Cattle Browsing Research Articles

Cattle change plant reproductive phenology, promoting community changes in a post-fire Nothofagus forest in northern Patagonia, Argentina

Variations in rates and length of flowering and fruiting not only affect the reproduction of a given plant species but also the behavior and reproduction of associated taxa. Flowering and fruiting variations may be influenced by herbivory, especially by large mammals. The aim of this study was to determine the effects of cattle browsing on the reproductive phenology of understory species in a subalpine post-fire Nothofagus forest in Patagonia. The effects of herbivory on plant reproductive phenology were studied in a set of experimental exclosures (fenced plots) installed since 2001 in a post-fire N. pumilio forest, located in Nahuel Huapi National Park (NHNP), Argentina. We monitored the beginning and duration of each reproductive phenological stage: floral bud, open flower, immature fruit and mature fruit. We also counted the number of flowers, fruits, seeds and viable seeds of the dominant plants to assess whether browsing modifies temporal patterns of the flowering and fruiting periods. Cattle reduced the total number of species flowering and fruiting and changed the reproductive phenology of some species. We found that palatable species seem to be negatively affected by browsing in terms of reduced fitness due to changes in flowering and fruiting periods. In contrast, cattle benefitted the reproduction of non-palatable species and could promote the invasion of shade-intolerant exotic forbs such as Cirsium vulgare. The effects of livestock reported in this study are important to understanding how browsing could alter native species establishment and possibly alter successional trajectories during recolonization after fire.

Demographic hurdles to persistence in Acacia peuce (F. Muell.): Effects of resources, fire and browsing on a threatened keystone tree species from arid Australia

We use a 31 year dataset to assess the effects of resources (rainfall, soil, relief) and disturbance (cattle browsing and fire) on regeneration and growth in a long-lived tree Acacia peuce from arid inland Australia. Temporal and spatial resource availability had an overwhelming effect on recruitment and stand density; but cattle browsing and fire limited sapling growth and stand persistence, respectively. Seedling establishment over the 31 years was effectively confined to a single prolonged high rainfall phase. Cattle browsing in productive (run-on) patches kept saplings short; while long-fenced and low cattle-use (run-off) patches provided spatial escape opportunities for sapling growth. Fire caused the death of standing plants, but it did not stimulate recruitment, and was therefore an additional limiting factor for stand persistence. Our study provided further support for the central role of prolonged large rainfall events for regeneration in long-lived arid trees, but it also emphasised how disturbance can strongly limit stand regeneration. Overall, we expect that desert trees such as Acacia peuce that are characterised by slow population dynamics will be adversely affected by climate change due to increasingly rare recruitment. Minimisation of disturbance factors will be an increasingly important requirement for the long-term persistence of this species.

Distribution and population patterns of the threatened palm Brahea aculeata in a tropical dry forest in Sonora, Mexico

The use of non-timber forest products (NTFPs) has great potential for the conservation of natural resources and rural development. Palms are important NTFPs, providing numerous products, including leaves. The harvest of palm leaves rarely results in the immediate death of individuals and can be considered one example of the sustainable use of forest resources. However, in most cases basic ecological information, such as distribution and abundance of the species is unknown, as is information on the ecological implications of human impacts, such as leaf harvest and livestock grazing. In the tropical dry forests of northwest Mexico, leaves from the threatened palm Brahea aculeata are harvested for roofing material and represent an important NTFP. In this study, we assessed the distribution and abundance patterns of this species across 52 plots in the tropical dry forest of Sierra de Álamos-Rio Cuchujaqui Reserve (SARCR) in Sonora, Mexico. We also evaluated patterns of leaf harvest and cattle browse intensity on palm populations. We found that B. aculeata density is highly variable across the landscape with a mean (±SE) of 121.7 ± 36.3 ha −1. Results indicate that B. aculeata is primarily distributed near to arroyos and rivers. The highest densities were found in sites with low incidence radiation (<0.06 MJ cm −2) and narrow stream width of arroyos/rivers (<9.5 m). Palm abundance also varied within the plots, and B. aculeata attained its highest densities near to the arroyo edge (first 20 m from the edge), perhaps indicating a microhabitat effect on palm demography. Overall, fewer than 6% of the stems were seedlings. Leaf harvesting and browsing appear to affect demographic vital rates of the species; specifically we found a significant effect of harvesting and browsing activity on the proportion of reproductive active adults. Thus, low levels of seedlings in the populations may be the result of reduced fruit production by adults and higher mortality rates of seedlings due to livestock herbivory. Result from interviews with land owners also indicated that past land use, especially along arroyos might also have important impacts on the observed distribution, low densities and absence of recruitment in some areas. We believe current distribution and abundance of NTFP, such as B. aculeata at SARCR may be a result of combined effects of environmental factors and human impacts. Results from this study will be used to develop appropriate conservation, management and restoration plans of B. aculeata in the area.

