St Johns Brook conservation park biological survey
St Johns Brook Conservation Park occupies a strip of land about 2 km wide straddling St John Brook, extending 17 km to the north from the Brook's confluence with the Blackwood River.
The location of the Park at the contact between the northern jarrah forest, the southern jarrah forest and the Donnybrook Sunklands means that it possesses aspects of the flora and fauna of all these areas. Examination of indicator plant species from these three areas shows that the reserve has a greater similarity with the southern jarrah forest than with other areas. Although technically within the Sunklands, the physiography of the Park is more similar to areas further north than to the sunklands themselves.
There are few features about the Park which are unique when it is compared with other areas- it seems to be fairly typical southern jarrah forest. The flora is relatively rich with over 288 vascular plant species recorded. One of these, Aponogeton hexatepalus is gazetted as rare and endangered. In common with most other jarrah forests, ground dwelling vertebrates were not particularly abundant or diverse. Twelve mammal species were recorded (most from scat analysis), while there were 6 reptiles and 4 amphibian species also sighted or trapped. Birds were more diverse with 38 species.
Considerable attention was paid to the Brook itself and to wetlands near the Brook. At the time of the year when the survey was conducted (Spring) the water flow in the Brook was high and the swamps were inundated. Water chemistry samples showed the Brook and wetlands to be fresh and not eutrophic. This was in contrast to the Blackwood River which had quite high levels of dissolved salts.
The invertebrate faunas of the wetlands and Brook were understandably different. However, both were rich and dense. There were four species of fish recorded in the Brook, all of widespread occurrence. Although no special attention was devoted to censusing marron in the Brook, the capture of large numbers of juveniles indicates that the population is in a very healthy state.
Within parts of the Park (as in most other areas of jarrah forest) there is evidence of dieback. However, at present this does not seem to be a serious problem. In the south Acacia dealbata is becoming a serious weed problem, although it is at present of limited extent. In the north around Cambray there are a number of introduced trees and other "garden" plants associated with the former settlement. At present these do not show any sign of actively invading the native vegetation and they do provide a link with the past land use of the area.
The coincidence of what now superficially appears• to be a fairly pristine forest, a reliable (if seasonal) and relatively unpolluted water course and some historical features make St Johns Brook Conservation Park an ideal area for incorporation into the State's reserve system.
|Murdoch Affiliation:||School of Biological and Environmental Sciences|
|Publisher:||School of Biological and Environmental Sciences, Murdoch University|
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