title: Do productivity and disturbance interact to modulate macroinvertebrate diversity in streams?

authors: Tonkin, Jonathan D.

subjects: Dynamic equilibrium mode

abstract: Although disturbance and productivity are clearly strong influences on lotic diversity, rarely have their interactive effects been studied in running water systems. We hypothesised that the presence or absence of canopy cover in streams would alter productivity-disturbance-diversity relationships due to differential effects on the food base, and tested this hypothesis in 47 mountain streams in the central North Island of New Zealand. Canopy cover had no influence on algal biomass in these streams, but a link between disturbance and productivity was found in open canopy streams where taxonomic richness of invertebrates increased log-linearly with increasing algal biomass and peaked at intermediate levels of disturbance. Community evenness declined with disturbance, but only at closed canopy sites where both invertebrate taxonomic richness and Simpson's diversity index were higher. Although there was a peak in richness at intermediate rates of disturbance, our results do not directly match predictions of the dynamic equilibrium model which predicts that the level of disturbance maximising diversity interacts with habitat productivity. Rather, we suggest the combined effects of productivity and disturbance are additive rather than multiplicative such that productivity simply sets the upper limit to richness in streams.

text: Do productivity and disturbance interact to modulate macroinvertebrate diversity in streams? Although disturbance and productivity are clearly strong influences on lotic diversity, rarely have their interactive effects been studied in running water systems. We hypothesised that the presence or absence of canopy cover in streams would alter productivity-disturbance-diversity relationships due to differential effects on the food base, and tested this hypothesis in 47 mountain streams in the central North Island of New Zealand. Canopy cover had no influence on algal biomass in these streams, but a link between disturbance and productivity was found in open canopy streams where taxonomic richness of invertebrates increased log-linearly with increasing algal biomass and peaked at intermediate levels of disturbance. Community evenness declined with disturbance, but only at closed canopy sites where both invertebrate taxonomic richness and Simpson's diversity index were higher. Although there was a peak in richness at intermediate rates of disturbance, our results do not directly match predictions of the dynamic equilibrium model which predicts that the level of disturbance maximising diversity interacts with habitat productivity. Rather, we suggest the combined effects of productivity and disturbance are additive rather than multiplicative such that productivity simply sets the upper limit to richness in streams.

year: 2013

title: Ensembles of balanced nested dichotomies for multi-class problems

authors: Dong, Lin

subjects: Science & Technology

abstract: A system of nested dichotomies is a hierarchical decomposition of a multi-class problem with c classes into c−1 two-class problems and can be represented as a tree structure. Ensembles of randomly generated nested dichotomies have proven to be an effective approach to multi-class learning problems [1]. However, sampling trees by giving each tree equal probability means that the depth of a tree is limited only by the number of classes, and very unbalanced trees can negatively affect runtime.

In this paper, we investigate two approaches to building balanced nested dichotomies—class-balanced nested dichotomies and data-balanced nested dichotomies—and evaluate them in the same ensemble setting. Using C4.5 decision trees as the base models, we show that both approaches can reduce runtime with little or no effect on accuracy, especially on problems with many classes. We also investigate the effect of caching models when building ensembles of nested dichotomies.

text: Ensembles of balanced nested dichotomies for multi-class problems A system of nested dichotomies is a hierarchical decomposition of a multi-class problem with c classes into c−1 two-class problems and can be represented as a tree structure. Ensembles of randomly generated nested dichotomies have proven to be an effective approach to multi-class learning problems [1]. However, sampling trees by giving each tree equal probability means that the depth of a tree is limited only by the number of classes, and very unbalanced trees can negatively affect runtime.

In this paper, we investigate two approaches to building balanced nested dichotomies—class-balanced nested dichotomies and data-balanced nested dichotomies—and evaluate them in the same ensemble setting. Using C4.5 decision trees as the base models, we show that both approaches can reduce runtime with little or no effect on accuracy, especially on problems with many classes. We also investigate the effect of caching models when building ensembles of nested dichotomies.

year: 2005-01-01

title: Joe Gillayley: A model of cultural hybridity in Keri Hulme’s novel The Bone People

authors: Cozma, Codrina

subjects: Literary analysis

abstract: Born and raised at the confluence of two cultures, Western and Māori, the New Zealand author Keri Hulme crafts in her 1983 novel, The Bone People, a vigorous literary discourse whose integrity and realism often topple consecrated stereotyping colonial theories. Joe Gillayley displays complex mechanisms of cultural hybridity in major areas of his private and social life. His initially ambivalent attitude towards both his Western and his Māori heritage are evident in his personal, social and economic life - in his interactions with his family, his semi-adopted son Simon/ Himi, his friend Kerewin, his work, school authorities, and tribal figures such as the mysterious prophet Tiaki Mira. Post-colonial scholarship provides the context in which the analysis provided here is conducted, an analysis that highlights the futility of colonial theories that are based on distorted, stereotypical images of both Western and indigenous life and values.

text: Joe Gillayley: A model of cultural hybridity in Keri Hulme’s novel The Bone People Born and raised at the confluence of two cultures, Western and Māori, the New Zealand author Keri Hulme crafts in her 1983 novel, The Bone People, a vigorous literary discourse whose integrity and realism often topple consecrated stereotyping colonial theories. Joe Gillayley displays complex mechanisms of cultural hybridity in major areas of his private and social life. His initially ambivalent attitude towards both his Western and his Māori heritage are evident in his personal, social and economic life - in his interactions with his family, his semi-adopted son Simon/ Himi, his friend Kerewin, his work, school authorities, and tribal figures such as the mysterious prophet Tiaki Mira. Post-colonial scholarship provides the context in which the analysis provided here is conducted, an analysis that highlights the futility of colonial theories that are based on distorted, stereotypical images of both Western and indigenous life and values.

year: 2004-02