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16,530 result(s) for "Range ecology"
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Rangeland systems : processes, management and challenges
\"This book provides an unprecedented synthesis of the current status of scientific and management knowledge regarding global rangelands and the major challenges that confront them. It has been organized around three major themes. The first summarizes the conceptual advances that have occurred in the rangeland profession. The second addresses the implications of these conceptual advances to management and policy. The third assesses several major challenges confronting global rangelands in the 21st century. This book will compliment applied range management textbooks by describing the conceptual foundation on which the rangeland profession is based. It has been written to be accessible to a broad audience, including ecosystem managers, educators, students and policy makers. The content is founded on the collective experience, knowledge and commitment of 80 authors who have worked in rangelands throughout the world. Their collective contributions indicate that a more comprehensive framework is necessary to address the complex challenges confronting global rangelands. Rangelands represent adaptive social-ecological systems, in which societal values, organizations and capacities are of equal importance to, and interact with, those of ecological processes. A more comprehensive framework for rangeland systems may enable management agencies, and educational, research and policy making organizations to more effectively assess complex problems and develop appropriate solutions.\"--Publisher description.
The politics of scale : a history of rangeland science
Rangelands are vast, making up one quarter of the United States and forty percent of the Earth's ice-free land. And while contemporary science has revealed a great deal about the environmental impacts associated with intensive livestock production—from greenhouse gas emissions to land and water degradation—far less is known about the historic role science has played in rangeland management and politics. Steeped in US soil, this first history of rangeland science looks to the origins of rangeland ecology in the late nineteenth-century American West, exploring the larger political and economic forces that—together with scientific study—produced legacies focused on immediate economic success rather than long-term ecological well being. During the late 1880s and early 1890s, a variety of forces—from the Homestead Act of 1862 to the extermination of bison, foreign investment, and lack of government regulation—promoted free-for-all access to and development of the western range, with disastrous environmental consequences. To address the crisis, government agencies turned to scientists, but as Nathan F. Sayre shows, range science grew in a politically fraught landscape. Neither the scientists nor the public agencies could escape the influences of bureaucrats and ranchers who demanded results, and the ideas that became scientific orthodoxy—from fire suppression and predator control to fencing and carrying capacities—contained flaws and blind spots that plague public debates about rangelands to this day. Looking at the global history of rangeland science through the Cold War and beyond, The Politics of Scale identifies the sources of past conflicts and mistakes and helps us to see a more promising path forward, one in which rangeland science is guided less by capital and the state and more by communities working in collaboration with scientists.
Post-Fire Soil Nutrient Dynamics in ISeriphium plumosum/I L. Encroached Semi-Arid Grassland of Gauteng Province, South Africa
Seriphium plumosum L. is an indigenous unpalatable shrub that occurs in fire-prone semi-arid South African grassland areas, yet research proposes the use of fire to control its encroachment of rangelands. This study investigated the interaction effects of burning and soil depth on components of soil fertility. Soil samples were collected from the surface (<10 cm) and subsurface (>10 ≤ 20 cm) soil, before and after burning in randomly selected paired subplots (25 m × 25 m), with six replicates. Data was analysed as a randomised complete block design, with repeated measures (before and after burning) in a 2 × 2 factorial analysis of variance (ANOVA) using generalised linear model (GLM) procedures. Components of soil fertility measured (K, Ca, Mg, Org C, P, pH and TN) showed a significant decrease with increasing soil depth both before and after burning, except for K and P, which were significantly higher in surface soils after burning. The results showed that the response of soil nutrients to fire depends on the temperature tolerance threshold of individual soil nutrient elements. Increasing surface soil available K and P concentrations after burning may improve the conditions for S. plumosum encroachment, with implications for similar environments and species worldwide.
Extreme Wildlife Declines and Concurrent Increase in Livestock Numbers in Kenya: What Are the Causes?
There is growing evidence of escalating wildlife losses worldwide. Extreme wildlife losses have recently been documented for large parts of Africa, including western, Central and Eastern Africa. Here, we report extreme declines in wildlife and contemporaneous increase in livestock numbers in Kenya rangelands between 1977 and 2016. Our analysis uses systematic aerial monitoring survey data collected in rangelands that collectively cover 88% of Kenya's land surface. Our results show that wildlife numbers declined on average by 68% between 1977 and 2016. The magnitude of decline varied among species but was most extreme (72-88%) and now severely threatens the population viability and persistence of warthog, lesser kudu, Thomson's gazelle, eland, oryx, topi, hartebeest, impala, Grevy's zebra and waterbuck in Kenya's rangelands. The declines were widespread and occurred in most of the 21 rangeland counties. Likewise to wildlife, cattle numbers decreased (25.2%) but numbers of sheep and goats (76.3%), camels (13.1%) and donkeys (6.7%) evidently increased in the same period. As a result, livestock biomass was 8.1 times greater than that of wildlife in 2011-2013 compared to 3.5 times in 1977-1980. Most of Kenya's wildlife (ca. 30%) occurred in Narok County alone. The proportion of the total \"national\" wildlife population found in each county increased between 1977 and 2016 substantially only in Taita Taveta and Laikipia but marginally in Garissa and Wajir counties, largely reflecting greater wildlife losses elsewhere. The declines raise very grave concerns about the future of wildlife, the effectiveness of wildlife conservation policies, strategies and practices in Kenya. Causes of the wildlife declines include exponential human population growth, increasing livestock numbers, declining rainfall and a striking rise in temperatures but the fundamental cause seems to be policy, institutional and market failures. Accordingly, we thoroughly evaluate wildlife conservation policy in Kenya. We suggest policy, institutional and management interventions likely to succeed in reducing the declines and restoring rangeland health, most notably through strengthening and investing in community and private wildlife conservancies in the rangelands.
