- Effects from climate change, adaptations and
greenhouse gas reduction at 2050

Abstract:

RATIONALE: Because of the wide-ranging appearance and high soil organic carbon (C) content of grasslands, their ecosystems play an important role in the global C cycle. Thus, even small changes in input or output rates lead to significant changes in the soil C content, thereby affecting atmospheric [CO2]. Our aim was to examine if a higher C supply provided under elevated CO2 will increase the soil C pool. Special attention was given to respirational processes, where CO2 emission rates and its sources (plant vs. soil) were considered. METHODS: The Giessen-FACE experiment started in 1998 with a moderate CO2 enrichment of +20% and +30% above ambient on an extensively managed grassland. The experiment consists of three control plots where no CO2 is applied, three plots where [CO2] is enriched by +20% and one plot receiving [CO2] +30%. To exclude initial CO2 step increase effects, a detailed examination of respirational processes over 30 months was carried out after 6 years of CO2 enrichment starting in June 2004. At that time, the ?13C signature of the enrichment-CO2 was switched from
25 ‰ to
48 ‰ without a concomitant change in CO2 concentration. RESULTS: After 9 years, the fraction of new C under [CO2] +20% was 37 ± 5.4% in the top 7.5cm but this decreased with depth. No CO2 effect on soil carbon content was detected. Between June 2004 and December 2006, elevated [CO2] +20% increased the ecosystem respiration by 13%. The contribution of root respiration to soil respiration was 37 ± 13% (5 cm) and 43 ± 14% (10 cm) for [CO2] +20% and 35 ± 13% and 40 ± 13% for [CO2] +30%, respectively. CONCLUSIONS: Our findings of an increased C turnover without a net soil C sequestration suggest that the sink strength of grassland ecosystems might decrease in the future, because the additional C may quickly be released as CO2 to the atmosphere.

Abstract:

Hyperspectral remote sensing is a promising tool for a variety of applications including ecology and geology but also analytical chemistry and medical research. Here, the new hsdar-package for R statistical software is presented, which allows to perform a large variety of analysis steps during a typical hyperspectral remote sensing approach. Therefore, the package introduces a new class to e?ciently store even large hyperspectral datasets such as hyperspectral cubes within R. The package includes several important hyperspectral analysis tools such as continuum removal, normalized ratio indices and integrates two widely used radiation transfer models. Besides this, the package provides methods to directly use the functionality of the caret-package for machine learning tasks. To demonstrate the range of functions of the hsdar-package, two case studies are included. The ?rst one shows the estimation of plant leave chlorophyll content and the second one the ability to detect cancer in the human larynx from hyperspectral data.

Abstract:

Using barcoded pyrosequencing fungaland bacterial communities associated with grape berry clusters (Vitis viniferaL.) obtained from conventional, organic and biodynamic vine yard plots were investigated in two subsequent years at different stages during berry ripening. The four mosta bundant operational taxonomic units (OTUs) based on fungal ITS data were Botrytis cinerea, Cladosporium spp., Aureobasidium pullulans and Alternaria alternata which represented 57% and 47% of the total reads in 2010 and 2011, respectively. Members of the genera Sphingomonas, Gluconobacter, Pseudomonas, Erwinia, and Massilia constituted 67% of the total number of bacterial 16S DNA reads in 2010 samples and 78% in 2011 samples. Viticultural management system had no significant effect on abundance of fungi or bacteria in both years and at all three sampling dates. Exceptions were A.alternata and Pseudomonas spp. which were more abundant in the carposphere of conventional compared to biodynamic berries, as well as Sphingomonas spp. which was significantly less abundant on conventional compared to organic berries at an early ripening stage in 2011. In general,there were no significant differences in fungal and bacterial diversity indices or richness evident between management systems. No distinct fungal or bacterial communities were associated with the different maturation stages or management systems, respectively. An exception was the last stage of berry maturation in 2011, where the Simpson diversity index was significantly higher for fungal communities on biodynamiccompared to conventional grapes.Our study highlights the existence of complex and dynamic microbial communities in the grape cluster carposphere including both phytopathogenic and potentially antagonistic microorganisms that can have a significant impact on grape production. Such knowledge is particularly relevant for development, selection and application of effective control measures against economically important pathogens present in the grape carposphere.

