In urban areas, plant communities are greatly affected by how humans decide to develop the surrounding areas. These plant communities exist in several forms: their original state, a state completely altered in composition by gardening, or even a state altered unintentionally through random side effects, such as changes in the soil pH from nearby roads. Urban development also affects how successful plants are at dispersing their seeds to other areas. For example, seeds dispersed in the middle of a parking lot would not be able to grow into trees because they are obstructed by concrete, which lacks the proper resources for growth. In addition to that, weeding also affects dispersal by reducing the number of ‘nuisance’ plants that grow in yards and other public spaces. In general, all these changes made by urban development create distinct patches of where plants are able to thrive.
The figure above was taken from the Zipperer et al. (1997)
paper.
The paper
“Urban tree cover: an ecological perspective” by Wayne Zipperer et al. (1997) explains
the significance of evaluating the tree cover in different tree patches that occur
within an entire urban landscape rather than only in small portions of it (as researchers
have done previously). Because little
was known about ecological processes of urban systems at the time the paper was
written, the authors wished for future researchers to approach the problem
through analysis of vegetation in different patches of trees. They proposed that these researchers determine
the differences between the patches through their origin (untouched or planted), structure of vegetation (e.g. leaf size or
canopy cover), landscape configuration (building or patch locations), and level
of management. One of the vegetation
structures that they looked at was species richness which, in one study, was
determined to decline due to clearing for development, but had the potential to
increase quickly as new species were planted.
With this and future research, the authors would be able to create
simulation models that would estimate ecological changes in urban areas.
Link to paper: http://link.springer.com/article/10.1023/A:1018587830636
This picture shows the tree
patch that we are studying. It is
located on the Grinnell campus between Noyce and the Forum.
The topics
presented in this paper contain components that are prevalent in our current
study. We are attempting to discover how
microhabitat affects tree sapling dispersion in a single patch between Noyce
and the Forum. Both we and the authors
want to determine the amount of tree cover, as it affects the survival of
dispersed seeds. However, we are only
looking at a single patch rather than for the entire urban area. In our case, we are looking at a patch that
has a woody-understory (one of the two types that Zipperer et al. wished to
study). One of the things that they
proposed was to determine whether or not the patches had been managed or had
been allowed to remain in a more natural state.
Our study focuses on a patch that is partially managed, but has seen
lack of recent tending.
In addition to our project, this paper has stimulated
research in at least 102 other projects.
References
Zipperer, W.C.,
S.M. Sisinni, R.V. Pouyat, T.W. Foresman, and T.W. Foresman. 1997. Urban tree
cover: an ecological perspective. Urban Ecosystems. 4:229-246
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