Friday, December 12, 2014

Nema-what? Nema-who?

Nematodes. No, these organisms have nothing to do with amphibians. Nematodes are a type of soil organisms that are grouped into the microfauna category; those organisms that are smaller than 0.1 mm in size. We are talking about microscopic little guys in the soil that you can't see without the aid of a magnifying device. Technically they are non-segmented roundworms (as opposed to segmented worms like earthworms where they can "disconnect" and both sides will continue to wiggle around). There are more than 20,000 different species of nematodes. They can survive in both "aquatic" and slightly drier parts of the soil. An example of a nematode's upper half is pictured below.

Before you go running away from this tremors-like figure, give me a second to explain what these guys do. Often people's first question about soil organisms is "Are these good or bad guys?" With nematodes as well as many soil organisms there are species that are beneficial and some that impact the system negatively. The nematode pictured above is known as Acrobeles complexus. You are looking at its mouth piece, which is slightly frightening, resembling a torture device. However, the only beings this worm is "hurting" are bacteria. Don't feel too bad for the little guys. Fungi and bacteria can often fight back!  Parasitic nematodes (omnivores) are can be trapped by certain species of fungi. An example of this is pictured below. 


Nematodes are grouped by their trophic group or basically what they choose to eat: fungi, bacteria, algae, nematodes, protozoa, insect larvae, and plants. These groups are often microscopically identified by their mouth-piece. These mouth parts serve the nematodes well. Bacterial feeders have a tube that can suck up bacteria much like a vacuum. The parasitic or omnivores have a "stylet" or a hollow piercing mouth part that can puncture through the plant and allows the nematode to withdraw plant tissue for consumption.

Figure 2. Nematode feeding types; mouthpart structures.
a) bacterial feeder, b) fungal feeder, c) plant feeder, d) predator, e) omnivore
Figure credit: Ed Zaborski (University of Illinois)

In the big picture or soil ecosystem, nematodes are known as "primary" as well as "secondary consumers." When they fulfill the role of primary consumers, they are eating live plants also known as herbivores. These parasitic nematodes as mentioned above are pests, especially in agriculture. Nematodes do millions of dollars in damage each year to food production. Root knot nematodes are the primary group that cause most of the damage for vegetables and fruit trees in California. They cause a swelling on the root that can be easily scene with the naked eye. Not very appetizing. To battle these guys some options are nematode resistant root stock can be utilized, soil fumigation takes place, or even planting nematode-suppressive plants such as French marigolds.

As secondary consumers, nematodes play a role in the soil food web (recycling and distribution of nutrients). The feeding strategies mentioned above (except the parasites) fall into this category as they are assisting in the control of populations of microorganisms, which in turn release nutrients as microflora such as bacteria and fungi are consumed. Bacteria and fungi often contain more nutrients than a nematode can use! The excess nutrients are released and available for plant uptake. For example, nematode activity can account for 30-40% of nitrogen availability in certain ecosystems. This is important as plant need nutrients to grow. The involvement of microorganisms in the process of nutrient cycling is critical for decreased dependency on fertilizers. Soil already has biological mechanisms built-in to provide for plants. However, the microorganisms must be present to facilitate this. Although, I won't go into the details of this nutrient cycling process in this blog post, I will leave you with a visual of this amazing complex cycle of which nematodes are an integral part!

Tuesday, November 25, 2014

Fall Colors

Most would say that autumn's splendid array of colors comes from the leaves turning (especially those on the east coast). However, there is another often overlooked emergence of color from another organism. After the first fall rains, fungi begin to come out of the woodwork (and soil)! Hiking through wooded and even grassy areas one begins to notice these little guys everywhere. Fungi can come in a variety of colors, shapes, and sizes*. We may immediately think of the traditional mushroom with a cap and stipe (stem). However, there are others that have many branching limbs or just resemble a large blob.

Hygrophorus spp.

