Arc Collector Activity 2: Putnam Prairie Research Project

Introduction

In the previous lab, the class used Arc Collector to add data to an online database that was created beforehand. For this project, each student needed to create their own infrastructure to collect data about a topic of their choice. The objectives were to think of a geospatial research question to design a project around, create a database with three or more feature classes that would implement the research objective and deploy it to Arc Collector, collect point features, and then write a report to explain the results. The report, of course, had to include maps and use the data to either support or refute the research question.
As a conservation biologist, it was natural to gravitate toward a biology research topic. Two semesters ago in the fall of 2015, the Conservation Biology 328 class implemented an invasive species removal plan in the Putnam Prairie area.  The project focused primarily on the mechanical removal and chemical treatment of invasive Black Locust trees (Robinia pseudoacacia). This invasive tree is prolific in the area and provides many management challenges, and there was some trepidation as to whether the removal strategies would help or just aggravate the problem.

This seemed a perfect opportunity to answer the question once and for all: Did the black locust removal attempt succeed in removing black locust from Putnam Prairie or did the control attempts worsen the problem?  

Some smaller questions to address:

·         Has black locust returned in the areas where we removed it?

·         Was the removal treatment effective in killing the treated stems?

Materials:

·         Nexus 9 Android tablet borrowed from the Geography department. (It has a built in GPS, unlike an iPad)

·         Arc Collector

Black Locust (Robinia pseudoacacia)

Black locust is a fast growing deciduous tree which is commonly 30-80 feet tall. Native to the Appalachian Mountains throughout Pennsylvania to Alabama, it has spread throughout most of the contiguous United States as an invasive species. Movement to new areas was often facilitated naively by landscapers, who valued the species for its aesthetics and rot-resistant wood. It thrives in disturbed habitats with full sunlight, such as prairies or floodplain forests. It grows best on well-drained soil with sparse competition.
It has pinnately compound leaves and highly fragrant white flowers which give way to hanging seed pods. Trees and saplings feature prominent woody spines along the trunk and branches, which makes it easy to identify a black locust even in the winter (Fig.1).

Figure 1 Identifiable characteristics of the species Robinia pseudoacacia. The prominent woody spines made identification simple, since there were no leaves, pods, or flowers at the time of data collection. 

Table taken from "A Weed Report" from the book Weed Control in Natural Areas in the Western United States, available through the UC Weed Research and Information Center.  

The tree produces numerous suckers from the roots and thus is capable of forming dense clonal colonies that exclude native vegetation. Root suckers, which form primarily where branch roots emerge from older roots, become new saplings very quickly when the main stem of the black locust is disturbed. This is known as vegetative regeneration and in black locust it is considered a more common means of reproduction than seed. Sprouting often occurs in response to stem or root damage due to cutting, fire, wind, or disease. This creates a huge challenge for the control of black locust, since areas of abundant sunlight allow for one tree to become a dense thicket of trees when any form of removal is attempted. (For more information on vegetative regeneration, click here!) 

Typically, the root system of an established black locust tree has a radial extent of 1 to 1.5 times tree height. Root extensions of 165 feet were documented in the Appalachians. In the sandy soil of Putnam Prairie, extensive lateral root systems are to be expected. (For more information on this, click here!)

Area of Interest

Putnam Prairie is a small area of land near the main UW Eau Claire campus (Fig.2). It is considered a “postage stamp prairie”, an area that has been a prairie since before the city of Eau Claire was built around it. Unfortunately, Putnam Prairie is being inundated with multiple invasive species, including burgeoning thickets of black locust, which are excluding the native grasses.

Figure 2 The Putnam Prairie is attached to upper Putnam Park, adjacent to the UW Eau Claire campus and Sacred Heart Hospital. 

Figure 3 These two images show a comparison between the Putnam Priaire in fall of 2015 and summer of 2016. The left image is from the ESRI basemap (TerraColor satellite imagery, NAIP2015 Source: USDA FSA) and shows “leaf off” conditions. The black locusts are more difficult to spot without summer foliage, but the 2016 photo (Source: Google Earth Pro) shows the extent of the invasion. With the exception of three jack pines, all of the trees within the blue boundary are invasive black locusts.

