Shifts in Apple Phenology under Climate Change in Switzerland and Implications for Exposure to Abiotic and Biotic Risks

It is expected that the development of plants and insects will be accelerated by global warming, resulting in an earlier occurrence of phenological stages in the future as compared to today. For plants, this could lead to a higher exposure to climatic shocks (late frosts in spring, and critical high temperatures in summer) and changes in the incidence of insect pests. Assessing the implications of such shifts in phenology is important to be able to devise, where necessary, means for reducing biotic and abiotic risks in plant production. In this contribution we present an analysis of the potential impacts of climate change on the risk of late frost and damages to fruits caused by critically high temperatures in apple orchards across Switzerland. We further discuss the possible effects of climate change on the appearance of the codling moth (Cydia pomonella L.), the key apple pest in many areas of the world. To conduct the analysis, we run carefully calibrated phenological models for different apple cultivars and the codling moth, feeding them with updated, transient climate change scenarios covering 1980-2100 developed for Switzerland on a 2 km x 2 km spatial-resolution grid. The climate scenarios represent three different emissions pathways allowing for consideration of a wide range of future climates. The results are discussed in a broader context by comparison with findings from other countries

Generic calibration of a simple model of diurnal temperature variations for spatial analysis of accumulated degree-days

Accumulated growing degree-days (aGDD) are widely used to predict phenological stages of plants and insects. It has been shown in the past that the best predictive performance is obtained when aGDD are computed from hourly temperature data. As the latter are not always available, models of diurnal temperature changes are often employed to retrieve the required information from data of daily minimum and maximum temperatures. In this study, we examine the performance of a well-known model of hourly temperature variations in the context of a spatial assessment of aGDD. Specifically, we examine whether a generic calibration of such a temperature model is sufficient to infer in a reliable way spatial patterns of key phenological stages across the complex territory of Switzerland. Temperature data of a relatively small number of meteorological stations is used to obtain a generic model parameterization, which is first compared with site-specific calibrations. We show that, at the local scale, the predictive skill of the generic model does not significantly differ from that of the site-specific models. We then show that for aGDD up to 800 °C d (on a base temperature of 10 °C), phenological dates predicted with aGDD obtained from estimated hourly temperature data are within ± 3 days of dates estimated on the basis of observed hourly temperatures. This suggests the generic calibration of hourly temperature models is indeed a valid approach for pre-processing temperature data in regional studies of insect and plant phenology

Simulating the Potential Distribution and Abundance of the Brown Marmorated Stink Bug (Halyomorpha halys) under Future Climate Scenarios in Switzerland

The climate in Switzerland is changing. Depending on the emission scenario and time period, the projected increase in temperature is 2.7-4.8°C and the projected decrease in precipitation is 18-28%. There is scientific evidence that climate change will increase economic damage by agricultural pests. The prevention and management options of alien species are cost and time intensive. Climate change will improve the long-term suitability of potential new areas and amplify the need for action. Therefore it is highly important to assess the risk of alien species under future climate conditions and to plan an efficient monitoring and to develop management strategies. The brown marmorated stink bug (Halyomorpha halys) is an extremely polyphagous insect and has invaded North America and Europe around 2004. Especially in Italy it has become a relevant fruit pest. In Switzerland fruit damage have been reported from the canton Ticino and since 2017 also from the canton Zurich. Climate Impact studies are of great importance to develop adaptation strategies. In this work we used high-resolution, gridded climate change scenarios for Switzerland to simulate the distribution and abundance of H. halys under present and future climate conditions. The simulations were performed with the software package CLIMEX (© CSIRO), a process-based bioclimatic niche model that simulates the mechanisms that limits species’ geographical distributions and determine their seasonal phenology, and to some extend their relative abundance. A recently published CLIMEX model for H. halys (Kriticos et al. 2017, J Pest Sci) was validated and calibrated for Switzerland considering adult trap catch data. The potential distribution and abundance under present and future climates was compared by means of the number of generations per year and the annual growth index (suitability of the climate for the growth of insects). Today H. halys is univoltine in Switzerland. Our results indicate that under future climate conditions a multivoltine behavior will be possible. Furthermore our simulations demonstrate an enhancement of the overall suitability for the growth of H. halys. Our results help to define regions and time periods at greatest risk and to design management strategies for H. halys under future climate conditions

