Monday August 9, 2010

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.