More Key Concepts and Terms: Unit 6
You have become much more informed about ecological concepts, but there is more to learn. In particular, you need to be able to do the following:
To start, read the chapters in Woodlot Biodiversity entitled "Woodlot Biodiversity" and "Exploring woodlot diversity” (Pages 9-22). Then familiarize yourself with the terms and concepts described below.
You have become much more informed about ecological concepts, but there is more to learn. In particular, you need to be able to do the following:
- Describe abiotic variables and discuss how variation in abiotic variables might influence species distributions
- Define ecological concepts of niche and habitat Discuss the importance of understanding temporal patterns in biodiversity
- Assemble and evaluate the controversy in science and biodiversity issues in society-at-large
- Explain why defensible evidence is needed to support claims of biodiversity
- Explain the different types of methods used to explore forest biodiversity
To start, read the chapters in Woodlot Biodiversity entitled "Woodlot Biodiversity" and "Exploring woodlot diversity” (Pages 9-22). Then familiarize yourself with the terms and concepts described below.
Abiotic variables: Abiotic factors are non-living. They include the physical and chemical factors that affect the ability of organisms to survive and reproduce; some examples of abiotic factors are light, temperature (heat), chemical products, water and atmosphere. In lecture we give examples of how these factors might influence the range of a species. For example, light is very important in limiting the growth of seedlings in a woodlot. This is mainly because some plants are shade tolerant and others require full sun. If you ever plant a tree, make sure you understand the light requirements for that species of tree. If you plant a shade tolerant tree in full sun it will probably soon desiccate if not watered profusely; conversely some trees require full sun and will not grow or may die in the shade. Why is light an important factor in forest ecosystems? Light constitutes the main supply of energy for organisms. Plants use chlorophyll to convert light energy into chemical energy via the process known as photosynthesis. This chemical energy is stored in complex organic substances that are used for growth, development of flowers and the production of fruit/seeds. Large amounts of biomass are stored in the forests using energy harnessed from the sun. Many plants have adapted to high or low light conditions; shade tolerant plants can dominate the understory of dense forest canopies. Light also regulates many biological rhythms of a large amount of species of both plants and animals. Plants use a photoreceptor protein (e.g., phytochrome or cryptochrome) to sense seasonal changes in photoperiod. This signals anthesis, whichis the development of flowers. Animals use light in various ways. For example, insects use ultraviolet light to differentiate flowers from another when harvesting nectar or pollen; this interaction contributes to pollination in plants, which is the subject of many co-evolutionary studies. Birds partially orient themselves by means of the perception of small differences in the reflection of light UV by the objects on land such as different types for forests, water, rocks, etc
Niche: One way to think about the occurrence of species is in “geographical space” - the species’ distribution as plotted on a map. However, it is important to also think about species occurring in “environmental space”; the space that an organism occupies, which is confined by environmental variables to which the species responds. The concept of environmental space is referred to in the literature as ecological niche theory. The great ecologist G. Evelyn Hutchinson (1957) provides a basic definition for ecological niche as follows: “niche is the set of biotic and abiotic conditions in which a species is able to persist and maintain stable population sizes.” The ecological niche is sub-divided into the fundamental and the realized niche. The fundamental niche is defined by the environmental conditions in which a species can survive and persist; however the species may not be present within all of this space. The realized niche includes the environmental and ecological conditions under which a species actually exists and persists. The figure below defines fundamental and the realized niche within two gradients (moisture & temperature). Where might you find such a gradient in the campus woodlots you're learning about?
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Niche: One way to think about the occurrence of species is in “geographical space” - the species’ distribution as plotted on a map. However, it is important to also think about species occurring in “environmental space”; the space that an organism occupies, which is confined by environmental variables to which the species responds. The concept of environmental space is referred to in the literature as ecological niche theory. The great ecologist G. Evelyn Hutchinson (1957) provides a basic definition for ecological niche as follows: “niche is the set of biotic and abiotic conditions in which a species is able to persist and maintain stable population sizes.” The ecological niche is sub-divided into the fundamental and the realized niche. The fundamental niche is defined by the environmental conditions in which a species can survive and persist; however the species may not be present within all of this space. The realized niche includes the environmental and ecological conditions under which a species actually exists and persists. The figure below defines fundamental and the realized niche within two gradients (moisture & temperature). Where might you find such a gradient in the campus woodlots you're learning about?
