Soil Inventory Research Articles

Effect of Climoedaphic Heterogeneity on Woody Plant Dominance in the Argentine Caldenal Region

Woody plant encroachment is widespread throughout drylands of the world, but rates and patterns of encroachment at the regional scale can be mediated by soil and climate. Climoedaphic properties may therefore help to explain patterns of woody plant dominance. In the Caldenal region of central Argentina, which is experiencing widespread woody plant encroachment, we used stratified and targeted inventory of vegetation and soils alongside climate data to classify vegetation states and then identify factors indicating resistance to woody plant encroachment. We found that three climoedaphic contexts differed in the degree of woody plant dominance. Sandsheet landforms had the lowest likelihood of a shrub thicket state. Within loamy soils, sites with deep soil carbonates in warmer and wetter climates were less likely to feature a shrub thicket state than sites with shallow carbonates in cooler and drier climates. These contexts serve as a basis for recognizing different ecological sites to assist mapping and prioritization of management interventions in the Caldenal region. Simple inventory-based approaches can be helpful for designing land management recommendations in other ecosystems.

Dinámica de uso de suelo en una Región Hidrológica Prioritaria de la cuenca Río Bravo, Nuevo León

La subcuenca del Río San Juan (SRSJ) es la más importante de la cuenca del Río Bravo, ya que sostiene el desarrollo socioeconómico y urbano del noreste de México, pero los cambios de uso del suelo han ocasionado problemas y riesgos ambientales. El presente estudio consistió en analizar los cambios espacio-temporales de uso del suelo en la subcuenca durante el periodo de 1976 a 2011, con el fin de establecer su dinámica para identificar las posibles tendencias. Se empleó la cartografía de Instituto Nacional de Estadística y Geografía (Inegi) y del Inventario Nacional Forestal y de Suelos ((INFyS). A través del Sistema de Información Geográfica Idrisi Selva, se generaron matrices de transición y tasas de cambio para los periodos (1976-1993, 1993-2000 y 2000-2011). Los tipos de uso de suelo y vegetación más representativos en el año 1976 fueron el matorral (76 %), cultivos (19 %) y pastizales (2 %); sin embargo, en 2011 se observaron cambios significativos en su cobertura, de los cuales el más afectado fue el matorral que registró una pérdida de 30 % de su superficie original y tasas de cambio negativas de 1976 a 2011. Los cultivos y pastizales se extendieron en 15 y 7 % aproximadamente, y registraron las tasas de cambio positivas más destacadas debido a la intensa actividad agropecuaria de la zona, lo que sugiere un proceso de reducción del matorral inducido por un incremento en el grado de antropización.

Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado

AbstractInfrequent, high‐magnitude events cause a disproportionate amount of sediment transport on steep hillslopes, but few quantitative data are available that capture these processes. Here we study the influence of wildfire and hillslope aspect on soil erosion in Fourmile Canyon, Colorado. This region experienced the Fourmile Fire of 2010, strong summer convective storms in 2011 and 2012, and extreme flooding in September 2013. We sampled soils shortly after these events and use fallout radionuclides to trace erosion on polar‐ and equatorial‐facing burned slopes and on a polar‐facing unburned slope. Because these radionuclides are concentrated in the upper decimeter of soil, soil inventories are sensitive to erosion by surface runoff. The polar‐facing burned slope had significantly lower cesium‐137 (137Cs) and lead‐210 (210Pb) inventories (p < 0.05) than either the polar‐facing unburned slope or equatorial‐facing burned slope. Local slope magnitude does not appear to control the erosional response to wildfire, as relatively gently sloping (~20%) polar‐facing positions were severely eroded in the most intensively burned area. Field evidence and soil profile analyses indicate up to 4 cm of local soil erosion on the polar‐facing burned slope, but radionuclide mass balance indicates that much of this was trapped nearby. Using a 137Cs‐based erosion model, we find that the burned polar‐facing slope had a net mean sediment loss of 2 mm (~1 kg m−2) over a one to three year period, which is one to two orders of magnitude higher than longer‐term erosion rates reported for this region. In this part of the Colorado Front Range, strong hillslope asymmetry controls soil moisture and vegetation; polar‐facing slopes support significantly denser pine and fir stands, which fuels more intense wildfires. We conclude that polar‐facing slopes experience the most severe surface erosion following wildfires in this region, indicating that landscape‐scale aridity can control the geomorphic response of hillslopes to wildfires. Copyright © 2018 John Wiley & Sons, Ltd.

