Accurate spatial prediction of soil organic carbon(SOC)and soil inorganic carbon(SIC)is vital for land management decisions.This study targets SOC/SIC mapping challenges at the watershed scale in central Iran by addre...Accurate spatial prediction of soil organic carbon(SOC)and soil inorganic carbon(SIC)is vital for land management decisions.This study targets SOC/SIC mapping challenges at the watershed scale in central Iran by addressing environmental heterogeneity through a random forest(RF)model combined with bootstrapping to assess prediction uncertainty.Thirty-eight environmental variables-categorized into climatic,soil physicochemical,topographic,geomorphic,and remote sensing(RS)-based factors-were considered.Variable importance analysis(via)and partial dependence plots(PDP)identified land use,RS indices,and topography as key predictors of SOC.For SIC,soil reflectance(Bands 5 and 7,ETM+),topography,and geomorphic units were most influential.Climatic factors showed minimal impact in the studied semi-arid watershed.The RF model achieved moderate prediction accuracy(SOC:R^(2)=0.43±0.13,nRMSE=0.28;SIC:R^(2)=0.47±0.11,nRMSE=0.37).Via and PDP analyses enhanced model interpretability by clarifying environmental influences on SOC/SIC spatial distribution.展开更多
<p> Understanding the variability of physico-chemical properties of soil along a toposequence is essential for smallholder farming communities. However, these resource constraint farmers in Ghana’s Moist Semi-D...<p> Understanding the variability of physico-chemical properties of soil along a toposequence is essential for smallholder farming communities. However, these resource constraint farmers in Ghana’s Moist Semi-Deciduous Forest (MSDF) zone poorly understand how slope positions affect soil properties. Therefore, soil variability assessment along a toposequence was carried out on Bekwai-Nzima/Oda compound association. From the summit to valley bottom slope positions, soil samples were taken at two depths (0 - 20 and 20 - 50 cm). As shown by the coefficient of variation, topsoil (0 - 20 cm) had the highest variation compared to the subsoil (20 - 50 cm). The variations observed in most soil attributes (clay, silt, pH, CEC, SOC and TN) for the 0 to 20 and 20 to 50 cm depths were between eroded (summit and upper slopes) and depositional (lower slope and valley bottom) zones. The highly variable soil attributes were silt, TN, Av. P, and Av. K. However, bulk density and sand were the least variable irrespective of soil depth or toposequence. Pearson correlation analysis indicated a significant correlation (p < 0.05) between most soil attributes at the 0 - 20 and 20 - 50 cm depths at different slope positions. Principal component (PC) analysis indicated that the first four PCs explained more than 80% and 70% of the total variation for the 0 - 20 and 20 - 50 cm soil depths, respectively. Statistically, our results revealed a significant effect of slope position on soil properties (p < 0.05) and topography influenced soil characteristics and development. Soil pH, sand, silt and clay contents were less affected by slope gradient, which confirms the inherent nature of these highly weathered tropical soils. The findings of this study can serve as a reference for the formulation of soil management strategies for smallholder farm communities. </p>展开更多
Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks ...Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks in different land-use systems and soil types. A total of eighty (80) composite soil samples at two depths (0 - 20 cm and 20 - 50 cm) were sampled from five land use types (Forest, Woodland savannah, Grassland, Fallow and Cropland) for laboratory analyses. Particle size distribution, bulk density, pH, SOC and TN were determined using standard procedures. Results of the study indicated that C and N stocks were significantly lower in croplands (p < 0.05) compared to other land-use systems. There were significant interactions (p < 0.05) within land-use systems, soil types, and soil depth for soil C and N stocks. Acrisol and associated soils had the highest C and N stocks. A strong positive significant correlation (p < 0.05) was observed between C and N stocks with an R<sup>2</sup> value of 0.85 and 0.93 for the 0 - 20 and 20 - 50 cm depth, respectively. Soil C and N stocks in the study area were estimated to be 34.56 kg/m<sup>2</sup> and 4.63 kg/m<sup>2</sup> for soil types and 26.89 kg/m<sup>2</sup> and 3.39 kg/m2 for land use types, respectively for the 0 to 50 cm soil depth. Our findings indicated that the conversion of native forest to arable land has significantly reduced soil C and N stocks in the top 50 cm (0.50 m) soil layer by 50.77% and 47.77%, respectively. Therefore, we conclude that land-use change, soil type, and soil depth influenced soil C and N stocks of land-use systems in the humid savannah agro-ecological zone of Ghana.展开更多
