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1.
内蒙古草地样带植物群落生物量的梯度研究   总被引:14,自引:0,他引:14       下载免费PDF全文
采用样带法对内蒙古草地植物群落生物量沿水热梯度的变化特征进行了研究,并对几种回归方法进行了比较。一元回归结果表明:在本样带的限定范围内,生物量与年均温、≥0 ℃年积温、≥10 ℃年积温、年实际日照总时数等热量因子呈负相关(年均温的相关性最高),而与年降水量、年均相对湿度等水分因子呈正相关(年均相对湿度的相关性最高),其中年均温和年均相对湿度对生物量的影响最为显著,二者对生物量的空间变异起着互为消长的作用,而海拔高度的影响则不显著。多元回归结果表明,作为半干旱区植物生长的主要限制因子,年降水量在大尺度上对生物量产生影响的途径更为复杂,但其作用不可低估。生物量和地下地上生物量比值会因不同的气候区、不同的植被类型和物种组成,对环境因子的响应程度不同,在经向、纬向和草地类型梯度上的变化特征也不同。水热的配比关系要比单一的水分和温度与植物的生长具有更紧密的关系,地下地上生物量比随着水热配比关系的变化也会呈现出不同的变化规律,其驱动因子并不一定始终都是降水。也许可以认为:半干旱/干旱的划分界限是本研究所涉及的草地样带上生物量和地下地上生物量比值沿草地类型梯度变化的一个转折界限,在此界限前后,气候对生物量的主导因素和生物量对此关键因子的响应程度都有所变化。  相似文献   

2.
温度与降水协同作用对短花针茅生物量及其分配的影响   总被引:3,自引:0,他引:3  
采用人工气候箱法模拟研究温度变化(对照、增温1.5、2.0、4.0、6.0℃)、降水变化(W-30%、W-15%、对照W0、W+15%、W+30%)(以1978—2007年6—8月的月均温和月均降水量为对照)及其协同作用对内蒙古荒漠草原优势种短花针茅生物量及其分配的影响表明:温度和降水协同作用显著影响短花针茅生物量及其分配。增温使短花针茅总生物量、叶和根生物量增加,茎生物量和根冠比分别在在增温1.5℃、4℃后随增温而减小。干旱高温使总生物量减小,增温和降水增加使总生物量、根和叶生物量增加,茎生物量在增温小于2℃时随降水增加而增加,则适当的增温和增加降水可促进短花针茅生物量的积累。短花针茅的各器官生物量分配对温度和降水协同作用的敏感性为茎生物量比叶生物量比根生物量比,最敏感性器官为茎。这表明,短花针茅可根据不同器官生物量对水热变化的敏感性,调节干物质累积分配来适应气候变化。  相似文献   

3.
降水控制对荒漠植物群落物种多样性和生物量的影响   总被引:3,自引:0,他引:3  
孙岩  何明珠  王立 《生态学报》2018,38(7):2425-2433
在全球气候变化背景下,干旱和极端降水事件将对荒漠区植物群落物种多样性和生产力产生深远影响,研究植物群落应对降水变化的响应机制对于荒漠生态系统的科学管理具有重要意义。通过人工增减雨措施利用遮雨棚和滴灌技术对研究区的降水量进行人为调控,探究极端干旱、干旱和降水增加等条件对荒漠植物群落物种多样性和生物量的影响。结果表明:经过一年的降水控制处理,发现灌木和草本层片物种多样性指数在极端干旱、干旱和降水增加等试验处理中差异不显著;灌木的生物量对不同降水控制条件的响应也不显著,而草本层片地上生物量对降水变化的响应最为明显,并随着降水量的增加呈线性增长趋势,极端干旱处理(D1)条件下草本生物量为(10.54±2.36)g/m~2,当降水增加50%(W1)后,草本生物量可达到(105.69±28.60)g/m~2;草本地上生物量与土壤浅表层(40cm)的含水量之间显著相关(P0.05),草本层片生物量与短期(一年)降水波动显著相关。通过定位控制试验进一步探究长时间序列降水变化如何作用于荒漠植物群落特征,研究结果对全球气候变化背景下荒漠生态系统响应机制方面的研究提供数据和理论支撑。  相似文献   

