ENVIR ST 260 1st Edition Lecture 8 Outline of Last Lecture I Species Dominant versus Keystone II Regulation Top Down versus Bottom Up III Succession and Stability IV Housekeeping Outline of Current Lecture I Succession and Stability a Natural Disturbances b Climax Community Concept c Disturbances and Society II Housekeeping Current Lecture Disturbance Ecology Not always a correct answer in disturbance ecology Succession and Stability Sometimes disturbances can be a cyclic system where the ecosystem never quite gets to the climax community that you d think they d end up with over time Succession usually starts out with some disturbance event Natural Disturbances Animal Disturbances Example Badger digging a hole Badgers do a lot of digging whether it is to burrow or to go after prey Whether they re going after prey or maintaining a burrow they re continuously disturbing a patch of dirt Example Gofer Tortes digging a hole in a sandy area It kicks out soil and covers vegetation These are small scale disturbances that create a little microhabitat There may be small plants that don t do well with competition so they take advantage of the big open space These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Trees provided If there are abandoned burrows you may get a pocket where a new community develops in a really small area Some plants kind of need these disturbances and only occur in spaces with low competition and jump from burrow to burrow Weather Disturbances Bigger disturbances Nature Leads in Brimfield Video From that clip we see there are some benefits from the tornado you open space for species that require a lot of sunlight and you get depressions that can fill with water which make a great breeding ground for amphibians American chestnut shot up all over as a result We ve talked about how most of it got knocked out by blight but there s still a seed source that can thrive in this newly opened space When there is a wind event a lot of trees get knocked down which makes room for grasses and forbs Overall it s a positive event Fire disturbances Similar to tornados in that people don t really like them Wild fires have potential to do a lot of damage but there are also a lot of benefits Climax Community Concept Clicker Questioin What is the climax community Mature pines and grasses Mix of pines hardwoods and grasses Hardwood forest Most people think hardwood forests However if you think of other grassy communities like a prairie there aren t really trees If prairies didn t burn they d eventually turn into a shrub and tree dominated ecosystem If we think about prairies being a community that can change over time but exist as grassland would that change your answer When she ran the poll again most people thought the answer was B This is something that ecologists debate about Some people would argue the hardwood forest is the climax because it s what the community moves towards given lack of certain circumstance There s a lot of other people that disagree and say the climax community is what s maintained by disturbances over time because those disturbances have been around for hundreds of thousands of years When disturbances are integral to maintaining the structure of an ecosystem they are something that we want to maintain as part of that ecosystem Fire for example is a process and can be argued for Clicker Question Can disturbances maintain stability Yes To help explain this think about the time scale that you re looking at We re heavily influenced by what s happening over the time that we can see For example look at grasslands and savannas that have widely spaced trees and grasses that go through burn cycles Over time you get more and more hardwood trees until you get a fire and the number drops down Then it continues in a cycle of trees increasing until fire drops the number down Time Zoomed In If you look over thousands of years it evens out It s a straight line over a long time scale Trees Time Zoomed Out Disturbances and Society Clicker Question Disturbances are natural but damages to society need to be minimized Strongly Agree Agree Neutral Disagree Strongly disagree Most people said agree That s pretty representative of most of society based on our actions How can we minimize the impact of disturbances Class discussion Improved building codes Less construction of roads which will make less of an impact on the aquatic ecosystem and have less influence on the water tables A lot of times when you build roads stream flow is screwed up and flooding occurs Better education on safety procedures People in high risk areas should have really good insurance Professor s idea People should build domes for homes in tornado zones They re an eye soar but withstand tornado force winds She recognizes that this probably will not happen though New Orleans has a levee system to try to protect themselves Hurricane Katrina in 2005 tested if this was a long term strategy that could be maintained It wasn t so much that the hurricane did damage to the city but that the levees failed and the city began to flood The forest service will provide wild fire protection by flying big planes low to the ground that drop retardant and water into the forest area where some people have houses However it doesn t always work House Keeping Practice essays will be posted on Friday Wednesday discussion should prep We should have content for STS workshop for Thurs Fri discussion Exams will be given back next week in discussion