黄土旱塬主要农林用地土壤水文特征对比

Comparison of soil hydrological characteristics for main cropland and orchard in dry highland of the Loess Tableland

土壤水分是黄土高原地区植被恢复与农林产业持续发展的主要限制因子,为明确主要农林用地土壤水分变化特征及其干化现状,利用CNC503B（DR）中子仪,于2014年4—10月,对长武塬区19龄果园、9龄果园、玉米地及小麦地0～600 cm的土壤水分进行长期监测,并利用土钻法进行校准。结果表明：1）0～600 cm土壤贮水量表现为9龄果园〉玉米地〉小麦地〉19龄果园,均值分别为186.5、183.6、158.6和132.8 cm,除9龄果园与玉米地间差异性不显著（P〉0.05）外,其他农林用地土壤贮水量两两比较均呈显著性差异（P〈0.05）;2）4块样地浅层（0～200 cm）土壤含水量波动程度为中等变异（10%600 cm;4）19龄苹果园土壤干化最严重,0～200 cm土壤干化程度呈季节性变化,200～250和250～320 cm土层分别为严重干燥化与强烈干燥化,320～600 cm呈极度干燥化,形成永久性土壤干层;其次为小麦地,0～100 cm产生临时性干层,250～300 cm发生强烈干燥化;玉米地与9龄果园干化程度较轻,在水分补给不足情况下,只在土壤浅层产生临时性土壤干层。长武塬区农业结构由大田作物转向苹果经济林建设具有一定理论基础;但是,随着苹果林达到盛果后期,土壤贮水量亏缺,土壤干化严重,苹果经济林的经济价值及生态作用等都将受到限制,需要采取合理用水措施及调整林分密度等科学方式,完成长武塬区经济与生态的可持续发展。

[ Background ] Soil water is the main factor limiting the recovery of vegetation and the sustainable development of agriculture and forestry in the region of the Loess Tableland. Soil water content in 9-year apple orchard, 19-year apple orchard, corn field, and wheat field was investigated in the Changwu Tableland to define the soil hydrological characteristics and soil drying state of main cropland and orchard on the Loess Plateau. I Methods] The water storage capacity of soil in a profile of 600 em was measured using a neutron probe （CNC503B） from April to October in 2014. [ Resultsl 1 ） The 9-year orchard had the largest soil water storage in 0 - 600 cm soil profile, followed by the corn field, wheat field and 19-year orchard in which soil water storage averaged 186.5, 183.6, 158.6 and 132.8 cm, respectively. There was no significant difference between the corn field and 9-year orchard, but significant differences existed among other fields. 2） Soil water content in shallow soil layer （0 - 200 cm） for the 4 fields showed medium variation （ 10% 〈 CV 〈 100% ） , while soil water content in deep soil layer was relatively stable （CV 〈 10% ）. 3） The depth of soil water depletion for the 19-year orchard was 500 cm, while the depths for the 9-year orchard, corn field and wheat field were all 300 cm. The rain replenishment depth of the 19-year orchard was 250 cm, while the depths for the 9-year orchard, corn field and wheat field were all deeper than 600 cm. 4） Compared with other fields, soil desiccation in the 19-year orchard occurred most severely. Specifically, the 0 -200 cm soil layer dried seasonally, the 200- 250 cm and 250 -320 cm soil layers dried severely, and the 320 -600 cm soil layer dried extremely. Thus, a persistent soil dry layer formed. Soil desiccation in the corn field and 9-year orchard occurred seasonally, and a temporary soil dry layer formed in the shallow soil layer in the case of water shortage. [ Conclusions] It is scientific to transfer the agricultural structure of Changwu Tableland from field crops to apple economic forest, but the soil-moisture storage will be absent and the soil drying will be severe after the apple forest reaching the later stage of full fruit period, as a result, the economic value and ecological effect of apple forest will be restricted, thus scientific methods shall be taken such as reasonable water management measures and adjusting stand density to realize the sustainable development of economy and ecology in the region of Loess Tableland.