title: Succession of subalpine vegetation to Libocedrus bidwillii forest on a landslide-initiated soil chronosequence, Mount Taranaki, New Zealand

authors: Boase, Murray Robert

abstract: Aspects of succession of subalpine vegetation on Mt Taranaki were examined in a vegetation chronosequence, initiated by four landslides on the same sideslope in 1333-1343 A.D., 1625 A.D., 1811-1817 A.D. and 1968-1971 A.D .. In three stands Libocedrus bidwillii (kaikawaka) subalpine low forest was displayed at different stages of development while the fourth stand without kaikawaka comprised mainly low herbaceous vegetation.

Core samples were collected from the three kaikawaka populations to establish the crossdating pattern. describe anomalous ring features, establish that the four stands formed a vegetation chronosequence and to examine the age-size relationships of this species.

The crossdating pattern found in the present study confirms that reported for kaikawaka at two other sites on Mt Taranaki. The absence of the 1934-1938 signature in cores from the youngest stand suggests the climatic signal is being suppressed in younger trees.

Various types of anomalous rings were described for kaikawaka and -frequencies per core given. A number of features not previously reported for this species were recognised:
1) resin bands as a type of false ring
2) the presence of-damaged rings, their synchronous occurrence within a tree, in different trees and with false rings
3) two types of partially absent rings
4) a highest frequency of absent rings for any single radius in datable cores of 3.4 % and
5) the phenomenon of displaced marker rings.

A linear relationship between tree age at 0 cm downslope and DBH of kaikawaka was found to be significant at the 0.1% level but as in other studies a wide variation of age within any one size class suggested that ages predicted from DBH data may be misleading.

Floristic composition of the four stands was recorded on a stratum basis and analysed by lists and through tables of species in common, species unique, total number and identity of species present and Jaccard's and Sorensen's similarity indices. These data showed that the most diverse stratum in all four stands was the ground cover and the major between-stand differences in floristic composition occurred in this stratum. The youngest stand was the most distinctive floristically with twenty-seven species of vascular plants exclusive to this stand. Few (<8) species were found exclusive to each of the 3 older stands. However, 11 species were exclusive to the two older stands and 25 species occurred in all 4 stands. These observations can be interpreted using a combination of the relay-floristic and initial-floristic-composition models. Some early-successional species
persist for a period less than 170 years, others invade throughout the period of the chronosequence and another group are part of the initial flora yet persist throughout. Kaikawaka was invading and regenerating in existing vegetation at the site (three older stands) so can participate in secondary succession.

The main species in each stratum were ranked in order of decreasing cover using a semiquantitative estimate method or a point-estimate transect method. The species replacement sequence in the top layer of the four stands was described and follows a trend with time of physiognomic dominance by species with larger size at maturity.

Life-form composition of the four stands (number and percentage of species per life-form category) was compared on a stratum basis through tables and lists. This analysis showed the three older stands were similar in life-form composition except for the presence of hemi-epiphytes exclusive to the oldest stand. The youngest stand was distinctive in life-form composition with a relatively large number of composite herb species present.

Kaikawaka population structures were examined and compared using DBH size-class frequency distributions which also showed size-class mortality patterns. These distributions in the three older stands were dissimilar and indicated waves or pulses of kaikawaka regeneration have occurred rather than continuous recruitment. This intermittent mode of regeneration was linked to disturbance of various kinds over a range of scales rather than to climatic change. Total basal area, mean basal area per tree and stem density were also calculated for each population and found to increase with time in the case of the former two parameters.

The cohort-senescence dieback theory and European forest life-cycle theory appear applicable to the study area and offer hypotheses to explain the widespread canopy dieback of kaikawaka found on Mt Taranaki. Whereas a full range of forest life-cycle phases were represented in the small area (<5ha) of the study site, elsewhere on a debris-fan only the dieback phase was evident over a much larger area (>200ha). This was interpreted as reflecting the dependence of disturbance regimes on topography, substrate and vegetation with different disturbance regimes operating in the two areas.

text: Succession of subalpine vegetation to Libocedrus bidwillii forest on a landslide-initiated soil chronosequence, Mount Taranaki, New Zealand Aspects of succession of subalpine vegetation on Mt Taranaki were examined in a vegetation chronosequence, initiated by four landslides on the same sideslope in 1333-1343 A.D., 1625 A.D., 1811-1817 A.D. and 1968-1971 A.D .. In three stands Libocedrus bidwillii (kaikawaka) subalpine low forest was displayed at different stages of development while the fourth stand without kaikawaka comprised mainly low herbaceous vegetation.

Core samples were collected from the three kaikawaka populations to establish the crossdating pattern. describe anomalous ring features, establish that the four stands formed a vegetation chronosequence and to examine the age-size relationships of this species.

The crossdating pattern found in the present study confirms that reported for kaikawaka at two other sites on Mt Taranaki. The absence of the 1934-1938 signature in cores from the youngest stand suggests the climatic signal is being suppressed in younger trees.

Various types of anomalous rings were described for kaikawaka and -frequencies per core given. A number of features not previously reported for this species were recognised:
1) resin bands as a type of false ring
2) the presence of-damaged rings, their synchronous occurrence within a tree, in different trees and with false rings
3) two types of partially absent rings
4) a highest frequency of absent rings for any single radius in datable cores of 3.4 % and
5) the phenomenon of displaced marker rings.

A linear relationship between tree age at 0 cm downslope and DBH of kaikawaka was found to be significant at the 0.1% level but as in other studies a wide variation of age within any one size class suggested that ages predicted from DBH data may be misleading.

