CES210: Chapter 5 Notes
CES210: Chapter 5 Notes CES 210
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This 5 page Class Notes was uploaded by Emma Eiden on Friday October 7, 2016. The Class Notes belongs to CES 210 at University of Wisconsin - Milwaukee taught by Mai Phillips in Fall 2016. Since its upload, it has received 10 views. For similar materials see Introduction to Conservation and Environmental Science in GN Natural Science at University of Wisconsin - Milwaukee.
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Date Created: 10/07/16
CES210: Conservation and Environmental Science Chapter Five: Biomes: Global Patterns of Life Case Study: Spreading Green across Kenya - Our environment provides all of us with food, fuel, and shelter, but the world’s poorest people often depend most directly on their environment – and they suffer most from a degraded environment. In remote areas of rural Kenya, subsistence farmers depend on local forests, soils, and groundwater for fuel, food, and water - The Greenbelt Movement, initiated by the environmental leader Dr. Wangari Maathai (1940-2011) is working to teach communities to help themselves by growing and planting trees TERRESTRIAL BIOMES Characteristics of biological communities vary with temperature, precipitation, and latitude Hot, humid regions generally have greater biological productivity than cold or dry regions We use climate graphs to describe and compare precipitation and temperature in different biomes - To understand what an expansive biological community should be like, it is helpful for us to identify some of the general types of communities with similar climate conditions, growth patterns, and vegetation types. We call these broad types of biological communities, biomes. - Humans’ use of biomes depends largely on those levels of productivity. Our ability to restore ecosystems and nature’s ability to restore itself depend largely on biome conditions - Temperature and precipitation are the most important determinants in biome distribution on land. If we know the general temperature range and precipitation level, we can predict what kind of biological community is likely to occur there in the absence of human disturbance - Temperature and precipitation change dramatically with elevation. In mountainous regions, temperatures are cooler and precipitation is usually greater at high elevations. Vertical zonation occurs as vegetation types change rapidly from warm and dry to cold and wet as you go up a mountain - Because temperatures are cooler at higher latitudes (away from the equator), temperature-controlled biomes often occur in latitudinal bands - Ocean environments are important because they cover 2/3 of the earth’s surface, provide food for much of humanity, and help regulate our climate through photosynthesis Tropical moist forests have rain year-round - Although there are several kinds of moist tropical forests, they share common attributes of ample rainfall and uniform temperatures - The soil of both of these tropical moist forest types tends to be old, thin, acidic, and nutrient-poor, yet an enormous number of species can be present - The nutrient cycles of these forests also are distinctive. Almost all (90%) of the nutrients in the system are contained in the bodies of the living organisms - Trees are being chopped down and the soil cannot handle the amount of cropping that is happening How Do We Describe Clime Regions? - Dry conditions could occur because it’s hot and evaporation is rapid or simply because there’s little precipitation. Tropical seasonal forests have yearly dry seasons - Many tropical regions are characterized by distinct wet and dry seasons, although temperatures remain hot year-round. These areas support tropical seasonal forests: drought-tolerant forests that look brown and dormant in the dry season but burst into vivid green during rainy months - Tropical dry forests have typically been more attractive than wet forests for human habitation and have suffered greater degradation. Clearing a dry forest with fire is relatively easy during the dry seasons. Soils of dry forests often have higher nutrient levels and are more agriculturally productive than those of a rainforest. Finally, having fewer insects, parasites, and fungal diseases than a wet forest makes a dry or seasonal forest a healthier place for humans to live. Consequently, these forests are highly endangered in many places. Less than 1% of the dry tropical forests of the Pacific coast of Central America or the Atlantic coast of South America, for instance remain in an undisturbed state Tropical savannas and grassland support few trees - Where there is too little rainfall to support forests, we find open grasslands or grasslands with sparse tree cover, which