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Soils As a Key Component of the Critical Zone 2
This volume comprises three parts: 1) from local to global, 2) what type of sustainable management? 3) territorial approaches. The first chapter demonstrates, from the French example, that better soil management is a societal issue. At the global level, the second chapter raises the question of land grabbing and land use conflicts. This book also raises the question of the legal status of the soil. It then shows how soils need to be integrated when defining sustainable agricultural systems. French and European examples illustrate how taking environmental problems into account depends as much on their acuity as on how problems are perceived by public and private, social or economic actors. Therefore, it is important to promote co-diagnosis involving the scientific community and the various other actors in order to improve the regulation on soils. This multi-actor soil governance is facilitated by the use of simple soil quality indicators. Finally, examples in France and Vietnam show how soils are to be considered as territorial commons within landscapes. This last chapter recommends in particular to put an end to the absolute right of soil ownership and to distribute the usufruct of land between various private and public beneficiaries.
eBook
Atmosphere–soil carbon transfer as a function of soil depth
The exchange of carbon between soil organic carbon (SOC) and the atmosphere affects the climate
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,
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and—because of the importance of organic matter to soil fertility—agricultural productivity
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. The dynamics of topsoil carbon has been relatively well quantified
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, but half of the soil carbon is located in deeper soil layers (below 30 centimetres)
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–
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, and many questions remain regarding the exchange of this deep carbon with the atmosphere
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. This knowledge gap restricts soil carbon management policies and limits global carbon models
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,
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. Here we quantify the recent incorporation of atmosphere-derived carbon atoms into whole-soil profiles, through a meta-analysis of changes in stable carbon isotope signatures at 112 grassland, forest and cropland sites, across different climatic zones, from 1965 to 2015. We find, in agreement with previous work
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,
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, that soil at a depth of 30–100 centimetres beneath the surface (the subsoil) contains on average 47 per cent of the topmost metre’s SOC stocks. However, we show that this subsoil accounts for just 19 per cent of the SOC that has been recently incorporated (within the past 50 years) into the topmost metre. Globally, the median depth of recent carbon incorporation into mineral soil is 10 centimetres. Variations in the relative allocation of carbon to deep soil layers are better explained by the aridity index than by mean annual temperature. Land use for crops reduces the incorporation of carbon into the soil surface layer, but not into deeper layers. Our results suggest that SOC dynamics and its responses to climatic control or land use are strongly dependent on soil depth. We propose that using multilayer soil modules in global carbon models, tested with our data, could help to improve our understanding of soil–atmosphere carbon exchange.
This study of whole-soil carbon dynamics finds that, of the atmospheric carbon that is incorporated into the topmost metre of soil over 50 years, just 19 per cent reaches the subsoil, in a manner that depends on land use and aridity.
Journal Article
Soil acidity and fertility status of surface soils under different land uses in Sayo district of Oromia, western Ethiopia
Land use conversion from natural forests to grassland, plantation forests, mono-cropping coffee and croplands is a significant causes of soil degradation, leading to aggravate soil acidity and nutrient depletion. However, there is limited information regarding comprehensive effect of land use conversion on soil fertility and acidity in western Oromia Region of Ethiopia. Hence, this study aims to assess the surface soil fertility and acidity across different land use types (forest, crop, eucalyptus land, grazing land, and coffee farmland) to provide management options. A total of 60 composite soil sample were collected from four villages representing these land uses and analyzed for selected soil fertility and acidity indicators. Accordingly, sand content was highest in eucalyptus lands, whereas clay content high in forestlands. The highest soil bulk density and exchangeable acidity were observed in eucalyptus lands. The lowest pH was observed in cropland soils and the highest in forestland soils. Organic matter, total nitrogen, and available phosphorus were low in eucalyptus lands and high in forestland soils. Forest and coffee farm lands showed higher exchangeable cations, cation exchange capacity, and percentage base saturation, whereas cultivated, grazing, and eucalyptus lands obtained high level of micronutrients and exchangeable acidity. Generally, the findings indicate that land conversion has caused for lower soil pH and diminished essential macronutrients. These negative impacts on soil quality emphasize the need for sustainable soil management practices to mitigate soil degradation includes soil acidity and fertility, which significantly improve agricultural production and environmental health.
