title: The role of Empodisma robustum litter in CO₂ exchange at Kopuatai bog

authors: Keyte Beattie, Alexandra Margaret

subjects: Empodisma robustum

abstract: Respiration from the decomposition of standing dead litter in peatlands influences the ecosystem carbon balance through its contribution to total ecosystem respiration (ER). This research determined the proportion of ER estimated at Kopuatai bog that is sourced from the decomposition of Empodisma robustum litter in the canopy. Canopy harvests were carried out to measure the mass of standing litter in the canopy; laboratory litter incubations were used to measure respiration rates over a range of temperatures and moisture contents; and a simple model was developed to estimate annual litter respiration using inputs of canopy wetness duration and canopy temperature.

E. robustum litter comprised an average of 51% of the total canopy biomass, with 0.92 kg m⁻² standing litter dry matter in 1.8 kg m⁻² of total canopy dry matter. The majority of this litter is located in the lower part of the canopy. Very low respiration rates were measured for the E. robustum litter, although respiration was significantly higher in litter which was more physically decomposed (R₁₀ = 0.44 (± 0.1) μmol kg⁻¹ s⁻¹) than that which was freshly dead (R₁₀ = 0.24 (± 0.05) μmol kg⁻¹ s⁻¹). Litter respiration showed a strong temperature response, and was moisture-limited below approximately 50% moisture content. The model of litter respiration estimated that standing dead E. robustum litter contributed 59 g C m⁻² yr⁻¹ (8.8%) to annual total ER. This represents an estimated litter turnover time of 7 – 8 years. While the contribution of litter respiration to ER is relatively small, the resulting large mass of recalcitrant litter in the canopy may contribute to E. robustum’s ability to engineer its environment.

text: The role of Empodisma robustum litter in CO₂ exchange at Kopuatai bog Respiration from the decomposition of standing dead litter in peatlands influences the ecosystem carbon balance through its contribution to total ecosystem respiration (ER). This research determined the proportion of ER estimated at Kopuatai bog that is sourced from the decomposition of Empodisma robustum litter in the canopy. Canopy harvests were carried out to measure the mass of standing litter in the canopy; laboratory litter incubations were used to measure respiration rates over a range of temperatures and moisture contents; and a simple model was developed to estimate annual litter respiration using inputs of canopy wetness duration and canopy temperature.

E. robustum litter comprised an average of 51% of the total canopy biomass, with 0.92 kg m⁻² standing litter dry matter in 1.8 kg m⁻² of total canopy dry matter. The majority of this litter is located in the lower part of the canopy. Very low respiration rates were measured for the E. robustum litter, although respiration was significantly higher in litter which was more physically decomposed (R₁₀ = 0.44 (± 0.1) μmol kg⁻¹ s⁻¹) than that which was freshly dead (R₁₀ = 0.24 (± 0.05) μmol kg⁻¹ s⁻¹). Litter respiration showed a strong temperature response, and was moisture-limited below approximately 50% moisture content. The model of litter respiration estimated that standing dead E. robustum litter contributed 59 g C m⁻² yr⁻¹ (8.8%) to annual total ER. This represents an estimated litter turnover time of 7 – 8 years. While the contribution of litter respiration to ER is relatively small, the resulting large mass of recalcitrant litter in the canopy may contribute to E. robustum’s ability to engineer its environment.

year: 2014

title: Sorption, degradation and transport of veterinary antibiotics in New Zealand pastoral soils

authors: Srinivasan, Prakash

subjects: Soils, Veterinary antibiotics

abstract: Veterinary antibiotics are used worldwide for prevention and treatment of various diseases of livestock animals. After administration, the majority of antibiotics are excreted in urine and faeces as unchanged parent compound, and/or as their metabolites. With increases in the intensive use of antibiotics in New Zealand agriculture and direct land application of waste as manure, there is concern that excreted compounds could migrate to the receiving environment with potential impact on surface and groundwater. Antibiotic residues in soil could give rise to a variety of ecotoxicological problems and could also confer antibiotic resistance. As a first step towards assessing the risk of these compounds, it is important to investigate their fate and behaviour in the soil environment. The focus of this work was to determine the fate and transport behaviour of selected group of veterinary antibiotics in several New Zealand pastoral soils. A macrolide (TT) and three sulfonamide antibiotics (SMO, SCP and SM) were chosen for this study as they are commonly used overseas as well as in New Zealand. 

A simple, yet robust analytical method was developed to detect and quantify TT and the three sulfonamides using high performance liquid chromatography and ultraviolet detection. The limits of detection at signal: noise ratio of 3 were 20.0 µg L⁻¹ and 50 µg L⁻¹ for all SA’s and TT respectively. The average recoveries for all SA’s and TT in aqueous matrices ranged from 95 to 105% across the six concentrations investigated. Recoveries from the residual soils were slightly lower for SA’s and TT (~ 50 to 60%).  

