In our last post we discussed hiking the South Trail in the White Tank Mountains. Now we'll move on toward a short section of the Goat Camp Trail and finally onto the Bajada Trail. The end of South Trail and this section of Goat Camp Trail is quite interesting for those who like to examine landscape patterns...
Most of the South Trail is rather straight and smooth, but close to Goat Camp Trail is sort of dips down a little and you will notice the surface becoming a lot more rocky and rugged. This is the second alluvial fan in the bajada. Typically this type of surface is closer to the mountain then the previous surface we discussed, so this bajada is sort of upside down. I suspect this odd configuration of alluvial fans is a result of this second alluvial fan resulting from a large avalanche or debris flow that came out of Goat Camp Canyon. The abundance of disorganized rocks and rugged surface could be in indication of an ancient avalanche. The dry wash at the beginning of the trail also is responsible for eroding away the smaller sediments and leaving behind the heavier rocks and a rugged surface. The major plant cover is brittle bush which prefers rocky and often unstable soil surfaces such as this one. Palo verde and jojoba also seem to like these soil conditions. There are also a decent number of cacti present and a few bursage in patches, indicating there is likely some caliche in the soil.
|This rocky and rugged soil alluvial fan surface is more typical higher upslope.|
After hiking through the rocky and rugged area and heading uphill slightly on the Bajada Trail from Goat Camp Trail, the trail returns to the same alluvial fan most of the South Trail covered. So same soil conditions and same plants as most of the South Trail. But here I want to point out the abundance of saguaro cacti, the icon of the Sonoran Desert. Saguaros are more abundant here than just about any other area west of Phoenix. The reason for this is, as mentioned before, the soil conditions and abundance of triangle-leaf bursage. In addition to that, this area receives about nine inches of rain annually and is relatively free of freezing temperatures. In areas east and north of Phoenix there are many populations of saguaros that are denser, as a result of greater rainfall, upwards to about 12 inches annually. These higher rainfall areas are also higher elevation and therefore more prone to freezing which can damage saguaros by causing their arms to droop towards the ground. Very few saguaros in this area have drooping arms in the area of these trails due to the lack of freezing temperatures. There are a few though. Nearly all of the Saguaros in this area are mid to older aged, you can tell the age of a saguaro simply by its height and presence of arms. The taller a saguaro is the older it is, and more arms usually indicates older age also. There are not a lot of young saguaros, which tells us there isn’t much reproduction going on, and if reproduction doesn’t increase in the next 50 or so years the population will decrease significantly. There is also a lack of very old cacti, which indicates that the population of saguaros was once much smaller than it is now. While I suspect the saguaro population may be decreasing due to lower rainfall during the past two decades, a few years of good rain could easily allow for the establishment of many young saguaros and cause the population to bounce back. So there is no immediate reason for us to fear the disappearance of the saguaro from the White Tank Mountains during our life time.
|A saguaro cactus with a drooping arm. Typically, arms drooping down like this means the cactus was damaged by freezing temperatures.|
And this concluded the White Tank Mountains South to Goat Camp to Bajada Trails tour. Hopefully it was interesting or helpful, even if you don’t hike these trails yourself. In my 150 mile hiking goal for 2012 I currently am at 15 miles. I have a few trails I have hiked and have yet to write about and you’ll be seeing them in the near future. Also, if you have any questions about anything pertaining to this post, or any post, let me know. I want to make everything here on Practical Biology of course practical, interesting, and educational. Thanks!
|A crested saguaro cactus along Bajada Trail.|