Full TGIF Record # 69631
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Web URL(s):https://link.springer.com/article/10.1023/A%3A1004640327512
    Last checked: 09/27/2017
    Access conditions: Item is within a limited-access website
    Notes: Guide page
Publication Type:
Author(s):Thornley, John H. M.; Cannell, Melvin G. R.
Author Affiliation:Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian, UK
Title:Dynamics of mineral N availability in grassland ecosystems under increased [CO₂]: hypotheses evaluated using the Hurley Pasture Model
Meeting Info.:Capri, Italy: September 24-27, 1998
Source:Plant and Soil. Vol. 224, No. 1, 2000, p. 153-170.
# of Pages:18
Publishing Information:Dordrecht, Netherlands: Kluwer Academic Publishers
Keywords:TIC Keywords: Nutrient availability; Grasslands; Ecosystems; Carbon dioxide; Climatic factors; Climatic change; Mineralization; Organic matter; Nitrogen; Nitrogen fixation; Nitrogen uptake; Plant physiology; Models; Nitrogen cycle; Carbon dioxide enrichment
Abstract/Contents:"The following arguments are outlined and then illustrated by the response of the Hurley Pasture Model to [CO₂] doubling in the climate of southern Britain. 1. The growth of N-limited vegetation is determined by the concentration of N in the soil mineral N pools and high turnover rates of pools (i.e., large input and output fluxes) contibute positively to growth. 2. The size and turnover rates of the soil mineral N pools are determined overwhelmingly by N cycling into all forms of organic matter (plants, animals, soil biomass and soil organic matter - `immobilisation' in a broad sense) and back again by mineralisation. Annual system N gains (by N₂ fixation and atmospheric deposition) and losses (by leaching, volatilisation, nitrification and denitrification) are small by comparison. 3. Elevated [CO₂] enriches the organic matter in plants and soils with C, which leads directly to increased removal of N from the soil mineral N pools into plant biomass, soil biomass and soil organic matter (SOM). `Immobilisation' in the broad sense then exceeds mineralisation. This is a transient state and as long as it exists the soil mineral N pools are depleted, N gaseous and leaching losses are reduced and the ecosystem gains N. Thus, net immobilisation gradually increases the N status of the ecosystem. 4. At the same time, elevated [CO₂] increases symbiotic and non-symbiotic N₂ fixation. Thus, more N is gained each year as well as less lost. Effectively, the extra C fixed in elevated [CO₂] is used to capture and retain more N and so the N cycle tracks the C cycle. 5. However, the amount of extra N fixed and retained by the ecosystem each year will always be small (ca. 5-10 kg N ha ¹ yr ¹) compared with amount of N in the immobilisation-mineralisation cycle (ca. 1000 kg N ha ¹ yr ¹). Consequently, the ecosystem can take decades to centuries to gear up to a new equilibrium higher-N state. 6. The extent and timescale of the depletion of the mineral N pools in elevated [CO₂] depends on the N status of the system and the magnitude of the overall system N gains and losses. Small changes in the large immobilisation-mineralisation cycle have large effects on the small mineral N pools. Consequently, it is possible to obtain a variety of growth responses within 1-10 year experiments. Ironically, ecosystem models - artificial constructs - may be the best or only way of determining what is happening in the real world."
Includes appendix: "The Hurley Pasture Model"; p. 168-170
ASA/CSSA/SSSA Citation (Crop Science-Like - may be incomplete):
Thornley, J. H. M., and M. G. R. Cannell. 2000. Dynamics of mineral N availability in grassland ecosystems under increased [CO₂]: hypotheses evaluated using the Hurley Pasture Model. Plant Soil. 224(1):p. 153-170.
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    Last checked: 09/27/2017
    Access conditions: Item is within a limited-access website
    Notes: Guide page
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