• Authors:
    • Schilling, B.
    • Reischl, A.
    • Hangen, E.
    • Geuß, U.
    • Spörlein, P.
    • Lützow, M. V.
    • Wiesmeier, M.
    • Kögel-Knabner, I.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Numerous studies have reported substantial changes of soil organic carbon (SOC) stocks after converting forests into agricultural land and vice versa. However, some studies suggested that agricultural soils might contain similar amounts of SOC as forest soils. Losses of SOC induced by cultivation might be overestimated due to shallow soil sampling and application of inaccurate pedotransfer functions. We investigated the impact of different land uses on total SOC storage down to the subsoil on the basis of 270 soil profiles in southeast Germany under similar climatic and pedogenic conditions using an equivalent soil mass (ESM) approach. Land use effects on SOC storage were strongly affected by soil class, which comprised soil types with similar pedogenesis. Both slightly lower (<20%) and even higher SOC stocks were found under cropland compared with forest land for different soil classes. A comparison of different soil classes under grassland and forest land also showed no considerable differences of SOC stocks. Soil cultivation may not generally be associated with a strong decline of SOC, as tillage probably promotes the formation of organo-mineral associations and a relocation of SOC with depth may decrease its decomposition. This finding should be taken into consideration when estimating and managing the emission and sequestration of C in soils. We assume that many studies based on topsoils alone may have underestimated agricultural SOC stocks, particularly when an ESM approach is used. Our results highlight the need for soil type-specific evaluations in terms of interpreting the effects of land use management on SOC stocks.
  • Authors:
    • Freese, D.
    • Medinski, T. V.
    • Bohm, C.
  • Source: AGROFORESTRY SYSTEMS
  • Volume: 89
  • Issue: 2
  • Year: 2015
  • Summary: Understanding of soil carbon dynamics after establishment of alley-cropping systems is crucial for mitigation of greenhouse CO 2 gas. This study investigates soil CO 2 fluxes in an alley-cropping system composed of tree strips of black locust ( Robinia pseudoacacia L.) and poplar ( Populus nigra * P. maximowiczii, Max 1) trees and adjacent to them crop strips ( Lupinus/Solarigol). Soil CO 2 flux was measured monthly over a period from March to November 2012, using a LI-COR LI-8100A automated device. Concurrently with CO 2 flux measurements, soil and air temperature, soil moisture, microbial C and hot water-extractable C were determined for the soils nearby soil collars. Root biomass was determined to a depth of 15 cm. In all sampling areas, soil CO 2 flux increased from May to July, showing a significant positive correlation with air and soil temperature, which can be a reflection of increase in photosynthesis, and therefore supply of carbohydrates from leaves to rhizosphere, over the warm summer months. A positive correlation between CO 2 flux and soil moisture over the warm period indicates an enhancing role of soil moisture on microbial mineralization and root respiration. Average CO 2 flux values observed over March-November period did not differ significantly between sampling areas, showing 2.5, 3.2, and 2.9 mol m -2 s -1 values for black locust, poplar and crops, respectively. Significantly higher CO 2 flux values over the summer period in trees could be attributed to the higher photosynthetic activity and higher root density compared to crops.
  • Authors:
    • Reibe,K.
    • Gotz,K. P.
    • Ross,C. L.
    • Doring,T. F.
    • Ellmer,F.
    • Ruess,L.
  • Source: Soil Biology & Biochemistry
  • Volume: 83
  • Year: 2015
  • Summary: The effects of biochar (maize biochar - MBC, wood biochar - WBC) and unfermented or fermented hydrochar (HTC) on the euedaphic Collembola Protaphorura fimata and on spring wheat were investigated in greenhouse experiments. The impact of char type, amount of fermented HTC, and MBC-Collembola interactions were assessed. Generally, shoot and root biomass as well as abundance of P. fimata were not affected by the different chars. However, with increasing amounts of fermented HTC the abundance of P. fimata declined, whereas shoot biomass of wheat increased. Moreover, MBC altered root morphology and resulted in thicker roots with higher volume. The latter was not apparent when Collembola were present.
  • Authors:
    • Weber-Blaschke, G.
    • Lampert, P.
    • Soode, E.
    • Richter, K.
