Upper Limits of Vegetation on Mauna Loa, HawaiiAuthor(s): F. R. FosbergSource: Ecology, Vol. 40, No. 1 (Jan., 1959), pp. 144-146Published by: Ecological Society of AmericaStable URL: http://www.jstor.org/stable/1929934 .

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144 NOTES AND COMMENT Ecology, Vol. 40, No. 1

UPPER LIMITS OF VEGETATION ON MAUNA LOA, HAWAII1

There seems to be almost no carefully recorded infor- mation on the vegetation on the upper slopes of the Mauna Loa volcano, on the island of Hawaii. Skottsberg (1931) discussed the flora of the high Hawaiian vol- canoes, Bartram (1933) mentioned the occurrence of a moss on the summit of the mountain, and Hartt and Neal (1940) gave an account of the neighboring, but rather different, Mauna Kea. Robyns and Lamb (1939, pp. 267- 268) gave the most adequate description of this area. The following notes are by no means a complete account, but, in the absence of a careful systematic study, may be of interest.

Through the courtesy of Dr. Chester K. Wentworth I was able on January 5, 1958, to drive up to the High Altitude Laboratory of the U. S. Weather Bureau, situ- ated at 11,134 ft. on the north slope of Mauna Loa, facing Mauna Kea. On the way down, notes on the vegetation were taken in conjunction with altimeter readings.

The north slope of Mauna Loa is a bleak waste of interlaced lava flows of various ages. The road to the Weather Bureau Station is relatively new, graded and bulldozed into the rough lava. It spirals on a rather gentle grade up the mountain from Kulani around to the west, overlooking the Humuula Saddle between Mauna Loa and Mauna Kea. The lower part of the road runs through fine wet forest of Metrosideros, much of which, unfortunately, is being destroyed and the land converted for grazing purposes. This forest decreases somewhat in stature upward on the mountain slope, but irregularly, depending on the age and character of the lava sub- stratum. It ends abruptly where the 1942 lava flow cuts across the road at about 6500 ft.

After this there is intermittent woodland of low stature with scrub in the openings. This is the mountain park- land formation of Robyns and Lamb. The scrub com- ponent is the typical montane xerophytic vegetation of the medium high slopes of the larger volcanoes of the islands-Mauna Loa, Mauna Kea, Hualalai, and Halea- kala, starting in the upper edges of the forest at different altitudes, depending on the exposure. This scrub reaches to the summit of Haleakala, Maui, and to different alti- tudes on the volcanoes on the island of Hawaii, apparently depending at least in part on substratum. It may be pre- vented by continuous low temperature from reaching the highest altitudes on Mauna Kea where the conditions otherwise might be favorable (see Hartt and Neal (1940, pp. 242-243) ). It is characteristically composed of Sty- phelia, Vaccinium, Dubautia, Geranium, Coprosma, Doo- donaea, small Metrosideros, and occasionally other genera. This is the subalpine belt of the zonation recognized by Skottsberg and by Hartt and Neal, the subalpine shrub zone of Robyns and Lamb, and the E2 zone of Ripperton and Hosaka. In structure this scrub is microphyllous, 1-2 m. tall, and from open to nearly or quite closed, but usually rather sparse.

As the road climbs stretches of lava become more prevalent, usually of the rough, clinkery "aa" type, less often of the smooth or ropy "pahoehoe" type. The vege- tation becomes more and more reduced to small "islands" or "kipukas" of older surfaces surrounded by newer lava with little vegetation. These kipukas may be very small or up to many acres in extent. The vegetation is com- monly open woodland of scrubby Metrosideros up to 3-5 m. tall, with scrub such as described above between

1 Publication authorized by the Director, U. S. Geo- logical Survey.

the trees, which are sometimes scarce or lacking. The highest trees and well developed scrub along the road are in kipukas at 8250 to 8300 ft. The scrub here has a number of species in the above mentioned genera.

Above this level are extensive aa lava fields with scattered kipukas of older pahoehoe lava. Shrubs are fairly numerous in these kipukas, but do not form a con- tinuious vegetation, and are only occasional on the aa around the kipukas, becoming very rare or absent on aa above 8300 ft. They are mainly Vaccinium with some Styphclia doiiglasii and Dubaltia. Above 8300 ft. the aa lava is practically without visible plant life except for occasional tufts of a gray moss in pockets.

Crossing the aa fields at about 8500 ft. and 8700 ft. are two fresh-looking flows of black shiny pahoehoe lava of low rounded relief. These have a few scattered Vac- ciiiiusn bushes with occasional Styphelia and Dubautia. At 8800 ft. are two small kipukas of an older pahoehoe with fairly abundant shrubs of the same three genera and tufts of a grass, Trisetumn glomneratuim. Dubautia ciliolata var. jtuniperoides (Gray) Keck reaches its high- est observed station here (no. 39296) .2 This vegetation is mainly on the pahoehoe but has slightly invaded the aa around the edges.

