scholarly journals Assessing biogeochemical and human-induced drivers of soil organic carbon to inform restoration activities in Rwanda

2020 ◽  
Author(s):  
Leigh Ann Winowiecki ◽  
Athanase Mukuralinda ◽  
Aida Bargués-Tobella ◽  
Providence Mujawamaria ◽  
Elisée Bahati Ntawuhiganayo ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Land Degradation ◽  
Spatial Scales ◽  
Stable Carbon Isotope ◽  
Health Indicators ◽  
Crop Productivity ◽  
Land Restoration ◽  
Wide Range

Abstract. Land restoration is of critical importance in Rwanda, where land degradation negatively impacts crop productivity, water, food and nutrition security. We implemented the Land Degradation Surveillance Framework in Kayonza and Nyagatare districts in eastern Rwanda to assess baseline status of key soil and land health indicators, including soil organic carbon (SOC) and soil erosion prevalence. We collected 300 topsoil (0–20 cm) and 281 subsoil (20–50 cm) samples from two 100 km2 sites. We coupled the soil health indicators with vegetation structure, tree density and tree diversity assessments. Mean topsoil organic carbon was low overall, 20.9 g kg−1 in Kayonza and 17.3 g kg−1 in Nyagatare. Stable carbon isotope values (d13CV-PDB ) ranged from −15.35 to −21.34 ‰ indicating a wide range of plant communities with both C3 and C4 photosynthetic pathways. Soil carbon content decreased with increasing sand content across both sites and at both sampling depths and was lowest in croplands compared to shrubland, woodland and grasslands. Field-saturated hydraulic conductivity (Kfs) was estimated based on infiltration measurements, with a median of 76 mm h−1 in Kayonza and 62 mm h−1 in Nyagatare, respectively. Topsoil OC had a positive effect on Kfs, whereas pH, sand and compaction had negative effects. Soil erosion was highest in plots classified as woodland and shrubland. Maps of soil erosion and SOC at 30-m resolution were produced with high accuracy and showed high variability across the region. These data and analysis demonstrate the importance of systematically monitoring multiple indicators at multiple spatial scales to assess drivers of degradation and their impact on soil organic carbon dynamics.

scholarly journals Assessing soil and land health across two landscapes in eastern Rwanda to inform restoration activities

SOIL ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 767-783
Author(s):  
Leigh Ann Winowiecki ◽  
Aida Bargués-Tobella ◽  
Athanase Mukuralinda ◽  
Providence Mujawamariya ◽  
Elisée Bahati Ntawuhiganayo ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Land Degradation ◽  
Stable Carbon Isotope ◽  
Health Indicators ◽  
Negative Effects ◽  
Infiltration Capacity ◽  
Nutrition Security ◽  
Wide Range ◽  
Biophysical Indicators ◽  
Land Health

Abstract. Land degradation negatively impacts water, food, and nutrition security and is leading to increased competition for resources. While landscape restoration has the potential to restore ecosystem function, understanding the drivers of degradation is critical for prioritizing and tracking interventions. We sampled 300–1000 m2 plots using the Land Degradation Surveillance Framework across Nyagatare and Kayonza districts in Rwanda to assess key soil and land health indicators, including soil organic carbon (SOC), erosion prevalence, vegetation structure and infiltration capacity, and their interactions. SOC content decreased with increasing sand content across both sites and sampling depths and was lowest in croplands and grasslands compared to shrublands and woodlands. Stable carbon isotope values (δ13C) ranged from −15.35 ‰ to −21.34 ‰, indicating a wide range of historic and current plant communities with both C3 and C4 photosynthetic pathways. Field-saturated hydraulic conductivity (Kfs) was modeled, with a median of 76 mm h−1 in Kayonza and 62 mm h−1 in Nyagatare, respectively. Topsoil OC had a positive effect on Kfs, whereas pH, sand, and erosion had negative effects. Soil erosion was highest in plots classified as woodland and shrubland. Maps of soil erosion and SOC at 30 m resolution were produced with high accuracy and showed strong variability across the study landscapes. These data demonstrate the importance of assessing multiple biophysical properties in order to assess land degradation, including the spatial patterns of soil and land health indicators across the landscape. By understanding the dynamics of land degradation and interactions between biophysical indicators, we can better prioritize interventions that result in multiple benefits as well as assess the impacts of restoration options.

