Patterns and processes of initial terrestrial‐ecosystem development     

Wolfgang Schaaf  Oliver Bens  Anton Fischer  Horst H. Gerke  Werner Gerwin  Uwe Grünewald  Hartmut M. Holländer  Ingrid Kögel‐Knabner  Michael Mutz  Michael Schloter  Rainer Schulin  Maik Veste  Susanne Winter  Reinhard F. Hüttl 《植物养料与土壤学杂志》2011,174(2):229-239

Ecosystems are characterized as complex systems with abiotic and biotic processes interacting between the various components that have evolved over long‐term periods. Most ecosystem studies so far have been carried out in mature systems. Only limited knowledge exists on the very initial phase of ecosystem development. Concepts on the development of ecosystems are often based on assumptions and extrapolations with respect to structure–process interactions in the initial stage. To characterize the effect of this initial phase on structure and functioning of ecosystems in later stages, it is necessary to disentangle the close interaction of spatial and temporal patterns of ecosystem structural assemblages with processes of ecosystem development. The study of initial, less complex systems could help to better identify and characterize coupled patterns and processes. This paper gives an overview of concepts for the initial development of different ecosystem compartments and identifies open questions and research gaps. The artificial catchment site “Chicken Creek” is introduced as a new research approach to investigate these patterns and processes of initial ecosystem development under defined boundary conditions. This approach allows to integrate the relevant processes with related pattern and structure development over temporal and spatial scales and to derive thresholds and stages in state and functioning of ecosystems at the catchment level.  相似文献   

立地和人为干扰对渭北黄土高原刺槐人工林个体生长过程的影响   总被引：4，自引：0，他引：4  

彭鸿 《山东农业大学学报(自然科学版)》2003,34(1):44-49

通过对渭北黄土高原刺槐人工林最大林木的树干解析和年轮分析描述了林分最大两株林木的树高、直径和材积生长过程。结果表明，矮林树高初期生长迅速，“好”立地的最大木高生长大于“差”立地上的最大木，矮林和“差”立地上的乔林之间树高生长过程达到最高峰的年龄为4—8a，“好”立地上的乔林为12a左右。直径生长可以分为速生期和缓馒生长期，年轮波动在速生期幅度大，进入缓馒生长期后幅度小但频度加大。依据直径生长过程可以区分为两组：第一组为最大木和次大木速生期为造林后6—8a的林分；第二组林木的速生期可持续到25a左右。年轮宽度的灵敏度指数在林分内最大木和次大木之间和在林分间差异都较大，刺槐矮林趋于比乔林大。生长越迅速，受到的人为干扰越强，年轮变化对于扰的反映越敏感，年轮灵敏度指数就越高。抚育间伐时常常伐去了利用价值高的个体，林分现保留木常是先前的被压木。  相似文献   

Visual pattern recognition in Drosophila is invariant for retinal position     

Tang S  Wolf R  Xu S  Heisenberg M 《Science (New York, N.Y.)》2004,305(5686):1020-1022

Vision relies on constancy mechanisms. Yet, these are little understood, because they are difficult to investigate in freely moving organisms. One such mechanism, translation invariance, enables organisms to recognize visual patterns independent of the region of their visual field where they had originally seen them. Tethered flies (Drosophila melanogaster) in a flight simulator can recognize visual patterns. Because their eyes are fixed in space and patterns can be displayed in defined parts of their visual field, they can be tested for translation invariance. Here, we show that flies recognize patterns at retinal positions where the patterns had not been presented before.  相似文献   

Developmental biology. Sex and poison in the dark     

Fischer R 《Science (New York, N.Y.)》2008,320(5882):1430-1431

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Development,growth, and nitrogen use of autumn- and spring-sown facultative wheat     

Reinhard W. Neugschwandtner  Katharina Böhm  Rea M. Hall  Hans-Peter Kaul 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(1):6-13

