Looking into the Iowa Deciduous Forests Past

In 1846 Iowa gained statehood and migrants rushed to the prairie taking advantage of free land made available by the government.  That same year, my German ancestors journeyed  across the Atlantic, through the eastern U.S. to the mighty Mississippi.  The country and forests look much different from what we have been discussing in previous blog entries on deciduous forests.  The Mississippi likely would have been the largest muddiest river they had ever seen.  Being the railroad would not have crossed into Iowa for four more years, migrants would have had to pass through the river bottomlands on foot or by wagon and cross the river by ferry.  Just thinking of crossing it would have been a daunting task.  Even if trails had already been blazed,  swamps, backwaters, islands, and mud in the bottomlands lining the mile or so wide river made crossing into Dubuque, Iowa from Illinois or Wisconsin quite an adventure.  The entire journey through bottomland muck and across the river could have been many miles.  Logging of the bottomlands would have begun at a larger scale 12 years prior to this time when the first sawmills were built in Dubuque, but the forests still would have largely been untouched by logging at this time.

A muddy bottomland forest.

First Steps in Iowa
Once crossing the Mississippi and setting foot in Iowa for the first time, it is likely migrants first entered an area covered with early successional Cottonwood and Willow forests along the river banks.  Being near the river, frequent flood disturbance and soggy soils would have maintained this forest type.  Heading inland, areas with slightly less soggy soils and less flood disturbance Boxelders, Ashes, Silver Maples, and Elms would have increased in abundance.  Elms of that time were very different from today.  Large, often several hundred year old Elms would have been common at that time.  Today however, Elms have been resorted into small understory trees only living a few decades at most due to the introduction of Dutch Elm Disease into the Midwest during the 1900's.  Further inland, less disturbed areas would have likely had more Sugar or Red Maple dominated forest than we see today.  Sugar and Red Maple, being a late successional climax species, would have likely been more abundant simply due to the lack of logging, allowing for succession to come to climax.

Moving upward, away from the river, more rarely flooded terraces would have had Oak-Hickory type forests.  Many types of Oaks would have been present including Swamp and Pin Oaks in wetter areas, White, Red, and Bur Oaks in the drier areas.  Bitternut Hickory would also have been in wetter areas and Shagbark Hickory in drier areas.  Some of the trees common below the terrace such as the Maples, Boxelder, and Elms would have also been present in this area, especially in moister locations.

Mature White Oak forest with widely spaced trees.  After coming out of the Mississippi River bottomland forests settlers likely found forests such as this one where wagons could easily move through the trees.  The floor of this forest is burned every few years, removing non-fire resistant vegetation.  Larger fire resistant oaks however survive the fires.

Entering the Prairie
Marking the end of the Mississippi river bottom, 200 to 300 foot steep limestone bluffs rise into the Tallgrass Prairie.  Moving up the bluff, the land became drier, and fire rather than flood became the major disturbance type.  All other species of trees slowly left the forest except for several species of Oaks.  White, Bur, and Red Oaks formed a woodland to savanna forest type.  These Oaks, due to their thick barks, easily survived the frequent prairie fires.  Non-fire adapted trees and shrubs, as well as smaller trees and seedlings of fire adapted species, were killed off by fire.  Larger Oaks however survived.  These forests were filled huge magnificent widely interspersed Oaks several hundred years old.  Today, most Midwestern forests are thick with vegetation and one could never imagine driving a wagon through them without running into a tree.  In 1846 however, the trees were so widely inter-spaced along the river bluffs that wagons were easily driven through.  Moving further from the river, trees likely became limited to valley and creek bottoms where they were protected from fire.  Ridge-tops, where it was driest and fires most frequent were primarily un-plowed prairie at this time.

Most free government issued homesteads were on these prairie ridge-tops.  This is simply because hills and valleys became less frequent and prairie became the most abundant ecosystem type the further away from the Mississippi you moved.  Prairie grass was so thick and tall it was difficult and dangerous to navigate through.  This grass was easy to get lost in and was home to buffalo and rattlesnakes, among other dangers.  Settlers often could not find their homesteads in this sea of grass.  So the Army Corp of Engineers at that time would burn the grass and mark the corners of the homestead.

An Oak Savanna, likely similar to what 1800's settlers would have seen.  These oaks have thick bark that  helps  these trees to survive frequent prairie fires.  

It is unknown how extensive Oak Savannas were prior to settlement.  These savannas contained relatively few Oaks, widely interspersed in the prairie grass.  Being Oaks were the most readily available building material these savannas were the first to be logged.  It is likely there were extensive savannas in Eastern Iowa, they were however logged prior to any scientific investigation.  The first settlers built their log homes, sheds, and barns out of these oaks.

Today, Oak Savannas are gone for the most part and only about one third of the overall Iowan forests remain.  These forests are almost all likely in earlier successional stages than they were in the mid-1800's.  This is simply due to the fact of logging and agricultural disturbance over the past 150 years.  Bottomland forests are about half what they were prior to settlement simply due to development within old bottomlands.  Oak-hickory forest types, once limited to bottomland terraces have expanded into uplands due to lack of fire disturbance.  But none of this is to be negative about Iowa's forests.  Though very different from what they were 100 plus years ago, they are still magnificent displays.

A large White Oak, similar to ones Iowan settlers would have seen in the 1800's.

August in the Sonoran Desert: Monsoon Season

The very large anvil portion of a large cumulus cloud from the Arizona Monsoon season.  Often huge anvils like this mean a strong monsoonal storm is coming.  Picture from:http://www.wrh.noaa.gov/fgz/science/monsoon.php?wfo=fgz 

So far this year monsoon season has been a flop.  We are towards the end of August with only an inch of rain or so in Phoenix, only 0.25 inches in the mountains west of Phoenix, and a fortunate 2 inches in the mountains east of Phoenix.  Other areas of the Sonoran Desert are also below the average summer rainfall totals, which are about twice or more than what we have received.  This is quite disappointing considering we haven't had good summer rainfall for several years now.  Us desert dwellers look forward to the break in the summer heat that rainfall provides.  But as is normal for the desert, there really isn't such thing as "normal" rainfall in the desert.  Fortunately, these poor rainfall reports could change to above average with a single large thunderstorm.

