Changing Ecosystems: Unit 3, Topic 2 Flashcards
What is Succession? What are the two type sof succession?
the natural process by which ecosystems change and develop over time. Where one community is replaced by the next occurs after disturbance.
Primary and Secondary
Keywords:
Sere: the entire sequence of communities
Seral community: Intermediate stage of ecological succession advancing towards the climax community
Pioneer plant: a plant capable of invading care sites.
Explain what Primary Succession is
The colonisation of plants in a barren place (no soil due to catastrophic events). he emergence of an entirely new ecosystem.
Nudation: the development of a bare site
- pioneers colonise the area. Thin soil is made from secreted acids.
- Thin soil layer allows for moss -> moss dies, giving nutrients to the soil.
- Bacteria, fungi, and invertebrates form a simple community.
- enough soil for grass, and fern -> when dead, more organic matter in added.
- Deeper soil holders more water
-> small shurbs colonise -> nutrients availability increases. - Trees establish -> development of the climax community on mature soil.
Explain what secondary succession is.
- The recolonisation of disturbed plant communities - soil is already present.
- Destroyed by natural forces (fire, flood) OR human activities.
- Grows faster and will quickly reach a climax community.
What are the differences of Primary and Secondary Succession?
Primary Succession:
- occurs in a land where there is no initial vegetation
- Surface soil covers is absent when primary succession starts
- Pioneer species come from outside environment
- need more time to complete
Secondary Succession:
- Occurs in land that has primary vegetation
- Occurs where soil cover is present
- Pioneer species develop partly from existing species
- Takes comparatively less time
What are the similarities between Primary and Secondary Succession?
- Results in a climax community
- Shrubs and small trees grow
- Community of organism inhabiting an area is gradually changing
What is a pioneer species? What are their traits?
Organisms (Typically plants) capable of establishing on bare environments - also referred to as opportunistic species.
Traits/features:
- tolerant of extreme conditions
- autotrophic
- small
- photosynthetic
fix nitrogen into the soil through their relationship with specialised bacteria.
- rapid seed germination/dispersal
- Rapid reproduction -> typically R-selected
- ability to grow in poor soils with low nutrients
What is a fossil record?
- Fossilised remains of organisms
- Biotic changes can be tracked using fossil records through ice/soil cores.
What is temporal and spatial change?
Temporal change - Change in time
Spatial change - change in space/place
What is Urbanisation?
- reduces biodiversity
- causes rapid change in large magnitudes.
- changes the ecosystem for a long time, often permanent
- increase the output of gaseous and material wastes that are disposed into the atmosphere/land/water.
- caused by humans most of the time
What is Habit Destruction?
- clearance of native vegetation poses threats to biodiversity.
- when native vegetation is cleared, habitats that were once continuous become fragmented (habitat fragmentation)
What is land and soil degradation?
reduced vegetation = less organic matter being returned to the soil -> causes nutrients depletion and increasing erosion
Explain what salinity is
When natural vegetation is replaced with crops (require irrigation) = salinity
irrigation increases groundwater -> raises the water table and its often-high salt content to the surface -> causes water logging (kills plants as water table rises into the root zone)
Explain what monoculture practices is
- When one species is grown -> biodiversity is reduced
- use of fertilisers, pesticides, and herbicides to reduce the natural tenancy of the community to diversify.
- more prone to pest outbreaks and diseases as they do not have good ecological defense mechanisms.
