Abstract We investigated whether mass and morphological spatial patterns in plants possibly induced the development of enlarged soft mouth parts in especially megaherbivores. We used power functions and geometric principles to explore allometric relationships of both morphological and foraging characteristics of mammalian herbivores in the South African savannah, covering a body size range of more than three orders magnitude. Our results show that, although intradental mouth volume scaled to a power slightly less than one to body mass, actual bite volume, as measured in the field, scaled to body mass with a factor closer to 1.75. However, when including the volume added to intradental mouth volume by soft mouth parts, such as tongue and lips (or trunks in elephant), mouth volume scaled linearly with actual bite volume and in a similar fashion as actual bite volume to body size. Bite mass and bite leaf mass scaled linearly with body size. We conclude that these scaling relationships indicate that large herbivores use their enlarged soft mouth parts to not only increase bite volume and thereby bite mass, but also select soft plant parts and thereby increase the leaf mass fraction per bite.
A paralytic condition of farm stock in South West Africa, characterized by prominent neuronal and some mild extraneuronal pigmentation, is described. The distribution of the pigment, which was mainly located in the larger neurones of the brain and spinal cord, is given. Experimental evidence, obtained by feeding the plant, is presented that the condition is caused by Trachyandra laxa var. laxa. The histochemical features of the pigment proved to be compatible with a lipofuscin.
1. Scaling theory predicts that organisms respond to different scales of resource patchiness in relation to their own size. We tested the hypothesis that the scale of nutrient patchiness mediates resource partitioning between large trees and small grasses in a semi-arid savanna. 2. In a factorial field experiment, Colophospermum mopane trees and associated grasses were fertilized at either a fine or coarse scale of patchiness with nitrogen (N), phosphorus (P) or N + P. The growth of marked tree shoots, herbaceous biomass and leaf N and P concentrations were monitored for 2 years following fertilization. 3. Responses of trees were partly scale dependent. Tree leaf N concentration and shoot length relatively increased with fertilization at a coarse scale. Tree leaf mass decreased when P was supplied at a fine scale of patchiness, suggesting intensified grass competition. 4. Phosphorus fertilization increased leaf P concentrations more in grasses than trees, whereas N fertilization increased leaf N concentration moderately in both trees and grasses. Herbaceous above-ground biomass around focal trees was negatively correlated with tree size when fertilized with N, suggesting intensified tree competition. 5. Synthesis. Our results support the hypothesis that trees benefit more from nutrients supplied at a relatively coarse scale of patchiness. No direct responses of grasses to scale were detected. In trees, the scale effect was surpassed by the effect of sample year, when rainfall varied.
Abstract: Elephant are believed to be one of the main ecological drivers in the conversion of savanna woodlands to grassland. We assessed the impacts of elephant on large trees (≥5 m in height) in the southern section of the Kruger National Park. Tree dimensions and utilization by elephant were recorded for 3082 individual trees across 22 transects (average length of 3 km and 10 m wide). Sixty per cent of the trees exhibited elephant utilization and 4% were dead as a direct result of elephant foraging behaviour. Each height class of tree was utilized in proportion to abundance. However, the size of the tree and the species influenced the intensity of utilization and foraging approach. Sclerocarya birrea was actively selected for and experienced the highest proportional utilization (75% of all trees). Interestingly, the proportion of large trees that were utilized and pushed over increased with distance from permanent water, a result which has implications for the provision of water in the KNP. We conclude that mortality is likely to be driven by a combination of factors including fire, drought and disease, rather than the actions of elephant alone. Further investigation is also required regarding the role of senescence and episodic mortality.
Protected areas are under increasing threat from a range of external and internal pressures on biodiversity. With a primary mandate being the conservation of biodiversity, monitoring is an essential component of measuring the performance of protected areas. Here we present a framework for guiding the structure and development of a Biodiversity Monitoring System (BMS) for South African National Parks (SANParks). Monitoring activities in the organisation are currently unevenly distributed across parks, taxa and key concerns: they do not address the full array of biodiversity objectives, and have largely evolved in the absence of a coherent, overarching framework. The requirement for biodiversity monitoring in national parks is clearly specified in national legislation and international policy, as well as by SANParks’ own adaptive management philosophy. Several approaches available for categorising the multitude of monitoring requirements were considered in the development of the BMS, and 10 Biodiversity Monitoring Programmes (BMPs) were selected that provide broad coverage of higher-level biodiversity objectives of parks. A set of principles was adopted to guide the development of BMPs (currently underway), and data management, resource and capacity needs will be considered during their development. It is envisaged that the BMS will provide strategic direction for future investment in this core component of biodiversity conservation and management in SANParks. Conservation implications: Monitoring biodiversity in protected areas is essential to assessing their performance. Here we provide a coordinated framework for biodiversity monitoring in South African National Parks. The proposed biodiversity monitoring system addresses the broad range of park management plan derived biodiversity objectives.
In savannas, the tree-grass balance is governed by water, nutrients, fire and herbivory, and their interactions. We studied the hypothesis that herbivores indirectly affect vegetation structure by changing the availability of soil nutrients, which, in turn, alters the competition between trees and grasses. Nine abandoned livestock holding-pen areas (kraals), enriched by dung and urine, were contrasted with nearby control sites in a semi-arid savanna. About 40 years after abandonment, kraal sites still showed high soil concentrations of inorganic N, extractable P, K, Ca and Mg compared to controls. Kraals also had a high plant production potential and offered high quality forage. The intense grazing and high herbivore dung and urine deposition rates in kraals fit the accelerated nutrient cycling model described for fertile systems elsewhere. Data of a concurrent experiment also showed that bush-cleared patches resulted in an increase in impala dung deposition, probably because impala preferred open sites to avoid predation. Kraal sites had very low tree densities compared to control sites, thus the high impala dung deposition rates here may be in part driven by the open structure of kraal sites, which may explain the persistence of nutrients in kraals. Experiments indicated that tree seedlings were increasingly constrained when competing with grasses under fertile conditions, which might explain the low tree recruitment observed in kraals. In conclusion, large herbivores may indirectly keep existing nutrient hotspots such as abandoned kraals structurally open by maintaining a high local soil fertility, which, in turn, constrains woody recruitment in a negative feedback loop. The maintenance of nutrient hotspots such as abandoned kraals by herbivores contributes to the structural heterogeneity of nutrient-poor savanna vegetation.
Tourism is critical source of financing for conservation in Africa. South African National Parks (SANParks) raises in excess of 80% of their own funds through tourism revenue. SANParks has a culture of co-learning between scientists and conservation managers through a process known as strategic adaptive management (SAM). Despite the critical role that tourism plays in SANParks, it has, until recently, not been formally incorporated in the SAM process. Moreover, SANParks recently adopted a new responsible tourism policy to guide the development and management of tourism across all national parks. The new policy calls for tourism that supports biodiversity conservation, is environmentally efficient and socially responsible. In 2011, SANParks initiated a tourism research programme to support the incorporation of tourism in SAM and to provide enabling information for the implementation of the responsible tourism policy. This article summarised the development of the tourism research programme in SANParks and its key research themes. Conservation implications: An active tourism research programme that integrates science and management is necessary for tourism to play a stronger role in delivering outcomes for conservation, neighbouring communities and broader society.
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