Managing the Soil, Pests, and Biomagnification PDF

# Managing the Soil Soils are among the most complex and poorly understood components of Earth's ecosystems, yet they are critical to our survival. We add nitrogen, phosphorus, and potassium to our soils because as plants grow, the nutrients go into the plants, and depletes the soil of those nutri...

# Managing the Soil Soils are among the most complex and poorly understood components of Earth's ecosystems, yet they are critical to our survival. We add nitrogen, phosphorus, and potassium to our soils because as plants grow, the nutrients go into the plants, and depletes the soil of those nutrients. Fertilizers can be natural (organic) or synthetic (chemical). Organic is the best choice for the local environment if used correctly. The use of synthetic fertilizers has environmental impacts because long term use disrupts the organisms that live in the soil, and soils can lose their supply of naturally occurring nutrients. These fertilizers also get into the groundwater through the process of leaching (nutrients are removed from the soil as water passes through it). Fertilizers in groundwater is harmful to aquatic ecosystems (causes an algal bloom). Farmers obtain water from surface sources such as lakes or rivers or from groundwater. Proper drainage must also be done by installing drainage tiles. Soil compaction is another issue - roots find it difficult to enter compacted soils and get the oxygen that they need. # Pests and Poisons Pests are organisms that might compete with or damage crop species. Weeds are plant pests, mosquitoes are insect pests, and mice are rodent pests. There are no pests in nature; it is only because they inconvenience humans. When farmers plant a monoculture, they create ideal conditions for pests. There are few natural predators, and there is a lot of the same environment in which they thrive. ## Pesticides Poisons that kill pests are pesticides. Herbicides are used to kill plants. Some long-lived pesticides persist for many years; others don't. * **Broad-spectrum** pesticides are toxic to a wide range of species. * **Narrow-spectrum** pesticides are toxic to a limited number of species. They work by interfering with biological processes, such as photosynthesis, or cause damage to vital organs. They can be carried away by the air when sprayed, and then become potential sources of soil, air, and water pollution. They can also harm other non-target species. The consequences can be serious. Some pest species may become resistant to the pesticide, which is another concern. # Biomagnification Pesticides accumulate in individual organisms. As they eat food with pesticides, it builds up in their body. This is called bioaccumulation. If organisms up on the food chain eat these poisoned organisms in great numbers, the toxins concentrate even higher in their bodies. Top consumers are especially vulnerable at the top of the food chain. This is called bioamplification. Organic farming uses no synthetic pesticides or fertilizers. The farmers accept crop losses to naturally occurring pests. Therefore, the food costs more to buy. # Equilibrium and Change Most natural ecosystems are in a state of: **Equilibrium:** The state of an ecosystem with relatively constant conditions over a period of time. When photosynthesis and cellular respiration are balanced, and abiotic conditions are stable, energy is flowing through the ecosystem, things can be stable. If they get disturbed (even dramatically), the process by which they recover is called **succession:** the process of establishing and replacing a community following a disturbance. **Primary Succession:** * Occurs on soil or bare rock, where no life previously existed (ex. volcanic rock) **Secondary Succession:** * Regrowth when some life still exists (ex. forest fire, pollution) # Examples A simple illustration of a food web and food chain. The food web is represented as a circle with arrows going both directions. The food chain is presented as a pyramid. * **Trophic level 1:** Grass * **Trophic level 2:** Grasshopper * **Trophic level 3:** Frog * **Trophic level 4:** Snake **Food web has more biodiversity** # Biodiversity Biodiversity is the variety of life found in an area. It is often measured by counting the number of species in an area. This number is the species richness. Species richness tends to be higher close to the equator. ## Biodiversity Under Attack Many species are dying out, or going extinct. Their habitats are being destroyed through deforestation, urban and agricultural expansion, pollution, and climate change. Humans may not even know anything about these species before it's too late. ## Species at Risk In order of increasing severity: 1. **Special concern:** a species that may become threatened or endangered because of a combination of factors. # Non-Native Species Introductions of non-native species usually fail because few species can tolerate an entirely new environment. Occasionally a new species is successful, and may lack natural population controls (no predators or diseases). ## Invasive Species Are introduced species with growing populations that spread and have a negative effect. # Controlling Introduced Species ## Chemical Control * Pesticide use is the most common control used. * There are environmental risks by killing non-target native species and pollute the air, water, and soil. ## Mechanical Control * Physical barriers or removal. * Plants' can be cut down, burned, or removed. * Invasive animals can be hunted or trapped. ## Biological Control * Intentionally introduced organisms to control the invasive species. # Aquatic Ecosystems There are two types of aquatic ecosystems: 1. **Freshwater:** (less than 1% Salt) 2. **Marine:** (about 3% Salt) - Properties of water are different as well. ## Freshwater Ecosystems Consists of moving bodies of water, such as rivers, and nearly stationary bodies of water, such as lakes. Some bodies of water can be quite low in nutrients. However, wetlands such as bogs and marshes are nutrients rich. They are large shallow water areas with saturated soils and support a wide variety of life. ## Watersheds Is an area of land through which all water drains into a single river or lake (a large surrounding body of water). ## Marine Ecosystems More than 70% of the Earth's surface is covered in oceans. # On the Next Test (Not the One on Monday) ## Ecosystem Services Natural ecosystems provide services to the biosphere and to humans. ## Cultural Services Include the recreational, aesthetic, and spiritual experience we receive when we interact with our natural surroundings. Ecotourism is an example of a cultural service. One must remember when visiting various ecosystems that you leave them alone (don't damage vegetation, leave garbage behind, etc). ## Ecosystem Products We hunt animals and harvest plants for personal and commercial use. Lakes and oceans provide us with seafood. ## Forestry Is one of the largest industries and employers in Ontario. It produces over $11 billion worth of products annually. ## Other Services Ecosystems can protect us from physical threats. For example, plants can protect the soil from wind and water erosion. They can also act like sponges to absorb excess water. # Influences on Ecosystems What determines the size of a population and where a particular species can and does live? Both abiotic and biotic factors determine where a species can live. ## Limiting Factor Any factor that restricts the size of a population. ## Influence of Abiotic Factors Temperature, light, soil, etc. can influence a species' ability to survive. They can live in their tolerance range where the upper and lower limits they will experience stress. The best is within the optimum range where numbers and reproduction will be highest. Some species can tolerate changing conditions better than others. # Energy Flow All organisms require energy to stay alive, and the source of almost all this energy is RADIANT ENERGY (from the sun). The Earth is being bombarded by both invisible energy (like UV light) and visible radiant energy, or LIGHT ENERGY. About 70% of this radiant energy is absorbed by Earth as heat. About 30% is reflected back into space! A very small percentage (Less than 1%) is absorbed using photosynthesis. ## Photosynthesis The process of converting light energy into chemical energy. Without it, life on Earth would not exist. ## Producers Organisms that photosynthesize are called producers, and they are mainly green plants (chlorophyll in their leaves make them green). Many organisms like algae live in the water, and can also photosynthesize. The chemicals involved in photosynthesis: $CO_2 + H_2O \rightarrow Sugar + O_2$ The sugar is the stored chemical energy that goes into building the plant (by rearranging the sugar molecule), but mostly stored as starch.