Grazing History Research Articles

Grazing and an invasive grass confound spatial pattern of exotic and native grassland plant species richness

Previous work has shown exotic and native plant species richness are negatively correlated at fine spatial scales and positively correlated at broad spatial scales. Grazing and invasive plant species can influence plant species richness, but the effects of these disturbances across spatial scales remain untested. We collected species richness data for both native and exotic plants from five spatial scales (0.5–3000m2) in a nested, modified Whittaker plot design from severely grazed and ungrazed North American tallgrass prairie. We also recorded the abundance of an abundant invasive grass, tall fescue (Schedonorus phoenix (Scop.) Holub), at the 0.5-m2 scale. We used linear mixed-effect regression to test relationships between plant species richness, tall fescue abundance, and grazing history at five spatial scales. At no scale was exotic and native species richness linearly related, but exotic species richness at all scales was greater in grazed tracts than ungrazed tracts. Native species richness declined with increasing tall fescue abundance at all five spatial scales, but exotic species richness increased with tall fescue abundance at all but the broadest spatial scales. Severe grazing did not reduce native species richness at any spatial scale. We posit that invasion of tall fescue in this working landscape of originally native grassland plants modifies species richness-spatial scale relationships observed in less disturbed systems. Tall fescue invasion constitutes a unique biotic effect on plant species richness at broad spatial scales.

Biodiversity of soil macrofauna in the New Forest: a benchmark study across a national park landscape

The New Forest National Park is a hotspot for biodiversity in the UK. A long history of grazing by ponies in the New Forest landscape has created a diverse mosaic of habitats that are of international significance. We investigated patterns of species diversity and composition across the New Forest landscape by sampling soil, leaf litter and ground macrofauna from woodland, grassland and heathland plots across the entire landscape. We used a spatially replicated design of hand sorted soil pits, Winkler extraction of leaf litter, and pitfall traps. We concentrated on diversity patterns of the following target groups: Coleoptera, Formicidae, Isopoda, Chilopoda, Diplopoda, Opiliones and Lumbricidae. The most striking difference in species assemblages is between wooded and open areas. Woodlands are the most diverse habitats and have a distinct assemblage, largely due to those leaf litter invertebrate species which are only present under a closed canopy. Open areas are less diverse, with diversity particularly low in the wet grasslands. However, the open areas do have a distinct fauna, especially in the wet and dry heaths which are home to a number of rare species, particularly of Formicidae. We discuss the potential conservation problems facing the New Forest and how these might affect soil macrofauna biodiversity in the future and conclude that climate change; over-grazing; and land use changes represent the largest threats. Although a relatively stable landscape which benefits from protection under UK law, changes in grazing intensity or management practices in the New Forest, particularly for some of the habitats of European importance (e.g. wet heathlands), could negatively affect soil macrofauna biodiversity. Climate change may also exacerbate biodiversity decline as a result of increased grazing intensity or changes in management.

Self-organization and complex dynamics of regenerating vegetation in an arid ecosystem: 82 years of recovery after grazing

Understanding the relative contributions of internal dynamics versus external factors in the process of community assembly is important for establishing guidelines for conservation and restoration of native vegetation. The role of internal dynamics and external factors in the process of community assembly at the local scale is a poorly understood issue in ecology, especially in highly variable environments. We analyse an 82-year spatiotemporal record of vegetation recovering from a history of overgrazing within a semi-arid environment to investigate the relative contribution of internal and external factors on community assembly. Community composition and spatial structure were used as indicators of change over time in four sites within a vegetation reserve, which were subjected to the same environmental constraints, climate and grazing history. The four sites follow remarkably different, asynchronous trajectories characterized by periods of stability interrupted by episodic change. The high variability between sites suggests that initial communities are internally reinforced through random chance events, directing them on different pathways of assembly and self-organization; hence external factors may play a less significant role in long-term community assembly at the local scale than previously believed. These results have important implications for rangeland restoration and conservation in many of the world's semi-arid regions.