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Habitat: A species' habitat is defined as the environment in which a species is known to occur. Habitats can be considered "environmental space" as we defined above, whihc is influenced by biotic and/or abiotic environmental variables. It can include any characteristic of the environment (e.g., a substrate such as a rock, or food quality) or use of a specific geographic area (e.g., mountain meadow) by an animal or plant. Habitats can be either large or small scales. For example, the habitat of woodland caribou is boreal forest biome, whereas a species of lichen may only occur on acidic rocks. Understanding habitat diversity within an ecosystem is essential to sampling biodiversity because if you miss key types of habitats you may not have sampled all the biodiversity within an ecosystem. Higher habitat diversity is often correlated with higher species richness in ecosystems.
Functional trait: How species function within a community or ecosystem can be defined by their functional traits. A trait is a measurable property of an organism that influences its performance and species have functional traits that are uniquely adapted to the ecological niche. We can think about our example of shade tolerance of plants in a woodlot or forest ecosystem. The shade tolerant species are at an advantage in the woodlot understory because they are able to competitively exclude other species of tree seedlings from establishing that are not shade tolerant. This is called the competitive exclusion principle. Other examples of functional traits include body size, tolerance and sensitivity to environmental conditions, and N-fixation ability. These traits determine how a species will interact with other species and the environment. One measure of biodiversity is called "functional diversity"; it accounts for the diversity of functional traits of all the species in a community/ecosystem.
Ecosystem engineering: Some organisms can control the availability of resources to other species. These are called ecosystem engineers as they can change, sustain and develop new habitats. In lecture we have discussed how organisms are subject to environmental pressures. Now we must consider how species modify habitats and influence the niche of other species. Niche construction is feedback mechanism of natural selection imparting forces on the abiotic niche. Some plants and animals organisms can modify conditions from local (e.g., a woodlot) to global scales (e.g., Boreal forest region), over time and even after death, such as decaying logs. A good example is the influence of Alder (genus Alnus) shrubs on the early succession in the boreal forest ecosystem. Species of Alder (e.g., Alnus incana) have an important symbiotic relationship with Frankia alni, which is a nitrogen-fixing bacterium found in root nodules of alders; dig up alder roots and you can find many small nodules that are light brown and the size of a pea. These nitrogen-fixing bacteria can take nitrogen from the atmosphere and convert it to a form that can be used by plants such as an Alder tree. Alder, in turn, provides the bacterium with carbon, which it produces through photosynthesis. Alder is one of the first woody plants to colonize a site after disturbance. It improves the fertility of the soils where it grows, and as a pioneer species, it helps provide additional nitrogen for the successional species which follow such as balsam fir and spruce. .
Functional trait: How species function within a community or ecosystem can be defined by their functional traits. A trait is a measurable property of an organism that influences its performance and species have functional traits that are uniquely adapted to the ecological niche. We can think about our example of shade tolerance of plants in a woodlot or forest ecosystem. The shade tolerant species are at an advantage in the woodlot understory because they are able to competitively exclude other species of tree seedlings from establishing that are not shade tolerant. This is called the competitive exclusion principle. Other examples of functional traits include body size, tolerance and sensitivity to environmental conditions, and N-fixation ability. These traits determine how a species will interact with other species and the environment. One measure of biodiversity is called "functional diversity"; it accounts for the diversity of functional traits of all the species in a community/ecosystem.
Ecosystem engineering: Some organisms can control the availability of resources to other species. These are called ecosystem engineers as they can change, sustain and develop new habitats. In lecture we have discussed how organisms are subject to environmental pressures. Now we must consider how species modify habitats and influence the niche of other species. Niche construction is feedback mechanism of natural selection imparting forces on the abiotic niche. Some plants and animals organisms can modify conditions from local (e.g., a woodlot) to global scales (e.g., Boreal forest region), over time and even after death, such as decaying logs. A good example is the influence of Alder (genus Alnus) shrubs on the early succession in the boreal forest ecosystem. Species of Alder (e.g., Alnus incana) have an important symbiotic relationship with Frankia alni, which is a nitrogen-fixing bacterium found in root nodules of alders; dig up alder roots and you can find many small nodules that are light brown and the size of a pea. These nitrogen-fixing bacteria can take nitrogen from the atmosphere and convert it to a form that can be used by plants such as an Alder tree. Alder, in turn, provides the bacterium with carbon, which it produces through photosynthesis. Alder is one of the first woody plants to colonize a site after disturbance. It improves the fertility of the soils where it grows, and as a pioneer species, it helps provide additional nitrogen for the successional species which follow such as balsam fir and spruce. .