title: Depth-differentiated, multivariate control of biopore number under different land-use practices

authors: Stolze, Katharina

subjects: earthworm communities

abstract: Earthworms and (tap-)roots impact the soil structure by creating large biopores, affecting infiltration capacity, seepage, nutrient cycling, and soil aeration. Despite the importance of biopores for the functions of soils and the fact that several hundreds of biopores >2 mm in diameter may occur on one square meter of soil, knowledge on the interdependence of soil properties, land-use intensity, and biopore number is still rudimentary. In this study, we investigate the linkage of the number of biopores (>2 mm i.d.) with the earthworm community, root biomass, and soil properties, including pH, water content, soil organic carbon (SOC), as well as the land-use intensity (pasture vs. cropland) as a function of the soil depth (15, 30 and 50 cm). Hypothesized causal relationships among these factors were analyzed by piecewise structural equation modelling (SEM). We found various and novel linkages between roots, earthworms, biopores, and soil properties depending on soil depth. In topsoil (at 15 cm depth), roots directly affected the number of small-sized biopores, and anecic earthworms were related to medium-sized biopores. These effects diminished with depth. We identified land-use intensity as the factor preponderating the relations between biopores, root biomass, and earthworm number in the topsoil horizons, thereby masking other interactions among variables. This appeared as high multicollinearity among variables in the SEM of the topsoil. Land-use intensity effects were found to impact the whole soil profile but decreased with soil depth. To further elucidate the single effects of soil properties on biopore-forming biota and number of biopores in the topsoil, we excluded land-use intensity as a variable in subsequent analyses. Biopores increased with soil pH and soil water content but decreased with increasing SOC. Based on our SEM analysis, we conclude that the occurrence, frequency, and persistence of biopores are the consequence of intricate interdependencies between earthworm communities, roots, and site-specific soil properties, governed by land-use intensity.

text: Depth-differentiated, multivariate control of biopore number under different land-use practices Earthworms and (tap-)roots impact the soil structure by creating large biopores, affecting infiltration capacity, seepage, nutrient cycling, and soil aeration. Despite the importance of biopores for the functions of soils and the fact that several hundreds of biopores >2 mm in diameter may occur on one square meter of soil, knowledge on the interdependence of soil properties, land-use intensity, and biopore number is still rudimentary. In this study, we investigate the linkage of the number of biopores (>2 mm i.d.) with the earthworm community, root biomass, and soil properties, including pH, water content, soil organic carbon (SOC), as well as the land-use intensity (pasture vs. cropland) as a function of the soil depth (15, 30 and 50 cm). Hypothesized causal relationships among these factors were analyzed by piecewise structural equation modelling (SEM). We found various and novel linkages between roots, earthworms, biopores, and soil properties depending on soil depth. In topsoil (at 15 cm depth), roots directly affected the number of small-sized biopores, and anecic earthworms were related to medium-sized biopores. These effects diminished with depth. We identified land-use intensity as the factor preponderating the relations between biopores, root biomass, and earthworm number in the topsoil horizons, thereby masking other interactions among variables. This appeared as high multicollinearity among variables in the SEM of the topsoil. Land-use intensity effects were found to impact the whole soil profile but decreased with soil depth. To further elucidate the single effects of soil properties on biopore-forming biota and number of biopores in the topsoil, we excluded land-use intensity as a variable in subsequent analyses. Biopores increased with soil pH and soil water content but decreased with increasing SOC. Based on our SEM analysis, we conclude that the occurrence, frequency, and persistence of biopores are the consequence of intricate interdependencies between earthworm communities, roots, and site-specific soil properties, governed by land-use intensity.

