Woodland encroachment impacts on forest/grassland ecotone soil, southwest Alberta, Canada
Date
2022-04
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Abstract
This multi-method analysis measures vegetation dynamics within a grassland-woodland ecotone. The ecotone study site, Ann and Sandy Cross Conservation Area (ASCCA) is situated in the southern Alberta Foothills Fescue ecodistrict and Foothills Parkland ecodistrict. Canadian native grasslands are threatened by land conversion, invasion of introduced pasture grasses, and tree encroachment. The unmitigated range expansion of trembling aspen, an early succession tree species, is problematic due to the alteration of soil conditions, which displaces native grasslands. This has occurred elsewhere in prairie grasslands, where soils shift from Chernozem into Luvisol, showing the transition from grassland to forest vegetation. Four vegetation type identified at ASCCA (forest, plowed and unplowed grassland, and the transition zone). Each vegetation type had 10 sites representing subpopulations within the heterogeneous landscape. The objective was to determine soil characteristics for each vegetation types and evaluate whether transition sites are more similar to grassland or forest soils. The results found transition sites can provide baseline knowledge, used to better understand soil characteristic and vegetation change - especially at the grassland-forest boundary. Transition sites were similar to forests and plowed grasslands. Altered grassland landscapes (through the mechanism of plowing, fire suppression, and removal of important keystone grazers) are likely onset sites of future soil alteration due to the mismanagement of adjacent woody encroachment. Plowed grasslands with gentle slope angles were more conducive to soil alteration from tree encroachment. Grasses find refuge on steeper slopes, however, are vulnerable in plowed grasslands, and need critical attention in these areas. Presently, only 2 % native grassland remains at ASCCA (AGRA, 1997). If plowed grasslands continue to persist without disturbances to manage tree encroachment, soil alteration in these areas can lead to native grassland corridor loss.
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Keywords
soil, dynamic soil properties, plant-soil relationships, forest-grassland, ecotones, reference plant communities
Citation
Radloff, C. (2022). Woodland encroachment impacts on forest/grassland ecotone soil, southwest Alberta, Canada (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.