太行低山区荆条耗水特征及其与参考作物蒸散量的关系

荆条是太行低山区常见的典型灌木，因其具有抗逆性强、耐贫瘠等特点，在水土保持、生态修复、山区绿化等方面广泛应用。研究荆条耗水变化规律不仅可以揭示其耗水机制，还能为植被恢复重建与管理提供理论依据。本研究采用大型称重式蒸渗仪搭配自动气象站的方法，对太行低山区乡土灌木荆条的耗水及气象因子进行观测，同时利用FAO-56 Penman-Monteith公式结合相关气象因子计算参考作物蒸散量（ET0），揭示不同时间尺度下荆条的耗水特征及其与ET0的关系。结果表明：（1）日内尺度上，荆条耗水表现为单峰曲线，与太阳辐射（Ra）、气温（Ta）及饱和水汽压亏缺（VPD）趋势一致，而与相对湿度（RH）相反，荆条耗水峰值出现时间略滞后于Ra。日尺度上，荆条耗水表现为“弱?强?弱”的趋势，即生长季前期与后期日耗水强度较小（分别为1.50mm和2.00mm）、中期较大（4.00mm），生长季内最大和最小日耗水分别出现在8月29日和10月9日，大小分别为6.38mm和0.20mm。月尺度上，荆条耗水表现为8月>7月>9月>10月>6月>5月，主要生长季节荆条共消耗水分513.5mm，同期降水526.6mm，整体上降水可满足荆条耗水需求，但5?6月降水较少，荆条易遭受季节性干旱。（2）荆条具有较强的环境适应性与生态可塑性。在雨季，荆条生长旺盛，水分传输率高，耗水量大；在干旱季节，荆条启动自适应机制，减少水分消耗。（3）荆条日耗水与日ET0之间关系表现为：干旱季节（5?6月）二者相关性较差，降水充沛的季节（7?10月）二者表现为很好的对数关系（R2=0.7431）。利用建立的拟合方程对荆条耗水进行估算，并与实测值进行对比，发现估算值与实测值具有较好的一致性，误差小，说明在降水充沛的季节可利用拟合方程对荆条耗水进行估算。

Water Consumption Characteristics of Vitex negundo in Hilly Region of Taihang Mountains and Its Relationship to Reference Evapotranspiration

Vitex negundo is the native shrub species which was very popular in low mountain area of Taihang Mountains. It is widely used in such aspects as mountain greening, soil and water conservation, and ecological restoration due to its characteristics of strong resistance, and tolerance to barrenness. Studying on the water consumption of Vitex negundowas could not only reveal its water consumption dynamics and influencing mechanism, but also provide theoretical basis for local vegetation restoration and management. The water consumption of Vitex negundo and meteorological factors were measured with large weighing lysimeter and the automatic weather station, respectively. At the same time, reference evapotranspiration (ET0) was calculated by the Penman-Monteith equation recommended by FAO-56. The objective of the paper was to study the water consumption of Vitex negundo on different time scales, to find the adaption capacity to the arid environment, to reveal the relationship with ET0, and to provide empirical model for estimating the water consumption of Vitex negundo under the conditions of lacking measured data. The results showed that: (1) diurnal variation of water consumption of Vitex negundo showed single peak curve on typical days , which was consistent with solar radiation, air temperature, and vapor pressure deficit, but contrary to the relative humidity. Meanwhile, the peak time of water consumption of Vitex negundo. was 2 hours behind that of solar radiation, and time lag was found between them. Water consumption trendy of Vitex negundo on daily time scale showed low water consumption in the early and later growth period, and high in the middle growth period, and the value was 1.50mm, 2.00mm, and 4.00mm per day, respectively. Maximum and minimum of daily water consumption was found on 29th in August and 9th in October, with the value of 6.38mm and 0.20mm, respectively. The water consumption of Vitex negundo on monthly time scale showed the tendency of August >July > September > October> June > May. The total water consumption of Vitex negundo during the growth period was 513.5mm, and the rainfall was 526.6mm. The precipitation could meet the needs of water consumption Vitex negundo from the perspective of water balance. However, seasonal drought existed from May to June due to the less rainfall. (2) Vitex negundo has the feature of environmental adaptability and ecological plasticity. In rainy seasons, Vitex negundo was in prosperous growth period, the water transmission rate was high, and the water consumption was large. Adaptive mechanism started in arid season to reduce water consumption. (3) Good logarithmic relationship was found between daily water consumption of Vitex negundo and reference evapotranspiration in rainy seasons (July to October), while poor correlation was discovered between them in dry seasons ( May to June). The estimated value of water consumption was calculated with the fitting equation, and was compared with the measured valued by the lysimeter. The good consistency and small error were found between the estimated and measured values, which conformed the precision of the fitting equation. It was indicated the fitting equation was accurate to estimate water consumption of Vitex negundo in rainy seasons of the local area, but inaccurate in dry seasons.