黄土丘陵区旱作枣树规格与枣林耗水量关系研究

以枣树为研究对象,通过对自然生长枣林与矮化密植枣林、截干枣林、极端矮化的枣树及不同修剪强度枣林土壤水分进行监测,采用水量平衡法分析上述情况下枣林耗水特点及枣树水分利用效率。结果表明:自然生长枣林每年在土壤中耗水量较矮化密植枣林大6.54 mm,耗水深度较矮化密植枣林大13.3 cm,水分利用效率最小,2014、2015年分别为2.1、1.8 kg/m~3;12龄枣林实施截干处理3年,其林下土壤水分恢复深度达460 cm,每年恢复深度达153.3 cm,是形成干层速度的3.41倍;极端矮化枣树规格降低1/2,其耗水量为同龄枣林的25%,水分利用效率是同龄枣林的1.26倍;枣树不同修剪强度与其蒸腾耗水关系紧密,随着修剪强度加大枣树蒸腾耗水量减小,林下土壤含水率可提高。研究显示,枣林可以通过对枣树规格的缩小来实现枣林耗水量及水分利用效率的调控,黄土高原半干旱区年降水量波动较大,确定当地适宜修剪强度指标时,建议参考多年平均降水量来制定。

Relationships between Tree Crown Size and Water Consumption of Rain-fed Jujube Plantation in Loess Hilly Region

In order to investigate the relationships between tree crown size and water consumption of rain-fed jujube plantations, soil moisture under different conditions (natural planting, high-density dwarfing, stem-cutting, extreme dwarfing and pruning with different intensities) were measured by using the CNC100 neutron gauges, meanwhile, water balance method was used to calculate the water consumption and water use efficiency of above-mentioned jujube plantations. Results showed that compared with natural plantation, high-density dwarfed jujube trees reduced annual water consumption of 6.54mm and water consumption depth of 13.3cm, respectively. Moreover, it increased the water use efficiency to 1.8kg/m3 (the lowest for natural jujube plantation was 2.1kg/m3). The soil moisture restoration of 12 years old cutting stem jujube plantation reached 460cm depth in the third year (153.3cm per year on average), which was 3.41 times faster than the formation of soil dry layer. Extremely dwarfed jujube with half of normal crown size decreased the water consumption by 25% and improved the water use efficiency by 1.26 times of natural jujube plantation, respectively. Pruning is an effective approach to improve soil water status and water use efficiency in jujube plantation because of the close relationship between crown size and jujube water usage. Furthermore, the reasonable pruning intensity, which aimed to obtain high yield and water use efficiency, should be determined based on local rainfall considering its high variability in the semi-arid Loess Plateau.