Diurnal variation in xylem hydraulic conductivity in white ash (Fraxinus americana L.), red maple (Acer rubrum L.) and red spruce (Picea rubens Sarg.)

Xylem hydraulic conductivity and percentage loss of conductivity (PLC) were measured on a ring-porous ( Fraxinus americana L., white ash), a diffuse porous ( Acer rubrum L., red maple) and a coniferous ( Picea rubens Sarg., red spruce) tree species in a temperate deciduous forest in central Massachusetts, USA. Measurements were made on current and 1-year-old branch segments in the afternoon and on the following morning. Afternoon PLC was 45 to 70% for the current year's extension growth in both white ash and red maple. Morning PLC was significantly lower (10–40%). Conductivity also varied diurnally suggesting, on average, a 50% recovery from cavitation overnight. Red spruce showed lower PLC and conductivity and a less pronounced night-time recovery. Diurnal variation in hydraulic conductivity and PLC suggests that embolism removal occurred in all three species despite the existence of tension within the xylem. Further evidence for embolism removal was observed with an in situ double-staining experiment in which dyes were fed to a transpiring branch during the late afternoon and the following morning. Examination of stem cross-sections showed that a larger number of vessels were conductive in the morning than on the preceding afternoon. Results of this study suggest that hydraulic capacity is highly dynamic and that conductivity measurements reflect a balance between two processes: cavitation and embolism removal.     

Needle chemistry in young Norway spruce stands after application of crushed wood ash

Nutrient concentrations in current and 1-year-old needles were analyzed annually for 5 years after application of hardened wood ash in 1–4-year-old Norway spruce (Picea abies (L.) Karst.) stands within a range of climate and fertility gradients. At each site, 3000 kg ha^–1 hardened wood ash of two types, Nymölla and Perstorp, was applied in a randomized block design. Wood ash Nymölla contained 12 kg ha^–1 P, 30 kg ha^–1 K, 891 kg ha^–1 Ca, 72 kg ha^–1 Mg and wood ash Perstorp contained 12 kg ha^–1 P, 60 kg ha^–1 K, 486 kg ha^–1 Ca, and 60 kg ha^–1 Mg. The ash was intended to compensate for nutrients removed at the preceding harvest when logging residues were collected and removed from the site (whole-tree harvesting). The climate gradient included four climate zones throughout Sweden and each of these included a fertility gradient of three sites classified according to their ground vegetation type. There were no effects on nutrient concentrations in the needles 1 year after the application of wood ash. Five years after ash application, the concentrations of P, K and Ca in current and 1-year-old needles were higher than in the control plots. The results were consistent over all stands, irrespective of climate zone and fertility status. P and K concentrations were higher in spruce needles from plots treated with Perstorp wood ash, whereas Ca concentrations were higher in those of Nymölla treated plots. Analyses across all study sites revealed a treatment effect in terms of increased ratios of P:N, K:N and Ca:N in 1-year-old needles. The ratio P:N tended to increase with time in the Perstorp wood ash treatment compared with the control. The needle concentrations of Mg and S were not affected by the ash applications. The increase in needle nutrient concentrations after application of hardened wood ash suggests that wood ash recycling could be used in order to replace nutrients removed at whole-tree harvesting.     

Effects of spring temperature and volcanic eruptions on wader productivity

Key demographic parameters often show substantial annual variation that can have important consequences for rates of population growth. Since 2011 we have conducted annual estimates of the productivity of Icelandic Black‐tailed Godwits Limosa limosa islandica over a large part of their breeding range. During this period, a volcanic eruption resulted in extensive dust deposition across the region. We show that Godwit productivity varies with spring temperatures but in the year of the volcanic eruption, productivity was reduced to almost zero. This rare but extreme event is likely to have had only a short‐term influence, whereas ongoing warming of sub‐Arctic regions is potentially a more substantial driver of the continued growth of this population.     

Wood-ash recycling affects forest soil and tree fine-root chemistry and reverses soil acidification

