Response of reed community to the environment gradient water depth in the Yellow River Delta, China

We investigated and monitored a reed community in the fields.Data on the bio-ecologieal characteristics and β-diversity of reed communities in different environmental gradients (mainly based on water depth) of the Yellow River Delta were collected through multianalysis,extremum analysis and β-diversity index analysis.In accordance with the square sum of deviations (Ward)cluster analysis,10 sampling plots were divided into six types with the dominant plants in different plots varying according to the change in environmental gradients.The dominant plants in these plots varied from aquatic plants to xerophytes and salt tolerant plants as water depth decreased.The average height and diameter of the reeds at breast level were significantly correlated with the average water depth.The fitness curves of average density and coverage with average water depth were nonlinear.When the average water depth was 0.3 m,the average density and coverage of reeds reached the apex value,while the height and diameter of the reeds at breast level increased with the water depth.There were obvious changes to the environmental gradient in the Yellow River Delta.The transitional communities were also found to exist in the Yellow River Delta by β-diversity analysis.Vicarious species appeared with the change in water depth.The occurrence of substitute species is determined by the function of common species between adjacent belts.The different functions of common species led to differences in community structure and function and differences in dominant plants.The result reflects the variations of species present in different habitats and directly reflects environmental heterogeneity.The values of//-diversity indices of adjacent plots were higher than those of nonadjacent plots.There are transition zones between the xerophytes and aquatic plants in the Yellow River Delta.In an aquatic environment,the similarity of reed community is higher than that of xeromorphic plants.The β-diversity index can reflect plant succession trends caused by the change in environmental gradients in the Yellow River Delta.The β-diversity index reveals plant responses to changes in environmental gradient and is helpful in observing changes in patterns of species diversity in relation to environmental gradient change and evolving trends in the future,which in turn plays a prominent role when environmental water requirements of wetland are discussed.     

黄河三角洲芦苇种群特征对水深环境梯度的响应

通过野外调查芦苇种群特征及获取的监测数据,应用多元统计法、函数极值法以及β多样性指数测度法,对黄河三角洲芦苇种群在不同环境梯度（以水深为主）条件下的生物生态学特征及β多样性进行了分析.（1）通过离差平方和聚类分析方法,将研究区的10个调查样地划分为6个类型.随水深环境梯度变化,各样地群落优势植物也发生相应变化.（2）芦苇的平均高度和平均茎粗与平均水深呈显著相关.芦苇平均密度和平均盖度值与平均水深拟合曲线的变化呈非线性变化趋势.在平均水深为0.3m时,芦苇平均密度和平均盖度出现明显的峰,随水深变化向峰两侧递减,而芦苇平均株高和平均茎粗随水深增加呈递葺增趋势.（3）通过β多样性分析,黄河三角洲存在明显的环境梯度变化,随着水深的变化,物种间存在明显的替代关系.通过离差平方和聚类分析后得出的各相邻样地（水深段）间的Sorensen指数值均大于不相邻样地（水深段）间的值.水生环境植物群落间的相似性程度较大,而旱生环境植物群落间相似性程度较小.     

黄河三角洲草地退化的研究

黄河三角洲位于东经118°7′—119°10′,北纬36°56′—38°12′;东自山东省小清河口,西至徒骇河口,以利津县宁海为顶点向渤海湾呈扇形分布。自50年代以来,随着国营及地方农场的建立以及人口的不断增长,这一地区的草地资源得到了广泛的开发利用。但是,由于一些单位只顾盲目地开垦草地和过度放牧、割草,30多年来整个黄河三角洲盐碱化、退化草地达6.67×10~4ha多,约占当地草地总面积的40%。本文研究了该地区草地退化的现状并就退化程度与累计开发时间的关系初步进行了数     

黄河三角洲芦苇种群高度和地上净生产量生长季动态

黄河三角洲位于山东省东北部。本地区自然植被的主要类型是盐生草甸,其中广泛分布在低平洼地、黄河故道以及池塘河渠的芦苇(Phragmites communis)种群是该地区重要的农业资源之一。通过在生长季中对这一种群的定位研究,初步揭示了种群高度和地上净生产量动态的基本规律。一、自然环境概况黄河三角洲在中国植被区划上属暖温带落     