Woody Cover and Local Farmers' Perceptions of Active Pasturelands in La Sepultura Biosphere Reserve Buffer Zone, Mexico

La Sepultura Biosphere Reserve—created in 1995 in Chiapas, Mexico—is well known for its biodiversity. Its buffer zone, harboring the upper “Tablón” river basin, has been intensively managed by peasants for 48 years. We carried out interviews with cattle producers at the Los Ángeles ejido, coupled with field surveys of vegetation presence, to determine the nature and allocation of different vegetation associations and their relation to indicators of tree regeneration (sapling presence). Our data showed that 96% of the producers surveyed owned areas with open pastures, and 83% owned at least 1 patch of forested pastures where cattle browse. For oak-forested pastures, the results suggest a trend of high sapling presence with high tree cover. In contrast, for deciduous pastures, the results suggest a trend of high sapling presence with intermediate tree cover. These results are consistent with the hypothesis that woody vegetation within grazing areas may facilitate natural tree recruitment around reserves. Furthermore, these vegetation cover results suggest that within the pasturelands found today in the Los Ángeles ejido, some ranchers may be inadvertently conducting practices that are consistent with agro-silvo-pastoral systems.

Cattle affect early post-fire regeneration in a Nothofagus dombeyi– Austrocedrus chilensis mixed forest in northern Patagonia, Argentina

In forest ecosystems where infrequent, severe fires have been an important process in shaping ecosystem structure, understanding the effects of introduced livestock on post-fire recovery of the vegetation is essential for effective forest resource management and preservation. In Nahuel Huapi National Park in northwestern Patagonia, we studied the effects of livestock on the post-fire recovery of a Nothofagus dombeyi– Austrocedrus chilensis forest that was burned in 1999. We experimentally excluded cattle by fencing plots and compared the vegetation characteristics of fenced and unfenced control plots over a 5-year period. Although cattle did not significantly reduce total plant cover or total species richness, they did reduce maximum heights of woody species including the dominant tree species. Chusquea culeou, a tall understory bamboo, can impede establishment and height growth of the dominant tree species. Although C. culeou accounts for the largest percentage of cattle diet, its mean cover and mean maximum height were not strongly affected by cattle. The reduction in the height growth of seedlings of N. dombeyi and Austrocedrus in the unfenced areas implies that presence of cattle in the recently burned areas may contribute to a post-fire transition from tall forest to bamboo-dominated shrubland that is already widespread in this landscape. Thus, these results provide support for the fencing of recently burned Nothofagus and Austrocedrus forests in the national parks for periods long enough to allow the dominant tree species to grow to heights at which they are no longer severely inhibited by cattle browsing.

Pastoralists’ perceptions and realities of vegetation change and browse consumption in the northern Kalahari, Namibia

Pastoral production around artificial watering points in semi-arid environments affects the density and composition of plant communities. In the Kalahari desert of southwestern Africa, bush encroachment is often regarded as the major form of land degradation resulting from pastoral production around watering points. We investigated the OvaHerero pastoralists’ perceptions of the extent of vegetation change since the establishment of artificial watering points in the northern Kalahari desert of Namibia, and related this to ecological data on vegetation change. We determined the utility of woody vegetation to pastoralists’ livelihoods in terms of provision of construction material, fuel wood and browse. We quantified local knowledge of cattle browse consumption and correlated this with field data. We also assessed the purposes for which major livestock types were used. Our results showed that: (1) pastoral knowledge of bush encroachment and browse consumption was consistent with concurrently collected field data, (2) the current level of bush encroachment was perceived to be beneficial for pastoral production, and (3) cattle played an important role in the production of milk and milk by-products for domestic use, and served as a source of cash income, while sheep and goats were primarily kept for meat consumption. This result contrasts with historical studies that mainly portray cattle as a symbol of social status among OvaHerero pastoralists.

