components of the watershed - natures...

Science Lesson 2 – Components of a Watershed

School District of Hillsborough County 1 The Southwest Florida Water Management District

Components of the Watershed

Essential Question: What are the components of a watershed? Objective: Students will be able to explain essential vocabulary, components, communities, and relationships within a watershed. Standard(s): SC.6.E.6.1 Describe and give examples of ways in which the Earth’s surface is built up and torn down by physical and chemical weathering, erosion, and deposition. SC.6.E.6.2 Recognize that there is a variety of different land forms on Earth's surface such as coastlines, dunes, rivers, mountains, glaciers, deltas and lakes, and relate these landforms as they apply to Florida. Next Generation Science Standard(s): MS-ESS2-1. Develop a model to describe the cycling of Earth’s materials and the flow of energy that drives this process. MS-ESS3-1. Construct a scientific explanation based on evidence for how the uneven distributions of Earth’s mineral, energy, and groundwater resources are the result of past and current geoscience processes.

Materials: • Components of the Watershed – Bell Work sheet • The Hillsborough River Watershed – Bell Work sheet • The four ecosystem sheets – Xeric Hammocks, Mesic Pinewoods, Hydric Hammocks and Riverine

Swamps • Sheets of chart paper • Markers • Book passage about a trip down a river. Possibilities include:

1. Trouble River by Betsy Byars (Midway through Chapter 8 there is a break. Read from here till the end of the chapter.

2. The River by Gary Paulsen (This book is available in Hillsborough Middle Schools) (Chapter 8, at the lake)

3. Three Days on a River in a Red Canoe by Vera B. Williams (entire book)

Set up and prep: Collaborative group structure for management of activities. Time needed: Bell Work (2) 5/10 minute sessions – Rest of the lesson two 50 minutes/two class periods Procedure: 1. Direct your students to do the bell work activities prior to the reading jigsaw activity. Idea: Have copies of

the passage on each group table with the questions Jigsaw. This will give practice for the activity. Have each group member share the answer for their respective question.

2. Begin the reading jigsaw activity by dividing the class into reading groups of four. 3. Pass out a different ecosystem sheets to each person in the group. 4. Explain that these are ecosystems they will observe at Nature’s Classroom. 5. Ask each person in the group to use their own paper to make a 4-column note sheet with the following

column headings, vocabulary, communities, components and relationships. 6. Explain that each person will read their ecosystem sheet and list of everything either in or indicated by the

passage that relates to the four topics. Idea: Students can also text mark for the different purposes prior to completing their 4-column note sheet. Encourage students to use visuals to assist with note taking as well.

7. Regroup the students by ecosystem. Have them share their findings and add to their columns where



needed. 8. Have them return to their original groups and share what they learned. 9. Have them construct a group concept map of what they expect to learn about the Hillsborough River

Watershed on their trip to Nature's Classroom. Keep the maps posted on board through the field study and ask the students to add to it based on their experiences.

10. Have reading material available for students throughout the experience to assist with adding to the learn/experiences portion of the concept map.

Assessment: • A list of information from their readings • Completed concept map



What is a Watershed? Bell Work

1. The landform called a watershed is created by the interaction of geology with the water cycle. The process of erosion driven by the water cycle creates a watershed. A watershed is a basin-like landform defined by highpoints and ridgelines that descend into lower elevations and stream valleys. How a watershed is shaped will determine how it drains, where flooding occurs, and how water quality is affected.

2. The Environmental Protection Agency defines a watershed as any body of land that flows

downhill into a waterway. Basically, "watershed" is a broad term used to describe how water flows across land to feed streams, rivers and lakes. All of these watersheds fit together like puzzle pieces to form our land masses.

3. The Southwest Florida Water Management District defines a watershed as an area of land

that water flows across as it moves toward a stream, river, lake or coast. Watersheds are separated from each other by areas of higher elevation called ridge lines or divides. Therefore, wherever you live, you live in a watershed. In Florida, because land surfaces are relatively flat, our watersheds are often separated by only slight changes in land elevation.

Directions: Answer these questions about your reading. 1. According to the article, what is the process of flowing water that creates a watershed?

