163 research outputs found
Projected loss of soil organic carbon in temperate agricultural soils in the 21<sup>st</sup>century: effects of climate change and carbon input trends
Climate change and stagnating crop yields may cause a decline of SOC stocks in agricultural soils leading to considerable CO2 emissions and reduced agricultural productivity. Regional model-based SOC projections are needed to evaluate these potential risks. In this study, we simulated the future SOC development in cropland and grassland soils of Bavaria in the 21st century. Soils from 51 study sites representing the most important soil classes of Central Europe were fractionated and derived SOC pools were used to initialize the RothC soil carbon model. For each site, long-term C inputs were determined using the C allocation method. Model runs were performed for three different C input scenarios as a realistic range of projected yield development. Our modelling approach revealed substantial SOC decreases of 11â16% under an expected mean temperature increase of 3.3â°C assuming unchanged C inputs. For the scenario of 20% reduced C inputs, agricultural SOC stocks are projected to decline by 19â24%. Remarkably, even the optimistic scenario of 20% increased C inputs led to SOC decreases of 3â8%. Projected SOC changes largely differed among investigated soil classes. Our results indicated that C inputs have to increase by 29% to maintain present SOC stocks in agricultural soils
Dynamics of soil organic carbon following land-use change: insights from stable C-isotope analysis in black soil of Northeast China
Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas emissions and soil erosion. However, the dynamic processes of soil organic carbon (SOC) in areas of either continuous cultivation or abandonment remain unclear and inconsistent. Our aims were to assess and model the dynamic processes of SOC under continuous tillage and after cultivation abandonment in the black soil of Northeast China. Soil profiles were collected of cultivated or abandoned land with cultivation history of 0â100 years. An isotope mass balance equation was used to calculate the proportion of SOC derived from corn debris (C4) and from natural vegetation (C3) to deduce the dynamic process. Approximately 40% of SOC in the natural surface soil (0â10 cm) was eroded in the first 5 years of cultivation, increasing to about 75% within 40 years, before a slow recovery. C4 above 30 cm soil depth increased by 4.5%â5% or 0.11â0.12 g·kgâ1 on average per year under continuous cultivation, while it decreased by approximately 0.34% annually in the surface soil after cultivation abandonment. The increase in the percentage of C4 was fitted to a linear equation with given intercepts in the upper 30 cm of soil in cultivated land. A significant relationship between the change of C4 and time was found only in the surface soil after abandonment of cultivation. These results demonstrate the loss and accumulation of corn-derived SOC in surface black soil of Northeast China under continuous tillage or cultivation abandonment
Global variation in the cost of increasing ecosystem carbon
Slowing the reduction, or increasing the accumulation, of organic carbon stored in biomass and soils has been suggested as a potentially rapid and cost-effective method to reduce the rate of atmospheric carbon increase(1). The costs of mitigating climate change by increasing ecosystem carbon relative to the baseline or business-as-usual scenario has been quantified in numerous studies, but results have been contradictory, as both methodological issues and substance differences cause variability(2). Here we show, based on 77 standardized face-to-face interviews of local experts with the best possible knowledge of local land-use economics and sociopolitical context in ten landscapes around the globe, that the estimated cost of increasing ecosystem carbon varied vastly and was perceived to be 16-27 times cheaper in two Indonesian landscapes dominated by peatlands compared with the average of the eight other landscapes. Hence, if reducing emissions from deforestation and forest degradation (REDD+) and other land-use mitigation efforts are to be distributed evenly across forested countries, for example, for the sake of international equity, their overall effectiveness would be dramatically lower than for a cost-minimizing distribution.Peer reviewe
The Permafrost-Agroecosystem Action Group: first results and future goals
Permafrost-agroecosystems encompass northern social-ecological systems which include both
cultivation of arable permafrost-affected soils, and animal husbandry practices. These heterogeneous
food and cultural systems are being affected by a warming climate. Examples include increasing
opportunities for growing crops through longer growing seasons, as well as impacts on animalsâ
local and long-distance migratory movements and their food sources. Furthermore, climate
change driven permafrost thaw and thaw accelerated by land clearance is rapidly changing the
biophysical and socioeconomic aspects of these systems. Therefore, an international collaboration
encompassing experts from North America, Europe and Asia is working on increasing our
understanding of permafrost-agroecosystems and contributing to the adaptation, resilience, and
sustainability strategy of these rapidly evolving systems.
