Scientific

Tree Biomass Challenge

Understanding the total amount of biomass (the total mass of all individuals) in forests is important for understanding the global carbon budget and how the earth will respond to increases in carbon dioxide emissions.

We don’t normally measure the mass of a tree, but take a measurement of the diameter or circumference of the trunk and then estimate mass using equations like M = 0.124 * D^2.53.

1. Estimate tree biomass for each species in a 96 hectare area of the Western Ghats in India using the following steps.

• Download the data and load the data into R.
• Write a function that takes a vector of tree diameters as an argument and
  returns a vector of tree masses. (Thanks to vector math this function is basically just the equation above).
• Create a dplyr pipeline that
  • Adds a new column (using mutate and your function) that contains masses calculated from the diameters
  • Groups the data frame into species using the SpCode column
  • And then calculates biomass (i.e., the sum of the masses) for each species (using summarize)
  • Stores the result as a data frame
• Display the resulting data frame

2. Plot a histogram of the species biomass values you just calculated.

• Use 10 bins in the histogram (using the bins argument)
• Use a log10 scale for the x axis (using scale_x_log10)
• Change the x axis label to Biomass and the y axis label to Number of Species (using labs)

[click here for output] [click here for output]