Ecosystem Dynamics

Functioning of Ecosystem 

Ecosystem processes are an integral part of biodiversity. The functioning of an ecosystem refers to the interactions between organisms and their environment. Life activities such as feeding, growing, moving, and excreting waste of plants, animals and microbes in their physical and chemical conditions also reflect ecosystem functioning. 

There are four functions of an ecosystem –

• Productivity
• Decomposition
• Energy Flow
• Nutrient Cycling

Productivity

The rate at which the biomass is produced is termed productivity. For an ecosystem to function and sustain, there will be a need for the basic constant input of solar energy. During photosynthesis, the amount of biomass produced per unit area over a time period by plants is referred to be primary production. It depends on the availability of nutrients, variety of environmental factors and photosynthetic capacity of plants. The rate of formation of new organic matter by consumers is referred to as secondary production. The productivity is expressed in terms of gm^-2yr^-1. Productivity can be divided into two. 

1. Gross primary productivity (GPP) – It is the rate of production of organic matter during photosynthesis. GPP is utilized by plants during respiration. 
2. Net primary productivity (NPP) – It is the available biomass for the consumption of heterotrophs. It is the GPP minus respiration loss (R). 

GPP – R = NPP 

Decomposition

It is the decomposition of complex organic matter into inorganic substances like carbon dioxide, water, and nutrients. The raw materials for decomposition are called detritus which include dead plant remains such as leaves, bark, flowers, and dead animal remains, including fecal matter. The chemical composition of detritus and climatic factors controls the rate of decomposition. There are five important steps in decomposition. 

1. Fragmentation – The process of breakdown of detritus into smaller particles by detritivores. 
2. Leaching – The process in which the water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts. 
3. Catabolism – The process in which bacterial and fungal enzymes degrade detritus into simpler inorganic substances. 
4. Humification – It refers to the process of accumulation of a dark-colored amorphous substance called humus. Being colloidal in nature, it serves as a reservoir of nutrients and is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. 
5. Mineralization – The process in which humus is further degraded by some microbes and release of inorganic nutrients. 

Energy flow

The sun is the only source of energy for all ecosystems on Earth except for the deep-sea hydrothermal ecosystem. Less than 50% of the incident solar radiation is photosynthetically active radiation (PAR). Plants capture only 2-10% of PAR. This small amount of energy sustains the entire world. A food web illustrates the energy flow. The natural interconnection of food chains makes the food web. The chain or web is formed because of interdependency. This illustrates the energy flow from producers to consumers. Detritus food web will begin with dead organic matter.  

1. Producers – All organisms depend on producers for their food. Producers are green plants in the ecosystem. Herbaceous and woody plants are producers in the terrestrial ecosystem, while various species like phytoplankton, algae and higher plants are producers in an aquatic ecosystem. 
2. Consumers – They depend on plants directly or indirectly for their food and are also called heterotrophs. Those who consume plants directly are called primary consumers or herbivores. Insects, birds and mammals in the terrestrial ecosystem and mollusks in the aquatic ecosystem are some of them. If the animals eat other animals, which in turn eat the plants, are called secondary consumers or carnivores. Those who feed herbivores primarily are called primary carnivores, and those who depend on the primary carnivores are called secondary carnivores. 

• Trophic level – Organisms occupying a specific place in the food chain based on the source of their nutrition or food. The food chain starts with primary producers in level 1, then moves to herbivores (primary consumers) at level 2, carnivores (secondary consumers) at level 3 and so on and finishes level 4 or 5 with apex predators (tertiary consumers).  

Example of a food chain operating in grassland is:  

Grass(producer) → Grasshopper(herbivore) → Frog (carnivore 1) → Eagle (carnivore 2). 

Here grass represents the first trophic level, grasshopper represents the second trophic level, frog represents the third trophic level, and eagle represents the fourth trophic level.  

• Energy Pyramid – It is also referred to as an ecological pyramid or trophic pyramid. It is a graphical representation of various organisms in an ecosystem. The energy pyramid consists of several bars, and each bar represents a different trophic level. Each trophic level represents the energy flow in the ecosystem. The energy flows from the bottom of the pyramid, where we have producers. During the transfer of energy from one organism to another along a food chain, an energy pyramid is useful. 

Nutrient Cycling

It is the movement of nutrient elements through the various components of an ecosystem. Also called biogeochemical cycles. Standing state of the nutrients is the amount of nutrients such as carbon, nitrogen, phosphorus, etc., present in the soil at any given time. Nutrient cycle is of two types: 

1. Gaseous – Example: Nitrogen cycle, Carbon cycle 
2. Sedimentary – Example: Sulfur cycle and Phosphorus cycle 

Resilience 

Resilience is the stability and capability of an ecosystem for tolerating disturbance and restoring itself. There are many factors that affect resilience such as water cycle, fertility, biodiversity, plant diversity and climate. Also, human activities such as deforestation, pollution, mining, recreation, overfishing and dumping of waste into the sea and climate change are also adversely affecting resilience. To increase the resilience of an ecosystem, maintain the genetic diversity of forest tree species and increase tree species diversity. 

Some human impacts –  

1. Agriculture – It can be seen as a significant example in which the adaptability of terrestrial ecosystems should be considered. The organic matter in the soil, which is supposed to be recharged by multiple shops, is the main source of nutrients for crop growth. At the same time, aggressive agriculture practices in response to global food demand and dearth involve the dumping of weeds and the use of fertilizers to increase food products. Still, as a result of the agricultural increase and the operation of weedicide to control weeds, fertilizers to accelerate and increase crop growth and fungicides to control insects. This leads to a reduction in soil fertility and productivity. Further sustainable agricultural practices would take into account and estimate the adaptability of the land and examine and balance the input and situation of organic matter.  

2. Deforestation – The term deforestation has a meaning that covers crossing the threshold of timber’s adaptability and losing its capability to return to its initial stable state. , A timber ecosystem needs suitable relations among climate conditions and bio-actions, and enough area to recover itself. In addition, the adaptability of a timber system allows recovery from a fairly small scale of damage of over 10% of its area. The larger the scale of damage, the more delicate it is for the timber ecosystem to restore and maintain its balance.  

3. Climate change – Climate adaptability is defined as “the capacity of social, profitable and ecosystems to manage with a dangerous event or trend or disturbance.” The crucial focus of adding climate adaptability is to reduce the climate vulnerability that communities and countries presently have with respect to the numerous goods of climate change. Presently, climate adaptability involves social, profitable, technological, and political strategies that are being enforced at all scales of society.  

4. Overfishing – It has been estimated by the United Nations Food and Agriculture Organization that over 70% of the world’s fish stocks are completely exploited or depleted, which means overfishing threatens marine ecosystem adaptability, and this is substantially by rapid-fire growth of fishing technology. One of the negative effects on marine ecosystems is that over the last half-century, the stocks of littoral fish have had a huge reduction as a result of overfishing for its profitable benefits. Blue fin tuna is at particular threat of extinction. Reduction of fish stocks results in lowered biodiversity and accordingly imbalance in the food chain and increased vulnerability to the complaint.