`star` Productivity
`star` Decomposition
`star` Factors affecting Decomposition


● A constant input of `color{violet}("solar energy")` is the `color{violet}("basic requirement")` for any `color{violet}("ecosystem")` to function and sustain.

● `color{brown}("Primary production")` is defined as the amount of `color{violet}("biomass")` or `color{violet}("organic")` matter produced per unit area over a `color{violet}("time period")` by `color{violet}("plants")` during `color{violet}("photosynthesis.")`

● It is expressed in terms of `color{violet}(weight")` `(g^( –2))` or `color{violet}("energy")` `(kcal m^(–2))`.

● The rate of `color{violet}("biomass production")` is called `color{violet}("productivity.")`

● It is expressed in terms of `g^(–2) yr^(–1)` or `(kcal m^(–2)) yr^(–1)` to compare the `color{violet}("productivity")` of different `color{violet}("ecosystems.")`

● It can be divided into `color{violet}("gross primary productivity (GPP)")` and `color{violet}("net primary productivity (NPP)")`.

● `color{brown}("Gross primary productivity")` of an ecosystem is the rate of production of organic matter during photosynthesis.

● A considerable amount of `color{brown}("GPP")` is utilised by `color{violet}("plants in respiration")`.

● `color{violet}("Gross primary productivity")` minus respiration losses `(R)`, is the `color{brown}("net primary productivity (NPP).")`

● `color{brown}("GPP – R = NPP")`

● `color{violet}("Net primary productivity")` is the available biomass for the consumption to `color{violet}("heterotrophs (herbiviores and decomposers).")`

● `color{brown}("Secondary productivity")` is defined as the `color{violet}("rate of formation")` of new organic matter by consumers.

● `color{violet}("Primary productivity")` depends on the `color{violet}("plant")` species inhabiting a particular area.

● It also depends on a `color{violet}("variety of environmental factors")`, availability of `color{violet}("nutrients and photosynthetic")` capacity of plants.

● Therefore, it varies in different types of `color{violet}("ecosystems.")`

● The `color{violet}("annual net primary productivity")` of the whole `color{violet}("biosphere")` is approximately 170 billion tons (dry weight) of organic matter.

● Of this, despite occupying about 70 % of the surface, the `color{violet}("productivity")` of the oceans are only 55 billion tons.

● Rest of course, is on `color{violet}("land.")`


● It is known that the `color{violet}("earthworm")` is referred to as the `color{violet}("farmer’s ‘friend’.")`

● This is so because they help in the `color{violet}("breakdown")` of complex organic matter as well as in loosening of the soil.

● Similarly, `color{violet}("decomposers break down")` complex organic matter into `color{violet}("inorganic substances")` like `color{violet}("carbon dioxide, water")` and `color{violet}("nutrients")` and the process is called `color{brown}("decomposition.")`

● `color{violet}("Dead plant")` remains such as `color{violet}("leaves, bark, flowers")` and `color{violet}("dead")` remains of `color{violet}("animals, including fecal matter, constitute ")` `color{brown}("detritus,")` which is the raw material for `color{violet}("decomposition.")`

● The important steps in the process of `color{violet}("decomposition")` are `color{violet}("fragmentation, leaching,")` `color{violet}("catabolism, humification")` and `color{violet}("mineralisation.")`

● `color{brown}("Detritivores")` (e.g., `color{violet}("earthworm")`) break down `color{violet}("detritus")` into smaller particles. This process is called `color{violet}("fragmentation.")`

● By the process of `color{brown}("leaching,")` `color{violet}("water soluble inorganic nutrients")` go down into the soil horizon and get precipitated as unavailable salts.

● `color{violet}("Bacterial")` and `color{violet}("fungal enzymes")` degrade `color{violet}("detritus ")` into simpler inorganic substances. This process is called as `color{brown}("catabolism.")`

● It is important to note that all the above steps in `color{violet}("decomposition")` operate simultaneously on the `color{violet}("detritus")`

● `color{violet}("Humification")` and `color{violet}("mineralisation")` occur during `color{violet}("decomposition")` in the soil.

● `color{brown}("Humification")` leads to accumulation of a `color{violet}("dark coloured")` amorphous substance called `color{brown}("humus")` that is highly resistant to `color{violet}("microbial")` action and undergoes `color{violet}("decomposition")` at an extremely slow rate.

● Being colloidal in nature it serves as a `color{violet}("reservoir of nutrients.")`

● The `color{violet}("humus")` is further degraded by some `color{violet}("microbes")` and release of `color{violet}("inorganic nutrients")` occur by the process known as `color{brown}("mineralisation.")`


● `color{violet}("Decomposition")` is largely an `color{violet}("oxygen-requiring process.")`

● The rate of `color{violet}("decomposition")` is controlled by `color{brown}("chemical composition")` of `color{violet}("detritus")` and `color{brown}("climatic factors.")`

● In a particular `color{violet}("climatic condition, decomposition rate")` is `color{violet}("slower")` if detritus is rich in `color{violet}("lignin and chitin,")` and quicker, if detritus is rich in `color{violet}("nitrogen")` and `color{violet}("water-soluble substances")` like `color{violet}("sugars.")`

● `color{brown}("Temperature")` and `color{brown}("soil moisture")` are the most important `color{violet}("climatic factors")` that regulate decomposition through their effects on the activities of `color{violet}("soil microbes.")`

● `color{violet}("Warm")` and `color{violet}("moist environment")` favour decomposition whereas `color{violet}("low temperature")` and `color{violet}("anaerobiosis")` inhibit decomposition resulting in build up of `color{violet}("organic materials.")`