Biomass production from NPP in the Earth Engine

Calculate world wide biomass production from the MODIS NPP.

The NPP can be used to estimate the production of biomass (kgm²). Biomass is the dry matter of vegetation that consists of carbohydrates (CH₂O). Total biomass production is calculated by including the molecular masses of hydrogen and oxygen into the equation.

Biomass = NPP * (30/12)

Yearly NPP is downscaled to an 8 daily time-series in this exercise.

Step 1: Open this script

Step 2: Add code below to calculate the biomass

// calculate the Biomass

var Biomass = function(myimg){
var biomass = myimg.multiply(2.5);
return biomass.copyProperties(myimg,['system:time_start']);
}

// map biomass production
var biomassCollection = npp8Collection.map(Biomass);

3. Add the fusion table of the Da basin and one of the Thai Binh province.

 // import the sub basins as a fusion table
var Da = ee.FeatureCollection('ft:15ytieQkq3UH8DPJPFmB_YnbvhSEhOQLtLIXa6kxA').geometry();
var ThaiBinh = ee.FeatureCollection('ft:1w0nJ-In_Tabrr9zS-C6pdw1sHwuZM1_YS9mxacOf').geometry();

// Set center of map
Map.centerObject(Da, 5);

// show the layer
Map.addLayer(Da,false,"Da basin");
Map.addLayer(ThaiBinh,false,"Thai Binh");

// create vizualtion settings
var biomass_viz = {min:300.0, max:800, palette:"b27c00,ffff33,58ff33,146003"};

// Add the layer
Map.addLayer(biomassCollection.mean().clip(Da),biomass_viz,"npp Da")
Map.addLayer(biomassCollection.mean().clip(ThaiBinh),biomass_viz,"npp Thai Binh")

4. Plot the temporal changes in a chart.

// Predefine the chart titles.
var title = {
  title: 'Biomass production in Da basin',
  hAxis: {title: 'Time'},
  vAxis: {title: 'Biomass (kg/m2)'},
};

// create chart
var biomassChartDa = ui.Chart.image.seriesByRegion(biomassCollection,
                                           Da,
                                           ee.Reducer.mean(),
                                           'Gpp',
                                           500,
                                           'system:time_start').setOptions(title);
// plot chart
print(biomassChartDa)

// Predefine the chart titles.
var title = {
  title: 'Biomass production in Thai Binh basin',
  hAxis: {title: 'Time'},
  vAxis: {title: 'Biomass (kg/m2)'},
};

// create chart
var biomassChartBinh = ui.Chart.image.seriesByRegion(biomassCollection,
                                          ThaiBinh,
                                           ee.Reducer.mean(),
                                           'Gpp',
                                           500,
                                           'system:time_start').setOptions(title);
// plot chart
print(biomassChartBinh)

Find an example here.