Book Reviews: World Food; Production and Use. Edited by Alfred R. Conklin,Jr. and Thomas C. Stilwell     

Rattan Lal 《洁净——土壤、空气、水》2008,36(2):141-141

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Assessing spatial variability in soil characteristics with geographically weighted principal components analysis   总被引：1，自引：0，他引：1  

Sandeep?KumarEmail author  Rattan?Lal  Christopher?D.?Lloyd 《Computational Geosciences》2012,16(3):827-835

Dimensionality reduction methods such as principal components analysis (PCA) provide a means of identifying trends in soil characteristics which may be represented by a wide range of variables. However, these characteristics may be highly spatially variable and so the results from PCA represent, in some sense, an “average” of locally distinct characteristics. One approach to account for these local differences is to introduce a geographical weighting scheme into the PCA process. In this paper, such an approach is assessed in the exploration of soil characteristics in the state of Pennsylvania, USA. Data from 878 georeferenced soil profiles which include different soil parameters (n = 12) were extracted from the National Soil Survey Center database. Where data are parts of compositions (e.g., percentages of sand, silt, and clay), analysis using raw data is not appropriate and such data were transformed using log ratios (specifically, balances). Single variables (i.e., those which are not parts of compositions) were logged. The first two principal components explain over 50% of the variance. The mapped values suggest marked spatial variation in soil characteristics, but it is not possible to assess which of these variables explain most variation in particular regions from the simple maps of raw variables. Geographically weighted PCA (GWPCA) provides additional information which is obscured by PCA, and it also provides a set of component scores and loadings at all data locations. The soil variable with the largest loading at most locations of Pennsylvania is the logged base saturation (BSln), and this supports the findings of the conventional PCA analysis. While BSln loads most highly in most of the eastern third, the middle and the south west of the state, the northwest is less spatially consistent in terms of the variables which explain most variation. For GWPC 1, the variable with the second largest loading at most locations (i.e., primarily the south and west) is CEC.B1 (the log ratio of Ca, Mg, and Na to K and EXACID), while CEC.B2 (the log ratio of Ca and Mg to Na), pHln (logged pH) and BSln dominate in other areas. The GWPCA results suggest that there is marked spatial variation in multivariate soil characteristics across Pennsylvania state and that results from standard PCA obscure this considerable variation.  相似文献   

Erosional effects on terrestrial resources over the last millennium in Reykjanes, southwest Iceland     

Guðrún Gísladóttir  Egill Erlendsson  Rattan Lal 《Quaternary Research》2010,73(1):20-32

The study presents the effect of soil erosion on vegetation, soil accumulation (SA), SA rate (SAR), soil quality, soil mass, and the soil organic carbon (SOC) pool in Brown Andosols and Histosols in a 24-km² area in southwest Iceland. Undisturbed prehistoric soils were distinguished from disturbed historic soils using tephrochronology. Soil erosion has been severe during historic time (last 1135 yr), resulting in the increase of the soil mass deposited in soils covered by vegetation by a factor of 7.3-9.2 and net loss of soil in unvegetated areas. The SAR correlated positively with SOC sequestration. SOC is easily transported and, given the extensive accumulation of soil, the net effect of burial and subsequent reduction in decomposition is to increase SOC storage. Nevertheless, the increased accumulation and soil depletion has decreased soil quality, including the SOC, and reduced soil resistance to erosion with the depleted SOC contributing to enrichment of atmospheric CO₂. The initial terrestrial disturbance was triggered by anthropogenic land use during the Medieval Warm Period, followed by volcanic activity approximately three centuries later. The combination of harsh climate during the Little Ice Age and drastic anthropogenic perturbations has led to land degradation at a catastrophic scale.  相似文献   

Circular Polarization Characteristics of South Polar Lunar Craters using Chandrayaan-1 Mini-SAR and LRO Mini-RF     

Om Prakash Narayan Calla  Shubhra Mathur  Monika Jangid  Kishan Lal Gadri 《Earth, Moon, and Planets》2015,115(1-4):83-100

