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EFFECTS OF BURNING AND GRAZING ON PLANT SPECIES PERCENTAGE COVER AND HABITAT CONDITION IN THE HIGHLAND GRASSLAND OF MPUMALANGA PROVINCE, SOUTH AFRICA.

Byline: M. K. Boakye, I. T. Little, M. D. Panagos and R. Jansen

ABSTRACT

Fire and grazing have long been used as a grassland management tool in South Africa for livestock production. Despite the ecological importance of fire and grazing to the grassland ecosystem, the appropriate use of fire and grazing as a land use management tool has been questioned. The effects of different burning frequencies and stocking rates on species composition were studied between January and March 2008 using a Modified-Whittaker design in commercial farms, communal land and a nature reserve stocked with game herbivores in the highland grassland of Mpumalanga Province of South Africa. The results revealed that species assemblages of an annually burned site were completely dissimilar from a biennially burned site. The annually burned site was dominated by flora that is considered as fire-tolerant species.

In contrast, the protection of some areas from burning in addition to regular burning of other areas ensured the presence of both fire-tolerant and fire-intolerant species and contributed to the high species composition of communal land. This study therefore suggests that biennial burning, or even longer intervals of burning of grazed land in addition to partial or mosaic burning should be employed to enhance the biodiversity conservation status of these montane grasslands.

Key words: fire, grazing, highland grassland, herbivores

INTRODUCTION

Fire and grazing has been used as a land use management tool in the Grassland Biome in South Africa by altering or manipulating the frequency of burn and stocking rates primarily to reinvigorate pastures for livestock production (Bond and Keeley, 2005; Mucina and Rutherford, 2006). Fire and grazing has been shown to have a detrimental effect on the biodiversity of Grassland Biome (Bond and Keeley, 2005). Fire, for instance, causes a reduction in species composition due to the large amount of biomass it consumes which consequently has an effect on the loss and degradation of biodiversity through the representation of fire-tolerant plants to the detriment of fire-intolerant plants (Bond et al. 2005, Bond and Keeley, 2005).

The loss and degradation of biodiversity as a result of grazing occurs through processes such as selective grazing that facilitate the dominance of grazing tolerant species (Sternberg et al., 2000) and trampling by herbivores that reduces the attractiveness and acceptance of plant species to livestock (Owen-Smith, 1999). The grazing effects result in changing the vegetation community species composition usually with dominance of unpalatable plants in grasslands (Afzal et al., 2007, Arshadullah et al., 2009, Mushtaque et al., 2010). However, protection of grassland from fire and grazing can lead to succession from grassland species to woodland species and a change in species composition (Bond and Keeley, 2005). Currently, frequency of burning far exceeds what would have occurred naturally in the Grassland Biome as well as elevated stocking rates.

When these thresholds are breeched, the ecosystem health of the Grassland Biome is compromised and these changes also take place quite slowly even when it is mismanaged due to the stable botanical composition and extremely low resilience of the Mesic Highveld Grassland (Rethman and Kotze, 1986). The appropriate use of fire and grazing as a land use management tool is critical since different fire regimes as well as grazing levels produce different landscapes as a result of its effect on the establishment of plant species. The aim of this study was to determine whether fire frequency and stocking rates have impacted negatively on plant species composition and cover of the Mesic Highland Grassland of Mpumalanga Province in South Africa.

MATERIALS AND METHODS

Study Area: The study was conducted in the Mesic Highveld Grassland (25o 42' 846'' S 30o 09' 818'' E) between the towns of Lydenburg and Belfast in the Mpumalanga Province, South Africa (Figure 1). The vegetation of the study area falls under the North-eastern Sandy Highveld classification of Acocks (1953). It occurs in the recently re-classified Mesic Highveld Grassland (Mucina and Rutherford, 2006) and specifically in the Lydenberg Montane Grassland vegetation unit and is dominated by sour grasses and classified as sourveld (Mucina and Rutherford, 2006). The region is characterized by high rainfall in summer (Bredenkamp et al., 1996; Mucina and Rutherford 2006) with a mean annual rainfall ranging between 660 - 1180 mm per annum (Mucina and Rutherford, 2006).

Temperatures in the region vary from below 0oC in winter to 39oC in summer with an average of 15oC per annum (Bredenkampet al., 1996). The mean rainfall during the data collection period was 210 mm, 102 mm and 125 mm in January, February and March 2008 respectively.

