TY - GEN A1 - Küppers, Manfred A1 - Küppers, Barbara I. L. A1 - Horna, Viviana A1 - Veste, Maik A1 - Zimmermann, Reiner A1 - Lauerer, Marianne A1 - Aas, Gregor T1 - Green barks of trees from drought deciduous forests ("bosque seco") in northern Peru/southern Ecuador do not perform CAM T2 - Basic and Applied Dryland research N2 - Trees from drought deciduous forests (“bosque seco”) in northern Peru and southern Ecuador regularly shed their leaves at the onset of seven months-long periods without rain. This way they very effectively reduce the bulk water consumption by leaf transpiration, still loosing small amounts of water through their bark, but at the risk of too little or no carbon gain when leaf-less. Seven species studied here have good developed green cortex tissue on stems and axes, as especially evident for the “bottle tree” Ceiba trischistandra (A. Gray) Bakhuisen (Bombacaceae). In several leaf-less tree species at the end of summer drought, when xylem sap flows are very low, indications of higher xylem flows at night as compared to day-time were found, which led to the question of whether the trees are capable of performing CAM in their axes. However, although quite low in some cases, the pH of the cortex tissues did not fluctuate diurnally. In addition, no night-time carbon uptake could be observed. Although no net carbon gain was measured in C. trischistandra and Erythrina smithiana Krukoff (Fabaceae) photosynthetic activity of the green cortex was sufficient to re-assimilate between 50% to 60% of the carbon released by mitochondrial respiration. In contrast, the obligate CAM plant Cereus diffusus (Britton & Rose) Werdermann (Cactaceae), which was studied as a reference in the same environment, showed both diurnal pH-fluctuations in its green tissue with lowest values before sun rise, and net carbon fixation at night. Y1 - 2015 UR - https://www.researchgate.net/publication/280945188 U6 - https://doi.org/10.1127/badr/2015/0002 SN - 1864-3191 ER - 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 - Küppers, Manfred A1 - Schmitt, Dieter A1 - Liner, Susanne A1 - Böhm, Christian A1 - Kanzler, Michael A1 - Veste, Maik T1 - Photosynthetic characteristics and simulation of annual leaf carbon gains of hybrid poplar (Populus nigra L. x P. maximowiczii Henry) and black locust (Robinia pseudoacacia L.) in a temperate agroforestry system T2 - Agroforestry Systems N2 - A leaf net photosynthesis model is presented driven by light and modulated by temperature and air humidity. From this the seasonal variation of CO2 uptake and release could be modelled to estimate the annual carbon fluxes of sun and shade leaves. In fully expanded leaves light is the major factor determining daily carbon balances, and highest observed daily carbon gains in sun leaves amounted to 748.9 mmol CO2 m-2 day-1 in poplar and to 536.3 mmol CO2 m-2 day-1 in black locust, while the annual carbon gains amounted to 46,824 mol CO2 m-2 in black locust and 66,803 mol CO2 m-2 in hybrid poplar. Results obtained via gas exchange measurements and from the leaf model clearly indicate a potentially better growth performance of the poplar compared to black locust on the investigated site. The presented photosynthesis model provides a good and realistic estimation for seasonal carbon balances on the leaf level for both species. Y1 - 2018 U6 - https://doi.org/10.1007/s10457-017-0071-z SN - 0167-4366 SN - 1572-9680 VL - 92 IS - 5 SP - 1267 EP - 1286 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 -