Temporal and spatial trends in nitrogen and phosphorus inputs to the watershed of the Altamaha River,Georgia, USA

The watershed of the Altamaha River, Georgia, is one of the largest in the southeastern U.S., draining 36,718 km² (including parts of metro Atlanta). We calculated both nitrogen (fertilizer, net food and feed import, atmospheric deposition, and biological N fixation in agricultural and forest lands) and phosphorus (fertilizer and net food and feed import) inputs to the watershed for 6 time points between 1954 and 2002. Total nitrogen inputs rose from 1,952 kg N km⁻² yr⁻¹ in 1954 to a peak of 3,593 kg N km⁻² yr⁻¹ in 1982 and then declined to 2,582 kg N km⁻² yr⁻¹ by 2002. Phosphorus inputs rose from 409 kg P km⁻² yr⁻¹ in 1954 to 532 kg P km⁻² yr⁻¹ in 1974 before declining to 412 kg P km⁻² yr⁻¹ in 2002. Fertilizer tended to be the most important input of both N and P to the watershed, although net food and feed import increased in importance over time and was the dominant source of N input by 2002. When considered on an individual basis, fertilizer input tended to be highest in the middle portions of the watershed (Little and Lower Ocmulgee and Lower Oconee sub-watersheds) whereas net food and feed imports were highest in the upper reaches (Upper Oconee and Upper Ocmulgee sub-watersheds). Although the overall trend in recent years has been towards decreases in both N and P inputs, these trends may be offset due to continuing increases in animal and human populations.     

Bibarba bibarba: A new genus and species of Cobitinae (Pisces: Cypriniformes: Cobitidae) from Guangxi Province (China)

A new genus of Cobitinae, Bibarba gen. n., and a new species, B. bibarba sp. n., were discovered and are described for the Chengjiang River, a tributary of the Hongshuihe River in Guangxi Province of southern China. This river region is characterized by a Karst landscape, and the river that is inhabited by the new genus is a slowly moving stream with arenaceous and cobblestone beds. The new genus resembles Cobitis Linnaeus, 1758 (subfamily Cobitinae) in the shape and pigmentation pattern of their body, the absence of scales on their head, and the presence of a suborbital spine, but differs from it by a single Lamina circularis on the third pectoral fin ray instead of on the base of the second pectoral fin ray; two pairs of barbels (one rostral pair and one maxillo-mandibular pair) instead of three pairs of barbels (one rostral pair, one maxillary pair, and one maxillo-mandibular pair); a relatively thick and short suborbital spine with a strong medio-lateral process instead of a suborbital spine without or with a weakly formed medio-lateral process as in Cobitis; and the lack of a black stripe extending from the occiput through the eye to the insertion of the rostral barbel. The first two characters have not been reported in any other genus of the subfamily Cobitinae. A morphometric character analysis based on PCA reveals differences between B. bibarba and C. sinensis in body size, barbel length, interorbital width, pectoral fin length in males, and the position of the dorsal and ventral fins. Type specimens of the new species are kept in the Freshwater Fishes Museum of the Institute of Hydrobiology at the Chinese Academy of Sciences in Wuhan, Hubei Province.     

Greater Sage-Grouse Population Response to Energy Development and Habitat Loss

ABSTRACT Modification of landscapes due to energy development may alter both habitat use and vital rates of sensitive wildlife species. Greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, have experienced rapid, widespread changes to their habitat due to recent coal-bed natural gas (CBNG) development. We analyzed lek-count, habitat, and infrastructure data to assess how CBNG development and other landscape features influenced trends in the numbers of male sage-grouse observed and persistence of leks in the PRB. From 2001 to 2005, the number of males observed on leks in CBNG fields declined more rapidly than leks outside of CBNG. Of leks active in 1997 or later, only 38% of 26 leks in CBNG fields remained active by 2004–2005, compared to 84% of 250 leks outside CBNG fields. By 2005, leks in CBNG fields had 46% fewer males per active lek than leks outside of CBNG. Persistence of 110 leks was positively influenced by the proportion of sagebrush habitat within 6.4 km of the lek. After controlling for habitat, we found support for negative effects of CBNG development within 0.8 km and 3.2 km of the lek and for a time lag between CBNG development and lek disappearance. Current lease stipulations that prohibit development within 0.4 km of sage-grouse leks on federal lands are inadequate to ensure lek persistence and may result in impacts to breeding populations over larger areas. Seasonal restrictions on drilling and construction do not address impacts caused by loss of sagebrush and incursion of infrastructure that can affect populations over long periods of time. Regulatory agencies may need to increase spatial restrictions on development, industry may need to rapidly implement more effective mitigation measures, or both, to reduce impacts of CBNG development on sage-grouse populations in the PRB.     