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Assessing the utility of 210Pb geochronology for estimating sediment accumulation rates on river floodplains in Fiji     

James P. Terry  Rajeev Lal  Sitaram Garimella 《Singapore journal of tropical geography》2011,32(1):102-114

Low‐energy gamma ray spectroscopy has been employed to estimate floodplain sedimentation rates using measurements of ²¹⁰Pb in floodplain alluvium. The utility of the technique is assessed through the analysis of excess (unsupported) ²¹⁰Pb profiles in three sediment cores taken from the floodplain of the Labasa River on Vanua Levu in northern Fiji. A low‐energy germanium spectrometer (LEGe) was used for the nondestructive determination of excess ²¹⁰Pb in a region cultivated intensively with sugarcane. Measured average historical (c. 25 years) vertical accretion rates are between 2.2 and 4.4 cm yr^?1. The findings are broadly comparable with published sedimentation rates from analyses of radionuclide profiles elsewhere in the tropical South Pacific Islands, but the rates are higher than those measured previously at the same Labasa River sites using ¹³⁷Cs profiles. Accelerated soil erosion owing to cane burning and land tillage seems to be largely responsible for sediment production, although flood‐related effects such as channel accretion by coarse bedload and the emplacement of large organic debris also influence floodplain sedimentation. However, application of the ²¹⁰Pb technique in Fiji (and perhaps neighbouring island countries) is found to have serious drawbacks compared to the more robust ¹³⁷Cs method, owing principally to the low ²¹⁰Pb concentrations in the sandy alluvial sediment tested.  相似文献   

Geology,structural and exhumation history of the Higher Himalayan Crystallines in Kumaon Himalaya,India     

R. C. Patel  Vikas Adlakha  Paramjeet Singh  Yogesh Kumar  Nand Lal 《Journal of the Geological Society of India》2011,77(1):47-72

The crystallines in the Kumaon Himalaya, India are studied along Goriganga, Darma and Kaliganga valleys and found to be composed of two high-grade metamorphic gneiss sheets i.e. the Higher Himalayan Crystalline (HHC) and Lesser Himalayan Crystalline (LHC) zones. These were tectonically extruded as a consequence of the southward directed propagation of crustal deformation in the Indian plate margin. The HHC and its cover rocks i.e. the Tethyan Sedimentary Zone (TSZ) are exposed through tectonic zones within the hinterland of Kumaon Himalaya. The HHC records history of at least one episode of pre-Himalayan deformation (D₁), three episodes of Himalayan deformation (D₂, D₃, D₄). The rocks of the HHC in Kumaon Himalaya are thoroughly transposed by D₂ deformation into NW-SE trending S_m (S₁+S₂). The extent of transposition and a well-developed NE-plunging L₂ lineation indicate intense strain during D₂ throughout the studied portion of the HHC. Ductile flow continued, resulting in rotation of F₁ and F₂ folds due NE-direction and NW-SE plunging F₃ folds within the HHC. The over thickened crystalline was finally, superimposed by late-to-post collisional brittle-ductile deformation (D₄) and exposed the rocks to rapid erosion.  相似文献   

美国俄亥俄州土壤有机碳密度空间分布(英文)   总被引：2，自引：1，他引：1  

Sandeep KUMAR  Rattan LAL  Desheng LIU  Rashid RAFIQ 《地理学报(英文版)》2013,23(2):280-296

Historical database of National Soil Survey Center containing 1424 geo-referenced soil profiles was used in this study for estimating the organic carbon(SOC) for the soils of Ohio,USA.Specific objective of the study was to estimate the spatial distribution of SOC density(C stock per unit area) to 1.0-m depth for soils of Ohio using geographically weighted regression(GWR),and compare the results with that obtained from multiple linear regression(MLR).About 80% of the analytical data were used for calibration and 20% for validation.A total of 20 variables including terrain attributes,climate data,bedrock geology,and land use data were used for mapping the SOC density.Results showed that the GWR provided better estimations with the lowest(3.81 kg m 2) root mean square error(RMSE) than MLR approach.Total estimated SOC pool for soils in Ohio ranged from 727 to 742 Tg.This study demonstrates that,the local spatial statistical technique,the GWR can perform better in capturing the spatial distribution of SOC across the study region as compared to other global spatial statistical techniques such as MLR.Thus,GWR enhances the accuracy for mapping SOC density.  相似文献   

