Time filter

Source Type

Auckland, New Zealand

Buckthought L.E.,Investigations and Monitoring Unit | Clough T.J.,Lincoln University at Christchurch | Cameron K.C.,Lincoln University at Christchurch | Di H.J.,Lincoln University at Christchurch | Shepherd M.A.,Agresearch Ltd.
New Zealand Journal of Agricultural Research | Year: 2016

The extent to which the wetted soil area of a urine patch influences surrounding pasture is relatively unknown. The study objective was to use 15N tracer to quantify pasture N uptake in the ‘wetted’ and periphery areas of a spring deposited bovine urine patch over 311 days. Ruminant 15N enriched urine was applied to soil creating a circular wetted area, ‘zone A’ (800 kg N ha−1), with and without urea fertiliser (35 kg N ha−1). Pasture yields, 15N recovery and soil inorganic-N dynamics were monitored from zone A and two peripheral zones, B and C. Fertiliser had no effect on cumulative urinary 15N recovery in pasture (50%–52%). Average cumulative pasture 15N recovery in zones A, B and C were 30.6%, 17.3% and 4.2%, respectively. Soil inorganic-15N recovery occurred in zones A and B, declining with distance from the wetted area. The results suggest an effective urine patch area of 0.95 m2 or 3.4 times the wetted area. © 2016 The Royal Society of New Zealand

Buckthought L.E.,Investigations and Monitoring Unit | Clough T.J.,Lincoln University at Christchurch | Cameron K.C.,Lincoln University at Christchurch | Di H.J.,Lincoln University at Christchurch | Shepherd M.A.,Agresearch Ltd.
Agriculture, Ecosystems and Environment | Year: 2015

Urine patches are the primary source of N loss from pastoral systems due to the high N loading that occurs over a relatively small area. However, few studies have sought to determine the effect of concurrently deposited urine and fertiliser on the fate of N in pastoral systems, even though the application of fertiliser soon after grazing is commonly practised, while no studies have examined seasonal effects of any interaction. The objective of this study was therefore, to understand how the combination of fertiliser-N and urine affected fertiliser-associated NO3 - leaching losses and plant uptake of N. A two year lysimeter study was undertaken with urine (800kg Nha-1) applied in either autumn or spring. Urea fertiliser enriched with 15N was applied to these lysimeters at rates equivalent to 200 or 400kg Nha-1 per year according to the standard regional practice.Urine and fertiliser at the 400kg Nha-1 rate increased total NO3 - leaching by up to 58kgha-1 (P<0.001), from urine applied in either autumn or spring. Fertiliser applied at 200kg Nha-1 did not increase N leaching from urine patches. Fertiliser 15N recovery in drainage was <2.2% and was not affected by fertiliser rate. Pasture uptake accounted for up to 52% of the fertiliser 15N recovery and this increased with increasing fertiliser rates, even in the presence of urine. Recovery of fertiliser 15N in the soil at the end of the experiment averaged 22% with the majority of this in the top 10cm soil.These results indicate that the potential for leaching of fertiliser N, applied to a urine patch, is low, and that avoiding fertiliser application over urine patches, reduces leaching losses of fertiliser-N by <2%, which is minimal in terms of total N loss mitigation. However, at high fertiliser application rates to urine patches (i.e. 400kg Nha-1), the total N leaching from non-fertiliser (non 15N-enriched) sources can increase. Further work is required to quantify these effects at the paddock scale. The results also show that NO3 - leaching losses were greater from autumn applied urine compared to spring applied urine by up to 306kg NO3 --Nha-1. © 2015 Elsevier B.V.

Dunphy B.J.,University of Auckland | Landers T.J.,Investigations and Monitoring Unit | Sagar R.L.,University of Auckland | Ranjard L.,University of Auckland | Rayner M.J.,University of Auckland
Marine Ecology Progress Series | Year: 2015

