Ecology: Ecosystem Processes and Succession

Plant Ecology

• Plant ecology is the scientific study of the relationship between plants and their environment.
• It's related to other branches of botany and science.
• Ecology derives from the Greek words: oikos (house) and logos (study of), denoting the study of relationships between organisms and their surroundings.
• Plant ecology has two main types:
  • Autoecology: studying specific plants in their natural habitats to understand how environmental factors influence them.
  • Synecology (Phytosociology): studying plant communities in an area to understand their structures, origins, development, distribution, and how factors like environmental conditions affect these communities.

Branches of Plant Ecology

• Autoecology, focusing on individual plants and their responses to the environment.
• Synecology (Phytosociology), focusing on plant communities and their interactions.

Relationship Between Plant Ecology and Other Branches of Botany

• Plant ecology is closely related to other branches of botany and science.
• Morphology and Anatomy: plant structure is often linked to environmental adaptations.
• Physiology: plant functions, like transpiration and osmotic pressure, are affected by ecological factors.
• Taxonomy: plant classification is crucial for understanding plant communities.
• Meteorology: accurate data on climate factors such as temperature, precipitation and wind are essential for understanding communities.
• Pedology: the study of soil properties is vital for understanding plant growth as roots need minerals and nutrients from soil.
• Hydrology: the study of water properties, like depth and currents, is crucial in ecosystems with aquatic plants.
• Geography: distribution pattersn of plants and their classification into groups.
• Geology: study of earth layers is needed for the study of old plants and evolution.

Definition of Environment and Habit

• Environment includes all factors that affect a plant's growth, reproduction, etc.
• Habitat or habit refers to the location where a plant lives.

Environmental Factors

• Environmental factors are classified into: climatic factors, edaphic factors, physiographic factors, and biotic factors.

Climatic Factors

• Climatic factors influence plant life directly and indirectly. Including:
  • Light: affects chlorophyll formation and number of chloroplasts
  • Temperature: crucial for all metabolic processes like germination, growth, reproduction, transpiration.
  • Wind
  • Humidity
  • Evaporation

Light

• Light affects the number and position of chloroplasts, and the formation of chlorophyll.
• Plants are divided into sun plants (growing directly under sunlight) and shade plants (growing indirectly under sunlight)

Temperature

• Plant temperature follows its medium. Shoot system is affected more by air temperature; root system is affected more by soil temperature
• All metabolic processes increase with increasing temperature (germination, growth, reproduction, transpiration).
• Each plant has a specific temperature range for growth, between a minimum and maximum temperature.

Temperature and Transpiration

• There are two main types of transpiration:
  • Stomatal transpiration: water vapor exits through plant stomata.
  • Cuticular transpiration: occurs at high temperatures where stomata are closed. This is more prevalent than stomatal transpiration.

Humidity

• Absolute humidity: the actual amount of water vapor in the air.
• Relative humidity: the proportion of water vapor in the air compared to the maximum amount it can hold at the given temperature.
• Factors affecting humidity: temperature, and wind

Evaporation and Wind

• Evaporation is water movement from any surface.
• Wind is air in motion that has both positive and negative effects on plants.
• Negative effects (harmful):
  • Desiccation
  • Dwarfing
  • Deformation
  • Abrasion
  • Erosion and deposition

Edafic Factors

• Edafic factors include all physical and chemical soil properties affecting plant growth, including soil texture, profile, moisture, organic matter, soil reactions, and mineral content.
• Plants heavily affected by edaphic factors are referred to as "Edaphic plant communities".

Importance of Soil

1. Fixation: Plants are fixed in soil through their roots.
2. Supplying plants with water and minerals.
3. The source of organic matter (humus).
4. Medium for root respiration and aeration

Origin of Soil

• Two main types of soil:
  • Residual soil: comes from the disintegration of local rocks.
  • Transported soil: moved from another location.

Soil Formation

• Soil forms from the outer layer of Earth's crust.
• Disintegration occurs through (mechanical processes) and physical factors:
  • Temperature change: heating and cooling causes mineral expansion and contraction, leading to disintegration.
  • Water influence: water absorption in porous rocks causes swelling and splitting, resulting in disintegration.
  • Wind and volcanoes: Wind carries soil particles; volcanoes erupt and deposit material.

Chemical Processes of Soil Formation

• Chemical processes change the chemical composition of soil materials, also known as weathering. This includes oxidation, reduction, hydration, and hydrolysis.
• Carbonation occurs from CO2 combining with soil bases to create carbonates and bicarbonates.
• Solution: acids formed in soil are more effective at decomposing rocks and minerals.