Spring-sown crops are expected to have a higher risk of drought during summer in the next decades in Central Europe due to expected climate change. Therefore, a two-year experiment was conducted under Pannonian growing conditions in Eastern Austria to investigate the effect of autumn- and spring-sowing of facultative wheat. Autumn-sowing of facultative wheat enhanced crop development, soil coverage, crop stand height, crop growth rate, and nitrogen (N) utilization efficiency during the vegetation period compared to spring-sowing; duration of growth stages was prolonged and crops were earlier ripe. In contrast, spring-sowing resulted in higher relative growth rates, higher N concentrations of aboveground dry matter, higher relative N uptake rates, and more mineral N in the soil. At harvest, grain yield and yield components ears m^?2 and thousand kernel weight (TKW) were higher in autumn-sown than in spring-sown wheat, resulting thereby in an increased seed yield. Spring-sown wheat had higher N concentrations in grain and in straw. Anyhow, N yield was slightly higher with autumn-sowing due to the higher grain and straw yields. Grain and straw yield, plant stand height, ears m^?2, and TKW were impaired in the second experimental year by a severe drought for both sowing dates as well as N concentrations and N yields of grain and straw, partial factor N use efficiency and N utilization efficiency. But the yield components harvest index, grains m^?2, and grains ear^?1 were strongly impaired with spring-sowing under drought conditions. Thus, autumn-sowing of wheat resulted in higher yield stability across both years, based on these yield components highlighting possible benefits of autumn-sowing with expected summer drought under climate change.  相似文献   

Comparison of three different sampling methods for canine skin lipids     

Mandy Angelbeck‐Schulze  Jessica Stahl  Susanne Brodesser  Karl Rohn  Hassan Naim  Marion Hewicker‐Trautwein  Manfred Kietzmann  Wolfgang Bäumer  Reinhard Mischke 《Veterinary dermatology》2013,24(2):233-e51

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A dynamic flow‐chamber‐based adhesion assay to assess canine platelet–matrix interactions in vitro     

Annika Ferkau  Silke Ecklebe  Kira Jahn  Simone Calmer  Gregor Theilmeier  Reinhard Mischke 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2013,42(2):150-156

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Development of high-performance strand boards: multiscale modeling of anisotropic elasticity     

Reinhard Stürzenbecher  Karin Hofstetter  Gerhard Schickhofer  Josef Eberhardsteiner 《Wood Science and Technology》2010,44(2):205-223

The interrelationships between microstructural characteristics and anisotropic elastic properties of strand-based engineered wood products are highly relevant in order to produce custom-designed strand products with tailored properties. A model providing a link between these characteristics and the resulting elastic behavior of the strand products is a very valuable tool to study these relationships. Here, the development, the experimental validation, and several applications of a multiscale model for strand products are presented. In a first homogenization step, the elastic properties of homogeneous strand boards are estimated by means of continuum micromechanics from strand shape, strand orientation, elastic properties of the used raw material, and mean board density. In a second homogenization step, the effective stiffness of multi-layer strand boards is determined by means of lamination theory, where the vertical density profile and different layer assemblies are taken into account. On the whole, this model enables to predict the macroscopic mechanical performance of strand-based panels from microscopic mechanical and morphological characteristics and, thus, constitutes a valuable tool for product development and optimization.  相似文献   

Accumulation of a low pathogenic avian influenza virus in zebra mussels (Dreissena polymorpha)     

Stumpf P  Failing K  Papp T  Nazir J  Böhm R  Marschang RE 《Avian diseases》2010,54(4):1183-1190

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Maiszünslerbekämpfung – Bekämpfung und neue Entwicklungen beim Trichogramma brassicae-Einsatz     

Reinhard Albert  Günter Maier  Kurt Dannemann 《Gesunde Pflanzen》2008,60(2):41-54

The European corn borer Ostrinia nubilalis (Huebner) is a well-known and investigated pest of corn and sweet corn particularly in the southwest of Germany since a long time. Nevertheless the pest can still surprise scientists and farmers. The first occurrence of a bivoltine race of the European corn borer in South Badenia in the years 2006 and 2007 is remarkable. The European corn borer had to be controlled in the last year on an area of approx. 60.000 hectares in Germany. An important antagonist of this pest is the parasitoid Trichogramma brassicae Bezdenko (Hym., Trichogrammatidae), which is already used for over 30 years on a continuously rising acreage for the control of Ostrinia nubilalis. The biology of the pest and its parasitoid are recapitulated particularly with regard to the biological control. The flight activities of the European corn borer are supervised with light traps in Southwest Germany. The data were inserted into a central data base at the LTZ Augustenberg, office Stuttgart (at first in 2007). The data can be used by advisors and farmers. They determinate the optimal time for the introduction of Trichogramma brassicae and optimize the application of insecticides. The annual randomized monitoring of the Trichogramma quantities and partially also qualities by the former state institute for plant protection and nowadays the LTZ Augustenberg helped to supply the farmers with good Trichogramma material. The efficiencies of the Trichogramma introduction reach up to over 70%. With the insecticide STEWARD (active ingredient Indoxacarb) similar and partly better efficiencies can be obtained. With the necessity of controlling Diabrotica virgifera virgifera with insecticides problems for the use of Trichogramma can arise – this will be discussed.  相似文献