Rhamnus Cathartica Research Paper

Introduction
Rhamnus cathartica L., otherwise known as common buckthorn, is a small shrub native to Europe and Asia that was introduced to North America in the 1800’s (Mascaro and Schnitzer 2007). R. cathartica is a deciduous, branched shrub that grows to heights of two to eight meters. Each shrub produces small, black berries containing seeds and bears up to 2000 fruit per tree (Archibold et al. 1997). The seeds are dispersed by fauna, mainly birds, which largely contributes to its accelerated invasion of fields, roadsides, and residential areas across North America (Archibold et al. 1997). With the invasion of R. cathartica comes the displacement of native species, the changes in the structure and function of ecosystems, and the loss of biodiversity

(Harrington et al. 1989).

Numerous solutions have been introduced to control the invasion of R.

cathartica, however many of these efforts have failed to mitigate growth and ultimately eradicate the species. In New England, a method that was implemented involved the introduction of sheep to consume R. cathartica (Milleken 2004). It was discovered that the sheep would readily browse on foliage, but avoid the stems, the trunk, and the roots in the ground (Mascaro and Schnitzer 2007). In Saskatchewan, an alternate method involving the spraying of the chemical, Garlon 4, onto the shrub, was used. This extremely costly solution did not eliminate R. cathartica, nor did it prevent seed production. Additionally, Garlon 4 weakened the native species surroundings the shrub and altered soil properties (River and Leach

1998).

The proposed solution for the eradication of Rhamnus cathartica L. is a multistep process. The first step is to control the main source of seed dispersion. This portion of the solution will introduce acoustic systems to guide the migration of the native birds out of the area of interest (Solman 1973).

The second step involves the elimination of R. cathartica’s foliage. The introduction of a larvae, lepidopterous larvae, to the isolated area of study will allow for the natural consumption of the leaves and prevent further photosynthesis (Schoonhoven et al. 1978).

The third step consists of the complete removal of the R.cathartica tree. Glyphosate, is an herbicide that targets R.cathartica; currently, it is sprayed on the trunk (xylem) of the tree, which ultimately leads to the fatality of R.cathartica (Pizzul et al. 2009).

The final step is centered on the soil restoration of the area that was previously occupied by R.cathartica. In order to re-establish the proper Carbon: Nitrogen ratios in the soil, the addition of organic molecules such as sugar and sawdust will regenerate the microbes needed for the regrowth of native species (Morghan et al. 1999). Additionally, Biochar and Activated carbon will aid in mitigating the allelopathic chemicals found in soil (Beesley et al. 2011).

Problem and Solution
Guided Bird Migration by Acoustic System
R. cathartica is a vital part of all ecosystems that it grows in and its removal from these niches could have negative effects on the animals that heavily rely on it (Archibold et al. 1997). R. cathartica has been discovered to be a primary food source for the American Robin, as well as several other species of birds, particularly during late fall to early spring periods of the year. This has been seen in stomach samples of birds, as well as in their feces (Knight 2006). Additionally, R. cathartica has been found to be suitable for nesting; many bird species have made this invasive species their habitat. This is partly due to the lack of native shrubs in regions where R. cathartica thrives (Vincent 1986). The consumption of R. cathartica berries causes an extreme laxative effect on the large intestine of birds, resulting in a dehydrated, weak, and malnourished organism (Gale 2000). The removal of this invasive species from ecosystems could have disastrous consequences on other species that occupy the same niche, making it vital the various bird species migrate while stopping the spread of R. cathartica.

The first step of the proposed solution consists of the installation of an acoustic system that sends alarms and distress calls of specific frequencies that are solely audible to birds.

