title: Accumulation of soil organic C and change in C:N ratio after establishment of pastures on reverted scrubland in New Zealand

authors: Schipper, Louis A.

subjects: soil organic C

abstract: Rates of organic carbon accumulation and changes in C:N ratio are reported for 10 New Zealand soils converted to pastures from scrub. The data were derived from archive papers originally published in 1964, but which did not report on changes in the C contents of the soils. The soils had been sampled to 0–7.5, 7.5–15, and 15–30 cm depths and chronosequences of up to 66 years obtained by selecting sites with differing times since pasture establishment. We calculated changes in the mass of C and N in the 0–7.5 cm depth and compared that to the mass in the 0–30 cm depth of soil. The shortest time over which organic matter change was assessed was 18 years and the longest was 66 years. Nine of the ten soils showed increases in the C contents of the 0–7.5 cm depth soil, and a natural logarithmic curve generally gave a better fit to the time course data than a linear fit. However, when the full 0–30 cm depth was considered, only two soils showed a significant increase in total C, changes in the C contents of other soils were non-significant, and two soils showed a decline in total C. The rates of change in the C contents were averaged over 0–5 years, 5–25 years and 25–50 years. Across all 10 soils, the mean rates of accumulation of C in the 0–7.5 cm depth were 1.07 (between 0 and 5 years), 0.27 (between 5 and 25 years) and 0.09 Mg C ha−1 year−1 (between 25 and 50 years) and significantly (P < 0.05) greater than zero. Very similar rates were obtained for the 0–30 cm depth of soil with mean rates across all soils 1.01 (0–5 years), 0.25 (5–25 years) and 0.09 Mg C ha−1 year −1 (25–50 years), respectively. In the 0–7.5 cm depth of soil, total Kjeldahl N (TKN) increased significantly in seven of the 10 soils. When expressed for the 0–30 cm depth of soil, only five soils still showed significant increases in TKN contents over time. Using the data for the 0–7.5 cm depth, the predicted time (mean and standard error) for the soils to reach a C:N ratio of <10 was 46 ± 17 years. The soils were originally sampled over 44 years ago, suggesting that currently (2009), very few of them could be expected to have capacity for further N storage in organic matter in the surface soil unless there was an increase in soil C. Changes in soil C and N in the shallow upper soil layers are easily masked by the relatively small changes in C and N contents and much greater masses of soil at lower depths.

text: Accumulation of soil organic C and change in C:N ratio after establishment of pastures on reverted scrubland in New Zealand Rates of organic carbon accumulation and changes in C:N ratio are reported for 10 New Zealand soils converted to pastures from scrub. The data were derived from archive papers originally published in 1964, but which did not report on changes in the C contents of the soils. The soils had been sampled to 0–7.5, 7.5–15, and 15–30 cm depths and chronosequences of up to 66 years obtained by selecting sites with differing times since pasture establishment. We calculated changes in the mass of C and N in the 0–7.5 cm depth and compared that to the mass in the 0–30 cm depth of soil. The shortest time over which organic matter change was assessed was 18 years and the longest was 66 years. Nine of the ten soils showed increases in the C contents of the 0–7.5 cm depth soil, and a natural logarithmic curve generally gave a better fit to the time course data than a linear fit. However, when the full 0–30 cm depth was considered, only two soils showed a significant increase in total C, changes in the C contents of other soils were non-significant, and two soils showed a decline in total C. The rates of change in the C contents were averaged over 0–5 years, 5–25 years and 25–50 years. Across all 10 soils, the mean rates of accumulation of C in the 0–7.5 cm depth were 1.07 (between 0 and 5 years), 0.27 (between 5 and 25 years) and 0.09 Mg C ha−1 year−1 (between 25 and 50 years) and significantly (P < 0.05) greater than zero. Very similar rates were obtained for the 0–30 cm depth of soil with mean rates across all soils 1.01 (0–5 years), 0.25 (5–25 years) and 0.09 Mg C ha−1 year −1 (25–50 years), respectively. In the 0–7.5 cm depth of soil, total Kjeldahl N (TKN) increased significantly in seven of the 10 soils. When expressed for the 0–30 cm depth of soil, only five soils still showed significant increases in TKN contents over time. Using the data for the 0–7.5 cm depth, the predicted time (mean and standard error) for the soils to reach a C:N ratio of <10 was 46 ± 17 years. The soils were originally sampled over 44 years ago, suggesting that currently (2009), very few of them could be expected to have capacity for further N storage in organic matter in the surface soil unless there was an increase in soil C. Changes in soil C and N in the shallow upper soil layers are easily masked by the relatively small changes in C and N contents and much greater masses of soil at lower depths.

