【Title】【Author】This study was conducted to determine the changes in the soil carbon stocks as influenced by land use in a humid zone of Deylaman district （10,876 ha）, a mountainous region of northern Iran. For t...【Title】【Author】This study was conducted to determine the changes in the soil carbon stocks as influenced by land use in a humid zone of Deylaman district （10,876 ha）, a mountainous region of northern Iran. For this, land use maps were produced from TM and ETM＋ images for 1985, 2000 and 2010 years; and this was supplemented by field measurement of soil carbon in 2010. The results showed that the mean soil organic carbon （SOC） density was 6.7±1.8 kg C m-2, 5.2±3.4 kg C m-2 and 3.2±1.8 kg C m-2 for 0-20 cm soil layer and 4.8±1.9 kg C m-2, 3.1±2 kg C m-2 and 2.7±1.8 kg C m-2 for 20-40 cm soil layer in forest, rangeland and cultivated land, respectively. During the past 25 years, 14.4% of the forest area had been converted to rangeland; and 28.4% of rangelands had been converted to cultivated land. According to the historical land use changes in the study area, the highest loss of SOC stocks resulted from the conversion of the forest to rangeland （0.45×104 Mg C in 0-40 cm depth layer）; and the conversion of rangeland to cultivated land （0.37×104 Mg C in 0-40 cm）, which typically led to the loss of soil carbon in the area studied. The knowledge on the historical land use changes and its influence on overall SOC stocks could be helpful for making management decision for farmers and policy managers in the future, for enhancing the potential of C sequestration in northern Iran.展开更多
The Three-River Headwaters(TRH), which is the source area of Yangtze River, Yellow River and Lancang River, is vulnerable and sensitive, and its alpine ecosystem is considered an important barrier for China’s ecologi...The Three-River Headwaters(TRH), which is the source area of Yangtze River, Yellow River and Lancang River, is vulnerable and sensitive, and its alpine ecosystem is considered an important barrier for China’s ecological security. Understanding the impact of climate changes is essential for determining suitable measures for ecological environmental protection and restoration against the background of global climatic changes. However, different explanations of the interannual trends in complex alpine ecosystems have been proposed due to limited availability of reliable data and the uncertainty of the model itself. In this study, the remote sensing-process coupled model(GLOPEM-CEVSA) was used to estimate the net primary productivity(NPP) of vegetation in the TRH region from 2000 to 2012. The estimated NPP significantly and linearly correlated with the above-ground biomass sampled in the field(the multiple correlative coefficient R2 = 0.45, significant level P < 0.01) and showed better performance than the MODIS productivity product, i.e. MOD17 A3,(R2 = 0.21). The climate of TRH became warmer and wetter during 1990-2012, and the years 2000 to 2012 were warmer and wetter than the years1990–2000. Responding to the warmer and wetter climate, the NPP had an increasing trend of 13.7 g m^–2(10 yr)^–1 with a statistical confidence of 86%(P = 0.14). Among the three basins, the NPP of the Yellow River basin increased at the fastest rate of 17.44 g m^–2(10 yr)^–1(P = 0.158), followed by the Yangtze River basin, and the Lancang River, which was the slowest with a rate of 12.2 g m^–2(10 yr)^–1 and a statistical confidence level of only 67%. A multivariate linear regression with temperature and precipitation as the independent variables and NPP as the dependent variable at the pixel level was used to analyze the impacts of climatic changes on the trend of NPP. Both temperature and precipitation can explain the interannual variability of 83% in grassland NPP in the whole region, and can explain high, medium and low coverage of 78%, 84% and 83%, respectively, for grassland in the whole region. The results indicate that climate changes play a dominant role in the interannual trend of vegetation productivity in the alpine ecosystems on Qinghai-Tibetan Plateau. This has important implications for the formulation of ecological protection and restoration policies for vulnerable ecosystems against the background of global climate changes.展开更多
Shifting sands are one of the main contributors to desertification in China.This paper briefly reviews the measures and techniques which are used to protect traffic lines by stabilizing and fixing sands in the desert ...Shifting sands are one of the main contributors to desertification in China.This paper briefly reviews the measures and techniques which are used to protect traffic lines by stabilizing and fixing sands in the desert and desertification-affected arid and semi-arid areas in north China.We introduce the types and features of these measures and techniques,including mechanical,chemical,and biological measures,and outline how they have been applied in different areas and in different traffic lines over the past six decades,from 1950 s to 2010 s,taking the Baotou-Lanzhou railway,the Qinghai-Tibet railway,and the Tarim Desert highway as examples Mechanical measures such as erecting sand-retaining wind walls and placing straw checkerboards have proved to be very efficient for stabilizing shifting sands and protecting traffic lines that pass through the desert areas.Chemical measures are not widely used in the current sand fixing systems because of their high cost and potential pollution risks.Biological measures are preferred because they exhibit much better sand fixation performance and longer duration than the former two types of measures despite their relatively high cost.A combination of different measures is usually adopted in some areas to attain better sand-fixing effects.Stabilizing sand dune surfaces with mechanical measures or irrigation from underground water or river if available helps early recruitment of some drought-tolerant plants(xerophytes).We also point out the restrictions for existing sand-fixing measures and techniques and future research orientation.This review has implications for addressing eco-environmental issues associated with infrastructure construction that is part of the Belt and Road Initiative in desert and desertification-affected arid and semi-arid areas in the Mongolian Plateau.展开更多
文摘【Title】【Author】This study was conducted to determine the changes in the soil carbon stocks as influenced by land use in a humid zone of Deylaman district （10,876 ha）, a mountainous region of northern Iran. For this, land use maps were produced from TM and ETM＋ images for 1985, 2000 and 2010 years; and this was supplemented by field measurement of soil carbon in 2010. The results showed that the mean soil organic carbon （SOC） density was 6.7±1.8 kg C m-2, 5.2±3.4 kg C m-2 and 3.2±1.8 kg C m-2 for 0-20 cm soil layer and 4.8±1.9 kg C m-2, 3.1±2 kg C m-2 and 2.7±1.8 kg C m-2 for 20-40 cm soil layer in forest, rangeland and cultivated land, respectively. During the past 25 years, 14.4% of the forest area had been converted to rangeland; and 28.4% of rangelands had been converted to cultivated land. According to the historical land use changes in the study area, the highest loss of SOC stocks resulted from the conversion of the forest to rangeland （0.45×104 Mg C in 0-40 cm depth layer）; and the conversion of rangeland to cultivated land （0.37×104 Mg C in 0-40 cm）, which typically led to the loss of soil carbon in the area studied. The knowledge on the historical land use changes and its influence on overall SOC stocks could be helpful for making management decision for farmers and policy managers in the future, for enhancing the potential of C sequestration in northern Iran.