Late Holocene dune mobilizations in the northwestern Negev dunefield, Israel: A response to combined anthropogenic activity and short-term intensified windiness

The study of the effects of past climates on ancient cultures is usually based on geologic records pertaining to rainfall and temperature fluctuations and shifts. This study proposes a paradigm of anthropogenic activity and windiness fluctuations to explain aeolian sedimentation and dune mobilization in the northwestern (NW) Negev Desert dunefield (Israel). The proposed paradigm contributes a different approach to estimating the effect of climate changes on the unprecedented agricultural and urban settlement expansion during the late Roman to Early Islamic period in the northern and central Negev Desert. This study builds upon the late Holocene cluster of luminescence ages, coupled with analysis of archaeological finds and historical texts. Whereas the NW Negev dunefield was generally stable during the Holocene, intermittent dune mobilization during the late Holocene, at ∼1.8 ka and mostly 1.4–1.1 ka (∼600–900 CE), are linked to periods of human occupation. The idea that the last glacial dune encroachments alone that formed the NW Negev dunefield is connected to cold-event windy climates that may have intensified East Mediterranean cyclonic winter storms, cannot explain the late Holocene dune mobilizations. A conceptual model indicates a connection between late Holocene dune mobilization, widespread anthropogenic occupation and activity, and windiness. Historic grazing and uprooting shrubs for fuel in the past by nomads and sedentary populations led to decimation of dune stabilizers, biogenic soil crusts and vegetation, causing dune erodibility and low-grade activity. Short-term events of amplified wind power in conjunction with periods of augmented anthropogenic activity that triggered major events of dune mobilization (elongation) and accretion have been preserved in the dune chronostratigraphy. Because they were short-lived, the dune mobilization events, corresponding windiness, and probable dustiness which were examined affected the northern Negev landscape differentially. However, they cannot be shown to have affected the environment sufficiently to influence the decline of the late Byzantine and Early Islam agricultural establishment. This study demonstrates the sensitivity of dunes in arid and semi-arid regions to a combination of local and short-term fluctuations in windiness at times of widespread grazing (anthropogenic activity). The results indicate that in similar future scenarios, sand mobilization may be similarly retriggered to varying degrees.

Applicability of 239Pu as a tracer for soil erosion in the wet-dry tropics of northern Australia

The technique of accelerator mass spectroscopy (AMS) has been employed to determine modern soil loss rates through the analysis of 239Pu profiles in soil cores from the Daly basin in Northern Territory, Australia. In areas in which soil conservation banks were not present or were only added recently (<25a) and which had a history of grazing and cultivation the measured soil loss rates over the past ∼50years were 7.5–19.5tha−1a−1. The measured rates are up to 5 times higher compared to agricultural and uncultivated areas within soil conservation banks in other parts of the catchment. High intensity seasonal rainfall combined with reduction in land cover due to grazing and episodic bush fires are primary factors influencing erosion although other impacts on the landscape such as tillage generated runoff and land clearing seem to be responsible for accelerated sediment production.

Grazing history influences biodiversity: a case study on ground-dwelling arachnids (Arachnida: Araneae, Opiliones) in the Natural Park of Alpi Marittime (NW Italy)

Alpine pastures are typical examples of “high nature value farmlands”, representing important habitats harbouring unique biological communities. Disturbance induced by overgrazing influences significantly ecosystem processes, in which invertebrates play a major role. To develop new models of sustainable management of pastures, more knowledge is needed of the animal communities, essential to the ecological functioning of pasture ecosystems. The apparent poor ecological state of several pastures in the Natural Regional Park of Alpi Marittime (NW-Italy) lead us to evaluate the influence of grazing history on biodiversity, using spider and harvestmen assemblages as key groups. Four different pastoral types characterized by four different grazing histories were identified using the Daget-Poissonet method. Spiders and harvestmen were collected by means of pitfall traps. Arachnid assemblages were characterized in terms of composition, abundance, species richness, richness of endemic species and taxonomic relatedness. Generalized linear mixed models (GLMM) were used to test differences among assemblages occurring in each pastoral type. Furthermore, we tested differences in terms of plant communities (species richness and percentage of zoogenic species). Specificity and fidelity of every spider and harvestmen species within pastoral types were explored by the IndVal (Indicator Value) procedure. Fifty-eight species of spiders and seven species of harvestmen were collected (2,304 individuals). Pastoral types related to intensive grazing were characterized by the dominance of diurnal wanderer spiders (namely Lycosidae) while, conversely, nocturnal wanderers (mainly Gnaphosidae) were more abundant in extensive pastoral types. Results show that both species richness and spider abundance were higher in abandoned areas of extensive grazing, while endemic assemblages were richer in extensive grazed areas, which also hosted the most diverse plant community. Furthermore, most of the indicator species of spiders of this type were endemic, characterized by more demanding ecological requirements.