______________________

2. According to the article, what three things are determined by the shape of a watershed? ____________________ ________________________ _______________________

3. According to the article, why are watersheds in Florida often separated by only slight changes in elevation?

A. ridge lines are often separated by great distances B. water flows across the land to feed streams C. the land surface is relatively flat D. the geology is affected by the water cycle



The Hillsborough River Watershed Bell Work 1.

2. In many ways, the watershed of the Hillsborough River resembles a flat shallow pan tilted up on one end. The highest part of this watershed or basin is north and east of the borders of Hillsborough County in an area known as the Green Swamp. 3. The lowest corner of the basin is at the mouth of the river where it empties into Tampa Bay. The southern boundary of this watershed roughly follows State Road 60 east almost to Lakeland. The western boundary roughly follows U.S. 41 north into Pasco County. 4. Within the Hillsborough River watershed, changes in elevation create different sets of abiotic or non-living conditions. These abiotic conditions include landforms such as hills, valleys, current and past sinkholes and waterways. Other abiotic factors are sunlight, temperature, air and soil moisture, soil type and elevation. These differences in abiotic environments provide a variety of habitats for biological communities of plants and animals. These biological communities in combination with their abiotic habitats are dynamic living systems called ecosystems. A variety of ecosystems typical of the Hillsborough River watershed are found at Nature’s Classroom. These include xeric hammocks, mesic pinewoods, hydric hammocks, and



riverine swamps. The figure on the next page shows the relationship between these systems at Nature’s Classroom.

Directions: Answer these questions about your reading. 1. According to the article where does the Hillsborough River Watershed begin? Locate the

area on the map. _______________________________

2. According to the article where does the Hillsborough River Watershed end? Locate the area on the map.

_______________________________

3. According to the diagram above, which community can be found at the highest elevation?

Justify your response. __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ 4. According to the diagram above, which community would be the wettest? Justify your

response. __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________



I. Xeric Hammocks 1.

Geology 2. In the highest portions of Nature’s Classroom, we find a dry or xeric habitat. This type of

habitat occurs on the tops and slopes of gently rolling hills around the edges of the watershed. The hills were once coastal sand dunes. These dunes were formed on ancient beaches during the ice age.



3. The hills are made up of deep yellow sands which are dry and low in nutrients. The nutrients which leach down through the sandy soil are returned to the surface by burrowing animals such as the gopher tortoise. After a rain, water sinks rapidly into the deep sandy soil with little runoff or evaporation. This makes this system an important aquifer recharge area.

Ecology 4. Covering these sandhills at Nature’s Classroom

are xeric oak hammock communities. The dominant plants in this community are the Sand Live Oaks. The branches of these evergreen oaks tower above the ground creating a shady canopy.

5. The deep shade allows only a small amount of light to reach the ground. This creates a park-like environment that the Native Americans called a "ha-mock" meaning shady place. These cool shady hammocks became ideal home sites for the cracker families who lived on the property that is now Nature's Classroom.

6. The leaves of the sand live oak help it survive in the xeric sandhills. They are small and thick. They have rolled edges. The dark green tops are coated with a wax that reduces water loss. The undersides are soft and fuzzy. The fuzz consists of tiny hairs that trap moisture.

7. The root system of the sand live oak spreads out like a giant net from the trunk of the tree. This net catches water when it falls as rain or runs down the grooves in the bark. 8. Only a few types of plants can grow in the shade of the sand live oaks. Some plants that can grow in the patches of light that come through the canopy are stinging nettles, bear grass, sensitive plant and wiregrass. In addition, carpet moss grows well on the trunks of the live oaks and a variety of lichens grow on the trees and on the ground. 9. The xeric hammock provides the perfect habitat for a number of animals. These include gopher tortoises, pocket gophers, gray fox and fox squirrels. Gopher tortoises dig their burrows in loose soil while pocket gophers build long tunnels in the ground as they search for the roots of their favorite plants. Bobwhite quail and indigo snakes also make their homes in this dry community. 10. The absence of fire plays an important role in the life of the sand live oak. Young live oaks are killed by fires every three to five years in a normal



sandhill habitat. But in the absence of fire, the oak trees get larger and they shade out pine seedlings. The thick build up of oak leaves and the increasing shade alters the environment, reducing the possibility of fires. Without wildfires, xeric oak hammocks will replace longleaf pine turkey oak communities in the sandhill habitats.



