城市生态系统健康综合评价

生态系统健康是生态学领域的研究热点之一.文中提出了对城市生态系统健康概念的理解; 从状态空间的角度, 解释了城市生态系统健康的内涵,并以此为基础,提出了目前研究中存在的不足; 从复合生态系统的角度,提出了一种新的城市生态系统健康评价方法——综合评价方法; 构建了城市生态系统健康综合评价模型,并将该方法应用于佛山市城市生态系统的健康评价.结果表明, 在研究时段内,佛山市城市生态系统健康水平逐年上升;综合评价方法不仅能反映城市整体健康状况,而且能辨别各子系统的相对健康水平,具有一定的理论价值和可操作性.     

Algology and Algologists at Bowling Green, a Short History

This paper summarizes the past 34 years of studies of algae by Rex Lowe and his students and collaborators at Bowling Green State University, Ohio, USA. Sixty-two students have received graduate degrees in this academic program focusing on systematics, ecology and environmental assessment. The taxonomic/floristic research initially focused on northern Ohio streams but is now continental to international in scope focusing on the algal flora of the Great Smoky Mountains National Park and on the South Island of New Zealand. Ecological research has focused on factors that regulate the structure and function of benthic algae. Variables that have been examined include abiotic resources (nutrients and light), grazers and physical disturbance. Studies on environmental assessment have focused primarily on the impact of point-source loads of chemicals into water bodies.     

Assessment of Pollution-Induced Microbial Community Tolerance to Heavy Metals in Soil Using Ammonia-Oxidizing Bacteria and Biolog Assay

This study attempted to investigate if the tolerance of soil bacterial communities in general, and autotrophic ammonia-oxidizing bacteria (AOB) in particular, evolved as a result of prolonged exposure to metals, and could be used as an indigenous bioindicator for soil metal pollution. A soil contaminated with copper, chromium, and arsenic (CCA) was mixed with an uncontaminated garden soil (GS3) to make five test soils with different metal concentrations. A modified potential ammonium oxidation assay was used to determine the metal tolerance of the AOB community. Tolerance to Cr, Cu, and As was tested at the beginning and after up to 13 months of incubation. Compared with the reference GS3 soil, the five CCA soils showed significantly higher tolerance to Cr no matter which form of Cr (Cr³⁺, CrO₄ ^2?, or Cr₂O₇ ^2?) was tested, and the Cr tolerance correlated with the total soil Cr concentration. However, the tolerance to Cu²⁺, As³⁺, and As⁵⁺ did not differ significantly between the GS3 soil and the five CCA soils. Community level physiological profiles using Biolog microtiter plates were also used to examine the chromate tolerance of the bacterial communities extracted after six months of exposure. Our results showed that the bacterial community tolerance was altered and increased as the soil Cr concentration was increased, indicating that the culturable microbial community and the AOB community responded in a similar manner.     

Opportunities for gene transfer from transgenic oilseed rape (Brassica napus) to related species

Before novel transgenic plant genotypes are grown outside containment facilities and evaluated under field conditions, it is necessary to complete a risk assessment to consider the possible consequences of that release. An important aspect of risk assessment is to consider the likelihood and consequences of the transgene being transferred by cross-pollination to related species, including other crops, weeds and ruderal populations. The purpose of this report is to review the literature to assess the ease with whichBrassica napus can hybridize with related species. The evidence for hybridization is considered at three levels: a) by open pollination, b) by hand pollination and c) by the use ofin vitro ovule and embryo rescue techniques; and also examines the fertility and vigour of the F₁, F₂ and backcross generations. Four species are reported to hybridize withB. napus by open pollination:B. rapa andB. juncea using fully fertile parents; andB. adpressa andR. raphanistrum using a male-sterileB. napus parent. Seventeen species are reported to form hybrids (including the four species above) withB. napus when pollination is carried out manually. At least 12 of these species were unable to form F₂ progeny, and eight were unable to produce progeny when the F₁ was backcrossed to one of the parental species. Many factors will influence the success of hybridization under field conditions, including: distance between the parents, synchrony of flowering, method of pollen spread, specific parental genotypes used, direction of the cross and the environmental conditions. Even where there is a possibility of hybridization betweenB. napus and a related species growing in the vicinity of a release, poor vigour and high sterility in the hybrids will generally mean that hybrids and their progeny will not survive in either an agricultural or natural habitat.     

森林生态系统DOM的来源、特性及流动

可溶性有机物质（Dissolved Organic Matter)是森林生态系统主要的可移动碳库及重要的养分库。系统综述了森林生态系统DOM的来源,组成,性质,季节动态;DOM释放与存留机制及影响因素,森林生态系统DOM的流动及干扰对DOM动态影响等,已有研究表明DOM的森林生态系统C、N、P循环,成土作用,污染物迁移等方面起着重要作用。今后森林生态系统DOM的研究应集中于以几方面：（1）确定森林生态系统中DOM源和汇;（2）评价森林水文条件对DOM释放与存留的调节作用;（3）探讨全球气候变化对森林生态系统DOM的影响;（4）可溶性有机氮（Dissolved Organic Nitrogen),可溶性有机磷（Dissolved Organic Phosphorus)动态与可溶性有碳（Dissolved Organic Carbon）动态的差别。     

生物土壤结皮的分布影响因子及其监测

生物土壤结皮在荒漠化地区广泛分布。本文详细论述了生物土壤结皮的分布规律及其影响因素,如海拔高度、土壤、维管植物群落水分条件和干扰,以及生物土壤结皮在生态系统和景观变化监测和评价中的作用等。同时对中国西北地区生物土壤结皮的生态学研究和开发应用提供了研究的重点和方向。     

