How long does such a model expect the trees to keep the carbon captured? Most (non-rain-)forests burn eventually, so for a long-term solution, we need to make s

How long does such a model expect the trees to keep the carbon captured? Most (non-rain-)forests burn eventually, so for a long-term solution, we need to make sure that the carbon that is captured stays captured. I saw some mention of special grass as a good option, since it stored most of its carbon in its roots.