Restricting the nonlinearity parameter in soil greenhouse gas flux calculation for more reliable flux estimates

The static chamber approach is often used for greenhouse gas (GHG) flux measurements, whereby the flux is deduced from the increase of species concentration after closing the chamber. Since this increase changes diffusion gradients between chamber air and soil air, a nonlinear increase is expected. Lateral gas flow and leakages also contribute to non linearity. Several models have been suggested to account for this non linearity, the most recent being the Hutchinson±Mosier regression model (HMR). However, the practical application of these models is challenging because the researcher needs to decide for each flux whether a nonlinear fit is appropriate or exaggerates flux estimates due to measurement artifacts. In the latter case, a flux estimate from the linear model is a more robust solution and introduces less arbitrary uncertainty to the data. We present the new, dynamic and reproducible flux calculation scheme, KAPPA.MAX, for an improved trade-off between bias and uncertainty (i.e. accuracy and precision). We develop a tool to simulate, visualise and optimise the flux calculation scheme for any specific static N2O chamber measurement system. The decision procedure and visualisation tools are implemented in a package for the R software. Finally, we demonstrate with this approach the performance of the applied flux calculation scheme for a measured flux dataset to estimate the actual bias and uncertainty. The KAPPA.MAX method effectively improved the decision between linear and nonlinear flux estimates reducing the bias at a minimal cost of uncertainty

Current distribution and voltinism of the brown marmorated stink bug, Halyomorpha halys, in Switzerland and its response to climate change using a high-resolution CLIMEX model

Climate change can alter the habitat suitability of invasive species and promote their establishment. The highly polyphagous brown marmorated stinkbug, Halyomorpha halys Stål (Hemiptera: Pentatomidae), is native to East Asia and invasive in Europe and North America, damaging a wide variety of fruit and vegetable crops. In Switzerland, crop damage and increasing populations have been observed since 2017 and related to increasing temperatures. We studied the climatic suitability, population growth, and the number of generations under present and future climate conditions for H. halys in Switzerland, using a modified version of the bioclimatic model package CLIMEX. To address the high topographic variability in Switzerland, model simulations were based on climate data of high spatial resolution (approx. 2 km), which significantly increased their explanatory power, and identified many more climatically suitable areas in comparison to previous models. The validation of the CLIMEX model using observational records collected in a citizen science initiative between 2004 and 2019 revealed that more than 15 years after its accidental introduction, H. halys has colonised nearly all bioclimatic suitable areas in Switzerland and there is limited potential for range expansion into new areas under present climate conditions. Simulations with climate change scenarios suggest an extensive range expansion into higher altitudes, an increase in generations per year, an earlier start of H. halys activity in spring and a prolonged period for nymphs to complete development in autumn. A permanent shift from one to two generations per year and the associated population growth of H. halys may result in increasing crop damages in Switzerland. These results highlight the need for monitoring th

How dose of biochar and biochar with nitrogen can improve the parameters of soil organic matter and soil structure?

Biochar application to agricultural soils has a significant potential to influence soil resource availability and thus crop performance. A factorial experiment investigating effects of different biochar application rates combined with nitrogen fertilizer was conducted in field conditions on a Haplic Luvisol. The aim of this study was to evaluate the effects of biochar and biochar combined with fertilization on soil organic matter and soil structure parameters. The treatments comprised combinations of biochar application of 0, 10 and 20 t ha−1 (B0, B10 and B20) and 0, 40 and 80 kg N ha−1 of nitrogen fertilizer (N0, N40, N80) applied in a full-factorial design. Biochar application rate of 20 t ha−1 significantly increased soil organic carbon content (SOC) and non-labile carbon content (CNL), but decreased carbon lability (LC). The addition of biochar at 10 t ha−1 together with 40 and 80 kg N ha−1 significantly increased the values of SOC and CNL. On the other hand, B10N80 treatment resulted in a considerable decrease of carbon lability (LC). Overall, the lowest average content of water-stable micro-aggregates was found in the B20N80 treatment and then with B10N0 < B20N40 < B20N0 < B10N80 < B0N0 < B10N40. Biochar applied at 20 t ha−1 increased the critical level of soil organic matter and decreased the crusting index