Temperature average was 17oC for the months of January and February and 15oC for the month of March with a high of 24oC in January, 26oC in February and 22oC in March. The region is situated within an altitudinal range of 1260 - 2160 m above sea level with undulating plains, mountain peaks and slopes (Mucina and Rutherford,2006). The dominant land use in the study area is livestock farming, primarily with cattle in the commercial farms and mixed herds of cattle, sheep and goats in the communal farms.

Experimental Design: Five study sites were selected which reflected the common farming practices in the study area. Table 1 details the characteristics of study sites that include the stock of herbivores on study sites, burning frequency and grazing intensity. The annually burned farm (Site 1) was the only study site that was completely burned in spring 2007 while the communal land (Site 3) was partially burned due to lack of proper burning management. Sites 2, 4 and 5 however were not burned in spring 2007 but were burned in spring 2006. Each study site had four replicates of 25 hectares (ha) in size with at least 500 m between replicates to avoid pseudo-replication. Relative grazing intensity was defined as the amount of hectares of grazing land available per large animal unit (ha/LAU).

One large animal unit was estimated to be equivalent to one cow or five sheep or goats and represents the metabolic equivalent of a 454 kg cow (Owen-Smith and Danckwerts, 1997. Heavy, moderate and low grazing intensity were assumed to be a stocking rate of 1 LAU on 3 ha or less, 1 LAU on 4 - 10 ha and 1 LAU on 11 - 25 ha respectively.

Vegetation composition and abundance sampling: A Modified-Whittaker sampling design was established in all four replicates of each study site to measure plant species composition and percentage cover. The Modified- Whittaker plot design has been found by Stohlgren et al. (1995) to sample the heterogeneity of plant communities with a higher level of accuracy than either true random sampling or the original Whittaker plot design. Only plant species cover was measured with the Modified- Whittaker design and species presence. Plant species composition recordings for each Modified Whittaker plot were conducted in January 2008. Plant species cover was measured within 1 m2 (10 replicates), 10 m2 (two replicates) and one 100 m2 subplots for each replicate of study site. Within each subplot, plant species cover was visually estimated using a cover class as this has been suggested as the most suitable percentage cover estimate as it removes extremes (McCune and Mefford, 1999).

This cover class and midpoint wereused as follows 1: 2.5%, 2: 7.5%, 3: 15%, 4: 25%, 5: 35%, 6: 45%, 7: 55%, 8: 65%, 9: 75%, and 10: 90%. Plants species that were not found in the subplots but were in the 1 000 m2 plot were noted without assigning a percentage cover. Plant species identification was undertaken at the South African National Biodiversity Institute herbarium located in Pretoria. The names of forbs and their families follow Germishuizen and Meyer (2003). The grazing value and status of grasses were based on van Oudtshoorn (2006).

Data analysis: The Bray-Curtis similarity index (Bray and Curtis, 1957) was used to assess similarity between sites based on presence and abundance of plant species using PC-ORD software program (McCune and Mefford 1999) and the results are presented as a cluster analyses.

RESULTS AND DISCUSSION

A total of 111 species were recorded in the five sites. Of the total number of species found in the sites, 20 were from the grass family (Poaceae) (Table 2). In terms of grass species composition, six grasses (Aristida junciformis, Eragrostis capensis, Eragrostis curvula, Sporobolus pectinatus, Trachypogon spicatus and Tristachya leucothrix) were present in all five sites. The remaining 91 species were from 32 families with the family Asteraceae having the highest prevalence in terms of species composition (25 species) while Cyperaceae and Fabaceae families both had seven species respectively which was observed to be the second highest species composition by a plant family (Table 3). Five species: Helichrysum acutatum, Helichrysum pilosellum, Tolpis capensis, Acalypha punctata and Hypoxis rigidula were found in all the sites (Table 3).

There was strong variation in taxonomic composition between study sites as shown in the cluster analysis (Figure 2) that indicated a clear response to the frequency of burning, selective grazing, stocking rate, and mixed proportion of herds. Across all sampling sites, Site 1 was the most dissimilar from all other sampling sites. Site 1 contained different assemblages of plant species to those sites under biennial burning as observed in the hierarchical cluster analysis results. This result is consistent with a study by Uyset et al. (2004). They observed frequently burned sites to contain different species assemblages from unburned sites in South African grasslands. The result of this study suggests that the flora of Site 1 represents a pool of fire- tolerant species. For instance, the adaptation of the genus Acalypha to disturbance prone environments such as fire may have accounted for the high percentage cover of Acalypha punctata on Site 1 since it was burned in spring 2007.

