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Flooded savannas are extensive in South America and this study was conducted to assess two digital soil mapping (DSM) approaches to predict the spatial distribution of soil organic carbon (SOC) content and stocks in the Orinoco flooded savannas of Casanare department, located in the eastern plains of Colombia. SOC was estimated using a total of 80 sites sampled at two soil depth intervals (0-10 cm and 10-30 cm). SOC ranged from 0.41% at 0-10 cm and 0.23% at 10-30 cm in drier soils found in continental dunes with sandy textures and low vegetation cover (steppe) to over 14.50% and 7.51% in soils that experienced seasonal flooding located in depressions with loamy textures and flooded savanna vegetation. Predictions of the spatial distribution of SOC were done through Expert Knowledge (EK) and Random Forest (RF) approaches across the study area at 0-10 cm and 10-30 cm soil depth. Both DSM approaches were assessed through root mean square errors, mean absolute errors, and coefficients of determination. Although both DSM approaches performed very well, EK was considered slightly superior to predict SOC in the Casanare flooded savannas. Covariates derived from vegetation coverage, topography, and soil texture properties were identified as key drivers in controlling its distribution at the study area. We found total SOC stocks of 55.07 Mt with a mean density of 83.13 ± 24.32 t ha-1 stored in the first 30 cm soil depth, with 12.3% of this being located in the flooded parts of the savanna landscape, which represented only 7.9% of the study area (664,752 ha). This study provides the first effort to systematically quantify SOC stocks in the Casanare flooded savannas and shows the importance of conserving this ecosystem with the aim of avoiding SOC losses and consequent increased CO2 emissions to the atmosphere. We estimate that the department of Casanare would release an average of 2,42 Mton of CO2 emissions per year over 30 years if there were large scale conversion of the flooded savannas to intensive agriculture, which corresponds to 62% of the current emissions of the department. At regional level, the impact of a large-scale land use conversion of the flooded Llanos del Orinoco ecosystem area (15 Mha) would represent 1/3 of the current net Colombian CO2 emission (AFOLU), which makes this region a potentially important source of emissions if correct decisions are not taken regarding the land management.

In Colombia, the rise of agricultural and pastureland expansion continues to exert increasing pressure on the structure and ecological processes of savannahs in the Eastern Plains. However, the effect of land use change on soil properties is often unknown due to poor access to remote areas. Effective management and conservation of soils requires the development spatial approaches that measure and predict dynamic soil properties such as soil organic carbon (SOC). This study estimates the SOC stock in the Eastern Plains of Colombia, with validation and uncertainty analyses, using legacy data of 653 soil samples. A random forest model of nine environmental covariate layers was used to develop predictions of SOC content. Model validation was determined using the Taylor series method, and root-mean-squared error (RMSE) and mean error (ME) were calculated to assess model performance. We found that the model explained 50.28% of the variation within digital SOC content map. Raster layers of SOC content, bulk density, and coarse rock fragment within the Eastern Plains were used to calculate SOC stock within the region. With uncertainty, SOC stock in the topsoil of the Eastern Plains was 1.2 G t ha−1. We found that SOC content contributed nearly all the uncertainty in the SOC stock predictions, although better determinations of SOC stock can be obtained with the use of a more geomorphological diverse dataset. The digital soil maps developed in this study provide predictions of extant SOC content and stock in the topsoil of the Eastern Plains, important soil information that may provide insight into the development of research, regulatory, and legislative initiatives to conserve and manage this evolving ecosystem.

