Herbivory by domestic and wild ungulates is a major driver of global vegetation dynamics. However, grazing is not considered in dynamic global vegetation models, or more generally in studies of the effects of environmental change on ecosystems at regional to global scale. An obstacle to this is a lack of empirical tests of several hypotheses linking plant traits with grazing. We, therefore, set out to test whether some widely recognized trait responses to grazing are consistent at the global level. We conducted a meta-analysis of plant trait responses to grazing, based on 197 studies from all major regions of the world, and using six major conceptual models of trait response to grazing as a framework. Data were available for seven plant traits: life history, canopy height, habit, architecture, growth form (forb, graminoid, herbaceous legume, woody), palatability, and geographic origin. Covariates were precipitation and evolutionary history of herbivory. Overall, grazing favoured annual over perennial plants, short plants over tall plants, prostrate over erect plants, and stoloniferous and rosette architecture over tussock architecture. There was no consistent effect of grazing on growth form. Some response patterns were modified by particular combinations of precipitation and history of herbivory. Climatic and historical contexts are therefore essential for understanding plant trait responses to grazing. Our study identifies some key traits to be incorporated into plant functional classifications for the explicit consideration of grazing into global vegetation models used in global change research. Importantly, our results suggest that plant functional type classifications and response rules need to be specific to regions with different climate and herbivory history.

Plant trait responses to grazing – a global synthesis

Miombo woodlands are the most extensive vegetation type in Africa south of the equator. These dry tropical woodlands cover some 2.5 million hectares and are home to over 40 million people. Miombo products are very important to the livelihoods and basic needs of an additional 15 million urban Africans. The book demonstrates how much livelihood strategies of rural communities depend on miombo goods and services, and indicates the strong differentiation of uses within communities and in space and time. The ecological constraints to human activity in the region are clearly articulated, ranging from nutrient-poor soils to the presence of the tsetse fly. The authors also trace the host of policies that have influenced miombo woodlands and their uses, from pre-colonial times to the present. The current importance of miombo products in markets, both locally and globally, is documented in a chapter on trade patterns. Options for management are outlined, including silvicultural treatment, fire management and grazing regimes. Institutional arrangements, both local and state, for the management of the woodlands are investigated, and the authors examine how local communities can be empowered to manage and benefit from the woodlands. The final chapter proposes a conceptual model of how all the diverse social, economic, political and ecological processes interact to shape how the household and woodland situations are changing. This conceptual framework is then used to identify key issues for research, which will reduce gaps in current understanding and facilitate formulation of new management strategies, policies and institutions. The Miombo in Transition is a resource for researchers, with over 250 pages reviewing and synthesising over 400 studies. There are numerous figures, tables and plates. The book contains contributions by a number of researchers, and yet has managed to ensure coherence, close linking of chapters and complete coverage of material through authors' workshops and tight editorial control. Each chapter was reviewed by international experts both in draft and final format, resulting in the high quality of the final produc

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The miombo in transition: Woodlands and welfare in Africa

Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y−1. Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cat...

Bush encroachment in southern Africa: changes and causes

Wildland Fire Management Handbook for Sub-Sahara Africa

http://directory.umm.ac.id/Data%20Elmu/jurnal/E/Ecological%20Economics/Vol33.Issue3.Jun2000/10691.pdf

SPECIAL SECTION: LAND USE OPTIONS IN DRY TROPICAL WOODLAND ECOSYSTEMS IN ZIMBABWE: A simulation model of miombo woodland dynamics under different management regimes

Brachystegia/Julbernardia veld was protected in the growing season and grazed by cows in the dry season for 60, 90 and 120 grazing days per ha per annum in combination with burning in the late dry season either annually, biennially or triennially. After 14 years of treatment there was evidence of a distinct improvement in grass species composition and in basal cover of grasses. While on veld cows were fed 800 g of cottonseed meal per head daily, and on average lost 4,38 kg in body mass per head per season. Burning at all frequencies reduced the number of trees and stunted their growth but the dominant species Brachystegia boehmii was reduced only by annual burning. It was concluded that resting the veld annually in the growing season and grazing only in the dry season is a simple and effective way of managing veld in the high rainfall areas of Zimbabwe where cultivated pastures are used for grazing during the growing season.

Effects of stocking rate and burning frequency on Brachystegia/Julbernardia veld in Zimbabwe

Prior to 1962 it was thought that 90 to 135 kg N per ha annually gave satisfactory yields of grass herbage Grasses were consequently selected for their productivity with this amount of applied nitrogen It was subsequently shown that the yield response of grasses was linear with up to 450 kg N per ha Thus it became necessary to test again many commonly‐grown grasses with this high rate of nitrogen Thirty grasses were fertilized annually with 450 kg N, 90 kg P2O5 and 65 kg K2O per ha Herbage yields were determined each time the grasses reached early anthesis  Mean herbage yields over four years varied from 1 700 to 17 900 kg dry matter per ha Results showed clearly that stoloniferous grasses were more productive than tufted grasses The significance of high yielding stoloniferous grasses in relation to beef production in Rhodesia is briefly discussed

Herbage yields of thirty grasses fertilized heavily with nitrogen

Recent pasture research at Henderson Research Station.

Star grass (Cynodon aethiopicus cv. No. 2) was grazed to leave stubble of 5, 15 or 25 cm in height after grazing. In the first year (1972–73) 350 kg N and 39 kg P per ha, and in the second year (1974–75) 500 kg N and 39 kg P per ha, were applied. Grazing was done at 15‐day intervals although in the first year this was not always possible because of poor rainfall which affected growth. In both years amounts of herbage harvested above the three stubble heights decreased as the height of stubble left after grazing increased. The relative proportions of green leaf, dead leaf and stem were similar with all stubble heights although there was slightly less green leaf in the 5 cm stubble.

M. G. W. Rodel

Papers

Effects of stocking rate and burning frequency on Brachystegia/Julbernardia veld in Zimbabwe

Herbage yields of thirty grasses fertilized heavily with nitrogen

Recent pasture research at Henderson Research Station.

The effects of height of stubble left after simulated rotational grazing on regrowth of star grass.

The effects of applied nitrogen on the herbage yields of star grass and Paraguay paspalum grown at two sites under irrigation.