The University of Adelaide - Senna Populations, Koonamore Vegetation Monitoring Project

The TGB Osborn Vegetation Reserve (or Koonamore Vegetation Reserve (KVR)) is a protected area on Koonamore Station which has been fenced off from grazing since the mid 1920's. In 1925, Professor Theodore George Bentley (TGB) Osborn and his colleagues established a vegetation reserve by fencing off 400 ha of a badly overgrazed portion of the Koonamore station to study the process of recovery of vegetation in the arid zone of South Australia after the removal of grazing pressure. The fence was established to initially keep sheep and later also rabbits from the reserve and allow vegetation regeneration. The resulting long-term vegetation monitoring project at Koonamore is now over 80 years old, making it one of the longest-running monitoring series of its type in the world.; Reserve History: In the mid 1920's Professor TGB Osborn and his colleagues extended their interests in ecology and field physiology of vegetation to the arid zone of South Australia. In 1892 Dixon had warned the Royal Society of South Australia of serious degradation of the soils and vegetation resulting from pastoralism and other alien influences in the region. Equally important to the origin of KVR was the new theory of vegetation succession derived from North American work early in the century. Osborn was particularly concerned with the question as to whether overgrazing by domestic and feral herbivores would result in return of the original vegetation via recognisable 'seral' stages, or whether the changes were ?artificial, mere destructions and as such outside the ecologist's proper field?. Although the concepts of 'succession' and the scope of ecology have developed and changed much since that time, nevertheless it was interest in 'succession to climax' that gave the initial impetus to KVR and many other long-term vegetation studies from that time. The theory of vegetation succession gave rise to the permanent charted quadrat as a technique for observing vegetation change. An extensive series of permanent quadrats was set up on KVR and supplemented by a series of fixed photopoints, in order to pursue the first aim. Although some of these were allowed to lapse within five years, many others were sampled more or less regularly, some almost annually up to the present. Several early publications reviewing the progress of vegetation change resulted. Nothing was done towards the second aim but autecological and population dynamics studies are still being carried out, based on KVR and its records. The Bibliography contains a complete listing of research publications arising from work done on the Reserve. Much of the continuity of the earlier records is due to the efforts of Miss Constance Eardley, who while a lecturer in the Department of Botany, organised annual visits of students and staff to take records and maintain KVR. However, after 1950 the rate of sampling had begun to decline and in the mid 1960's ceased altogether for a period of several years. In the 1970's Dr Russell Sinclair reactivated the recording programme and also began a sustained effort at rabbit control. Although the Reserve was originally fenced with rabbit-proof netting, the rabbits were never eradicated and the population has fluctuated greatly with the seasons. Beginning in 1975, numbers have been kept very low by careful annual inspection and control. Since that time there has been marked seedling establishment of several tree and shrub species which showed little previous regeneration. The Reserve records now contain a history of the vegetation over 50 years without sheep grazing followed by over 30 years without significant grazing by either sheep or rabbits. Kangaroos and emus have never been excluded from the Reserve, as they can jump the fence, and their numbers vary with the seasons. The monitoring work at KVR and the curation of its records is continuing under the direction of Dr Sinclair. The Reserve is also used for post-graduate study and complements the arid-zone research interests of Environmental Biology at the Middleback Field Sation near Whyalla.; Site Description: The Reserve is located in the centre of Koonamore Station, a sheep-grazing lease 400 km north-east of Adelaide, South Australia (Lat. 32Âº07'S, Long. 139Âº20'E) in predominantly chenopod shrubland with mean annual rainfall of about 200mm. The area consists of a complex of low sand dunes alternating with sand plain and harder loam soils with travertine limestone on the intervening flats. The tree cover is a low open woodland formation. The sand dunes carry Acacia aneura (mulga), A. burkittii and Eremophila spp., the sand plain a dense stand of Casuarina pauper (blackoak, belah), and the harder loam soils a mixed community of Myoporum platycarpum (false sandalwood) and Alectryon oleifolius (bullock bush, rosewood). Understorey shrubs, which also form low chenopod shrubland communities in some areas, include Atriplex vesicaria (bladder saltbush), A. stipitata and Maireana sedifolia (bluebush). Numerous other chenopodiaceous shrubs also occur, and grass and ephemeral herb cover varies with the seasons. Several species of Senna, Eremophila and other shrubs also occur.; Monitoring activities: Some or all of the following monitoring activities are carried out during visits to the TGB Osborn Vegetation Reserve: Vegetation Quadrats, Photopoints, Senna Quadrat (Cassia Corner), Myoporum platycarpum Plants, Saltbush Transects, Senna Populations, Kangaroo Transects, Rabbit Activity Monitoring and Control.; Senna Populations: Many very young Senna seedlings were identified close to the Northern boundary of the TGB Osborn Vegetation Reserve, both inside and outside of the reserve in 1997. To study the effects of grazing on these seedlings outside the reserve, three populations were identified and measured to the north of the fence, and a fourth population just south of the fence, i.e. on the reserve. Different fencing treatments were applied to the plants outside the reserve fence. One was protected from sheep, the second from both sheep and rabbits, the third left unprotected. The population inside the reserve was assumed to be protected from all grazing by the reserve fence. Plants were given numbers, marked on roofing nails in the ground beside the plant, and mapped on chart cards.

Tags: Flora, Senna sp.
Organization: Terrestrial Ecosystem Research Network's Data Discovery