Search

In order to produce long-term aerosol optical depth (AOD) dataset over land from the Advanced Very High Resolution Radiometer (AVHRR), AVHRR data quality in terms of radiometric calibration must be maintained. A vicarious calibration method have been developed by incorporating well calibrated Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) radiance data over several pseudo-invariant targets to inter-calibrate the channel 1 of AVHRR based on Bidirectional Reflectance Distribution Functions (BRDFs) and spectral band adjustment factor (SBAF) models for different targets. Comparison of our calibration coefficients with those of Pathfinder Atmospheres Extended (PATMOS-x) indicate the calibration accuracy to be within 2.5%. The operational L1B and recalibrated AVHRR radiance are applied to derive AOD maps over East America (dark surface) and West Africa (bright surface) using the land aerosol and bidirectional reflectance inversion by times series technique (LABITS) algorithm. Preliminary comparisons show that significant difference in the retrieved AOD from the two different calibration is expected, while the spatial distribution of AOD difference is\ud complicated due to different surface brightness and deficiencies of numeric solutions.

By using fast chlorophyll fluorescence induction dynamics analysis technique (JIP-test), this paper studied the photosynthesis characteristics and fast chlorophyll fluorescence induction dynamics of 1-year old Pistacia chinensis seedlings under the stress of NaCl at the concentrations 0% (CK), 0.15%, 0.3%, 0.45%, and 0.6%. With the increasing concentration of NaCl, the contents of Chl a, Chl b, and Chl (a+b) in the seedlings leaves decreased, the Chl a/b ratio decreased after an initial increase, and the carotenoid content increased. The net photosynthetic rate (P(n)) and stomatal conductance (g(s)) decreased gradually with increasing NaCl concentration. The decrease of P(n) was mainly attributed to the stomatal limitation when the NaCl concentration was lower than 0.3%, and to the non-stomatal limitation when the NaCl concentration was higher than 0.3%. The trapped energy flux per RC (TR0/CS0), electron transport flux per RC (ET0/CS0), density of RCs (RC/CS0), and yield or flux ratio (psi(0) or phi(E0)) decreased, but the absorption flux per CS (ABS/CS0) and the K phase (W(k)) and J phase (V) in the O-J-I-P chlorophyll fluorescence induction curves increased distinctly, indicating that NaCl stress damaged the leaf oxygen-evolving complex (OEC), donor sides, and PS II reaction centers. When the NaCl concentration reached 0.3%, the maximum photochemical efficiency (F(v)/F(m)) and performance index (PI(ABS)) decreased 17.7% and 36.6%, respectively, as compared with the control.

Taking one-year-old dormant shoots of Pistacia chinensis and Koelreuteria integrifoliola as test materials and the shoots of northern indigenous tree species K. paniculata as the control, the changes of their membrane-lipid peroxidation, antioxidative enzyme activity, and organic osmoregulatory substance content under artificial cooling were studied, aimed to analyze the differences of the three tree species in cold resistance. With the decrease of temperature, the ion leakage percentage of the three tree species increased in S-shape, and the SOD and POD activities decreased after an initial increase. The MDA, soluble protein, and soluble sugar contents of K. integrifoliola and K. paniculata under decreasing temperature decreased after an initial increase, while those of P. chinensis had an increasing trend. The semi-lethal temperature (LT50 ) of K. paniculata, K. integrifoliola, and P. chinensis calculated by the Logistic equation of ion leakage percentage was -27.2 degrees C, -23.7 degrees C, and -27.0 degrees C, respectively. Among the three tree species, K. paniculata had the strongest cold resistance, followed by P. chinensis, and K. integrifoliola.

With potted Hovenia dulcis and Gleditsia sinensis seedlings as test materials, their plant growth, chlorophyll fluorescence characteristics, and active oxygen metabolism under stress of different concentration (0, 0.15%, 0.30%, 0.45%, and 0.60%) NaCl were studied. The results showed that with increasing concentration of NaCl, the plant growth, leaf chlorophyll content, photochemical efficiency of PS II (Fv/Fm), quantum yield of PS II (phi(PS II)), and photochemical quenching (q(P)) decreased gradually, while the non-photochemical quenching of fluorescence (q(N)) was in adverse. After 10 days of 0. 15% NaCl stress, the leaf chlorophyll content, Fv/Fm, phi(PS II), and q(P) of H. dulcis seedlings decreased by 19.77%, 2.94%, 29.03%, and 8.16%, respectively, with significant differences (P0.05) to the control, while no significant differences were observed for G. sinensis seedlings. Compared with the control, the Fv/Fm and phi(PS II), of G. sinensis seedlings in treatment 0.30% NaCl decreased significantly by 1.91% and 14.66%, and the chlorophyll content and q(P) of the seedling in treatment 0.45% NaCl decreased significantly by 29.28% and 11.36%, respectively (P0.05). With increasing concentration of NaCl, the SOD activity of G. sinensis seedlings showed a consistent increasing trend, and that of H. dulcis seedlings increased first and decreased then. The POD and CAT activities of G. sinensis and H. dulci seedlings tended to increase first and decrease then, with the increment being higher for G. sinensis than for H. dulci, while the MDA content of the seedlings had an increasing trend, with the increment being higher for H. dulcis than for G. sinensis, suggesting that the cell membrane lipid peroxidation of H. dulcis was more serious than that of G. sinensis. It was concluded that G. sinensis had greater salt tolerance than H. dulcis, which was related toits higher anti-oxidation enzyme activities.