关键词: CO₂浓度增高, 土壤, 蔗糖酶, 木聚糖酶, 纤维素酶, 酶活性

Abstract: This paper analyzed the vertical distribution of sediment grain size in the Dongfeng reservoir (oligotrophic state), Hongyan reservoir (meso-trophic), and Wujiangdu reservoir (eutrophic) on the Wujiang River, and by using advanced sequential extraction method (SEDEX), studied the distribution of different phosphorous (P) forms in the sediments. In the three reservoirs, sediment grain size decreased with increasing sediment depth. Dongfeng reservoir had the largest sediment grain size, followed by Hongyan reservoir, and Wujiangdu reservoir. The total P contents in the sediments of Wujiangdu, Hongyan and Dongfeng reservoirs
 were 2.07, 1.22 and 1.11 mg·g^-1, in which, inorganic P occupied 53.8%, 44.5% and 81.9%, and organic P occupied 41.9%, 55.5% and 18.1%, respectively. The exchangeable P was higher in Wujiangdu reservoir, which was consistent with the trophic state of the reservoir. In the surface layer (0-10 cm) of the sediments, all P forms in Wujiangdu reservoir decreased with depth, those in Dongfeng reservoir had less change, and only exchangeable P in Hongyan reservoir changed obviously. Due to the cascade exploitation of hydropower, the reservoir in the downstream had smaller grain size, and thus, the sediments in the reservoir had stronger adsorption capability to overlaying water P. It was suggested that sediment total P, organic-P, Ca-bound P, and Fe-bound P could be the useful indicators for the evolution of the trophic levels of reservoirs.

Key words: Free-air CO₂ enrichment(FACE), Soil, Invertase, Xylanase, Cellulase, Enzyme activity