The results of the kinetics studies showed that sorption was rapid in the first few hours of the contact time (0 to 2 h for SA’s and 0 to 4 h for TT) and thereafter an apparent equilibrium concentration was achieved slowly. Batch sorption results performed in six different pastoral soils showed that Freundlich isotherms were nonlinear (N ≠ 1) for most of the compounds. The degree of isotherm linearity (N) for SCP and SM varied between 0.87–1.11 in the six soils. SMO showed a highly non-linear pattern (N = 0.75) in just one soil (Manawatu). Isotherms of both TT and SMO were non-linear, with the degree of non-linearity for TT (N = 0.41–0.73) being greater than for SMO (0.88–1.21) in all soils. Concentration-dependent effective distribution coefficient (Kdeff ) values for the SMO, SCP and SM antibiotics in the soils ranged from 0.37 to 4.6 L kg⁻¹ and for TT Kdeff ranged from 1.2 to 500 L kg⁻¹. The sorption affinity for all soils followed an order: TT > SCP > SM > SMO. Statistical analysis of sorption data revealed a correlation between the sorption coefficients and soil properties such as % organic carbon, cation exchange capacity and clay content.  Sorption of TT onto soils is mostly driven by the cation exchange capacity of the soil whereas for sulfonamides it is primarily due to hydrophobic interactions due to hydrophobic interactions.

On further investigation it was found that sorption of the SMO antibiotic to soils was highly dependent on pH, ionic strength, and organic matter of the soil. Sorption of SMO decreased with the increases in pH, and increased with increasing ionic strength and organic carbon content. A hydrophobic pH-partitioning model linking sorbate speciation with species-specific sorption coefficients describing the pH dependence of the apparent sorption coefficients was successfully used to derive the fraction of each species of SMO that are likely to be present in the environment. 

The results from the biochar amended sorption studies showed that certain biochars can be used as a potential tool to remove residues of antibiotics. Soil amended with pine saw dust biochar was found to be the most effective in adsorbing antibiotics. Pine sawdust biochar absorbed 30 times more antibiotics than soil alone. This was attributed to its high surface area, which was four times higher than that of other biochars, or could be due to its high carbon content (91%). The results have shown that biochar applied at the rate of 0.5 to 1% by soil weight could prove to be an effective way to slow down the release of these contaminants to a manageable level thereby reducing the risk of ecotoxicity and antibiotic resistance.

SMO degraded slowly in agricultural soils. The degradation times (DT₅₀) for SMO in Hamilton clay, Te Kowhai and Horotiu soils under non-sterilized conditions were 9.24, 4.3 and 13.33 days respectively. Soil dehydrogenase activities were directly correlated with degradation kinetics of SMO antibiotic. Results from degradation studies have shown that SMO is not likely to persist more than 90 days in all three soils suggesting that natural biodegradation may be sufficient for the removal of these contaminants from the soil. Both the degree of biological activity and temperature of the soil influenced overall degradation.  SMO degradation in sterile soils indicated abiotic degradation and abiotic factors such as strong sorption of the antibiotic onto soil components also played a role in the degradation of SMO in soil. Four kinetic models, a single first-order model (SFO) and three biphasic kinetic models, were applied to fit the observed SMO degradation kinetics data. The results showed that the First-order double-exponential decay (FODED) and first-order two-compartment (FOTC) model was superior to the bi-exponential model (BEXP) and all three biphasic models were superior when compared to the SFO model for describing SMO degradation data. Use of the FOTC model enabled the estimation of the degradation endpoints. 

The results from two soil lysimeters indicate that the three sulfonamides were highly mobile and that at field collected soil pH mobility was similar to the mobility of the conservative bromide. The breakthrough curves of the three sulfonamides varied depending on soil type with Hamilton soil showing more retardation than Matawhero soil. For the three sulfonamides studied the order of breakthrough was generally observed to be: SM > SMO > SCP for both Matawhero and Hamilton soils. Residual antibiotic concentrations for SMO and SCP were detected up to depths of 18 cm. The CXTFIT model study described the peak arrival time as well as the maximum concentration of the antibiotic breakthrough curves but showed some underestimation at advanced stages of sulfonamide leaching, especially in the Hamilton soil. Results showed that the sulfonamides have weak sorption affinity and relatively high mobility in soils.

text: Sorption, degradation and transport of veterinary antibiotics in New Zealand pastoral soils Veterinary antibiotics are used worldwide for prevention and treatment of various diseases of livestock animals. After administration, the majority of antibiotics are excreted in urine and faeces as unchanged parent compound, and/or as their metabolites. With increases in the intensive use of antibiotics in New Zealand agriculture and direct land application of waste as manure, there is concern that excreted compounds could migrate to the receiving environment with potential impact on surface and groundwater. Antibiotic residues in soil could give rise to a variety of ecotoxicological problems and could also confer antibiotic resistance. As a first step towards assessing the risk of these compounds, it is important to investigate their fate and behaviour in the soil environment. The focus of this work was to determine the fate and transport behaviour of selected group of veterinary antibiotics in several New Zealand pastoral soils. A macrolide (TT) and three sulfonamide antibiotics (SMO, SCP and SM) were chosen for this study as they are commonly used overseas as well as in New Zealand. 

