EstSoil-EH: a high-resolution eco-hydrological modelling parameters dataset for Estonia

https://essd.copernicus.org/articles/13/83/2021

Isotopologue Ratios of N 2_{2} O and N 2_{2} Measurements Underpin the Importance of Denitrification in Differently N-Loaded Riparian Alder Forests

Known as biogeochemical hotspots in landscapes, riparian buffer zones exhibit considerable potential concerning mitigation of groundwater contaminants such as nitrate, but may in return enhance the risk for indirect N2O emission. Here we aim to assess and to compare two riparian grey alder forests in terms of gaseous N2O and N2 fluxes and dissolved N2O, N2, and NO3- in the near-surface groundwater. We further determine for the first time isotopologue ratios of N2O dissolved in the riparian groundwater in order to support our assumption that it mainly originated from denitrification. The study sites, both situated in Estonia, north-eastern Europe, receive contrasting N loads from adjacent uphill arable land. Whereas N2O emissions were rather small at both sites, average gaseous N2-to-N2O ratios inferred from closed-chamber measurements and He-O laboratory incubations were almost four times smaller for the heavily loaded site. In contrast, groundwater parameters were less variable among sites and between landscape positions. Campaign-based average 15N site preferences of N2O (SP) in riparian groundwater ranged between 11 and 44 ‰. Besides the strong prevalence of N2 emission over N2O fluxes and the correlation pattern between isotopologue and water quality data, this comparatively large range highlights the importance of denitrification and N2O reduction in both riparian grey alder stands

Erosion Induced Heterogeneity of Soil Organic Matter in Catenae from the Baltic Sea Catchment

Soil organic matter (SOM) is unevenly distributed in arable fields in undulated landscapes, but the chemical composition resulting from their turnover, transport and deposition processes is insufficiently known. Therefore, we aimed at disclosing the molecular-chemical composition of SOM in four different catenae at shoulderslope, backslope and footslope positions in arable fields in the Baltic Sea catchment, Europe. The backslope positions always had the lowest organic C-contents (Corg) (1.6…11.8 g·kg−1) and C-stocks (3.8…8.5 kg·m−2) compared to the shoulderslopes and footslopes (1.7…17.7 g·Corg·kg−1, 5.4…15 kg·Corg·m−2). In the SOM-poor backslope positions, the organic matter was characterized by relatively high proportions of carbohydrates, phenols + lignin monomers, alkylaromatic compounds, N-compounds and amides, indicating intensive microbial decomposition. By contrast, the footslopes had the largest Corg-contents (9.3…16.5 g·kg−1) and C-stocks (8.9…15 kg·m−2) in the catenae and particular enrichments in lipids, lignin dimers, sterols and free fatty acids. These relatively stabile SOM compound classes are interpreted as leftovers from erosive downslope transport and concurrent microbial decomposition, e.g., they are pronounced at backslope positions, followed by restricted microbial decomposition. This heterogeneous SOM distribution calls for an adapted soil management that reduces erosion and places amendments to field areas, such as the shoulderslope and backslope

Isotopologue Ratios of N₂O and N₂ Measurements Underpin the Importance of Denitrification in Differently N‑Loaded Riparian Alder Forests

Known as biogeochemical hotspots in landscapes, riparian buffer zones exhibit considerable potential concerning mitigation of groundwater contaminants such as nitrate, but may in return enhance the risk for indirect N₂O emission. Here we aim to assess and to compare two riparian gray alder forests in terms of gaseous N₂O and N₂ fluxes and dissolved N₂O, N₂, and NO₃^– in the near-surface groundwater. We further determine for the first time isotopologue ratios of N₂O dissolved in the riparian groundwater in order to support our assumption that it mainly originated from denitrification. The study sites, both situated in Estonia, northeastern Europe, receive contrasting N loads from adjacent uphill arable land. Whereas N₂O emissions were rather small at both sites, average gaseous N₂-to-N₂O ratios inferred from closed-chamber measurements and He–O laboratory incubations were almost four times smaller for the heavily loaded site. In contrast, groundwater parameters were less variable among sites and between landscape positions. Campaign-based average ¹⁵N site preferences of N₂O (SP) in riparian groundwater ranged between 11 and 44 ‰. Besides the strong prevalence of N₂ emission over N₂O fluxes and the correlation pattern between isotopologue and water quality data, this comparatively large range highlights the importance of denitrification and N₂O reduction in both riparian gray alder stands