华北土石山区荆条潜在蒸散量及作物系数分析

目的 研究荆条灌丛的潜在蒸散量及作物系数变化趋势，为半干旱区水资源管理及植被建设提供依据。 方法 利用河南黄河小浪底地球关键带国家野外观测站2021年5—10月份的蒸渗仪数据、逐日气象数据、荆条叶面积指数（LAI）及新梢生长量数据，利用Penman-Monteith公式计算参考作物蒸散量（ET0），分析生长状况基本一致、水分充足条件下的荆条不同生育期的潜在蒸散量、作物系数的变化趋势及其与生长指标的关系。 结果 （1）在荆条生育期内，ET0值整体呈下降趋势，5、6月份较高，7月份后开始下降，ET0总值为630.86 mm，日均值为3.43 mm·d−1。（2）荆条生育期内荆条灌丛的潜在蒸散量呈抛物线式变化，表现为开花期最大，总值为336.26 ± 18.19 mm，日均值为5.51 ± 0.30 mm·d−1；结果期和展叶期次之，落叶期最小，总值为41.57 ± 3.61 mm，日均值为1.98 ± 0.17 mm·d−1；整个生育期的总值为716.47 ± 40.21 mm，日均值为3.89 ± 0.22 mm·d−1。（3）荆条灌丛LAI和新梢生长量在5、6月增长较快，之后变缓。其中LAI在8月达到最大值（2.93 ± 0.07），之后开始下降，10月降为最小值（1.63 ± 0.08）。新梢在5月增长量最大，为6.85 ± 0.25 cm，10月基本停止生长。（4）荆条作物系数在生育期内呈先增后降的变化趋势，结果期最大（1.45 ± 0.22），开花期次之（1.25 ± 0.13），展叶期（0.98 ± 0.05）和落叶期（0.95 ± 0.14）最小，整个生育期平均为1.28 ± 0.16。作物系数与叶面积指数呈极显著正相关（p＜0.01），决定系数R2为0.736，与新梢生长量相关性不显著（p＞0.05）。

Analysis of Potential Evapotranspiration and Crop Coefficient of Vitex negundo L. var. heterophylla (Franch.) Rehd. in the Rocky Mountainous Areas of North China

Objective To reveal the variation of potential evapotranspiration and crop coefficient of Vitex negundo L. var. heterophylla (Franch.) Rehd., for providing a basis for water resources management and vegetation construction of semiarid area. Method Based on the lysimeter data, daily meteorological data, leaf area index (LAI) data and growth of new shoot length data from May to October in the year of 2021 in Henan Yellow River Xiaolangdi Earth Key Belt National Field Science Observatory, combined with the Penman-Monteith formula, the trends of potential evapotranspiration (ET0)and crop coefficient of Vitex negundo L. var. heterophylla (Franch.) Rehd. under abundant water conditions in different growth stages and their relationship with physiological growth indexes were analyzed. Result (1) During the growth stage of Vitex negundo L. var. heterophylla (Franch.) Rehd., the ET0 value showed a downward trend. The ET0 value was higher in May and June, and began to decline after July. The total value of ET0 was 630.86 mm, and the daily average value was 3.43 mm·d−1. (2) The potential evapotranspiration during the growth period of Vitex negundo L. var. heterophylla (Franch.) Rehd. showed a parabolic trend. The potential evapotranspiration was the largest at blossom stage, with total value of 336.26 ± 18.19 mm and daily average value of 5.51 ± 0.30 mm·d−1, followed by fruiting stage and leaf unfolding stage, and the lowest value was found at defoliation stage with a total value of 41.57 ± 3.61 mm and a daily average value of 1.98 ± 0.17 mm·d−1, respectively. The total value of potential evapotranspiration during growth stage of Vitex negundo L. var. heterophylla (Franch.) Rehd. was 716.47 ± 40.21 mm, with a daily average value of 3.89 ± 0.22 mm·d−1. (3) LAI and new shoot length increased rapidly in May and June, and then the growth rate slowed down gradually. The maximum value of LAI reached its maximum value (2.93 ± 0.07) in August, then began to decline, and the minimum value was found in October, with the value of 1.63 ± 0.08. The growth of new shoots was the largest in May, 6.85 ± 0.25 cm, and basically stopped growing in October. (4) During the growth stage, the crop coefficient showed a parabolic trend, with the largest fruiting stage (1.45 ± 0.22), followed by blossom stage (1.25 ± 0.13), leaf unfolding stage (0.98 ± 0.05) and defoliation stage (0.95 ± 0.14) was the smallest, and the average of the whole growth stage was 1.28 ± 0.16. There was a significant positive correlation between crop coefficient and LAI (p < 0.01), with the coefficient of determination R 2 0.736, and there was no significant correlation between crop coefficient and growth of new shoot length (p > 0.05).