[Climate-growth relationships of Picea koraiensis and causes of its recent decline in Xiaoxing' an Mountains, China].

Two tree-ring width chronologies of Picea koraiensis at two altitudes in Fenglin National Nature Reserve of Xiaoxing'an Mountains, China were developed by using dendrochronological methods. To identify main limiting factors of P. koraiensis radial growth at the two altitudes, the relationships between the chronologies and local temperature, precipitation, Palmer drought severity index (PDSI), and large-scale climatic factors were investigated. Meanwhile, the reasons of P. koraiensis growth decline in recent years were also explored. Results showed that radial growth of P. koraiensis in Xiaoxing'an Mountains was mainly limited by temperatures, especially by the minimum temperature in growing season, while the limiting effect of precipitation was relatively weak. Climate responses of P. koraiensis growth at the different altitudes showed significant differences. Radial growths of P. koraiensis at the low altitude were positively correlated with precipitation in the current growth season (June-September) and whole year, and negatively correlated with soil temperatures at different depths, especially at 80 cm depth in growing season. Meanwhile, it was signi-ficantly positively correlated with PDSI in growing season. However, the relationships between radial growth of P. koraiensis at the high altitude and precipitation, air and soil temperatures, and PDSI were not significant as that at the low altitude. Growth decline of P. koraiensis in Xiaoxing'an Mountains could be related to the phase changes in Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO) and the significant global warming since 1980. The coupling effects of the above changes might result in increased soil evaporation and exacerbated warming and drying phenomena, consequently causing the growth decline of P. koraiensis at the low altitude.

How is the AIE mechanism profoundly changed in an ESIPT family: the novel introduction of a tetraphenylethene group onto (Z)-3-(quinolin-2-ylmethylene)-3,4-dihydroquinoxalin-2(1H)-one.

It is reported that two derivatives of (Z)-3-(quinolin-2-ylmethylene)-3,4-dihydroquinoxalin-2-(1H)-one (1) with a tetraphenylethene (TPE) group introduced at amide N atom of the dihydroquinoxalinone moiety (2) or at phenyl ring of the quinoline fragment (3) are synthesized, and the derivatives exhibit a remarkably enhanced aggregation-induced emission (AIE) activity than the parent. Although both the parent and the derivatives have the characteristic of an excited state intramolecular proton transfer (ESIPT), the AIE mechanism of 2 and 3 is totally different from that of 1. The considerably stronger emission of 3 than that of 2 should be attributed to the unique crystallization-induced emission enhancement (CIEE) effect.