【摘要】 为确定土壤质地对旱生植物长柄扁桃（Amygdalus pedunculata Pall）和沙柳（Salix psammophila）幼苗不同生理指标水分有效性的影响,采用盆栽控水试验,研究了黄土高原2种典型质地土壤（砂土和壤土）下长柄扁桃和沙柳幼苗不同生理指标随相对土壤含水率（土壤含水率占田间持水率的比值）的动态变化。结果表明:2种质地土壤下长柄扁桃和沙柳幼苗各生理指标相对值在相对含水率降低至土壤水分阈值之前保持相对稳定,低于此阈值时随相对含水率的降低而迅速下降,且均可用非线性连续函数来拟合（R²=0.8905～0.9864）。2种植物土壤水分有效性因选取指标的不同而略有差异,当以瞬时气体交换指标(相对净光合速率R_Pn和相对气孔导度R_Gs)为评价指标时,砂土水分有效性高于壤土;当以相对水分利用效率R_WUE为评价指标时,壤土水分有效性高于砂土。瞬时气体交换指标(R_Pn和R_Gs)的水分阈值高于日变化指标(相对日蒸腾速率R_Td),表明土壤质地和时间尺度均会影响植物生理指标对土壤水分有效性的响应。因此,在黄土高原进行植被恢复与生态建设时应考虑土壤质地对植物水分有效性的影响。更多还原

【Abstract】 【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 CO₂ 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 R² ranging between 0.890 5 and 0.986 4.The inflexions on the curves could be deemed as soil moisture threshold（W₀）, which varied with species of the shrub and index selected, and with type of the soil too. The soil moisture threshold（W₀） 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（W₀） corresponding to the water use efficiency（WUE）. The soil moisture threshold（W₀） 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.更多还原