Commentary

Mangroves in South Africa occur at one of the most southerly locations in the world, which provides a unique opportunity to study their dynamic responses to anthropogenic and natural perturbations. The exposed high-energy South African coastline restricts mangroves to 32 sheltered estuaries of which 18 (56%) are predominantly open to the sea. A large area of mangrove (47% of the country total) occurs in the uMhlathuze Estuary – a novel ecosystem formed by the creation of an artificial mouth. A Drivers-Pressures-State-Impacts-Response (DPSIR) framework was applied to understand factors of change and highlight governance and management responses. The largest mangrove area (440 ha) was lost during the construction of Durban Bay harbour. Mangroves (~7 ha) no longer occur in 10 small KwaZulu-Natal estuaries as a result of catchment and mouth disturbance. In the Eastern Cape, pressures are escalating in the form of harvesting for wood, cattle browsing and changes in mouth condition. Climate related warming and an increase in CO2 are positive conditions for mangroves to expand their distribution to higher latitudes but this will depend on propagule dispersal between estuaries and the availability of suitable habitats. Many of the small estuaries are temporarily closed to the sea for different periods thus limiting recruitment. An increase in the intensity of freshwater floods will scour banks and completely remove mangroves. It is important that these dynamic responses are understood and incorporated into management plans so that mangrove forests can be better protected and conserved.

Commentary

Mangroves in South Africa occur at one of the most southerly locations in the world, which provides a unique opportunity to study their dynamic responses to anthropogenic and natural perturbations. The exposed high-energy South African coastline restricts mangroves to 32 sheltered estuaries of which 18 (56%) are predominantly open to the sea. A large area of mangrove (47% of the country total) occurs in the uMhlathuze Estuary – a novel ecosystem formed by the creation of an artificial mouth. A Drivers-Pressures-State-Impacts-Response (DPSIR) framework was applied to understand factors of change and highlight governance and management responses. The largest mangrove area (440 ha) was lost during the construction of Durban Bay harbour. Mangroves (~7 ha) no longer occur in 10 small KwaZulu-Natal estuaries as a result of catchment and mouth disturbance. In the Eastern Cape, pressures are escalating in the form of harvesting for wood, cattle browsing and changes in mouth condition. Climate related warming and an increase in CO2 are positive conditions for mangroves to expand their distribution to higher latitudes but this will depend on propagule dispersal between estuaries and the availability of suitable habitats. Many of the small estuaries are temporarily closed to the sea for different periods thus limiting recruitment. An increase in the intensity of freshwater floods will scour banks and completely remove mangroves. It is important that these dynamic responses are understood and incorporated into management plans so that mangrove forests can be better protected and conserved.

Short-Term Effects of Cattle Browsing on Tree Sapling Growth in Mountain Wooded Pastures

Browsing by livestock has been identified as an important factor preventing tree regeneration in wooded pastures. Two field experiments were performed to investigate the effects of cattle browsing on tree sapling growth in a mountainwooded pasture. Two size classes (ca. 12–17 cm and 41–59 cm) of each of 4 species (Picea abies, Abies alba, Acer pseudoplatanus and Fagus sylvatica) were exposed to zero, low and high grazing intensities. We measured the proportion of saplings browsed and the effect of browsing on growth. A mowing treatment within the zero grazing intensity treatment showed no significant effect on sapling growth. One percent of the large saplings but 25% of the small saplings escaped browsing. Saplings were better protected when surrounded by taller vegetation. The proportion of saplings browsed was not significantly different among species although evergreen tree saplings lost a larger proportion of biomass than deciduous species when browsed. Under grazing, average current-year shoot production and total aboveground biomass of all species were significantly reduced. Browsing effects tended to be smaller at the lower grazing intensity. Because the deciduous species were least reduced in aboveground growth, especially under the low grazing intensity, we conclude that at least in short-term, deciduous species are less affected by cattle browsing.

