Discussion about ecology on the chaparral community

I want to do home work for bio 120
Exercise 13ECOLOGY: THE CHAPARRAL COMMUNITYStudent Learning OutcomesAt the completion of this exercise you should:(1) Be able to identify 12 common shrubs found on north-facing and south-facing slopes of the chaparral community in the Grossmont College Wildlife Sanctuary.(2) Be able to estimate the percent cover of the dominant shrub species on the north-facing and south-facing slopes.(3) Be able to use ecological field equipment like an infrared thermometer, Kestrel meter and soil thermometer to measure selected physical factors on the north-facing and south-facing slopes.(4) Be able to describe how the following physical factors can be measured: soil moisture, soil temperature, air temperature and relative humidity.(5) Be able to compose a written analysis describing the interrelationships between physical and biological factors in the ecosystem and explaining the observed differences in biotic communities on the north-facing and south-facing slopes in terms of those interrelationships.IntroductionA terrestrial community includes the living things within its boundaries, but it is more than just a collection of plants and animals. Interrelationships exist among them– both competitive and cooperative. Each organism is dependent upon and modifies the physical environment in which it lives. Plants are usually the most conspicuous components of the terrestrial ecosystem. When we use such terms as “chaparral,” “ecosystem type meadow,” “cypress swamp,” or a “stand of pine,” we recognize communities and, to a limited extent, we describe them. A more complete description of any community requires that many additional specific and general characteristics be observed and stated.The Chaparral CommunityChaparral is a type of vegetation, not a particular plant. It exists wherever a particular physical environment exists. The particular physical conditions occur between 30° and 40° north and south latitude, just above the world desert belts. In these latitudes, air subsides “permanently.” Subsidence compresses and dries the air, resulting in relatively permanent high pressure areas. Thus, the summers and autumns are dry. During winter and spring, cold air from the poles pushes the high pressure areas closer toward the equator, and rain can push into the chaparral latitudes.Chaparral tolerates only mild climates, with the temperatures rarely below 28°F or above 100° F. These conditions exist where there are large bodies of water that modify extreme temperatures. The latent heat of water results in mild winters and mild summers. Thus, chaparral grows near oceans, along coasts. In such areas, the rainfall is less than 20 inches per year, with only a trace of rain from June to September, and an average of three inches per month from December to March. There may be some summer fog, but in general, there is a great deal of light, hence heat, hence drought.These physical conditions exist in six places in the world: the California coast, around the Mediterranean Sea, on the west coast of Spain and Portugal, the west side of Cape Horn, the west coast of Chile, and the southwest corner of Australia. A non-botanist visitor to any of these places would be struck by the similar climate and appearance of the plant growth.In a dry, wooded climate, fire is an omnipresent threat. But drought is an even greater threat. The chaparral vegetation must be adapted to both conditions, even though drought is the more serious. To prevent excess water loss, the leaves are often covered with resins, waxes, oils, and/or hairs (called trichomes). The leaves and branches are dry. The ground litter is dry. All the devices which prevent water loss cause chaparral to be highly inflammable. Unlike redwoods, which grow in mild but constantly moist climates, and have fire-resistant bark because it has no pitch in it, the chaparral’s response creates fire hazards.Because chaparral does not require rain or additional water in the dry season, it will grow on the thin, rocky, steep slopes of mountains, where much of the rainfall runs off even in winter. Where the slopes meet the flat alluvium of sand and gravel, even chaparral cannot grow, and grasses usually take over. Some species of chaparral tolerate serpentine soil; a few are even serpentine indicators. Serpentine soil is very alkaline, being high to toxic in magnesium, chromium, and nickel, and low in calcium, phosphorus, potassium, and nitrogen. Serpentine soil is particularly subject to landslides, absorbing water and slumping down or decomposing into talc and magnesium carbonate. Where serpentine underlies soil, it holds water very poorly during the dry season. The surface of the soil can reach temperatures of 125°F. Plants must grow through this interface.The interrelationships between the plants, the biotic factors, do not remedy the heat and drought. The plants are tangled but sparse. The temperature is hot even underneath the plants. The plant litter is sparse and dry, decomposing slowly. Humus, or soil organic matter, makes up the organic material of the soil. It is comprised of decomposing animal and plant material. The amount of humus in the soil is important to ecosystems; the more humus, the more fertile the soil. Humus also increases water retention. Ashes which remain after a fire do not contribute greatly to nutrients in the soil. The total environment is not “rich.”Chaparral plants are adapted to the poor environment in its structure and functions. The roots, which must be able to reach water, grow 25 to 30 or more feet deep. The area occupied by roots is often several times larger than that of the plant above ground. The roots hold the thin, easily eroded soil particularly well. The leaves are adapted to conserve water. They often contain tannins which may act to increase osmotic pressure and help prevent water loss. The stomates are reduced in number and may often occur only on the underside of the leaf. Hairs (trichomes) act to insulate the leaf against heat and may be long and fuzzy or felt-like. The hairs are frequently white and reflect light (give albedo quality). The cuticle is thick and waterproof. The leaf