louis Schipper | University of Waikato (original) (raw)
Papers by louis Schipper
Soil organic matter contains more C than terrestrial biomass and atmospheric CO2 combined, and re... more Soil organic matter contains more C than terrestrial biomass and atmospheric CO2 combined, and reacts to climate and land-use change on timescales requiring long-term experiments or monitoring. The direction and uncertainty of soil C stock changes has been difficult to predict and incorporate in decision support tools for climate change policies. Moreover, standardization of approaches has been difficult because historic
Agriculture, Ecosystems & Environment, 2015
Ecological Engineering, 2000
Porous treatment walls are increasingly used for remediating contaminated groundwater. These wall... more Porous treatment walls are increasingly used for remediating contaminated groundwater. These walls are constructed below the water table and perpendicular to the groundwater flow. Successful nitrate removal from groundwater has been demonstrated in porous walls amended with sawdust but the mechanism responsible has not been identified. The objective was to determine whether denitrification rates in such a wall were high
Water research, 2008
Adoption of land-based effluent treatment systems can be constrained by the costs and availabilit... more Adoption of land-based effluent treatment systems can be constrained by the costs and availability of land. Sufficient land area is needed to ensure nitrate leaching from applied effluent is minimised. One approach to decrease required land area is to enhance N removal by denitrification. Layers of organic matter (100 mm thick) were installed below topsoil of a site irrigated with dairy factory effluent. These "denitrification" layers were tested to determine whether they could decrease nitrate leaching by increasing denitrification. Four plots (10x10 m2 each) were constructed with a denitrification layer installed at 300 mm below the surface, and N losses were measured in leachate using suction cups every 3 weeks for 19 months. N in leachate was compared with 4 control plots. Denitrifying enzyme activity, nitrate concentrations, and carbon availability were measured in samples collected from the denitrification layers. These measurements demonstrated that denitrification ...
Agriculture, Ecosystems & Environment, 2015
Journal of Contemporary Water Research & Education, 2013
An International Perspective on Wetland Rehabilitation, 1999
... There are two main restiad bog species: the smaller, Empodisma minus (henceforth called Empod... more ... There are two main restiad bog species: the smaller, Empodisma minus (henceforth called Empodisma), is found throughout New Zealand (it also occurs in eastern Australia) and is the major raised bog peat former; the larger restiad, Sporadanthus traversii sl (henceforth called ...
There are still large uncertainties in peatland methane flux dynamics and insufficient understand... more There are still large uncertainties in peatland methane flux dynamics and insufficient understanding of how biogeochemical processes scale to ecosystems. New Zealand bogs differ from Northern Hemisphere ombrotrophic systems in climatic setting, hydrology, and dominant vegetation, offering an opportunity to evaluate our knowledge of peatland methane biogeochemistry gained primarily from northern bogs and fens. We report eddy covariance methane fluxes from a raised bog in New Zealand over 2.5 years. Annual total methane flux in 2012 was 29.1 g CH 4 m À2 yr À1 , whereas during a year with a severe drought (2013) it was 20.6 g CH 4 m À2 yr À1 , both high compared to Northern Hemisphere bogs and fens. Drier conditions led to a decrease in fluxes from~100 mg CH 4 m À2 d À1 to~20 mg CH 4 m À2 d À1 , and subsequent slow recovery of flux after postdrought water table rise. Water table depth regulated the temperature sensitivity of methane fluxes, and this sensitivity was greatest when the water table was within 100 mm of the surface, corresponding to the shallow rooting zone of the dominant vegetation. A correlation between daytime CO 2 uptake and methane fluxes emerged during times with shallow water tables, suggesting that controls on methane production were critical in determining fluxes, more so than oxidation. Water table recession through this shallow zone led to increasing methane fluxes, whereas changes in temperature during these periods were not correlated. Models of methane fluxes should consider drought-induced lags in seasonal flux recovery that depend on drought characteristics and location of the critical zone for methane production.
Many years of research have demonstrated that denitrification in riparian zones is an important m... more Many years of research have demonstrated that denitrification in riparian zones is an important mechanism for reducing non-point source pollution of surface waters. Further understanding of the environmental factors controlling denitrification at the catchment scale has also ...
