title: The eco-physiology of New Zealand forest lichens with special reference to carbon dioxide exchange

authors: Snelgar, W.P.

abstract: This study of lichen ecological physiology was carried out in four parts:

(i) The growth rates of specimens of Pseudocyphellaria homoeophylla and Sticta caperata growing in the Urewera National Park (New Zealand) were measured photographically. The mean radial increase of P. homoeophylla was related to thallus diameter and rates as high 27 mm yr⁻¹ (32 cm diameter) were recorded. The growth of S. caperata was not influenced by thallus size and the mean radial increase was 7.0 mm yr⁻¹.

(ii) The intraspecific morphological variations of Pseudocyphellaria dissimilis populations are assessed and are related to the nitrogenase activity and water relations of each population. The effect of thallus water content on CO₂ exchange in eight lichen and one bryophyte species was studied using an infrared gas analyser operating as a discrete sample analyser. Species from moist habitats showed a net loss of CO₂ at low thallus water contents whilst some other species showed a depression of net photosynthesis (NP) at high thallus water contents. In Sticta latifrons this depression was less apparent when the lower surface was dried. Experiments with a split chamber demonstrated that virtually all CO₂ uptake occurs through the lower, cyphellate surface. These results suggest that the cyphellae of S. latifrons act as air pores and that blockage of these pores with water results in a depression of NP.

(iii) Low oxygen concentrations (1% v/v) were shown to increase NP in S. latifrons, P. homoeophylla and P. billardierii by up to 55%. This stimulation was considered to result from the repression of photorespiration. The oxygen effect was separated into two components; (a) the sensitivity of the carboxylation system and (b), the rate of CO₂ evolution in the light at zero CO₂. Of the lichen species studied all but P. billardierii had a carboxylation sensitivity typical of the values expected in C3 plants. P. billardierii had an unusually low carboxylation sensitivity. The rate of CO₂ evolution in the light showed large inter and intraspecific variations. Low rates of CO₂ evolution were often associated with a high CO₂ refixation ability.

(iv) Total CO₂ diffusion resistance - water content curves for six lichen species are presented. All species show increased resistances at low thallus water contents and some also show high resistances at high thallus water contents. The total CO₂ resistances of S. latifrons and P. amphisticta are separated into transport and carboxylation components. Cyphella, pseudocyphella, and medulla resistances are calculated from morphological data. Although transport resistances are often larger than carboxylation resistances the results suggest that at ambient CO₂ levels carboxylation processes limit photosynthesis. The relationship between resistance to water vapour loss and resistance to CO₂ uptake in P. homoeophylla and S. latifrons is established and the ecological implications are discussed.

In a general summary, the size of the internal and external water holding capacities of several lichen species is estimated. The effectiveness of these reserves in maintaining lichens in a moist condition in the field is calculated and the results are related to the ecology of the species. Morphological adaptations of Stictaceae lichens which maximise water holding capacity yet minimise CO₂ diffusion resistances are considered. It is suggested that lichen water contents should be related to thallus area, rather than thallus weight, as the former parameter appears to be of greater physiological significance. 

The relevance of this work to that of previous authors is discussed, particularly in regard to photorespiration, CO₂ uptake, and thallus water content in lichens.

text: The eco-physiology of New Zealand forest lichens with special reference to carbon dioxide exchange This study of lichen ecological physiology was carried out in four parts:

(i) The growth rates of specimens of Pseudocyphellaria homoeophylla and Sticta caperata growing in the Urewera National Park (New Zealand) were measured photographically. The mean radial increase of P. homoeophylla was related to thallus diameter and rates as high 27 mm yr⁻¹ (32 cm diameter) were recorded. The growth of S. caperata was not influenced by thallus size and the mean radial increase was 7.0 mm yr⁻¹.

(ii) The intraspecific morphological variations of Pseudocyphellaria dissimilis populations are assessed and are related to the nitrogenase activity and water relations of each population. The effect of thallus water content on CO₂ exchange in eight lichen and one bryophyte species was studied using an infrared gas analyser operating as a discrete sample analyser. Species from moist habitats showed a net loss of CO₂ at low thallus water contents whilst some other species showed a depression of net photosynthesis (NP) at high thallus water contents. In Sticta latifrons this depression was less apparent when the lower surface was dried. Experiments with a split chamber demonstrated that virtually all CO₂ uptake occurs through the lower, cyphellate surface. These results suggest that the cyphellae of S. latifrons act as air pores and that blockage of these pores with water results in a depression of NP.

(iii) Low oxygen concentrations (1% v/v) were shown to increase NP in S. latifrons, P. homoeophylla and P. billardierii by up to 55%. This stimulation was considered to result from the repression of photorespiration. The oxygen effect was separated into two components; (a) the sensitivity of the carboxylation system and (b), the rate of CO₂ evolution in the light at zero CO₂. Of the lichen species studied all but P. billardierii had a carboxylation sensitivity typical of the values expected in C3 plants. P. billardierii had an unusually low carboxylation sensitivity. The rate of CO₂ evolution in the light showed large inter and intraspecific variations. Low rates of CO₂ evolution were often associated with a high CO₂ refixation ability.