may be covered with a waxy coat, or be sticky or resinous, all of which are waterproof. The leaves are small, thick, and leathery. Some plants have leaves which turn their edge (either vertically or folded like a taco) to the sun to reduce the light striking them. Internally, the cells are small, and are mainly vertical palisade cells with chloroplasts. This condition helps to control the amount of energy entering the leaf system, and hence controls the water loss.The branches and leaves are rigid and tough. The branches grow at right angles to the main stems. The rigidity helps to prevent wilting, which causes irreversible mechanical cell damage. The shrubs of the chaparral community are from two to ten feet high, and often have branches modified to thorns or spines. This condition is frequently associated with aridity and may be a form of protection from herbivores.The chaparral is mostly evergreen. It becomes dormant when there is not enough water, in summer or winter, or it is too cold to grow. The growth period is dependent upon a temperature-moisture balance and takes place from December in mild years to May or June, with the last of the water. The evergreen habit allows the plants to be “ready to go.”Studies have indicated that fires naturally occur at intervals ranging from 25 to 45 years. Some of the species can grow from the old roots or stumps the spring following a fire which has burned the shrub to the ground. Other species bear seeds which can remain viable for 50 years. Some of the seeds sprout immediately, but the littered, shaded ground prevents their growing. Other seeds actually require the heat of a fire to allow them to grow. The fire may act in several ways: it may mechanically damage the hard coat, it may break down the oils in the seed coat and allow water to enter, and it may stimulate the embryo to grow. The seeds are extremely dry, containing less than 10% water, which reduces the seed’s metabolism, and also prevents it from “cooking” in a fire.Fires, especially in urbanized areas, are being prevented by man. Some species of chaparral plants are dependent upon fires, and chaparral is a relatively short-lived type of vegetation. We do not know what will happen to areas now covered by chaparral when it dies out. Fire clears the ground of mature plants, opens the surface to light, and heats the seeds, allowing renewed growth.Chaparral serves as watershed on steep slopes where nothing else can grow successfully. It replaces logged or burned forests, pioneering the bared soil and making it acceptable to trees again. It is a fire-adapted community, where naturally occurring fires are common. It serves wildlife and stock as forage and can be replaced agriculturally by olives and grapes. Chaparral grows where little else can, covering the landscape with a furry green blanket.Question 1. List several ways chaparral plants are well-adapted to an arid (dry) climate.Question 2. List several ways chaparral plans are well adapted to a fire community.I. Field Study: Investigation of North-Facing and South-Facing SlopesThe first 2 hours of the lab will be spent gathering data in the field. When you return to the lab, record your team’s data on the whiteboard as directed by your instructor. Be very careful in your collection of plant data. You will be sharing it with the rest of the class.A. Get Familiar with the Chaparral PlantsExamine the labeled plant samples provided and spend a few minutes learning their names and getting familiar with their key characteristics, such as leaf size, waxy leaves, etc.. Concentrate on the ones listed in Table 1. Other specimens will also be encountered, so try to learn these also. A partial list is found below.B. Initial Observations of the Field Site:From Grossmont College perimeter road, you can get a good view of both slopes. Discuss what you see with the other members of your team and record these general observations below:Observations:Question 3. Suggest some questions an ecologist might ask:The numbers and kinds of plants in any environment are usually determined by counting all specimens in a given sample area. In this study, however, each group will be assigned to make observations and measurements on only one distinct area of trail on both the north and south-facing slopes. (See Figure 1.)Figure 1. Grossmont College Wildlife Sanctuary:North-Facing and South-Facing SlopesQuestion 4. Observe Figure 1. Which side (A or B) faces north? _____Which side (A or B) faces south? _______ Label this in Figure 1 above.Question 5. Label the stations from the top to the bottom as N1 through N3 and S1 through S3 according to the slope they face (not which slope they are on!).Question 6. While viewing the trails from this vantage point, what do you notice about the difference between north- and south-facing slopes?Question 7. What could account for the differences?Question 8. How does this relate to the position of the sun in relationship to San Diego (or anywhere in the northern hemisphere)?C. Biotic Data: Plant Population Analysis1. Your group’s first objective will be to gather data on the plants (see Table l) which border on one side of the trail in your assigned study area.2. Together with the rest of your team, walk down the trail and locate your assigned area. Stay on the trail at all times! We need to maintain the integrity of the wildlife sanctuary.3. Start at 0 m along the measuring tape and face down slope (not down trail).4. Run the 30-meter measuring tape on the down-slope side of entire length of the trail in your station. (This is not the same as down trail.) This is called a ribbon transect. (A transect is a line along which sampling is done in ecological studies.) Stay on the trail at all times! Walking off trail causes soil damage.5. Table 1 has been divided into separate portions for each station. Locate the part of Table 1 that refers to your station. We will collect the entire class’ data later.6. Write down in Table 1 (Initial Data) the plant you first see when moving along the measuring tape. Note the measurement along the tape that plant started and ended. Continue recording the plants and their measurement data until you reach the end of the 30-meter tape.7. Make