内蒙古东部两大沙地土壤理化特性沙漠化演变规律的比较   总被引：2，自引：0，他引：2  

赵哈林  李玉强  周瑞莲  赵学勇  张铜会  王进 《地球科学进展》2011,26(7):779-786

为了了解不同地带沙地土壤理化特性沙漠化演变规律的差异及其机制,研究比较了科尔沁沙地和呼伦贝尔沙地土壤理化特性的沙漠化演变特征,得到以下结论:沙漠化过程中,2个沙地的土壤黏粉粒含量均大幅度下降,沙粒含量明显增加,但科尔沁沙地土壤机械组成的变化幅度要大于呼伦贝尔沙地,而且前者黏粉粒主要释放期早于后者;科尔沁沙地土壤温度趋于...  相似文献   

Discovery of Messinian canyons and new seismic stratigraphic model,offshore Provence (SE France): Implications for the hydrographic network reconstruction     

《Marine and Petroleum Geology》2014

The interpretation of high-resolution 2D marine seismic profiles together with the analysis of sea-bottom cores allowed a stratigraphic and structural framework of the Provence continental shelf to be proposed. The integration of onshore and offshore stratigraphy, structure and geomorphology provided new insights into Messinian paleotopography and paleohydrography. A geological map of the offshore Provence continental shelf, isobath map of the base Plio-Quaternary surface are presented for the first time in this area. The base Plio-Quaternary surface is a polyphased unconformity that is composed of deep canyons developed by fluvial erosion during the Messinian event, and wave-cut surfaces formed during post-Messinian transgressions. The study evidenced a deep, E–W-trending canyon (Bandol canyon) connected to the head of the Cassidaigne canyon, and filled with up to 600 m-thick Plio-Quaternary deposits. The development of canyons on the Provence margin during the Messinian event was dominantly controlled by the lithology and structure of pre-Messinian formations. A map of the Messinian paleo-drainage network is proposed to explain the presence of deep canyons in the Eastern area and the lack of incision in the Western area. An underground karst drainage scheme is proposed, linked with the current submarine Port-Miou spring.  相似文献   

基于遥感数据的内蒙古草原灌丛物候变化研究   总被引：1，自引：0，他引：1  

范瑛  李小雁  李广泳 《干旱气象》2014,32(6):902-908

植被物候研究是全球气候变化研究的重要内容,但国际上有关干旱半干旱区灌丛物候变化的研究还很缺乏。为了探讨气候变化对内蒙古草原灌丛物候的影响,利用2000~2011年的MODIS EVI时间序列影像,采用动态阈值法得到6种灌丛12 a物候年际变化情况,结合样点附近气象站的气温和降水数据,分析了灌丛物候与气候变化的动态关系。结果表明：（1）内蒙古中西部草原灌丛返青期、枯黄期都呈现提前的趋势,生长季长度缩短;（2）春季均温升高和前一年秋冬降水增加可以提前灌丛返青期,是影响返青期的主要因素;（3）秋季降水减少和夏秋均温上升都利于枯黄期提前,夏季降水的作用则因灌丛种类不同而略有差异;（4）夏秋均温上升缩短了生长季长度,夏秋降水量、春季均温则多与生长季长度呈正相关。  相似文献   

知识图谱在构建东北土地环境研究知识谱系中的应用     

郑翔天  关思萍  任红鸽  徐容乐  项波 《地球信息科学学报》2021,23(6):1002-1016

我国东北地区的自然环境状况一直备受关注,其土地沙化、荒漠化、林地草地退化、森林退化、土地盐碱化等土地环境变化的原因及监测一直是科研的焦点。随着“美丽中国中脊带”的提出,位于该线东北段附近的土地环境相关的研究也不断开展。在涉及该区域土地状况的研究中,常用研究方法有实地考察以及基于遥感卫星影像来进行分析,而本文利用知识图谱技术来构建相关文献研究的知识谱系,从另一个角度探究东北土地的环境状况变化因素。首先,由于知识图谱可以广泛探究文本数据之间的关联,且便捷高效,因此本文用科学知识图谱的有关方法对目前探究东北地区土地环境变化影响因素的4318篇CNKI文献进行挖掘,再用关键词共现的方法提取大量文献中已探明的目标因素,从而构建比较全面的基于东北地区环境研究的知识谱系,这一方法不仅省时省力,而且可以归纳出比较全面的影响因素;其次,结合聚类分析归纳出影响东北地区土地变化的主要因素,并进行分析。最后,选取词频前十的因素进行汇总,统计得出东北地区土地环境变化的影响因素,如影响土地沙化的因素中,频数最高的关键词有生态环境破坏、水土流失、沙尘暴等,影响土地沙化的因素中,水土流失、土壤沙化、水资源不足等频数最高,这些因素分别代表了我国东北地区土地沙化、荒漠化、盐碱化、草地草场退化、林地退化、森林退化以及黑土地退化等土地环境变化的最主要因素。这一方法将为今后从知识图谱文本挖掘的方面深入探究地理、气候等自然现象的影响因素提供新的思路。  相似文献   