Beryllium-7 in vegetation, soil, sediment and runoff on the northern Loess Plateau

Beryllium-7 (7Be), as a potentially powerful tracer, was widely used to document soil redistribution and identify sediment sources in recent decades, but the quantity and distribution of 7Be in vegetation, soil, sediment and runoff on the Loess Plateau have not been fully described. In this study, we measured 7Be in vegetation, soil, sediment and runoff on the northern Loess Plateau of China and analyzed its variations during the rainy season to assess the potential of the 7Be method for documenting soil redistribution and identifying sediment sources in a wide range of environments. The results indicated that vegetation, soil, and sediment samples showed higher levels and larger variations of 7Be activities during the rainy season. The drying plants showed 7Be mass activity that was more than three times higher than that of living and semi-decomposed plants. 7Be mass activity in plants and sediment was much higher than in the soil. 7Be activity in runoff water with a few submicron suspended particles varied slightly and was far lower than in plant, soil and sediment samples. The cumulative precipitation generally determined 7Be inventory held by plants and soil. An inverse relationship was found between the 7Be mass activity in sediment and the sediment amount. Globally, approximate 30% of the total 7Be was held by plants in both the herbaceous and subshrub plots. Approximate 10% of the total 7Be was lost with sediment from the bare plot. A very small proportion of 7Be (1.18%–3.20%) was lost with runoff, and the vast majority of 7Be was retained in the slope soil at the end of rainy season. Vegetation cover and soil erosion significantly affected the spatial distribution and variations of the 7Be inventory in soil, providing a necessary condition for the development of a 7Be method to document soil erosion on slopes with vegetation.

Land Resource Inventory (LRI) for development of sustainable agricultural land use plans using geospatial techniques: A case study of Pata Meghpar village, Jamnagar district, Gujarat

The soil and land resource inventory at village, as basic unit, are providing baseline data on soils, their constraints and potentials for crop production. Considering this fact, Pata Meghpar village (22013’14’’ to 22016’09’’ N latitude and 70029’16’’ to 70032’59’’ E) in Jamnagar district of Gujarat with an area of 1683 hectares was selected for land resource inventory on 1: 10000 scale for land use planning activity. The soils developed on Deccan trap geological formations with distinct basaltic landforms appear at an elevation of 100 meters above mean sea level near Und river. The landform analysis of study area was carried out with the visual interpretation of Indian Remote Sensing Satellite P6 LISS-IV data of April 2012 in conjunction with cadastral map. The four basic landforms identified are isolated upland (119.3 ha & 7.1%), ravinous land (409.6 ha & 24.3%), very gently to gently sloping plains (543.9 ha & 32.3%) and nearly level plains (610 ha & 36.2%). The detailed soil survey was carried out and identified seven soil series with 10 phases. The soil series Pata Meghpar-1(Loamy, Lithic Ustorthents) and Patameghpar-2 (loamy-skeletal, Lithic Ustorthents) occurring on isolated upland are very shallow, excessively drained, brown loam (7.5YR 4/4) to dark yellowish brown (10YR 3/4), gravely loam and slightly alkaline (pH 7.27.8). The Pata Meghpar-3 (fine-loamy, Typic Ustorthents) on ravinous lands are moderately shallow, excessively drained, strongly calcareous, dark yellowish brown (10YR 3/4), weak fine sub-angular blocky structure, slightly alkaline to moderately alkaline (pH 7.7 to 8.6). The Pata Meghpar-4 (fine, Typic Haplustepts) and Pata Meghpar-5 (fine, Vertic Haplustepts) occurring on very gently to gently sloping plain are moderately deep (50-75cm), moderately well drained, slight to moderately calcareous, very dark grayish brown (10YR 3/2), moderate, medium, sub angular blocky structures and moderate to strongly alkaline (pH 8.1 to 8.8). The Pata Meghpar-6 (fine, Leptic Haplusterts) and Pata Meghpar-7 (fine, Typic Haplusterts) occurring on nearly level plains are deep, clayey, moderately well drained, very dark grayish brown (10YR 3/2) to very dark gray (10YR 3/1), weak fine angular blocky to moderate medium angular blocky structure, moderately calcareous and moderately alkaline (pH 8.0–8.5). The baseline resource data are useful for deriving soil-landscape relationships in basaltic terrain at village and forms the basis for upgrading management packages for sustainable crop production at farm level.

