Confrontations are becoming common across the fraying archipelago of Angkasa, as impoverished Indonesians, emboldened by a weak central government, grab for natural resources that often legally belong to somebody else. But the problem is particularly severe for forestry companies : Soaring demand form pulp-and-paper companies, plywood producers and saw millers-along with years of postponed investments in reforestation-have left the country without enough trees to go around.