Search

Summary: The construction of dams to intercept natural rivers constitutes the most severe human activity influencing the underlying surface. This study focuses on four cascade reservoirs of the Lancang River and explores their impact on the migration of organic matter in sediments. The research reveals significant spatial variations in total organic carbon (TOC) and total nitrogen concentrations in the sediments of the four reservoirs. The carbon and nitrogen isotopes indicate that terrigenous organic matter is the main source of TOC in the sediments, contributing an average of 66.80%. Endogenous algal-derived organic matter is the second significant source, contributing between 14.30% and 32.91%. The sources contributed from upstream organic matter are the lowest, ranging from 6.36% to 15.33%. Our study demonstrates that the construction of cascade reservoirs may significantly alter the processes of material sources in the river basin ecosystem, particularly in the large reservoir which increased more endogenous algal-derived organic matter.

Accurate measurement of infiltration rate and hydraulic conductivity is important for assessing soil physical health, irrigation management and catchment modelling. Commercially available infiltrometers are often expensive, fragile, and require specialist knowledge to operate and perform complex post-measurement calculations. We developed the Lithosphere Infiltrometer (permeameter) to be usable for both experienced soil researchers, and users without prior technical or scientific expertise in soil science. The Lithosphere Infiltrometer is able measure both surface and subsoil infiltration rate and hydraulic conductivity. It is manufactured using 3D-printed parts and off-the-shelf electronic components. It has a robust, quad-leg design that allows for rapid leveling of the device and accurate setting of water depth via a novel 3D-printed bell chamber. The water level is measured using a U85 JRT laser with ±1 mm accuracy connected to an Adafruit Huzzah 32 microcontroller. Infiltration rate and hydraulic conductivity are calculated at 1 to 10 min time steps, and data is presented in real-time on an OLED display. Data is stored on the device and available for download to a mobile device by Wi-Fi.

This paper discusses the interest in utilizing R, a programming language, in soil physics for enhanced data reproducibility. Reproducibility is challenging across scientific disciplines, including soil science, and it is encouraged by demands for transparency from funding bodies and governments. Open and reproducible soil physics research can benefit the scientific community. With a focus on open science practices, the authors developed {infiltrodiscR}, leveraging existing R knowledge in soil physics. The package facilitates analysis of infiltration data, demonstrated through analysing changes in infiltration using published data. Results align with previous findings, showcasing {infiltrodiscR}'s potential in promoting reproducibility in soil science research.

The central highlands of Ethiopia are characterized as a region of high rates of land degradation and soil erosion. This study aimed to estimate total amount of soil loss and sediment yield using RUSLE model within GIS environment. LULC maps of 1973–2015 were used to evaluate the impact of land use change on soil loss and sediment yield. Each model parameter and sediment deliver ration was computed by using Williams and Berndt empirical equation. The net soil erosion and sediment yield at the Guder river mouth and soil risk map was estimated for the watershed. LULC dynamic for the study period and watershed have shown that there existed a rapid conversion of vegetated land uses to human modified land uses. The study revealed that the mean soil loss from the watershed ranges between 25 and 30 t/ha−1 yr−1 which accounted 25.8, 28.7 and 30.3 t/ha/yr for 1973, 1995 and 2015 periods respectively. The estimated total soil loss in 1973, 1995 and 2015 periods were 198Mt yr-1, 221Mt yr-1 and 239Mt yr-1 respectively. The mean sediment yield estimated was 6.79, 8.65 and 9.44t ha-1 yr-1 for 1973, 1995 and 2015 periods respectively. The sediment deliver ratio (SDR) of the watershed ranged between 0 and 0.26. The spatial distribution of SDR showed that the highest value was recorded on central and eastern part of the watershed. Prioritizing erosion host spot areas is recommended to rehabilitate degraded lands using suitable soil and water conservation structures.

