Remarks on the Succession of Bryophytes on Hawaiian Lava Flows 
Harvey Alfred Miller 1 
The Hawaiian Islands are well known for 
their volcanic origin and for continuing vol- 
canic activity on the largest island, Hawaii. On 
May 13, 1955, Hawaii experienced a volcanic 
eruption and lava flow of considerable magni- 
tude. Professor Maxwell Doty undertook a series 
of surveys to outline the plant succession on 
this new flow. 2 
The first bryophyte was observed and col- 
lected at about a 950-ft. elevation on December 
20, 1955, when a tiny juvenile colony of 
Carnpylopus introflexus (perhaps C. boswelli, 
though this species was not collected later) was 
discovered in the folds of lava blisters. A sub- 
stantial portion of the collection was sent to me 
in half of a foil chewing-gum wrapper — which 
indicates the extreme youth of the colony. The 
individual plants were 3-5 mm. high, or about 
the length of IV 2 leaves. On February 22, 1956, 
Carnpylopus densifolius, in about the same stage 
of development as the first moss collected, was 
taken at about 900 ft., in the Kamaili Home- 
steads at Puna. In late March more colonies of 
C. densifolius were discovered on the lilewa 
flow, and C. exasperatus was discovered growing 
on old lava adjacent to the new flow. Specimens 
of apparently living Macromitrium owahiense 
were collected from the bark of a Metrosideros 
( Ohia lehua) tree which had been killed by 
the encroachment of hot lava. In August, Cam- 
pylopus introflexus was found on the flow about 
p 2 mi. east of McKenzie Park. In subsequent 
collections this species seemed to be established 
in several places on the new flow. Two species 
previously unrecorded for the lilewa flow were 
discovered at about 950 ft. in April, 1957, and 
Rhacopilum cuspidigerum and Rhacomitrium 
lanuginosum var. pruinosum were added to the 
1 Department of Botany, Miami University, Oxford, 
Ohio. Publication of this paper has been aided by 
NSF Grant G7115. Manuscript received March 4, 
1959. 
2 This study was aided by NSF Grant G1922. 
growing list of pioneer bryophytes. The Decem- 
ber, 1958, collections contained Carnpylopus 
exasperatus and Vunaria hygrometrica, along 
with species previously found on the flows. 
In general, exposed lava flows support few 
species of bryophytes and these are restricted to 
protected crevices or small shaded niches. The 
several species of Carnpylopus establish them- 
selves rather readily in lava under climatic condi- 
tions of the type favorable for the growth of 
Metrosideros. It is of interest that Carnpylopus 
fumarioli becomes established in the steam fis- 
sures at Kilauea. In Hawaii, species of Campylo- 
pus appear to play a significant pioneer role in 
rock succession and are often found on rocks 
devoid of other plants. Rhacopilum cuspid- 
igerum is the most ubiquitous moss in Hawaii 
and with its obviously great range of tolerance 
would be expected to be a pioneer species on 
new lava as well as on older rocks. It produces an 
abundance of spores throughout the year, which 
is another factor favoring rather rapid establish- 
ment in unoccupied habitats in frost-free re- 
gions. 
Rhacomitrium lanuginosum var. pruinosum 
has a much greater altitudinal range than Rhac- 
opilum and is found in more exposed situations. 
The upper half of each leaf is hyaline and the 
striking silver-grey tufts of Rhacomitrium can 
be easily seen and recognized. Above 8,000 ft. 
on the barren lava flows of Mauna Loa this 
species of Rhacomitrium and Grimmia tricho- 
phylla are the only plants to be found. I have 
collected both of these mosses on the unexposed 
sides of lava clinkers at 11,000 ft. The Rha- 
comitrium has been collected at the summit of 
Mauna Loa by several people. In spite of its 
great tolerance of seemingly arid conditions, 
Rhacomitrium plays an important role in bog 
formation in the Alakai Swamp on Kauai. It is 
suggested that the acid nature of the bog may 
represent a physiologically, though not phys- 
ically, arid habitat with the cloud moisture 
246 