The Fall 2015 Conservation Biology 328 class, under the instruction of UW Eau Claire Biology Professor Dr. Paula Kleintjes-Neff, completed a project early in December 2015 that centered around removal of black locust trees from Putnam Prairie. (The class report on this project can be viewed here.) Two physical control methods were used:  total removal by either by hand saw, or girdling using hand saws or serrated knives. All the removed or girdled trees were then treated using a mixture of the chemical herbicide triclopyr and mineral oil. This herbicide, advertised under names including Garlon or Crossbow, is selective in managing woody plants as well as herbaceous weeds.  When mixed with mineral oil, triclopyr is less toxic to native wildlife, and due to the selective nature of this chemical, native grasses are minimally affected by it. The class was informed that the most successful method for application is to cut the tree down and saturate the remaining base with this mixture (Fig.4).

Figure 4 An actual photo from the black locust removal performed by the students of Conservation Biology 328 in December 2015. The triclopyr herbicide was applied using spray bottles and applied liberally to the stumps or girdled area. Photo credit: Alexandra Johnson. 

The Fall 2015 Conservation Biology class was not the most recent class to implement invasive species removal in the Putnam Prairie. According to Dr. Kleintjes-Neff, the Spring 2016 Biology 328 class also cut, girdled, and treated black locust trees. According to Dr. Kleitjes-Neff, many of the trees treated December 2015 had new shoots regenerating from the stumps or and they were treated again by the Spring class, as well as many small trees that had not been treated previously. The future spring section of Biology 328 (Spring 2017) is also forecasted to participate in the removal.  

Methods

Step 1: Prepare the data in ArcGIS for Desktop

The ESRI online tutorial provided simple guidelines. 

1. A geodatabase called “Putnam_Prairie” was set up in ArcCatalogue.
2. Next, geodatabase domains were defined. This provided a list of choices the data collector can choose from while working, and cuts down on data entry error. For this project, data needs to be collected about tree height, whether the tree has been treated for removal, type of removal attempt (girdling/herbicide, hand saw and herbicide), and whether the tree is alive or dead.  Out of trees that are alive, are the roots regenerating shoots or not.
3. To define the feature class: “Black_Locust”, a point feature class, was added to the geodatabase. Coordinate system as WGS 1984 Web Mercator (auxiliary sphere).
4. Set up the fields. This is a key part of the information model. Fields provide the structure of the information collected in the field and provide rules for the types of information collected about a feature.

o   Tree_height: height of target plant (feet)

§  Range: 0-40 feet

o   Treated: Was the tree treated for removal last year?

§  Yes or No

o   Removal_type: What method of removal was attempted?

§  Girdling (A ring was cut around the trunk and then the stripped area was sprayed with herbicide) or Saw (Trunk removed by saw, stump treated with herbicide)

o   Status:

§  Alive or Dead

o   Regenerating: New shoots forming?

§  Yes (New shoots from stump or base of trunk) or No (No evidence of new shoots)

5. Theme the data: The symbology was set to green circles to keep the map simple.

6. Publish the data: The map was deployed to ArcGIS Online for mobile offline data collection.

Step 2: Data Collection 

Data was recorded over two days in mid-November by Amanda Senger using the Android tablet. The weather was just above 50 degrees F and windy. Attributes and photos were recorded for 197 black locust trees. The study area consisted of two main thickets of black locust with trees ranging from 2 to 7 feet tall (Fig.5). The three most common tree types to find were small untreated saplings, treated stumps that were sprouting new shoots, and girdled trees that were surrounded by young clones (Fig.6). 

Figure 5 This was a common sight in Putnam Prairie. The clonal colony of black locust was so thick it was difficult to walk through. Data collection was as unbiased and inclusive of all heights and treatment statuses as possible. 

Figure 6 These were the three most common cases. The sapling on the left is less than four feet tall. Girdling was common on the medium-large trees. 

Results and Discussion

Data analysis revealed that 119 out of 197 of the trees that were sampled had been treated for removal. Of those 119 stems treated, only 59 of them exhibited no signs of regeneration. This means that the Conservation Biology class had a removal success rate of less than 50% (Fig.7). According to the literature, these trees likely reproduced vegetatively by sending out root suckers after the treatment disturbed the main stem. 

Figure 7 Only 59 out of the 119 trees (meaning individual stems) that were treated for removal over the last year were dead. The others were either unphased by the treatment or showed signs of increased sprouting or vegetative reproduction. 

