Macrozoobenthic community structure in a large shallow lake: Disentangling the effect of eutrophication and wind-wave disturbance     

《Limnologica》2016

Biological communities in shallow lakes are often subject to the combined effects of eutrophication and wind-wave disturbance. However, their relative importance in regulating macrozoobenthic community assembly has not been well addressed. In the present study, a monthly sampling of macrozoobenthos and environmental parameters was conducted at ten sites from December 2012 to November 2013 in Lake Hongze, the fourth largest freshwater lake in China, which has undergone serious water quality deterioration over the past few decades. A total of 30 taxa were recorded during the 12 sampling occasions, including 6 chironomids, 6 bivalves, 4 gastropods, 4 oligochaetes, 4 polychaetes, 4 crustaceans and 2 other aquatic insects. The mean abundance and biomass of total macrozoobenthos varied greatly among the ten sites and presented distinctive taxonomic composition between the protected bays and the offshore zone. Three eutrophication parameters (including permanganate index (COD_Mn), chlorophyll a, and total phosphorus in surficial sediments) and three wind-wave variables (including Secchi depth, turbidity, and mean effective fetch) were highly related to spatial variation of macrozoobenthic assemblages. When eutrophication variables were controlled, there was a significant correlation between community similarity and wind-wave disturbance condition, and vice versa. Variation partitioning showed that wind wave disturbance explained 15.9% of the variation in benthic community composition, slightly lower than that explained by eutrophication (17.9%). These results indicate that wind-wave disturbance is as important as eutrophication in regulating benthic community structure in this large shallow lake. Wind-wave disturbance imposed opposite effects on benthic community relative to eutrophication, and were more prominent in the offshore zone weakening the role of eutrophication.  相似文献   

太湖浮游藻类的后向散射分离及其叶绿素a浓度反演     

阎福礼  刘韶菲  王世新  周艺 《地球信息科学学报》2014,16(6):989-996

浮游藻类的后向散射是水体光谱构成的重要组成部分,作为水体辐射传输模型中的重要参数,高精度的藻类后向散射系数对水体叶绿素a浓度的遥感反演精度至关重要。本文以简化的辐射传输模型-生物光学模型为基础,尝试性分离了太湖浮游藻类的后向散射系数。通过藻类后向散射规律分析,建立了浮游藻类吸收、后向散射特征的叶绿素a反演模型,改善了叶绿素a浓度的遥感反演精度。分析表明：藻类颗粒物的后向散射系数与吸收系数之间存在反比关系,且在560 nm、700 nm附近存在明显的散射峰,与叶绿素a浓度之间相关性显著;低密度藻类水体总悬浮颗粒的后向散射以非色素颗粒为主导,适合采用经典的指数模型模拟后向散射系数,而藻类密度较高的富营养化水体,水体总悬浮颗粒的后向散射以藻类颗粒为主导,传统的指数模型已不适用;采用分离藻类后向散射系数的方法,使得叶绿素a浓度的反演值与真实值相关系数从0.66提高到0.98,相对误差从55%降低到38%,均方根误差(RMSE)也由60.95 μg/L降低至13.98 μg/L。其真实性检验表明,与经典指数模型方法相比,利用藻类颗粒后向散射分离方法反演叶绿素a浓度,能够显著改善反演精度。  相似文献   

中全新世以来乌鲁木齐东道海子B剖面沉积物源探讨与分析   总被引：2，自引：1，他引：1  

马妮娜  穆桂金  阎顺 《干旱区地理》2005,28(2):188-193

用激光粒度仪对乌鲁木齐河尾闾的东道海子B剖面样品进行测试,获得机械组成的原始数据。样品粒度分布频率曲线可以分为4种类型。不同类型的曲线反映了不同的碎屑物源组成和不同的沉积环境：在该剖面正态尖峰代表风沙物源,偏态宽峰代表河水物源,正态尖峰和偏态宽峰的叠加代表风沙物源与河水物源的混合,鞍状宽峰可能与深水环境有关。整个剖面反映了从约5000aBP到约200aBP湖面逐步扩大、湖水加深,碎屑物源由以风沙补给为主,逐步转为水源碎屑的趋势。剖面下部的风沙沉积层代表全新世大暖期晚期的暖干环境。约自4500aBP碎屑物源反映湖面开始扩张,4500至3100aBP显示3次快速气候波动,3100aBP之后水深增加,除1980aBP前后显示有短暂的风沙活动之外,主要反映河流碎屑入湖变化情况和湖水水深变化。  相似文献   

