Posted: Tue Aug 30, 2011 9:42 am
edfrank wrote:This is one of the flaws of many old growth definitions. As dendrochronologists push back the maximum ages of the many tree species, under a one-half of the maximum ages criterion more and more old trees will be excluded. So dendrochronologists are wiping out old growth forests as we speak in areas with this type of a definition.
If we could determine a standard shape family for the decline in numbers of trees in a species, then perhaps a half life could simply be derived based upon that shape and the maximum age tail. Even if another tree a hundred years older was found, that likely would not make much of an impact on the median age. I do know that half-the-maximum age isn't really appropriate for longer lived species.
Ed - i have to say that the first paragraph quoted above had me laughing out loud this morning [LOL, i guess]. i wondered: do the trees wither into the ethers when a new max age is discovered? And, do they gasp, "help me! i'm fading!!" as they wither?
As per the second paragraph: it is a very interesting idea. Like, is there an extreme max age and then a standard max age within most species? That kind of knowledge would be interesting and helpful. It can likely only be calculated for a handful of species world wide based on fairly reliable ages. It'd be neat to see how these kinds of longevities differ between species.
But, I'm not sure it would be helpful in ID'ing OG forests. The 1/2-max age definition used by the state of MD is a serious conceptual and practical limitation. I was out with the man whose job it was to ID old-growth forests for MD one week. He kept going on and on about this site tripping him up in his search and documentation. He finally took me to the site where it was obvious that it was OG. The problem was that he could not match the 1/2 max age criterion. Part of the problem was the use of the 900 yr old age for eastern hemlock that can be found in the literature, an age not even approached through the coring of hundreds of hemlocks in the east. The other was that the slope is so steep [but having decent soils], that it is highly unlikely a tree could stand on the slope for >300 yrs, let alone 450 yrs. It could happen, but the likelihood seems small. Regardless, they missed that stand of OG.
But, don't ask me for a definition of OG. I only know it when I see it and associated evidence.....