Abstract: An outdoor experiment was carried out to investigate the effects of elevated ultraviolet-B radiation on the chemical composition of wheat straw, and an indoor incubation test was conducted to study the effects of the amendment of the straw on soil N₂O emission.Outdoor experiment showed that the enhanced UV-B decreased the aboveground biomass of wheat, increased the lignin and total N contents of wheat straw by 94.2% and 12.3%, respectively, and decreased the C/N ratio of the straw. Incubation test showed that comparing with the amendment of conventional wheat straw, the amendment of  wheat straw received enhanced UV-B radiation during plant growth increased  soil N₂O emission under the dry-land and flooded conditions significantly. When nitrate was applied, the soil N₂O emission in the treatment with straw received enhanced UV-B radiation during plant growth was 3.2 times higher than that with the conventional straw under dry-land condition, but did not differ significantly under flooded condition. The amendment of wheat straw which received UV-B radiation during plant growth had no significant effects on soil respiration.

Key words: ultraviolet-B radiation, chemical composition, straw decomposition, N₂O emission, land economic ecological niche, landscape index, landscape pattern, Jinghe County.