@misc{FischerKholiavkoSchaafetal., author = {Fischer, Thomas and Kholiavko, Tatiana and Schaaf, Wolfgang and Veste, Maik}, title = {Soil respiration responses of moss and lichen biocoenoses to moderate and severe rain events after summer drought in a temperate early-successional ecosystem}, series = {Ecohydrology}, volume = {16}, journal = {Ecohydrology}, number = {7}, issn = {1936-0592}, doi = {10.1002/eco.2578}, abstract = {It is commonly accepted that CO2 efflux increases with soil water content in aerated soils and that rewetting after periods of soil drying can result in respiration pulses. It has further been shown that soil pores may become water logged which can impede soil gas exchange. The present study aimed to quantify the carbon response of moss (Polytrichum piliferum) and lichen (Cladonia coniocraea) biocoenoses to different quantities of rain in an artificial catchment, which granted that the starting point of the development of both biocoenoses was the same. To address this aim, we conducted in situ soil moisture and soil respiration measurements, where soil respiration was hypothesised to emerge from a cryptogamic vegetation layer and from mineral soil beneath. We found that higher water-holding capacity of the moss layer and higher accumulation of organic matter in the upper mineral soil under mosses result in higher amounts of water stored near the surface. As a consequence, evaporation of water as well as pulses of CO2 efflux after moderate rain following a period of drought were higher in the moss biocoenosis, where the upper mineral soil was of key importance. In contrast, the lichen biocoenosis facilitated penetration of rainwater into the deep soil. Superimposing rewetting pulses, near-saturation of soil pores with water after severe rain resulted in gas exchange inhibition and diminished soil respiration until subsequent aeration in both biocoenoses}, language = {en} } @misc{MaWeberKratzetal., author = {Ma, Yunyao and Weber, Bettina and Kratz, Alexandra and Raggio, Jos{\´e} and Colesie, Claudia and Veste, Maik and Bader, Maaike Y. and Porada, Philipp}, title = {Exploring environmental and physiological drivers of the annual carbon budget of biocrusts from various climatic zones with a mechanistic data-driven model}, series = {Biogeosciences}, volume = {20}, journal = {Biogeosciences}, number = {13}, issn = {1726-4189}, doi = {10.5194/bg-20-2553-2023}, pages = {2553 -- 2572}, abstract = {Biocrusts are a worldwide phenomenon, contributing substantially to ecosystem functioning. Their growth and survival depend on multiple environmental factors, including climatic ones, and the relations of these factors to physiological processes. Responses of biocrusts to individual environmental factors have been examined in a large number of field and laboratory experiments. These observational data, however, have rarely been assembled into a comprehensive, consistent framework that allows quantitative exploration of the roles of multiple environmental factors and physiological properties for the performance of biocrusts, in particular across climatic regions. Here we used a data-driven mechanistic modelling framework to simulate the carbon balance of biocrusts, a key measure of their growth and survival. We thereby assessed the relative importance of physiological and environmental factors for the carbon balance at six study sites that differ in climatic conditions. Moreover, we examined the role of seasonal acclimation of physiological properties using our framework, since the effects of this process on the carbon balance of biocrusts are poorly constrained so far. We found substantial effects of air temperature, CO2 concentration, and physiological parameters that are related to respiration on biocrust carbon balance, which differ, however, in their patterns across regions. The ambient CO2 concentration is the most important factor for biocrusts from drylands, while air temperature has the strongest impact at alpine and temperate sites. Metabolic respiration cost plays a more important role than optimum temperature for gross photosynthesis at the alpine site; this is not the case, however, in drylands and temperate regions. Moreover, we estimated a small annual carbon gain of 1.5  by lichen-dominated biocrust and 1.9  by moss-dominated biocrust at a dryland site, while the biocrusts lost a large amount of carbon at some of the temperate sites (e.g. -92.1 for lichen-dominated and -74.7  for moss-dominated biocrust). These strongly negative values contradict the observed survival of the organisms at the sites and may be caused by the uncertainty in environmental conditions and physiological parameters, which we assessed in a sensitivity analysis. Another potential explanation for this result may be the lack of acclimation in the modelling approach, since the carbon balance can increase substantially when testing for seasonally varying parameters in the sensitivity analysis. We conclude that the uncertainties in air temperature, CO2 concentration, respiration-related physiological parameters, and the absence of seasonal acclimation in the model for humid temperate and alpine regions may be a relevant source of error and should be taken into account in future approaches that aim at estimating the long-term biocrust carbon balance based on ecophysiological data.}, language = {en} } @misc{OpreiSchreckingerKholiavkoetal., author = {Oprei, Anna and Schreckinger, Jos{\´e} and Kholiavko, Tatiana and Frossard, Aline and Mutz, Michael and Risse-Buhl, Ute}, title = {Long-term functional recovery and associated microbial community structure after sediment drying and bedform migration}, series = {Frontiers in Ecology and Evolution}, volume = {Vol. 11}, journal = {Frontiers in Ecology and Evolution}, issn = {2296-701X}, doi = {10.3389/fevo.2023.1112519}, abstract = {Climate change and erosion from agricultural areas cause increased drying periods and bedform migration of riverbeds, respectively, worldwide. Both sediment drying and bedform migration can independently stress the microbial community residing in the riverbed. Here, we investigated the microbial response after exposure to these stressors with a focus on long-term recovery. We conducted an in situ experiment to investigate the long-term (8 months) functional and structural recovery of benthic microbial communities from either sediment drying (episodic severe stressor) or bedform migration (frequent moderate stressor). Stressed sediment associated communities were rewetted (dried sediments) and immobilized (migrated sediments) and exposed in the River Spree (north-eastern Germany) to initiate the recovery process. We then evaluated the microbial function (community respiration, net community production and extracellular enzymatic activities) as well as the bacterial, fungal and diatom community structure (16S rRNA gene and ITS region metabarcoding, and microscopic diatom morphotype classification). We observed different recovery times for community respiration (less than 7 days) and gross primary production (more than 5 months), implying a shift toward net heterotrophy in the first few months after stress exposure. Similarly, we observed a strong autotrophic community response (particularly associated with the diatoms Navicula and Fragilaria), especially in migrated sediments. The bacterial and fungal community response to sediment drying was stronger than to bedform migration (particularly associated with the bacterium Flavobacterium and the fungi Alternaria sp. and Aureobasidium pullulans). Our results show that sediment drying and bedform migration had a significant impact on the microbial community function and structure, which persisted for several months after the stress. Due to the surprising long period of recovery, successive stress events combined with seasonal effects will likely hamper the ongoing recovery process with severe alterations to the microbial function and structure. These findings extend the concept of ecosystem resilience and stability on the dimensions of timescale and seasonal environmental variations. Legacy effects are expected to play a key role when facing future stress.}, language = {en} } @misc{PohlWinklerRuecknageletal., author = {Pohl, Lydia and Winkler, Pauline and R{\"u}cknagel, Jan and Gerwin, Werner}, title = {Charakterisierung und Stabilit{\"a}t organo-mineralischer Bodenhilfsstoffe aus Eisenhydroxidschl{\"a}mmen}, series = {Jahrestagung der Deutschen Bodenkundlichen Gesellschaft (DBG) 2023 "B{\"o}den - divers \& multifunktional" 2. - 8. September 2023 in Halle (Saale)}, journal = {Jahrestagung der Deutschen Bodenkundlichen Gesellschaft (DBG) 2023 "B{\"o}den - divers \& multifunktional" 2. - 8. September 2023 in Halle (Saale)}, pages = {S. 534}, language = {de} }