Climate Change Is Likely to Increase the Development Rate of Anthelmintic Resistance in Equine Cyathostomins in New Zealand

Climate change is likely to influence livestock production by increasing the prevalence of diseases, including parasites. The traditional practice of controlling nematodes in livestock by the application of anthelmintics is, however, increasingly compromised by the development of resistance to these drugs in parasite populations. This study used a previously developed simulation model of the entire equine cyathostomin lifecycle to investigate the effect a changing climate would have on the development of anthelmintic resistance. Climate data from six General Circulation Models based on four different Representative Concentration Pathways was available for three New Zealand locations. These projections were used to estimate the time resistance will take to develop in the middle (2040–49) and by the end (2090–99) of the century in relation to current (2006–15) conditions under two treatment scenarios of either two or six yearly whole-herd anthelmintic treatments. To facilitate comparison, a scenario without any treatments was included as a baseline. In addition, the size of the infective and parasitic stage nematode population during the third simulation year were estimated. The development of resistance varied between locations, time periods and anthelmintic treatment strategies. In general, the simulations indicated a more rapid development of resistance under future climates coinciding with an increase in the numbers of infective larvae on pasture and encysted parasitic stages. This was especially obvious when climate changes resulted in a longer period suitable for development of free-living parasite stages. A longer period suitable for larval development resulted in an increase in the average size of the parasite population with a larger contribution from eggs passed by resistant worms surviving the anthelmintic treatments. It is projected that climate change will decrease the ability to control livestock parasites by means of anthelmintic treatments and non-drug related strategies will become increasingly important for sustainable parasite control

Multimodel Evaluation of Nitrous Oxide Emissions From an Intensively Managed Grassland

Process‐based models are useful for assessing the impact of changing management practices and climate on yields and greenhouse gas (GHG) emissions from agricultural systems such as grasslands. They can be used to construct national GHG inventories using a Tier 3 approach. However, accurate simulations of nitrous oxide (N$_{2}$O) fluxes remain challenging. Models are limited by our understanding of soil‐plant‐microbe interactions and the impact of uncertainty in measured input parameters on simulated outputs. To improve model performance, thorough evaluations against in situ measurements are needed. Experimental data of N$_{2}$O emissions under two management practices (control with typical fertilization versus increased clover and no fertilization) were acquired in a Swiss field experiment. We conducted a multimodel evaluation with three commonly used biogeochemical models (DayCent in two variants, PaSim, APSIM in two variants) comparing four years of data. DayCent was the most accurate model for simulating N$_{2}$O fluxes on annual timescales, while APSIM was most accurate for daily N$_{2}$O fluxes. The multimodel ensemble average reduced the error in estimated annual fluxes by 41% compared to an estimate using the Intergovernmental Panel on Climate Change (IPCC)‐derived method for the Swiss agricultural GHG inventory (IPCC‐Swiss), but individual models were not systematically more accurate than IPCC‐Swiss. The model ensemble overestimated the N$_{2}$O mitigation effect of the clover‐based treatment (measured: 39–45%; ensemble: 52–57%) but was more accurate than IPCC‐Swiss (IPCC‐Swiss: 72–81%). These results suggest that multimodel ensembles are valuable for estimating the impact of climate and management on N$_{2}$O emissions

Modelling biological N fixation and grass-legume dynamics with process-based biogeochemical models of varying complexity

This work was conducted by the Models4Pastures consortium project under the auspices of FACCE-JPI. Funding was provided by: the New Zealand Government to support the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases; AgResearch’s Strategic Science Investment Fund as a contribution to the Forages for Reduced Nitrate Leaching (FRNL) research programme; the input of UK partners was funded by DEFRA and also contributes to the RCUK-funded projects: N-Circle (BB/N013484/1), UGRASS (NE/M016900/1) and GREENHOUSE (NE/K002589/1). R.M. Rees and C.F.E. Topp also received funding from the Scottish Government Strategic Research Programme. Lutz Merbold and Kathrin Fuchs acknowledge funding received for the Swiss contribution to Models4Pastures (FACCE-JPI project, SNSF funded contract: 40FA40_154245/1) and for the Doc.Mobility fellowship (SNSF funded project: P1EZP2_172121). Lorenzo Brilli, Camilla Dibari and Marco Bindi acknowledge funding received from the Italian Ministry of Agricultural Food and Forestry Policies (MiPAAF).Peer reviewedPublisher PD

Evaluating the Potential of Legumes to Mitigate N2O Emissions From Permanent Grassland Using Process-Based Models

