海南八门湾红树林柱状沉积物中有机生物标志物的分布和降解   总被引：1，自引：0，他引：1  

孙蕴婕  吴莹  张经 《热带海洋学报》2011,30(2)

对海南岛红树林柱样中有机生物标志物等生物地球化学参数进行了初步研究.结果显示红树林中有机碳(OC)与总氮(TN)比值范围为5.35-7.47,碳稳定同位素(δ13C)值范围为-25‰--22.9‰.脂肪酸与正构烷烃浓度分布范围分别为7.8-21.8μg·g-1(干重)和3.2-25μg·g-1(干重).在表层沉积物中,红树林植物、细菌与浮游生物的脂肪酸生物标志物各占总脂肪酸的25.4%、12.9%和7.5%,结合较低的OC/TN比值和较高的δ13C值,表征了当地微生物和外源浮游植物的有机质贡献.各类脂肪酸在柱样中表现出不同的降解特征:多不饱和脂肪酸(PUFAs)优先被降解,而长链脂肪酸(LCFAs)则较为稳定,没有明显的降解.碳优势指数(CPI)和平均碳链长度(ACL)显示,埋藏深度越深,有机物的生物化学改造程度越大.  相似文献   

Determining suspended sediment concentration and settling velocity from PC-ADP measurements in the Beibu Gulf, China     

于建清  姜静波  龚德俊  李思忍  徐永平 《中国海洋湖沼学报》2011,29(3):691-701

Modeling sediment transport depends on several parameters, such as suspended sediment concentration (SSC), shear stress, and settling velocity. To assess the ability of Pulse-Coherent Acoustic Doppler Profiling (PC-ADP) to non-intrusively quantify spatial and temporal SSC and settling velocity at seabed, a field experiment was conducted in the Beibu Gulf (Tonkin Gulf), in the South China Sea. The spatial profiles and temporal variations in SSC at 1 m above bottom were derived from PC-ADP acoustic backscatter intensity determinations after being calibrated with the optical backscatter sensor (OBS) measurements at the same elevation. The PC-ADP and OBS results agreed well. The temporal settling velocity obtained from Rouse profiles agreed well with the Soulsby formula based on size information by LISST (laser in situ scattering and transmissometry). Tides and tidal currents are diurnal in the gulf. SSC increased with increasing ebb and flood flow, and it rapidly decreased with the increase of distance from the seabed. The maximum SSC at 0.16 m and 1.3 m above bottom reached 816 mg/L and 490 mg/L during spring tides, respectively. The sediments consisted of mineral particles 23-162 μm in diameter and 0.05-2.04 cm/s in settling velocity. Generally, both the SSC and settling velocity followed variations in the bottom friction. Results suggest that PC-ADP is able to provide reasonable SSC and settling velocity measurements of both profiles and time series for a long study period.  相似文献   

Adaptive management to climate change for Norway spruce forests along a regional gradient in Finland     

Zhen-Ming Ge  Seppo Kellomäki  Heli Peltola  Xiao Zhou  Hannu Väisänen 《Climatic change》2013,118(2):275-289

We hypothesized that the responses of boreal Norway spruce (Picea abies) forests to climate change would be region-specific due to regional differences in temperature and water availability. In this context, we analyzed the adaptive effects of varied thinning intensities on the gross primary production (GPP), total stem wood growth, and timber yield over a 100-year period using a process-based ecosystem model. Our simulations represented Norway spruce forests for five different bioclimatic zones spanning southern to northern Finland (61–67^oN). Ten thinning regimes with thinning intensities ranging from 5 to 50 %, as well as an unthinned regime, were included in the calculations. The results showed that at the southern sites without thinning, the cumulative GPP and total stem wood growth were lower under the changing climate than in the current climate over the simulation period due to greater water depletion via evapotranspiration and reduced soil water availability. At the central and the northern sites, the climate changes increasingly enhanced the GPP and total stem wood growth due to the mitigation of low-temperature limitation and the improved soil water availability. Thinning generally mitigated the soil water deficit by reducing water evaporation and led to a reduction of the natural mortality. At the southern sites, light and moderate thinning intensities increased the GPP and total stem wood growth relative to sites with a changing climate that experienced no thinning. Moreover, moderate thinning resulted in the greatest timber yield. Heavy thinning, in which a large proportion of standing trees were removed, reduced the GPP and total stem wood growth despite allowing increased soil water availability. At the northern sites, all levels of thinning, including light thinning, decreased the GPP and stem wood growth, indicating that soil water availability was not a limiting factor for growth prior to thinning.  相似文献   

