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Biomass production from grassland - Supply

<font 14.0pt/inherit;;black;;inherit>General description:</font>

<font 12.0pt/inherit;;inherit;;inherit>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).</font><font 12.0pt/inherit;;inherit;;inherit>Figure</font> <font 12.0pt/inherit;;inherit;;inherit>1</font><font 12.0pt/inherit;;inherit;;inherit>describes</font><font 12.0pt/inherit;;inherit;;inherit>in</font><font 12.0pt/inherit;;inherit;;inherit>detail</font><font 12.0pt/inherit;;inherit;;inherit>the</font><font 12.0pt/inherit;;inherit;;inherit>calculation</font><font 12.0pt/inherit;;inherit;;inherit>procedure</font><font 12.0pt/inherit;;inherit;;inherit>to</font><font 12.0pt/inherit;;inherit;;inherit>derive</font><font 12.0pt/inherit;;inherit;;inherit>the</font><font 12.0pt/inherit;;inherit;;inherit>Supply</font><font 12.0pt/inherit;;inherit;;inherit>(DM kg/ha) for each local administrative units (LAU2) of the Alpine Space.</font>

<font 12.0pt/inherit;;inherit;;inherit>Input data:</font>

  • <font 12.0pt/inherit;;inherit;;inherit>DEM (slope, aspect)</font>* <font 12.0pt/inherit;;inherit;;inherit>Precipitation (in mm)</font>* <font 12.0pt/inherit;;inherit;;inherit>Climate Data (number of Vegetation days, start of growing season)</font>* <font 12.0pt/inherit;;inherit;;inherit>Land use types (intensively used, moderately used and extensively used grassland, Natural Grassland (CLC)…</font>

<font 12.0pt/inherit;;inherit;;inherit>Calculation processes:</font>

<font 12.0pt/inherit;;inherit;;inherit>(1) Calculate Vegetation Days</font><font 12.0pt/inherit;;inherit;;inherit>(</font><font 12.0pt/inherit;;inherit;;inherit>days</font><font 12.0pt/inherit;;inherit;;inherit>with</font><font 12.0pt/inherit;;black;;inherit>T</font> <font 12.0pt/inherit;;black;;inherit>mean</font><font 12.0pt/inherit;;black;;inherit>≥ 5 C)</font>

<font 12.0pt/inherit;;inherit;;inherit>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.</font>

<font 12.0pt/inherit;;inherit;;inherit>(2) Calculate Optimal Yield</font>

<font 12.0pt/inherit;;inherit;;inherit>This</font><font 12.0pt/inherit;;inherit;;inherit>is</font><font 12.0pt/inherit;;inherit;;inherit>done</font><font 12.0pt/inherit;;inherit;;inherit>according</font><font 12.0pt/inherit;;inherit;;inherit>to</font><font 12.0pt/inherit;;inherit;;inherit>the</font><font 12.0pt/inherit;;inherit;;inherit>productivity</font><font 12.0pt/inherit;;inherit;;inherit>type</font><font 12.0pt/inherit;;inherit;;inherit>of</font><font 12.0pt/inherit;;inherit;;inherit>the</font><font 12.0pt/inherit;;inherit;;inherit>grassland</font><font 12.0pt/inherit;;inherit;;inherit>types</font><font 12.0pt/inherit;;inherit;;inherit>of</font><font 12.0pt/inherit;;inherit;;inherit>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.</font>


<font 12.0pt/inherit;;inherit;;inherit>Land use type</font>
<font 12.0pt/inherit;;inherit;;inherit>Productivity type</font>

<font 12.0pt/inherit;;inherit;;inherit>Permanent Grassland</font>
<font 12.0pt/inherit;;inherit;;inherit>4</font>

<font 12.0pt/inherit;;inherit;;inherit>Natural Grassland (CLC)</font>
<font 12.0pt/inherit;;inherit;;inherit>3</font>

<font 12.0pt/inherit;;inherit;;inherit>Natural Grassland (HRL)</font>
<font 12.0pt/inherit;;inherit;;inherit>3</font>

<font 12.0pt/inherit;;inherit;;inherit>Bogs</font>
<font 12.0pt/inherit;;inherit;;inherit>2</font>

<font 12.0pt/inherit;;inherit;;inherit>Dwarf bushes</font>
<font 12.0pt/inherit;;inherit;;inherit>2</font>

<font 12.0pt/inherit;;inherit;;inherit>Larch meadows</font>
<font 12.0pt/inherit;;inherit;;inherit>1</font>

<font 12.0pt/inherit;;inherit;;inherit>Alpine grasses</font>
<font 12.0pt/inherit;;inherit;;inherit>1</font>

<font 12.0pt/inherit;;inherit;;inherit>The optimal yield is then derived using the following functions, where x is the number of vegetation days.</font>


<font 12.0pt/inherit;;inherit;;inherit>Forage type</font>
<font 12.0pt/inherit;;inherit;;inherit>Yield function (dt/ha)</font>

<font 12.0pt/inherit;;inherit;;inherit>4</font>
<font 12.0pt/inherit;;inherit;;inherit>y=(0.0021*(x²))-(0.419*x)+93.774</font>

<font 12.0pt/inherit;;inherit;;inherit>3</font>
<font 12.0pt/inherit;;inherit;;inherit>y=(0.0007*(x²))-(0.1513*x)+26.585</font>

<font 12.0pt/inherit;;inherit;;inherit>2</font>
<font 12.0pt/inherit;;inherit;;inherit>y=(0.0006*(x²))-(0.1613*x)+25.321</font>

