In general, you have to do a destructive sampling - if there isn't already a allometric regression model of your poplar species at hand. These allometric regression models are very side specific. So there is a difference if tree grow in the desert or in a dense forest, right?

Dear, have a look at this important attachment.

Consisting over all guideline for biomass estimation.

Good luck!

@C.P. Wow, thank you very much for the comment and sending me these links. However, this question was asked 4 years before and I have done my study. Thank you :)

Best,

Abhishek

Question asked six years ago is still relevant to you?

If yes, consult Jha 2017 in Notulae Scientia Biologicae (Open access) and relevant cross references in it. "Tree/root harvest and soil excavation" frequently adapted by European scientists.

Cost you need to assess yourself.

Hi

You can try this model, we developed some years ago,

its specifically for poplars below ground biomass Article Stump and Root Biomass of Poplar Stands

good luck