Abstract: In order to understand the characteristics of greenhouse gases emission from artificial reservoirs, the distribution characteristics of partial pressure of dissolved carbon dioxide (pCO₂) in inflow waters, outflow waters, and the waters in Hongjiadu reservoir, a newly-built reservoir located in Guizhou Province of Southwest China, were analyzed in April, July and October 2006 and January 2007. The results showed that the pCO₂ value in inflow waters was spring <summer<autumn<winter, and the annual average pCO₂ in the inflow waters from Liuchong river and Washui river was 488 and 624 μatm, respectively. The pCO₂ in reservoir epilimnion reached to the highest value (925 μatm) in winter and the lowest (279 μatm) in spring, with the annual average of 598 μatm. The pCO₂ in water column increased with water depth. In the outflow waters, pCO₂ was the highest (8 417 μatm) in summer and the lowest in winter (382 μatm), with the annual average value of 3 260 μatm. The annual average pCO₂ in inflow waters, reservoir epilimnion, and outflow waters was higher than that of air (380 μatm pCO₂), and the diffusion flux of CO₂ at waterair interface was 3.93-6.29, 4.87-7.79 and 64.29-102.86 mmol·m^-2·d^-1, respectively, showing that the reservoir should be a CO₂ source of the atmosphere. Through the action of the reservoir, the diffusion flux of CO₂ was enhanced, with the pCO₂ in outflow waters being 16 and 13 folds of that in inflow waters and reservoir epilimnion, respectively. Accordingly, much attention should be paid on the CO₂ emission from the outflow waters of the reservoir.

Key words: Weibei dry upland, Apple planting subarea, Soil moisture characteristics, Dried soil layer