黄河三角洲土壤运行多样性初步调查研究

1995－1996年对黄河三角洲9个代表性样区,进行了土壤运动定性,定量调查,并对古代,近代,现代黄河三角洲3个代表性样区开展了土壤动物周年调查,研究了土壤动物的种类组成,分布和节季变化,以及土壤动物多样性,调查研究结果,黄河三角洲共鉴定出土壤运动38种,土壤运动种类组成和数量分布因三个三角洲成土年龄不同而存在差异,土壤运动多样性以夏季为丰富,黄河三角洲土壤运动多样性]与均匀度表现为正相关关系,与单纯度呈负相关趋势。     

黄河改道以来黄河三角洲演变过程及其驱动机制

基于1976—2009年的23期遥感影像,并结合1976—2008年利津站水沙数据以及黄河流域年均降水量数据,定量分析黄河入海水沙特征以及黄河三角洲演变过程及其驱动机制.结果表明:1976—2008年间,黄河入海年径流量和年输沙量呈现出年际变化大和丰枯水(沙)年交替的特征,但总体均呈下降趋势;清水沟流路河口三角洲岸线和面积变化总体呈淤积增长趋势,三角洲的发育过程大致分1976—1985年、1986—1995年和1996—2009年3个阶段,3个阶段的增长速率逐阶段递减;黄河三角洲岸线和面积与利津站累积输沙量之间均呈显著的指数函数关系;黄河流域降水量的年际波动与利津站入海输沙量年际波动基本同步,并具有相关性,说明黄河流域降水量的年际波动是引起入海径流量和输沙量波动的重要原因.     

Dioxin-like Polychlorinated Biphenyls Contamination and Distribution in Soils from the Modern Yellow River Delta,China

The concentrations of 12 dioxin-like Polychlorinated Biphenyls (dl-PCBs) were determined from 37 soil samples collected from the modern Yellow River Delta (China) in March 2006. The PCB concentrations were determined by dual capillary GC-ECD. The total dl-PCBs concentrations were in the range of 108.7 to 2153 ng/kg with an average of 800.5 ng/kg. The toxic equivalency (TEQ) in this area varies from 2.3 × 10^{? 5} to 9.5 × 10^{? 5} ng-TEQ/kg, so the delta is slightly polluted by PCBs. PCB118, the main congener, accounted for 46.7% of the total dl-PCB. More than 60% dl-PCBs were penta-PCBs. The spatial distribution of the dl-PCBs is discussed in detail. The distribution of the PCBs suggests that water runoff is the main source of the total contaminant burden in the delta, and that atmospheric precipitation plays an important role.     

A management-oriented valuation method to determine ecological water requirement for wetlands in the Yellow River Delta of China

A wide range of human impacts have resulted in changes to wetland water regimes throughout the natural reserve of the Yellow River Delta. Specific local impacts which affect wetland water regimes include hydrological alterations associated with urban and agricultural development. Increasingly, management decisions must be made regarding the amount and timing of water required to maintain the ecosystem's diversity and its ecological characteristics. In this paper, based on the practice in the natural reserve and the important request of Ramsar for the “wise use” of wetlands in which ecological characteristics need to be reserved, a set of management objectives for the wetland natural reserve is proposed. The objectives include protecting the ecosystem and the waterfowl resources in the new wetland, renewing biodiversity and maintaining the function of the ecosystem. By means of a correlation analysis between the wetland biota and water regime, the ecological water requirement for the wetlands is proposed and classified into three classes, i.e., minimum, moderate and perfect water requirement, corresponding to the basic, moderate and perfect management objective, respectively. The results show that the minimum, moderate and perfect water requirements, respectively, are 37.94×10⁸, 49.47×10⁸ and 64.57×10⁸ m³ per year if the water required for sediment flushing is not considered in the wetland natural reserve. If the water required for sediment flushing is included, the amount will be 187.94×10⁸, 199.47×10⁸ and 214.57×10⁸ m³ per year, respectively, which cover 47%, 50% and 54% of the available ecological water quantities observed in the lower Yellow River during the 1950s.     

