基于InVEST模型的1980–2100年长江中下游地区动植物生境质量时空变化研究

20世纪80年代以来,人类活动加速了长江流域的土地利用变化,这对当地动植物的生境质量造成了影响,在中国生态文明建设和长江经济带发展战略不断推进的大背景下,对长江中下游地区的生境质量变化开展长时间多时段的研究具有重要的现实意义。本研究以长江中下游地区7省的土地利用覆盖数据(1980–2018年)与未来土地利用模型模拟出未来四种情景(A1B,A2,B1,B2)下的土地利用覆盖数据(2050年,2100年)为基础,借助环境服务与权衡综合评估(In VEST)模型评估了长江中下游地区的生境质量时空变化。结果表明:(1)2000–2015年,研究区的坡度(R=0.502,P <0.01)和海拔(R=0.003,P <0.05)、人口密度(R=0.299,P <0.01)、NDVI(R=0.366,P <0.01)与生境质量显著相关;(2)从1980年到2018年,研究区总面积61.93%的土地生境质量下降,38.07%的土地生境质量上升;在A2情景(人口密度大,环境技术投入少,传统能源成本高)和B2情景(中等人口密度,中等绿色技术,区域政府间缺乏合作)下,研究区的生境质量将下降;(3)长江下游的生境质量恶化程度高于中游,研究区北部的生境质量恶化程度低于南部。整体上,积极的环境保护政策是有效的,但并未根本上遏制生境质量的整体退化趋势。区域发展应加大环境保护力度,控制人口增长,鼓励绿色技术创新,在处理生态问题时,要注重省际合作。本研究可为区域野生动植物保护规划和国际上的类似流域研究提供科学参考。     

Chironomids as quantitative indicators of mean July air temperature: validation by comparison with century-long meteorological records from northern Sweden

This study evaluates the potential of using chironomid assemblages to estimate past temperature changes by comparing chironomid-inferred temperatures to meteorological data for the last 87 years. This comparison is made using high-resolution (i.e., sub-decadally resolved) short cores of four lakes along a gradient of altitude (Lake Njulla, 999 m a.s.l., Lake 850, 850 m a.s.l., Lake Alanen Laanijavri, 365 m a.s.l. and Lake Vuoskkujavri, 348 m a.s.l.), vegetation (pine forest to alpine tundra vegetation) and temperature (mean July temperature of 12.4 to 8.1°C). Patterns of chironomid-inferred changes in mean July air temperature were highly comparable to changes in the meteorological data. Moreover, instrumental data were almost always within the specific errors of the quantitative estimates using chironomids. These results indicate that chironomids can be used as a powerful tool to reconstruct temperatures and that chironomids are sensitive enough to record temperature changes of low magnitude such as those recorded during the Holocene. Although this relationship between temperature and chironomid community is strong for the last 87 years, we cannot assume that other environmental factors such as organic matter, changes of lake water depth or oxygen availability were not more significant over longer temporal scales of the Holocene, or longer.     

Abundance of seagrass (Zostera marina L.) and macroalgae in relation to the salinity-temperature gradient in Yaquina Bay, Oregon, USA

The relative abundances of the seagrass,Zostera marina L., and associated macroalgae were examined for Yaquina Bay, Oregon, U.S.A., to investigate variability in autotroph abundance along the salinity-temperature gradient and the potential for nuisance algal blooms. Possible explanations for the patterns in autotroph abundances were explored through examination of their correlations with the physicochemical characteristics of the water column. Study sites were established in each of three zones in the estuary defined by temperature and salinity and were sampled monthly June through September 1998 and in July 1999.Z. marina and macroalgal cover andZ. marina shoot density were measured in 0.25-m² plots at each site. After cover estimates and shoot counts were made, material was harvested for determination ofZ. marina and macroalgal biomass. Water column variables were measured from stations near each study site and composited on a depth-averaged, monthly basis for each zone. BothZ. marina and green macroalgal abundance differed between sites, over the summer in 1998, and between years. Seasonal patterns were most obvious forZ. marina at the site closest to the ocean while the pattern in macroalgal abundance suggested a bloom moving up river as summer progressed. The physicochemical characteristics of the zones differed with the season and could be related to the patterns inZ. marina and macroalgal abundance. In particular, salinity was positively correlated withZ. marina abundance, while abundance of both autotrophs was related to light availability.Z. marina biomass ranged 19–109 g dry weight m^?2; green macroalgae biomass ranged 5–234 g dry weight m^?2. The biomass of the green macroalgae at several sites and dates equaled or exceed that of theZ. marina suggesting the potential for nuisance algal blooms does exist in Yaquina Bay.     

Temporal and spatial patterns in abundance and diversity of fish assemblages in Elkhorn Slough,California

Assemblages of ichthyofauna of shallow inshore habitats along Californía’s central coast are described in terms of species composition, abundance, and life-style categories. A total of 22,334 fishes from 65 species and 27 families was collected with otter trawls at six sites in the main channel and tidal creeks of Elkhorn Slough, a tidal embayment and seasonal estuary, and two nearshore ocean stations in Monterey Bay during 44 months between August 1974 and June 1980. Greater than 90% of the catch comprised 10 species. The four dominant species,Cymatogaster aggregata, Leptocottus armatus, Phanerodon furcatus, andEmbiotoca jacksoni, occurred during most or all seasons and were classified as residents or partial residents. Several abundant species were marine immigrants that seasonally use the slough as spawning and nursery grounds; this resulted in higher abundance and species richness during summer. Species collected during winter largely were slough residents. Species compsosition and richness varied with distance from the slough entrance. The ocean assemblage was most different, and its similarity to other stations decreased progressively with distance inland and into the tidal creeks. During our study, 5,074 fishes were collected by beach seine in Bennett Slough, a remote shallow marsh basin adjacent to the entrance of Elkhorn Slough. Species richness was relatively low and three euryhaline species accounted for >80% of the total catch. The species assemblage was most similar to those at the tidal creek and most shallow stations of Elkhorn Slough. Resident species numerically dominated assemblages in Bennett Slough and the most inland areas of Elkhorn Slough. The high relative abundance of marine-related fishes (classified as marine, marine immigrant, and partial resident), entering Elkhorn Slough early in life or as spawning adults indicates the importance of this habitat to nearshore fish assemblages.     