INFLUENCE OF HERBIVORY ON REGROWTH OF RIPARIAN SHRUBS FOLLOWING A WILDLAND FIRE1

ABSTRACT:Streamside vegetation frequently regenerates faster than upland vegetation following wildland fire and contributes to the recovery of riparian and stream ecosystems. Limited data are available, however, on the post‐fire growth of riparian species and the influence of herbivory on regeneration. To determine post‐fire regrowth of riparian vegetation, height, crown area, crown volume, and browse levels were measured for key riparian shrub species in streamside burned and unburned plots along second‐order streams in western Wyoming. Shrubs in the burned plots were subject to high levels of browse ‐ up to 84 percent of the leaders were browsed ‐ by native ungulates in 2002, the second post‐fire year (September 2001 to September 2002). In summer 2003, the burned watershed was also grazed by livestock, resulting in increased browse levels and decreased shrub heights for several species. In the third post‐fire year, September 2002 to September 2003, four of the six most common species showed no increase in crown area or crown volume, indicating that the combination of native ungulate and cattle browsing suppressed their growth. Potential impacts of grazing on post‐fire recovery of stream and riparian ecosystems are discussed.

Catastrophic drought-induced die-off of perennial chenopod shrubs in arid Australia following intensive cattle browsing

Cover and survivorship of perennial chenopods, Atriplex vesicaria and Maireana astrotricha, declined markedly during a prolonged dry period at Roxby Downs in arid South Australia. Despite their resilience to browsing in favourable seasons, only 2% of the A. vesicaria shrubs browsed heavily by cattle survived the drought. M. astrotricha exhibited greater drought survivorship, although the post-drought cover retention in browsed shrubs was only half that of unbrowsed controls. Survivorship was highest for unbrowsed chenopods growing in moisture-enhanced run-on or dune-base environments. Maintenance of these patchy areas with reduced water-stress is hence important for the persistence of browsed chenopod shrublands. Light browsing by either European Rabbits ( Oryctolagus cuniculus) or Greater Stick-nest Rats ( Leporillus conditor) had no measurable impact upon chenopod survivorship.

Survival and growth of tree seedlings in anthropogenically disturbed Mexican montane rain forests

Abstract. The montane rain forest in Chiapas, Mexico has been subject to continuous human disturbance, mainly by wood extraction, cattle grazing and fire. To address the effect of this kind of disturbance regime on regeneration, survival and growth of naturally established tree seedlings were evaluated during a 3‐yr period in three forest stands which varied in frequency and intensity of human disturbance. Frequency of cattle browsing on transplanted seedlings of Cornus disciflora, Liquidambar styraciflua and Oreopanax xalapensis planted on different facing slopes was evaluated over an 18‐mo period, their survival and growth was also determined. The density of seedlings, number of species and survival of naturally recruited tree seedlings decreased with increased intensity of disturbance. Only seedlings of Pinus and Quercus species were recorded in heavily disturbed conditions. Seedlings grew more vigorously under moderately disturbed than in undisturbed or heavily disturbed conditions. More extreme microclimatic variation (air temperature, relative humidity and solar radiation) was recorded in heavily vs moderately disturbed forest. Survival and growth of transplanted tree seedlings differed with species. Grazing damage varied among seedlings located on different facing slopes. Plants located on NE facing slopes survived better than those on other slope positions. The mean proportion of surviving individuals of L. styraciflua (80%) and C. disciflora (78%) was higher than those for O. xalapensis (60%). A higher number of C. disciflora and O. xalapensis seedlings were grazed than L. styraciflua in any slope orientation treatment. The results suggest that human disturbance negatively affects natural recruitment, reduces richness of tree seedlings and favours a small number of tree species.

Changes in shrub fecundity in fourwing saltbush browsed by cattle

Shrub fecundity is critical to long term persistence of fourwing saltbush (Atriplex canescens (Pursh) Nutt.) populations at our research site on the shortgrass steppe in Colorado. We conducted a 2-year experiment to test hypotheses concerning the impact of cattle-browsing on fecundity-related variables in fourwing saltbush. Protection from cattle browsing was significantly associated with floral phenotype shifts toward femaleness, occurring mostly in monecious shrubs (1% and 13% of grazed and protected shrubs, respectively). Sex shifts observed at the individual shrub level did not translate into detectable alterations of sex ratios at the pasture level. Shrubs exhibiting no flowers were considerably more abundant in browsed pastures (26.5%) than in exclosures (1.5%). Nonflowering occurred as frequently in female (3.6%) as it did in male (1.8%) phenotypes. Percent utricle fill was not related to previous year's cattle browsing regime (39% and 44% in protected and grazed shrubs, respectively) but rather to crown volume of the fruiting female and to the gender of and distance to the nearest neighboring shrub. The influence of cattle-browsing on reproductive output of fourwing saltbush occurred mainly through its inhibition of flowering.

