I continued my efforts to remove Japanese Stilt Grass from near the stream.
Before:
After:
After pulling Stilt Grass, I decided to move across the stream and attack a different weed: the Mile-a-Minute vine. It appears that the State of Maryland planted a number of Oak trees and the Mile-a-Minute vines were doing their best to crowd them out and cover them.
Before:
After:
I cleared these vines from five trees and did not best to up-root more from the surrounding areas.
I found one encouraging site: a native Virginia Creeper [Parthenocissus quinquefolia]:
I picked up about 50 pounds of trash, including a rusted bike.
Today I selected an area and cleared a sizeable patch of Japanese Stilt Grass near the stream.
Before:
After:
The water plant, which I have photographed in the past, was mostly washed away by the recent storms.
I was encouraged, as I walked along the trail, to see a number of native plants thriving:
Indian Grass [Sorghastrum nutans]
Mcdowell’s Sunflower [Helianthus occidentalis]
Blue Wild Indigo [Baptisia australis]
Here is a another patch of native grass:
I walked, and cleaned about 0.5 miles of Turkey Branch. I picked up about 50 pounds of the usual cans, bottles, and plastic bags along with a car jack, a lawn mower, and a DVD of the Da Vinci Code!
We had a very violent storm this week which had a dramatic impact on Turkey Branch. Some of the rock dams, which were constructed to slow the water flow, were overwhelmed by the stream as it cut channels around these barriers forming rapids.
The storm also caused huge areas of deposition – in areas that were previously water – of sand and gravel. There were noticeably fewer Darter fish in the stream this week. I fear that the shifting silt and sand buried many of these fish as they were hiding beneath the rocks during the storm.
Here is a "Before" and "After" film clip which shows how much Turkey Branch's morpology has changed as a result of this Summer's storms:
Success in Removing Invasive Plants and Restoring Native Species
As in the past two weeks I selected a number of areas, measuring 3 feet by 3 feet, in places that I weeded 1-8 weeks ago. As in the earlier weeks, I uprooted and counted every invasive plant. I also counted the native plants that were left in the ground. I selected areas that I weeded from between 1 week and 8 weeks earlier, comparing the average number of plants/square yard with my control [non-weeded areas'] average.
I used the Student t Test:
to determine if the difference in the means of the study and areas the control areas is statistically significant.
X1 = the average number of invasive plants/square yard in areas I have not weeded X2 = the average number of invasive plants/square yard in areas I weeded
s1 is that variance of untreated areas and s2 the variance of the weeded areas and n1 and n2 are the number of samples.
For my anaylsis, I started with my "control" group which consists of 20 areas [3 feet by 3 feet] which I did not weed. I selected these areas by selecting the squares, every 10 feet, in a cross section beginning at the stream and ending at the trail. I recorded the various invasive plants that I found in each sample area and calculated "TOTAL Invasives". I calculated an average number of invasive plants/square yard [180.7] by adding the "TOTAL Invasives" for each area and dividing that number by the number of areas [20].
I subtracted the average from each of the "TOTAL Invasive" sample values (x - mean) to calculate the variance. I then squared each variance and added all of the squared variances and divided this number by the number of samples [20].
I made the same calculations [for the mean, variance and variance squared] for the areas that I weeded - these areas were classified according to how many weeks ago they were weeded. I subtracted the sample mean from the control mean and divided that value by the square root of the sum the squared variances of the "control" and sample areas. This t value is compared to the value in the t Test Table, according to the "degrees of freedom" [sum of the number of "control" plus sample areas minus 2] at the 99% confidence interval.
My Null Hypothesis is that there is no difference between the mean number of invasive plants/square yard of the unweeded ["control" areas] and the weeded areas.
My Research Hypothesis is that there is a difference between these means. If my calculated t value is greater than the t Test Table, I accept the Research Hypothesis and reject the Null Hypothesis.
Here is the "Control" samples for Native Plants/Square Yard:
7-8 Weeks Since Last Weeded
At the 99% confidence interval, with 38 degrees of freedom ((n1+n2) – 2) the table value is 2.7, while my t-test value is 3.3 which indicates that the average number of invasive plants/square yard are different [significantly less] - statistically - in areas that were weeded than in the control area.
There appears to be no statistically significant difference between the numbers of native plants per square yard between weeded and control areas.
4-6 Weeks Since Last Weeded
At the 99% confidence interval, with 39 degrees of freedom ((n1+n2) – 2) the table value is 2.7, while my t-test value is 3.3 which indicates that the average number of invasive plants/square yard are different [significantly less] - statistically - in areas that were weeded than in the control area.
There appears to be no statistically significant difference between the numbers of native plants per square yard between weeded and control areas.
1-3 Weeks Since Last Weeded
At the 99% confidence interval, with 33 degrees of freedom ((n1+n2) – 2) the table value is 2.75, while my t-test value is 3.5 which indicates that the average number of invasive plants/square yard are different [significantly less] - statistically - in areas that were weeded than in the control area.
