干旱半干旱地区草原灌丛荒漠化及其 生物地球化学循环

doi:10.11820/dlkxjz.2007.04.005

摘要/Abstract

摘要：

干旱和半干旱地区草地生态系统木本植物入侵及其导致的草原灌丛化已经成为全球范围普遍发生的现象，是草地沙化和荒漠化的一个重要标志。干旱生态系统中，此种类型的植被变化将对区域和全球生物地球化学循环产生显著影响。过度放牧、区域气候干旱化和自然火过程是导致灌丛入侵和发展的主要控制因子。草原灌丛化过程中，草地生态系统分布较为均匀的土壤养分及相关元素在水平和垂直方向发生分异，关键生命元素C、N、P 、S 生物地球化学循环的变化将对全球气候变化产生显著作用。全球气候变化与草原灌丛荒漠化之间存在潜在的反馈机制，人类扰动的影响将使这种反馈作用变得更加迅速和灵敏。

关键词: 草地生态系统, 干旱、半干旱地区, 灌丛荒漠化, 全球变化, 生物地球化学循环, 沃岛

Abstract:

As one of the most widespread vegetation types worldwide, Grasslands cover nearly one - fifth of the world' s land surface area and play a significant role in the global climate change and biogeochemistry cycle. However, a large area of grasslands in the world has been faced a serious problem- degradation and desertification. One form of desertification is the conversion of homogeneous grasslands into shrub- dominated ecosystems and shrubs encroachment has become a widespread phenomenon in arid grasslands and savannas over the past century. The transition has greatly affected ecosystem structure and function in semiarid and arid ecosystems. Overgrazing, regional climate drought and natural fires are the critical factors controlling shrubs encroachment and development. During the process of shrubs encroachment, the wind erosion and water erosion of soil will be strengthened and the soil nutrients and other noessential elements distributed uniformly in grasslands will gradually develop horizontal and vertical patterns in soil dimensions and finally lead to the formation of "islands of fertility", which makes the spatial heterogeneity of soil resource more evident. In addition, the enhancement of wind erosion with the encroachment of shrubs also increased the loss of soil resource, such as C, N, P, S and further influenced the redistribution of these elements among soil, atmosphere and biosphere. The shrubs encroachment and accompanied changes of biogeochemistry cycles will be markedly contributed to the global climate change through increasing the content of aerosol, carbon dioxide and nitrous oxide in the atmosphere and there exists a sensitive feedback mechanism between them. China has an area of grasslands of about 4 ×106 km² or about 40% of the nation's total land surface and most of these areas have been affected by desertification, but reports on the biogeochemical effects of grass- shrub transition are limited. Therefore, Reinforcing research on shrub encroachment of grassland ecosystem along with the accompanied transformation of plant and soil resource distribution pattern is crucial for accurately understanding the desertification process and predicting the potential changes of elements biogeochemical cycle the in semi- arid and arid grasslands.

Key words: biogeochemistry cycles, fertile islands, global climate change, grassland ecosystem, semiarid and arid regions, shrub encroachment

金钊,齐玉春,董云社. 干旱半干旱地区草原灌丛荒漠化及其生物地球化学循环[J]. 地理科学进展, 2007, 26(4): 23-32.

JIN Zhao,QI Yuchun,DONG Yunshe. Shrub Encroachment and Accompanied Changes of Biogeochemistry Cycles in Semiar id and Ar id Gr asslands[J]. PROGRESS IN GEOGRAPHY, 2007, 26(4): 23-32.

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