The use of the land survey record to reconstruct pre-European vegetation patterns in the Darling Downs, Queensland, Australia
The Darling Downs is an extremely arable district in south eastern Queensland that has lost the majority of its native vegetation cover to agriculture. Vegetation references from land survey charts produced during the late 19th and early 20th century aided the reconstruction of the original vegetation patterns in the Darling Downs. Nearly 5000 references to vegetation were located for the study area and formed the basis of a vegetation map. The survey plans contain reference to seventy-three plant names which could generally be aligned to existing species, the majority of which are trees. The surveyors also referred to vegetation structure with terms such as ‘open’, ‘shrubby’ and ‘dense’. The ambiguous use of some references and the lack of adequate coverage of surveyor's charts for some sections of the study area did not allow for the production of an accurate and comprehensive map using the survey record in isolation. An iterative process evolved where (i) a working map of the vegetation was produced from the survey record; (ii) the map was ground-truthed with existing remnants and ambiguities in surveyors’ terminology clarified; (iii) for gaps in the record, hypotheses concerning eradicated vegetation were erected from knowledge of the environmental correlates of existing remnants; and (iv) these hypotheses were tested from areas where the survey record is comprehensive. Some vegetation types cannot be distinguished reliably on the basis of their physical environment and the distinction between these types for mapping was reliant on either the evidence from the survey record or remaining paddock trees. These processes enabled relatively accurate mapping of the pre-European vegetation of the study area at 1:100,000 scale. Comparison of the survey record and the vegetation of existing remnants suggests that overstorey composition and understorey density have changed little during European management within remnants.
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