Soil salinization is one of the most common land degradation processes. In this study, spectral measurements of saline soil samples collected from the Yellow River Delta region of China were conducted in laboratory an...Soil salinization is one of the most common land degradation processes. In this study, spectral measurements of saline soil samples collected from the Yellow River Delta region of China were conducted in laboratory and hyperspectral data were acquired from an EO-1 Hyperion sensor to quantitatively map soil salinity in the region. A soil salinity spectral index (SSI) was constructed from continuum-removed reflectance (CR-reflectance) at 2052 and 2203 nm, to analyze the spectral absorption features of the salt-affected soils. There existed a strong correlation (r = 0.91) between the SSI and soil salt content (SSC). Then, a model for estimation of SSC with SSI was established using univariate regression and validation of the model yielded a root mean square error (RMSE) of 0.986 and an R2 of 0.873. The model was applied to a Hyperion reflectance image on a pixel-by-pixel basis and the resulting quantitative salinity map was validated successfully with RMSE = 1.921 and R2 = 0.627. These suggested that the satellite hyperspectral data had the potential for predicting SSC in a large area.展开更多
The balance,accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper,based on long-term observations to the soil organ...The balance,accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper,based on long-term observations to the soil organic matter,input and standing biomass of litter and coarse woody debris,and dissolved organic carbon carried in the hydrological process of subtropical climax forest ecosystem—monsoon evergreen broad-leaved forest,and its two successional forests of natural restoration—coniferous and broad-leaved mixed forest and Pinus massoniana forest,as well as data of root biomass obtained once every five years and respiration measurement of soil,litter and coarse woody debris respiration for 1 year.The major results include:the belowground carbon pools of monsoon evergreen broad-leaved forest,coniferous and broad-leaved mixed forest,and Pinus massoniana forest are 23191±2538 g·m?2,16889±1936 g·m?2 and 12680±1854 g·m?2,respec-tively,in 2002.Mean annual carbon accumulation rates of the three forest types during the 24a from 1978 to 2002 are 383±97 g·m?2·a?1,193±85 g·m?2·a?1 and 213±86 g·m?2·a?1,respectively.The belowground carbon pools in the three forest types keep increasing during the observation period,suggesting that belowground carbon pools are carbon sinks to the atmosphere.There are seasonal variations,namely,they are strong carbon sources from April to June,weak carbon sources from July to September;while they are strong carbon sinks from October to November,weak carbon sinks from December to March.展开更多
Quantitative estimation of vegetation water content(VWC)using optical remote sensing techniques is helpful in forest fire as-sessment,agricultural drought monitoring and crop yield estimation.This paper reviews the re...Quantitative estimation of vegetation water content(VWC)using optical remote sensing techniques is helpful in forest fire as-sessment,agricultural drought monitoring and crop yield estimation.This paper reviews the research advances of VWC retrieval using spectral reflectance,spectral water index and radiative transfer model(RTM)methods.It also evaluates the reli-ability of VWC estimation using spectral water index from the observation data and the RTM.Focusing on two main definitions of VWC-the fuel moisture content(FMC)and the equivalent water thickness(EWT),the retrieval accuracies of FMC and EWT using vegetation water indices are analyzed.Moreover,the measured information and the dataset are used to estimate VWC,the results show there are significant correlations among three kinds of vegetation water indices(i.e.,WSI,NDⅡ,NDWI1640,WI/NDVI)and canopy FMC of winter wheat(n=45).Finally,the future development directions of VWC detection based on optical remote sensing techniques are also summarized.展开更多
基金Supported by the Open Foundation of State Key Laboratory of Remote Sensing Science,the Institute of Remote Sensing Applications of the Chinese Academy of Sciences and Beijing Normal University (No.2009KFJJ002)the National Natural Science Foundation of China (No.30590370)
文摘Soil salinization is one of the most common land degradation processes. In this study, spectral measurements of saline soil samples collected from the Yellow River Delta region of China were conducted in laboratory and hyperspectral data were acquired from an EO-1 Hyperion sensor to quantitatively map soil salinity in the region. A soil salinity spectral index (SSI) was constructed from continuum-removed reflectance (CR-reflectance) at 2052 and 2203 nm, to analyze the spectral absorption features of the salt-affected soils. There existed a strong correlation (r = 0.91) between the SSI and soil salt content (SSC). Then, a model for estimation of SSC with SSI was established using univariate regression and validation of the model yielded a root mean square error (RMSE) of 0.986 and an R2 of 0.873. The model was applied to a Hyperion reflectance image on a pixel-by-pixel basis and the resulting quantitative salinity map was validated successfully with RMSE = 1.921 and R2 = 0.627. These suggested that the satellite hyperspectral data had the potential for predicting SSC in a large area.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KSCX2-SW-120)the National Natural Science Foundation of China(Grant No.30470306).
文摘The balance,accumulation rate and temporal dynamics of belowground carbon in the successional series of monsoon evergreen broadleaved forest are obtained in this paper,based on long-term observations to the soil organic matter,input and standing biomass of litter and coarse woody debris,and dissolved organic carbon carried in the hydrological process of subtropical climax forest ecosystem—monsoon evergreen broad-leaved forest,and its two successional forests of natural restoration—coniferous and broad-leaved mixed forest and Pinus massoniana forest,as well as data of root biomass obtained once every five years and respiration measurement of soil,litter and coarse woody debris respiration for 1 year.The major results include:the belowground carbon pools of monsoon evergreen broad-leaved forest,coniferous and broad-leaved mixed forest,and Pinus massoniana forest are 23191±2538 g·m?2,16889±1936 g·m?2 and 12680±1854 g·m?2,respec-tively,in 2002.Mean annual carbon accumulation rates of the three forest types during the 24a from 1978 to 2002 are 383±97 g·m?2·a?1,193±85 g·m?2·a?1 and 213±86 g·m?2·a?1,respectively.The belowground carbon pools in the three forest types keep increasing during the observation period,suggesting that belowground carbon pools are carbon sinks to the atmosphere.There are seasonal variations,namely,they are strong carbon sources from April to June,weak carbon sources from July to September;while they are strong carbon sinks from October to November,weak carbon sinks from December to March.
基金supported by the National Natural Science Foundation of China(Grant No.40771147)the National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2006AA10Z213)the New Technique Project of CMA(Grant No.CMATG2009MS23)
文摘Quantitative estimation of vegetation water content(VWC)using optical remote sensing techniques is helpful in forest fire as-sessment,agricultural drought monitoring and crop yield estimation.This paper reviews the research advances of VWC retrieval using spectral reflectance,spectral water index and radiative transfer model(RTM)methods.It also evaluates the reli-ability of VWC estimation using spectral water index from the observation data and the RTM.Focusing on two main definitions of VWC-the fuel moisture content(FMC)and the equivalent water thickness(EWT),the retrieval accuracies of FMC and EWT using vegetation water indices are analyzed.Moreover,the measured information and the dataset are used to estimate VWC,the results show there are significant correlations among three kinds of vegetation water indices(i.e.,WSI,NDⅡ,NDWI1640,WI/NDVI)and canopy FMC of winter wheat(n=45).Finally,the future development directions of VWC detection based on optical remote sensing techniques are also summarized.
