By using the related remote sensing data

statistical data and the four main carbon sources of fertilizer

agro-film

tillage and agro-machinery in 2010

a calculation of the carbon sources and sinks of agro-ecosystem in Guanzhong area was made in reference to the improved CASA (Carnegie-Ames-Stanford Biosphere) model

taking county (district or city) as a unit. The findings are as follows: (1) The total carbon absorption of the Guanzhong agro-ecosystem was about 6.44×106 tons

with the high values of carbon absorption in June

July and August and the low values in December

January

February and March. The counties whose value of carbon absorption was more than 2.0×105 tons were distributed in the north of Baoji City

west of Xianyang City

and middle and southwest of Weinan City. (2) The total amount of carbon emission of the Guanzhong agro-ecosystem was about 1.46×106 tons. Fertilizer was the main carbon source

accounting for 89%. The regions whose value of carbon emission was more than 60 000 tons were distributed in the middle of Weinan City and mid-south of Xianyang City. (3) The total carbon sink of the Guanzhong agro-ecosystem was about 5 033 500 tons. The value of carbon sink more than 200 000 tons was centered in the northwest of Guanzhong area.