There are several factors not investigated in the present study which could have influenced the riparianvegetation structure and composition of Gonarezhou major rivers. It is apparent that degraded sites of Save and Runde riparianareas have been also influenced by areas formerly disturbed by humans in Gonarezhou (O'Connor and Campbell, 1986; Gandiwa and Kativu, 2009; Mombeshora and Le Bel, 2009). The then resident people vacated these areas in 1968, because of the legislative removal of inhabitants from areas proclaimed as game sanctuaries (ZPWMA, 2011). Changes in plant structure in Gonarezhou riverine woodlands and mixed shrub woodlands during the dry season have been also attributed to termite activity (O'Connor and Campbell, 1986). Moreover, droughts have been noted as important in reducing the protective tree cover along river banks in Gonarezhou as a result of tree mortality (e.g., Tafangenyasha, 1997). However, in this present study, we recorded a relatively low density of dead plants in the riparianareas. Gonarezhou is located in the downstream of the south-easterly flowing rivers that drain Zimbabwe, and as a result, it is at risk of receiving adverse hydrological changes from upstream developments. The effects directly impact on the fauna and flora, for example, if large quantities of silt are transported downstream the river water pools inevitably disappear, and if water is not released from upstream impoundments the recharge in the rivers diminish with consequent loss in aquatic life and related degradation on floodplain vegetation.
Accepted 24 January, 2013
The objectives of this study were: i) to establish the status of woodyvegetation structure and composition, and ii) to determine the main factors influencing woodyvegetation structure and composition across GonarezhouNationalPark, Zimbabwe. We divided the park into three large strata based on natural and artificial features. A total of 137 sample plots were randomly placed to gather data on woodyvegetation in the three study strata across GonarezhouNationalPark from May to June 2011. Trees constituted 66% and shrubs 34% of the woody plants sampled. A total of 132 woody plant species were recorded. Significant differences were found in basal area, shrub density, browsed plants density and woody species diversity across GonarezhouNationalPark. In contrast, no significant differences were recorded in tree height, densities of trees, stems, dead plants and fire damaged plants. Our results suggest that there are some variations in woodyvegetation structure and composition across GonarezhouNationalPark. These variations could be attributed to both natural and anthropogenic disturbance factors including elephant (Loxodonta africana Blumenbach) browsing, fires, droughts and previous tsetse fly (Glossina spp.) (Diptera: Glossinidae) eradication activities in the park.
We investigated the structure and composition of Spirostachys africana woodlands in GonarezhouNationalPark (GNP), southeast Zimbabwe. We divided the GNP into three strata, namely northern, central and southern GNP, based on physical feature such as major perennial rivers. The main objective was to determine whether the structure and composition of S. africana woodlands varied across the GNP. In addition, we evaluated whether herbivory and fires played important roles in influencing the structure and composition of S. africana woodland stands. A stratified random sampling design was used and data were collected from a total of 60 sample plots. The following variables were recorded in each study plot: woody plant height, species name, plant status (alive or dead), fire or browse evidence and number of stems per plant. A total of 2,588 woody plants comprising of 73 woody species were recorded from the sampled S. africana woodlands in the GNP. Our results showed that woody species diversity, woody plant heights, shrub density, density of dead plants, sapling density, density of fire damaged plants, and number of stems per plant were significantly different across the S. africana woodlands in GNP. In contrast, only densities of trees and browsed plants did not differ significantly across the GNP. Most plots in the southern GNP had higher tree and sapling densities and taller trees whereas those in the northern GNP had higher densities of fire damaged plants. In addition, plots from central GNP were characterised with higher shrub densities of S. africana woodlands. Overall, our results suggest that there are both structural and compositional differences of S. africana woodland stands across the GNP. Evidence of herbivory did not differ significantly across the GNP suggesting that plants were uniformly affected by herbivores. However, fire evidence seemed to vary across the GNP, with areas having frequent fires being more degraded and having to some extent more woodyvegetation species diversity.
