TY - GEN A1 - Gypser, Stella A1 - Diez, Miriam A1 - Boelli, Daniel A1 - Wachendorf, Magnus A1 - Küppers, Manfred A1 - Veste, Maik T1 - Monitoring of biocrust development and physiological activity in disturbed ecosystems in Central Europe T2 - Biocrust 4 - 4th International Workshop on Biological Soil Crusts N2 - In many ecosystems of the earth, biocrusts influence the successive development of vegetation through their influence on the soil formation. This change in soil structure, e.g. due to the accumulation of organic material and the ability of biological nitrogen fixation, results in significant feedback and controls of ecosystem processes, especially in arid regions. In Brandenburg, located in NE Germany, the dry grasslands on sand dunes and the post-mining landscapes, characterized by edaphic drought and lack of nutrients as well as disturbances, are ecologically interesting locations for investigations of the biocrusts. In recent years, the species composition, structure, N-fixation, C-fluxes, and accumulation as well as their soil hydrological properties of biocrusts have been characterized and ecophysiological measurements of biocrust activity and CO2 exchange of different biocrust types under standardized environmental conditions have been performed in the laboratory. These ecophysiological measurements were correlated for the first time with NDVI measurements using a modified consumer camera, thus enabling a spatial analysis of the photosynthesis hotspots and a transfer from the lab into the landscape. The development and physiological activity of biocrusts are significantly influenced by microclimatic boundary conditions and moisture-dry cycles. The duration of these moisture phases is decisive for their spatial and temporal development and for the differentiation of the developmental stages. The permanent recording of moisture in the biocrusts in the uppermost millimeters using a newly developed biocrust wetness sensor in combination with NDVI measurements enable detailed information about biocrust activities and carbon fluxes. These continuous measurements of NDVI and physiological activity with PRI sensors allows determining seasonal activity phases in relation to microclimatological site conditions. More recent technological developments in sensor technology make it possible to carry out detailed and cost-effective investigations of the biocrust activity over the course of the year. KW - biological soil crusts KW - physiological activity KW - ecosystem development Y1 - 2019 U6 - https://doi.org/10.13140/RG.2.2.11042.99523 VL - 2019 CY - North Stradbroke Island, Queensland , Australia ER - TY - GEN A1 - Dietz, Miriam A1 - Küppers, Manfred A1 - Wachendorf, Magnus A1 - Stefan, Thorsten A1 - Veste, Maik A1 - Gypser, Stella T1 - Modelling photosynthesis and carbon fluxes of moss- and lichen-dominated biological soil crusts in temperate dry acid grasslands in Brandenburg T2 - GfÖ 2019, Science Meets Practice, 49th Annual Meeting of the Ecological Society of Germany, Austria and Switzerland, university of Münster, 9-13 September 2019 N2 - Top soils in temperate climates are regularly covered by cryptogames. Depending on the climatic and environmental conditions and their development stage, these biocrusts are built up by different species of cyanobacteria, bacteria, green algae, mosses, liverworts, lichens and fungi, which crosslink the uppermost soil particles. Biocrusts create a thin surface layer of high biotic activity, with high C and nutrient pools and fluxes to deeper soil layers, where the soil tends to be biotically and biogeochemically less active. Changes in soil structure, e.g. due to the accumulation of organic material and the ability of biological nitrogen fixation, result in significant feedback and control of biogeochemical processes. We analysed the response of photosynthesis and respiration to changing temperature and light in two moss-and lichen-dominated soil crusts from a dry acid grassland in the vicinity of a pine forest in Brandenburg, Germany. For the estimation of carbon fluxes, we combined lab-based CO2 gas exchange measurements and continuous determination of biocrust drying and rewetting cycles under field conditions. These experiments facilitated the development of an empirical photosynthesis model that allows for an estimation of the carbon dynamics of biological soil crusts based on their ecophysiological performance. Y1 - 2019 UR - https://www.gfoe-conference.de/WEBS/GFOe2019.pages.download/Book_of_Abstracts2019.pdf SP - 223 CY - Münster ER - TY - GEN A1 - Wachendorf, Magnus A1 - Schloz, Mona A1 - Küppers, Manfred A1 - Güney, Aylin A1 - Veste, Maik T1 - Wintertime photosynthesis and spring recovery of Ilex Aquifolium L. T2 - iForest Biogeosciences and Forestry N2 - Former studies using the chlorophyll fluorescence technique on evergreen Ilex aquifolium L. showed that its photosynthetic potential for electron transport in winter recovers quickly when exposed to more favorable conditions. Since little is known, however, about its photosynthetic carbon gain in winter, we investigated its leaf gas exchange over an entire winter and spring period. Measurements were made rotationally in the field and in the laboratory to also investigate if I. aquifolium profits from warmer phases during winter in terms of net carbon gain. From the end of autumn until the end of spring, three different climate-driven phases of photosynthetic responses could be distinguished: first, an acclimation phase which lasted until February and was characterized by a gradually decreasing light-saturated gross photosynthesis (Amax(gross)), decreasing apparent quantum yield of CO₂-assimilation (ɸi) and a decreasing ability of these parameters to recover overnight inside the laboratory. At the same time, maximal quantum yield of PSII (Fv/Fm) could fully regenerate. In this phase, single warmer days had a positive effect on carbon assimilation. Second, a phase of relatively constant but low photosynthesis which was virtually unaffected by temperature, lasting for almost two months occurred. Here, Amax(gross) and ɸi had lost their ability to recover from winter conditions in the field, while Fv/Fm was much less affected. I. aquifolium was still able to conduct positive light-saturated net photosynthesis at a leaf temperature of -0.5°C, but during this time it could not profit from milder temperatures in terms of carbon gain. Third, a phase of increasing photosynthesis (spring recovery) occurred, starting in March when the 5-day average temperature was above 5°C and radiation in the field increased, and where all parameters slowly recovered from winter depressions. Our findings show that I. aquifolium is photosynthetically active over the whole winter, even at temperatures around 0°C. In terms of carbon gain, however, I. aquifolium does not profit from warmer phases during winter, despite the fast recovery seen in chlorophyll fluorescence measurements. Y1 - 2019 U6 - https://doi.org/10.3832/ifor2983-012 SN - 1971-7458 VL - 12 IS - 4 SP - 389 EP - 396 ER -