Rapid assessment of postfire plant invasions in coniferous forests of the western United States.

Fire is a natural part of most forest ecosystems in the western United States, but its effects on nonnative plant invasion have only recently been studied. Also, forest managers are engaging in fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences such as nonnative plant species introductions. Increased availability of light, nutrients, and bare ground have all been associated with high-severity fires and fuel treatments and are known to aid in the establishment of nonnative plant species. We use vegetation and environmental data collected after wildfires at seven sites in coniferous forests in the western United States to study responses of nonnative plants to wildfire. We compared burned vs. unburned plots and plots treated with mechanical thinning and/or prescribed burning vs. untreated plots for nonnative plant species richness and cover and used correlation analyses to infer the effect of abiotic site conditions on invasibility. Wildfire was responsible for significant increases in nonnative species richness and cover, and a significant decrease in native cover. Mechanical thinning and prescribed fire fuel treatments were associated with significant changes in plant species composition at some sites. Treatment effects across sites were minimal and inconclusive due to significant site and site x treatment interaction effects caused by variation between sites including differences in treatment and fire severities and initial conditions (e.g., nonnative species sources). We used canonical correspondence analysis (CCA) to determine what combinations of environmental variables best explained patterns of nonnative plant species richness and cover. Variables related to fire severity, soil nutrients, and elevation explained most of the variation in species composition. Nonnative species were generally associated with sites with higher fire severity, elevation, percentage of bare ground, and lower soil nutrient levels and lower canopy cover. Early assessments of postfire stand conditions can guide rapid responses to nonnative plant invasions.     

A Diverse and Endangered Aquatic Ecosystem of the Southeast United States

We document the biodiversity and conservation status of an extraordinarily diverse and endangered ecosystem in the United States that has failed to attract the same attention as tropical ecosystems—the rivers and streams of Alabama and adjoining states. Relative to North America as a whole, Alabama is a highlight of aquatic diversity supporting 38% of native fresh water fishes, 43% of native freshwater gill-breathing snails, 60% of native mussels, and 52% of native freshwater turtles. Of these, 41%, 77%, 34%, and 22% of the fishes, snails, mussels, and turtles, respectively, are endemic to Alabama and an adjacent state. Like many tropical systems of developing nations, this fauna is in an imperiled state, with 10%, 65%, 69%, and 43% of Alabama's fishes, gill-breathing snails, mussels, and turtles, respectively, considered either extinct, endangered, threatened, or of special concern. Unlike tropical systems, however, little effort has been made to protect the taxa and their habitats. Only 40% of fishes, 1% of gill-breathing snails, 32% of mussels, and 20% of freshwater turtles are formally listed as either threatened or endangered via the U.S. Endangered Species Act of 1973; no critical habitat has been protected. Clearly, the biodiversity crisis in not limited to tropical systems of developing nations. Although the Endangered Species Act of 1973 helps to ensure a future of sustainable diversity, efforts must be made to hasten recognition, protection, and recovery of critical habitat, particularly for hotspots such as the aquatic systems of Alabama.     

天然次生林人工更新后对土壤物理性质及碳贮量的影响

天然林被人工林取代后对土壤水文物珲性质及土壤碳贮量有重要的影响.文章以海南天然次生林人工更新为尾细桉(Eucalyptus urophylla×E.tereticornis)和马占相思(Acacia mangium)林前后的土壤为研究对象,研究分析了人工植被更新对土壤水文物理性质和土壤碳贮量的影响.结果表明:天然次生林更新为桉树、马占相思人工林后,土壤容重增加,土壤总孔隙度、毛管孔隙度和非毛管孔隙度减小,0～80 cm土壤的最大贮水量、毛管贮水量和非毛管贮水量降低,桉树和马占相思人工林最大贮水量分别降低19.8 mm和43.3mm,桉树人工林0～40cm土壤碳贮量降低6.77t·hm-2,马占相思人工林的增加14.68t·hm-2.     

A simple economic model of endangered species preservation in the United States

Concern for the acceleration in threats to species diversity in the United States led to the passage of the Endangered Species Act of 1973. In this paper, this legislation is examined in an economic context. A simple model is developed where management and constraints on economic activity are substitutes in the production of species stocks. Whether economic growth constraints (the primary policy tool of the 1973 Act) are justified for preservation purposes depends on technical substitution possibilities, relative cost ratios, and the existence of budget constraints for species management. Since the same combination of these factors will not occur for all species, it is argued that more flexibility in endangered species policy may preserve the same levels of species stocks at lower costs to society.     

