川中丘陵地区近25年来农田土壤有机碳密度变化——以四川省盐亭县为例

根据盐亭县第二次全国土壤普查23个土壤剖面的采样记录,2007年采集了这23个土壤剖面样品,并分析测定其土壤有机碳含量,对比发现,盐亭县近25年来土壤平均有机碳密度上升2.70 t/hm2,上升幅度为5.65%,该县农田土壤具有微弱的碳汇效应.近25年来该县土壤有机碳密度变化复杂,不同土壤类型之间的变化差异较大.其中,水稻土、黄壤和紫色土有机碳密度均有不同程度的上升,而冲积土的有机碳密度则明显下降.而就土地利用方式而言,水田土壤的有机碳密度呈明显上升趋势(上升幅度15.38%),而旱地土壤有机碳密度则基本上保持稳定少变.该区今后应主要通过改良耕作措施,推广生态农业技术,增加土壤有机物质归还量;加强生态环境建设,搞好水土保持;灌溉水利工程建设进一步稳定和扩大水田面积等措施,以达到稳定和提高农田土壤有机碳储量的目的.     

The progress and prospects of nebkhas in arid areas

Nebkhas are often extensively distributed in arid and semi-arid areas, and play an important role in the stabilization of ecological environment in these areas. This paper reviews the following aspects, including formation and succession, spatial distribution, shape and surface airflow characteristics, balance between erosion and deposition, ecological and physiological characteristics of vegetation, response to precipitation and groundwater, soil properties as well as the protection measures. We found that nebkhas were studied without differentiation of succession periods, and shape characteristics, surface airflow, soil properties as well as vegetation dynamics in different succession periods were not fully understood, which made it difficult to explain the succession dynamics of nebkhas and its affecting factors. Previous studies of nebkhas were over-emphasized for its role as an indicator of land degradation, while its ecological functions in degraded ecosystems were neglected, which was unfavorable for the ecological restorations in arid and semi-arid areas. Future studies should pay more attention to the variation of vegetation, soil as well as hydrological process in the succession of nebkhas and its interaction between different influencing factors. In addition, positive role of nebkhas in degraded ecosystems in arid and semi-arid areas should be fully discussed. According to the data got from the above, effective protection measures of nebkhas should be explored.     

Geomorphological,pedological, and hydrological characteristics of karst lakes at Conversano (Apulia,southern Italy) as a basis for environmental protection

The land around Conversano (Apulia, southern Italy) is part of the Murge karst, interesting limestones and dolomitic limestones of Upper Cretaceous age, in a flat environment with sub-horizontal setting. Dolines and karst depressions are the most typical landforms in the area. Filling of these landforms with eluvial deposits locally created the possibility of water stagnancy at the surface. The Conversano territory presents ten karst lakes that represented, until some decades ago, the only water resource available for the local people, who built the typical bell-shaped wells to collect water volumes satisfying local needs during the dry season. Currently, these lakes have no great importance as water supplies, but represent habitats of great naturalistic value that are still able to support the ecological functionality and the wet environments with self-vegetation. Hydrological and hydrogeological studies have been carried out with the aim to fully estimate the related environmental problems. For this purpose, the hydrogeologic data of historical time series have been collected and compared to those of the last 5 years; successively, according to the Thornthwaite method, a hydrological monthly balance has been evaluated to quantify the distribution of water volumes interacting annually between the surface water bodies and the underlying carbonate groundwater. This evaluation has highlighted the need to carefully consider all the parameters concurring to a right definition of water balance for a karst environment, where pedological features, climatic conditions and anthropogenic modifications to the environment represent the elements of a very delicate system. Particularly, on the basis of recent soil map and field surveys, a re-evaluation of the available water capacity, estimated in some 40 mm, has been carried out. The studies have highlighted the need to extend the environmental protection rules to larger areas around the lakes, e.g. at the catchment scale, with definition of buffer zones; in this manner, it will be possible to constantly monitor the protected land and the local anthropogenic activities, that represent real polluting sources for both the surface water resources and the underlying carbonate groundwaters.     

兴文世界地质公园化石遗迹保护研究

四川兴文世界地质公园内含有丰富的二叠系化石遗迹。然而近年来在地质公园开发和建设的过程中,化石遗迹遭受了比较严重的破坏,因而景区化石遗迹保护工作思路和模式值得研究。通过对兴文石海化石遗迹的种类、丰度和当前保存现状的分析,认为自然因素和人为因素是导致兴文石海化石遗迹遭受破坏的两大原因,据此提出了保护兴文化石遗迹完整性的措施。     

探讨漳州某基坑支护工程设计与施工

通过漳州某基坑支护工程实例,介绍深层搅拌桩加锚杆在基坑支护工程中的设计、施工、监测等方面的运用,并对该支护模式在深基坑支护工程中的适应性进行了探讨,分析了基坑南侧偏东处出现险情的原因,以此作为经验供参考借鉴。     

四川省宜宾市江安硅化木群地质遗迹资源特征及保护策略建议

宜宾市江安县的怡乐镇的硅化木群主要赋存于体罗系上统蓬莱镇组下段的灰黄色钙质长石砂岩中,根据初步显微观察,硅化木为保存次生木质部的一种松柏类植物。江安硅化木群在研究长江流域古气候、古地理、古生态演化和地壳变动等具有重要的价值,当前保护现状令人担忧。本文分析了该地质遗迹资源的特征,研究分析了其保护意义,提出了相应的保护策略建议。     

退耕还林还草研究之进展

在综合阐述我国自实行退耕还林还草以来有关退耕的研究成果及存在的问题之时,比较分析了中外退耕还林还草实践中的退耕目的、基础及政策方面的差异。并针对目前国内退耕研究存在的问题和不足,提出应加强除坡耕地以外的其他类型耕地的退耕和对退耕适宜性评价的研究,大尺度区域范围内采用先进的遥感和地理信息技术的研究方法和手段将是今后退耕还林还草规划和决策分析的重要手段。     

广西防雷产业十年发展的启示

广西从1990年起开展防雷减灾工作以来,经历了起步经营、调整探索、依法管理三个发展阶段,本文分析了在不同的发展阶段,广西防雷减灾机构、防雷减灾管理职能的变化、防雷产业的发展状况,以及目前存在的主要问题,对如何确保防雷事业持续发展提出了相应的对策和措施。     

桂林市中小学校防雷现状及防御对策探讨

通过对桂林市中小学校的防雷现状的分析,提出防御对策。     

Geoscientific Significance and Classification of NationalGeoparks of China

The conservation of geological remains in China, especially in renowned sites with historical or cultural significance, has long been paid attention to. As the urban residents become more interested in returning to and harmony with the nature, tourism related sciences and knowledge gets more attractive. Geosites and geoparks can definitely play an important role to lead this historic tendency.