Lecture # 3: Biogeochemical Cycle

Objectives:1.To Define Biogeochemical cycle2. To Discuss the Phases of Biogeochemical cycle3.To Classify Biogeochemical cycle4.To Discuss Water Cycle5.To Discuss the Importance of Biogeochemical

cycle in Ecosystem

Presented by Abul Kalam Azad

Senior Lecturer, GEDNorthern University Bangladesh

E-mail: kalamadd@gmail.com

Introduction

For proper growth and development of living organisms, nearly 30 to 40 elements (nutrients) are required. Most essential of these are N, K, Ca Fe (Iron) for Mg CHOPS, B, Zn, Cl, Mo, Co, I and F. These materials flow from abiotic to biotic components and back to the non-living component again in a cyclic manner. This is known as the biogeochemical cycle or inorganic-organic cycle. The flow of these elements through the ecosystem must be cyclic. Let’s define the concept, first and then classify and discuss its importance.

N = Nitrogen Zn = Zinc K = Potassium Cl = Chlorine Ca = Calcium Mo = Molybdenum Fe = Iron Co = Cobalt Mg = Magnesium I = Iodine C = Carbon F = Fluorine H = Hydrogen O = Oxygen P = Phosphorus S = Sulfur B = Bran

Essential Nutrients and Symbols

Definition of Biogeochemical Cycle

The cyclic process through which the flow of nutrients is occurred is called biogeochemical cycle (Geography Dictionary).

Encyclopedia Britannica defined biogeochemical cycle as “any of the natural circulation pathways of the essential elements of living matter. These elements in various forms flow from the nonliving (abiotic) to the living (biotic) components of the biosphere and back to the nonliving again.”

Phases of biogeochemical Cycle:

There are two phases of biogeochemical: 1. Environmental Phase

2. Organismic Phase

1. Environmental Phase In this phase, nutrients exist in water, air,

soil etc. 2. Organismic Phase In this phase, nutrients exist in the active

tissues of the living organisms.

Phases of biogeochemical Cycles

Environmental Phase; Air, water, soil and nutrients

Nutrient

Plants

Animals

Man

Waste material and dead bodies

DECOMPOSITION

Kinds of Biogeochemical Cycle

There are major three types of biogeochemical cycles:1. Hydrologic or Water cycle2. Gaseous cycle e.g., Oxygen cycle, Carbon

cycle, Nitrogen cycle and3. Sedimentary cycle e.g., Sulphar Cycle,

Phosphorus Cycle etc.

For example, water cycle is discussed below:

Water Cycle

The Earth's water is always in continuous cyclical movement. Since the water cycle is truly a "cycle," there is no beginning or end. Water can change states among liquid, vapor, and ice at various places in the water cycle. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go in a hurry, but there is always the same amount of water on the surface of the earth.

The water cycle has no starting or ending point. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. Rising air currents take the vapor up into the different processes are as follows:

1. PrecipitationPrecipitation is condensed water vapor that falls to the Earth's surface. Most precipitation occurs as rain, but also includes snow, hail, fog and drip.

Approximately 505,000 km³ of water fall as precipitation each year, 398,000 km³ of it over the oceans.

2. Snowmelt refers to the runoff produced by melting snow.

3. Runoff includes the variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may infiltrate into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.

4. Infiltration is the flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater.

5. Evaporation is the transformation of water from liquid to gas phases as it moves from the ground or bodies of water into the overlying atmosphere. The source of energy for evaporation is primarily solar radiation.

6. Evaporation often implicitly includes transpiration from plants, though together they are specifically referred to as evapotranspiration.

Sublimation is the state change directly from solid water (snow or ice) to water vapor

Condensation is the transformation of water vapour to liquid water droplets in the air, producing clouds and fog.

Importance of biogeochemical Cycle:

Supply of light, water, temperature, flow air and nutrient are important to continue the normal system of ecosystem. Members of ecosystem can live easily only at that situation when the mentioned conditions will be fully filled. Biogeochemical cycle plays an important role here to continue the optimum situation in ecosystem. That is why the importance of biogeochemical cycle is undoubtedly paramount and unavoidable.