Variations of nutrient element contents of plants and soils in the process of karst rocky desertification

The present research on karst rocky desertification is mainly focused on qualitative analysis and obviously lack of quantitative and successive mechanism studies. Currently, classification of rocky desertification grades mainly depends on ratio of rocky coverage or ratio of plant and soil coverage. The process of rocky desertification was divided into latent, slight, medium and serious grades without mention of soil degradation. The Cha＇eryan catchment in the Huajiang Gorge of Guizhou Province was selected as the research area in this paper. Soil basic physical characteristics, nutrient element contents of soil and plant were studied in the process of rocky desertification. The karst soil characteristics elucidated that the clay content was high, the contents of soil organic matter, nutrient element （except potassium and sodium）, available contents of elements （except of potassium） were also high; ashes of plants were rich in calcium and nitrogen, and poor in iron, zinc, potassium and phosphorus. Meanwhile, the contents of plant ashes showed a significant positive relationship with calcium content of plant. There were no clear relations between soil degradation and succession of rocky desertification according to current classification standard. Soil particle size distribution, specific gravity, soil organic matter content, total and available nutrient element contents did not vary with the succession of rocky desertification.     

基于网格GIS的喀斯特石漠化治理过程中生态系统健康变化诊断——以贵州花江示范区为例

喀斯特石漠化地区生态系统健康是生态建设和石漠化综合治理的目标,以贵州省花江石漠化综合治理示范区为例,运用遥感影像解译方法,结合社会调查与水文气象监测数据,从生态环境支撑系统、资源环境支撑系统和社会经济支撑系统三个方面,构建石漠化治理过程中生态系统健康变化诊断指标体系,在格网GIS技术支持下,对各诊断指标实现5 m×5 m尺度的网格化表达,运用栅格数据的空间叠加方法实现生态系统健康模型诊断,揭示石漠化治理过程中生态系统健康的时间动态与空间格局。结果表明:（1）花江示范区生态系统很健康的区域不存在;（2）近十年来,花江示范区生态系统健康整体状况有所改善,石漠化综合治理取得一定成效,但整体上仍然以不健康和亚健康的区域为主,占区域总面积78.68%;（3）空间上呈现出区域差异的特点,示范区东北部海拔大于1 000 m的峰丛陡坡上生态系统健康状况较差,峰丛洼地区生态系统健康状况则相对较好。      

花江喀斯特峡石漠化治理示范区水资源赋存特点及开发条件评价

文章阐述了贵州花江喀斯特峡谷石漠化治理示范区水资源赋存特点:降水资源比较丰富,但垂直差异大、干湿季节明显;坡面径流比较丰富,但时空分布不均;过境河流水量丰富,但水质较差;地下水资源量大,但空间分异明显.然后,从资源、经济、技术等不同层面综合分析了示范区水资源开发利用条件,指出示范区水资源开发利用中存在的主要问题:"三水"资源开发利用程度低,工程性缺水严重;"三水"资源时空分布不均,调控相对困难,有些技术还需开展攻关研究.最后简要提出相应的对策建议.     

中国东部沙区的荒漠化过程与起因

历史时期中国东部沙区的荒漠化是在自然与人为因素共同作用下实现的,但是不合理的人类活动才是导致荒漠化发生、发展的决定因素。对毛乌素沙地而言,其腹地的荒漠化主要是全新世湖沼层在人类活动参与下被破坏而使未次冰期的古风成砂翻新的结果;而在毛乌素沙地与黄土高原交接带(即沙漠－黄土边界带),荒漠化过程要复杂得多,除了人为因素起决定性作用外,流水侵蚀、风力吹蚀及重力崩塌也共同参与在使古风成砂翻新的荒漠化过程之中。在沙漠－黄土边界带,历史时期荒漠化主要与末次盛冰期、末次冰期阶段3中期及阶段4时期的古风成砂被翻新有关,更老的古风成砂由于埋藏较深、受人类活动影响较小因而不是历史时期荒漠化的主要沙源。     

石漠化智能化解译系统初探

从石漠化智能化遥感解译系统的系统设计目的、系统的框架及功能等方面叙述了系统的初步建立,各部分的功能、专家知识库的初始化和优化等。利用石漠化专家对区域性的石漠化因子信息的认识和对岩溶地区野外地质现象的感知,并将其记录于计算机,建立专家知识库,最终用于石漠化信息的自动提取和石漠化分类。利用所建立的系统对贵阳市一部分区域进行石漠化信息的自动提取和石漠化分类,取得了较为理想的结果。      

