| Popis: |
The response of nitrogen cycle processes to anticipated changes in climate will depend both on the direct effects of these changes (e.g. increased temperature, changes in rainfall amount and distribution, increased atmospheric CO2) and on indirect effects such as modifications of land use or cropping patterns prompted by the warmer environment. This paper outlines how climate change will influence different N-cycle processes and focuses on the complexity of interactions between soil, plant and atmosphere. A model of the nitrogen cycle is used to investigate the impact of some climate change scenarios, for the UK, on the organic nitrogen content of soil under two different cropping sequences over a run of eighty years, and to examine how patterns of mineralisation, leaching and denitrification change over the course of the run. The results indicate that, should CO2 fertilisation of crops in the field lead to more carbon being returned to the soil, this additional input of C would, for some time, maintain the organic nitrogen (and carbon) content by compensating for the increased rate of decomposition induced by higher temperatures. Eventually, assuming a 0.6°C rise in temperature every twenty years, the rate of turnover would be sufficient to cause a decline in organic nitrogen content. The greater mineralisation so caused would potentially increase N losses. A change in cropping sequence from continuous winter cereals to an alternating winter and spring rotation led to a greater decline in soil organic N. |
