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A selection of sites occupied by the EU-protected marsh fritillary (Euphydryas aurinia) in western Czech Republic were subjected to a vegetation survey 15 years ago and again recently. In the 66 time-replicated 25 m2 plots from 12 sites, representing the diversity of E. aurinia-occupied oligotrophic grasslands in the Slavkovský les Protected Landscape Area (and covering a fifth of the currently-occupied Czech sites), we recorded quantitative representation of vascular plants and mosses. We analysed the data using multivariate ordinations, asking how the vegetation changed between the surveys, how was it affected by the conservation management applied and how it affected occupancy by the butterfly larval nests; the vegetation patterns were interpreted using Ellenberg’s plant indicator values. Between the two surveys, the overall representation of the larval host plant, Succisa pratensis, did not change; tree and herbs layers (both grasses and forbs) increased and the moss layer decreased. Across surveys, the main driver of vascular plants’ species composition was moisture, followed by soil reaction and nitrogen, whereas in mosses, nitrogen was the main factor. The main change between the surveys was the increase of nitrogen accompanied by decreased light, probably due to increase of competitively strong plants. Butterfly occupancy declined at sites with high soil moisture and increased at sites with higher soil reaction. Mowing of moist nitrogen-rich sites, but not drier nitrogen-poor sites, increased occupancy, illustrating the need for context-dependent interventions. All the evidence thus shows that E. aurinia prefers drier, warmer and less acidic conditions within the generally moist acidic grasslands and that ongoing eutrophication represents a potential problem in the future.

Nitrogen (N) loads from municipal and mine wastewater discharges typically increase N concentrations in recipient water bodies which should get more attention especially in cold-climate regions. This study compared N removal efficiency of six constructed wetlands (CWs) treating mine waters and three CWs polishing municipal wastewater. There were clear impacts of point source N loading to recipient water bodies in all cases studied and >300-fold increase in N was seen in some cases. First-order N removal coefficient was determined for seven of these CWs. All CWs studied were observed to remove N efficiently during the warm growing season but the amount of N released increased significantly during the cold season. Although some year-round purification was achieved by both peat-based and pond-type CWs, removal of nitrate + nitrite-N ((NO3− + NO2−)-N) was low during winter. The first-order N removal coefficient varied from 4.9 · 10−6 to 1.9 · 10−3 d−1 and showed that peat-based CWs were slightly more efficient in N removal than pond-type CWs. However, purification efficiency was steadier and higher for pond-type CWs, as lower hydraulic load or longer water residence time compensated for purification performance. Pond-type CWs showed mean removal efficiency of 59% and 46% for ammonium-N (NH4+-N) and (NO3− + NO2−)-N, respectively, whereas peatland-type CWs had lower removal efficiency for NH4+-N (mean of 26%) and in many cases negative removal for (NO3− + NO2−)-N. Correlation analysis revealed no clear, systematic relationship between temperature and N removal. However, in some CWs the highest correlation was between temperature and (NO3− + NO2−)-N, reflecting lower denitrification rate at lower temperature. More than 50% removal was found to require a hydraulic load below 10 mm d−1. In order to achieve 70% of NH4+-N removal, Ntot load lower than 75 g m−2 year−1 and a residence time longer than 80 d are needed in CWs in cold-climate regions.

Fertilizer application during sugarcane cultivation is a main source of nitrogen (N) loads to groundwater on small islands in southwestern Japan. The aim of this study was to quantify the effect of reducing the N fertilizer application rate on sugarcane yield, N leaching, and N balance. We conducted a sugarcane cultivation experiment with drainage lysimeters and different N application rates in three cropping seasons (three years). N loads were reduced by reducing the first N application rate in all cropping seasons. The sugarcane yields of the treatment to which the first N application was halved (T2 = 195 kg ha−1 N) were slightly lower than those of the conventional application (T1 = 230 kg ha−1 N) in the first and third seasons (T1 = 91 or 93 tons ha−1, T2 = 89 or 87 tons ha−1). N uptake in T1 and T2 was almost the same in seasons 1 (186–188 kg ha−1) and 3 (147–151 kg ha−1). Based on the responses of sugarcane yield and N uptake to fertilizer reduction in two of the three years, T2 is considered to represent a feasible fertilization practice for farmers. The reduction of the first N fertilizer application reduced the underground amounts of N loads (0–19 kg ha−1). However, application of 0 N in the first fertilization would lead to a substantial reduction in yield in all seasons. Reducing the amount of N in the first application (i.e., replacing T1 with T2) improved N recovery by 9.7–11.9% and reduced N leaching by 13 kg ha−1. These results suggest that halving the amount of N used in the first application can improve N fertilizer use efficiency and reduce N loss to groundwater.

Agriculture has long been considered a great source of nitrogen (N) to surface waters and a major cause of eutrophication. Thus, management practices at the farm-scale have since attempted to mitigate the N losses, although often limited in tile-drained agricultural catchments, which speed up the N transport, while minimizing natural removal in the landscape. In this context, surface-flow constructed wetlands (SFWs) have been particularly implemented as an edge-of-field strategy to intercept tile drains and reduce the N loads by re-establishing ecosystems services of previously drained water ponded areas. These systems collect the incoming water volumes in basins sufficiently large to prolong the hydraulic residence time to a degree where biogeochemical processes between the water, soil, sediments, plants, macro and microorganisms can mediate the removal of N. Despite their documented suitability, great intra and inter-variability in N treatment is still observed to date. Therefore, it is essential to thoroughly investigate the driving factors behind performance of SFWs, in order to support their successful implementation according to local catchment characteristics, and ensure compliance with N removal goals. This review contextualizes the aforementioned issue, and critically evaluates the influence of hydrochemistry, hydrology and biogeochemistry in the treatment of N by SFWs.