干旱荒漠区人工植物群落演替模式及其生态学机制研究

以我国干旱荒漠区包兰铁路沙坡头地段人工植被防护林体系作为研究对象，研究了区域植被建立与发展过程中，优势植物种的种群动态和人工植物群落的演替模式，探讨了植物群落演替的内在动因和生态学机制．结果表明，该区人工植被经过40余年的演变，其植物种组成发生了很大的变化，已由原来的灌木、半灌木人工植物群落演变为一年生草本植物占优势的人工-天然荒漠植物群落．在此演替过程中，人工栽植的灌木种如柠条、花棒等的重要值不断减少，逐渐从人工植物群落中退出；而天然繁衍的一年生草本植物如小画眉草、雾冰藜、刺蓬、虎尾草等相继侵入，并逐渐成为该区的优势植物种；油蒿由于具有天然下种自行更新能力，在群落中始终占有重要地位．这种物种替代模式与该地区降水资源严重匮乏以及沙地表面结皮的增厚，致使沙子下层含水量降低。深根系的灌木及多年生草本的繁衍受到限制密不可分．

Succession pattern of artificial vegetation community and its ecological mechanism in an arid desert region

Focusing on the artificial vegetation protection system of the Shapotou section of Baotou-Lanzhou railway in the arid desert region of China, this paper examined the dynamics of dominant plant species and the succession pattern of artificial plant community in the process of establishing and developing regional artificial vegetation. It also studied the driving force and the ecologically intrinsic mechanism of the community succession. The results demonstrated that the species composition of the artificial vegetation dramatically changed after 40 years of succession, from original artificial plant community of shrub and semi-shrub to artificial-natural desert plant community with annual herb dominated. During the process of succession, the importance values of artificial shrubs, such as Caragana korshinskii and Hedysarum scoparius, decreased and gradually retreated from the artificial plant community, while the naturally multiplied annual herb, such as Eragrostis poaeoides, Bassia dasyphylla, Salsola ruthenica, Chloris virgata and etc., were presented one after another and gradually became dominant. Besides, Artemisia ordosica always played a key role in the community due to its ability of naturally sowing and self-replacement. This type of succession pattern was closely related to the shortage of precipitation resource in this region and the formation of soil crust which inhibited the reproduction of shrub and perennial herb with deep root systems. This study provided a theoretical ground for realizing persistent development of artificial plant community.