Lichenometric dating (lichenometry) and the biology of the lichen genus rhizocarpon:challenges and future directions

Lichenometric dating (lichenometry) involves the use of lichen measurements to estimate the age of exposure of various substrata. Because of low radial growth rates and considerable longevity, species of the crustose lichen genus Rhizocarpon have been the most useful in lichenometry. The primary assumption of lichenometry is that colonization, growth and mortality of Rhizocarpon are similar on surfaces of known and unknown age so that the largest thalli present on the respective faces are of comparable age. This review describes the current state of knowledge regarding the biology of Rhizocarpon and considers two main questions: (1) to what extent does existing knowledge support this assumption; and (2) what further biological observations would be useful both to test its validity and to improve the accuracy of lichenometric dates? A review of the Rhizocarpon literature identified gaps in knowledge regarding early development, the growth rate/size curve, mortality, regeneration, competitive effects, colonization, and succession on rock surfaces. The data suggest that these processes may not be comparable on different rock surfaces, especially in regions where growth rates and thallus turnover are high. In addition, several variables could differ between rock surfaces and influence maximum thallus size, including rate and timing of colonization, radial growth rates, environmental differences, thallus fusion, allelopathy, thallus mortality, colonization and competition. Comparative measurements of these variables on surfaces of known and unknown age may help to determine whether the basic assumptions of lichenometry are valid. Ultimately, it may be possible to take these differences into account when interpreting estimated dates

Interpretive provisions in human rights legislation: a comparative analysis

This thesis considers interpretive provisions in human rights legislation in the United Kingdom (UK), New Zealand and two Australian jurisdictions: the Australian Capital Territory and the State of Victoria. It deals with the relationship between certain common law interpretive principles which protect human rights and the rules under the interpretive provisions. It also considers what effect the interpretive provisions have on the overall approach to statutory interpretation, particularly in terms of their impact on the roles of intention and purpose. One of the themes of the thesis is that it is possible to identify a common methodology for the application of the various interpretive provisions. This is facilitated by an emphasis on the concept of purpose, which is flexible and capable of being identified and applied at higher levels of abstraction than the concept of intention as commonly applied by the courts. Despite this common methodology, the results of attempts at legislative rights-consistent interpretation in the relevant jurisdictions differ. We shall see that the UK courts have taken a broader interpretive approach than have their New Zealand and Australian counterparts. This will be explained by reference to the respective contexts of the human rights legislation in each jurisdiction, particularly in terms of legislative history. It will be argued that the purpose of the UK legislation to provide remedies in domestic courts for breaches of the European Convention on Human Rights provides the basis for the UK courts’ approach. The absence of this factor is the primary point of distinction between the UK on the one hand, and New Zealand and Australia on the other, though other issues will be explored. Finally, while as a matter of the interpretation of the UK legislation, and especially of the relevant interpretive provision, the approach of the UK courts is defensible, the significant risk to the principle of legal certainty which it poses will be highlighted.</p

Interpretive provisions in human rights legislation: a comparative analysis

This thesis considers interpretive provisions in human rights legislation in the United Kingdom (UK), New Zealand and two Australian jurisdictions: the Australian Capital Territory and the State of Victoria. It deals with the relationship between certain common law interpretive principles which protect human rights and the rules under the interpretive provisions. It also considers what effect the interpretive provisions have on the overall approach to statutory interpretation, particularly in terms of their impact on the roles of intention and purpose. One of the themes of the thesis is that it is possible to identify a common methodology for the application of the various interpretive provisions. This is facilitated by an emphasis on the concept of purpose, which is flexible and capable of being identified and applied at higher levels of abstraction than the concept of intention as commonly applied by the courts. Despite this common methodology, the results of attempts at legislative rights-consistent interpretation in the relevant jurisdictions differ. We shall see that the UK courts have taken a broader interpretive approach than have their New Zealand and Australian counterparts. This will be explained by reference to the respective contexts of the human rights legislation in each jurisdiction, particularly in terms of legislative history. It will be argued that the purpose of the UK legislation to provide remedies in domestic courts for breaches of the European Convention on Human Rights provides the basis for the UK courts’ approach. The absence of this factor is the primary point of distinction between the UK on the one hand, and New Zealand and Australia on the other, though other issues will be explored. Finally, while as a matter of the interpretation of the UK legislation, and especially of the relevant interpretive provision, the approach of the UK courts is defensible, the significant risk to the principle of legal certainty which it poses will be highlighted.This thesis is not currently available in ORA

Growth of crustose lichens : a review

Crustose species are the slowest growing of all lichens. Their slow growth and longevity, especially of the yellow-green Rhizocarpon group, has made them important for surface-exposure dating (lichenometry). This review considers various aspects of the growth of crustose lichens revealed by direct measurement including: 1) early growth and development; 2) radial growth rates (RGR, mm yr−1); 3) the growth rate–size curve; and 4) the influence of environmental factors. Many crustose species comprise discrete areolae that contain the algal partner growing on the surface of a non-lichenized fungal hypothallus. Recent data suggest that 'primary' areolae may develop from free-living algal cells on the substratum while 'secondary' areolae develop from zoospores produced within the thallus. In more extreme environments, the RGR of crustose species may be exceptionally slow but considerably faster rates of growth have been recorded under more favourable conditions. The growth curves of crustose lichens with a marginal hypothallus may differ from the 'asymptotic' type of curve recorded in foliose and placodioid species; the latter are characterized by a phase of increasing RGR to a maximum and may be followed by a phase of decreasing growth. The decline in RGR in larger thalli may be attributable to a reduction in the efficiency of translocation of carbohydrate to the thallus margin or to an increased allocation of carbon to support mature 'reproductive' areolae. Crustose species have a low RGR accompanied by a low demand for nutrients and an increased allocation of carbon for stress resistance; therefore enabling colonization of more extreme environments