Cluster analysis of post-landfall tracks of landfalling tropical cyclones over China   总被引：1，自引：0，他引：1  

Wei Zhang  Yee Leung  Yuanfei Wang 《Climate Dynamics》2013,40(5-6):1237-1255

In this paper, we apply finite-mixture-model-based clustering algorithms to cluster post-landfall tracks of tropical cyclones (TCs) making landfall over China. Because existing studies find that landfall surfaces or elevations affect post-landfall TC movements, we also take account of elevations in addition to time orders in this model. Our study reveals three clusters, with cluster 1 making landfall in Hainan province and moving across the western coast of Guangdong province. Most of the TC tracks in cluster 1 move over the ocean and make secondary landfalls over Yunnan province of China and Vietnam. Cluster 1 finally dissipates inland and moves westward as a result of the westward-shift subtropical high, westward steering flow, easterly vertical wind shear and strong mountainous blocking. Cluster 2 makes landfall over Guangdong and Fujian provinces. TCs in cluster 2 subsequently move inland and disappear due largely to westward-shift subtropical high, easterly steering flow, easterly vertical wind shear and relatively strong mountainous blocking. Cluster 3 makes landfall along the Fujian and Zhejiang coast and sustains a long period of time, recurving mostly to the mid-latitude region owing to the surrounding eastward-shift subtropical high, westerly vertical wind shear, weak mountainous blocking and westerly steering flow. Because cluster 2 is significantly associated with La Niña events, TCs more likely make landfall over southeastern China coast and move westward or northwestward without recurving. Cluster 3 sustains a longer time than clusters 1 and 2 in spite of its weak horizontal and vertical water vapor supply. TCs in cluster 3 interact actively with westerlies during the post-landfall period. However, we cannot observe any analogous interactions with the mid-latitude westerlies in clusters 1 and 2. TCs of clusters 1 and 2 are influenced by summer monsoon flows. Moreover, summer monsoon exerts a greater influence on cluster 1 than cluster 2. The composite 200 hPa divergence of cluster 3 is stronger than that of clusters 1 and 2. This explains to some degree why cluster 3 sustains longer than clusters 1 and 2 after making landfall.  相似文献   

A regional climate model downscaling projection of China future climate change     

Shuyan Liu  Wei Gao  Xin-Zhong Liang 《Climate Dynamics》2013,41(7-8):1871-1884

Climate changes over China from the present (1990–1999) to future (2046–2055) under the A1FI (fossil fuel intensive) and A1B (balanced) emission scenarios are projected using the Regional Climate Model version 3 (RegCM3) nests with the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM). For the present climate, RegCM3 downscaling corrects several major deficiencies in the driving CCSM, especially the wet and cold biases over the Sichuan Basin. As compared with CCSM, RegCM3 produces systematic higher spatial pattern correlation coefficients with observations for precipitation and surface air temperature except during winter. The projected future precipitation changes differ largely between CCSM and RegCM3, with strong regional and seasonal dependence. The RegCM3 downscaling produces larger regional precipitation trends (both decreases and increases) than the driving CCSM. Contrast to substantial trend differences projected by CCSM, RegCM3 produces similar precipitation spatial patterns under different scenarios except autumn. Surface air temperature is projected to consistently increase by both CCSM and RegCM3, with greater warming under A1FI than A1B. The result demonstrates that different scenarios can induce large uncertainties even with the same RCM-GCM nesting system. Largest temperature increases are projected in the Tibetan Plateau during winter and high-latitude areas in the northern China during summer under both scenarios. This indicates that high elevation and northern regions are more vulnerable to climate change. Notable discrepancies for precipitation and surface air temperature simulated by RegCM3 with the driving conditions of CCSM versus the model for interdisciplinary research on climate under the same A1B scenario further complicated the uncertainty issue. The geographic distributions for precipitation difference among various simulations are very similar between the present and future climate with very high spatial pattern correlation coefficients. The result suggests that the model present climate biases are systematically propagate into the future climate projections. The impacts of the model present biases on projected future trends are, however, highly nonlinear and regional specific, and thus cannot be simply removed by a linear method. A model with more realistic present climate simulations is anticipated to yield future climate projections with higher credibility.  相似文献   