Above this are broad fields of fresh looking aa. The last lichens were noticed at 9100 ft., but they had not been common even well below this elevation. Between 9100 and 9200 ft. Vaccinium is rather frequent on light brownish weathered pahoehoe and Styphelia douglasii (no. 39297) is occasional and reaches its upper limit here. Between 9200 and 9300 ft. these shrubs are at best widely scattered, but on pahoehoe a number of individuals are likely to be seen in any field of vision. Above 9300 it. shrubs are very local or absent. At 1400 ft. a population of 6 individual Vaccinium shrubs is seen, both Vaccinium reticulatum Sm. (nos. 39301, 39303) and V. peleanum Skottsb. (nos. 39299, 39300, 39302). Rhacomitrium, the gray moss is common here in north-facing cracks.

At about 10,000 ft., on a tiny patch of rather rough pahoehoe, surrounded by aa, were two small gnarled Vaccinium reticuilatum? (no. 39304) bushes, the highest woody plants seen along the road. Pellaea ternifooha is fairly common here in crevices. This is also the high- est spot where Rhacoinitrium, or any plant, was seen on aa lava.

From 10,000 up to 11,150 ft is mostly aa lava with occasional exposures of an older pahoehoe. The surface of the pahoehoe is somewhat checked and cracked, the cracks showing up because of an efflorescence of white mineral. On an exposure of this type at 10,550 ft. the gray moss is very common in north-facing crevices, and a specimen from here was determined by H. A. Miller as Rhaconiitriim lanuginosurn var. pruinosum Hook. & Wils. (no. 39307). The fern, Pellaea ternifolia (no. 39305), and the grass, Trisetuin glonieratum (no. 39306), are occasional here in very small tufts in crevices at any angle of exposure, but mostly exposed upward. These crevices are either quite deep or are covered by an accumulation of small rock debris which protects the root crowns and rhizomes from undue desiccation.

On a similar elongate pahoehoe exposure crossing the road at 10,800 ft. Rhacomnitrium is again common in north-facing crevices. It was noticed that none of the tufts were exposed to the direct sun at 4 :00 p.m. but that

2 Numbers refer to Fosberg collections, deposited in the U. S. National Herbarium.

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January, 1959 NOTES AND COMMENT 145

some were beginning to be hit by the sun at 4:15. Near the top of this exposure at perhaps 10,950 or 11,000 ft. tufts of Trisetum were seen, but no Pellaea. Another such exposure of pahoehoe continued on up the slope beyond a short stretch of aa, but time was not available to examine it. In all probability at least the moss would have been present there, as it showed no signs of becom- ing scarcer or less vigorous up to the top of the lower exposure. However, on pahoehoe of similar character at perhaps 11,160 to 11,200 ft. just above and beyond the weather observatory no plants at all, not even moss, were seen.

Time was not available for exploration farther up the mountain. However, Miller informs me that he has col- lected Rhacomnitrium at 11,500 ft. on this same road and Bartram (1933, p. 101) recorded it from the summit of Mauna Loa at 13,600 ft., collected by Brumaghim, so it is probably found in suitable sheltered crevices on pahoe- hoe lava all the way up.

One interesting observation about these high-altitude occurrences of plants is that there seems to be no eco- logical relation or dependence between them, whatever. The moss, fern, grass and shrubs occur in separate niches or in isolated examples of the same niche. The moss does not seem in any way to precede or prepare the way for the higher plants, nor the fern and grass to prepare

the habitat for the shrubs. Cracking of the lava seems to be the only requisite or preparation required for any of them, and this is the result either of the original cooling or of frost. This lack of interdependence is probably the outstanding characteristic of the true alpine zone on Mauna Loa. Even the influence of man is not in any way apparent. The highest introduced plant seen, Hypochoeris radicata L., was at 8100 ft. (no. 39,298). The only evident control of the vegetation above about 8300 ft. is by the physical environmental complex.

Comparison with data available on the vegetation of Mauna Kea shows that the upper limits of individual plant species as well as of the corresponding vegetation types or zones are generally higher on Mauna Kea than on Mauna Loa. For example, Robyns and Lamb quote Hillebrand as giving the upper limit of the upper forest zone on Mauna Kea as 11,000 ft. and Hartt and Neal give timberline there as 9500 ft., but the highest trees seen by me on Mauna Loa were 8300 ft. The highest shrub on Mauna Kea was seen by Hartt and Neal at 12,250 ft., while the highest seen by me on Mauna Loa was 10,000 ft. The highest vascular plant seen on Mauna Kea by Hartt and Neal, Trisetum glomeratum, was at 13,400 ft., and on Mauna Loa I saw the same species, also the high- est vascular plant, at 11,000 ft.

