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Leaf morphological traits vary along elevational gradients so that plants can adapt to their surrounding habitat. However, the abiotic factors that shape those traits are still debatable, especially for plants at high elevations where the environment can be very harsh. Quercus guyavifolia H. Léveillé (Fagaceae) is a woody plant found along the southeastern boundary of the Qinghai-Tibet Plateau. Distribution elevations of the species range from 2000 m to 4500 m approximately, providing an excellent opportunity to explore correlations among leaf traits and environmental factors. We used multiple-regression models to investigate spatial trends in leaf morphology and their environmental determinants. As elevation increased, values for leaf area, length, width, the ratio of leaf length to width, shape factor, and petiole length and width decreased significantly and all were positively correlated with mean annual precipitation. Leaf length, the ratio of leaf length to width, and petiole length were negatively correlated with the daily mean maximum intensity of ultraviolet (UV)-B irradiation during the growing season. Our results indicated that the amounts of both precipitation and UV irradiation largely shape the leaf morphology in Q. guyavifolia along the elevation gradient. This study provides evidence for the adaptive plasticity of leaves in response to environments in regions at high elevations. [ABSTRACT FROM AUTHOR]

Background: Although the effect of water level on germination in soil seed banks has been documented in many ecosystems, the mechanism is not fully understood, and to date no empirical studies on this subject exist. Further, no work has been done on the effect of water level on seed banks of drying and saline-alkaline wetlands in alpine areas on the Tibetan Plateau. Methodology: We examined the effects of water level (0 cm, 5 cm and 10 cm) on seed germination and seedling establishment from soil seed banks at 0–5 cm and 5–10 cm depths in typical, drying, and saline-alkaline wetlands. We also explore the potential role of soil seed bank in restoration of drying and saline-alkaline wetlands. Principal Findings: Species richness decreased with increase in water level, but there almost no change in seed density. A huge difference exists in species composition of the seed bank among different water levels in all three wetlands, especially between 0 cm and 5 cm and 0 cm and 10 cm. Similarity of species composition between seed bank and plant community was higher in 0 cm water level in drying wetland than in the other two wetlands. The similarity was much higher in 0 cm water level than in 5 cm and 10 cm water levels in all three wetlands. Species composition of the alpine wetland plant community changed significantly after drying and salinization, however, species composition of the seed bank was unchanged regardless of the environment change. Conclusions/Significance: Water level greatly affects seed bank recruitment and plant community establishment. Further, different water levels in restored habitats are likely to determine its species composition of the plant community. The seed bank is important in restoration of degraded wetlands. Successful restoration of drying and salinization wetlands could depend on the seed bank. [ABSTRACT FROM AUTHOR]