A test of two mechanisms proposed to optimize grassland aboveground primary productivity in response to grazing

Aims mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence, grassland species have numerous adaptations allowing them to respond favourably to grazing. although empirical evidence has been equivocal, theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production (aNPP; grazed aNPP > ungrazed aNPP) under certain conditions. We tested two specific predictions from theory. First, overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate aNPP. second, overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure. Methods

The Response of Soil Nematode Community to Nitrogen, Water, and Grazing History in the Inner Mongolian Steppe, China

Nutrient nitrogen and water availability are co-limiting factors for grassland productivity in the Inner Mongolian steppe. The objective of this study was to evaluate the interactive effects of water and nitrogen (N) addition on soil abiotic factors and soil nematode community composition. A 3-year experiment with addition of water (with and without irrigation simulating wet year precipitation) and nitrogen (0, 25, and 50 kg N ha−1) was conducted at two sites in Inner Mongolia with histories of heavy grazing (HG) and moderate grazing (MG). The results showed that HG had several lower nematode ecological indicators; namely, the Simpson index (P < 0.01), maturity index (MI, including free-living nematodes), and plant parasite index (PPI, including plant-parasitic nematodes). In addition, HG had a lower proportion of omnivores–predators and higher proportion of bacterivores (P < 0.01), with reduced soil moisture, total nitrogen and total carbon (C), and increased C/N ratio. A relatively low addition of N did not influence soil total carbon and total nitrogen and had only a slight effect on the composition and structure of the soil nematode community. Water addition increased the proportion of plant parasites, reduced the proportion of bacterivores and omnivores–predators and increased the soil total carbon and total nitrogen. Redundancy analysis revealed that grazing history alone explained more variation in nematode taxon composition (17.4%, P < 0.01) and PPI (35.6%, P < 0.01) and MI (17.5%, P < 0.01) and Simpson index (10.5%, P < 0.01). Water addition explained more variation in the nematode feeding group (24.4%, P < 0.01), total nematodes (7.9%, P < 0.01) and PPI (78.7%, P < 0.01). Nitrogen addition explained variation in the nematode taxon composition (6.2%, P < 0.01). These results suggested that HG caused soil degradation, and water addition facilitated plant parasites and enhanced soil properties, whereas application of small amounts of nitrogen to N-limited semiarid grasslands did not induce clear changes in this system in the short term.

Invasion or retreat? The fate of exotic invaders on the northern prairies, 40 years after cattle grazing

Despite the detrimental impacts of invasive plants on native biodiversity, ecosystem function, and management cost, few studies have focused on the long-term persistence of invaders. Here, we use a unique, long-term dataset to examine the recovery of northern rough fescue prairie communities, 41 years after the removal of livestock from Riding Mountain National Park, Manitoba, Canada. Our 1973 data suggest that summer grazing of plains’ rough fescue (Festuca hallii (Vasey) Piper) leads to its displacement from the plant community and increased dominance by exotic invaders. After 41 years of recovery time, historic grazing intensity remained an excellent predictor of community structure and composition. Areas classified as heavily grazed in 1973 remained characterized by exotic grasses and had significantly lower richness and diversity. While some exotic invaders persisted despite 41 years of community recovery, others were ephemeral. For example, both Poa pratensis (L.) and Bromus inermis (Leyss.) persisted, increasing in abundance across all classes of grazing intensity, suggesting that their control requires active restoration of the invaded areas. In contrast, passive restoration may be possible for a subset of ephemeral exotic species such as Taraxacum officinale, which had virtually disappeared from invaded prairies by 2010. Our long-term data provide a rare perspective into the long-term dynamics of plant invasions. Based on our findings, conservation managers will need to consider the dichotomy between persistent and ephemeral invaders and their impact on the recovery of northern prairie communities as they focus their restoration efforts against the mounting impacts of exotic plant invaders.

