Unformatted text preview: Biology 1M03 TUTORIAL 5| FOREST FIRES & THE INTERMEDIATE DISTURBANCE HYPOTHESIS Student Package Objectives Students will be able to: !"Calculate species diversity using the Shannon Index !"Create a properly labeled bar graph and interpret trends !"Discuss the impact of forest fires on the environment !"Apply the Intermediate Disturbance Hypothesis (IDH) to Forest Fire Management ! Analyze species diversity values in relation to the IDH ! Read Box 53.1 (p. 1218) and Sections 53.1 “Species Interactions: Competition” (pp. 1196‐1202), 53.3 “Community Dynamics” & 53.4 “Species Richness in Ecological Communities” (pp. 1212‐1219) in Freeman’s Biological Science, 3rd Ed. Note: The Species diversity values in Box 53.1 are incorrect. They should be as follows: Community 1: 1.38, Community 2: 1.81, Community 3: 1.61 ! Read the Introduction and Tutorial Activity (p. 1‐7) in this Tutorial manual ! Complete the Multiple Choice ELM pre‐Tutorial quiz ! Calculator ! Printed Student Package Preparation Materials This tutorial will help you understand how ecological indicators can be used to observe and measure ecological conditions, with a focus on the assessment of biodiversity. In this tutorial we will use the Shannon Index of species diversity to test the Intermediate Disturbance Hypothesis in relation to forest fire management. BACKGROUND INFORMATION INTRODUCTION: As our population expands and develops, humans are having an ever increasing effect on the ecosystems of the world (referred to as the anthropogenic impact). Scientists are trying to measure and quantify the impact that we have by using a series of ecological indicators. These indicators are measures of characteristics that can be used to assess the health and status of ecological communities and ecosystems. The basis for the use of ecological indicators is that biotic and abiotic components of an environment will react to changes in the environment and therefore reflect the quality of a community or ecosystem as a whole. Ecological indicators can assess ecosystem health by quantifying factors such as water quality, biodiversity and the abundance of degradation tolerant species (Niemi, et al, 2004). In this tutorial we use the Shannon Index of Species Diversity to test the Intermediate Disturbance Hypothesis. 1 SHANNON INDEX: Biologists use a variety of indices to quantify characteristics of environments and ecosystems. Here we will look at the measurement of species diversity. This diversity is a measure of the variety and relative abundance of the species present in a given ecological community. Succession, disturbance, human influences and other factors drive changes in species diversity over time (Freeman, p. 1212‐ 1216). While several indices have been developed to quantify species diversity (e.g., Simpson Index), this tutorial will focus on the use of the Shannon Index (a.k.a. the Shannon‐Weiner Index), which calculates a value for diversity based on the abundance of individual species in an area (Freeman, Box 53.1). You can calculate the Shannon Diversity values using the following equation: Where: !"pi is the relative abundance (=proportion) of each species !" H’ is the diversity value, where a larger H’ value indicates a more diverse community structure, i.e. higher species diversity. For example, a community where H’=3.6 would be more diverse than a community where H’=1.4 Example: Calculating the Shannon Diversity a Deciduous Forest Species Count Total Maple /// 3 Oak /// 3 Elm //////// 8 Aspen // 2 Birch //// 4 Step One: Calculate pi for each species Maple: pmaple = (# maple)/(total #) poak = 3/20 = 0.15 = 3/20 pelm = 8/20 = 0.40 = 0.15 paspen = 2/20 = 0.10 pbirch = 4/20 = 0.20 Step Two: Use pi values in the Shannon Index Equation H’=‐!"i ln(pi) =‐[0.15ln(0.15)+0.15ln(0.15)+0.40ln(0.45)+0.10ln(0.10)+0.20ln(0.20)] = 1.48 H’=‐! [pi ln(pi)] 2 INTERMEDIATE DISTURBANCE HYPOTHESIS (IDH): Organisms in an ecosystem can be killed or badly damaged by disturbances, both natural and human‐induced, resulting in changes in the composition of the ecological community. The Intermediate Disturbance Hypothesis (IDH) states that communities with moderate levels of disturbance will have the highest species richness and diversity, as opposed to those that undergo either high Frequent Infrequent Large Small or low levels of disturbance More Intense Less Intense (Freeman, 53.4). The impact of Figure 1: The Intermediate Disturbance Hypothesis. Species Diversity a disturbance is considered to changes with varying size, frequency and intensity of disturbance be a factor of three variables: (modified from Connell, 1978). the type of disturbance, its frequency and its severity (Freeman, 53.3). According to the IDH, regions with moderate type, frequency and severity of disturbance should have high