(iv) Total CO₂ diffusion resistance - water content curves for six lichen species are presented. All species show increased resistances at low thallus water contents and some also show high resistances at high thallus water contents. The total CO₂ resistances of S. latifrons and P. amphisticta are separated into transport and carboxylation components. Cyphella, pseudocyphella, and medulla resistances are calculated from morphological data. Although transport resistances are often larger than carboxylation resistances the results suggest that at ambient CO₂ levels carboxylation processes limit photosynthesis. The relationship between resistance to water vapour loss and resistance to CO₂ uptake in P. homoeophylla and S. latifrons is established and the ecological implications are discussed.

In a general summary, the size of the internal and external water holding capacities of several lichen species is estimated. The effectiveness of these reserves in maintaining lichens in a moist condition in the field is calculated and the results are related to the ecology of the species. Morphological adaptations of Stictaceae lichens which maximise water holding capacity yet minimise CO₂ diffusion resistances are considered. It is suggested that lichen water contents should be related to thallus area, rather than thallus weight, as the former parameter appears to be of greater physiological significance. 

The relevance of this work to that of previous authors is discussed, particularly in regard to photorespiration, CO₂ uptake, and thallus water content in lichens.

year: 1981

title: A simple forecasting scheme for predicting low rainfalls in Funafuti, Tuvalu

authors: Vavae, Hilia

subjects: long-range forecasting

abstract: The development of some ability for forecasting low rainfalls would be helpful in Tuvalu as rainwater is the only source of fresh water in the country. The subsurface water is brackish and saline so the entire country depends totally on rainwater for daily domestic supplies, agricultural and farming activities. More importantly, these atolls are often influenced by droughts which consequently make inadequate drinking water an issue. A simple graph-based forecasting scheme is developed and presented in this thesis for forecasting below average mean rainfall in Funafuti over the next n-month period. The approach uses precursor ocean surface temperature data to make predictions of below average rainfall for n = 1, 2   12. The simplicity of the approach makes it a suitable method for the country and thus for the Tuvalu Meteorological Service to use as an operational forecasting tool in the climate forecasting desk. The graphical method was derived from standardised monthly rainfalls from the Funafuti manual raingauge for the period January 1945 to July 2007. The method uses lag-1 and-lag 2 NINO4 sea surface temperatures to define whether prediction conditions hold. The persistence of predictability tends to be maintained when the observed NINO4 ocean surface temperatures fall below 26.0oC. Although the developed method has a high success probability of up to 80 percent, this can only be achieved when conditions are within the predictable field. A considerable number of below average rainfall periods are not within the predictable field and therefore cannot be forecast by this method. However, the graphical approach has particular value in warning when an existing drought is likely to continue.

text: A simple forecasting scheme for predicting low rainfalls in Funafuti, Tuvalu The development of some ability for forecasting low rainfalls would be helpful in Tuvalu as rainwater is the only source of fresh water in the country. The subsurface water is brackish and saline so the entire country depends totally on rainwater for daily domestic supplies, agricultural and farming activities. More importantly, these atolls are often influenced by droughts which consequently make inadequate drinking water an issue. A simple graph-based forecasting scheme is developed and presented in this thesis for forecasting below average mean rainfall in Funafuti over the next n-month period. The approach uses precursor ocean surface temperature data to make predictions of below average rainfall for n = 1, 2   12. The simplicity of the approach makes it a suitable method for the country and thus for the Tuvalu Meteorological Service to use as an operational forecasting tool in the climate forecasting desk. The graphical method was derived from standardised monthly rainfalls from the Funafuti manual raingauge for the period January 1945 to July 2007. The method uses lag-1 and-lag 2 NINO4 sea surface temperatures to define whether prediction conditions hold. The persistence of predictability tends to be maintained when the observed NINO4 ocean surface temperatures fall below 26.0oC. Although the developed method has a high success probability of up to 80 percent, this can only be achieved when conditions are within the predictable field. A considerable number of below average rainfall periods are not within the predictable field and therefore cannot be forecast by this method. However, the graphical approach has particular value in warning when an existing drought is likely to continue.

year: 2008

title: ‘Doctoring’ our own: Confessions of a Māori doctoral supervisor

authors: Hohepa, Margie Kahukura

subjects: Māori doctoral student

abstract: There is very little literature, empirically based or otherwise, on the supervision of Māori doctoral students (Fitzgerald, 2005; Pope, 2008; Kidman, 2007; Smith, 2007). There is even less relating to Māori supervisors working with Māori doctoral students (Kidinan, 2007), let alone Māori supervisors working with non- Māori students. While the relatively large corpus of literature on doctoral supervision may be of some assistance to Māori supervisors, there is also a dearth of studies that focus on the pedagogical aspects. Research undertaken by Elizabeth McKinley and her co-researchers (McKinley, Grant, Middleton, Irwin & Williams, 2009) will now help to fill the literature gap on the teaching and learning process of supervision as it pertains to Māori.

text: ‘Doctoring’ our own: Confessions of a Māori doctoral supervisor There is very little literature, empirically based or otherwise, on the supervision of Māori doctoral students (Fitzgerald, 2005; Pope, 2008; Kidman, 2007; Smith, 2007). There is even less relating to Māori supervisors working with Māori doctoral students (Kidinan, 2007), let alone Māori supervisors working with non- Māori students. While the relatively large corpus of literature on doctoral supervision may be of some assistance to Māori supervisors, there is also a dearth of studies that focus on the pedagogical aspects. Research undertaken by Elizabeth McKinley and her co-researchers (McKinley, Grant, Middleton, Irwin & Williams, 2009) will now help to fill the literature gap on the teaching and learning process of supervision as it pertains to Māori.

year: 2010