Our understanding of belowground tree physiology
and the importance of belowground C transport to ecosystem
processes has greatly benefitted from girdling studies. These
studies, where the phloem transport was terminated by physically
removing the conducting tissue, have shown that the soil
CO2 efflux in boreal forests was reduced by 52–65%, implying
that belowground C allocation of recently produced photosynthates
dominates C-flow in these forest ecosystems