Weathering losses of forage species on the fescue grassland in southwestern Alberta

Abstract

Weathering losses of forage species on the fescue grassland in southwestern Alberta. Can. J. Plant Sci. 78: 265-272. Rough fescue grasslands are readily damaged by heavy grazing pressure in the summer but tolerate grazing in winter. The grasslands have physical and nutritive properties that make them suitable for winter grazing by cattle thereby reducing the cost of winter feeding while preserving the integrity of the grasslands. However, their forage value declines during winter through the degradation of biomass yield and quality. This study took place at the Agriculture and AgriFood Canada, Range Research Substation located on the Porcupine Hills in southwest Alberta. The objectives of this study were to determine the dynamics of litter biomass for important forage species over winter, to examine the role of leaf position in the plant on biomass loss from leaves, and to determine the associated changes in crude protein, phosphorus, and acid detergent fibre of the leaves, and carbon and nitrogen. Leaves of Parry oat grass (Danthonia parryi Scribn.), Idaho fescue (F. idahoensis Elmer), and rough fescue (F. campestris Rydb.) were sampled at monthly intervals from August to March over 3 yr to determine weight and chemical composition. Decomposition of these species, together with smooth aster (Aster laevis L.), was also tested for decomposition in the litter mass using nylon bags. Degradation of standing litter was most rapid in late summer and tended to decline toward stability by December. Biomass losses in leaves from August to March were similar (P > 0.05) among grass species. Overwinter losses in the litter mass tended to be greatest for smooth aster. Changes in the mineral and fibre concentrations of the herbage were typical of the trends expected for the period, that included late senescence and weathering, and followed closely the losses of biomass for the period. Forage decomposition is an important ecological process in mineral cycling and affects the quantity and quality of forage available for delayed grazing. Il reste que leur valeur fourragère baisse durant l'hiver, à la fois en quantité qu'en qualité. Nos expériences avaient lieu à la Sous-station de recherches sur les parcours (ministère de l'Agriculture et de l'Agroalimentaire du Canada) dans les Porcupine Hills au sud-ouest de l'Alberta. Nos objectifs étaient d'établir la dynamique de la formation de la litière à partir des espèces fourragères importantes durant l'hiver, d'examiner le rôle de la position des feuilles sur la tige sur les pertes de biomasse foliaire et d'élucider les modifications concomittantes des teneurs en protéine brute, en P et en lignocellulose des feuilles ainsi que celle du bilan du carbone et de l'azote. Les feuilles de la danthonie de Parry (Danthonia parryi Scribn.), de la fétuque de l'Idaho (F. idahoensis Elmer) et de la fétuque rude (F. campestris Rydb.) étaient prélevées tous les mois à partir d'août jusqu'en mars pendant 3 ans, pour en mesurer le poids et la composition chimique. La décomposition de ces espèces ain...

Isolating the role of soil resources, defoliation, and interspecific competition on early establishment of the late successional bunchgrassFestuca campestris

“…Defoliation during the growing season is known to be detrimental to F. campestris (Willms & Fraser ; Willms et al ; Bogen et al ). Our observations suggest these negative effects further depend on seedling age and competition from neighboring plants.…”

Assessing the Impact of Parameter Uncertainty on Modeling Grass Biomass Using a Hybrid Carbon Allocation Strategy

“…In cases where site‐ or species‐specific values for relevant parameters were not available, we used default values previously assigned for general grassland ecosystems (White et al, ). We reference the numerous sources used for site‐specific values which are fully detailed in the supporting information (Adler et al, ; Fernández & Reynolds, 2002; Gill & Jackson, ; Goodwin et al, ; Kassem et al, ; Monson et al, ; Murphy et al, ; Reich et al, ; Risser, ; Ryan ; Sage et al, ; Schulze et al, ; Sims et al, ; Turner et al, ; Vanderbilt et al, ; Vinton & Burke, ; Vivanco & Austin, ; Weaver & Haglund, ; White et al, ; Willms et al, ).…”

Estimating Economic Carrying Capacity for an Ungulate Guild in Western Canada

“…Weathering loss is greatest after senescence, when vegetation becomes decumbent from snow loads [100]. The fragmented leaves and vegetative parts begin decomposition by weathering, leeching [99], photochemical processes [101] and microbial degradation [102,103]. Moisture, temperature and wind can enhance vegetation decomposition rates, as experiments monitoring cotton-rotting rates found high decomposition rates during wetter seasons and were associated with microhabitats such as wetter slopes [104].…”

“…Weathering could have accounted for substantial reduction of available forage biomass [98,99] and may be a critical but unquantified factor in estimating carrying capacity on northern ranges. In southeast Alberta on ungrazed pastures, total over-winter weathering loss to available vegetation was up to 60%, and also varied with forage class, whereby forbs could disappear almost completely while losses for grasses ranged between 27-52% [100,101].…”

“…In addition, because a large component of grasses and sedges sought by bison and wapiti are near water bodies, vegetation that is trampled may be exposed to moist soil, with increased susceptibility to decomposition. If annual weathering losses of grasses in Alberta are found to be near 50% [101], or between 27-52% depending on grass species [99], then this loss should be taken into account for annual estimates where annual requirements of wildlife need to be met [42,119,120].…”