LASmoons: Kwanghun Choi

Kwanghun Choi (recipient of three LASmoons)
Biogeographical Modelling Department, University of Bayreuth, Germany
Complex TERRain and ECOlogical Heterogeneity (TERRECO)

Background:
Soyang lake is one of the biggest artificial reservoirs in Korea and used for drinking water, irrigation, and electricity production. A sustainable maintenance of water resources is important for a stable supply of these services. Because 85% of the watershed is covered by forest (John et al., 2011), an accurate prediction of the forest water balance is needed. Forests regulate water by retention in the vegetation, storage in the soil, and evapotranspiration (ET) – the sum of evaporation and plant transpiration. ET is considered the main regulating factor (Bonan, 2008; Sheffield et al., 2009; Deng et al., 2011) and precise estimates at watershed scales are essential. Ground-based methods (e.g. sap flow measurement, …) are precise but only suitable at plot or field scale, airborne LiDAR method are precise but equipment costs are high, while estimates using satellite imagery are not suited for predicting future ET (Shuttleworth, 2008).

OLYMPUS DIGITAL CAMERAGoal:
This research aims to determine the relationship between forest structures (e.g. basal area, stem density) and evapotranspiration (ET). First, I will derive the precise forest structure using LiDAR. Second, I will try to find out the relation between ET and forest structure because prior research suggests that species composition and vertical structure are strongly related to ET. Third, I will predict future forest ET with the computed forest structure using the forest dynamics model LandClim.

Data:
800 square kilometers of LiDAR around Chuncheon, Korea.
+  point density around 4 points per square meters

LAStools processing:
1) 
change projection of LiDAR to that of MODIS ET using las2las
2)  remove duplicate points using lasduplicate (-unique xyz option)
3)  merge LAS files and create a tiling using lastile
4)  classify ground and non-ground points using lasground
5)  calculate height of points using lasheight
6)  generate DSMs, DTMs, and CHMs using las2dem
7)  create raster about physical features of forest structure using lascanopy

References:
Bonan, G. B. (2008). Forests and climate change: forcings, feedbacks, and the climate benefits of forests. Science, 320, 1444–1449.
Deng, H., Zheng, P., Liu, T. & Liu, X. (2011). Forest ecosystem services and eco-compensation mechanisms in China. Environmental management, 48, 1079–1085.
Farahani, H. J., Howell, T. A., Shuttleworth, W. & Bausch, W. C. (2007). Evapotranspiration: Progress in measurement and modeling in agriculture. Transactions of the ASABE, 50, 1627–1638.
John, T., Seo, B., Kim, I., Arnhold, S., Shope, C. & Park, S. (2011). Spatial setting of the terreco project in the soyang lake watershed of gangwan-do and the haean catchment of yanggu-gun. 2011 TERRECO Science Conference.
Sheffield, J., Ferguson, C. R., Troy, T. J., Wood, E. F. & McCabe, M. F. (2009). Closing the terrestrial water budget from satellite remote sensing. Geophysical Research Letters, 36, L07403.
Shuttleworth, W. (2008). Evapotranspiration measurement methods. Southwest Hydrology, 7, 22–23.

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