Forest Ecology and Management, 2009, Vol.258(10), pp.2163-2174
Knowledge of site-specific water conditions is important in forestland evaluation and fundamental for a sustainable forest management. In Central Europe, traditional site mapping has followed an integrated ecological approach. The assessment of soil water availability is based on overlaying relief and descriptive soil information. It is a relative system referring to an (hypothetical) equilibrium between relief-dependent soil conditions and the potential natural forest association at a given regional climate. Accordingly, the climatic settings are supposed to be constant and are mostly based on long-term means of precipitation and air temperature. However, long-term climate changes, as well as infrequent climatic extremes have not been considered adequately. Furthermore, the feedback of forest management itself on available soil water cannot be addressed. To overcome these shortcomings, we developed an approach in which the soil hydrological model LWF-BROOK90 is organized in a GIS-frame to simulate the daily water fluxes and soil moisture status. Spatially distributed meteorological input data is generated from long-term station data using special regionalization procedures. Model parameterization for soil physical properties by horizon are derived from detailed forest soil maps using pedotransfer functions. Thus, we obtained data on all components of the water balance depending on climate, aspect, slope, vertical soil properties, and stand conditions in a spatial resolution of 25 m × 25 m. In addition to the common output of site water balance models, additional indicators were implemented to enable the quantification of ‘transpiration stress’, ‘soil drought stress’, and ‘excess soil water stress’. Soil water evaluation is based on the number of days exceeding defined thresholds of parameter values. The implemented soil water indices were suitable to reflect relevant differences in the soil water conditions between sites whereas focusing on individual and extreme years rather than on long-term averages seems to be more appropriate for assessing water-related tree growth conditions. The next step will be to produce forest site maps based on such ‘stress’ indicators. The novel approach provides a more objective description of variable soil water conditions than the currently used mapping approach. Furthermore, it makes spatial hydrological data (e.g. groundwater recharge) available for use beyond forest management.
Forest Site Mapping ; Forest Site Evaluation ; Forest Climatology ; Soil Water Modelling ; Eco-Hydrology ; Hydropedology ; Forestry ; Biology
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