This system would emit two stimuli that would repel birds from entering a specific area and guide them to an alternate location for nesting (Solman 1973). Mott and Timbrook (1988) examined the effect of an acoustic system sending these two signals on Canada geese and discovered that over 70% of the geese did not enter the area of research. The effectiveness of an acoustic system has also been examined by Cook et al. (2008) by performing an experiment on the presence of gulls at landfill sites. It has been discovered that various distress and alarm calls are the most effective method of deterring the birds from entering the area, after lethal methods (Cook et al. 2008). Additionally, many airports in Canada use a sound broadcast system, the Phoenix Wailer System, which emits a variety of sounds audible to birds and uses this system as a bird deterrent (Davis 1998). The Phoenix Wailer system consists of two low frequency speakers and four high frequency speakers with adjustable duration, speaker location, and source level (Davis 1998). The biological basis behind this system relies on the avoidance of locations with predators for survival (Bomford 1990). As the population of birds decreases, the removal of R. cathartica could proceed immediately. The implementation of a sound-emitting system is

relatively cost-friendly and many types of these systems are available commercially (Davis 1998).

The ramifications of the first step of the solution include possible disturbance to bird species, and could have minor effects on the lengths of mating season.

Consumption of Foliage by Lepidopterous Larvae
The foliage of R. cathartica is the site of photosynthesis (Prati et al. 2003). The removal of the leaves would inhibit this metabolic process by halting the intake of sunlight energy to produce glucose and carbon dioxide.

Following the controlled migration of the birds, the shrub R. cathartica will be targeted. Upon isolating the trees in a closed system, a species of lepidopterous larvae will be introduced to consume the foliage (Schoonhoven et al. 1978). It has been discovered that the larvae develop preferences for food at their hatching sites (Schoonhoven et al. 1978). Proceeding leaf consumption, the larvae will be released within the ecosystem that it was introduced to, as they pose no threat and will mature to be butterflies (Prati et al. 2003). This process will be tested in a lab setting prior to its introduction to a larger environment. The results of this solution can be measured by the amount of leaves that remain before and after the introduction of the lepidopterous larvae. This solution is a natural approach to foliage removal of the invasive plant, posing few risks. Ramifications of the lab testing could include: a prolonged timeline, increased manual labor and additional costs.

Complete Eradication of Rhamnus cathartica
The consumption of leaves by the larvae will be effective in eliminating foliage, however it is not sufficient for the complete eradication of R. cathartica. The rapid growth potential of R. cathartica is partly due to its photosynthetic capacity (Knight et al. 2007). Due to the consumption of the foliage by the larvae, photosynthesis can no longer occur, however, R. cathartica is unique in that it will regenerate new leaves and spread even once the foliage is removed (Knight et al. 2007). Therefore, to prevent further growth and invasion, it is imperative that the trunks and roots of R. cathartica are completely expunged from all areas that it is non-native to (Pizzul et al. 2009).

This portion of the solution involves the spraying of glyphosate, an herbicide to target R. cathartica. In its pure form, glyphosate is very low in toxicity (Pizzul et al. 2009). Due to this property, restoring forest communities after this treatment is untroublesome (Gale 2000). Glyphosate will be sprayed on the upper and lower portions of the trunk to target the xylem, as it is a major pathway for the uptake of the herbicide (Pizzul et al. 2009). Glyphosate inhibits the shikimic pathway, which is an enzyme pathway that produces amino acids that are essential for plant growth (Amrhein et al. 1980). In the absence of these amino acids, R. cathartica will die over the course of several weeks (Amrhein et al. 1980).After spraying, glyphosate levels in the sediment will rise and then decline due to degradation by microbial metabolic processes in enzymes that remain in the soil (Pizzul et al. 2009). Resultantly, there will be no excess chemicals left in the ground, allowing for soil restoration and reintroduction of native fauna and flora (Pizzul et al. 2009). Additionally, the vapor pressure of glyphosate is very low, causing little to no volatilization (Pizzul et al. 2009). Trials involving glyphosate being sprayed on R. cathartica in Arlington, Virginia were 90-100% effective in eradicating the plant with little damage to non-target species (Converse 2007). Delony and Archibold (2007) found that to this date, more than 347,000 R. cathartica have been successfully treated with glyphosate.