Earth Observation for Accurate Mapping of Soil Functional Properties, Land Health and Soil Infiltrability in Rwanda

2020 ◽  
Author(s):  
Tor-Gunnar Vågen ◽  
Leigh Ann Winowiecki ◽  
Aida Bargues-Tobella
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Properties ◽  
Spatial Resolution ◽  
Land Degradation ◽  
Earth Observation ◽  
Single Ring ◽  
Land Health

<p>Earth observation (EO) has a large potential for mapping of soil functional properties such as soil organic carbon, soil pH or acidity, soil fertility parameters and soil texture. Recent advances in the application of EO data in combination with systematic field data sampling, standardized soil data reference analysis and the use of soil spectroscopy have shown these approaches to be both robust and scalable. We present a case study from Rwanda where we apply EO data in combination with field and laboratory data collected using the Land Degradation Surveillance Framework (LDSF) to map functional soil properties, soil erosion prevalence and land cover at fine spatial resolution. Digital soil maps were produced at a spatial resolution of 30m with an accuracy of 85 to 90%, while soil erosion prevalence was mapped with an accuracy of 86% using Landsat satellite imagery and machine learning models. </p><p>We also assess interactions between spatial assessments of soil organic carbon, soil erosion prevalence and land cover at a spatial resolution of 30m in order to identify land degradation hotspots and better target interventions to restore degraded land across four districts in Rwanda. We further explore the effects of soil erosion, root-depth restrictions and soil organic carbon content on saturated hydraulic conductivity in three LDSF sites in Nyagatare, Kayonza and Bugesera districts, respectively. Saturated hydraulic conductivity was modeled based on single-ring measurements of infiltration capacity using a modified Reynolds & Elrick steady-state single ring model for 48 LDSF plots per site. The results show significant spatial variation in infiltrability within sites.</p><p>The results of the study show the importance of rigorous protocols for sampling and analyses of soil properties and indicators of land health across landscapes. By simultaneously assessing soil properties, indicators of land degradation and soil infiltrability we demonstrate the utility of these approaches in understanding drivers of land degradation across multiple spatial scales for targeting of options for land restoration and monitoring of the effectiveness of these interventions over time across multiple dimensions of land health.</p>

Interacting abiotic, biochemical and management factors explain soil organic carbon in Pyrenean grasslands

2020 ◽  
Author(s):  
Antonio Rodríguez ◽  
Rosa Maria Canals ◽  
Josefina Plaixats ◽  
Elena Albanell ◽  
Haifa Debouk ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Large Scale ◽  
Plant Biomass ◽  
Spatial Scales ◽  
Grazing Management ◽  
Quality Factors ◽  
Wide Range ◽  
Herbage Quality ◽  
Management Factors

<p>Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because there are scale-dependent effects, and large scale drivers affecting SOC both directly and through drivers working at fine spatial scales. Here we address how regional and landscape factors, and grazing management, soil properties and nutrients, and herbage quality factors affect SOC in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we fitted a set of models with explicative purposes including variables that comprise a wide range of environmental and management conditions. We found that temperature seasonality (MMT) was the most important abiotic driver of SOC in our study. MMT was positively related to SOC but only under certain conditions: exposed hillsides, steep slopes and relatively highly grazed areas. High MMT conditions probably are more favourable for plant biomass production, but landscape and grazing management factors buffer the conversion of this biomass into SOC. Concerning biochemical SOC predictors, we obtained some unexpected interaction effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial factor modulated by effects of livestock species and neutral-detergent fibre content of vegetation. Herbage recalcitrance effects varied depending on grazer species. These results highlight the need to expand knowledge about grassland SOC drivers under different environmental and management conditions.</p><p> </p>

Soil organic carbon losses by water erosion in a Mediterranean watershed

Soil Research ◽  
2017 ◽  
Vol 55 (4) ◽  
pp. 363 ◽  
Author(s):  
Ahmet Cilek
Keyword(s):  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
River Basin ◽  
Land Degradation ◽  
Agricultural Land ◽  
Water Erosion ◽  
Assessment Model ◽  
Ecosystem Functions ◽  
The Mediterranean

