• 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

Stress-induced changes in carbon allocation among metabolite pools influence isotope-based predictions of water use efficiency in Phaseolus vulgaris

Understanding how major food crops respond to environmental stress will expand our capacity to improve food production with growing populations and a changing climate. This study uses chemical and physiological adaptations to heat, water deficit and elevated light stresses in Phaseolus vulgaris L. to identify changes in carbon (C) allocation that, combined with post-photosynthetic fractionation of C isotopes, influences water use efficiency (WUE) predictions. The chemical stress response was explored through changes in C allocation to the carbohydrate and cyclitol pools using GC–triple quadrupole MS. Carbon allocation to the sucrose pool fluctuated significantly among treatments, and the putative osmolytes and osmoprotectants (myo-inositol and D-ononitol) accumulated under stress. Significant osmotic adjustment (P < 0.05), quantified via pressure–volume curve analysis, was detected between control and stress treatments, although this was not attributable to active accumulation of the metabolites. Compound-specific 13C isotope abundance was measured using liquid chromatography isotope ratio MS to predict intrinsic WUE. In contrast to other metabolites measured, the δ13C of the sucrose pool fluctuated according to treatment and was proportional to predicted values based upon modelled Δ13C from gas exchange data. The results suggest that the accuracy and precision of predicting WUE may be enhanced by compound-specific analysis of Δ13C and that changes in the allocation of C among metabolite pools may influence WUE predictions based upon analysis of total soluble C. Overall, the plants appeared to use a range of mechanisms to cope with adverse conditions that could be utilised to improve plant breeding and management strategies.

Lockhart R, Wild B, Richter A, Simonin K, Merchant A
2016 - Functional Plant Biology, 1149-1158

Nitrogen isotope fractionation during N uptake via arbuscular mycorrhizal and ectomycorrhizal fungi into grey alder

Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi affect plant nitrogen (N) dynamics. Plant
N isotope patterns have been used to characterise the contribution of ECM fungi to plant N uptake. By
quantifying and comparing the effects of an AM and an ECM fungus on growth, N uptake and isotopic
composition of one host plant grown at different relative N supply levels, the aim of this study was to
improve the mechanistic understanding of natural 15N abundance patterns in mycorrhizal plants and
their underlying causes.
Grey alders were inoculated with one ECM fungus or one AM fungus or left non-mycorrhizal. Plants
were grown under semi-hydroponic conditions and were supplied with three rates of relative N supply
ranging from deficient to luxurious.
Neither mycorrhizal fungus increased plant growth or N uptake. AM root colonisation had no effect
on whole plant 15N and decreased foliar 15N only under N deficiency. The roots of these plants were
15N-enriched. ECM root colonisation consistently decreased foliar and whole plant 15N.
It is concluded, that both mycorrhizal fungi contributed to plant N uptake into the shoot. Nitrogen
isotope fractionation during N assimilation and transformations in fungal mycelia is suggested to have
resulted in plants receiving 15N-depleted N via the mycorrhizal uptake pathways. Negative mycorrhizal
growth effects are explained by symbiotic resource trade on carbon and N and decreased direct plant N
uptake.
© 2016 Elsevier GmbH. All rights reserved.

2016 - Journal of Plant Physiology, 205: 84-92

Little effects on soil organic matter chemistry of density fractions after seven years of forest soil warming

Rising temperatures enhance microbial decomposition of soil organic matter (SOM) and thereby increase the soil CO2 efflux. Elevated decomposition rates might differently affect distinct SOM pools, depending on their stability and accessibility. Soil fractions derived from density fractionation have been suggested to represent SOM pools with different turnover times and stability against microbial decomposition.

To investigate the effect of soil warming on functionally different soil organic matter pools, we here investigated the chemical and isotopic composition of bulk soil and three density fractions (free particulate organic matter, fPOM; occluded particulate organic matter, oPOM; and mineral associated organic matter, MaOM) of a C-rich soil from a long-term warming experiment in a spruce forest in the Austrian Alps. At the time of sampling, the soil in this experiment had been warmed during the snow-free period for seven consecutive years. During that time no thermal adaptation of the microbial community could be identified and CO2 release from the soil continued to be elevated by the warming treatment. Our results, which included organic carbon content, total nitrogen content, δ13C, Δ14C, δ15N and the chemical composition, identified by pyrolysis-GC/MS, showed no significant differences in bulk soil between warming treatment and control. Surprisingly, the differences in the three density fractions were mostly small and the direction of warming induced change was variable with fraction and soil depth. Warming led to reduced N content in topsoil oPOM and subsoil fPOM and to reduced relative abundance of N-bearing compounds in subsoil MaOM. Further, warming increased the δ13C of MaOM at both sampling depths, reduced the relative abundance of carbohydrates while it increased the relative abundance of lignins in subsoil oPOM. As the size of the functionally different SOM pools did not significantly change, we assume that the few and small modifications in SOM chemistry result from an interplay of enhanced microbial decomposition of SOM and increased root litter input in the warmed plots. Overall, stable functional SOM pool sizes indicate that soil warming had similarly affected easily decomposable and stabilized SOM of this C-rich forest soil.

 
Schnecker J, Borken W, Schindlbacher A, Wanek W
2016 - Soil Biology and Biochemistry, 103: 300-307

Lecture series

LC-MS Approaches in Metabolomics

Gunda Köllensperger, Prof.
University of Vienna, Department of Analytical Chremistry
09.12.2016
13:15 h
Seminar Room 'Ökologie', UZA 1