Friday, September 23, 2011

Northern Arizona Juniper Woodlands

Utah Juniper Woodland and Semi-Desert Grassland near Ash Fork, Arizona.  This is the high  elevation portion of the Great Basin Desert.
I recently spent some time exploring Northern Arizonas Juniper Woodlands and Semi-Desert Grasslands.  Arizona is an interesting state in that it has many different desert types including the semi-tropical Sonoran Desert, the hot Chihuahuan and Mojove Deserts, and the cool Great Basin Desert.  Of these deserts they also have high and low elevation portions.  Northern Arizona for the most part is high elevation Great Basin Desert.  West of Williams, Arizona Semi-Desert Grasslands composed of grasses such as Tobosa, Side-Oats Grama, and Galleta dominate below 3000 or so feet.  The area I spent time in was about 4300 feet and had these grasses with interspersed Utah Juniper trees.  Most people do not find these woodlands nearly as attractive, and many consider them a nuisance, compared to higher elevation conifer forests.  Spending a little time in them, observing and absorbing them for what they are will show these are in-fact beautiful and interesting forests to be appreciated.

The most obvious feature of Juniper Woodlands is of course the Junipers.  As trees go, the Utah Juniper is rather small, only growing to 12 feet or so.  Northern Arizona around Ash Fork west of Flagstaff is characterized by poor dry soils, cold wet winters, and hot dry summers.  When most people think of the desert they do not think of trees, grass and snow but the Great Basin Desert of northern Arizona is exactly that.  Amazingly, last winter I got stuck in 24 inches of snow in this same area.  The Utah Juniper and Desert Grassland thrive under these conditions.  

Utah Junipers and Side-Oat Grama Grass growing among basalt rocks.

Hiking among the Junipers a few birds make themselves obvious as the fly from tree to tree, the Scrub Jay and Ringneck Dove.  Both birds are particularly fond of the Juniper, but especially the Jay.  Utah Junipers produce an abundance of marble sized green to brown colored berries these birds depend on.  These berries often remain on the tree up to two years just waiting for some animal or bird to come by.  Yes, it does actually seem that these berries wait for birds to eat them being they not only provide the bird with food, the bird also helps the tree.  When the bird eats the berry, the seed passes through the bird unharmed.  Seeds passed through birds or other animals actually significantly increase their chances of germination and are transported to new locations.  Not only that, Jays may cache, or hide, berries in the ground for later use, which may be forgotten later and grow into baby Junipers.  If it were not for these birds the large berry and seed would simply fall to the ground beneath the tree.   Then, if the seed did germinate it would have to compete with its mother for soil and moisture, which of course is the wrong way to start off life.  So as a result, these birds are responsible for the planting of these Juniper woodlands.

Tobosa and Grama grasses growing in the finer textured soils.

Apart from Junipers, Ash Fork, Arizona is known as the flagstone capital of the world.  Flagstone is a particular type of sandstone that breaks into smooth flat rocks people use as patio pavers.  Numerous flagstone mines can be found among the sandstone and basalt lava flow hills in the area.  This sandstone creates sandy soils while the basalt breaks down into rocky clay soils.  Exploring the area and doing a little examination of the soils, it can quickly be found that Junipers, especially the larger ones, prefer the rockier soils along with Side-oats Grama Grass.  Alluvial, or water deposited, fine textured soils are generally characterized by grasses such as Tobosa, different Gramas, and Gallete.  Also interesting were the numerous very small Junipers within these finer textured soils.  Historically these fine textured alluvial soils have only had grasses being junipers seem to prefer the drier rockier areas.  Fire exclusion during the past century however has allowed seeds carried to these areas by birds and other animals to grow unhindered.  

A Colorado Pinon Pine growing Under the canopy of a Juniper.  This pine most likely was carried here as a seed and planted here by a Scrub Jay.

While almost all of the trees in the area are Utah Juniper, a few small Single-Leaf and Colorado Pinon Pines can be found.  This is quite odd considering I couldn’t find a significant mature pine for miles and great numbers of Pinons are even further away.  How did these small trees get here?  Pinon nuts are large and heavy so they couldn’t have blown or washed here.  The answer lays again in the Scrub Jay.  All these small Pinon Pines likely were carried as seed by Scrub Jays and hidden under the Junipers so they could have a snack later on.  Unfortunately, the Jay forgot and the seed germinated, growing into a small tree.  This is both good and bad for the tree.  In this area at least it got to grow into a tree but there is not enough rain to support a Pinon Pine for long.  Junipers do much better with 12-14 inches of rain annually than Pinons do.  Pinons need at least a few more inches of rain to do well.  

The grassy openness of these woodlands make walking through them quite easy and enjoyable except for the occasional cholla or prickly pear cactus.  The trees are big enough however to make orientation through the area difficult at times.  While it is open, you can’t see far most of the time, so finding your way can be difficult.  This also makes it quite easy for wildlife to make a quick escape.  Elk are abundant in these areas and utilize the Junipers to hide as well as food.  Elk are most commonly seen in the early morning feeding in open grassy areas.  Coyotes also are abundant and can provide some great night time yipping and howling entertainment.  But after a few hours of day light or less, these animals easily hide themselves from intruding humans among the Junipers.

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