Germination and growth of colonizing species in artificial gaps of different sizes in dipterocarp rain forest

Abstract

Population dynamics and height growth of colonizing seedlings were monitored for three years in newly created artificial gaps and beneath intact canopy in primary lowland rain forest in Sabah, Malaysia. The effects of gap size, soil surface conditions and competition from advance regeneration were assessed. Recruitment during the first two years was less than 100 seedlings m -2, or less than 5% of the estimated seed bank in the top 5 cm of the soil prior to disturbance. Overall, germination was not obviously affected by gap size, but was increased markedly by soil exposure or disturbance. The diversity of the colonizing vegetation at the end of two years appeared to be negatively related to gap size. Seedling mortality was less both at larger gap size and in the absence of competition from advance regeneration, whereas the opposite appeared true for seedling growth. The results indicate that gap size is unlikely to influence the composition of colonizing vegetation by controlling seed germination, but an effect operating through differential mortality cannot be discounted.