Journal Article
Active and passive soil organic carbon pools as affected by different land use types in Mizoram, Northeast India
Soil organic carbon plays an important role in the stability and fertility of soil and is influenced by different management practice. We quantified active and passive carbon pools from total soil organic carbon (TOC) in seven different land use systems of northeast India. TOC was highest (2.75%) in natural forest and lowest in grassland (1.31%) and it decreased with increasing depth in different pools of lability. Very Labile Carbon (VLC) fraction ranged from 36.11 to 42.74% of TOC across different land use system. Active carbon (AC) pool was highest in Wet Rice Cultivation (61.64%) and lowest (58.71%) in natural forest. Higher AC pools (VLC and less labile) in most land use systems barring natural forests suggest that the land use systems in the region are vulnerable to land use change and must adopt suitable management practice to harness carbon sequestration.
Journal Article
The Health of Vineyard Soils: Towards a Sustainable Viticulture
Soil health encompasses the effects the uppermost part of the land have on human wellbeing in a broad sense, because soil is where most food ultimately comes from, and because it more inconspicuously fulfils other ecological functions, as important as feeding, for our planet’s welfare, which is ours. Viticulture exploits the soil’s resources from which wine, its most valuable produce, boasts to obtain some of its unique quality traits, which are wrapped within the terroir concept. However, using conventional methods, viticulture also has harsh impacts on the soil, thus jeopardizing its sustainability. How long will the terroir expression remain unchanged as vineyard soil degradation goes on? While this question is difficult to answer because of the complex nature of terroirs, it is undeniable that conventional soil management practices in viticulture leave, in general, ample room for improvement, in their impact on vineyards as much as on the environment. In response, viticulture must adopt practices that enable the long-lasting preservation of its grounds for both on-farm and off-farm benefits. In this regard, the increase in the soil’s organic matter alongside the enhancement of the soil’s biological community are key because they benefit many other soil properties of a physical, chemical, and biological nature, thus determining the soil’s healthy functioning, where the vines may thrive for a long time, whereas its surroundings remain minimally disturbed. In the present review, the importance of soil health as it relates to vineyards is discussed, the soil degradation factors and processes that threaten winegrowing areas are presented, successful soil-health enhancement practices are shown, and future research trends are identified for the benefit of researchers and stakeholders in this special agricultural industry.
Journal Article
A global meta-analysis of livestock grazing impacts on soil properties
Grazing effects on soil properties under different soil and environmental conditions across the globe are often controversial. Therefore, it is essential to evaluate the overall magnitude and direction of the grazing effects on soils. This global meta-analysis was conducted using the mixed model method to address the overall effects of grazing intensities (heavy, moderate, and light) on 15 soil properties based on 287 papers published globally from 2007 to 2019. Our findings showed that heavy grazing significantly increased the soil BD (11.3% relative un-grazing) and PR (52.5%) and reduced SOC (-10.8%), WC (-10.8%), NO.sub.3 .sup.- (-23.5%), and MBC (-27.9%) at 0-10 cm depth, and reduced SOC (-22.5%) and TN (-19.9%) at 10-30 cm depth. Moderate grazing significantly increased the BD (7.5%), PR (46.0%), and P (18.9%) (0-10 cm), and increased pH (4.1%) and decreased SOC (-16.4%), TN (-10.6%), and P (-23.9%) (10-30 cm). Light grazing significantly increased the SOC (10.8%) and NH.sub.4 .sup.+ (28.7%) (0-10 cm). Heavy grazing showed much higher mean probability (0.70) leading to overgrazing than the moderate (0.14) and light (0.10) grazing. These findings indicate that, globally, compared to un-grazing, heavy grazing significantly increased soil compaction and reduced SOC, NO.sub.3 .sup.-, and soil moisture. Moderate grazing significantly increased soil compaction and alkalinity and reduced SOC and TN. Light grazing significantly increased SOC and NH.sub.4 .sup.+ . Cattle grazing impacts on soil compaction, SOC, TN, and available K were higher than sheep grazing, but lower for PR. Climate significantly impacted grazing effects on SOM, TN, available P, NH.sub.4 .sup.+, EC, CEC, and PR. Heavy grazing can be more detrimental to soil quality based on BD, SOC, TN, C: N, WC, and K than moderate and light grazing. However, global grazing intensities did not significantly impact most of the 15 soil properties, and the grazing effects on them had insignificant changes over the years.
Journal Article
Environment,scarcity,and violence
The Earth's human population is expected to pass eight billion by the year 2025, while rapid growth in the global economy will spur ever increasing demands for natural resources. The world will consequently face growing scarcities of such vital renewable resources as cropland, fresh water, and forests. Thomas Homer-Dixon argues in this sobering book that these environmental scarcities will have profound social consequences--contributing to insurrections, ethnic clashes, urban unrest, and other forms of civil violence, especially in the developing world.
