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The Impact of Trail Horses on Plant Communities

November 14, 2016
Woodland Path--340

Horseback riders on a recreational trail. Photo Credit: http://www.morguefile.com

Exotic plant species, also known as non-native plant species, are a potential threat to the native plants in an environment. A “healthy” plant community is desirably dominated by native vegetation, so the presence of non-native species often suggests competition of the available resources. This may cause native species to die off and the biodiversity of plants and plant-dependent organisms in the community to decline, deeming a community as “unhealthy”. It is important to find the source of non-native plant species in different environments in order to control or eliminate the introduction of these potentially invasive plants. In many forests and parks, there are recreational horseback riding trails available to the public. These trails could very well be the sites where exotic plant species are introduced or transported to a plant community. Horses have the ability to disperse seeds via manure (endozoochory) and also by carrying the seeds on their coat (epizoochory). Depending on the home location of the horses, the seeds may be of native or non-native species. Since non-native species may be introduced to plant communities via horses, we can assume that trail horses pose as a threat to these communities.

Can Horses Introduce Non-Native Plant Species Along Trails?

Horses have a tendency to defecate indiscriminately—or poo where they please. Since non-native plants are often found in pastures, trail horses with pasture access are able to act as shuttles for non-native seeds by consuming them and  transporting them to a new community where they may germinate, or start to grow. Seeds from the pasture may also stick to the horses and simply fall or get knocked off while on a trail. Hay-fed horses can also obtain seeds from hay. Horses that consistently consume hay transport more seeds through their manure than by their coat or hooves (Gower 2008). It has been established that seeds may remain viable in the horses’ digestive tract for up to two months, although a seed generally passes through the digestive tract within 48 hours of being eaten (Campbell and Gibson 2000; Törn et al. 2009). With this knowledge, it is possible that a seed found in manure came from a distant community, which makes it a little more likely to be exotic.

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Horses grazing in a pasture are susceptible to the discrete seed dispersal of non-native species. Photo Credit: http://www.photobucket.com

How Do Horses Impact the Germination of Seeds?

There are many ways in which a horse affects seed germination along trails. They trample the ground, defoliate vegetation, and cause changes in the soil nutrient status by urination and defecation (Törn et al. 2009). Disturbance of the ground has been shown to assist in the spreading of seeds along trails. It has also been known to enhance the germination of seeds by creating open gaps and pockets in the ground. The amount of different species, known as richness, has been found to be higher right along trails, although this includes both native and non-native species (Campbell and Gibson 2000). This suggests that the soil disturbance along trails assists in germination. Many invasive plant species are easily germinable and therefore, if present, may benefit from ground disturbance by horses.

The effects of trampling, however, don’t only include disturbance of the soil. Often times trampling compacts the soil rather than stirring it up. Soil compaction has been associated with a decrease in seed germination. It increases the soil strength and reduces the ability for water to soak in. It also affects plant root growth and raises soil temperature (Ostermann-Kelm et al. 2009). In areas with high soil strength and compaction, there is usually low plant diversity along the trail. So, depending on the dryness or wetness of the environment, trampling may assist in or stop the germination of species.

Despite the species of the seeds, manure serves as a favorable growing site and seems to be an ideal substrate for germination in a controlled environment (Törn et al. 2009). Areas near horse manure have shown significant plant diversity compared to areas further from manure, yet the diversity consisted mostly of native plants to the area of study (Ostermann-Kelm et al. 2009). Nonetheless, if a horse defecates in a plant environment and there happens to be an exotic seed nearby (whether or not it was present due to consumption by the horse or by some others means of dispersal), the seed may germinate and grow to be an invasive exotic plant that competes and takes over native plants in the area.

IMG_0561

The sprouting of a seed in nutrient-rich soil. Photo Credit: http://www.photobucket.com

So, Are Horses a Threat to Natural Plant Communities?

It is true that horses may carry a variety of non-native plant species and contribute to seed germination, but the environment itself plays a major role on whether or not an exotic seed will grow along a trail. Without enough nutrients and moisture available to the plant as it matures, the species has a low survival rate (this also depends on the plant species). The growth of the plant will also depend on factors such as sunlight and wind. Ultimately, horses are a limited threat to natural plant communities due to the exotic species that may be present in manure (Campbell and Gibson 2000) and the resources that may be available. This form of non-native seed dispersal is only found where horses travel and therefore is not as threatening as some other modes of seed dispersal, such as wind or pollinators. Although exotic seeds are not found all the time in horse poo, it is still important to take precautions toward preventing the introduction of non-native plant species.