Ramaria formosa

Pseudohydnum gelatinosum

So why do we have to wait for a change in weather for these guys to come out of hiding? Furthermore how do mushrooms or fruiting body of the fungus form? 

Well as stated, mushrooms are the fruiting body of the fungus. The mushroom is not the organism itself, it is part of the organism, just as an apple is part of the tree. Not all fungi form these structures. Think of a bread mold. It would be pretty crazy to pull a moldy loaf of bread out of the cupboard and see a mushroom trying to break out of the bag. When are are talking about mushrooms we are talking about basidiomycetes and acsomycetes. These fungal phylum differ in how they product their spores. Basidiomycetes have their spores on the outside of a cell known as a basidium, This looks like a club with small roundish microscopic objects attached at the end. Ascomycetes produce spores that are encased inside of an ascus or long microscopic sack. This is where our story begins - the fungal spore. The spore is released from the basidium or ascus to a new substrate (soil, wood, plant material). The spore germinates or begins to grow by sending out a germ tube. This "tube" begins to form hyphae (thin threads). Fungi can undergo sexual reproduction where DNA from these hyphae are brought into one hypha (there are lots of steps I am skipping here. If you want a few more details you can check out this diagram Basidiomycete Life Cycle). These hyphae grow and grow forming mycelia (many hyphae together) through out the soil, duff layer, or wood gathering nutrients via excretion of enzymes. After enough nutrients are gathered and the environment is damp (but not flooded) and cool (not cold) the fungus can bring hyphae together into larger bunches, to form what we know as the mushroom. First a "button" is formed where the cap and stalk are inside an "egg." As the stalk grows it pushes the cap through the egg. This egg is known as the universal veil. The remnants of this veil can be seen on Amanitas.

Button stage with universal veil breaking a part. 

Veil remnants or "scales" 

     Mature fruiting body or mushroom

Mushrooms can be found on growing a various different substrates: wood, soil, duff, or even dung! This is due to the fact that fungi have different feeding strategies that all boil down to how they acquire carbon. Some are more adapted to being able to digest complex carbohydrates from dead woody materials such as cellulose and lignin. These guys produce enzymes that allow them to break down these compounds for energy. We will typically find them growing on logs. These guys are known as saprotrophic fungi. 

                              Hygrophorus russula                                    

Other fungi can obtain carbon from trees via a symbiotic relationship (see earlier post of mycorrhizae). Specifically, those associated with trees like the one shown below are ectomycorrhizal fungi (EMF). They have hyphae (see explanation above) that grow from the base of the fruiting body into tree root tips where the exchange of carbon for nutrients occurs. However, some EMF's have been shown saprotrophic capabilities when carbon from a host is limited.

 Suillus spp. (One of the Slippery Jacks)

Finally, a third type of feeding strategy are the pathogenic fungi. These fungi cause disease for living plants and animals.  These absorb nutrients directly from the cells of the host, but unlike EMF's do not give back to the plant. Pathogenic fungi typically weaken and eventually will kill the plant they colonize. 

        Tramella mesenerica

As Thanksgiving is approaching, I will leave you with well wishes and Turkey Tails (Trametes spp.). Take a look around while hiking (or walking very slowly) post gorge-fest this Thursday. You may notice a whole other world of fall colors you might have normally missed in the past!

*Although I have had a lot of classes/training in mycology, I am not a mycologist. Fungal identification is based on my best educated guess from books/web resources. All fungi were observed at Big Basin Redwood State Park in California. If you have any additions or corrections, please feel free to add them in the comments section. Thanks!

Thursday, November 13, 2014

Playing in the Mud!

After a precipitation event (i.e. rain), there are recommendations to avoid contact with the soil. We are advised in both recreation and business to restrict personal and mechanical activity during this time as tractors, construction or logging equipment, and even our own feet can impact soil negatively leading to compaction and erosion. However, getting muddy brings us back to our childhood. As an adult, activities that bring us in contact with soil often elicit feelings of joy and maybe even a bit of mischievousness at the thought of bringing home a little dirt on our shoes to a house where mom and dad won't yell at us. So why, despite these youthful urges to go out and play, do we need to give the soil a break for a few hours to days before we head out to plow the fields or ride our mountain bikes?

