Soil water is the key abiotic limiting factor in desert areas and hydrological processes determine the vegetation composition, patterns and processes in desert regions. The hydrological processes can be altered by veg...Soil water is the key abiotic limiting factor in desert areas and hydrological processes determine the vegetation composition, patterns and processes in desert regions. The hydrological processes can be altered by vegetation succession. In this paper, we review the major advances in ecohydrological research and their potential impact on plant-water relations in revegetated desert communities. The major advances in ecohydrological research over the past 50 years in desert areas were analyzed using a case study that investigated the long-term ecosystem effects of sand-binding vegetation in the Tengger Desert. Key challenges and opportunities for ecohydrology research in the future are also discussed in the context of the major scientific issues affecting sand binding vegetation.展开更多
Surface greenness reflects the situation of vegetation cover.Vegetation index calculated from the Red and Near Infrared bands of remote sensing images,whose values indicate the level of photosynthetic activity,is mono...Surface greenness reflects the situation of vegetation cover.Vegetation index calculated from the Red and Near Infrared bands of remote sensing images,whose values indicate the level of photosynthetic activity,is monotonically related to surface greenness when vegetation canopy does not fully cover the background soil.Especially for desert regions,vegetation index is positively correlated with vegetation coverage.Therefore,vegetation index can be used to study the change in greenness of desert areas.This study collected MODIS Normalized Difference Vegetation Index (NDVI) data from 2000 to 2010 and analyzed their change over China in this period.The results showed that an increasing trend of NDVI occurred over 66.84% (OLS fitting) or 64.27% (LAD fitting) of China,indicating that China's greenness is increasing overall.Meanwhile,desertification of China decreased.Areas showing large increase in greenness are found in Shaanxi,Shanxi,Ningxia,Henan,Shandong,Qinghai,and Gansu while regions with large decrease in greenness are found in Northeast Inner Mongolia,South Tibet,Jiangsu,and Shanghai.Changes of Qinghai,Gansu,Xinjiang and South Tibet could probably be driven by climate factors.Decrease of greenness in Northeast Inner Mongolia was related to agricultural reclamation.Decrease of greenness in Jiangsu and Shanghai was related to rapid urbanization.Climate factors did not exhibit obvious correspondence to the large increase in greenness in Shaanxi,Shanxi,Ningxia and Gansu,indicating that the changes might have been caused by human factors.The reduction of desert areas in China could probably have been caused by human management and protection at the national scale.展开更多
In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in diffe...In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in different commu-nities. Chenopodiaceae pollen percentages are highest in Kalidium communities and Ceratoides communities (higher than 45%, average is 63.4%), but high Ephedra pollen per-centages (higher than 3.3%, average is 16.5%)in Ceratoides communities make it distinguished from Kalidium communi-ties. Artemisia pollen percentages (more than 50%) are much higher than Chenopodiaceae (less than 35%) in Artemisia Communities. Nitraria pollen percentages (higher than 2%, average is 13.6%) are highest in Nitraria communities com-pared with those in other community patterns. Tamariceae pollen percentages (higher than 2%, average is 8.6%) are highest both in Tetraena and Reaumuria communities com-pared with those in other community patterns. But in Reau-muria communities, Artemisia pollen percentages are higher than Chenopodiaceae with some other pollen types such as Gramineae, Compositae, Leguminosae; on the contrary, in Tetraena communities, Artemisia pollen percentages are less than Chenopodiaceae with few other pollen types. Calli-gonum pollen only appears in Calligonum communities (higher than 2%,average is 5%). The results of cluster analysis (CLA) and detrended correspondence analysis (DCA) show that the pollen indication to source plants can be reflected by association indices (A), over-representation in-dices (O), under-representation indices (U), R-value, the av-erage pollen percentages where parent plants are absent (Xa) and the average pollen percentages where parent plants are present (Xp). Zygophyllum, Calligonum, Tetraena, Tribulus and Tamariceae can indicate source plants very well, owing to high A scores. Artemisia, Chenopodiaceae and Gramineae have high R-values, and Nitraria, Cruciferae and sedum have high O scores, so they are over-represented types, but the higher Xp and the lower Xa valu展开更多
基金supported by the National Natural Science Foundation of China for Distinguished Young Scholars (40825001)the National Basic Research Program of China (2013CB429906)
文摘Soil water is the key abiotic limiting factor in desert areas and hydrological processes determine the vegetation composition, patterns and processes in desert regions. The hydrological processes can be altered by vegetation succession. In this paper, we review the major advances in ecohydrological research and their potential impact on plant-water relations in revegetated desert communities. The major advances in ecohydrological research over the past 50 years in desert areas were analyzed using a case study that investigated the long-term ecosystem effects of sand-binding vegetation in the Tengger Desert. Key challenges and opportunities for ecohydrology research in the future are also discussed in the context of the major scientific issues affecting sand binding vegetation.
