Bryophytes in perennially moist forests of Papua New Guinea: ecological orientation and predictions of disturbance effects

Water relations of bryophytes must be understood along at least four dimensions: hydration/dehydration frequency; hydration duration; dehydration duration; degree of water loss. All these are biomass-dependent functions such that large colonies of bryophytes may maintain hydration longer than smaller colonies. The spread of a bryophyte colony allows lateral movement of capillary water; contiguous clones will thus allow lateral conduction of that water. In contrast, separated tufts or cushions may store water but will contribute very little to its transfer over the surface of the phorophyte.
Many of the tropical rainforests of New Guinea have a larger mass of epiphytic bryophytes than any temperate forest. The primary effect of disturbance in these forests is a reduction in bryomass, presumably due to desiccation because of increased insolation and wind movement. The reduction of bryomass will decrease water and mineral retention in the bryophyte clones; and the reduction in the size of those clones will reduce their contiguity and thus interfere with bryophyte-mediatcd water and mineral transfer. Disturbance may alter bryophyte species frequency but, under present agricultural and forestry practices in New Guinea, I have seen no evidence of significant loss of bryophyte species.