What is the Monsoon?
Monsoon season in the Sonoran Desert technically begins June 15th and ends September 30th.  During this time period, the normal dry heat of the desert is replaced with humidity from the Pacific Ocean and Gulf of Mexico.  Extreme summer heat in the desert causes rising air, creating a low pressure system pulling in this tropical humidity.  Wind patterns change as a result of this low pressure, shifting the normal dry western winds to humid winds out of the southeast.  This shifting wind pattern is where the monsoon gets its name, and means "wind-shift" in Arabic.  In order for rain to fall, high level humidity must be in place from the Gulf of Mexico (called the Bramuda High) and low level humidity must be in place from the Pacific Ocean and Gulf of California.

An anvil cloud, a type of cumulus cloud that results from hot rising humid air.  The flat top is a result of cooler air higher in the atmosphere.  There are no obvious cirrus clouds surrounding this cloud.    Picture from Wikipedia.

How to predict a monsoonal thunderstorm without the weatherman
1. High temperature around 100 to 108 degrees are optimal.  These temperatures heat moist air causing it to rise and form rain clouds.  This heated rising air is called convention and the resulting clouds are known as convection clouds.
2. High due points above 50 to 55 degrees, the higher the better.  This supplies the moisture to form clouds and rain due to rising air.
3. Winds generally coming out of anywhere from the south to east to north.  These winds are blowing humid air into low pressure systems and rise to form clouds.
4. Low level cumulus clouds, another indication of lower level atmospheric humidity.  These clouds should form with convection causing moist air to rise due to afternoon heat.  And of course, you need clouds for rain.
5. Large cumulus clouds that form flat-tops called anvils.  The larger the anvil generally the larger the storm.  Clouds wider then they are tall bring the most rain. Smaller, or tall skinny clouds with or without anvils and may appear to be leaning to one side, may bring small amounts of rain, or rain may never hit the ground.
6. High level cirrus clouds.  These clouds may indicate no rain if scattered.  Cirrus clouds are not always present, but a good storm will almost always have cirrus clouds proceeding it around the anvil.

Monsoonal thunderstorms in the Sonoran Desert are quite complex, it takes a lot of different things to be in place for a good storm to happen.  For example, if low level moisture is in place but high level moisture is not in place, clouds will form and some rain may fall from these clouds but may never reach the ground.  Clouds that form under these conditions often will be small, bent in one direction.  If however high and low level moisture are in place, rising humid air will form cumulus clouds lower in the atmosphere that continue to rise until they hit higher level cooler air.  This will result in an anvil cloud, which is a type of cumulus cloud with a flat top like an anvil.  This rising humid air hitting cooler air can form some pretty amazing storm clouds and at times some pretty amazing rainfall.

Monsoon Thunderstorms in the Desert
The drenching rain, spectacular lightning, and violent winds are something to behold.  Experiencing this type of storm will most definitely leave an impact on anyone.  Everything in the desert waits longingly for these storms.  In the dry hot months prior to monsoon season, the land becomes painfully dry, causing plants to shrivel up and die or go dormant.  Watering holes also dry-up, forcing many animals such as javelina and mule deer to stay near more permanent water holes in the mountains.  Mountain lions take advantage of these times by stalking prey near these watering holes, making life even worse for these thirsty animals.  Other animals and birds simply hide away from the heat, only coming out at night or limiting their activity all together.  Everything hides from the heat and dryness, waiting for rain.

An Ocotillo leafing out after some modest summer rainfall.   Most of the year this plant remains leafless in order to conserve water.  When it rains however, the plant quickly grows leafs.  These leafs remain on the plant until the soil drys out.  Once dry the leafs turn yellow and fall off, waiting to leaf out until the next rainstorm.

However, when a drenching rain hits, temperatures can at times drop from the 100's to the 70's or lower.  The ground becomes soaked. If rain comes hard and fast enough the washes fill with water, sending flash floods through the mountain canyons and into basins below, creating new and filling old waterholes to the brim.  With this water, life and energy return to the desert once again.  If you go hiking after a major rain, one of the first things you will notice is the new flurry of insect activity.  Ants will dig out highways in the washes.  Swarms of tiny mosquitoes will form (the one time of year you will want bug spray).  All sorts of gnats will also come out.  This also seems to awaken bird life feeding on these insects.  Animals that were limited to the areas around waterholes in the mountains the day before will once again venture out.  Even in the city, the most non-outdoorsy people will venture outside to experience the break in heat and dryness.  Several days after rainfall, plant life begins to awaken.  Dried out Triangle Leaf Bursage, Brittlebrush, and Creosotebush green-up and begin to grow again forming new leaves.  Ocotillos, which spend most of the year leafless form new leaves.  The Palo Verdes will also grow new leaves.  Annual plants like Prickly Poppies and Sacred Daturas will germinate and grow.

All this activity will slowly wane after days to weeks of time if rain doesn't return.  With the decline of monsoon season towards the end of September though, life does not return to the dull seemingly lifeless heat.  Rather, temperatures have cooled considerably and often more water remains across the landscape as we head into fall.

More information on the Arizona Monsoon: http://geoplan.asu.edu/monsoon.html

How to Map Soils

Looking at this landscape a little knowledge of soils can explain a lot of things.  Learn how to piece together landscape stories with the information on soil distributions and mapping in this blog entry.

