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161.
Litter- and ecosystem-driven decomposition under elevated CO2 and enhanced N deposition in a Sphagnum peatland 总被引:1,自引:0,他引:1
Andy Siegenthaler Alexandre Buttler Luca Bragazza Edwin van der Heijden Jean-Michel Gobat 《Soil biology & biochemistry》2010,42(6):968-977
Peatlands represent massive global C pools and sinks. Carbon accumulation depends on the ratio between net primary production and decomposition, both of which can change under projected increases of atmospheric CO2 and N deposition. The decomposition of litter is influenced by 1) the quality of the litter, and 2) the microenvironmental conditions in which the litter decomposes. This study aims at experimentally testing the effects of these two drivers in the context of global change. We studied the in situ litter decomposition from three common peatland species (Eriophorum vaginatum, Polytrichum strictum and Sphagnum fallax) collected after one year of litter production under pre-treatment conditions (elevated CO2: 560 ppm or enhanced N: 3 g m−2 y−1 NH4NO3) and decomposed the following year under treatment conditions (same as pre-treatment). By considering the cross-effects between pre-treatments and treatments, we distinguished between the effects on mass loss of 1) the pre-treatment-induced litter quality and 2) the treatment conditions under which the litters were decomposing. The combination between CO2 pre-treatment and CO2 treatment reduced Polytrichum decomposition by −24% and this can be explained by litter quality-driven decomposition changes brought by the pre-treatment. CO2 pre-treatment reduced Eriophorum litter quality, although this was not sufficient to predict decomposition. The N addition pre-treatment reduced the decomposition of Eriophorum, due to enhanced lignin and soluble phenols concentrations in the initial litter, and reduced litter-driven losses of starch and enhanced litter-driven losses of soluble phenols. While decomposition indices based on initial litter quality provide a broad explanation of quantitative and qualitative decomposition, they can only be taken as first approximations. Indeed, the microbial ATP activity, the litter N loss and resulting litter quality, were strongly altered irrespective of the compounds' initial concentration and by means of processes that occurred independently of the initial litter-qualitative changes. The experimental design was valuable to assess litter- and ecosystem-driven decomposition pathways simultaneously or independently. The ability to separate these two drivers makes it possible to attest the presence of litter-qualitative changes even without any litter biochemical determinations, and shows the screening potential of this approach for future experiments dealing with multiple plant species. 相似文献
162.
Apart from influencing the amount of leaf-deposited particles, tree crown morphology will influence the local distribution of atmospheric particles. Nevertheless, tree crowns are often represented very rudimentary in three-dimensional air quality models. Therefore, the influence of tree crown representation on the local ambient PM10 concentration and resulting leaf-deposited PM10 mass was evaluated, using the three-dimensional computational fluid dynamics (CFD) model ENVI-met® and ground-based LiDAR imaging. The modelled leaf-deposited PM10 mass was compared to gravimetric results within three different particle size fractions (0.2–3, 3–10 and >10 μm), obtained at 20 locations within the tree crown. Modelling of the LiDAR-derived tree crown resulted in altered atmospheric PM10 concentrations in the vicinity of the tree crown. Although this model study was limited to a single tree and model configuration, our results demonstrate that improving tree crown characteristics (shape, dimensions and LAD) affects the resulting local PM10 distribution in ENVI-met. An accurate tree crown representation seems, therefore, of great importance when aiming at modelling the local PM distribution. 相似文献
163.
喷射沉积Al-8.5Fe-1.3V-1.7Si(8009)耐热铝合金板坯是由基体金属和孔隙、少量颗粒边界的氧化膜组成的,微观组织缺乏良好的冶金结合,直接采用轧制使其致密化产生塑性变形,在工艺上存在极大的难度,轧制时易出现板坯表面裂纹及边裂。本文研究了8009合金的包套轧制、交叉横轧工艺,实验结果表明:采用包套轧制、交叉横轧工艺,有效地改善了喷射沉积板坯的轧制成形性能,成功制备出厚度为0.6~1.0mm的薄板。 相似文献
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166.
