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Lecture 19

BIOL 1070 Lecture Notes - Lecture 19: Statistical Hypothesis Testing, Rhamnus Cathartica, Intermediate Disturbance Hypothesis

Course Code
BIOL 1070
Shoshanah Jacobs

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Learning Outcomes for Unit 7
The Province of Ontario in the "Places to Grow Act - 2005" designated specific parts of
the province that will be developed to accommodate future population growth. This act
states that, "directing a significant portion of new growth to the built-up areas of the
community through intensification" with an explicit focus on "intensification areas". What
this means is that, for a city like Guelph that is included in the "outer ring" of the Greater
Golden Horseshoe Area (see the map below from the act), it must actively plan to
accommodate a growth by a third in the next 17 years.
Remember when Mr. Neumann (Manager of Forestry for the City of Guelph)
described his experiences with Trees for Guelph - and how recently the urban spaces
that Trees for Guelph plants trees are now much more focused on schools than
industrial spaces. "Those opportunities don't seem to exist anymore" - due to the
increased emphasis on intensification.
A(nother) final reminder about development on the University of Guelph Campus
Campus Master Plan. This plan, “describes the history of the Campus and provides
guidelines for future development. The guiding/planning principles are environmental
quality; spatial structure and composition; project design; movement and associated
systems; land use locations; and implementation.” The most current version is from
Intermediate Disturbance Hypothesis The Intermediate Disturbance Hypothesis
(IDH) predicts that the highest species richness will occur at an intermediate level of
intensity or frequency of natural disturbance. This is because low levels of disturbance
do not create many habitats to support a variety of species, whereas high levels of
disturbance will eliminate many habitats that support species diversity. Communities are
constantly changing in response to varying levels of disturbance. For example, when a
single tree falls in a woodlot it creates a “gap” that has higher levels of light, which
support a new community of species. These species are optimally suited to high light
conditions in which they can establish themselves and out-compete other shade tolerant
species. Large, infrequent, disturbances are often catastrophic and include
disturbances such as floods, forest fire, hurricanes and volcanic activity. A less severe
fire may transform a maple woodlot into one that is dominated by ash and popular
seedlings. Natural disturbances are very important in shaping landscapes and
influencing ecosystem processes.
Last week we introduced the concepts of "ecosystems" and "ecosystem processes".
This week we add two related concepts:
Ecosystem Function: Ecosystem function includes the exchange of energy and
nutrients among plants, animals and thier environment. For example in the woodlot
there is a great deal of carbon in the form of branches and leaf litter that is decomposing
and producing biomass.
Ecosystem Service: Ecosystem Services refers to the processes within ecosystems
that provide fundamental resources such as water, clean air or even the decomposition
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