Papers by Hermann Jungkunst
HAL (Le Centre pour la Communication Scientifique Directe), May 15, 2008
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Shifting perspectives on natural ecosystems in the high Andes
Highly resolved thermal analysis as a tool for soil organic carbon fractionation - methodological considerations
EGUGA, Apr 1, 2015
Scientific Reports, Mar 20, 2023
Soils contain significantly more carbon than the atmosphere, hence we should understand how best ... more Soils contain significantly more carbon than the atmosphere, hence we should understand how best to stabilize it. Unfortunately, the role of human interventions on soil organic carbon (SOC) persistence in the Anthropocene remains vague, lacking adequate sites that allow unbiased direct comparisons of pristine and human influenced soils. Here we present data from a unique study system in the High Andes that guarantees pristineness of the reference sites by physical inaccessibility through vertical cliffs. By comparing the isotopic signatures of SOC, mineral related carbon stabilization, and soil nutrient status across grazed versus pristine soils, we provide counterintuitive evidence that thousands of years of pastoralism increased soil C persistence. Mineral associated organic carbon (MAOC) was significantly higher in pastures. Land use increased poorly crystalline minerals (PCM's), of which aluminum correlated best with MAOC. On the other hand, human's acceleration of weathering led to acidification and higher losses of cations. This highlights a dilemma of lower soil quality but higher persistence of SOC due to millennia of pastoralism. The dynamics of soil genesis in the Anthropocene needs better understanding, but if human-induced weathering proves generally to promote soil carbon persistence it will need to be included in climate-soil feedback projections. Humans dominate soil development in the ongoing Anthropocene 1-4 but resulting biogeochemical processes are yet to be fully understood. There are examples of positive human influence on soil organic carbon (SOC) storages most prominently Terra Preta, and Plaggic or Hortic Anthrosols 5,6 . However, process understanding of carbon (C) persistence in soils remains one of the greater challenges to understand anthropogenic modifications adding to climate change science 7,8 . To separate human influences from other factors, a comparison to pristine counterparts is required, but these barely exist on our planet 2 . The alternative of studying processes happening in soils that have been taken out of use leads to different insights. What is needed, then, is the ability to directly compare pristine, reference sites with sites that have been influenced by historical human activities like grazing. Such a unique study system exists in the High Andes, where intensive studies have shown that soilforming processes would have played out similarly in the accessible grazed versus inaccessible pristine sites in the absence of pastoralism . Soils formed from very similar parent material and erosion was ruled out. Physical inaccessibility by vertical cliffs guaranteed that pristine sites were never grazed, therefore any differences in soil properties, like lower exchangeable cation nutrients, could be related to human influence by grazing 9,10 . Like in most other studies total C stocks of pasture soils did not differ significantly from soil C of comparably less disturbed forest stands but were even higher 11 . However, carbon quality or persistence, the cause for relatively high carbon stocks under pastures, was yet to be studied in that unique Andean system. To unravel the reasons
Environmental Science and Pollution Research, May 22, 2021
Phosphate fertilization contributes to an input of uranium (U) in agricultural soils. Although it... more Phosphate fertilization contributes to an input of uranium (U) in agricultural soils. Although its accumulation and fate in agricultural soils have been previously studied, its colloidal transport and accumulation along slopes through erosion have been studied to a lesser extent in viticulture soils. To bridge this gap, the contents and potential mobility of U were investigated in vineyard model soils in the Rhineland-Palatinate region, Germany. In addition to elevated U contents, U was expected to associate with colloids and subject to erosion, thus accumulating on slope foots and in soils with fine structure, and reflecting a greater variability. Moreover, another expectation was the favorable erosion/mobility of U in areas with greater carbonate content. This was tested in three regional locations, at different slope positions and through soil horizon depths, with a total of 57 soil samples. The results show that U concentrations (0.48-1.26 ppm) were slightly higher than proximal non-agricultural soils (0.50 ppm), quite homogenous along slope positions, and slightly higher in topsoils. Assuming a homogeneous fertilization, the vertical translocation of U in soil was most probably higher than along the slope by erosion. In addition, carbonate content and soil texture correlated with U concentrations, whereas other parameters such as organic carbon and iron contents did not. The central role of carbonate and soil texture for the prediction of U content was confirmed using decision trees and elastic net, although their limited prediction power suggests that a larger sample size with a larger range of U content is required to improve the accuracy. Overall, we did not observe neither U nor colloids accumulating on slope foots, thus suggesting that soils are aggregate-stable. Lastly, we suggested considering further soil parameters (e.g., Ca 2+ , phosphorus, alkali metals) in future works to improve our modelling approach. Overall, our results suggest U is fortunately immobile in the studied locations.
