Pacificforest.org is not exactly a neutral source, and that's a pretty confusing article (are they talking about sequestering in plant material, or respiration?

Pacificforest.org is not exactly a neutral source, and that's a pretty confusing article (are they talking about sequestering in plant material, or respiration?). In terms of annual growth (which is a decent proxy for the amount sequestered from the atmosphere), trees peak (the culmination of the periodic annual increment), and then every year sequester less than the year before. See page 3 here [1]. There's a reason they mention 90 years as that's approximately the culmination of mean annual increment (the highest average growth over a rotation) for PNW douglas fir forests, which is what Pacific Forest Trust principally focuses on. A very old forest reaches statis and stops sequestering carbon all together, and as we see in the intermountain west, they can become very large sources of emissions as you lose forests to stochastic events like fire.