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Different hay sources contain a variety of seed species. Photo Credit: http://www.morguefile.com

How Can We Help Prevent Invasion of Non-Native Species?

Overall, research has shown that horses have the ability to introduce non-native plant species to a plant community along a trail. Although many other factors contribute to the germination and growth of an exotic seed, the horse is the first step that makes the seed available to the environment. In order to help with the prevention of non-native species growth along horse trails in protected areas, we can collect manure along trails and limit the amount of horses allowed on the trail (Törn et al. 2009). Proper disposal of any unused or spoiled hay would also decrease chances of exotic plant growth or invasion (Gower 2008). While recreational horseback riding may be enjoyable to humans, it is not always as fun for plant communities, so it is important that we be helpful and clean up after ourselves and the horses. If the communities could thank us, they would!

References


1. Gower S.T. (2008) Are horses responsible for introducing non-native plants along forest trails in the eastern United States?. Forest Ecology and Manag 256:997-1003. doi: 10.1016/j.foreco.2008.06.012


2. Törn A, Siikamäki P, Tolvanen A (2009) Can horse riding induce the introduction and establishment of alien plant species through endozoochory and gap creation?. Plant Ecology 208:235-244. doi: 10.1007/s11258-009-9701-5


3. Campbell J.E., Gibson D.J. (2000) The effect of seeds of exotic species transported via horse dung on vegetation along trail corridors. Plant Ecology 157: 23-35. doi: 10.1023/A:1013751615636


4. Ostermann-Kelm S.D., Atwill E.A., Rubin E.S., Hendrickson L.E., Boyce W.M. (2009) Impacts of feral horses on a desert environment. BMC Ecology 9:22. doi: 10.1186/1472-6785-9-22

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Rethinking Historic Fire Behaviors in Ponderosa Pine Forests

October 26, 2016

Contrary to popular belief, fire can actually be beneficial to forests. In fact, ponderosa forests rely on fire to create favorable germination conditions (Taylor 2009), as well as to provide structural diversity (Brown et al. 2015). The lack of fire not only gives rise to unhealthy, dense forests, but also causes highly intense fires that destroy them entirely. These fires, referred to as mega fires, are always detrimental. Ironically, the practice of fire suppression has ultimately lead to mega fires. The increasing frequency of these highly intense fires is concerning, and indicates that fire is required to maintain forest health. Scientists use models of  historic fire behaviors to determine how fire should be used to manage each forest. New studies have produced evidence that contradicts current models of ponderosa forest fire behaviors and suggests the need for an updated model.

Fire has a different niche in each forest type and affects each forest differently. The fire regime, which is the collection of fires and their characteristics and behaviors recorded over time (Odion et al. 2014), explains the variation in niches from forest to forest. A fire regime includes:

  • Frequency
  • Size
  • Seasonality
  • Severity

Frequency and severity are the two factors that are used most commonly in determining fire regimes, and each ranges from low to high. On the lowest end of the severity spectrum, fires remain close to the ground and cause no deaths among trees. The other end of the spectrum results in high mortality rates and fire that burns in the canopy as well as on the ground (Odion et al. 2014). Usually there areas within a fire that have varying fuel loads or moisture contents that cause the fire to express a gradient of severities. In this case, a fire may have areas of both high and low severity, but be classified as the most dominant severity.

This picture shows an aerial view of a fire scar. There are areas of completely black trees, indicating high severity fire, areas of red trees, indicating moderate severity fire, and areas of green trees, indicating low severity fire.

This mosaic burn pattern shows evidence of multiple levels of fire severity that is common among forest fires. Photo credit: flickr.com.

Scientists previously classified historic ponderosa pine forests as having a low or low to moderate severity fire regime. They believed the frequent, low severity fires were thought to thin out understory vegetation, such as brush and young ponderosas that weren’t entirely fire-adapted, resulting in what is referred to as “park-like conditions”(Odion et al. 2014). The picturesque scene of large, mature trees evenly spread throughout a park is a lot like how scientists imagined historic ponderosa forests looked. They also thought that they had very little structural diversity.

This picture shows a historic ponderosa forest consisting of large, mature ponderosas spread out in an even manner. There is very little understory saplings or shrubs and almost no litter.

The original model of a ponderosa forest would look like this picture from flickr.com.