The genus Acalypha spp. is known to have the capacity to resprout from a rootstock with numerous new shoots developing after burning (Pywell et al., 2003). Pywell et al. (2003) consider heavy allocation to vegetative reproduction (e.g. ease of germination, short- life cycles, early flowering, and heavy allocation to reproduction) after burning as a trait associated with plants that tend to be good colonizers after disturbances and may explain the high percentage cover of Acalypha on Site 1 (Table 3).

The dissimilarity in species assemblages as observed in the hierarchical cluster analysis results found on the annually burned Site 1 from biennially burned sites (Sites 2 and 3) can also be attributed to the immediate grazing following burning in that this may have affected the phenological stages such as plant establishment, seed set and dispersal due to the sensitivity of some plants to grazing. Changes in vegetation species composition can be related to the phenological status of vegetation during grazing (O'Connor et al., 2004) which may have affected the species composition of Site 1 due to the immediate introduction of livestock following fire. Selective grazing from mixed herds due to their differences in dietary preferences may have accounted for the differences in grass species composition and percentage cover. Hardy et al. (1999) found selective grazing to cause an increase in the abundance of "wire" grasses such as A. junciformis, particularly in the Mesic Highveld grassland.

The dominance of A. junciformis in Site 5 can therefore be attributed to the complementary feeding behavior from mixed game herbivores that grazed within Site 5 which may have promoted selective grazing. This in turn may have resulted in the observed high percentage cover of low value grazing grasses such as A. junciformis in Site 5 (Table 2). The low cover class of T. triandra in Site 3 (Table 2) which was grazed by livestock can be attributed to the effect of different herds of livestock, particularly by sheep and cattle. Selective grazing by sheep, in addition to the ability to graze close to the ground, results in the shortening of grass tuft leaving the edges of tillers shorter and reducing their chances of survival compared to cattle that tend to graze less on grass tufts (Kirkman, 2002).

This reduces the successful establishment of tufted grasses such as T. triandra (Kirkman, 2002) which may account for the low percentage cover of T. triandra within Site 3 that was grazed by both cattle and sheep compared to Sites 1 and 2 which were only grazed by cattle.

Ecological status has often been used as a veld condition assessment tool in the Grassland Biome by determining the reaction of each grass species to different levels of disturbance, particularly from grazing. Sites that are dominated by decreaser grasses are often classified as well managed veld. The use of ecological status as a veld condition assessment tool can however, be regarded as overly simplistic based on the results of this study. Site 1 was observed to have a high percentage cover of decreaser grasses (Table 2) although it was found to be the worst form of management practice based on the outcome of the hierarchical cluster analysis results.

Hubbert et al. (2006) found areas in grazed land such as vleis and marshes, to be avoided by livestock during grazing and are also rarely consumed by fire. The Mesic Highveld Grassland has also been described as heterogeneous, characterized by differences in elevation and slope (Hardy et al., 1999; Mucina and Rutherford, 2006) which has resulted in a variation in floristic composition and pattern of growth and subsequent variation in utilization by livestock (Hardy et al., 1999). Hardy's view is supported by Jansen et al. (2001) who also found plant percentage cover in the Mesic Highveld Grassland to positively correlate with microhabitat, irrespective of grazing intensity, which is an indication that livestock avoid utilizing certain areas within the landscape.

The variation in plant utilization by livestock and consumption by fire may have accounted for the high percentage cover of decreaser grasses in Site 1 since the landscape was observed to be dominated by wet and rocky areas that may hae been avoided by livestock during grazing as well as fire during the spring 2007 burn. The dominance of Helictotrichon turgidulum and the high abundance of Setaria sphacelata var. sericea, both of which are decrease grasses on Site 1, (Table 2) may therefore attest to this view since both species prefer damp habitats such as vleis and marshes (van Oudtshoorn, 2006). In addition to habitat preference by grass species, grazing management may have also influenced the ecological status of grasses.

