干旱区沙漠化逆转过程中优势种群及其根系特征研究

Dominant populations and its root characteristics in progressive succession of desertification land in arid area

根系是植物群落演替的重要内容,对植被演替过程具有十分重要影响作用。采用时空替代法,选择不同恢复阶段,研究了干旱荒漠区植被恢复演替不同阶段优势种群及其根系生态特征。结果表明:沙漠化逆转过程中,优势种群更替过程为:沙米-沙蒿-油蒿-紫婉木、针茅;在恢复演替初期(初始阶段,先锋阶段)植被根系浅(平均<50 cm)而水平分布范围广,侧根数量少但生长旺盛;随着恢复时间的加长,优势种群根系分布深度增加,侧根数量增加但水平生长受到一定的抑制,根幅逐渐减小;优势种群根冠比的变化趋势为沙米(初始阶段)<沙蒿(先锋阶段)<油蒿(发展阶段)<针茅(原生群落)。研究同时发现,同一种群在不同的演替阶段具有不同的根系分布特征和规律。对于沙蒿种群来说,根冠比是发展阶段(0.56)>先锋阶段(0.36),而地上、地下生物量却是先锋阶段(360.83g,161.33g)>发展阶段(32.8g,16.81g);而油蒿根冠比则是发展阶段(0.61)>相对稳定阶段(0.21)。各演替阶段根系和土壤环境因子之间存在相互影响,优势种群根系生物量及生物量分布与土壤颗粒组成、土壤水分的空间分布有着密切的关系。

Roots play an important role in plant progressive succession. The dominant population and its root characteristics under different recovery phases in progressive succession on desertification land in arid area were studied with the method of substituting time with space. The results indicated that：In the desertification revert process, the dominant population changed from Agriophyllum squarrosum to Artermisia sphaerocephala to Artermisia ordosica to Stipa plareosa and Asterothamnus centrali - asiaticus. In the early time of progressive succession （the initial stage and the pioneer stage） , the dominant populations had shallow root system （an average of 〈 50 cm）, but the horizontal distribution was wide. There were a few lateral roots but grew exu -berantly. With the increase of enclosure time, the root depth of dominant population increased but horizontal growth was inhibited. The root- shoot ratio for dominant population was Agriophyllum squarrosum （the initial stage） 〈 Artermisia sphaerocephal（ the pioneer stage） 〈 Artermisia ordosica （ the development stage） 〈 Stipa plareosa （ Original vegetation）. The study also found that the same populations in different stages of succession had different root distribution system and the laws. Root biomass had a close relation with soil particles and the spatial distribution of soil moisture.