Stand biomass and tree mortality from permanent forest plots on Krakatau, Indonesia, 1989-1995

Forest closure on the three original Krakatau Islands (Panjang, Rakata, and Sertung) took place ca 1930, about 50 yr after the apparent sterilization of the islands due to volcanic eruptions. Two permanent forest plots were e stablished on each of these islands in 1989. A full enumeration of these pl ots, of two additional Rakata plots, and of two "mainland" plots from the U jung Kulon National Park, West Java, was undertaken in 1992. These data pro vide the first estimates of aboveground biomass from Krakatau. The values r eported for Krakatau are below the local West Javan figures, with considera ble variation occurring within the islands. In 1992, the fourth Krakatau is land, Anak Krakatau, began an eruption sequence which continued through the study period, depositing ash on the study sites of Panjang and Sertung. A further partial survey of these plots in 1994-1995 revealed a significant i ncrease in mortality since the volcanic activity recommenced, with an incre ase in deaths of larger stems. Although Rakata has not been influenced dire ctly by volcanism, three sites surveyed on Rakata in 1994-1995 have experie nced increased tree mortality, in two cases as a consequence of storm damag e and in particular, of lightning strikes. Stand dynamics on Krakatau thus appear to be strongly influenced by episodic environmental disturbance with varying degrees of dependence on the volcanic activity of Anak Krakatau.