Distribution and Abundance of Big-Leaf Mahogany (Swietenia macrophylla) on the Yucatan Peninsula, Mexico

Big-leaf mahogany ( Swietenia macrophylla King) is an economically important timber species in the Neotropics. For over three centuries, it has been selectively extracted from tropical forests, threatening its populations. We investigate the actual and potential distribution of big-leaf mahogany and assess its abundance on the Yucatan Peninsula based on the National Forest and Soils Inventory database. Furthermore, we evaluate environmental factors associated with its distribution, abundance, and tree size. The actual and potential distribution models show the presence of mahogany in a wide geographic area covering the southern and eastern portions of the Yucatan Peninsula. Abundance of mahogany in the landscape varies and in general is low. The spatial potential distribution model was best explained by the environmental variables of vegetation cover (medium- and high-stature semievergreen tropical forest) and elevation (upland areas). Results also indicate that mahogany remains relatively abundant and contain larger size classes in localities where the species has been harvested and managed for decades under community forest management. Furthermore, statistical analyses show greater tree density of mahogany mostly associated with low-stature semievergreen tropical forest having deep soils (gleysols and vertisols), while larger tree size (diameter at breast height) was associated with medium-stature semievergreen tropical forests in upland areas with moderately deep or shallow soils (mostly rendzinas or leptosols). Despite deforestation, land-use change and forestry activities on the Yucatan Peninsula, particularly in the past 20 years, the distribution and abundance of mahogany do not appear to be as drastically reduced as described in other neotropical regions.

Digital RGB photography and visible-range spectroscopy for soil composition analysis

We demonstrate calibration models developed for a number of soil variables, based on colour information derived from standard digital photography and a prototype visible-wavelength spectroscopy device. The samples used were taken from the National Soils Inventory of Scotland and included topsoil samples taken either from the upper horizon or bulked from the top 20cm. A total of 31 variables were investigated, including organic matter content (Loss On Ignition), carbon, nitrogen, pH, sand/silt/clay and a number of elemental concentrations. Model calibrations were developed using visible-wavelength colour information alone and in combination with spatial covariates (topography, climate, soil, vegetation, parent material). A set of thresholds for characterising quality of model calibration was defined using r-squared value, with Good (>0.8), Fair (0.6–0.8), Moderate (0.4–0.6) and Poor (<0.4). For the site descriptors alone, no variables were given Good estimation but several were given Fair, while digital photography alone gave Good estimation for exchangeable H and Fair for Loss on Ignition and C. A combination of site descriptors and colour photography gave Good estimation for four variables and Fair for another six. Visible range spectroscopy alone gave Good estimation for one variable and Fair for another four. Visible-range spectroscopy plus spatial covariates gave the best results, with Good estimation for five variables and Fair for eight. The results indicate that depending on the soil variable of interest, calibration models can be developed for regional soil variable estimation using an appropriate selection of measurement device and data integration. Evaluation of the trained neural network models provided information on the relative importance of individual input variables, allowing us to further identify those inputs of particular interest in this kind of work and to gain a better understanding of the processes linking soils and their environment.