II. Mesic Pinewoods 1.

Geology 2. At lower elevations at Nature’s Classroom, we find a mesic habitat that gently slopes toward the river. Mesic habitats occur between xeric habitats and hydric ones. These types of landforms were created by changes in the sea level during Pleistocene glacial times. As sea levels increased, vast expanses of flat land were flooded and thick layers of sand were deposited on the land. As the sea levels receded, early pioneer species such as pine trees were able to establish in the sandy soil. The relatively flat topography, sandy soils, and the seasonal water cycle are the principal abiotic conditions in this mesic habitat.

3. These habitats are characterized by low, flat to gently sloping topography. The soil usually consists of one to three feet of fine, acidic sand. The high acid content of pine needles covering the soil surface creates acidic conditions in the soil. Water percolates quickly down through the sand after rains. If a hardpan, or densely packed subsoil, is found beneath the sand it affects the percolation of water. The water percolates through the sand until it hits this hardpan layer and goes no further. Water is trapped in the sand layer above the hardpan. As a result, mesic flatwood soils become saturated, waterlogged and poorly aerated during the summer rainy season. This can result in

Photo Source: Florida Geological Survey



sheetflow of water across the land if the water levels become high enough. 4. While the availability of water varies with the local topography and seasonal rainfall, the soil may stay wet for part of the year. In flat areas of this habitat, water run-off is reduced. In low elevations, the land may hold water for several months. At higher elevations, where the water table is deep, little or no surface water may be visible. 5. During the winter dry season, high evapotranspiration draws most of the water out of the upper soil horizons above the hardpan, drying them out. This can create persistent drought conditions through the dry season. As a result, during the dry season, groundwater is not available for plants whose roots can not penetrate hardpan to reach the water table. Ecology 6. The primary community found growing in mesic habitats is the pine flatwoods. Pine flatwoods are the predominant natural ecosystems of the coastal lowland watersheds. Approximately 50% of the land area of Florida is covered by this ecosystem. To live and reproduce in flatwoods, plants have to be adapted to standing in water, seasonal droughts, decades-long droughts and even fire. This creates stressful conditions for plants both in the wet and in the dry season.

7. The mesic pine flatwoods is a fire climax community. Fire is considered the essential to this system. Nearly all of its plants and animals are adapted to periodic fires. Most fires occur in early June at the end of the dry season when thunderstorms first begin. These thunderstorms bring both the lightning to start the fire and the water to put it out. While natural fires were historically numerous, the extent of any given fire was probably small. Frequent, low-intensity surface fires generally characterize this system. Historical evidence suggests a fire frequency of 1 to 3 years. (Modified from: Florida Natural Areas Inventory 1989)

8. Wildfire recycles the nutrients locked in dead pine needles and palmetto fronds. This is necessary to maintain this community. Fires in this ecosystem, every few years, control the spread of the hardwood trees such as oaks into the area. Without fire every few years, succession may change the pine flatwood into hardwood forest ecosystems. 9. The mesic pine flatwoods habitat is dominated by a south Florida slash pine or longleaf pine canopy. This open canopy allows abundant amounts of sunshine to reach the forest floor. The sunlight supports an extensive low growing understory. South Florida slash pine seedlings have a grass stage that, like longleaf pine, greatly increases resistance to fire damage. Fire stimulates slash pine seedlings to sprout, promoting their growth as pioneers of burned land.

Photo Credit: Dr. David LaHart



10. Mesic pine flatwoods are distinct from hydric and xeric pine flatwoods. They usually have a midstory covered by saw palmetto and scrub species such as fetterbush, tarflower, rusty lyonia, cabbage palm, and wax myrtle (Myrica cerifera). 11. The mesic pine flatwoods provide essential forested habitat for a variety of wildlife species. Historically, wide-ranging, large carnivores such as the Florida panther and the Florida black bear occurred in this ecosystem. Mid-sized carnivores such as bobcats and foxes were also common. Other mammals included fox squirrels and deer.

