Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2011
Authors
Markus Reichstein Miguel D. Mahecha Nuño Carvalhais Gitta Lasslop Sonia I. Seneviratne Holger Lange Alessandro Cescatti Mirco MigliavaccaAbstract
The release of carbon dioxide (CO2) from the land surface via different respiratory processes is a major flux in the global carbon cycle, antipodal to CO2 uptake via photosynthesis. Understanding the sensitivity of respiratory processes to temperature is central for quantifying the climate–carbon cycle feedback. In a recent study we approximated the sensitivity of terrestrial ecosystem respiration to air temperature (Q10) across 60 FLUXNET sites. For this objective, we developed a novel methodology that circumvents seasonally confounding effects. Contrary to previous findings, our results suggest that Q10 is independent of mean annual temperature, does not differ among biomes, and is confined to values around 1.4 ± 0.1. However, the shape of the strong relation between photosynthesis and respiration is highly variable among sites. The results may partly explain a less pronounced climate–carbon cycle feedback than suggested by current carbon cycle climate models. In the talk we put our findings into context with other recent results and critically discuss their potential for evaluating temperature sensitivity of respiration in terrestrial biosphere models and parameterizing future land surface schemes.
Authors
Miguel D. Mahecha Markus Reichstein Nuño Carvalhais Gitta Lasslop Holger Lange Sonia I. Seneviratne Rodrigo Vargas Christof Ammann M. Altaf Arain Alessandro Cescatti Ivan A. Janssens Mirco Migliavacca Leonardo Montagnani Andrew D. RichardsonAbstract
We estimated the sensitivity of terrestrial ecosystem respiration to air temperature across 60 FLUXNET sites by minimizing the effect of seasonally confounding factors. Graf et al. now offer a theoretical perspective for an extension of our methodology. However, their critique does not change our main findings and, given the currently available observational techniques, may even impede a comparison across ecosystems.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
2010
Abstract
The effects of genetically modified (GM) maize (Zea mays L.) expressing the Bacillus thuringiensis Berliner Cry1Fa2 protein (Bt) and phosphinothricin or glyphosate herbicide tolerance on soil chemistry (organic matter, N, P, K and pH), compared with non-GM controls, were assessed in field and pot experiments. In the field experiment, NH4+ was significantly higher in soil under the crop modified for herbicide tolerance compared to the control (mean values of 11 and 9.6 mg N/kg respectively) while P was significantly higher in soil under the control compared to under the GM crop (mean values of 6.9 and 6.4 dg P/kg, respectively). No significant differences were found as a result of growing Bt/herbicide tolerant maize. In the pot experiment, using soils from three sites (Gongzhuling, Dehui and Huadian), significant effects of using Bt maize instead of conventional maize were found for all three soils. In the Gongzhuling soil, P was significantly higher in soil under the control compared to under the GM crop (mean values of 4.8 and 4.0 dg P/kg, respectively). For the Dehui soil, the pH was significantly higher in soil under the control compared to under the GM crop (mean values for {H+} of 1.1 and 2.4 μM for the control and the GM crop respectively). In the Huadian soil, organic matter and total N were both higher in soil under the GM crop than under the control. For organic matter, the mean values were 3.0 and 2.9% for the GM crop and the control, respectively, while for total nitrogen the mean values were 2.02 and 1.96‰ for the GM crop and the control respectively. Our results indicate that growing GM crops instead of conventional crops may alter soil chemistry, but not greatly, and that effects will vary with both the specific genetic modification and the soil.
Abstract
No abstract has been registered
Abstract
The aliphatic biopolyesters cutins and suberins have been suggested to significantly contribute to the stable pool of soil organic matter (SOM), and to be tracers for the above- or belowground origin of plant material. Contrary to other plant-derived aliphatic molecules found in the lipid fraction of soils, the stable isotope derived estimates of turnover of cutins and suberins have never been studied in soils. The aim of this study was to analyse the dynamics of shoot- and root-derived biomarkers in soils using a wheat and maize (C3/C4) chronosequence, where changes in the natural 13C abundance can be used to evaluate the incorporation of new carbon into SOM at the molecular level. The relative distribution of aliphatic monomers in wheat and maize roots and shoots suggested that a,u-alkanedioic acids can be considered as root-specific markers and mid-chain hydroxy acids as shoot-specific markers. The contrasting distribution of the plant-specific monomers in plants and soils might be explained by different chemical mechanisms leading to selective degradation or stabilization of some biomarkers. The changes of the 13C isotopic signatures of these markers with years of maize cropping after wheat evidenced their contrasted behaviour in soil. After 12 years of maize cropping, shoot markers present in soil samples probably originated from old C3 vegetation suggesting that new maize cutin added to soils was mostly degraded within a year. The reasons for long-term stabilization of shoot biomarkers remain unclear. By contrast, maize root markers were highly incorporated into SOM during the first six years of maize crop, which suggested a selective preservation of root biomass when compared to shoots, possibly due to physical protection.
Abstract
No abstract has been registered
Authors
Martin Lorenz Nicholas Clarke Elena Paoletti Andrzej Bytnerowicz Nancy Grulke Natalia Lukina Hiroyuki Sase Jeroen StaelensAbstract
No abstract has been registered
Authors
Aldo Marchetto Rosario Mosello Gabriele A. Tartari Kirsti Derome Nils König Nicholas Clarke Anna KowalskaAbstract
A second Working Ring Test (WRT) was organised within the framework of the EU/Life+ FutMon Project (`Further Development and Implementation of an EU-level Forest Monitoring System`, LIFE07 ENV/D/000218), to evaluate the overall performance of the laboratories responsible for analysing atmospheric deposition and soil solution samples in European forests, and to verify improvements in the analytical quality resulting from the QA/QC work carried out in the laboratories which participated in previous WRTs organized in the framework of the UN/ECE ICP Forests Monitoring Programme. The WRT was carried out in accordance with International ISO and ILAG guide proficiency test both for sample preparation and numerical elaboration of the results. Five natural atmospheric deposition and soil solution samples and 3 synthetic solutions were distributed to 42 laboratories for analysis using their routine methods for the following variables: pH, conductivity, calcium, magnesium, sodium, potassium, ammonium, sulphate, nitrate, chloride, total alkalinity, total dissolved nitrogen (TDN), dissolved organic carbon (DOC). Two tolerable limits were defined for each variable on the basis of the measured value, the results of previous WRTs, a comparison with the Data Quality Objectives of other international networks, and the importance of the variable in deposition and soil solution monitoring. In the ring test 12% of the results from all the laboratories did not fall within the tolerable limits. This enabled us to identify those variables and laboratories for which improvements in analytical performance are required. The results of the exercise clearly show that the use of data check procedures, as described in the ICP Forests manual for sampling and analysis of atmospheric deposition, makes it possible to detect the presence of inaccurate or outlying results, and would therefore greatly improve the overall performance of the laboratories. A discussion of the improvement of the results in this WRT compared to the previous WRTs is also included, showing a relevant improvent for several variables and underlining the importance of participating to these exercises for the overall analytical quality of the monitoring network.