Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical...Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical area. Few studies have focused on changes in the physical and chemical properties of soils at high altitudes. Our aim was to identify the spatial distribution of soil physical and chemical properties in cold and arid climatic region. We also tried to explore relationship between soil organic carbon （SOC） and total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN）, available phosphorus （AP）, soil particle size distribution （PSD）. Samples were collected at 44 sites along a 300 km transect across the alpine grassland of northern Tibet. The study results showed that grassland type was the main factor influencing SOC, TN and TP distribution along the Gangdise Mountain-Shenzha-Shuanghu Transect. SOC, TN and TP contents were significantly higher in alpine meadow than alpine steppe ecosystems. SOC, TN, TP and AN contents in two soil layers （0-15 cm and 15-3o cm） showed no significant differences, while AP content in top soft （0-15 cm） was significantly higher than that in sub-top soil （15-30cm）. SOC content was correlated positively with TN and TP content （r = 0.901and 0.510, respectively）. No correlations were detected for clay content and fractal dimension of particle size distribution （D）. Our study results indicated the effects of vegetation on soil C, N and P seem to be more important than that of rocks itself along latitude gradient on the northern Tibetan Plateau. However, we did not found similar impacts of vegetation on soil properties in depth. Inaddition, this study also provided an interesting contribution to the global data pool on soil carbon stocks.展开更多
Species richness and diversity indices （Shannon-Wiener index, Simpson dominance index and Pielou evenness index） in alpine grassland ecosystems （alpine meadow, alpine steppe and desert steppe） under grazing-exclud...Species richness and diversity indices （Shannon-Wiener index, Simpson dominance index and Pielou evenness index） in alpine grassland ecosystems （alpine meadow, alpine steppe and desert steppe） under grazing-excluded and freely grazed sites were investigated along the Northern Tibetan Plateau Alpine Grassland Transect during summer 2009 and 2010. We found that species richness and diversity have not been significantly altered by short-term grazing exclusion since 2006 at vegetation and regional scales. Species richness and diversity were mainly driven by growing season precipitation （GSP）, which accounted for over 87 % of the total variation observed, Species richness and diversity at grazing- excluded and freely grazed sites appear to respond to growing season precipitation in parallel. Species richness exponentially increased with GSP while diversity indices showed positively linear relationships with GSP. This indicates that GSP on the Northern Tibetan Plateau is crucial in regulating species richness and diversity and should be taken into account in future studies on alpine grassland conservation.展开更多
Clarifying the spatial and temporal variations in precipitation-use efficiency （PUE） is helpful for advancing our knowledge of carbon and water cycles in Tibetan grassland ecosystems. Here we use an integrated remot...Clarifying the spatial and temporal variations in precipitation-use efficiency （PUE） is helpful for advancing our knowledge of carbon and water cycles in Tibetan grassland ecosystems. Here we use an integrated remote sensing normalized difference vegetation index （NDVI） and in-situ above-ground net primary production （ANPP） measurements to establish an empirical exponen- tial model to estimate spatial ANPP across the entire Tibetan Plateau. The spatial and temporal variations in PUE （the ratio of ANPP to mean annual precipitation （MAP））, as well as the relationships between PUE and other controls, were then investigated during the 2001- 2012 study period. At a regional scale, PUE increased from west to east. PUE anomalies increased significantly （〉 0.1 g.m^-2.mm^-1/10 yr） in the southern areas of the Tibetan Plateau yet decreased （ 〉 0.02 g. m^-2. mm 1/10 yr） in the northeastern areas. For alpine meadow, we obtained an obvious breaking point in trend of PUE against elevation gradients at 3600 m above the sea level, which showed a contrasting relationship. At the inter-annual scale, PUE anomalies were smaller in alpine steppe than in alpine meadow. The results show that PUE of Tibetan grasslands is generally high in dry years and low in wet years.展开更多
基金supported by the Western Action Plan Project of the Chinese Academy of Sciences(Grant No.KZCX2-XB3-08)the Strategic Pilot Science and Technology Projects of Chinese Academy of Sciences(Grant No.XDB03030505)the One Hundred Young Persons Project of the Institute of Mountain Hazards and Environment(Grant No.SDSQB-2010-02)