Embedded is an interactive map of the study area which displays the sampled trees, treatment type, and whether the treatment was successful in killing the stem (Fig.8). It was not feasible to determine which trees shared a root structure, and which trees were vegetative offshoots of nearby stems, so each stem that possessed a singular trunk was counted as its own tree. Clusters of trunks that were touching at the base also counted as one tree. 

Figure 8 To view the interactive results map, click here. 

 Trees with heights exceeding 20 feet were considered large trees for the study area. There is a feature class in the map above displaying a minimal estimation of the ground area reached by their radial root structure. Since the literature stated that root suckers (responsible for clonal colonies) form primarily where branch roots emerge from older roots, and radial root area is 1-1.5 times tree height, it can be expected that dense clonal colonies could form quickly around these areas. My observations in the park corroborated this; the largest black locust trees were centered in the densest black locust thickets. This supports the hypothesis that those dense thickets were clonal colonies that were sprouting through vegetative regeneration from the existing root structure of established black locust trees.

 A proportional symbol map of the estimated root radius of each tree demonstrates the estimated root overlap of the trees. The dense colony areas are so overlapped that it is likely that they are sharing root structures (Fig.8).
 

Figure 8 The tan circles on this map represent the most modest possible estimate of root radius relative to tree height. With the amount of overlap occurring in the main thicket areas, it is clear that the black locust has not suffered at all from the removal treatment, and has likely increased sprouting in response.

Conclusions

·         Has black locust returned in the areas where we removed it?  Yes

·         Was the removal treatment effective in killing the treated stems? No

Did the removal attempt help or make the problem worse? The literature asserts that black locust seedlings grow rapidly when planted on sandy sites with little shade and sparse competition, especially when a site has been disturbed. According to these criteria, Putnam Prairie is an ideal habitat for black locust. Even without removal attempts, germination from seedlings and root suckers was inevitable and the trees would have continued to take over the prairie whether or not human intervention accidentally increased the rate of spread.   

Since trees do not begin producing seeds for the first 6 years of life (on average), and there were only 10 trees taller than 20 feet, it is likely that there are very few trees in the study area mature enough to be producing seeds. Root suckers are the most prevalent form of natural reproduction in mature trees, and dramatically moreso in Putnam Prairie. Suckers usually appear in the fourth or fifth year when the tree has not been aggravated, but is occurring on first year saplings in Putnam Prairie. The high rate of proliferation witnessed in the study area indicates that the trees are sending out more root suckers and are undergoing increased vegetative reproduction as a response to the disturbance of removal attempts. So yes, unfortunately, it is likely the removal attempts have made the black locust problem in Putnam Prairie worse. Some possible reasons that the treatment was so ineffective include not enough herbicide being applied or the triclopyr solution potentially being too diluted. Or perhaps the soil conditions are just too good in this prairie and black locust cannot be contained.  

However, the fact remains that Putnam Prairie would have an invasive species problem regardless. At least an attempt to help restore the prairie ecosystem is being made. As the old adage states, Better to do something imperfectly than to do nothing perfectly.


Overall, this project emphasized the importance of planning ahead and keeping the research objectives in mind while setting up the geodatabase and attribute fields. There were a few hiccups in the attribute field setup that caused redundant data to be collected (such as stating that the tree is dead and then having to fill out fields to say that it exhibits no sprouting). Domains made data collection very streamlined, and greatly increased the efficiency of data collection. For future GIS projects using this study area, research could be done to determine whether the Spring 2017 Conservation Biology 328 course meets with more success in their attempts to control the black locust outbreak.

Sources

Conservation Biology 326, Fall 2015. http://conservationbiologyuwec.blogspot.com/

http://wric.ucdavis.edu/information/natural%20areas/wr_R/Robinia.pdf

Huntley, J. C. (n.d.). Robinia pseudoacacia L. Retrieved November 27, 2016, from http://www.na.fs.fed.us/Spfo/pubs/silvics_manual/volume_2/robinia/pseudoacacia.htm

Stone, Katharine R. 2009. Robinia pseudoacacia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2016, November 28]. 

Special thanks to Dr. Paula Kleintjes-Neff for providing information regarding the Biology 328 classes’ removal work and procedures.