Unless you are a little unusual, you probably rarely consider the soil we walk across.  But its OK to be a little unusual, the benefits can be great.  If when we are hiking, or even in our own backyard, we were to consider the soil we stand on and how different types of soil are distributed around us, the education we would receive would be great.  Far to often even seasoned research scientists will forget about the soil they walk over, even if it makes a huge difference to what they are studying.  It would literally pay for these scientists to have a little soil education.  By using the clues outlined in this article you can begin to piece together where specific types of soils are located, and begin to develop a story to how the land, plants, and animals came into their present state.  This also helps in understanding gardening or landscaping projects.  Every landscape has a story to tell, and very often that story starts with the rocks and dirt.  Here are the clues to look for:

Parent Material
What is the general type of rock that you find in an area?  A good rock book will help you figure this out.  Certain rocks will produce certain soils (click here for a previous blog on this subject).  Fortunately, there are only a handful of different types of rocks most soils are made out of.  Where I live in the Arizona Sonoran Desert the most common rock parent materials are granite, gneiss, basalt, and schist.  Where I grew-up and still visit often in Iowa limestone and sandstone are the most common rocks.  In Iowa however, rocks are usually not present and the parent material is glacial deposits (glacial till), alluvial (water deposited along rivers or streams), or loess (wind deposited).  The lack of rocks also is a good indicator of a particular soil type.  If there are no rocks try to use landform or landscape position to identify soil.

An example of landforms in the Sonoran Desert.  The foreground of this picture is a flat basin with only 1 to 2% slope.  In the middle of the picture is a long narrow hill called a banali.  In the distance are mountains.  Each of these landforms will have their own soil types.   

Landform
What types of landforms are near you or are you on?  Hills, mountains, basins, plateaus, plains, depressions, small rises will all produce different soil types.


Landscape Position
Where in the landscape do you find yourself?  This is similar to landform but more specific to where you find yourself on a particular landform.  Do you find yourself on a hillside, a hilltop, a flat plain along a river, a mountain?  Are you close to a mountain or far away from a mountain?  All these different areas will have different soils.  Also consider elevation.  Are their multiple plains, or flat areas, each with different elevations?  Each individual plain will likely have different soils.

This granite rock and the lack of other rocks in the area indicates glacial till as the parent material.  This rock was carried by a glacier from Canada to Iowa during the ice age.  The landforms in this picture also indicate different soils.  The flat area in the mid to foreground are one type of soil and the hill in the background has a different type of soil.  Behind where this photo was taken is another flat area, lower in elevation and with finer textured soil along the Cedar River, indicates another soil type.  Difference in vegetation does not indicate different soil types in this picture due to different disturbance histories.  The grassy area is disturbed by burning every few years while the forest is not burned.  

Slope
What is the general slope of the landform you stand on?  Again, this overlaps with landscape positions and landform, but helps you narrow down a particular area to a particular soil type.  Is the slope steep, flat, moderate?  Approximately, what is the percent of slope?  Consider landform or landscape position again, hilltops will have one particular slope, hillsides another, and basins or plains another.  Each will have a different soil type.

Soil Color
What is the soil color?  Refer to this previous blog entry to find more about what that soil color means.  One particular soil is going to have one general soil color.

Soil Texture
What is the soil texture?  Refer to this previous blog entry to find out how to determine and what that soil texture means.  One particular soil type is going to have one general soil texture.

Plant Communities
Generally, plant communities correspond directly to soil types.  Meaning, two different soil types are going to have two different plant communities.  The differences in plant communities may not be obvious.  Also, if there is a history of disturbance using plant communities as an indicator for soil becomes worthless.  For example, using plant communities as an indicator in deserts works extremely well due to the fact that deserts usually lack fire or agricultural disturbance.  In the Midwest however, fire is a normal part of prairie management but not of forest management.  And depending on when agricultural or logging disturbances in the Midwest happened will also determine what stage of succession a forest is in.  So depending on when and what type of disturbance has happened historically, one particular soil type may have several different plant communities.

So piecing all these things together, you can determine that an area has one particular soil type if: 1. the area is on a particular landform, 2. the area is on one particular landscape position on that landform, 3. that area also has similar parent materials, 4. The area also has a general soil color, 5. the area also has a similar soil texture.  Lastly, plant communities may or may not indicate a soil, depending on disturbance history.

This may seem like a lot of information, but with some practice this becomes a lot easier.  Landscape stories can be quite fascinating and often, most of the information you need is right under your feet.

Science is for Everyone! Biomimicry

Picture from article below.

This is an unbelievable example of how science is in-fact for everyone, not just Ph.D's!  A 13 year old boy made some basic observations and identified some patterns in tree design.  Wondering why trees had this organization he decided to design his own tree with similar branching patterns to natural trees, and with solar panels as "leafs".  Amazingly, he discovered when the solar panels were organized on a "tree" with similar branching patters to natural trees, the solar panels collected significantly more light.  This has huge implications for the solar industry and will surely have huge benefits for society in the future.  All this stemmed from a 13 year old going on a hiking trip.  This is a great example of biomimicry which we discussed in a previous post.

Here's the article: The Secret of the Fibonacci Sequence in Trees

I love this because this discovery all started with a young boy on a hike making some basic observations.  Basic observations, like this one, are exactly how all science begins.  Everyone is capable of doing this.  Science then asks: why or how does this work?  From there, an experiment is made to answer the question.  This is also an example of how even the basics of nature have yet to be discovered and simply how amazing it can be!

Looking Into Forest Past and Future: Eastern Deciduous Forest Succession

Red Cedar trees that have invaded a dry prairie in Eastern Iowa.  Cedars require full sun and will likely be succeeded by Elms, Dogwoods, and Black Cherry which are more shade tolerant.  

