Zhao, P*; L├╝ers, J: Dynamics of CO 2 exchange of irrigated and non- irrigated crops in Haean Catchment, South Korea
Poster, Review of TERRECO Phase II, Bayreuth, Germany: 2013-01-17

Agricultural areas comprise nearly 40% of the land surface of the earth. In order to meet the demands of the increasing human population and growing economies, the intensification of crop cultivation has led to rapid land use and land cover change. In the context of global change, major efforts are being made to understand the role of cropland ecosystems in atmosphere/biosphere CO 2 exchange, in potential carbon sequestering versus release, and to relate CO 2 exchange to future agricultural production and yields. The objective of this study is to better understand the CO 2 exchange between cropland ecosystems and the atmosphere under monsoon climate conditions in Korea by assessing the dynamics of the CO 2 exchange during entire growing seasons for major crops. Field campaigns were carried out in an irrigated rice field and a non-irrigated potato field in Haean Catchment, South Korea during the growing seasons in 2010 and 2011. Eddy-covariance technique was used to observe net ecosystem CO 2 exchange (NEE). Meteorological variables and biomass change of both crops were additionally measured. State-of-the-art quality control approaches were applied to confirm the reliability of the data-sets. Conventional and new gap-filling methods together with partitioning methods were used to provide continuous time series of NEE and gross primary production (GPP) of the croplands. We found that the primary causal factors for seasonal changes in GPP were related to the changes in Leaf Area Index (LAI) for both crops. The diurnal change in GPP is driven primarily by solar radiation. The photosynthetic efficiency of rice under cloudy conditions (leading to predominance of diffuse radiation) is 20% greater than under clear sky conditions (with direct radiation). The photosynthetic efficiency of potatoes showed no difference between sunny and cloudy days. The seasonal change in ecosystem respiration at the reference temperature in the rice field follows the change in rate of LAI. Vapor pressure deficit (VPD) plays a significant role in the dry, pre-monsoon growing stage of non-irrigated crops, and a minor role under Asian monsoon weather conditions.

last modified 2013-06-27