关键词: 灌木, δ¹³C值, 蒸腾耗水, 水分利用效率

Abstract: [Objective] The objectives of this study were to find out the water use strategies of native shrubsatthe southern foot of Taihang Mountain, and to providea theoretical guidance for species selection and community succession management for vegetation restoration.[Method] The stable carbon isotope technique, thermal dissipation probe (TDP) and soil humidity sensors were used to measure the leaf δ¹³C value,sap flow density and soil water contentin order to obtain the differences and seasonal variations of water use strategies among three native shrubs Vitex negundo var. heterophylla, Ziziphus jujuba var. spinosa and Grewia biloba.[Result] Seasonal droughts occurred during spring (115 days) and autumn (2 months) of the year 2013 in the study area. The water consumption of V. negundo, Z. jujuba var. spinosa and G. biloba in the growing season were 42.32, 13.23 and 96.17 mm, respectively. The three shrubs all consumed more water in summer, and less water in May and September. G. biloba consumed more water than V. negundo and Z. jujuba var. spinosa did duringthe whole growingperiod. The leaf δ¹³C value of the three shrubs was the highest in spring, the nextin autumn, and the least in middle and later summer. The G. biloba had lower leaf δ¹³C value than V. negundo and Z. jujuba var. spinosa did, which suggests that G. biloba had a lower water use efficiency, as higher leaf δ¹³C value indicates higher water use efficiency. The leaf δ¹³C value of V. negundo and Z. jujuba var. spinosa increased one week earlier than that of G. biloba during autumn drought event. The result indicates that the firsttwo shrubs were more sensitive to drought and can increase water use efficiency promptly when drought occurs. During seasonal drought period, the leaf δ¹³C value and water use efficiency in V. negundo were higher than in Z. jujuba var. spinosa, whereas Z. jujuba var. spinosa can maintain higher water content in both leaves and twigs, indicating a strong water retention capacity. The twig water content of G. biloba increased immediately with a great amount after rainfall event.[Conclusion] The water consumption and water use efficiency showed similar seasonal variation in the three shrubs. However, they had different water use strategies. The Z. jujuba var. spinosa and V. negundo consumed less water, with a higher water use efficiency, and water use from deep water source. Thus, the two species can be used as pioneer materials in afforestation. The G. biloba had water use strategies with a higher water consumption, lower water use efficiency and shallow water source. It is suitable for medium term restoration.

Key words: shrub, δ¹³C, transpiration, water use efficiency