Soil organic carbon (SOC) sequestration is important in the global carbon cycle and an integral part of many initiatives and policies to mitigate climate change. For efficient targeting of measures leading to SOC sequestration, it is necessary to know the actual SOC content (%) and a realistic target SOC content (in contrast to the saturation content, which may not be easily achievable) under local biophysical and socioeconomic conditions. We developed a new method for the practical assessment of achievable SOC sequestration concerning soil texture based on a non-linear boundary plane approach, also applicable for mapping of SOC sequestration hotspots. The method was tested at two spatial scales (a 125 km2 catchment and a 4 km2 sub-area of that catchment) in a region in Western Kenya characterized by smallholder farming. Moreover, we assessed the associated benefits of increasing the SOC content from a crop production perspective and found significant correlations between SOC and other soil properties (pH, cation exchange capacity, and various plant-available macro- and micronutrients). This indicates a possible improvement in soil fertility when the SOC content is raised to the modeled target levels, which should be attainable without major changes in land use or agricultural systems.

Soil organic carbon (SOC) dynamics along land-use changes influences the terrestrial and global carbon cycle, the climate, soil fertility, agricultural productivity, and food security. Taking soils under native forests as an appropriate ecological reference, we studied changes in soil organic carbon stock along eight land-use types in the highlands of Ethiopia. The general objective of the study was to investigate the dynamics of SOC stock following chrono-sequence land-use/cover systems in the highlands of Ethiopia. The specific objectives were to: (1) analyze loss due to land degradation; (2) analyze gain due to land restoration; and (3) estimate partial balance of SOC stock for the highlands of Ethiopia. The study followed the principle of the Forest Transition Theory (FTT). Eleven sub-areas were considered from the highlands of Ethiopia. A total of 241 auger composite samples from the topsoil (0−20 cm depth) were collected during December 2017 to June 2018, and analyzed at CropNut soil lab in Nairobi. The study results revealed that there were statistically significant variations (P gains in soils of enclosures (3.17 Mg ha−1) > gains in soils of afforestation (2.35 Mg SOC ha−1), which signifies that converting degraded lands to either controlled grazing lands, enclosures, or afforestation would be a promising practice for an enhanced carbon sequestration across the highlands of Ethiopia. This practice is in line with the United Nations’ Sustainable Development Goals. The estimated regional partial stock balance revealed that the loss and gain ratio was 35.1 in 1991, and it declined to 15.4 in 2001, 2.2 in 2011 and 1.8 in 2015. These decreasing ratios indicate the possibility of closing the gap between the losses and the gains in the near future, and eventually shifting to higher rates of gains than losses. It is also important to note that determined efforts towards the effective protection of natural forests and the creation of enclosures and reforestation areas by local communities for enhanced carbon sequestration will benefit them from payments of carbon emission reduction (CER) credits.

As humanity’s demand for resources continues to rise and productive arable lands become increasingly scarce, many of Earth’s remaining intact regions are at heightened risk of destruction from agricultural development. In situations where agricultural expansion is inevitable, it is important to manage intact landscape transformation so that impacts on environmental values are minimised. Here, we present a novel, spatially explicit, land use planning framework that addresses the decision making needed to account for different, competing economic-environment objectives (agricultural production value, biodiversity conservation, ecosystem service retention) when land use change is inevitable within an intact landscape. We apply our framework to the globally significant savannahs of the Orinoquia (Colombia), which in a post-conflict era is under increased agricultural development pressure. We show that while negative environmental impacts can be reduced through planning, the total area of land converted to agriculture is the unavoidable principal driver of biodiversity and ecosystem service loss. We therefore identify planning solutions that perform well across all objectives simultaneously, despite trade-offs among them. When 15%, 20%, 30% and 40% of the study area is allowed to be converted to agriculture, on average planning can improve species persistence and ecosystem service retention by up to 16%, 15%, 12%, and 9%, respectively, when compared to agricultural-focused solutions. Development in the region so far has had an unnecessarily large impact on environmental objectives due to a lack of effective land use planning, creating an ‘opportunity debt’. Our study provides an evidence base to inform proactive planning and the development of environmentally sensible agricultural development policy and practice in the region. This framework can be used by stakeholders to achieve agriculture expansion goals and maximise economic profit while minimising impacts on the environment in the Orinoquia, or any relatively intact region that is being developed.