Do you ever wonder what a forest used to look like decades ago?  Or do you wonder what a forest will look like in the future?  The key to finding these answers lays in determining what stage of succession the forest is currently in.  Previous posts on Eastern Deciduous Forests of Iowa the concept of succession has been discussed several times.  Simply put, succession is the progression of one group of species to another and to another and again, until a climax community is reached or disturbance starts the process all over again.  Anyone can observe this process in an old abandoned field or even garden.  First herbaceous plants colonize the area, followed by shrubs, then trees, and lastly different types of mature trees.  For those who know what to look for in a forest, a little knowledge can tell you a lot about what a forest was like in the past and what it will be in the future.  

An early succesional stage, or pioneering stage, forest composed of Willow and Cottonwood.

All plant communities start with "pioneer" species.  These are species that first colonize a plot of land and are typically herbaceous like weeds and grasses.  Anywhere from years to decades after herbaceous plants are established, woody plants will begin to colonize.  The first woody plants established require full sunlight, are usually quick growing, and often short lived.  Sumac and Aspen are two good examples of early succession trees that require full sun, are quick growing, and are short lived, usually only living for decades.  Other early succession trees such as Red, White, and Bur Oaks, as well as Red Cedar, also require full sun for establishment but are much longer lived, often living for centuries, and are often slow growing.  Other common early succession trees are Hackberry, Ash, Cottonwood, Willow and Birch.  So if you are hiking and find a grove with some of these trees, you know it is rather young and will become a mid-successional forest in decades to come.

An older pioneering forest composed of primarily of Ash.  There are some smaller younger Oaks growing in the shade of these Ashes.  The Oaks will one day replace the Ashes and this will likely become an Oak-Hickory forest.

Unfortunate for these pioneering plants, they eventually grow large enough to actually shade themselves out.  Pioneer plants require full sunlight and cannot grow in shady environments.  For this reason these plants will not reproduce and instead more shade-tolerant trees will replace them.  Often in early successional forest, if you look at the younger trees growing in the shade you will know the future of the forest.  These smaller younger trees likely will replace the larger trees they grow under.  In Iowa and other parts of the Midwest, Oaks, Walnut, and Hickory trees are more shade tolerant and will eventually replace the pioneering plant community.  Yes, Oaks can be both pioneering and mid-successional depending on the environment.  Longer lived early successional trees such as the Oaks and Red Cedars can also survive into the mid-successional forest.  This middle aged forest also begins to form a more complex structure with a canopy of mature trees, and understory of smaller trees, a shrub layer, and ground cover.  This layering is present in pioneering forests also but becomes more defined with age.  Dogwoods are common shrubs with Ironwood and Elm being common understory trees in these forests.

Again though, lurking in the understory may be trees that will soon become the next successional stage, also called the climax stage.  If you are in an Oak-Hickory forest and find an abundance of small Maple trees growing in the shade you can know that in several decades this will become a Maple forest.  Maples and Basswood are very shade tolerant trees.  If an Oak-Hickory or other type of forest becomes overly shady the Oaks and Hickories will not be able to reproduce being they require sunlight to grow.  Maples and Basswood are quite at home growing in the shade and will slowly grow until the larger trees die or are shaded out.  In Iowa the Maple-Basswood forest is the most stable forest type because these trees are able to continue reproducing themselves, even in their own shade.  So, without any disturbances the Maple-Basswood forest is very stable and will grow indefinitely, and for this reason they are called a "climax community".  Another community of trees will not replace this community until fire, floods, logging, disease, drought, or storms disturb this community, killing off the trees.  Once the community is disturbed we start over with the original pioneering, early successional stage.

Pioneering Stage: Shade intolerant trees 

Mid-successional Stage: Partial shade tolerant trees

Climax Stage: Very shade tolerant trees

Disturbance during any one of these stages starts the process over at pioneering.

This grove of Bigtooth Aspen and Sumac are in the middle of an Oak forest.  It is likely that this area was an Oak forest that was disturbed by logging, which caused the pioneering Aspen and Sumac trees to become established in the full sunlight.

Not all areas will reach a Maple-Basswood climax.  Areas with sandy dry soil will often climax with an Oak forest.  And areas that are frequently disturbed with low burning ground fires will also climax with Oak forests.  Maples and Basswoods are easily killed by fire but Oaks have thick bark adapted to surviving ground fires.  For this reason, Oak forests were the most common type of forest in the uplands prior to settlement in Iowa.  Pre-settlement prairie fires were very common and would have killed trees not adapted to fire but allow fire adapted species such as Oaks to survive.  It was only the wetter areas, typically the bottomland forests along rivers, which were too wet for fire where the Maple-Basswood climax would have been found historically.

This mature Oak forest at the Indian Creek Nature Center near Cedar Rapids, Iowa, is managed by having controlled burns every few years.  These surface fires kill trees not adapted to fire such as Maples, Basswoods, or Hickories.  Oaks however, survive due to their thick bark.  

How to look into a forests past and/or future
1. What types of trees are present in the canopy?  Are they pioneering, mid-successional, or climax species? Use the list of trees in the descriptions above to find out.  You can also use this list of trees by shade tolerance to help you find out.
2. What types of trees grow in the understory?  If they are Oaks, Maples, or Basswood they will eventually replace the current forest type.
3. Look for evidence of disturbance.  Do you find old stumps as evidence of logging?  Dead trees as evidence of flooding or disease?  These things should result in a return to a pioneering forest.  Or do you find charred woody materials as evidence of burning?  This should result in an Oak forest or savanna and the absence of other species.
4. Where are you in the landscape?  Uplands or bottomlands?  Is the soil sandy and therefore dry or have higher clay content and therefore wetter?  Drier soils will more likely climax with Oaks, especially if fire is present.  Wetter soils will more likely climax with a Maple-Basswood forest.

So along with simply enjoying the magnificent trees you hike through, with this information you can hopefully do a little detective work.  Often this process can be difficult but it sure can add a lot to you knowledge of the forest making you hike a little more interesting.

Prickly Pear Fruit Harvesting and Natural History

Prickly Pear cactus with ripe fruits.  