year: 2010

title: Graph convolutional LSTM model for traffic delay prediction with uncertainty

authors: Townsend, Dale

subjects: Deep learning

abstract: Traffic flow in an urban environment exhibits a complex spatio-temporal in- teraction. The propogation of traffic flow through a transportation network depends on a number of factors, including the structure of the network and the time of day. Current analysis of this data by road controlling authorities is of- ten simplified and lacks a detailed understanding of how traffic moves through the network. A deep learning model which models both the spatial and tempo- ral interactions present in the data is able to capture complex patterns present in the data and allows for a more detailed understanding of traffic flow. A GC- LSTM model is explored for Hamilton City to predict traffic delay. It is found to have improved prediction accuracy over a standard LSTM by incorporating the spatial structure of the Hamilton road network. Additionally, Bayesian layers are integrated into the model to obtain a probability distribution over each prediction. By quantifying the uncertainty over each prediction, the de- cision making process based on the analysis can be carried out with a higher degree of confidence than a single point prediction from the model.

text: Graph convolutional LSTM model for traffic delay prediction with uncertainty Traffic flow in an urban environment exhibits a complex spatio-temporal in- teraction. The propogation of traffic flow through a transportation network depends on a number of factors, including the structure of the network and the time of day. Current analysis of this data by road controlling authorities is of- ten simplified and lacks a detailed understanding of how traffic moves through the network. A deep learning model which models both the spatial and tempo- ral interactions present in the data is able to capture complex patterns present in the data and allows for a more detailed understanding of traffic flow. A GC- LSTM model is explored for Hamilton City to predict traffic delay. It is found to have improved prediction accuracy over a standard LSTM by incorporating the spatial structure of the Hamilton road network. Additionally, Bayesian layers are integrated into the model to obtain a probability distribution over each prediction. By quantifying the uncertainty over each prediction, the de- cision making process based on the analysis can be carried out with a higher degree of confidence than a single point prediction from the model.

year: 2021

title: Tarāwhai Tāngata Rau

authors: Hiini, Anaha Te Wheoro

subjects: Tarāwhai

abstract: Ngāti Tarāwhai are a unique tribal group from the Te Arawa confederation of tribes.  Located around their traditional stronghold of Lake Okataina, Tarāwhai have endured throughout history to become a proud and noble clan, maintaining their culture and distinctive tribal practises.  Part of their survival throughout time has been their ability to rely on particular traits and attributes that have been portrayed and maintained by members of Tarāwhai across the generations.  These special characteristics have not only supported the development of Tarāwhai, but have also helped the evolution of Tarāwhai’s identity.

This thesis is concerned with four aspects that have been identified as common traits throughout Ngāti Tarāwhai history.  In particular, this study will look at the roles of leaders, tohunga, warriors and carving experts and explore how these qualities have featured significantly within Tarāwhai’s history for many generations.  Furthermore, this thesis will discuss how these aspects have influenced the development of the tribe from early time through to the present day.

It is the proposition of this thesis that the above mentioned attributes have shaped the people of Tarāwhai into the tribal group that they are today.  In addition, while Māori society has changed dramatically in the last 100 years, Tarāwhai continue to display these characteristics in a modern world, and they are still central to the reaffirmation of Tarāwhai identity and the overall wellbeing of the people.  Finally this thesis believes that these attributes must be maintained and perpetuated for Tarāwhi to have a secure place in the future.

text: Tarāwhai Tāngata Rau Ngāti Tarāwhai are a unique tribal group from the Te Arawa confederation of tribes.  Located around their traditional stronghold of Lake Okataina, Tarāwhai have endured throughout history to become a proud and noble clan, maintaining their culture and distinctive tribal practises.  Part of their survival throughout time has been their ability to rely on particular traits and attributes that have been portrayed and maintained by members of Tarāwhai across the generations.  These special characteristics have not only supported the development of Tarāwhai, but have also helped the evolution of Tarāwhai’s identity.

This thesis is concerned with four aspects that have been identified as common traits throughout Ngāti Tarāwhai history.  In particular, this study will look at the roles of leaders, tohunga, warriors and carving experts and explore how these qualities have featured significantly within Tarāwhai’s history for many generations.  Furthermore, this thesis will discuss how these aspects have influenced the development of the tribe from early time through to the present day.

It is the proposition of this thesis that the above mentioned attributes have shaped the people of Tarāwhai into the tribal group that they are today.  In addition, while Māori society has changed dramatically in the last 100 years, Tarāwhai continue to display these characteristics in a modern world, and they are still central to the reaffirmation of Tarāwhai identity and the overall wellbeing of the people.  Finally this thesis believes that these attributes must be maintained and perpetuated for Tarāwhi to have a secure place in the future.

year: 2013