4.
姜基春  王国强  郭宁  焦峰 《西北植物学报》2019,39(10):1861-1867
以黄土高原草本群落为研究对象,选取陕西省榆林市榆阳区至延安市富县的4种植被带,测定草本群落物种多样性和生物量,结合研究区近20年的气象数据资料,分析4种植被带草本群落物种多样性和生物量的分布特征以及它们对降水变化的响应规律,以期为黄土高原植被恢复和水土保持生态建设提供参考。结果表明:(1)4种植被带草本群落Margalef指数、Pielou指数以及Shannon-Wiener指数均为草原-荒漠带数值最小,森林带数值最大,且都随着年均降水量的增加呈先增大后减小的变化趋势,最大值都出现在森林-草原带。(2)地上、地下和总生物量的大小顺序均为草原-荒漠带森林带草原带森林-草原带,它们随着年均降水量的增加呈"单峰曲线"的变化趋势,曲线的拐点都出现在森林-草原带;地下/地上生物量与年均降水量之间存在显著正相关关系。  相似文献   

5.
中国草地样带贯穿我国主要草原区域,具有规律性的草地类型转换和气候条件变化,探究其不同功能群植物氮磷含量随水热因子(温度和降水)的变化规律,对于揭示区域植物N、P元素特征对气候变化的响应机制具有重要意义。本文以中国草地样带为平台,共设置132个样地,采集329份植物叶片样品,基于生态化学计量学理论,对中国草地样带青藏高原高寒区域和内蒙古温性草原区域植物群落功能群组成(豆科、禾本科、莎草科、杂类草)进行N、P元素组分分析,揭示青藏高原高寒区域和内蒙古温性草原区域植物N、P元素含量随温度和降水的变化规律。结果显示:1)青藏高原高寒区域的植物N、P元素含量显著高于内蒙古温性草原区域;2)豆科植物N、P元素含量最高,禾草类植物N、P元素含量最低;3)总体上,随年降水量和年均温度变化,不同功能群中仅杂类草与莎草科植物叶片N、P元素含量变化显著。研究表明,物种组成会影响到草地植被N、P元素生态化学计量学特征,不同功能群植物N、P元素含量对温度和降水变化的响应不同,杂类草和莎草科植物元素含量对中国草地样带植物整体水平N、P元素含量随水热因子的变化规律有重要贡献。  相似文献   

6.
理解植物多样性变化的影响因素一直是群落生态学和生物地理学研究的重要内容。大量研究显示, 植物多样性受到海拔、古气候、现代气候、土壤养分和地上生物量等一系列因素的影响。然而, 很少有研究综合考虑这些因素对植物多样性的影响和相对重要性。本研究以北疆一年生早春短命植物为研究对象, 以2017年和2018年对32个样地调查的物种丰富度为基础, 通过一般线性模型和偏最小二乘通径模型分析了海拔、气候因素(年平均温度、冬季降水、2‒5月降水以及末次冰期以来2‒5月降水变化距平)、土壤养分(pH、土壤有机碳、全氮、全磷、碳氮比、碳磷比和氮磷比)和地上生物量与该类植物物种丰富度平均值的关系及其相对重要性。结果显示: (1)一年生早春短命植物物种丰富度与海拔、年均温度、2‒5月降水、末次冰期以来2‒5月降水变化距平、土壤pH、土壤碳氮比和地上生物量均呈现显著的单峰型关系, 而与冬季降水之间表现为先降低后增加的变化趋势, 表明该类植物多样性同时受到多种因素的影响; (2)海拔、气候因素和土壤养分不仅对该类植物物种丰富度存在显著的直接影响, 也可通过改变地上生物量进而对其物种丰富度产生间接影响; (3)这些因素中, 气候因素是影响一年生早春短命植物物种丰富度的最主要影响因素, 其次分别为地上生物量、海拔和土壤养分。海拔、土壤养分、气候因素及地上生物量共同驱动了北疆地区一年生早春短命植物丰富度的变化。  相似文献   

