Abstract:

Making use of the Motic Digital Imaging microscope and the stable carbon isotope technique, the tempo-spatial variations in the stomatal densities and δ¹³C values in leaves of Quercus liaotungensis in different vegetation regions were studied. About 240 plant specimens in the years from 1930's to 1980's were taken from the Herberhem of Northwestern Institute of Botany, Chinese Academy of Sciences. The results showed that the variety ranges of stomatal densities and δ¹³C values in Q. liaotungensis were 535～800 stoma·mm^-2and -28.47‰～-25.02‰, respectively, with the mean value of 703 stoma·mm^-2 and -26.83‰, respectively. In warm temperate deciduous broadleaf forest (WTDB), the time distribution from 1930's to 1980's, both stomatal densities and δ¹³C values in Q. liaotungensis descended significantly. Correspondingly, in that period, stomatal densities increased but δ¹³C values descended in subtropical evergreen-broadleaf forest (STEB), and δ¹³C values increased but stomatal densities had little changes in the Ti-betan Plateau alpine-cold vegetation zone(TPAC). The tendency for space distribution showed that, in 1930's, stomatal densities and δ¹³C values of Q. liaotungensis in WTDB, STEB and TPAC all decreased, indicating that water use efficiency (WUE) of it all fell down in these regions. In 1950's, stomatal densities appeared a fluctuation in four vegetation regions, which were higher in temperate coniferous-broadleaf mixed forest (TCBM) and STEB than those in WTDB and TPAC. However, the δ¹³C values in four vegetation regions were little different. In 1980's, stomatal densities and δ¹³C values decreased from WTDB in the east to the temperate grassland region (TGR) in the west. Therefore, except several regions, the tempo-spatial distributions of stomatal densities and δ¹³C values in Q. liaotungensis all decreased from 1930's to 1980's in time and from WTDB, STEB to TPAC in space.

Key words: Quercus liaotungensis, stomatal density, &delta, ¹³C value, tempo-spatial variation