Linking ecosystem resistance, resilience, and stability in steppes of North Patagonia

The main objective of an ecosystem sustainable management is to preserve its capacity to respond and adapt to current disturbances and/or future changes, and maintain the provision of environmental goods and services. Two very important properties linked to this objective are the ecosystem resilience and resistance to disturbance factors. The Structural–Functional State and Transition Model (SFSTM) is a conceptual framework that allows evaluating the ecosystem resilience and resistance based on structural and functional attributes. On the other hand, the Landscape Functional Analysis (LFA) presents a method to assess the rangeland “health” based on structural vegetation and soil indicators, creating indexes to evaluate the ecosystem functional integrity. The aim of this study is to integrate LFA and SFSTM as an approach to help validate indicators and indexes associated with the resistance, resilience, and stability of a temperate rangeland ecosystem. States and transitions model for a shrubby-grasses steppe of the Western Patagonian District was used as a reference system. Changes in vegetation structure, soil surface, and loss of soil due to erosion were determined in sites with different grazing histories. Based on the SFSTM, we assessed the relationships between ecosystem structural changes with the recruitment process of the plant community and ecosystem integrity indexes (sensu LFA). Our results indicate that the decrease in the recruitment process, related to different grazing histories, was associated with a loss of ecosystem functional integrity. This was associated to a decrease in the ability to retain, store, and use rain water, and also in nutrient cycling. This suggests that the integration of the LFA methodology to the SFSTM can be used for indexes validation, which in turn allows the identification of critical thresholds associated with ecosystem resilience loss. Finally, throughout the integration of indicators of LFA into SFSTM, we established relationships between ecosystem resistance, resilience, and stability in response to a disturbance factor (e.g. overgrazing). Thus, we used this information to define states in stable, unstable, mixed-unstable, and indifferent-stable dynamic equilibriums. Our proposed approach provides a tool for ecosystem assessment regarding the identification of states that can be restored and those that might be more susceptible to degradation. Such information might help in the prevention of crossing a critical threshold and be used for sustainable management programs in rangelands.

Changing distribution patterns of an endangered butterfly: Linking local extinction patterns and variable habitat relationships

Multiple processes are increasingly recognized as being responsible for species’ extinctions. We evaluated population extinctions between 1930 and 1998 for the endangered Quino checkerspot (Euphydryas editha quino) butterfly relative to agricultural history, human population growth, climate variability, topographical diversity, and wildflower abundance. Overall agricultural land use was calculated for extinct and extant populations based upon cultivation and grazing intensities averaged across five time periods reflecting distinct agricultural practices from 1769 to present. Extinct populations were associated with a history of more intensive agriculture and greater human population growth at time of extinction. A long history of intensive livestock grazing was the strongest agricultural predictor of extinction. Based upon historic vegetation maps, extinct butterfly populations were typically isolated from other known populations by 1930, and in landscapes fragmented by cultivation and development. Precipitation and topographical variability were not important predictors of extinction. Wildflower host plants and nectar sources have declined across the butterfly’s range because of invasive plants and habitat loss. The proportion of years considered average or abundant in wildflowers declined significantly during extinction periods. The Quino checkerspot has shifted in distribution from the coast into foothills and mountains. Newly discovered higher elevation populations experience more precipitation and are buffered from drought. Efforts to conserve Quino checkerspot are enhanced by understanding that the butterfly’s decline and shifting distribution is a complex multi-scale process related to agricultural history, human population growth, climate variability, and wildflower decline.

Effect of spatial and temporal patterns of stress and disturbance intensities in a sub-Mediterranean grassland

The present study examined a sub-Mediterranean pastoral system in the central Apennines (Italy) with a long history of grazing, where winter cold stress is alternated with summer drought stress. The research goals were to ascertain whether different floristic structures correspond to different stress conditions (xeric and semimesic), and whether peculiar functional plant traits (such as avoidance and tolerance mechanisms) respond to stress/disturbance intensities, and understand how vegetation reacts to changeable livestock pressure (through floristic and plant trait variations). Cluster analysis indicated that separate communities develop under different stress intensities. Other analyses highlighted how avoidance strategies predominate within the pastoral system. Observations of grazed and ungrazed patches conducted in 10-m transects revealed spiny cushion formation in semimesic grassland, where a brief period of overgrazing occurs in late summer, causing variations in plant community structure. All these results confirm the importance of historical grazing and current land use, showing how small disturbances and stress variations cause ecosystem responses. Best practices for management were identified. In xeric conditions, it is advisable that the intensity of disturbance be lessened, while in semimesic grassland overgrazing should be forbidden during the dry period, because it could facilitate the development of spiny patches, and subsequent spread of Brachypodium rupestre.