7.
植物多样性是植物群落维持生态系统稳定的基础。虽然荒漠草原植被稀少,但其在防风固沙等方面仍发挥着不可替代的生态服务功能,然而对荒漠植物多样性如何响应长期极端降水量变化尚缺乏深入理解。该研究依托2014年在宁夏荒漠草原设立的降水量变化(减少50%、减少30%、自然、增加30%和增加50%)的野外实验样地,研究了2020年5–10月植物生物量和物种多样性的变化特征,分析了二者与土壤性质的关系。随着生长季推移,植物群落生物量、Patrick丰富度指数和Shannon-Wiener多样性指数呈先增加后降低的时间动态,Pielou均匀度指数和Simpson优势度指数无明显的变化规律。与自然降水量相比,降水量减少对植物生物量和多样性影响较小,尤其是降水量减少30%的处理下;多数情况下,降水量增加刺激了苦豆子(Sophora alopecuroides)、短花针茅(Stipa breviflora)、白草(Pennisetum centrasiaticum)等物种生长,提高了植物生物量,但亦未明显改变植物多样性(尤其是降水量增加30%的处理下)。对植物生物量影响显著的土壤因子包括脲酶活性、温度、含水量...  相似文献   

8.
荒漠优势物种生物量的定量测量是荒漠土壤管理的重要依据。为精确估计民勤典型绿洲-荒漠过渡带中优势物种生物量,我们用随机选取的82个10 m×10 m的样方进行优势物种调查。结果显示试验地物种结构简单,而且总盖度仅为16.12%。选取5种荒漠优势物种(白刺(Nitraria tangutorum)、沙拐枣(Calligonum mongolicum)、梭梭(Haloxylon ammodendron)、沙蓬(Agriophyllum squarrosum)和盐生草(Halogeton arachnoideus)),利用全挖法测定其地上和地下生物量。用测定生物量80%的数据分析每一种植物地上和地下干、鲜生物量与其自身的形态参数地径、高度和冠幅之间的相关关系,再利用线性回归分析方法,以相关性显著的形态参数为自变量确定了预测试验地每一优势物种最适宜的地上及地下干、鲜生物量的回归模型。研究结果证实包括地茎(除白刺)和盖度为自变量的回归方程和5种优势荒漠植物的生物量拟合度很好,用测定生物量20%的数据对所有模型进行检验,证实所有生物量的估测模型能够精确预测优势荒漠物种生物量。  相似文献   

9.
增加氮素放大了水分对物种组成变化和生产力提高的影响 水分和氮素是旱地生态系统中的重要资源,二者对群落结构和生态系统功能的影响存在着复杂的交互作用。未来降水(降雨与降雪)变化将如何影响地上净初级生产力(ANPP)尚未研究清楚,尤其是当降水变化与氮沉降引起的氮有效性增加相互结合时。在本研究中,我们探讨了半干旱温带典型草原对增加降水(降雨与降雪)和氮素的响应,包括群落生产力、两种主要植物功能群、多年生根茎禾草(PR)和多年生丛生禾草(PB)的多度和地上生物量的变化。研究结果发现,夏季增雨略微增加了群落的ANPP,显著增加了PR的多度和地上生物量,而对PB的多度和地上生物量没有影响。夏季增雨提高了PR生物量在ANPP中的占比,降低了PB生物量的占比。春季增雪对上述两个植物功能群地上生物量均无显著影响,尽管它对群落ANPP有一定的提高。在夏季增雨条件下,氮素添加显著增加了群落ANPP,主要是由于增加了PR的生物量,说明氮和水分添加对群落ANPP存在较强的交互作用,并在很大程度上通过提高PR生物量来实现。我们发现随着降水量的增加,施氮对生产力的正效应呈非线性增加。上述结果表明,在未来大气氮沉降增加的情景下,降水增加对草地生产力的影响将得到进一步放大。  相似文献   

10.
 实测了青藏高原植被样带22个地区不同植被类型的地上部分生物量并进行了格局分析。对于未受人为干扰的以常绿阔叶林为基带的亚高山天然植被,随着海拔升高,地上生物量呈递增趋势,在一定海拔高度达最大,海拔继续升高地上生物量则迅速下降。这一垂直分异规律在一定程度上反映了全球地带性森林植被最大生物量分布的纬向分异性。基于Weber定律的回归分析表明,地上生物量与水热因子的相关关系可用Logistic函数拟合,1月平均气温、7月平均气温、年平均气温、年降水量及其组合因子可解释高原植被样带地上生物量变化的28%~53%,其中年降水量及其同年平均气温的组合与地上生物量的相关性最高(R2为0.46~0.53,p<0.001)。但是,年降水量和平均气温的变化不足以解释西藏色齐拉山暗针叶林具有最高的地上生物量。我们认为,自然植被地上部分生物量的分布格局受到更为复杂的气候因子的制约,例如太阳辐射、湿度、风、水分和能量平衡等。  相似文献   