基于ENVI的巴里坤草地动态变化信息提取及分析     

邢文渊 《沙漠与绿洲气象(新疆气象)》2014,8(1):61-65

利用250m的EOS／MODIS数据,结合1：250000的土地利用分类图,借助ENVI软件对巴里坤草地变化进行研究,制作掩膜,剔除巴里坤的非草地NDVI信息,只保留草地的NDVI信息,提取巴里坤县2003--2012年连续10a的草地NDVI信息数据,并以2003年巴里坤草地NDVI为本底数据,计算巴里坤草地面积的动态变化。结果表明：巴里坤草地NDVI差值动态变化较大的主要发生在区间[0．001,0．1）与（-0．1,-0．001],两区间面积合计能占到巴里坤草地面积的90％以上;其次位于区间[0．1,O．2）与（-0．2,-0．11,两区间面积合计占比不到巴里坤草地面积的6％。表明其年际间发生的变化是以微幅变动为主,其发生区域主要集中在覆盖度较低的荒漠化草地和低盖度草地;NDVI差值动态变化发生较大范围变化的面积占比并不大,表明当地的草地生态系统具有一定的相对稳定性。草地NDVI的差值动态变化更能体现出局部区域的细微变化。  相似文献   

Response of artificial grassland carbon stock to management in mountain region of Southern Ningxia,China   总被引：1，自引：1，他引：0  

Long Tang  Xiaohu Dang  Guobin Liu  Chuanke Shao  Sha Xue 《中国地理科学(英文版)》2014,24(4):436-443

Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.  相似文献   

Vegetation traits and soil properties in response to utilization patterns of grassland in Hulun Buir City,Inner Mongolia,China   总被引：2，自引：1，他引：1  

Miao Liu  Guohua Liu  Xing Wu  Hao Wang  Li Chen 《中国地理科学(英文版)》2014,24(4):471-478

Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human disturbance （e.g., grazing, mowing and fencing） triggered significant variation of biomass partitioning and carbon reallocation. Besides, there existed some differences of species diversity and soil fertility. To address these hypotheses of grassland with diverse utilization patterns in Hulun Buir City, Inner Mongolia, China, we sampled in situ about aboveground biomass （AGB） and belowground biomass （BGB） to evaluate their biomass allocation. Species diversity and soil properties were also investigated. Subsequently, we discussed the relationship of species diversity with environmental conditions, using data collected from 23 sites during the ecological project period of Returning Grazing Lands to Grasslands （RGLG） program. The results were as follows： 1） both AGB and BGB were lower on grazing regime than those on fencing and mowing, but the ratio of root-to-shoot （R/S） was higher on grazing regime than the other two utilization patterns; 2） neither of evenness and Simpson Index was different significantly among all grassland utilization patterns in desert, typical, and meadow grassland at 0.05. In meadow grassland, species richness of fencing pattern was significantly higher than that of grazing pattern （p 〈 0.05）; 3） both of soil organic carbon content and soil available phosphorous content were increased significantly on fencing pattern than grazing pattern （p 〈 0.05） in desert grassland, and mowing patterns increased the soil nutrients （soil organic carbon, soil total phosphorous, soil available phosphorous, and soil total nitrogen） significantly compared with grazing patterns （p 〈 0.05） in typical grassland. However, there were no significant differences among utilization patterns in meadow grassland. In conclusion, both of AGB and BGB were increased s  相似文献   

Antarctic Intermediate Water influence on Mediterranean Sea Water outflow     

Essyllt Louarn  Pascal Morin 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(9):932-942