Abstract:

Methane (CH4) emissions have increased by more than 150% since 1750, with agriculture being the major source. Further increases are predicted as permafrost regions start thawing, and rice and ruminant animal production expand. Biochar is posited to increase crop productivity while mitigating climate change by sequestering carbon in soils and by influencing greenhouse gas fluxes. There is a growing understanding of biochar effects on carbon dioxide and nitrous oxide fluxes from soil. However, little is known regarding the effects on net methane exchange, with single studies often reporting contradictory results. Here we aim to reconcile the disparate effects of biochar application to soil in agricultural systems on CH4 fluxes into a single interpretive framework by quantitative meta-analysis. This study shows that biochar has the potential to mitigate CH4 emissions from soils, particularly from flooded (i.e. paddy) fields (Hedge's d ¼ 0.87) and/or acidic soils (Hedge's d ¼ 1.56) where periods of flooding are part of the management regime. Conversely, addition of biochar to soils that do not have periods of flooding (Hedge's d ¼ 0.65), in particular when neutral or alkaline (Hedge's d ¼ 1.17 and 0.44, respectively), may have the potential to decrease the CH4 sink strength of those soils. Global methane fluxes are net positive as rice cultivation is a much larger source of CH4 than the sink contribution of upland soils. Therefore, this meta-study reveals that biochar use may have the potential to reduce atmospheric CH4 emissions from agricultural flooded soils on a global scale.

Abstract:

An increase in mean soil surface temperature has been observed over the last century and it is predicted to further increase in the future. The effect of increased temperature on ecosystem carbon fluxes in a permanent temperate grassland, was studied in a long term (6 years) field experiment, using multiple temperature increments induced by IR-lamps. Ecosystem respiration (R-eco) and net ecosystem exchange (NEE) were measured, and modelled by a modified Lloyd and Taylor model including a soil moisture component for R-eco (average R2 of 0.78) and inclusion of a photosynthetic component based on temperature and radiation for NEE (R2=0.65). Modelled NEE values ranged between 2.3 and 5.3 kg CO2 m-2 year-1, depending on treatment. An increase of 2 or 3°C led to increased carbon losses, lowering the carbon storage potential by around 4 tonnes of C ha-1 year-1. The majority of significant NEE differences were found during night-time compared to daytime. This suggests that during daytime the increased respiration could be offset by an increase in photosynthetic uptake. This was also supported by differences in ?13C and ?18O, indicating prolonged increased photosynthetic activity associated with the higher temperature treatments. However, this increase in photosynthesis was insufficient to counteract the 24hr increase in respiration, explaining the higher CO2 emissions due to elevated temperature.

Abstract:

Over the last century an increase in mean soil surface temperature has been observed and it is predicted to increase further in the future. To evaluate the legacy effects of increased temperature on both nitrogen (N) transformation rates in the soil and nitrous oxide (N2O) emissions, an incubation experiment was conducted with soils taken from a long term in situ warming experiment on temperate permanent grassland. In this experiment the soil temperature was elevated by 0 (control), 1, 2 or 3°C (4 replicates per treatment) using IR-lamps over a period of 6 years. The soil was subsequently incubated under common conditions (20°C and 50% humidity) and labelled with NO315NH4 Gly, 15NO3NH4 Gly or NO3NH4 15N-Gly. Both inorganic N (NO3-+NH4+) and NO3- contents were higher in soil subjected to the +2 and +3°C temperature elevations. Analyses of N transformations using a 15N tracing model, showed that, following incubation, gross organic (and not inorganic) N transformation rates decreased in response to the prior soil warming treatment. This was also reflected in reduced N2O emissions associated with organic N oxidation and denitrification. A newly developed source partitioning model showed the importance of oxidation of organic N as a source of N2O. Concluding, long term soil warming can cause a legacy effect which diminishes organic N turn over and the release of N2O from organic N and denitrification.