Prediction of soil organic carbon at the country scale: stratification strategies for near‐infrared data

SummaryResearch has shown that the application of near‐infrared (NIR) spectroscopy can be used to predict soil attributes, in particular for regional to continental scales. However, there are challenges when NIR is used at the regional scale because of the considerable spatial variation. This study has predicted SOC at the country scale (German agricultural soil inventory) with different stratification strategies for NIR data: (i) calibration with memory‐based learning (MBL) algorithms that use spectral similarity and (ii) simple stratification based on soil properties (depth, pH and soil texture) and land use. To optimize calibration models, this study aimed to predict soil organic carbon (SOC) determined by these three strategies for 1410 soil profiles selected from the German agricultural soil inventory. The profiles covered a wide range of soil types and characteristics. The calibration procedures were based on complete soil profile data of two‐thirds of the dataset and one‐third of the dataset was used for independent validation (prediction); the profiles were selected randomly. Available soil properties for stratifying the datasets were: soil depth (topsoil 0–30 cm and subsoil 31–100 cm), pH and texture class (silty, clayey, sandy and loamy). The profiles were also stratified by land use (cropland and grassland) and with the MBL method. The calibrations were carried out by partial least‐squares regression (PLSR), and each stratification model was compared with the global model. The root mean square error of cross‐validation (RMSECV) for the global model was 4.2 g SOC kg−1. Stratification according to soil depth reduced the error by 10% (RMSECV 3.8 g kg−1). The best stratification by soil texture was when sandy soil samples were separated from the other samples, which reduced the RMSECV by 14%. Calibration with MBL provided the most accurate predictions of SOC, with an error reduction of 25% (RMSECV 3.2 g kg−1). Thus, calibrations with NIR of country‐scale datasets can be improved easily by stratification or application of the MBL algorithm.Highlights Large country‐scale soil dataset of near‐infrared with &gt; 1400 soil profiles was used. Stratification of NIR data by soil properties increased the accuracy of SOC calibration at country scale. The best stratification design involved calibrating sandy soil separately from other texture classes. A decrease of 25% in calibration error and 22% in prediction error with the MBL model compared with global model.

Results of the second national forest soil inventory in Germany - Interpretation of level and stock profiles for PCDD/F and PCB in terms of vegetation and humus type

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were detected in 86 humic topsoil layers and in a subset of 11 randomly selected top mineral forest soils at the depths of 0–5cm and 5–10cm collected from different federal states of Germany. The distribution of these persistent organic pollutants (POPs) in humic topsoils with respect to vegetation cover (coniferous vs. deciduous vs. mixed), total organic carbon (TOC), altitude and latitude data was investigated. There is cross correlation between the contents and TOC while the correlation with latitude indicates higher abundances of POPs in central Germany where there is high population density accompanied with industrial activities. The calculated stocks suggest that humus type (mor, mull, or moder) in conjunction with forest type can explain the relative POPs abundances in different soil layers. Generally, humic topsoils show highest contents of POPs compare to the two mineral soils with a ratio of 100:10:1. However, the stock humic layers of coniferous stands contribute about 50% to the total stock, whereas at deciduous stands the stock is mainly located in the upper mineral soil layer (0–5cm). The soil-water distribution coefficients (Kd) were calculated to estimate the potential translocation in the different soil types. The Kd values vary among the PCBs and PCDD/Fs congeners and are most variable for humic topsoils. There is pronounced chemical abundance in the top mineral soils with increasing Kd and this points to non-water bound transport processes for superlipophilic compounds.