End of July through August tasty tunas ripen all over the Sonoran Desert.  Tunas in the desert you may ask?  Tunas are simply a common name utilized for Prickly Pear fruit in the Southwest, actually having nothing to do with the fish and are much sweeter.  After blooming in spring, a green fruit appears at the base of the flower.  After months of ripening through blazing summer heat, the green fruit turns pink, then red, and finally a dark red wine color.  Once fruits are red, they are ready for picking but flavor can change considerably as the color changes.  After ripening, if the fruit is not eaten it simply dries up and falls to the ground.  Prickly Pear is most abundant in areas receiving greater than eight inches of rain annually and where much of this rain comes in summer.  Mountainous areas in the eastern Sonoran Desert, such as west of Phoenix and around Tucson, can have huge thickets of Prickly Pears often blanketing the landscape in places.  The number of fruits a plant produces annually depends on how much rain was received during winter months.  However, even in average rainfall years, so many fruits are produced even the animals will not be able to eat them all.  Luckily, these fruits keep for a month or so on the plant.  Even then, most of the fruits will not be eaten.

Desert Tulip Prickly Pear flower blooming in April (Opuntia phaeacantha)

As with all fruits, fruits are meant to be eaten.  The Prickly Pear produces brightly colored sweet fruits, attracting birds of many types as well as Javelina, Deer, Chipmunks, Coyotes, Kit Fox, Pack Rats and just about any other desert dwelling animal, including humans!  All cacti produce a brightly colored fruit with seeds filling the pulp inside.  Most cacti, such as Saguaros, produce tiny black seeds that are highly adapted to being eaten by birds.  Prickly Pears, however, contain tan seeds, many times larger that are as hard as rocks.  Oddly, if you were to simply to plant one, water it, and wait for it to grow, nothing would probably happen.  These rock hard seeds are rock hard for a reason.  They are designed to be eaten by animals and have their seed coat partially digested, making them ready for germination.

In Mexico, South America, and the Mediterranean region domestic Prickly Pears are cultivated for both their pads and fruit.  Depending on the variety, large red, green, yellow, or orange fruits can be produced.  In the wild however, red is the only edible fruit color.  Many different species produce edible fruits, but in the Sonoran Desert Engelmann's and the Desert Tulip Prickly Pears (Opuntia engelmannii and phaeacantha) are probably the most abundant that produce edible fruits.  Many species produce inedible fruits, but they aren't poisonous, the fruits simply dry out before they can be eaten.  Native Americans generally did not eat too many fruits at one time however, being too many fruits can produce a fever for some unknown reason.  The same is true today, if you eat wild prickly pear fruit don't eat too many, or you likely will be running a fever.  The fruits are extremely tasty and refreshing, something like a cross between strawberry and watermelon.

How to Harvest Prickly Pear Fruit
1.  Find a Prickly Pear cactus with red fruits on it during the months of July or August.  Fruits will taste different depending on their color, species, location, and time of day harvested.  Experiment and find what tastes best to you, but don't worry about it, if ripe they all taste pretty darn good.
2. Using a grill tongs pick the fruit off the cactus.  The tongs will help you avoid being poked by the spines.  A few dozen fruits will be plenty to start.
3. Freeze the fruits for several days.  This burst the cells containing the juice.
4. Thaw out the fruits and then mash them in a bowl.
5. Once the fruits are mashed, strain out the juice into another container.
6. This juice should be boiled and can be used for a variety of different recipes.  I simply like to drink some of it.

Another version of the above is to place the fruits in water and boil.  Boiling, like freezing, bursts cells releasing the juice.  After boiling, mash the fruits and strain out the juice.

Website with Prickly Pear fruit recipes: http://www.cooks.com/rec/search/0,1-0,prickly_pear,FF.html

Soil Stories: Natural Resources Conservation Service

This 30 minute Soil Stories video from the Natural Resources Conservation Service is a great introduction to all the major aspects of soils.  I believe this video is valuable to just about anyone who is interested in soil such as hikers, gardeners, farmers, nature lovers, land owners, landscapers, and anyone who eats; so pretty much everyone.  Everything is presented in a very clear manor using real scientists and real scientific work.  Here it is:

We have been covering many of these aspects of soil in recent blog entries and this video sums them up pretty well.  I plan on covering a few more aspects of soil in the near future.  Then we will be moving on from soils to plants and animal ecology.

http://www.nrcs.usda.gov/wps/portal/nrcs/home

NRCS soil mapping tool: http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm

Cryptobiotic Crusts: What's a Biological Soil Crust?

The black stuff between the rocks is cryptobiotic soil crust, composed of cyanobacteria, algae, and fungi interwoven together.  If you look closely green may be also seen on the crust.  These green areas are the beginnings of moss growing on the crust, indicating a healthy crust that hasn't been disturbed for many decades or longer.  White Tank Mountains, west of Phoenix in the Sonoran Desert.

Cryptobiotic is sort of an obscure weird word.  Cryptobiotic soil crust probably is even weirder, like some odd disgusting thing nobody really wants anything to do with.  The reality is, these crusts are very useful and important to all desert life.  The very word "crypto" means obscure or hidden, and many desert hikers may have walked past miles of this crust without every noticing it.  "Biotic" means living, which is also odd being most of these crusts simply look like... well... crusts.  If we were to zoom in on these crusts with a microscope however we would find a complex interweaving of cyanobacteria, algae, and fungi.  This seemingly lowly inconspicuous  crust is essential to the desert, and without it desert life and landscapes can become much different.

