Download BayCEER Workshop 2009

Element cycles in mountain regions in Korea under different land use
J. Kettering1 & Y. Kuzyakov1
1 University of Bayreuth
Dept. of Agroecosystem Research, Universitätsstraße 30, D-95440 Bayreuth
[email protected]
Introduction and Research Aims
Study Area
While crop production is considered desirable, negative effects include high inputs of
nutrients, greater erosion rates, removal of nutrients and carbon in harvests and decreases
in the quality of SOM. The strongest impacts occur in mountainous landscapes.
The sites of the project are located in the Haean Catchment in the central part of Korea, just south of
the demilitarised zone (see Fig.2+3). The landscape of Haean Catchment consists of three zones
including deciduous forest, dry land farming, and rice paddies (see Fig.1).
The International Research Group TERRECO examines the way to carry out land
management in mountain regions, in order to ensure sustainable yield of ecosystem
services. The higher goal of this project (T-8) within TERRECO is to examine the influence
of forest conversion to agriculture on nutrient cycles at the farm level as well as to
reconstruct the history of previous erosion and nutrient losses, and attempt to define best
agricultural management practices.
Intensive land use due to the low percentage of flat land in Korea, high levels of fertilisation together
with extreme precipitation during the summer monsoon can be found on-site. Korean chemical
fertilizer applications for intensive agriculture are extremely high on a worldwide scale, increasing
from 230 kg/ha/yr in 1980 to 450 kg/ha/yr in 1994. Annual erosion of topsoil may reach 40 cm year-1
(see Fig.6+7). Therefore, the impacts on this mountainous terrain are considered to be profound.
North
Korea
South
Korea
Lake
Soyang
Haean
Catchment
Seoul
Lake
Soyang
Fig.1: Panoramic view of the study area, the Haean Catchment, Yanggu Gun, South Korea
Picture: Dr. Jan Fleckenstein, University of Bayreuth.
Fig.3: Satellite image of Korean Peninsula
Fig.2: Map indicating the location of Haean
indicating locations of Seoul and the Soyang
Catchment within the Lake Soyang
Lake Reservoir; Red = Mixed Forest; Green =
Watershed
Croplands
Fig.5: Cultivated area at slopes in Korea (right),
soil erosion during the summer monsoon in Korea (left)
Pictures: Professor Jae E. Yang, KNU, Chuncheon
Fig.4: Satellite (left) and terrain (right) image of Haean Basin
Sources: left: Google Earth 2009 ; right: Google Maps 2009
Methods – Research Plans for the 1st phase
Experiment (1) – Decomposition rates of organic polymers
Field Work
In the initial phase of the study, the focus of the field work will be put on estimation of
fertiliser budgets and on estimation of fertilizer losses by runoff or leaching and their
outflow in aquatic systems. Calculations will be based on specific crop areas, NPK input
and NPK withdraw by harvest. Another aspect of investigation will be soil carbon
dynamics in soils under maize, using 13C natural abundance. The approach is based on
the discrimination of 13C isotopes during CO2 assimilation by plants with different
photosynthesis types. Therefore, by growing a C4 plant on soils with former C3
vegetation, the amount of C4 plant derived C can be estimated on the basis of the
changing δ13C values of SOC.
Layout: Incubation experiment under controlled conditions
Aims: Evaluation of period for which organic polymers have direct and indirect effect on soil
stabilisation; Effects of polymers on microbial mass, SOM decomposition and C sequestration
Prerequisite: δ13C of polymers should be for at least 10‰ different from δ13C of the soils
Analyses:
- total CO2 efflux from soil (effect of polymers on SOM decomposition and C sequestration)
- δ13C of CO2 (decomposition rate of the polymers)
- Microbial biomass by fumigation/extraction method (FEM)
- Aggregate size, composition and stability (effect of polymers on aggregate stabilization)
Outlook: 3-5 “best” polymers will be chosen for the following experiments
Collaboration:
- Prof. Yong Sik Ok, Dept. of Biological Environ., KNU: polymers, soil aggregates, erodibility, C
sequestration
- Prof. Taeseok Ahn, Dept. of Environ. Science, KNU: enzymes, DGGE of microorganisms
Laboratory work
The methods of our research are based on application of isotopes: 14C and 13C labelling.
Goals of the laboratory work focus on the analysis of organic polymers locally used for
soil stabilisation against erosion by Prof. Yong Sik Ok. Experiments include analysing the
degradation of these polymers as well as their effects on microbial mass, SOM
decomposition and C sequestration. Afterwards, 3-5 polymers will be chosen and in
following experiments tested both for their effect on decomposition of plant residues and
for their incorporation into SOM and microbial mass. Finally, another experiment will deal
with the question of the effect of polymers on DOM leaching and aggregate stability.
Experiment (2)+(3) – Effect of polymers on decomposition of plant residues
Layout: Incubation experiment under controlled conditions
Aims: Effect of these 3-5 “best” polymers on decomposition of plant residues and their incorporation
into SOM and microbial biomass
Prerequisite: 14C labelled plant residues will be produced (maize and rice)
Analyses:
- Total CO2 efflux from soil (effect of polymers on SOM decomposition and on plant residue
decomposition)
- 14C of CO2 (decomposition rate of plant residues)
- Microbial biomass by fumigation/extraction approach
- 14C in microbial biomass (incorporation of plant residues into microbial biomass)
- Enzyme activities
Collaboration:
- Prof. Yong Sik Ok (see Experiment 1)
- Prof. John Tenhunen, Dept. Of Plant Ecology, UBT: C budgeting in rice
Experiment (4) – Effect of polymers on DOM leaching and aggregate stability
Layout: Column experiment
Aims: Effect of 2-3 polymers on soil aggregation; Effects of polymers on DOM leaching
Prerequisite: Presence of DOM added on soil surface (DOM will be labelled by 14C)
Collaboration:
- Prof. Bernd Huwe, Dept. of Soil Physics, UTB: erosion experiments
Fig.6: Overview illustration of the integration of Project 8 within TERRECO; red = DFG projects, blue = Korean projects
Source: Proposal for an International Training Group 2009, available at: www.bayceer.unibayreuth.de/terreco/en/forschung/43708/65489/proposal.pdf
International Research and Training Group TERRECO - Complex Terrain and Ecological Heterogeneity
http://www.bayceer.uni-bayreuth.de/terreco/