Soil organic carbon (SOC) is one of the primary elements required in the functioning of ecosystems. Soil erosion, a major mechanism of land degradation, removes SOC and transfers it to the hydrosphere or the atmosphere, thereby affecting key ecosystem functions and services. The Mediterranean region is highly susceptible to land degradation because of erosion due to heavy rains following long, dry, hot summers. Although the Mediterranean landscape typically has a high altitude and incline, the soil is brittle and soft and is easily washed away by rain. Thus, vast regions in Turkey have been afflicted by this type of soil degradation. This study aimed to (1) estimate the temporal distribution of water erosion in the Seyhan River Basin, (2) assess the spatial distribution of SOC and (3) estimate the depletion of SOC through soil erosion using the Pan-European Soil Erosion Risk Assessment model, a physically based, regionally scaled soil erosion model. The annual amount of soil eroded from the Seyhan River Basin is estimated to be 7.8million tonnes per hectare (tha–1year–1). The amount of fertile soil loss from agricultural areas is ~1.2million tonnes per year. The maximum amount of soil erosion occurs in maintenance scrubland and degraded forest areas, contributing to 68% of erosion, followed by that in agricultural land, contributing to 27% of erosion, with the remaining in forests and urban areas.

scholarly journals Interactions between biogeochemical and management factors explain soil organic carbon in Pyrenean grasslands

2020 ◽  
Author(s):  
Antonio Rodríguez ◽  
Rosa Maria Canals ◽  
Josefina Plaixats ◽  
Elena Albanell ◽  
Haifa Debouk ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Plant Biomass ◽  
Spatial Scales ◽  
Grazing Management ◽  
Interactive Effects ◽  
Testable Hypothesis ◽  
Wide Range ◽  
Herbage Quality ◽  
Management Factors

Abstract. Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large scale drivers affecting SOC both directly and through drivers working at detailed spatial scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients and herbage quality factors affect SOC in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we fit a set of models with explicative purposes using data that comprise a wide range of environmental and management conditions. We found that temperature seasonality (MMT) was the most important geophysical driver of SOC in our study. MMT was positively related to SOC but only under certain local conditions: exposed hillsides, steep slopes and relatively highly grazed areas. High MMT conditions probably are more favourable for plant biomass production, but landscape and grazing management factors buffer the accumulation of this biomass into SOC. Concerning biochemical SOC predictors, we obtained some surprising, interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial factor modulating effects of livestock species and neutral detergent fibre content of plant biomass and herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in the knowledge about SOC drivers in grassland under different environmental and management conditions, and they may serve to generate testable hypothesis in latter studies directed to climate change mitigation policies.

scholarly journals A method to detect soil carbon degradation during soil erosion

2009 ◽  
Vol 6 (11) ◽  
pp. 2541-2547 ◽  
Author(s):  
C. Alewell ◽  
M. Schaub ◽  
F. Conen
Keyword(s):  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
Swiss Alps ◽  
Wetland Soils ◽  
Soil Material ◽  
Process Indicator ◽  
Erosion Processes

Abstract. Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable carbon isotope signatures (process indicator of mixing versus degradation of carbon pools) we were able to show that degradation of carbon occurs during soil erosion processes at the investigated mountain grasslands in the central Swiss Alps (Urseren Valley, Canton Uri). Transects from upland (erosion source) to wetland soils (erosion sinks) of sites affected by sheet and land slide erosion were sampled. Analysis of 137Cs yielded an input of 2 and 4.6 tha−1 yr−1 of soil material into the wetlands sites. Assuming no degradation of soil organic carbon during detachment and transport, carbon isotope signature of soil organic carbon in the wetlands could only be explained with an assumed 500–600 and 350–400 years of erosion input into the wetlands Laui and Spissen, respectively. The latter is highly unlikely with alpine peat growth rates indicating that the upper horizons might have an age between 7 and 200 years. While we do not conclude from our data that eroded soil organic carbon is generally degraded during detachment and transport, we propose this method to gain more information on process dynamics during soil erosion from oxic upland to anoxic wetland soils, sediments or water bodies.

scholarly journals A method to detect soil carbon degradation during soil erosion

2009 ◽  
Vol 6 (3) ◽  
pp. 5771-5787 ◽  
Author(s):  
C. Alewell ◽  
M. Schaub ◽  
F. Conen
Keyword(s):  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Carbon Isotope ◽  
Stable Carbon Isotope ◽  
Swiss Alps ◽  
Wetland Soils ◽  
Soil Material ◽  
Process Indicator ◽  
Erosion Processes

Abstract. Soil erosion has been discussed intensively but controversial both as a significant source or a significant sink of atmospheric carbon possibly explaining the gap in the global carbon budget. One of the major points of discussion has been whether or not carbon is degraded and mineralized to CO2 during detachment, transport and deposition of soil material. By combining the caesium-137 (137Cs) approach (quantification of erosion rates) with stable carbon isotope signatures (process indicator of mixing versus degradation of carbon pools) we were able to show that degradation of carbon occurs during soil erosion processes at the investigated mountain grasslands in the central Swiss Alps (Urseren Valley, Canton Uri). Transects from upland (erosion source) to wetland soils (erosion sinks) of sites affected by sheet and land slide erosion were sampled. Analysis of 137Cs yielded an input of 2 and 2.6 t ha−1 yr−1 of soil material into the wetlands sites. Assuming no degradation of soil organic carbon during detachment and transport, carbon isotope signature of soil organic carbon in the wetlands could only be explained with an assumed 800 and 400 years of erosion input into the wetlands. The latter is highly unlikely with alpine peat growth rates indicating that the upper horizons might have an age between 7 and 200 years. While we do not conclude from our data that eroded soil organic carbon is generally degraded during detachment and transport, we propose this method to gain more information on process dynamics during soil erosion from oxic upland to anoxic wetland soils, sediments or water bodies.

scholarly journals Topographic Position, Land Use and Soil Management Effects on Soil Organic Carbon (Vineyard Region of Niš, Serbia)

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1438
Author(s):  
Snežana Jakšić ◽  
Jordana Ninkov ◽  
Stanko Milić ◽  
Jovica Vasin ◽  
Milorad Živanov ◽  
...  
Keyword(s):  
Land Use ◽  
Surface Layer ◽  
Spatial Distribution ◽  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Soil Compaction ◽  
Soil Management ◽  
Forest Land ◽  
Topographic Position

Spatial distribution of soil organic carbon (SOC) is the result of a combination of various factors related to both the natural environment and anthropogenic activities. The aim of this study was to examine (i) the state of SOC in topsoil and subsoil of vineyards compared to the nearest forest, (ii) the influence of soil management on SOC, (iii) the variation in SOC content with topographic position, (iv) the intensity of soil erosion in order to estimate the leaching of SOC from upper to lower topographic positions, and (v) the significance of SOC for the reduction of soil’s susceptibility to compaction. The study area was the vineyard region of Niš, which represents a medium-sized vineyard region in Serbia. About 32% of the total land area is affected, to some degree, by soil erosion. However, according to the mean annual soil loss rate, the total area is classified as having tolerable erosion risk. Land use was shown to be an important factor that controls SOC content. The vineyards contained less SOC than forest land. The SOC content was affected by topographic position. The interactive effect of topographic position and land use on SOC was significant. The SOC of forest land was significantly higher at the upper position than at the middle and lower positions. Spatial distribution of organic carbon in vineyards was not influenced by altitude, but occurred as a consequence of different soil management practices. The deep tillage at 60–80 cm, along with application of organic amendments, showed the potential to preserve SOC in the subsoil and prevent carbon loss from the surface layer. Penetrometric resistance values indicated optimum soil compaction in the surface layer of the soil, while low permeability was observed in deeper layers. Increases in SOC content reduce soil compaction and thus the risk of erosion and landslides. Knowledge of soil carbon distribution as a function of topographic position, land use and soil management is important for sustainable production and climate change mitigation.

Interactive effects of land use and soil erosion on soil organic carbon in the dry-hot valley region of southern China

CATENA ◽  
2021 ◽  
Vol 201 ◽  
pp. 105187
Author(s):  
Yawen Li ◽  
Xingwu Duan ◽  
Ya Li ◽  
Yuxiang Li ◽  
Lanlan Zhang
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Southern China ◽  
Interactive Effects ◽  
Effects Of Land Use
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