For the majority of the year these crusty organisms are all dried out and dormant, appearing almost completely lifeless.  Even in this crunchy dry state cryptobiotic soil crust function in extremely crucial ways by covering the soil, thus preventing it from blowing away and also helping to retain water in the soil.  Given even a little rain however these crunchy crusts soften and become biological powerhouses.  As rain drops fall, the crusts protect the soil again by holding it in place, preventing erosion and therefore preserving the soil and landscape.  Infiltration of these raindrops is also facilitated so more water goes into the soil.  Lastly, cyanobacteria remove nitrogen into the air and fixes it into the soil, increasing soil nutrients.  So basically, these crusts protect the soil, increase and preserve soil water content, and enrich the soil with nutrients.

Cryptobiotic soil crust with pink lichens forming on the surface in the Sonoran Desert.

So why are all these function important?  Well, preserving the soil, increasing soil water content, and increasing soil nutrients all allow for more plants to be established.  Being deserts are in short supply of both water and nutrients even modest increases of these can have significant effects on the food chain.  When more plants are established the more animals an area can support.  More and healthier plants also means a healthier more stable habitat.  This is known as a bottom-up effect in ecosystems or food chains.  The bottom-up effect is when things at the bottom of the food chain, such as cryptobiotic soil crusts, have strong effects on organisms higher up the food chain.

Found at: http://www.soilcrust.org

Being these crusts have such a strong bottom-up effect, their destruction can have huge effects on entire landscapes.  Foot traffic, trampling by grazing animals, and off-road vehicles all can quickly destroy crusts that took anywhere from years to century's to form.  Grazing and off-road vehicles are especially destructive being these activities cover so much area so quickly.  Once a cryptobiotic soil crust is destroyed the soil becomes prone to erosion and there are less nutrients and water in the soil, harming the entire food chain.  So the best way to preserve these crusts is to limit grazing and keep all foot and vehicle traffic on the trail or road.
After disturbance, it can take anywhere from years to centuries for a crust to form again.  Deserts with summer rains, such as the Sonoran, form crusts more quickly in a matter of years to decades.  Cooler deserts with winter precipitation, such as the Great Basin, can take centuries to form crusts.  If a crust is undisturbed for very long periods of time mosses, liverworts, lichens and even ferns will colonize on top of the cyanobateria, algae, and fungi.  Protecting soil crusts is essential to maintaining healthy desert ecosystem function.

For a lot more great information check out: http://www.soilcrust.org
This website even has a great free downloadable field guide for soil crusts.

Desert Pavement

This black rocky area is known as desert pavement.  Notice basically no plants grow in the desert pavement, instead growing in the gray/tan surface where the pavement is absent.  The interlocked rocks and dense soils of desert pavement prevent water from penetrating the soil, therefore preventing plant growth.

Traveling from east to west in the Sonoran Desert rainfall decreases from 12 inches annually near Tucson to the hyper-arid two to four inches of rain received along the Colorado river.  This results in extremely sparse vegetation across vast areas of the landscape within this hyper-arid region.  Often the desert ground appears as painted black over broad areas, forbidding nearly all life.  Taking a closer look at the black covered soil you would notice a network of black rocks that appear to have been puzzle pieced together.  These areas, have very hard ground not unlike pavement, which is in-fact where it derives the name desert pavement.  Walking across this pavement is quite easy being it is a relatively smooth, hard, and level surface.  Though easy to walk across, summertime on this pavement is quite forbidding with scorching sun and heat, being only a little better than walking across a blacktop parking lot.

Close up of some desert pavement.  Notice how the rocks are closely interconnected, often like a puzzle.  This results in rainwater not penetrating the soil and instead running off.  Plant and other live are nearly absent to areas like this.

When scientists initially found these vast areas of pavement more then 100 years ago they thought overgrazing by cattle had trampled and compacted the ground making it infertile and inhospitable to plant life. Later it was determined desert pavement was actually a natural phenomena, not caused by cattle grazing.  Over long periods of time, decades to millenniums, a desert soil surface has smaller soil particles like sand and clay either washed or blown away.  Heavier rocks stay in place becoming interlocked.  Most of these rocks are not normally black in coloration but over time become covered with desert varnish.  This varnish forms when magnesium and iron rich dust falls on the rocks staining them through the action of bacteria.  Both desert pavement and varnish are more common the drier a desert is.  This is why Tucson has far less desert pavement and varnish than areas around the Colorado River.  The more rain an area has, the more unstable the soil surface is.  Significant rainfall amounts result in rocks being washed away through erosion, preventing pavement and varnish from forming.

In our previous entry we discussed desert soil horizons, and if you were wondering, desert pavement is part of the A horizon.  Soil horizons are extremely important in determining where water accumulates and therefore where and what types of plants grow.  Desert pavement, as mentioned before, prevents water from penetrating deep into the soil due to its hard pavement like surface.  Typically, desert pavement also indicates underlying thick layers of caliche, both of which can strongly impede water and plant roots from penetrating.  Water may only penetrate a few centimeters deep, even after a good rain, and many years may pass between times where there is enough rainfall to penetrate to adequate depths to support plant life.  Outside of the pavement though water penetrates more often and a lot deeper as evidenced by obviously thicker vegetation. Every five or so years through there is significant rainfall to penetrate deeper into desert pavement soils and short lived flowers can color the normally black desert ground yellow.

Normally black and barren desert pavement covered with wildflowers after strong winter rainfall.  Picture from:http://www.desertmuseum.org/programs/flw_mohave.php

Basic desert soil horizons

A dry wash that has cut into the soil creating a cut bank on the left of the picture.  The cut bank exposes caliche which is common to old desert soils. 

Walking over the surface of the land not many of us think much of what we are walking on.  Most people probably only think they are walking over a disorganized pile of dirt.  However, as we saw in our last entry, soils are a lot more complicated, containing organized O, A, B, and C soil horizons.  Odd as it might soils, soil is organized, and organization is exactly what differentiates a soil from a pile of disorganized dirt.  Dirt becomes a soil when the dirt becomes organized into horizons.  When initially dumped on the ground by a glacier, wind, water, or falling off the side of a cliff, dirt it is disorganized.  After siting for many hundreds to thousands of years horizons develop and the dirt becomes a soil.  Generally the longer the soil sits in place the more developed the soil horizons become.