Funding Information: This modeling study was a joint effort of the Models4Pastures project within the framework of FACCE-JPI. Lutz Merbold and Kathrin Fuchs acknowledge funding received for the Swiss contribution to Models4Pastures (FACCE-JPI project, SNSF funded contract: 40FA40_154245/1) and for the Doc. Mobility fellowship (SNSF funded project: P1EZP2_172121). Lutz Merbold further acknowledges the support received for CGIAR Fund Council, Australia (ACIAR), Irish Aid, the European Union, the Netherlands, New Zealand, Switzerland, UK, USAID, and Thailand for funding to the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) as well as for the CGIAR Research Program on Livestock. The NZ contributors acknowledge funding from the New Zealand Government Ministry of Primary Industries to support the aims of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases and from AgResearch's Strategic Science Investment Fund (the Forages for Reduced Nitrate Leaching (FRNL) research program). The UK partners acknowledge funding by DEFRA and the RCUK projects: N-Circle (BB/N013484/1), UGRASS (NE/M016900/1), and GREENHOUSE (NE/K002589/1). R.M. Rees and C.F.E. Topp also received funding from the Scottish Government Strategic Research Programme. Lorenzo Brilli, Camilla Dibari, and Marco Bindi received funding from the Italian Ministry of Agricultural Food and Forestry Policies (MiPAAF). The FR partners acknowledge funding from CN-MIP project funded by the French National Research Agency (ANR-13-JFAC-0001) and from ADEME (no. 12-60-C0023). Open access funding enabled and organized by Projekt DEAL Funding Information: This modeling study was a joint effort of the Models4Pastures project within the framework of FACCE‐JPI. Lutz Merbold and Kathrin Fuchs acknowledge funding received for the Swiss contribution to Models4Pastures (FACCE‐JPI project, SNSF funded contract: 40FA40_154245/1) and for the Doc. Mobility fellowship (SNSF funded project: P1EZP2_172121). Lutz Merbold further acknowledges the support received for CGIAR Fund Council, Australia (ACIAR), Irish Aid, the European Union, the Netherlands, New Zealand, Switzerland, UK, USAID, and Thailand for funding to the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) as well as for the CGIAR Research Program on Livestock. The NZ contributors acknowledge funding from the New Zealand Government Ministry of Primary Industries to support the aims of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases and from AgResearch's Strategic Science Investment Fund (the Forages for Reduced Nitrate Leaching (FRNL) research program). The UK partners acknowledge funding by DEFRA and the RCUK projects: N‐Circle (BB/N013484/1), UGRASS (NE/M016900/1), and GREENHOUSE (NE/K002589/1). R.M. Rees and C.F.E. Topp also received funding from the Scottish Government Strategic Research Programme. Lorenzo Brilli, Camilla Dibari, and Marco Bindi received funding from the Italian Ministry of Agricultural Food and Forestry Policies (MiPAAF). The FR partners acknowledge funding from CN‐MIP project funded by the French National Research Agency (ANR‐13‐JFAC‐0001) and from ADEME (no. 12‐60‐C0023). Open access funding enabled and organized by Projekt DEAL Publisher Copyright: ©2020. The Authors. Open access funding enabled and organized by Projekt DEALPeer reviewedPublisher PD

Factors influencing vegetation distribution on a slope in South Westland, New Zealand

The vegetation of a slope consisting of two surfaces- a late Otira Glaciation moraine overlying an early Otira outwash surface is reported. The study area was located between the Omoeroa and Waikukupa Rivers in Westland National Park. Three transects, from the bottom of the slope (on the outwash surface), up the slope to the top of the moraine were established. A total of 43 plots were assessed primarily for vascular species abundance and tree species basal area. Classification of species abundance along these transects using the TWINSPAN procedure resulted in seven vegetation types. These showed an orderly grouping from pakihi and 'heath forest' (pink pine/manuka) vegetation on the older surface, to rimu/kamahi/rata forest on the younger moraine. These vegetation type boundaries were reinforced by establishing the distribution of the basal areas of the major tree species found along one of the transects. The soils of the vegetation types found along one of the transects were characterized. No distinct differences in the measured chemical properties were found between the soils; however, slope position influenced the moisture regime and hence the soil profile morphologies. The main factors influencing the distribution of the vegetation appeared to be the difference in the age of the two surfaces, differences in the soil moisture regimes and the presence of fire on the oldest surfaces