However, recent studies have found characteristics of ponderosa forests that don’t fit the model of primarily low severity fire. For example, there was much more structural diversity in historic ponderosa pine forests than is suggested by the previous model. While low severity fire only slightly changes forest structure, high severity fire has the most impact on structural changes (Hessburg et al. 2016). Groupings of similar aged trees are indicative of high severity fire as it produces areas in which all of the trees die and are replaced with saplings. The successional regrowth would result in groups of young trees surrounded by groups of older trees, thus increasing structural diversity within the forest (Brown et al. 2015).

This picture shows an aerial view of a forest. Within the forest are groupings of different tree ages. There are clear areas of younger trees and older trees.

High severity fire causes similar groupings of even aged trees like shown in this picture. Photo credit: publicdomainpictures.net.

Increased understanding of fire behaviors implies a model that includes high severity fire. Scientists found that at or above wind speeds of approximately 32 kilometers per hour (20 mph), high intensity fire is almost certain to occur regardless of vegetative conditions (Odion et al. 2015). Therefore, commonly dry ponderosa forests surely experienced high intensity fire more often than is suggested by the low severity model.

With the inclusion of high severity fire, ponderosa forests can no longer be classified as having a low or low to moderate fire regime. Instead, this new evidence proposes that they be classified as having a mixed severity fire regime, which consists of much more variation. Of course, this new model isn’t denying that there were often low severity fires. Instead, it is suggesting that ponderosa forests would’ve experienced both low and high severity fires, but would’ve more commonly experienced fires that are combinations of the two (Hessburg et al. 2016).

This redefined regime is significant not only for managing the health of the forest, but also in furthering our understanding of the relationship between fire and ponderosa forests. With greater structural diversity in forests due to high severity fire, the likelihood of a mega fire, disease, or insect outbreak destroying the whole forest decreases dramatically (Brown et al. 2015). Utilizing high severity fire in managing forests will break up the continuous fuel beds of dense canopy in modern-day ponderosa forests. The structural variation within the forest will decrease the spread of wild fires and decrease the threat of the whole forest being destroyed. Scientists’ ability to understand the ponderosa forest fire regime will enable them to maintain healthy, beautiful forests.

Citations:

Brown PM, Battaglia MA, Fornwalt PJ, et. al (2015) Historical (1860) forest structure in              ponderosa pine forests of the northern Front Range, Colorado. Canadian Journal of Forest Research, 45 (11), 1462-1473.

Hessburg PF, Spies TA, Perry DA, et al. (2016) Tamm Review: Management of mixed-severity fire regime forests in Oregon, Washington, and Northern California. Forest Ecology and Management, 366:221-50.

Odion DC, Hanson CT, Arsenault A, et al. (2014) Examining Historical and Current Mixed-Severity Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America. PLoS ONE 9(2): e87852. doi:10.1371/journal.pone.0087852

Taylor AH (2009) Fire disturbance and forest structure in an old-growth Pinus ponderosa forest, southern Cascades, USA. Journal of Vegetation Science21, 561-572.

Picture Citations:

First picture:
Slide Fire Aerials 05.27.14 (102)” by Coconino National Forest is licensed under CC BY-SA 2.o.

Second picture:
321441 Ponderosa Pine near Ochoco RS, Ochoco, OR 1936” by Forest Service is licensed under CC BY 2.0.

Third picture:
Aerial Tree Tops” by Petr Kratochvil is licensed under CC0 1.0.

Betrayal: Non-rewarding Orchids Use Devious Means to Attract Pollinators

October 3, 2016

Did you know that the exotic and beautiful orchids that we so admire and value practice betrayal on a regular basis? It sounds laughable, but it’s true. Orchids are almost exclusively dependent on animal pollinators for their sexual reproduction, but a full third of the species in this extremely large plant family are non-rewarding. Pollinators aren’t just paying a social call when they land on an orchid or other flower, they visit with the expectation of a reward in the form of nectar or some other needed substance; however, when they visit an orchid, they walk or fly away unrewarded — victims of these deceptive plants.

It may seem as though I am attributing some malice or ill-intent on the part of the orchids, and obviously this is not true. Orchids are plants, not sentient beings. They have evolved their deceptive practices in order to survive and surely don’t deserve our derision for that deception. Instead, if you consider it, orchids have evolved some rather amazing ways to attract pollinators without having any reward with which to entice them.

There are many ways in which non-rewarding orchids attract pollinators, and I’d like to present just a few of the most common to give you an idea of how amazing these plants really are. These methods are floral mimicry, the magnet species effect, and brood site mimicry.