The Palaearctic steppe biome: a new synthesis
The Palaearctic steppes range from the Mediterranean basin towards China, forming one of the largest continuous terrestrial biomes. The literature on steppe ecology and conservation is vast but scattered and often not available in English. We provide a review of some key topics based on a new definition of steppes, which includes also Mediterranean steppes and alpine rangelands of the Asian Highlands. Revisiting the terrestrial ecoregions of the world, we estimate that the Palaearctic steppe biome extends over ca. 10.5 million km 2 . Major chorological regions differ in their macroclimatic niche with a clear distinction between Middle Asia with its winter precipitation and the Central Asian summer-rain regions of the Mongolian plateau and of Tibet. Steppe soils store large amounts of carbon, yet the sequestration potential is debated and depends on land use. Major physiognomic-ecological steppe types include forest-, typical-, desert-, and alpine-steppe, which vary in the importance of grasses, mainly C3 species. The steppes host a specialised fauna, and Middle Asia, Tibet, and especially Mongolia, have large herds of migrating ungulates. The share of pristine and protected sites is low in the steppe regions, with conversion into croplands being the most important land use impact in Europe, Middle Asia, and the Mediterranean, while grazing has a severe impact in some parts of Mongolia and Tibet. There are major gaps in our knowledge on: (1) the effects of climate change on the crucial seasonal patterns; (2) the role of steppe soils in the global carbon budget; and (3) the ecology and distribution of most animal groups except vertebrates.
Historical and contemporary range expansion of an invasive mussel, Semimytlius algosus, in Angola and Namibia despite data scarcity in an infrequently surveyed region
Understanding the spread of invasive species in many regions is difficult because surveys are rare. Here, historical records of the invasive marine mussel, Semimytilus algosus, on the shores of Angola and Namibia are synthesised to re-construct its invasive history. Since this mussel was first discovered in Namibia about 90 years ago, it has spread throughout the western coast of southern Africa. By the late 1960s, the species was well established across a range of 1005 km of coastline in southern Angola and northern Namibia. Although only coarse spatial resolution data are available since the 1990s, the distribution of S. algosus clearly increased substantially over the subsequent decades. Today, the species is distributed over 2785 km of coastline, appearing in southern Namibia in 2014, whence it spread across the border to northern South Africa in 2017, and in northern Angola in 2015. Conspicuously, its current range appears to be relatively contiguous across at least 810 km of shore in southern Angola and throughout Namibia, with isolated, spatially disjunct occurrences towards the southern and northern limits of its distribution. Despite there being few occurrence records that are unevenly distributed spatially and temporally, data for the distributional patterns of S. algosus in Angola and Namibia provide invaluable insights into how marine invasive species spread in developing regions that are infrequently monitored.
Perennial grass seed bank in litter patches. Co-occurrence with forb and annual grass seed banks constraints the reestablishment in disturbed Patagonian Monte rangelands
We assessed the effect of grazing and plant patchiness on the perennial grass seed bank in litter patches in relation to co-occurring shrub, annual grass, and forb seed banks in disturbed rangelands of the Patagonian Monte. We hypothesized that litter patches in disturbed rangelands have a perennial grass seed bank but co-occurring seed banks of annual lifeforms reduce the opportunities for perennial grass reestablishment at these patches. We evaluated the effect of microsite (bare soil vs. vegetated) and grazing (grazed vs, non-grazed) on the (1) size (seeds m−2) of the four seed banks, (2) frequency of microsites with the respective seeds, and (3) frequency of co-occurrence of the perennial grass with shrub, annual grass and forb seed banks in litter patches at 5 dates (2009–2011). We found the smallest perennial grass and annual grass seed banks in litter patches under grazing and in bare soil microsites. The shrub and forb seed banks in litter patches were smaller at vegetated than at bare soil microsites under grazing and the reverse occurred in non-grazed conditions. The sizes of all seed banks were positively related to the frequency of litter patches with the respective seeds. In these litter patches, the size of perennial grass and shrub seed banks did not vary with grazing, and/or microsite while the size of annual grass and forb seed banks decreased with grazing and increased in vegetated microsites. The perennial grass seed bank in litter patches co-occurred mostly with forb and annual grass seed banks (several times larger). This is probably a constraint for the reestablishment of perennial grasses. However, although scarce, litter patches with exclusive perennial grass seed bank or co-occurring perennial grass and shrub seed banks could be an opportunity for perennial grass reestablishment.