Agricultural land quality assessment of karst mountain areas is an impor-tant means to protect and manage cultivated land quality of karst mountain areas. With Jingxi County as a case, the data resources included achi...Agricultural land quality assessment of karst mountain areas is an impor-tant means to protect and manage cultivated land quality of karst mountain areas. With Jingxi County as a case, the data resources included achievements of cultivat-ed land grade, achievements of second land investigation, investigation of local con-ditions and the other data resources. With the overlay tool of MapGIS, attribute data of evaluation index were obtained, which can reflect agricultural land＇ characteris-tics, and agricultural land quality scores were calculated and land quality was grad-ed using the model of comprehensive evaluation of multiple factors to make further analysis on characteristics and spatial distribution. The results showed that used agricultural land is dominated by middle and high-grade lands in Jingxi County mainly, representing 68.58% of Jingxi County’s agricultural lands. On the other hand, the quality of paddy land is general y higher than that of dry land, and quality of agricultural land showed higher in middle and eastern Jingxi, and lower in north-western region, which provides references for national land management.展开更多
Accurate and up-to-date land cover data are important for climate-change modeling. Quality assessment is becoming critical, as many satellite-based land cover products of differing scales have been released to meet th...Accurate and up-to-date land cover data are important for climate-change modeling. Quality assessment is becoming critical, as many satellite-based land cover products of differing scales have been released to meet the needs of scientific studies. In this study, the authors assessed the Moderate Resolution Imaging Spectroradiometer(MODIS) land cover products by analyzing the probability of interannual change from 2001 to 2012. The authors found that, cumulatively, 43.0% of MODIS land cover had changed over China from 2001 to 2012 at least once. Of this percentage, 12.1% was considered unreasonable change, 6.1% was considered reasonable change, and areas of confusion accounted for about 24.8%, giving rise to great uncertainty in the products. MODIS Collection 51 products clearly have less uncertainty than the Collection 5 products. Areas of reasonable change occurred in transition zones of ecological, biophysical, and climate gradients, while areas of unreasonable change appeared in heterogeneous landscapes. The misclassifications at three spatial scales of horizontal grids used in regional climate models occurred largely in the heterogeneous landscapes, and the areal percentage of misclassification decreased with larger horizontal grid spacing. In addition, the misclassifications in MODIS products often occurred among specific classes, which are geographically, ecologically, and spectrally similar, with low discriminative spectral-temporal signals. The effect of classification uncertainty should be made known, and further improvements are still needed for application in regional climate models. The authors' findings have important implications for better understanding the uncertainties of MODIS land cover products, and for improving the land surface parameterization for regional climate models.展开更多
Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequen...Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.展开更多
A total of 107 soil samples were taken from the city of Qingdao,Shandong Province,China.Soil water retention data at 2.5,6,10,33,100,300,and 1 500 kPa matric potentials were measured using a pressure membrane apparatu...A total of 107 soil samples were taken from the city of Qingdao,Shandong Province,China.Soil water retention data at 2.5,6,10,33,100,300,and 1 500 kPa matric potentials were measured using a pressure membrane apparatus.Multiple linear regression (MLR) was used to develop pedotransfer functions (PTFs) for single point estimation and van Genuchten parameter estimation based on readily measurable soil properties,i.e.,MLR-based point (MLRP) PTF and MLR-based parametric (MLRV) PTF.The double cross-validation method was used to evaluate the accuracy of PTF estimates and the stability of the PTFs developed in this study.The performance of MLRP and MLRV PTFs in estimating water contents at matric potentials of 10,33,and 1 500 kPa was compared with that of two existing PTFs,the Rawls PTF and the Vereecken PTF.In addition,geostatistical analyses were conducted to assess the capabilities of these PTFs in describing the spatial variability of soil water retention characteristics.Results showed that among all PTFs only the Vereecken PTF failed to accurately estimate water retention characteristics.Although the MLRP PTF can be used to predict retention characteristics through traditional statistical analyses,it failed to describe the spatial variability of soil water retention characteristics.Although the MLRV and Rawls PTFs failed to describe the spatial variability of water contents at a matric potential of 10 kPa,they can be used to quantify the spatial variability of water contents at matric potentials of 33 and 1 500 kPa.展开更多
基金Supported by Supplemented Project of Guangxi Zhuang Autonomous Region Agricultural Land Quality Grade Achievements(GXKLJ20133073-E)~~
文摘Agricultural land quality assessment of karst mountain areas is an impor-tant means to protect and manage cultivated land quality of karst mountain areas. With Jingxi County as a case, the data resources included achievements of cultivat-ed land grade, achievements of second land investigation, investigation of local con-ditions and the other data resources. With the overlay tool of MapGIS, attribute data of evaluation index were obtained, which can reflect agricultural land＇ characteris-tics, and agricultural land quality scores were calculated and land quality was grad-ed using the model of comprehensive evaluation of multiple factors to make further analysis on characteristics and spatial distribution. The results showed that used agricultural land is dominated by middle and high-grade lands in Jingxi County mainly, representing 68.58% of Jingxi County’s agricultural lands. On the other hand, the quality of paddy land is general y higher than that of dry land, and quality of agricultural land showed higher in middle and eastern Jingxi, and lower in north-western region, which provides references for national land management.