Old-Growth Mangrove Forests in the United States

Criteria used to identify old-growth forests in the Pacific Northwest have not been proven applicable in other ecological life zones. For example, Pacific Northwest criteria are not suitable for the identification of old-growth mangrove forests. To identify old-growth mangroves one has to take into account differences in stand structure and function due to geomorphology, within-site environmental gradients, and regional disturbance regimes. A flexible and holistic approach is needed. Stand age, defined in terms of Pacific Northwest forests, is not necessarily the best criterion for identifying for conservation mangrove forests or any forest outside the Pacific Northwest. No single stand will have all old-growth characteristics, and even if they are present in a stand, these characteristics do not necessarily assure that the stand is old growth. Whether a mangrove stand reaches old-growth stage depends on the dynamics of coastal conditions under which it grows. Moreover, it is necessary to differentiate between the age of trees in a stand and the age of the mangrove system, which includes the substrate. Old-growth mangrove stands are improbable states for this ecosystem type, and they can revert to younger stages. Mangroves offer a challenge to the concept of the old-growth forest, and through our analysis of this system we show that when ecosystem functions and states are evaluated it is necessary to avoid geographic biases based on particular ecological conditions.     

Status of Marine Mammals in the United States

Abstract: The 1994 amendments to the U.S. Marine Mammal Protection Act required, for the first time, an assessment of the status of every marine mammal stock in the United States. We draw conclusions about the status of marine mammals from assessments of 153 stocks conducted to meet the requirements of these amendments. We found important regional differences in the status of stocks. Most stocks in the Atlantic and Pacific experience human-induced mortality (takes), primarily from gill-net fisheries. The proportion of stocks with takes was lower in the Gulf of Mexico and Hawaii, areas with few gill-net fisheries. Estimated takes exceeded removal limits for 29% of stocks in the Atlantic, 14% in the Pacific, 8% in Alaska, 7% in the Gulf of Mexico, and 0% in Hawaii. Twenty-eight stocks are listed as threatened or endangered under the U.S. Endangered Species Act. Most, but not all, baleen whale stocks are recovering after cessation of commercial harvests. Many species of pelagic cetaceans, including beaked and sperm whales, are vulnerable to mortality in pelagic drift-net fisheries. Most pinniped stocks experience takes, but none of these takes exceeds removal limits, and all pinniped stocks on mainland coasts of the United States are increasing in abundance. Quantitative data on trends in abundance are available for few cetacean stocks, emphasizing the difficulty of monitoring trends in these species. These stock assessments have greatly advanced our understanding of the status of marine mammals in the United States, but information gaps remain, particularly regarding stock structure and possible mortality in unmonitored fisheries.     

Legislating soil reconstruction on surface-mined land in the United States

The author, who participated with an interdepartmental team in advising the US Congress in writing the Surface Mining Control and Reclamation Act, outlines the often conflicting requirements which determined the genesis of the Act. The paper also discusses the criteria for judging the effectiveness of restoring soil productivity and the emphasis on the restoration of prime farmland. It also notes that the nature of the balance between environmental protection, farmland productivity and the needs of coal are still uncertain and that there is a contradiction in US attempts to alleviate hunger while national soil resources are being destroyed.From 1972 to 1977, the author participated with an interdepartmental tcam that assisted the U.S., Congress in writing the Surface Mining Control and Reelamation Act.     

中国农田作物植被碳储量研究进展

作物植被碳储量是全球陆地生态系统碳库的重要组成部分。中国农田作物植被碳储量的估算主要采用参数估算法、遥感资料反演法和环境参数模型法。通过对中国近几十年来全国和区域尺度作物植被碳储量的估算研究,获得了一些作物的经济系数、含碳率和作物收获部分水分系数等估算参数值,探讨了遥感反演和环境参数模型方法,并提出加强农田基本建设、改进农业生产技术与管理、调整作物结构和加强作物秸秆利用等固碳措施。目前对中国农田作物植被碳储量的估算仍存在较大的不确定性,获取的估算参数尚不充分,估算方法和模型有待完善,对作物植被碳储量变化的源/汇效应尚未取得统一认识。虽然在农田生态系统中土壤碳储量（密度）普遍大于作物植被碳储量（密度）,但作物植被碳储量仍然是一个数量可观、并有增加潜力和可能的碳库,其大小及秸秆利用情况直接影响着土壤碳库。因此,对农田作物植被碳储量应分时段和区域具体分析,才能认识其源/汇效应。今后应在以下几方面进一步加强作物植被碳储量的研究：进一步完善和改进估算方法;加强作物植被碳储量估算及固碳措施的区域个例研究,探索不同空间尺度作物植被碳储量的尺度转换;开展作物碳储量动态及固碳机理的综合研究。此外,还应就气候变化与作物植被碳储量的相互耦合关系进行探讨。     