Homer-Dixon synthesizes work from a wide range of international research projects to develop a detailed model of the sources of environmental scarcity. He refers to water shortages in China, population growth in sub-Saharan Africa, and land distribution in Mexico, for example, to show that scarcities stem from the degradation and depletion of renewable resources, the increased demand for these resources, and/or their unequal distribution. He shows that these scarcities can lead to deepened poverty, large-scale migrations, sharpened social cleavages, and weakened institutions. And he describes the kinds of violence that can result from these social effects, arguing that conflicts in Chiapas, Mexico and ongoing turmoil in many African and Asian countries, for instance, are already partly a consequence of scarcity.
Homer-Dixon is careful to point out that the effects of environmental scarcity are indirect and act in combination with other social, political, and economic stresses. He also acknowledges that human ingenuity can reduce the likelihood of conflict, particularly in countries with efficient markets, capable states, and an educated populace. But he argues that the violent consequences of scarcity should not be underestimated--especially when about half the world's population depends directly on local renewables for their day-to-day well-being. In the next decades, he writes, growing scarcities will affect billions of people with unprecedented severity and at an unparalleled scale and pace.
Clearly written and forcefully argued, this book will become the standard work on the complex relationship between environmental scarcities and human violence.
eBook
Comparing infiltration rates in soils managed with conventional and alternative farming methods: A meta-analysis
Identifying agricultural practices that enhance water cycling is critical, particularly with increased rainfall variability and greater risks of droughts and floods. Soil infiltration rates offer useful insights to water cycling in farming systems because they affect both yields (through soil water availability) and other ecosystem outcomes (such as pollution and flooding from runoff). For example, conventional agricultural practices that leave soils bare and vulnerable to degradation are believed to limit the capacity of soils to quickly absorb and retain water needed for crop growth. Further, it is widely assumed that farming methods such as no-till and cover crops can improve infiltration rates. Despite interest in the impacts of agricultural practices on infiltration rates, this effect has not been systematically quantified across a range of practices. To evaluate how conventional practices affect infiltration rates relative to select alternative practices (no-till, cover crops, crop rotation, introducing perennials, crop and livestock systems), we performed a meta-analysis that included 89 studies with field trials comparing at least one such alternative practice to conventional management. We found that introducing perennials (grasses, agroforestry, managed forestry) or cover crops led to the largest increases in infiltration rates (mean responses of 59.2 ± 20.9% and 34.8 ± 7.7%, respectively). Also, although the overall effect of no-till was non-significant (5.7 ± 9.7%), the practice led to increases in wetter climates and when combined with residue retention. The effect of crop rotation on infiltration rate was non-significant (18.5 ± 13.2%), and studies evaluating impacts of grazing on croplands indicated that this practice reduced infiltration rates (-21.3 ± 14.9%). Findings suggest that practices promoting ground cover and continuous roots, both of which improve soil structure, were most effective at increasing infiltration rates.
Journal Article
Climate-induced changes in continental-scale soil macroporosity may intensify water cycle
Soil macroporosity affects field-scale water-cycle processes, such as infiltration, nutrient transport and runoff
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,
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, that are important for the development of successful global strategies that address challenges of food security, water scarcity, human health and loss of biodiversity
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. Macropores—large pores that freely drain water under the influence of gravity—often represent less than 1 per cent of the soil volume, but can contribute more than 70 per cent of the total soil water infiltration
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, which greatly magnifies their influence on the regional and global water cycle. Although climate influences the development of macropores through soil-forming processes, the extent and rate of such development and its effect on the water cycle are currently unknown. Here we show that drier climates induce the formation of greater soil macroporosity than do more humid ones, and that such climate-induced changes occur over shorter timescales than have previously been considered—probably years to decades. Furthermore, we find that changes in the effective porosity, a proxy for macroporosity, predicted from mean annual precipitation at the end of the century would result in changes in saturated soil hydraulic conductivity ranging from −55 to 34 per cent for five physiographic regions in the USA. Our results indicate that soil macroporosity may be altered rapidly in response to climate change and that associated continental-scale changes in soil hydraulic properties may set up unexplored feedbacks between climate and the land surface and thus intensify the water cycle.
Soil macroporosity responds rapidly to climate variations and may induce wide-ranging changes in soil hydraulic conductivity by the end of the century.
Journal Article