陆地生态系统中水溶性有机物动态及其环境学意义

水溶性有机物(DOM)是陆地生态系统中最活跃的有机碳库,也是土壤圈层与相关圈层进行物质与能量交换的重要表现形式,它对重金属、养分元素和有机污染物的活化、迁移与生态毒性有较大影响,在农业土壤溶液中DOM浓度通常在10～80mgC·L^-1,湿地土壤中多数在25～50mgC·L^-1,与森林土壤剖面淋滤水中的DOM相近,但在某些微域土壤环境(如根际和有机肥施用点附近)中DOM浓度可高达200～1000mgC·L^-1,不同来源的DOM在土壤中的迁移性与降解性明显不同,含低分子量组分或亲水性组分较多的DOM不易被土壤吸持而易被微生物降解,pH值相对较高的土壤(如石灰性土壤)对DOM吸附较弱,但pH较低和含有大量氧化物的土壤(如红壤、赤红壤和砖红壤等)则对DOM的吸附较强,施用石灰、土壤淹水或干湿交替、温度升高等有利于土壤保持较高的DOM浓度,由于DOM-金属配合物的形成,DOM能明显促进土壤重金属活化和向下迁移,而且DOM中低分子量或亲水性组分所占比例越低活化作用越强,同样地,由于DOM具有两亲性质,也能明显提高疏水性有机污染物(如农药和持久难降解有机污染物)的水溶性,增加其对环境污染的风险,特别是含疏水性组分越多的DOM这种作用越强．可以认为,继续加强有关DOM在陆地生态系统中产生与消长规律,特别是DOM及其与污染物的配合物从陆地生态系统向水体迁移的机理及其通量的研究,对合理预测污染物的环境行为和科学地进行环境风险评估有重要意义。     

Are Seafood PCB Data Sufficient to Assess Health Risk for High Seafood Consumption Groups?

Some populations in Washington's Puget Sound area consume much more seafood than the general population. Mean consumption rates are 61?g/person/day for the Tulalip and Squaxin Island Tribes and 117.2?g/person/day for Asian and Pacific Islanders (API). There is concern about possible health risks from seafood PCB exposure for these groups, but exposure evaluation is difficult due to inadequacies of environmental data. Available seafood PCB data were matched to results from recent seafood consumption surveys. To rate quality of matches and identify data gaps, a ranking system based on species specificity, data quality, and location compatibility was developed. Sensitivity of total PCB and congenerspecific PCB testing (for use in TCDD toxic equivalency approaches) necessary for cancer risk assessment was explored and included in the ranking scheme. For the Squaxin Tribe, appropriate total PCB data for risk assessment were available for 58% of seafood consumed, which is dominated by local salmon. For API, appropriate total PCB data were identified for only 4% of seafood consumed, which is dominated by commercial shellfish. Insufficient sensitivity of commercial seafood PCB analysis and overall lack of sufficiently sensitive PCB congener analysis are major gaps in ability to characterize PCB exposure and risk for these groups.     

Predictive systems ecology

Human societies, and their well-being, depend to a significant extent on the state of the ecosystems that surround them. These ecosystems are changing rapidly usually in response to anthropogenic changes in the environment. To determine the likely impact of environmental change on ecosystems and the best ways to manage them, it would be desirable to be able to predict their future states. We present a proposal to develop the paradigm of predictive systems ecology, explicitly to understand and predict the properties and behaviour of ecological systems. We discuss the necessary and desirable features of predictive systems ecology models. There are places where predictive systems ecology is already being practised and we summarize a range of terrestrial and marine examples. Significant challenges remain but we suggest that ecology would benefit both as a scientific discipline and increase its impact in society if it were to embrace the need to become more predictive.     

The ecosystem wilting point defines drought response and recovery of a Quercus-Carya forest

Soil and atmospheric droughts increasingly threaten plant survival and productivity around the world. Yet, conceptual gaps constrain our ability to predict ecosystem-scale drought impacts under climate change. Here, we introduce the ecosystem wilting point (Ψ_EWP), a property that integrates the drought response of an ecosystem's plant community across the soil–plant–atmosphere continuum. Specifically, Ψ_EWP defines a threshold below which the capacity of the root system to extract soil water and the ability of the leaves to maintain stomatal function are strongly diminished. We combined ecosystem flux and leaf water potential measurements to derive the Ψ_EWP of a Quercus-Carya forest from an “ecosystem pressure–volume (PV) curve,” which is analogous to the tissue-level technique. When community predawn leaf water potential (Ψ_pd) was above Ψ_EWP (=−2.0 MPa), the forest was highly responsive to environmental dynamics. When Ψ_pd fell below Ψ_EWP, the forest became insensitive to environmental variation and was a net source of carbon dioxide for nearly 2 months. Thus, Ψ_EWP is a threshold defining marked shifts in ecosystem functional state. Though there was rainfall-induced recovery of ecosystem gas exchange following soaking rains, a legacy of structural and physiological damage inhibited canopy photosynthetic capacity. Although over 16 growing seasons, only 10% of Ψ_pd observations fell below Ψ_EWP, the forest is commonly only 2–4 weeks of intense drought away from reaching Ψ_EWP, and thus highly reliant on frequent rainfall to replenish the soil water supply. We propose, based on a bottom-up analysis of root density profiles and soil moisture characteristic curves, that soil water acquisition capacity is the major determinant of Ψ_EWP, and species in an ecosystem require compatible leaf-level traits such as turgor loss point so that leaf wilting is coordinated with the inability to extract further water from the soil.