Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in ...Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in structure and species composition, are dominant along these river banks: Aquatic vegetation, Wetbanks, Palmiet, Scrub, Forest and Shrubland(Fynbos). The study aims to correlate the vegetation patterns to flooding patterns, in particular the inundation frequency and stream power. A problem arises: because these catchments are ungauged, like most mountain catchments, with the only weirs at the downstream end of the catchment. Discharge data at the weirs are extrapolated to the sites upstream by multiplication with a factor based on the size of the subcatchment that drains through a sample site. In this way, recurrence intervals for floods in mountain streams are derived. Discharges at sites are also calculated using bed roughness(Manning's n) and slope in straight sections with uniform flow conditions. Stream power is derived from the discharges calculated in this manner. The combination of stream power and recurrence intervals explains the occurrence of most vegetation types occurring on the banks, except for one type: Afromontane Forest. This type is probably more dependent on other factors, such as protection from fire and the depth of the groundwater table.展开更多
The assessment of the policy framework governing Invasive Alien Species(IAS) control is of critical importance in conservation. The undertaking of a SWOT analysis of such a framework is necessary because it enhances t...The assessment of the policy framework governing Invasive Alien Species(IAS) control is of critical importance in conservation. The undertaking of a SWOT analysis of such a framework is necessary because it enhances the efficacy of IAS control. The aim of this study is to carry out a SWOT analysis of the policy framework guiding the control of the spreading of Acacia mearnsii and other IAS in the Golden Gate Highlands National Park in South Africa,as well as the implementation of restorative measures in the park and adjacent communities in line with the recommendations of the Convention on Biodiversity. A comparative analysis of this framework and the hierarchical framework that was developed during the European Union Conference on Freshwater Invasives- Networking for Strategy in 2013 is undertaken. The results indicate the need to strengthen parkcommunity relations,upgrade existing legislation,and boost the technical capacity of South African national parks to identify,detect,monitor and predict IAS invasions,both within the parks and their surroundings. This knowledge is important for developing future policies on IAS control in South Africa.展开更多
Morphometric studies of 3D micro CT-scanned images can provide insights into the evolution of the brain and sensory structures but such data are still scarce for the most diverse mammalian order of rodents.From review...Morphometric studies of 3D micro CT-scanned images can provide insights into the evolution of the brain and sensory structures but such data are still scarce for the most diverse mammalian order of rodents.From reviewed and new data,we tested for convergence to extreme aridity and high elevation in the sensory and brain morphology of rodents,from morphometric data from micro-CT X-ray scans of 174 crania of 16 species of three distantly re-lated African murid(soft-furred mice,Praomyini,laminate-toothed rats,Otomyini,and gerbils,Gerbillinae)clades and one North American cricetid(deer mice and white-footed mice,Peromyscus)clade.Recent studies demon-strated convergent evolution acting on the oval window area of the cochlea(enlarged in extremely arid-adapted species of Otomyini and Gerbillinae)and on endocranial volume(reduced in high elevation taxa of Otomyini and Peromyscus).However,contrary to our predictions,we did notfind evidence of convergence in brain struc-ture to aridity,or in the olfactory/respiratory system(turbinate bones)to high elevation.Brain structure differed,particularly in the petrosal lobules of the cerebellum and the olfactory bulbs,between Otomyini and Gerbillinae,with extreme arid-adapted species in each clade being highly divergent(not convergent)from other species in the same clade.We observed greater“packing”of the maxillary turbinate bones,which have important respiratory functions,in Peromyscus mice from high and low elevations compared to the high-elevation African Praomyini,but more complex patterns within Peromyscus,probably related to trade-offs in respiratory physiology and heat exchange in the nasal epithelium associated with high-elevation adaptation.展开更多
Terrestrial and aquatic ecosystems are increasingly threatened by pesticide pollution resulting from extensive use of pes-ticides,and due to the lack of regulatory measures in the developing world,there is a need for ...Terrestrial and aquatic ecosystems are increasingly threatened by pesticide pollution resulting from extensive use of pes-ticides,and due to the lack of regulatory measures in the developing world,there is a need for affordable means to lessen environmental effects.This study aimed to investigate the impact of biochar amendment on the toxicity of imidacloprid to life-cycle parameters and biomarker responses of the earthworm Eisenia fetida.E.fetida was exposed to 10%biochar-amended and non-amended OECD artificial soils spiked with 0,0.75,1.5,2.25 and 3 mg imidacloprid/kg for 28 days.An LC50 of 2.7 mg/kg was only computed in the non-amended soil but not in the biochar-amended soil due to insignificant mortality.The EC50 calculated in the non-amended soil(0.92 mg/kg)for reproduction(fertility)was lower than the one computed in the biochar amended(0.98 mg/kg),indicating a decrease in toxicity in the biochar-amended substrate.Significant weight loss was observed at the two highest imidacloprid treatments in the non-amended soil and only at the highest treatment in the biochar-amended substrate,further highlighting the beneficial effects of biochar.Catalase activity decreased significantly at the two highest concentrations of non-amended soil.Yet,in the amended soil,the activity remained high,especially in the highest concentration,where it was significantly higher than the controls.This indicated more severe oxidative stress in the absence of biochar.In all non-amended treatments,there was a significant acetylcholinesterase inhibition,while lower inhibition percentages were observed in the biochar-amended soil.In most endpoints,the addition of biochar alleviated the toxic effects of imidacloprid,which shows that biochar has the potential to be useful in soil remediation.However,there is still a need for field studies to identify the most effective application rate of biochar for land application.展开更多
基金supported by funding from the National Research Foundation to C. Boucher and the VSB Funds (the Netherlands) to E. Siebenadditional funding from the Water Research Commission
文摘Zonation patterns of riparian vegetation have been sampled and described in mountain streams in two catchments in the Hottentots-Holland Mountains, Western Cape, South Africa. Six main vegetation types that differ in structure and species composition, are dominant along these river banks: Aquatic vegetation, Wetbanks, Palmiet, Scrub, Forest and Shrubland(Fynbos). The study aims to correlate the vegetation patterns to flooding patterns, in particular the inundation frequency and stream power. A problem arises: because these catchments are ungauged, like most mountain catchments, with the only weirs at the downstream end of the catchment. Discharge data at the weirs are extrapolated to the sites upstream by multiplication with a factor based on the size of the subcatchment that drains through a sample site. In this way, recurrence intervals for floods in mountain streams are derived. Discharges at sites are also calculated using bed roughness(Manning's n) and slope in straight sections with uniform flow conditions. Stream power is derived from the discharges calculated in this manner. The combination of stream power and recurrence intervals explains the occurrence of most vegetation types occurring on the banks, except for one type: Afromontane Forest. This type is probably more dependent on other factors, such as protection from fire and the depth of the groundwater table.
