ECONOMY · Plant Ecology for Nitrous Oxide Mitigation and Sustainable Productivity

Plant Ecology for Nitrous Oxide Mitigation and Sustainable Productivity

For millennia the productivity of most agricultural systems has been limited by the supply of nitrogen (N). Due to this limited availability, natural processes were highly efficient in using mineral N as a resource. However, since application of artificial N fertilizers became widespread in the 1950’s, humans have disrupted the global N cycle at an immense pace, increasing twofold the N inputs entering the Earth’s soil. When N fertilizers are applied to agricultural soils, around half of the N is taken up by the plants leading to higher crop productivity. The other half is lost to surface waters or the atmosphere with detrimental effects on the environment. An important N-loss is the potent ozone-depleting greenhouse gas nitrous oxide (N2O), which is mainly produced through microbial nitrification and denitrification. Grasslands represent 68% of agricultural land across the globe and thus play a pivotal role in the N cycle. It is therefore paramount to identify ways to mitigate N2O emissions from intensive grasslands without compromising high quality food supply. Research conducted in natural ecosystems indicates that increasing plant species richness in a plant community may augment complementary in time and space for soil nutrient acquisition, enhancing biomass productivity. In intensively managed grasslands this may reduce N2O emissions due to increased N uptake by vegetation and hence reduced availability of soil mineral N for nitrifiers and denitrifiers. However, other studies have shown that targeted selection of species with specific traits or trait diversity may be more important than increasing species richness per se in terms of enhancing complementarity and N use efficiency. In combination with the current understanding of the microbiology behind soil N2O emissions and of plant-trait based ecology, these findings provide a promising framework to develop a novel N2O mitigation strategy. Climate change has a major impact on N2O emissions because N losses and primary productivity strongly respond to climatic conditions. However, this effect may be regulated to some extent by the presence of specific plants or plant combinations, as there is now increasing evidence that some of the most significant effects of climate change on ecosystem N dynamics are mediated via plants and their interactions with soil microorganisms. Within the context of climate change, the intensification of weather extremes has emerged as one of the most important aspects in terms of consequences for ecological systems and for human welfare. The debate over the last few years has shifted from an analysis of trends to a realization that extreme events rather than average trends may exert the most important controls on soil-plant and plant-plant interactions and ecosystem functioning. Yet, the outcome of such weather-driven interactions in terms of N2O emissions and the mechanisms involved remain poorly understood. The overall objective of this project was to reveal how plants and plant interactions via their traits and trait combinations can be used to reduce N2O emissions under current and future climatic conditions.

Data: CORDIS, © European Union