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    from summer 2021

  • 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

An unexpected source of nitrogen for root uptake: positively charged amino acids dominate soil diffusive nitrogen fluxes. Commentary.


This article is a Commentary on Homyak et al. (2021), 231: 2162–2173.


 


Soils typically contain a large variety of nitrogen (N) forms, including inorganic N and a range of organic N compounds of varying molecular size (Warren, 2013). Inorganic N was long been considered to constitute the main source of N for plants, but this view has changed considerably since plants were shown to be capable of directly taking up and metabolizing organic N forms, including amino acids, peptides, proteins and quaternary ammonium compounds (Näsholm et al., 2009; Warren, 2013). Amino acid uptake especially has been demonstrated in every plant species studied thus far and the underlying uptake mechanisms have been investigated extensively (Näsholm et al., 2009; Narcy et al., 2013). Yet even if plants have the potential to take up amino acids, those N forms first have to be bioavailable and have to be consistently replenished at root surfaces. However, reliably estimating such N availability is challenging due to the sheer complexity of soils and plant root systems.

Inselbacher E, Wanek W
2021 - New Phytologist, 231: 2104-2106

Glacier forelands reveal fundamental plant and microbial controls on short-term ecosystem nitrogen retention

 

  1. Human activities have massively increased the amount of reactive nitrogen in the biosphere, which is leading to increased nitrogen (N) inputs in terrestrial ecosystems. The retention of N is a crucial ecosystem function of both managed and natural ecosystems, and there is a long history of experimental, observational, and conceptual studies identifying its major controls. Yet, the plant and soil microbial controls on the retention of added N remain elusive.
  2. Here, we used three ecosystem chronosequences in front of retreating glaciers in the European Alps to test our hypothesis that the retention of added reactive 15N increases as succession proceeds, and to identify the plant and microbial controls on ecosystem N retention.
  3. We found that the uptake and retention of N did not change during succession, despite consistent changes in plant, soil, and microbial properties with increasing time since deglaciation. Instead, we found that plant and microbial properties that remained constant during succession controlled 15N uptake and retention: low root and microbial C/N ratios, as well as high root biomass, increased plant and microbial uptake of added N. In addition, high soil concentrations of nitrate and ammonium reduced the uptake of N in microbes and roots, respectively.
  4. Synthesis. Our results demonstrate that plant and microbial N demand, as well as soil N availability, drive the short-term retention of added N during succession in glacier forelands. This finding represents an advance in our understanding of the fundamental controls on ecosystem N retention and the role of plant-microbial interactions in this process. Such understanding is crucial for predicting and mitigating the response of terrestrial ecosystems to the ever-increasing amounts of reactive N in the biosphere.

 

  1. Human activities have massively increased the amount of reactive nitrogen in the biosphere, which is leading to increased nitrogen (N) inputs in terrestrial ecosystems. The retention of N is a crucial ecosystem function of both managed and natural ecosystems, and there is a long history of experimental, observational, and conceptual studies identifying its major controls. Yet, the plant and soil microbial controls on the retention of added N remain elusive.
  2. Here, we used three ecosystem chronosequences in front of retreating glaciers in the European Alps to test our hypothesis that the retention of added reactive 15N increases as succession proceeds, and to identify the plant and microbial controls on ecosystem N retention.
  3. We found that the uptake and retention of N did not change during succession, despite consistent changes in plant, soil, and microbial properties with increasing time since deglaciation. Instead, we found that plant and microbial properties that remained constant during succession controlled 15N uptake and retention: low root and microbial C/N ratios, as well as high root biomass, increased plant and microbial uptake of added N. In addition, high soil concentrations of nitrate and ammonium reduced the uptake of N in microbes and roots, respectively.
  4. Synthesis. Our results demonstrate that plant and microbial N demand, as well as soil N availability, drive the short-term retention of added N during succession in glacier forelands. This finding represents an advance in our understanding of the fundamental controls on ecosystem N retention and the role of plant-microbial interactions in this process. Such understanding is crucial for predicting and mitigating the response of terrestrial ecosystems to the ever-increasing amounts of reactive N in the biosphere.
de Vries F, Thion C, Bahn M, Pinto BB, Cecillon S, Frey B, Grant H, Nicol G, Wanek W, Prosser J, Bardgett R
2021 - Journal of Ecology, 109: 3710-3723

Isotopic Elucidation of Microbial Nitrogen Transformations in Forest Soils

Soil nitrogen (N) transformations between labile N forms (extractable organic N [EON], ammonium [NH4+], and nitrate [NO3]) regulate soil N availability. However, it has long been difficult to quantify the transformations of total soil organic and labile N forms in soils, which has left large uncertainties in evaluating atmospheric N deposition effects on soil N dynamics. Based on concentrations and natural abundances of N isotopes of soil organic N, EON, NH4+, and NO3 across 11 forests with variant N deposition levels, we established a quantitative isotopic framework to estimate the fractions of soil N depolymerization (fD), mineralization (fM), nitrification (fN), and of NO3 losses (fL) via denitrification and leaching. Based on the fractions, the gross production and storage of corresponding soil labile N were estimated for forests of China and Japan. We found that fDfM, and fN increased, while fL decreased with the increase of N deposition among the study forests. And the contribution of denitrification (relative to the NO3 leaching) to total NO3 losses also increased with increasing N deposition. Our method provides new and straightforward insights into the present soil N transformations and allows to evaluate the soil N status. These findings are useful for modeling forest N cycles under different N deposition regimes.

Xu S-Q, Liu X-Y, Sun Z-C, Hu C-C, Wanek W, Koba K
2021 - Global Biogeochemical Cycles, 35: Article e2021GB00707

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
27.06.2019
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
15.11.2018
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
25.10.2018
12:00 h
Lecture Hall HS2 (UZA 1), Althanstraße 14, 1090 Vienna