CO2 storage in trees

We are in the process of measuring CO2 storage in trees. In our two food forest projects in Weurt and Grootstal (Nijmegen) there are a lot of thin trees with a diameter of less than five centimeters. The description states that in a young forest you have to count all thicknesses at heights of more than 130 cm. Is it ultimately a total measurement of all measured thicknesses together including dead trees? Or is it convenient to note individual trees separately in the count? In other words, do individual trees play a role in the final notation or is only the total sum of measured trees important, all added together?

Regards, Heleen van Splunter