Within breath-hold diving endotherms, procellariiform seabirds present an intriguing anomaly as they regularly dive to depths not predicted by allometric models. How this is achieved is not known as even basic measures of physiological diving capacity have not been undertaken in this group. To remedy this we combined time depth recorder (TDR) measurements of dive behaviour with haematology and oxygen store estimates for 3 procellariiform species (common diving petrels Pelecanoides urinatrix urinatrix; grey-faced petrels Pterodroma macro ptera gouldi; and sooty shearwaters Puffinus griseus) during their incubation phase. Among species, we found distinct differences in dive depth (average and maximal), dive duration and dives h-1, with sooty shearwaters diving deeper and for longer than grey-faced petrels and common diving petrels. Conversely, common diving petrels dove much more frequently, albeit to shallow depths, whereas grey-faced petrels rarely dived whatsoever. Such differences in dive behaviour were reflected in haematological parameters, with sooty shearwaters having higher red blood cell counts and haematocrit (Hct) values compared to common diving and grey-faced petrels; whereas common diving petrels had significantly lower Hct but possessed higher haemoglobin concentrations per cell and greater respiratory oxygen stores than both sooty shearwaters and grey-faced petrels. Such results provide the first insights into the physiological traits underpinning procellariiform dive behaviour, and confirm the trend for deep-diving seabirds to have proportionally lower blood and respiratory oxygen stores than shallow divers. © Inter-Research 2015.

Duggan I.C.,University of Waikato | Neale M.W.,Investigations and Monitoring Unit | Robinson K.V.,NIWA - National Institute of Water and Atmospheric Research | Verburg P.,NIWA - National Institute of Water and Atmospheric Research | Watson N.T.N.,University of Waikato
Aquatic Invasions | Year: 2014

The North American calanoid copepod Skistodiaptomus pallidus is an emerging invader globally, with non-indigenous populations recorded from constructed waters in New Zealand, Germany and Mexico since 2000. We examined the effects of S. pallidus establishment on the zooplankton community of a natural lake, Lake Kereta, where it was first recorded in late-2008, coincident with releases of domestically cultured grass carp (Ctenopharyngodon idella). Although not present in any of our samples prior to August 2008, S. pallidus was found in all samples collected in the subsequent five years. ANOSIM indicated zooplankton community composition significantly differed between samples collected before and after S. pallidus invasion, whether the invader was included in the analysis or not. Zooplankton species affected most greatly were the copepods Calamoecia lucasi and Mesocyclops sp., which decreased in their relative importance, and the cladocerans Bosmina meridionalis and Daphnia galeata, which increased. Rotifer species were relatively unaffected. As the length of grass carp released were >6.5 cm, direct predatory effects by this species on the zooplankton community are unlikely. Associated reductions in macrophyte biomass could explain increases in the relative abundances of planktonic cladocerans (B. meridionalis and D. galeata). However, the effect of macrophyte reduction by grass carp on zooplankton communities is considered to be limited elsewhere, while the reduced macrophyte biomass cannot explain the decrease in relative abundance of the native planktonic calanoid copepod C. lucasi. Competition between C. lucasi and S. pallidus is the most compelling explanation for the reduction in importance of the native calanoid copepod species. Skistodiaptomus pallidus appears to have undergone a "boom-and-bust" cycle in Lake Kereta, increasing in relative abundance in the first three years following establishment, before declining in importance. © 2014 The Author(s).

Lau K.E.M.,University of Auckland | Washington V.J.,University of Auckland | Fan V.,University of Auckland | Neale M.W.,University of Auckland | And 4 more authors.
Freshwater Biology | Year: 2015

In stream ecosystems, bacterial communities play an important role in nutrient and energy cycling processes as they are among the most numerous and active organisms at the basal trophic level of the stream food web. Bacterial communities in stream biofilms have been shown to correlate well with different catchment land use and therefore provide an opportunity for the development of a novel ecological indicator of stream ecosystem health. In this study, a bacterial community index (BCI) model was developed and validated using a national data set of biofilm bacterial community profiles collected from 223 streams across seven geographical regions in New Zealand. The six-component BCI model was generated using the partial least squares regression method to associate the multivariate bacterial community profile with the macroinvertebrate community index, which is a well-established indicator of stream health. Despite strong regional clustering of the bacterial community profiles, the BCI was indicative of the level of disturbance in the catchment, as shown by significant correlations with a wide range of independent indicators of water quality, macroinvertebrate community data, ecosystem functioning and catchment land-use data. The BCI was able to explain 35% of the variation in a multi-metric index incorporating ten common ecological parameters, suggesting that the stream bacterial communities could provide useful information about the ecosystem integrity. The BCI provides a novel ecosystem assessment tool, which can be used to complement existing stream health measures in the management of anthropogenic impacts on freshwater streams and rivers. © 2015 John Wiley & Sons Ltd.

Discover hidden collaborations