Rangeland condition and feed resources in Metema District, North ...

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the relatively good rangeland condition in ranches and kalos may show the fact that overgrazing has contributed to rangeland degradation. 2.5 Factors affecting rangeland vegetation 2.5.1 Climate and soil Climate plays a primary role in determining the main types and growth responses of vegetation used for grazing (Alemayehu 2004; 2005). The amount and distribution of rainfall determine the form and productivity of the natural vegetation. Edaphic characteristics may substantially modify climatic factors in various ways. High natural soil fertility levels increase the vegetation’s response to moisture while soil volume and water holding characteristics condition the soil water storage capacity. Surface characteristics determining run-off and infiltration of water, and subsurface characteristics determined the level of drainage. Over grazing can lead to bareness and loss of topsoil by erosion to such an extent that the vegetation assumes a drier appearance than the rainfall data suggests. 2.5.2 Animal management Livestock grazing can have profound impact on vegetation. The general pattern of grazing-induced vegetation change is well documented (Alemyehu 2004; 2005). It is known that less palatable plants increase at the expense of more palatable species. Community structure is vastly altered when improper grazing continues for long period. The poor animal production experienced in rangelands has long been attributed to the poor quality of forage. This is generally confirmed by chemical analysis of the range plants. However, sampling of such material often overlooked selective grazing by animals between species and deferent parts of species and selectivity is of considerable importance (Holechek et al. 1994). 2.6 Factors influencing vegetation composition of the rangeland The species composition of rangeland varies depending on topography, climate and soil types. Different grasslands contain various types of grasses, legumes, and other herbaceous species. The botanical composition of a plant community can change because of many factors, including altitude, grazing practices, burning, drought, and temperature effects, pest, and erosion. Depending on the nature of this compositional change, the productivity of an area (in terms of its capacity to support livestock) may 8
change. A change in plant composition results because of the relative adaptability of different species to these influences (Alemyehu 2004; 2005). 2.6.1 Effects of grazing on vegetation composition Natural pasture communities are very complex consisting of a large range of grasses, shrubs and herbaceous species among which only few species are palatable. Livestock are able to selectively graze a small proportion of the palatable herbage available and ignore the undesirable ones. The most palatable species are selected first and closely defoliated. If the grazing pressure is high, then a decline in the quality and productivity of rangeland occurs (Cossins and Upton 1985). This causes reduced vigour, less seed production and eventually plant death. Overgrazing can also lead to extensive sheet and gully erosion (Alemyehu 2005). Since the whole of plant organism, leaves, stems, and roots react to the degree of trampling or grazing which it receives, a weakening of the top growth results in a lighter short root system that dies back from the bottom. Grass roots continue normal growth when not more than about 40–50% of the vegetative parts are removed (grazed) during the period of active growth. Therefore, the effects of overgrazing can be overcome if rangelands are properly managed. According to Laze and Swain (1969), grasses naturally need certain rest periods to develop, to grow, to seed and to be able to build reserves for the next growing season. 2.6.2 Response of plants to grazing The response to grazing by various plants is dependent on the reduced vigour of plants grazed repeatedly without the opportunity to replenish food reserves. It is also based on the high degree of selectivity exhibited by grazing livestock. Cattle prefer grasses, sheep prefer forbs, deer prefer browse. Within each category, there are ice-cream plants (decreasers), which the grazing animal will seek out. Repeated grazing will have the same effect as repeated clipping. A third factor independent of the plant–animal interaction is the presence or absence in the climax plant community. The classification of decreaser and increaser is based largely on the preference exhibited by the livestock. This is dependent on two major criteria: (1) the range site and (2) the livestock. The range site is important because it limits the selectivity available. This explains why some plants are decreasers on one site and increasers on another. In the first case they are the most palatable species, while in the second there are other plants that are more palatable. The kind of livestock will determine general categories of preference.̕ 9
Page 1 and 2: www.ipms-ethiopia.org www.eap.gov.e
Page 3 and 4: Authors’ affiliations Tesfaye Des
Page 5 and 6: 4.7 Availability of natural pasture
Page 7 and 8: Table 20. Common and dominant grass
Page 9 and 10: Abbreviations ADF ADL AEZ ANOVA ANR
Page 11 and 12: Abstract The study was conducted in
Page 13 and 14: 1 Introduction Ethiopia, with its d
Page 15 and 16: 2 Background 2.1 Livestock resource
Page 17 and 18: availability of rainfall. Alemayehu
Page 19: fauna composition or a transition f
Page 23 and 24: The four classes of range condition
Page 25 and 26: 2.8 Biomass estimation methods Biom
Page 27 and 28: are the Gumuz people. Until recentl
Page 29 and 30: Enclosures used as benchmark was se
Page 31 and 32: the distribution was assessed as fo
Page 33 and 34: samples for herbaceous species and
Page 35 and 36: The overall educational status of t
Page 37 and 38: Table 6. Mean ± SE land holding an
Page 39 and 40: Table 8. Livestock herd structures
Page 41 and 42: espectively, while 93.6, 4.3 2.1% r
Page 43 and 44: 4.7.2 Crop residues production and
Page 45 and 46: Table 13. Percentages of respondent
Page 47 and 48: than in P. spheslatum and C. ciliar
Page 49 and 50: of the respondents (69.3%) water th
Page 51 and 52: Table 20. Common and dominant grass
Page 53 and 54: owsing height of the animals. Accor
Page 55 and 56: Grazing types Herbaceous species Ca
Page 57 and 58: Table 25. Herbaceous species compos
Page 59 and 60: low density a decade ago, but curre
Page 61 and 62: 2004). Based on the results of this
Page 63 and 64: at the landscape scale; short tempo
Page 65 and 66: Soil compaction also directly restr
Page 67 and 68: Dry matter biomass 18000 16000 1400
Page 69 and 70: i.e. 312,300 ha, about 71% is natur
Page 71 and 72:
• Transhumance production system
Page 73 and 74:
Beruk Yemane and Tafesse Mesifin, 2
Page 75 and 76:
van der Westhuizen, HC van Rensburg
Page 77 and 78:
Appendix Table 2. Criteria for the
Page 79 and 80:
Appendix Table 4. Herbaceous specie
Page 81 and 82:
Appendix Table 5. Correlation matri
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Source: IPMS (2005). Appendix Figur
Page 89 and 90:
Appendix Figure 5. Partial view of
Page 91 and 92:
Appendix Figure 9. Communal grazing
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Rangeland condition and feed resources in Metema District, North ...

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