105 research outputs found
Spatial distribution of tree and grassland fine roots in an alley cropping system
No full textAlley cropping systems are known as more sustainable land use alternatives compared to monoculture cropland. In addition to the improvement of above-ground structures and creation of biotopes relevant to nature conservation, the improvement of resource development through various root systems plays a major role. We studied the interaction of the root systems in an alley cropping system combining permanent grassland and willows and at a reference grassland site. The system was established 12 years prior to our study on a site with a shallow groundwater table at 130 cm depth. We measured carbon stocks in the topsoil and determined the share of root-bound carbon relative to the total carbon pool and extracted soil cores up to a depth of 150 cm along a distance gradient to the trees and at a reference grassland site with no tree influence. The maximal rooting depth of the grassland roots increased with increasing distance to the tree lines and total root biomass was higher than under the grassland reference up to a distance of 2.5 m from the tree line. Tree roots extended up to a distance of 5.5 m from the trees and we could distinguish zones of tree root dominance very close to the trees, zones of grassland root dominance at distances ≥
8.5 m and an interaction zone in between those two extremes. We conclude that alley cropping increases belowground biomass as compared to grassland and has therefore a higher potential to store carbon in the subsoil.Open-Access-Publikationsfonds 202
Perceptual Influence of Elementary Three-Dimensional Geometry: 1) Object-ness
No full textCommonly complex cognitive concepts cannot consistently be connected to simple features of the world. Geometrical shape parameters and (e.g. edge features, compactness, color) may play a role for defining individual objects, but might be too variable to allow for concept formation. Earlier works had suggested that the formation of object concepts is strongly influenced by the division of our world along convex to concave surface transitions. In this first paper in a sequence of two we address this issue using abstract 3D geometrical structures (polycubes). In a first experiment, we let our subjects manipulate and compare polycubes with different compactness and different concavity/convexity asking which of them they would perceive as an object. Both parameters (compactness and concavity/convexity) are not correlated in these stimuli. Nonetheless, we find that subjects with clear prevalence choose compact and convex ones. We continue to ask how strongly this influences the way we construct objects. Thus, in a second experiment we let humans combine polycubes to form an object. Also here we find that they prefer compact and convex configurations. This suggests that this simple geometric feature may underlie our cognitive understanding of object-ness not only with respect to perception but also by influencing how we build our world
Alley cropping tree lines alter temperature and light quantity and influence daily growth rates of grassland
No full textTree lines do not reduce grassland productivity and herbage quality in alley cropping under drought
No full textAdjusting nitrogen fertilization to spatial variations in growth conditions in silvopastoral systems for improved nitrogen use efficiency
No full textAbstract Grass swards in silvopastoral systems have a lower herbage production near trees than open grassland. This is related to a lower nitrogen (N) uptake in an area close to the tree lines. The N use efficiency for the whole field can then be improved when N input is spatially adjusted and the overall amount reduced. We performed a 2-year field experiment to gain insights into this idea for making savings on N inputs by studying the response of the grass sward to fertilizer N input in relation to the distance from trees. We hypothesized an interaction between N input rate and position to the tree line on grassland herbage production and N uptake and, accordingly, N use efficiency. The field trial was carried out in a silvopastoral system in Germany consisting of the factors year (2019 and 2020), position (2.5, 6.5 and 24.5 m distances to tree line), annual N application rate (0, 15 and 30 g N m −2 ) and harvest date (four harvests per year). We found significant interactions between position × N rate for all target variables, and usually also in interactions with the harvest date or year. The N application close to trees at a distance < 6.5 m had in most cases no significant influence on herbage production but significantly increased herbage production by up to 35% at positions further away. Omitting the N fertilization in a corridor of 6.5 m near the trees would contribute directly to the saving of fertilizer N without a negative trade-off in herbage production.Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347Georg-August-Universität Göttingen 50110000338
Tree lines influence soil temperatures, sward growth dynamics and litter decomposition in permanent grassland
No full textFunder:
http://dx.doi.org/10.13039/501100010571
BMBF Berli
Perceptual Influence of Elementary Three-Dimensional Geometry: 2) Fundamental object parts
No full textObjects usually consist of parts and the question arises whether there are perceptual features which allow breaking down an object into its fundamental parts without any additional (e.g. functional) information. As in the first paper of this sequence, we focus on the division of our world along convex to concave surface transitions. Here we are using machine vision to produce convex segments from 3D-scenes. We assume that a fundamental part is one, which we can easily name while at the same time there is no natural subdivision possible into smaller parts. Hence in this experiment we presented the computer vision generated segments to our participants and asked whether they can identify and name them. Additionally we control against segmentation reliability and we find a clear trend that reliable convex segments have a high degree of name-ability. In addition, we observed that using other image-segmentation methods will not yield nameable entities. This indicates that convex-concave surface transition may indeed form the basis for dividing objects into meaningful entities. It appears that other or further subdivisions do not carry such a strong semantical link to our everyday language as there are no names for them