文摘Soil carbon and nutrient contents and their importance in advancing our understanding of biogeochemical cycling in terrestrial ecosystem, has motivated ecologists to find their spatial patterns in various geographical area. Few studies have focused on changes in the physical and chemical properties of soils at high altitudes. Our aim was to identify the spatial distribution of soil physical and chemical properties in cold and arid climatic region. We also tried to explore relationship between soil organic carbon （SOC） and total nitrogen （TN）, total phosphorus （TP）, available nitrogen （AN）, available phosphorus （AP）, soil particle size distribution （PSD）. Samples were collected at 44 sites along a 300 km transect across the alpine grassland of northern Tibet. The study results showed that grassland type was the main factor influencing SOC, TN and TP distribution along the Gangdise Mountain-Shenzha-Shuanghu Transect. SOC, TN and TP contents were significantly higher in alpine meadow than alpine steppe ecosystems. SOC, TN, TP and AN contents in two soil layers （0-15 cm and 15-3o cm） showed no significant differences, while AP content in top soft （0-15 cm） was significantly higher than that in sub-top soil （15-30cm）. SOC content was correlated positively with TN and TP content （r = 0.901and 0.510, respectively）. No correlations were detected for clay content and fractal dimension of particle size distribution （D）. Our study results indicated the effects of vegetation on soil C, N and P seem to be more important than that of rocks itself along latitude gradient on the northern Tibetan Plateau. However, we did not found similar impacts of vegetation on soil properties in depth. Inaddition, this study also provided an interesting contribution to the global data pool on soil carbon stocks.
基金National Key Technology Research and Development Program (No.2010BAE00739 & 2007BAC06B01)National Natural Science Foundation of China (No.41171044)Strategic Priority Research Program of Chinese Academy of Sciences, Climate Change: Carbon Budget and Relevant Issues (No. XDA05060700)
文摘Species richness and diversity indices （Shannon-Wiener index, Simpson dominance index and Pielou evenness index） in alpine grassland ecosystems （alpine meadow, alpine steppe and desert steppe） under grazing-excluded and freely grazed sites were investigated along the Northern Tibetan Plateau Alpine Grassland Transect during summer 2009 and 2010. We found that species richness and diversity have not been significantly altered by short-term grazing exclusion since 2006 at vegetation and regional scales. Species richness and diversity were mainly driven by growing season precipitation （GSP）, which accounted for over 87 % of the total variation observed, Species richness and diversity at grazing- excluded and freely grazed sites appear to respond to growing season precipitation in parallel. Species richness exponentially increased with GSP while diversity indices showed positively linear relationships with GSP. This indicates that GSP on the Northern Tibetan Plateau is crucial in regulating species richness and diversity and should be taken into account in future studies on alpine grassland conservation.
基金Acknowledgements We thank Hongsheng Liu, Xiujing Yang, Lei Li, Yibo Liu, Weiliang Fan, Hui Zhan and others for help with sampling. This study was supported by the National Natural Science Foundation of China （Grant Nos. 41271118, 41471227, and 41371013） and the Strategic Priority Research Program of the Chinese Academy of Sciences （XDA05050209）. We are grateful to Yuanhe Yang and coauthors for sharing their in-situ data, and thank Drs. Muhammad Hasan Ali Baig and A. Gonsamo for providing valuable suggestions.
文摘Clarifying the spatial and temporal variations in precipitation-use efficiency （PUE） is helpful for advancing our knowledge of carbon and water cycles in Tibetan grassland ecosystems. Here we use an integrated remote sensing normalized difference vegetation index （NDVI） and in-situ above-ground net primary production （ANPP） measurements to establish an empirical exponen- tial model to estimate spatial ANPP across the entire Tibetan Plateau. The spatial and temporal variations in PUE （the ratio of ANPP to mean annual precipitation （MAP））, as well as the relationships between PUE and other controls, were then investigated during the 2001- 2012 study period. At a regional scale, PUE increased from west to east. PUE anomalies increased significantly （〉 0.1 g.m^-2.mm^-1/10 yr） in the southern areas of the Tibetan Plateau yet decreased （ 〉 0.02 g. m^-2. mm 1/10 yr） in the northeastern areas. For alpine meadow, we obtained an obvious breaking point in trend of PUE against elevation gradients at 3600 m above the sea level, which showed a contrasting relationship. At the inter-annual scale, PUE anomalies were smaller in alpine steppe than in alpine meadow. The results show that PUE of Tibetan grasslands is generally high in dry years and low in wet years.