基金the Afromontane Research Unit (ARU) for providing financial support for this study
文摘The assessment of the policy framework governing Invasive Alien Species(IAS) control is of critical importance in conservation. The undertaking of a SWOT analysis of such a framework is necessary because it enhances the efficacy of IAS control. The aim of this study is to carry out a SWOT analysis of the policy framework guiding the control of the spreading of Acacia mearnsii and other IAS in the Golden Gate Highlands National Park in South Africa,as well as the implementation of restorative measures in the park and adjacent communities in line with the recommendations of the Convention on Biodiversity. A comparative analysis of this framework and the hierarchical framework that was developed during the European Union Conference on Freshwater Invasives- Networking for Strategy in 2013 is undertaken. The results indicate the need to strengthen parkcommunity relations,upgrade existing legislation,and boost the technical capacity of South African national parks to identify,detect,monitor and predict IAS invasions,both within the parks and their surroundings. This knowledge is important for developing future policies on IAS control in South Africa.
文摘Morphometric studies of 3D micro CT-scanned images can provide insights into the evolution of the brain and sensory structures but such data are still scarce for the most diverse mammalian order of rodents.From reviewed and new data,we tested for convergence to extreme aridity and high elevation in the sensory and brain morphology of rodents,from morphometric data from micro-CT X-ray scans of 174 crania of 16 species of three distantly re-lated African murid(soft-furred mice,Praomyini,laminate-toothed rats,Otomyini,and gerbils,Gerbillinae)clades and one North American cricetid(deer mice and white-footed mice,Peromyscus)clade.Recent studies demon-strated convergent evolution acting on the oval window area of the cochlea(enlarged in extremely arid-adapted species of Otomyini and Gerbillinae)and on endocranial volume(reduced in high elevation taxa of Otomyini and Peromyscus).However,contrary to our predictions,we did notfind evidence of convergence in brain struc-ture to aridity,or in the olfactory/respiratory system(turbinate bones)to high elevation.Brain structure differed,particularly in the petrosal lobules of the cerebellum and the olfactory bulbs,between Otomyini and Gerbillinae,with extreme arid-adapted species in each clade being highly divergent(not convergent)from other species in the same clade.We observed greater“packing”of the maxillary turbinate bones,which have important respiratory functions,in Peromyscus mice from high and low elevations compared to the high-elevation African Praomyini,but more complex patterns within Peromyscus,probably related to trade-offs in respiratory physiology and heat exchange in the nasal epithelium associated with high-elevation adaptation.
基金The financial assistance of the National Research Foundation(NRF)of South Africa(grant number SFH160619172260)to Ngitheni Nyoka is hereby acknowledged.Opinions expressed and conclusions arrived at are those of the authors and are not necessary to be attributed to the NRF.
文摘Terrestrial and aquatic ecosystems are increasingly threatened by pesticide pollution resulting from extensive use of pes-ticides,and due to the lack of regulatory measures in the developing world,there is a need for affordable means to lessen environmental effects.This study aimed to investigate the impact of biochar amendment on the toxicity of imidacloprid to life-cycle parameters and biomarker responses of the earthworm Eisenia fetida.E.fetida was exposed to 10%biochar-amended and non-amended OECD artificial soils spiked with 0,0.75,1.5,2.25 and 3 mg imidacloprid/kg for 28 days.An LC50 of 2.7 mg/kg was only computed in the non-amended soil but not in the biochar-amended soil due to insignificant mortality.The EC50 calculated in the non-amended soil(0.92 mg/kg)for reproduction(fertility)was lower than the one computed in the biochar amended(0.98 mg/kg),indicating a decrease in toxicity in the biochar-amended substrate.Significant weight loss was observed at the two highest imidacloprid treatments in the non-amended soil and only at the highest treatment in the biochar-amended substrate,further highlighting the beneficial effects of biochar.Catalase activity decreased significantly at the two highest concentrations of non-amended soil.Yet,in the amended soil,the activity remained high,especially in the highest concentration,where it was significantly higher than the controls.This indicated more severe oxidative stress in the absence of biochar.In all non-amended treatments,there was a significant acetylcholinesterase inhibition,while lower inhibition percentages were observed in the biochar-amended soil.In most endpoints,the addition of biochar alleviated the toxic effects of imidacloprid,which shows that biochar has the potential to be useful in soil remediation.However,there is still a need for field studies to identify the most effective application rate of biochar for land application.