Uncertainties remain as to the ability of certain carbonate rocks to form the red soils covering them. These doubts, which have been the subject of debate for several decades, become real when carbonate rocks are pure...Uncertainties remain as to the ability of certain carbonate rocks to form the red soils covering them. These doubts, which have been the subject of debate for several decades, become real when carbonate rocks are pure and low in insoluble residues. In the carbonate rocks of the Taoudeni basin in Burkina Faso, brown-red to red soils develop, at the top of hillsides and in karstic cavities. No study in the region has yet shown the existence in these carbonate rocks of sufficient insolubles to form soils after decalcification. The objective of this study was therefore to identify and quantify the minerals of carbonate rocks in order to identify the origin of red soils. Petrographic, chemical (XRF) and mineralogical (XRD) investigations on dominant carbonate rocks features in the study area show that the rocks studied are mainly magnesian dolomites (Dolomite > 50% of carbonate minerals and Ca/Mg ratio < 1.5). Non-carbonate residues from detrital and hydrothermal origin, negligible in certain pure dolomites (<2%), are on the other hand significant (>12%) in other dolomitic features. These insoluble silicates formed of quartz, potassium feldspar (orthoclase), clays (talc, phlogopite and kaolinite) and iron oxides constitute the main original material of reddened soils in karstic cavities.展开更多
The ever-increasing human population has resulted in political pressure to increase crop production. Currently, smallholder farmers are expected to be environmentally considerate, adapt to extreme climatic conditions ...The ever-increasing human population has resulted in political pressure to increase crop production. Currently, smallholder farmers are expected to be environmentally considerate, adapt to extreme climatic conditions and deal with financial instability. Despite these recent developments, farmers and their farming activities in these rural environs of developing countries need to improve household food and income security on a sustainable basis. A minimum data set selected from extensive data was used to determine indicators for soil sustainability assessment. This method involved expert opinion and statistical data reduction techniques. The results indicated that SOC, MBC, BS, EC, Spo and sand were the most important variables selected as MDS using PC analysis. Forest and Grassland had a high sustainability index (SI) while Savannah woodland, Fallow and Cropland were rated not sustainable (NS). For Cumulative rating using the total dataset (CR-TDS), Forest had a high sustainability index (HS), Savannah woodland and Grassland were sustainable (S) compared to Fallow and Cropland, which were sustainable with high input (SWHI). Also, for cumulative rating using the minimum dataset (CR-MDS), Forest, Savannah woodland and Grassland had high sustainability (SH) indices compared to Fallow and Cropland, which were considered sustainable with high input (SWHI). Sustainability index (SI) and Cumulative rating (CR) using the total dataset (CR-TDS) had a strong correlation (R<sup>2</sup> = 0.91, p < 0.05) compared to SI versus CR-MDS (R<sup>2</sup> = 0.44, p < 0.05) and CR-TDS versus CR-MDS (R<sup>2</sup> = 0.60, p < 0.05). These methods consider that these management goals dictate soil functions affecting the selection of indicators. Using PCA and variance analysis, silt, clay, EC, SOC, MBC and CEC relating to soil texture and fertility were identified as the most influential (sensitive) indicators for soil sustainability assessment. The selected soil attributes can serve as target indicators for soil fertility restoration, erosion control and management in the Nkoranza district. Therefore, a farm-level sustainability index for small-scale and commercial farms is proposed based on readily available data for the Savannah Transition Agro-ecozone of Ghana.展开更多
Evaluation of prediction models is crucial to achieving valid information on erosion processes and their management choices.WEPP model efficiency in predicting ephemeral gully(EG)erosion was recently tested and compar...Evaluation of prediction models is crucial to achieving valid information on erosion processes and their management choices.WEPP model efficiency in predicting ephemeral gully(EG)erosion was recently tested and compared with both EGEM and empirical models.The models abilities to predict EG erosion were validated using measured estimates at the 6 eroding locations around Mubi area in Northeast Nigeria between April 2008 and October 2009.Each location consisted of 3 watersheds where data on soils,climate,slope,management practices,EG shapes and dimensions were collected.Data on relevant soil properties were collected in the field and then analyzed in laboratory.The mass of soil loss(MSL)predicted by empirical,EGEM and WEPP models were compared with the measured using paired T-test,regression graphs(r^(2)-values),error analysis,and analysis of variance(ANOVA)in a completely ran-domized design.The EG erosion losses varied significantly(P≤0.05)between sites and years.No sig-nificant(P≤0.05)differences were observed between measured and the empirically predicted aggregate MSL.The measured aggregate MSL strongly correlated with those predicted by empirical(r^(2)=0.67),than with EGEM(r^(2)=0.57),and WEPP(r^(2)=0.53)models.Slight over and under-prediction instances against the measured erosion were noted with all the models.The WEPP model was found to slightly over-predict MSL when compared to either the empirical or EGEM model.The prediction quality of the models was generally impressive.Future works should focus more on local inputs such as climate,plants,management,and tillage data for use with WEPP.展开更多
基金The Iranian National Science Foundation(INSF)provided financial support for this research under Project Number 4004169the authors would like to thank Isfahan University of Technology and the University of Isfahan for their valuable contributions.