Sarah P. fellow mountain biker with her muddy bike (2012). 

In order to answer this, we have to start with some basics. Soil particle size! Soil particles are split into various size classes. Basically the diameter of the particle determines what size class it falls into. The two groups are coarse fragments (the big stuff - gravel cobbles,and boulders) and fine earth fraction (sand, silt, and clay). Particles that are 2 mm and smaller fall into the fine earth fraction (per USDA classification). Sand is the largest ranging from 2-0.05 mm with various subdivisions within this, ranging from very coarse to very fine. Silt ranges from 0.05-0.002 mm and clay is 0.002 mm and smaller.  The range from boulders to clay is separated by 6 orders of magnitude. This means a clay particle is 1 millionth the size of a boulder!  So how do these sizes compare in a more visual sense?

We can see that at the current scale, clay doesn't even show up it is so tiny! So how do these particles influence soil's reaction to water and the pressure we put on it? The combination of these particles (percentages) determine the soil texture. Some of the soil textures you may have heard of are sand, clay, and loam. There are 12 textural classes in total. For example, if soil to has a "clay" texture, it has at least 40% clay sized particles within it. These textures can have an added "modifier" if a certain percent of the sample by volume contains particles in the gravel, cobble, or boulder categories. You could have a soil that is a "gravelly loam" (pictured below). For this blog post I won't go into specifics about how these coarse fraction particles can affect soil, but know their presence can change soils in various areas.

Ok, we have learned about particles and how particle combinations result in different textures. How does this play a role in soil compaction after it has rained? Picture your self the size of a sand particle and you are hanging out between the particles. This area between the particles is known as pore space. Most of the spaces between the particles right after a good rain will be filled with water (you can have scuba gear for this imagery if being immersed in water terrifies you!). Now there is pressure exerted from the soil surface, which pushes the soil particles together and fills in the pores (gaps) in between the particles. 

Strawberry fields with reduced infiltration.

Why is compaction bad? Compacted soils have higher bulk densities. Bulk density is the mass per volume a soil takes up. Soils with higher bulk densities have reduced infiltration rates. When irrigating, if the rate at which water enters the soil is reduced you can have more runoff and evaporation (lost water). Another problem is reduced air permeability. Reduction in air affects the plant roots and microbes, which can reduce nutrient cycling and over all plant growth. The increase in bulk density means that the soil has to change shape or "structure" is altered and/or reduced. Briefly, structure of the soil is determined by the particles that make up the soil. Generally speaking, soils with more clay (material that can bind particles), will have more structure than those with more sand. Think of the beach. The soil is just one big "massive" accumulation of sand sized material. Where as in your garden you will see small round/crumbles or blocky shapes resulting from clay as well as other constituents in the soil. The presence of water in the soil allows the particles to move more easily over and around each other. This results in loss of soil shape and settling of particles into the pore spaces.

In areas where farming, construction, or logging occur pausing the work so that plant growth is not impacted makes sense. However, what about trails? There isn't vegetation on the path when you are hiking, mountain biking, or trail riding, so why should we care? As mentioned when soils become compacted soil structure is lost. When soil loses its shape the particles no longer stick together and can become subject to erosion via wind and water (Remember that reduced infiltration concept? Water not entering a soil will travel elsewhere, such as running over a slope. When this happens, it  can carry soil particles with it). With soil loss you begin to expose roots. For mountain bikers this adds obstacles, which is fun. However, it can affect the plant life present. The larger roots may be more resistant, but the fine roots holding the soil together can become impacted resulting in further soil loss. Soil loss essentially leads to trail loss and no more fun for you and me.

Compacting soil reduces overall soil quality and plant growth and can result in erosion and and soil loss. Although we would love to be able to get out and hike, ride, even get work done on occasion, it is necessary after a precipitation event to allow for the soil to dry out somewhat before we jump back in the saddle.