Agricultural producers grapple with low farm yields and declining ecosystem services within their landscapes. In several instances, agricultural production systems may be considered largely unsustainable in socioeconomic and ecological (resource conservation and use and impact on nature) terms. Novel technological and management options that can serve as vehicles to promote the provision of multiple benefits, including the improvement of smallholder livelihoods, are needed. We call for a paradigm shift to allow designing and implementing agricultural systems that are not only efficient (serving as a means to promote development based on the concept of creating more goods and services while using fewer resources and creating less waste) but can also be considered synergistic (symbiotic relationship between socio-ecological systems) by simultaneously contributing to major objectives of economic, ecological, and social (equity) improvement of agro-ecosystems. These transformations require strategic approaches that are supported by participatory system-level research, experimentation, and innovation. Using data from several studies, we here provide evidence for technological and management options that could be optimized, promoted, and adopted to enable agricultural systems to be efficient, effective, and, indeed, sustainable. Specifically, we present results from a study conducted in Colombia, which demonstrated that, in rice systems, improved water management practices such as Alternate Wetting and Drying (AWD) reduce methane emissions (~70%). We also show how women can play a key role in AWD adoption. For livestock systems, we present in vitro evidence showing that the use of alternative feed options such as cassava leaves contributes to livestock feed supplementation and could represent a cost-effective approach for reducing enteric methane emissions (22% to 55%). We argue that to design and benefit from sustainable agricultural systems, there is a need for better targeting of interventions that are co-designed, co-evaluated, and co-promoted, with farmers as allies of transformational change (as done in the climate-smart villages), not as recipients of external knowledge. Moreover, for inclusive sustainability that harnesses existing knowledge and influences decision-making processes across scales, there is a need for constant, efficient, effective, and real trans-disciplinary communication and collaboration.

O solo é um dos recursos naturais de maior importância cuja heterogeneidade reflete na variabilidade de seus atributos químicos e físicos. Esta heterogeneidade é decorrente do processo de formação natural e do uso e manejo realizados pelo homem. Assim, o objetivo deste estudo foi avaliar a variabilidade espacial dos atributos químicos e físicos do solo e elaborar seus mapas de distribuição espacial na Sub-Bacia das Posses, Extrema. Para isto foram coletadas amostras em 150 pontos nas profundidades de 0-0,20 e determinados os atributos físicos e químicos. As variáveis: Ca, Mg, K, P, pH, matéria orgânica (MO), diâmetro médio geométrico dos agregados (DMGcp), diâmetro médio ponderado dos agregados (DMPcp) e índice de floculação (IF). IF apresentaram estrutura de dependência espacial, o que permitiu seu mapeamento a partir de técnicas geoestatísticas. O P, DMGsp e DMPsp apresentaram estrutura com efeito pepita puro, possivelmente decorrente de uma distância insuficiente para captar dependência espacial na amostragem para esses atributos e interferências antrópicas. A variação verificada para o Ca pode ser explicada pela aplicação localizada de calcário, a qual foi realizada em algumas pequenas propriedades localizadas nas sub-bacias. O DMGp, DMPp, e IF avaliados foram ajustados em conformidade entre si indicando boa agregação do solo. Soil is one of the most important natural resource and its heterogeneity reflects the variability of its chemical and physical attributes. Soil heterogeneity occurs due to the natural process of formation and use by men and management. The objectives of this study were to evaluate the spatial variability of physical and chemical soil attributes and map the spatial distribution of these in Posses sub-basin, Extrema, representative of the Atlantic Forest biome present in southern Minas Gerais. For this, samples (0-0.20 m depth) were collected at 150 points, and their physical and chemical attributes were determined. Variables: Ca, Mg, K, P, pH, organic matter (MO), geometric mean diameter of aggregates (DMGcp), weighted mean diameter of aggregates (DMPcp) and flocculation index (IF) showed spatial dependence structure, which allowed mapping from geostatistical techniques. P, DMGsp and DMPsp presented structure with nugget effect, possibly due to an insufficient distance to capture spatial dependence in the sample for these attributes, and human interferences. The variation for Ca can be explained due to lime application, which occurred in some small properties located in the sub-basin. The DMGcp, DMPcp, and IF evaluated were adjusted in line with each other, indicating good soil aggregation.