Biochar and biochar with N-fertilizer affect soil N2O emission in Haplic Luvisol

The benefits of biochar application are well described in tropical soils, however there is a dearth of information on its effects in agricultural temperate soils. An interesting and little explored interaction may occur in an intensive agriculture setting; biochar addition may modify the effect of commonplace N-fertilization.We conducted a field experiment to study the effects of biochar application at the rate of 0, 10 and 20 t ha−1 (B0, B10 and B20) in combination with 0, 40 and 80 kg N ha−1 of N-fertilizer (N0, N40, N80).We followed nitrous oxide (N2O) emissions, analysed a series of soil physicochemical properties and measured barley yield in a Haplic Luvisol in Central Europe. Seasonal cumulative N2O emissions from B10N0 and B20N0 treatments decreased by 27 and 25% respectively, when compared to B0N0. Cumulative N2O emissions from N40 and N80 combined with B10 and B20 were also lower by 21, 19 and 25, 32%, respectively compared to controls B0N40 and B0N80. Average pH was significantly increased by biochar addition. Increased soil pH and reduces NO−3 content seen in biochar treatments could be the two possible mechanisms responsible for reduced N2O emissions. There was a statistically significant increase of soil water content in B20N0 treatment compared to B0N0 control, possibly as a result of larger surface area and the presence of microspores having altered pore size distribution and water-holding capacity of the soil. Application of biochar at the rate of 10 t ha−1 had a positive effect on spring barley grain yield

Assessing climate change impacts on fruit plant and pest phenology and their synchrony: the case of apple and codling moth

Temperature is a main climatic driver of plant phenology and the dominant abiotic factor directly affecting insect pests. Global warming is therefore expected to accelerate the development of plants and insects alike. In the case of multivoltine pest species, it was shown that higher temperatures lead to the appearance of additional generations toward the end of the warm season (Stöckli et al., 2012), which also has implications for pest management. The same effect was shown for the timing of flowering termination of apple trees (Stöckli and Samietz, 2015), the time when a pest can attack a fruit. In practice, however, much would depend on whether plant and pest phenology remain synchronized or not. Focusing on Switzerland, in this contribution we present an analysis of potential impacts of climate change on plant and pest phenology. and their interlinkages at the example of the apple tree (Malus pumila L.) and the codling moth (Cydia pomonella L.), a fruit crop of economic relevance worldwide. Key developmental stages of the apple and the codling moth were simulated by means of two heat summation models. The models were calibrated with lab and field data from Switzerland and subsequently run with observed weather data and various climate change scenarios. The time period between flowering termination and the harvest of the apples was compared to the appearance of the second and third generation of codling moth larvae to study the interlinkage between host and pest. To illustrate the potential for practical applications of the phenology models, we used spatial temperature data of Switzerland to produce risk maps that can serve as a basis for further studies and decision support

Application of phenology models for Climate Services

Global warming is expected to accelerate the development of plants and insects leading to earlier occurrence of phenological stages than under today’s climate. This can alter the exposure of plants to extreme climate events and further change the synchrony between host plants and pest insects. Assessing the implications of earlier development for the exposure to risks is necessary to inform adaptation. In this contribution we present an analysis of potential impacts of climate change on (i) the risk of early frost in apple orchards and damages to apple fruits due to critically high temperatures, (ii) the time of apple picking, and (iii) the potential of damages caused by the codling moth (Cydia pomonella L.), for three different apple cultivars in Switzerland. To this aim, carefully calibrated phenological models for apple trees and the codling moth are run with updated climate change scenarios. The climate scenarios comprises three different emissions scenarios. To underline the utility of phenological models and data for informing society, we show how this assessment is integrated into a recent initiative to implement National Climate Services in Switzerland in response to the Global Framework for Climate Services issued by the World Meteorological Organisation

Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

Methane (CH4) from ruminants contributes one-third of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d−1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head−1 d−1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.ISSN:1726-4170ISSN:1726-417