Abstract: Leaf water stable isotopes can indicate material and energy exchange between the inside and outside of the leaf. They can also reflect the climate and ecological information of plant growth. Based on the observed data of the leaf water stable isotope δ¹⁸O variations of Platycladus orientalis, Quercus variabilis and Vitex negundo in Xishan Mountain, Beijing, combined with soil water δ¹⁸O and meteorological observation, this study explored the diurnal and seasonal variations of leaf water δ¹⁸O characteristics and its relationship with meteorological factors. The results showed that, in dry/rainy season, the stem water δ¹⁸O of the three species was relatively stable, and the stem water δ¹⁸O of the three species in rainy season was larger than that in dry season. However, because the enrichment and the variation of the leaf water δ¹⁸O of the three species was greater in dry season than in rainy season, the daily average leaf water δ¹⁸O of the three species was greater in dry season than in rainy season. The slope and intercept between leaf water δ¹⁸O and δD of the three species in dry season were larger than those in rainy season, indicating that RH was an important factor causing the difference of leaf water δ¹⁸O of the three species. The leaf water δ¹⁸O of Q. variabilis and V. negundo was more sensitive to meteorological factors (RH, PAR, air temperature, pressure, VPD) in dry season than in rainy season, while P. orientalis leaf water δ¹⁸O had no significant correlation with these meteorological factors in either dry or rainy season.

Key words: genetically modified soybean, survival rate, reproductive rate, body length, Folsomia candida