Resumen pt: O uso dos sistemas de informacoes geograficas (SIG) possibilita extrapolar informacoes pontuais permitindo maior rapidez, menor custo e elevada acuracia ...

Digital soil mapping (DSM) permits continuous mapping soil types and properties through raster formats considering variation within soil class, in contrast to the traditional mapping that only considers spatial variation of soils at the boundaries of delineated polygons. The objective of this study was to compare the performance of SoLIM (Soil Land Inference Model) for two sets of environmental variables on digital mapping of saturated hydraulic conductivity and solum depth (A + B horizons) and to apply the best model on runoff risk evaluation. The study was done in the Posses watershed, MG, Brazil, and SoLIM was applied for the following sets of co-variables: 1) terrain attributes (AT): slope, plan curvature, elevation and topographic wetness index. 2) Geomorphons and terrain attributes (GEOM): slope, plan curvature, elevation and topographic wetness index combined with geomorphons. The most precise methodology was applied to predict runoff areas risk through the Wetness Index based on contribution area, solum depth, and saturated hydraulic conductivity. GEOM was the best set of co-variables for both properties, so this was the DSM model used to predict the runoff risk. The runoff risk showed that the critical months are from November to March. The new way to classify the landscape to use on DSM was demonstrated to be an efficient tool with which to model process that occurs on watersheds and can be used to forecast the runoff risk.

The Brazilian Cerrado makes up one of the most biodiverse savannas in the world and it harbors a mosaic of plant physiognomies that include from open forms (grasslands) to forest (dense woodlands), possessing high structural, functional and life forms diversity. Little valued traditionally, the Cerrado has been neglected in most of the conservationist initiatives because its vegetation is considered sparse and of low value. The Brazilian Cerrado comprises an area of 2,036,448 km2 [1]. Its largest part is within the Aw type of Kopen climatic classification (tropical seasonal savanna), with a rainy period, from October to March, followed by a dry period, from April to September. In this environment, the irregular distribution of the rain and the existence of short droughts constitute serious limitation for farming in the absence of irrigation. The main soils of the Cerrado area are Latosols (Oxisols) that correspond to 46%, followed by Neosols (Entisols) with 16% and Argisols (Ultisols) with 15%. Latosols occupy a flat to gentle rolling topography in the landscape, which facilitates the mechanized management, those soils being of high potential for the production of annual and perennial crops and also pasture. In recent decades the Cerrado has undergone various transformations as to its land use, mainly due to the high investments in soil correctives, fertilizers and various crop varieties adapted to this biome. This generated a disordered occupation of the land, with a rampant increase of

The fast changes in soil use and higher vegetal resource demands favor the triggering of water erosion that needs to have its rates expressed in space and time for the proper adaptation of control practices and resources for agricultural planning. The physical processes of disaggre‐ gation, transport and soil deposition that define the erosive process are hydrologically directed and the movement of the water on the soil undergoes the interference of the topography, climate, soil class and land use, so that the studies regarding the theme are based on the intense experimentation of the effects of the variations of these factors on the sediment production. The estimate of the topographic variables, although benefitted by automatic generation and spatial distribution made possible by the Geographical Information Systems (GIS’s), is the target of controversy related to the formulation of algorithms for this end, so that its threedimensional calculation is not a current procedure in the geoprocessing programs [1].