we call savannas - Savanna and grassland plants have many adaptations to survive drought, heat, and fires. Many have deep, long-lived roots that seek groundwater and that persist when leaves and stems above the ground die back. After a fire, or after a drought, fresh green shoots grow quickly from the roots Deserts are hot or cold, but all are dry - You may think of deserts as barren and biologically impoverished. Their vegetation is sparse, but it can be surprisingly diverse, and most desert plants and animals are highly adapted to survive long droughts and extreme heat, and many can survive extreme cold. Deserts occur where precipitation is rare and unpredictable, usually with less than 30 cm of rain per year - Warm, dry, high-pressure climate conditions create desert regions at about 30 degrees latitude north and south - Sparse, slow-growing vegetation is quickly damaged by off-road vehicles. Desert soils recover slowly Temperature grasslands have rich soils - As in tropical latitudes, temperature (midlatitude) grasslands occur where there is enough rain to support abundant grass but not enough for forests - Deep roots help plants in temperate grasslands and savannas survive drought, fire, and extreme heat and cold. These roots, together with an annual winter accumulation of dead leaves on the surface, produce-think, organic-rich soils in temperature grasslands. Because of this rich soil, many grasslands have been converted to farmlands - Most remaining grasslands in this region are too dry to support agriculture, and the greatest threat to them is overgrazing. Excessive grazing eventually kills even deep-rooted plants Temperate shrublands have summer drought - Many dry environments support drought-adapted shrubs and trees, as well as grass - Periodic fires burn fiercely in this fuel-rich plant assemblage and are a major factor in plant succession. Annual spring flowers often bloom profusely, especially after fire. In California this landscape is called chaparral (thicket). These areas are inhabited by drought-tolerant animals such as jackrabbits, kangaroo rats, mule deer, chipmunks, lizards, and many bird species Temperature forests can be evergreen or deciduous - Temperature, or midlatitude, forests occupy a wide range of precipitation conditions but occur mainly between about 30 and 55 degrees latitude. - In general we can group these forests by tree types, which can be broadleaf deciduous (losing leaves seasonally) or evergreen coniferous (cone-bearing) - Deciduous forests can regrow quickly because they occupy moist, moderate climates - The coniferous forests of the Pacific coast grow in extremely wet conditions. The wettest coastal forests are known as temperate rainforest, a cool, rainy forest often enshrouded in fog Boreal forests occur at high latitudes - Because conifers can survive winter cold, they tend to dominate the boreal forest, or northern forests, that lie between about 50 and 60 degree north - The extreme, ragged edge of the boreal forest, where forest gradually gives way to open tundra, is known by its Russian name, taiga. - Here the extreme cold and short summers limit the growth rate of trees. A 10 cm diameter tree may be over 200 years old in the far north Tundra can freeze in any mouth - Where temperatures are below freezing most of the year, only small, hardy vegetation can survive. Tundra, a treeless landscape that occurs at high latitudes or on mountaintops, has growing season of only two to three months, and it may have frost any month of the year - Some people consider tundra a variant of grasslands because it has no trees; others consider it very cold desert because water is unavailable (frozen) most of the year - Arctic tundra is an expansive biome that has low productivity because it has a short growing season. During midsummer, however 24-hour sunshine supports a burst of plant growth and an explosion of insect life - Global climate change may be altering the balance of some tundra ecosystems, and air pollution from distant cities tens to accumulate at high latitudes MARINE ECOSYSTEMS - Often it is algae or tiny, free-floating photosynthetic plants that support a marine food web, rather than the trees and grasses we see on land. In oceans, photosynthetic activity tends to be greatest near coastlines, where nitrogen, phosphorus, and other nutrients wash offshore and fertilize primary producers. Ocean currents also contribute to the distribution of biological productivity, as they transport nutrients and phytoplankton far from shore - Vertical stratification is a key feature of aquatic ecosystem, mainly because light decreases rapidly with depth, and communities below the photic zone (light zone, often reaching about 20 m deep) must rely on energy sources other than photosynthesis