232 BOTANICAL GAZETTE [MARCH 
Secondary succession 
The burn succession 
The effect of fire upon the climax forest is to bring about a 
return to a more or less xerophytic condition, which is followed by 
a readvance leading to the climax. Two general cases may be 
distinguished. 
1. Humus little harmed.—The coniferous element is destroyed, 
but the birches survive in their underground portions and sprout 
abundantly from the stump, usually producing a nearly pure 
3 B[Lrke Rock Shore CLIMAX _ FOREST 
= E Succession (Abies, Betula, Picea canadensis) 
S|z* 
Rs 
bia 
= 2 
be] 
_ > rn Forest 
bd lefsprou 
ae OF s) Xerophytic Forest Bog Forest ve Maxie Swamp Forest 
| é ireweeds, sie dgpiandanar (are a ices ariana) ee 
a = —, — ce oe Shrubs _ f a nigra) 
naphal hus crispa, 
ae eas — st ; ifera, sicratal. Seem ee 
ea a alix spp, Shi de yrica, 
Bog ay cent sy Alnus incana) 
(Chamaedaphne, Andromeda) t 
Andromeda, a Grasses 
Cladonias Crevice Shrubs Shrubs Shrubs Alnus incana) me (Calamagrostss 
f (Juniperus, (Vaccinium (Rubus idaeus, “s._ canadensis) 
Foliose Lichens, Arctostaphylos) uliginosum) Diervilla, os, 
Hedwigia Physocarpus) aia at ed | Mat 
Crustose Lichens, Crevice Herbs Turf Mat af Herbs Aquatics Aquatics 
Grimma otentilla ; Gcirpus A 
Rock Surface Crevice Rock Pool 
Subsuccession Subsuccession Subsuccession | I 
Se 
Rock SHQRE Succession Beacu Succession Boc Succession DeLtaSwamPSuccESsion 
“, eo 
XERARCH SUCCESSIONS HYDRARCH SUCCESSIONS 
PRIMARY SUCCESSIONS 
Fic. 55.—Diagram to illustrate the courses of the various successions upon Isle 
Royale. 
forest of birches growing in clumps. Seedling birches and aspens 
are usually present also. Conifers gradually return, finally bringing 
about the reestablishment of the climax. 
2. Humus destroyed; bare rock exposed.—The reestablishment 
of the climax follows closely along the line of the rock shore succes- 
sion, but progress is usually more rapid because of the presence of 
soil materials and numerous invaders, and frequently protection 
from wind. 
The courses of the various successions and their relations to 
each other are shown graphically in the diagram (fig. 55). 
Pato ALTO, CALIFORNIA 
