The effect of small-scale logging on stand characteristics and soil biogeochemistry in mangrove forests of Timor Leste

The impact of small-scale cutting of mangroves by family groups was examined in three high-salinity forests on the dry tropical, north coast of Timor Leste. Before logging, these forests were characterized by moderately dense stands (3633-9610 stems ha(-1)) of Ceriops tagal, Rhizophora apiculata, Bruguiera gymnorrhiza, and Avicennia marina, with average basal areas of 13-34 m(2) ha(-1), total above-ground biomass of 51-221.5 t ha(-1), canopy cover of 61-73%, and leaf area index (LAI) of 4.9-5.4 m(2) leaf area m(-2) ground area. Approximately 1 year after the start of harvesting, these forests experienced a 30-50% decline in live stems and a 46-86% loss of above-ground biomass with more canopy gaps between less dense, smaller trees. There was some evidence of selectivity of trees 5-15 cm dbh in size, interpreted as a trade-off between cutting trees small enough for women and children to carry but large enough to warrant cost/benefit of selling for firewood. Concentrations of most particulate nutrients increased in surface soils in the harvested stands, reflecting bark, leaves, twigs, and small branches discarded on the forest floor. Interstitial concentrations of dissolved sulfide, metals, and ammonium also increased due to enhanced soil desiccation (evidenced by increased salinity) and decline in solute uptake and 0, translocation to live roots. Rates of anaerobic soil metabolism (sulfate reduction) declined after the onset of cutting, attributed to the decline in live roots and their metabolic activities. These cutting operations, although small-scale, are unsustainable as these forests are likely to be slow-growing in such highly saline soils. A community-based approach to conservation and sustainable management of the remaining mangrove forests of Timor Leste is recommended. (C) 2007 Elsevier B.V. All rights reserved.