Floristic composition of the four stands was recorded on a stratum basis and analysed by lists and through tables of species in common, species unique, total number and identity of species present and Jaccard's and Sorensen's similarity indices. These data showed that the most diverse stratum in all four stands was the ground cover and the major between-stand differences in floristic composition occurred in this stratum. The youngest stand was the most distinctive floristically with twenty-seven species of vascular plants exclusive to this stand. Few (<8) species were found exclusive to each of the 3 older stands. However, 11 species were exclusive to the two older stands and 25 species occurred in all 4 stands. These observations can be interpreted using a combination of the relay-floristic and initial-floristic-composition models. Some early-successional species
persist for a period less than 170 years, others invade throughout the period of the chronosequence and another group are part of the initial flora yet persist throughout. Kaikawaka was invading and regenerating in existing vegetation at the site (three older stands) so can participate in secondary succession.

The main species in each stratum were ranked in order of decreasing cover using a semiquantitative estimate method or a point-estimate transect method. The species replacement sequence in the top layer of the four stands was described and follows a trend with time of physiognomic dominance by species with larger size at maturity.

Life-form composition of the four stands (number and percentage of species per life-form category) was compared on a stratum basis through tables and lists. This analysis showed the three older stands were similar in life-form composition except for the presence of hemi-epiphytes exclusive to the oldest stand. The youngest stand was distinctive in life-form composition with a relatively large number of composite herb species present.

Kaikawaka population structures were examined and compared using DBH size-class frequency distributions which also showed size-class mortality patterns. These distributions in the three older stands were dissimilar and indicated waves or pulses of kaikawaka regeneration have occurred rather than continuous recruitment. This intermittent mode of regeneration was linked to disturbance of various kinds over a range of scales rather than to climatic change. Total basal area, mean basal area per tree and stem density were also calculated for each population and found to increase with time in the case of the former two parameters.

The cohort-senescence dieback theory and European forest life-cycle theory appear applicable to the study area and offer hypotheses to explain the widespread canopy dieback of kaikawaka found on Mt Taranaki. Whereas a full range of forest life-cycle phases were represented in the small area (<5ha) of the study site, elsewhere on a debris-fan only the dieback phase was evident over a much larger area (>200ha). This was interpreted as reflecting the dependence of disturbance regimes on topography, substrate and vegetation with different disturbance regimes operating in the two areas.

year: 1988

title: Investigating paradoxical hysteresis effects in the mouse neocortical slice model

authors: Voss, Logan J.

subjects: anesthesia

abstract: Clinically, anesthetic drugs show hysteresis in the plasma drug concentrations at induction versus emergence from anesthesia induced unconsciousness. This is assumed to be the result of pharmacokinetic lag between the plasma and brain effect-site and vice versa. However, recent mathematical and experimental studies demonstrate that anesthetic hysteresis might be due in part to lag in the brain physiology, independent of drug transport delay — so-called “neural inertia”. The aim of this study was to investigate neural inertia in the reduced neocortical mouse slice model. Seizure-like event (SLE) activity was generated by exposing cortical slices to no-magnesium artificial cerebrospinal fluid (aCSF). Concentration–effect loops were generated by manipulating SLE frequency, using the general anesthetic drug etomidate and by altering the aCSF magnesium concentration. The etomidate (24 μM) concentration–effect relationship showed a clear hysteresis, consistent with the slow diffusion of etomidate into slice tissue. Manipulation of tissue excitability, using either carbachol (50 μM) or elevated potassium (5 mM vs 2.5 mM) did not significantly alter the size of etomidate hysteresis loops. Hysteresis in the magnesium concentration–effect relationship was evident, but only when the starting condition was magnesium-containing “normal” aCSF. The in vitro cortical slice manifests pathway-dependent “neural inertia” and may be a valuable model for future investigations into the mechanisms of neural inertia in the cerebral cortex.

text: Investigating paradoxical hysteresis effects in the mouse neocortical slice model Clinically, anesthetic drugs show hysteresis in the plasma drug concentrations at induction versus emergence from anesthesia induced unconsciousness. This is assumed to be the result of pharmacokinetic lag between the plasma and brain effect-site and vice versa. However, recent mathematical and experimental studies demonstrate that anesthetic hysteresis might be due in part to lag in the brain physiology, independent of drug transport delay — so-called “neural inertia”. The aim of this study was to investigate neural inertia in the reduced neocortical mouse slice model. Seizure-like event (SLE) activity was generated by exposing cortical slices to no-magnesium artificial cerebrospinal fluid (aCSF). Concentration–effect loops were generated by manipulating SLE frequency, using the general anesthetic drug etomidate and by altering the aCSF magnesium concentration. The etomidate (24 μM) concentration–effect relationship showed a clear hysteresis, consistent with the slow diffusion of etomidate into slice tissue. Manipulation of tissue excitability, using either carbachol (50 μM) or elevated potassium (5 mM vs 2.5 mM) did not significantly alter the size of etomidate hysteresis loops. Hysteresis in the magnesium concentration–effect relationship was evident, but only when the starting condition was magnesium-containing “normal” aCSF. The in vitro cortical slice manifests pathway-dependent “neural inertia” and may be a valuable model for future investigations into the mechanisms of neural inertia in the cerebral cortex.

year: 2012-01

title: Māori diaspora: Being Māori on the Gold Coast

authors: Henderson, Eve Ngāwaiata

subjects: Māori

abstract: An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

text: Māori diaspora: Being Māori on the Gold Coast An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

year: 2021