Seed and establishment limitation contribute to long‐term native forb declines in California grasslands

The effects of exotic species invasions on biodiversity vary with spatial scale, and documentation of local-scale changes in biodiversity following invasion is generally lacking. Coupling long-term observations of local community dynamics with experiments to determine the role played by exotic species in recruitment limitation of native species would inform both our understanding of exotic impacts on natives at local scales and regional-scale management efforts to promote native persistence. We used field experimentation to quantify propagule and establishment limitation in a suite of native annual forbs in a California reserve, and compared these findings to species abundance trends within the same sites over the past 48 years. Observations at 11 paired sites (inside and outside the reserve) indicated that exotic annual plants have continued to increase in abundance over the past 48 years. This trend suggests the system has not reached equilibrium > 250 years after exotic species began to spread, and 70 years after livestock grazing ceased within the reserve. Long-term monitoring observations also indicated that six native annual forb species went extinct from more local populations than were colonized. To determine the potential role of exotic species in these native plant declines, we added seed of these species into plots adjacent to monitoring sites where plant litter and live grass competition were removed. Experimental results suggest both propagule and establishment limitation have contributed to local declines observed for these native forbs. Recruitment was highest at sites that had current or historical occurrences of the seeded species, and in plots where litter was removed. Grazing history (i.e., location within or outside the reserve) interacted with exotic competition removal, such that removal of live grass competition increased recruitment in more recently grazed sites. Abundance of forbs was positively related to recruitment, while abundance of exotic forbs was negatively related. Thus, exotic competition is likely only one factor contributing to local declines of native species in invaded ecosystems, with a combination of propagule limitation, site quality, and land use history also playing important and interactive roles in native plant recruitment.

Cover and density of semi-desert grassland plants in permanent quadrats mapped from 1915 to 1947

This historical data set consists of 178 permanent 1-m2 quadrats located on semi-desert grasslands at the Santa Rita Experimental Range, Arizona, USA. Individual plants in these quadrats were identified and mapped annually (in most cases) from 1915 to 1933 and again in 1947. Quadrats were located in ungrazed exclosures and in pastures grazed at various intensities by livestock. These data provide unique opportunities to test the interactive effects of grazing and climate variables on demographic rates, plant–plant interactions, and population and community dynamics. We provide the following data and data formats: (1) the digitized maps in shapefile format; (2) a tabular representation of centroid or point location (x, y coordinates), basal or canopy cover (m2) for plants mapped as polygons, perimeter length (m), and seedling and clone status for each individual plant record; (3) quadrat information including elevation, livestock grazing history, and proximity to closest long-term rainfall gauge; (4) month...

Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia

The potential of grazing lands to sequester carbon must be understood to develop effective soil conservation measures and sustain livestock production. Our objective was to evaluate the effects of grazing on soil organic carbon (SOC), total nitrogen (TN), microbial biomass carbon (MBC) in Typical steppe and Desert steppe ecosystems, which are both important grassland resources for animal grazing and ecological conservation in China, and to derive region-specific soil C changes associated with different stocking rates (ungrazed, UG; lightly grazed, LG; moderately grazed, MG; heavily grazed, HG). This study substantiated that significant higher SOC, TN and MBC appeared with the treatment of LG in typical steppe. From 2004 to 2010, grazing treatments increased soil carbon storage in desert steppe, which was partly due to the grazing history. The higher MBC concentration and MBC/SOC suggest a great potential for carbon sequestration in the desert steppe ecosystem. The greater MBC in desert steppe than typical steppe was mainly the result of higher precipitation and temperature, instead of soil substrate. The change of MBC and the strong positive relationships between MBC and SOC indicated that MBC in the soil was a sensitive index to indicate the dynamics of soil organic carbon in both steppes in Inner Mongolia of China.

Is livestock grazing compatible with amphibian diversity in the High Mountains of Córdoba, Argentina?