year: 2022

title: Return on investment: Investigating managerial preferences for alternative return on investment reports

authors: Lys, Brendan John

subjects: ROI

abstract: Responses of 32 Officers and 1 Non Commissioned Officer, of the Royal New Zealand Navy, to three return on investment (ROI) training reports were investigated. The three report types were presented as a function of two ROI calculations: Critical Outcome Technique, and Utility Analysis - with Utility Analysis being used as the basis for two of the three reports. Participants were placed into one of three groups, each group consisted of 11 participants. Each participant group was presented with one of the three report types. Responses from participants were gained using a survey instrument for two constructs: perceived usefulness, and perceived understanding and clarity. The results of this study replicated the findings of previous studies in this area (i.e. Carson, Becker & Henderson, 1998; Macan & Foster, 2004). An analysis of quantitative data using Kruskal-Wallis statistical test failed to show significantly different perceptions of either perceived usefulness, or perceived understanding and clarity between the three groups. While the presented reports lacked high levels of support from participants, the findings of Latham and Whyte’s study (1994) are brought further into question (i.e. Cronshaw, 1997; Macan & Foster, 2004) as utility analysis based reports did not negatively influence participants on the uptake of the hypothetical training initiative. Content analysis of the qualitative data, revealed a number of potential factors which may have caused a lack of significance between report type preferences. Most critically these causes may not be limited to this this study alone, but may have implications for both previous and future studies into ROI acceptance.

text: Return on investment: Investigating managerial preferences for alternative return on investment reports Responses of 32 Officers and 1 Non Commissioned Officer, of the Royal New Zealand Navy, to three return on investment (ROI) training reports were investigated. The three report types were presented as a function of two ROI calculations: Critical Outcome Technique, and Utility Analysis - with Utility Analysis being used as the basis for two of the three reports. Participants were placed into one of three groups, each group consisted of 11 participants. Each participant group was presented with one of the three report types. Responses from participants were gained using a survey instrument for two constructs: perceived usefulness, and perceived understanding and clarity. The results of this study replicated the findings of previous studies in this area (i.e. Carson, Becker & Henderson, 1998; Macan & Foster, 2004). An analysis of quantitative data using Kruskal-Wallis statistical test failed to show significantly different perceptions of either perceived usefulness, or perceived understanding and clarity between the three groups. While the presented reports lacked high levels of support from participants, the findings of Latham and Whyte’s study (1994) are brought further into question (i.e. Cronshaw, 1997; Macan & Foster, 2004) as utility analysis based reports did not negatively influence participants on the uptake of the hypothetical training initiative. Content analysis of the qualitative data, revealed a number of potential factors which may have caused a lack of significance between report type preferences. Most critically these causes may not be limited to this this study alone, but may have implications for both previous and future studies into ROI acceptance.

year: 2011

title: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo

authors: Kusabs, Ian Andrew

abstract: The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

text: The biology and general ecology of the Koaro (Galaxias brevipinnis) in some tributary streams of Lake Taupo The ecology and general biology of Galaxias brevipinnis were studied in three tributary streams of Lake Taupo between May 1988 and April 1989. Adult koaro were found in relatively high densities in the Waipehi and Omori streams but in low densities in the larger Waiotaka stream. The results of population estimation studies suggest that the distribution and abundance of koaro is negatively correlated with that of trout. There was a general decline in the population density of stream-resident koaro in the winter months. Juvenile koaro were found to migrate into the tributaries from August to December, with migrations being at a peak in October and November.

Population length-frequency distributions and otoliths used to age koaro indicated that there were up to 5 age classes. Growth was allometric and was adequately described by the von Bertalanffy equation after the first year of life. Koaro were found to be in best condition in the Spring and lowest in Winter.

Spawning appeared to occur from December through to April peaking in late Summer to early in the Waipehi Stream was Autumn. The mean fecundity of koaro approximately 5500. A sex-ratio of approximately 1:1 (males: females) were found in the koaro populations in the Omori and Waipehi streams, but during spawning there were always more ripe males than gravid females.

There was considerable overlap in the diets of both koaro and juvenile rainbow trout in the Waipehi and Omori streams, with invertebrates being consumed according to their relative abundance in the benthos. Ephemeroptera larvae were numerically the most important food item in the diet of both species. However, by weight, fish (juvenile koaro) were the most important food · item in the diet of koaro and rainbow trout in the Waipehi stream. In the Omori stream in Winter, trout eggs were the most important food item in terms of weight. Terrestrial prey was found to be of relatively minor importance in the diets of koaro and rainbow trout in the Waipehi and Omori streams.

year: 1989