title: Extent estimates and land cover relationships for functional indicators in non-wadeable rivers

authors: Collier, Kevin J.

subjects: metabolism

abstract: Functional indicators are being increasingly used to assess waterway health but their responses to pressure in non-wadeable rivers have not been widely documented or applied in modern survey designs that provide unbiased estimates of extent. This study tests the response of river metabolism and loss in cotton strip tensile strength across a land use pressure gradient in non-wadeable rivers of northern New Zealand, and reports extent estimates for river metabolism and decomposition rates. Following adjustment for probability of selection, ecosystem respiration (ER) and gross primary production (GPP) for the target population of order 5–7 non-wadeable rivers averaged −7.3 and 4.8 g O2 mˉ² dˉ¹, respectively, with average P/R < 1 indicating dominance by heterotrophic processes. Ecosystem respiration was <−3.3 g O2 mˉ² dˉ¹ for 75% of non-wadeable river length with around 20% of length between −10 and −20 g O2 mˉ² dˉ¹. Cumulative distribution functions of cotton strength loss estimates indicated a more-or-less linear relationship with river km reflecting an even spread of decay rates (range in k 0.0007–0.2875 dˉ¹) across non-wadeable rivers regionally. A non-linear relationship with land cover was detected for GPP which was typically <5 g O2 mˉ² dˉ¹ where natural vegetation cover was below 20% and greater than 80% of upstream catchment area. For cotton strength loss, the relationship with land cover was wedge-shaped such that sites with >60% natural cover had low decay rates (<0.02 dˉ¹) with variability below this increasing as natural cover declined. Using published criteria for assessing waterway health based on ER and GPP, 232–298 km (20–29%) of non-wadeable river length was considered to have severely impaired ecosystem functioning, and 436–530 km (42–50%) had no evidence of impact on river metabolism.

text: Extent estimates and land cover relationships for functional indicators in non-wadeable rivers Functional indicators are being increasingly used to assess waterway health but their responses to pressure in non-wadeable rivers have not been widely documented or applied in modern survey designs that provide unbiased estimates of extent. This study tests the response of river metabolism and loss in cotton strip tensile strength across a land use pressure gradient in non-wadeable rivers of northern New Zealand, and reports extent estimates for river metabolism and decomposition rates. Following adjustment for probability of selection, ecosystem respiration (ER) and gross primary production (GPP) for the target population of order 5–7 non-wadeable rivers averaged −7.3 and 4.8 g O2 mˉ² dˉ¹, respectively, with average P/R < 1 indicating dominance by heterotrophic processes. Ecosystem respiration was <−3.3 g O2 mˉ² dˉ¹ for 75% of non-wadeable river length with around 20% of length between −10 and −20 g O2 mˉ² dˉ¹. Cumulative distribution functions of cotton strength loss estimates indicated a more-or-less linear relationship with river km reflecting an even spread of decay rates (range in k 0.0007–0.2875 dˉ¹) across non-wadeable rivers regionally. A non-linear relationship with land cover was detected for GPP which was typically <5 g O2 mˉ² dˉ¹ where natural vegetation cover was below 20% and greater than 80% of upstream catchment area. For cotton strength loss, the relationship with land cover was wedge-shaped such that sites with >60% natural cover had low decay rates (<0.02 dˉ¹) with variability below this increasing as natural cover declined. Using published criteria for assessing waterway health based on ER and GPP, 232–298 km (20–29%) of non-wadeable river length was considered to have severely impaired ecosystem functioning, and 436–530 km (42–50%) had no evidence of impact on river metabolism.

year: 2013

title: Heat Transfer Enhancement in Heat Recovery Loops Using Nanofluids as the Intermediate Fluid

authors: Tarighaleslami, Amir Hossein

abstract: In this paper, the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) have been modelled. Generally, nanofluids are prepared by distributing a nanoparticle through a base fluid such as water. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. With the addition of 1.5 vol.% CuO nanoparticles to the HRL fluid using constant temperature storage method, heat recovery from liquid-liquid heat exchangers increases between 5 % and 9 %. In the case of air-liquid exchangers, the air-side heat transfer coefficient limits the impact of using a nanofluid. In other cases, the duty available from the process stream, such as a condenser, significantly restricts the heat transfer benefit of using a nanofluid. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid-liquid matches.

text: Heat Transfer Enhancement in Heat Recovery Loops Using Nanofluids as the Intermediate Fluid In this paper, the effect of replacing water with various nanofluids as the heat transfer media in an industrial Heat Recovery Loop (HRL) have been modelled. Generally, nanofluids are prepared by distributing a nanoparticle through a base fluid such as water. Suspended nanoparticles slightly affect the thermal and physical properties of the base fluid. Primarily nanoparticles are added to improve the fluid’s heat transfer characteristics by increasing its Reynolds number and thermal conductivity. Results show that by applying various HRL design methods and a nanofluid as an intermediate fluid, an increase in heat recovery is possible without the need for extra heat exchanger area and infrastructure. With the addition of 1.5 vol.% CuO nanoparticles to the HRL fluid using constant temperature storage method, heat recovery from liquid-liquid heat exchangers increases between 5 % and 9 %. In the case of air-liquid exchangers, the air-side heat transfer coefficient limits the impact of using a nanofluid. In other cases, the duty available from the process stream, such as a condenser, significantly restricts the heat transfer benefit of using a nanofluid. Alternative to increasing heat recovery, results show that applying a nanofluid in the HRL design phase enables heat exchanger area to decrease significantly for liquid-liquid matches.

year: 2015-08-27

title: Harakeke (Phormium tenax) ecology and historical management by Maori: The changing landscape in New Zealand

authors: Wehi, Priscilla M.