《Land Degradation \u0026amp; Development》2017,28(8):2432-2445
We combine high‐resolution soil sampling with lead (Pb) analyses (concentrations and stable isotopes) in two temperate podzols, together with previous data obtained with selective Al and Fe dissolution techniques. We aim to assess how atmospheric Pb is incorporated into the soils during pedogenesis. Partial least squares modelling for Pb concentrations shows that the podzolization process has the largest effect on Pb concentration (80·3% of the variance). The proportion of inorganic secondary compounds, the input of fresh organic matter from the soil surface and the relative abundance of Fe versus Al are responsible for a small part of the Pb concentration variance. Lead isotopic composition (206Pb/207Pb ratios) depends on soil organic matter content either fresh/poorly humified (57·3% of the variance) or humified (24·7% of the variance). The Pb linked to inorganic compounds and the overall podzolization process play a minor role in isotopic signature (5·3 and 3·7% of the variance respectively). Soil pH appears to be the controlling variable of the different transport and retention mechanisms. The relatively low isotopic ratios observed in spodic horizons result from geogenic Pb released through the preferential dissolution of the isotopically distinct most weatherable minerals of the parent material in the eluvial horizons, which undergoes downward mobilization. An accurate knowledge of soil reactive components and formation mechanisms is essential to a correct diagnose of the scope of Pb pollution and a more effective design of remediation strategies. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
167.
Summary In this study, the application of molecular markers to optimise genetic diversity in a polycross breeding program of perennial
ryegrass (Lolium perenne L.) was evaluated. The genetic diversity among 98 potential parental plants from three maturity groups (early, intermediate
and late flowering) was investigated using amplified fragment length polymorphism (AFLP) markers. For each maturity group,
two polycrosses of six parental plants with contrasting levels of genetic diversity were composed. Average genetic diversity
among parents selected for narrow polycrosses was 36% lower than among parents selected for wide polycrosses. Diversity within
first generation synthetic progenies (Syn1) was proportional to the diversity within the respective parental polycrosses.
However, differences were less pronounced with Syn1 progenies from narrow polycrosses showing 16% reduced diversity when compared
to Syn1 progenies from wide polycrosses. Multivariate analyses allowed for a clear separation of the six Syn1 progenies based
on AFLP markers and demonstrated their genetic distinctness. Evaluation of dry matter yield, date of ear emergence and stem
length of Syn1 and Syn2 progenies showed progenies from wide polycrosses to be constantly higher yielding when compared to
progenies from narrow polycrosses. On the other hand, there was no significant difference in variability for the two morphological
traits between progenies of narrow- and wide polycrosses. The results presented here provide evidence for an efficient application
of molecular markers to select genetically diverse polycross parents which resulted in an average yield increase of 3.8%. 相似文献
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169.
太湖地区地表水氮污染源的评论 总被引:11,自引:0,他引:11
The nitrogen (N) pollution status of the 12 most important rivers in Changshu, Taihu Lake region was investigated. Water samples were collected from depths of 0.5-1.0 m with the aid of the global positioning system (GPS). The seasonal variations in the concentrations of different N components in the rivers were measured. Using tension-free monolith lysimeters and ^15N-labeled fertilizer, field experiments were carried out in this region to determine variations of iSN abundance of NO3^- in the leachate during the rice and wheat growing seasons, respectively. Results showed that the main source of N pollution of surface waters in the Taihu Lake region was not the N fertilizer applied in the farmland but the urban domestic sewage and rural human and animal excreta directly discharged into the water bodies without treatment. Atmospheric dry and wet N deposition was another evident source of N pollutant of the surface waters. In conclusion, it would not be correct to attribute the N applied to farmlands as the source of N pollution of the surface waters in this region. 相似文献
170.
秸秆覆盖畦田灌溉水流特性及灌水质量分析 总被引:2,自引:0,他引:2
在陕西杨凌张家岗村覆盖玉米秸秆的冬小麦地进行了畦田规格和灌水技术要素对灌水效率和灌溉均匀度影响的田间试验,并SRFR406软件对秸秆覆盖畦灌的水流推进进行了数学模拟.结果表明,给出的地面灌溉模型及软件可较好的模拟秸秆覆盖畦田水流运动.畦田规格与技术要素的选择对灌水效率及灌水均匀度均有影响.在覆盖秸秆畦田以畦长小于50 m,畦宽2~3 m,单宽流量以6~8 L/(m·s),坡度以3‰~5‰为宜.为提高秸秆覆盖灌水效率,应加强耕作管理,消除反坡. 相似文献