Succession

Question 1

what is succession?

Answer 1

changing sequence of communities that live in an ecosystem overtime. each community changes the habitat in ways that make it less hostile and so create niches for the next community of plants

Question 2

what is each plant community called?

Answer 2

a sere

Question 3

what is the final plant community called?

Answer 3

climax community
this climax community is stable and potentially very long lasting

Question 4

how does a primary succession start?

Answer 4

the initial conditions in a habitat has hostile abiotic conditions:
- dry (no soil to retain water)
- few available minerals
- high light intensity - no shade3 from other plants
- extremes of temp
- windy

Question 5

what is a pioneer community?

Answer 5

the organsim taht colonies the habitat that is adapted to cope with hostile conditions

Question 6

describe the pioneer community

Answer 6

on bare rock, lichens are the pioneer
- they can survive with little water or nutrient - providing soil
- they can anchor themselves in cracks and can dissolve bare rock to get minerals
- they can withstand prolonged periods of drought

on sand dunes, marram grass is the pioneer species

Question 7

how do conditions become less hostile from the pioneer species?

Answer 7

• when the lichens die, they decompose to become dead organic matter (humus)
• this creates a thin soil which is able to retain some moisture and slowly release nutrients through decomposition
• this creates niches in which less resilient plants can grow, conditions become less hostile

Question 8

what are the next few seres?

Answer 8

1) pioneer
2) moss sere - some grasses germinate and grow, their decomposition adds to the developing layer of soil
3) herbaceous sere - small non woody plants, ferns and grasses germinate and grow in the less hostile conditions. they have good seep dispersal mechanisms producing small wind dispersed seeds that germinate rapidly in thin soil. these will out compete the pioneers ad mosses for light and space. Taller plants will also reduce wind speed and light intensity at soil level helping to retain more moisture
4) shrub sere - soil is deeper, conatisn more humus and has a pH closer to neutrak than the underlying rock. Other abiotic factors such as water availability, light intensity and wind speed will have improved so that more demanding larger shrubs can grow. These larger plants from the sub climax community, out competing the lower level herbaceous species for light and space
5) tree sere - woody trees grow slowly but when established they out compete the shrubs for light, minerals and water. this final community provides a diverse set of niches to support a large variety of insects and other animal species. has many trophic interactions

Question 9

what are the key points of succession?

Answer 9

• each seral community changes conditions in such a way as to promote the growth of the next sere
• conditions become less hostile
• each new seral community out competes the previous community
• as time passes the plant and animal community becomes more diverse and there is greater stability due to abiotic and biotic variables being less hostile

Question 10

what does the details of species found in each sere depend upon?

Answer 10

• climate
• type of rock

Question 11

what is secondary succession?

Answer 11

• occurs when a climax community is removed
• pioneers and other plants will re-establish and succession starts again
• the process of secondary succession is usually much quicker because there is already a well developed soil which possibly contains los of seeds

Question 12

how would a climax community be removed?

Answer 12

• removed by humans eg forestation
• destroyed by fire or storm (natural disasters)

Question 13

what is plagioclimax?

Answer 13

A plagioclimax is a human managed community. Human activity often deliberately stops, or reverses a primary succession to maintain an earlier stage of the succession eg grassland

Question 14

how do humans stop succession?

Answer 14

often use animals to graze any plants which would move the succession on

Question 15

what are conservation methods?

Answer 15

1) managing succession - eg sheep grazing
2) seed banks - store of preserved seeds so that if a species become extinct in the wild they can be revived
3) captive breeding - breeding of endangered species in a controlled environment to maintain a population for reintroduction should the species become extinct in the wild
4) protected areas - national parks and conservation areas where regulations manage conflicts between humans and wildlife eg restriction on hunting
5) fishing quotas - limits placed on sizes and numbers of figh caught to sustain wild populations