Abstract: This paper reports the characteristics of ecosystem carbon storage and its distribution in mature evergreen broad-leaved forest and orchard, and the effects of transformation from forest to orchard on the ecosystem carbon stock. The ecosystem carbon storage in evergreen broad-leaved forest and orchard was 241.91 and 161.47 t·hm^-2, while the vegetation carbon storage was 136.40 and 77.20 t·hm^-2, and soil carbon storage (0-100 cm) was 103.99 and 83.12 t·hm^-2 respectively. The difference in soil carbon storage between evergreen broad-leaved forest and orchard mainly centralized in the surface soil. The proportions of carbon storage in the upper 40 cm soil to that in the whole soil in evergreen broad-leaved forest and orchard were 67% and 56%, respectively. The carbon storage of vegetation was higher than that of soil and litter in evergreen broad-leaved forest. The vegetation carbon storage was very close to soil carbon storage in orchard. After the conversion of evergreen broad-leaved forest to orchard, an 80.44t·hm^-2 decrease of ecosystem carbon storage was found; from the viewpoint of both amount and proportion, the degree of the carbon storage loss was higher in vegetation than in soil. Ecosystem carbon storage in mature evergreen broad-leaved forest in Guangzhou was close to that in evergreen broadleaved forest in Dinghushan Biosphere Reserve that stands for the climax zonal vegetation. Protecting evergreen broad-leaved forest will be beneficial to maintain the higher regional carbon storage.

Key words: rice, nitrogen fertilizer, yield, quality, nitrogen use efficiency