Upper limits of alpine zone species are shown in Table I.

TABLE I. Upper altitudinal limits, in feet, on Mauna Loa and Mauna Kea.

Mauna Loa Fosberg Mauna Kea

Asplenium adiantum-nigrum. L. ................................. not seen 13,500 (Judd; fide Hartt & Neal) Pellaea ternifolia (Cav.) Link ............................... 10,550 10,400 (Hartt & Neal) Trisetum glomeratum (Kunth) Trin. .......................... 11,000 13,400 Agrostis sandwicensis Hbd. not seen 13,100 Vaccinium peleanum Skotsb .9,400 12,250 Vaccinium reticulatum Sm.. 10,000 not seen Styphelia douglasii (Gray) F. Muell. 9,150 11,600

(as Styphelia sp.) Coprosma montana Hbd. not seen 10,400 (Skottsberg) Argyroxiphium sandwicense DC. not seen 12,250 (Hartt & Neal) Dubautia arborea (Gray) Keck .not seen 9,750 (Skottsberg) Dubautia ciliolata (DC.) Keck .8,800 9,900 Dubautia strutholoides (Gray) Keck .not seeni 11,375 Tetramolopium humile (Gray) Hbd. not seen Alpine zone, acc. Hartt and

Neal but no altitude given.

Introduced species found in the Alpine zone of Mauna Kea by Hartt and Neal were Anthoxanthum odoratum L., Poa annuia L., Poa pratensis L., Rumex acetosella L., Cirsium vulgare (Savi) Airy-Shaw, Sonchus oleraceus L. (found by Rock at 12,000 ft.), Senecio sylvaticus L., and Taraxacum officinale Weber. On Mauna Loa no introduced plants were found in the Alpine zone; the highest being that mentioned above, Hypochoeris radicata, near the upper edge of the Subalpine at 8100 ft.

An explanation for the generally better development of vegetation at higher altitudes on Mauna Kea com- pared with Mauna Loa is probably to be sought in two factors-the prevalence of ash rather than fresh lava on Mauna Kea, and the much greater age of the substratum on Mauna Kea, with consequently greater weathering and more advanced soil formation. On the portions of Mauna Loa observed the lava was all relatively recent.

A few comments on the bearing of these observations

on the vegetation classifications adopted by previous writers may be of interest. Skottsberg's paper (1931) is mainly a floristic account and mentions the vegetational aspects only incidentally. He regards timber line as an important boundary but does not describe its occurrence. Hartt and Neal also speak of timber line, and talk about it at length but do not describe it in a way that gives any clear idea of where it is or how definite it is. On Mauna Loa nothing like a true timber line was observed, though one may exist on some parts of the mountain. The mosaic of recent interlacing lava flows of varied ages would not give much reason to expect a timber line in the sense that it exists on mountains of other sorts.

There seems to be general agreement that an Alpine and a Subalpine zone should be recognized. Skottsberg, Hartt and Neal, and Robyns and Lamb all regard the Alpine zone as that above timber line and the Sub- alpine zone as the Upper Forest Zone of previous authors.

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146 NOTES AND COMMENT Ecology, Vol. 40, No. 1 Robyns and Lamb, in addition, give altitudinal limits of 7,000 to 9,000-10,000 ft. for the Subalpine zone and above this for the Alpine zone. They also interpose a Parkland zone between the Mountain forest zone and the Sub- alpine zone which obviously is the lower part of the Subalpine of Skottsberg and Hartt and Neal. Ripperton and Hosaka (1942) treat the high mountain area only incidentally, as it is not suitable for pasture. They do not name their zones but their Zone E corresponds to the Subalpine and Alpine, combined, and they divide this into three numbered subdivisions, E3 being the Alpine zone of the other authors, the two others being differentiated as being "open forest and shrub" (E1) and "mainly up- land open shrub" (E2). They are distinguished altitudi- nally, also, but the stated altitudinal limits of El 4,000- 7,000 ft.; E2 7,000-10,000 ft.; and E3 over 10,000 ft. seem not to hold up at all well on their map. There seems little doubt, however, that their zones which actually correspond rather well with those of Robyns and Lamb, do represent real differences in aspect of the vegetation.

As might be expected at such a level of generalization some contradiction and inconsistency exist both within and between these systems of zones, as when Robyns and Lamb (1939, p. 275) give the upper limit of tree growth as about 7,000 ft. and on p. 244 quote Hillebrand as say- ing that the upper forest zone extends up to 6,000 or 9,000 or, on Mauna Kea, to 11,000 ft. Hartt and Neal give 9,500 ft. as the altitude of timber line on the same mountain.

