Toward understanding the contribution of waterbodies to the methane emissions of a permafrost landscape on a regional scale—A case study from the Mackenzie Delta,Canada

Waterbodies in the arctic permafrost zone are considered a major source of the greenhouse gas methane (CH₄) in addition to CH₄ emissions from arctic wetlands. However, the spatio‐temporal variability of CH₄ fluxes from waterbodies complicates spatial extrapolation of CH₄ measurements from single waterbodies. Therefore, their contribution to the CH₄ budget of the arctic permafrost zone is not yet well understood. Using the example of two study areas of 1,000 km² each in the Mackenzie Delta, Canada, we approach this issue (i) by analyzing correlations on the landscape scale between numerous waterbodies and CH₄ fluxes and (ii) by analyzing the influence of the spatial resolution of CH₄ flux data on the detected relationships. A CH₄ flux map with a resolution of 100 m was derived from two aircraft eddy‐covariance campaigns in the summers of 2012 and 2013. We combined the CH₄ flux map with high spatial resolution (2.5 m) waterbody maps from the Permafrost Region Pond and Lake Database and classified the waterbody depth based on Sentinel‐1 SAR backscatter data. Subsequently, we reduced the resolution of the CH₄ flux map to analyze if different spatial resolutions of CH₄ flux data affected the detectability of relationships between waterbody coverage, number, depth, or size and the CH₄ flux. We did not find consistent correlations between waterbody characteristics and the CH₄ flux in the two study areas across the different resolutions. Our results indicate that waterbodies in permafrost landscapes, even if they seem to be emission hot spots on an individual basis or contain zones of above average emissions, do currently not necessarily translate into significant CH₄ emission hot spots on a regional scale, but their role might change in a warmer climate.     

A global climate niche for giant trees

Rainforests are among the most charismatic as well as the most endangered ecosystems of the world. However, although the effects of climate change on tropical forests resilience is a focus of intense research, the conditions for their equally impressive temperate counterparts remain poorly understood, and it remains unclear whether tropical and temperate rainforests have fundamental similarities or not. Here we use new global data from high precision laser altimetry equipment on satellites to reveal for the first time that across climate zones ‘giant forests’ are a distinct and universal phenomenon, reflected in a separate mode of canopy height (~40 m) worldwide. Occurrence of these giant forests (cutoff height > 25 m) is negatively correlated with variability in rainfall and temperature. We also demonstrate that their distribution is sharply limited to situations with a mean annual precipitation above a threshold of 1,500 mm that is surprisingly universal across tropical and temperate climates. The total area with such precipitation levels is projected to increase by ~4 million km² globally. Our results thus imply that strategic management could in principle facilitate the expansion of giant forests, securing critically endangered biodiversity as well as carbon storage in selected regions.     

Topography shapes the structure,composition and function of tropical forest landscapes

Topography is a key driver of tropical forest structure and composition, as it constrains local nutrient and hydraulic conditions within which trees grow. Yet, we do not fully understand how changes in forest physiognomy driven by topography impact other emergent properties of forests, such as their aboveground carbon density (ACD). Working in Borneo – at a site where 70‐m‐tall forests in alluvial valleys rapidly transition to stunted heath forests on nutrient‐depleted dip slopes – we combined field data with airborne laser scanning and hyperspectral imaging to characterise how topography shapes the vertical structure, wood density, diversity and ACD of nearly 15 km² of old‐growth forest. We found that subtle differences in elevation – which control soil chemistry and hydrology – profoundly influenced the structure, composition and diversity of the canopy. Capturing these processes was critical to explaining landscape‐scale heterogeneity in ACD, highlighting how emerging remote sensing technologies can provide new insights into long‐standing ecological questions.     

Scaling phenology from the local to the regional level: advances from species‐specific phenological models

Plant phenology, the study of seasonal plant activity driven by environmental factors, has found a renewal in the context of global climate change. Phenological events, such as leaf unfolding, exert strong control over seasonal exchanges of matter and energy between the land surface and the atmosphere. Phenological models that simulate the start of the growing season should be efficient tools to predict vegetation responses to climatic changes and related changes in energy balance. Species‐specific phenological models developed in the eighties have not been used for global‐scale predictions because their predictions were inaccurate in external conditions. Recent advances in phenology modelling at the species level suggest that prediction at a large scale may now be possible. In the present study, we tested the performance of species‐specific phenological models in time and space, looking at their ability (i) to predict regional phenology when previously fitted at a local scale, and (ii) to predict phenological trends, linked to climate changes, observed over a long‐term. For that task we used an historical phenological dataset from Ohio from the late ninetieth century and an airborne pollen dataset from Ontario, Québec and Maryland from the late twentieth century. The results show that the species‐specific phenological models used in this study were able to predict regional phenology even though they were fitted locally. The reconstruction of a phenological time series over the twentieth century showed a significant advancement of 0.2 days per year in the date of flowering of Ulmus americana, but very weak trends for Fraxinus americana and Quercus velutina.     