subjects: ethnobotany

abstract: Harakeke (Phormium tenax: Phormiaceae) is an important weaving resource for the indigenous Maori people of New Zealand. This research project investigates Maori knowledge of harakeke ecology and management practices prior to the early 20th century within the context of a study of relevant environmental parameters that limit its natural distribution. Ecological information referring to harakeke was analysed from interviews with elders and ancestral sayings (whakatauki). As well, documents from the late 181h to the early 20th century were examined, and environmental parameters for both harakeke and wharariki (Phormium cookianum) were quantified and analysed using correlative models. 
Interviews with 11 elders (from Waikato and Northland) identified key issues in harakeke management, including 'correct' harvesting procedures, use of natural harakeke stands, and specific use of different varieties. Planting practices varied regionally. Three different methods of excess harakeke disposal were reported, including burning. The 15 whakatauki analysed emphasise the interconnectedness of ecosystems, including pollinator-plant relationships for kaka and bellbirds. Four whakataukirefer to environmental tolerances for harakeke and two to the use of fire to stimulate harakeke growth. Others refer to competition between shoots, nutrient requirements, and the growth and multiplication of harakeke offsets. 
Numerous early reports indicate that harakeke has been cultivated throughout much of New Zealand, with cultivations ranging in size from a few bushes to at least several acres. Thirty six varieties were linked to specific weaving uses. Twenty varieties were cultivated, but ten prized fibre varieties were also harvested from natural stands. Numbers of recorded varieties varied between districts, with 31 recorded in Taranaki but only two recorded by name for Northland. Valued varieties, including raumoa and oue, were dispersed throughout the North Island. Mapping different varieties revealed a wide spatial spread for varieties such as rataroa and oue. Specific management techniques included seed germination as well as vegetative propagation. Early records of harakeke pests were not found. Records of harakeke irrigation and the use of fire indicate that Maori created suitable conditions for new cultivations or pii harakeke, which may also have prevented insect infestation. Cumulatively, there is evidence of extensive active management of harakeke. Wharariki and harakeke were found to have distinct environmental niches, with wharariki better able to withstand cooler temperatures, higher rainfall and greater frequency of ground frost than harakeke.
Predictive mapping of harakeke for the northern region of New Zealand shows a low probability of naturally occurring harakeke in much of the Northland and Waikato interior, and a high probability in coastal areas with warm temperatures. It seems likely that Maori transported harakeke into areas where it was unlikely to have occurred naturally and that some apparently 'natural' stands ofharakeke were created and maintained by Maori.
Maori cultivation, dispersal and active management of harakeke, as well as possible creation of wetland areas, emphasises the importance of harakeke as an economic resource prior to European colonisation, and indicates how the New Zealand landscape may have been transformed. Maori ecological knowledge can contribute new perspectives to restoration ecology and ecosystem research.

text: Harakeke (Phormium tenax) ecology and historical management by Maori: The changing landscape in New Zealand Harakeke (Phormium tenax: Phormiaceae) is an important weaving resource for the indigenous Maori people of New Zealand. This research project investigates Maori knowledge of harakeke ecology and management practices prior to the early 20th century within the context of a study of relevant environmental parameters that limit its natural distribution. Ecological information referring to harakeke was analysed from interviews with elders and ancestral sayings (whakatauki). As well, documents from the late 181h to the early 20th century were examined, and environmental parameters for both harakeke and wharariki (Phormium cookianum) were quantified and analysed using correlative models. 
Interviews with 11 elders (from Waikato and Northland) identified key issues in harakeke management, including 'correct' harvesting procedures, use of natural harakeke stands, and specific use of different varieties. Planting practices varied regionally. Three different methods of excess harakeke disposal were reported, including burning. The 15 whakatauki analysed emphasise the interconnectedness of ecosystems, including pollinator-plant relationships for kaka and bellbirds. Four whakataukirefer to environmental tolerances for harakeke and two to the use of fire to stimulate harakeke growth. Others refer to competition between shoots, nutrient requirements, and the growth and multiplication of harakeke offsets. 
Numerous early reports indicate that harakeke has been cultivated throughout much of New Zealand, with cultivations ranging in size from a few bushes to at least several acres. Thirty six varieties were linked to specific weaving uses. Twenty varieties were cultivated, but ten prized fibre varieties were also harvested from natural stands. Numbers of recorded varieties varied between districts, with 31 recorded in Taranaki but only two recorded by name for Northland. Valued varieties, including raumoa and oue, were dispersed throughout the North Island. Mapping different varieties revealed a wide spatial spread for varieties such as rataroa and oue. Specific management techniques included seed germination as well as vegetative propagation. Early records of harakeke pests were not found. Records of harakeke irrigation and the use of fire indicate that Maori created suitable conditions for new cultivations or pii harakeke, which may also have prevented insect infestation. Cumulatively, there is evidence of extensive active management of harakeke. Wharariki and harakeke were found to have distinct environmental niches, with wharariki better able to withstand cooler temperatures, higher rainfall and greater frequency of ground frost than harakeke.
Predictive mapping of harakeke for the northern region of New Zealand shows a low probability of naturally occurring harakeke in much of the Northland and Waikato interior, and a high probability in coastal areas with warm temperatures. It seems likely that Maori transported harakeke into areas where it was unlikely to have occurred naturally and that some apparently 'natural' stands ofharakeke were created and maintained by Maori.
Maori cultivation, dispersal and active management of harakeke, as well as possible creation of wetland areas, emphasises the importance of harakeke as an economic resource prior to European colonisation, and indicates how the New Zealand landscape may have been transformed. Maori ecological knowledge can contribute new perspectives to restoration ecology and ecosystem research.

year: 2005