Wednesday, October 22, 2014

Drowning in Dust...

The striking and memorable events of last week will be imprinted on my brain for many years to come. While driving through California's Central Valley, I was hit unexpectedly by a dust storm in which visibility was down to five feet in some areas. Trying to avoid stopped cars in front of us, getting rear ended, and oncoming traffic, was more terrifying than any snow storm I've driven in (see Facebook post from October 14 for additional pictures). One image in particular that will remain with me was the sight of a black Labrador retriever laying next to a barbwire fence on the bare ground that had lost his life due to the hazy conditions. In light of this storm, I've decided to refresh your memory about the Dust Bowl, introduce erosion, and give you some additional information about current trends toward repeating this horrific time in history in California and beyond.

G. Rey assisting with accident in front of us. 

The Dust Bowl. Last time you may have heard about this was your high school history class when discussing the Great Depression. This greatest environmental disaster in US history resulted from the combination of a decade long drought starting in 1931, poor ranching and cultivation practices, and an increase in farmland. These factors worked together to create the perfect conditions for vast amounts of soil erosion via wind.

Photo Credit NRCS Photo Gallery (

The panhandle of Oklahoma, northern Texas, northeast New Mexico, southeast Colorado, and southwest Kansas experienced the most intense erosion during the Dust Bowl Era. The drought during this time contributed to the failing crops and exposed soil, but let's back up just a tick and look at what was going on prior to the 1930's. The Great Plains are known for having fertile grasslands. This allowed ranchers to provide abundant feed for their stock. However, as with any resource overuse will degrade and diminish it. Overgrazing decreased these bunch grasses found on the plains. Bunch grasses are perennial meaning they continue to grow from year to year and can build up extensive root systems. The root systems act as a glue to hold the soil together. Decreasing the population of these grasses increases the chance of soil escaping via erosion. With the decrease in grasses, the grazing land was converted into farmland. Wheat dominated this area. With plenty of precipitation during the 1920's more and more folks were attracted to farming and more land converted (losing those extensive root systems holding the soil together). When the drought of the 1930's hit loss of crops and the absence of drought tolerant plants to hold the soil together combined with winds resulted mass transport of soil.

Photo Credit NRCS Photo Gallery (

So how did we find our way out of this mess? Mother nature helped with the return of rain in 1939. However, before this there were measures taken to reduce the effects and help prevent future disasters such as this. The Soil Erosion Service was established in 1933 and the concept of "soil conservation" began to spread across the country. Protecting the soil and preserving fertility became the main message touted by the agency via the director, Hugh Hammond Bennett. During the 1920's Bennett had already begun to talk about erosion in his publications, including "Soil Erosion: A National Menance," which is considered his most influential writing. In addition to the Soil Erosion Service was the establishment of soil erosion experiment stations as well as soil and water conservation districts. 

Today's focus by the NRCS has continued this line of thinking. Soil health is at the forefront of their message -
for farmers and ranchers. Various adjustments to these practices such as cover cropping, short-rotation grazing, less intense tillage can help to improve soil conditions. Changing up practices can be complicated and sometimes costly in the short-run, but without evolution in how we grow food, fuel, and clothing the soil will essentially turn on us. This was made apparent by driving through the Central Valley of California where farmers struggle with lack of water from drought and reductions in government allocation of irrigation water. It is a complex situation in which everyone and no one is to blame. What is most important is figuring out way out of this one by using what we know from history and the tools at our disposal. This applies to California as well as other states in the US and beyond our borders. A colleague in South Africa passed a long the photo below of similar issues they are having with soil erosion due to drought and past cultivation practices.

 Photo courtesy of C. Fraenkel

Some thoughts to leave you with by Secretary of Agriculture Henry Wallace in 1936:

"The nation that destroys its soil destroys itself. The soil is indespensible. Heedless wastage of wealth which nature has stored in the soil cannot long continue without the effects being felt by every member of the society...Wind and water are seldom harmful when the natural environment is undisturbed. But, when soil resources are used unwisely, wind and water write a tragic story in dust storms and muddy rivers that carry good soil to the ocean."