Floral Mimicry

Orchids Trichocentrum ascendens and Rossioglossum ampliatum (left and right); Malpighiaceae (center). Photo credit: Papadopulos et al. 2013.

Orchids Trichocentrum ascendens and Rossioglossum ampliatum (left and right); Malpighiaceae (center). Photo credit: Papadopulos et al. 2013.

The relationship between pollinators and plants is generally a win-win. The pollinators visit plants to get a reward, such as nectar, and in return they carry the plants’ pollen to other plants giving a chance for cross-pollination to occur. In floral mimicry, non-rewarding orchids take advantage of this existing relationship between pollinators and the reward-producing plants by mimicking the appearance of the flowers of the reward-producing plants, especially their color.

A recent study by Alexander S. T. Papadopulos, et al., on neotropical orchids presents a good example of this type of mimicry. The yellow flowers of the orchid species Trichocentrum ascendens and Rossioglossum ampliatum are so close in hue to the yellow flowers of neighboring Malpighiaceae plants, that “a visiting bee cannot differentiate between flowers of the two groups with respect to flower color” (2013).  So, while buzzing from yellow flower to yellow flower, the bees are likely to visit both the orchids and the rewarding flowers, not realizing the difference between them until it’s too late.

Magnet Species Effect

Orchids also score visits from pollinating insects simply by growing in proximity to populations of “magnet” species, or rewarding plants. Just as a

This orchid, Anacamptis morio, takes advantage of pollinators visiting neighboring rewarding plants. Photo credit: Didier Desouens.

This orchid, Anacamptis morio, takes advantage of pollinators visiting neighboring rewarding plants. Photo credit: Didier Desouens.

magnet attracts iron shavings, a magnet species attracts pollinators. It’s not a magnetic attraction per say, really it’s the lure of a reward that draws pollinators to the area. By growing in the same location, orchids get to benefit from the same pollinators who chances are will stop by to check them out while they are in the area. This magnet species effect can be seen in a study done in 2001 by S. D. Johnson, et al., on the island of Öland, Sweden. In this study, the pollination success of the non-rewarding orchid species Anacamptis morio is shown to significantly increase when grown near to two rewarding plant species, Geum rivale and Allium schoenoprasum (2003). The bumblebees that are there to get the nectar from the rewarding plants tend to visit the orchids too.

Brood Site Mimicry

Hoverflies are duped into visiting these Epipactis veratrifolia by the distress pheromones they release. Photo credit: Hans Stieglitz.

Hoverflies are duped into visiting these Epipactis veratrifolia by the distress pheromones they release. Photo credit: Hans Stieglitz.

In brood site mimicry, orchids mimic conditions that would make an optimal site for pollinators to lay their eggs. An excellent example of this can be seen in the orchid species Epipactis veratrifoli which grows in the eastern Himalayas. This species has evolved an amazing way of attracting its only pollinators, female hoverflies seeking the perfect location to lay their eggs (Jin et al. 2014)Since hoverfly young survive on a diet of aphids, the flowers of this fantastic mimic actually release the same pheromones that aphids do when in distress (Jin et al. 2014)What female hoverfly ready to unload her precious cargo could resist the scent of aphids in trouble?

This species of orchids actually isn’t quite as deceptive as some of the other species of non-rewarding orchids. Aphids can be found on their blooms, especially early in the flowering season, and at least some of the hatching hoverflies will find their expected food source. Unfortunately, there’s not enough to feed them all. Some will surely starve to death, but at least there is a reward for some!

I hope that the next time you see a beautiful orchid, you’ll look at it with a new appreciation for its amazing evolution. Orchids may be deceptive, but their ability to attract pollinators without being able to offer a reward is an amazing adaptation. There is still much to be studied to truly understand why so many orchids have evolved to be non-rewarding instead of evolving a reward for their pollinators. However, even without our complete understanding, orchids truly deserve all of the admiration and value we place on them.

References

Gumbert A, Kunze J (2001) Colour similarity to rewarding model plants affects pollination in a food deceptive orchid, Orchis boryi. Biol J Linn Soc 72.3:419-433.

Jersakova J, Johnson SD, Kindlmann P (2006) Mechanisms and evolution of deceptive pollination in orchids. Biol Rev Camb Philos Soc 81.2:219-235.

Jin X, Ren Z, Xu S, Wang H, Li D, & Li Z (2014) The evolution of floral deception in epipactis veratrifolia (orchidaceae): From indirect defense to pollination. BMC Plant Biol 14.1:63. doi:http://dx.doi.org/10.1186/1471-2229-14-63.

