Web URL(s): https://link.springer.com/article/10.1023/A%3A1004640327512 Publication Type:
i
Refereed 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." Language: English References: 58 Note: Figures ASA/CSSA/SSSA Citation (Crop Science -Like - may be incomplete ): Plant Soil. 224(1):p. 153-170.Fastlink to access this record outside TGIF: https://tic.msu.edu/tgif/flink?recno=69631 If there are problems with this record, send us feedback about record 69631 . Choices for finding the above item : Web URL(s): https://link.springer.com/article/10.1023/A%3A1004640327512 SB 13 .P55 Find from within TIC: Request through your local library's inter-library loan service (bring or send a copy of this TGIF record)
