Temperature dependence of CO2 emissions rates and isotopic signature from a calcareous soil

In the context of climate change, studies have focused on the temperature dependence of soil CO2 emissions. Although calcareous soils cover over 30% of the earth's land surface, few studies have considered calcareous soils where soil inorganic carbon (SIC) makes the analysis of the C fluxes at the soil to air interface more complex. This study tested how temperature could affect the contributions of soil organic carbon (SOC) and SIC to the CO2 emitted from a calcareous soil. The soil pH, CO2 emissions and delta C-13 signatures of CO2 were measured after soil incubations at 4 temperatures (20 degrees C, 30 degrees C, 40 degrees C and 50 degrees C). The CO2 emissions and the C-delta 13 signature of the emitted CO2 increased with temperature. The proportion of SIC-derived CO2 in these emissions seemed to be stimulated by temperature. Three processes were discussed: (1) isotopic fractionations, (2) temperature impacts on SIC- and SOC-derived CO2, and (3) isotope exchanges between SIC-and SOC-derived CO2. The use of delta C-13 signature analysis to determine the contribution of SIC and SOC to the total CO2 emissions from soil is not straightforward. An increase in the SIC signature of emitted CO2 does not directly imply an increase in SIC as a source of CO2

Effects of 5-year application of municipal solid waste compost on the distribution and mobility of heavy metals in a Tunisian calcareous soil

A

Physical protection of soil carbon in macroaggregates does not reduce the temperature dependence of soil CO2 emissions

In a warmer world, soil CO2 emissions are likely to increase. There is still much discussion about which soil organic C (SOC) pools are more sensitive to increasing temperatures. While the temperature sensitivity of C stabilized by biochemical recalcitrance or by sorption to mineral surfaces has been characterized, few studies have been carried out on the temperature sensitivity—expressed as Q10—of C physically protected inside soil macroaggregates (0.2–2 mm). It has been suggested that increasing the availability of labile SOC by exposing C through macroaggregate crushing would decrease Q10, i.e., the temperature dependence of soil CO2 emissions. To test this hypothesis, the temperature dependence of CO2 emissions from C physically protected in macroaggregates was measured through 21-d laboratory incubations of crushed and uncrushed soils, at 18°C and 28°C. 199 topsoil samples, acidic or calcareous, with SOC ranging from 2 to 121 g kg−1 soil were investigated. The CO2 emissions were slightly more sensible to temperature than to C deprotection: about 0.3 mg C g−1 soil (= 13 mg C g−1 SOC) and 0.2 mg C g−1 (= 12 mg C g−1 SOC) were additionally mineralized, in average, by increasing the temperature or by disrupting the soil structure, respectively. The mean Q10 index ratio of CO2 emitted at 28°C and 18°C was similar for crushed and uncrushed soil samples and equaled 1.6. This was partly explained because Q10 of macro-aggregate-protected C was 1. The results did not support the initial hypothesis of lower temperature dependence of soil CO2 emissions after macroaggregate disruption, although a slight decrease of Q10 was noticeable after crushing for soils with high amounts of macroaggregate-protected C. Field research is now needed to confirm that soil tillage might have no effect on the temperature sensitivity of SOC stocks

Towards a harmonisation of the soil map of Africa at the continental scale

In the context of major global environmental challenges such as food security, climate change, fresh water scarcity and biodiversity loss, the protection and the sustainable management of soil resources in Africa are of paramount importance. To raise the awareness of the general public, stakeholders, policy makers and the science community to the importance of soil in Africa, the Joint Research Centre of the European Commission has produced the Soil Atlas of Africa. To that end, a new harmonised soil map at the continental scale has been produced. The steps of the construction of the new area-class map are presented, the basic information being derived from the Harmonized World Soil Database (HWSD). We show how the original data were updated and modified according to the World Reference Base for Soil Resources classification system. The corrections concerned boundary issues, areas with no information, soil patterns, river and drainage networks, and dynamic features such as sand dunes, water bodies and coastlines. In comparison to the initial map derived from HWSD, the new map represents a correction of 13% of the soil data for the continent. The map is available for downloading

Sub-chapter 3.5.3. Soil carbon as an indicator of Mediterranean soil quality

Two forms of carbon in Mediterranean soils Soils are considered as one of the largest C pools on Earth, after the oceanic and geologic reservoirs. The soil C pool comprises two distinct components: soil organic carbon (SOC) and soil inorganic carbon (SIC), which roughly contribute 2/3 and 1/3, respectively (Batjes, 1996). Soil organic carbon (SOC) represents about 50% of soil organic matter, by consequence “soil organic matter” and “soil organic carbon” are often confused and used interchange..

