Moderate Cattle Grazing Research Articles

LEPIDOPTERA OF THE MYKHAILIVSKA TSILYNA NATURE RESERVE

This work presents the results of the analysis of literature sources and the results of own research on the Lepidoptera of the Nature Reserve “Mykhailivska tsilyna”. In total, during 2019-2023, about 800 specimens of lepidopterans were collected on the reserve territory. The work presents a generalized list of lepidopteran species documented on the territory of the reserve which is supplemented by the results of research over the past three years. Since the Nature Reserve foundation in 2009, livestock grazing has been banned and haying areas have been limited, which has led to significant overgrowth and forestation of reserve’s territory. In some places the crown closure of the new stands reaches more than 70%. The data obtained by us on the group of pyralid butterflies of the reserve indicate a small proportion of the steppe component in their fauna. Unfortunately, we are not able to compare the data over a long period of time - before 2015, even if there were any studies on this group, they were of a non-systematic nature. Currently, the fauna of the lepidoptera registered by us in the Nature Reserve “Mykhailivska tsilyna”, as well as those reported in the literature, includes 340 species from 18 family groups.
 The work planned in the territory organization project to reduce tree growth and remove forest strips are likely to reduce biodiversity in this area. At the same time, further overgrowth of the steppe will reduce the number or loss of butterfly species whose development is associated with steppe vegetation. In our opinion, it is necessary to stop and prevent further forestation of the reserved area. This can be done by applying one of the following methods: periodic mowing of the steppe areas that are still preserved; moderate cattle grazing; release of a wild population of large ungulates into the territory and ensuring their living conditions; periodic controlled burning of certain areas in the fall. However the current environmental legislation prohibits the use of all of the above methods on the territory of nature reserves.

Influence of Cattle Grazing on the Spatiotemporal Activity of Wildlife

Cattle (Bos taurus) grazing on public lands is widespread across the globe. Public rangelands are managed for multiple purposes, including preservation of wildlife populations; therefore, to manage public rangelands, it is imperative to understand how cattle grazing affects wildlife. Despite this, there is mixed evidence for the impacts of cattle on wildlife and few studies investigate both spatial and temporal aspects of wildlife activity. To improve understanding of how cattle grazing impacts spatiotemporal wildlife activity, we analyzed camera data from three California Department of Fish and Wildlife properties in California, the United States from 2019 to 2021. We recorded 2 863 detections of cattle across all properties and the most abundant wildlife were coyotes (Canis latrans, 572 detections) and mule deer (Odocoileus hemionus; 1 415 detections). We used generalized linear mixed models and daily activity estimates to quantify cattle, coyote, and mule deer spatial and temporal activity and compared activity during grazing and nongrazing periods (properties were grazed 3−6 mo per year) and between sites with higher and lower cattle use. Mule deer spatial activity changed seasonally and at one property decreased during grazing seasons, but there were no overall significant effects of cattle detections on mule deer spatial activity. However, deer were more nocturnal at sites with higher cattle use, indicating that they may have been partitioning areas temporally with cattle. This shift in activity also increased deer overlap with more nocturnal species, like coyotes. Coyotes increased use of sites with higher activity of their prey and increased use of times with higher cattle activity. Our study suggests that low to moderate cattle grazing does not result in significant spatial displacement of common large mammals; however, shifts in temporal activity patterns of wildlife due to cattle presence may impact predator-prey interactions and wildlife energy expenditure and needs further monitoring.

UAV−Enabled Quantification of Grazing-Induced Changes in Uniformity of Green Cover on Semiarid and Mesic Grasslands

Coverage of living (green) vegetation influences rangeland processes and biodiversity but remains a challenge to quantify at small spatial grain. We describe a technique for rapid airborne (unmanned aerial vehicle) measurements of continuous spatial coverage of living vegetation at a resolution (spatial grain) of 8 cm ground sampling distance. We then applied this technique at the pasture (paddock) scale (tens of hectares) in two contrasting grassland ecosystems (semiarid shortgrass steppe in northeastern Colorado, United States and mesic grassland in central Texas, United States) to determine effects of locally relevant grazing treatments on spatial variability and dependence (pattern) in fractional coverage of green vegetation (fractional vegetation cover; FVC). Site-specific regression models developed using reflectance in visible and near-infrared wavebands explained 90% and 89% of variance in FVC for semiarid and mesic grassland, respectively. Mean FVC was similar among shortgrass steppe pastures differing in grazing treatment (light or heavy grazing by cattle, moderate cattle grazing with prairie dogs present). In contrast, FVC was lower with rotational compared with continuous, year-long grazing in the mesic grassland. Heavy grazing in shortgrass steppe and rotational grazing in mesic grassland increased the spatial uniformity in FVC by reducing spatial variability and increasing spatial dependence in FVC, the latter by increasing the similarity in FVC values among spatially separated patches. Unmanned aerial vehicle−enabled remote sensing provides for FVC at sufficiently small spatial grain to characterize spatial variation in FVC at the pasture scale. Results can be used to evaluate the effectiveness of management actions intended to alter spatial variation in FVC to achieve conservation or diversity objectives. Enhanced capacity to monitor FVC at small spatial grain promotes adaptive management of grasslands.

Browsing wildlife and heavy grazing indirectly facilitate sapling recruitment in an East African savanna.

Management of tree cover, either to curb bush encroachment or to mitigate losses of woody cover to over-browsing, is a major concern in savanna ecosystems. Once established, trees are often "trapped" as saplings, since interactions among disturbance, plant competition, and precipitation delay sapling recruitment into adult size classes. Saplings can be directly suppressed by wildlife browsing and competition from adjacent plants, and indirectly facilitated by grazers, such as cattle, which feed on neighboring grasses. Yet few experimental studies have simultaneously quantified the effects of cattle and wildlife on sapling growth, particularly over long time scales. We used a series of replicated 4-ha herbivore-manipulation plots to investigate the net effects of wildlife and moderate cattle grazing on Acacia drepanolobium sapling growth over 10years that encompassed extended wet and dry periods. We also simulated more intense cattle grazing using grass removal treatments (0.5-m radius around saplings), and we quantified the role of intraspecific tree competition using neighborhood tree surveys (trees within a 3-m radius). Wildlife, which included elephants, had a positive effect on sapling growth. Wildlife also reduced neighbor tree density during the 10-yr study, which likely caused the positive effect of wildlife on saplings. Although moderate cattle grazing did not affect sapling growth, grass removal treatments simulating heavy grazing increased sapling growth. Both grass removal and neighbor tree effects on saplings were strongest during above-average rainfall years following drought. This highlights that livestock-driven reductions in grass cover and catastrophic wildlife damage to trees during droughts present a need, or an opportunity, for targeted management of sapling growth and woody plant cover during ensuing wet periods.

Recovery of the herbaceous component of degraded sagebrush steppe is unimpeded by 75 years of moderate cattle grazing

AbstractUnderstanding the effects of contemporary cattle grazing on herbaceous perennial communities in big sagebrush steppe is important for managing for wildlife habitat, plant diversity, and productivity, yet potentially complicated by legacy impacts of historic, often higher intensity, livestock grazing. Here, we evaluate whether recovery of herbaceous communities in eastern Oregon, USA, after the cessation of intense spring sheep grazing (1935) was affected by moderate cattle grazing in paired plots with or without grazing over the past 75 yr (1936–2011). We tested for the effects of cattle grazing on herbaceous community recovery, as indicated by changes over time in plant density, and composition, as measured by Bray–Curtis dissimilarity. We also included current and prior to sampling year precipitation anomalies, to account for the weather effects, and a random term for pasture location of plot pairs to include potential subtle differences in abiotic environment and grazing management. We further tested whether time since cessation of intense sheep grazing and moderate cattle grazing were associated with convergence or divergence in community composition indicated by changes in evenness, richness, species relative abundance (rank order), and turnover or species appearance or disappearance. Total perennial herbaceous, forb, and grass density increased over time in sites grazed and ungrazed by cattle, though species varied in the direction of their response to contemporary cattle grazing. Community composition metrics indicated convergence over time including increasing evenness, decreasing Bray–Curtis dissimilarity, decreasing shifts in species relative abundance (rank order), and lower rates of species turnover (and gain and loss). Contemporary cattle grazing was not associated with convergence or divergence in composition. Precipitation anomalies for the current or prior water year were only occasionally significant in herbaceous density and community composition change models. Our results indicate similar long‐term recovery trajectories occurred in sites with moderate cattle grazing or removal of all livestock following cessation of intense sheep grazing. Management planning and resource assessment focused on herbaceous perennial communities in sagebrush steppe should seek to separate the impacts of historic from contemporary livestock grazing practices.