<font 12.0pt/inherit;;inherit;;inherit>1</font>
<font 12.0pt/inherit;;inherit;;inherit>y=(-0.00007*(x²))+(0.1084*x)-4.7726</font>

<font 9.0pt/inherit;;inherit;;inherit>(Figure 1: Yield calculations Source: Egger, G., et al.</font> <font 9.0pt/inherit;;inherit;;inherit>(2004). GIS-gestützte Ertragsmodellierung zur Optimierung des Weidemanagements auf Almweiden.</font> <font 9.0pt/inherit;;inherit;;inherit>Irdning, Irdning: BAL. Modified by Jaeger and Tasser)</font>

<font 12.0pt/inherit;;inherit;;inherit>(5) Indicate Growing</font> <font 12.0pt/inherit;;inherit;;inherit>Season</font><font 12.0pt/inherit;;inherit;;inherit>Start</font><font 12.0pt/inherit;;inherit;;inherit> and End in days of the year (DOY)</font>

<font 12.0pt/inherit;;inherit;;inherit>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.</font>

  • <font 12.0pt/inherit;;inherit;;inherit>(3) Calculate start of growing season based on DEM</font><font 12.0pt/inherit;;inherit;;inherit>(DOY)</font>* <font 12.0pt/inherit;;inherit;;inherit>Here the example function we used for the entire Alpine space: (0.0689*DEM)+0.4444</font>
  • <font 12.0pt/inherit;;inherit;;inherit>(4) Calculate end of growing season</font>
    • <font 12.0pt/inherit;;inherit;;inherit>Start of Growing Season + Vegetation Days (in DOY).</font>

<font 12.0pt/inherit;;inherit;;inherit>(6) Calculate average precipitation needed during growing season</font>

  • <font 12.0pt/inherit;;inherit;;inherit>Sum the average precipitation data for the growing season (in mm).</font>

<font 12.0pt/inherit;;inherit;;inherit>(7) Optimizing (reducing) regional yield by applying a correction factor if precipitation during the growing season is below a certain threshold</font>

  • <font 12.0pt/inherit;;inherit;;inherit>precipitation sums (in mm) in vegetation season are lower than (Vegetation days * 3.33) then the regional yield (unit: dt) ⇒ regional yield = 1)
1)
Precipitation in growing season (in mm) / Vegetation days * 3.33) * optimal yield)</font> * <font 12.0pt/inherit;;inherit;;inherit>else use optimal yield.</font> <font 12.0pt/inherit;;inherit;;inherit>8) Calculate slope yield</font>
  • <font 12.0pt/inherit;;inherit;;inherit>Calculate the yield reduction caused by slope because of radiation reduction</font> * <font 12.0pt/inherit;;inherit;;inherit>the slope is > 10, then use the following formula [(1- (Slope/ 100)) * regional yield], else keep the regional yield value.</font>
<font 12.0pt/inherit;;inherit;;inherit>(9) Reclassify</font><font 12.0pt/inherit;;inherit;;inherit>the “Aspect raster” to “Aspect modified” in preparation of step (10)</font>
  • <font 12.0pt/inherit;;inherit;;inherit>For the purposes of the model, simplified aspect values are required that account for losses caused by radiation decrease due to unfavorable exposition. Only values between 0° (north) – 180° (south) are valid inputs, where 90° refers to both east and west exposition. The reduction factors range between 0% and 20%, respectively for southerly and northerly facing slopes. We applied a linear distribution of the reduction factor from south to north.</font> * <font 12.0pt/inherit;;inherit;;inherit>Hence, first aspect values have to be reclassified and inverted using the following formula:</font><font 12.0pt/inherit;;inherit;;inherit>aspect_recl =</font> <font 12.0pt/inherit;;inherit;;inherit>180 - (180 - (Aspect - 180) </font>
  • <font 12.0pt/inherit;;inherit;;inherit>And second, this raster has to be multiplied with its specific reduction factor.</font><font 12.0pt/inherit;;inherit;;inherit>Aspect modified = aspect_recl * reduction factor</font>
<font 12.0pt/inherit;;inherit;;inherit>The result is the layer „Aspect modified“ with cell values ranging from 0 (for southern faced slopes) up to 20 (for northern faced slopes).</font> <font 12.0pt/inherit;;inherit;;inherit>(10) Calculate local yield</font>
  • <font 12.0pt/inherit;;inherit;;inherit>In the final step local yield is calculated without the losses caused by exposition:</font> * <font 12.0pt/inherit;;inherit;;inherit>the Annual Precipitation ⇐ 1500 mm then use the following formula: [(100 - (Aspect modified / 2)) / 100) * Slope Yield] else this other formula [((100 – Aspect modified) / 100) * Slope Yield)].</font>
<font 10.0pt/inherit;;inherit;;inherit>References:</font> <font 10.0pt/inherit;;inherit;;inherit>Krautzer, Bernhard, Christian Uhlig, and Helmut Wittmann. “Restoration of Arctic–Alpine Ecosystems.”</font><font 10.0pt/inherit;;inherit;;inherit>Restoration Ecology: The New Frontier 189 (2012)</font> <font 10.0pt/inherit;;inherit;;inherit>Egger, G., et al. (2004). GIS-gestützte Ertragsmodellierung zur Optimierung des Weidemanagements auf Almweiden.</font><font 10.0pt/inherit;;inherit;;inherit>Irdning, Irdning: BAL. modified by Jaeger and Tasser et al.</font> <font 10.0pt/inherit;;inherit;;inherit>Urthaler, K. (2016). Modellierung und Validierung des landwirtschaftlichen Ertrages der Grünlandflächen Südtirols. Institut für Ökologie. Innsbruck, Leopold Franzens Universität. Master of Science</font>
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