Post Drought Range Ecology Trends In Different Agro-Ecological Zones, Kordofan, Sudan

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Abdelrahim Salih Fedail, Mohamed
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Agro-ecological zones (AEZs) variations in terms of range condition and ecological trends in natural rangelands in North Kordofan and part of South Kordofan States, Sudan were studied. Vegetation measurements and the relative importance during two consecutive growing stages of rainy season of 2007/2008 were also made within protected and unprotected grazing lands. Trends in biomass production and rainfall were further assessed in Semi-Arid AEZ on sand for the period 2005-2008.Range measurements data were arranged in a split plot design where the ecological zone represented the main plot while the range site (protected and unprotected) the sub plot. Remote sensing technology was applied to create both land use/land cover categories. These determinations were done for the different vegetation densities covering the period 1987-2006 in the different agro-ecological zones to assess trend in rangelands conditions. The Normalized Difference Vegetation Index (NDVI) was used to assess variation in vegetation in four agro-ecological zones. NDVI maps of study areas were prepared for historical years (1987, 1996, 1999 and 2006) separately. A computer-based programme (Resource Assessment for Pastoral Systems- RAPS) was used for analyzing land and forage resources productivity and livestock support capacity, taking systems complexity into account. Input data for land and forage units were collected from field work, research and governmental statistics. The ultimate objective of the study was to assess environmental effects of post-drought good rainy season on natural rangelands and ecological trends in Kordofan and similar agro-ecological areas. Agro-ecological zones had significant main effects on density, cover and dry matter production (P<0.001). The Semi-Desert AEZ had the highest density and the lowest cover and dry matter. Arid AEZ had also lower density and cover. Semi-Arid on sand and clay AEZ recorded similar density and cover. Dry matter in Semi-Arid on clay AEZ had higher values. Agro-ecological zone had, also, significant main effects on plants, litter and bare soil (P<0.001). The Semi-desert and Semi Arid zone on clay recorded higher live plants whereas the highest percentages of bare soil were found in the Arid AEZ and semi-desert zone, respectively.The highest litter was recorded in the Semiarid on sand AEZ. Growing season had significant main effect on plant density, vegetation cover (P<0.001) and dry matter (P<0.01) production. Plant density was reduced with advancing growing stage while cover and dry matter were increased. Also growing stage had significant effect on percentage live plants, litter and bare soil. Seed setting stage recorded the highest litter and bare soil percentages whereas the flowering stage resulted in the highest percentage of live plants. ix Range protection significantly (P<0.00) increased plant density, cover, live plants and dry matter (P<0.001) and significantly (P<0.001) reduced bare soil compared with unprotected grazing lands. Interactions effects due to AEZ x growth stage were significant (P<0.001) on plant density, cover and dry matter production. AEZ x management was also significant (P<0.001) for dry matter. Furthermore, AEZ x growth stage interactions were significant (P<0.001) on live plants, bare soil and litter percentage. The dominant plants in unprotected sites were a mixture of less to more palatable (%70) ones. Range plants of high nutritive valuewere found to be less prevalent in the northern parts of the State. Plants found to be dominant in the northern parts of Kordofan were Fimbristylsdichotomo (Umfisaisat), Eragrostistremula (Bano),Trianthemapentandra (Rabaa) Aristida sp. (Gao), Tribulusterrestris(Dreaisa), Chlorisprieurii (Abo Asabi), Indigofrasemitrijiuga(Halma),Cymbopgonnervatus (Nal), Aristidahordeace (Danab El bashoam) and Justiciakostchyi (Nana). Mostof the dominant plants (70.0%) under the protected siteswere found to be more palatable(70%) and had high nutritive value. These were Eragrostistremula, Chlorisprieurii (Abo Asabi), Ipomea sp. (Huntot),Aristida sp., Justiciakotschyi(Nana), Monsoniasenegalensis (Garen),Chlorisgayana, Cymbopogonnervatus and Acanthus sp. (TamrElfar). Dominant trees and shrubs under open range (unprotected sites) were less dense compared with those under protection.Acaciatortilis (Seyal), Letadeniapyrotechnia (Marekh) and Balanitesaegyptiaca (Hegleig) were found to dominate open rangelands, while Acaciatortilis, Leptadeniapyrotechniaand Acacia senegal (Hashab), Acacia mellifera (Kitir), Bosciasenegalensis (Korsan), Acacia nubica (loat) Acacia senegal, Balanitesaegyptiaca, Faidherbiaalbida (Haraz), Combretumaculeatum(Shehait), Cadabarotundi folia (Kormota) and Acacia seyal (Taleh) were the most prevalent under protected areas. High fluctuations were found in annual rainfall on the Semi-Arid on sand AEZ. However, biomass production started with the lowest rates and recorded higher peak at both years under study 2007 and 2008. Interpretation of satellites images coupled with field work indicated that land use/land cover categories in State could be broadly divided into 50% natural vegetation, 24% cultivated land and 26% bare areas. The Desert AEZ was found to represent only 5.3% of x the state area, with little vegetation (1%), the Semi-Desert AEZ 47.5% with very small cultivation 2.8% and 55% of tree and shrub savanna, grasses and scattered trees. The Arid AEZ comprised 25% of the state area, with trees and shrubs savanna and woodland representing 57% of its area, and 38.6% occupied by cultivated land. The Semi-Arid on sand AEZ occupied 17% of the State area, with 86.6% its area composed of tree and shrub savanna, grassland and woodland and the rest of the zone area (13.4%) occupied by traditional cultivation on sand. The Semi-Arid on clay AEZ was the smallest zone in the State (4.8%), the majority of which (90%) being composed of tree and shrub savanna, grassland and woodland and mechanized farming on one tenth (10.0%). NDVI values were classified into 5 categories: bare soil, sparse vegetation, medium dense vegetation, high dense vegetation and very dense vegetation. Size of bare area was in descending manner, except in the semi-arid on sand, there was no change in the percentage of bare soil (1%). No or little increase in percentage of sparse vegetation in all AEZs, except in semi-arid on sand, which had decreased by 11%. However, under the semi-arid on clay, there was an increase on medium dense category, the highest was recorded in the semi-desert zone (10%) and that at all AEZs, and therewas an observed increase in high dense vegetation and very high dense vegetation. Using of RAPS model to quantify the resources. Semi-Arid/Sand AEZ was found to have the largest grazing land 47%, while Semi-Arid/clay had the smallest area, out of it, 44% natural rangeland. The greatest amount of total dry matter was produced in Semi-Arid/Sand AEZ (6.4 million tons), whereas the Semi-Arid/clay AEZ recorded the smallest amount (2.2). Greatest numbers of livestock classes were found in the Semi-Arid/Sand and the small numbers were under the Semi-Arid/Clay zone. Trends in dry matter production over a 10-year period (2007-2016) for various AEZs were found to experience varying fluctuations depending on agro-ecological zone. It was indicated that, despite high variability and differences among the different agro-ecological zones in Kordofan, protection of rangelands could be a viable management tool in enhancing biomass production, protecting biodiversity and provision of favorable condition for palatable plants recovery following droughts. It could be concluded with caution that post-drought range ecology trends showed some recovery. Rainfall could, sensibly, be assumed to have contributed to the observed improvement, coupled with disappearance (endangered) of some high nutritive value range species
Post Drought, Range, Ecology ,Trends,Agro-Ecological Zones, Kordofan, Sudan