Das Projekt "Antagonism in the mycorrhizal symbiosis - a search for mechanisms" wird vom Umweltbundesamt gefördert und von Forschungsanstalt Agroscope Reckenholz-Tänikon ART durchgeführt. Lead: Plant growth responses to arbuscular mycorrhizal fungi (AMF) are highly variable, ranging from mutualism in a wide range of plants, to antagonism in some non-mycorrhizal plant species and plants characteristic of disturbed environments. This project focuses on a number of potential mechanisms that can explain why AMF suppress growth of some plant species. Background: Arbuscular mycorrhizal fungi (AMF) play a key role in ecosystems by influencing plant growth and ecosystem functioning. Most studies have focused on the positive effects of AMF on plant growth and nutrition. However, plant growth responses to arbuscular mycorrhizal fungi (AMF) are highly variable, ranging from mutualism in a wide range of plants, to antagonism in some non-mycorrhizal plant species and plants characteristic of disturbed environments. The precise mechanisms responsible for the negative effects of AMF on some plants received almost no attention as most research focused on the positive effects of AMF on plant growth. This project focuses on a number of potential mechanisms that can explain why AMF suppress growth of some plant species. Aims: The following key hypothesis are investigated in this project: 1. The cost-benefit relationship with AMF varies among plant species. Plants that respond negatively to AM fungi invest carbon into AMF, without benefit (nutrients) in return. 2. Plants that respond negatively to AM fungi invest carbon in mycorrhizal networks while coexisting plant species receive the benefit of such networks. 3. AM fungi suppress growth of some plants by exuding allelopathic compounds. 4. Plants that respond negatively to AM fungi cannot block colonization by AM fungi under conditions in which AM fungi are unfavorable. Relevance: Recent studies have provided important insights into the role of AM fungi in ecosystems. These soil fungi can stimulate plant diversity and productivity and enhance stress resistance in a wide range of plants. Until now, research largely focused on the positive effects of AM fungi on plant growth, ignoring that an estimated 17'000 - 39'000 species are non-mycorrhizal, including a large number of weeds. A few recent studies suggest that many non-mycorrhizal plants may be suppressed by AM fungi. Moreover, the fact that some mycorrhizal plants also respond negatively to AM fungi points to surprising interactions in the rhizosphere. AM fungi may exude allelopathic compounds with suppressive effects on plants, including a number of weeds. The findings of this project will be highly relevant for sustainable agricultural production. Moreover, the study will lead to a better understanding of plant-microbe interactions, mycorrhizal and soil ecology, and crop-weed interactions, and will stimulate our understanding of the role that microbes play in the soil.
Das Projekt "Microbial control of ecosystem functioning" wird vom Umweltbundesamt gefördert und von Forschungsanstalt Agroscope Reckenholz-Tänikon ART durchgeführt. Nutrient loss from ecosystems has become of global major global concern as it reduces the sustainability of ecosystems and because it causes eutrophication of surface water. In this project we investigate whether soil fungi enhance ecosystem sustainability by preventing nutrient leaching loss after rainfall. Background: Leaching of nutrients (nitrogen and phosphorus) from fertile agricultural ecosystems has become of major global concern because it causes eutrophication of surface water with adverse consequences for human health and water quality. Moreover, losses from infertile ecosystems can reduce plant productivity and ecosystem sustainability if there is no additional nutrient input. Hence, it is of critical importance to understand which mechanisms prevent nutrient loss and retain nutrients inside ecosystems. Besides lateral transport of nutrients via soil erosion and surface runoff, vertical movement through the soil profile (e.g. leaching) has been recognized as an important process contributing to nutrient loss. Until now there are no studies that tested whether mycorrhizal fungi can reduce nutrient losses. This is surprising because mycorrhizal fungi are often very abundant in the soil and play a key role in the nutrient cycle of plant communities. Mycorrhizal fungi can forage highly effectively for nutrients in the soil and, by doing so they could prevent leaching of nutrients (e.g. in winter or during periods with heavy rainfall). Aims: The following key questions are investigated in this project: 1. Can mycorrhizal fungi reduce nutrient loss from experimental grassland? 2. Can arbuscular mycorrhizal fungi reduce nutrient leaching losses at high soil fertility, low temperatures and when rainfall intensity increases? 3. Is ecosystem sustainability (measured as nutrient retention and reduced nutrient loss after rainfall) enhanced by the presence of diverse communities of arbuscular mycorrhizal fungi? Relevance: It has been reported that the available phosphate sources will be depleted in about 50 years and some authors suggest that we will face a phosphate crisis endangering agricultural production. Thus, it is of critical importance to understand whether mycorrhizal fungi can reduce phosphorus loss from soils. Moreover, the production of nitrogen fertiliser is energetically expensive and high levels of nitrate in groundwater are of concern because they can pose a significant health risk and have a negative impact on downstream ecosystems. Hence, this shows that there is a need to better understand which factors influence the N-cycle and reduce N-losses.