Nitrogen and the leaf growth of temperate cereals

Under agricultural conditions where soil moisture is adequate, low nitrogen (N) availability is usually the main soil factor limiting the growth and yield of temperate cereals. A major part of the positive response of plant growth to additional N is a result of greater leaf area, an important determinant of plant photosynthetic capacity. This thesis investigated various aspects of the influence of N on the leaf growth of temperate cereals. Data were presented in Chapter 2 which investigated the influence of additional N as nitrate (NO₃⁻) or ammonium (NH₄⁺) on reserve mobilisation and seedling growth prior to emergence from the substrate. The amount of N assimilated was similar with either form of N, but as a result of enhanced endosperm mobilization, seedling dry weight (d.wt) was greater with NO₃⁻. When seedlings were supplied chloride, reserve mobilisation and seedling growth were as great as with NO₃⁻. It was concluded that the increased rate of mobilisation of seed reserves and subsequently greater seedling growth with additional NO₃⁻ were due to greater seedling water uptake, probably acting via increased seed water contend A similar mechanism, but acting directly via the seed, was suggested for enhanced reserve mobilisation with increased levels of endogenous seed N. Chapter 3 investigated the influence of N form and availability on the growth of individual main stem and tiller leaves. With increasing external N concentrations over the range 0 to 2.5 - 5 mol m⁻³ leaf growth characteristics and maximum leaf area attained were similar with N supplied as NO₃⁻, NH₄⁺ or glutamine. Leaf area increased further with increasing external concentrations of NO₃⁻ or glutamine to 20 mol m⁻³ but with NH₄⁺ it usually declined substantially. As leaf growth was similar with NO₃⁻ or glutamine over a wide range or external N concentration, it was suggested that the site of N assimilation is probably not a major factor in determining the extent of individual leaf area development. However, it is possible that factors associated with NH₄⁺toxicity influence the growth of leaves. It was demonstrated in Chapter 4 that greater individual leaf area with additional NO₃⁻ was associated with an increase in both cell number and size. Increased cell division was thought to be due to increased availability of both photosynthate and N. It was proposed that greater cell size with additional NO₃⁻ was due to an increase in the availability of osmoticum, primarily sucrose. Also, it was suggested that at higher external NO₃⁻ concentrations, additional types of osmotica, such as NO₃⁻, counter ions and organic acids, are also available as a result of assimilation and storage of NO₃⁻ in the leaves. The influence of N availability and form on shoot to root d.wt ratio (S:R) and leaf d.wt as a fraction of total plant d.wt (LWR) were investigated in Chapter 5. It was shown that regardless of whether N was supplied as NO₃⁻, NH₄⁺ or glutamine, increasing external N concentration resulted in an increase in plant reduced-N content and S:R or LWR, though at any given total plant d.wt, all three parameters were greater for plants supplied NH₄⁺ or glutamine. Hence, at any given plant N content, S:R or LWR were similar, regardless of N form supplied. These results were discussed in terms of a proposed mechanism for the control of S:R by N. It was also shown that leaf area produced per unit leaf N was greater for plants supplied NO₃⁻ compared to NH₄⁺ or glutamine; this does not appear to have been reported previously. In Chapter 6 it was demonstrated that despite relatively high initial levels of soil N, fertilizer N applied at sowing had positive effects on the grain yield of all the temperate cereals investigated. The reason for the increase was similar for all species: additional N increased the fraction of available photosynthetically active radiation (PAR) intercepted by increasing the rate of canopy development. As a result, crop dry matter (DM) production increased and as harvest index (HI) was not affected, grain yield was greater with additional N. Differences between species in the amount of grain produced were not associated with the amounts of PAR intercepted or DM produced, but were related to differences in HI

Some effects of topographic aspect on grassland responses to elevated CO2

Grasslands are distributed globally across various topographies. In non-flat grasslands, aspect (the direction that a slope faces) influences the amounts of radiation and consequent effects on temperature and soil moisture, all of which are important drivers of plant growth. Aspect is important not only in hill and mountain areas but also in more moderate topographies such as plateaux, steppes and prairies. Here, we tested the aboveground growth response to an important driver of climate change – elevated carbon dioxide (eCO2) – of two temperate grass species grown under simulated north (unshaded) and south (shaded) aspects. We used trellis-like structures to create the appropriate radiation regimes; irrigation ensured that only radiation and hence soil temperatures were different. We utilised the long-running New Zealand Free-Air Carbon Dioxide Enrichment (FACE) experiment and established turves of Lolium perenne L. and Agrostis capillaris L. The aboveground dry matter (DM) was regularly harvested over 10 months. For the main effects, there was no overall response to CO2 but Agrostis produced about 50% more DM than Lolium while the north aspect produced about 15% more DM than the south. There was an interaction between CO2 level and aspect: for both species production was about 20% greater under eCO2 on the north aspect but had no effect on the south aspect. Given that a large proportion of the world’s grasslands is on slopes, this aspect × CO2 interaction causes us to reconsider the up-scaling of CO2 responses from FACE experiments that have been universally carried out on flat terrain

Climatic factors influencing New Zealand pasture resilience under scenarios of future climate change

New Zealand’s intensively managed pastoral agricultural systems are vulnerable to climate change because of their dependence on grazing livestock and pasture as the primary feed supply. Drawing from recent modelling results, annual pasture yields in New Zealand are projected to be robust to a changing climate due to more favourable growing conditions in winter and early spring and increased plant efficiencies from the CO2 fertilization effect. However, growth is also expected to become more variable and unpredictable, particularly in water-limited regions. A combination of short-term, incremental changes (already part of current practice) and longer-term strategic interventions will be necessary to maintain consistent feed supply under future climate change