The High Mountains of Cordoba, Argentina have a long evolutionary history of grazing by large herbivores. However, about 400 years ago, European livestock were introduced and gradually replaced native herbivores. Since the 1920s, domestic herbivores have been the only large herbivores present in the area, causing severe soil erosion and a threat to the system diversity. The endemic fauna of the region includes four amphibian species. We evaluated the effect of livestock rearing on amphibian diversity and water bodies in woodlands and grasslands of the High Mountains of Cordoba. The work was conducted on stream stretches and ponds in two contrasting grazing situations: an area with livestock presence and another area where livestock was excluded 14 years ago. The following variables were recorded at each sampling site: amphibian richness and abundance, percentage of emergent, submerged and peripheral vegetation in areas surrounding the water bodies, water pH, and water dissolved O2. No significant differences were detected in amphibian diversity between streams of both grazing situations, whereas a greater diversity (p < 0.01) was observed in ponds in grazed grasslands. Our results suggest that livestock rearing, qualitatively measured as grazing and 14 years of livestock exclusion, in the study area would not have negative effects on amphibian diversity. This finding might be due to the long evolutionary grazing history of the area, large-scale livestock exclusion exhibiting a novel scenario. The ongoing reintroduction of native grazers may provide the benefits of grazing without the consequent soil erosion and habitat degradation associated with domestic livestock.

Using insect diversity for determining land restoration development: Examining the influence of grazing history on ant assemblages in rehabilitated pasture

Ant assemblages, used widely as bioindicators of land management practices, were sampled in rehabilitated pastures and surrounding habitats at Norwich Park Coal Mine in central Queensland, Australia. As the end-use goal of a number of rehabilitated mine sites in the region is sustainable pasture-land, the aim of this study was to investigate the influence of varying grazing histories on ant fauna, to provide further understanding on the function of rehabilitated agroecosystems and multi-trophic interactions. Examination of seven study sites revealed three distinct ant assemblages, broadly reflecting mining and grazing history. Rehabilitated pastures where grazing had ceased 2 years prior to ant sampling contained low species richness with a basic ant composition, regardless of stocking rate, and was similar to ungrazed rehabilitated pasture. The rehabilitated pasture with continual low intensity grazing showed ant compositional similarities to the neighboring unmined pasture, although assemblage descriptors were intermediate between unmined and rehabilitated sites. Buffel grass (Pennisetum ciliare, basionym Cenchrus ciliaris) and other stoloniferous or rhizomatous grasses were the principal influence on ant assemblages, with grazing reducing the ground dominance of such grasses and providing a more favorable habitat for a wider range of ant species.

Variation in terrestrial mammal abundance on pastoral and conservation land tenures in north‐eastern Australian tropical savannas

AbstractThe introduction of domestic cattle into systems that have had little historical grazing by large herbivores, such as the case in Australia, can lead to both direct and indirect changes in native flora and fauna. In this study, we investigate the differences in native mammal abundance between pastoral land managed for cattle production and conservation land in Australian tropical savannas. We systematically sampled 68 sites for mammals in north‐eastern Queensland representing the two land tenures, which represent land with introduced stock and native herbivores present, and land where only native herbivores occur. We recorded 17 species of mammals representing five families and two functional groups (small mammals and macropods). Generalized linear mixed effects models identified that there was a significant positive relationship between increasing total ground cover and small mammal abundance and also the abundance of two species, Pseudomys desertor and P. gracilicaudatus. We recorded a reduction in abundance on pastoral land for macropods and small mammals, and four species, M. robustus, M. rufus, Leggadina lakedownensis, P. gracilicaudatus. Total ground cover and perennial grass cover was lower on pastoral land. Small mammal abundance on pastoral land was less even with increasing ground cover. Our results suggest that on pastoral land, native mammal abundance is affected and this has some relationship to ground cover changes. We recognize that there are other confounding management differences between pastoral and conservation lands such fire use, dingo baiting, and the manner of weed invasion and control that could influence mammal pattern. We conclude that conservation strategies for mammals in Australia's tropical savannas need to include a variety of land management schemes and tenures including land free from grazing by domestic livestock.

