Why does succession take so long?. Different plant species have different ecological requirements. A beech or live-oak needs shade as a seedling. They also need soil moisture which means the soil must have a high organic content.
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Example of facilitation: shade provided by pines allows seedlings of broad-leaved trees to survive.
Growth of a nitrogen-fixing plant on sandy (nutrient poor) soils such as alder enriches the soil sufficiently for other species to colonize.
Primary Succession: Colonization of new areas
Importance of alder (ALRU) as a nitrogen fixer and Ceanothus (CEVE), early in succession.
Rotmoos Glacier, Italian alps 1895
Rotmoos Glacier, Italian alps 1999
5 yrs: Harvestman-
a glacial specialist
10 yrs: 4 spp. Of ground beetle, occupying separate niches.
20 yrs: assorted spiders
30 yr Centipedes, under rocks
50 yrs: herbivorous beetles as vegetation density increases.
70 yr: millipedes
100 yrs: 1 sp.
Of ant occupies
140 yrs: Densest
Fagan & Bishop
(American Naturalist 2000)
Krakatau is west