ОЦЕНКА ВЛИЯНИЙ ТЕХНОЛОГИИ ВЫПАСА НА СОСТОЯНИЕ ПОЧВЕННОГО ПОКРОВА ПАСТБИЩ ПОЛУПУСТЫННОЙ ЗОНЫ

Managing pasture resources of Western Kazakhstan is complicated due to the deterioration of the physicochemical parameters of soils manifestating degradation and alkalinization as a result of intensive grazing. The research has been aimed at studying the technology of cattle grazing for preserving the physicochemical parameters of soils and increasing the efficiency of pasture use. The assessment and analysis of physicochemical indicators of soils were carried out with standard methods during 2018-2020, which allowed identifying the most optimal grazing technology. The results of research showed that under the influence of intensive grazing, physicochemical parameters worsened, a decrease in the humus reserves by 28.50% was detected, soil degraded to the third degree and became alkaline as a result of increase in exchangeable sodium to 1.66 mg(equiv.)/100g. Technology of moderate cattle grazing favorably affects the physicochemical parameters of the soils of pasture ecosystems. The chestnut soils of the pastures, where moderate grazing technology was applied, remained resistant to degradation and salinization. With this technology, the soil humus was reliably preserved at the level of 1.17%, mobile phosphorus was within the optimal level of 0.88 mg/100g.

CHANGES IN THE PHYSICOCHEMICAL PARAMETERS OF CHESTNUT SOILS IN WESTERN KAZAKHSTAN UNDER THE INFLUENCE OF THE GRAZING TECHNOLOGIES

Managing pasture resources of Western Kazakhstan is complicated due to the deterioration of the physicochemical parameters of soils, manifesting degradation, and alkalinization as a result of intensive grazing. The research has been aimed at studying the technology of cattle grazing for preserving the physicochemical parameters of soils and increasing the efficiency of pasture use. The assessment and statistical analysis of physicochemical indicators of soils were carried out with standard methods during 2018 – 2019, which allowed identifying the most optimal grazing technology. The results of the research showed that under the influence of intensive grazing, physicochemical parameters worsened, a decrease in the humus reserves by 10.88-12.35% was detected, soil degraded to the third degree, and became alkaline as a result of the increase in exchangeable sodium to 1.65 cmol (equiv.)/kg. The technology of moderate cattle grazing favorably affects the physicochemical parameters of the soils of pasture ecosystems. The chestnut soils of the pastures, where moderate grazing technology was applied, remained resistant to degradation and salinization. With this technology, the soil humus was reliably preserved at the level of 1.15-2.50%, mobile phosphorus was within the optimal range of 0.87-1.60 mg/100 g. It has been concluded that it is important to use the technology of moderate cattle grazing to improve the management of pasture resources, which is the scientific novelty of the research.