Everson (1999) found continuous grazing following burning to favor the establishment of increaser II grasses which may explain the frequent occurrence of increaser II species in all the sites (Table 2) as stock was introduced immediately following burning in all the sites. The use of ecological status as a method for veld condition assessment should be critically examined in order to ensure poor grassland management practices are not promoted based on our simplistic mode of assessment. The observed inconsistencies in the responses of grass species to this rigid ecological status classification of species based on their grazing response calls for a caution against the uncritical designation of species into groups. This study will therefore suggest that, grassland condition assessment take into consideration the niche preference

Table 1. Characteristics of study sites based on burning frequency and grazing intensity

Study###Stock###Frequency of burning###Grazing intensity

site###

1###Herbivores (Cattle)###Annual###Heavy

2###Herbivores (Cattle)###Biennial###Heavy

3###Herbivores (mixed proportion of cattle, goats and sheep)###No strict burning management regime###Heavy

4###Indigenous herbivores (Blesbok)###Biennial###Low

5###Indigenous herbivores (mixed proportion of Blesbok, Black###Biennial###Moderate

wildebeest, Zebra, Oribi, Grey redbuck and Reedbuck

Table 2. Grass species and their grazing value and ecological status for the different study sites.

Names of grass species###Grazing value###Ecological status###Grass species cover

###Site 1###Site 2###Site 3###Site 4###Site 5

Agrostis eriantha###Low###Increaser II grass###2###4###

Alloteropsis semialata###Average###Increaser I grass###5###

Andropogon appendiculatus###High###Decreaser grass###3###1###

Andropogon schirensis###Average###Increaser I grass###1###1###2###

Aristida junciformis###Low###Increaser III grass###4###5###3###4###6

Digitaria monodactyla###Average###Increaser II grass###3###4###

Elionurus muticus###Low###Increaser III grass###1###

Eragrostis capensis###Average###Increaser II grass###2###2###2###1###2

Eragrostis curvula###High###Increaser II grass###3###6###3###3###3

Eragrostis racemosa###Average###Increaser II grass###2###3###2###2

Helictotrichon turgidulum###Average###Decreaser grass###5###

Harpochlo afalx###Average###Increaser I grass###1###1###

Koeleria capensis###Low###Increaser II grass###1###1###2###1

Loudetia simplex###Average###Increaser I/II grass###5###4###4###5

Panicum natalensis###Low###Decreaser grass###3###3###

Setaria sphacelata###High###Decreaser grass###3###

Sporobolus pectinatus###Average###Increser II grass###3###4###2###2###1

Themeda triandra###High###Decreaser grass###3###4###2###6###

Trachypogon spicatus###Low###Increaser I grass###2###4###3###4###2

Tristachya leucothrix###Average###Increaser I grass###2###1###2###2###1

Conclusion: This study revealed that species assemblage on an annually burned site was completely dissimilar from biennially burned sites and was dominated by flora that is considered as fire-tolerant species. In contrast, the lack of fire or degree of rockiness or kloofs in some areas from burning in addition to regular burning of other areas contributed to the high species composition of communal land which was partially burned and ensured the presence of both fire-tolerant and fire-intolerant species. The study therefore suggests the partial burning or mosaic style of burning on grazed habitats as a mean of improving species composition. In addition, the effect of different game herbivores on species composition should be investigated due to the dissimilarity in species assemblage between mix proportion of herds and single herd grazed game sites. The use of ecological status as a method for grassland condition assessment should be critically re-examined.

Acknowledgments: We thank the farmers of the Dullstroom district who provided access to their farms and the management of VerlorenValei Nature Reserve for their support in the use of the reserve. We are also thankful to the staff of the South African National Biodiversity Institute's herbarium located in Pretoria, particularly Beate Sachse for her assistance in the identification of plants and Tshwane University of Technology for providing financial assistance.

REFERENCES

Acocks, J. P. H. (1953). Veld types of South Africa. 3rd ed. Mem Bot. Surv. S. Afr. No. 57. Botanical Research Institute. Department of Agriculture and Water Supply.

Afzal, J., M. A. Ullah, and M. Anwar, (2007). Assessing carrying capacity of Pabbi Hills Kharian Range. J. Anim. Pl. Sci. 17(1-2): 27-29.

Arshadullah, M., M. Anwar and Azim, A. 2009. Evaluation of various exotic grasses in semi-arid conditions of Pabbi Hills, Kharian Range. J. Anim. Pl. Sci. 19(2): 85-89.

Bond, W. J., F. I. Woodward, and G. F. Midgley (2005). The global distribution of ecosystems in a world without fire. New Phytol. 165: 525-538.