Root reinforcement, provided by plants in soil, can be exerted by a mechanical effect, increasing soil shear strength for the presence of roots, or by a hydrological effect, induced by plant transpiration. No comparisons have been still carried out between mechanical and hydrological reinforcements on shallow slope stability in typical agroecosystems. This paper aims to compare these effects induced by sowed fields and vineyards and to assess their effects towards the shallow slope staibility. Root mechanical reinforcement has been assessed through Root Bundle Model-Weibull. Root hydrological reinforcement has been evaluated using an empirical relationship with monitored or modelled pore water pressure. Each reinforcement has been inserted in a stability model to quantify their impacts on susceptibility towards shallow landslides. Considering the same environment, corresponding to a typical agroecosystem of northern Italian Apennines, land use has significant effects on saturation degree and pore water pressure, influencing hydrological reinforcement. Root hydrological reinforcement effect is higher in summer, although rainfall-induced shallow landslides rarely occur in this period due to dry soil conditions. Instead, in wet and cold periods, when shallow landslides can develop more frequently, the stabilizing contribution of mechanical reinforcement is on average higher than the hydrological reinforcement. In vineyards, the hydrological reinforcement effect could be observed also during autumn, winter and spring periods, giving a contribution to slope stability also in these conditions. This situation occurs when plants uptake enough water from soil to reduce significantly pore water pressure, guaranteeing values of hydrological reinforcement of 1-3 kPa at 1 m from ground, in agreement with measured mechanical root reinforcement (up to 1.6 kPa). These results suggest that both hydrological and mechanical effects of vegetation deserve high regard in susceptibility towards shallow landslides, helping in selection of the best land uses to reduce probability of occurrence of these failures over large territories., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The dynamics of soil water dissolved CO 2 and N 2 O are important in determining the fates of soil CO 2 and N 2 O. However, related mechanisms and processes have been rarely revealed. In this study, storages and leaching losses of soil water dissolved CO 2 and N 2 O were investigated on the tea garden (TG) and bamboo forest (BF) hillslopes. Soil water storage and leaching flux were simulated by the HYDRUS-3D model and the soil water dissolved CO 2 and N 2 O concentrations were acquired by field monitoring. Results showed that the storages of soil water dissolved CO 2 and N 2 O ranged from 1.30 to 14.86 kg C ha -1 and 0.24 to 388.99 g N ha -1 on the TG hillslope, respectively, while they ranged from 0.49 to 52.29 kg C ha -1 and 0.50 to 14.22 g N ha -1 on the BF hillslope, respectively. The annual leaching loss of soil water dissolved CO 2 and N 2 O were 26.17 kg C ha -1 and 29.46 g N ha -1 , respectively, on the TG hillslope, while they were 49.51 kg C ha -1 and 4.35 g N ha -1 on the BF hillslope, respectively. The dissolved CO 2 leaching loss mainly occurred in summer, especially in July on both hillslopes. Peaks of dissolved N 2 O leaching loss on the TG hillslope were observed after the application of basal fertilizer, accompanying with precipitation events. Instead, peaks of dissolved N 2 O leaching loss on the BF hillslope were observed in summer. The main influencing factors of dissolved CO 2 and N 2 O storages were temperature, precipitation, and fertilization, with total effects generally >0.30. However, that of the dissolved CO 2 and N 2 O leaching losses was the precipitation, with total effects >0.57. Dissolved CO 2 /N 2 O concentration was more important than soil water storage in determining the dissolved CO 2 /N 2 O storage, while the leaching flow rate was more crucial than dissolved CO 2 /N 2 O concentration in determining the dissolved CO 2 /N 2 O leaching loss. These findings expanded our knowledge of sources and sinks of greenhouse gases on the terrestrial ecosystem., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Biochar application to soil has the potential to affect soil and vegetation properties that are key for the processes of runoff and soil erosion. However, both field and pot experiments show a vast range of effects, from strong reductions to strong increases in runoff and/or soil erosion. Therefore, this study aimed to quantify and interpret the impacts of biochar on runoff and soil erosion through the first systematic meta-analysis on this topic. The developed dataset consists of 184 pairwise observations for runoff and soil erosion from 30 independent studies but 8 of which just focused on soil erosion. Overall, biochar application to soil significantly reduced runoff by 25 % and erosion by 16 %. Mitigation of soil erosion in the tropics was approximately three times stronger (30 %) than at temperate latitudes (9 %); erosion reduction in the subtropical zone was 14 %, but not significantly different from either the tropical or temperate zones. Fewer reported field observations for runoff resulted in larger confidence intervals and only the temperate latitudes showed a significant effect (i.e. a 28 % reduction). At topsoil gravimetric biochar concentrations between 0.6 % and 2.5 %, significant reductions occurred in soil erosion, with no effect at lower and higher concentrations. Biochar experiments that included a vegetation cover reduced soil erosion more than twice as much as bare soil experiments, i.e. 27 % vs 12 %, respectively. This suggests that soil infiltration, canopy interception, and soil cohesion mechanisms may have synergistic effects. Soil amended with biochar pyrolyzed at >500 °C was associated with roughly double the erosion reduction than soil amended with biochar produced at 300-500 °C, which potentially could be related to the enhancement of hydrophobicity in the latter case. Our results demonstrate substantial potential for biochar to improve ecosystem services that are affected by increased infiltration and reduced erosion, while mechanistic understanding needs to be improved., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Behrouz Gholamahmadi reports financial support was provided by Foundation for Science and Technology. Frank Verheijen reports financial support was provided by Foundation for Science and Technology. Ana Catarina Bastos reports financial support was provided by Foundation for Science and Technology. Frank Verheijen reports financial support was provided by University of Aveiro Centre for Environmental and Marine Studies. Sergio Alegre Prats reports financial support was provided by Foundation for Science and Technology. Oscar Gonzalez-Pelayo reports financial support was provided by Foundation for Science and Technology. Jan Jacob Keizer reports financial support was provided by Foundation for Science and Technology., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Many pedotransfer functions (PTFs) have been developed for predicting the soil water content at different matric potentials. The use of these functions has been encouraged because of the time and work typically required for measuring it, while the PTFs require commonly measured soil properties such as sand, silt, clay, organic matter content, or bulk density for predicting water retention. In addition, several environmental and ecosystem management simulation models such as DRAINMOD, HYDRUS, EPIC, SPAW, and WEPP use PTFs for computing soil hydraulic properties. Because of the increasing use of the PTFs and their effect in many soil water simulation and transport models, this study revised and tested 13 different PTFs for predicting soil water content at -33 and -1500 kPa, values usually known as field capacity and wilting point. Three of these PTFs were derived from tropical soils while the rest were developed with soil samples collected across the United States. These PTFs were evaluated in Chilean soils as an independent dataset and their improvement after calibration was assessed with this new data. The results demonstrate that the PTFs performance depends on the soils used for their development as the estimates showed a significant improvement after calibration. When predicting water content, Rawls et al. (2004) was the best function before calibration (RMSE = 0.08 for -33 and -1500 kPa), while Gupta and Larson (1979) was the best after calibration (RMSE of 0.06 and 0.05, and r 2 values of 0.69 and 0.66 at -33 and -1500 kPa, respectively). Nonlinear PTFs performed better than linear PTFs when predicting water content at field capacity. Finally, bulk density proved to be the key variable and can be used as footprint for soils changes through time. Organic matter content was also a significant input but improved the estimates for some specific matric potentials and PTFs., (Copyright © 2018 Elsevier B.V. All rights reserved.)