Key Factors Affecting Productivity in Ecosystems
Productivity
Productivity is all about how much work a participant produces in a unit of time. In the market economy, it is defined as the measure of the number of goods and services produced per worker per hour.
The productivity of the economy increases when the cost to produce each unit decreases. Ecosystem functions have traditionally been measured by the number of goods and services produced per unit of time. As the value of time increases, so does the importance of productivity. Increased productivity has historically been accompanied by improved standards of living. As productivity increased, the cost of a basket of goods used by consumers decreased.
Productivity standards in the US have declined relative to those in other countries. This can be explained in part by the inability of the US economy to keep up with advancements in information technology. There are many productivity standards. The US Bureau of Labour Statistics has published four main performance standards that have been used in the U.S. since the late 1800s. These standards include:
The Bureau of Labour Statistics has published two other productivity measures that are based on different economic assumptions. The following productivity measures are based on the expenditure concept. The formula for these measures is the same as for the first three.
Ecosystem
The ecosystem of a particular place refers to the living and nonliving things that are found in that place and their interactions with one another. It is crucial for productivity to understand this ecosystem because of the natural resources in our area.
An ecosystem includes many things from trees to birds to fish to different species of insects and how they interact with one another. The thing that controls an ecosystem is the amount of land, temperature, and whether that is present in that area. The productivity of a place can be affected by the ecosystem.
Human development is important because it affects our environment and our quality of life. When people try to change the ecosystem of a place, that affects the community. For example, when developers try to increase their land so they can build more houses for people to live in, this affects the animals, insects, and other organisms that live in that area. An ecosystem is where the whole system as a whole creates itself. It creates things like weather, soil, and plants in a certain area. An ecosystem creates and regulates the water, soil, and nutrients in that area. It is a process that can be both positive and negative, such as some plants need light while others do not. Humans may pollute an ecosystem by burning a forest that contains many different trees. This could cause them to all die in the process, or it could cause them to change the ecosystem in the wrong way and make the area worse than it was before. People also try to reduce their waste as much as possible and recycle. This helps the environment by reducing toxic material.
What is Productivity per unit of land? Productivity is directly tied to the number of available resources in an area. Ty in Ecosystem?
Productivity in an ecosystem refers to the percentage of energy that enters the ecosystem in the form of biomass at a particular trophic level. It is the rate at which biomass is formed in the ecosystem. At each trophic level in the ecosystem, a characteristic amount of biomass is present. Energy enters the ecosystem through primary producers. Thus, the total productivity of its ecosystem is measured based on two aspects- Primary productivity and secondary productivity.
Primary Productivity
Primary productivity is the generation of biomass by autotrophy. The autotrophy could be photoautotrophs or chemoautotrophs. In photoautotrophs, living things synthesize their food from inorganic elements in the presence of light that acts as a source of energy. Plants are the primary autotrophs and with the help of photosynthesis, they create organic matter from inorganic substances. Chemoautotrophy is the process by which simple living organisms of the ecosystem like bacteria and archaea, derive energy from chemical processes other than photosynthesis.
Primary Productivity Further has two Aspects:
Gross Primary Productivity
The rate at which photosynthetic primary producers that are the plants incorporate energy from the sun is called gross primary productivity. The organic matter or biomass thus produced is referred to as the gross primary productivity. Gross primary productivity is dependent on environmental factors and photosynthetic elements.
Net Primary Productivity
Some of the energy produced by gross productivity is lost by activities like respiration and metabolic heat loss. Net productivity is what remains after this loss of energy. It is what is available to the primary consumers at the next trophic level. Net primary productivity is estimated by subtracting loss of energy by gross primary productivity.
Therefore, Net primary productivity = GPP – Energy lost.
The net energy is stored in plants which are then used as food for the animals that feed on plants. Researchers consider the net primary productivity which is the amount of organic matter produced in a community in a given time. Nearly 170 billion tons of net primary productivity occurs over the entire biosphere per year.
Net primary productivity varies among ecosystems and is dependent on factors like solar energy input, weather conditions, moisture levels, carbon dioxide levels in the ecosystem, availability of nutrients, and interactions in the community. These factors influence the number of autotrophs that capture light energy and how efficiently they can perform their role.
Secondary Productivity
Secondary productivity is influenced by heterotrophs in the ecosystem. It is the energy accumulated at the consumer level. The biomass generation in secondary productivity is driven by the transfer of organic compounds between trophic levels through feeding. So, it is not like productivity at the primary level because it keeps moving from one organism to another. It can also be stated as the rate of increase in the biomass of heterotrophs. Animals, fungi, bacteria, and numerous other protists influence Secondary Production.
Unit of Productivity
Productivity is given by units of mass per unit volume (or surface) per unit time.