Johnson SD, Peter CI, Nilsson LA, Aagren J (2003) Pollination success in a deceptive orchid is enhanced by co-occurring rewarding magnet plants. Ecol 84.11:2919-2927.

Papadopulos AST, Powell MP, Pupulin F, Warner J, Hawkins JA, Salamin N, Chittka L, Williams NH, Whitten WM, Loader D, Valente LM, Chase MW, Savolainen V (2013) Convergent evolution of floral signals underlies the success of Neotropical orchids.  Proc Biol Sci R Soc 280.1765:20130960.

Photo Credits

Top:  from Papadopulos AST, Powell MP, Pupulin F, Warner J, Hawkins JA, Salamin N, Chittka L, Williams NH, Whitten WM, Loader D, Valente LM, Chase MW, Savolainen V (2013) Convergent evolution of floral signals underlies the success of Neotropical orchids.  Proc Biol Sci R Soc 280.1765:20130960.

Middle: by Didier Desouens http://commons.wikimedia.org/wiki/File:Anacamptis_Fleur_global.jpg

Bottom: by Hans Stieglitz http://commons.wikimedia.org/wiki/File:Epipactis_veratrifolia.jpg

The Cause of Plant Tumors

September 9, 2016

Bacterial infections are more commonly thought to be associated with humans. However, bacteria just as frequently affects plant populations. Agrobacterium tumefaciens (A. tumefaciens) is one of the many bacteria typically located in soil, which is responsible for infections found in a variety of plant species (Cubero, J., Lastra, B). This bacterium is the primary cause of crown gall disease. Crown gall disease is responsible for the growth of large tumor-like galls on the roots and lower trunks of plants. This generates problems with development, root structures, and the transportation of water and minerals throughout the plant (Cubero, J., Lastra, B). The plant becomes bound by A. tumefaciens bacteria. It infects the plant by transferring DNA coding for tumor formation. Tumors then develop within the root systems, and the bacterial DNA becomes incorporated into the plants genetic makeup. Plants undergo various responses in regards to the different stages of infection. Read more…

Bad Vibes

December 15, 2014
by

D. plexippus eating a leaf

A larva feeding on a leaf sends vibrations throughout the plant, which will initiate a defensive response

I think that, mobile, intelligent creatures that we are, humans have an unconscious disdain for plants and their unique methods of protecting themselves from predators. I also think that this disdain stems from a certain ignorance of the way a plant will handle an herbivorous threat. Plants don’t respond to stimuli the same way humans do: If we are too hot in the sun, we can move to shade; if we are in the rain, we can move to shelter; if we feel threatened, we can move away from the threat. Plants cannot respond to stimuli through movement; nevertheless, a response does occur, no matter that it can’t be observed to the naked eye.

There are many types of plant defense mechanisms: physical, like thorns; location, like growth on the face of a cliff; timing, like variation of seasonal growth patterns; and chemical, to name a few. While defense is the focus of this article, first it must be understood how scientists study these mechanisms. One method is the use of model organisms. All model organisms have three things in common: they have been studied extensively and thoroughly, they grow or mature quickly, and are easy to maintain in a laboratory.There are hundreds of thousands of plant species that we know of, but a very select few are used in experimental studies as model organisms.  One model organism, Arabidopsis thaliana, is a small flowering plant that is commonly used in molecular biology, plant biology, and genetics experiments. This plant has one of the smallest genomes of all flowering plants, making it an ideal model organism for its simplicity. It is commonly found in Europe, Asia, and northwestern Africa, and is an annual plant.

Flowering Arabidopsis thaliana

Flowering Arabidopsis thaliana

 

In 2014 a study was conducted with Arabidopsis thaliana to examine the chemical response to vibrations caused by caterpillar feeding (Appel et al. 2014). Two scientists at the University of Missouri asked whether the acoustic energy generated by the feeding of herbivorous insects was detected by plants, and if so, what was their reaction. Two experiments were done. In the first, each plant had a module with a pre-recorded vibration of caterpillar feeding behavior placed on one leaf. Twenty four hours later, the leaves were harvested, freeze-dried, and ground into a powder to prepare for chemical extraction. The second experiment was similar to the first, but in addition to feeding vibrations, they also had wind and insect song vibrations placed on individual leaves, to see if the plants could distinguish herbivory from other, non-violent vibrations.

