ENVIR ST 260 1st Edition Lecture 18 Outline of Last Lecture I II III Ideas from Last Lecture Questions of Monetary Value in Forest Ecosystems Conservation and Restoration Challenges Outline of Current Lecture I Forests and Climate Change II Deserts a Factors that Form Deserts b Plant and Animal Adaptations Current Lecture Forests and Climate Change Things we need to consider Increased CO2 could lead to increased tree growth rates where there s enough rain On a global scale there could be increased growth rates but you still need enough water Water is the limiting factor Range Shifts species may migrate north or to higher altitudes If you have forest species that live in one region a lot of them will migrate further north as climate changes With altitude you get changes in precipitation and temperature It s similar to moving north in latitude as elevation More extreme More extreme events a slight shift in temperature combined with these extremes might be the thing people need to be concerned about Droughts Flooding Precipitation To accommodate shift in latitude or altitude 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 Wildlife corridors would be very import to allow this shift on the landscape Wildlife corridors are green spaces that connect one protected area to another they allow for movement between the two This idea seems plausible but it doesn t work quite as well for plants They move very slowly and it takes a long time to get from point A to point B In addition to setting up green pathways with animals in mind there are suggestions to plant the species from one place in another more northern place Deserts Factors that Form Deserts What is a desert Areas where evaporation exceeds rainfall This is the biggest thing There can be cold and hot deserts but all that matters is that evaporation exceeds rainfall Clicker What do you think is the most important factor in the formation of deserts Topography Wind currents Ocean temperatures Latitude Soil Nutrients Answers were all over the place Depending upon sources that you look at people will argue about what the most important factor is Topography is a good answer Wind currents are also a big contributing factor With soil nutrients it s a bit tricky because yes they re low in nutrients but it s not that being nutrient poor causes a desert to occur but the factors that cause deserts to occur lead to low nutrients Latitude Where deserts occur on global scale You don t really have deserts along the equator but they come a lot closer to 30 degree latitude For the most part they re fairly concentrated along these lines Why we see deserts in these latitudes There are air currents around the world In some regions high pressure dominates and others low pressure dominates You end up with places without much wind and it shifts fronts and moisture systems away from this region That s where latitude is a contributing factor Topography Big mountain ranges can affect the formation of deserts As fronts move across mountain ranges it forces the moisture out of the clouds so you get a lot of rain and snow on one side However by the time the air masses drop to the downward side there isn t a lot of moisture in the air Now you have less precipitation than evaporation Plant and Animal Adaptations Focus on Southwester US Hot Deserts Factors Species Need to Adapt To Limited rainfall Extreme temperatures High solar radiation Plants Adaptations Sonoran Desert Roots Big Cacti They send out shallow fibrous roots just under the surface so that when it does rain they can take the water from the soil and put it right up into the stem Trees They send down long tap roots in the hopes of hitting the water table A lot of times you ll find them by streams that form when it does rain or natural sinks for water where the water table may be higher Small leaves They have little tiny leaflets They don t need big leaves because they already have a lot of sun Small leaves are effective for absorbing solar energy and they minimize the area for water loss Water Storage Pleats in Cacti They expand and contract to store water Aloe plant has a similar system where the leaves can swell and store water This system of water storage is fairly common in desert ecosystems world wide Photosynthesis Typically plants photosynthesize in full sun during the day during which they transfer gases through pores on the leaves Desert plants essentially store the energy they pick up from the sun during the day and keep the pores closed during the day so they don t lose water through them when giving out gas Then when it gets later and temperatures drop they can photosynthesis at night By shifting the timing of when plants are photosynthesizing they re losing less water Pointy Cacti have spines It s meant to keep things from eating them They re really slow growing plants it takes them hundreds of years to reach big sizes By adapting spines things are less likely to eat them Desert leaves often build up a waxy exterior so they re less palatable to insects and animals that might be trying to eat them Seeds A lot of desert plants are good at creating seed banks in the top layer of the soil The seeds will remain dormant until they re trigged to start growing by rain This is good because if they sprout immediately without rain it ll be too hot or dry and they d fail The success rate is still fairly low because very few seeds will end up in the right place to be able to maintain a full size If they re in the shadow of tree they ll do better than if they re out in the open Lots of animals eat these seeds If you have this huge deposit of seeds in the soil plants are hedging their bets to have a few that don t get eaten and land in the right spot with a little bit of shade and take advantage of where there is a bit of moisture Thinking about adaptations Desert ecosystems are less likely to have problems with invasive plant species True or False Half and half Why people thought True Potential that you have an invasive that s adapted is less likely Why people thought False Humans may move another desert species from a different area that would be well adapted Correct Answers They re just as likely to have invasive species The unique adaptations of their species do not make them immune to invasives Buffalo Grass It s a non native invasive species that was imported and grows really well in desert