Fungal Ecology by Tessa Camenzind

Contact:

Freie Universität Berlin, Germany

Institute of Biology - Plant Ecology

tessa.camenzind [at] fu-berlin.de

@t_camenzind

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Main research interests

At the moment I am working as a postdoc in the Plant Ecology group at Freie Universität Berlin. My studies focus on the role of fungi and microbes in soil nutrient cycling and carbon dynamics, with a strong emphasis on fungal nutrient use efficiency and carbon cycling in soil. 

While my expertise is clearly focused on fungal ecology, I aim to use novel (and old) physiological knowledge on fungi to explain relevant processes in soil. This includes for example results on (i) fungal nutrient demands, (ii) the shift in mycelial growth dynamics under resource limitations or (iii) the unexpected stoichiometric flexibility of fungal mycelia. in the context of soil C sequestration, we applied the results on varying stoichiometric C:N:P ratios in ageing hyphae to inform our incomplete understanding of microbial necromass composition. Following an in-depth literature review on microbial death studied in microbiology, this led to the theory of microbial death pathways affecting necromass composition (microbial necromass ≠ microbial biomass), and consequently soil C sequestration. 

In my current DFG project within the SPP SoilSystems, I use the whole experimental gradient from individual fungal isolates grown on defined C substrates (high mechanistic resolution) to fungal communities in complex soils (maximized realism). The aim is to investigate fungal C use dynamics in saprobic fungi  in detail in order to understand fungal-driven processes in soil, focusing on carbon-use efficiency, thermodynamic principles and fungal traits of C substrate use. First results are on the way and will be presented soon.



culturing of fungal isolates in the lab; picture ©Sybille Neumeyer

large fungal mycelium on a Ø 20 cm plate ©Tessa Camenzind

thick mycelial cords on tropical litter ©Tessa Camenzind

hyphal characteristics visualized by fluorescence stains ©Tessa Camenzind

Former research projects

Interesting patterns of fungal physiology under varying nutrient supply, and their implications for soil processes

We designed fungal growth media suitable to test for growth limitations by individual elements. Responses to N and P limitations tested in many fungal isolates covering three fungal phyla showed very distinct shifts in trait expressions, indicating a switch from explorative growth under low nutrient conditions to exploitative growth with dense and highly active mycelia in high nutrient patches. A parallel analysis of fungal stoichiometric patterns indicated a non-homeostatic shift in C:N:P ratios, contradicting common assumptions of microbial homeostasis. Mechanisms explaining this stoichiometric flexibility also relate to the mycelial lifestyle, which enables nutrient translocation and recycling within the mycelium. 

Further projects aim to translate these physiological findings under more controlled conditions towards observations in soil, in order to understand the relevance of stoichiometric fungal shifts in soil, predict carbon versus nutrient limited growth and activity in soil and improve current models of microbial mediated carbon and nutrient cycling dynamics.

  Nutrient limitations on microbial growth

The simple agricultural concept of Liebig´s law of the minimum predicts that only the most limiting element in soil restricts plant growth. In natural diverse ecosystems, productivity is indeed often limited by nitrogen (N) and phosphorus (P) availability, though patterns were revealed to be far more complex - with co-limitations occurring, overlooked elements playing important roles and functional or phylogenetic groups being affected differentially by various elements. In recent years a growing number of interesting studies based on nutrient manipulation experiments revealed new insights on this topic, though often with a focus on plants and aboveground processes. Since plant growth and primary productivity depend on nutrient recycling in soil, nutrient demands of soil microbes mediating those processes and above- belowground interactions are of equal relevance. Summarizing available findings on soil microbial responses to nutrient manipulations gave valuable insights on nutrient limitations of soil microbes in general (Camenzind et al. 2018). Additional case studies combining large- and small-scale nutrient manipulation approaches allow for a more detailed analysis of microbial element demands, especially of saprobic fungi (Camenzind et al. 2019). Potential demands for elements like carbon, nitrogen, phosphorus, calcium, potassium or sodium are quantified in controlled media, and actual limitations tested in parallel in field experiments (see Publications).

©Tessa Camenzind

 Arbuscular mycorrhizal fungi in response to increasing nutrient inputs

This interest in soil element cycling already started with my PhD thesis “Responses of arbuscular mycorrhizal fungi to nutrient additions in a tropical montane forest”. This exciting project not only got me hooked on working in diverse tropical forests, expanding my knowledge to different ecosystems, but also on thinking more deeply about the interplay of microbes with elements in soil. For years I studied the fascinating symbiosis of arbuscular mycorrhizal fungal communities with plants in respect to soil nutrient status in pristine tropical forests, Dark Earth soils in tropical Africa, as well as tropical but also temperate pasture and grassland systems. Based on the gained knowledge my research interests broadened towards nutrient limitations of other microbial groups in soil, especially saprobic fungi, and consequent implications for ecosystem processes. 

©Tessa Camenzind

The ubiquitous group of arbuscular mycorrhizal fungi (AMF) is not only relevant for plant and microbial community dynamics and soil processes, but especially enhances plant nutrient uptake. Thus, nutrient limitations and alteration in element inputs by anthropogenic activities affect this important plant-fungus association. We investigated in multiple study systems the responses of AMF to nutrient manipulations, analyzing extra- and intraradical AMF abundance as well as AMF community structure. In most systems nitrogen (N) and phosphorus (P) availablity strongly control the AMF association and especially species composition (see Publications), though unifying patterns and functional implications are difficult to derive from those complex results. Next steps are to combine observational data with functional experiments, to understand implications of shifts in AMF abundance and communities for ecosystem processes, and combine findings from different systems to detect common patterns enabling us to predict future responses to environmental change.

For details on my research projects please refer to my Publications

Traveling the world as an ecologist

I aimed to be biologist for many reasons, but one of them was definitely to have a job enabling me to explore many places on this planet. Though my Curriculum Vitae may not reflect this passion adequately - for personal reasons I was not able to change my location for longer periods - I still used every opportunity to make short journeys for field trips, scientific exchange and international conferences. I very much enjoyed these interactions, but also the work within the inspiring large international research group of Matthias Rillig and for a long time also as part of the Ecuadorian research unit funded by the Deutsche Forschungsgemeinschaft.