A One-Way ANOVA using STATISTICA statistical software with strata as categorical predictors and vegetation variables as dependent variables was performed to test the main effects of variables and strata (P-value at 0.05 significance level). For variables with significant differences, differences among means were tested using the Fisher Least Significant Difference (LSD) post-hoc tests to detect differences between the three soil categories. Data were further analyzed through a combination of classification and ordination techniques to explore the associations, patterns and structure of woodyvegetation across the three strata. A Principal Component Analysis (PCA) was used to define both the pattern and structure of variables  in the different strata using the vegetation variables. Hierarchical Cluster Analysis (HCA) using the weighted pair group average linkage method was performed using a matrix of 30 plots and 41 species, using the species abundance data to classify sampling plots on the basis of their floristic similarity.
Fully protected areas such as national parks are often assumed to be the best way to conserve biodiversity (Banda et al., 2006; Gaston et al., 2008). Interestingly, the present study results also revealed that Save-Runde Junction IBA which occurs inside a protected area had a higher species richness (59) and species diversity (H′ = 3.28) compared to Manjinji Pan IBA which had a species richness of 43 and a species diversity of 2.90. Similarly, Save-Runde Junction IBA had a higher number of bird species of special concern than Manjinji Pan IBA (Table 1). The lower woody plant species richness and diversity in Manjinji Pan IBA could be attributed to its relatively smaller area and isolation as compared to Save-Runde IBA (Fig. 1) and to the likely loss of woody plant species within the IBA. Loss of woody species in Manjinji Pan IBA could have resulted from targeted extraction of certain plant species for construction or firewood. Human influence has undoubtedly influenced the woodyvegetation structure and composition of several terrestrial ecosystems (Luoga et al., 2002; Gaugris and Van Rooyen, 2010). The present study results are consistent with those of Higgins et al. (1999) who also recorded lower species richness in woody communities occurring in communal land as compared to protected private game reserves in South African semi-arid savanna. In Save- Runde Junction IBA, the higher species richness and species diversity of woody plants could be a result of low current woody species extraction due to strict law enforcement inside GonarezhouNationalPark (Gandiwa et al., 2013).
The map introduced in this study represents the status of the vegetation structure in 2013–2014, thus representing a 20-year update in the park’s mapping, and encompasses HNP plus a 50 km buffer around it, to which safari areas, forest reserves, communal lands and research and conservation endeavours have expanded in the last decade. In addition, the map herein was subject to a statistical accuracy assessment, making it particularly suitable for analyses involving the modern geo data sets that come with positional precision estimates, such as Global Positioning System (GPS) telemetry, and which have been collected on a suite of species living in HNP over the last two decades. In addition to budgetary constraints, its production required overcoming challenges related to (1) difficulty of visiting remote areas on the ground, (2) marked differences in ground colour because of soil and fire and (3) asynchronicity in phenology. As explained earlier, we overcame these using free images, products and software. We believe that our procedure could be used for retrospective analyses of vegetation change in HNP and the production of future maps of the area, as well as for mapping similar classes of savanna vegetation structure within and around other protected areas. We hope the detailed information concerning the making of a vegetation structure map ‘from scratch’ provided here may represent a case study for practitioners with similar needs elsewhere.
The study results recorded no significant differences in shrub density, shrub ca- nopy volume and browsed plant density across the study strata (Table 1). This suggested presence of highly browsed woody plants and dominance of shrubs in some sections of northern GNP as reported by earlier studies   . However, this can impact positively to black rhinos feeding habits and pattern which are known as selective for woody plant species and size . The study highlighted a high shrub density across the study strata (Table 1). According to earlier studies  and , this is a key parameter of woodyvegetation struc- ture of importance to black rhino forage since mostly consumed shrubs are of a height below 2 m. The importance of woodyvegetation to black rhinos largely depends on the availability of preferred quality browse within the reach (plant height ≤ 2 m) of the rhinos . The synergy between the commonly reported fires and intense herbivory in GNP    will likely continue to contri- bute to the general modification of habitats, for example, reduced woody plant height and increased number of stems per plant, thereby, replacing woodlands with shrublands patches. This woodyvegetation structural change likely to prolife- rate and persist across northern GNP, given the recorded no significant difference in shrub density and shrub canopy volume across the study strata could contin- ue to set this section of the park as an ideal area for black rhino re-introduction.