Most people are very surprised to find out that deserts have soils.  Amazing but true.  In-fact deserts have some of the most organized and interesting soils in the world.  Being deserts lack rain and haven't been glaciated, their soils can range from very young to very old.  Other places further north that receive more rainfall and have been glaciated have much younger soils.  The wide range of ages in desert soil results in a wide range of soil types.  Deserts have the same O, A, B, and C horizons the rest of the world has.  However, they have some features that make them distinct from soils from other regions.  We will cover desert soils horizon by horizon.

The black and green stuff covering the ground between the rocks is a cryptobiotic soil crust.  This type of soil crust is common in desert areas that have not be disturbed.

O horizon:  Due to sparse vegetation O horizons are pretty much absent in any desert.  Any organic material that does fall to the ground seems to disintigrate into nothing over a very long period of time, resulting in no O horizon.  Wind does however cause dead leaves to accumulate under shrub and tree canopies, resulting in a very thin O horizon.  For this and other reasons, soils under tree and shrub canopies are richer than surrounding desert soils.  In many circumstances desert soils if left undisturbed for very long periods of time (years to decades to centuries) will form a living crust as an O horizon.  This living crust is called a cryptobiotic soil crust and is made of algae and fungi.  These microbes help water absorb into the soil, increase soil nutrients, and help retain soil moisture, all very similar to how other types of O horizons work.

A horizon: Nothing really special about the A horizon in deserts.  This horizon is usually the sandiest and often covered with a layer of rocks and or cryptobiotic soil crusts (the O horizon).  The rocks and soil crust both serve to slow water runoff, increasing water penetration into the soil.  Soil crusts also enrich the soil with nitrogen which aids plant growth.

B horizon:  This is where things get interesting.  Clay and calcium deposited by wind on soil surfaces is carried deeper into the soil by rain water.  Over thousands of years, clay accumulates into a dense and highly organized argillic horizon, generally one to two feet under the soil surface.  On the bottom side or just below, about two to three feet deep, calcium accumulates into caliche.  Caliche is a rock-like accumulation of calcium.  The older a soil is the large and more developed argillic and caliche horizons become.  These horizons prevent plant roots and water from penetrating, therefore also preventing the growth of deep rooted plants.  Many shallow rooted plants do take advantage of water that accumulates above these horizons, and will proliferate in these soils.

Caliche remains along a dry wash bank after the A, C, and parts of B horizon have been washed away by flash floods.

A relatively accurate way of knowing if a soil has developed caliche and or an argillic horizon without digging a hole, is to look at soil color.  Tan to grayish soils typically do not have caliche or an argillic.  Reddish brown soils will have caliche and probably an argillic.  Soils become increasingly red with age as more iron is deposited by dust fall.  Calcium and clay content also increases as a soil ages forming caliche and argillics.  So as a soil turns red, caliche and argillics also form.  The more red a soil, the stronger the caliche and or argillic horizons. 

Grayish-tan soil, indicating this soil does not have an argillic or caliche.

Reddish-brown soil, indicating this soil does have both an argillic and caliche.

C horizon: This is the originally disorganized pile of dirt, generally three or more feet under the surface.  Often, if you are digging, this layer can be quite difficult to get too if you have to dig through dense argillics and rock-like caliches.  Interestingly, nearly all desert C horizons are water deposited.  They were simply washed off a mountain or hillside, deposited, and then developed into the A and B horizons we discussed above.  Odd as it might sound, water is one of the most important soil forming factors in lands severely deficient in it.  In-fact, nearly the entire desert landscape is sculpted by water.

Basic soil horizons

This is the side of a hole dug into the dirt.  Notice the two different colors which indicated two soil horizons.  The dark soil on the surface is the A horizon, with the dark color indicating high organic content.  The lighter color is the B horizon, with the lighter color indicating low organic content. 

Have you ever noticed how soil changes in color or texture as you dig down-wards?  These differing layers of color or texture are called soil horizons.  Knowledge of soil horizons can prove valuable in gardening, landscaping, and understanding plant and some animal distributions.  In a future entry I will discuss desert soil horizons but with this entry I will discuss basic soil horizons and how they are important to the average person.  There are four basic soil horizons O, A, B, and C, with the first three being the most important and easiest to find.

O, the organic horizon.  This is the surface of the soil and contains dead and decaying plant materials.  Typically you will find deserts to have the absence of O horizons due to the lack of vegetation.  Forests and grasslands will have varying thicknesses of O horizons, but usually two inches or so deep at the most.  This horizon contains almost exclusively organic material and little to no minerals such as sand, silt, or clay.  Digging through an O horizon can be quite interesting, or gross depending on your prospective.  Of course, I personally find them fascinating.  This is where plant litter falls and decays so various bugs and fungi are quite abundant here as they eat through the dead materials, turning them into rich compost.  Fungi can be identified by tiny white, moldy like threads that penetrate through dead materials.  With some careful digging you can also identify many different species of bugs in a very small area.  Even more careful digging you might be able to identify how long it takes for plant materials to decay.  You may find whole leaves from the previous year, and mostly decomposed leaves from two years ago.  O horizons function like mulch in the garden, holding in soil moisture, create biologically active soils below, and serve to fertilize or enrich soil below.  Gardeners should imitate or create their own O horizon by mulching.

A diagram of the soil profile containing the major soil horizons.  Taken from Wikipedia. 