  • Source: Agriculture Article
  • Volume: 87
  • Year: 2015
  • Summary: Global climate change problem can be linked to production efficiency and everyday consumption patterns by calculating the greenhouse gas emissions resulting from each product. This is usually referred to as product carbon footprint (PCF). Only limited information is available about the PCF of German horticultural products. We measured the cradle-to-grave PCF of German strawberries, asparagus, roses and orchids in different production systems and compared it to the PCF of the same products grown in other countries. For the production and customer stage we collected primary data, for the comparison with products in other countries we used literature data. The results showed that the average consumer stage constitutes 3-71% of the PCF, the best case consumer scenario 1-39% and the worst case 60-99%. The consumer shopping trip was a hotspot in all analysed systems where a private car was used. Electricity for production, fuel use for soil management, and cooking and washing dishes were also among the most often identified hotspots. German open field strawberries perform better, German open field roses and asparagus are on the similar level with the same products produced abroad. However, asparagus transported by plane, and strawberries and roses grown in greenhouses have several times higher PCF regardless of the producing country. Consumers as well as producers are responsible for reducing the climate impact of horticultural products. Shopping trip on foot or by bike and using renewable energy can reduce the PCF significantly. We recommend extending the analysis to the life cycle assessment or product environmental footprint to consider more indicators to identify which products are less harmful to the environment.
  • Authors:
    • Hanewinkel, M.
    • Yousefpour, R.
  • Source: Article
  • Volume: 130
  • Issue: 2
  • Year: 2015
  • Summary: Forestry professionals' perceptions of the risks and uncertainties associated with climate change were investigated in a questionnaire survey in south-west Germany. The respondents were employed in forestry in either public or private forests or working for state authorities. They were specifically asked about the related impacts of climate change on forest ecosystems, adaptive forest management and the potential of forestry to mitigate climate change. A factor analysis of the responses revealed significant variables explaining the major part of the variance and the key variable groups were identified in a canonical analysis. The majority of respondents (72 %) said they were under-informed, but most (83 %) view climate change as a reality, human-caused, and a significant risk. These forestry professionals were particularly concerned about extreme hazards, water scarcity, and changes in climatic zones. They generally said the potential of forestry to mitigate climate change is low, and saw few realistic measures like increased harvesting to substitute fossil fuels and energy-intensive materials for mitigation. Despite the uncertainty involved, adaptation strategies like using better-adapted tree species and provenances were mainly perceived as helpful, and tools such as spatially-explicit maps with recommendations for adapted species and indices of biotic and abiotic risks as important. The forestry professionals reported obtaining their information about climate change from advanced forestry training, the media, and scientific literature. The findings of the study are discussed in the light of the ongoing debate on climate change in Germany and recommendations made, including periodically checking and improving forestry professionals' knowledge about climate change.
  • Authors:
    • Aldana Jague,E.
    • Sommer,M.
    • Saby,N. P. A.
    • Cornelis,J. -T
    • Van Wesemael,B.
    • Van Oost,K.
  • Source: Soil & Tillage Research
  • Volume: 156
  • Issue: 3
  • Year: 2015
  • Summary: The identification of soil management strategies as well as the evaluation of their effectiveness requires detailed information on the spatial and temporal patterns of soil organic carbon storage. High-resolution SOC profile data are generally not available and traditional methods for collecting these are time consuming and costly. Recent studies use geo-statistical approaches to assess the three-dimensional patterns of SOC storage. However, there is still a large discrepancy between the continuous and high resolution mapping of the horizontal SOC variability on the one hand, and the coarse and discontinuous mapping of the vertical SOC profile on the other. In this study, we combine spectroscopic techniques with spatial modeling in a small, cultivated catchment in Germany and we evaluate the contribution of soil redistribution processes and topographical parameters to the observed spatial and vertical patterns. Using high-resolution data from soil cores, we evaluated the robustness of a third order polynomial function to model the vertical SOC profile. Using a crossvalidation, our results show that this approach results in a robust model (RSME=0.24%) and performs better than the widely used exponential depth model (RMSE=0.39%). In a next step, we evaluated the relationship between the parameters of the SOC depth model and co-variables including soil redistribution (inferred from 137Cs data) and topographical indices using a multiple linear regression model. The performance was calculated by cross-validation and we found a low robustness of the models because of the low number of profiles (i.e. n =19). A statistical evaluation of the co-variables highlighted two key factors influencing the SOC vertical distribution. Soil redistribution processes mainly influenced the surface SOC content (first centimeters) whereas the shape of the depth distribution was controlled by slope curvature alone. The mapping of polynomial parameters was validated using an external SOC profile dataset and showed a poor prediction of the surface content but a good prediction of the depth distribution once the surface SOC content is known (RMSE=0.15-0.25%C). This suggests that estimating the vertical SOC profile from topsoil data by applying remote sensing data, in combination with our SOC profile model, is promising and can will result in an accurate mapping of 3D SOC patterns at a very high resolution. © 2015 Elsevier B.V.