A simple, yet robust analytical method was developed to detect and quantify TT and the three sulfonamides using high performance liquid chromatography and ultraviolet detection. The limits of detection at signal: noise ratio of 3 were 20.0 µg L⁻¹ and 50 µg L⁻¹ for all SA’s and TT respectively. The average recoveries for all SA’s and TT in aqueous matrices ranged from 95 to 105% across the six concentrations investigated. Recoveries from the residual soils were slightly lower for SA’s and TT (~ 50 to 60%).  

The results of the kinetics studies showed that sorption was rapid in the first few hours of the contact time (0 to 2 h for SA’s and 0 to 4 h for TT) and thereafter an apparent equilibrium concentration was achieved slowly. Batch sorption results performed in six different pastoral soils showed that Freundlich isotherms were nonlinear (N ≠ 1) for most of the compounds. The degree of isotherm linearity (N) for SCP and SM varied between 0.87–1.11 in the six soils. SMO showed a highly non-linear pattern (N = 0.75) in just one soil (Manawatu). Isotherms of both TT and SMO were non-linear, with the degree of non-linearity for TT (N = 0.41–0.73) being greater than for SMO (0.88–1.21) in all soils. Concentration-dependent effective distribution coefficient (Kdeff ) values for the SMO, SCP and SM antibiotics in the soils ranged from 0.37 to 4.6 L kg⁻¹ and for TT Kdeff ranged from 1.2 to 500 L kg⁻¹. The sorption affinity for all soils followed an order: TT > SCP > SM > SMO. Statistical analysis of sorption data revealed a correlation between the sorption coefficients and soil properties such as % organic carbon, cation exchange capacity and clay content.  Sorption of TT onto soils is mostly driven by the cation exchange capacity of the soil whereas for sulfonamides it is primarily due to hydrophobic interactions due to hydrophobic interactions.

On further investigation it was found that sorption of the SMO antibiotic to soils was highly dependent on pH, ionic strength, and organic matter of the soil. Sorption of SMO decreased with the increases in pH, and increased with increasing ionic strength and organic carbon content. A hydrophobic pH-partitioning model linking sorbate speciation with species-specific sorption coefficients describing the pH dependence of the apparent sorption coefficients was successfully used to derive the fraction of each species of SMO that are likely to be present in the environment. 

The results from the biochar amended sorption studies showed that certain biochars can be used as a potential tool to remove residues of antibiotics. Soil amended with pine saw dust biochar was found to be the most effective in adsorbing antibiotics. Pine sawdust biochar absorbed 30 times more antibiotics than soil alone. This was attributed to its high surface area, which was four times higher than that of other biochars, or could be due to its high carbon content (91%). The results have shown that biochar applied at the rate of 0.5 to 1% by soil weight could prove to be an effective way to slow down the release of these contaminants to a manageable level thereby reducing the risk of ecotoxicity and antibiotic resistance.

SMO degraded slowly in agricultural soils. The degradation times (DT₅₀) for SMO in Hamilton clay, Te Kowhai and Horotiu soils under non-sterilized conditions were 9.24, 4.3 and 13.33 days respectively. Soil dehydrogenase activities were directly correlated with degradation kinetics of SMO antibiotic. Results from degradation studies have shown that SMO is not likely to persist more than 90 days in all three soils suggesting that natural biodegradation may be sufficient for the removal of these contaminants from the soil. Both the degree of biological activity and temperature of the soil influenced overall degradation.  SMO degradation in sterile soils indicated abiotic degradation and abiotic factors such as strong sorption of the antibiotic onto soil components also played a role in the degradation of SMO in soil. Four kinetic models, a single first-order model (SFO) and three biphasic kinetic models, were applied to fit the observed SMO degradation kinetics data. The results showed that the First-order double-exponential decay (FODED) and first-order two-compartment (FOTC) model was superior to the bi-exponential model (BEXP) and all three biphasic models were superior when compared to the SFO model for describing SMO degradation data. Use of the FOTC model enabled the estimation of the degradation endpoints. 

