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University of Regina (2009)

The impacts of drought on species at risk and their habitat in the northern mixed grass prairies

Rever, Susan Michelle

Titre : The impacts of drought on species at risk and their habitat in the northern mixed grass prairies

Auteur : Rever, Susan Michelle

Université de soutenance : The University of Regina

Grade : Master of Science 2009

Résumé
Climatologists suggest that global warming will bring higher temperatures and more frequent and extreme droughts to areas such as the West Block of Grasslands National Park (GNP). Since drought is closely linked to land degradation, future management of mixed prairie grasslands will require an improved understanding of past and future trends in regional aridity. The objectives of my research were : (1) to spatially analyze temporally discrete data for climate and grassland productivity from 1978 to 2006 ; (2) to develop statistical models of climate-vegetation relationships for the West Block of Grasslands National Park ; (3) to assess past and predict future aridity ; (4) to forecast the probability of future drought using Monte Carlo analysis ; (5) to assess the effects climate change will have on the eight species-at-risk (SAR) chosen for my study ; and (6) to develop management options and risk analysis for the eight SAR. Past grassland productivity analyses show that vegetation index (numerical indicator that analyzes radiometric measurements that indicate relative abundance and activity of green vegetation) averages were typically lower during drought years, except for the moisture stress index (MSI), which is an inverted vegetation index. In this case, higher values indicate greater water stress. During a severe drought, photosynthesis is significantly reduced, which decreases grassland productivity. I found that the normalized difference vegetation index (NDVI) and soil adjusted vegetation index (SAVI) are negatively correlated with temperature, while the normalized difference moisture index (NDMI) is positively correlated with precipitation and aridity, and negatively correlated with potential evapotranspiration (PET). The MSI is positively correlated with PET, and negatively correlated with precipitation and aridity. This means that vegetation indices are strongly associated with climate variables. The multiple linear regression models, which evaluated how accurately the vegetation index variables can be predicted by precipitation, temperature, and PET, for the NDMI and MSI vegetation indices, were significant. Past aridity measurements for the West Block of GNP indicate that this area was a semi-arid ecoregion during 1978 to 2006. If current trends continue, GNP will fall into the arid classification by 2020, for the month of July. By 2050 and 2080, GNP will be classified as arid for both July and August. Based on the Palmer Drought Severity Index (PDSI), the West Block of GNP was affected by droughts during the 1980s. Mild droughts also occurred in 2001 and 2006. The NDVI, SAVI and NDMI are positively correlated with the PDSI, while the MSI is negatively correlated with the PDSI. The simple linear regression models, which evaluated how accurately the vegetation index variables can be predicted by the PDSI, for the NDVI and SAVI vegetation indices, were significant. When estimates of future conditions of density and vigour of vegetation were calculated, all three global climate models (GCMs) (CGCM2 A21, CSIROMk2b B11 and HadCM3 B21) predict that the amount of vegetation within the West Block of GNP will remain relatively stable until 2020. By 2050, all three GCMs predict a significant decrease in density and vigour of vegetation. By the year 2080, all three GCMs predict that most of the above ground biomass (plant matter) will decrease in density and vigour. A decrease in grassland productivity, vegetation density, vigour and canopy water content, along with a more arid climate, will have a considerable impact on the vegetation communities that currently dominate the West Block of GNP. This highlights the importance of monitoring SAR population sizes, and theft vegetation and food requirements during prolonged droughts and times of increased aridity. Management options will need to be adopted to help protect mixed prairie grasslands and ensure viable populations of SAR to prevent future extinctions.

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Page publiée le 30 août 2010, mise à jour le 6 février 2018