  • Authors:
    • Möller,K.
  • Source: Agronomy for Sustainable Development
  • Volume: 35
  • Issue: 3
  • Year: 2015
  • Summary: Sustainability in agriculture means the inclusion of several aspects, as sustainable agriculture systems must not compromise not only their ability to satisfy future needs by undermining soil fertility and the natural resource base but also sustainable agriculture has had to address a range of other issues including energy use, efficient use, and recycling of nutrients, the effects on adjacent ecosystems including the effects on water bodies and climate change. Organic manures are an important factor to keep the soil fertility level of soils. However, their management is often related to large emissions. In this context, anaerobic digestion is—similarly to composting—a treatment option for stabilization of biogenic wastes leading to a residual product called digestates, enabling the sanitation and the recycling and use as fertilizer. It is also a means to obtain energy from wastes as well as from dedicated energy crops. Therefore, anaerobic digestion potentially addresses several aspects of agricultural sustainability. This review discusses the current state of knowledge on the effects of anaerobic digestion on organic compounds in digestates and the most important processes influencing N emissions in the field, as well as the possible long-term effects on soil microbial biomass and soil fertility. The main findings are that (1) the direct effects of anaerobic digestion on long-term sustainability in terms of soil fertility and environmental impact at the field level are of minor relevance. (2) The most relevant effects of anaerobic digestion on soil fertility as well as on N emissions will be expected from indirect effects related to cropping system changes such as changes in crop rotation, crop acreage, cover cropping, and total amounts of organic manures including digestates. Furthermore, (3) the remaining organic fraction after anaerobic digestion is much more recalcitrant than the input feedstocks leading to a stabilization of the organic matter and a lower organic matter degradation rate after field application, enabling a similar reproduction of the soil organic matter as obtained by direct application of the feedstock or by composting of the feedstock. (4) Regarding emissions, the main direct effect of anaerobic digestion on a farm level is the influence on gaseous emissions during manure or digestate treatment and handling, whereas the direct effects of anaerobic digestion on a field level on emissions (NH3− and N2O− emissions, NO3- leaching) are negligible or at least ambiguous. (5) The main direct effects of anaerobic digestion on the field level are short-term effects on soil microbial activity and changes in the soil microbial community. Therefore, in terms of the effects on agricultural sustainability, potential cropping system-based changes induced by introduction of biogas plants are probably much more relevant for the overall performance and sustainability of the cropping system than the direct effects triggered by application of digestates in comparison to the undigested feedstocks. Furthermore, to get the full potential advances from implementation of biogas plants in terms of improvement of the nutrient use efficiency and reduction of greenhouse gas emissions, there is the need to introduce more sophisticated techniques to avoid counteracting effects by pollution swapping, e.g., by gas-tight closure of the digestate stores and direct soil incorporation of the field-applied digestates. © 2015, INRA and Springer-Verlag France.
  • Authors:
    • Wagner, S.
    • Soderberg, J.
    • Spring, J.
    • Siegfried, W.
    • Rohr, C.
    • Riemann, D.
    • Retso, D.
    • Pribyl, K.
    • Nordli, O.
    • Kotyza, O.
    • Kiss, A.
    • Litzenburger, L.
    • Limanowka, D.
    • Labbe, T.
    • Himmelsbach, I.
    • Herget, J.
    • Gruenewald, U.
    • Contino, A.
    • Camenisch, C.
    • Burmeister, K. H.
    • Bieber, U.
    • Barriendos, M.
    • Alcoforado, M.
