Fall Leaves in a Sonoran Desert Riparian Zone

A Sonoran Desert riparian area in fall along Cottonwood Creek.

The desert is most definitely not known for spectacular fall colors.  Fall colors do however, find their place along some of the wetter desert water courses.  If perennial water sources are available, even if it is hidden below ground a short distance, the roots of large deciduous trees will find there way to it.  Sycamores, cottonwoods, and willows are all relatively common along streams and washes with perennial sources of water.  Even Arizona walnut and ash trees can be found in some of the more stable riparian zones.  These trees do not display the brilliant hues of red and orange common to eastern forests but do show off bright yellows that are in stark contrast to the dried out browns and greens of the desert.    Desert fall leaves are quite a rarity and are quite unique.  Typically, perennial water sources are considered perched water tables.  A perched water table simply is water that accumulated above the surrounding water sources, most often a result of bedrock that prevents water from penetrating deeper into the soil and out of reach of plant roots.

A recent hike I took demonstrated this concept extremely well.  The hike was along Cottonwood Creek near Lake Pleasant north west of Phoenix.  The majority of this hike is along Cottonwood Creek, which really isn't much of a creek considering water only flows in this creek a few hours every year.  The rest of the year the wash remains mostly dry, except for a few locations.  Nearly all washes in the desert are called dry washes, and for good reason: they are completely bone dry the majority of the year.  A few washes, such as Cottonwood Creek are fortunate enough to have areas that always remain wet.  Cottonwood Creek owes this moisture to its underlying geology.  First off, the creek bed lays at the base of two small bajadas between two small mountain ranges.  One bajada lays to the north of the creek bed and one to the south.  These bajadas and bedrock of the mountains are relatively steep and provide ample runoff to Cottonwood creek so it will run during periods of heavy rainfall.  Moisture is quickly lost into the deep sediments of the bajada and placed out of reach of deciduous tree roots.  In areas where bedrock are shallow though, moisture cannot penetrate deeply and remains closer to the surface within reach of plant roots.  Bedrock can also push water flowing underground towards the surface.  At these locations large deciduous trees take advantage of the shallow moisture and can in a few places form small but beautiful wooded areas.

Wildlife may not be obvious in these small wooded areas, but if you look at the ground you are sure to see evidence of animals.  Javelina and mule deer heavily utilize these small areas and their hoof prints are normally abundant.  In some area, such as along Cottonwood Creek, wild donkey's are also abundant and heavily utilize these areas.  The abundance of shade, food, water, and cooler conditions during hot dry summers gives great value to these areas for every creature.

Happy Halloween! A biologists view of Halloween

Halloween is one of those weird "holidays" no one really knows why we do it.  And oddly, I'm going to try and give a biological perspective to it.  Often we think of the celebration of death or the occult and all the weird things that center around those as the "reason" for Halloween.  Fortunately, that isn't entirely true, though their is that element of it.  Our version of Halloween in the United States today is really a hodge-podge of all sorts of holidays from all over the world.  Historically, Halloween like celebrations were much closer to Thanksgiving celebration except with more singing, dancing, games, and fun stuff like that.  Many cultures have their own version of the holiday to celebrate the end of and abundance of the harvest season.  This is partially where all the pumpkins come in being they often are harvested in October.  So the end of the harvest which does line-up well with the end of October is a great biological perspective we can have of Halloween.  Honestly, Thanksgiving in the end of November is far too late to be celebrating the summers harvest (OK just my opinion!).

Jack-o-lanterns obviously are a well established Halloween traditions that also rooted in the harvest celebration.  This tradition was founded in Britain and Ireland during the 1800's.  For hundreds of years prior to this people made turnip lanterns, which seems much less exciting and much more difficult to make.  These vegetable lanterns were part of a pagan form of trick-or-treating.

One of the latest Halloween traditions, and one of the most exciting I think, is the growing of gigantic pumpkins.  People that grow monster pumpkins learn all kinds of secrets about how to breed and grow these giants.  The entire process can be quite intense and people have been producing pumpkins over 1000 pounds for many years now.  Competitive growing of pumpkins is advancing in the United States so fast that world records are made nearly every year.  This fall the world record was broken again with a 1810 pound gourd!  It won't many years before a 2000 pound is grown.

"Everything you want to know about pumpkins"

http://www.backyardgardener.com/pumkin.html

http://www.foodmuseum.com/halloween.html

Dentists also give us another perspective on Halloween.  As you would guess, they hate it because too much candy really does rot the teeth.  But several dental studies have asked the question, "How can we eat trick-or-treat candy and not rot our teeth?"  Common sense tells us that maybe if you eat it a little bit every night it will be better for you.  In this case however common sense is wrong and research has shown it is better to gorge yourself and eat it all in one night.  Which I am sure most people want to do but rather use some misguided "common sense."  When I tell people this they say, "Of course, then you will get sick and never want to eat it again."  While there probably is some truth to that, the real reason dentists say it is better to eat it in one night is because then your teeth are only covered in sugar for one night as opposed to being covered in a little sugar every night for a longer time.  Here is an article on the subject:

http://today.msnbc.msn.com/id/45080807/ns/health-childrens_health/#.Tqsl50Mr2so