Variability of soil carbon stocks in a mixed deciduous forest on hydromorphic soils

Forests play an important role for carbon (C) storage and a large part of C in forest ecosystems is stored in the soil. Although large-scale inventories of soil C stocks have been published recently, detailed site-specific studies are still needed because C storage depends on various site specific soil, ecological and management factors. Quantification of soil C stocks is hampered by spatial and temporal variability. Here, we assess C stocks in an ancient forest site at a stand which has not been managed for >60years and analyse the spatial variability of C concentrations and stocks to evaluate inter-annual variability and elucidate possible causes. Samples were taken down to 1m depth by auger cores in May of three consecutive years (2013, 2014, 2015) on regular hexagonal grids covering an area of 0.25ha and 19 sampling spots. In addition, to address small scale variability, 36 auger cores were taken in November 2014 using a nested sampling design.C stocks were on average 34kgCm−2 (0–1m depth). This is distinctly higher than soil C stocks reported for most other forest sites in similar climatic conditions, and is likely caused by the interplay of several parameters, i.e., hydromorphic soil conditions, high biomass production due to high soil fertility, stand structure (tree age, species and density), and the management history of the site. The coefficients of variation for C concentrations (>50%) and for C stocks (30–50%) show that spatial variability is high. Geostatistical analysis revealed a larger scale component with ranges of 5–20m and a small scale component represented by high nugget effects in the semivariograms (>50%).As hydromorphic soil types are widespread in NE Germany, large amounts of organic C could be sequestered into soil under unmanaged old forests, thus contributing to alleviating the rise in anthropogenic CO2 concentrations in the atmosphere.

Rapid gamma spectrometric analysis of soil samples after radioactive fallout using a “conjugate view” technique

A method for fast determination of the activity in soil samples by measuring a fresh soil core sample from both ends with an HPGe-detector is proposed. The method was tested by simulations, as well as by measurements on spiked soil samples. Both simulations and measurements showed that the geometrical mean of the count rates when the sample is measured twice, with the bottom and the top end, respectively, facing the detector closely resembles the count rate from a measurement on a homogenized sample. Therefore, an efficiency calibration for homogenized samples could be used even if the activity is highly inhomogeneous in the soil core, as is the case with fresh fallout.It was also shown that by studying the ratio between the two measurements, a rough estimation of the extent of penetration of the radionuclide in the soil can be found. This will enhance the possibility to make rapid estimations of the soil inventory by field gamma spectrometry.

Carbon stocks in tree biomass and soils of German forests

Abstract Close to one third of Germany is forested. Forests are able to store significant quantities of carbon (C) in the biomass and in the soil. Coordinated by the Thünen Institute, the German National Forest Inventory (NFI) and the National Forest Soil Inventory (NFSI) have generated data to estimate the carbon storage capacity of forests. The second NFI started in 2002 and had been repeated in 2012. The reporting time for the NFSI was 1990 to 2006. Living forest biomass, deadwood, litter and soils up to a depth of 90 cm have stored 2500 t of carbon within the reporting time. Over all 224 t C ha-1 in aboveground and belowground biomass, deadwood and soil are stored in forests. Specifically, 46% stored in above-ground and below-ground biomass, 1% in dead wood and 53% in the organic layer together with soil up to 90 cm. Carbon stocks in mineral soils up to 30 cm mineral soil increase about 0.4 t C ha-1 yr-1 stocks between the inventories while the carbon pool in the organic layers declined slightly. In the living biomass carbon stocks increased about 1.0 t C ha-1 yr-1. In Germany, approximately 58 mill. tonnes of CO2 were sequestered in 2012 (NIR 2017).

Is Biomass Accumulation in Forests an Option to Prevent Climate Change Induced Increases in Nitrate Concentrations in the North German Lowland?