马桶冲水行为与微生物气溶胶传播

有关卫生间马桶冲水行为可能产生的微生物气溶胶扩散与病原微生物传播的情况一直受到广泛关注,相关研究或报道时有出现。本文意在总结与马桶冲水行为产生的生物气溶胶相关的研究及进展,讨论马桶冲水行为、开关马桶盖冲水行为以及马桶表面等因素在病毒、细菌及寄生虫等病原微生物通过生物气溶胶进行传播的过程中起到的作用。此外,本文还探讨了与马桶相关的微生物气溶胶的产生可能为人体健康带来的潜在健康风险,并就公众健康防护以及未来研究方向提出建议。     

Edge influence detection using aerial LiDAR in Northeastern US deciduous forests

The northeastern United States is currently experiencing a decline in forested lands, primarily due to the expansion of human development. Of particular concern is the loss of “core areas” or the areas within forests that are not influenced by other land cover types. Core areas are of significant importance to native flora and fauna, since they generally are less vulnerable to invasion by exotics and are more resilient to the effects of climate change. However, the exact reduction of core area in the northeast is still unknown. Current methods of estimation are not particularly precise, since areas of edge influence are quite variable and situational. Therefore, the purpose of this study is to devise a new method for identifying edge influence areas using remote sensing techniques. Eight transects were sampled perpendicular to the edge of an abandoned golf course within Harvard Forest in Petersham, MA. Vegetation inventories as well as Photosynthetically Active Radiation (PAR) at different heights within the canopy were used to determine edge depth in the field. Small-footprint discrete aerial LiDAR datasets were comparatively used to identify edge depths. LiDAR returns were binned and transformed into canopy height profiles before the sum of squared differences was used to determine where edge influence diminished, creating a LiDAR derived edge depth. LiDAR estimated edge depths were not significantly different from the field identified edge depths, indicating it might be a low-cost method for estimating edge depths.     

Outdoor airborne fungi captured by viable and non-viable methods

Volume assessments of the concentration of airborne fungi may provide different results depending on the methodology used. This work simultaneously analyses two methods for samples obtained outdoors and analysed in the context of meteorological conditions. The study was carried out in Badajoz (SW Spain) from Mar. 2009 to Jul. 2011. A Burkard fixed spore trap was used for the non-viable sampling, and three different methods were used for the viable sampling: a Burkard portable spore trap with two inlet port types and a Sampl'air AES trap. Daily average total concentrations of 285 CFU m⁻³ and 1 954 spores m⁻³ were recorded for the viable and non-viable methods, respectively. The spore/colony ratio showed important differences among the most relevant fungal types: Alternaria (2.6), Aspergillus–Penicillium (2.0) and Cladosporium (11.1). Although the two sampling types were essentially equivalent at showing temporal variations in outdoor airborne fungi, quantitative differences in the number of total colonies recorded depended on the culture media and conditions used.     

Effect of Microsphaeropsis ochracea on Production of Sclerotia-borne and Airborne Conidia of Botrytis squamosa

Onion leaf blight, caused by Botrytis squamosa (Walker), is a destructive disease of onion. Conidia produced on overwintered sclerotia are the main source of initial inoculum, and those produced on lesions are responsible for secondary inoculum build-up. The biological control agent Microsphaeropsis ochracea (Carisse &; Bernier) was evaluated for its ability to control sclerotia-borne inoculum, to colonize onion leaves and reduce the production of conidia under field conditions. Colonisation by M. ochracea of onion leaves at different growth stages was monitored and its effect on B. squamosa sporulation on necrotic leaves was evaluated. Onion plots were treated with either Dithane® or with M. ochracea at 7–10-day intervals and according to inoculum production index (IPI). The concentration of airborne conidia and the number of lesions per leaf, on 20 plants per plot, were evaluated throughout the cropping season. The number of conidia produced per sclerotium treated with M. ochracea, was reduced by 75.5%. In the field, M. ochracea colonised only senescent or necrotic leaves and reduced the production of conidia on these leaves by an average of 82% as compared with untreated leaves. Best disease control was obtained by Dithane®, followed by M. ochracea applied at 7–10-day intervals. For the three years of the study, there were no significant differences in airborne concentrations of conidia in plots treated at 7–10-day intervals with Dithane® or M. ochracea. Fall application of M. ochracea could be used as a sanitation practice to reduce initial inoculum or as a part of an IPM program during the season.     

BATHYMETRIC STUDIES ON THE PONGOLO RIVER FLOODPLAIN

SUMMARY

Thirteen of the major pans on the Pongolo river floodplain have been studied. Most are shallow (>2.5 m) and regularly lose up to 70% of their water each year, although few dry out. Floods inundate considerable areas (1000 ha) around pans situated in the flatter parts of the floodplain. Whilst inundated, these areas provide an allochthonous energy and nutrient source for the pan and, as the water levels recede, the exposed Cynodon dactylon (L.) Pers lawns provide grazing for cattle. The suitability of the various pans for fish production is discussed.     

2007～2011年鄂州市气传致敏真菌调查及其与支气管哮喘的相关性

目的 探讨2007年5月～ 2011年4月鄂州市气传致敏真菌和支气管哮喘关系,以了解该地区支气管哮喘情况.方法 运用暴片调查法和暴皿调查法统计和记录鄂州市气传致敏真菌的种类及数量.选择该时期内鄂州市100例支气管哮喘患者采用真菌变应原浸液作过敏原皮试发现有35例患者皮内试验阳性,将35例发作期患者和40例稳定期支气管哮喘患者行曲霉特异性IgE测定.结果 100例支气管哮喘患者皮内实验组阳性35例,阳性率为35％,而在35例患者中IgE阳性有31例,检测符合率为88.58％,稳定期患者中阳性反应例数2例,阳性率为5％,两组阳性率比较差异具有显著性（P＜0.05）.结论 鄂州市气传致敏真菌和支气管哮喘密切相关,主要致病菌为曲霉,是支气管哮喘的致敏原之一,需要注意环境卫生以减少气传致敏真菌的数量.