Intensification of agriculture in lake catchments of the Rotorua region has accelerated eutrophic... more Intensification of agriculture in lake catchments of the Rotorua region has accelerated eutrophication in some lakes, while others remain minimally impacted. Seasonal patterns of hypoxia, ammonium (NH 4 + ) release from sediments, nitrate (NO 3 - ) generation and subsequent NO 3 - loss ...
ABSTRACT Buried allophanic soils developed on sequences of well-dated tephras sequester organic m... more ABSTRACT Buried allophanic soils developed on sequences of well-dated tephras sequester organic matter over long time periods. Allophane in these paleosols also potentially enables DNA to be preserved, and this ancient DNA (aDNA) could provide a means for reconstructing past environments from terrestrial sequences comparable to, for example, phytolith analysis. We undertook experiments to better understand mechanisms of DNA adsorption on synthetic and natural allophane. We showed that DNA binds chemically to allophane and helps the formation of allophane nanoaggregates which subsequently adsorb DNA physically within interstices. However, humic acids can reduce DNA adsorption on allophane by occupying active bonding sites, namely aluminol (Al−OH) groups. DNA then binds to humic acids chemically and so attaches to allophane indirectly. We developed a two-step DNA extraction method including (i) first extraction using an alkaline buffer, and (ii) second extraction by oxalate. After trials with synthetic allophane and salmon-sperm DNA, we extracted DNA from a sequence of buried allophanic soils (on rhyolitic tephras) near Mt Tarawera to a depth of 2.5 m. The extracted DNA was separated from humic acids chromatographically through gel electrophoresis followed by PCR amplification, cloning, and Sanger sequencing. From a paleosol on the Rotoma tephra (tephra deposited ~9400 years ago), plant DNA (trnL) of Araliaceae (ivy family) and Myrtaceae (myrtle family) was found. The present-day land surface is characterised by pasture. The preserved plant DNA in the Rotoma paleosol may have originated from ancient plants growing on the Rotoma soil prior to its burial (by Whakatane tephra) ~5500 years ago, or from ‘modern’ plants growing (some decades) prior to the current vegetation. More work is needed to enable us to separate these hypotheses. We conclude that our new extraction method, with further development, provides the potential to exhume genetic materials that have been preserved in allophane-rich soils or paleosols.
Soil organic matter contains more C than terrestrial biomass and atmospheric CO2 combined, and re... more Soil organic matter contains more C than terrestrial biomass and atmospheric CO2 combined, and reacts to climate and land-use change on timescales requiring long-term experiments or monitoring. The direction and uncertainty of soil C stock changes has been difficult to predict and incorporate in decision support tools for climate change policies. Moreover, standardization of approaches has been difficult because historic
Agriculture, Ecosystems & Environment, 2015
Ecological Engineering, 2000
Porous treatment walls are increasingly used for remediating contaminated groundwater. These wall... more Porous treatment walls are increasingly used for remediating contaminated groundwater. These walls are constructed below the water table and perpendicular to the groundwater flow. Successful nitrate removal from groundwater has been demonstrated in porous walls amended with sawdust but the mechanism responsible has not been identified. The objective was to determine whether denitrification rates in such a wall were high
Water research, 2008
Adoption of land-based effluent treatment systems can be constrained by the costs and availabilit... more Adoption of land-based effluent treatment systems can be constrained by the costs and availability of land. Sufficient land area is needed to ensure nitrate leaching from applied effluent is minimised. One approach to decrease required land area is to enhance N removal by denitrification. Layers of organic matter (100 mm thick) were installed below topsoil of a site irrigated with dairy factory effluent. These "denitrification" layers were tested to determine whether they could decrease nitrate leaching by increasing denitrification. Four plots (10x10 m2 each) were constructed with a denitrification layer installed at 300 mm below the surface, and N losses were measured in leachate using suction cups every 3 weeks for 19 months. N in leachate was compared with 4 control plots. Denitrifying enzyme activity, nitrate concentrations, and carbon availability were measured in samples collected from the denitrification layers. These measurements demonstrated that denitrification ...
Agriculture, Ecosystems & Environment, 2015
Journal of Contemporary Water Research & Education, 2013
An International Perspective on Wetland Rehabilitation, 1999
... There are two main restiad bog species: the smaller, Empodisma minus (henceforth called Empod... more ... There are two main restiad bog species: the smaller, Empodisma minus (henceforth called Empodisma), is found throughout New Zealand (it also occurs in eastern Australia) and is the major raised bog peat former; the larger restiad, Sporadanthus traversii sl (henceforth called ...