Rangeland Sharing by Cattle and Bees: Moderate Grazing Does Not Impair Bee Communities and Resource Availability

Rangelands are a dominant anthropogenic land use and a main driver of natural habitat loss worldwide. Land sharing, the integration of agricultural production and biodiversity conservation, may provide a platform for managing rangelands to fulfill multiple ecosystem services. However, livestock grazing can greatly affect biodiversity and little is known about its effects on providers of focal ecosystem services, such as pollinators. We investigated the effect of cattle grazing on bee communities and their foraging and nesting resources in Mediterranean rangelands. Specifically, we explored the effect of moderate cattle grazing on flowering plant abundance, species richness and composition, the diversity of nesting substrates, and consequently, the possible effects on wild bee and honey bee foraging activity, species diversity, and community composition. We conducted field research in the Mediterranean rangelands of Israel during the main bee activity season, in the spring of 2012 and 2013, comparing paired cattle-grazed and ungrazed areas. The availability of floral and nesting resources for bees was unaffected or positively affected by grazing. Similarly, wild bee abundance, species richness, and composition were not affected by grazing, but were instead shaped by spatiotemporal factors. Nor was honey bee activity level impaired by grazing. The foraging preferences of bees, as well as flower species composition and peak bloom differed between grazed and ungrazed areas. Therefore, in our studied rangelands, grazing had its main effect on the foraging choices of honey bees and wild bees, rather than on their abundance and diversity. Moreover, our results indicate the potentially important role of ungrazed patches in increasing nectar and pollen diversity and availability in rangelands for both honey bees and wild bees in the spring. Hence, maintaining a mosaic of moderately grazed and ungrazed patches is expected to provide the greatest benefits for wild bee conservation and honey bee activity in Mediterranean rangelands. Our findings support the notion of rangeland sharing by cattle and bees in Mediterranean ecosystems under moderate grazing intensities, mimicking the coexistence of honey bees, wild bees, and cattle in Mediterranean ecosystems on an evolutionary timescale.

Rangeland sharing by cattle and bees: moderate grazing does not impair bee communities and resource availability.

Rangelands are a dominant anthropogenic land use and a main driver of natural habitat loss worldwide. Land sharing, the integration of agricultural production and biodiversity conservation, may provide a platform for managing rangelands to fulfill multiple ecosystem services. However, livestock grazing can greatly affect biodiversity and little is known about its effects on providers of focal ecosystem services, such as pollinators. We investigated the effect of cattle grazing on bee communities and their foraging and nesting resources in Mediterranean rangelands. Specifically, we explored the effect of moderate cattle grazing on flowering plant abundance, species richness and composition, the diversity of nesting substrates, and consequently, the possible effects on wild bee and honey bee foraging activity, species diversity, and community composition. We conducted field research in the Mediterranean rangelands of Israel during the main bee activity season, in the spring of 2012 and 2013, comparing paired cattle-grazed and ungrazed areas. The availability of floral and nesting resources for bees was unaffected or positively affected by grazing. Similarly, wild bee abundance, species richness, and composition were not affected by grazing, but were instead shaped by spatiotemporal factors. Nor was honey bee activity level impaired by grazing. The foraging preferences of bees, as well as flower species composition and peak bloom differed between grazed and ungrazed areas. Therefore, in our studied rangelands, grazing had its main effect on the foraging choices of honey bees and wild bees, rather than on their abundance and diversity. Moreover, our results indicate the potentially important role of ungrazed patches in increasing nectar and pollen diversity and availability in rangelands for both honey bees and wild bees in the spring. Hence, maintaining a mosaic of moderately grazed and ungrazed patches is expected to provide the greatest benefits for wild bee conservation and honey bee activity in Mediterranean rangelands. Our findings support the notion of rangeland sharing by cattle and bees in Mediterranean ecosystems under moderate grazing intensities, mimicking the coexistence of honey bees, wild bees, and cattle in Mediterranean ecosystems on an evolutionary timescale.

Herbivory and drought interact to enhance spatial patterning and diversity in a savanna understory