species richness and diversity. When disturbances occur frequently in an ecosystem fewer species are able to resist damage and establish populations that are able to survive. As well, species that disperse more slowly will not be able to establish themselves before another disturbance event takes place (Connell, 1978). As the time between disturbances increases, diversity also increases; more time is available for species to move into an area allowing slower or less easily dispersed species to develop. However, as the time between disturbances continues to increase further diversity will begin to decrease for two reasons: (1) The species that are able to best exploit the resources available or best able to outcompete other species will eliminate the majority of the diversity, or (2) If all species have equal ability to compete for resources, the species that are best able to resist damage or death will fill the majority of an ecosystem (Connell, 1978). Disturbances disrupt the processes of competitive exclusion and remove individuals of some species to create open space or habitat with different qualities (niches) in an environment (Freeman, 53.1). 3 FOREST FIRE MANAGEMENT Fire is a natural part of the forest ecosystem and is necessary for the proper functioning of the forest environment in many temperate and some dry tropical forests. However, due to the danger that forest fires present to humans and human developments, the natural disturbance introduced by forest fires is altered in many cases by human intervention. When a fire travels through a forest it removes dead plant material on the ground, clears overgrown cover, alters soil conditions and can trigger the growth of some species of vegetation (Oberle, 1969). We will look at the disturbances that result from three categories of fires management: (1) fires in areas left to burn naturally, (2) forests in which fires are suppressed and (3) areas where controlled burning occurs. CONTROLLED BURNS: Controlled burns are fires that are intentionally set in forests in order to remove potential fuel sources (dead vegetation, ground cover, etc). These fires generally burn slowly along the ground burning grasses, shrubs and small/young trees and may or may not affect the canopy of larger/older trees. Controlled burns occur frequently, often set each year to remove fuel sources. This removal of fuel sources on a regular basis greatly decreases the likelihood of natural fires occurring. NATURAL BURNING: Fires that begin are left to burn out on their own; there is no interference by fire fighters or officials. This generally only occurs in areas that are far from human developments. Natural fires tend to be more intense then controlled burn fires, as they move more quickly and burn larger areas, often affecting parts of the canopy as well as ground cover. However, natural fires occur much less frequently than controlled burns, in Canada the fire return interval (time between forest fires in a particular area) is estimated to be 100 years in natural conditions (Stocks, 2004). FIRE SUPPRESSION: Fire suppression involves the immediate extinguishing of any and all fires that ignite in a forest ecosystem, and often also involves the removal of potential fuel sources from the environment. This practice is most common in areas near human developments to protect people from the dangers that forest fires pose. Due to suppression efforts, the fire return interval is approximately 500 years (Stocks, 2004). Figure 2: Different Forest Fire Management Approaches: (1) Controlled Burns (2) Natural Burning (3) Fire Suppression 4 TUTORIAL ACTIVITY PART 1: PREDICTING THE IMPACT OF FIRE MANAGEMENT For this tutorial you will be split into groups of 3, each analyzing one of the fire management categories (controlled burns, natural or suppression) and filling in the following chart. The class will then come back together to discuss what the groups have come up with. When analyzing the disturbance think about WHY you are choosing the answers you are: HOW does fire impact animals, vegetation, etc. WORKSHEET #1: PREDICTING THE IMPACT OF FIRE MANAGEMENT Name: Student #: Group Members: Forest Management Strategy (circle one): Natural Burning Controlled Burns Fire Suppression Impacts of Forest Fire On The Natural Environment On the Human Environment How does competition affect the structure of communities following fires? Impacts of Fire Management answer based on your assigned strategy How would you describe the intensity of the fires? (circle one) High Moderate Low How would you describe the frequency of the fires? (circle one) Very Frequent High Moderately Frequent Moderate Infrequent Low Overall, How would you rate the disturbance level of these fires? 