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TANG Si-ling1, JIA Xin1**, GUO Jian-bin1, CHEN Zhi-hao1, ZHA Tian-shan1, QIN Shu-gao1, YANG Lin2
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Abstract: Leaf area index (LAI) of a semiarid Artemisia ordosica community at Yanchi, Ningxia was measured with both direct (allometric equations) and indirect (Li-2000 canopy analyzer) methods throughout the growing season of 2012. Our objectives were to compare the direct and indirect measurements, to explore how actual leaf area index (LAIa) values obtained from allometric equations can be used to calibrate effective leaf area index (LAIe) measured by Li-2000, and to model seasonal LAIa variations using climatic variables. Results showed that bivariate functions of height and canopy area generally predicted individual total leaf area better than did the functions of canopy area alone, and the fitting achieved highest coefficient of determination (R2) in July and August. Both LAIe and LAIa showed humpshaped seasonal patterns. A midseason stable period started from early July and ended in midSeptember. LAIe was always greater than LAIa over the growing season, with the mean values of LAIe and LAIa in the stable period being 1.15 and 0.31 m2·m-2, respectively. LAIe and LAIa showed a twophase linear relationship over the growing season, separated by late August. LAIe and LAIa showed a weak relationship with rainfall or soil water content in the growing season. LAIa varied with accumulated temperature above 5 °C (∑D), first increasing with ∑D, and then being stable during the midseason. LAIa showed a negative exponential relationship with the ratio of photosynthetically active radiation reflectance (ρp) to shortwave radiation reflectance (ρs) (ρp/ρs). Our results contribute to the understanding of LAI patterns in semiarid A. ordosica communities, could aid in the development of efficient and accurate methods for measuring LAI, and provide ground-based data for calibrating remotely-sensed information and for parameterizing processbased ecosystem carbon cycle models.
Key words: improved TOPSIS method, early warning, Zhangjiajie, grey GM (1,1) model., tourism ecological security
TANG Si-ling1, JIA Xin1**, GUO Jian-bin1, CHEN Zhi-hao1, ZHA Tian-shan1, QIN Shu-gao1, YANG Lin2. Measuring and modeling leaf area index for Artemisia ordosica.[J]. cje.
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URL: http://www.cje.net.cn/EN/abstract/abstract21333.shtml
http://www.cje.net.cn/EN/Y2014/V33/I2/547