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进入20世纪90年代以来,由于人口的增加和经济的发展,荒漠化问题日益引起世界各国政府、国际组织和科学家的普遍关注。有关荒漠化程度评价的问题已成为当前土地科学研究领域一个新的热点。先从荒漠、荒漠化、荒漠化评价的概念入手,阐述了荒漠化评价的目的意义,进而说明土地荒漠化的原因、荒漠化过程和荒漠化发展程度、速率,自然环境的脆弱性,以及土地退化的原因等。详细介绍了荒漠化评价的国内外现状,着重探讨了以下几个问题:荒漠化评价类型,荒漠化评价原则,荒漠化评价方法,荒漠化评价的分级标准等。由于荒漠化研究是一门年轻的学科领域,许多荒漠化基础理论问题有待发展和完善,特别是荒漠化评价指标体系的建立还明显存在很多不足,有待进行进一步的研究 相似文献
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内蒙古中西部地区位于我国北部边疆,处于生态环境脆弱的农牧交错带上,自然演变的过程漫长且复杂,是灾害多发的地带,是极易土地沙化的区域,对各种自然和人为扰动极为敏感。在阐述内蒙古中西部地区气候形成概况的基础上,通过文献资料回顾了人类古代历史文化期的气候的变化与沙化情况。研究结果表明,历史上冷暖干湿气候差异性的交替运行,导致区域生态环境的波动变化和易灾、易沙化的趋势;气候的变化还通过早期人类活动的集聚格局,间接地影响了历史时期土地沙化的发展。 相似文献
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Land degradation is not uniform, even in the same landscape, but nevertheless an overall consensus seems to grow on the fact that many areas are under way of rehabilitation. It is a debateable question whether the improving areas are improving because of interventions—or whether this has more to do with processes of innovation and adaptation. The international symposium ‘HighLand2006’ on land degradation and land rehabilitation, held in Mekelle (Ethiopia), from 21 to 25 September 2006, created a forum for those conducting research in East African Highlands as well as in similar regions around the globe to discuss findings. Tropical highlands (>1000 m a.s.l.) cover 4.5 million km2 with an average population density of 33 inhabitants km−2. Nearly all tropical highlands suffer from land degradation, especially medium to very high water erosion. Exchange of experiences during in-door sessions and excursions led to results which are condensed in this special issue. Studies presented tend to invalidate hypotheses on irreversibility of land degradation in tropical mountain areas. Circumstances are that in highly degraded environments, with high pressure on the land, no other alternatives are left open but to improve land husbandry; and that this is particularly successful in places where decision making processes at different levels in society give the highest priority to the implementation of soil and water conservation and other land rehabilitation, in situ and at catchment level. 相似文献
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Benqiang Rao Yongding Liu Weibo Wang Chunxiang Hu Shubin Lan 《Soil biology & biochemistry》2009,41(12):2387-2393
Dew is an important water source for desert organisms in semiarid and arid regions. Both field and laboratory experiments were conducted to investigate the possible roles of dew in growth of biomass and photosynthetic activity within cyanobacterial crust. The cyanobacteria, Microcoleus vaginatus Gom. and Scytonema javanicum (Kütz.) Born et Flah., were begun with stock cultures and sequential mass cultivations, and then the field experiment was performed by inoculating the inocula onto shifting sand for forming cyanobacterial crust during late summer and autumn of 2007 in Hopq Desert, northwest China. Measurements of dew amount and Chlorophyll a content were carried out in order to evaluate the changes in crust biomass following dew. Also, we determined the activity of photosystem II(PSII) within the crust in the laboratory by simulating the desiccation/rehydration process due to dew. Results showed that the average daily dew amount as measured by the cloth-plate method (CPM) was 0.154 mm during fifty-three days and that the crust biomass fluctuated from initial inoculation of 4.3 μg Chlorophyll a cm−2 sand to 5.8-7.3 μg Chlorophyll a cm−2 crust when dew acted as the sole water source, and reached a peak value of approximately 8.2 μg Chlorophyll a cm−2 crust owing to rainfalls. It indicated that there was a highly significant correlation between dew amounts and crust moistures (r = 0.897 or r = 0.882, all P < 0.0001), but not a significant correlation between dew and the biomass (r = 0.246 or r = 0.257, all P > 0.05), and thus concluded that dew might only play a relatively limited role in regulating the crust biomass. Correspondingly, we found that rains significantly facilitated biomass increase of the cyanobacterial crust. Results from the simulative experiment upon rehydration showed that approximately 80% of PSII activity could be achieved within about 50 min after rehydration in the dark and at 5 °C, and only about 20% of the activity was light-temperature dependent. This might mean that dew was crucial for cyanobacterial crust to rapidly activate photosynthetic activity during desiccation and rehydration despite low temperatures and weak light before dawn. It also showed in this study that the cyanobacterial crusts could receive and retain more dew than sand, which depended on microclimatic characteristics and soil properties of the crusts. It may be necessary for us to fully understanding the influence of dew on regulating the growth and activity of cyanobacterial crust, and to soundly evaluate the crust's potential application in fighting desertification because of the available water due to dew. 相似文献
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在共和县沙珠玉乡荒漠区进行了造林配置研究,分析了深栽造林、不同沙障类型及形式在荒漠区的造林效果。结果表明:深栽造林树苗的成活率高达91.7%,较常规的植苗造林成活率提高29.2%,而沙障类型中格状式沙障形式较行列式沙障形式苗木的成活率提高30%-56%。 相似文献
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防治西北地区荒漠化 促进社会可持续发展 总被引:2,自引:1,他引:1
西北地区自然条件恶劣,风沙危害和水土流失十分严重,荒漠化逐年扩展是实现西部地区可持续发展的最大障碍。荒漠化土地面积占国土面积的27.04%,主要分布在干旱和半干旱地区,多因自然因素、人为因素和政策因素造成。防治荒漠化应全面规划,综合防治,预防为主,因地制宜,加强管理,重视效益。做到生物措施与工程措施相结合,生态、经济和社会效益的协调一致,促进社会可持续发展。 相似文献