How root exudates alter gas diffusion in soil
EGU General Assembly Conference Abstracts, Apr 1, 2019
Does deciduous tree species identity affect carbon storage in temperate soils
EGUGA, Apr 1, 2015
Journal of Plant Nutrition and Soil Science, May 4, 2021
Background: Gaseous matter exchanges in soil are determined by the connectivity of the pore syste... more Background: Gaseous matter exchanges in soil are determined by the connectivity of the pore system which is easily clogged by fresh root exudates. However, it remains unclear how a hydrogel (e.g., mucilage) affects soil pore tortuosity and gas diffusion properties when drying. Aims: The aim of this viewpoint study is to extend the understanding of gas exchange processes in the rhizosphere by (a) relating it to the patterns formed by drying mucilage within pore space and (b) to give a concept of the effect of drying mucilage on soil gas diffusivity using the combination of experimental evidence and simulations. Methods: To describe the effect of mucilage on soil gas exchanges, we performed gas diffusion experiments on dry soil-mucilage samples and took images of glass beads mixed with mucilage to visualize the formation of mucilage after drying, using Environmental Scanning Electron Microscopy. Finally, we set up simulations to characterize the geometric distribution of mucilage within soil during the drying process. Results: Experiments of gas diffusion show that mucilage decreases gas diffusion coefficient in dry soil without significantly altering bulk density and porosity. Electron microscopy indicates that during drying mucilage forms filaments and interconnected structures throughout the pore space reducing gas phase connectivity. The evolution of these geometric structures is explained via pore scale modelling based on identifying the elastic strength of rhizodeposition during soil drying. Conclusion: Our results suggest that releasing mucilage may be a plant adaption strategy to actively alter gas diffusion in soil.
Nitrification inhibition by polyphenols from invasive <i>Fallopia japonica</i> under copper stress
Journal of Plant Nutrition and Soil Science, Nov 18, 2022
BackgroundThe invasive plant species Fallopia japonica is suspected to use polyphenols as a novel... more BackgroundThe invasive plant species Fallopia japonica is suspected to use polyphenols as a novel weapon to inhibit nitrification in soil. Both specific polyphenols and their entry pathways are yet to be determined. As plants may increase the production of polyphenols under copper (Cu) stress, an additive effect can be expected in contaminated (riparian) areas.AimsThis study aimed to identify the entry pathways of total and specific polyphenols in F. japonica and to test whether polyphenols inhibit nitrification with Cu contamination.MethodsCombining F. japonica and a Cu gradient in a 2‐year mesocosm experiment, total polyphenol, emodin, and resveratrol concentrations were analyzed in the plant (roots, root exudates, vital and senescent leaves) and soil (rhizosphere, non‐rooted soil) representing different entry pathways. We measured the potential nitrification rate (PNR) under stress caused by F. japonica and Cu as well as the response of PNR under resveratrol and emodin addition.ResultsEmodin and resveratrol were detected in all plant tissues. Emodin concentrations significantly increased in senescent leaves under Cu stress, while no Cu effect was observed for resveratrol or total polyphenols. Resveratrol decreased the PNR. The stressors had neither a synergistic nor additive effect. Nitrification inhibition was lower in the rhizosphere compared to the non‐rooted soil, suggesting that F. japonica reduced nitrate availability for co‐occurring plants.ConclusionsJoint occurrence of F. japonica and Cu did not amplify the PNR inhibition over the individual effect. Our study emphasizes the effectiveness of F. japonica in inhibiting the PNR in invaded riparian ecosystems with potentially negative effects on biodiversity.
Frontiers in Climate
Humans play an interconnecting role in social-ecological systems (SES), they are part of these sy... more Humans play an interconnecting role in social-ecological systems (SES), they are part of these systems and act as agents of their destruction and regulation. This study aims to provide an analytical framework, which combines the concept of SES with the concept of tipping dynamics. As a result, we propose an analytical framework describing relevant dynamics and feedbacks within SES based on two matrixes: the “tipping matrix” and the “cross-impact matrix.” We take the Southwestern Amazon as an example for tropical regions at large and apply the proposed analytical framework to identify key underlying sub-systems within the study region: the soil ecosystem, the household livelihood system, the regional social system, and the regional climate system, which are interconnected through a network of feedbacks. We consider these sub-systems as tipping elements (TE), which when put under stress, can cross a tipping point (TP), resulting in a qualitative and potentially irreversible change of ...
