I-Tree Canopy is efficient and free software for calculating estimates of tree coverage and its environmental benefits in a predefined area based on Google Earth aerial photography. Using imagery of historical maps, I-tree Canopy also can study changes in canopy over time. The land cover data from I-Tree Canopy can be used by I-Tree Hydro to analyze the effects of trees on hourly stream flows and water quality.
A nice feature of I-tree Canopy is that everyone can learn to use it. The program asks the user 1) to delineate a geographical area, 2) to provide other types of land coverage categories besides trees (building, impervious, grass, etc.), and 3) to determine for each random dot the program creates in the delineated area on the map whether this dot is a tree or something else. The percentage of tree canopy is then determined by the number of dots classified as a tree. The more dots the user includes in the project, the greater the accuracy of the estimated tree canopy coverage.
I-tree Canopy is mostly used for geographical areas such as townships, cities, and counties. However, we chose Marquand Park to demonstrate its use. Based on just 200 data points, the results indicated that 51% of the park was covered by tree canopy (red dots), and 33% covered with grass (blue dots). The estimated environmental benefit of the tree canopy were relatively modest but the park is only a small 17-acre area.
When you venture in the wooded area of Marquand park, you may notice fallen trees and large branches on the ground. In this area of the park called natural woods, trees grow, mature, reproduce, die, and decompose without human intervention. Because dead trees are left undisturbed, natural woods have a healthier and more diverse ecosystem than wooded areas where fallen trees are routinely cleared.
When a fallen tree begins to rot on the ground, fungi and other microorganisms that live on dead wood break down the tree’s cell wall, thereby releasing carbon, nitrogen, phosphorus, and other essential nutrients to the soil. This decomposition produces rich organic matter for other trees to use.
Even standing dead trees, called snags, play an important role in the forest by supplying food and microhabitats. You may find snags stripped of their bark because in particular, deer and other small animals like to eat the bark. Woodpeckers bore deep holes in snags to get at insects or larvae within. These holes become nesting sites for woodland birds. Rotting tree bases provide homes for small mammals. Finally, birds of prey use standing dead trees as lookouts.
To read more about the importance of natural woods:
The recent discovery of Japanese knotweed (Fallopia japonica) around the parking lot of Marquand Park demands some attention. The perennial has a bamboo-like reddish stem, heart-shaped bright green leaves, and when blooming pretty little white-flower tassels. Introduced in Europe at the beginning of the 19th century, Japanese knotweed became popular as a garden plant because of its soft and pleasing effect. In the United States, Frederic Law Olmsted was responsible for planting it in Central Park.
Over time, the plant has become the most pernicious weed in Great Britain posing a threat to building structures and road surfaces. In the United States, Japanese knotweed is considered an invasive in 38 states and occurs on the New Jersey Invasive Plant Species List. The weed likes to grow along roads and in areas disturbed by human activity. It spreads like wildfire. Eradicating a cluster of plants is not easy. A home improvement website called the Spruce describes techniques such as using tarp to smother the weed; cutting and digging up the plant and its root system; and spraying and injecting knotweed with herbicides. In the United Kingdom, scientists are experimenting with the release of a plant eating insect called Aphalara itadori that feeds on the Japanese knotweed and kills the plant.
John Claudius Loudon (1783 – 1843), often called the father of the English garden, wrote books and articles on gardening and growing plants which were widely read and used in the creation of private and public gardens in the 19th century. Loudon did not believe that gardens should imitate nature. His gardenesque style allowed for the placement of specially designed planting areas where plants could grow under optimal conditions. These planting areas were geometrically shaped like squares, triangles, and circles.
In his Suburban Gardener and Villa Companion, published in 1838, Loudon describes the construction of a circular flower bed on a grassy lawn. The outside of this flowerbed was made of a circle of bricks with the short sides of the bricks facing each other (a). The raised slope inside the circle (c) was covered by another row of bricks (b) laid perpendicular to the bricks forming the outside circle. A year after the publication of Loudon’s book, the description of this circular bed with accompanying illustrations was republished in The Magazine of Horticulture, Botany, and All Useful Discoveries and Improvements in Rural Affairs (Volume 5, 1839, p.133) in America. The circular bed was praised as an inexpensive method of creating desirable planting areas for growing a mixture of verbenas, and other plants with maybe a tall fuchsia as a center piece in the middle. In the next edition of this magazine, Mr. R.S. Field of Princeton is praised for having introduced this circular flower bed with “the result being quite pleasing and worth imitation.” The article recognizes Field as an innovator willing to experiment with building these new planting areas.
In 1840 when the article was written, Richard Stockton Field was still living on Stockton street across from the Morven estate and had not yet bought the property that later became Marquand Park. Thus, it is uncertain if he ever constructed similar flowerbeds on his newly purchased estate. But Field’s association with Loudon’s work is interesting. He most likely owned a copy of the Suburban Gardener and Villa Companion or was familiar with Loudon’s gardening methods from local publications. When, the time came for designing and constructing his newly purchased estate, then called Fieldwood, Field did not follow Loudon’s gardenesque style but preferred the more natural and pitturesque garden designs popularized by Andrew Jackson Downing. But even in this more natural landscape design, the construction of some circular flowerbeds could be easily imagined.
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