Influences of chronic contamination of oil field exploitation on soil nematode communities at the Yellow River Delta of China

Oil production related activities have led to many environmental problems. Around 80% of the total output of crude oil is generated from terrestrial oilfields in the world. However, the impact of oil exploitation procedures on soil animal communities has not been fully understood. This study investigated the responses of soil nematode communities to the oil exploitation activities in the Yellow River Delta of China. By setting 10 oilfield sites and 5 relatively uncontaminated sites (controls), we found that the content of soil total petroleum hydrocarbons (TPH) was significantly higher at oilfield sites than at controls. With a longer oil exploitation history, the content of soil TPH increased. Soil nematode community structure at oilfield sites was largely different from that at controls. Soil nematodes were significantly less abundant but more diverse at oilfield sites than at controls. The proportions of fungal feeders were significantly lower at oilfield sites than at controls, attaining only half of those at controls. The nematode trophic diversity and genus number negatively correlated with the duration of petroleum exploitation history. This study elucidated the difference in soil nematode communities caused by oilfield exploitation and indicated that the nematode diversity was most obviously influenced by the soil TPH content and the oil exploitation history.     

Influences of chronic contamination of oil field exploitation on soil nematode communities at the Yellow River Delta of China

Oil production related activities have led to many environmental problems. Around 80% of the total output of crude oil is generated from terrestrial oilfields in the world. However, the impact of oil exploitation procedures on soil animal communities has not been fully understood. This study investigated the responses of soil nematode communities to the oil exploitation activities in the Yellow River Delta of China. By setting 10 oilfield sites and 5 relatively uncontaminated sites (controls), we found that the content of soil total petroleum hydrocarbons (TPH) was significantly higher at oilfield sites than at controls. With a longer oil exploitation history, the content of soil TPH increased. Soil nematode community structure at oilfield sites was largely different from that at controls. Soil nematodes were significantly less abundant but more diverse at oilfield sites than at controls. The proportions of fungal feeders were significantly lower at oilfield sites than at controls, attaining only half of those at controls. The nematode trophic diversity and genus number negatively correlated with the duration of petroleum exploitation history. This study elucidated the difference in soil nematode communities caused by oilfield exploitation and indicated that the nematode diversity was most obviously influenced by the soil TPH content and the oil exploitation history.     

Arbuscular mycorrhizal status of wild plants in saline-alkaline soils of the Yellow River Delta

A survey was made of the arbuscular mycorrhizal (AM) status of five dominant wild plants Tamarix chinensis, Phragmites communis, Suaeda glauca, Aeluropus littoralis var. sinensis and Cirsium setosum in saline-alkaline soils of the Yellow River Delta that show low plant diversity. All of the species were colonized and showed typical AM structures (arbuscules, vesicles). The colonization percentage ranged from 0.2% to 9.5%, where C. setosum was the highest. The species richness of AMF at the different sites ranged from 2.00 to 2.40 per 50 ml soil, with an average of 2.16. Species diversity ranged from 1.99 to 2.22 per 50 ml soil, with an average of 2.13. Spore density ranged from 3 to 30 per 50 ml soil, with an average of 12. Glomus was the dominant genus, with a frequency and relative abundance of 88.1% and 68.4%, respectively. G. caledonium, with a frequency and relative abundance of 15.0% and 4.6%, respectively, was the dominant species. Differences were also observed in the distribution of AMF in different soil layers. Although there were still AM fungal spores in the layer 40 cm below the surface, most spores were found at a depth of 0–40 cm.     

Towards a Complex, Plural and Dynamic Approach to Diversity: Rejoinder to Myers and Patil, Podani, and Sarkar

This reply paper includes two brief remarks in rejoinder to the commentary papers of Myers and Patil, Podani, and Sarkar. The first observation concerns the fundamental nature of ecological diversity measures, while the second one specifically addresses some interesting mathematical connections between α- and β-diversity.     

Distribution and Contamination Risk Assessment of Dissolved Trace Metals in Surface Waters in the Yellow River Delta

This study investigated the dissolved trace metal contamination levels of Zn, Sr, B, Al, Ba, Fe, Mn, Li, V, Be, Cd, Cr, Cu, Mo, Ni, Se, and Pb in 23 surface waters of the Yellow River Delta (YRD) in China. Coefficients of variation with 66–260% reflected large spatial variations of concentrations of metals. Compared to drinking water guidelines established by the World Health Organization and the U.S. Environmental Protection Agency, the primary trace metal pollution components (Al, B, V, and Zn) were above drinking water standard levels by 82.6%, 47.8%, 52.2%, and 52.2%, respectively. Preliminary risk assessments were determined via the Hazard Quotient (HQ) to evaluate the human health risk of these metals. HQ_ingestion of V indicated potential deleterious health effects for residents. Hierarchical cluster results revealed that clusters 1, 2, and 3 were primarily affected by pollution from industrial and domestic activities, natural and agriculture activities, and oil fields, respectively. Principal component analysis results indicated Fe, Mn, Al, and Ba were controlled by natural sources, whereas anthropogenic activities led to high pollution levels of Al, B, V, Zn, and Sr.     