Vascular plant extinction in the continental United States and Canada

Extinction rates are expected to increase during the Anthropocene. Current extinction rates of plants and many animals remain unknown. We quantified extinctions among the vascular flora of the continental United States and Canada since European settlement. We compiled data on apparently extinct species by querying plant conservation databases, searching the literature, and vetting the resulting list with botanical experts. Because taxonomic opinion varies widely, we developed an index of taxonomic uncertainty (ITU). The ITU ranges from A to F, with A indicating unanimous taxonomic recognition and F indicating taxonomic recognition by only a single author. The ITU allowed us to rigorously evaluate extinction rates. Our data suggest that 51 species and 14 infraspecific taxa, representing 33 families and 49 genera of vascular plants, have become extinct in our study area since European settlement. Seven of these taxa exist in cultivation but are extinct in the wild. Most extinctions occurred in the west, but this outcome may reflect the timing of botanical exploration relative to settlement. Sixty-four percent of extinct plants were single-site endemics, and many occurred outside recognized biodiversity hotspots. Given the paucity of plant surveys in many areas, particularly prior to European settlement, the actual extinction rate of vascular plants is undoubtedly much higher than indicated here.     

Status of Species Conservation Banking in the United States

Abstract:  Receiving financial gains for protecting habitat may be necessary to proactively protect endangered species in the United States. Species conservation banking, the creation and trading of "credits" that represent biodiversity values on private land, is nearly a decade old. We detail the biological, financial, and political experience of conservation banking in the United States. We contacted agencies, nongovernmental organizations, and bank owners and compiled comprehensive accounts of the experiences of current banks. There are 76 properties identified as conservation banks in the United States, but only 35 of these are established under a conservation banking agreement approved by the U.S. Fish and Wildlife Service (USFWS). The 35 official conservation banks cumulatively cover 15,987 ha and shelter a range of biodiversity, including more than 22 species listed under the U.S. Endangered Species Act. Financial motives drove the establishment of 91% of conservation banks, and the majority of for-profit banks are breaking even or making money. With credit prices ranging from $3,000 to $125,000/0.41 ha (1 acre), banking agreements offer financial incentives that compete with development and provide a business-based argument for conserving habitat. Although the bureaucracy of establishing an agreement with the USFWS was burdensome, 63% of bank owners reported they would set up another agreement given the appropriate opportunity. Increasing information sharing, decreasing the time to establish agreements (currently averaging 2.18 years), and reducing bureaucratic challenges can further increase the amount of private property voluntarily committed to banking. Although many ecological uncertainties remain, conservation banking offers at least a partial solution to the conservation versus development conflict over biodiversity.     

Forecasting the Expansion of Zebra Mussels in the United States

Abstract:  Because zebra mussels spread rapidly throughout the eastern United States in the late 1980s and early 1990s, their spread to the western United States has been expected. Overland dispersal into inland lakes and reservoirs, however, has occurred at a much slower rate than earlier spread via connected, navigable waterways. We forecasted the potential western spread of zebra mussels by predicting the overland movement of recreational boaters with a production-constrained gravity model. We also predicted the potential abundance of zebra mussels in two western reservoirs by comparing their water chemistry characteristics with those of water bodies with known abundances of zebra mussels. Most boats coming from waters infested with zebra mussels were taken to areas that already had zebra mussels, but a small proportion of such boats did travel west of the 100th meridian. If zebra mussels do establish in western U.S. water bodies, we predict that population densities could achieve similar levels to those in the Midwestern United States, where zebra mussels have caused considerable economic and ecological impacts. Our analyses suggest that the dispersal of zebra mussels to the western United States is an event of low probability but potentially high impact on native biodiversity and human infrastructure. Combining these results with economic analyses could help determine appropriate investment levels in prevention and control strategies .     

Species Imperilment and Spatial Patterns of Development in the United States

Abstract:  Conservation biologists and others hypothesize that humankind's "ecological footprint" is affected not only by the sheer intensity of human activity but also by its spatial arrangement. We used a multivariate statistical model and state-level data to evaluate correlations between species imperilment and the level and spatial distribution of human settlement and infrastructure development in the United States. The level of human activity—measured by the number of people and households, incidence of roads, and intensity of nighttime lights—was significantly correlated with the ecological imperilment of species. Our regression models consistently showed that a 1% increase in the level of human activity across the United States was associated with about a 0.25% increase in the proportion of plant and animal species considered at risk of extinction by The Nature Conservancy. The distribution of human activity did not affect species imperilment. Our results point to rising levels of human activity—and not some particular (e.g., sprawling) distribution of human activity—as the most relevant anthropogenic factor explaining biodiversity loss in the United States.     