文摘Surface greenness reflects the situation of vegetation cover.Vegetation index calculated from the Red and Near Infrared bands of remote sensing images,whose values indicate the level of photosynthetic activity,is monotonically related to surface greenness when vegetation canopy does not fully cover the background soil.Especially for desert regions,vegetation index is positively correlated with vegetation coverage.Therefore,vegetation index can be used to study the change in greenness of desert areas.This study collected MODIS Normalized Difference Vegetation Index (NDVI) data from 2000 to 2010 and analyzed their change over China in this period.The results showed that an increasing trend of NDVI occurred over 66.84% (OLS fitting) or 64.27% (LAD fitting) of China,indicating that China's greenness is increasing overall.Meanwhile,desertification of China decreased.Areas showing large increase in greenness are found in Shaanxi,Shanxi,Ningxia,Henan,Shandong,Qinghai,and Gansu while regions with large decrease in greenness are found in Northeast Inner Mongolia,South Tibet,Jiangsu,and Shanghai.Changes of Qinghai,Gansu,Xinjiang and South Tibet could probably be driven by climate factors.Decrease of greenness in Northeast Inner Mongolia was related to agricultural reclamation.Decrease of greenness in Jiangsu and Shanghai was related to rapid urbanization.Climate factors did not exhibit obvious correspondence to the large increase in greenness in Shaanxi,Shanxi,Ningxia and Gansu,indicating that the changes might have been caused by human factors.The reduction of desert areas in China could probably have been caused by human management and protection at the national scale.
基金This work was supported by the National Natural Science Foundation of China(Grant No.40171095)the National Natural Science Foundation of Hebei Province(Grant No.402615)+1 种基金the Special Foundation for Preliminary Research of Key Research Project,Science and Technology Ministry of China(Grant No.2003CCA01800)the National Natural Foundation for the Famous Young(Grant No.49920205).
文摘In order to investigate the indication of major pollen types to source plants, 39 surface pollen samples are collected from 39 plant communities. The results show that diversity of pollen assemblages presents in different commu-nities. Chenopodiaceae pollen percentages are highest in Kalidium communities and Ceratoides communities (higher than 45%, average is 63.4%), but high Ephedra pollen per-centages (higher than 3.3%, average is 16.5%)in Ceratoides communities make it distinguished from Kalidium communi-ties. Artemisia pollen percentages (more than 50%) are much higher than Chenopodiaceae (less than 35%) in Artemisia Communities. Nitraria pollen percentages (higher than 2%, average is 13.6%) are highest in Nitraria communities com-pared with those in other community patterns. Tamariceae pollen percentages (higher than 2%, average is 8.6%) are highest both in Tetraena and Reaumuria communities com-pared with those in other community patterns. But in Reau-muria communities, Artemisia pollen percentages are higher than Chenopodiaceae with some other pollen types such as Gramineae, Compositae, Leguminosae; on the contrary, in Tetraena communities, Artemisia pollen percentages are less than Chenopodiaceae with few other pollen types. Calli-gonum pollen only appears in Calligonum communities (higher than 2%,average is 5%). The results of cluster analysis (CLA) and detrended correspondence analysis (DCA) show that the pollen indication to source plants can be reflected by association indices (A), over-representation in-dices (O), under-representation indices (U), R-value, the av-erage pollen percentages where parent plants are absent (Xa) and the average pollen percentages where parent plants are present (Xp). Zygophyllum, Calligonum, Tetraena, Tribulus and Tamariceae can indicate source plants very well, owing to high A scores. Artemisia, Chenopodiaceae and Gramineae have high R-values, and Nitraria, Cruciferae and sedum have high O scores, so they are over-represented types, but the higher Xp and the lower Xa valu