The leaves that had experienced feeding vibrations from the module released two chemicals. One, glucosinolate, is a pungent compound that is toxic in high amounts and is shown to act as a natural pesticide by altering the eating behavior of herbivores. This short-term defense is a generalized response to deter a large variety of herbivores after damage has occurred; it is a reactive mechanism.  The other chemical, anthocyanin, is believed to visually repel insects by indicating toxic properties through color. This chemical is responsible for the red, blue, and purple colors of many flowers, as well as the autumn foliage of many trees. This long-term defense is preventative. It is a specific, targeted response; a co-evolution of the plant and its common enemies who will recognize the threatening colors (Karageorgou et al. 2005). Interestingly, the researchers found that Arabidopsis thaliana could not only distinguish when their leaves were being eaten, but could also tell whether the vibrations were from wind or an insect song. Note that in this instance, the insect song the researchers used was for the purpose of mating or pollination, not herbivory.

This is only some of the many plant chemical defenses in nature. Some plants, when attacked by herbivores, will release salicylic acid, a plant hormone capable of causing chemical burns at high concentrations. Salicylic acid is also a crucial element of plant development and growth, as well as photosynthesis and the transportation of water throughout the plant. Other plants will release jasmonic acid when their leaves are eaten, another plant hormone that plays a role in regulating plant growth. Both jasmonic acid and salicylic acid prohibit growth and development in insect larvae (War et al. 2014).

Wind blowing through T. monococcum and M. chamomilla

Although wind will cause vibrations, plants recognize this as a non-hostile force

It is clear that plants are not intelligent as humans would understand it. They are not mobile, they cannot see, hear, or feel as humans do. What plants have is more subtle: millennia of evolution have provided a sensitivity to the very vibrations in the air. This sensitivity is so precise that plants can distinguish an herbivorous attack from an insect song or a breeze, and they have numerous chemical deterrents in response to threats. Plants may be sessile, but they are not helpless. This research sheds new light on plants and I believe it also lends them a certain amount of respect for the methods developed to protect them from harm.

Resources:

      1. War A, Sharma H (2014) Effect of Jasmonic Acid and Salicylic Acid Induced Resistance in Groundnut on Helicoverpa Armigera. Physio Entomol 39:136-142. doi: 10.1111/phen.12057
      2. Appel H, Cocroft R (2014) Plants Respond to Leaf Vibrations Caused by Insect Herbivore Chewing. Oecologia 175:1257-266. doi: 10.1007/s00442-014-2995-6
      3. Karageorgou P, Manetas Y (2005) The importance of being red when young: anthocyanins and the protection of young leaves of Quercus coccifera from insect herbivory and excess light. Tree Physiol 26:613-621. doi: 10.1093/treephys/26.5.613

How stand age affects transpiration in trees of the Pacific Northwest

December 7, 2014
a large Douglas fir tree, also known as an Oregon pine or Douglas spruce

The Douglas fir, scientifically named Pseudotsuga menziesii, is an evergreen conifer species native to western North America. Moore et al. (2003) studied these trees in relation to transpiration rates and stand age. Photo credit: morguefile.com

Introduction

Plants have an uncanny ability to pull on their environment and draw in the needed resources for their survival.  One of the most important mechanisms they utilize to achieve this is transpiration, which is the loss of water through the stomata (pores) of a plant into the surrounding atmosphere.  Transpiration, which could be considered the process of a plant sweating, is the phenomenon that functions as the driving force for the pull of water and dissolved minerals upward and into plant tissues.  Due to cohesion (molecules of the same type “sticking” to each other), tension builds on a leaf’s inner water molecules as the outmost water molecules continue to evaporate into the air.  This results in an overall pulling, or negative pressure gradient, and can be deemed a cascade effect, as water molecules in the plant’s tissues are drawn together in an upward tow.  This incredible occurrence is what allows a plant to distribute water and minerals throughout its entire body without expending energy; it is truly a solar-powered process. Read more…

The Secret Handshake of Plants

November 30, 2014
The scientist enters the forest.

The harbinger.

A wayward scientist bounces inside his off-road buggy on his way to his research site. Stopping well before his destination, he disembarks and hikes his way to the pristine research site. His fluorescent little flags mark his territory. He slows his walk and carefully wades through his subjects, a herd of grass, ready to be measured.

This budding experimenter may not be doing enough to mitigate his affects on his subjects. The grass has sensed his presence and has already begun the stampede, or at least the plant equivalent of one. Motionless and secretive, the plants fortify and call the alarm for the perceived danger: the invasive species of the sapien. The experimenter sees nothing but the wind on the leaves and soon begins fiddling with measuring instruments. Read more…