There are still large uncertainties in peatland methane flux dynamics and insufficient understand... more There are still large uncertainties in peatland methane flux dynamics and insufficient understanding of how biogeochemical processes scale to ecosystems. New Zealand bogs differ from Northern Hemisphere ombrotrophic systems in climatic setting, hydrology, and dominant vegetation, offering an opportunity to evaluate our knowledge of peatland methane biogeochemistry gained primarily from northern bogs and fens. We report eddy covariance methane fluxes from a raised bog in New Zealand over 2.5 years. Annual total methane flux in 2012 was 29.1 g CH 4 m À2 yr À1 , whereas during a year with a severe drought (2013) it was 20.6 g CH 4 m À2 yr À1 , both high compared to Northern Hemisphere bogs and fens. Drier conditions led to a decrease in fluxes from~100 mg CH 4 m À2 d À1 to~20 mg CH 4 m À2 d À1 , and subsequent slow recovery of flux after postdrought water table rise. Water table depth regulated the temperature sensitivity of methane fluxes, and this sensitivity was greatest when the water table was within 100 mm of the surface, corresponding to the shallow rooting zone of the dominant vegetation. A correlation between daytime CO 2 uptake and methane fluxes emerged during times with shallow water tables, suggesting that controls on methane production were critical in determining fluxes, more so than oxidation. Water table recession through this shallow zone led to increasing methane fluxes, whereas changes in temperature during these periods were not correlated. Models of methane fluxes should consider drought-induced lags in seasonal flux recovery that depend on drought characteristics and location of the critical zone for methane production.
Many years of research have demonstrated that denitrification in riparian zones is an important m... more Many years of research have demonstrated that denitrification in riparian zones is an important mechanism for reducing non-point source pollution of surface waters. Further understanding of the environmental factors controlling denitrification at the catchment scale has also ...
Intensification of agriculture in lake catchments of the Rotorua region has accelerated eutrophic... more Intensification of agriculture in lake catchments of the Rotorua region has accelerated eutrophication in some lakes, while others remain minimally impacted. Seasonal patterns of hypoxia, ammonium (NH 4 + ) release from sediments, nitrate (NO 3 - ) generation and subsequent NO 3 - loss ...
ABSTRACT Buried allophanic soils developed on sequences of well-dated tephras sequester organic m... more ABSTRACT Buried allophanic soils developed on sequences of well-dated tephras sequester organic matter over long time periods. Allophane in these paleosols also potentially enables DNA to be preserved, and this ancient DNA (aDNA) could provide a means for reconstructing past environments from terrestrial sequences comparable to, for example, phytolith analysis. We undertook experiments to better understand mechanisms of DNA adsorption on synthetic and natural allophane. We showed that DNA binds chemically to allophane and helps the formation of allophane nanoaggregates which subsequently adsorb DNA physically within interstices. However, humic acids can reduce DNA adsorption on allophane by occupying active bonding sites, namely aluminol (Al−OH) groups. DNA then binds to humic acids chemically and so attaches to allophane indirectly. We developed a two-step DNA extraction method including (i) first extraction using an alkaline buffer, and (ii) second extraction by oxalate. After trials with synthetic allophane and salmon-sperm DNA, we extracted DNA from a sequence of buried allophanic soils (on rhyolitic tephras) near Mt Tarawera to a depth of 2.5 m. The extracted DNA was separated from humic acids chromatographically through gel electrophoresis followed by PCR amplification, cloning, and Sanger sequencing. From a paleosol on the Rotoma tephra (tephra deposited ~9400 years ago), plant DNA (trnL) of Araliaceae (ivy family) and Myrtaceae (myrtle family) was found. The present-day land surface is characterised by pasture. The preserved plant DNA in the Rotoma paleosol may have originated from ancient plants growing on the Rotoma soil prior to its burial (by Whakatane tephra) ~5500 years ago, or from ‘modern’ plants growing (some decades) prior to the current vegetation. More work is needed to enable us to separate these hypotheses. We conclude that our new extraction method, with further development, provides the potential to exhume genetic materials that have been preserved in allophane-rich soils or paleosols.