In spite of the fact that weeded does not appear to encourage the growth and re-growth of native plants, some bright spots can be found, such as this Western Sunflower [Helianthus occidentalis]:
A Graphical Analysis of the Effectiveness of Weeding Invasive Plants
It is clear that the number of invasive plants per square yard increases as the time since the area was last weeded becomes greater.
Here is a scatter-graph showing no relationship between native plants/square yard and weeks since last weeded:
Stream Cleanup
The storm also swept an unusual amount of litter [about 80 pounds] into the stream including a shopping cart from a store nearly two miles away!
I selected 20 areas, measuring 3 feet by 3 feet, in an area that I weeded 9 to 12 weeks ago. I uprooted and counted every invasive plant and also counted the native plants that were left in the ground. I selected 20 areas, measuring 3 feet by 3 feet, in an area that I did not weed as a control - I selected a section every 10 feet moving from the stream to the trail. I uprooted and counted the invasive plants in these square sample areas and counted the natives that remained in the ground.
I compared the average number of native plants/square yard in the weeded areas with the un-weeded "control" areas from last week. I started with my "control" group which consists of 20 areas [3 feet by 3 feet] which I did not weed. I recorded the various invasive plants that I found in each sample area and calculated "TOTAL Invasives". I calculated an average number of invasive plants/square yard [180.7] by adding the "TOTAL Invasives" for each area and dividing that number by the number of areas[20] .
I subtracted the average from each of the "TOTAL Invasive" sample values (x - mean) to calculate the variance. I then squared each variance and added all of the squared variances and divided this number by the number of samples [20].
I used the Student t Test to determine if the means between the unweeded "control" areas are significantly different the the areas that I weeded. In other words, are my efforts making a difference in restoring the ecosystem of Turkey Branch?
X1 = the average number of invasive plants/square yard in areas I have not weeded X2 = the average number of invasive plants/square yard in areas I weeded
s1 is that variance of untreated areas and s2 the variance of the weeded areas and n1 and n2 are the number of samples.
Here are the calculations for the "Control" Areas' Invasive Plants/Square Yard
Here are the calculations for the "Control" Areas' Native Plants/Square Yard:
Success in Removing Invasive Plants
Here are my data along with a calculation of the mean number of invasive plants per square yard:
I made the same calculations [for the mean, variance and variance squared] for the areas that I weed. These areas were classified according to how many weeks ago they were weeded. I subtracted the sample mean from the control mean and divided that value by the square root of the sum the squared variances of the “control” and sample areas. This t values is compared to the value in the t Test Table, according to the “degrees of freedom [sum of the number of “control” plus sample areas minus 2] at the 99% confidence interval.
My Null Hypothesis is that the is no difference between the mean number of invasive plants/square yard of the unweeded ["control" areas] and the weeded areas.
My Research Hypothesis is that there is a difference between these means. If my calculated t value is greater than the t Test Table, I accept the Research Hypothesis and reject the Null Hypothesis.
At the 99% confidence interval, with 38 degrees of freedom ((n1+n2) – 2) the table value is 2.7, while my t-test value is 3.2 which indicates that the average number of invasive plants/ square yard are different[significantly less] - statistically - in areas that were weeded than in the control area.
Success in Restoring Native Plants
Next, I did the same type of analysis for the native plants.
There appears to be no statistically significant difference between the number of native plants per square yard between weeded and control areas.
However, it is encouraging to see native flowers and grasses growing in areas that I weeded months ago.
I finished the day by collecting litter along the stream bed.
The water levels are very low in the stream because of the lack of rain. There is also a large amount of algae.
I picked up approximately 25 pounds of beer cans, plastic water bottles, and an old shoe.
The goal of my personal project is to adopt a section of a creek [Turkey Branch], which flows into Rock Creek, and to restore it, as closely as is possible, to its natural ecology. I was inspired to take on the restoration of Turkey Branch after participating in a community clean-up of this stream. This stream is in very bad ecological condition. It is full of liter, invasive plant species, and has poor water quality.
There are a number of things that I hope to learn by doing this project. The “over-arching” goal for learning is: can a polluted ecosystem be restored?
This restoration will begin with:
1. Cleaning the creek
2. Monitoring its ecology and removing invasive plant species.
3. By removing invasive species, an opportunity will be created for native plant species (especially those species that are endangered)to establish/re-establish themselves in this ecosystem.
4. Work towards the further restoration of the stream, and all of Matthew Henson Park, by acting as an advocate with local government and the community.
Turkey Branch is a stream in suburban Montgomery County Maryland. This stream flows into Rock Creek which flows into the Potomac River and ultimately into the Chesapeake Bay. Turkey Branch has a watershed drainage area of 2,412 acres (or about 3.8 square miles) and is 3.6 miles in length. Turkey Branch has a number of environmental and ecological problems. These include serious down-cutting erosion, fecal pollution, and a proliferation of non-native invasive plant species.
