Studies on early recovering phases of canopy gaps created by a 1987 typhoon in the Tatera Forest Reserve, Tsushima.

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Tatera Forest Reserve supports the primeval evergreen broad-leaved forest from low (ca. 120 m) to high elevations (560 m). The present project consists of six aspects : 1) tree population (dbh>5cm) census in a 4 ha permanent quadrat of low elevbation Castanopsis/Distylium forest, 2) the same in a belt-transect from low- to high-elevation Quercus acuta forest, 3) gradient analysis of phytocoenose over the elevation gradient, 4) vegetation study in canopy gaps, 5) bryophyte study in the gaps, 6) growth analysis of seedlings and saplings found in canopy gaps. The results obtained were as follows. 1) The size of canopy gaps ranges 5-20 m in diameter, found mostly in low-elevation Castanopsis/Distylium forests. The gaps occupy 17.1% of the low-elevation forest tract. 2) There are three types in dbh distributions : bimodal type (e. g. Castanopsis cuspidata), reversed-J type (Distylium racemosum, Cleyera japonica), and normal-curve type (Quercus salicina). The distribution of all tree populations is a reversed-J type. 3) Plant distributions in tree, shrub and herbaceous populations change rather abruptly around the 350-400 m elevation belt, while species density per 100 m^2 does not change and species diversity indices decrease gradually along the same elevation gradient. 4) Indicators of canopy gaps are (in order of occurrence frequency) Idesia polycarps, Mallotus japonicus, Actinidia arguta, Zanthoxylum ailanthoides, Rhus succedanea, Broussonetia papyrifera, and Berchemia racemosa var. magna. 5) Bryophytic indicators of gaps are Leucobryum juniperoideum, Syrrhopdon japonicus, Neckeropsis obtusata, Fauriella tenuis, and Eurhynchium hians. 6) Plants of high growth-rate are (in order from high to low) Elaeagnus glabra, Michelia compressor, Zanthoxylum ailanthoides, Broussonetia papyrifera, and Symplocos lucida.