    • Zorita, E.
    • Seneviratne, S. I.
    • Luterbacher, J.
    • Glaser, R.
    • Dobrovolny, P.
    • Brazdil, R.
    • Wetter, O.
    • Pfister, C.
    • Werner, J. P.
  • Source: Article
  • Volume: 131
  • Issue: 2
  • Year: 2015
  • Authors:
    • Pohl,M.
    • Hoffmann,M.
    • Hagemann,U.
    • Giebels,M.
    • Borraz,E. Albiac
    • Sommer,M.
    • Augustin,J.
  • Source: Biogeosciences
  • Volume: 12
  • Issue: 9
  • Year: 2015
  • Summary: The drainage and cultivation of fen peatlands create complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater levels (GWLs). To date, the significance of such sites as sources or sinks for greenhouse gases such as CO2 and CH4 is still unclear, especially if the sites are used for cropland. As individual control factors such as GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL - defined as dynamic C and N stocks - play a key role in the regulation of the plant- and microbially mediated CO2 fluxes in these soils and, inversely, for CH4. To test this assumption, the present study analysed the C gas exchange (gross primary production - GPP; ecosystem respiration - R-eco; net ecosystem exchange - NEE; CH4) of maize using manual chambers for 4 years. The study sites were located near Paulinenaue, Germany, where we selected three soil types representing the full gradient of GWL and SOC stocks (0-1 m) of the landscape: (a) Haplic Arenosol (AR; 8 kg C m(-2)); (b) Mollic Gleysol (GL; 38 kg C m(-2)); and (c) Hemic Histosol (HS; 87 kg C m(-2)). Daily GWL data were used to calculate dynamic SOC (SOCdyn) and N (N-dyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 +/- 30 g C m(-2) yr(-1) in AR to -305 +/- 123 g C m(-2) yr(-1) in GL and -127 +/- 212 g C m(-2) yr(-1) in HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and N-dyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP : R-eco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via R-eco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalisable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape.
  • Authors:
    • Cardenas-Galindo, P.
    • Prosperi, P.
    • Flammini, A.
    • Jacobs, H.
    • Golec, R. D. C.
    • Biancalani, R.
    • Rossi, S.
    • Federici, S.
    • House, J.
    • Ferrara, A. F.
    • Salvatore, M.
    • Tubiello, F. N.
    • Schmidhuber, J.
    • Sanchez, M. J. S.
    • Nalin, S.
    • Smith, P.
  • Source: Research Article
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: We refine the information available through the IPCC AR5 with regard to recent trends in global GHG emissions from agriculture, forestry and other land uses (AFOLU), including global emission updates to 2012. Using all three available AFOLU datasets employed for analysis in the IPCC AR5, rather than just one as done in the IPCC AR5 WGIII Summary for Policy Makers, our analyses point to a down-revision of global AFOLU shares of total anthropogenic emissions, while providing important additional information on subsectoral trends. Our findings confirm that the share of AFOLU emissions to the anthropogenic total declined over time. They indicate a decadal average of 28.71.5% in the 1990s and 23.62.1% in the 2000s and an annual value of 21.21.5% in 2010. The IPCC AR5 had indicated a 24% share in 2010. In contrast to previous decades, when emissions from land use (land use, land use change and forestry, including deforestation) were significantly larger than those from agriculture (crop and livestock production), in 2010 agriculture was the larger component, contributing 11.20.4% of total GHG emissions, compared to 10.01.2% of the land use sector. Deforestation was responsible for only 8% of total anthropogenic emissions in 2010, compared to 12% in the 1990s. Since 2010, the last year assessed by the IPCC AR5, new FAO estimates indicate that land use emissions have remained stable, at about 4.8 Gt CO 2 eq yr -1 in 2012. Emissions minus removals have also remained stable, at 3.2 Gt CO 2 eq yr -1 in 2012. By contrast, agriculture emissions have continued to grow, at roughly 1% annually, and remained larger than the land use sector, reaching 5.4 Gt CO 2 eq yr -1 in 2012. These results are useful to further inform the current climate policy debate on land use, suggesting that more efforts and resources should be directed to further explore options for mitigation in agriculture, much in line with the large efforts devoted to REDD+ in the past decade.