The results from two soil lysimeters indicate that the three sulfonamides were highly mobile and that at field collected soil pH mobility was similar to the mobility of the conservative bromide. The breakthrough curves of the three sulfonamides varied depending on soil type with Hamilton soil showing more retardation than Matawhero soil. For the three sulfonamides studied the order of breakthrough was generally observed to be: SM > SMO > SCP for both Matawhero and Hamilton soils. Residual antibiotic concentrations for SMO and SCP were detected up to depths of 18 cm. The CXTFIT model study described the peak arrival time as well as the maximum concentration of the antibiotic breakthrough curves but showed some underestimation at advanced stages of sulfonamide leaching, especially in the Hamilton soil. Results showed that the sulfonamides have weak sorption affinity and relatively high mobility in soils.

year: 2013

title: Raising Māori Medium Students' Academic Oral Language Proficiency Through Self and Peer Assessment

authors: Shandley, Rosina Mary

subjects: Māori Medium Education

abstract: In 2012 there were 24,474 year 1 to 8 students being educated in the range of Māori medium bilingual and immersion programmes that exist throughout Aotearoa. This figure made up 25% of the total primary school population.

To ensure the survival of te reo Māori, and the cognitive advantages associated with bilingualism, Māori medium students need to reach a high level of proficiency in both the English and Māori languages over their time at school. They need to develop their language skills beyond basic conversational competency to academic language proficiency.

As well as academic success, Māori medium whānau expect their students to gain a level of competence in te reo Māori that enables them to actively engage in authentic Māori cultural contexts. This is crucial as the interruption to the intergenerational transfer of te reo Māori caused by colonisation means that today Māori medium graduates make up the main pool of speakers who can transmit our language into the future.

Substantial research has evidenced effective pedagogies for supporting students’ second language acquisition internationally. However, to date there have been no empirical studies to evidence effective second language pedagogies that can raise Māori medium students’ academic language in particular. This study aimed to bridge that gap by providing evidence of effective classroom practices that can raise Māori medium students’ academic language proficiency, with a particular focus on oral language competency.

This action research project aimed to raise a group of Māori medium students’ academic oral language proficiency through the practice of self and peer assessment. The participants were a group of eight year 5 and 6 students being educated in a level one Māori medium classroom in a mainstream school in Southland, New Zealand.

Over the 20 weeks of the study the students used a newly developed language matrix of writing outcomes to self and peer assess their learning in their literacy programme. The quantitative and qualitiative results of the study revealed that the confluence of self and peer assessment practices and the new language scaffolds raised the students’ academic oral and written language competency significantly beyond what was normally expected in a Māori medium programme in 20 weeks.

The study findings provide an option for those teachers wishing to develop their Māori medium students’ academic Māori language proficiency. The study also highlights the need for further research into Māori language acquisition pathways, to inform Māori medium oral language progressions and associated assessment development.

text: Raising Māori Medium Students' Academic Oral Language Proficiency Through Self and Peer Assessment In 2012 there were 24,474 year 1 to 8 students being educated in the range of Māori medium bilingual and immersion programmes that exist throughout Aotearoa. This figure made up 25% of the total primary school population.

To ensure the survival of te reo Māori, and the cognitive advantages associated with bilingualism, Māori medium students need to reach a high level of proficiency in both the English and Māori languages over their time at school. They need to develop their language skills beyond basic conversational competency to academic language proficiency.

As well as academic success, Māori medium whānau expect their students to gain a level of competence in te reo Māori that enables them to actively engage in authentic Māori cultural contexts. This is crucial as the interruption to the intergenerational transfer of te reo Māori caused by colonisation means that today Māori medium graduates make up the main pool of speakers who can transmit our language into the future.

Substantial research has evidenced effective pedagogies for supporting students’ second language acquisition internationally. However, to date there have been no empirical studies to evidence effective second language pedagogies that can raise Māori medium students’ academic language in particular. This study aimed to bridge that gap by providing evidence of effective classroom practices that can raise Māori medium students’ academic language proficiency, with a particular focus on oral language competency.

This action research project aimed to raise a group of Māori medium students’ academic oral language proficiency through the practice of self and peer assessment. The participants were a group of eight year 5 and 6 students being educated in a level one Māori medium classroom in a mainstream school in Southland, New Zealand.

Over the 20 weeks of the study the students used a newly developed language matrix of writing outcomes to self and peer assess their learning in their literacy programme. The quantitative and qualitiative results of the study revealed that the confluence of self and peer assessment practices and the new language scaffolds raised the students’ academic oral and written language competency significantly beyond what was normally expected in a Māori medium programme in 20 weeks.

The study findings provide an option for those teachers wishing to develop their Māori medium students’ academic Māori language proficiency. The study also highlights the need for further research into Māori language acquisition pathways, to inform Māori medium oral language progressions and associated assessment development.

year: 2013