Eucalyptus leachate inhibits reproduction in a freshwater fish

1. Dissolved organic carbon (DOC) can induce lethal and sub‐lethal effects in exposed biota via hypoxic blackwater events and the toxicity of leached compounds. Little is known of how DOC exposure affects fish reproduction despite the fact that its release can coincide with spawning‐associated flow pulses. 2. River red gum (Eucalyptus camaldulensis) leaf leachate is a major source of DOC in Australian freshwaters and includes the toxic plant secondary metabolites polyphenols and tannins. High concentrations of leachate are released when leaves on floodplains or dry stream channels are inundated by water. 3. Southern pygmy perch (Nannoperca australis) from naturally high and naturally low Eucalyptus leachate environments in south‐east Australia were exposed to elevated leachate levels to investigate the effects of DOC on reproduction and to explore whether response patterns were consistent with populations becoming locally adapted to historical leachate levels. 4. Fish exposed to leachate were half as likely to reach sexual maturity as control fish. Fish from a naturally high‐exposure population tended to reach sexual maturity earlier than those from a naturally low‐exposure population. Leachate exposure had no effect on either egg size or fecundity. 5. Our results suggest that leachate‐exposed mothers did not reproduce because they were physiologically stressed or perceive the environment to be unsuitable, which raises the potential of plastic or adaptive responses to this stressor. The negative sub‐lethal effects observed have important fitness implications for individuals, the viability of populations and the management of environmental flows and riparian zones.     

A bioregional analysis of the distribution of rainforest cover,deforestation and degradation in Papua New Guinea

Papua New Guinea (PNG) is an extensively forested country. Recent research suggests that despite commencing a trajectory of deforestation and degradation later than many counties in the Asia–Pacific region, PNG is now undergoing comparable rates of forest change. Here we explore the bioregional distribution of changes in the forest estate over the period 1972–2002 and examine their implications for forest protection. This is undertaken through the development of a novel bioregional classification of the country based on biogeographic regions and climatic zones, and its application to existing forest cover and forest‐cover change data. We found that degradation and deforestation varied considerably across the 11 defined biogeographic regions. We report that the majority of deforestation and degradation has occurred within all the lowland forests, and that it is these forests that have the greatest potential for further losses in the near term. The largest percentage of total change occurred in the east of PNG, in the islands and lowlands of the Bismarck, D'Entrecasteaux, East Papuan Islands and in the South‐East Papua–Oro region. The only region with a significant highlands component to undergo deforestation at a comparable magnitude to the islands and lowland regions was the Huon Peninsula and Adelbert region. Significant changes have also occurred at higher elevations, especially at the interface of subalpine grasslands and upper montane forests. Lower montane forests have experienced proportionally less change, yet it is these forests that constitute the majority of forests enclosed within the protected area system. We find that protected areas are not convincingly protecting either representative areas of PNG's ecosystems, nor the forests within their borders. We conclude by suggesting a more expansive and integrated approach to managing the national forest estate.     

The provision of winter bird food by the English Environmental Stewardship scheme

Environmental Stewardship (ES) is the main mechanism for reversing the decline in farmland birds in England, and includes a range of options designed to provide winter foraging for seed‐eating species. We estimated granivorous songbird densities on ES options designed to provide winter food, on farms within the Entry Level (ELS) or Higher Level (HLS) strata of ES. ES Wild Bird Mixtures (WBMs) hosted higher densities and a wider range of granivores than non‐ES game covers, although in East Anglia the enhanced HLS WBM was used no more than the basic ELS WBM. In the West Midlands there were low densities of granivores on all WBMs and game covers. The widespread ELS WBM appeared to provide little food for buntings but supported finches, partially through greater weed burdens. There was a weak, non‐significant trend for Skylarks Alauda arvensis to make greater use of ELS cereal stubbles than non‐ES stubbles, possibly because of post‐harvest herbicide restrictions allowing overwinter weed growth. At the field scale, this work demonstrates that although some ES options provide winter food resources for birds, there is limited evidence for additional benefits of Higher Level vs. Entry Level Stewardship to wintering farmland songbirds.     

不同生态型摩西球囊霉菌株对蜈蚣草砷吸收的影响

砷超富集植物——蜈蚣草无论是在野外或是在室内均能被丛枝菌根真菌(AM真菌)侵染,但其对蜈蚣草砷吸收及转运的机理尚不清晰.本研究将分离于湖南省郴州市金川塘某铅锌尾矿蜈蚣草根际土壤(Glomus mosseae BGC GD01,简称污染菌株)和云南省未污染土壤(G.mosseae BGC YN05,简称非污染菌株)的2种摩西球囊霉菌株分别接种于非污染生态型和污染生态型蜈蚣草根际,8周后利用菌根化蜈蚣草幼苗在浓度为100 μmol·L-1砷(Na2HAsO4·7H2O)营养液中进行为期24 h的水培试验.结果表明,2种生态型摩西球囊霉菌株分别与蜈蚣草形成中等程度侵染,侵染率为25.2％ ～31.3％.无论是接种污染菌株或是非污染菌株,均明显促进了蜈蚣草根部对磷的吸收.在24 h水培试验期间,接种非污染菌株显著促进了蜈蚣草根部砷的吸收,但接种污染菌株对蜈蚣草根部砷吸收的促进作用有限,说明AM真菌对蜈蚣草砷吸收存在种内差异.     

Establishment of native perennial shrubs in an agricultural landscape

Abstract Native vegetation has been destroyed or dramatically modified throughout agricultural regions of southern Australia. Extensive restoration of native perennial vegetation is likely to be crucial in these areas for the persistence of native plant and animal species, to ameliorate dryland salinity and soil degradation, and to maintain long‐term agricultural production. The long‐term resilience of these systems will be dependent on the ability of key functional taxa, such as perennial shrubs, to recruit and persist. In this study, we examine the factors limiting establishment of two perennial shrubs in formerly cropped land, the rare Maireana rohrlachii and the common Maireana decalvans. Field and laboratory observations suggest that establishment of both species is not limited by life‐history traits following cultivation. Both species established and persisted under varying levels of plant competition. Similarities existed between species in their initial germination rates. Weak differences were found between species in the growth and survival rates under different levels of competition. The main difference between the two species was in the decline of germinability of fruits with increasing fruit age. From the data, it is difficult to determine what factors limit the establishment of perennial shrubs in these landscapes. The main hypothesis that can be advanced is that establishment of shrub species appears to be limited by propagule availability and this is likely to be a function of past and present grazing management rather than cultivation per se. Further investigation of these land‐use practices may give greater insight into the factors affecting the establishment of this life form across these landscapes.