The International Permafrost Association Permafrost-Agroecosystem Action Group is composed of
~30 members from 7 countries. The objectives of our action group are to share knowledge and
build networking capacities through meetings and webinar presentation as well as to collaborate
on publications and produce the first geospatial dataset of permafrost-agroecosystems. Our poster
presentation provides an overview of the groupâs activities including providing case studies from a
range of high-latitude and high-altitude areas as part of a group manuscript in preparation and an
update on our mapping activities
Socioecological dynamics of diverse global permafrost-agroecosystems under environmental change
Permafrost-agroecosystems include all cultivation and pastoral activities in areas underlain by
permafrost. These systems support local livelihoods and food production and are rarely considered
in global agricultural studies but may become more relevant as climate change is increasing
opportunities for food production in high latitude and mountainous areas. The exact locations
and amount of agricultural production in areas containing permafrost are currently unknown,
therefore we provide an overview of countries where both permafrost and agricultural activities
are present. We highlight the socioecological diversity and complexities of permafrostagroecosystems
through seven case studies: (1) crop cultivation in Alaska, USA; (2) Indigenous
food systems and crop cultivation in the Northwest Territories, Canada; (3) horse and cattle
husbandry and Indigenous hay production in the Sakha Republic, Russia; (4) mobile pastoralism
and husbandry in Mongolia; (5) yak pastoralism in the Central Himalaya, Nepal; (6) berry picking and
reindeer herding in northern Fennoscandia; and (7) reindeer herding in northwest Russia. We
discuss regional knowledge gaps associated with permafrost and make recommendations to policy
makers and land users for adapting to changing permafrost environments. A better understanding
of permafrost-agroecosystems is needed to help sustainably manage and develop these systems
considering rapidly changing climate, environments, economies, and industries
Soil water improvements with the long-term use of a winter rye cover crop
AbstractThe Midwestern United States, a region that produces one-third of maize and one-quarter of soybean grain globally, is projected to experience increasing rainfall variability. One approach to mitigate climate impacts is to utilize crop and soil management practices that enhance soil water storage and reduce the risks of flooding as well as drought-induced crop water stress. While some research indicates that a winter cover crop in maize-soybean rotations increases soil water availability, producers continue to be concerned that water use by cover crops will reduce water for a following cash crop. We analyzed continuous in-field soil water measurements from 2008 to 2014 at a Central Iowa research site that has included a winter rye cover crop in a maize-soybean rotation for thirteen years. This period of study included years in the top third of the wettest on record (2008, 2010, 2014) as well as drier years in the bottom third (2012, 2013). We found the cover crop treatment to have significantly higher soil water storage at the 0â30cm depth from 2012 to 2014 when compared to the no cover crop treatment and in most years greater soil water content on individual days analyzed during the cash crop growing season. We further found that the cover crop significantly increased the field capacity water content by 10â11% and plant available water by 21â22%. Finally, in 2013 and 2014, we measured maize and soybean biomass every 2â3 weeks and did not see treatment differences in crop growth, leaf area or nitrogen uptake. Final crop yields were not statistically different between the cover and no cover crop treatment in any of the seven years of this analysis. This research indicates that the long-term use of a winter rye cover crop can improve soil water dynamics without sacrificing cash crop growth in maize-soybean crop rotations in the Midwestern United States
Multi-objective calibration of RothC using measured carbon stocks and auxiliary data of a long-term experiment in Switzerland
Interactions between model parameters and low spatiotemporal resolution of available data mean that conventional soil organic carbon (SOC) models are often affected by equifinality, with consequent uncertainty in SOC forecasts. Estimation of belowground C inputs is another major source of uncertainty in SOC modelling. Models are usually calibrated on SOC stocks and fluxes from longâterm experiments (LTEs), whereas other point data are not used for constraining the model parameters. We used data from an agricultural longâterm (> 65 years) fertilization experiment to test a multiâobjective parameter estimation approach on the RothC model, combining SOC data from different fertilization treatments with microbial biomass, basal respiration and Zimmermannâs fractions data. We also compared two methods to estimate the belowground C inputs: a conventional scaling of belowground biomass from crop harvest yield and an alternative approach based on constant belowground C for cereals measured experimentally in the field. The resulting posterior parameter distributions still suffered from some equifinality; the most stable C pool kinetic constants and composition of exogenous organic matter were the most sensitive parameters. The use of fixed belowground C inputs for cereals improved the model performance, reducing the importance of treatmentâspecific parameters and processes. The introduction of microbial biomass and basal respiration data was effective for increasing determination of the calibration, but also suggested a change in the model structure: the microbial biomass pool, which is proportional to the C inputs in the traditional models, could be represented by different microbial physiology functions
Carbon inputs from Miscanthus displace older soil organic carbon without inducing priming
The carbon (C) dynamics of a bioenergy system are key to correctly defining its viability as a sustainable alternative to conventional fossil fuel energy sources. Recent studies have quantified the greenhouse gas mitigation potential of these bioenergy crops, often concluding that C sequestration in soils plays a primary role in offsetting emissions through energy generation. Miscanthus is a particularly promising bioenergy crop and research has shown that soil C stocks can increase by more than 2 t C haâ1 yrâ1. In this study, we use a stable isotope (13C) technique to trace the inputs and outputs from soils below a commercial Miscanthus plantation in Lincolnshire, UK, over the first 7 years of growth after conversion from a conventional arable crop. Results suggest that an unchanging total topsoil (0â30 cm) C stock is caused by Miscanthus additions displacing older soil organic matter. Further, using a comparison between bare soil plots (no new Miscanthus inputs) and undisturbed Miscanthus controls, soil respiration was seen to be unaffected through priming by fresh inputs or rhizosphere. The temperature sensitivity of old soil C was also seen to be very similar with and without the presence of live root biomass. Total soil respiration from control plots was dominated by Miscanthus-derived emissions with autotrophic respiration alone accounting for âŒ50 % of CO2. Although total soil C stocks did not change significantly over time, the Miscanthus-derived soil C accumulated at a rate of 860 kg C haâ1 yrâ1 over the top 30 cm. Ultimately, the results from this study indicate that soil C stocks below Miscanthus plantations do not necessarily increase during the first 7 years
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