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Invertebrate diversity in afrotemperate forests : spatial and seasonal changes and implications for conservation.Uys, Charmaine Janet. January 2006 (has links)
Forests in the Drakensberg Mountains, although generally small and fragmented, represent a wealth of globally significant biodiversity. This is especially true of the invertebrate fauna, which includes a range of localized endemic species. Ground dwelling, flightless invertebrates living in forests show relative immobility and poor dispersal abilities compared to birds, butterflies and other animal taxa. The naturally fragmented state of Afrotemperate forests also geographically isolates these taxa. No quantified, systematic surveys of flightless invertebrates have been conducted in Afrotemperate forests in the Drakensberg Mountains. This means that, to date, invertebrates have not been considered in the management of these habitats. However, invertebrates are vitally important in ecosystem functioning and maintenance and must be included in management plans. This study quantified flightless invertebrate diversity in Afrotemperate forest patches in the Drakensberg by investigating spatial patterns and seasonal changes in invertebrate diversity. The broad objectives were to: 1) Determine the appropriate spatial scale at which conservation of flightless invertebrates should be implemented; 2) Determine which season, taxa and sampling methods are most suitable for biodiversity assessment and monitoring in Afrotemperate forest; and 3) Investigate methods of prioritizing Afrotemperate forests for conservation of flightless invertebrate diversity. Seventeen forest patches in six valleys in four Drakensberg reserves (Rugged Glen Nature Reserve, Royal Natal National Park, Cathedral Peak and Injisuthi) were sampled in the summer of 2004/2005. In addition, three forests at Injisuthi were sampled in March, June, September and December 2004 to enable seasonal comparisons. Sampling methods included soil samples, leaf litter samples, pitfall traps, active search quadrats and tree beats. The study focused on terrestrial molluscs (Class Gastropoda), earthworms (Class Annelida), onychophorans (Class Onychophora), centipedes (Class Chilopoda), millipedes (Class Diplopoda) and ants (Class Insecta). Target taxa were sorted to morphospecies and then identified to species by taxonomic experts. Seventy-two species and a total of 5261 individual specimens from the six target taxa were collected. Species composition of sites varied along the north-south gradient, and species turnover (beta diversity) was related to the distance between sites. Flightless invertebrate species richness and community structure fluctuated seasonally. Therefore, I recommend that sampling should take place during the wet season (summer months). Molluscs were the most suitable taxon among those surveyed to represent flightless invertebrate diversity and leaf litter samples and active search quadrats are the most suitable sampling methods for flightless invertebrates in forest. This study compared approaches to prioritizing Afrotemperate forests in terms of their invertebrate diversity using ranked species richness with complementarity indices of species presence/absence, taxonomic distinctness (orders, families and genera) and endemicity. There was no consistent spatial trend in the priority ranking of forests based on species richness. Complementarity based on species richness only required eight out of 17 forests to represent all 62 species. Although complementarity based on taxonomic distinctness and endemicity required fewer sites, not all species were represented. The minimum set of sites identified using complementarity based on species richness and augmented with information on taxa of conservation importance (local endemic and threatened species) was the most rigorous approach to prioritizing Afrotemperate forest patches in the Drakensberg for flightless invertebrate conservation. Urgent conservation interventions are required because invertebrates play a critical role in ecosystem functioning. As many forest patches and invertebrate populations as possible should be protected to conserve the full complement of invertebrate species of the region. Special management attention should be paid to the eight forests identified as priority sites in the complementarity analyses. Forest patches cannot survive in isolation, so it is important to manage the grassland, riverine vegetation, forest ecotone and forests holistically. Provisional targets were set for the conservation of flightless invertebrates, based on estimates of the requirements for persistence of invertebrates in Afrotemperate forest, made within the constraints of available information and expert opinion. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
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The effect of burning frequency on invertebrate and indigenous flowering forb diversity in a Drakensberg grassland ecosystem.Arnott, Wendy Lynn. January 2006 (has links)
The KwaZulu-Natal Drakensberg, South Africa, is predominantly a grassland ecosystem maintained by fire. The effect of the current burning regime on invertebrate and flowering forb diversity in this ecosystem is poorly understood. The overall aim ofthis study was to contribute towards the development of an effective burning regime for the KwaZulu-Natal Drakensberg that will conserve invertebrates and indigenous forbs, two major components of biodiversity. The objectives were to examine the effect of fire and fire frequency on flowering forb and invertebrate species diversity, to determine whether fire frequency, time since last burn or locality were influencing species composition, and to identify potential biodiversity indicators that reflect overall species richness for use in monitoring of invertebrates and forbs. Sampling took place in March, September and November of 2002 at Giants Castle Game Reserve. Invertebrates were sampled using sweep netting and targeted netting along transects, yellow pan traps and soil quadrats. Invertebrate taxa sampled were ants (Formicidae), butterflies (Lepidoptera), grasshoppers (Orthoptera), leafboppers (Cicadellidae), bees (Apoidea), bee flies (Bombyliidae), hover flies (Syrphidae), robber flies (Asilidae), spiders (Araneae), earthworms (Oligochaeta) and millipedes (Diploda). These were identified to species level with the assistance of taxon experts. Flowering forbs were sampled using five replicates of five by five metre quadrats randomly placed in each site. Overall flowering forb and invertebrate species diversity was higher in grasslands that were burnt for two consecutive years in 2001 and 2002 than in grasslands that were not burnt during those two years. Frequently (annual) and intermediately (biennial) burnt grasslands had significantly higher invertebrate and flowering forb diversity than infrequently (five years without burning) burnt grasslands. This, together with the fact that grasslands burnt during the year of sampling had higher species richness than grasslands burnt two and five years previously suggests that invertebrates and forbs are generally resilient to fire and many forb species appear to be stimulated by fire. However, each burn frequency had its own suite of unique flowering forb and invertebrate species. Invertebrate communities were influenced mostly by locality and the length of time past since the last fire and flowering forb communities were influenced mostly by the length oftime past since the last fire. Fire frequency had the least influence on both invertebrate and forb communities. Ecological succession occurred after each fire in the invertebrate communities but forb communities appear to need more than five years without fire for ecological succession to occur. The findings of this study therefore suggest that using a combination of three fire frequencies would result in patches of grassland in various stages of ecological succession, and would conserve species unique to each burning frequency, and would therefore conserve maximum diversity. Flowering forb species richness and certain invertebrate taxa (ants, leafboppers, spiders and bees) have the potential to act as indicators of overall invertebrate species richness for use in monitoring programmes. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
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