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The contribution of mycorrhizal fungi to multifunctionality in global drylands

Periodic Reporting for period 1 - MYFUN (The contribution of mycorrhizal fungi to multifunctionality in global drylands)

Reporting period: 2021-01-07 to 2023-01-06

Dryland ecosystems cover 45% of the Earth´s surface and support over 38% of the total global population, being a key terrestrial biome. Their functioning and the goods and services they provide are vulnerable to land degradation and desertification, which are exacerbated by global environmental change drivers such as increasing land-use intensity and climate aridification. Mycorrhizal fungi, i.e. obligate plant symbionts colonizing the roots of 90% of all land plants, contribute substantially to dryland diversity and functioning and the goods and services provided by drylands. These fungi trade their benefits in terms of increased nutrient uptake and water availability with the plants in exchange for photosynthetically acquired carbon. Carbon trade and hence plant-mycorrhizal interactions and their effect on ecosystem functioning will consequently depend on the plant economic strategies present in the vegetation, but we lack an understanding of the exact mechanism yet. We also do not know how the contribution of mycorrhizal fungi to the functioning of drylands might change under forecasted climate aridification and increasing grazing pressure, two major landmarks of global environmental change in these ecosystems.
To fill these knowledge gaps the MYFUN project aimed to assess the relative contribution of the most common types of mycorrhizal fungi (AM and ECM fungi) to the multifunctionality of drylands in response to environmental stress (increased aridity, grazing pressure) and plant functional diversity in resource use economy.
The work of the MYFUN project was performed in three major steps (work packages - hereafter called WPs):

WP1 and WP2 used the same database approach to link mycorrhizal fungal abundance and diversity to dryland multifunctionality and assess how these linkages change under increasing levels of climatic stress and grazing pressure. WP1 and WP2 used data on global drylands from an existing database stemming from the project BIODESERT and covering 95 drylands sites from 25 countries. Extracted data included plot-level information on molecular data of soil fungal community composition (including mycorrhizal fungi), parameters on soil ecological processes related to nutrient cycling, productivity, and decomposition, and information on climatic stress and grazing pressure. The parameter of soil ecological processes was summarised in one index of ecosystem multifunctionality. Regression models revealed that weakly to moderately grazed drylands with high multifunctionality also have high fungal diversity and abundance, but non-grazed or intensively grazed drylands do not. Grazing effects on did not vary with climatic conditions. One can conclude that dryland multifunctionality is susceptible to high grazing pressures due to the decline in fungal-supported ecosystem processes. The publication of these results in form of a scientific article is currently under preparation. Parts of this work have been shared with a wider audience too at international conferences, institutional seminars and outreach activities during and at the end of the project. Inspired by WP1 and WP2, a card game was developed for one outreach activity to make the relevance of multiple ecosystem processes simultaneously for dryland resilience to environmental stressors tangible to children.

WP3 had two aims: 1) to test the causality behind the observed linkages in the database approach of WP1 and WP2; 2) to test whether the linkages between soil fungi and ecosystem multifunctionality besides climate and grazing pressure also depend on plant resource economy. With a combined experimental and database approach WP3 used 1) the BIODESERT data to detect resource strategies and ecosystem processes that are strongly related to soil fungal diversity and abundance in drylands; and 2) conducted a soil fungal inoculation experiment, to quantify fungal impacts and plant resource economy impacts on ecosystem functioning. Results of WP3 are currently processed as the experiment was harvested in July 2022 only. Results will quantify mycorrhizal fungal effects on ecosystem multifunctionality, while plant trait information will aid in better understanding the dependence of fungal effects on plant resource economy.
The MYFUN focus, i.e. understanding changes in multifunctionality and mycorrhizal symbiosis along environmental gradients, is a cutting-edge field within ecology. The knowledge created by MYFUN thereby strengthens the European excellence in biodiversity and climate-change research by opening new perspectives for the development of further models and experiments incorporating mycorrhizal fungi as modulators of biodiversity and ecosystem processes as well as potential tools for sustainable agriculture under global change. The results of WP1 and WP2, e.g. show a potential threshold of grazing pressure beyond which drylands and their functioning is degraded, which can help identify hotspots of protection especially susceptible to grazing pressure. Thereby, the project will contribute to solving the European societal challenges of maintaining healthy, diverse ecosystems, and food security under a changing climate. Past and future outreach activities have will raise awareness about the relevance of soil biodiversity for sustainable and stable ecosystems under current global changes.

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