高寒河谷灌丛冠层降雨再分配特征及影响因素   总被引：1，自引：0，他引：1  

马育军  高尚玉  李小雁  鲁瑞洁  张思毅  李广泳 《中国沙漠》2012,32(4):963-971

通过植被冠层的降雨被分割成冠层截留、穿透雨和树干茎流3个部分,这个过程（冠层降雨再分配）是高寒河谷灌丛生态演变的关键驱动因子之一,对于认识高寒河谷灌丛的水文循环过程及水分收支规律也具有重要意义。选取青海湖流域最重要的河谷灌丛--具鳞水柏枝作为研究对象,通过野外定点观测,深入分析了冠层降雨再分配特征及影响因素\.结果显示:①穿透雨量、树干茎流量、冠层截留量占同期降雨量的比例平均为48.40%、4.04%和47.56%,并在不同降雨量等级之间存在显著差异;②冠层降雨再分配各组成要素（穿透雨、树干茎流、冠层截留）与降雨特征参数存在高度相关性,伴随降雨量和降雨历时的增加,穿透雨量、树干茎流量、冠层截留量占同期降雨量的比例均逐渐趋于稳定,极限稳定值分别介于60.45%～61.07%、6.45%～7.42%、33.11%～34.17%;③产生穿透雨和树干茎流的临界降雨量分别为1.10 mm和1.87 mm,表明2 mm以下的降雨对土壤水分的补给基本没有贡献。因此,高寒河谷灌丛冠层降雨再分配与其他林木类型存在明显差异,需要深入研究其内在机制及水分利用规律。  相似文献   

青海湖湖东沙地风沙沉积物的粒度特征   总被引：3，自引：1，他引：2       下载免费PDF全文

张登山  田丽慧  鲁瑞洁  唐清亮  石昊 《干旱区地理》2013,36(2):203-211

通过对青海湖湖东沙地克土沙区不同类型沙丘地表沉积物粒度特征的水平变化和0～20 cm垂直变化的分析,可知自然固定沙丘的表层沉积物以细砂为主,其他沙丘以中砂为主,粒度参数随着地形起伏有不同的变化特征;随着深度的增加,粗颗粒逐渐增多,细颗粒逐渐减少,粒度参数随着深度的增加呈波动减小的趋势。通过比较分析,可得出人工治理措施对沙地地表环境的影响较大,能促进细颗粒物质的沉积,有效减少地表的风蚀量。  相似文献   

柴达木盆地察尔汗湖相沉积物的粒度分布模式及其环境意义          下载免费PDF全文

安福元  马海州  魏海成  樊启顺  韩文霞 《干旱区地理》2013,36(2):212-220

对柴达木盆地察尔汗地区ISL1A孔的湖相沉积物样品进行了粒度分布特征分析,研究表明：（1）样品的粒度特征呈三峰模式,部分高盐阶段样品缺失第三峰,为双峰模式;（2）2～10 μm部分以湖成组份为主;10～70 μm和70～650 μm部分以风成组份为主;（3）<2 μm的组份可能与湖泊的生物化学成因有关。上述各组份与气候变化密切相关,且各自代表的环境意义也不同：<2 μm和2～10 μm部分反映了湖泊淡化-咸化程度和水量变化过程。10～70 μm部分可能在一定程度上反映了东亚冬季风的强度;70～650 μm部分反映了尘暴天气的程度。环境指标的对比分析很好地验证了ISL1A孔样品粒度各个组份划分的准确性,并可反演92.9 ka以来该地区的古气候演化过程。  相似文献   

基于MapReduce的空间数据并行划分算法     

付艳丽  吴艳民  张金标  郑坤  赵长虹  郑康  方发林 《测绘通报》2017,(11):96-100

针对海量空间数据分布式存储中存在的不顾及空间邻近性、分布不均和数据倾斜的问题,基于MapReduce并行编程模型,对Hilbert空间曲线层次分解的思想和节点容量感知的方法进行了研究,提出了一种层次分解的空间数据并行划分策略,并通过临界值判定实现空间数据的均衡存储。最后通过实例分析说明该方法可以在保证空间数据邻近特性的同时,解决海量空间数据分布式存储不均和数据倾斜的问题。  相似文献   

A Study of Pretreatment Methods for Terrigenous Grain-Size Analysis of Marine Sediments     

