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BIOL 1070
Wright& Newmaster

Inquiry Case #2 Unit 7 Managing Forest Biodiversity This week we will consider one of the major hypotheses concerning forest biodiversity; the intermediate disturbance hypothesis. You will also explore the concepts of forest ecosystem function and service, which have implications for major concepts in ecosystem management. This includes adaptive management and co-management. Our case on woodlot biodiversity concludes this week as we learn the final thoughts from our cast of characters about the three woodlots. Think about the challenges involved in making real decisions about forest conservation and management when you go to the field and sample woodlot diversity within the University of Guelph Dairy Bush. There are many issues to consider (e.g., development, thinning, tree disease) regarding this rather unique forest located within Guelph. Concluding Remarks from the Stakeholders Once again, you will hear from the stakeholders who have concerns about this development. They will share with you thier final thoughts on each of the three woodlots. Gather this information and complete your concept map adding the new knowledge you have gained for all three woodlots. Consider how adaptive and/or co-management may be used to help you reach a decision regarding which of the three woodlots should be developed. In class we also learned that Old Field Woods has been invaded by giant hogweed, which many people believe is a major problem. Consider, for example, this video produced by WorkSafe BC: ------------------------------------------------------------------------------- Ms. Fields — Environmental Consultant “We have verified that there are many young Butternut trees at the Old Field Woods site.” -------------------------------------------------------------------------------- Ms. Flowerpot — Environmentalist “These woodlots are a legacy for our children and as environmentalists we will protest any further developments in either Majestic Pine Woods or Maple Ridge Woods!” -------------------------------------------------------------------------------- Mr. Stumpage — Forester “I noticed that there was a misidentification on your list of the shrubs in Old Field Woods. The dominant saplings are not Black Walnut, but rather Butternut, which is healthy and will develop into a nice forest. We can spray herbicides on the Giant Hogweed!” -------------------------------------------------------------------------------- Mr. Woods — Conservation Officer “COSEWIC designates Butternut as a rare and endangered species.” -------------------------------------------------------------------------------- Mr. Burnz — Developer “We could plan a wildlife corridor within the new development that will consider sensitive environments like the streams and provide habitat for rare species like butternut.” -------------------------------------------------------------------------------- YOU — Biology Intern “I’ve learned what I can from consulting the stakeholders. Soon I will have to make my recommendation.” -------------------------------------------------------------------------------- -> species colonizing (feDisturbance Theory. Whereas natural systems have a certain degree of organization and order, they also exhibit constant change and disturbance at varying levels. Disturbance ecology often centers around a concept known as the intermediate disturbance hypothesis (Figure 17). This hypothesis explains why diversity is often highest in systems with intermediate levels of disturbance. Few species are capable of colonizing an area that either experiences high frequency or intensity of disturbance (e.g. frequent or intense flooding). In areas of low or infrequent disturbance, a small number of species optimally suited to local conditions establish themselves and outcompete other potential colonizers, so here too diversity tends to be lower. The importance of natural disturbances in shaping landscapes and influencing ecosystems is well-documented in the scientific literature. Ecologists generally distinguish between relatively small, frequent disturbances and large, infrequent, so-called “catastrophic” disturbances. Much has been recently learned of the former, while a relativew species are Intermediate Disturbance Hypothesis (Connell 1978): 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 outcompete other shade tolerant species. Large, infrequent, disturbances are often catastrophic and include disturbances such as floods, forest fire, hurricanes and volcanic activity. A woodlot may be transformed by a severe fire into an open field dominated by herbs and grasses. 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 their 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. There is a host of organisms including insects, bacteria and fungi that literally keep the logs and branches from piling up on the woodlot floor. Look around the dairy bush and arboretum for evidence of fungi on logs and sticks. Forest Ecosystem Function and Productivity Ecosystem Service: Ecosystem Services refers to the processes within ecosystems that provide fundamental resources such as water, clean air or even the decomposition of waste
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