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The approach presented here is comprised of two main parts. The first part (steps 1 and 2) assesses the optimal yield (ES potential) according to the length of the growing season, the respective growth functions and the specific land use types. The second part refines the biomass productivity according to region-specific precipitation patterns (steps 3 to 7) and local small-scale topographic conditions (steps 8 to 10), in order to provide more reliable local yield estimates (ES status). Flowchart below describes in detail the calculation procedure to derive the Supply (DM kg/ha) for each local administrative units (LAU2) of the Alpine Space.
(1) Calculate Vegetation Days (days with Tmean≥ 5 C)
The approach is based on the assumption that biomass production does not start if the daily average temperature is below 5°C, hence the year is divided into a growing season and a dormant season.
(2) Calculate Optimal Yield
This is done according to the productivity type of the grassland types of your study area. In the table below you find the factors we used for the Alpine-wide approach according to the dataset we had at our disposal.
The optimal yield is then derived using the following functions, where x is the number of vegetation days.
(Yield calculations Source: Egger, G., et al. (2004). GIS-gestützte Ertragsmodellierung zur Optimierung des Weidemanagements auf Almweiden. Irdning, Irdning: BAL. Modified by Jaeger and Tasser)
(5) Indicate Growing SeasonStart and End in days of the year (DOY)If no specific data is available for your test region, you can use a DEM-based method (i.e. Krautzer et. al. 2012) to approximate the start of the growing-season.
(6) Calculate average precipitation needed during growing season
(7) Optimizing (reducing) regional yield by applying a correction factor if precipitation during the growing season is below a certain threshold
(8) Calculate slope yield
(9) Reclassify the “Aspect raster” to “Aspect modified” in preparation of step (10)
The result is the layer „Aspect modified“ with cell values ranging from 0 (for southern faced slopes) up to 20 (for northern faced slopes).
(10) Calculate local yield
Krautzer, Bernhard, Christian Uhlig, and Helmut Wittmann. "Restoration of Arctic–Alpine Ecosystems."Restoration Ecology: The New Frontier 189 (2012)
Egger, G., et al. (2004). GIS-gestützte Ertragsmodellierung zur Optimierung des Weidemanagements auf Almweiden.Irdning, Irdning: BAL. modified by Jaeger and Tasser et al.
Urthaler, K. (2016). Modellierung und Validierung des landwirtschaftlichen Ertrages der Grünlandflächen Südtirols. Institut für Ökologie. Innsbruck, Leopold Franzens Universität. Master of Science