White Tank Mountains Bajada Trail Nature Hike

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.

White Tank Mountains South Trail Nature Hike

Two Saguaro cacti in the White Tank Mountains Regional Park.

When it comes to viewing Saguaro Cacti and an unusual bajada or alluvial fan formations, the South and Bajada Trails in the White Tank Mountains  are about as easy and as they come, at least for the western portion of Phoenix, Arizona.  The trail begins at the South Trail near the entrance of the regional park, heading towards a short section of Goat Camp trail, and then to the Bajada trail, entire length about 3.5 miles and all pretty flat for some relaxed hiking.  The entire length of trail transects the bajadas, or alluvial fans, that were deposited by ancient erosion and avalanches descending from the surrounding mountainsides to the north and south of the trails and Goat Camp Canyon to the west of the trails.  Different types of deposits and differing types of drainage patterns has resulted in two major alluvial fans forming a bajada that is seemingly backwards in formation.  One of these alluvial fans though is ideal habitat for the iconic Saguaro Cacti as I will explain below.  This post will be in two parts, this first post will cover mainly South Trail.  The second post on Monday will cover mainly Bajada Trail. 

Desert dry wash along the South-Goat Camp-Bajada Trails in the White Tank Mountains.

Beginning at the South Trail trailhead near the entrance to the park, you immediately hike down into a dry wash.  This wash is one of at least a few washes that are responsible for the unusual bajada formation along the trail further along.  As most people would expect, a dry wash, also known as an ephemeral drainage, is where runoff water concentrates and flows for short periods of time following heavy rainfall.  The water only flows a short period of time because it is quickly absorbed into the loose sand in the channel where it can infiltrate very deep.  Deep in these wash sediments the water is protected from the extreme heat on the surface and is therefore a reservoir during long dry periods.  Only deep rooted plants, however, can access these reservoirs and that is why there is a concentration of ironwood and palo verde trees.  Even shallow rooted plants such as cacti and triangle-leaf bursage are in higher concentration here through, simply because there is more moisture in these washes then the surrounding soils.  Along with transporting water, washes similar to this one also transport sediments eroded from further upslope.  Washes, as they transport sediments down slope, are the major creators of alluvial fans.  Many alluvial fans were once at the end of a dry wash where the wash sort of spewed out over the surface all the sediments it transported from upslope during short periods of water flow.  Washes also are the major destroyers of alluvial fans being they erode into and carry away the sediments that compose the fans.  Because of these things, if you are familiar with the washes on a Sonoran Desert alluvial fan or bajada you can know a lot about the history of these landforms.  We will see this later on in the hike towards the end of the South Trail.

The plant community along the South Trail is mainly Cacti, Bursage, and some Palo Verde. 

Once hiking out of the wash the trail crosses onto another alluvial fan surface with a different soil type.  This soil type continues for most of South Trail.  The vegetation is characterized by shallow rooted plants, mainly cacti and triangle-leaf bursage.  This tell me that the soil is well developed, probably with a caliche horizon and maybe with a weak argillic.  Caliche is simply a rock-like calcium layer that forms about 20 inches below the soil surface in deserts and argillic horizons are deposits of clay just above the caliche.  Both layers prevent deep roots from penetrating and help shallow rooted plants become established, the most important of which is triangle-leaf bursage.  This small shrub grows everywhere along most of South and Bajada Trails and because of its abundance there is also an abundance of cacti.  Bursage functions as a nurse plant for many desert plants.  Odd as it might sound, most desert conditions are too hot, dry, and sunny for most desert plants to establish themselves without the aid of another plant.  Being bursage can establish without help of other plants, it provides the shade and slightly cooler and moister conditions required for cacti to germinate and grow under their small canopy.  The presence of bursage, along with the soil conditions, is therefore why there are so many cacti present along the South and Bajada Trails.

 To be continued Monday...

Do Plants Breathe? How do Plants Breathe?

Plants breathe quite the opposite of the way we breathe.  They do breathe though, and they do it through tine holes called stomata located on their leaves.

Oops, I thought I posted this on Monday.  But here you go, better late than never!

It’s common knowledge that humans and animals inhale oxygen and exhale carbon dioxide in a process called respiration.  A lot of people also know that plants do just the opposite, “inhaling” carbon dioxide and “exhaling” oxygen, in a process called photosynthesis.  As a result plants and animals cycle oxygen and carbon dioxide between each other, one producing a waste that is used by the other and so on.  Obviously, animals breath through their mouths and nostrils but the way plants breath is far less obvious.  Nothing on a plant resembles a mouth or nose in the way animals breath.  And if we look at the chemical reaction for photosynthesis and respiration we will see they are sort of opposites, or reflections, to one another.  What one produces the other consumes.  So because of the differences we should expect totally different ways of breathing between the two.

Photosynthesis

Water + Carbon Dioxide + Light → Sugar + Oxygen

Respiration

Sugar + Oxygen → Carbon Dioxide + Water

Stomata are the round holes in the photo above.  This is a microscopic image of a fingernail polish peel taken from a leaf surface.  Most plants open these during the day in order to breathe.  Only cacti and agaves open them at night to breathe

The only way to find the structures through which plants breathe is by searching microscopically.  Very simply, by painting a square inch or so of a leaf with clear fingernail polish, then peeling it off and viewing it under a microscope we should be able to find the stomata, which are tiny microscopic holes through which plants breathe.  The dried fingernail polish retains the cellular imprint of the leaf surface so when viewed under a microscope every structure on the leaf surface can be seen.  On the fingernail polish peal, the stomata appears as a tiny hole with two crescent shaped cells on either side. These crescent cells are known as guard cells being they open and close the stomata in order to let “breathing” to occur or not, and to preserve water.  Stomata can be found on any green surface of a plant, but typically are located in the highest concentrations on the underside of leaves.  Location on leaf undersides prevents exposure to the sun which helps prevent excess water loss through the stomata.  

Different types of plants have different patterns and forms of stomata.  Most trees have lots of relatively small oval stomata evenly spaced all over their leaves.  Desert trees and shrubs generally have fewer stomata to conserve water.  Corn and other grasses often have more rectangular stomata organized in rows along vessels.  Cacti have relatively few round stomata located in pits, but they are huge compared to other plants.  Types and shapes of stomata generally depend on how much water a plant has available and its general physiology.  Plants with lots of stomata have lots of water while plants with fewer stomata have less water.  If you have a microscope try making a fingernail polish peal to view the stomata, it takes a few tries but after that becomes extremely easy. 

Here is a website with more details on how to do this experiment:  Stomata Experiment

Sorry, I completely forgot to update the blog on Monday.  I became so busy with writing things up for this site that I thought I posted something new!