Nitrogen mineralisation and plant nitrogen acquisition in a nitrogen-limited calcareous grassland

Unkovich, M.; Jamieson, N. D.; Monaghan, Rachel; Barraclough, D.

doi:10.1016/s0098-8472(98)00038-0

Cited by 18 publications

(11 citation statements)

References 37 publications

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“…In general, biomass nutrient concentrations were low (Marschner 2005), but in line with data on biomass stoichiometry in calcareous grasslands (Unkovich et al 1998). Differences in soil nutrients were hardly reflected by nutrient concentrations and fibre contents in the aboveground biomass.…”

Section: Effects Of Abiotic Site Conditions and Seasonality On Biomassupporting

confidence: 78%

Effects of grazing on seasonal variation of aboveground biomass quality in calcareous grasslands

2011

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Low-intensive grazing is a widely used management tool to conserve the outstanding biodiversity of calcareous grasslands. As conservation management is cost-intensive and often hampered by limited financial resources, combining adequate management for biodiversity conservation with feasible livestock production may be relevant for both conservationists and land managers. However, profound knowledge of the effect of grazing in nonintensively used grasslands on seasonal variation in biomass quality is scarce. We analyzed the floristic composition, abiotic soil properties and the chemical composition of aboveground biomass in a grazed calcareous grassland in NW Germany. Sampling took place in monthly intervals during one growing season. To separate the impact of grazing and nongrazing on biomass quality, an exclosure experiment was performed. Floristic composition of the studied calcareous grasslands was mainly related to two gradients representing the trophic status and the longterm management intensity. Differences in abiotic site conditions were hardly reflected by nutrient concentrations in the biomass. Irrespectively of abiotic site conditions, the chemical composition of the biomass showed a clear seasonal trend. Nutrient concentrations strongly declined from May to July but increased again in August, probably because of favourable current-year weather conditions. Sheep grazing improved biomass quality indicating that grazing modifies the environment beneficially for the animals. We conclude that early spring and late summer grazing is an appropriate management scheme to balance requirements of both feasible livestock production and biodiversity conservation, which is promising for sustainable and long-term conservation management.

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Section: Effects Of Abiotic Site Conditions and Seasonality On Biomassupporting

confidence: 78%

Effects of grazing on seasonal variation of aboveground biomass quality in calcareous grasslands

2011

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“…In other studies, both short and long term N additions in other studies increased net N mineralization, nitrification rates and leaching of nitrate in both improved and calcareous grasslands (Wedin and Tilman, 1996;Ledgard et al, 1998;Unkovich et al, 1998). However, these experimental studies all added N at rates of 50 -300 kg N ha -1 year -1 , considerably overshooting our more realistic levels of 7.5 -15 kg N ha -1 year -1 , which much more accurately reflect the situation of long-term increased deposition from atmospheric nitrogen which affect a considerable proportion of semi-natural habitats in Europe and indeed globally (Phoenix et al 2006).…”

Section: Impact Of N Additionmentioning

confidence: 67%

Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland

Ford

Roberts

Jones

2016

Science of The Total Environment

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Atmospheric nitrogen (N) deposition alters plant biodiversity and ecosystem function in grasslands worldwide. This study examines the impact of 6 years of nutrient addition and grazing management on a sand dune grassland. Results indicate that co-limitation of N and phosphorus (P) moderates the impact of realistic rates of N addition (7.5, 15 kg N ha −1 year −1 ). Combined NP addition (15 kg N + 10 kg P ha −1 year −1 ) was the only nutrient treatment to differ significantly from the control, with greater above-ground biomass (mainly moss), and enhanced N and P mineralisation rates. Grazing management altered plant functional group composition, reduced above-ground biomass and meso-faunal feeding rates, and decoupled N and P mineralisation. There were no synergistic effects of grazing and N treatment. Although NP co-limitation apparently prevents adverse impacts of N deposition above the critical load, excess N is likely to be stored in moss biomass and soil, with unknown future consequences.Capsule: This study shows that at realistic levels of N addition, NP co-limitation in a dune grassland appears to prevent adverse impacts of N on plant growth and nutrient cycling.

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“…Nitrogen additions stimulate mineralization when they are accompanied by organic matter, such as occurs with manure or compost additions (Zaman et al 1999, Burger andJackson 2003;Shi et al 2004) or in cases where long-term N additions have been incorporated in organic matter (Hall and Matson 1999, Bradley et al 2000b, Hatch et al 2000b). However, additions of mineral N alone will not necessarily stimulate and may even depress mineralization (Unkovich et al 1998, Fisk and Fahey 2001, Corre et al 2003) and SOM decomposition rates (Berg 2000, Allison andVitousek 2001). As expected, nitrification is often stimulated by N additions (Hall and Matson 1999, Zaman et al 1999, Fisk and Fahey 2001, Stockdale et al 2002, Hall and Matson 2003.…”

Section: Fertilization Effects On Gross Ratesmentioning

confidence: 99%

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

Booth

Stark

Rastetter

2005

Ecological Monographs

927

105

729

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Abstract. Isotope pool dilution studies are increasingly reported in the soils and ecology literature as a means of measuring gross rates of nitrogen (N) mineralization, nitrification, and inorganic N assimilation in soils. We assembled data on soil characteristics and gross rates from 100 studies conducted in forest, shrubland, grassland, and agricultural systems to answer the following questions: What factors appear to be the major drivers for production and consumption of inorganic N as measured by isotope dilution studies? Do rates or the relationships between drivers and rates differ among ecosystem types? Across a wide range of ecosystems, gross N mineralization is positively correlated with microbial biomass and soil C and N concentrations, while soil C:N ratio exerts a negative effect on N mineralization only after adjusting for differences in soil C. Nitrification is a log-linear function of N mineralization, increasing rapidly at low mineralization rates but changing only slightly at high mineralization rates. In contrast, NH 4 ϩ assimilation by soil microbes increases nearly linearly over the full range of mineralization rates. As a result, nitrification is proportionately more important as a fate for NH 4 ϩ at low mineralization rates than at high mineralization rates. Gross nitrification rates show no relationship to soil pH, with some of the fastest nitrification rates occurring below pH 5 in soils with high N mineralization rates. Differences in soil organic matter (SOM) composition and concentration among ecosystem types influence the production and fate of mineralized N. Soil organic matter from grasslands appears to be inherently more productive of ammonium than SOM from wooded sites, and SOM from deciduous forests is more so than SOM in coniferous forests, but differences appear to result primarily from differing C:N ratios of organic matter. Because of the central importance of SOM characteristics and concentrations in regulating rates, soil organic matter depletion in agricultural systems appears to be an important determinant of gross process rates and the proportion of NH 4 ϩ that is nitrified. Addition of 15 N appears to stimulate NH 4 ϩ consumption more than NO 3 Ϫ consumption processes; however, the magnitude of the stimulation may provide useful information regarding the factors limiting microbial N transformations.

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Nitrogen mineralisation and plant nitrogen acquisition in a nitrogen-limited calcareous grassland

Cited by 18 publications

References 37 publications

Effects of grazing on seasonal variation of aboveground biomass quality in calcareous grasslands

Effects of grazing on seasonal variation of aboveground biomass quality in calcareous grasslands

Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland

Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data

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