草地生态系统土壤呼吸研究进展   总被引：26，自引：1，他引：25  

刘立新  董云社  齐玉春 《地理科学进展》2004,23(4):35-42

土壤呼吸是草地生态系统碳循环过程中的关键环节,也是草地生态系统中碳素向大气输出的主要途径。土壤中碳素的释放能够显著增加大气中CO₂的浓度,增强温室效应,从而对全球气候和环境变化产生重要影响。文章综合介绍了国内外有关土壤呼吸的各种测定方法,特别是分析了影响草地土壤呼吸的主要环境因素,并就草地土壤呼吸与根系呼吸的区分方法等进行了详细的讨论。  相似文献   

在全数字方式下对宁夏草地覆盖的遥感宏观研究   总被引：18，自引：8，他引：10  

颜长珍  王一谋  冯毓荪  王建华  吴薇 《中国沙漠》2000,20(3):298-300

以TM影象为信息源,在全数字方式下运用遥感技术与地理信息系统技术结合建立了宁夏草地覆盖的TM影象数据库、图形数据库和属性数据库。通过分析得出全区现有草地面积2 481 345 hm²,占全区面积的47.92%,其中高覆盖度草地占3.93%,中覆盖度草地占43.45%,低覆盖度草地占52.62%。  相似文献   

Ecometrics and the paleoecological implications of Pleistocene faunas from the western coastal plains of the Cape Floristic Region,South Africa     

J. Tyler Faith  David R. Braun  Benjamin Davies  Larisa R. G. DeSantis  Matthew J. Douglass  Irene Esteban  Vincent Hare  Naomi E. Levin  Julie Luyt  Robyn Pickering  Mitchell J. Power  Judith Sealy  Deano Stynder 《第四纪科学杂志》2020,35(8):1007-1020

The Pleistocene ungulate communities from the western coastal plains of South Africa's Cape Floristic Region (CFR) are diverse and dominated by grazers, in contrast to the region's Holocene and historical faunas, which are relatively species-poor and dominated by small-bodied browsers and mixed feeders. An expansion of grassy habitats is clearly implied by the Pleistocene faunas, but the presence of ruminant grazers that cannot survive the summer dry season typical of the region today suggests other important paleoecological changes. Here we use dental ecometrics to explore the paleoecological implications of the region's Pleistocene faunas. We show that the dental traits (hypsodonty and occlusal topography) of the ungulates that occurred historically in the CFR track annual and summer aridity, and we use these relationships to reconstruct past aridity. Our results indicate that the Pleistocene faunas signal paleoenvironments that were on average less arid than today, including during the summer, consistent with other lines of evidence that suggest a higher water table and expansion of well-watered habitats. Greater water availability can be explained by lower temperature and reduced evapotranspiration during cooler phases of the Pleistocene, probably coupled with enhanced groundwater recharge due to increased winter precipitation.  相似文献   

Ice processes on medium‐sized north‐temperate lakes     

Sarah S. Ariano  Laura C. Brown 《水文研究》2019,33(18):2434-2448

Lake ice supports a range of socio‐economic and cultural activities including transportation and winter recreational actives. The influence of weather patterns on ice‐cover dynamics of temperate lakes requires further understanding for determining how changes in ice composition will impact ice safety and the range of ecosystem services provided by seasonal ice cover. An investigation of lake ice formation and decay for three lakes in Central Ontario, Canada, took place over the course of two winters, 2015–2016 and 2016–2017, through the use of outdoor digital cameras, a Shallow Water Ice Profiler (upward‐looking sonar), and weekly field measurements. Temperature fluctuations across 0°C promoted substantial early season white ice growth, with lesser amounts of black ice forming later in the season. Ice thickening processes observed were mainly through meltwater, or midwinter rain, refreezing on the ice surface. Snow redistribution was limited, with frequent melt events limiting the duration of fresh snow on the ice, leading to a fairly uniform distribution of white ice across the lakes in 2015–2016 (standard deviations week to week ranging from 3 to 5 cm), but with slightly more variability in 2016–2017 when more snow accumulated over the season (5 to 11 cm). White ice dominated the end‐of‐season ice composition for both seasons representing more than 70% of the total ice thickness, which is a stark contrast to Arctic lake ice that is composed mainly of black ice. This research has provided the first detailed lake ice processes and conditions from medium‐sized north‐temperate lakes and provided important information on temperate region lake ice characteristics that will enhance the understanding of the response of temperate lake ice to climate and provide insight on potential changes to more northern ice regimes under continued climate warming.  相似文献   

安卓手机的草地信息协同采集系统     

胡云锋  董群  陈祖刚  董昱  戴昭鑫  张云芝 《测绘科学》2017,42(6)

针对传统的草地资源调查方法流程繁琐、效率较低、多人协同能力较差等问题,该文提出了基于安卓手机的草地信息协同采集系统架构,设计了位置获取、地图显示、采样规划、信息采集、数据展示、报表生成、数据同步等系统核心功能模块,并应用Java语言开发,完整实现了系统各项功能。在内蒙古自治区及河北省的野外考察验证表明,该系统能够满足草原监察和科研部门对于草地资源调查的基本需求。  相似文献   