Friday, October 3, 2014

I'll take an order of the Andisol, please.

To understand and characterize soils better United States soil taxonomists (those who define and name) came up with a a system that divides soils by various distinct and unique features. Soils in their broadest sense are grouped into divisions called orders. There are twelve soil orders in the USDA system of naming (yes, different countries and organizations have different ways of naming soils, just to make life more interesting!). In alphabetical order they are as follows:

Alfisols - Andisols - Aridisols - Entisols - Gelisols -
 Histosols - Inceptisols - Mollisols - Oxisols -Ultisols -Vertisols

Twelve Orders of Soil Taxonomy poster
Photo credit USDA NRCS - 
This poster can be downloaded or purchased from this link. 

Since the Japanese volcano, Mt. Ontake, erupted just recently, I thought it would be appropriate to begin with andisols! Soil orders are grouped by their major diagnostic horizons (layers within the soil that have specific characteristics), minerology (minerals present in the soil), soil moisture and temperature regimes. Andisols are unique in that they typically form from volcanic materials (ash or tephra, pumice, lava, and cinders) which have a very different type of mineralogy than other soils types. I'll forgo a long-winded discussion about this, but you may have seen volcanic glass (e.g. obsidian) and noticed how it doesn't look like a typical rock. As this glassy material weathers (breaks down) it creates a soil - an Andisol. The rocks int the volcanic explosions (tephra) also contribute to these soils.

Soil with volanic deposits that many many years from now could turn into an Andisol. 
Photo Credit: D. Beaudette USDA-NRCS. 

Obsidian - cooled volcanic material that appears "glassy."

The complex mineralogy (glassy and rocky materials) in these soils allow for high fertility (lots of nutrients for plants). However, in cooler climates, many of the andisols are on steep slopes this high fertility is limited to production of forests. For anyone who has visited the Pacific Northwest's Cascade Mountains, you have seen these soils in action.  Some of the great trees in these areas can attribute their size these soils. In warmer climates these soils are used for agriculture. However, a draw back of this soil is it's capacity to "fix" phosphorus making it unavailable to plants. Additions of more phosphorus fertilizer often do not help either. This would be similar to buying flour at the store, bringing it home, and placing it on a high shelf in your kitchen, and then throwing away the step-stool you used to place it there. You have flour to make cookies, but cannot access it (lets just pretend you have no other chairs and cannot climb on the counters to get at it). You go to the store and buy more flour, come home and place it on the high shelf again removing the step stool once again. Continue this process over and over and you will begin to understand this issue with phosphorus fertilization in andisols. Some creative solutions have been approached, such as soaking potato tubers in a phosphate solution prior to planting so that they have access to phosphorus.

Because andisols occur in many different climates the resulting soils can look very different. Below is the distribution in the United States and a few examples.


From top to bottom - Andisols found in Idaho, New Zealand, and Iceland.

Interested in the major soil order near you? 
Post the location in the comments and I'll address
it the next time I blog on soil orders!  

Friday, September 26, 2014

Gals who weren't afraid to get their hands dirty...

One of the aspects of history that I find quite interesting is looking beyond the big players. When you delve deeper in the story, you find that, yes, the well known people in history were important. However, there are often more folks involved in the development of historical events. This is very true in science especially since researchers "stand on the shoulders of giants." Meaning as a scientist you aren't reinventing the wheel every time. You thankfully glean knowledge from those who have come before you. The development of soil science is no exception. Even during my education which occurred in the early 2000's the focus was on the key male scientists in soils. To learn about the lesser known folks in my beloved profession I decided for this post to focus on a few of the females in soil science that intrigued me. This may be a multiple part series as there so many interesting women in soils!

Campus garden. Photo courtesy OSU Archives.