江苏宜兴龙池山现代植被表土孢粉的初步研究

江苏宜兴龙池山森林自然保护区表土花粉分析结果表明,表土孢粉植物群主要以栎属(Quercus)、松属(Pinus)、青冈属(Cyclobalanopsis)、栲属(Castanopsis)/柯属(Lithocarpus)、栗属(Castanea)占优势的木本植物组成,混生有枫香属(Liquidambar)、杨梅属(Myrica)、冬青属(Ilex)、女贞属(Ligustrum)、紫树属(Nyssa)、盐肤木属(Rhus)、黄连木属(Pistacia)等亚热带常见植物类型。研究区不同海拔高度的表土孢粉组合特征基本反映了当地现今的植物构成、植被面貌及其垂直分布规律。结合长江三角洲及其周边地区其他代表性表土花粉资料,首次提出以常绿阔叶木本植物与落叶阔叶木本植物含量之比(E/D),并结合重要优势、标志木本植物科属,初步识别和确立各地带性森林植被的表土花粉指标,为这一地区开展第四纪古植被和古气候等孢粉研究提供参考性依据。     

云县罗扎河下游落叶季雨林的群落生态学研究

对罗扎河下游鲜为人知的落叶季雨林进行了群落生态学研究,结果表明:罗扎河下游落叶季雨林群落高度在15~20m之间;群落乔木层以厚皮树(Lannea coromandelica)、一担柴(Colonafloribunda)、粗糠柴(Mallotus philippensis)、毛果扁担杆(Grewia eriocarpa)、灰毛浆果楝(Cipadessa cinerascens)等树种为优势种;灌草层以刚莠竹(Microstegiumciliatum)盖度最大,其余如飞机草(Eupatoriumodoratum)、藿香蓟(Agera-tumconyzoides)、蹄盖蕨(Athyriumsp.)等种的盖度也比较大;群落中乔木和附生、藤本植物种类较少,而灌木和草本植物种类较多;多数乔木层植株胸径在5~10cm之间,大径级乔木比较少,即使群落中的优势种也主要是通过较多数量的中小径级个体体现出来。多样性指数计算表明,本落叶季雨林的生物多样性指数虽然比典型热带山地雨林为低,但大致相当于季风常绿阔叶林。     

Population genetic structure of Vitex negundo (Verbenaceae) in Three-Gorge Area of the Yangtze River: The riverine barrier to seed dispersal in plants

Previous studies have demonstrated that large rivers can influence inter- and intra-specific gene flow for many animals. The effects of large rivers on the genetics of plant populations have focused on either hydrochoric impacts of water current on gene flow or genetic differentiation among populations from different watersheds. Few studies have explicitly tested the barrier effects on plant gene flow across banks of large rivers, especially their relative effects on pollen and seed dispersals. The Yangtze River (Changjiang River), one of the major rivers of the world, provides an excellent model to evaluate the impacts of rivers on gene flow in plants. Using RAPD (random amplified polymorphic DNA) and cpDNA (chloroplast DNA) markers, we investigated the genetic structure of 10 populations of Vitex negundo in two regions of Three-Gorge Area along the Yangtze River. Each region contained two populations on the north bank, two on the south bank and one island population along the river. The analyses indicated low RAPD between banks, and similar or a little higher differentiation between populations within the same bank. In contrast, a large proportion of chloroplast polymorphism was ascribed to among-bank variation but much lower cpDNA differentiation was among populations within the same bank. These results indicate that the Yangtze River represents a general barrier to the dispersal of seeds but not to the movement of pollen in V. negundo. The cpDNA genetic distances or differentiations between the island populations and those on either bank of the river are intermediate to those between the banks across the river, implying that the islands in the Yangtze River may serve as a stepping-stone for seed dispersal. Our results suggest that large rivers may serve as a general barrier, not only for the movement of animals, but also for the dispersal of plants, which should be of great significance for the conservation of biodiversity around the rivers.     

Impact of hydrology on aquatic communities of floodplain lakes along the Daugava River (Latvia)

During July 2004, various limnological characteristics of 24 floodplain lakes and reservoirs have been explored along the Middle Daugava for the first time in order to reveal possible impact of the long-term mean annual flooding frequency on their phytoplankton, zooplankton, macrozoobenthos and macrophyta communities. Obtained data series were analysed by Spearman’s rank correlation method, Principal Component Analysis (PCA) method and Renkonen’s similarity test. UPMGA method was used for single linkage clustering of the lakes based on the abundance of phyto- and zooplankton taxa. Low similarity between the obtained cluster trees and hydrological grouping was stated indicating minor impact of the flooding hydrology on summer plankton communities of these lakes. Significant correlation between the flooding frequency and several physicochemical and biological parameters was found. Six main factors, which explain observed variations, were extracted by PCA. Significant negative impact of hydrological connectivity on zooplankton species diversity as well as positive impact on Oligochaeta density was stated, whereas other biotic parameters were affected by local factors, such as lake morphology, internal loading of nutrients from sediments, throphic interactions as well as local source of dissolved organic matter.     