to persist. Temperature also decreases with depth Depth controls light penetration and temperature - The open ocean is often referred to as a biological desert because it has relatively low productivity Coastal zones support rich, diverse communities - Some shoreline communities, such as estuaries, have high biological productivity and diversity because they are enriched by nutrients washing off from the land. But nutrient loading can be excessive. Around the world, more than 200 “dead zones” occur in coastal areas where excess nutrients stimulate bacterial growth that consumes almost all oxygen in the water and excludes most other life. - Coral reefs are among the best-known marine ecosystems because of their extraordinary biological productivity and their diverse and beautiful organisms. Reefs are aggregations of minute colonial animals (coral polyps) that live symbiotically with photosynthetic algae - The greatest threat to the reefs is global warming - Elevated water temperatures cause coral bleeding, in which corals expel their algal partner and then die - Mangroves are trees that grow in salt water. They occur along calm, shallow, tropical coastlines around the world - Estuaries are bays where rivers empty into the sea, mixing fresh water with salt water. Salt marshes, shallow wetlands flooded regularly or occasionally with seawater, occur on shallow coastlines, including estuaries - Nearly 2/3 of all marine fish and shellfish rely on estuaries and saline wetlands for spawning and juvenile development - Tide pools are depressions in a rocky shoreline that are flooded at high tide but retain some water at low tide. These areas remain rocky where wave action prevents most plant growth or sediment (mud) accumulation. Extreme conditions, with frigid flooding at high tide and hot, desiccating sunshine at low tide, make life impossible for most species. But the specialized animals and plants that do occur in this rocky intertidal zone are astonishingly diverse and beautiful - Barrier islands are low, narrow, sandy islands that form parallel to a coastline. They occur where the continental shelf is shallow and rivers or coastal current provide a steady source of sediments - Human occupation often destroys the value that attracts us there in the first place. Barrier islands and beaches are dynamic environments, and sand is hard to keep in place. Wind and eave erosion is a constant threat to beach developments. Walking or driving vehicles over dune grass destroys the stabilizing vegetative cover and accelerates, or triggers, erosion. Cutting roads through the dunes further destabilizes these islands making them increasingly vulnerable to storm damage FRESHWATER ECOSYSTEM - Freshwater environments are often small, but they are disproportionally important in biodiversity. Wetlands support concentrations of species that can live nowhere else, such as amphibians, fish, aquatic plants, and many insects and birds. Temperature and light vary with depth in lakes - Freshwater lakes, like marine environments, have distinct vertical zones - Anaerobic bacteria (not using oxygen) may live in low-oxygen sediments Local conditions that affect the characteristics of an aquatic community include… 1. Availability (or excess) of nutrients, such as nitrates and phosphates 2. Suspended matter, such as silt, that affects light penetration 3. Depth 4. Temperature 5. Currents 6. Bottom characters, such as muddy, sandy, or rocky floor 7. Internal currents 8. And connects to, or isolation from other aquatic and terrestrial systems Wetlands are shallow and productive - Wetlands are shallow ecosystems in which the land surface is saturated or submerged at least part of the year - These relatively small systems support rich biodiversity, and they are essential for both breeding and migrating birds. Although wetlands occupy less than 5% of the land in the United States - These mild conditions favor great photosynthetic activity, resulting in high productivity at all trophic levels. In short, life is abundant and varied. Wetlands are major breeding, nesting, and migration staging areas for waterfowl and shorebirds HUMAN DISTURANCE - Humans have become dominant dominant organisms over most of the earth, damaging or disturbing more than half of the world’s terrestrial ecosystems to some extent. - In Indonesia, almost all the mangrove swamps that once lined the coasts of Java have been destroyed, while in the Philippines and Thailand more than 2/3 of coastal mangroves have been cut down for firewood or conversion to shrimp and fish ponds Additional source to study terms from this chapter: https://quizlet.com/151146399/conversations-and-environmental-science-chapter- five-biomes-flash-cards/
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