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Degraded peatlands are significant sources of carbon greenhouse gases (CGHG), and their recovery can make significant contributions to climate change mitigation as well as deliver biodiversity benefits. Sphagnum mosses are key species for northern peatland formation and re-introduction is often needed for successful ecohydrological restoration of degraded bogs, but natural sources are scarce and often protected. Micropropagated Sphagnum moss products (BeadaMoss®) were developed to alleviate this constraint. This research explored in detail, for the first time, the CGHG fluxes on a cut-over lowland peatland restoration site where micropropagated Sphagnum was introduced to an existing 'nurse crop' of Eriophorum angustifolium, and tested the influence of vegetation maturity. Ecosystem CGHG flux was measured using closed chambers at plot scale in areas of both mature and immature E. angustifolium with and without application of BeadaGel™ Sphagnum, with control plots on bare peat. Studies were conducted over two years of contrasting weather patterns. In Year 1, mean net (CO2e) CGHG uptake on vegetated plots was -2.33 (minimum 1.55, maximum -5.55) t ha-1 yr-1 with increasing CGHG uptake as vegetation matured. In Year 2, gross photosynthesis reduced significantly during the 2018 summer drought resulting in a small mean net CGHG emission of 0.11 (minimum 2.21 maximum -1.22) t ha-1 yr-1. Sphagnum application within immature vegetation resulted in greater CGHG uptake in both years, but was not as beneficial within mature vegetation. CGHG emission from bare peat (3.79 t ha-1 yr-1 overall) showed the magnitude of avoided losses. Methane flux contributed significantly to CGHG emission but was not closely related to water table depth. Application of Sphagnum within E. angustifolium can deliver good CGHG flux results in the early stages of degraded lowland bog recovery but cannot fully mitigate vulnerability to climate change scenarios. [ABSTRACT FROM AUTHOR]

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Habitat creation and restoration schemes on former agricultural soils can be constrained by high residual soil fertility, a weedy seed bank, and a lack of suitable species in the seed rain. Topsoil inversion has been trialled across the United Kingdom as a novel technique to address these constraints. We investigated 15 topsoil inversion sites ranging in age (time since inversion) from 6 months to 5 years. We assessed surface soil fertility compared to adjacent noninverted soil, and vegetation composition with respect to the species introduced at each site. Soil organic matter, total and extractable N and P were lower in topsoil inversion surface soils, demonstrating that topsoil inversion can successfully reduce surface soil fertility prior to habitat creation and restoration. This reduction was maintained over the timescale of this study (5 years). Cornfield annual nurse crops provided instant visual appeal and gave way to grassland species over time. Sown species varied widely in their establishment success, and sowings were more successful than plug plantings. Grasses colonized naturally following sowing forb-only seed mixes, allowing introduced forbs to establish early on with reduced competition from the seed bank. Plant communities did not yet resemble seminatural communities, but all were in the early stages of community development. Results indicate that topsoil inversion can successfully lower surface soil fertility and reduce competition between sown species and agricultural weeds. [ABSTRACT FROM AUTHOR]

Damage to terrestrial ecosystems from long-term atmospheric nitrogen pollution is a key conservation challenge in many industrialized countries. An important research and management priority is the identification of bioindicators to allow pollution exposure and ecological impacts to be determined at an individual site. We evaluate the impacts of nitrogen (N) deposition and identify methods with bioindication potential across a national-scale pollutant deposition gradient for British heather moorlands. Nitrogen deposition is associated with distinct changes in plant community structure, including reduced bryophyte and vascular plant species richness, and changes in the frequency of many species. Notable results include positive correlation with nitrogen for the invasive bryophyte Campylopus introflexus and negative correlation for the pollution-sensitive Hylocomium splendens and Pleurozium schreberi. Higher nitrogen deposition is associated with increased plant foliar N in a dwarf shrub and a bryophyte, increased extractable litter N, and reduced activity of the enzyme phenol oxidase. Although gradient study results cannot prove causation it is clear that Nitrogen deposition exerts a widespread impact on the ecology and biogeochemistry of heather moorlands. Bioindicators can be used to evaluate exposure and impacts, a promising approach could combine plant species richness and litter nitrogen analyses. [ABSTRACT FROM AUTHOR]

