Forest canopy mitigates soil N2O emission during hot moments

Riparian forests are known as hot spots of nitrogen cycling in landscapes. Climate warming speeds up the cycle. Here we present results from a multi-annual high temporal-frequency study of soil, stem, and ecosystem (eddy covariance) fluxes of N2O from a typical riparian forest in Europe. Hot moments (extreme events of N2O emission) lasted a quarter of the study period but contributed more than half of soil fluxes. We demonstrate that high soil emissions of N2O do not escape the ecosystem but are processed in the canopy. Rapid water content change across intermediate soil moisture was a major determinant of elevated soil emissions in spring. The freeze-thaw period is another hot moment. However, according to the eddy covariance measurements, the riparian forest is a modest source of N2O. We propose photochemical reactions and dissolution in canopy-space water as reduction mechanisms.Peer reviewe

Global patterns in endemicity and vulnerability of soil fungi

Fungi are highly diverse organisms, which provide multiple ecosystem services. However, compared with charismatic animals and plants, the distribution patterns and conservation needs of fungi have been little explored. Here, we examined endemicity patterns, global change vulnerability and conservation priority areas for functional groups of soil fungi based on six global surveys using a high-resolution, long-read metabarcoding approach. We found that the endemicity of all fungi and most functional groups peaks in tropical habitats, including Amazonia, Yucatan, West-Central Africa, Sri Lanka, and New Caledonia, with a negligible island effect compared with plants and animals. We also found that fungi are predominantly vulnerable to drought, heat and land-cover change, particularly in dry tropical regions with high human population density. Fungal conservation areas of highest priority include herbaceous wetlands, tropical forests, and woodlands. We stress that more attention should be focused on the conservation of fungi, especially root symbiotic arbuscular mycorrhizal and ectomycorrhizal fungi in tropical regions as well as unicellular early-diverging groups and macrofungi in general. Given the low overlap between the endemicity of fungi and macroorganisms, but high conservation needs in both groups, detailed analyses on distribution and conservation requirements are warranted for other microorganisms and soil organisms

Indicators of nutrients transport from agricultural catchments under temperate climate: A review

International audienceThe flow of chemical materials along spatial elements is a fundamental aspect of landscape ecology. The research renders indicators for water pollution, which are utile for functional water management and land use planning. Ecologists identify mechanisms of nutrients transfer and mitigate their environmental impacts using freshwater wetlands and riparian buffers. In order to estimate the N (nitrogen) and P (phosphorus) loss risk, current research combines indicators into index models. The objective of this work was to review the factors of transport from upland source areas to surface water as N and P indicators, and to report on the magnitudes of N and P fluxes in agricultural landscapes under temperate climate. We reviewed the ISI Web of Science for recent developments on N and P transport factors and nutrient index models, and we suggested how to improve these schemes. We presented conceptual diagrams of N and P transport. Catchment-scale index models use factors of contributing distance, connectivity, soil properties, and erosion as indicators. P losses are mainly dependent on overland flow conduits and barriers, whereas subsurface flows control N more. Riparian vegetation accumulates great N and P amounts, while it is usually just a temporary sink. Riparian soil is a smaller but a more permanent store, whereas it may turn to a nutrient sink, too, when saturated. Anaerobic soil microbes denitrify somewhat less N, while this process is irreversible, and therefore equally crucial. In spite of this, most nutrient index models do not consider wetlands and riparian buffers. Hence we suggest to include the removal capacity of the riparian buffer zone in both catchment N and P index models. In general, we propose a landscape framework, which considers upland source areas, transit, and hydric riparian landscape elements as a single system

Nitrogen-rich organic soils under warm well-drained conditions are global nitrous oxide emission hotspots

International audienceNitrous oxide (N 2 O) is a powerful greenhouse gas and the main driver of stratospheric ozone depletion. Since soils are the largest source of N 2 O, predicting soil response to changes in climate or land use is central to understanding and managing N 2 O. Here we find that N 2 O flux can be predicted by models incorporating soil nitrate concentration (NO 3 −), water content and temperature using a global field survey of N 2 O emissions and potential driving factors across a wide range of organic soils. N 2 O emissions increase with NO 3 − and follow a bell-shaped distribution with water content. Combining the two functions explains 72% of N 2 O emission from all organic soils. Above 5 mg NO 3 −-N kg −1 , either draining wet soils or irrigating well-drained soils increases N 2 O emission by orders of magnitude. As soil temperature together with NO 3 − explains 69% of N 2 O emission, tropical wetlands should be a priority for N 2 O management