Female students in Horticulture at Oregon State University preparing a vegetable garden near Benton Hall (~late 1800's). Photo Credit
Many of the first women working in the government organization now known at Natural Resources Conservation Service (formally Soil Conservation Service and preceded by Soil Erosion Service) were clerks and secretaries. A clerk out of Montana, Marjory A. McTavishdescribes driving in the USDA-SCS vehicles and stopping at a gas station. She asked the attendant to fill up the vehicle with gas. The man walked around the car and came back to the window asking "Does the government let women drive their cars?" 

During the 1930-40's, one of the first women that held a scientific/technical role in the SCS was Lois Olson. She was head of the Erosion History section under the Climatic and Physiographic Division of SES, which researched various documents and maps to determine characteristics of the landscape. Dr. Arthur Hall and her lectures on soil erosion history laid the foundation for many of the ways we think about soil erosion to this day. 

Article by Lois Olson and Helen Eddy published in Agricultural History
Vol. 17, No. 2 (Apr., 1943), pp. 65-72

The first woman to receive her Ph.D. in soil science was Ester Parsons Perry from the University of Berkeley in 1939. Her dissertation was titled "Profile studies of the more extensive primary soils derived from granitic rocks in California.” For anyone who has studied soil in California knows there are quite a few derived from granite as the Sierra Nevada Mountains are a granitic batholith. She began working for the California Agricultural Experiment Station (UC Berkeley) directly after where she remained for the whole of her career. She made her way up the ranks to the position of soils "specialist," but despite her contributions to soils in California she was never awarded the position of associate professor or a tenure track position. Perry ran the lab where well known soil chemist Gary Sposito was a student. She was also the first woman to join the American Society of Agronomy (ASA). 

Finally, we have the first woman to attend Soils 105, an infamous soil survey field course that began in the 1930's and is offered through UC Davis and UC Berkeley even to this day. In 1953, Eva Esterman, a UCB honors student, asked to take the class. She was given the option to graduate without taking the course, but declined. She attended the class chauffeured in a separate car and chaperoned by Dr. Earl Story's wife. Esterman was also given "comfort" breaks. The academic dean at the time, Dr. Frank Haridine, thought this was a complete disaster and stated that no woman would ever attend this class again. Obviously this was not the case as I know many women in my profession that have attended this class over the years. This is partly due to the aforementioned Ester Perry. She created Soils 105F, an all female version of the Soils 105 class that occurred from 1956 to 1959.  

A photo from the 2007 Soils 105 class, attended by many female students.

These are just a few of the stories about women in soils that I came across. There will be more posts to come that discuss woman and soils. Stay tuned!

Thursday, September 18, 2014

Turning, churning, worming....

In soil there is a term called "bioturbation." This process occurs in your yard, garden, field, and forest.  Ok so what exactly is bioturbation? Let's first break this word down into a couple parts.

"Bio" - living as in insects, animals, etc

"Tur" or ter - wearing away or breaking down

Bioturbation is the movement of soil by living organisms. Soil can move laterally, upward, or downward. Very obvious forms of this occur as gopher mounds! (Think Bill Murray's sisyphusian quest in Caddy Shack).

Photo Credit:

Less obvious are those by plant roots and smaller organisms such as ants, earthworms, bivalves (e.g. clams), or even crabs.

Bioturbation of beach sand in Florida by crabs. 

Unfortunately, in the context of homeowners, golf course grounds keepers, or landscaping professionals bioturbation can appear as an aesthetic nightmare! The urge to run outside and play "whack a mole" can strike. However, when bioturbation occurs there are many benefits that these organisms are providing to the soil!

The benefits of bioturbation starts with in the simplest sense soil movement. Soil is moved around in the profile (i.e. 3D space that the soil occupies). With this movement there is transfer of organic matter from the surface to deeper in the profile or laterally to other areas. This incorporation of organic matter helps to improve water holding capacity, soil structure, and nutrient cycling. Earthworms are an example of soil fauna that consume organic matter, move through the soil, and deposit their excrement (i.e. worm castings) throughout the soil, which can improve soil conditions. Earthworms can turnover tons of soil in the course of a year. Over 10-20 years they can completely recycle the top 6 inches of soil.