基金National Key Research and Development Program of China(2016YFC0500203)Science and Technology Program of Qinghai Province(2018-ZJ-T09,2017-SF-A6)
文摘The Three-River Headwaters(TRH), which is the source area of Yangtze River, Yellow River and Lancang River, is vulnerable and sensitive, and its alpine ecosystem is considered an important barrier for China’s ecological security. Understanding the impact of climate changes is essential for determining suitable measures for ecological environmental protection and restoration against the background of global climatic changes. However, different explanations of the interannual trends in complex alpine ecosystems have been proposed due to limited availability of reliable data and the uncertainty of the model itself. In this study, the remote sensing-process coupled model(GLOPEM-CEVSA) was used to estimate the net primary productivity(NPP) of vegetation in the TRH region from 2000 to 2012. The estimated NPP significantly and linearly correlated with the above-ground biomass sampled in the field(the multiple correlative coefficient R2 = 0.45, significant level P < 0.01) and showed better performance than the MODIS productivity product, i.e. MOD17 A3,(R2 = 0.21). The climate of TRH became warmer and wetter during 1990-2012, and the years 2000 to 2012 were warmer and wetter than the years1990–2000. Responding to the warmer and wetter climate, the NPP had an increasing trend of 13.7 g m^–2(10 yr)^–1 with a statistical confidence of 86%(P = 0.14). Among the three basins, the NPP of the Yellow River basin increased at the fastest rate of 17.44 g m^–2(10 yr)^–1(P = 0.158), followed by the Yangtze River basin, and the Lancang River, which was the slowest with a rate of 12.2 g m^–2(10 yr)^–1 and a statistical confidence level of only 67%. A multivariate linear regression with temperature and precipitation as the independent variables and NPP as the dependent variable at the pixel level was used to analyze the impacts of climatic changes on the trend of NPP. Both temperature and precipitation can explain the interannual variability of 83% in grassland NPP in the whole region, and can explain high, medium and low coverage of 78%, 84% and 83%, respectively, for grassland in the whole region. The results indicate that climate changes play a dominant role in the interannual trend of vegetation productivity in the alpine ecosystems on Qinghai-Tibetan Plateau. This has important implications for the formulation of ecological protection and restoration policies for vulnerable ecosystems against the background of global climate changes.
基金The Strategic Priority Research Program of Chinese Academy of Sciences(Pan-TPE,XDA2003020202)The National Natural Science Foundation of China(31961143022)。
文摘Shifting sands are one of the main contributors to desertification in China.This paper briefly reviews the measures and techniques which are used to protect traffic lines by stabilizing and fixing sands in the desert and desertification-affected arid and semi-arid areas in north China.We introduce the types and features of these measures and techniques,including mechanical,chemical,and biological measures,and outline how they have been applied in different areas and in different traffic lines over the past six decades,from 1950 s to 2010 s,taking the Baotou-Lanzhou railway,the Qinghai-Tibet railway,and the Tarim Desert highway as examples Mechanical measures such as erecting sand-retaining wind walls and placing straw checkerboards have proved to be very efficient for stabilizing shifting sands and protecting traffic lines that pass through the desert areas.Chemical measures are not widely used in the current sand fixing systems because of their high cost and potential pollution risks.Biological measures are preferred because they exhibit much better sand fixation performance and longer duration than the former two types of measures despite their relatively high cost.A combination of different measures is usually adopted in some areas to attain better sand-fixing effects.Stabilizing sand dune surfaces with mechanical measures or irrigation from underground water or river if available helps early recruitment of some drought-tolerant plants(xerophytes).We also point out the restrictions for existing sand-fixing measures and techniques and future research orientation.This review has implications for addressing eco-environmental issues associated with infrastructure construction that is part of the Belt and Road Initiative in desert and desertification-affected arid and semi-arid areas in the Mongolian Plateau.
