title: Stacked generalization: when does it work?

authors: Ting, Kai Ming

subjects: stacking

abstract: Stacked generalization is a general method of using a high-level model to combine lower-level models to achieve greater predictive accuracy. In this paper we resolve two crucial issues which have been considered to be a ‘black art’ in classification tasks ever since the introduction of stacked generalization in 1992 by Wolpert: the type of generalizer that is suitable to derive the higher-level model, and the kind of attributes that should be used as its input. 
We demonstrate the effectiveness of stacked generalization for combining three different types of learning algorithms, and also for combining models of the same type derived from a single learning algorithm in a multiple-data-batches scenario. We also compare the performance of stacked generalization with published results of arcing and bagging.

text: Stacked generalization: when does it work? Stacked generalization is a general method of using a high-level model to combine lower-level models to achieve greater predictive accuracy. In this paper we resolve two crucial issues which have been considered to be a ‘black art’ in classification tasks ever since the introduction of stacked generalization in 1992 by Wolpert: the type of generalizer that is suitable to derive the higher-level model, and the kind of attributes that should be used as its input. 
We demonstrate the effectiveness of stacked generalization for combining three different types of learning algorithms, and also for combining models of the same type derived from a single learning algorithm in a multiple-data-batches scenario. We also compare the performance of stacked generalization with published results of arcing and bagging.

year: 1997-01

title: Forest canopy restoration has indirect effects on litter decomposition and no effect on denitrification

authors: Wallace, Kiri Joy

subjects: Science & Technology

abstract: Forest restoration has potential to recover degraded ecosystem functions in disturbed environments. Decomposition and denitrification are two critical functions involved in forest nutrient cycling that are often compromised in degraded ecosystems. As forest canopy structure develops following initial plantings, it may indirectly impact ecosystem functions by altering abiotic conditions. It is likely, however, that there are other abiotic factors that affect decomposition and denitrification that are unrelated to forest canopy structure. Here, we aimed to determine whether forest canopy openness, topography, and soil sand content would affect litter decomposition and denitrification by regulating the microclimate, the herbaceous plant layer, soil chemistry, and soil moisture. Research occurred in restored native temperate rainforest patches in two New Zealand cities. Urban forests are an excellent context for measuring impact of canopy restoration on ecosystem properties such as microclimate due to the extreme swings in city conditions (e.g., urban heat island). Decomposition rates were determined using leaf litter bags and denitrification rates through denitrification enzyme activity assays. We used structural equation modeling to quantify the direct and indirect drivers of these ecosystem functions. Results indicated that decomposition rates were positively related to soil moisture, relative humidity, and herbaceous plant cover. Interestingly, forest canopy openness indirectly affected decomposition through counteracting forces, meaning greater canopy openness in young forests permitted dense herbaceous plant growth which enhanced decomposition, while less canopy openness in older forests enhanced humidity levels which increased decomposition. Denitrification was negatively related to soil pH and positively related to soil moisture, but these abiotic factors were unrelated to the forest canopy. Discovering drivers of ecosystem functions can improve approaches to the restoration of degraded ecosystems, especially in disturbed urban areas. Identifying counteracting effects on ecosystem functions could improve management by focusing restoration actions on specific drivers to elicit desired changes. Some ecosystem processes, like denitrification, are not affected by forest canopy restoration or management, but are instead driven by edaphic and landscape factors.

text: Forest canopy restoration has indirect effects on litter decomposition and no effect on denitrification Forest restoration has potential to recover degraded ecosystem functions in disturbed environments. Decomposition and denitrification are two critical functions involved in forest nutrient cycling that are often compromised in degraded ecosystems. As forest canopy structure develops following initial plantings, it may indirectly impact ecosystem functions by altering abiotic conditions. It is likely, however, that there are other abiotic factors that affect decomposition and denitrification that are unrelated to forest canopy structure. Here, we aimed to determine whether forest canopy openness, topography, and soil sand content would affect litter decomposition and denitrification by regulating the microclimate, the herbaceous plant layer, soil chemistry, and soil moisture. Research occurred in restored native temperate rainforest patches in two New Zealand cities. Urban forests are an excellent context for measuring impact of canopy restoration on ecosystem properties such as microclimate due to the extreme swings in city conditions (e.g., urban heat island). Decomposition rates were determined using leaf litter bags and denitrification rates through denitrification enzyme activity assays. We used structural equation modeling to quantify the direct and indirect drivers of these ecosystem functions. Results indicated that decomposition rates were positively related to soil moisture, relative humidity, and herbaceous plant cover. Interestingly, forest canopy openness indirectly affected decomposition through counteracting forces, meaning greater canopy openness in young forests permitted dense herbaceous plant growth which enhanced decomposition, while less canopy openness in older forests enhanced humidity levels which increased decomposition. Denitrification was negatively related to soil pH and positively related to soil moisture, but these abiotic factors were unrelated to the forest canopy. Discovering drivers of ecosystem functions can improve approaches to the restoration of degraded ecosystems, especially in disturbed urban areas. Identifying counteracting effects on ecosystem functions could improve management by focusing restoration actions on specific drivers to elicit desired changes. Some ecosystem processes, like denitrification, are not affected by forest canopy restoration or management, but are instead driven by edaphic and landscape factors.

year: 2018

title: ‘Indigenous Rights’ or ‘Racial Privileges’: The rhetoric of ‘race’ in New Zealand politics

authors: Barber, Keith

subjects: indigeneity

abstract: The New Zealand parliamentary election campaign of 2005 was marked by a significant break in the consensus between the two major political parties, Labour and National, in the area of Maori affairs: a consensus that had previously been articulated in terms of a shared commitment to 'biculturalism' and the Treaty of Waitangi. In January 2004, the National Party launched an attack on government policies, describing them as giving unfair privileges to Maori based purely on 'race'. The present paper examines the National Party's adoption of the rhetoric of 'race' and the conceptual, political and ideological considerations behind it. It also examines attitudinal, social policy and socioeconomic factors to explain the widespread acceptability of this rhetoric among the New Zealand public. These events are considered within the context of a growing academic and political critique of 'culturalism' in New Zealand social policy and social science.

text: ‘Indigenous Rights’ or ‘Racial Privileges’: The rhetoric of ‘race’ in New Zealand politics The New Zealand parliamentary election campaign of 2005 was marked by a significant break in the consensus between the two major political parties, Labour and National, in the area of Maori affairs: a consensus that had previously been articulated in terms of a shared commitment to 'biculturalism' and the Treaty of Waitangi. In January 2004, the National Party launched an attack on government policies, describing them as giving unfair privileges to Maori based purely on 'race'. The present paper examines the National Party's adoption of the rhetoric of 'race' and the conceptual, political and ideological considerations behind it. It also examines attitudinal, social policy and socioeconomic factors to explain the widespread acceptability of this rhetoric among the New Zealand public. These events are considered within the context of a growing academic and political critique of 'culturalism' in New Zealand social policy and social science.

year: 2008