Abstract:

In order to reveal the decline mechanism of Pinus sylvestris var. mongolica plantation in sandy land, using grassland as the control group, Pinus sylvestris (24 a, 38 a and 49 a) plantation of three different forest ages in the north wind sandy land of western Liaoning Province were taken as the research objects. The morphological characteristics of soil preferential flow and the influence of root system of Pinus sylvestris var. mongolica plantation of different forest ages were studied by means of field dye tracing. The results showed that the preferential infiltration depth of soil in Pinus sylvestris of different ages was 26?38 cm, and the maximum staining depth of preferential infiltration in 24-, 38-, and 49-year-old Pinus sylvestris stands and control samples were 26.66, 32.07, 35.38, and 37.31 cm, respectively. The depth of preferential infiltration deepened significantly with the growth of forest age. The dry wasteland soil lacking good soil structure was more prone to preferential flow phenomenon. In addition, the depth of infiltration was significantly related to the natural water content of the soil and the content of soil organic matter. As the age of Pinus sylvestris increased, the root length density and the dye area ratio increased, in which the large soil pore space produced by the root system and the pore space produced by root death had a decisive effect. Plant roots can significantly affect soil preferential flow. Different root indicators had different degrees of influence, among which root length density had a significant impact on soil preferential flow. With the growth of Pinus sylvestris var. mongolica forest age, it will grow slowly until a certain age and even appear premature aging phenomenon. There was a significant difference between root characteristic indexes of Pinus sylvestris var. mongolica forest at different ages, which directly affected the preferential inflow and infiltration characteristics of soil. The results can provide scientific basis and countermeasures for exploring the movement process and redistribution of the roots of Pinus sylvestris var. mongolica to soil water, the utilization of water resources and the decline mechanism of Pinus sylvestris var. mongolica plantation in the windy sandy land in the northwest of Liaoning Province.

Key words: wind sandy land, dyeing depth, root length density, preferential flow, Pinus sylvestris var. mongolica

摘要：

为揭示沙地樟子松人工林衰退机制，以辽西北风沙地24、38、49 a等3种不同林龄樟子松（Pinus sylvestris L. var. mongholica）人工林与对照组荒草地为研究对象，采用野外染色示踪的方法研究不同林龄樟子松人工林土壤优先流的形态特征及根系影响。结果表明，不同林龄樟子松人工林的土壤优先流入渗深度在26—38 cm，24、38、49 a樟子松林地与对照样地土壤优先流最大染色深度依次为26.66、32.07、35.38、37.31 cm，优先流入渗深度随着林龄的增长明显加深，缺乏良好土壤结构且干燥的荒草地土壤更容易出现优先流现象。并且入渗深度与土壤自然含水率、土壤有机质的含量关系密切；随着樟子松林林龄的增加，根长密度也增加，染色面积比也增加，其中根系所产生的土壤大孔隙和根系死亡所产生的孔隙有决定性的影响效果；植物根系可以显著影响土壤优先流，且不同根系指标的影响程度不同，其中根长密度对土壤优先流的影响达到显著水平；随着樟子松林龄增长，到一定年限则生长缓慢，甚至会出现早衰现象，不同林龄樟子松林地根系特征指标间差异显著，这也直接影响土壤优先流特征。研究结果可为深入探究辽西北风沙地樟子松根系对风沙土土壤水分运动过程及其再分布、风沙地水资源利用以及沙地樟子松人工林衰退机制提供科学依据以及应对措施。

关键词: 风沙土, 染色深度, 根长密度, 优先流, 樟子松