Wood ash was applied to a forest ecosystem with the aim to recycle nutrients taken from the forest and to mitigate the negative effects of intensive harvesting. After two years, the application of 8,000 kg ha⁻¹ of wood ash increased soil exchangeable Ca and Mg. Similarly, an increase in Ca and Mg in the Norway spruce fine roots was recorded, leading to significant linear correlations between soil and root Ca and soil and root Mg. In contrast to these macronutrients, the micronutrients Fe and Zn and the toxic element Al decreased in the soil exchangeable fraction with the addition of wood ash, but not in the fine roots. Only Mn decreased in soil and in fine roots leading to a significant linear correlation between soil and root Mn. In soil, as well as in fine roots, strong positive correlations were found between the elements Ca and Mg and between Fe and Al. This indicates that the uptake of Mg resembles that of Ca and that of Al that of Fe. With the wood ash application, the pH increased from 3.2 to 4.8, the base saturation from 30% to 86%, the molar basic cations/Al ratio (BC/Al) of the soil solution from 1.5 to 5.5, and the molar Ca/Al ratio of the fine roots from 1.3 to 3.7. Overall, all below-ground indicators of soil acidification responded positively to the wood ash application within two years. Nitrate concentrations increased only slightly in the soil solution at a soil depth of 75–80 cm, and no signs of increased heavy metal concentrations in the soils or in the fine roots were apparent. This suggests that the recycling of wood ash could be an integral part of sustainable forest management because it closes the nutrient cycle and reverses soil acidification.     

利用改进方法预测白蜡窄吉丁在国内的适生区

白蜡窄吉丁Agrilus planipennis在我国正由一种本土次要害虫上升为主要害虫,明确其可能的适生范围、指导各地区及早采取防范措施非常必要.本研究考虑气候、寄主树种分布、气候-寄主树种分布综合数据分别构建模型进行白蜡窄吉丁潜在适生区预测和分析,以期建立一种能够更加准确预测钻蛀类害虫潜在分布区的改进方法.除气候条件外,寄主树种的分布是影响白蜡窄吉丁分布的重要因素,应参与蛀干类昆虫适生区的预测.将非生物因素(气候)以及生物因素(寄主树种分布)作为单一变量时得到的预测结果进行叠加,更加符合白蜡窄吉丁分布现状和生存特性.白蜡窄吉丁在我国仍有继续向中部、南部等未发生区传播扩散的风险,限制敏感寄主树种的栽植是有效防范该虫危害的重要手段.     

Distribution patterns of Cd,Cu, Mn,Pb and Zn in wood fly ash emitted from domestic boilers

Abstract

Wood fuels being a renewable source of primary energy have been considered environmentally friendly. However, wood combustion in domestic boilers is a source of air pollution. The lack of a dust collection device is the reason why flue gases emit a significant load of particulate pollutants into the air, including heavy metals. The aim of this research was to assess the environmental hazard caused by both emissions of heavy metals during wood combustion in domestic boilers and their chemical forms present in fly ash.

From the various wood fuels burnt in domestic boilers, the fly ash selected for this study came from the combustion of briquettes of softwood from non-polluted areas, and from burning hardwood fuel from trees exposed to pollutants from heavy traffic. The wood fuels satisfy the quality demands determined in the EN 14961 Solid Biofuels - Fuel quality assurances. However, the concentrations of Cd, Cu, Pb and Zn in the fly ash are considerably higher than the appropriate limit values determined for soil improvers. Sequential extraction shows that Cd and Zn are associated mainly with the water leaching and carbonate fractions, regarded as mobile and bioavailable, and pose the potentially greatest hazard to the environment and human health. Cu, Mn and Pb associated with less mobile fractions may not pose a direct air quality hazard but, due to their high concentrations, medium-term and long-term effects on soils and surface and subsurface waters should be considered.     

Characterization of thermal power-plant fly ash for agronomic purposes and to identify pollution hazards

Ash samples were collected from a dumping site (fly ash) and an electrostatic precipitator (ESP ash) of a 440 MW thermal power plant for characterization. Analysis of ash samples showed that the major matrix elements in fly ash were Si and Al, together with significant percentages of K, Fe, Ca and Mg. Some of the biologically-toxic elements, Ni, Cr, Pb, B and Mo, were also present in substantial amounts. Ash collected directly from electrostatic precipitator (ESP ash) was finer in texture, lower in pH and generally richer in nutrients than the ash collected from dumping sites (fly ash). The saturation moisture percentages of both the ashes were higher, but the bulk density was lower, than the normal cultivated soils. Calcium was the dominant cation of the exchange complex, followed by Mg²⁺, Na⁺ and K⁺. Contents of available sulphur were quite high. Among DTPA extractable micronutrients, only iron was present in significant amounts, but the contents of hazardous constituents were very low. Compositions of watersoluble constituents of both the ashes were substantially affected by water: fly ash ratio and decreased with dilution. The rate of release of sodium was found to be much less than calcium and magnesium.     

Loss detection of aquatic habitats in Italian volcanic lakes using historical data

Italian volcanic lakes represent an important hotspot of aquatic plant diversity. By comparing original data collected in 2009/10 with historical data, we detected species extinction and loss of habitats 3140 and 3150 (Habitats Directive 92/43/EEC). The speed of change detected claim for frequent monitoring and rapid management interventions.