I know it is ecology101, but I had never actually done the road trip version of driving from the Sonora desert biome into the alpine/Canadian biome in around an hour. To get the same sorts of changes you see as you climb Mt Lemon from the roughly 2500 ft near Tucson to around 9000 ft at the peak, you would have to drive from southern Arizona up to just south of Hudson Bay.
You start in the scrub and cactus forest on the lower slopes. Next is semi-arid grassland. Soon you get into junipers, some cottonwoods and oak woodland, followed by montane ponderosa pine and then the spruce of the boreal forests. The biomes mix and match in ways they would not if spread over a larger area, as subtle changes in elevation and topography create micro-climates.
It was more than twenty degrees cooler on the top than on the bottom the day I went up.
They call these “sky islands” because boreal and montane forests are islands of this sort of vegetation in a sea of desert. As with all islands, the environments on them are fragile because of its isolation. If species are eliminated from a relatively small area, there may be no nearby seed stocks to bring them back. These communities have been in place since then end of the last ice age, when the cool weather systems were present all around. We can think of the deserts like rising water as the earth warmed 10,000 year ago.
It is important to manage these islands carefully, but sometimes good management seems counter intuitive. It seems to make sense to protect the ecosystems from destructive forces such as fire, but years of fire protection have endangered them. Fire is a natural part of the ecology. When it is artificially excluded by human efforts, the ecological communities change and large amounts of fuel are left standing in the forests or lying on the ground. Instead of being a useful and healthy clearing process, fires under the man-made conditions become major disasters.
When people see these fires they often demand even greater “protection” making things worse and worse. Above you can see the results of a fire made too big by years of fire suppression. If we continue to “protect” this land from regular fires, the forest will grow back – again too thickly – until the next big fire. Below is one of the reasons we exclude and fight fires. The new cabins are named “Adam,” “Hoss” & “Little Joe” after the characters on Bonanza. Hoss is the biggest.
Fire is a natural and necessary part of a healthy ecological process. If we exclude fire, we change the environment in undesirable ways and make it less robust. Smokey the Bear should probably be put on pension or at least modify his pitch. He has done too good a job. Smokey is cute, but when he hired on we didn’t understand as much about the environment.