That's a tought one, Bob, I've got an itchy trigger finger...
On Tue, Jan 12, 2010 at 10:52 AM, <[email protected]> wrote: > Gaines, > > Oh boy, I hope a rift doesn't develop here in ENTS. Those of us obsessed > with tree heights will naturally want to limit damage by birds perching in > the crowns, especially their highest parts. I'm definitely not suggesting > anyone get out his/her youthful slingshot, but in time the temptation could > grow. Giving this line of thinking a foothold could prompt Jennifer Dudley > to establish a bird safety patrol to keep a close eye on us measurers. > Jenny's wrath would be swift and terrible. Resist the temptation Will. > Resist the temptation Scott, John, Dale, .......... Resist. Resist. > > Bob > > > > ----- Original Message ----- > From: "Gaines McMartin" <[email protected]> > To: [email protected] > Cc: [email protected] > Sent: Tuesday, January 12, 2010 10:07:42 AM GMT -05:00 US/Canada Eastern > Subject: Re: [ENTS] Projected heights > > Jess: > > I had thought about mentioning it before, but when you say that the > growth rate of a pine tree is influenced by its current height, you > bring up an important consideration. Strictly speaking it is better > to say that growth rate is influenced by age, and it is this > relationship that the growth curves are representing. > > But the growth rate/height relationship is something that is too > often ignored. Years ago I read a report of a provenance trial of > white oine, that said that the best way to measure results is not the > height of the trees after some set period of time, but to measure > their growth rate at various specific heights. The idea behind this, > if I remember rightly, is that different sites, including microsites > (my term) influence the early growth of the seedlings differently, but > this influence is minimized in the data if the growth rates of trees > are compared when they are at the same heights (comparably > established, comparably developed). And this kind of measurement would > best predict the trees’ overall growth potential over time. > > Now the data that prompted me to open the white pine growth topic > showed that the growth rate of white pine on the better sites declines > more rapidly than that of white pine growing on the poorer sites, so > much so that after age 55, the growth rates are the same—one foot per > year. I thought this had some application in the discussion of > whether or not white pines could, or did grow to 250 feet. Thus if > the fastest growing pines maintain their relatively fast growth rate > for only 55 years, then the best growing white pines would not grow as > much taller than white pines with more ordinary growth rates as we > might have thought. White pines 100 feet tall in 50 years is good, > but “ordinary.” Growth of 120 feet is excellent, but after gaining 20 > feet over the more ordinary trees in 50 years, and maybe a foot or two > in the next five, no further advantage will be gained. All that made > me think 250 foot white pines, if view of the fact that none exist > today, less likely than I might have thought. > > Sorry—I said all that before. But I wanted to re-establish the context. > > Now to the height/growth rate relationship: lost is the above data > may be the fact that the trees with the most outstanding growth will, > in spite of any decline in growth rates down to the level of other > white pine trees after age 55, still be growing faster at any specific > height. > > Of course as Will and others have pointed out, there is the risk of > storm damage. I would add to that the damage from large bird perch. > The bird perch issue is not recognized by all foresters, but I have > observed it first hand many, many times. The tallest trees in my pine > and spruce stands are the ones usually hit. The new growth is often > completely mashed down. If this happens early enough in the growing > season, especially with the Norway spruce, a leader can be > re-established. I can imagine that slower growing very tall old trees > would have some difficulty doing that, and the damage could > accumulate. This would be a significant influence on the ability of > older, very tall trees to make good further progress upward. > > This relates to the ability of second growth stands to exceed the > growth of trees in the virgin forest. I will take this up in my next > response. Enough for one post here already. > > --Gaines >