A horizon.  Given the name A simply because A comes first.  Yes scientists can be really creative...  This is the first real soil horizon being it is composed primarily of mineral content such as sand, silt, and clay.  For the farmer or gardener this is the most important soil horizon being almost all plant roots are contained in it.  This is also why in many environments the A horizon is darker than underlying horizons.  Again deserts due to their lack of vegetation will have light colored A horizons.  Grasslands having the darkest and forests the second darkest colored A horizons.  Anyone growing plants will want to make sure their soil has a dark A horizon anywhere from one to two feet deep.  If you are not lucky enough to have a dark A horizon simply work compost into it to improve fertility, drainage, and biological activity.  Engineering your own high organic content A horizon greatly benefits lawns, gardens, and landscapes.  To engineer  a high organic content A horizon simply add compost and mulch on the O horizon.  Both will build organic material in the soil below.

B horizon.  Given how original some scientists are the B horizon is named thus, simply because B comes after A.  The B horizon is always below the A horizon and typically is thicker then the A horizon.  This horizon is usually less of a concern to the gardener than the A horizon being most plant roots are in the A horizon.  Deserts have a different story though, but more on that some other time.  Most of the time the B horizon is lighter in color and has been enriched with clay.  Clay particles simply are leached, or washed downwards, by water moving through the soil.  The clay particles are deposited lower in the soil and form a B horizon.  For the gardener if you have a very small A horizon you might want to add sand and/or organic matter to the B horizon, making it into an A horizon.  B horizons are not completely useless however.  Being the B horizon often has higher clay content, and that clay holds water very well, a gardener can utilize a B horizon to keep plants well watered even in times of drought.  Some roots will penetrate the B horizon and collect water even if the A horizon is completely dry.  The key to this is simply soaking the soil.  The A horizon will dry out first but the B horizon will hold water much longer.  A lot of people complain about clay soils but the reality is they are easier to engineer then sandy soils.  Sandy soils, and especially sandy B horizons, are quite frustrating.  You can water them like crazy and most of the water simply drains right through.  Fortunately most soils have a higher clay content.

C horizon.  This particular horizon is simply the parent material that the above horizons originally developed from.  You typically have to dig at least three feet deep, if not eight feet deep or more, to find this horizon.  Save yourself some time and energy and don't worry about this horizon much.  The gardener simply needs to be concerned with the O, A, and B horizons.  Every garden or yard should have a healthy O, A, and B horizon.  Concern yourself with these and you can forget the C horizon...

These are the most important basics, it obviously can get a lot more complicated.  So if you are ready to be bedazzled with more information check out Wikipedia Soil Horizons.

What Makes a Broadleaf Deciduous Forest: If I Were An Oak...

A mature White Oak.

If you were an Oak tree, where would you plant yourself?  This is not some flippant decision, planting an Oak  is quite a commitment.  As an Oak, you are committed to that spot for the rest of your 500 or so year life (if you are one of the few to survive).  Over the past weeks several entries have been on different types of Eastern Deciduous Forests found in Iowa.  This begs the question, why are eastern forests located in the east anyway?  So imagine: you are an Oak tree.  Where would you plant yourself?  Of course real trees can't plant themselves, they rely on gravity, water, wind, birds, or animals to carry seeds to hopefully ideal place to grow.  This process is sort of cruel in that greater than 99 percent of these seeds will die before growing to maturity, and of course I don't want 99 percent of my hypothetical trees to die.  Instead, imagine you are already a mature Oak tree and can plant yourself anywhere.  No irrigation or fertilizer allowed.  Since we are talking about the Eastern Deciduous Forest you can choose to be a White, Red, or Bur Oak.  You must choose somewhere you will be protected and have everything you will ever need for survival.  Plants aren't like animals, plants can't move around to find their energy and nutrients, everything must be obtained right where they are at.  This immediately excludes a lot of very scenic locations such as mountain tops.  Mountain tops just too windy and cold for Oak trees.  To answer this question we must first consider what our needs are as Oak trees. 

Bur Oak

White Oak

What an Oak needs
First, what is an Oak?  First, an oak has broadleafs.  This basically means large leaves, which are unlike conifer or pine trees that have needles for leaves.  Secondly, oaks are deciduous, meaning they loose their leaves in the fall and grow new ones in the spring.  So an Oak is a broadleaf deciduous tree, what are the requirements for this type of tree?  Well, growing leaves on an annual basis takes a lot of time, energy, and resources.  So we must plant ourselves in a location with a long growing season, plenty of sun for photosynthetic energy, and plenty of water and nutrients.  Deciduous leafs require plenty of water evenly throughout the growing season and can't have extremely hot or cold or dry conditions during the growing season, otherwise they fall off and the trees die.  So we can narrow our planting locations down to areas with stable moisture through the growing season and where temperatures consistently are warm but not too warm during growing season. 

Summary of broadleaf deciduous requirements

1. Long growing season, 2. Plenty of moisture through out the growing season,

3. Not too hot and not too cold during growing season, 4. Plenty of sun, 5. Good soil.

Red Oak

A desert has a long growing season and has plenty of sun, but lacks moisture, is too hot, and has poor soil.  The entire western half of the United States can be eliminated for these reasons.  Alaska might have plenty of moisture and good soil, but lacks a long growing season, lacks sufficient sun, and its too cold.  Almost all of the northern portion of North America can be eliminated here also.  This leaves the eastern portion of the United States.  Yes, I know, big surprise...  But why do broadleaf deciduous forests grow in the eastern United States?  The growing season is long, often six or more months a year.  Climate and seasons are very predictable, winter, spring, summer, and fall happen the same time every year and have consistent temperature and rainfall patterns.  Temperatures never get excruciatingly hot and never freeze during summer.  Rainfall is even throughout the growing season minimizing drought.  Finally, there is plenty of sun and good soil.

An oak forest

So you would plant yourself in the eastern United States, but lets be more specific.  You would also want an area protected from extreme fires so you don't burn down.  Oak trees can easily survive small surface fires but not anything larger.  Good soil is a must, so you would have enough moisture and nutrients.  Avoiding areas where their is too much water or flooding would also be important.  So based on these requirements, select a spot and plant yourself!  (Hypothetically speaking)