HAWAI`I VOLCANOES Invasion and Recovery of Vegetation after a Volcanic Eruption in Hawaii NPS Scientific Monograph No. 5

Plant Cover Development (continued)

Habitat 6

Figure 16 shows that no life-form group covered much more than 10% in years 7 and 9. The four most important, and about equally abundant, life-form groups were the sclerophyllous nanophanerophytes (sPN), the sclerophyllous woody chamaephytes (sCH frut), the caespitose chamae-hemicryptophytes [Ch(H) caesp], and rhizome-geophytes (G rhiz).

Fig. 16. Life-form spectra technology—habitat 6. (Symbols explained in Appendix VII).

The species in the sPN group were the surviving Metrosideros polymorpha, Dubautia ciliolata, Styphelia tameiameiae, and Vaccinium reticulatum. Those in the sCh frut group were mostly the same species of lower (less than 25 cm) stature. The Ch(H) caesp group included primarily sedges (Machaerina angustifolia, Gahnia gahniaeformis, Cyperus polystachyos)¹ and grasses (Andropogon virginicus¹, Agrostis avenacea). The G rhiz group includes mostly ferns such as Sphenomeris chusana, Polypodium pellucidum, Nephrolepis hirsutula¹, Pityrogramma calomelanus¹, and Pteris cretica.

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¹Exotics

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Figure 17.1 shows a section of habitat 6 in year 1 (1960) after the ash fallout. Here the pumice blanket was only 10-20 cm deep. The damage of the woody plants was manifested primarily in sheared-off shoot systems, while remnant crowns survived. Several such remnant crowns are seen in the photograph (Fig. 17.1). Figure 17.2 shows the same section in year 3 (1962). The recovery of sclerophyllous native shrubs (sPN and sCh frut in Fig. 16) was remarkable. The bush in the foreground in Fig. 17.2 is Dubautia ciliolata. The taller individuals in the background are shrubby Metrosideros trees of about 2-3 m in height. Figure 18.1 shows an excavated main branch of an ash-buried Vaccinium reticulatum shrub that was not broken off the root. Several new branches sprouted at the new surface line from the main branch, while the branch itself developed a few lateral roots. A similar resprouting occurred at the new surface line on the main stem of the Metrosideros shrub shown in Fig. 18.2. Also, several lateral roots developed from the buried main stem in the new ash layer. These excavations show the development in year 4 (1963) after the disturbance.

Fig. 17.1. Segment of habitat 6 photographed in year 1 (1960). Here the pumice blanket was only 10-20 cm deep.

Fig. 17.2. The same habitat segment photographed in year 3 (1963).

Fig. 18.1. Excavated stem of recovered Vaccinium reticulatum shrub that was buried under 25-cm-deep ash in habitat 6. Photograph taken in year 4 (1963) after the ash fallout.

Fig. 18.2. Excavated stem of small Metrosideros polymorpha tree buried under 25-cm-deep ash in habitat 6, photographed in year 4 (1963).