Earthworm castings improving soil structure by creating "aggregates." 
Photo Credit:

Other soil fauna burrowing and tunneling through the soil can help to break up soil compaction and allow for improved porosity. The increase in pores allows for better water and oxygen flow through the soil. This improvement is beneficial for plants and the microbial community (e.g. bacteria, fungi, and other oxygen lovers) in the soil. Increases in growth and nutrient cycling can result from this process.

So yes, the unsightly mounds from the larger fauna in the soil can disrupt the pastoral appearance of your yard. However, keep in mind the aforementioned benefits! This process of bioturbation can actually help to improve your soil for better plant growth and soil health. Resulting in sustained productivity in your soil for years to come!

Tuesday, September 9, 2014

Summer Oddities

This summer I was fortunate enough to take a few small trips where I came across some unusual organisms and of course amazing soil. With this blog entry I'd like to share a few of these.

The first oddity falls in the fungal designation.I came across this giant "puffball" hiking in Nevada just outside of Paradise Valley (northern NV). As evidenced by this organism not all of the state is a dry desert. The hike followed a creek that had various drainages contributing to it. This guy was in one of the wetter microclimates. The chapstick tube in the lower left corner gives you an idea of the scale of this fungi! I left the fungus in tact, but my best guess is that this is a West Giant Puffball (Calvatia booniana) commonly found in arid to semi-arid regions in late spring or summer. 

 Puffball fungi are ascomycetes, which have acsospores that release into the air. 
This puffball is filled with millions of spores!

The next specimen is a plant, but with animalistic tendencies! California Pitcher Plant a.k.a. Cobra Lily (Darlingtonia californica) is a canivorous plant. This plant can consume insects for nutrients. This is achieved by trapping insects inside the "pitcher" part. The long stem is hollow (see bottom left plant) except for very fine hairs and a slippery substance along the walls. The insects have difficulty getting out since the opening is not straight up. They eventually tire and are "digested" by the plant. These plants are known to produce an enzyme that breaks down the insect for absorption. 

CA Pitcher plant found in Shasta-Trinity National Forest.

The last notable encounter from this summer are serpentine soils/rocks. Note: serpentine is California's state rock! These soils develop from serpentine rocks that are composed of a variety of minerals. The minerals are similar in that they have an iron magnesium silicate backbone. The rocks weather (break-down) into soil. The serpentine soils have chemistry that is different from most in that there is a larger amount of magnesium than calcium. These quantities are typically in reverse in most soils. So why does this matter? Well, the plants that grow on these soils must be able to deal with this shift in soil chemistry. Serpentine soils have many "endemic" plants. This means there are plants growing in this soils that are specifically adapted and may only grow in this specific type of soil. Some examples are Leather Oak (Quercus durata), Milkwort Jewel Flower (Streptanthus polygaloides), and Kaweah River phacelia (Phacelia egena). Other plants such as Jefferey Pine (Pinus jeffreyi) and Incense Cedar (Calocedrus decurrens) are capable of growing on serpentine and less chemically challenging soils.

Serpentine soils in Plumas National Forest

Serpentine rock in Shasta-Trinity National Forest.

Friday, August 22, 2014

Misconceptions of Mycorrhizas

Many biological products are out on the market that promise increased plant vigor, more fruit, and healthier plants. This posts hopes to clear up a little of the confusion on these, specifically, those containing mycorrhizal fungi. 

So what are mycorrhizal fungi??

