Regeneration rate of nature after environmental catastrophes
It sounds like you are asking about plants taking up carbon at different stages of Ecological Succession that occur after some catastrophic event (e.g. a wildfire or lava flow).  

If the prior ecosystem was dominated by live vegetation such that the detritus emitting $\ce{CO_2}$ was much less than the $\ce{CO_2}$ uptake by plants, then a catastrophe will generally lower the $\ce{CO_2}$ uptake. 

When the catastrophe (e.g. lava flow or land slide) creates a new land-surface, then primary succession begins with the establishment of generally small forms of life and $\ce{CO_2}$ sequestration would be minimal. Otherwise, if the catastrophe leaves behind some form of the prior ecological community, then secondary succession can occur and the region would be able to return to higher $\ce{CO_2}$ sequestration rates much sooner relative to a primary succession event.

You might enjoy the following references:


"Carbon sequestration is related to mycorrhizal fungal community shifts during long-term succession in boreal forests."
available here: http://www.ncbi.nlm.nih.gov/pubmed/25494880
"Chapter 3: Effects of Disturbance, Succession and Management on Carbon Sequestration" in the book "Carbon Sequestration in Forest Ecosystems" available here: http://link.springer.com/chapter/10.1007%2F978-90-481-3266-9_3