Changes in the population structure,growth and mortality of striped weakfish <Emphasis Type="Italic">Cynoscion guatucupa</Emphasis> (Sciaenidae,Teleostei) of southern Brazil between 1976 and 2002

Siphonophores are exclusively marine cnidaria and their predatory role in plankton food-webs is well recognised. In this study, we analyse the structure and the spatial extent of siphonophore assemblages in relation to changes in freshwater outflows and food availability in the southern Gulf of Mexico during a high (October) and a low (April) outflow periods. A total of 149 samples were collected using a 505 μm multiple closing net at 1–6 levels (0–100 m) of the water column, depending on the bathymetry. Data on siphonophore species biovolumes (ml 100 m⁻³) were treated by means of the Bray-Curtis Dissimilarity Index, and two distinctive assemblages were identified: the ‘inner’ and the ‘outer’ assemblages, located over the inner and outer shelves. Temperature, salinity, zooplankton biomass, and siphonophore species were included in a Principal Component Analysis (PCA) to identify the factors associated with each assemblage. Geographical distribution of the assemblages practically remained the same during both seasons and its cross-shelf variability was stronger than the vertical one. Seasonally, diversity values were higher in October, when the highest river discharges occur. Spatially, the lowest diversity and mean siphonophore biovolumes values were registered in the ‘inner assemblage’, where the highest and lowest salinity values were recorded. We suggest that even when extreme salinity values (>36.5 or <34) might depress siphonophore populations in the coastal area, enough food availability in the concerned areas might mitigate the negative effect of salinity, since a positive and significant (p < 0.05) relationship was found between siphonophores biovolume and zooplankton biomass. Bassia bassensis, Diphyes dispar and Enneanogum hyalinum, present in both assemblages during both seasons, were able to survive in a wide range of salinity values, following perhaps, their prey. All the 23 species here registered were found in the ‘outer assemblage’; however, Abylopsis eschscholtzi, Chelophyes appendiculata and Diphyes bojani were more associated with the ‘outer’ group according to the PCA results. Enneagonum hyalinum was the only species frequently encountered and abundant in the ‘inner assemblage’ during both seasons and, supporting previous observations, this species might be considered as an indicator of nearshore waters. Handling editor: K. Martens     

Long-term changes in a benthic assemblage associated with artificial reefs

The aim of the study was to evaluate the long-term development of a hard bottom benthic assemblage over a period of 20 years in an area off the mouth of a large river. The artificial reef of Fregene was selected because benthic assemblage data were available for the period 1981–1992. This artificial reef is located in the mid Tyrrhenian Sea, 5 nautical miles north of the two mouths of the Tevere River (Latium, Italy) and 1.5 nautical miles offshore from Fregene (Rome, Italy). The artificial reef was deployed in March 1981 for fisheries enhancement in 10–14 m of water on a sandy-silty seabed. The Tevere River carries suspended materials and a heavy load of organics since it transports Rome’s effluent, resulting in the eutrophic state of area waters. Benthic sampling was conducted in 2001 by SCUBA diving; two standard surfaces of 400 cm² were scraped from the vertical walls of the same uppermost block in four different periods. All organisms were identified and counted. The methodology used is the same as that adopted in the previous periods, so that the 2001 data could be compared with past collected data. The benthic assemblage was analysed by cluster analysis using the Bray-Curtis index and clustered using the group average clustering algorithm. The SIMPER procedure was used to identify those taxa that characterize each station group identified by cluster analysis. Changes in benthic assemblages and hydrological trends of the Tevere River were investigated using the cumulative sum series method. The 20-year development of the benthic community, starting from the new substratum, is composed of different phases characterised by different benthic assemblages. In particular five different phases were distinguished: 1. Pioneer species recruitment (May 1981–June 1981); 2. Mytilus galloprovincialis (mussel) dominance (August 1981–November 1983); 3. M. galloprovincialis regression (July 1984–October 1985); 4. M. galloprovincialis absence (91–92); 5. Bryozoans bioconstruction dominance (2001). The dynamic succession of the observed benthic assemblages exhibited a good relation with the Tevere River flow. The Tevere River flow, and the subsequent sedimentation process, seems to have strongly influenced the benthic assemblage succession of the Fregene artificial reef. Guest editors: G. Relini & J. Ryland Biodiversity in Enclosed Seas and Artificial Marine Habitats