The combination of abiotic stress and consumer stress can have complex impacts on plant community structure. Effective conservation and management of semi-arid ecosystems requires an understanding of how different stresses interact to structure plant communities. We explored the separate and combined impacts of episodic drought, livestock grazing, and wild ungulate herbivory on species co-occurrence and diversity patterns in a relatively productive, semi-arid Acacia savanna. Specifically, we analyzed 9 years of biannual plant community data from the Kenya long-term exclosure experiment, a broad-scale manipulative experiment that has excluded different combinations of large mammalian herbivores from 18 4-ha plots since 1995. During droughts, we observed low species diversity and random species co-occurrence patterns. However, when rain followed a major drought, areas exposed to moderate cattle grazing displayed high species diversity and evidence of significant species aggregation. These patterns were not apparent in the absence of cattle, even if other large herbivores were present. To explore possible mechanisms, we examined patterns separately for common and rare species. We found that aggregation patterns were likely driven by rare species responding similarly to the availability of open micro-sites. Our results indicate that in a productive, fire-suppressed savanna, the combination of periodic drought and moderate cattle grazing can enhance plant biodiversity and fine-scale spatial heterogeneity by opening up space for species that are otherwise rare or cryptic. Our findings also emphasize that domestic herbivores can have significantly stronger impacts on plant community dynamics than wild herbivores, even in an ecosystem with a long history of grazing.

Experimental warming induces degradation of a Tibetan alpine meadow through trophic interactions

Summary 1. It is well known that climate change alters abiotic factors (temperature and water availability) that directly affect ecosystem properties. However, less is known about the indirect impacts of climate change on ecosystem structure and function. Here, we show that experimental warming may deteriorate ecosystems via trophic interactions. 2. In a Tibetan alpine meadow, plant species composition, size, coverage and above-ground biomass were investigated to reveal the effect of artificial warming (c. 1 � Cm ean annual temperature at the soil surface), which was accomplished using warmed and ambient open top chambers. In addition, rodent damage to plants was assessed. 3. The dicot forb silverweed Potentilla anserina increased significantly, while other species groups remained unchanged or decreased in plant community dominance rank after 2 years of artificial warming. The change in community structure was attributed to the difference in biomass allocation and growth form among species. 4. In the third year, plateau zokors Myospalax fontanierii, a widespread rodent herbivore, damaged plants in the warmed chambers, while leaving plants in the ambient chambers mostly undamaged. Above-ground biomass was found to be smaller in the warmed chambers than the controls in the third year, in contrast to the trend of the first 2 years. In addition, zokor burrow density was positively correlated with silverweed biomass and its dominance within communities, which was consistent with findings of independent field investigations that silverweed-dominated plots were more likely to be visited and damaged by the zokors than sites-dominated by grass species. 5. Synthesis and applications. The top-down negative effect of zokor damage on above-ground biomass in the warmed chambers was induced by the bottom-up effect of changes in species composition and community structure on zokor foraging behaviour, which were driven by artificial warming. Such trophic interactions may invalidate some predictions of ecological effects by current species-climate envelope models. Furthermore, because management measures including increasing the water table, planting grass and moderate cattle grazing may prevent silverweed dominance, we suggest that these interventions could be employed to control zokor damage in alpine meadows that are predicted to be drier and warmer in the future.

Habitat selection by the highly endangered long-horned beetle Rosalia alpina in Southern Europe: a multiple spatial scale assessment

Despite the popularity of the saproxylic cerambycid Rosalia alpina as a flagship species, its ecology is still poorly know, especially in the southern part of its range. Detailed information on its habitat preferences is needed to plan appropriate management. We set our multiple spatial scale assessment of habitat preferences in a beech forest of central Italy whose landscape, featuring both unmanaged forest and two types of grazed open forest, allowed us to look at the influence of different land uses. Preferred trees occurred in open sites, and those close to tall undergrowth were avoided. A range of moribund or dead trees were used: those preferred had a lower percentage canopy closure, significantly thicker bark, and were more sun-exposed, than the average. Logistic regression showed that the most important variables for selection were distance from nearest occupied tree, bark thickness, undergrowth height and irradiation. Occurrence likelihood augmented as the distance from nearest other occupied tree increased. Despite being mostly unmanaged, forest was avoided, whereas open forest (with trees pruned by ‘shredding’) was used more than expected. Although intensive forestry limits the availability of dead wood, closed forest may be unsuitable when shadowing useful substrate. The disappearance of traditional forms of forest management as shredding and moderate cattle grazing may lead to woody vegetation expansion and habitat closure eventually threatening the persistence of R. alpina. The return to traditional habitat management would be beneficial to R. alpina, an issue that conservation plans should carefully take it into account.

