Soil degradation in the tropical forests of the Dominican Republicʹs Pedernales province in relation to heavy metal contents

Two of the National Parks of the only Biosphere Reserve in the Caribbean Islands, the Jaragua–Bahoruco–Enriquillo reserve, occur mostly within the Pedernales province (Dominican Republic). In these National Parks, Jaragua and Bahoruco, almost every tropical forest ecosystem is represented, as are the land uses most common to the Dominican Republic. Despite soil being a key natural resource that needs to be considered in any sustainable development programme, the literature contains very little information on the soils of this region. In this study, we analysed 41 topsoil samples representing the main forest types and land uses of the province. The factors examined were fertility (OM, N, P, K) and heavy metal contents (Cu, Cr, Pb, Cd, Ni, Zn). Mean OM, N and total and available metal levels were almost invariably higher in the natural forest soils compared to those given over to human activities, especially cultivated soils. This difference suggests the uptake of metals by the crops and, to a lesser extent, by animals feeding on crop remains and grassland plants. This hypothesis is supported by high total and available metal contents, especially of Zn, Cu, Pb and, in smaller measure, of Cr recorded in the solid waste landfill of the city of Pedernales. It appears that the cutting down and burning practices of a nomad type of cultivation, as well as the pressures of intensive agriculture and livestock rearing have resulted in heavy metals bound to the soilʹs OM. We propose this is an important point to consider for the management of these lands.