网上零售企业的空间组织研究——以"当当网"为例   总被引：5，自引：1，他引：4  

汪明峰  卢姗 《地理研究》2011,30(6):965-976

零售商业活动及其空间组织历来是城市和经济地理学研究的重要主题之一.伴随着新的信息和通信技术的应用和普及,一种新的商业业态--网上购物,正在被越来越多的商家和消费者所接受.这一趋势对零售业的价值链、商业模式以及空间组织均产生了不可忽视的影响.本文试图通过对国内主要的电子商务企业之一"当当网"的研究,初步探讨网上零售企业的...  相似文献   

基于森林详查与遥感数据降尺度技术估算中国林龄的空间分布   总被引：2，自引：0，他引：2  

戴铭  周涛  杨玲玲  贾根锁 《地理研究》2011,30(1):172-184

森林的林龄结构及空间分布是评估区域尺度森林生态系统碳汇潜力的重要参数.以第五次全国森林详查获取的省级优势树种的平均林龄及分布面积为基础,以同期生长季节的NOAA/AVHRR NDVI遥感数据为辅助,在空间降尺度统计技术的支持下,得出了全国8km分辨率下的森林林龄的定量分布.结果表明:中国林龄在空间分布具有很大异质性.东...  相似文献   

地方性形成机制的结构主义与人文主义分析——以798和M50两个艺术区在城市地方性塑造中的作用为例   总被引：11，自引：3，他引：8  

周尚意  杨鸿雁  孔翔 《地理研究》2011,30(9):1566-1576

探讨地方性的形成机制对保护传统的地方性和发展新的地方性十分必要。本文选择北京和上海两个艺术类文化创意产业集聚区,分析人文主义机制和结构主义机制的相互作用。按照结构主义的分析思路,调查了艺术区与外界的社会关系;按照人文主义的分析思路,调查了艺术家、画廊经营人和消费者对地方性的认同程度。研究发现：（1）结构主义和人文主义机...  相似文献   

基于游客满意度的旅游目的地转型升级策略研究——以郴州市为例     

肖海平  谷人旭  陈敏  杜涛 《世界地理研究》2011,(3):135-144

有关游客满意度的研究多以其评价模型或方法本身为研究对象,运用研究也往往是从归纳的角度,以实证检验为目的。而将它作为一般理论工具对相关问题进行演绎研究的文献尚不多见。论文以湖南省郴州市为例,采用模糊综合评价模型和方法,在对旅郴游客满意度进行定量评价的基础上,从演绎的角度,提出了更具针对性和操作性的郴州市旅游开发转型的相应对策。此研究思路也能为其他旅游目的地转型升级研究提供一种方法借鉴和决策辅助工具。  相似文献   

基于河网水系的江南水乡风貌和文化保护途径——以上海朱家角镇为例   总被引：2，自引：0，他引：2  

刘辰  金妍  杨凯  车越 《世界地理研究》2011,20(2):169-176

以上海朱家角镇为研究对象,结合遥感影像数据分析、历史资料收集整理、实地调查访谈,探讨基于河网水系的江南水乡风貌和文化保护途径,结果显示：@2006年朱家角共有河道374条,其中88．7％为村级河道;镇内水环境质量不容乐观,除溶解氧及化学需氧量外其余监测指标均未达到Ⅱ类地表水标准;②1965-2006年朱家角河网水系结构趋于主干化和简单化,期间消失河流164条,消失河流总长达27．77km,消失河流面积共0．45km2,消失河流均为村级河流;近40年,水乡文化在桥梁、街巷、民居、宗教性建筑及地名等要素上产生了相应变化;③从末端河道重视程度、城镇水环境整治、水乡文脉保育等方面提出建议,以便开展基于河网水系的江南水乡文化保护工作。  相似文献