12. Mesic flatwoods provide nesting areas for tree-cavity dependent and tree-nesting birds. They also offer food and cover for ground nesting birds such as bob-white quail. They serve as resting areas for migrant birds. 13. Mesic pinewoods are rich in reptiles including gopher tortoises, box turtles, eastern diamondback rattlesnake, and black racers. They are also home to a variety of toads and tree frogs.

Source: USFWS



III. Hydric Hammock

1.

Geology 2. Lying between the mesic pine forests and the swamps along the river is an interesting land form. This habitat was created during the Pleistocene epic. During this time period, sea level changed many times. At times sea level rose and covered what today is dry land. At other times, sea level dropped and Tampa Bay was dry. This changing of sea level caused both surface and subsurface erosion of the land. Eventually, this erosion created low terraces along channels that became the rivers we see in central Florida today. This habitat is covered by a biological community known as a hydric hammock. 3. Soils in this habitat are variable. There is often a clay layer or limestone layer just below the sand. As a result, the soils are poorly drained, have a high water table or occasionally flood. In



contrast to the acidic soils of the mesic pinewoods, hydric hammock soils are slightly acidic or mildly alkaline.



4. Hydric hammocks are generally found between edges of the flatwoods or other mesic communities and the river swamps. Moisture in these wetland communities comes from wet season flooding, rainfall and seepage of ground water from the uplands. Flooding of the hammock usually occurs only during the rainy season. The organic material from decomposing leaves mixes with the sand and silt. This rich soil absorbs water like a sponge during the rainy season and slowly releases it during the dry season. Ecology

5. Hydric hammocks are upland, drier versions of hardwood swamps. They are found in moist areas which may flood during the summer rainy season. They are covered by a mixture of broadleaf evergreen and deciduous trees such as laurel oaks and maples. Typical hydrologic indicators include buttressing, loop roots, elevated lichen lines and crayfish chimneys. 6. A hydric hammock is a well developed evergreen hardwood and/or palm forest. It has a variable understory

often dominated by palms and ferns occurring on moist soils, often with limestone very near the surface. While species composition varies, the community generally has a closed canopy of oaks and palms. There is an open understory and a sparse to a moderate groundcover of grasses and ferns. The canopy is dominated by swamp laurel oak and/or Virginia live oak. Also found are varying amounts of cabbage palm, American elm, sweetbay magnolia, red maple, sugarberry, sweetgum and water oak. 7. The midstory contains shrubs such as American hornbeam, swamp dogwood, small-leaf viburnum, swamp bay, wax myrtle and dwarf palmetto. Vines are very common. Poison ivy, peppervine, trumpet creeper, greenbriers, and wild grapes all find the hydric hammock a suitable environment. Herbs include grasses and ferns. Species composition of a hydric hammock is mainly influenced by flooding patterns. 8. Fire is a big

ecological change agent in hydric hammocks. Although they are usually too wet to burn, if a fire does enter a hammock it will destroy most of the hardwoods and can even damage the soil.

buttressed trunk and lichen lines



9. Fire resistant plants such as Virginia live oaks, cabbage palms and grasses dominate

hammocks that are frequently burned. (Modified from: Florida Natural Areas Inventory) 10. The deciduous trees shed their leaves every winter during the middle of the dry season. The laurel oaks play an especially important role as they develop a fungal infection called "black heart disease". The fungus attacks the tissue on the inside of the trunk and limbs. As a result, as the tree ages, it develops a variety of cavities and hollow areas which house insects that feed on the decaying tissue. These decaying areas are attacked by woodpeckers and other animals which feed on the insects. As a result, the laurel oak, as it ages, becomes a major habitat for many types of animals who live in holes and hollows. 11. Hydric hammocks provide nesting habitat for the southern bald eagle, osprey and little blue heron. In addition, the barred owl, red-shouldered hawk, blue jay, cardinal and wild turkey can be seen feeding in this area. Mammals found in these scenic wetlands include gray fox, striped skunk, gray squirrel, black bear, opossum, bobcat and raccoon.

12. Numerous reptiles can be seen in hydric hammocks. These include the five-lined skinks, the yellow rat snakes, black racers, green anoles and box turtles.