The state of change of Erica scoparia L. heathland through cattle grazing and oak colonization

Summary. — Our aim was to ascertain whether changes in plant species richness and other vegetation features occur in heathland dominated by Erica scoparia L. (besom heath) through the impact of cattle grazing and oak colonization. Our study took place in the Brenne Regional Natural Park (center of France) where this ericaceous species, locally called ‘ brande’, is now considered of patrimonial interest and protected at regional and European level. We selected 10 sites in a private property, covering a wide range of ecological conditions (shallow and deep soils, grazed and non-grazed besom heath, pure and oak-colonized besom heath). Vegetation (percent occupancy of plant species) was sampled in May-June 2006 (105 samples, 1m2 each) and the impact of shrub and tree vegetation on plant biodiversity was assessed by correspondence analysis (CA) and total and partial Mantel tests (Monte-Carlo procedure). An environmental gradient of decreasing light incidence from grazed heath to old heath to oak-wood was depicted, along which a number of ecological, morphological and physiological plant traits (growth habits, Ellenberg values, Grime strategies, Tolerance Index of the plant community) were observed to vary. Species richness decreases when ericaceous or, although to a lesser extent, oak cover increases and it increases under low to moderate cattle grazing. Consequences for the sustainable management of ‘ brande’ are discussed.

Effects of altitude and livestock on the regeneration of two tree line forming Polylepis species in Ecuador

Regeneration is known to be limited at many temperate tree lines, but very little data is available on the impacts of altitude and anthropogenic disturbance on regeneration patterns along tropical tree lines. The study focused on the reproductive traits of two Polylepis species in the Paramo de Papallacta in Ecuador along an altitudinal gradient, and involved different intensities of cattle trampling within subsequent altitudinal ranges. We analyzed flowering, fruit set, seed viability, germination, and seedling establishment as well as stand structure of Polylepis incana and P. pauta. The numbers of P. incana inflorescences and seedlings per m² showed a marginally significant decrease with increasing altitude. Mean tree height was significantly lower at higher altitudes, while stem number increased. The number of P. pauta inflorescences also decreased significantly upslope. In both forest types, trampling was found to have a positive impact on seedling abundance, presumably due to the removal of the litter layer. Thus, there was no evidence of negative effects of moderate cattle grazing on both tree line species. However, sapling establishment was minimal inside the forest stands at all altitudes and grazing levels, and we consequently observed a low proportion of narrow stems within all investigated forests. Our results show that, along with vegetative growth limitations of adult trees, important regeneration traits such as seedling and inflorescence numbers are also influenced by altitude, which might contribute to the formation of the upper tree line. Nevertheless, recruitment in the forest interior was low overall indicating that further factors, such as light conditions, affect regeneration of the studied species.

A fuzzy and neuro-fuzzy approach to modelling cattle grazing on pastures with low stocking rates in Central Europe

This paper describes a fuzzy and neuro-fuzzy approach to spatial explicit modelling of cattle grazing intensity in temperate zones in Central Europe on pastures with low stocking rates. The aim was to create a simple model based on datasets that could be collected as easily as possible in order to predict the grazing intensity. Large-scale moderate cattle grazing has been introduced in many areas across Europe as a low cost management initiative for the restoration or conservation of open landscapes. As a consequence of the heterogeneity and large size of the pastures under investigation, the relationships between the various investigated factors are often poorly understood and the data collected have a high degree of uncertainty. A fuzzy approach was selected which allowed for operation with vague knowledge and data of high uncertainty. Two fuzzy rule-based models of extensive grazing are presented in this paper. The first is a model based on the Mamdani-type of inference. The linguistic rules of this model were formulated by a domain expert. The second is a model based on the Sugeno-type rules and on a given input–output dataset. The number of rules and the initial membership function parameters were established by a simple and effective clustering algorithm (subtractive clustering). Using the neuronal network technique (ANFIS), optimal model parameters were identified. These parameters minimize the root mean squared error of the model. A dataset of a pasture in North Germany was used as training data for an ANFIS learning procedure. In order to check the generalization capability of the two models, the grazing intensity predicted by both models was compared with grazing intensity data gathered on three pastures over two years. The Mamdani- and Sugeno-type models were implemented using the Fuzzy Logic Toolbox of MATLAB ©. The results of both models confirm a suitability of these models for the modelling of cattle grazing.

