摘要
土壤养分的变化与荒漠化植被演替有密切的关系,当草地生态系统演变为以灌丛为主的生态系统时,土壤养分的空间变异性增强,形成以灌丛为核心的'肥岛';风蚀是造成荒漠化土壤养分迁移的重要动力,而降尘对荒漠化表层土壤养分具有富集作用;如果降尘作用大于风蚀作用,土壤养分将增加,如亚马逊盆地通过降尘每年获得的磷为1～4 kg/hm2.水蚀也是荒漠化地区土壤养分损失的主要途径,灌丛生境每年径流的损失量比草地生境的径流损失量大得多,而且草地生境发生荒漠化时其灌丛的入侵可能与土壤氮素的损失有关.在荒漠化地区,火烧可导致凋落物中43%的全氮在燃烧中逸失,火烧后土壤的侵蚀模数增加,频繁的火烧会导致灌丛草原的'肥岛'消失.对荒漠化地区自然土壤的农业开垦一般导致土壤有机质质量分数的下降,风蚀作用加强而往往导致土壤退化;但经过恢复植被和土壤改良,表层土壤养分可明显提高.目前专门针对荒漠化土壤养分循环的模型尚未报道;但荒漠化地区主要集中于干旱、半干旱地区的草原、荒漠草原地区,针对草地生态系统中土壤C、N、P、S等养分循环已经有不少模型,如EIPC模型、SPUR模型、CENTRUY模型等;它们也可以用来揭示荒漠化土壤的养分循环以及与荒漠化之间的关系;把这些模型进一步与GIS相结合,研究区域尺度上土壤养分的变化与荒漠化的关系更有现实价值.文章从多方面概括了风蚀、水蚀、火烧、植被演替、农业措施对荒漠化土壤养分的影响,以及目前荒漠化土壤养分的空间变异和荒漠化土壤养分循环的定量化研究现状.
The changes in the soil nutrients impact the pathways of the plant succession in the desertification area. As the grassland ecosystem change into desert shrub dominant ecosystem, the spatial heterogeneity of the soil nutrients became higher with the development of 搃slands of fertility?under shrubs. Changes in the distribution of soil properties may be a useful index of desertification in arid and semiarid grasslands worldwide. Wind erosion is the main transmiting force of soil nutrients. Strong wind erosion causes the nutrients in topsoil to lose fastly, but the air deposits make a richment of nutrients in topsoil if the deposition was stronger than the wind erosion, for an example, Saharan dust enters the Central Amazon Basin in bursts which accompany major wet season rain systems. Deposition of phosphate, associated with this dust amounts to 1~4 kg/hm2 annually. Similarly, the water erosion is another main force drivig the soil nutrients transference.It showed the runoff take more soil nutrients from the desert shrub land than from the grassland, and the losses of soil nutrients may promote the invasion and persistence of shrubs and cause potential feedbacks between desertification. Under frequent burning, nutrient contents in the soil declined sharply and usually enhanced the soil erosion, and at last make the islands of fertility?disappeared in the shrubland. The reclamation often made the soil organic matrer and nutrients content decline, but some measures such as vegetation resuming, and erosion-preventing treatments could improved the soil nutrients content. There were several models which could be used to research the soil nutreints circulation in the desertification area, such as EPIC model, SPURE model, and CENTURY model. All of these models were wholly systems models which could simulate the main elements (C, N, P, and S) movement in the ecosystem。To combine thes models with GIS is helpful to research the regional soil nutrients circulation. This paper summarize the nutrition changes in desertification soils under the influence of erosion (wind and water), fire, plant succession and agricultural massures in desertification soils. It also discuss the the spatial variability of the soil nutrients in the desertification ecosystem and the models of nutrition circulation.
出处
《生态环境》
CSCD
2003年第4期473-477,共5页
Ecology and Environmnet
基金
国家自然科学基金重大项目(39990490)
关键词
荒漠化
土壤养分
风蚀
水蚀
空间变异
dertification
soil nutrients
wind erosion
water erosion
spatial variance