Geochemical speciation and ecological risk assessment of heavy metals in surface soils collected from the Yellow River Delta National Nature Reserve,China

In this study, a comprehensive assessment of soil heavy metal (HMs) pollution in the Yellow River Delta National Nature Reserve (YRDNNR) was conducted. Spatial distributions, chemical fractions, and sources of eight HMs (Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni) in 46 soil samples in the studied region were analyzed. In addition, the potential risks of the HMs were evaluated. The results showed that the mean concentrations of Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni were 19.4, 65.2, 38.4, 55.9, 0.078, 41546.5, 510.3, and 27.5 mg kg^?1, respectively. It indicates that the concentrations of most HMs, with exception of Pb and Fe, in samples were similar to the background value of soil in China. Principal component analysis results showed that the HMs originated mainly from natural sources, but Pb pollution in the studied area was significantly caused by anthropogenic activities. In addition, Ecological risk assessment statistical analysis indicates that the HM contamination level in YRDNNR ranged from low to moderately polluted, however, the environmental risk due to Mn and Pb contamination was high.     

陕西省黄河中游湿地冬季鸭科鸟类群落结构

2002～2007年冬季,对黄河中游湿地4种典型生境包括滩涂、人工渔塘、芦苇沼泽和莲池中的鸭科鸟类群落进行了调查.共记录到鸭科鸟类7属20种,采用频率指数法确定的优势种为斑嘴鸭、绿翅鸭、赤膀鸭、绿头鸭、普通秋沙鸭,其数量之和占总数量的65.6%.对4种不同生境的物种多样性、丰富度、均匀度、优势度进行分析,结果表明芦苇沼泽的多样性和丰富度指数最高,莲池的多样性和丰富度指数最低.人类活动引起的隐蔽场所和食物资源的变化是造成分布差异的主要原因.     

黄河三角洲莱州湾柽柳低效次生林质效等级评价

以黄河三角洲莱州湾柽柳次生灌木生态林为对象,选取林分生长和土壤理化性状等24项指标,采用综合因子法研究柽柳林低效的主要影响因子和低效林划分的主要参数.结果表明:柽柳树木生长指标与反映土壤质量状况的主要指标相关性不明显,仅依据树木的生长状况不能反映柽柳林的低效程度,需采用树木生长和土壤改良指标来综合判断.土壤含盐量、林龄、土壤含水量、单株地上茎和叶生物量及地径是反映低效柽柳林分质效高低的主要指示因子,其次为土壤容重、孔隙度及土壤养分特征.莱州湾柽柳低效林可划分为生长潜力型、轻度低质型、中度低效型、中度低质低效型和重度低质低效型5大类型.依据聚类分析的类平均值探讨了其林分特征、低效原因及经营改造方法.     

黄河三角洲莱州湾湿地柽柳种群分布特征及其影响因素

为探明黄河三角洲莱州湾柽柳(Tamarix chinensis Lour)灌丛环境因子的基本特征及其对柽柳灌丛空间分布类型的影响,采用样地与样方相结合的测定方法,对柽柳灌丛样地距海远近、地下水水位、土壤盐碱含量、土壤容重和孔隙度等基本物理参数以及土壤有机质、速效氮、磷养分等13个环境因子参数进行相关性和主成分分析。结果表明:莱州湾柽柳种群空间分布表现为聚集型分布,林分密度与距海距离和地下水水位呈极显著正相关,与土壤含水量呈极显著负相关;土壤含盐量与土壤含水量呈极显著正相关,与地下水水位和土壤孔隙度呈极显著负相关;土壤含水量与地下水位呈极显著负相关。莱州湾柽柳灌丛13个环境因子的变异系数在0.060—1.296之间,土壤K+含量、土壤含盐量和林分密度变化幅度较大;其次为土壤有机质和有效磷,地下水水位的空间变异性高于至海距离,而土壤p H值、土壤容重和总孔隙度等基本物理性状变化幅度较小。土壤盐碱含量分别为0.47%和p H为8.48,呈重盐土和偏碱性特征。主成分分析表明,土壤盐碱含量是影响黄河三角洲莱州湾湿地柽柳灌丛分布的主导因素,其次是距海距离,土壤速效磷和地下水位次之。     

