Plant composition of northern temperate pastures and their disturbance history in Alberta, Canada

This data set includes the plant composition of 102 pastures sampled in north-central Alberta, Canada. Sampled pastures were located in the Central Parkland and Dry Mixed-Wood natural subregions, and were largely comprised of introduced species. In this study, we examined the influence of pasture disturbance history on vegetation, soil properties, and rangeland health. Disturbance history includes estimates of pasture age, cultivation history, fire history, grazing history (including stocking rates), and other pasture management activities/inputs (manure, fertilizer, etc.).

Methods
Methods copied from our accepted manuscript: Pyle, Lysandra A., Hall, Linda, and Bork, Edward W. (In Press). Northern temperate pastures exhibit divergent plant community responses to management and disturbance legacies identified through a producer survey. Applied Vegetation Science.

1.  Study location

We surveyed 102 pastures during 2012 (n=44) and 2013 (n=58) between May 24 and July 6, distributed across agricultural lands within 80 km of Edmonton, Alberta, Canada.  About half the pastures were in the Central Parkland (n=50), with the remainder in the Dry Mixedwood (n=50) and Central Mixedwood (n=2) subregions. A large and well-distributed sample size ensured wide variation in soil textures, seeded and non-seeded vegetation, and management actions.

Pastures were selected using a stratified random approach, separated by at least 800 m. Pastures were identified through consultation with municipal county staff, then driving roadsides to confirm suitable fields visually. Pastures had to accommodate a 260 m long transect (minimum of 4 ha) with buffer zones from wetlands (30 m), forests and fence lines (10 m), with larger pastures given preference. Acquisition of sites was constrained by landowners’ willingness to grant permission to their land, although refusals were uncommon (n < 10). A privacy agreement with landowners prohibits us from releasing the locations of pastures.

2. Producer management and disturbance history

            Pasture management and disturbance history were acquired for all 102 pastures through a retrospective, in-person interview. Interviews were approved by the University of Alberta’s Research Ethics Board (ID: Pro0030842). Interviews identified historical and current land-use practices and natural disturbances potentially influencing soil and vegetation. Managers were initially asked about ownership and whether the pasture had been previously cultivated. If cultivated, managers estimated when it was planted (grassland age) and how (seeding history was described in Pyle, Hall, & Bork, 2018); cultivation status could also be classified as unknown (attributed to land-turnover or rented pasture). Recent management actions were summarized, including grazing history (grazing system, timing of grazing, number of animals, type of livestock, supplemental feeding with hay), mechanical treatments (aerated, harrowed, or swathed/mowed), nutrient addition (fertilizer or manure), or herbicide application. Livestock stocking rates [in animal-unit-months per ha (AUM ha-1)] were calculated for pastures (n=80) where adequate information on grazing activities was obtained (see Pyle, Hall, & Bork, 2018), where one AUM is the forage required to support a mature cow (with or without a calf) for one month. Other natural disturbances capable of influencing vegetation, such as a known history of recent fire, were recorded. All management actions and disturbance factors are described in Appendix S1 (Applied Vegetation Science manuscript).

3. Plant cover, ground cover, and soil properties

           Following the interview, a grassland assessment was conducted. To begin sampling, a random point was located from which a 260 m long ‘W-transect’ was laid out (Thomas, 1985). Plant composition and ground cover were assessed at nine equidistant locations using a 0.25 m2 quadrat. Foliar cover was estimated for each plant species, with trace species recorded as 0.1%. Plants were identified (Moss & Packer, 1983) and nomenclature updated using VASCAN (Brouillet et al., 2018). Plant species were later grouped into major cover components by origin (total native, total introduced) and growth form [forbs, graminoids (grasses, sedges, rushes)], as well as functional groups such as introduced grasses (seeded or widely naturalized), introduced legumes (seeded or widely naturalized), introduced ruderal forbs (agronomic weeds), noxious weeds [defined by the Weed Control Act (Province of Alberta, 2010)], native perennial graminoids, native perennial forbs, native ruderal forbs, and native woody plants. These functional groups are related to rangeland health, which evaluates key forages, along with unpalatable and disturbance-induced plants. For each pasture, plant community richness, diversity (effective number of species), and Pielou’s evenness were summarized for inclusion in multivariate analyses.

At all locations where cover was observed, the area of litter and exposed mineral soil on the ground surface were estimated, and litter depth was measured at five random locations within the 0.25 m2 frame. Mineral soil was sampled to a depth of 15 cm at ten random locations. During preparation of soil cores (Pyle, Hall, & Bork, 2019), charcoal layers in the top 15 cm of mineral soil were often found, indicating fire occurrence in the pasture’s history and not reported by managers. For each grassland, soil properties including % total carbon (C), % total nitrogen (N), carbon to nitrogen ratio (C:N), organic matter (OM), pH, electrical conductivity (EC), and texture (% clay, % sand, % silt) were measured. Procedures and specific responses are summarized elsewhere (Pyle, Hall, & Bork, 2019).

4. Rangeland health

           Rangeland health was assessed using the Tame Pasture Assessment Form developed by Alberta Environment and Parks (Adams et al., 2010; resources available at https://www.alberta.ca/range-health.aspx). In brief, this process evaluated grasslands based on six criteria, including: (1) vegetation composition and forage cover (tame or modified-tame), (2) the status of vegetation as either desirable (i.e., tall, productive forages) or non-desirable (non-palatable) species in tame pasture, (3) hydrologic function and nutrient cycling (abundance of litter), (4) site stability (exposed mineral soil and evidence of erosion), (5) noxious weeds, and (6) encroachment by woody plants (scoring is summarized in Pyle, Hall, & Bork, 2018). In total, 60% of the health score arises from vegetation attributes, 25% from hydrologic function, and 15% from site stability (Adams et al., 2010).

5. Literature Cited

Adams, B. W., Ehlert, G., Stone, C., Lawrence, D., Alexander, M., Willoughby, M., Hincz, C., Moisey, D., Burkinshaw, A., Carlson, J., & France, K. (2010). Rangeland health assessment for grassland, forest and tame pasture. Public Lands and Forests Division, Alberta Sustainable Resource Development, Alberta, Canada.

Brouillet L, Desmet P, Coursol F, Meades SJ, Favreau M, Anions M, Bélisle P, Gendreau C, Shorthouse D, & Contributors. (2018). Database of Vascular Plants of Canada (VASCAN). Online at http://data.canadensys.net/vascan. https://doi.org/10.3897/phytokeys.25.3100  [accessed in August 2018]

Moss, E. H., & Packer, J. G. (1983). Flora of Alberta: a manual of flowering plants, conifers, ferns, and fern allies found growing without cultivation in the Province of Alberta, Canada (2nd ed.). University of Toronto Press, London, Ontario, Canada.

Province of Alberta. 2010. Weed Control Act. Her Majesty the Queen in the Right of Alberta, Edmonton, Alberta, Canada.

Pyle, L. A, Hall, L. M. & Bork, E. W. (2018). Linking management practices with range health in northern temperate pastures. Canadian Journal of Plant Science, 98(3), 657-671. https://doi.org/10.1139/cjps-2017-0223

Pyle, L. A, Hall, L. M., & Bork, E. W. (2019). Soil properties in northern temperate pastures do not vary with management practices and are independent of rangeland health. Canadian Journal of Soil Science, 99(4), 495-507. https://doi.org/10.1139/CJSS-2019-0076

Thomas, A. G. (1985). Weed survey system used in Saskatchewan for cereal and oilseed crops. Weed Science, 33(1), 34-43. https://doi.org/10.1017/S0043174500083892