Frontier science and challenges on offshore carbon storage

● The main direct seal up carbon options and challenges are reviewed. ● Ocean-based CO₂ replacement for CH₄/oil exploitation is presented. ● Scale-advantage of offshore CCS hub is discussed. Carbon capture and storage (CCS) technology is an imperative, strategic, and constitutive method to considerably reduce anthropogenic CO₂ emissions and alleviate climate change issues. The ocean is the largest active carbon bank and an essential energy source on the Earth’s surface. Compared to oceanic nature-based carbon dioxide removal (CDR), carbon capture from point sources with ocean storage is more appropriate for solving short-term climate change problems. This review focuses on the recent state-of-the-art developments in offshore carbon storage. It first discusses the current status and development prospects of CCS, associated with the challenges and uncertainties of oceanic nature-based CDR. The second section outlines the mechanisms, sites, advantages, and ecologic hazards of direct offshore CO₂ injection. The third section emphasizes the mechanisms, schemes, influencing factors, and recovery efficiency of ocean-based CO₂-CH₄ replacement and CO₂-enhanced oil recovery are reviewed. In addition, this review discusses the economic aspects of offshore CCS and the preponderance of offshore CCS hubs. Finally, the upsides, limitations, and prospects for further investigation of offshore CO₂ storage are presented.     

Effects of productivity on biodiversity in forest ecosystems across the United States and China

In the global campaign against biodiversity loss in forest ecosystems, land managers need to know the status of forest biodiversity, but practical guidelines for conserving biodiversity in forest management are lacking. A major obstacle is the incomplete understanding of the relationship between site primary productivity and plant diversity, due to insufficient ecosystem‐wide data, especially for taxonomically and structurally diverse forest ecosystems. We investigated the effects of site productivity (the site's inherent capacity to grow timber) on tree species richness across 19 types of forest ecosystems in North America and China through 3 ground‐sourced forest inventory data sets (U.S. Forest Inventory and Analysis, Cooperative Alaska Forest Inventory, and Chinese Forest Management Planning Inventory). All forest types conformed to a consistent and highly significant (P < 0.001) hump‐shaped unimodal relationship, of which the generalized coefficients of determination averaged 20.5% over all the forest types. That is, tree species richness first increased as productivity increased at a progressively slower rate, and, after reaching a maximum, richness started to decline. Our consistent findings suggest that forests of high productivity would sustain few species because they consist mostly of flat homogeneous areas lacking an environmental gradient along which a diversity of species with different habitats can coexist. The consistency of the productivity–biodiversity relationship among the 3 data sets we examined makes it possible to quantify the expected tree species richness that a forest stand is capable of sustaining, and a comparison between the actual species richness and the sustainable values can be useful in prioritizing conservation efforts.     

Lifestyle and polybrominated diphenyl ethers in human milk in the United States: A pilot study

Polybrominated diphenyl ethers (PBDE) are a class of brominated flame retardants with some congeners having the ability to accumulate in body lipids. The incorporation of PBDE in consumer products found primarily in the indoor environment suggests that routes of exposure include inhalation of indoor air and contact with indoor dust. The purpose of this study was to test the hypothesis that lifestyle factors, and in particular the proximity and use of products likely to contain PBDE in the indoor environment, are primarily responsible for levels of PBDE found in human milk. Human milk samples were taken from two populations of lactating women in the same geographic region of the United States: one “typical” of US suburban lifestyle, and the other practicing a traditional Amish lifestyle, which excludes many modern amenities containing PBDE, such as computers and televisions. For a subset of the cohort, persistent organic pesticides and polychlorinated biphenyls (PCB) were also measured in human milk samples. Despite the small number of participants, there is evidence suggestive of Amish women having lower PBDE concentrations in their milk. In addition, the nonsignificant differences in levels of PCBs and pesticides between the two groups of women as compared to the significant differences in levels of PBDE suggest an important route of exposure for PBDE other than diet. Information prepared for study participants is provided to initiate a dialogue on how to best communicate biomonitoring findings to study participants and to the public in general.     

Composition of Floating Debris in Harbours of the United States

As part of a programme to characterize floating anthropogenic debris in the aquatic environment, the US Environmental Protection Agency (EPA) conducted 18 field surveys in the harbours of major metropolitan cities of the east, west, and Gulf coasts of the United States and the Mid-Atlantic Bight. the surveys were designed to provide information on the types, relative amounts, and distributions of aquatic debris in different geographic regions of the United States. Neuston nets (0.33 mm mesh) were used to collect surface debris during outgoing tides on two or three consecutive days in selected areas of each city. After each net tow, the debris, which ranged in size from small resin pellets to large plastic sheeting pieces, was identified, categorized, and counted. the data are being used to qualitatively characterize aquatic debris in coastal metropolitan areas, to examine potential regional variations, and to tentatively identify potential sources.