• Global Warming:

    the threat of a permafrost Carbon – climate feedback

  • We develop and improve

    stable isotopes techniques for ecological applications

  • Plants, fungi and bacteria interact

    at the root-soil interface

  • Probing the future:

    Climate Change experiments

  • Soil is fundamental to human life

  • Tropical rainforests

    hold the key to global net primary productivity

TER News

Latest publications

Cutting out the middle clam: lucinid endosymbiotic bacteria are also associated with seagrass roots worldwide

Seagrasses and lucinid bivalves inhabit highly reduced sediments with elevated sulphide concentrations. Lucinids house symbiotic bacteria (Ca. Thiodiazotropha) capable of oxidising sediment sulphide, and their presence in sediments has been proposed to promote seagrass growth by decreasing otherwise phytotoxic sulphide levels. However, vast and productive seagrass meadows are present in ecosystems where lucinids do not occur. Hence, we hypothesised that seagrasses themselves host these sulphur-oxidising Ca. Thiodiazotropha that could aid their survival when lucinids are absent. We analysed newly generated and publicly available 16S rRNA gene sequences from seagrass roots and sediments across 14 seagrass species and 10 countries and found that persistent and colonising seagrasses across the world harbour sulphur-oxidising Ca. Thiodiazotropha, regardless of the presence of lucinids. We used fluorescence in situ hybridisation to visually confirm the presence of Ca. Thiodiazotropha on roots of Halophila ovalis, a colonising seagrass species with wide geographical, water depth range, and sedimentary sulphide concentrations. We provide the first evidence that Ca. Thiodiazotropha are commonly present on seagrass roots, providing another mechanism for seagrasses to alleviate sulphide stress globally.

Martin BC, Middleton JA, Fraser MW, Marshall IPG, Scholz VV, Hausl B, Schmidt H
2020 - The ISME Journal, in press

Climatic and edaphic controls over tropical forest diversity and vegetation carbon storage

Tropical rainforests harbor exceptionally high biodiversity and store large amounts of carbon in vegetation biomass. However, regional variation in plant species richness and vegetation carbon stock can be substantial, and may be related to the heterogeneity of topoedaphic properties. Therefore, aboveground vegetation carbon storage typically differs between geographic forest regions in association with the locally dominant plant functional group. A better understanding of the underlying factors controlling tropical forest diversity and vegetation carbon storage could be critical for predicting tropical carbon sink strength in response to projected climate change. Based on regionally replicated 1-ha forest inventory plots established in a region of high geomorphological heterogeneity we investigated how climatic and edaphic factors affect tropical forest diversity and vegetation carbon storage. Plant species richness (of all living stems >10 cm in diameter) ranged from 69 to 127 ha−1 and vegetation carbon storage ranged from 114 to 200 t ha−1. While plant species richness was controlled by climate and soil water availability, vegetation carbon storage was strongly related to wood density and soil phosphorus availability. Results suggest that local heterogeneity in resource availability and plant functional composition should be considered to improve projections of tropical forest ecosystem functioning under future scenarios.

Hofhansl F, Chacón-Madrigal E, Fuchslueger L, Jenking D, Morera-Beita A, Plutzar C, Silla F, Andersen KM, Buchs DM, Dullinger S, Fiedler K, Franklin O, Hietz P, Huber W, Quesada CA, Rammig A, Schrodt F, Vincent AG, Weissenhofer A, Wanek W
2020 - Scientific Reports, 10: Article 5066

Nitrogen Isotope Fractionation During Archaeal Ammonia Oxidation: Coupled Estimates From Measurements of Residual Ammonium and Accumulated Nitrite

The naturally occurring nitrogen (N) isotopes, 15N and 14N, exhibit different reaction rates during many microbial N transformation processes, which results in N isotope fractionation. Such isotope effects are critical parameters for interpreting natural stable isotope abundances as proxies for biological process rates in the environment across scales. The kinetic isotope effect of ammonia oxidation (AO) to nitrite (NO2), performed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), is generally ascribed to the enzyme ammonia monooxygenase (AMO), which catalyzes the first step in this process. However, the kinetic isotope effect of AMO, or εAMO, has been typically determined based on isotope kinetics during product formation (cumulative product, NO2) alone, which may have overestimated εAMO due to possible accumulation of chemical intermediates and alternative sinks of ammonia/ammonium (NH3/NH4+). Here, we analyzed 15N isotope fractionation during archaeal ammonia oxidation based on both isotopic changes in residual substrate (RS, NH4+) and cumulative product (CP, NO2) pools in pure cultures of the soil strain Nitrososphaera viennensis EN76 and in highly enriched cultures of the marine strain Nitrosopumilus adriaticus NF5, under non-limiting substrate conditions. We obtained εAMO values of 31.9–33.1‰ for both strains based on RS (δ15NH4+) and showed that estimates based on CP (δ15NO2) give larger isotope fractionation factors by 6–8‰. Complementary analyses showed that, at the end of the growth period, microbial biomass was 15N-enriched (10.1‰), whereas nitrous oxide (N2O) was highly 15N depleted (−38.1‰) relative to the initial substrate. Although we did not determine the isotope effect of NH4+ assimilation (biomass formation) and N2O production by AOA, our results nevertheless show that the discrepancy between εAMO estimates based on RS and CP might have derived from the incorporation of 15N-enriched residual NH4+ after AMO reaction into microbial biomass and that N2O production did not affect isotope fractionation estimates significantly.

Mooshammer M, Alves RJE, Bayer B, Melcher M, Stieglmeier M, Jochum L, Rittmann SK-MR, Watzka M, Schleper C, Herndl G, Wanek W
2020 - Frontiers in microbiology, 11: Article 1710

Lecture series

Microbial ecology of nitrogen cycling in paddy soils

Yong-Guan Zhu
Research Centre for Eco-Environmental Sciences & Institute of Urban Environment, Chinese Academy of Sciences
09:00 h
Lecture Hall HS 5, UZA2 (Geocentre), Althanstrasse 14, 1090 Vienna

How to meet the Paris 2°C target: Which are the main constraints that will need to be overcome?

Ivan Janssens
Centre of Excellence of Global Change Ecology, University of Antwerp, Belgium
12:00 h
Lecture Hall HS2 (UZA 1), Althanstraße 14, 1090 Vienna

Soil C dynamics –when are microbial communities in control?

Naoise Nunan
Institute of Ecology and Environmental Sciences IEES Paris, France
12:00 h
Lecture Hall HS2 (UZA 1), Althanstraße 14, 1090 Vienna