文摘Accurate spatial prediction of soil organic carbon(SOC)and soil inorganic carbon(SIC)is vital for land management decisions.This study targets SOC/SIC mapping challenges at the watershed scale in central Iran by addressing environmental heterogeneity through a random forest(RF)model combined with bootstrapping to assess prediction uncertainty.Thirty-eight environmental variables-categorized into climatic,soil physicochemical,topographic,geomorphic,and remote sensing(RS)-based factors-were considered.Variable importance analysis(via)and partial dependence plots(PDP)identified land use,RS indices,and topography as key predictors of SOC.For SIC,soil reflectance(Bands 5 and 7,ETM+),topography,and geomorphic units were most influential.Climatic factors showed minimal impact in the studied semi-arid watershed.The RF model achieved moderate prediction accuracy(SOC:R^(2)=0.43±0.13,nRMSE=0.28;SIC:R^(2)=0.47±0.11,nRMSE=0.37).Via and PDP analyses enhanced model interpretability by clarifying environmental influences on SOC/SIC spatial distribution.
文摘<p> Understanding the variability of physico-chemical properties of soil along a toposequence is essential for smallholder farming communities. However, these resource constraint farmers in Ghana’s Moist Semi-Deciduous Forest (MSDF) zone poorly understand how slope positions affect soil properties. Therefore, soil variability assessment along a toposequence was carried out on Bekwai-Nzima/Oda compound association. From the summit to valley bottom slope positions, soil samples were taken at two depths (0 - 20 and 20 - 50 cm). As shown by the coefficient of variation, topsoil (0 - 20 cm) had the highest variation compared to the subsoil (20 - 50 cm). The variations observed in most soil attributes (clay, silt, pH, CEC, SOC and TN) for the 0 to 20 and 20 to 50 cm depths were between eroded (summit and upper slopes) and depositional (lower slope and valley bottom) zones. The highly variable soil attributes were silt, TN, Av. P, and Av. K. However, bulk density and sand were the least variable irrespective of soil depth or toposequence. Pearson correlation analysis indicated a significant correlation (p < 0.05) between most soil attributes at the 0 - 20 and 20 - 50 cm depths at different slope positions. Principal component (PC) analysis indicated that the first four PCs explained more than 80% and 70% of the total variation for the 0 - 20 and 20 - 50 cm soil depths, respectively. Statistically, our results revealed a significant effect of slope position on soil properties (p < 0.05) and topography influenced soil characteristics and development. Soil pH, sand, silt and clay contents were less affected by slope gradient, which confirms the inherent nature of these highly weathered tropical soils. The findings of this study can serve as a reference for the formulation of soil management strategies for smallholder farm communities. </p>
文摘Land-use conversion and unsustainable farming practices are degrading native forest ecosystems of Ghana’s humid savannah agro-ecological zone. This study assessed the impact of land-use change on soil C and N stocks in different land-use systems and soil types. A total of eighty (80) composite soil samples at two depths (0 - 20 cm and 20 - 50 cm) were sampled from five land use types (Forest, Woodland savannah, Grassland, Fallow and Cropland) for laboratory analyses. Particle size distribution, bulk density, pH, SOC and TN were determined using standard procedures. Results of the study indicated that C and N stocks were significantly lower in croplands (p < 0.05) compared to other land-use systems. There were significant interactions (p < 0.05) within land-use systems, soil types, and soil depth for soil C and N stocks. Acrisol and associated soils had the highest C and N stocks. A strong positive significant correlation (p < 0.05) was observed between C and N stocks with an R<sup>2</sup> value of 0.85 and 0.93 for the 0 - 20 and 20 - 50 cm depth, respectively. Soil C and N stocks in the study area were estimated to be 34.56 kg/m<sup>2</sup> and 4.63 kg/m<sup>2</sup> for soil types and 26.89 kg/m<sup>2</sup> and 3.39 kg/m2 for land use types, respectively for the 0 to 50 cm soil depth. Our findings indicated that the conversion of native forest to arable land has significantly reduced soil C and N stocks in the top 50 cm (0.50 m) soil layer by 50.77% and 47.77%, respectively. Therefore, we conclude that land-use change, soil type, and soil depth influenced soil C and N stocks of land-use systems in the humid savannah agro-ecological zone of Ghana.
