Succession 演替

What is Succession? It is a gradual(逐漸的),orderly and predictable(可預料的)changes in the communities(群落). From pioneer community(先鋒群落) to climax community(頂極群落).

Types of succession Primary succession.(原生演替) It occurs on a new or previously sterile land surface or water. Has not been previously occupied (佔領)by community

succession

Pioneer Plants(先鋒植物) The first plants start the series of succession For example:Fungi ,Lichens

They grow on rock surface. 1.cling(附著) the rock and hold water 2.CO2 dissolve in watercorrode rocks 3.Their rhizoidssplit the rocks Produce acid to break the rock into smaller fragment(碎片)

Pioneer Plant(dead) provide food and shelter bacteria ,insects,small animals enrich the soil

Mosses stage(苔蘚) When it establishedcompete with lichens Compete area,nutrients,water Gradually eliminate(淘汰) the lichens Produce acid to breakdown the rockssoil

Herb Stage(草本植物) It compete with mosses. Why it can eliminate mosses? 1.taller than mossescover it(no sun light)no photosynthesisdead For example:grass

Shrub stage(灌木) It is taller than herb. Provide a shade(陰暗)placeherb can’t do photosynthesisdead Windbreak(防風林)soil become moisture

Tree Stage(forest) When they grow,they will gradually increase the density of vegetation(a forest) It shade out the shrubs. It is a climax community It will remain equilibrium if environment doesn’t change.

Secondary Succession The previous management has been discontinued Caused by deforestation(伐林)and fire Community has been removed

Succession of animals At mosses stagesome insects.invertebrates At herb stagemore insects(bees,grasshopers) At shrub and tree stage large mammels (rabbit)

In Hong Kong Most of the forest was damaged (deforestation and fire) Most of them are secondary succession. Afforestation(植林 ) by government

香港溫帶濶葉落葉林(climax)

濕生演替：湖泊或河岸→沉水植物→浮水植物→挺水植物→莎草與水苔→混生草本→灌木→陽性樹木→中性樹木→陰性樹木 中生演替：潮濕岩石或土壤→一年生草本→多年生草本→混生草本→灌木→陽性樹木→中性樹木→陰性樹木 乾生演替：乾燥岩石或土壤→殼狀地衣→葉狀地衣與苔蘚→苔蘚與一年生草本→多年生草本→混生草本→灌木→陽性樹木→中性樹木→陰性樹木

重新植林計劃是一個成功的故事。最明顯的地方就是薄扶林郊野公園和龍虎山郊野公園的山峰和山谷

1870年至1930年 afforestation 1900年 30% woodland and forest in H.K island 1930至1945年second world war,大量難民湧入deforestation 1960至nowafforestation

The relationship between woodland and environment At the beginning:植林計劃大部分只採用單品種的樹木 速改善泥土的質素 WHY?落葉的積聚改善了泥土質素 Then,使用較多的原生品種，使整體生態得益 樹林已經廣泛分佈 種子的自然散播 .

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