Pure glyphosate is acutely toxic to humans when ingested and dermal absorption is very low. Undeterred by the low toxicity, low volatility, and low body absorption of glyphosate, it is recognized that there are few health risks associated with the herbicide and it is advised that workers applying glyphosate should wear a backpack sprayer and full protective clothing (Pizzul et al. 2009). A second ramification involves additional manual labor after R.cathartica have been treated with the herbicide. Removal of stems and roots via mechanical means such as using tools and hand-pulling is required (Gale 2000). This manual labor not only adds to the cost of the project, but also increases the timeline. Overall the entire portion of this project is costly and timely. At a price of $4.50 per liter of glyphosate in addition to paying workers, the cost of the removal of R. cathartica from North America will be high. Lastly, re-application of glyphosate may be needed if the first application was not effective enough.

Methods that are currently being implemented such as the introduction of sheep in ecosystems to ingest the species are quite expensive, time consuming and often fail to eradicate R. cathartica (Gale 2000). This is partly due to the need for continuous labor throughout the year. Staying consistent with these treatments becomes difficult, particularly throughout the winter months (Gale 2000). Controlled burning is another method that is currently being used to eradicate R.cathartica (Hobbs and Rooney 2000). It it highly disruptive to ecosystems as it causes extensive damage to habitats, loss of biodiversity and loss of soil moisture (Hobbs and Rooney 2000). It is therefore suggested that fire is rarely effective at controlling woody invaders (Hobbs and Rooney 2000). Thus, the introduction of glyphosate provides an alternate approach with less ramifications and a higher success rate.

Re-establishment of Soil Conditions
R. cathartica alters soil properties of invaded regions, in a manner where long-term conservation management needs to consider these altered properties (Heneghan et al. 2005). Areas invaded by R. cathartica showed evidence of alkaline soil, high water content, the presence of allelopathic chemicals and a higher percentage of nitrogen and carbon content (Heneghan et al. 2005; Klionsky et al. 2011). These changes in soil properties often cause reduced germination, growth, and flowering of native flora (Klionsky et al. 2011). Current restoration efforts involve bush cutting and manual removal, however if soil conditions have been altered R. cathartica may continue to damage native flora and fauna (Heneghan et al. 2005). Emodin is a major allelopathic chemical that is excreted by R. cathartica into the soil and prevents the growth of other plants (Klionsky et al. 2011).

The addition of organic matter, such as sawdust and sugar, with high carbon content has been proven to stimulate microbial growth in invaded areas. This has helped re-establish the C: N ratio in the soil (Morghan et al. 1999). This inexpensive solution can provide beneficial effects to the restoration efforts at a low cost and a small time frame. Biological ramifications would be minimal since the added organic matter would decompose over several years and pose no threat to native flora and fauna (Morghan et al. 1999).

Through numerous trials, it has been discovered that Activated Carbon and Biochar absorb allelopathic chemicals in various soil types (Beesley et al. 2011). In combination, these soil fertility treatments re-establish the C: N ratio (Beesley et al. 2011). Activated Carbon can be made from many materials including coconut husks, wood, and nutshells. These materials will naturally decompose and leave no chemical residue in the soil.

Although this method is environmentally friendly, ramifications include a long time line and consistent applications to thoroughly eliminate the allelopathic chemicals and to restore a proper C: N ratio. This could take up to 5 years to accomplish.

Conclusions
Prior attempts for the removal of R.cathartica in North America have occurred over short time periods, have exceeded budget limits and have ultimately failed to eradicate the invasive species. The multi-step solution proposed provides a controlled, safe and experimentally proven approach that will span over five to ten years. This governmentally-funded project could cost up to millions of dollars as it aims to eliminate R. cathartica throughout the continent of North America. The results of this solution can be measured by the presence of native species prior and antecedent to the treatment of R. cathartica. Lastly, public awareness through media publicity will be vital to ensure the extermination of Rhamnus cathartica. These efforts will ensure that the invasive species will no longer harm and dominate ecosystems.