文摘Uncertainties remain as to the ability of certain carbonate rocks to form the red soils covering them. These doubts, which have been the subject of debate for several decades, become real when carbonate rocks are pure and low in insoluble residues. In the carbonate rocks of the Taoudeni basin in Burkina Faso, brown-red to red soils develop, at the top of hillsides and in karstic cavities. No study in the region has yet shown the existence in these carbonate rocks of sufficient insolubles to form soils after decalcification. The objective of this study was therefore to identify and quantify the minerals of carbonate rocks in order to identify the origin of red soils. Petrographic, chemical (XRF) and mineralogical (XRD) investigations on dominant carbonate rocks features in the study area show that the rocks studied are mainly magnesian dolomites (Dolomite > 50% of carbonate minerals and Ca/Mg ratio < 1.5). Non-carbonate residues from detrital and hydrothermal origin, negligible in certain pure dolomites (<2%), are on the other hand significant (>12%) in other dolomitic features. These insoluble silicates formed of quartz, potassium feldspar (orthoclase), clays (talc, phlogopite and kaolinite) and iron oxides constitute the main original material of reddened soils in karstic cavities.
文摘The ever-increasing human population has resulted in political pressure to increase crop production. Currently, smallholder farmers are expected to be environmentally considerate, adapt to extreme climatic conditions and deal with financial instability. Despite these recent developments, farmers and their farming activities in these rural environs of developing countries need to improve household food and income security on a sustainable basis. A minimum data set selected from extensive data was used to determine indicators for soil sustainability assessment. This method involved expert opinion and statistical data reduction techniques. The results indicated that SOC, MBC, BS, EC, Spo and sand were the most important variables selected as MDS using PC analysis. Forest and Grassland had a high sustainability index (SI) while Savannah woodland, Fallow and Cropland were rated not sustainable (NS). For Cumulative rating using the total dataset (CR-TDS), Forest had a high sustainability index (HS), Savannah woodland and Grassland were sustainable (S) compared to Fallow and Cropland, which were sustainable with high input (SWHI). Also, for cumulative rating using the minimum dataset (CR-MDS), Forest, Savannah woodland and Grassland had high sustainability (SH) indices compared to Fallow and Cropland, which were considered sustainable with high input (SWHI). Sustainability index (SI) and Cumulative rating (CR) using the total dataset (CR-TDS) had a strong correlation (R<sup>2</sup> = 0.91, p < 0.05) compared to SI versus CR-MDS (R<sup>2</sup> = 0.44, p < 0.05) and CR-TDS versus CR-MDS (R<sup>2</sup> = 0.60, p < 0.05). These methods consider that these management goals dictate soil functions affecting the selection of indicators. Using PCA and variance analysis, silt, clay, EC, SOC, MBC and CEC relating to soil texture and fertility were identified as the most influential (sensitive) indicators for soil sustainability assessment. The selected soil attributes can serve as target indicators for soil fertility restoration, erosion control and management in the Nkoranza district. Therefore, a farm-level sustainability index for small-scale and commercial farms is proposed based on readily available data for the Savannah Transition Agro-ecozone of Ghana.
文摘Evaluation of prediction models is crucial to achieving valid information on erosion processes and their management choices.WEPP model efficiency in predicting ephemeral gully(EG)erosion was recently tested and compared with both EGEM and empirical models.The models abilities to predict EG erosion were validated using measured estimates at the 6 eroding locations around Mubi area in Northeast Nigeria between April 2008 and October 2009.Each location consisted of 3 watersheds where data on soils,climate,slope,management practices,EG shapes and dimensions were collected.Data on relevant soil properties were collected in the field and then analyzed in laboratory.The mass of soil loss(MSL)predicted by empirical,EGEM and WEPP models were compared with the measured using paired T-test,regression graphs(r^(2)-values),error analysis,and analysis of variance(ANOVA)in a completely ran-domized design.The EG erosion losses varied significantly(P≤0.05)between sites and years.No sig-nificant(P≤0.05)differences were observed between measured and the empirically predicted aggregate MSL.The measured aggregate MSL strongly correlated with those predicted by empirical(r^(2)=0.67),than with EGEM(r^(2)=0.57),and WEPP(r^(2)=0.53)models.Slight over and under-prediction instances against the measured erosion were noted with all the models.The WEPP model was found to slightly over-predict MSL when compared to either the empirical or EGEM model.The prediction quality of the models was generally impressive.Future works should focus more on local inputs such as climate,plants,management,and tillage data for use with WEPP.