Changes in Shrub Fecundity in Fourwing Saltbush Browsed by Cattle

Shrub fecundity is critical to long term persistence of fourwing saltbush (Atriplex canescens (Pursh) Nutt.) populations at our research site on the shortgrass steppe in Colorado. We conducted a 2-year experiment to test hypotheses concerning the impact of cattle-browsing on fecundity-related variables in fourwing saltbush. Protection from cattle browsing was significantly associated with floral phenotype shifts toward femaleness, occurring mostly in monecious shrubs (1% and 13% of grazed and protected shrubs, respectively). Sex shifts observed at the individual shrub level did not translate into detectable alterations of sex ratios at the pasture level. Shrubs exhibiting no flowers were considerably more abundant in browsed pastures (26.5%) than in exclosures (1.5%). Nonflowering occurred as frequently in female (3.6%) as it did in male (1.8%) phenotypes. Percent utricle fill was not related to previous year's cattle browsing regime (39% and 44% in protected and grazed shrubs, respectively) but rather to crown volume of the fruiting female and to the gender of and distance to the nearest neighboring shrub. The influence of cattle-browsing on reproductive output of fourwing saltbush occurred mainly through its inhibition of flowering. DOI:10.2458/azu_jrm_v56i1_cibils

Survival and growth of tree seedlings in anthropogenically disturbed Mexican montane rain forests

Abstract The montane rain forest in Chiapas, Mexico has been subject to continuous human disturbance, mainly by wood extraction, cattle grazing and fire. To address the effect of this kind of disturbance regime on regeneration, survival and growth of naturally established tree seedlings were evaluated during a 3-yr period in three forest stands which varied in frequency and intensity of human disturbance. Frequency of cattle browsing on transplanted seedlings of Cornus disciflora, Liquidambar styraciflua and Oreopanax xalapensis planted on different facing slopes was evaluated over an 18-mo period, their survival and growth was also determined. The density of seedlings, number of species and survival of naturally recruited tree seedlings decreased with increased intensity of disturbance. Only seedlings of Pinus and Quercus species were recorded in heavily disturbed conditions. Seedlings grew more vigorously under moderately disturbed than in undisturbed or heavily disturbed conditions. More extreme microc...

Stubble Height as a Tool for Management of Riparian Areas

Stubble height, a measure of the herbaceous vegetation remaining after grazing, has been widely used in recent years to gage the impacts of grazing use in riparian areas. Stubble height is a short-term management guide that should only be applied to help attain long-term ecological objectives; it should not be thought of as a long-term management objective. Maintaining a minimum stubble height helps preserve forage plant vigor, retain sufficient forage to reduce cattle browsing of willows (Salix spp.), stabilize sediments, indirectly limit streambank trampling, maintain cattle gains, and provide an easily communicated management criterion. Based on limited specific research of riparian system response and on knowledge of the characteristics of how cattle graze, a 10-cm residual stubble height is recommended by the authors as a starting point for improved riparian grazing management. Monitoring should then be conducted to determine if an adjustment is needed. In some situations, 7 cm or even less stubble height may provide for adequate riparian ecosystem function, particularly when streambanks are dry and stable or possibly at high elevations where vegetation is naturally of low stature. In other situations, 15-20 cm of stubble height may be required to reduce browsing of willows or limit trampling impact to vulnerable streambanks. The recommended criterion would apply to streamside and nearby meadow sites with hydrophilic or potentially hydrophilic vegetation, but not directly to dry meadows or even to all wet meadows. Stubble height may have little application where the streambanks are stabilized by coarse substrates, or the channels are deeply incised. The effects of residual stubble height in riparian functions have received limited direct experimental examination. Consequently, much of the information in this review was derived from studies indirectly related to the questions raised and, to some extent, from observations of experienced professionals. The authors have identified areas of scientific investigation needed to improve our understanding of the effects of stubble height on riparian function and grazing management.

