Plants control the seasonal dynamics of microbial N cycling in a beech forest soil by belowground C allocation

Soil microbes in temperate forest ecosystems are able to cycle several hundreds of kilograms of N per hectare per year and are therefore of paramount importance for N retention. Belowground C allocation by trees is an important driver of seasonal microbial dynamics and may thus directly affect N transformation processes over the course of the year. Our study aimed at unraveling plant controls on soil N cycling in a temperate beech forest at a high temporal resolution over a time period of two years, by investigating the effects of tree girdling on microbial N turnover. In both years of the experiment, we discovered (1) a summer N mineralization phase (between July and August) and (2) a winter N immobilization phase (November-February). The summer mineralization phase was characterized by a high N mineralization activity, low microbial N uptake, and a subsequent high N availability in the soil. During the autumn/winter N immobilization phase, gross N mineralization rates were low, and microbial N uptake exceeded microbial N mineralization, which led to high levels of N in the microbial biomass and low N availability in the soil. The observed immobilization phase during the winter may play a crucial role for ecosystem functioning, since it could protect dissolved N that is produced by autumn litter degradation from being lost from the ecosystem during the phase when plants are mostly inactive. The difference between microbial biomass N levels in winter and spring equals 38 kg N/ha and may thus account for almost one-third of the annual plant N demand. Tree girdling strongly affected annual N cycling: the winter N immobilization phase disappeared in girdled plots (microbial N uptake and microbial biomass N were significantly reduced, while the amount of available N in the soil solution was enhanced). This was correlated to a reduced fungal abundance in autumn in girdled plots. By releasing recently fixed photosynthates to the soil, plants may thus actively control the annual microbial N cycle. Tree belowground C allocation increases N accumulation in microorganisms during the winter which may ultimately feed back on plant N availability in the following growing season.     

Yolk hormones and sexual conflict over parental investment in the pied flycatcher

Female birds might be able to manipulate the parental effort of their male partner through elevated transfer of hormones to the eggs, since these hormones affect many chick traits that males might use as cues for adjusting the level of their investment. We experimentally studied whether female pied flycatchers Ficedula hypoleuca could manipulate male investment via yolk androgens. There is much more variation in yolk androgen levels between females than within clutches, and in order to change the androgen levels of the eggs, we swapped whole clutches between nests. To estimate the androgen levels of the clutch, we measured the androgen content of a single egg per clutch. Females did not succeed in manipulating male effort using yolk androgens, since there was no relationship between the division of parental care within a pair and either original or foster egg androgen levels. One of these relationships should have occurred if females were manipulating males. The proportion of feeding visits by the male was higher when the male was old (55%) than when he was young (45%) and females laid eggs with higher androgen levels when mated with a young male. Young males did not exhibit any responses to yolk androgen levels either, which indicates that females cannot exploit their effort more than that of old males. We suggest that females may allocate yolk androgens to adjust the growth trajectories of the chicks to poor growing conditions when mated with young males that are poor providers or occupying a poor territory.     

Characterization of the ignition by repetitive streamer discharges using laser diagnostics

Repetitive streamer discharges caused by transients, e.g. due to high frequency overvoltages, can ignite combustible mixtures, which has to be taken into account concerning the safety assessment of electrical apparatus for usage in hazardous areas. Hydrogen/air mixtures were ignited inside a closed vessel using a rod/plane electrode configuration. Alternating voltage with a frequency between 600 and 750 kHz and amplitudes of up to 20 kV was used to produce streamer discharges. The ignition process and the subsequent flame front propagation were examined with respect to mixture composition and several electrical parameters using time-resolved measurements of planar laser-induced fluorescence (PLIF) of OH radicals. A multiple pulse laser and detection system was used to assemble four images during one experiment. These measurements have given detailed information about the point of ignition and flame velocities. The experimental results will be used to validate numerical simulations of ignition by streamer discharges, which will yield deep insights into this specific ignition process.     