Movement of Energy Between Trophic Levels
The energy passes from one trophic level to the next when organic molecules from an organism's body are eaten by another organism. The transfer of energy between trophic levels is not completely efficient. Only about 10% of the energy stored as biomass in one trophic level gets stored as biomass in the next trophic level. That is from primary producers to primary consumers. Here, net productivity drops by a factor of ten from one trophic level to the next
FAQs on Ecosystem Productivity: Understanding Energy Flow and Measurement
1. What is meant by productivity in an ecosystem?
In ecology, productivity refers to the rate at which biomass or organic matter is generated in an ecosystem per unit area over a specific period. It is essentially a measure of energy flow. This production forms the base of the food web, supporting all higher trophic levels. It is typically expressed in units of mass per unit area per unit time (e.g., g/m²/year) or energy per unit area per unit time (e.g., kcal/m²/year).
2. What are the two main types of productivity in an ecosystem?
Ecosystem productivity is divided into two main categories based on the source of energy synthesis:
- Primary Productivity: This is the rate at which energy is converted into organic substances by autotrophs (producers), primarily through photosynthesis. It forms the foundation of the ecosystem's energy budget.
- Secondary Productivity: This is the rate at which consumers or heterotrophs generate new biomass by assimilating energy from the organic matter they consume.
3. How are Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) different?
The key difference lies in accounting for the energy used by producers themselves. Gross Primary Productivity (GPP) is the total rate of photosynthesis, representing the entire amount of organic matter produced. However, producers use some of this energy for their own metabolic activities, like respiration (R). Net Primary Productivity (NPP) is the remaining organic matter after subtracting the energy lost to respiration. The formula is: NPP = GPP - R. Therefore, NPP is the energy that is actually available to the next trophic level (herbivores).
4. Why is Net Primary Productivity (NPP) considered more ecologically important than Gross Primary Productivity (GPP)?
NPP is considered more ecologically significant because it represents the net available energy for the entire ecosystem. While GPP indicates the total photosynthetic capacity of producers, it's the NPP that is transferred to herbivores, carnivores, and decomposers. Therefore, the biomass, energy flow, and carrying capacity of all consumer trophic levels are directly dependent on the Net Primary Productivity at the producer level.
5. What is secondary productivity and which organisms are responsible for it?
Secondary productivity is the rate of formation of new organic matter by consumers. It involves the assimilation of energy from consumed food into the consumer's own biomass. The organisms responsible for this are heterotrophs, which cannot produce their own food. This includes all animals, from herbivores (primary consumers) that eat plants to carnivores (secondary and tertiary consumers) that eat other animals, as well as decomposers like fungi and bacteria.
6. What are the key factors that limit primary productivity in an ecosystem?
Primary productivity is limited by several environmental factors that vary between terrestrial and aquatic ecosystems:
- In Terrestrial Ecosystems: The most critical factors are solar radiation (sunlight), temperature, soil moisture (water availability), and the availability of essential nutrients like nitrogen and phosphorus in the soil.
- In Aquatic Ecosystems: The primary limiting factor is typically light availability, as it decreases with water depth. In addition, the concentration of nutrients, particularly nitrogen, phosphorus, and iron, is a major constraint on productivity, especially in open oceans.
7. Which ecosystems exhibit the highest and lowest primary productivity?
The productivity of ecosystems varies greatly across the globe.
- Highest Productivity: Ecosystems like tropical rainforests, coral reefs, and estuaries show the highest net primary productivity due to abundant sunlight, warm temperatures, high rainfall, and rich nutrient availability.
- Lowest Productivity: Ecosystems such as deserts, arctic tundra, and the deep open ocean have the lowest productivity because of limiting factors like extreme temperatures, lack of water, or insufficient light and nutrients.
8. How does the '10% law' of energy transfer relate to an ecosystem's productivity pyramid?
The 10% law directly explains the structure of the productivity pyramid. It states that during the transfer of energy from one trophic level to the next, only about 10% of the energy is stored as biomass and becomes available to the next level. The rest is lost, primarily as metabolic heat during respiration. This inefficient transfer means that the total productivity (and biomass) decreases significantly at each successive trophic level, creating a pyramid shape and limiting the number of possible trophic levels in a food chain.
9. Could an ecosystem have a high Gross Primary Productivity (GPP) but a very low Net Primary Productivity (NPP)? What would this imply?
Yes, it is possible for an ecosystem to have a high GPP but a low NPP. This would imply that the producers (like plants) are capturing a large amount of solar energy but are also using up a significant portion of it for their own respiration (R). Such a situation might occur in mature ecosystems like old-growth forests, where large trees have high respiratory costs for maintaining their massive biomass, leaving less net energy for new growth or for consumers.
10. Why is the open ocean, despite covering 70% of the Earth, have low productivity compared to land?
Despite its vast size, the open ocean has a surprisingly low average net primary productivity per unit area. This is primarily due to two limiting factors:
- Nutrient Scarcity: Unlike on land where soil retains nutrients, essential nutrients like nitrogen and phosphorus are scarce and widely dispersed in the vast photic (sunlit) zone of the ocean.
- Light Penetration: Sunlight, the primary energy source, can only penetrate the upper layers of the ocean, restricting photosynthesis to this narrow photic zone.
In contrast, areas of upwelling and coastal zones where nutrients are more abundant are significantly more productive.