11.
The coastline of southern Brazil is characterized by vast sand dunes. From March 1982 to April 1984 the dune vegetation was sampled along a transect between the Atlantic shore and an inland freshwater marsh, and phenological cycles of plant species were observed at monthly intervals.The occurrence of 23 annual species in the local dunes and peak germination, growth and flowering of 21 perennial species during spring, summer and fall, suggest that unfavourable temperatures and inundation of slacks during winter are seasonally limiting factors for this flora.Differences in the floristic composition between this region and its southern and northern extremes in the southwestern Atlantic together with a marked seasonality of the total species number and of germination and flowering periods, suggest that this area corresponds to a warm temperate biogeographic transition zone between northern tropical and southern cold temperate regions.  相似文献   

12.
Thermal regimes of Florida lakes   总被引:3,自引:3,他引:0  
Water column temperatures were determined monthly for 24 lakes and bimonthly for 5 lakes in peninsular Florida during 1979. Three geographical groups (north, central, south) were delineated from mean monthly water column temperatures for individual lakes. On a monthly basis, northern lakes were least similar to southern lakes, while central Florida lakes displayed greater affinity to the southern than to the northern lake group. Temperature differences between lake groups broke down during late summer. Subtropical lakes have been defined tentatively as those Florida lakes south of 28° latitude which possess warm monomictic circulation and a mean annual temperature of 24.2 ± 4.8 °C with minimum water column temperature rarely less than 14 °C and summer maxima rarely exceeding 31 °C. While all lakes in Florida are clearly warm monomictic annual nutrient cycling and productivity patterns may be influenced by inter-group differences in the timing and duration of water column circulation.  相似文献   

13.
群落生物量和物种多样性是表征草地生态系统数量特征的重要指标。该研究以新疆阿尔泰山南麓两河源放牧区草地为研究对象,利用样方法对两河源不同放牧区的草地植被进行调查,分析研究区生物量和物种多样性变化,探讨二者与环境因子之间的关联性,为草地群落物种保护以及草地可持续利用提供理论依据。结果表明:(1) 两河源不同牧区间群落盖度、高度、植株密度、地上生物量和单位盖度生物量存在差异。(2) 两河源牧区草地群落地上生物量与群落盖度、植株密度呈显著正相关关系(P<0.05),且地上生物量主要受草地群落盖度的影响;不同牧区的物种多样性指数有一定差异,但物种分布相对均匀。(3)两河源牧区草地群落生物量及物种多样性主要受气温和降水的影响。  相似文献   

14.
Aims We examined growth of red maple (Acer rubrum L.) to evaluate environmental controls of its northern distributional limit in Eastern North America and its potential response to future climate change.Methods We collected growth data from nine sites located along a 300-km transect (47–49°N), which included frontier population of red maple and covered three bioclimatic domains in western Quebec. We analyzed three growth variables: growth rates during the first 30 years of maple lifespan, cumulative basal area increment (BAI) over the most recent decade (2000–2009) and annual growth rate over the whole tree lifespan ranging from 58 to 112 years. We also examined growth sensitivity to climate by using response function analysis.Important findings Three different proxies of maple absolute growth (initial growth rate, BAI during 2000–09 and mean diameter growth rate) indicated a better growth with an increase in latitude. We speculate that stand history effectively overrode the direct effects of colder climate on maple growth along the S-N gradient. Regeneration of maple in the southern sites likely occurred in canopy gaps, whereas in the north it was contingent upon large disturbances such as stand-replacing fires, which apparently provided more favorable light environment for maple growth than canopy gaps. The annual growth variability, which reflects effects of annual weather on growth and is largely independent from the absolute growth rate, was significantly affected by monthly climate, suggesting a positive effect of higher summer temperature in the northern part of the transect (48–49°N) and a negative effect of summer drought in the south (47–48°N). In the future, the natural and human disturbance regimes will be dominant controls of the actual biomass productivity of red maple at the northern limit of its present distribution range. Direct effects of climate on maple growth would likely be less important in this context, and will likely entail negative effect of increased summer drought in the southern part of the study area and positive effects of increased temperatures in the north.  相似文献   

