ORCID Profile
0000-0001-7724-3738
Current Organisations
Landcare Research New Zealand
,
Manaaki Whenua - Landcare Research
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Publisher: Wiley
Date: 13-04-2014
DOI: 10.1111/GEB.12172
Publisher: Wiley
Date: 15-03-2011
Publisher: Telecommunications Association Inc.
Date: 29-06-2021
Abstract: On 24 March 2021, TelSoc hosted the sixth Broadband Futures Forum, held online, with a focus on regional and rural broadband access. Mr Gavin Williams from NBN Co, the developer of Australia’s National Broadband Network (NBN), spoke about developments in Fixed Wireless and Satellite services and described NBN Co’s commitment to ongoing enhancement of broadband access in regional and rural Australia. A question-and-answer session followed the presentation in which Mr Williams fielded a variety of questions on broadband access and technological developments.
Publisher: Wiley
Date: 27-06-2013
Publisher: Informa UK Limited
Date: 03-07-2019
Publisher: Springer Science and Business Media LLC
Date: 19-10-2022
Publisher: Wiley
Date: 07-03-2011
Publisher: Springer Science and Business Media LLC
Date: 22-10-2020
Publisher: Wiley
Date: 24-07-2016
DOI: 10.1111/WRE.12219
Publisher: Wiley
Date: 22-07-2016
DOI: 10.1111/WRE.12218
Publisher: Wiley
Date: 21-02-2020
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/FP08112
Abstract: The influence of defoliation on nitrogen (N) re-translocation and the source for N remobilisation by the invasive shrub, Buddleia davidii Franch. (buddleia) was determined. Eighty plants were grown over two growing seasons, and half were repeatedly defoliated by removing 66% of their leaf area. During the second season, the N supply was labelled with 15N (10 atom% enrichment), to distinguish the use of stored N (unlabelled) from N taken up by roots (labelled) for growth. Defoliation significantly decreased root (39%) and total biomass (26%). Old leaves were the main source of N for remobilisation which was accelerated and increased (by 50% in the second season) in response to defoliation. In spring, root uptake of N increased by 57% in defoliated plants. Thus, defoliation induced changes in N remobilisation and uptake as compensatory growth increased the demand for N. Continued leaf removal decreased the pool of stored N and caused a significant decline in biomass production, especially in roots (39%) and flowers (31%). This has important implications for the efficacy of defoliation as a control measure, as smaller roots suggest a reduced capacity for uptake of nutrients from the soil and reduced flower production may assist in reducing the invasive spread of the species. These findings clearly show that, although the success of B. davidii is associated, in part, with efficient remobilisation of N from storage, this advantage can be overcome by continued defoliation.
Publisher: Wiley
Date: 27-01-2011
DOI: 10.1111/J.1469-8137.2010.03640.X
Abstract: Patterns in the natural abundance of nitrogen (N) isotopes (¹⁵N and ¹⁴N) can help in the understanding of ecosystem processes along environmental gradients, because some processes fractionate against the heavier isotope. We measured δ¹⁵N in many components of the Franz Josef soil chronosequence in New Zealand to see how each component varied along the sequence and within sites, and to see what this variation can tell us about how ecosystem processes such as N losses change with soil age. We analyzed δ¹⁵N in foliage from 18 woody species, abscised leaves from seven woody species, three soil horizons, bryophytes, lichens, bulk deposition, and nodules from the N-fixing tree Coriaria arborea (Coriariaceae). Foliar δ¹⁵N varied significantly across plant species. Foliage and bulk litter became ¹⁵N-depleted as soil age increased. Soil N from organic and mineral horizons was significantly more ¹⁵N-enriched than bulk litter N at each site. Increasing precipitation also decreased foliar and soil δ¹⁵N. Comparing input and whole ecosystem δ¹⁵N revealed limited evidence for net fractionation during N losses. These trends are consistent with some combination of increasing fractionation during plant N uptake, mycorrhizal transfer, within-plant processing, and soil decomposition as soils age.