Copper Retention Influenced by an Invasive and a Native Plant in Riparian Soil
Scientific Reports
Soils contain significantly more carbon than the atmosphere, hence we should understand how best ... more Soils contain significantly more carbon than the atmosphere, hence we should understand how best to stabilize it. Unfortunately, the role of human interventions on soil organic carbon (SOC) persistence in the Anthropocene remains vague, lacking adequate sites that allow unbiased direct comparisons of pristine and human influenced soils. Here we present data from a unique study system in the High Andes that guarantees pristineness of the reference sites by physical inaccessibility through vertical cliffs. By comparing the isotopic signatures of SOC, mineral related carbon stabilization, and soil nutrient status across grazed versus pristine soils, we provide counterintuitive evidence that thousands of years of pastoralism increased soil C persistence. Mineral associated organic carbon (MAOC) was significantly higher in pastures. Land use increased poorly crystalline minerals (PCM’s), of which aluminum correlated best with MAOC. On the other hand, human’s acceleration of weathering le...
SystemLink: Moving beyond Aquatic–Terrestrial Interactions to Incorporate Food Web Studies
Limnology and Oceanography Bulletin
Influence of soil geomorphic factors on vegetation patterns in a model white sands ecosystem complex
CATENA
The Nitrogen Games – the invasive success of Fallopia japonica
The high invasion success of Fallopia japonica in Europe and North America is related to its nich... more The high invasion success of Fallopia japonica in Europe and North America is related to its niche construction strategy. A hotly debated and prominent possibility is that F. japonica uses weapons for chemical niche construction, which could have considerable consequences for plant nutrition and ecosystem functioning. At least one of its phenolic compounds is capable of inhibiting nitrification and nitrification is actually lower in F. japonica invaded systems. It was assumed that F. japonica has a higher affinity for ammonium and can therefore outcompete native plants that prefer nitrate. However, the uptake of ammonium by F. japonica has only been minimally studied and it has been shown that nitrogen-use efficiency seems to be the main trait. In a lab study using stable isotope labelling we tested nitrogen and carbon uptake of F. japonica against the strongest native competitor in European riparian zones U. dioica. We hypothesized that F. japonica has a greater potential to take u...
Tipping the Amazon Rainforest: Regional deforestation and land-climate interactions
The Amazon rainforest is globally relevant and is considered a tipping element in the global clim... more The Amazon rainforest is globally relevant and is considered a tipping element in the global climate system. Studies suggest that deforestation in the Amazon by around 30% may disturb regional convective rain patterns, which could increase drought frequencies and intensities locally and, may activate a cascade of tipping elements in the global climate system. Here, we aim to assess the relationship between deforestation and climate responses at a convection-permitting scale by employing a non-hydrostatic mesoscale Weather Research and Forecasting (WRF) model. For this, we first developed a spatially explicit deforestation model for the South-Western Amazon to see an effect of deforestation intensity ranging from 10% to 60%, and then based on 30% deforestation, we further see the role of deforestation pattern (e.g. deforestation alongside the roads, as a large single or small multiple circular plots, and their geographical positions), and shifts to anticipated land use. Then for each...
A potential bias using averaged climate projection multi model ensembles when forecasting nitrous oxide emissions from soils under climate change
Increasing extreme events and drastic shifts in the variability, intensity and frequency of droug... more Increasing extreme events and drastic shifts in the variability, intensity and frequency of droughts, heavy precipitation and frost are predicted to accompany further climate change. It is most likely that an increasing occurrence of such events will be accompanied by soil feedback of GHG emissions, particularly of nitrous oxide (N2O) known to be an extremely sensitive GHG. The increase in extreme events can lead to an increased occurrence of short-term emission pulses, referred to as ‘hot moments’, which can contribute significantly to the total annual N2O emission balance. To account for this potential feedback to the climate system, biogeochemical models driven by climate projections of multi-model ensembles (CPM) can be used to generate scenarios observing future trends in N2O emission behavior. Most commonly, the CPM average is used as climate input in biogeochemical models. While averaging CPM’s may provide the best overall comparison with real mean climate change, it poses th...
The Western Amazon social-ecological system at risk of tipping: A transdisciplinary modelling approach
The Amazon rainforest is a tipping element of the global climate system due to its high carbon st... more The Amazon rainforest is a tipping element of the global climate system due to its high carbon storage potential and its flying rivers providing rain for South America. Studies suggest that land use and land cover change (LUCC) in the Amazon, i.e. deforestation, strongly disturb regional convectional rain pattern, which could lead to an increase of drought frequencies and intensities. Under increasing drought stress, the evergreen tropical rainforest may transform into a seasonal forest or even a savannah ecosystem. Such a transformation would likely activate the Amazon tipping element and may affect global climate change by triggering other critical tipping elements of the global climate system. Here we present our transdisciplinary research approach in the Western Amazon rainforest developed in context of the PRODIGY research project. We apply a social-ecological system approach to account for the dynamic interactions and feedbacks between people and nature, which could either st...
Mapping bark pH to better understand the cortisphere
AGUFM, Dec 1, 2016
Regionally Diverse Land-Use Driven Feedbacks from Soils to the Climate System
Soil and Climate, 2018
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Papers by Hermann Jungkunst