The Effects of Livestock on California Ground Squirrels (Spermophilus beecheyii)

Understanding the impacts of livestock grazing on wildlands is important for making appropriate ecosystem management decisions. Using livestock exclosures, we examined the effects of moderate cattle grazing on the abundance of California ground squirrels (Spermophilus beecheyii Richardson) and the spatial distribution of active burrows within their colonies in grassland and blue oak (Quercus douglasii Hook. & Arn.) savanna habitats in the coastal range of California over a 3-year period (1991–1994). Overall, relative population densities of California ground squirrels declined significantly throughout the experiment, but did not differ between grazed and ungrazed colonies or between habitats. There was also no significant interaction between these 2 factors. The spatial distribution of burrows, as measured by the mean nearest neighbor distance of active entrances within a colony, did not differ significantly between grazed and ungrazed colonies or between habitats, nor was the interaction significant. Thus, low to moderate levels of cattle grazing did not appear to have a strong effect on the population dynamics of California ground squirrels, and grazing may be compatible with maintenance of ground squirrel populations. Based on multivariate analysis of variance of 1994 data, live plant cover, native plant cover, and standing biomass were lower where the number of burrows was higher on grazed colonies but were little affected on ungrazed colonies. Ground squirrels may increase the impact of livestock grazing and thus reduce the capacity of the land to support other activities. However, it is clear that the effects of livestock grazing are complex and that detailed studies of potential mechanisms by which grazing impacts California ground squirrel populations are necessary.

The Effects of Livestock on California Ground Squirrels (Spermophilus beecheyii)

Understanding the impacts of livestock grazing on wildlands is important for making appropriate ecosystem management decisions. Using livestock exclosures, we examined the effects of moderate cattle grazing on the abundance of California ground squirrels (Spermophilus beecheyii Richardson) and the spatial distribution of active burrows within their colonies in grassland and blue oak (Quercus douglasii Hook. Arn.) savanna habitats in the coastal range of California over a 3-year period (1991-1994). Overall, relative population densities of California ground squirrels declined significantly throughout the experiment, but did not differ between grazed and ungrazed colonies or between habitats. There was also no significant interaction between these 2 factors. The spatial distribution of burrows, as measured by the mean nearest neighbor distance of active entrances within a colony, did not differ significantly between grazed and ungrazed colonies or between habitats, nor was the interaction significant. Thus, low to moderate levels of cattle grazing did not appear to have a strong effect on the population dynamics of California ground squirrels, and grazing may be compatible with maintenance of ground squirrel populations. Based on multivariate analysis of variance of 1994 data, live plant cover, native plant cover, and standing biomass were lower where the number of burrows was higher on grazed colonies but were little affected on ungrazed colonies. Ground squirrels may increase the impact of livestock grazing and thus reduce the capacity of the land to support other activities. However, it is clear that the effects of livestock grazing are complex and that detailed studies of potential mechanisms by which grazing impacts California ground squirrel populations are necessary.

Vegetation changes in a semiarid tropical savanna, northern Australia: 1973 - 2002

