石羊河下游人工梭梭水分利用策略季节变化

作为石羊河下游主要固沙造林树种,人工梭梭(Haloxylon ammodendron)抗逆性和生态适应性强,构成了风沙灾害防治的第一道防线.本研究基于原位观测与稳定同位素示踪的方法,研究了人工梭梭水分来源的季节性变化,以期为民勤绿洲边缘退化防护体系的修复提供理论依据.结果表明:在生长季,人工梭梭根际垂直0?200 cm土层平均土壤水分含量为0.87％,120 cm深度处土壤水分偏高;水分季节变化表现为5月(1.22％)>4月(1.05％)>6月(0.83％)>7月(0.80％)>10月(0.67％)>8月(0.65％).不同季节人工梭梭0-60 cm表层根际土壤水δ18O富集效应明显,变化剧烈,60?200 cm土层δ18O逐渐减小且相对稳定.IsoSource模型表明,人工梭梭春季对120?200 cm深层土壤水分利用比例为45.15％,60?120 cm中层土壤水分的利用比例为20.6％,20?60 cm浅层土壤水分的利用比例为20.1％;夏季对0?20 cm表层、60?120 cm中层、120?200 cm深层土壤水分的利用比例分别为32.5％、24.75％、22.1％;秋季主要对0?20 cm表层、120?200 cm深层土壤水分利用较多,利用比例分别为44.4％和48.75％.不同深度土壤水分是人工梭梭重要的季节水分来源,建议在日常抚育管理中可采取人工辅助降水入渗的方法来维持林地土壤水分平衡.

Research on seasonal water use strategy of artificial Haloxylon ammodendron in the lower reaches of the Shiyang River

As the main sand-fixing afforestation tree species, artificial Haloxylon ammodendron has strong stress resistance and ecological adaptability, which are also the first lines of defense against wind-sand hazards in the lower reaches of the Shiyang River. Based on the methods of in-situ observation and isotope tracing, we studied the seasonal patterns of the water source of artificial H. ammodendron, which has important practical guiding significance for the restoration of the degraded protection system in the Minqin oasis. In the growing season, the average soil moisture in the 0－200 cm vertical soil layer of the rhizosphere of artificial H. ammodendron was 0.87%, and the soil moisture content in the 120 cm depth was relatively high. Soil moisture content seasonally showed the pattern: May (1.22%) > April (1.05%) > June (0.83%) > July (0.80%) > October (0.67%) > August (0.65%). Soil moisture δ18O in the 0???60 cm surface layer showed obvious enrichment, with drastic changes being observed, whereas that in the middle and lower layers was decreased and relatively stable. In spring, the proportions of soil water in the deep layer of 120???200 cm, the middle layer of 60???120 cm, and 20???60 cm shallow layer were 45.15%, 20.6%, and 20.6%, respectively. In summer, the soil water utilization ratios of 0???20 cm surface layer, 60???120 cm middle layer, and 120???200 cm deep layer were 32.5%, 24.75%, and 22.1%, respectively. In autumn, the soil water utilization ratios in the 0???20 cm surface layer and the 120???200 cm deep layer were relatively high, accounting for 44.4% and 48.75%, respectively. Soil water at different depths is an important seasonal water source of artificial H. ammodendron. It has been suggested that the methods of artificial supplementary rainfall infiltration were optimal to maintain the soil water balance of forestland in tending management.