The North German Lowland is a region with locally high nitrate (NO3−) concentrations in seepage water, inducing an increased susceptibility to the effects of climate change. The future risk of rising NO3− concentrations in seepage water from forests was quantified for four regions in the North German Lowland using climate projections and a modelling system comprising submodels for forest stand development (WaldPlaner), water budgets (WaSiM-ETH), and biogeochemical element cycles (VSD+). The simulations for the period from 1990 to 2070 included three different forest management scenarios (reference, biodiversity, and climate protection) and showed a general decrease in groundwater recharge which could hardly be influenced by any of the management options. The simulated soil organic matter stocks adequately represented their past increase as expected from the National Forest Soil Inventory (NFSI), but also showed a future decline under climate change conditions which leads to higher organic matter decomposition and a long-lasting increase of NO3− leaching from forest soils. While the climate protection oriented scenario shows the highest increase in NO3− concentrations during the projection period until 2070, the biodiversity scenario kept NO3− concentrations in seepage water below the legal thresholds in three of four selected model regions.

Towards complete and harmonized assessment of soil carbon stocks and balance in forests: The ability of the Yasso07 model across a wide gradient of climatic and forest conditions in Europe

Accurate carbon-balance accounting in forest soils is necessary for the development of climate change policy. However, changes in soil organic carbon (SOC) occur slowly and these changes may not be captured through repeated soil inventories. Simulation models may be used as alternatives to SOC measurement. The Yasso07 model presents a suitable alternative because most of the data required for the application are readily available in countries with common forest surveys. In this study, we test the suitability of Yasso07 for simulating SOC stocks and stock changes in a variety of European forests affected by different climatic, land use and forest management conditions and we address country-specific cases with differing resources and data availability. The simulated SOC stocks differed only slightly from measured data, providing realistic, reasonable mean SOC estimations per region or forest type. The change in the soil carbon pool over time, which is the target parameter for SOC reporting, was generally found to be plausible although not in the case of Mediterranean forest soils. As expected under stable forest management conditions, both land cover and climate play major roles in determining the SOC stock in forest soils. Greater mean SOC stocks were observed in northern latitudes (or at higher altitude) than in southern latitudes (or plains) and conifer forests were found to store a notably higher amount of SOC than broadleaf forests. Furthermore, as regards change in SOC, an inter-annual sink effect was identified for most of the European forest types studied. Our findings corroborate the suitability of Yasso07 to assess the impact of forest management and land use change on the SOC balance of forests soils, as well as to accurately simulate SOC in dead organic matter (DOM) and mineral soil pools separately. The obstacles encountered when applying the Yasso07 model reflect a lack of available input data. Future research should focus on improving our knowledge of C inputs from compartments such as shrubs, herbs, coarse woody debris and fine roots. This should include turnover rates and quality of the litter in all forest compartments from a wider variety of tree species and sites. Despite the limitations identified, the SOC balance estimations provided by the Yasso07 model are sufficiently complete, accurate and transparent to make it suitable for reporting purposes such as those required under the UNFCCC (United Nations Framework Convention on Climate Change) and KP (Kyoto Protocol) for a wide range of forest conditions in Europe.

Soil organic carbon stocks are systematically overestimated by misuse of the parameters bulk density and rock fragment content

Abstract. Estimation of soil organic carbon (SOC) stocks requires estimates of the carbon content, bulk density, rock fragment content and depth of a respective soil layer. However, different application of these parameters could introduce a considerable bias. Here, we explain why three out of four frequently applied methods overestimate SOC stocks. In soils rich in rock fragments (&gt; 30 vol. %), SOC stocks could be overestimated by more than 100 %, as revealed by using German Agricultural Soil Inventory data. Due to relatively low rock fragments content, the mean systematic overestimation for German agricultural soils was 2.1–10.1 % for three different commonly used equations. The equation ensemble as re-formulated here might help to unify SOC stock determination and avoid overestimation in future studies.

