Observations on vegetation responses to improved grazing systems in Somalia
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Published source details
Thurow T.L. & Hussein A.J. (1989) Observations on vegetation responses to improved grazing systems in Somalia. Journal of Range Management, 42, 16-19.
Published source details Thurow T.L. & Hussein A.J. (1989) Observations on vegetation responses to improved grazing systems in Somalia. Journal of Range Management, 42, 16-19.
Summary
High intensity, continuous livestock grazing of communal lands in coastal southern Somalia has resulted in development of short-lived annual forb-dominated plant communities of low palatability which provide little dry-season forage. This has implications both for human livelihoods and wildlife. Changes in the plant community resulting from livestock grazing deferral or reduced intensity grazing aimed at promoting vegetation recovery, were compared near the town Afgoi (2ºl0’N, 45º05’E).
The study site was used by semi-nomadic pastoralists and heavily continuously grazed (HCG) i.e. 5 ha/animal unit (AU); 67% cattle, 24% goats, 5% camels. In October 1985, a 2 ha fenced exclosure was erected and livestock excluded (EX). A l ha area was also fenced and moderately stocked (10 ha/AU; 65% cattle and 35% goats) using a short-duration system (MSG) simulating a 10 pasture grazing rotation (10-1; 3:30 day).
Plant cover, standing crop and litter were sampled monthly (October 1985-February 1988) within 10, 0.25 m² plots randomly placed in each of the three areas. Standing (live and dead) grass and forbs were clipped and litter collected. This was dried and weighed. Plant cover was sampled monthly within 10 permanent 0.25 m² plots in each area.
In November 1985 and 1987, 10, 30-m transects were established in each area and foliar cover by species determined at 30-cm intervals along each.
Seasonal rainfall greatly influenced vegetation cover and standing crop. Forbs (mostly annuals) rapidly increased standing crop during the growing season but died soon after the rainy season; biomass was generally similar among pastures. Grass standing crop followed the same cycle but was greatest in the MSG and lowest in the HCG pasture.
Species composition and relative cover was markedly different between pastures after 2 years (1987). In 1987 forb cover was greatest in HCG and lowest in MSG (HCG 95.1%, MSG 64.9%, EX 76.4%); conversely grass cover was lowest in HCG and highest in MSG (HCG 3.3%, MSG 33.7%, EX 21.9%)
Low palatability species e.g. Indigofera tinctoria (a woody forb) and Oxygonum sagittatum dominated the HCG pasture.
By 1987, palatable vines (Ipomoea garckeana and Commelina forskalaei) dominated in the EX and MSG pastures, but they died and decomposed soon after the rainy season ended thus providing little dry season forage. In the EX pasture they formed a mat over other species, but grazing in the MSG pasture opened the mat and enabled grasses to establish. Grass cover became significantly greater on the MSG pasture (dominants being of moderate palatability e.g. Cenchrus ciliaris and Eragrostis ciliaris) compared to the EX (in which cover of highly palatable grasses Leptothrium senegalense and Cynodon dactylon, was highest) or HCG pastures. These grasses provided dry season forage.
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