that the presence of fire-resistant adult trees for many years buffers the system against frequent fires (Hanan et al. 2008). We recorded a high number of dead plants, mostly shrubs, in HFF sites, particularly in C. mopane woodland. Miller (2000) stated that plant mortality reflects the amount of meristematic tissues killed by heat. It is, however, suggested that high fire frequency is not responsible for the death of large trees as flame heights of a burning grass layer are usually low (Bond & Van Wilgen 1996). In savanna woody species, topkill is much more frequent than complete mortality after fire (Hoffmann & Solbrig 2003). Grass fire, instead, suppresses the recruitment of small individuals to the canopy layer (Bond & Van Wilgen 1996). It is possible that the high number of dead woody plants recorded in C. mopane woodland with increasing fire frequency may be a coincidence, as other factors may have interacted with fire, leading to an increase in woody plant deaths. However, it is also likely that the high number of dead plants, particularly small trees, recorded in C. mopane woodland may have resulted from the cumulative effects of fire over a long time. We attribute the large tree mortalities recorded in the RFF sites to droughts, old age and disease. Tafangenyasha (1998) reported a large drought- related tree dieback in the southeast lowveld of Zimbabwe associated with the 1991/92 drought. Other studies have associated woodland change in semi-arid savanna with fire and droughts (e.g. Fensham et al. 2003; Mosugelo et al. 2002). The present study suggests a link between fire frequency and basal area among woody plants in C. mopane woodland (see Figure 4). The decreasing basal area associated with increasing fire frequency is attributed to the high number of thin stems recorded in MFF and HFF sites that result from basal coppicing and high shrub densities. In contrast, high mean basal areas were observed in RFF sites. We attribute this to the existence of tall, huge and single-stemmed trees. Our observations are consistent with several other researchers’ findings (e.g. Enslin
exhibited on basalt (Pringle et al., 2010). Because of the general uniformity of the basalt landscape, the probability of mounds occupying at any point in space is high. Although topography is an important factor influencing the distribution of mounds (Davies et al., 2014a), in this extreme semi-arid savanna system, topography may not have an effect on the distribution of termites because even low lying areas are occupied by mounds due to low risk of water inundation (Levick et al., 2010). Furthermore, mounds occupied a much larger proportion of the landscape on granite (6%) relative to basalt (0.4%) showing that at the landscape scale, mounds on nutrient-poor geologies could have a significant effect on vegetation heterogeneity (Chapter 4). Due to the snapshot nature of this study, causes of patterns observed were mostly inferential; future studies should establish experiments where mechanisms can be determined. Ecological patterns are not static, but rather dynamic over time, hence I suggest the establishment of permanent plots where periodic assessments of recruitment of new mounds can be undertaken to better understand termite mound dynamics and inform direction for the conservation of termites and the important ecosystem roles they perform. Also, genetic tests of large and budded colonies can be carried out. Although the ecology of Macrotermes species is similar, further studies on the spatial distribution of mounds should seek to identify all the mounds to the level of the termite species, in order to establish mechanisms leading to the observed patterns. It is not only the termite species that need to be considered in ecosystem management and conservation, but also the mounds that they build because these can last for centuries, with several recolonisations, and thereby improve ecosystem heterogeneity and function.
experiences two contrasting seasons, a dry and wet season. It receives an average annual rainfall of approximately 466 mm (Gandiwa & Kativu, 2009). The study area is endowed with diverse flora and fauna. The dominant vegetation types are Colophospermum mopane shrubland or woodland, wooded and bushed grassland, dry deciduous woodland and riverine woodland (Martini et al., 2016). There is a wide variety of large herbivores in the study area and these include hippopotamus (Hippopotamus amphibious), African buffalo (Syncerus caffer), African elephant, giraffe (Giraffa camelopardalis), waterbuck (Kobus ellipsiprymnus), Burchell’s zebra (Equus quagga), kudu (Tragelaphus strepsiceros) and wildebeest (Connochaetes taurinus) (Gandiwa et al., 2013).