Zhao Shaohua  Liu Zhifei 《地球科学进展》2017,32(7):769-780

The prerequisite for obtaining variations of terrigenous grain-size of marine sediments is how to effectively remove non-terrigenous matters and preserve terrigenous particles synchronously. Combined with observations under biological microscope and scanning electron microscope, a comparative study of biogenic debris removal effect and terrigenous grain-size analysis under different pretreatment condition was performed on core sediments, which were retrieved in the South China Sea during the MD190 cruise. Our new results showed that the main three biogenic particles, namely, organic matter, carbonate, and opal in marine sediments could be removed effectively by 30% H₂O₂ in a stirring water bath at 60 ℃ for 3 h, 0.5% HCl for 1 h, and 2 mol/L Na₂CO₃ in a stirring water bath at 85 ℃ for 5 h, in turn. Such pretreatments achieved the goals of biogenic debris removal efficiency and relatively well-preserved terrigenous particles. Prior to selecting an appropriate pretreatment method, this study suggested that the actual effects of biogenic detritus on grain-size results of diverse marine sediment samples should be taken into account. If the laboratory data are ensured to be closer to the natural grain-size distribution of terrigenous particles, the removals of all biogenic debris are not always needed, and the less pretreatment processes the better. For example, opal particles have little effect on terrigenous grain-size distribution when their percentage is lower than 2%. Thus, there is no use to remove them from marine sediments before laboratory grain-size analysis of terrigenous particles. Additionally, ultrasonic is not suggested through the whole process of terrigenous grain-size analysis because the strong energy of ultrasonic can lead to the fragmentation of some fragile terrigenous particles.  相似文献   

The relative importance of physicochemical factors and crustacean zooplankton as determinants of rotifer density and species distribution in lakes adjacent to the Yangtze River, China   总被引：2，自引：0，他引：2  

Songbo Wang  Ping Xie  Hong Geng 《Limnologica》2010,40(1):1-7

The planktonic community of freshwater Rotifera in 27 subtropical lakes was studied to assess the relative importance of physicochemical factors and crustacean zooplankton as determinants of rotifer density and species distribution. Factor analysis and multiple linear regressions showed that 21.9% and 29.9% of the variance in rotifer density was explained by physicochemical factors and crustaceans, respectively. Larger rotifer density was possible in shallower lakes with higher concentration of inorganic nitrogen and less herbivorous crustaceans such as Sinocalanus dorrii and Daphnia. Redundancy analysis showed that the variances of rotifer species distribution explained by crustaceans and physicochemical factors were 26.9% and 31.0%, respectively. Further analysis demonstrated that the variances explained by pure crustaceans and pure physicochemical factors were 12.5% and 16.6%, respectively. However, these two percentages were not statistically different. Rotifer species distribution was strongly associated with Chl a and Moina micrura. Their coexistence with crustaceans seemed to be determined by their defense against potential predators and competitors.  相似文献   

动态高压下陨石矿物的冲击熔融和分离结晶及其地球化学意义          下载免费PDF全文

谢先德  陈鸣 《地学前缘》2009,16(1):134

应用近代微束矿物学分析测试技术,对在中国陨落的随州、寺巷口和岩庄等三块球粒陨石中矿物的冲击熔融和分离结晶作用进行了较系统的研究。查明存在有硅酸盐单矿物熔体、硅酸盐矿物混合熔体和全岩熔体三种组成不同的冲击熔体。研究结果显示:(1)三种熔融相与未熔相之间在主成分和微量元素组成上没有明显差别,说明它们是原地熔融的产物,但在较大的冲击熔块中,也发现冲击熔融作用引发了一部分元素,如亲铁元素、硒元素和轻重稀土元素的分异现象;(2)查明Al2O3、Cr2O3、Na2O和CaO等优先进入从冲击熔体结晶的辉石常压相或辉石的高压相——镁铁榴石(属地幔过渡带矿物)中;(3)Al元素能进入阿基莫石(即辉石的钛铁矿结构相,属下地幔矿物)中,以固熔体形式稳定下来。ELNES的测定查明,其氧化铁组分中Fe3+/∑Fe的比值高达0.67(3);(4)陨石全岩熔体中硅酸盐相与金属-硫化物相之间为完全不混熔,后者以孤立的共结体团块产于硅酸盐熔体之中,除Zn、Na、Cr、Co和Cu在硫化物相中和Na在金属相中有明显富集外,其他元素的浓度则无明显变化;(5)在寺巷口陨石熔脉的金属-硫化物共结团块内发现了FeNi金属-硫化铁-磁铁矿组合,进一步证实了S和O等轻元素可以加入到以Fe-Ni金属为主要组成的地核成分中去;(6)在岩庄陨石的FeNi金属-硫化铁共结体团块的硫化铁内发现了Na、Mn和Fe的磷酸盐矿物小球体,说明P和Na、Mn等元素也能成为地核的组成元素。以上研究在行星演化、地幔矿物学和地球化学,以及陨石学研究上均有着重要的科学意义。  相似文献