IV. Riverine Swamps 1.

Geology 2. Lining the edges of the channel of the Hillsborough River is a broad floodplain. The shape and structure of this habitat changes seasonally as the river erodes sediment from some areas and deposits it in others. The sediment of the floodplain is a mixture of silt, sand and organic material. The organic material is the dead remains of plants and animals. Often a layer of fine-grained clay is found at the bottom of the soil layers. The soil in the floodplain is usually anaerobic, that is, it contains little or no oxygen. During the dry season, the soil may be exposed to the air. When this happens, the organic material in the soil can be eroded by oxidation. The water in the swamp gets its color from tannic acid. This tannic acid comes out of plant leaves and bark when they are saturated with water. 3. The soil of the floodplain is spread on top of a shelf of limerock that is marine in origin. The eroding power of the moving water has cut a channel, or in some cases, many channels, through this limerock. This alkalinity of limerock buffers tannic acid released from the plants that grow in this habitat. The pH of the water may vary seasonally. It becomes more acidic during the spring dry season when it may be standing in isolated pools filled with leaves, bark and twigs of



the trees. During the summer rainy season, the water may be more alkaline.



Ecology 4. The riverine swamp is a closed-canopy forest of flood tolerant trees occurring on frequently or permanently flooded hydric soils. They grow adjacent to stream and river channels and in depressions and oxbows within floodplains. These swamps fill with water as the river rises during the rainy season. They store and slowly release water during the dry season. 5. Riverine swamps are among the most productive ecosystems in Florida. This is measured in

two ways. First is rate of organic matter production in such forms as leaves, stems, fruit, and nuts. Second is the diversity of vertebrate and invertebrates found in the swamps. Water moving through a swamp brings nutrients to the trees. It also oxygenates saturated soils and removes toxins that have accumulated in the root zone. Long periods of flooding, especially when water is standing, affect plant communities dramatically. Species diversity and productivity are both reduced. The range in physical conditions, habitats and food sources explains why so many wildlife species find food, nesting sites or cover in river swamps. (Modified from: The Case for Restoring the Free-Flowing Ocklawaha River)

6. Plants that live in this system have to be able to live with their roots covered by water most of the year. They also have to be able to hold on to the soil during floods. The amount of sunlight reaching the floor of the forest is very low in the riverine swamps.

7. One of the largest plants found growing in riverine swamps is the bald cypress tree. These trees can live to be thousands of years old. 8. Cypress trees have many adaptations that help them grow in very wet places. This lets them live in places where other trees cannot survive. They have a variety of adaptations that assist them in living in swamps. The trunks of Cypress trees grow wide and fat. This process called buttressing is seen in a variety of trees that grow in flooded wetlands. 9. Another adaptation of bald cypress trees is

their knees. These special roots grow up from their horizontal roots. They stick up out of the water. Knees continue to grow until they get tall enough to stick above the normal high flood level. The knees connect the roots to the air. Scientists cannot agree on how knees help the trees to survive in the swamp but there are several theories. One is that they help hold the tree and keep it from tipping over. Another is that by sticking up out of the water, they can provide air to the roots. 10. Most of the giant ancient cypresses along the Hillsborough River were cut about a century ago. This altered the ecology of the swamp. Today the swamp is dominated by water ash and



water locust trees. It was not economical to cut all of the old cypresses as some were hollow. These became the mother trees for the cypresses you find growing in the swamp today. 11. A diverse variety of wildlife lives in the riverine swamp. These include many types of wading birds, fish, reptiles, amphibians and mammals. Many types of invertebrates live in the water or the soil.

12. The top carnivore found in the swamp is the American alligator. This large reptile can reach over 16 ft. in length. They are highly camouflaged throughout their lives. The babies are medium green with pale yellow stripes. This helps them blend into the vegetation and avoid being eaten. As they grow older, the color changes to dark grey or black. With their rough scaly skin they look like large logs. Not recognizing this deception has cost many an animal its life.

Photo Credit: Jason Chilson



Four Column Notes Directions: Write notes about your assigned topic in each category. Be sure to cite the paragraph.

You will be sharing the information from your notes with others. Topic:

VOCABULARY

COMMUNITIES

COMPONENTS

RELATIONSHIPS

____

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