Bond, W. J. and J. E. Keeley (2005). Fire as a global 'herbivore': the ecology and evolutionof flammable ecosystems. Trends Ecol. Evol.20(7): 387-394.

Bray, J. R. and J. T. Curtis (1957). An ordination of the upland forest communities of southern Wisconsin. Ecol. Mono. 27: 325-449.

Bredenkamp, G., J. E. Granger, and N. van Rooyen (1996).Moist Sandy Highveld Grassland. In: Low, A. B. and A. G. Rebelo (eds.) Vegetation of South Africa, Lesotho and Swaziland. Department of Environmental Affairs and Tourism, Pretoria.

Everson, C. S. (1999). Veld burning. Veld burning in different vegetation types: Grassveld. In: Tainton, N. M. (ed.). Veld Management in South Africa. University of Natal Press, Pietermaritzburg. pp. 228-235.

Germishuizen, G. and N. L. Meyer (2003). Plants of southern Africa: an annotated checklist. Strelitzia 14. South African National Biodiversity Institute, Pretoria. Hardy, M. B., D. L. Barnes, A. Moore, and K. P.Kirkman (1999). The management of different types of veld: Sour grassveld. In: Tainton, N. M. (ed.). Veld Managementin South Africa. University of Natal Press, Pietermaritzburg. pp 280-333.

Hubbert, K. R., H. K. Preisler, P. M. Wohlgemuth, R. C. Graham, and M. G. Narog (2006). Prescribedburning effects on soil physical properties and soil water repellency in a steep chaparral water shed, southern California, USA. Geoderma1 30: 284 - 298.

Jansen, R., E. R. Robinson, R. M. Little and T. M. Crowe (2001). Habitat constraints limit thedistribution and population density of redwing francolin, Francolinus levaillantii, in the highland grassland of Mpumalanga province, South Africa. Afr. J. Ecol. 39: 146-155.

Kirkman, K. P. (2002). The influence of various types and frequencies of rest on the production and condition of sourveld grazed by sheep or cattle, 1. Proportional species composition. Afr. J. Range. For. Sci. 19: 55-62.

McCune, B. and M. J. Mefford (1999). PC-ORD Multivariate analysis of ecological data.Version 4. MjM software design, Oregon, USA.

Mucina, L. and M. C. Rutherford (2006).The Vegetation of South Africa, Lesotho and Swaziland. Strelitzia 19. South African National Biodiversity Institute, Pretoria. pp 349-436.

O'Connor, T. G., R. G. Uys, and A. G. Mills (2004).Ecological effects of fire-breaks in the montane grasslands of the southern Drakensberg, South Africa. Afr. J. Range. For. Sci. 21(1): 1-9.

Owen-Smith, N. and E. J. Danckwerts (1997) Herbivory. In: Cowling, R. M., D. M. Richardson and S. M. Pierce (eds). Vegetation of Southern Africa. Cambridge University Press, Cambridge, pp:397-420.

Owen-Smith, N. (1999). The animal factor in veld management. In: Tainton, N. M. (ed.). Veld Management in South Africa. University of Natal Press, Pietermaritzburg. pp 117-138.

Pywell, R. F., J. M. Bullock, D. B. Roy, L. Warman, K. J.Walker and P. Rothery (2003). Plant traits as predictors of performance in ecological restoration.J . Appl. Ecol. 40: 65-77.

Rethman, N. F. G. and G. D. Kotze (1986). Veld condition in the southeastern Transvaal and its effect on grazing intensity. J. Grassland Society of Southern Africa 3(4): 134-140.

Stohlgren, T. J., M. B. Falkner and L. D. Schell (1995). A Modified-Whittaker nested vegetation sampling method. Vegetatio 117:113-121.

Uys, R. G., W. J. Bond, T. M. Everson (2004). The effect of different fire regimes on plant diversity in southern African grasslands. Biol. Conserv. 118:489-499.

vanOudtshoorn, F.(2006). Guide to grasses of Southern Africa. 2nd ed. Briza Publications, Pretoria.

van Rooyen, N. (2002). Veld management in the savannas. In: Bothma, J. du. P. (ed.). Game ranch management 4th ed. Van Schaik Publishes, Pretoria. pp. 571-620.

Mushtaque, M., M. Ishaque and M. Ahmad alias Haji A. Bakhush (2010). Studies on growth behavior and herbage yield of fountain grass. Pakistan J. Sci. 62 (4): 238-242.
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