Lindner, S*; Lee, B; Zhao, P; Kettering, J; Kwon, H; Otieno, DO; Tenhunen, J: Variation in carbon dioxide gas exchange and productivity of the major crops of the Haean Catchment, South Korea
Poster, Review of TERRECO Phase II, Bayreuth, Germany: 2013-01-17

Conversion of natural ecosystems to croplands is a direct manifestation of human activities within the biosphere. Land use and land cover changes modify the biophysical properties of the land surface (e.g. surface roughness and albedo), altering energy flows and biogeochemical cycles. Intensive agricultural production with input-intensive practices (fertilizer, pesticides, machinery) as witnessed in the Haean?myun Catchment of South Korea significantly influence the regional carbon (C) budget. The Haean?myun Catchment is dominated by three vegetation zones distinctively organized along an elevation gradient. Forests are distributed at the upper zone at an elevation range of ca. 750 to 1100 m, with an area of 39 km 2 , constituting 61 % of the total land surface area. The dryland farms, primarily growing summer vegetables, orchards and ginseng, occur at an elevation range of ca. 500 to 750 m (covering 17 km 2) and constitute about 27 % of the land area. Rice paddies occur in the catchment basin, covering an area of 5 km 2 , which is 8 % of the land surface area. Characterizing CO 2 exchange in each of these zones is important in order to discern their roles in atmospheric C fluxes and to estimate net C uptake and storage (usable agricultural yields and forest products). Relating crop phenology to C uptake, plant productivity and agricultural yields is complex when the production phases of the crops are overlapping. In this case, information on the response of individual landscape elements is needed. This study focuses on providing such information for the major crops (radish, potato, cabbage, bean, rice) in the Haean Catchment. We hypothesized that the productivity (consumable biomass) of the agricultural crops is determined by C uptake capacity, the duration of C uptake and the pattern of C partitioning. To test these ideas, we quantified the rates of net ecosystem CO 2 exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (Reco) in non-irrigated/ rain-fed crop ?elds (radish, potato, cabbage, bean) and rice paddies during the growing seasons of 2009 and 2010, with manually operated gas exchange chambers. Aboveground biomass and total leaf area (LA) were determined for each of the crops (plots) after the gas exchange measurements. The samples were further analyzed for C/N content. The maximum GPP rates were 41, 39, 25 μmol m -2 s -1 for radish, potato and rice, respectively, while the respective Reco rates were 14, 17 and 4 μmol m -2 s -1 , occurring during July. The highest NEE during the growing period occurred in July and were ?27, ?23, ?21 μmol m -2 s -1 for radish, potato and rice, respectively. GPP and NEE varied significantly (P<0.05) during the season in response to changing biomass, while daily fluctuations were due to changing light intensities. Changes in Reco were due to changing soil temperatures. Up-scaling from plot to landscape level C fluxes using eddy covariance data and the PIXGRO?model is planned. The three levels of CO 2 exchange will be related to biomass harvests and farm produce information from the local agricultural offices in order to characterize the agro-ecosystem carbon budget of the Haean catchment.

last modified 2013-06-27