基金supported by the National Basic Research Program of China (Grant No. 2012CB956202)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05090201)
文摘Accurate and up-to-date land cover data are important for climate-change modeling. Quality assessment is becoming critical, as many satellite-based land cover products of differing scales have been released to meet the needs of scientific studies. In this study, the authors assessed the Moderate Resolution Imaging Spectroradiometer(MODIS) land cover products by analyzing the probability of interannual change from 2001 to 2012. The authors found that, cumulatively, 43.0% of MODIS land cover had changed over China from 2001 to 2012 at least once. Of this percentage, 12.1% was considered unreasonable change, 6.1% was considered reasonable change, and areas of confusion accounted for about 24.8%, giving rise to great uncertainty in the products. MODIS Collection 51 products clearly have less uncertainty than the Collection 5 products. Areas of reasonable change occurred in transition zones of ecological, biophysical, and climate gradients, while areas of unreasonable change appeared in heterogeneous landscapes. The misclassifications at three spatial scales of horizontal grids used in regional climate models occurred largely in the heterogeneous landscapes, and the areal percentage of misclassification decreased with larger horizontal grid spacing. In addition, the misclassifications in MODIS products often occurred among specific classes, which are geographically, ecologically, and spectrally similar, with low discriminative spectral-temporal signals. The effect of classification uncertainty should be made known, and further improvements are still needed for application in regional climate models. The authors' findings have important implications for better understanding the uncertainties of MODIS land cover products, and for improving the land surface parameterization for regional climate models.
文摘Sequential chemical extraction procedure has been widely used to partition particulate trace metals into various fractions and to describe the distribution and the statue of trace metals in geo environment. One sequential chemical extraction procedure was employed here to partition various fractions of Mn in soils. The experiment was designed with quality controlling concept in order to show sampling and analytical error. Experimental results obtained on duplicate analysis of all soil samples demonstrated that the precision was less than 10%(at 95%confidence level). The accuracy was estimated by comparing the accepted total concentration of Mn in standard reference materials (SRMs) with the measured sum of the individual fractions. The recovery of Mn from SRM1 and SRM2 was 94.1%and 98.4%, respectively. The detection limit, accuracy and precision of the sequential chemical extraction procedure were discussed in detailed. All the results suggest that the trueness of the analytical method is satisfactory.
基金Supported by the National Natural Science Foundation of China (Nos. 40771095,40725010,and 41030746)the Water Conservancy Science & Technology Foundation of Qingdao City,China (No. 2006-003)
文摘A total of 107 soil samples were taken from the city of Qingdao,Shandong Province,China.Soil water retention data at 2.5,6,10,33,100,300,and 1 500 kPa matric potentials were measured using a pressure membrane apparatus.Multiple linear regression (MLR) was used to develop pedotransfer functions (PTFs) for single point estimation and van Genuchten parameter estimation based on readily measurable soil properties,i.e.,MLR-based point (MLRP) PTF and MLR-based parametric (MLRV) PTF.The double cross-validation method was used to evaluate the accuracy of PTF estimates and the stability of the PTFs developed in this study.The performance of MLRP and MLRV PTFs in estimating water contents at matric potentials of 10,33,and 1 500 kPa was compared with that of two existing PTFs,the Rawls PTF and the Vereecken PTF.In addition,geostatistical analyses were conducted to assess the capabilities of these PTFs in describing the spatial variability of soil water retention characteristics.Results showed that among all PTFs only the Vereecken PTF failed to accurately estimate water retention characteristics.Although the MLRP PTF can be used to predict retention characteristics through traditional statistical analyses,it failed to describe the spatial variability of soil water retention characteristics.Although the MLRV and Rawls PTFs failed to describe the spatial variability of water contents at a matric potential of 10 kPa,they can be used to quantify the spatial variability of water contents at matric potentials of 33 and 1 500 kPa.