15.
The influence of different drivers on changes in North American and European boreal forests biomass burning (BB) during the Holocene was investigated based on the following hypotheses: land use was important only in the southernmost regions, while elsewhere climate was the main driver modulated by changes in fuel type. BB was reconstructed by means of 88 sedimentary charcoal records divided into six different site clusters. A statistical approach was used to explore the relative contribution of (a) pollen‐based mean July/summer temperature and mean annual precipitation reconstructions, (b) an independent model‐based scenario of past land use (LU), and (c) pollen‐based reconstructions of plant functional types (PFTs) on BB. Our hypotheses were tested with: (a) a west‐east northern boreal sector with changing climatic conditions and a homogeneous vegetation, and (b) a north‐south European boreal sector characterized by gradual variation in both climate and vegetation composition. The processes driving BB in boreal forests varied from one region to another during the Holocene. However, general trends in boreal biomass burning were primarily controlled by changes in climate (mean annual precipitation in Alaska, northern Quebec, and northern Fennoscandia, and mean July/summer temperature in central Canada and central Fennoscandia) and, secondarily, by fuel composition (BB positively correlated with the presence of boreal needleleaf evergreen trees in Alaska and in central and southern Fennoscandia). Land use played only a marginal role. A modification towards less flammable tree species (by promoting deciduous stands over fire‐prone conifers) could contribute to reduce circumboreal wildfire risk in future warmer periods.  相似文献   

16.
浙江沿岸产卵场春、夏季鱼类资源密度和群落多样性研究   总被引:1,自引:0,他引:1  
根据2015年4月(春季)和7月(夏季)在浙江沿岸产卵场进行的渔业资源底拖网调查资料, 采用多重比较(LSD)和分类回归树(CART)方法研究了浙江沿岸产卵场春、夏季群落多样性和鱼类资源的变化, 以及多样性与诸多环境因子(生物和非生物)的关系, 结果表明: (1)该水域春季共捕获鱼类92种, 隶属17目50科77属, 夏季捕获鱼类114种, 隶属16目59科92属; (2)春季全区生物量平均为434.40 kg/km2, 中部和南部生物量差异极显著(P=0.005), 全区尾数密度平均为58.42千尾/km2, 不同区域差异不显著; 夏季全区生物量平均为1532.73 kg/km2, 北部生物量与中部差异极显著(P=0.000), 与南部差异显著(P=0.017), 全区尾数密度平均为205.50千尾/km2, 北部尾数密度与南部差异显著(P=0.034), 其他区域间差异不显著; (3)春季H′平均值为1.52, D平均值为2.18, 北部和南部D差异显著(P=0.048), 其他区域间H′和D差异均不显著; 夏季H′平均值为1.34, D平均值为1.81, 中部和北部H′差异极显著(P=0.000), 和南部差异接近极显著(P=0.01), 北部和中部D差异显著(P=0.039), 其他区域间差异不显著; (4)CART分析表明, 影响春季多样性和丰富度的主要因素有水深、浊度和溶氧; 秋季多样性水平主要受的水深、桡足类、温度和浊度的影响; (5)从空间和时间上与其他水域的多样性水平相比较得出, 在空间上, 纬度与H′并不存在简单的线性关系, 但当纬度跨度比较大时, 低纬度水域的H′值明显高于高纬度水域的H′值; 在时间上, 多样性水平较2008年明显升高, 但与2011年的调查结果相近, 表明产卵场(南部)近几年渔业生态环境处于相对较稳定的状态。  相似文献   

17.
Summer phytoplankton distributions in the Weddell Sea   总被引:4,自引:4,他引:0  
Summary The quantitative composition of phytoplankton was studied along a transect of 14 hydrographic stations, between the southern coast of the Weddell Sea and the Antarctic Peninsula, during the austral summer of 1984–1985. The most apparent feature of the phytoplankton distribution was the presence of a bloom of Phaeocystis at a frontal zone over the shelf break, and the marked contrast between a southern region, with high phytoplankton biomass, and a poorer region north of the shelf break. The most widely distributed diatom genus was Nitzschia (Fragilariopsis section). The phytoplankton assemblage of the southern region included the silicoflagellate Distephanus speculum, the diatom Rhizosolenia alata and several heterotrophic dinoflagellates such as Protoperidinium antarcticum and P. applanatum. The northern assemblage could be characterized by the abundance of flagellates and small dinoflagellates, and by diatoms such as Chaetoceros criophilum, Corethron criophilum Nitzschia kerguelensis and other Nitzschia species of the Fragilariopsis section.  相似文献   