This study of the mixing of Mediterranean Sea Water (MW) with the surrounding waters was made possible by the Semane 2002 cruise (Sortie des Eaux Meditérranéennes dans l'Atlantique Nord-Est) that took place in the Gulf of Cadiz in July 2002. Potential temperature, salinity, oxygen, nutrients and CFC data are used to describe the water masses present in the Gulf. In the southern part of the basin, a water mass characterised by low oxygen, high nutrient and low CFC concentrations occurs along the African continental slope. This water has been identified as the modified Antarctic Intermediate Water (AAIW). It has been previously observed south of this section, at the latitude of the Canary Islands, as a northward flow between the African shelf and the islands. The modified AAIW found in the Gulf of Cadiz is situated at a density of 27.5 kg m⁻³. Above, at 27.3 kg m⁻³, the lower limb of the North Atlantic Central Water is observed as a salinity minimum. The modified AAIW enters the Gulf of Cadiz along the south-western part of the continental shelf. It flows cyclonically and exits north-westward. In the northern part of the gulf, due to the presence of the Mediterranean Undercurrent (MU), the AAIW flows off the coast. An optimum multiparameter analysis was conducted to evaluate the influence of the AAIW on the MW northwest of the basin. We show that the AAIW is present in the lower core of the MU at a proportion of 12.9±8.2% and is absent in the upper core.  相似文献   

Feeding ecology of Ammothella longipes (Arthropoda: Pycnogonida) in the Mediterranean Sea: A fatty acid biomarker approach     

Anna Soler-Membrives  Sergio Rossi  Toms Munilla 《Estuarine, Coastal and Shelf Science》2011,92(4):819-597

Fatty acid analysis has proved valuable in determining seasonal trophic links and the feeding behavior in organisms in which these diet and trophic links cannot be inferred from stomach content analyses. Seasonal variations in total free fatty acid content (TFFA) and fatty acid composition of seston (<250 μm), the brown macroalgae Stypocaulon spp., polychaetes (Nereididae) and the pycnogonid Ammothella longipes have been used to establish their trophic links, with particular focus on seasonality and feeding ecology of A. longipes. Samples were collected in a coastal environment (NW Mediterranean Sea) at 7–10 m depth, in five different periods (August and October 2008, February, June and September 2009). Seston and Stypocaulon spp. samples did not show significant seasonal variations in TFFA content, while nereids showed a significant variation. Analysis of fatty acid profile showed high similarities of fatty acid composition between seston and Stypocaulon spp. Nereids were closer to seston and Stypocaulon spp. than A. longipes, which seemed to follow a seasonal trend. The results of this study reveal that A. longipes may change its feeding behavior depending on the season and available food. This pycnogonid species appears to be carnivore during spring and early summer but seems to feed on detritus when availability of prey diminishes during winter. Notable high amounts of odd-chain fatty acids are found in summer–autumn for this species, which may come from bacteria acquired from the detrital diet or from de novo biosynthesis from propionate. The results obtained provide new and valuable data on the understudied feeding biology of pycnogonids in general, and contribute to the understanding of their functioning of Mediterranean shallow oligotrophic systems and their trophic links.  相似文献   

Anthropogenic CO₂ fluxes in the Otranto Strait (E. Mediterranean) in February 1995     

Evangelia Krasakopoulou  Ekaterini Souvermezoglou  Catherine Goyet 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(11):1103-1114

This study presents the distribution and fluxes of dissolved inorganic carbon (C_T), total alkalinity (A_T) and anthropogenic carbon (C_ant) along the Otranto strait, during February 1995. Based on a limited number of properties (temperature, dissolved oxygen, total alkalinity and dissolved inorganic carbon), the composite tracer TrOCA was used to estimate the concentration of anthropogenic CO₂ in the Otranto strait.Total alkalinity exhibits high values and weak variability throughout the water column of the strait, probably associated with the dense water formation processes in the Adriatic basin that induce a rapid transport of the coastal alkalinity to the deep waters. Elevated C_ant concentrations and high anthropogenic pH variations are observed in the bottom layer of the strait, associated with the presence of Adriatic Deep Water (ADW). The study shows that large amounts of C_ant have penetrated the highly alkaline Eastern Mediterranean waters, thereby causing a significant pH reduction since the pre-industrial era.Estimates of the transports of C_T and C_ant through the strait indicate that during February 1995, the Adriatic Sea imports through the Otranto strait natural and anthropogenic carbon and acts as a net sink of carbon for the Ionian Sea. The anthropogenic carbon that is imported to the Adriatic Sea represents less than 1% of the net C_T inflow. The Levantine Intermediate Water (LIW) contributes to about one-third of the total C_T and C_ant inflow. Although the amounts of C_ant annually transported by LIW and ADW are almost equal, the contribution of C_ant to the C_T transported by each water mass is slightly higher in ADW (3.1%) than in LIW (2.6%), as a result of its higher mean C_ant concentration. The ADW, despite its weak contribution to the total outflow of C_ant, has a vital role for the sequestration and storage of the anthropogenic carbon, as this water mass is the main component of the Eastern Mediterranean Deep Waters and, thus, the anthropogenic CO₂ is transferred in the deep horizons of the Eastern Mediterranean, where it remains isolated for many years.  相似文献