Question; 
**Given that, how many trees would I need to plant to solve the global climate change crisis? Should I optimize for a specific type of tree, or would pine work as well as oak or black walnut?**

First, you need to think it as a forest. In a forest there are also trees which lose the game of evolution in addition to trees that win.

Second, you need to look where (in terms of climate) your forest is, and what's its soil. This defines the tree type.

Third, you need to cut your forest on time to optimize it' growth rate. 26 years is optimum, so roughly 4 times a century. 

This way you can [reach growth rates like 4.8 tn/ha Year in Finland][1] or   
[5.16 tons/acre/year in the USA.][2] I am not sure about the unit used in this source, but if their ton is 907 kg and an acre is 4046.85 m2, this results in 11.56 tn/ha/ year. 

If the used carbon amount is $9.2 x10^9$ tons, and [half of wood weight is carbon][3] then you need $1.6 x10^9$ ha or 16 000 000 km2 of forest.  

[There is 39 500 000 km2 of forest in the world.][4] 
If 40% of it is used optimally, it would enough at present rates. The CO2 concentration is not a problem; human population growth is.


  [1]: http://www.puuproffa.fi/PuuProffa_2012/7/puun-kasvu/metsan-kasvu
  [2]: http://www.forestresearchgroup.com/Newsletters/V8No2.pdf
  [3]: http://www.fpl.fs.fed.us/documnts/pdf1984/pette84a.pdf
  [4]: https://en.wikipedia.org/wiki/Forest#Forest_land_area