Net ecosystem CO2 exchange and controlling factors in a steppe—Kobresia meadow on the Tibetan Plateau     

Shi  Peili  Sun  Xiaomin  Xu  Lingling  Zhang  Xianzhou  He  Yongtao  Zhang  Dongqiu  Yu  Guirui 《中国科学:地球科学(英文版)》2006,49(2):207-218

Knowledge of seasonal variation of net ecosystem CO₂ exchange (NEE) and its biotic and abiotic controllers will further our understanding of carbon cycling process, mechanism and large-scale modelling. Eddy covariance technique was used to measure NEE, biotic and abiotic factors for nearly 3 years in the hinterland alpine steppe—Korbresia meadow grassland on the Tibetan Plateau, the present highest fluxnet station in the world. The main objectives are to investigate dynamics of NEE and its components and to determine the major controlling factors. Maximum carbon assimilation took place in August and maximum carbon loss occurred in November. In June, rainfall amount due to monsoon climate played a great role in grass greening and consequently influenced interannual variation of ecosystem carbon gain. From July through September, monthly NEE presented net carbon assimilation. In other months, ecosystem exhibited carbon loss. In growing season, daytime NEE was mainly controlled by photosynthetically active radiation (PAR). In addition, leaf area index (LAI) interacted with PAR and together modulated NEE rates. Ecosystem respiration was controlled mainly by soil temperature and simultaneously by soil moisture. Q ₁₀ was negatively correlated with soil temperature but positively correlated with soil moisture. Large daily range of air temperature is not necessary to enhance carbon gain. Standard respiration rate at referenced 10°C (R ₁₀) was positively correlated with soil moisture, soil temperature, LAI and aboveground biomass. Rainfall patterns in growing season markedly influenced soil moisture and therefore soil moisture controlled seasonal change of ecosystem respiration. Pulse rainfall in the beginning and at the end of growing season induced great ecosystem respiration and consequently a great amount of carbon was lost. Short growing season and relative low temperature restrained alpine grass vegetation development. The results suggested that LAI be usually in a low level and carbon uptake be relatively low. Rainfall patterns in the growing season and pulse rainfall in the beginning and at end of growing season control ecosystem respiration and consequently influence carbon balance of ecosystem.

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Net ecosystem CO<Subscript>2</Subscript> exchange and controlling factors in a steppe—<Emphasis Type="Italic">Kobresia</Emphasis> meadow on the Tibetan Plateau     

Shi Peili  Sun Xiaomin  Xu Lingling  Zhang Xianzhou  He Yongtao  Zhang Dongqiu  Yu Guirui 《中国科学D辑(英文版)》2006,49(2):207-218

Knowledge of seasonal variation of net ecosystem CO₂ exchange (NEE) and its biotic and abiotic controllers will further our understanding of carbon cycling process, mechanism and large-scale modelling. Eddy covariance technique was used to measure NEE, biotic and abiotic factors for nearly 3 years in the hinterland alpine steppe—Korbresia meadow grassland on the Tibetan Plateau, the present highest fluxnet station in the world. The main objectives are to investigate dynamics of NEE and its components and to determine the major controlling factors. Maximum carbon assimilation took place in August and maximum carbon loss occurred in November. In June, rainfall amount due to monsoon climate played a great role in grass greening and consequently influenced interannual variation of ecosystem carbon gain. From July through September, monthly NEE presented net carbon assimilation. In other months, ecosystem exhibited carbon loss. In growing season, daytime NEE was mainly controlled by photosynthetically active radiation (PAR). In addition, leaf area index (LAI) interacted with PAR and together modulated NEE rates. Ecosystem respiration was controlled mainly by soil temperature and simultaneously by soil moisture. Q ₁₀ was negatively correlated with soil temperature but positively correlated with soil moisture. Large daily range of air temperature is not necessary to enhance carbon gain. Standard respiration rate at referenced 10°C (R ₁₀) was positively correlated with soil moisture, soil temperature, LAI and aboveground biomass. Rainfall patterns in growing season markedly influenced soil moisture and therefore soil moisture controlled seasonal change of ecosystem respiration. Pulse rainfall in the beginning and at the end of growing season induced great ecosystem respiration and consequently a great amount of carbon was lost. Short growing season and relative low temperature restrained alpine grass vegetation development. The results suggested that LAI be usually in a low level and carbon uptake be relatively low. Rainfall patterns in the growing season and pulse rainfall in the beginning and at end of growing season control ecosystem respiration and consequently influence carbon balance of ecosystem.  相似文献   

湖南金矿床类型和分布规律   总被引：1，自引：0，他引：1  

钟东球 《湖南地质》1990,9(4):9-14,22

湖南金矿床类型按成矿地质环境和成矿作用划分为产于前寒武系浅变质岩中的变质热液金矿床、产于浅成相中酸性侵入体与沉积岩接触部位的次火山热液金矿床、产于中深成相花岗岩与前寒武系变质岩接触带周边的岩浆热液金矿床、产于泥盆系沉积岩中的浸染型金矿床,产于硫化矿床氧化带中的风化壳型金矿床,以及产于第四系河床冲积层中的砂金矿床六大类型。按照金矿床(点)集中区的大地构造特征和成矿控制因素的相似性,划分为湘西、湘东北、湘中、湘西南和湘南五个成矿区。  相似文献