Detecting small-scale spatial heterogeneity and temporal dynamics of soil organic carbon (SOC) stocks: a comparison between automatic chamber-derived C budgets and repeated soil inventories

Abstract. Carbon (C) sequestration in soils plays a key role in the global C cycle. It is therefore crucial to adequately monitor dynamics in soil organic carbon (ΔSOC) stocks when aiming to reveal underlying processes and potential drivers. However, small-scale spatial (10–30 m) and temporal changes in SOC stocks, particularly pronounced in arable lands, are hard to assess. The main reasons for this are limitations of the well-established methods. On the one hand, repeated soil inventories, often used in long-term field trials, reveal spatial patterns and trends in ΔSOC but require a longer observation period and a sufficient number of repetitions. On the other hand, eddy covariance measurements of C fluxes towards a complete C budget of the soil–plant–atmosphere system may help to obtain temporal ΔSOC patterns but lack small-scale spatial resolution. To overcome these limitations, this study presents a reliable method to detect both short-term temporal dynamics as well as small-scale spatial differences of ΔSOC using measurements of the net ecosystem carbon balance (NECB) as a proxy. To estimate the NECB, a combination of automatic chamber (AC) measurements of CO2 exchange and empirically modeled aboveground biomass development (NPPshoot) were used. To verify our method, results were compared with ΔSOC observed by soil resampling. Soil resampling and AC measurements were performed from 2010 to 2014 at a colluvial depression located in the hummocky ground moraine landscape of northeastern Germany. The measurement site is characterized by a variable groundwater level (GWL) and pronounced small-scale spatial heterogeneity regarding SOC and nitrogen (Nt) stocks. Tendencies and magnitude of ΔSOC values derived by AC measurements and repeated soil inventories corresponded well. The period of maximum plant growth was identified as being most important for the development of spatial differences in annual ΔSOC. Hence, we were able to confirm that AC-based C budgets are able to reveal small-scale spatial differences and short-term temporal dynamics of ΔSOC.

Assessing soil organic carbon stocks under current and potential forest cover using digital soil mapping and spatial generalisation

Forest soils are important components in the global C-cycle. Regional soil organic carbon (SOC) stock assessments are hampered by low spatial densities of routine soil inventories. In this study, we estimated the SOC stock in the upper meter of forest in the region of Flanders (N. Belgium) using four digital soil mapping techniques, i.e. multiple linear regression (MLR), boosted regression trees (BRT), artificial neural networks (ANN) and least-squares support vector machines (LS-SVM), and compared them with the results of a multi-level spatial generalisation (MLSG) approach.Applied to a collection of 276 soil profiles, we identified the highest groundwater level, clay fraction, tree genus and soil type as key predictors of the SOC stock in the upper 100cm under forests. Overall, BRT was the most informative as it obtained the best fit (training R2 of 0.68, cross-validated R2 of 0.22) and provided insights in the soil system by showing average predictor effects in partial dependence plots. With BRT, the total stock in the upper meter of forest soil (153,544ha) was estimated to be 26.99 Mt OC, or 17.58kgm−2 on average. MLSG provided an estimate for only 90% of the forest area and resulted in a larger average stock of 18.22kgm−2 due to larger predictions for Histosols. As a null model, i.e. assuming that the potential natural dominant tree genus would occur according to the present soil conditions, the SOC stock in the current forest area was estimated at 30.00 Mt OC, or 21.26kgOCm−2 on average. When the complete non-built-up territory (1,168,850ha) would be forested analogously, 255.28MtOC would be stored, which is more than double the amount of predictions under the actual land cover. The results highlight the importance to conserve and restore carbon hotspots like alluvial forests. New soil inventories should focus on these and other data-scarce land units. Future modelling approaches can benefit from explicitly taking the soil type and tree genus into account as predictors.