Along the road above Kulani on Mauna Loa the Park- land zone would extend from somewhat above 6,500 ft. to perhaps 8,300 ft., though the greater part of this area is bare lava. The Subalpine Shrub zone would be from 8,300 ft. to perhaps 10,000 ft., with scattered shrubs only and the greater part of the area again bare lava. This manifestation of the montane scrub vegetation of these volcanoes is sparse, indeed, and it may be questioned whether much clarity is gained by placing this scattering of shrubs in the same zone with the much denser scrub vegetation of, for instance, Haleakala volcano, Maui. However, there do seem to be definite altitudinal limits to shrub growth on Mauna Loa and they are much lower than on Mauna Kea.

The areas above the limits of shrub growth are de- scribed by Robyns and Lamb, and following them, by Ripperton and Hosaka, as belonging to the "Moss-Lichen

formation," though it is not too clear that this formation does not include also part of the area characterized by shrubs. They start by saying "Above all the zones of seed bearing plants" but continue by mentioning several seed plants, as well as ferns and mosses, and then men- tion a moss as extending to the summit of Mauna Loa. Then they say "Above the Moss-Lichen formation on Mauna Loa are extensive fields of barren lava extending to the top of the mountain." This does not add up to a very satisfactory picture of what they regard as com- prising this formation. It is notable that in spite of their terms "Moss-Lichen Formation" and "Alpine Moss- Lichen" no lichens are mentioned, nor were any observed in this area on Mauna Loa. In their terminology they are apparently following the terminology of Clements in his "general classification of climax formations." This may possibly be justified in the interests of generalization and of regional correlation. However, it is only proper to point out that the terminology is, in this case, some- what misleading. It is also well to point out that this entire situation is an excellent example of the subjective nature of this kind of generalization resulting in formu- lation of major categories of vegetation and of life zones or vegetation zones. These are excellent tools to further understanding of natural situations, but it should never be assumed that such terminology can be carried over from one worker to another without redefinition or clear reference to examples.

F. R. FOSBERG U. S. GEOLOGICAL SURVEY

WASHINGTON, D. C.

REFERENCES

Bartram, E. B. 1933. Manual of Hawaiian mosses. Bishop Mus. Bull. 101: 1-275.

Hartt, C. G. and M. C. Neal. 1940. The plant ecology of Mauna Kea, Hawaii. Ecology 21: 237-266.

Ripperton, J. C. and E. Y. Hosaka. 1942. Vegetation zones of Hawaii. Hawaii Agr. Expr. Sta. Bull. 89: 1-60.

Robyns, W. and S. H. Lamb. 1939. Preliminary eco- logical survey of the island of Hawaii. Bull. Jard. Bot. Bruxelles 9: 241-293.

Skottsberg, C. 1931. Remarks on the flora of the high Hawaiian volcanoes. Acta Horti Gothob. 6: 47-65.

SOME PALEOBOTANICAL ASPECTS OF TUNDRA DEVELOPMENT

Tundras or tundra-like landscapes are probably as old as land vegetation itself. Any evidence of past glaciation is indicative of conditions under which tundras could have developed. There is no reason to doubt that there were tundras in the Precambrian, and they must have been expansive during the Permian. Even during those rela- tively warm intervals, such as the Pennsylvanian and the late Eocene, small tundralike environments must have existed at high altitudes. However, if we try to specu- late on the kinds of plants that covered a Precambrian or Pennsylvanian tundra, even reasonable guesswork is impossible.

In narrating the chain of events that led to the expan- sion of those tundras that today cover 26% of the surface of the land, we must go back to the early part of the Tertiary period. During the late Eocene and early Oli- gocene, worldwide warmth which began to manifest itself in the late Cretaceous reached its maximum. Tropical

and temperate plants were able to thrive far north of their present ranges. For example, imprints of huge palm leaves, along with an abundance of foliage of other plants that thrive today only in warm places, are promi- nently displayed in the Eocene rocks of northwestern Washington and adjacent Canada. A boreal unit of the temperate Tertiary flora was discovered many years ago in Grinnell Land only 8.5 degrees from the North Pole (Heer 1878). It contained fragmentary leaves of Meta- sequoia or Taxodium, Pinus, Picea, Cercidiphyllum, and betulaceous leaves resembling Corylus. This florule prob- ably thrived during the late Eocene. Farther south, but still above the Arctic Circle, are several other floras of temperate and cool-temperate aspect that have been de- scribed in detail by Heer, Nathorst, Seward, and Krysh- tofovich.

The circumpolar distribution of temperate and boreal Tertiary floras has been used as an argument against

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