20th century works for viola/violin and orchestra ; herbert kegel legendary recordings ; vol.5 - Muziekweb
20th century works for viola/violin and orchestra ; herbert kegel legendary recordings ; vol.5
Davia Binder (altviool)
Györgi Garay (viool)
Stuk voor altviool en orkest, "Gedicht", 1962 Volume 29, Issue 4, 2010
Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Volume 29, Issue 4, December 2010
Volume 29, Issue 4, December 2010
Verspreiding en habitats van Unio caffer Krauss, 1848 (Bivalvia: Unionoida: Unionidae) in Suid-Afrika gebaseer op die rekords in die databasis van die Nasionale Varswaterslakversameling : navorsings- en oorsigartikels
Authors: Kenne De Kock and Corrie Wolmarans
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 29, pp 173 –185 (2010)
Die kosmopolities-verspreide Unionoida bereik hul grootste diversiteit in Noord-Amerika. In Suid-Afrika word twee genera van die familie Unionidae, naamlik Unio en Coelatura wat vier spesies insluit, aangetref. Hierdie artikel handel oor die verspreiding en habitats van Unio caffer Krauss, 1848 gebaseer op die rekords in die Nasionale Varswaterslakversameling (NVWSV) van Suid-Afrika. Alhoewel dit elders in Suid-Afrika sporadies aangetref is, is die Wes-Kaap die enigste provinsie waarvan geen monster op rekord in die databasis van die NVWSV is nie. Van die 58 monsters wat op rekord is, is die meerderheid in riviere (32.8%) en damme (20.7%) versamel en in watertoestande wat as standhoudend, staande, helder en vars beskryf is. 'n Temperatuur-indeks wat vir hierdie spesie bereken is, het dit vyfde in rangorde geplaas van die 12 Bivalvia-spesies wat in die databasis verteenwoordig word op grond van 'n assosiasie met lae omgewingstemperature. 'n Besluitnemingsboom-analise het aangedui dat temperatuur, substratum en waterbronne die mees betekenisvolle bydrae gelewer het tot die daarstelling van die gedokumenteerde geografi ese verspreiding van U. caffer. Omdat omvattende opnames van varswater Mollusca deur staatsinstansies reeds in die tagtigerjare van die vorige eeu uitgefaseer is en die meerderheid versamelpunte sedertdien nie weer gemonster is nie, is kennis oor hul huidige stand van bewaring en spesiediversiteit gebrekkig. Negatiewe resultate by drie voormalige lokaliteite van U. caffer wat wel intussen deur die outeurs besoek is, dui egter daarop dat die voortbestaan daarvan, soos van sommige verwante spesies elders in die wêreld, bedreig word. Dit word bepleit dat opnames van varswater Mollusca met die gedokumenteerde verspreiding in die databasis van die NVWSV as riglyn, beplan en uitgevoer behoort te word. Die resultate van sulke opnames behoort 'n groot bydrae te lewer om die huidige stand van die verspreiding en spesiediversiteit van die varswater Mollusca van Suid-Afrika sinvol te evalueer.
Distribution and habitats of Unio caffer Krauss, 1848 (Bivalvia: Unionoida: Unionidae) in South Africa based on the records in the database of the National Freshwater Snail Collection
The distribution of the Unionoida is almost cosmopolitan and reaches its greatest diversity in North America with 860 currently recognized valid species. Two genera of the family Unionidae,Unio and Coelatura, comprising four species, occur in South Africa. This article focuses on the distribution and habitats of Unio caffer Krauss, 1848 based on the records in the database of the National Freshwater Snail Collection (NFSC) of South Africa. This bivalve is considered to be endemic to South Africa and although it was sporadically reported from elsewhere in South Africa, the Western Cape is the only province from which no samples are on record in the database of the NFSC. The majority of the 58 samples on record was recovered from rivers (32.8%) and dams (20.7%) and from water conditions described as perennial, clear and fresh and 22 of the samples were collected in water bodies with a predominantly sandy substratum. A temperature index calculated for this species ranked it in fifth position of the 12 bivalve species represented in the database on account of its association with low climatic temperatures. An integrated decision-tree analysis indicated that temperature, substratum and water bodies per se were the most important factors of those investigated that played a significant role in establishing the geographical distribution of this species in South Africa. Comprehensive surveys for freshwater molluscs conducted by state and local health authorities were discontinued during the eighties of the previous century and the majority of sampling sites have not been revisited since. Therefore hardly any recent data pertaining to the conservation status and species diversity of the mollusc fauna of South Africa are available. However, during relatively recent surveys conducted by the authors at three previously positive sites for U. caffer no specimens of this species could be recovered and it is also reported in literature that its range in the south-western Cape has decreased in recent years. With regard to its conservation status, the above findings seem to suggest that U. caffer should at least be considered as vulnerable - if not endangered - as reported for some related species elsewhere in the world. Although speculative, several reasons are suggested to explain the global phenomenon of decline in freshwater bivalves. These include, amongst others, construction of impoundments, introduction of alien species, wetland drainage and canalization and pollution. However, the unique lifecycle of the Unionoida could also play an important role in this respect due to the fact that their larval stages are obligatory parasites on fish. These bivalves are therefore dependent on fish for their survival and dispersal and without their host fish populations will disappear. To sustain a viable population a water body should therefore be suitable not only for the bivalves themselves but also for their host fish. As mentioned earlier, the majority of samples of U. caffer were recovered from dams and rivers, water body types both under pressure of over exploitation and pollution. It is therefore recommended that thorough surveys should be planned and conducted in specific areas which could be selected with the documented geographical distribution in the database of the NFSC as guideline. A comparison of the results of such surveys with the data in the database of the NFSC could make a considerable contribution towards assessing the current conservation status and diversity of the freshwater molluscs of South Africa.