Soil carbon as an indicator of Mediterranean soil quality

This book, coordinated by AllEnvi, is published on the occasion of the 22nd Conference of the Parties to the United Nations Framework Convention on Climate Change (COP22, Marrakech, 2016)Soil carbon as an indicator of Mediterranean soil qualit

Studying the physical protection of soil carbon with quantitative infrared spectroscopy

International audienceNear infrared (NIR) and mid-infrared (mid-IR) reflectance spectroscopy are time- and cost-effective tools for characterising soil organic carbon (SOC). Here they were used for quantifying (i) carbon (C) dioxide (CO2) emission from soil samples crushed to 2 mm and 0.2 mm, at 18°C and 28°C; (ii) physical C protection, calculated as the difference between CO2 emissions from 0.2 mm and 2 mm crushed soil at a given temperature; and (iii) the temperature vulnerability of this protection, calculated as the difference between C protection at 18°C and 28°C. This was done for 97 topsoil samples from Tunisia, mostly calcareous, which were incubated for 21 days. Soil CO2 emission increased with temperature and fine crushing. However, C protection in 0.2–2 mm aggregates had little effect on the temperature vulnerability of CO2 emission, possibly due to preferential SOC protection in smaller aggregates. In general, NIR spectroscopy, and to a lesser extent mid-IR spectroscopy, yielded accurate predictions of soil CO2 emission (0.60 ≤ R2 ≤ 0.91), and acceptable predictions of C protection at the beginning of incubation (0.52 ≤ R2 ≤ 0.81) but not over the whole 21 day period (R2 ≤ 0.59). For CO2 emission, prediction error was the same order of magnitude as, and sometimes similar to, the uncertainty of conventional determination, indicating that a noticeable proportion of the former could be attributed to the latter. The temperature vulnerability of C protection could not be modelled correctly (R2 ≤ 0.11), due to error propagation. The prediction of SOC was better with NIR spectroscopy and that of soil inorganic C (SIC) was very accurate (R2 ≥ 0.94), especially with mid-IR spectroscopy. Soil CO2 emission, C protection and its vulnerability were best predicted with NIR spectra, those of 0.2 mm samples especially. With 2 mm samples, mid-IR spectroscopy yielded the worst predictions in general. NIR spectroscopy prediction models suggested that CO2 emission and C protection depended (i) on aliphatic compounds (i.e. labile substrates), dominantly at 18°C; (ii) on amides or proteins (i.e. microbial biomass), markedly at 28°C; and (iii) negatively, on organohalogens and aromatic amines (i.e. pesticides). Models using mid-IR spectra showed a negative influence of carbonates on CO2 emission, suggesting they did not contribute to soil CO2 emission and might form during incubation. They also suggested that CO2 emission and C protection related to carboxylic acids, saturated aliphatic ones especially

Soil Atlas of Africa

The sustainable management of natural resources in Africa is a formidable challenge yet crucial for the survival of over one billion people! Africa has the capacity to feed itself yet the continent has a history of land developments, often driven by a desire for a quick economic return, that completely ignore the capabilities of the soil to support it. Reliance on inappropriate cultivation practices, a lack of concern about how natural ecological cycles have maintained soil fertility in Africa over millennia and a high level of rural poverty has led to land degradation throughout Africa. Understanding the evolution of soils and associated vegetation patterns in relation to their use by society is fundamental if we wish to assess fully the impacts of processes driving change in Africa. This applies equally to climate change, population growth and food security. The evidence for soil degradation and environmental change is apparent in many parts of Africa. For this reason we are pleased to see that the Joint Research Centre (JRC) is taking responsibility to highlight these issues. By building on existing cooperation with researchers from Africa, EU Member States and international organisations, the JRC has used science to bring together people from diverse national and political backgrounds to address a common goal. Given its scientific understanding of the issues, the JRC is carrying out a crucial role in communicating science to the wider society. This innovative “Soil Atlas of Africa” is intended to be a step towards raising public awareness on the importance and the key role of soil in Africa. The atlas compiles existing information on different soil types in easily understandable maps that cover the entire African continent. While it is intended primarily for the general public, the educational sectors and policy makers, the atlas aims to bridge the gap between soil science and society at large. Recognising the importance of soil as a nonrenewable resource which provides many critical ecological functions that are crucial to human existence will support the development of protective measures that will safeguard soils for current and future generations.JRC.H.5-Land Resources Managemen

The Mediterranean region under climate change

This book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines