scholarly journals Multi-predictor mapping of soil organic carbon in the alpine tundra: a case study for the central Ecuadorian páramo

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Johanna Elizabeth Ayala Izurieta ◽  
Carmen Omaira Márquez ◽  
Víctor Julio García ◽  
Carlos Arturo Jara Santillán ◽  
Jorge Marcelo Sisti ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Structure Stability ◽  
Landsat 8 ◽  
Soil Taxonomy ◽  
Slope Length ◽  
Water Storage Capacity ◽  
Geological Unit ◽  
Average Annual Temperature

Abstract Background Soil organic carbon (SOC) affects essential biological, biochemical, and physical soil functions such as nutrient cycling, water retention, water distribution, and soil structure stability. The Andean páramo known as such a high carbon and water storage capacity ecosystem is a complex, heterogeneous and remote ecosystem complicating field studies to collect SOC data. Here, we propose a multi-predictor remote quantification of SOC using Random Forest Regression to map SOC stock in the herbaceous páramo of the Chimborazo province, Ecuador. Results Spectral indices derived from the Landsat-8 (L8) sensors, OLI and TIRS, topographic, geological, soil taxonomy and climate variables were used in combination with 500 in situ SOC sampling data for training and calibrating a suitable predictive SOC model. The final predictive model selected uses nine predictors with a RMSE of 1.72% and a R2 of 0.82 for SOC expressed in weight %, a RMSE of 25.8 Mg/ha and a R2 of 0.77 for the model in units of Mg/ha. Satellite-derived indices such as VARIG, SLP, NDVI, NDWI, SAVI, EVI2, WDRVI, NDSI, NDMI, NBR and NBR2 were not found to be strong SOC predictors. Relevant predictors instead were in order of importance: geological unit, soil taxonomy, precipitation, elevation, orientation, slope length and steepness (LS Factor), Bare Soil Index (BI), average annual temperature and TOA Brightness Temperature. Conclusions Variables such as the BI index derived from satellite images and the LS factor from the DEM increase the SOC mapping accuracy. The mapping results show that over 57% of the study area contains high concentrations of SOC, between 150 and 205 Mg/ha, positioning the herbaceous páramo as an ecosystem of global importance. The results obtained with this study can be used to extent the SOC mapping in the whole herbaceous ecosystem of Ecuador offering an efficient and accurate methodology without the need for intensive in situ sampling.

Conservation tillage positively influences soil organic carbon through earthworm excrement physical structure stability in a Chinese Mollisoil

2020 ◽  
Author(s):  
Xuewen Chen ◽  
Aizhen Liang ◽  
Donghui Wu ◽  
Shuxia Jia ◽  
Yan Zhang
Keyword(s):  
Tensile Strength ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Surface Area ◽  
Conservation Tillage ◽  
Water Repellency ◽  
Physical Structure ◽  
Structure Stability ◽  
Pore Surface ◽  
Pore Surface Area

<p>Identifying the relationship between earthworm activity and soil organic carbon is vital for both planning and performing farming operations. Numerous studies have emphasized that earthworms affect soil organic carbon greatly. However, the extent of this effect is still somewhat vague, and very little is known, not to mention the role of earthworm excrement. The objective for this study is to determine the effect of earthworm excrement on soil organic carbon following different tillage practices based on physical structure stability parameters. Both no tillage (NT) and ridge tillage (RT) led to significant total pore surface area, permeability, fluid conductivity, water resistance index and tensile strength increment than moldboard plow (MP) (p<0.05), whereas water repellency significant decrement (p<0.05). Similar to soil organic carbon, NT and RT significantly increase organic carbon in earthworm excrement than MP (p<0.05). A significant positive correlation (p<0.05) was found between organic carbon in earthworm excrement and total pore surface area, water repellency, tensile strength, respectively. This finding demonstrates that conservation tillage increase organic carbon in earthworm excrement through physical structure stability namely aggregation effect of earthworm excrement on soil water movement and gas diffusion, potentially important for the soil organic carbon increment.</p>

scholarly journals Incorporation of globally available datasets into the roving cosmic-ray neutron probe method for estimating field-scale soil water content

2016 ◽  
Vol 20 (9) ◽  
pp. 3859-3872 ◽  
Author(s):  
William Alexander Avery ◽  
Catherine Finkenbiner ◽  
Trenton E. Franz ◽  
Tiejun Wang ◽  
Anthony L. Nguy-Robertson ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Water Content ◽  
Bulk Density ◽  
Soil Water Content ◽  
Cosmic Ray ◽  
Soil Bulk Density ◽  
Local Soil ◽  
Calibration Parameters

Abstract. The need for accurate, real-time, reliable, and multi-scale soil water content (SWC) monitoring is critical for a multitude of scientific disciplines trying to understand and predict the Earth's terrestrial energy, water, and nutrient cycles. One promising technique to help meet this demand is fixed and roving cosmic-ray neutron probes (CRNPs). However, the relationship between observed low-energy neutrons and SWC is affected by local soil and vegetation calibration parameters. This effect may be accounted for by a calibration equation based on local soil type and the amount of vegetation. However, determining the calibration parameters for this equation is labor- and time-intensive, thus limiting the full potential of the roving CRNP in large surveys and long transects, or its use in novel environments. In this work, our objective is to develop and test the accuracy of globally available datasets (clay weight percent, soil bulk density, and soil organic carbon) to support the operability of the roving CRNP. Here, we develop a 1 km product of soil lattice water over the continental United States (CONUS) using a database of in situ calibration samples and globally available soil taxonomy and soil texture data. We then test the accuracy of the global dataset in the CONUS using comparisons from 61 in situ samples of clay percent (RMSE  =  5.45 wt %, R2  =  0.68), soil bulk density (RMSE  =  0.173 g cm−3, R2  =  0.203), and soil organic carbon (RMSE  =  1.47 wt %, R2  =  0.175). Next, we conduct an uncertainty analysis of the global soil calibration parameters using a Monte Carlo error propagation analysis (maximum RMSE  ∼  0.035 cm3 cm−3 at a SWC  =  0.40 cm3 cm−3). In terms of vegetation, fast-growing crops (i.e., maize and soybeans), grasslands, and forests contribute to the CRNP signal primarily through the water within their biomass and this signal must be accounted for accurate estimation of SWC. We estimated the biomass water signal by using a vegetation index derived from MODIS imagery as a proxy for standing wet biomass (RMSE  <  1 kg m−2). Lastly, we make recommendations on the design and validation of future roving CRNP experiments.

scholarly journals Land Use/Land Cover (LU/LC) Changes and its impact on Soil Organic Carbon Stock in Killiar River Basin, Kerala, India: A Geospatial Approach

2021 ◽  
Vol 16 (3) ◽  
pp. 662-664
Author(s):  
Sabu Joseph ◽  
Rahul R ◽  
Sukanya S
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Soil Organic Carbon ◽  
Land Cover ◽  
River Basin ◽  
Carbon Stock ◽  
Landsat 8 ◽  
Soil Organic Carbon Stock ◽  
The Impact ◽  
Organic Carbon Stock

The changes in the pattern of land use and land cover (LU/LC) have remarkable consequences on ecosystem functioning and natural resources dynamics. The present study analyzes the spatial pattern of LU/LC change detection along the Killiar River Basin (KRB), a major tributary of Karamana river in Thiruvananthapuram district, Kerala (India), over a period of 64 years (1957-2021) through Remote Sensing and GIS approach. The rationale of the study is to identify and classify LU/LC changes in KRB using the Survey of India (SOI) toposheet (1:50,000) of 1957, LISS-III imagery of 2005, Landsat 8 OLI & TIRS imagery of 2021 and further to scrutinize the impact of LU/LC conversion on Soil Organic Carbon stock in the study area. Five major LU/LC classes, viz., agriculture land, built-up, forest, wasteland and water bodies were characterized from available data. Within the study period, built-up area and wastelands showed a substantial increase of 51.51% and 15.67% respectively. Thus, the general trend followed is the increase in built-up and wastelands area which results in the decrease of all other LU/LC classes. Based on IPCC guidelines, total soil organic carbon (SOC) stock of different land-use types was estimated and was 1292.72 Mt C in 1957, 562.65 Mt C in 2005 and it reduced to 152.86 Mt C in 2021. This decrease is mainly due to various anthropogenic activities, mainly built-up activities. This conversion for built-up is at par with the rising population, and over-exploitation of natural and agricultural resources is increasing every year.

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