Belangrike faktore vir die keuse van ekotipe spesies vir veldherstelbehandeling : navorsings- en oorsigartikels
Authors: Loraine Van den Berg and Klaus Kellner
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 29, pp 186 –195 (2010)
Die tipe veldherstelbehandeling wat gebruik word in gedegradeerde weivelde hang van die graad van agteruitgang af. Gedegradeerde areas wat reeds verby die drumpel van natuurlike herstel is, benodig gewoonlik aktiewe ingryping. Dit sluit die versteuring van die grondoppervlak of die verwydering van ongewenste en uitheemse spesies wat kompeteer met bestaande plantegroei, in. Een van die hoofdoelwitte van veldherstel is die verhoging van weidingskapasiteit vir veeproduksie. Daar word aanbeveel dat veldherstel die hersaai van plaaslike ekotipe spesies, wat by spesifi eke grond- en klimaatstoestande aangepas is, insluit. Om saadontkieming en saailingvestiging te fasiliteer, moet 'n vorm van beskerming, soos die pak van takke of enige bedekking met organiese materiaal, ingesluit word. Die tyd van hersaai is afhanklik van die seisoenaliteit en reënval, veral in areas waar reënval onvoorspelbaar en ongereeld is. Verder is die hersaai van groot gedegradeerde areas met spesifieke ekotipe spesies grootliks afhanklik van die beskikbaarheid van saad. Dit is 'n belangrike beperkende faktor. Meeste saad, wat in die handel by saadmaatskappye in groot hoeveelhede beskikbaar is, word vir aangeplante weiding gebruik. Hierdie saad is gewoonlik nie van plaaslike ekotipe spesies, wat vir 'n sekere habitat aangepas is nie. Dit is gewoonlik nie koste- en arbeidseffektief om groot hoeveelhede saad van 'n spesifieke habitat te versamel nie. Die kwaliteit, kiemkragtigheid en suiwerheid van versamelde saad is ook gewoonlik baie laag. Dit kan lei tot swak resultate. Alhoewel die ekonomiese aspek en korttermyn resultate van veldherstel beskou word as 'n bepalende faktor, kan die ekologiese belangrikheid van die verbetering van veldkondisie nie uit die oog verloor word nie. Veldherstel moet uitgevoer word volgens 'n vooropgestelde plan en moet aspekte soos monitering en goeie bestuurspraktyke oor die langtermyn insluit.
Important factors for local ecotype selection in restoration applications
The type of restoration application in degraded natural rangelands will depend on the degree of degradation. Degraded areas that are beyond the threshold of natural recovery normally need active restoration interventions. This includes the disturbance of the soil surface or the removal of undesired and alien species to reduce the competitive effect on the existing vegetation. One of the main goals of restoration in degraded arid and semi-arid rangelands is to increase the grazing capacity for livestock production. Active restoration interventions include re-seeding or revegetation with local ecotype selected species, adapted to the specific soil and climatic conditions of the area. To facilitate seed germination and seedling establishment, the restoration practice should also include protection measures such as brush packing or any cover by other organic matter. The timing of re-seeding is dependent on the seasonality and precipitation, especially in areas where rainfall events are erratic and unpredictable. Re-seeding of large degraded areas with specific ecotype selected species greatly depends on the availability of seed. This is a major limiting factor as most seed available from seed merchants are used for cultivated pastures, and do not include seed of local ecotype species that are adapted to a certain environment. To collect large quantities of seed represented by a specific habitat is very labor intensive and often not cost effective. Furthermore, if local ecotype selected seed is used, the quality, viability and purity are often not of a high standard, leading to poor restoration results. Although the economic implication and short term results of a restoration application are often regarded as determining factors, the ecological importance and improvement in the range condition should not be underestimated. Restoration applications have to be implemented according to a predetermined plan and should include monitoring and sound long-term management principles.
Biologie-opsommings, 2009 : referate
Source: Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie 29, pp 197 –230 (2010)
Die suurstofverbruikskoers van eiers en die vermivorme lewenstadia van die rondewurm, Pratylenchus zeae (Graham, 1951) tydens pre- en post-anhidrobiose
'n Studie van die insekte van die oewer van die Tweelopiespruit in die Krugersdorp Natuurreservaat
Die invertebraat-gemeenskapstruktuur van rietpanne op die Mpumalanga Hoëveld - nog 'n unieke ekosisteem wat uitsterwing in die gesig staar?
Aspekte van paring by Argulus japonicus
Die biomagnifikasie van kwik in 'n akwatiese ekosisteem
Inseketende vlermuise en vlermuishuise in landbougebiede
Plantegroeiklassifikasie in die voorgestelde Heritage Park, Noordwes Provinsie, Suid-Afrika
Veranderinge in die antioksidantmetabolisme en fotosintese vermoë van Canolaplante (Brassica napus L.) in reaksie tot begassing met swaeldioksied
Die effek van silikon tot fosfaatverhoudings op die groei en lipiedproduksie van twee inheemse diatome
Die uitwerking wat SO2-besoedeling het op canolaplante
Die antimikrobiese vatbaarheid van die middelderm-bakterieë van die mieliestamboorder, Busseola fusca (Lepidoptera: Noctuidae)
Vergelyking van gesondheidsrisikofaktore tussen 'n stedelike en 'n plattelandse bevolking
Oefening, werksverrigting en sportvisietoetsing onder meer realistiese toetsingsomstandighede
Die invloed van 'n gewigsverlies-oefenprogram en dieet op die liggaamsamestelling van oorgewig vroue
Die invloed van 'n oefenprogram en dieet op liggaamsamestelling van mans
Die benutting van erdwurms om die effek van goudmynbedrywighede op die omgewing te bepaal