Environmental change over two decades since dredging and excavation of the lower Boro River, Okavango Delta, Botswana

The Okavango Delta, southern Africa's largest wetland, is situated on the fringe of the semi-arid Kalahari Desert. It is a large alluvial fan, occupying a graben structure which is an extension of the East African Rift system. Of the 16 km³ of water which enters the Delta each year, 96% is lost to the atmosphere by evapotranspiration, 2% to groundwater and only 2% leaves as surface flow. In order to increase surface outflow to meet human needs, the distal Boro channel–floodplain system was dredged, excavated and bunded between 1971 and 1974. The immediate impact of these measures was the destruction of in-channel flora. After 20 years, the aquatic flora has recovered in the excavated channel. However, little recovery has occurred along the channel reach which was dredged. Moreover, there has been significant encroachment of terrestrial species onto the floodplain in the region of the dredged channel. In addition, dredging created a nick point which has been migrating upstream by headward erosion since dredging ceased. The average rate of advance of the nick point has been about 500 m per year. Incision associated with nick point migration has produced a channel which is indistinguishable in form from the dredged channel and, like the dredged channel, is almost completely devoid of in-channel aquatic flora. The adverse environmental impact of dredging has therefore continued to propagate in an upstream direction, although the height of the nick point has decreased, suggesting a natural attenuation process. This is likely to result in eventual elimination of the nick point.     

珠三角典型稻田生态沟渠型人工湿地的非点源污染削减功能

为了评价珠江三角洲地区农业非点源污染控制技术的开发与削减功能,本研究以珠海市斗门区上洲村典型稻田系统为例,提出了一种适应当地实际情况的生态沟渠型人工湿地构建技术,并进行了示范工程建设和防治效果评价。结果表明:该生态沟渠利用农田既有的排灌系统,经过适当改建而成;在满足原有排灌功能的前提下,对稻田排水径流中固体悬浮物(SS)、总磷(TP)、总氮(TN)、化学需氧量(CODCr)、铵态氮(NH4+-N)、生化需氧量(BOD5)的去除效率分别达到71.7%、63.4%、49.9%、26.6%、14.5%和11.6%;对营养型和颗粒态污染物质净化作用效果较好,对有机型污染物净化作用有限;其中对SS和TP的作用最为明显。该技术和工程成本效益良好,既减轻了稻田排水对附近水体的污染负荷,又增加了农田的景观效果。在珠三角及类似的经济发达而人地关系紧张的地区具有一定的推广价值。     

Application of a progressive-difference method to identify climatic factors causing variation in the rice yield in the Yangtze Delta, China

Time series of rice yields consist of a technology-driven trend and variations caused by climate fluctuations. To explore the relationship between yields and climate, the trend and temporal variation often have to be separated. In this study, a progressive-difference method was applied to eliminate the trend in time series. By differentiating yields and climatic factors in 2 successive years, the relationship between variations in yield and climatic factors was determined with multiple- regression analysis. The number of hours of sunshine, the temperature and the precipitation were each defined for different intervals during the growing season and used as different regression variables. Rice yields and climate data for the Yangtze Delta of China from 1961 to 1990 were used as a case study. The number of hours of sunshine during the tillering stage and the heading to milk stage particularly affected the yield. In both periods radiation was low. In the first period, the vegetative organs of the rice crop were formed while in the second period solar radiation was important for grain filling. The average temperature during the tillering to jointing stage reached its maximum, which affected rice yields negatively. Precipitation was generally low during the jointing and booting stages, which had a positive correlation with yield, while high precipitation had a negative effect during the milk stage. The results indicate that the climatic factors should be expressed as 20- to 30-day averages in the Yangtze Delta; a shorter or longer period, e.g. 10 or 40 days, is less appropriate. Received: 30 May 2000 / Revised: 27 October 2000 / Accepted: 30 October 2000