We classified the vegetation of GNP through the analysis of woody species composition. Woody plants represent one of the most distinguishing features of the vegetation in southern Africa (Germishuizen & Meyer 2003; O’Brien, Field & Whittaker 2000), and have been widely used for modelling vegetation structure and physiognomy in the region and elsewhere (Daru et al. 2015; Kubota et al. 2014; O’Brien 1993). A total of 330 relevés were conducted between March and July 2010 (Figure 2), following the methodology of Timberlake, Nobanda and Mapaure (1993). Sampling was targeted to distinct vegetation communities that were clearly recognisable on satellite imagery (Landsat and Google Earth) and/or in the field. A plotless method was used for each relevé, whereby all woody species present within an area of 0.5 ha – 2 ha were recorded and classified in five height classes: seedlings, less than 0.5 m (mainly regeneration), 0.5 m – 3 m (shrubs and young trees), trees taller than 3 m (tall shrubs and trees); and mature trees (canopy height trees). Each species was allocated to a cover-abundance value in each layer using a six-point modified Braun–Blanquet scale: + = < 2%, 1 = 2% – 10%, 2 = 11% – 25%, 3 = 26% – 50%, 4 = 51% – 75% and 5 = 76% – 100%. Any species that could not be reliably identified in the field was collected and later compared with the collection available at the National Herbarium in Harare.
breeding season for the study species. Thus, it is likely that we may have missed some of the African fish eagles’ nests, particularly the active nests, along the study rivers since our belt transects width were relatively small, i.e. only focusses on areas adjacent to the riverbanks. Furthermore, previous research in Gonarezhou has reported that vegetation close to rivers is generally negatively affected by elephant herbivory, hence reducing the densities of large trees along the study rivers (Tafangenyasha, 1997; Zisadza-Gandiwa et al., 2013b), and consequently leading to reduced nesting sites. Similarly, it is likely that past tsetse control clearing activities led to the removal of large trees along some section of the study rivers (Gandiwa and Kativu, 2009), thus affecting the present day nesting sites for the fish eagles. Given the level of present day human influence, Runde and Mwenezi rivers are less affected than Save River which borders the local communities, thus we infer that Runde and Mwenezi rivers have a healthier riparian system than Save River which borders local communal areas.
Although precipitation may be the primary determinant of vegetation biomass in dry savanna ecosystems (Deshmukh 1984; Prins and Loth 1988; Sankaran et al 2005), in GonarezhouNationalPark (hereafter, Gonarezhou), disturbances, such as herbivory, mainly from African elephant (Loxodonta africana ) herbivory on baobabs (Adansonia digitata), droughts, fires and human activities may also likely influence baobab woodlands (Tafangenyasha 1997; Mpofu et al 2012; Kupika et al 2014). Between the year 1980 and 2012, elephant population in Gonarezhou increased from approximately 4700 to 9125 (Dunham 2012). Taken with the results of other aerial elephant surveys conducted post 1992 drought, elephants in Gonarezhou have increased at a mean annual rate of 6% during the past sixteen years. Such a high elephant population annual rate with a
Key words: Aerial survey, Africa, conservation, encroachment, habitat, livestock,
Domestic livestock graze more than one third of the world’s land area, often sharing space and resources with native ungulates (de Haan et al. 1997). Free grazing by livestock in natural areas is known to affect natural vegetation and faunal communities in various ways (Cumming et al. 1997; Lambin et al. 2003; Shackleton et al. 2001; Steinfeld et al. 2006). Effects of livestock grazing vary from place to place depending upon their spatio-temporal use of habitat, abundance, niche overlap with wild ungulates and primary pro- ductivity. This issue has attracted attention of several researchers around the globe (Acebes et al. 2012; Bhatnagar et al. 2006; de Boer & Prins 1990; de Iongh et al. 2011; du Toit & Cumming 1999; Kittur et al. 2010; Odadi et al. 2011; Prins & Olff 1998; Walker 1993; Young et al. 2005). Direct competition for forage resources between domestic and wild herbivores can lead to changes in foraging behaviour and population dynamics of the latter (de Leeuw et al. 2001; Madhusudan 2004).
Two-thirds of the riparian communities are considered well- reserved, using the rather weak criterion of secure reservation in two or more spatially separated situations. Security of riparianvegetation in reserves is likely to depend partly on the degree and nature of up-catchment factors such as alteration to hydrological regimes, spread of exotic species, sedimentation and water quality. With six of the poorly- reserved or unreserved riparian communities, the conversion of one or two insecure reserves to secure reserves would put them in the well-reserved category. Community 12 is not known from any reserve at all, but there is potential for adequate reservation on land owned by the State government. In the present study sampling was restricted to native riparianvegetation in near natural condition. A significant proportion of Tasmania’s remaining native riparianvegetation remains unexplored, undocumented and, in many regions, unreserved and unmanaged. Significant community variation in riparianvegetation in mainland Tasmania has been established. However, there is a need to sample degraded riparianvegetation in gap areas, especially remnants of native riparianvegetation outside existing reserves, with some prioritization of their importance and likely persistence at different levels of management.