Stubble height as a tool for management of riparian areas

Stubble height, a measure of the herbaceous vegetation remaining after grazing, has been widely used in recent years to gage the impacts of grazing use in riparian areas. Stubble height is a short-term management guide that should only be applied to help attain long-term ecological objectives; it should not be thought of as a long-term management objective. Maintaining a minimum stubble height helps preserve forage plant vigor, retain sufficient forage to reduce cattle browsing of willows (Salix spp.), stabilize sediments, indirectly limit streambank trampling, maintain cattle gains, and provide an easily communicated management criterion. Based on limited specific research of riparian system response and on knowledge of the characteristics of how cattle graze, a 10-cm residual stubble height is recommended by the authors as a starting point for improved riparian grazing management. Monitoring should then be conduted to determine if an adjustment is needed. In some situations, 7 cm or even less stubble height may provide for adequate riparian ecosystem function, particularly when streambanks are dry and stable or possibly at high elevations where vegetation is naturally of low stature. In other situations, 15-20 cm of stubble height may be required to reduce browsing of willows or limit trampling impact to vulnerable streambanks. The recommended criterion would apply to streamside and nearby meadow sites with hydrophilic or potentially hydrophilic vegetation, but not directly to dry meadows or even to all wet meadows. Stubble height may have little application where the streambanks are stabilized by coarse substrates, or the channels are deeply incised. The effects of residual stubble height in riparian functions have received limited direect experimental examination. Consequently, much of the information in this review was derived from studies indirectly related to the questions raised and, to some extent, from observations of experienced professionals. The authors have identified areas of scientific investigation needed to improve our understanding of the effects of stubble height on riparian function and grazing management.

Using a Grazing Pressure Index to Predict Cattle Damage of Regenerating Tree Seedlings

This research investigated the potential for using cattle grazing pressure (AU Mg-1 ha-1) and stocking rate (Animal Unit Days ha-1) for predicting basal scarring and browsing of lodgepole pine (Pinus contorta Dougl.) seedlings on cutblocks in southern British Columbia from 1989 to 1992. Cattle browsing on lodgepole pine seedlings occurred almost exclusively during the first 2 years of grazing. Browsing increased (P 10% of sample trees when grazing pressure exceeded 12.0 AU Mg-1 ha-1. This threshold grazing pressure value of 12.0 AU Mg-1 ha-1, however, cannot likely be extrapolated directly to other sites. Grazing pressure values and associated basal scarring are unquestionably influenced by many factors (e.g., pasture size, kind of grazing animal, forage species, tree height, water availability, topography, and weather patterns during the grazing period). Nonetheless, our work provides evidence that grazing pressure provides a useful index for predicting the potential for trampling damage of lodgepole pine seedlings by cattle.

Salt-wind induced wave regeneration in coastal pine forests in New Zealand

Strong onshore winds and airborne sea salt can gradually defoliate trees at the exposed margin of temperate pine stands in New Zealand and induce a slowly moving front of dieback and regeneration. Overcrowded mature stands are vulnerable to crown abrasion: abrasion affects trees 20 m ahead of the dieback front; suppressed trees 12 m ahead die before the front reaches them. At the stand margin, trees die from abrasion and salt wind induced dieback. The dieback zone lets sunlight enter the stand; light-demanding pine seedlings establish, but a gradient of increasing litter depth from the dieback front and summer dryness restrict successful seedling establishment to a narrow zone that moves parallel with the dieback front and 11-13 m ahead of it. Further seedlings establish for 4-10 years before the juveniles form a closed canopy; competing vegetation is partly suppressed by infrequent cattle browsing. Regenerating juvenile maritime pine (Pinus pinaster Ait.), show a strict age-related gradation from the dieback front and indicate that wind and salt deposition have been constant for 30 years. Stands further from the sea, with lower stocking rates and other pine species, did not have a clear-cut regeneration zone, because there were no strong gradients of litter depth and light intensity.

Using a Grazing Pressure Index to Predict Cattle Damage of Regenerating Tree Seedlings

This research investigated the potential for using cattle grazing pressure (AU Mg-1 ha-1) and stocking rate (Animal Unit Days ha-1) for predicting basal scarring and browsing of lodgepole pine (Pinus contorta Dougl.) seedlings on cutblocks in southern British Columbia from 1989 to 1992. Cattle browsing on lodgepole pine seedlings occurred almost exclusively during the first 2 years of grazing. Browsing increased (P 10% of sample trees when grazing pressure exceeded 12.0 AU Mg-1 ha-1. This threshold grazing pressure value of 12.0 AU Mg-1 ha-1, however, cannot likely be extrapolated directly to other sites. Grazing pressure values and associated basal scarring are unquestionably influenced by many factors (e.g., pasture size, kind of grazing animal, forage species, tree height, water availability, topography, and weather patterns during the grazing period). Nonetheless, our work provides evidence that grazing pressure provides a useful index for predicting the potential for trampling damage of lodgepole pine seedlings by cattle.