O desenvolvimento da erosão hídrica ocorre em resposta ao modo como a água se move através e sobre uma determinada paisagem. O modelo digital de elevação (MDE) deve, portanto, ser o mais preciso possível, uma vez que constitui a base para a análise do relevo. Este trabalho teve como objetivo definir um modelo digital de elevação hidrologicamente consistente (MDEHC) e o método de direção de fluxo mais adequado para a definição da rede de drenagem na sub-bacia do horto florestal Terra Dura, município de Eldorado do Sul, RS. Foram testados os modelos gerados com os interpoladores Topogrid e redes triangulares irregulares (Triangulated Irregular Network -TIN) linear (TIN L) e TIN natural neighbor (TIN NN). A qualidade em relação às análises hidrológicas foi avaliada por meio da comparação das curvas de nível geradas pelos modelos testados com as curvas originais da sub-bacia (escala 1:10.000); da avaliação da quantidade de áreas planas; e da comparação da drenagem gerada pelos modelos a partir dos métodos de direção de fluxo Deterministic (D8) e Deterministic infinity (D∞ ou D infinito) com a drenagem original. Entre os modelos avaliados, o Topogrid apresentou maior consistência hidrológica, verificada na melhor continuidade das curvas de nível (menos arestas) e maior detalhamento da área de drenagem e divisores, acarretando menor quantidade de áreas planas e caminhos de fluxo mais detalhados, independentemente do método de direção de fluxo utilizado. Em relação à rede de drenagem, o método distribuído D∞ obteve melhor desempenho na descrição dos caminhos de fluxo, comparado ao método de direção única D8. O MDEHC Topogrid associado ao método D∞ proporcionou a identificação mais precisa dos caminhos preferenciais do fluxo que formam a rede de drenagem. The development of water erosion occurs in response to the way water moves through and over a given landscape. The digital elevation model (DEM) must therefore be as accurate as possible, since it is the basis for the analysis of a relief. The objectives of this study were to define a hydrologically consistent digital elevation model (HCDEM) and the most appropriate method to determine the flow direction of the drainage network in the sub-basin of the Terra Dura forest stand, in Eldorado do Sul, RS. The generated models were tested with Topogrid interpolation, Triangulated Irregular Networks (TIN) linear (TINL) and natural neighbor TIN (TIN NN). The quality of the hydrological analysis was evaluated by comparing the contours generated by the test models with the original curves of the sub-basin (scale 1:10.000); assessment of the amount of flat areas; and comparison of the original drainage with that generated by the models using the Deterministic (D8) and Deterministic infinity (D∞ or infinite D) flow direction methods. The hydrological consistency of Topogrid was the best of the studied models, as indicated by the better contour continuity (fewer contact points) and more details of the drainage area and water divides, resulting in a lower number of flat areas and more detailed flow paths, independently of the method used to determine the flow direction. In relation to the drainage network, the description of the flow paths by the D∞ distributed method was better than that by the D∞ single direction method. In conclusion, the Topogrid HCDEM associated with the D∞ method identified the preferential flow paths that form the drainage network most precisely.

Legacy soil data have been produced over 70 years in nearly all countries of the world. Unfortunately, data, information and knowledge are still currently fragmented and at risk of getting lost if they remain in a paper format. To process this legacy data into consistent, spatially explicit and continuous global soil information, data are being rescued and compiled into databases. Thousands of soil survey reports and maps have been scanned and made available online. The soil profile data reported by these data sources have been captured and compiled into databases. The total number of soil profiles rescued in the selected countries is about 800,000. Currently, data for 117, 000 profiles are compiled and harmonized according to GlobalSoilMap specifications in a world level database (WoSIS). The results presented at the country level are likely to be an underestimate. The majority of soil data is still not rescued and this effort should be pursued. The data have been used to produce soil property maps. We discuss the pro and cons of top-down and bottom-up approaches to produce such maps and we stress their complementarity. We give examples of success stories. The first global soil property maps using rescued data were produced by a top-down approach and were released at a limited resolution of 1 km in 2014, followed by an update at a resolution of 250 m in 2017. By the end of 2020, we aim to deliver the first worldwide product that fully meets the GlobalSoilMap specifications.