We have taken a much narrower view and the Grass lands of the study area are here considered to include only those areas where Restionaceae, Ericaceae and Pro- teaceae are totally absent. Campbell’s (1985) criteria for recognizing Grassland are difficult to use because of the gradual decrease of fynbos elements along the tran sition from Grassy Fynbos to Grassland. Our concept therefore includes only part of Campbell’s Hankey Grassland and seems to be identical to Lubke’s Setaria sphacelata Grassland. As such it is perhaps the most uni form vegetation unit of all and occurs mostly on steep northern and western slopes. What variation there is, appears to be the result of soil depth and rockiness. Some species (Acacia karroo, Diospyros lycioides and Aloe ferox for example) are restricted to deep soils on lower northern slopes, while succulents such as Euphor bia polygona are locally dominant only in very rocky areas.
Riparianareas provide many ecosystem ser- vices, such as flood prevention, nutrient cycling, carbon dioxide binding, sediment deposits, timber production, recreation and wildlife habitats [1, 2]. These areas, however, are undergoing extensive reductions and changes in their natural composi- tion into agricultural and urban areas , defor- estation , blockage of flow and industrial activ- ities . Riparian plant species are highly selec- tive in their habitat selection, as they are sensitive to changes in flood frequency and duration [5, 6, 7]. As floods have occurred, overbank deposition causes microtopographic variations along the floodplain, which in frequency will become exces- sive or deficient, thus affecting the composition of vegetation species [4, 5, 8, 9]. The relationship be- tween the vegetation distribution pattern and the riparian topography factor has been assumed to typically represent a biome-specific or vegetation- specific constant . However, most of the re-
Wildfires are a common feature of this area. High intensity wildfires burnt most of Warra NP in 1988, 1994 and 2001 though Wattleridge was not burnt by these fires. When Warra was managed by NSW State Forests, prescribed fire intervals were 3–5 years for plateau areas, 4–7 years for gorge country and more than 10 years for wetter areas at higher altitudes, though how diligently these regimes were adhered to, is not known. Grazing permits existed within Warra at various times while under State Forest management, and though most leases were only lightly grazed, burning to create ‘green pick’ for cattle, was an integral part of grazing practice. On much of the better grazing areas, on the more open and less rugged plateau areas, leaseholders probably kept low intensity fire frequency close to every three years.
Figure 5: Woody species diameter (a) and height (b) classes of Kafta-sheraro NationalPark The analysis of population structure of Kafta-sheraro nationalpark individual tree species in nine DBH classes dominantly showed eight patterns of population structure. First pattern consists of individual species concentrated only in the first DBH class (2.5-10cm) but absent in the rest classes and represented by Acacia mellifera (F.g.6a). Species in this group are Acacia senegal, Dalbergia melanoxylon, Acacia oerfota, Dicrostachy scinerea and Acacia seyal. Second pattern occupied both first (2.5-10cm) and second (10.1-20cm) DBH classes and represented by Combretum hartmannianum and Boswellia papyrifera (F.g.6b). Third pattern was an Inverted-J shaped in which the highest number of individuals was present in lower DBH classes and species Anogeissus leiocarpus only (F.g.6c). Fourth pattern was J-shaped in which a higher proportion of individuals were present at higher DBH classes and the trend decreased towards lower DBH classes. Species of this pattern was Ziziphus spina-christi and Tamarindus indica (F.g.6d). Fifth pattern was bell shaped in which a higher proportion of species were present in intermediate DBH classes and the trend decreased in lower and higher DBH classes. Species in this category were Balanites aegyptiaca and Terminalia brownii (F.g.6e). Sixth pattern occurred in the second DBH class (10.1-20cm) and the only representative species is Diospyros mespiliformis (F.g.6f). Seventh pattern shows irregular distribution over diameter classes. Some DBH classes had small number