High and dry: Barley (Hordeum vulgare) yield benefits from tree presence in a temperate alley cropping system during a drought year
No full textAbstract Alley cropping systems (ACS) are promoted as sustainable, resilient and multifunctional land-use systems. However, concerns about yield reductions persist and whether these are driven by microclimate alterations or below-ground competition for water remains unclear. In this study, we measured wind speed, air temperature, and global radiation at seven positions within a 48 m wide crop alley of a short rotation ACS in Germany with summer barley ( Hordeum vulgare ) and poplar ( Populus nigra × P. maximowiczii and P. trichocarpa Torrey & A. Gray ) and on a treeless reference field (OF) during a particularly dry and warm year. Additionally, gravimetric soil water content and crop yield were assessed with high spatial resolution. Our results show that tree strips influenced all measured parameters. Global radiation and air temperature patterns varied dynamically with shading, while night-time air temperatures were unexpectedly highest on the OF. Wind speeds were reduced by up to 98% near tree strips and 81% further away. Soil water content displayed a U-shaped pattern, with higher values near tree strips, a rare observation in ACS. Crop yields in the ACS were twice as high as in the OF, despite being lower near tree strips. Yields were strongly correlated with global radiation but not with air temperature, wind speed, or soil water content. These findings provide preliminary evidence that tree presence in ACS can, under certain conditions, contribute to increased crop yields. The results suggest that ACS provide potential benefits for sustainable land-use, but further multi-year and multi-site studies are needed to validate the observed yield patterns across different environments and years, particularly under varying climatic conditions. Further research should also explore the indirect effects of microclimate modifications on soil water dynamics, including evapotranspiration.German Federal Ministry of Education and ResearchBrandenburgische Technische Universität Cottbus - Senftenberg http://dx.doi.org/10.13039/50110002202
Rahel Varnhagen von Ense Collection 1793-1974
No full textOriginal correspondence from Rahel Varnjagen as well as from her husband Karl August. Annotated handwritten transcripts of lost correspondence from and to Rahel Varnhagen, prepared before WW II. Also included are commentaries, essays, etc.digitizedBorn in Berlin on May 26, 1771, Rahel Levin was an author and salon hostess. She married Karl August Varnhagen von Ense in 1814 and died in Berlin on March 7, 1833.Erich Loewenthal prepared the transcripts of the correspondence between Rahel Varnhagen and her brother Ludwig Robert before WW II with the intention to have it published. The letters were held in Berlin’s Staatsarchiv Unter den Linden, before being moved to Silesia and destroyed in WW II. Erich Loewenthal was killed in Auschwitz.Behrend, Fritz. Bokelmann, Wilhelm. Brinkmann, Gustav. Friedländer, Rebecca
Rahel Varnhagen : the life of a Jewess /
No full text"She was, Hannah Arendt wrote, "my closest friend, though she has been dead for some hundred years." Born in Berlin in 1771 as the daughter of a Jewish merchant, Rahel Varnhagen would come to host one of the most prominent salons of the late eighteenth and early nineteenth centuries. Arendt discovered her writings some time in the mid-1920s and soon began to reimagine Rahel's inner life and write her biography. Long unavailable and never before published as Arendt intended, Rahel Varnhagen: The Life of a Jewess returns to print in an extraordinary new edition." "For this first complete and critical edition of the book in any language, Liliane Weissberg reconstructs the notes Arendt planned for Rahel Varnhagen but never fully executed. She reveals the full extent to which Arendt wove the biography largely from the words of Rahel and her contemporaries. In her extended introduction, Weissberg reflects on Rahel's writings, on Arendt's reading of Rahel's work and life, and on the importance of this text in the development of Arendt's political theory. But the book was important to its author in other ways as well, Weissberg reveals, as she uncovers the hidden story of how Arendt manipulated documents relating to Rahel Varnhagen to claim for herself a university position and reparation payments from the postwar German state."--Jacket."Published in cooperation with the Leo Baeck Institute"--Title page verso.Includes bibliographical references (pages 369-380) and index."She was, Hannah Arendt wrote, "my closest friend, though she has been dead for some hundred years." Born in Berlin in 1771 as the daughter of a Jewish merchant, Rahel Varnhagen would come to host one of the most prominent salons of the late eighteenth and early nineteenth centuries. Arendt discovered her writings some time in the mid-1920s and soon began to reimagine Rahel's inner life and write her biography. Long unavailable and never before published as Arendt intended, Rahel Varnhagen: The Life of a Jewess returns to print in an extraordinary new edition." "For this first complete and critical edition of the book in any language, Liliane Weissberg reconstructs the notes Arendt planned for Rahel Varnhagen but never fully executed. She reveals the full extent to which Arendt wove the biography largely from the words of Rahel and her contemporaries. In her extended introduction, Weissberg reflects on Rahel's writings, on Arendt's reading of Rahel's work and life, and on the importance of this text in the development of Arendt's political theory. But the book was important to its author in other ways as well, Weissberg reveals, as she uncovers the hidden story of how Arendt manipulated documents relating to Rahel Varnhagen to claim for herself a university position and reparation payments from the postwar German state."--Jacket
- …