Soil Organic Matter (Humus)

• An essential difference between fertile soil and infertile soil is whether the former contains organic matter.
• Soil humus is the end product of organic matter decomposition from plant and animal organic matter.
• Humus is dark-colored, and resistant to decomposition. It is composed of long-branched chains,.
• Importance of humus:
  • Source of nitrogen (N) from proteins
  • Increases water holding capacity (from colloid content)
  • Increases soil aeration (from aggregate formation).

Soil Texture

• Soil properties heavily depend on particle size which can be determined using sieve methods.
• Based on particle size, soil can be classified into coarse particles (gravel,sand), intermediate particles (silt), and fine particles (clay).
• Important groupings of soils based on their characteristics include:
  • Sandy Soil
  • Loamy Soil
  • Mud Soil

Effect of Soil Texture on Soil Features

• Water holding capacity: high ratio of fine particles can absorb large quantities of water compared with coarser particles.
• Infiltration of water: Sandy soil absorbs water easily, while clay soil absorbs slowly.
• Fertility: A high proportion of fine particles usually correlates with higher fertility.
• Mechanical resistance to root penetration: Heavy clay soils are harder for roots to penetrate compared with lighter sandy soils.
• Rate of water movement: Water movement is fastest through sands and slowest through clays.
• Aeration: Sandy soil has good aeration; whereas, clay soil has poor aeration.

Soil Profile

• Soil profile is a vertical section of soil that shows different layers with different characteristics. Layers are called horizons.
• Horizons of soil profile include:
  • A-horizon: upper, surface layer.
  • B-horizon: lower layer, concentration of minerals.
  • C-horizon: consists of weathered parent material.
  • D-horizon: original rocks.

Water Content of Soil

• Water is vital for living organisms.
• Types of soil water:
  • Gravitational water
  • Capillary water
  • Hygroscopic water
  • Combined water

Topographic Factors (Physiographic Factors)

• Controlled by landforms (altitude, slope, exposure).
• They influence local climates and factors like wind and rainfall.
• Important for plant distribution, density, and the type of plants in a particular habitat.

Biotic Factors

• Green plants are influenced by other living organisms.
• Plants influence each other by factors like shading.
• Other biotic factors: grazing (animals eating plants), pollination (animals aiding in reproduction), dissemination (seeds dispersal by animals).

Ecosystems

• Ecosystems consist of two basic components:
  • Autotrophic (produces its own food): green plants
  • Heterotrophic (depends on other organisms for food): animals, fungi
• Components of ecosystem based on its structure:
  • Abiotic components: non-living (soil, water, air).
  • Biotic components: living (producers, consumers, decomposers).

Food Chains and Food Webs

• Food chain: a sequence of organisms where each eats the one before it.
• Food web: the network of interconnected food chains. Food web demonstrates interdependence among organism in an ecosystem.
• Types of food chains:
  • Predator chain: starts with a plant to a predator eating a larger animal.
  • Parasitic chain: starts with a larger organism to a smaller parasite.
  • Saprophytic chain: starts with dead matter to microorganisms.

Vegetation

• Vegetation is the sum total of plants in an area.
• Basic units of vegetation are plant communities.

Plant Communities

• A plant community is a group of plants found in the same habitat with growth controlled by similar environmental conditions.
• Plant community orders:
  • Plant formations (based on life form, like forest, grassland, etc)
  • Associations (groups of related plant types)
  • Consociations (one dominant species)
  • Societies (highly organized communities)

Methods of Vegetation Analysis

• Quadrate method: using plots (quadrates) to determine species, frequency, density, and distribution. Different types of quadrats include list, count, cover.
• Transect method: using a line or strip to sample plants (belt transect, line transect)

Succession

• Succession is the gradual change of plant communities in an area over time.
• Two main types of succession:
  • Hydrosere (starts in water)
  • Xerosere (starts on dry land)

Stages of Hydrosere

• Submerged stage: pioneer plants like Elodea and Ceratophyllum are completely submerged.
• Floating stage: plants like Eichhornia and Nymphaea develop, with leaves floating on the water surface.
• Reed-swamp stage: the ecosystem is now filled with reeds and other emergent vegetation.
• Sedge-meadow stage: grasses and herbs dominate.
• Woodland stage: trees begin to appear and shade-loving herbs die back.
• Climax forest: a mature forest develops and the dynamics of the ecosystem stabilize.

This quiz explores key processes involved in ecosystem operation, focusing on the interactions between biotic and abiotic factors. You'll learn about the concept of succession in ecology and how changes within a community can influence the ecosystem. Test your understanding of these critical ecological principles!