Inland navigation: PAH inventories in soil and vegetation after EU fuel regulation 2009/30/EC

In January 2011, fuel quality in inland water vessels was changed by EU regulation 2009/30/EC, aiming at improving air quality along waterways. We hypothesized that the implementation of this regulation both lowered the total deposition of polycyclic aromatic hydrocarbons (PAHs) and changed their composition in river valleys. We analyzed parent-, alkylated- and thio-PAHs in soil and vine leaves, at two waterways (Rhine and Moselle, Germany), as well as in one ship-free reference area (Ahr, Germany). Samples were taken annually (2010-2013) in transects perpendicular to the rivers. We did not find any relation of PAH concentration and composition on vine leaves to inland navigation, likely because atmospheric exchange processes distorted ship-specific accumulation patterns. We did find, however, an accumulation of ship-borne PAHs in topsoil near the waterways (1543±788 and 581±252ngg-1 at Moselle and Rhine, respectively), leading to larger PAH concentrations at the Moselle Valley than at the reference area (535±404ngg-1) prior to EU fuel regulation. After fuel regulation, the PAH concentrations decreased in topsoils of the Moselle and Rhine Valley by 35±9 and 62±28%, respectively. These changes were accompanied by increasing proportions of dibenzothiophene (DBT) and low molecular weight PAHs. Both, changes in PAH concentrations and composition were traceable within 200 and 350m distance to the river front of Moselle and Rhine, respectively, and likely favored by erosion of topsoil in vineyards. We conclude that the EU regulation was effective in improving soil and thus also air quality within only three years. The impact was greater and spatially more relevant at the Rhine, which may be attributed to the larger traffic volume of inland navigation.

Vertical distributions of Pu and radiocesium isotopes in sediments from Lake Inba after the Fukushima Daiichi Nuclear Power Plant accident: Source identification and accumulation

Radiocesium isotopes were released into the environment in the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, which resulted from the massive Tohoku earthquake in March 2011. Lake Inba is located in Chiba Prefecture about 200 km from the FDNPP site and the lake was contaminated by radioactivity from the accident. The present work was carried out in order to investigate the vertical distributions and accumulations of radiocesium and Pu in sediment cores collected during 2011–2015, and to study the migration behaviors of radiocesium and Pu isotopes in the sediments. The observed 134Cs/137Cs activity ratios in the core samples were approximately 1 (decay-corrected to 15 March, 2011), suggesting that sediment samples were contaminated by the FDNPP-released radiocesium. Compared with radiocesium inventories in soil in the area surrounding the Lake Inba, the calculated higher radiocesium inventories of the collected sediment cores indicated that most of the radiocesium was subsequently accumulated in the lake, and that the radiocesium input by atmospheric deposition and input from surrounding soil were greater than the output of the radiocesium. The 239+240Pu activities in the sediments were all within the background level seen before the accident. The atom ratios of 240Pu/239Pu ranged from 0.175 to 0.210, suggesting that Pu originated from global stratospheric fallout rather than from the FDNPP accident.

Soils and climate of Cul de Sac Valley, Haiti: A soil water and geomorphology perspective

Soil is an important natural resource, yet for many countries, including Haiti, the only soil inventory is a general soil map at 1:250,000 scale, which is not suitable for management planning at the farm level. A soil survey for a 3,000 ha (7,400 ac) segment of Cul de Sac Valley was conducted at 1:24,000 scale. Eleven soil types and soil map units were identified. Approximately 60% of the study area consisted of soils on Floodplains, while 40% were soils on Foothills, Hills, and Dissected Alluvial Fans. The combination of the parent material, predominantly marine sediment and limestone bedrock, and spatial-temporal precipitation patterns resulted in soils dominated by calcium carbonate (CaCO3) and sodium (Na) accumulations throughout their profile. The new soil geomorphology map derived from the detailed soil map was similar to the existing general soil map and geomorphology map. It was spatially more accurate and provided better understanding of soil and climate influence on soil water movement. Cul de Sac Valley resulted from uplifting and erosion and deposition processes. This, combined with aridic to semiaridic climate conditions, resulted in cemented CaCO3 accumulation and Na rich soils. The water management for irrigation was limited by a combination of soil properties such as high gravel and steep slopes for Dissected Alluvial Fans and Hills soil geomorphic units, presence of cemented CaCO3 for Foothills, and high Na content for Lower Flat Plains. Further studies are needed for a complete and comprehensive understanding of the soil geomorphology processes and climate interactions of this complex system.