Alterations form Natural state, defined?
Howdy all, interesting thread. In general it is probably true that it is hard to define natural state for all "forest types". But here in much of California for any ONE specific area it is pretty easy to describe what the climax community would look like,errrggh has traditionally been, in the abscence of stand-altering human activity..
A few selections have to be made first. Perhaps there is no sense in talking about natural state after "European" intervention since it is at most 200 years (in the west) and that is a mere blip on the biologiocal time scale. But in communites like the mixed coniferous and chaparral of SoCal human presence and activitiy on the wildland-Urban-interface have created conditons TOTALLY unlike what existed before major non-native habitiation. So that leaves the question of wether Native American practices altered the plant community enough to matter. Right now the common assumption is probably no, they did not modify it enough to matter, but I think it depends a lot on which native group, and what type of "forest".
Still, in the case of any one specific area the climax community can usually be identified. For example the forested areas of the EASTERN Sierra Nevada in Central California, Pinyon Juniper woodlands would be dominant, while on the Western side a Mixed coniferous forest would be the norm. The "ologists" (my term, my TM LOL!) then argue over what name to give to each plant community, and how many sub-groups to break each community down into based on the presence and relative abundance of various species. But regardless of what name they give it, it is only one community. Usually fire is the agent that causes stand replacement or conversion to another vegetation type, but it could also be avalanche, shading, or rockslide. Firescars, naturalists+explorers' descritions, old photos, or other methods can give a pretty good record of the period before major non-native human alteration. So if we know the interval to stand replacement, and what the climax community is, we have a pretty good idea of what dynamic existed in the plant community before Euro-contact.
The easiest way to explain this is with an example. I am going to hack up the fine work of Dr Richard Minnich of UCRIVERSIDE, and use 2 places in the Californias as examples. One mixed coniferous forest is in the San Bernadinos, and has massive human alteration. Home to the largest urban forest in the US, in developed areas like around Lake Arrowhead domiciles and related structures are 20 percent of the average fuel load per acre. Landscaping and fire suppression have resulted in tree densties if up to several hundred per ace, and often 80 to 100 mature trees per acre.
Now compare that to the Sierra San Perdo Martir about 250 miles osuth in Baja. There is virtually no development, aand almost no suppression. This area has a similar climate in terms of total ppt, with perhaps a bit more summer moisture, and less from northern systems in the winter. Old photos of the San Bernadinos show big similarities between the SBDos around 1900 and the SPMs now.
Many areas in the SBDos have suffered stand replacing fires. The fire return interval is shortened to as little as 20 or 30 years, and suppression has non-randomized large fires into the worst possible weather conditions, 5% humidity with high winds. (this is almost always the only conditions under which fires seriously escape intial attack). Even attempts to counter the effects of past fire suppression with prescribed burns may fail if the prescribed burns do not have sufficient intensitry and flame height to kill almost all the recruitment trees and leave a mostly even-aged stand of trees over 100 years old. In the SBDos as they now exist, most tree mortality occurs at once, in a catastrophic fire. Only costly mechanical fuel removal can reduce the immediate danger around developed areas.
By contrast in the SPMs, most tree mortality occurs between 10 and 50 years of age. Most fires are small, and burn 1-5 thousand acres. One study area (I forgot to write down the size, probably 1000 hectarias) had 212 microburns in a twoweek period in 1991, mostly from lightning. Forest density typically is 40 trees per acre, plus or minus 10 or so.
I know all the ologists are still fighting over HOW past best practices have altered the natural landscape, and HOW to get back to a plant community closer to the stable ones that existed before development and supression were widespread. But WHAT the natural community and it associated and defining fire regime looked like can probably be figured out pretty accurately by research, and looking south to the SPM and the Mexican cismontaine chaparral community.