半干旱区植物篱侵蚀及养分控制过程的试验研究   总被引：8，自引：2，他引：8  

唐政洪  蔡强国  许峰  李忠武  王忠科 《地理研究》2001,20(5):593-600

针对目前国内外对于温带及半干旱地区植物篱的侵蚀及养分控制过程研究较少的状况,利用冀西北黄土丘陵区较为完备的试验小区的长年观测资料,并结合野外全坡面的大型人工模拟降雨试验,定量地分析黄土丘陵区坡面侵蚀分异规律,得到了在暴雨条件下细沟产生并导致侵蚀剧烈增加的临界坡长为10～15m,从而以此作为植物篱在该区域布设的理论依据。本研究模拟和分析了植物篱对养分流失拦蓄的形态、植物篱改变坡面侵蚀过程、控制细沟产生以及拦蓄泥沙而达到控制侵蚀及养分的目的,对于植物篱———农作复合农林技术在温带及半干旱地区的实践具有科学价值。  相似文献   

Sedimentary indicators of lake-level changes in the humid temperate zone: a critical review   总被引：15，自引：0，他引：15  

J. A. Dearing 《Journal of Paleolimnology》1997,18(1):1-14

Evidence for lake-level changes derived from stratigraphic sequences in cores from littoral zones is reviewed in the context of lake sedimentation processes. These are illustrated with published case-studies which have used multiple-core data. Possible approaches for choosing optimum sites are examined. Sedimentation controls which may change over time are also considered; these include, wind strength and frequency, wind exposure, water depth and underwater slopes, sediment type and littoral vegetation. A final section discusses how lake-level studies can be optimised so that results can be used with confidence in paleoclimatic and paleohydrological reconstructions. Sedimentary data showing shifts in littoral vegetation along shallow underwater gradients in sheltered margins, and transitions between sediment compositions linked to specific hydrological conditions give the strongest lines of evidence.  相似文献   

发展草地农业推进我国西部可持续发展   总被引：26，自引：1，他引：26  

任继周  侯扶江  张自和 《地球科学进展》2000,15(1):19-24

在我国,人与草地的关系经历了4个发展阶段,最终应发展成为草地农业生态系统,这是人类与自然和谐共处的可持续发展模式,人工草地的作用不容忽视。根据草地资源、草业经济结构和生产水平状况,我国西部10省、自治区、直辖市可分为6个发展区域,各区域可因地制宜地发展各具特色的草地农业系统,同时区域之间可以实行广泛的系统耦合;建议设立6个草地农业示范项目和3个研究性生产基地。  相似文献   

Multispectral remote sensing for mapping grassland degradation using the key indicators of grass species and edaphic factors     

Khalid Mansour  Onisimo Mutanga  Elhadi Adam 《国际地球制图》2016,31(5):477-491

Land degradation is believed to be one of the most severe and widespread environmental problems. In South Africa, large areas of land have been identified as degraded, as shown by the lower vegetation cover. One of the major causes of grassland degradation is change in plant species composition that leads to presence of unpalatable grass species. Some grass species have been successfully used as indicators of different levels of grassland degradation in the country. This paper, therefore explores the possibility of mapping grassland degradation in Cathedral Peak, South Africa, using indicators of grass species and edaphic factors. Multispectral SPOT 5 data were used to produce a grassland degradation map based on the spatial distribution of decreaser (Themeda triandra) and increaser (Hyparrhenia hirta) species. To improve mapping accuracy, soil samples were collected from each species site and analysed for nutrient content. A t-test and machine learning random forest classification algorithm were applied for variable selection and classification using SPOT 5 data and edaphic variables. Results indicated that the decreaser and increaser grass species can be mapped with modest accuracy using SPOT 5 data (overall accuracy of 75.30%, quantity disagreement = 2 and allocation disagreement = 23). The classification accuracy was improved to 88.60%, 1 and 11 for overall accuracy, quantity and allocation disagreements, respectively, when SPOT 5 bands and edaphic factors were combined. The study demonstrated that an approach based on the integration of multispectral data and edaphic variables, which increased the overall classification accuracy by about 13%, is a suitable when adopting remote sensing to monitor grassland degradation.  相似文献   

The Sponge Community in a Semi-Submerged Temperate Sea Cave: Density, Diversity and Richness     

James J. Bell 《Marine Ecology》2002,23(4):297-311

Abstract. The sponge communities inhabiting a temperate semi-submerged sea cave were investigated at Lough Hyne Marine Nature Reserve, Co. Cork, Ireland. Thirty-one species of sponge were reported, the majority of which exhibited either an encrusting or massive morphology. Sponge density (averaged over depth) increased with horizontal distance (5  m intervals) into the cave until approximately 30  m, corresponding to the maximum algal intrusion (algal information from Norton et al. , 1971) . Species diversity and richness (averaged over depth) were highest at 10  m horizontal distance from the cave entrance. Variability in sponge density, diversity and richness was observed with increasing vertical depth (0.5  m intervals) at most horizontal intervals sampled (5  m apart). These three variables increased initially with depth, but then decreased towards the seabed. Bray-Curtis Similarity Analysis and Multi-Dimensional Scaling (MDS) showed cave sponge community composition to have greater similarity (50 %) with local loose rock habitats than the nearby cliffs. Similar processes structuring cave and loose rock sponge communities may account for this situation. Information collected from this and previous studies on the biotic (algal communities, other fauna and competition) and abiotic factors (water flow rate, depth, aerial exposure, light, cave morphology, nutrient depletion and humidity) affecting this and other caves is discussed with respect to its influence on the sponges inhabiting different parts of the cave. Although horizontal zonation patterns have been considered analogous to vertical distribution patterns for algal communities (due to similar decreases in light), this was not the case for the studied sponge communities.  相似文献