Document: DOW-3-87-8

Topographic consideration on evapotranspiration, primary production, and soil respiration: An integrated spatially explicit ecosystem model.

KANG, S.*, S.KIM and D.LEE

Seoul National University, Seoul, South Korea 1

Abstract:
In a rugged montane area, topography generates considerable spatial variability in solar incident radiation, soil temperature, and soil moisture content, which results in heterogeneity of evapotranspiration, primary production, and soil respiration at a landscape scale. To quantify the effect of topography on hydrological and ecological processes, several models were developed in this study. A model of daily topographic radiation aimed to account for spatial and temporal variability in incident radiation. A model of daily-mean soil temperature describes the effect of canopy and forest floor litter and topography. The models require data of maximum and minimum air temperature and digital elevation model (DEM). Air temperature was interpolated with data of adjacent weather stations. Using a radiation model, evapotranspiration was estimated with Penman-Monteith method and primary production with radiation utilization efficiency based on vapor pressure deficit, soil water deficit, and soil temperature. Spatial and temporal patterns of soil respiration were simulated using soil temperature model and Q10 of soil respiration. The radiation model simulated spatial variability in a montane area (6~13 MJ day-1 in annual mean) well. Topographic radiation varied with grid size nonlinearly. When the radiation model was incorporated into soil temperature model, it predicted temporal and spatial patterns of measured data (MAE=0.96 degree in Celcius, bias=0.03 degree in Celcius) successfully. Potential evapotranspiration (PET) ranged from 24 to 30 cm yr-1. The model results showed that topography could generate considerable spatial heterogeneity in hydrological and ecological processes. Since our approach was based on simple models and data commonly available, it would be applied to other areas with little efforts on parameterization.

Keywords: Topography,radiation,soil temperature,NPP,Soil respiration

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This abstract is being presented at: 10:15 AM in session:
Oral Session #9: Respiration and Isotopes.