5 PART 2: USING THE SHANNON INDEX TO TEST THE IDH IN FOREST FIRE MANAGEMENT Now that we have discussed the impacts that fire management can have on a forest environment we will use the different fire management strategies to test the Intermediate Disturbance Hypothesis. The data in Table 1 provide information on the vegetation found in three different forests: Forest #1 is left to burn naturally, Forest #2 is subject to controlled burns and in Forest #3 fires are suppressed. Each species present was recorded along with how many individual plants were observed. Use Table 2 to calculate the Shannon Index diversity values for each forest. You will then be required to graph your H’ values against the level of disturbance to test if the diversity observed reflects the Intermediate Disturbance Hypothesis TABLE 1: FOREST SPECIES OBSERVATIONS Data will be provided by your TA in Tutorial COMMON NAME Red Ash SPECIES NAME Fraxinus pennsylvancica IMAGE FOREST #1 FOREST #2 FOREST #3 Sugar Maple Acer saccharum Jack Pine Pinus banksiana Dogwood Cornus sericea Poison Ivy Toxicodendron radicans Nannyberry Viburnum nudum Dandelion Taraxacum officinale Crab Grass Digitaria ischaemum Garlic Mustard Alliaria petiolata 6 WORKSHEET 2: INTERMEDIATE DISTURBANCE HYPOTHESIS CALCULATION Using the Data in Worksheet #1 fill in the following charts to calculate H’ using the Shannon Index Equation. Round your H’ values to 2 decimals. Also, determine the species richness of each forest. Name: Student #: TABLE 2: SHANNON INDEX CALCULATIONS FOREST #1 SPECIES TOTAL pi ln(pi) Species Richness= H’= FOREST #2 SPECIES TOTAL pi ln(pi) Species Richness= H’= FOREST #3 SPECIES Species Richness= H’= TOTAL pi ln(pi) 7 POST‐TUTORIAL ASSIGNMENT (1) Name:________________________________________ Student #:_____________________ TA:________________________ ___ Marks Tutorial Section: __ ___ 1. Other than forest fires, give one (1) example of an ecological disturbance that is a result of HUMAN activities, and one (1) example of a NATURAL disturbance. /2 Human: Natural: 2. Rank the Forests from Part 2 in order of highest to lowest disturbance level: /2 Highest Lowest /1 3. A) You are in charge of developing a plan for managing fires in a forest located in a remote area of northern Ontario. In respect to biodiversity, what fire management technique would be best to utilize in this forest? Briefly explain in terms of the IDH. /3 /3 B) Would you change how you managed fires in this forest if it were located in Southern Ontario? Why or why not? /2 /2 8 POST‐TUTORIAL ASSIGNMENT (2) Name:________________________________________ Student #:_____________________ Tutorial Section: __ ___ 4. TA:________________________ ___ Marks Create a bar graph that shows the relationship between species diversity (H’) and level of disturbance from your calculations in Table 2. Your y‐axis should be H’ while your x‐axis will be a category of disturbance (high, moderate, low). Make sure to properly label your axes, include units and give your graph an appropriate title. /3 5. Does your graph of the Shannon Index Values above support the IDH? I have attached Worksheet #1: Predicting the Impact of Fire Management " I have attached Worksheet #2: Intermediate Disturbance Hypothesis Calculation " /1 /2 /6 TOTAL /20 9 POST‐TUTORIAL TASKS 1. Answer the Post‐Tutorial Questions that are found on pages 8‐9 of the manual. 2. Submit Worksheet #1, Worksheet #2, and BOTH of the Post‐Tutorial Assignment sheets to your Tutorial drop box by 1pm the day following the Tutorial. This information is copyright material (intellectual and academic property of Dr. L. Kajiura, Dr. J. Kolasa, Mr. A. Tracey, and Ms. L. Wheeland, Department of Biology, McMaster University). It may be used only for study purposes and only by students enrolled in 2009‐2010 Fall/Winter Biology 1M03 (Biodiversity, Evolution, and Humanity). This information may not be reproduced for any other purpose, nor distributed to any person (using any type of media), who is not enrolled in the course, except by written permission of the Biology 1M03 professors and staff. References Connell, J.H., 1978. Diversity in Tropical Rainforests and Coral Reefs. Science, 199(4335): 1302‐1310 Li, J., Loneragan, A., Duggin, J., Grant, C., 2004. Issues Affecting the Measurement of Disturbance Response Patterns in Herbaceous Vegetation: A Test of the Intermediate Disturbance Hypothesis. Plant Ecology, 172(1): 11‐26 Niemi, G., & McDonald, M., 2004. Applications of Ecological Indicators. Annu. Rev. Ecol. Syst., 35:89‐111 Oberle, M., 1969. Forest Fires: Suppression Policy has its Ecological Drawbacks. Science, 165(3893):568‐571 Stocks, B., 2004. Forest Fires in the Boreal Zone. International Forest Fire News, 31:122‐131 10 ...
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- Spring '11
- Biology, IDH, Forest Fire, INTERMEDIATE DISTURBANCE HYPOTHESIS, Shannon Index of Species Diversity