Abstract:

Biochar (BC) has been shown to increase the potential for N retention in agricultural soils. However, the form of N retained and its strength of retention are poorly understood. Here, we examined if the N retained could be readily extractable by standard methods and if the amount of N retained varied with BC field ageing. We investigated soil and field-aged BC (BCaged) particles of a field experiment (sandy soil amended with BC at 0, 15, and 30 t ha-1) under two watering regimes (irrigated and rain-fed). Throughout the study, greater nitrate than ammonium retention was observed with BC addition in topsoil (0–15 cm). Subsoil (15–30 cm) nitrate concentrations were reduced in BC treatments, indicating reduced nitrate leaching (standard 2 mol L-1 KCl method). The mineral-N release of picked BCaged particles was examined with different methods: standard 2 mol L-1 KCl extraction; repeated (10×) extraction in 2 mol L-1 KCl at 22 ± 2°C and 80°C (M0); electro-ultrafiltration (M1); repeated water + KCl long-term shaking (M2); and M2 plus one repeated shaking at 80°C (M3). Nitrate amounts captured by BCaged particles were severalfold greater than those in the BC-amended soil. Compared with M0, standard 2 mol L-1 KCl or electro-ultrafiltration extractions retrieved only 13 and 30% of the total extractable nitrates, respectively. Our results suggest that “nitrate capture” by BC may reduce nitrate leaching in the field and that the inefficiency of standard extraction methods deserves closer research attention to decipher mechanisms for reactive N management.

Abstract:

Recenttechnologicaladvanceshaveenabledthewiderapplicationofautomatedchambers for soil greenhouse gas (GHG) ?ux measurements, several of them commercially available. However, only few studies addressed the di?culties and challenges associated with operating these systems. In this contribution we compared two commercial5 soil GHG chamber systems–the LI-8100A Automated Soil CO2 Flux System and the Greenhouse Gas Monitoring System AGPS. From April 2014 until August 2014, the two systems monitored in parallel soil respiration (SR) ?uxes at a recently harvested poplar plantation, which provided a bare ?eld situation directly after the harvest as well as a closed canopy later on. For the bare ?eld situation (15 April–30 June 2014),10 the cumulated average SR obtained from the un?ltered datasets of the LI-8100A and the AGPS were 520 and 433g CO2 m?2, respectively. For the closed canopy phase (01 July–31 August 2014), which was characterized by a higher soil moisture content, the cumulated average SR estimates were not signi?cantly di?erent with 507 and 501g CO2 m?2 for the AGPS and the LI-8100A, respectively. Flux quality control and ?ltering15 did not signi?cantly alter the results obtained by the LI-8100A, whereas the AGPS SR estimates were reduced by at least 20%. The main reasons for the observed di?erences in the performance of the two systems were (i) a lower data coverage provided by the AGPS due to technical problems; (ii) incomplete headspace mixing in the AGPS chambers; (iii) lateral soil CO2 di?usion below the collars during AGPS chamber mea-20 surements; (iv) increased root growth within the LI-8100A collars; and (v) a possible overestimation of nighttime SR ?uxes by the LI-8100A. In contrast to the LI-8100A, the AGPS had the gas sample inlets installed inside the collars and not the chambers. This uniquedesignfeatureenabledforthe?rsttimethedetectionofdisturbedchambermeasurements during nights with a strati?ed atmosphere, resulting in unbiased nighttime25 SR estimates. Thus besides providing high temporal frequency ?ux data, automated chamber systems o?er another possibility to greatly improve our understanding of SR ?uxes.

Abstract:

Global climate change is expected to increase the frequency and intensity of extreme precipitation events, which can dramatically alter soil nitrous oxide (N2O) emissions. However, our ability to predict this effect is limited due to the lack of studies under real-world conditions. We conducted a ?eld experiment in a maize-cultivated black soil in northeast China with six treatments: control without nitrogen (N) application (CK) and N-fertilized treatments with the ratio of urea N to manure N at 100:0 (NPK), 75:25 (OM1), 50:50 (OM2), 25:75 (OM3) and 0:100 (OM4). The experimentalyear was the wettest on record with an extreme rainfall event of 178 mm occurring in summer 2013. Annual N2O emissions from CK and NPK were increased by 168% and 171%, respectively, relative to normal wet years. Extreme rainfall saturated soils, resulted in low N2O ?uxes (<20 mgNm
2 h
1) lasting for 25 d. However, N2O ?ux peaked (169e264 mgNm
2 h
1) in all treatments as the soil dried. Total N2O emissions were 0.43 e0.74 kg N ha
1 over the drying period, accounting for 47.5e51.2% of the annual budget. High N2O ?uxes occurred when the ratio of soil nitrate (NO3
) to dissolved organic carbon was 0.07e0.10 mg N mg
1 C, NO3
concentration was >3 mg N kg
1 and water-?lled pore space was 67e76%. Distinctly higher N2O ?uxes were also identi?ed during the spring thaw period, accumulating to 20.1e49.4% of the nongrowing season emissions. Emissions upon thawing were likely related to denitri?cation induced by high moisture conditions as a result of lag effect of the extreme rainfall. Annual N2O emissions progressively reduced as the ratio of urea N:manure N shifted towards manure, which was also the case during soil drying after waterlogging. Total N2O emissions were reduced by 25.6% for OM4 than NPK. Overall, our results suggest that soil N2O emissions were increased in the record wet year but a shift from urea towards manure with more N applied as starter N can minimize the N2O losses.

