中国南方湿润区红层荒漠化问题

A preliminary study of desertification in red beds in the humid region of Southern China

通过回顾国内外荒漠化概念的演变和国内对荒漠化问题的研究,认为发生在湿润区和半湿润区的极端土地退化也是一种特殊的荒漠化。中国南方湿润区的红层分布区由于岩性的特殊性,在人类的不合理开发利用影响下,产生了一种特殊的土地退化现象,暂称之为红层荒漠化。作为对该问题研究的初步成果,本文提出了红层荒漠和红层荒漠化的概念,重点阐述了红层软岩区荒漠化的地貌特征、生态特征和土壤特征。然后以南雄盆地为例,分析了劣地式红层荒漠的分布特征及盆地尺度的荒漠化格局,认为红层荒漠最初以点状揭露的方式形成,然后发展为呈斑块状分布;劣地式荒漠化基本都发生在盆地中部由软岩构成的缓丘和岗地区域。在面上调查和案例地深入研究的基础上,从岩石特性、自然影响和人为干扰等方面探讨了劣地式红层荒漠化的形成机理,劣地式红层荒漠化过程的诱发因素较复杂,主要是人为影响,可概括为:粗放开垦、林地过火、旱地退化、人为取表土以及村庄内的多因素干扰。红层暴露后在自然力和人为作用下都可能发生荒漠区扩展。

The development of domestic and foreign concepts, and previous research of desertification are reviewed in this paper. We conclude that extreme land degradation in sub- humid and humid regions should be classified as desertification. Due to the lithology of the soft redbed rocks, along with excessive resource exploitation by humans and the humid climate, a special kind of desertification occurred in redbed regions in Southern China. As preliminary research conceming redbed desertification, we put forward the concepts of redbed deserts and redbed desertification. We also elaborate on features of desertification developing in redbed regions, such as landform features, ecological features, and soil features. Then, utilizing Nanxiong Basin as a case study, the spatial patterns of redbed desertification and the patterns of desertification at the basin scale are analyzed. The process of redbed desertification begins as spotty uncovering, and then develops into patches. Redbed desertification has mostly occurred on hills formed of soft rock in the central part of the basin. Based on the field work, the mechanism of redbed desertifieation is discussed from the aspects of lithological features, natural impacts, and human activities. The triggers of redbed badland desertification are complex, but are mainly impacted by activities such as severe reclamation, forest fires, tree planting disturbances, dry-land degradation, acquirement of topsoil, and so on. Once red beds are exposed, the extension of the desert region can be caused by both nature and human activities.