@article{HoffmannWirthBessleretal.2017, author = {Hoffmann, Mathias and Wirth, Stephan J. and Bessler, Holger and Engels, Christof and Jochheim, Hubert and Sommer, Michael and Augustin, J{\"u}rgen}, title = {Combining a root exclusion technique with continuous chamber and porous tube measurements for a pin-point separation of ecosystem respiration in croplands}, series = {Journal of plant nutrition and soil science = Zeitschrift f{\"u}r Pflanzenern{\"a}hrung und Bodenkunde}, volume = {181}, journal = {Journal of plant nutrition and soil science = Zeitschrift f{\"u}r Pflanzenern{\"a}hrung und Bodenkunde}, number = {1}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1436-8730}, doi = {10.1002/jpln.201600489}, pages = {41 -- 50}, year = {2017}, abstract = {To better assess ecosystem C budgets of croplands and understand their potential response to climate and management changes, detailed information on the mechanisms and environmental controls driving the individual C flux components are needed. This accounts in particular for the ecosystem respiration (R-eco) and its components, the autotrophic (R-a) and heterotrophic respiration (R-h) which vary tremendously in time and space. This study presents a method to separate R-eco into R-a [as the sum of R-a (shoot) and R-a (root)] and R-h in order to detect temporal and small-scale spatial dynamics within their relative contribution to overall R-eco. Thus, predominant environmental drivers and underlying mechanisms can be revealed. R-eco was derived during nighttime by automatic chamber CO2 flux measurements on plant covered plots. R-h was derived from CO2 efflux measurements, which were performed in parallel to R-eco measurements on a fallow plot using CO2 sampling tubes in 10 cm soil depth. R-a (root) was calculated as the difference between sampling tube CO2 efflux measurements on a plant covered plot and R-h. R-a (shoot) was calculated as R-eco - R-a (root) - R-h. Measurements were carried out for winter wheat (Triticum aestivum L.) during the crop season 2015 at an experimental plot located in the hummocky ground moraine landscape of NE Germany. R-eco varied seasonally from < 1 to 9.5 g C m(-2) d(-1), and was higher in adult (a) and reproductive (r) than juvenile (j) stands (gC m(-2) d(-1): j = 1.2, a = 4.6, r = 5.3). Observed R-a and R-h were in general smaller compared to the independently measured R-eco, contributing in average 58\% and 42\% to R-eco. However, both varied strongly regarding their environmental drivers and particular contribution throughout the study period, following the seasonal development of soil temperature and moisture (R-h) as well as crop development (R-a). Thus, our results consistently revealed temporal dynamics regarding the relative contribution of R-a (root) and R-a (shoot) to R-a, as well as of R-a and R-h to R-eco. Based on the observed results, implications for partitioning of R-eco in croplands are given.}, language = {en} } @article{BauerMoeckNordenetal.2010, author = {Bauer, Klaus and Moeck, Inga and Norden, Ben and Schulze, Alexander and Weber, Michael H. and Wirth, Holger}, title = {Tomographic P wave velocity and vertical velocity gradient structure across the geothermal site Groß Schoenebeck (NE German Basin) : relationship to lithology, salt tectonics, and thermal regime}, issn = {0148-0227}, doi = {10.1029/2009jb006895}, year = {2010}, abstract = {Seismic wide-angle data were collected along a 40-km-long profile centered at the geothermal research well GrSk 3/90 in the Northeast German Basin. Tomographic inversion of travel time data provided a velocity and a vertical velocity gradient model, indicative of Cenozoic to Pre-Permian sediments. Wide-angle reflections are modeled and interpreted as top Zechstein and top Pre-Permian. Changes in velocity gradients are interpreted as the transition from mechanical to chemical compaction at 2-3 km depth, and localized salt structures are imaged, suggesting a previously unknown salt pillow in the southern part of the seismic profile. The Zechstein salt shows decreased velocities in the adjacent salt pillows compared to the salt lows, which is confirmed by sonic log data. This decrease in velocity could be explained by the mobilization of less dense salt, which moved and formed the salt pillows, whereas the denser salt remained in place at the salt lows. We interpret a narrow subvertical low-velocity zone under the salt pillow at GrSk 3/ 90 as a fault in the deep Permian to Pre-Permian. This WNW-ESE trending fault influenced the location of the salt tectonics and led to the formation of a fault-bounded graben in the Rotliegend sandstones with optimal mechanical conditions for geothermal production. Thermal modeling showed that salt pillows are related to chimney effects, a decrease in temperature, and increasing velocity. The assumed variations in salt lithology, density, and strain must thus be even higher to compensate for the temperature effect.}, language = {en} } @article{AllanWeisserFischeretal.2013, author = {Allan, Eric and Weisser, Wolfgang W. and Fischer, Markus and Schulze, Ernst-Detlef and Weigelt, Alexandra and Roscher, Christiane and Baade, Jussi and Barnard, Romain L. and Bessler, Holger and Buchmann, Nina and Ebeling, Anne and Eisenhauer, Nico and Engels, Christof and Fergus, Alexander J. F. and Gleixner, Gerd and Gubsch, Marlen and Halle, Stefan and Klein, Alexandra-Maria and Kertscher, Ilona and Kuu, Annely and Lange, Markus and Le Roux, Xavier and Meyer, Sebastian T. and Migunova, Varvara D. and Milcu, Alexandru and Niklaus, Pascal A. and Oelmann, Yvonne and Pasalic, Esther and Petermann, Jana S. and Poly, Franck and Rottstock, Tanja and Sabais, Alexander C. W. and Scherber, Christoph and Scherer-Lorenzen, Michael and Scheu, Stefan and Steinbeiss, Sibylle and Schwichtenberg, Guido and Temperton, Vicky and Tscharntke, Teja and Voigt, Winfried and Wilcke, Wolfgang and Wirth, Christian and Schmid, Bernhard}, title = {A comparison of the strength of biodiversity effects across multiple functions}, series = {Oecologia}, volume = {173}, journal = {Oecologia}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0029-8549}, doi = {10.1007/s00442-012-2589-0}, pages = {223 -- 237}, year = {2013}, abstract = {In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 \% of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.}, language = {en} }