Publisher: Wiley
Date: 08-07-2008
Publisher: Wiley
Date: 09-02-2021
DOI: 10.1002/FEE.2285
Publisher: Wiley
Date: 15-12-2014
Publisher: Springer Science and Business Media LLC
Date: 19-01-2005
DOI: 10.1007/S00442-004-1803-0
Abstract: We measured the response of dark respiration (R(d)) to temperature and foliage characteristics in the upper canopies of tree species in temperate rainforest communities in New Zealand along a soil chronosequence (six sites from 6 years to 120,000 years). The chronosequence provided a vegetation gradient characterised by significant changes in soil nutrition. This enabled us to examine the extent to which changes in dark respiration can be applied across forest biomes and the utility of scaling rules in whole-canopy carbon modelling. The response of respiration to temperature in the dominant tree species differed significantly between sites along the sequence. This involved changes in both R(d) at a reference temperature (R(10)) and the extent to which R(d) increased with temperature (described by E(o), a parameter related to the energy of activation, or the change in R(d) over a 10 degrees C range, Q(10)). Site averaged E(o) ranged from 44.4 kJ mol(-1) K(-1) at the 60-year-old site to 26.0 kJ mol(-1) K(-1) at the oldest, most nutrient poor, site. Relationships between respiratory and foliage characteristics indicated that both the temperature response of respiration (E(o) or Q(10)) and the instantaneous rate of respiration increased with both foliar nitrogen and phosphorus content. The ratio of photosynthetic capacity (Whitehead et al. in Oecologia 2005) to respiration (A(max)/R(d)) attained values in excess of 15 for species in the 6- to 120-year-old sites, but thereafter decreased significantly to around five at the 120,000-year-old site. This indicates that shoot carbon acquisition is regulated by nutrient limitations in the retrogressing ecosystems on the oldest sites. Our findings indicate that respiration and its temperature response will vary according to soil age and, therefore, to soil nutrient availability and the stage of forest development. Thus, variability in respiratory characteristics for canopies should be considered when using models to integrate respiration at large spatial scales.
Publisher: New Zealand Ecological Society
Date: 09-06-2022
Publisher: Springer Science and Business Media LLC
Date: 29-10-2020
Publisher: Wiley
Date: 11-04-2019
DOI: 10.1111/BRV.12511
Publisher: Wiley
Date: 09-01-2009
Publisher: Springer Science and Business Media LLC
Date: 15-04-2005
DOI: 10.1007/S00442-005-0068-6
Abstract: Measurements of photosynthesis at saturating irradiance and CO2 partial pressure, Amax, "adjusted" normalised difference vegetation index, RaNDVI, and photochemical reflectance index, RPRI, were made on trees s led along a soil chronosequence to investigate the relationship between carbon uptake and ecosystem development in relation to nutrient availability. Measurements were made on the three most dominant species at six sites along the sequence in South Westland, New Zealand with soil age ranging from < 6 to 120,000 years resulting from the retreat of the Franz Josef glacier. The decrease in soil phosphorus availability with increasing soil age and high soil nitrogen availability at the two youngest sites, due to the presence of a nitrogen-fixing species, provided marked differences in nutrient availability. Mean Amax was high at the two youngest sites, then decreased markedly with increasing site age. Analysis of the data for in idual species within sites revealed separation of groups of species in the response of Amax to Nm and Pm, suggesting complex interactions between the two nutrients. There were strong linear relationships for leaf-level RaNDVI and RPRI with Amax, at high irradiance, showing that measurements of reflectance indices can be used to estimate Amax for foliage with a range in morphology and nutrient concentrations. Notwithstanding the change in species composition from angiosperms to conifers with increasing site age, the presence of nitrogen-fixing species, the variability in foliage morphology from flat leaves to imbricate scales and a wide range in foliar nitrogen and phosphorus concentrations, there were strong positive linear relationships between site average Amax and foliage nitrogen, Nm, and phosphorus, Pm, concentrations on a foliage mass basis. The results provide insights to interpret the regulation of photosynthesis across natural ecosystems with marked gradients in nitrogen and phosphorus availability.
Publisher: Oxford University Press (OUP)
Date: 05-2019
Publisher: Wiley
Date: 28-03-2018
DOI: 10.1111/WRE.12304
Publisher: New Zealand Ecological Society
Date: 10-2022
No related grants have been discovered for Duane Peltzer.