粤北典型岩溶山区土地石漠化景观格局动态分析

利用1988年和2004年的2期TM遥感数据,在GIS和FRAGSTAT景观格局分析软件支持下,定量地分析粤北典型岩溶山区及其4县（市）的土地石漠化类型变化及其景观格局时空动态特征。结果表明：16 a来各种类型石漠化土地无论是在数量、面积和空间分布特征方面都发生了十分显著的变化,总面积减少721.67 km²,斑块数减少了1 900块;2004年粤北4县（市）石漠化土地的面积占各区的比例分别是:连州为3.33％、阳山为7.28％、英德为1.54％、乳源为5.11％;粤北及其4县（市）石漠化土地的总体景观空间格局动态变化趋势基本一致,但在程度上有所差异,均表现为景观异质性减弱,破碎度降低,而景观优势度增加;随着相关石漠化治理措施地开展,中度与重度石漠化土地成为研究区内重点关注区域,尤其在阳山与乳源,这种空间格局变化的特征更为明显。     

若尔盖盆地沙漠化驱动机制

作为世界上最大的高寒泥炭沼泽湿地,若尔盖盆地是黄河水源的重要补给区,素有黄河"蓄水池"之称.作为生态敏感区,在自然环境和不合理的人为活动的影响下,若尔盖盆地出现了湿地萎缩、草场退化、沙地增加等一系列严重的生态环境问题.本文通过分析若尔盖盆地沙漠化现状及其驱动因素,进而阐述和分析沙漠化驱动机制.结果表明:若尔盖盆地广泛分布的古风沙沉积物是现代沙漠化的沙物质来源,地表致密草皮层的机械破坏,使下伏松散的古风沙沉积物暴露,是形成沙漠化的关键一步;随后在风蚀、雨水冲刷及生物因素的共同作用下,松散的古风沙沉积物被侵蚀,引起草皮层坍塌,导致古沙丘活化,风沙活动加剧,形成风沙沉积;若尔盖沙漠化是人为因素与自然因素共同作用的结果,其中人为因素是其主导驱动因素,鼠类活动和热融沉陷、滑塌是沙漠化的诱发因素.     

西北干旱区水资源的合理开发利用与荒漠化防治

西北干旱区分布的巨大内陆盆地,如准噶尔、塔里木、柴达木盆地和河西走廊等,被认为是典型的戈壁沙漠地区,约占国土总面积的25％。由冰雪融水与降水补给形成的山区河流,流入山前平原,在戈壁带入渗地下,转化为地下水,并在绿洲带溢出地表,成为绿洲耕地的主要灌溉水源。自20世纪50年代以来,由于大规模的水利化建设,导致水资源条件发生巨大变化,生态环境严重恶化,最终导致大片土地荒漠化。因此,重点论述干旱区在人类经济活动影响下,水文系统的演变及其与水环境和生态环境之间的相互影响、相互制约关系。     

Vertical distribution of soil moisture and surface sandy soil wind erosion for different types of sand dune on the southeastern margin of the Mu Us Sandy Land, China

Soil moisture is a critical state affecting a variety of land surface and subsurface processes. We report investigation results of the factors controlling vertical variation of soil moisture and sand transport rate of three types of dunes on the southeastern margin of the Mu Us Sandy Land. Samples were taken from holes drilled to a depth of 4 m at different topographic sites on the dunes, and were analyzed for soil moisture, grain-size distribution and surface sediment discharge. The results show that: (1) The average soil moisture varies in different types of dunes, with the following sequences ordered from highest to lowest: in the shrubs-covered dunes and the trees-covered dunes the sequence is from inter-dunes lowland to windward slope to leeward slope. The average moisture in the bare-migratory sand dunes is sequenced from inter-dunes lowland to leeward slope to windward slope. (2) Vegetation form and surface coverage affect the range of soil moisture of different types of dunes in the same topographic position. The coefficient of variation of soil moisture for shrubs-covered dunes is higher than that of other types of dune. (3) The effect of shrubs on dune soil moisture is explained in terms of the greater ability of shrubs to trap fine-grained atmospheric dust and hold moisture. (4) The estimated sand transport rates over sand dunes with sparse shrubs are less than those over bare-migratory dunes or sand dunes with sparse trees, indicating that shrubs are more effective in inhibiting wind erosion in the sandy land area.     

Analysis of soil biogeochemical characteristics in the process of karst rocky desertification

The sampling method of karst soil is always the one used for non-karst area. However, if the samples can represent the plot, it still needs further investigation due to high degree of spatial variability of karst soil. The study results of soil from the Maolan karst virgin forest in Guizhou Province elucidated that only the surface area-weighted samples could represent plot soils in the karst ecosystem. The remediation of karst rocky desertification has currently become a national issue, but soil degradation research on rocky desertification genesis types and processes is still insufficient. Soil physical, chemical, biological characteristics and enzymes activities from plots of different rocky desertification genesis types and grades in the Cha＇eryan catchment in the Huajiang Gorge area, Guizhou, were studied. The results showed that woodcutting and land reclamation influenced soil biogeochemical characteristics, and the influence of different disturbing ways was huge. The author suggested a soil degradation index system which could illustrate the rocky desertification genesis type and extent. The degraded modes of woodcutting and reclamation sequence were different, both had no synchronism with rocky desertification grades divided by current landscape index. Only soil of serious grade degraded evidently in wood cutting sequence. On the contrary, soils of slight, medium and serious grades degraded evidently in the reclamation sequence.