Experimental studies of predation on polychaetes associated with seagrass beds

Predation on benthic polychaetes associated with seagrass beds was examined in laboratory and field predator inclusion experiments with one fish and three invertebrate predators. Predation had differential effects on polychaete taxa which depended on their microhabitat utilization patterns. The magnitude of predation effects strongly depended on the predator species, with the shrimpPenaeus duorarum having the greatest impact and the pinfishLagodon rhomboides the least. Abundance of spionid polychaetes, which are located near the sediment-water interface, was reduced most often by predation. Nereid and capitellid polychaete abundances were reduced by some predators and not by others. The results emphasize the need for more detailed natural history information on polychaete species in order to improve the interpretation of results from predation experiments.     

Chemical and isotopic variations in an iron-rich lava flow from the Kirkpatrick Basalt,north Victoria Land,Antarctica: implications for low-temperature alteration

Chemical and isotopic (Sr, O, H) variations have been examined in an iron-rich lava flow of the Kirkpatrick Basalt from the Mesa Range in north Victoria Land, Antarctica. The flow is homogeneous with respect to the less mobile elements, whereas variations observed in K, Na, Si, Fe, and Rb result largely from alteration of glassy matrix material. Whole-rock Rb–Sr isotope data fall along a poorly-defined 103 Ma array attributed to secondary mobilization of Rb during the mid-Cretaceous. Alteration at that time is suggested by paleomagnetic data and would also account for discordant K–Ar dates. Whole-rock ¹⁸O values vary from +5.8 to +8.2 and a plagioclase separate has a ¹⁸O value of +5.6, reflecting the original composition of the magma. The range of ¹⁸O values for the whole-rock samples results from low-temperature alteration occurring primarily in the Jurassic and/or mid-Cretaceous. Whole-rock D values (-201 to -243) are markedly depleted, approaching equilibrium with modern meteoric water. In light of these data, variable Sr and O isotopic ratios in the underlying sequence of flows, previously interpreted in terms of an assimilation-fractionation model, may largely reflect post-magmatic alteration.     

A numerical study of the effects of wind forcing on the Chile Current System

A high-resolution, multi-level, primitive equation ocean model is used to examine the response of the coastal region from 22.5°S to 35°S of the Chile Current System to both equatorward and climatological wind forcing. The results from both types of forcing show that an equatorward surface current, a poleward undercurrent, upwelling, meanders, filaments and eddies develop in response to the predominant equatorward wind forcing. When climatological wind forcing is used, an offshore branch of the equatorward surface current is also generated. These features are consistent with available observations of the Chile Current System. The model results support the hypothesis that wind forcing is an important mechanism for generating currents, eddies and filaments in the Chile eastern boundary current system and in other eastern boundary current regions which have predominantly equatorward wind forcing.     

A Large-Scale Seasonal Modeling Study of the California Current System

A high-resolution, multi-level, primitive equation ocean model has been used to investigate the combined role of seasonal wind forcing, seasonal thermohaline gradients, and coastline irregularities on the formation of currents, meanders, eddies, and filaments in the entire California Current System (CCS) region, from Baja to the Washington-Canada border. Additional objectives are to further characterize the meandering jet south of Cape Blanco and the seasonal variability off Baja. Model results show the following: All of the major currents of the CCS (i.e., the California Current, the California Undercurrent, the Davidson Current, the Southern California Countercurrent, and the Southern California Eddy) as well as filaments, meanders and eddies are generated. The results are consistent with the generation of eddies from instabilities of the southward current and northward undercurrent via barotropic and baroclinic instability processes. The meandering southward jet, which divides coastally-influenced water from water of offshore origin, is a continuous feature in the CCS, and covers an alongshore distance of over 2000 km from south of Cape Blanco to Baja. Off Baja, the southward jet strengthens (weakens) during spring and summer (fall and winter). The area off southern Baja is a highly dynamic environment for meanders, filaments, and eddies, while the region off Point Eugenia, which represents the largest coastline perturbation along the Baja peninsula, is shown to be a persistent cyclonic eddy generation region. This revised version was published online in July 2006 with corrections to the Cover Date.     

Computerized balanced cross-section LOCACE to reconstruct an allochthonous salt sheet, offshore Louisiana

The evolution of an allochthonous salt sheet underlying the Mississippi fan is quantified using the two-dimensional LOCACE balanced section program. A first set of tests shows that the shape of the principal normal fault associated with the salt sheet is inconsistent with a roll-over geometry when using flexural slip or simple 120° linear shear criteria with a fixed footwall geometry. The next test with corrected fault geometry allows coherent restoration at the early Lower Miocene using the flexural slip criterion. In two-dimensional reconstructions, the area of salt cannot be balanced, i.e. the area available for salt is considerably wider than the actual salt area shown on the initial section. Thus either salt was dissolved or, perhaps more likely, salt moved outside the plane of section calling for a three-dimensional volumetric reconstruction procedure. The final interpretation is geometrically consistent and suggests that since early Lower Miocene time a large amount of salt moved out of the plane of section forming the allochthonous salt masses. An attempt to approximately balance salt volumes in three dimensions suggests that the amount of salt escaping the system is at least 18%.