whole-mcmurray-thesis.pdf (4.51 MB)
An investigation of tree decline on Tasmanian farms
thesisposted on 2023-05-26, 00:51 authored by McMurray, SK
Little attention has been given to the death and decline of remaining native trees on Tasmanian farms. This phenomenon is prevalent in the pastoral Midland region of the state and, so far, is unstudied. The present study, as an exploratory investigation, seeks to ascertain certain characteristics of this loss of farm trees. The rate of loss of scattered, native trees on 14 grazing properties was estimated from tree counts of aerial photographs, separated by a period of 32 years. A mean rate of 54 per cent was found for this period. This considerably exceeds estimated rates of tree decline found in similar studies in mainland states. Factors associated with tree decline were also investigated. Photographic interpretation and landholder interviews enabled areas within properties to be classified according to pasture type and associated management practices. Tree count data from these areas showed an increasing rate of tree decline appeared to be associated with increasing intensity of land management. Biological and physico-chemical factors potentially associated with tree decline were assessed through landholder interviews. Drouqht emerged as an important non-lethal incitant in farm tree decline, althouqh other biophysical factors were not widely implicated in causal or predisposing capacities. In this respect, neither severe insect defoliation nor excessive soil salinity, important in tree decline elsewhere, is apparent in the Midlands. Tree decline in the region appears largely to be a land-use related phenomenon. The finding that there has been a high rate of loss of remaining farm trees in the region is seen as timely. It coincides with initial efforts by governmcnt to encouraqe replacement of trees on farms. These efforts are in need of considerable expansion. Land-holders, generally, did not recognize tree decline and efforts are also required to raise awareness to the existence of, and problems associated with, such a hiqh rate of tree loss.
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