Distributions of O3, CO and NMHCs over the rural sites in central India     

S. Lal  L. K. Sahu  S. Venkataramani  T. A. Rajesh  K. S. Modh 《Journal of Atmospheric Chemistry》2008,61(1):73-84

The surface level measurements of O₃, CO, CH₄ and light NMHCs were made at eight different rural sites in the central part of India during February, 2004. The online analyzer was used for in-situ measurement of O₃ while air samples were collected for the analyses of CO, CH₄ and NMHCs using the gas chromatography techniques. The average mixing ratios of O₃, which were in the range of 60–90 ppbv, are significantly higher compared to the typical values reported for urban sites of India. The increase rates of O₃ in the forenoon hours were estimated to be in the range of about 8.8–10 ppbv h⁻¹. The slopes of ∆O₃/∆CO, which is an indicator of the efficiency of photochemical production, were in the range of 0.24–0.33 ppbv ppbv⁻¹. However, levels of primary pollutants e.g., NMHCs, CO, etc. at these sites were much lower than urban sites, but higher compared to previously observed values surrounding marine region of India. The estimated ratios of NMHCs and CO indicate fossil fuel combustion process as the dominant source of primary pollutants in this corridor.  相似文献   

Emission characteristic of ozone related trace gases at a semi-urban site in the Indo-Gangetic plain using inter-correlations     

S. Lal  L. K. Sahu  S. Gupta  S. Srivastava  K. S. Modh  S. Venkataramani  T. A. Rajesh 《Journal of Atmospheric Chemistry》2008,60(3):189-204

Measurements of surface O₃, CO, NO_x and light NMHCs were made during December 2004 at Hissar, a semi-urban site in the state of Haryana in north-west region of the Indo-Gangetic Plain (IGP). The night-time O₃ values were higher when levels of CO, NO and NO₂ were lower but almost zero values were observed during the episodes of elevated mixing ratios of CO (above 2000 ppbv) and NO_x (above 50 ppbv). Slopes derived from linear fits of O₃ versus CO and O₃ versus NO_x scatter plots were also negative. However, elevated levels of O₃ were observed when CO and NO_x were in the range of 200–300 ppbv and 20–30 ppbv, respectively. Slope of CO-NO_x of about 33 ppbv/ppbv is much larger than that observed in the US and Europe indicating significant impact of incomplete combustion processes emitting higher CO and lesser NO_x. Correlations and ratios of these trace gases including NMHCs show dominance of recently emitted pollutants mostly from biomass burning at this site.  相似文献   

Very high-resolution climate simulation over Fiji using a global variable-resolution model     

Murari Lal  John L. McGregor  Kim C. Nguyen 《Climate Dynamics》2008,30(2-3):293-305

A high-resolution climate model simulation has been performed for the first time for Fiji’s climatology. The simulation involved a numerical experiment for a 10-year period (1975–1984), and was conducted at a horizontal resolution of 8 km in a stretched-grid configuration, which is currently the highest resolution at which a global climate model has been applied for regional climatological simulations. Analysis of model-generated data demonstrates a fairly good skill of the CSIRO Conformal-Cubic Atmospheric Model (C-CAM) in the simulation of the annual cycles of maximum and minimum temperatures and rainfall at selected locations in Fiji. The model has also successfully reproduced the pattern of maximum and minimum surface air temperatures between the western and central divisions of Fiji. Model simulation of spatial and temporal distribution of monthly total rainfall (10-year mean) over the main island of Viti Levu in Fiji shows that it reproduces the observed intraseasonal and interannual variability; the influence of the El Niño phenomena has also been captured well in the model-simulated rainfall.  相似文献