Abstract

VELASCO HERRERA, José Armando; FLORES GARNICA, José Germán; MARQUEZ-AZUA, Bertha  and  LOPEZ, Sergio. Homogeneous response areas for forest fuel sampling. Rev. mex. de cienc. forestales [online]. 2013, vol.4, n.15, pp.41-54. ISSN 2007-1132.

Dead forest fuels are assessed in situ, requiring sampling sites located in a systematic way, with a sampling intensity of 1-3% with respect to the whole area. Although this entails a large investment of financial, human and time resources, the accuracies obtained are still low. Therefore, we propose an alternative sampling strategy identifying areas with similar features known as homogeneous response areas (HRAs). These are the basis for the structuring of a stratified sampling design tending to reduce the variance within each HRA in order to increase the accuracy of the estimates. This work was carried out in the Selva El Ocote Biosphere Reserve, located in the state of Chiapas. 19 HRAs were defined based on ten different kinds of vegetation: rainfed annual crops, live oak groves, cultivated grasslands, human-induced grasslands, savannahs, tall/medium evergreen forests, tall/medium evergreen forests with secondary bushy and herbaceous vegetation, and low deciduous and sub-deciduous forests. Besides, three altitude intervals were considered: 180-633 m, 634-1 086 m, and 1 087-1 540 m. Each HRA comprises several zones. The largest HRA consists of tall/medium evergreen forests and is located between 634 and 1 086 m of altitude, with a surface of 38 808 ha; while the smallest is constituted by savannahs, at an altitude of 180 to 633 m and with a surface of 3.4 ha.

Keywords : Forest fuels; exposure; forest fires; remote sensing; Selva El Ocote Biosphere Reserve; GIS.