Abstract:

Climate change, particularly the combined effects of elevated CO2 and temperature, is likely to alter the internal nitrogen (N) cycle of agricultural ecosystems. However, little is known about such phenomena in paddy soils, which are expected to expand in the near future due to population increase. A 15N tracer study, with soil taken from field manipulation treatments, showed that elevated CO2, either alone or combined with elevated temperature, stimulated the mineralization of labile organic N 37-fold but decreased the mineralization of recalcitrant organic N. In contrast, elevated temperature alone accelerated the mineralization of recalcitrant organic N approximately 2-fold but had no effect on the mineralization of labile organic N. Ammonium immobilization increased under elevated CO2 and elevated temperature. Gross and net NO3
production decreased under elevated CO2 and the combined treatments, whereas elevated temperature caused an increase in both rates. Dissimilatory reduction of NO3
to NH4þ increased under elevated CO2 but decreased with elevated temperature. Our findings suggest that progressive N limitation can be alleviated by increasing gross N transformation rates under each climate change treatment and that counteraction will dominate the interactive responses of CO2 and temperature. Because we expect a concomitant increase in both CO2 and temperature, we only expect minor effects of these particular factors arising as a result of climate on soil N dynamics in paddy soils.

Abstract:

Biochar may become a key instrument at the nexus of managed carbon flows, including value added potential in soil amelioration, climate protection, energy supply and organic waste management. This article reflects the potential use of biochar in agriculture from the perspective of the farming economy. Biochar soil amendment in crop production is regarded as a win
win situation, both for assumed increases in cropping yields and carbon sequestration in soil organic matter. However, an extensive review on biochar effect on crop yield has not yet been able to provide compelling arguments to foster more widespread biochar use in cropping systems. Furthermore, the half-lives of biochars are frequently shorter than commonly suggested, and other financial incentives, such as including biochar in carbon credit systems, are not in place to compensate for the extra cost of applying biochar. As a result, we conclude with a somewhat skeptical view for a widespread use of biochar in agriculture in the near future.

Abstract:

Satellite map of the Umweltbeobachtungs und Klimafolgenforschungsstation Linden

Abstract:

Soil respiration of terrestrial ecosystems, a major component in the global carbon cycle is affected by elevated atmospheric CO2 concentrations. However, seasonal differences of feedback effects of elevated CO2 have rarely been studied. At the Gießen Free-Air CO2 Enrichment (GiFACE) site, the effects of +20% above ambient CO2 concentration have been investigated since 1998 in a temperate grassland ecosystem. We defined five distinct annual seasons, with respect to management practices and phenological cycles. For a period of 3 years (2008–2010), weekly measurements of soil respiration were carried out with a survey chamber on vegetation-free subplots. The results revealed a pronounced and repeated increase of soil respiration under elevated CO2 during late autumn and winter dormancy. Increased CO2 losses during the autumn season (September–October) were 15.7% higher and during the winter season (November–March) were 17.4% higher compared to respiration from ambient CO2 plots. However, during spring time and summer, which are characterized by strong above- and below-ground plant growth, no significant change in soil respiration was observed at the GiFACE site under elevated CO2. This suggests (1) that soil respiration measurements, carried out only during the growing season under elevated CO2 may underestimate the true soil-respiratory CO2 loss (i.e. overestimate the C sequestered), and (2) that additional C assimilated by plants during the growing season and transferred below-ground will quickly be lost via enhanced heterotrophic respiration outside the main growing season.