Shieling Areas: Historical Grazing Pressures and Landscape Responses in Northern Iceland

Historical domestic livestock grazing in sensitive landscapes has commonly been regarded as a major cause of land degradation in Iceland. Shieling areas, where milking livestock were taken to pasture for the summer, represented one element of grazing management and in this paper we consider the extent to which historical shieling-based grazing pressure contributed to land degradation. Based on a grazing model to assess pressures and tephrochronology -based soil accumulation rates allied to micromorphology as a proxy for land degradation, our findings suggest that the shieling sy stem contributed to the maintenance of upland vegetation cover and related productivity levels without causing land degradation from settlement through to ca. AD 1300. As land degradation accelerated from ca. AD 1477 it is likely that shieling management continued to operate effectively contributing to the overall resilience of livestock farming.

Seasonal Patterns of Forage Availability in the Fescue Grasslands Under Contrasting Grazing Histories

Grazing by large herbivores has been shown to condition vegetation in a manner that improves grassland quality for subsequent herbivory. Fescue grasslands evolved with disturbance from fire and winter grazing by bison but are now grazed primarily by cattle during summer. We examined the effect of long-term summer grazing on the seasonal forage production and quality of fescue grasslands in an examination of the hypothesis that long-term grazing had conditioned fescue grasslands to benefit livestock. This hypothesis was examined by comparing, between grazed and ungrazed plots, the biomass and composition of herbage components, concentrations of nitrogen (N) and acid detergent fiber (ADF) therein, and the ability of major plant types to maintain their biomass and quality throughout the growing season. The study was conducted in southern Alberta at five sites that had long-term exclosures (20+ yr) on grasslands that had been moderately grazed. Grazing had no effect on the N concentration of associated grasses, but grasses had lower N concentration than forbs. Concentrations of ADF followed a reciprocal trend to N. Grazing increased the mass of forbs from about 10% to 20% as a proportion of total biomass, which in turn, was not affected by grazing history. However, this grazing-induced shift to a higher quality vegetation type was not sufficient to affect total mass of N or total digestible nutrients at the community level. Rather than changes in current growth and quality, the predominant effect of summer grazing was in reducing litter mass, which also had the potential for affecting forage production and selection by herbivores. Finally, grazing reduced the relative contribution of rough fescue to total biomass by about 30%, and despite no significant effect on the potential to support summer grazing, this change could reduce the quality of these grasslands for winter grazing. El Pastoreo por grandes herbívoros ha demostrado que mejora la vegetación incrementando la calidad de los pastizales para un pastoreo subsecuente. Los pastizales de Festucas evolucionaron con perturbaciones de fuego y pastoreo por el búfalo durante el invierno, pero ahora son pastoreados principalmente durante el verano por ganado doméstico. Examinamos el efecto a largo plazo del pastoreo de verano sobre la producción de forraje estacional y la calidad de los pastizales de Festuca, y probamos la hipótesis de que el pastoreo a largo plazo ha acondicionado los pastizales de Festuca en beneficio del ganado doméstico. Esta hipótesis se examinó por comparación entre parcelas pastoreadas y no pastoreadas, la biomasa y la composición de componentes del forraje, las concentraciones de nitrógeno (N) y fibra detergente ácido (ADF) y en la capacidad de la mayoría de tipos de plantas para mantener su biomasa y calidad a lo largo de la temporada de crecimiento. El estudio se realizó en el sur de Alberta en cinco sitios que tenían exclusiones a largo plazo (más de 20 años) en pastizales ha habían sido pastoreado moderadamente. El pastoreo no tuvo ningún efecto en la concentración de N de los pastos asociados, pero las gramíneas tenían una menor concentración de N que las herbáceas. Las concentraciones de ADF siguieron una tendencia recíproca al N. El pastoreo aumentó la masa de herbáceas de alrededor del 10% al 20% como proporción de la biomasa total, que a su vez, no se afectó por la historia de pastoreo. Sin embargo, este cambio inducido por el pastoreo a un tipo de vegetación de mejor calidad, no fue suficiente para afectar la masa total de N o TDN a nivel de la comunidad. En lugar de los cambios en el crecimiento real y en la calidad, el efecto predominante de pastoreo de verano fue en la reducción de la masa del mantillo, que también tenía el potencial de afectar la producción de forraje y selección por herbívoros. Finalmente, el pastoreo redujo la contribución relativa de Festuca aproximadamente un 30%, de la biomasa total a pesar de no mostrar ningún efecto significativo sobre el potencial de apoyar el pastoreo de verano, este cambio podría reducir la calidad de estos pastizales para el pastoreo durante el invierno.