additional comments in the space below your table. As examples, there may be young silverback ferns or wildflowers present in the spring, or you may observe signs of animal life such as scat (feces), birds’ nests, wood rat nests, or animal burrows. Live animals such as insects, lizards, birds, or even the occasional mammal might also be seen. Keep your eyes open – you may be surprised!Abiotic DataThe science of ecology emphasizes the principle of measurement in field biology. This includes measurements of factors of the physical environment, as well as various measurements of statistics involving organisms. For this exercise we will study the interrelationships of the plants and physical factors in the nearby chaparral. We will estimate the percent coverage (area of occupancy) and the frequency of the more common plants found on adjacent north-facing and south-facing slopes in the chaparral.We will also attempt to measure some nonliving factors of the environment which affect the growth of plants in the area. By comparing your findings for a north-facing slope with those of a south-facing slope you will try to evaluate the data in terms of their functional effects in the community.Air Temperature ()1. Stay on the trail at all times! Adjust the Kestrel meter until you see the symbol of a thermometer (). Make sure the readings are in Celsius (°C).2. Walk to the 15 m mark along your station’s transect to take air, trail and soil temperatures. Air temperatures are taken on the trail by holding the Kestrel meter at chest high, with the body shading the meter.3. Enter the data for your station in Table 3.Soil Temperature1. Stay on the trail at all times! Soil temperature should be taken in two places: Under a bush or shrub and on the open trail where the sun strikes the ground. (See following instructions) Walk to the 15 m mark along your station’s transect.a. Using the InfraRed Thermometer to the trail temperature. Be sure to read the User’s Manual that is in the bag. Make sure the readings are in Celsius (°C).b. Face up slope (not up-trail), and push the metal soil thermometer into the soil under a bush, avoiding rocks and large roots. Push the soil thermometer approximately 6 cm (2.5 inches) below the surface, while shading the thermometer. Readings should be in Celsius taken after five minutes.2. Enter the soil and trail temperature data for your station in Table 3.Relative Humidity (S%)Soil moisture and humus contentSoil moisture and humus content could be measured at each station. Time prohibits us from doing this however. Below in Table 4 are some “average” values recorded in the Wildlife Sanctuary during another lab period. Moisture readings were collected one day after a December rain shower.Results1. In the Initial Data portion of Table 1, calculate the total width of each particular plant along the transect by subtracting the starting measurement from the ending measurement.2. Write each of the different plant species you see in the Combined Data portion of Table 1 for your station.3. Then calculate the Combine Total Width by adding the data for each species from the Initial Data table.4. Finally, calculate the Percent Cover of each species by dividing Combined Total Width by 30 (the length of the entire transect = 30 m), and multiply by 100. Record the data in Table 1.5.Once you have recorded the Percent Cover data in Table 1, write your data in Table 2 which includes the Percent Cover data for all the stations.6.Write down all of the abiotic data from your station into the class data table (on the white board or computer, depending on your instructor). Then copy all of the data into Table 3 of your lab manual.Table 1. Plant Types and Percent Cover for Your Group________________-Facing Slope Station #_____ (______)(Initial Data) (Combined Data)Table 2. Plant Types and Percent Cover Comparing North and StationsTable 3. Air, Trail, and Soil Temperature (°C) and Relative Humidity (S%) of North- and South Facing Slopes Each at Three StationsNorth-Facing Slope South-Facing SlopeTable 4. Soil Moisture and Humus ContentNorth-Facing Slope South-Facing SlopeII. Review QuestionsComparison of the North and South-Facing Slope CommunitiesUsing the following list of plants, answer Questions 7 and 8:ChamiseMonkey FlowerBlack SageMission ManzanitaFlat-Top BuckwheatLaurel Leaf SumacCalifornia SagebrushScrub OakRedberryLemonade BerryChaparral BroomDeer WeedQuestion 9. List the four most dominant plant species (in terms of % coverage) on the North-facing slope:Question 10. List the two most dominant plant species on the South-facing slope:Question 11. We observed that one of the slopes is steeper than the other. State which one is steeper and briefly describe:Question 12. State which slope receives the greatest amount of light intensity throughout the year, and briefly explain why this is the case:Question 13. Why is there higher air temperature primarily on one slope vs. the other?Question 14. How do relative humidity (of the air) relate to transpiration? (Hint: if you’ve ever lived in a humid area (such as the southeastern United States), you know how it affects your ability to cool off via evaporation!)Question 15. How does soil humus relate to soil moisture?Question 16. In general, describe how the light intensity of a slope receives directly or indirectly affects the following characteristics of the slope’s environment:1. soil temperature2. air temperatures3. soil moisture holding capabilities4. soil humus (organic) levels.Indicate which slope is higher and which slope is lower for the following variables:Question 17. Briefly explain the relationship between light intensity and soil temperature at the molecular level:Question 18. Briefly explain the relationship between light intensity and air temperature at the molecular level:Question 19. How do air and soil temperature relate to soil moisture, that is, water available to plants?Question 20. Briefly explain the long-term relationship between light intensity and a soil’s moisture holding ability:Question 21. Briefly explain the long-term relationship between soil humus (organic) content and soil’s water holding ability:

 

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