Abstract:

A major issue of our today's research is to help meeting the challenges of future food security. One task is to assess and develop crop management strategies adapted to predicted future climatic conditions. Yet, both the variability of environmental conditions and the uncertainty of climate projections as well as the orchestra of multiple plant responses and their interaction with the environment make it difficult to predict plant behavior in the field. Recent studies have demonstrated the usefulness of classical crop models as a tool to investigate crop productivity under predicted climate conditions. These models use data on plant architecture only to a limited extent as they usually follow a systems approach by focusing on processes for predicting dry matter production. However, plant architecture is a major determinant of the crops’ resource use efficiency. Moreover, plants show time dependent structural changes as they grow and develop, and these processes are affected by various environmental factors and stresses. Virtual plant models consider both the three-dimensional plant architecture and concepts of plant physiology. Here, we outline the way in which virtual plant modelling can further improve our understanding on the impact of climate change on food production. Greenhouse and growth chamber experiments may serve as data sources for model parameterization, in particular of response functions with respect to environmental stimuli. Data from field experiments in free air carbon enrichment (FACE) facilities, such as those obtained in the new Geisenheim FACE for special crops, may be used to evaluate virtual plant models with respect to future climatic conditions. A combination of field data and virtual plant model simulations may then allow us to assess the specific role of plant architecture in resource use efficiency and help to develop advanced strategies for future crop production.

Abstract:

Future vegetable crop production might be affected by Climate Change with the projected increase in atmospheric CO2 concentration and changes in precipitation pattern. Elevated CO2 as one main component of photosynthesis is assumed to increase the yield of many crops while alleviating negative effects of drought stress and, thereby, increasing the water use efficiency. However, the responses of field grown vegetable crops to elevated CO2 are still unknown as previous findings are mainly derived from experiments conducted under controlled environments. In addition, the field vegetable production is characterized by several sets per season, varying growth conditions during the production periods and a high water demand usually provided by an irrigation system. Moreover, vegetable crops differ in the harvest organs, e.g. fruits, root tuber, bulbs or leaves, which are predominantly harvested in an early development stage. These vegetable-specific aspects have not been considered in past Free Air Carbon Dioxide Enrichment (FACE) experiments. Therefore, we aim at analyzing the short and long impacts of elevated CO2 with limited water supply on field vegetable crop productivity for three different crops (Cucumis sativus L., Raphanus sativus var. sativius L., Spinacia oleracea L.). Here, we present the methodological framework. Experiments will be conducted in the newly established FACE facility for vegetable crops at Geisenheim University, Germany. The facility is designed to raise the ambient CO2 concentration at the experimental field site by about 20% to approximately 480 ppm and to regulate the water supply with a drip irrigation system, resulting in a split plot design with three replications. In each replication an annual crop rotation with several production cycles of the three different vegetable crops are realized. Measurements of the CO2 and H2O gas exchange on leaf level as well as non-destructive and destructive recordings of plant growth and development are planned.

Abstract:

The rising concentration of carbon dioxide in the atmosphere ([CO2]) has a direct effect on terrestrial vegetation through shifts in the rates of photosynthetic carbon uptake and transpirational water-loss. Free Air CO2 Enrichment (FACE) experiments aim to predict the likely responses of plants to increased [CO2] under normal climatic conditions. The Giessen FACE system operates a lower [CO2] enrichment regime (480 mmol mol–1) than standard FACE (550–600 mmol mol–1), permitting the analysis of a mixed species temperate meadow under a [CO2] level equivalent to that predicted in 25–30 years. We analysed the physiological and morphological responses of six species to investigate the effect of moderate [CO2] on spring biomass production. Carbon dioxide enrichment stimulated leaf photosynthetic rates and supressed respiration, contributing to enhanced net assimilation and a 23% increase in biomass. The capacity for photosynthetic assimilation was unaffected by [CO2] enrichment, with no downregulation of rates of carboxylation of Rubisco or regeneration of ribulose- 1,5-bisphosphate. Foliar N content was also not influenced by increased [CO2]. Enhanced [CO2] reduced stomatal size, but stomatal density and leaf area index remained constant, suggesting that the effect on gas exchange was minimal.