In the most basic sense, these fungi live in the soil and beneficially associate with plants. These fungi have what is called a "mutualistic relationship" with the plant they inhabit. Each player gives a little to the benefit of the other. Depending on the feeding strategy organisms receive carbon (essential ingredient of our metabolic processes) from various sources. Plants take up carbon in the form of carbon dioxide from the air, decomposer fungi receive carbon from wooden logs by excreting enzymes. Mycorrhizal fungi need carbon as well, but they often get this from their "hosts" or in other words the plant shares the carbon (sugars) it produces with the fungi! So what does the plant get out of this? Well, quite a bit actually. Plants receive nutrients, a larger area to access nutrients from, disease protection, and even assistance with drought tolerance. Nice deal for both parties!

The quintessential mycorrhiza on pine tree cover photo on Smith and Read's, Mycorrhizal Symbiosis

They are several groups of mycorrhizal fungi, but the two main are arbuscular mycorrhizal fungi or AMF (formally known as vesicular-arbscular mycorrhizas or VAM), which grow into the plant cells. This makes them endomycorrhizal. The AMF fungi have a "tree-like" structure that can be seen inside the cells where nutrient exchange takes place. The other main group is ectomycorrhizal fungi (EMF). These fungi grow into the plant, but grow around the cells.

Arbuscule inside a plant cell. Photo credit - Shachar-Hill Lab MSU (

Ok, so here we go back to the main point of this blog entry. The two main groups AMF (endos) and EMF (ectos) are associated with different types of plants. Over 80% of Earth's plants have a mycorrhizal association. However, AMF's association is only with certain plants (typically herbaceous/non-woody) and EMF's associate with the other plants (usually woody plants). Note: Every now and then there is some cross-over, but I'll go over that in a future posting.  Ok with the concept of host-specificity in mind (certain mycorrhizae associating with certain plants) we start to look at what certain products are providing to you as the consumer.

Pine Amanita ECM

Ectomycorrhiza on a root. Photo credit: Mycorrhizal Associations (

I have seen these biological products that are designed for specific plants (citrus, turf, roses, etc). These products are providing both AMF and EMF in these products when in actuality only AMF fungi are appropriate. The addition of both of these types of fungi will not hurt your plants and if the company supplying the product wants to provide both then fine. However, what is not helpful to you the consumer is that these companies are making you think that more organisms = better product. In actuality, adding proper organisms, not more, may be a better approach!

If you are interested in which mycorrhizal group your plants fall into, please click on the following link:

There is a lot to be learned about microorganisms in soil, but hopefully what we do know (as in the case of mycorrhizas) can be applied in more of a scientific approach to help you grow the best plants possible! What are your thoughts on biological products with mycorrhizas that you have used? Yea or nay?

Thursday, August 14, 2014

Passion for the ignored, misunderstood, and disregarded...

Soil science was something I stumbled upon the summer between my sophomore and junior year of college. I began working for a government agency with an amazing group of scientists that had devoted their lives to exploring the universe below our feet. Up until this point I had noticed soil as "brown," which looking back astounds me. I had gone hiking with my parents as a young child, attended summer camp, been indoctrinated at a young age that saving paper = saving trees, so I had a well developed appreciation for the outside world. How I had never noticed that which lies beneath my feet still boggles my mind. 

However, the real love affair began when I started graduate school. The excitement my professors had for soil science was something I had rarely experienced during my education. Every now and then I would find a teacher who inspired (obviously I found a few along the way otherwise science would not have been my preferred path in school), but to find a whole group of people that couldn't get enough of digging soil pits, discussing research, and getting their hands dirty was a whole new world for me. During this time I fell head over heels in love with SOIL. What I had viewed as just a "brown" surface became this dynamic, 3-D ecosystem full of chemical and physical processes, living organisms, and variable environmental conditions reflected in more colors than I ever could have imagined. 

Through my education, I found that soil played a role in virtually every aspect our lives. From food and water to clothing and shelter, soil is connected to even the most basic parts of our lives and cannot be ignored.  Despite its ubiquitous appearance, soil is not an unlimited resource and needs more people to "heart" it. With this blog I hope to shed some light on this complex world below your feet and frankly, my dear, to inspire you to give a damn...