Atmospheric nitrogen ( N) deposition is a global and increasing threat to biodiversity and ecosystem function. Much of our current understanding of N deposition impacts comes from field manipulation studies, although interpretation may need caution where simulations of N deposition (in terms of dose, application rate and N form) have limited realism. Here, we review responses to simulated N deposition from the UKREATE network, a group of nine experimental sites across the UK in a diversity of heathland, grassland, bog and dune ecosystems which include studies with a high level of realism and where many are also the longest running globally on their ecosystem type. Clear responses were seen across the sites with the greatest sensitivity shown in cover and species richness of bryophytes and lichens. Productivity was also increased at sites where N was the limiting nutrient, while flowering also showed high sensitivity, with increases and declines seen in dominant shrub and forb species, respectively. Critically, these parameters were responsive to some of the lowest additional loadings of N (7.7-10 kg ha−1 yr−1) showing potential for impacts by deposition rates seen in even remote and 'unpolluted' regions of Europe. Other parameters were less sensitive, but nevertheless showed response to higher doses. These included increases in soil % N and 'plant available' KCl extractable N, N cycling rates and acid-base status. Furthermore, an analysis of accumulated dose that quantified response against the total N input over time suggested that N impacts can 'build up' within an ecosystem such that even relatively low N deposition rates can result in ecological responses if continued for long enough. Given the responses have important implications for ecosystem structure, function, and recovery from N loading, the clear evidence for impacts at relatively low N deposition rates across a wide range of habitats is of considerable concern. [ABSTRACT FROM AUTHOR]

The response of glasshouse crops to the nitrogen oxide pollutants which may be generated during enrichment with CO2 has been studied in controlled environments. Lettuce (Lactuca sativa L. ev. Ambassador) was grown in air containing either low CO2 (380 μmol mol-1), high CO2 (1200 μmol mol-1), or high CO2 plus oxides of nitrogen (NOx). Carbon dioxide enrichment increased the rate of emergence and expansion of leaves and the growth of young plants. Addition of NOx (2 μmol mol-1 NO and c. 0.5 μmol mol-1 NO2) to CO2-enriched air significantly reduced the yield, compared with the 'clean', high CO2 treatment, without producing visible symptoms of toxicity. Fumigation of single plants in high CO2 with NOx rapidly inhibited photosynthesis per unit leaf area. This did not appear to be due to a reduction in stomatal conductance. Removal of NOx from the atmosphere caused a rapid and complete recovery in the rate of photosynthesis. Studies were made of the effects of growing plants for long periods in atmospheres containing high CO2and NOx on the photosynthetic capacity of single leaves when measured in NOx-free air. The decrease in photosynthetic rate as the fourth leaf aged occurred earlier in plants grown in CO2-enriched air than in those from the low CO2 treatment. Leaves which developed in the CO2-enriched air containing NOx did not suffer any long-term damage to photosynthetic activity in comparison with those of the 'clean' high CO2. In mature leaves the principal long-term effect of enrichment (with or without NOx) was to reduce the rate of photosynthesis in saturating CO2. In contrast, there was less effect on the rate of photosynthesis in low CO2. [ABSTRACT FROM AUTHOR]

A single treatment with simulated acid rain [pH 3.0 delivered as a 30 min spray to glasshouse-grown seedlings of cabbage (Brassica oleracea L.)] caused extensive damage to the adaxial surface of the cotyledons. The extent of this injury was compared between plants which had been grown under different environmental conditions. Seedlings which were germinated and grown out of doors during springtime at a time of low minimum temperatures (full range: 7 to 32 °C) were less injured by the acid spray than were those grown in the glasshouse under warmer conditions (18 to 36 °C). The influence of temperature alone was studied further in controlled environments. Plants grown at 10 °C showed less damage from acid sprays, in terms of visible injury and in the effect on the subsequent rate of growth, than did those grown at 20 °C. In addition to the influence of low temperature, an insufficient supply of either water or nutrients during growth also reduced the extent of visible damage to the cotyledons from simulated acid rain. Estimates of the contact angles between water droplets and cotyledon surfaces, and SEM studies of the epicuticular wax, indicated that temperature-induced changes in the sensitivity of the cotyledon to acidity were not related simply to the wettability and morphology of the surface wax. The results indicate that laboratory or indoor experiments with stimulated acid rain should be interpreted cautiously; in the natural environment the direct effect of acidity on higher plants may change seasonally and spatially according to the plants' growing conditions. [ABSTRACT FROM AUTHOR]

Brassica oleracea L. (cabbage) was grown in glasshouse and controlled environments and exposed to simulated rains delivered as sprays at pH 5.6-2.8. A single rain treatment of pH 3.0 given to 10 d old plants elicited a marked downward curvature in the cotyledons, occurring within the duration of the 30-min spray. Subsequent to this initial response, the cotyledon surface was extensively damaged. In contrast, the older 'true' leaves showed little or no injury after similar treatments. Estimates of the contact angles between rain droplets and leaf surfaces, and SEM studies of adaxial surfaces, indicated that the contrasting morphology of the epicuticular wax on cotyledons and leaves was a major factor determining the extent of acid rain damage. Simulated rain treatments of pH 3.2 and 2.8, starting at the cotyledons stage, reduced plant growth by 17 and 15% respectively over a 20 d period. However, the same treatments given at later stages in development when the 'true' leaves were predominant, had no significant effect on growth. In the natural environment the occurrence of rate, highly acidic rain events during different stages of plant development may be an important determinant of the impact of rainfall on vegetation. The young, seedling stage of species, such as B. oleracea, in which cotyledons show poor development of surface wax, may be particularly vulnerable. [ABSTRACT FROM AUTHOR]