18.
The distribution of copepod taxa at a basin scale was analysed using three Atlantic transects (U.K. – Malvinas 1997, Malvinas – U.K. 1997, and South Africa – U.K. 1998). Integrated 200 m to surface zooplankton samples were taken daily, using WP2 nets (200-m mesh). The zooplankton were size-fractionated and sub-samples taken for carbon analysis. The remainder of the samples was preserved for taxonomic analysis of copepod genera. Multidimensional scaling (MDS) was used to identify zoogeographic regions from the copepod genera. Seven regions were identified: northern temperate, northern subtropical, equatorial, southern tropical, southern sub-tropical, southern temperate and Benguela upwelling. Analysis of similarity showed that most regions were significantly different from each other except: northern temperate and southern temperate, northern temperate and southern subtropical, and northern subtropical and southern subtropical. The genera significant in determining the regions were identified. These regions were compared to other schemes of biological and hydrographic areas. The MDS also showed that the copepod composition in the tropical and subtropical regions was less variable than the temperate and Benguela stations. Latitudinal trends in diversity and size were also investigated. Copepod genera showed a reduction in richness at higher latitudes. Copepod size did not show any substantial or consistent change with latitude along these transects, as demonstrated by both the numerical abundances in each size category, and the carbon biomass per individual. The proportion in each size fraction was quite uniform over the transect.  相似文献   

19.
Seasonal variations in the horizontal and depth distributions of Neomysis mercedis and longfin smelt (Spirinchus thaleichthys) were examined using night-time mid-water trawl and Bongo net samples collected in Lake Washington from July 1989 to February 1992. Mysid density varied spatially, seasonally and yearly. For example, during summer, and fall (odd years), mysid abundance was highest in the northern, and lowest in the southern sections of the lake, except in December 1991 when they were uniformly distributed. In fall (November 1990), mysid density was highest in the central basin of the lake. Furthermore, in winter of even years, highest mysid density occurred in the southern region of the lake, but in the central region in winter (February) of odd year. Longfin smelt horizontal distribution also varied seasonally. For example, density of the 1988 YC smelt (1+) was highest in the northern area of Lake Washington in summer but highest in the southern area in fall. During winter, distribution seemed random. The abundance of the 1990 YC smelt (YoY) was also highest in the northern section of the lake in summer, but highest in the southern section in fall; density remained high in the southern section in winter. But, by late spring when they were more than one year old, the distribution had changed such that highest abundance occurred in the northern and mid-section of the lake. By winter when they were about two years old and about to begin spawning, density had become highest again in the southern section. These suggest extensive movement of mysids and smelt from one area to another, perhaps driven by wind-induced water currents in the lake. Depth distribution patterns of mysids and smelt are discussed. Smelt were captured mainly in the shallow strata (8 m) of the lake during all seasons except during winter when they predominated at 50 m. Mysids were also mainly caught in the shallow strata of the lake during all seasons, although a significant proportion occurred at greater depths (> 30 m). The abundance of both species was positively correlated in spring and summer but negatively correlated in fall. A poor correlation was observed in winter. Negative correlation in fall was primarily due to the occurrence of mysids and smelt in different areas of the lake whereas poor correlation in winter was particularly due to their occurrence at different depths. Because of considerable overlap in the distribution of both species in the lake, mysids face a high risk of predation by smelt. This piece of information is consistent with the hypothesis that smelt control mysid abundance in Lake Washington. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

20.
南黄海、东海鲐鲹鱼索饵场浮游动物生态特征   总被引:11,自引:3,他引:8  
本文采用比较的方法,研究了黄海南部东海北部和东海中南部两个鲐鲹鱼索饵场浮游动物生态特征。结果表明,南部渔场生物量的极差、变异系数小于北部渔场。若扣除个别站位的影响,则南部渔场的平均值高于北部渔场。北部渔场群落多样度、均匀度、丰富度、单纯度较高,南部渔场则相反。北部渔场浮游动物优势种较少,且大多数种具有较高的聚集强度;而南部渔场优势种较多,优势度低,聚集性差。  相似文献   

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