16, 2010 

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