• Centre for Microbiology and Environmental Systems Science

  • CUBE - Computational Systems Biology

  • DOME - Microbial Ecology

  • EDGE - Environmental Geosciences

  • TER - Terrestrial Ecosystem Research


Latest publications

Broad- and small-scale environmental gradients drive variation in chemical, but not morphological, leaf traits of vascular epiphytes

  1. Variation in leaf functional traits along environmental gradients can reveal how vascular epiphytes respond to broad- and small-scale environmental gradients. Along elevational gradients, both temperature and precipitation likely play an important role as drivers of leaf trait variation, but these traits may also respond to small-scale changes in light, temperature and humidity along the vertical environmental gradient within forest canopies. However, the relative importance of broad- and small-scale environmental gradients as drivers of variation in leaf functional traits of vascular epiphytes is poorly understood.
  2. Here, we examined variation in morphological and chemical leaf traits of 102 vascular epiphyte species spanning two environmental gradients along Cofre de Perote mountain in Mexico: (i) a broad-scale environmental gradient approximated by elevation as well as by species' lower and upper elevational limits, and (ii) small-scale environmental gradients using the relative height of attachment of an epiphyte on a host tree as a proxy for variation in environmental conditions within the forest canopy. We also assessed whether variation in morphological and chemical leaf traits along these gradients was consistent across photosynthetic pathways (CAM and C3).
  3. Broad- and small-scale environmental gradients explained more variation in chemical traits (marginal R2: 11%–89%) than in morphological traits (marginal R2: 2%–31%). For example, leaf carbon isotope signatures (δ13C), which reflects water-use efficiency, varied systematically across both environmental gradients, suggesting a decrease in water-use efficiency with increasing lower and upper elevational limits and an increase in water-use efficiency with relative height of attachment. The influence of lower and upper elevational limits on trait variation differed between photosynthetic pathways, except for leaf dry matter content and leaf nitrogen-to-phosphorus ratio. Contrary to our expectations, broad- and small-scale environmental gradients explained minimal variation in morphological leaf traits, suggesting that environmental conditions do not constrain morphological leaf trait values of vascular epiphytes.
  4. Our findings suggest that assessing multiple drivers of leaf trait variation among photosynthetic pathways is key for disentangling the mechanisms underlying responses of vascular epiphytes to environmental conditions.
Guzmán-Jacob V, Guerrero-Ramírez NR, Craven D, Paterno GB, Taylor A, Kromer T, Wanek W, Zotz G, Kreft H
2022 - Functional Ecology, 36: 1858-1872

Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil

Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the climate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein2016Shi et al.2018). Using natural geothermal soil warming gradients of up to +6.4C in subarctic grasslands (Sigurdsson et al.2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (−2.8 t ha−1C−1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (>50 years) warming revealed that all SOC stock reduction occurred within the first 5 years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon–climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions and that SOC stock reduction was only visible in topsoil (0–10 cm). SOC stocks in subsoil (10–30 cm), where plant roots were absent, showed apparent conservation after >50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

Verbrigghe N, Leblans NIW, Sigurdsson BD, Vicca S, Fang C, Fuchslueger L, Soong JL, Weedon JT, Poeplau C, Ariza-Carricondo C, Bahn M, Guenet B, Gundersen P, Gunnarsdóttir GE, Kätterer T, Liu Z, Maljanen M, Marañon-Jimenez S, Meeran K, Oddsdóttir ES, Ostonen I, Schiestl RH, Richter A, Sardans J, Sigurðsson P, Torn MS, Van Bodegom PM, Verbruggen E, Walker TWN, Wallander H, Janssens IA
2022 - Biogeosciences, 19: 3381-3393

Limnospira fusiformis harbors dinitrogenase reductase (nifH)-like genes, but does not show N2 fixation activity

East African soda lakes (EASLs), some of them world-renowned for their large flocks of flamingos, range amongst the most productive aquatic ecosystems worldwide. The non-heterocytous filamentous cyanobacterium Limnospira fusiformis (formerly Arthrospira fusiformis or Spirulina platensis), forming almost unialgal blooms, is supposed to be a key driver in those ecosystems and is gaining increasing attention because of its nutritional value. Compared to phosphorus and carbon availability, these lakes show reduced nitrogen supply. We studied the possibility of molecular nitrogen (N2) fixation in Limnospira, as contradictory statements have been published, and some closely related taxa were confirmed as N2 fixers (diazotrophs). We cultivated nine isolates originating from various EASLs under nitrate-rich and nitrate-depleted conditions. We detected dinitrogenase reductase (nifH)-like genes in all strains; however, the genes grouped within nifH cluster IV that mostly contains nitrogenases not functioning in N2 fixation. Accordingly, incubations with 15N2 gas did not support N2 fixation activity of the investigated strains. Under laboratory conditions, all strains faded during nitrate-depleted growth after approximately three weeks. Both phycocyanin and chlorophyll-a dropped to a threshold, and chlorophyll fluorescence indicated a severe problem with nitrogen supply. In summary, our data indicate that the investigated Limnospira fusiformis strains are not capable of N2 fixation.


Schagerl M, Angel R, Donabaum U, Gschwandner AM, Woebken D
2022 - Algal Research, 66: 102771