We measured vegetation changes inside and outside two exclosures built in 1973 on red calcareous loam soils located in Conkerberry Paddock on Victoria River Research Station in northern Australia. These two exclosures were unburnt since their establishment in 1973 until exclosure 1 was unintentionally burnt late in the dry season (October) of 2001. Data from permanent transects and examples from photopoints illustrate that from mostly bare soils in 1973, total pasture biomass recovered relatively rapidly both inside and outside exclosures (in about five years). This initial recovery was primarily due to the establishment of annual grasses and forbs. After this five year period, there was a consistent increase in the biomass of perennial grasses, such as Heteropogon contortus and Dichanthium spp. Also in the first five years after exclosure, the exotic shrub, Calotropis procera,invaded the study area, but then largely disappeared in a period of lower wet-season rainfall in the late 1980s. The density of native tree species, particularly Hakea arborescens, Eucalyptus pruinosa and Lysiphyllum cunninghamii increased in general, but more so inside one or other of the exclosures. Although the late dry-season fire of 2001 reduced the density of larger H. arborescens and L. cunninghamii inside the exclosure at Site 1, this effect was not apparent for smaller trees and for trees outside this exclosure. Our findings show that savanna vegetation can change massively in the medium term (29 years) and that exclosure from cattle grazing can contribute to our understanding of the role of livestock in such change. However, exclosures by themselves do not provide adequate information about the processes leading to vegetation change replicated experimental studies are needed. That substantial increase in the biomass and proportion of perennial grasses occurred with light to moderate cattle grazing implies that these rangelands can be managed for production, although control of woody vegetation is an issue.

Fire and Cattle Grazing on Wintering Sparrows in Arizona Grasslands

This paper reports on the results of a 3-year field study of the effects of spring/summer burning and cattle grazing on wintering sparrows in the grasslands of southeastern Arizona. The effects of fire were studied with 1 year of pre-burn data and 1 year of post-burn data from 1 fire, plus limited sampling from a second fire at Buenos Aires National Wildlife Refuge in Pima County, Ariz. The effects of grazing were studied by comparing study plots at a site that has not been grazed by cattle since 1968 with a nearby grazed pasture in Santa Cruz County, Ariz. Sparrow abundance was measured as the number of captures from flush-netting sessions conducted by groups of 13-30 volunteers. Vesper (Pocecetes gramineus (Gmelin)) and Savannah (Passerculus sandwichensis (Gmelin)) Sparrows responded positively to fire, while Cassin's Sparrows (Aimophila cassinhi (Woodhouse)) responded negatively. The ecologically and geographically restricted Baird's (Ammodramus bairdil (Audubon)) and Grasshopper (A. savannarum (Gmelin)) Sparrows utilized burned areas during the first post-burn winter and did not significantly respond to fire. Both Ammodramus sparrows also utilized the grazed pasture; they were more abundant there than in the ungrazed study area in 1 year. While field observations and a prior study suggest that heavy grazing can have a strong detrimental effect on Ammodramus sparrows, the results of this study suggest that moderate cattle grazing may be compatible with the conservation of these species. DOI:10.2458/azu_jrm_v53i4_gordon

Fire and cattle grazing on wintering sparrows in Arizona grasslands

This paper reports on the results of a 3-year field study of the effects of spring/summer burning and cattle grazing on wintering sparrows in the grasslands of southeastern Arizona. The effects of fire were studied with 1 year of pre-burn data and 1 year of post-burn data from 1 fire, plus limited sampling from a second fire at Buenos Aires National Wildlife Refuge in Pima County, Ariz. The effects of grazing were studied by comparing study plots at a site that has not been grazed by cattle since 1968 with a nearby grazed pasture in Santa Cruz County, Ariz. Sparrow abundance was measured as the number of captures from flush-netting sessions conducted by groups of 13-30 volunteers. Vesper (Pocecetes gramineus (Gmelin)) and Savannah (Passerculus sandwichensis (Gmelin)) Sparrows responded positively to fire, while Cassin's Sparrows (Aimophila cassinhi (Woodhouse)) responded negatively. The ecologically and geographically restricted Baird's (Ammodramus bairdil (Audubon)) and Grasshopper (A. savannarum (Gmelin)) Sparrows utilized burned areas during the first post-burn winter and did not significantly respond to fire. Both Ammodramus sparrows also utilized the grazed pasture; they were more abundant there than in the ungrazed study area in 1 year. While field observations and a prior study suggest that heavy grazing can have a strong detrimental effect on Ammodramus sparrows, the results of this study suggest that moderate cattle grazing may be compatible with the conservation of these species.