科研之友
微信
新浪微博
Facebook
分享链接
摘要
【Objective】Amygdalus pedunculata Pall and Salix psammophila are shrubs of the Loess Plateau in China, which have widely been used in recent years as pioneer plants in vegetation restoration on the Loess Plateau, thanks to their good ecological adaptability and high economic value. However, how Amygdalus pedunculata Pall and Salix psammophila utilize soil water and its influencing factors are still unclear.This study is oriented to investigate soil water availability in soils under and two types of shrubs (i.e., Amygdalus pedunculata Pall and Salix psammophila seedlings) typical of the Loess Plateau, but different in physiological indices and its influencing factors. 【Method】 A pot experiment, designed to have two species of shrub (Amygdalus pedunculata Pall and Salix psammophila) planted separately in pots containing separately two types of soil (sandy soil and a loamy soil) combined with five levels of water regime (100%, 80%, 60%, 40% and 20% of the soil water holding capacity) and 5 replicates for each treatment, was carried out. Dynamics of physiological indices (net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO 2 concentration (Ci), water use efficiency (WUE), leaf water potential (Ψw), daily transpiration rate (Td), cumulative transpiration rate (Tc)) of the seedlings in each treatment were monitored.【Result】 Results show that all the physiological indices of the Amygdalus pedunculata Pall and Salix psammophila seedlings in the pots regardless of type of the soil they containedremained relatively constant in relative value till the relative water content fell below the soil moisture threshold and then they declined rapidly with soil water depletion going on. The variation curves of the indices could all be fitted with the nonlinear continuous function with R 2 ranging between 0.890 5 and 0.986 4. The inflexions on the curves could be deemed as soil moisture threshold (W 0 ), which varied with species of the shrub and index selected, and with type of the soil too. The soil moisture threshold (W 0 ) corresponding to the instantaneous gas indices (Pn and Gs) was higher in the loamy soil than in the sandy soil, whereas a reverse trend was observed with soil moisture threshold (W 0 ) corresponding to the water use efficiency (WUE). The soil moisture threshold (W 0 ) corresponding to the daily transpiration rate (Td) was higher in the sandy soil than in the loamy soil. Water availability was higher in the sandy soil than in the loamy soil when instantaneous gas exchange indices (relative net photosynthetic rate (R Pn ) and relative stomatal conductance (R Gs )) were used as evaluation index, whereas an opposite trend was observed with relative water use efficiency (R WUE ) used as evaluation index. The soil moisture thresholds based on instantaneous gas exchange indices (R Pn and R Gs ) at the transient scale were higher than those based on index at the daily scale (relative daily average transpiration rate, R Td ). 【Conclusion】 All the findings in this study demonstrate that both soil texture and time scale affect response of the plant in physiological indices to soil water availability. Continuous nonlinear function can be used to well describe dynamics of water availability under Amygdalus pedunculata Pall and Salix psammophila. Net photosynthetic rate (Pn), stomatal conductance (Gs), water use efficiency (WUE) and the transpiration rate (Td) can be used as indices for evaluating soil water availability. It is, therefore, essential to take into account effects of soil texture on water availability to plants in vegetation restoration and ecological construction on the Loess Plateau.
- 单位