波罗的海未来冰情的数值研究

全球气候变化被认为对波罗的海物理和生态特性有影响.通过全球海气循环模型(AOGCM)的结果统计或动态缩减规模法可以预测未来气候对某一地区的影响.本文用两种不同的波罗的海冰-海耦合模型来模拟现在和未来约100年的冰情.已使用大气气候模型进行了两次以10年为期限的模拟实验,一个实验说明了工业化前的气候状况l检验模拟).另一个是CO2这种温室气体浓度增加150%时的全球气候变暖实验(方案模拟).模型模拟真实地再现了当前气候学冰情和一年里的变化.两个模型模拟的波罗的海每年最大结冰范围是l80～420×10xkm2(检验模拟)和45～270×103km2(方案模拟).检验模拟和方案模拟中每年的最大冰厚分别是32～96cm和11～60cm.对比早期的预测,海冰仍是每年冬天在波的尼亚湾北部和芬兰湾最东部形成总之,两个模型模拟得到的量的变化--像结冰范围和冰厚及其一年里的变化等--相对相似,这是值得注意的.因为这两个冰-海耦合模拟系统是独立研制的.这增加了预测波罗的海未来冰情的可靠性.     

Recent European initiatives in marine protection policy: towards lasting protection for Europe's seas?

The seas and oceans are increasingly a focus of policy interest in Europe. This is mirrored in wide-ranging activities to manage and protect the marine environment, which raises the question of whether such activities go towards developing sustainable management of the seas. Sustainable management calls for an integrated and cross-sectoral approach in order to protect highly valuable marine biodiversity from sea- and land-based activities of all kinds. While some recent developments are fairly promising, there are still no moves on the policy agenda towards uniting all relevant European policy sectors – and particularly the Common Agricultural Policy and the Common Fisheries Policy – under the shared objective of sustainable management and protection of the marine environment and its resources.     

The bridge between diversity and adaptivity: Answering McIntosh and Jeffrey

SUMMARY

The emerging concept of industrial ecology (IE) has been applied in practice in few case studies on local/regional industrial recycling networks. Analogously to a natural ecosystem, the aim is to develop material cycles and energy cascades between local cooperative actors. An optimal resource basis of an industrial ecosystem is the sustainable use of local renewable natural resources. In this paper, we consider the region of North Karelia in Finland, with 19 municipalities, and hence somewhat expand the system boundaries of an industrial ecosystem case study. The current situation and two scenarios of municipal heating energy production are presented. The heating system consists of individual, district and electric heating. The heat production and related greenhouse gas emissions are considered. The current fuel use is based on imported oil and regional fuels (peat, wood wastes). Also, shares for co-production of heat and electricity (CHP) are shown. In scenario one, we assume the majority of the fuel basis in oil and absence of CHP. Scenario two illustrates nearly complete dependence on regional wood wastes and firewood with the current share of CHP. The North Karelia region provides the IE theory with a fruitful case study because the supply of waste fuels and local renewables is vast and waste utilisation technologies (CHP, fluidized bed burning) constitute a significant part of energy production. Implications of the applied scenario approach are discussed in the context of regional decision making and, in particular, for its implementation with the concepts of a regional environmental management system (EMS) and a regional industrial ecosystem management system (RIEMS).     

Bidirectional coupling of macroscopic and microscopic pedestrian evacuation models

In this contribution, a combination of a macroscopic and a microscopic model of pedestrian dynamics using a bidirectional coupling technique is presented which allows to obtain better predictions for evacuation times. While the macroscopic model is derived from dynamic network flow theory, the microscopic model is based on a cellular automaton. Output from each model is fed into the other, thus establishing a control cycle. As a result, the gap between the evacuation times computed by both models is narrowed down: The coupled model considers both optimized routing strategies as well as microscopic effects. Accordingly the typical underestimation of evacuation times by purely macroscopic approaches is reduced. At the same time the microscopic model is enhanced by a steering component which reflects the macroscopic knowledge and the impact of supervising personnel on the distribution of pedestrian flows.