Range condition assessment to document the extent of degradation on selected semi-arid rangelands of the Eastern cape, South Africa
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Date
2016
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University of Fort Hare
Abstract
The assessment of communal rangelands and Nature Reserve capability is crucial in order to
prevent resource degradation and facilitate adaptive management practice. This study was
conducted to document the extent of land degradation in three selected semi-arid rangelands
of the Eastern Cape, South Africa. These comprised the Great Fish River Nature Reserve,
Glenmore and Ndwayana communal rangelands. Each rangeland was demarcated into two
homogenous vegetation units (HVU’s) toplands, bottomlands and a benchmark site.
Botanical composition (woody and herbaceous), aboveground biomass production, soil seed
bank composition and density and soil micro nutrients (Cu, Mn, Zn) and macro nutrients (N,
P, K, OC, Mg, Ca, Na) were determined. Twenty two (22) perennial grass species and some forbs were recorded in all the HVU’s. In general the grass species composition consisted of 59 percent pioneer (Increaser II) species, 36.4 percent mesophytes (Decreaser) species and the remaining were 4.54 percent sub-climax/climax (Increaser I) species. The grazing value of the grass species was: High 41 percent, Moderate 14 percent and Low45 percent. Six dominant grass species and were recorded, comprising mainly of Increaser species in all the HVU’s, (except for Digitaria eriantha). Biomass production in the benchmark (2700 kg/ha) was significantly higher (p<0.05) in summer than all the other HVU’s, but in winter (1715 kg/ha) it was not significantly different (p>0.05) from the bottomlands of the Great Fish RNR. There was an increasing trend in mean basal cover from the benchmark to
Ndwayana toplands (0.0-15.75cm). The results showed that the benchmark had higher dense
cover (0.0 to 1.5cm) than all of the other HVU’s. There were 27 woody species, where 56 percent were acceptable to browsers while 44 percent were not acceptable. Of these woody plants 41 percent had thorns or spines whilst 59 percent had no thorns or spines. Ptaeroxylon obliquum (14 percent) was the most dominant species and the least dominant being Pappea capensis (0.05 percent) respectively.Glenmore had significantly higher (p<0.05) bush density (1181.25 and 1337.5Trees/ha) and TE (1069 TE/ha) than all the other HVU’s. Soil samples from each sample plot were collected with an auger from a 20 cm layer with the use of a 0.25m2 quadrat distributed within the four 100 m transects in each sample plot. The
samples were analyzed for N, P, K, OC, Na, Ca, Mg, Zn, Cu and Mn and pH using
photospectrometer. There were significant differences (p<0.05 in the concentration levels of
all the macro nutrients N, OC, P, K, Ca, and Na (except Mg) in different HVU’s. There were
significant differences (p<0.05) in the soil content of Cu, Mn, Zn and pH between the
different HVU’s. In the soil seed bank experiment, a total of 21 species found (9 grasses, 9 forbs and 3 sedges). Most of the grass species identified in the seed bank were mainly found in the Benchmark site while the rest of the homogenous vegetation units were dominated by either forbs or sedges. Seed bank grass composition comprised 67 percent perennial and 33 percent annual species. Of these grasses, 29 percent were unpalatable, 48 percent of low, 14 percent high and 9 percent moderately palatability. Pseudognaphalium undulataum (14.59 percent ) was the most abundant species, followed by Medicago laciniata (8.44 percent), Hypertelis bowkeriana (8.41 percent) and Sutera campulata (8.36 percent) with Tragus species (0.23 percent) followed by Panicum stapfianum (0.5 percent) being the least
abundant species. There were significant differences (p<0.05) in the seed bank density
between the Great Fish RNR and the communal areas of Glenmore and Ndwayana (both
toplands and bottomlands). Similarities between the seed bank and the above ground
vegetation were tested using Sorensen’s Similarity Index. The coefficients were as follows;
Glenmore toplands (40 percent), Glenmore bottomlands (37.5 percent), Ndwayana toplands (25 percent), Ndwayana bottomlands (28.57 percent), Great Fish RNR toplands and bottomlands were (0 percent) with the benchmark comprising of (80 percent). Rangaland degradation is found in all the study sitesand it was more in the communal areas than in the Great Fish RNR excluding the benchmark.
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Keywords
Rangelands -- South Africa -- Eastern Cape, Land degradation -- South Africa -- Eastern Cape, Soil degradation -- South Africa -- Eastern Cape, Land tenure -- South Africa -- Eastern Cape