Detecting tropical dry forest succession in a shifting cultivation mosaic of the Yucatan Peninsula, Mexico

摘要

The detection of secondary growth stages is fundamental to understanding the dynamics of forest loss and recovery at broad geographic scales. This study combines three remote-sensing techniques: vegetation indices, principal components analysis, and texture analysis, to distinguish forest successional stage and forest fallow length in a landscape of smallholder shifting cultivation (milpa) in the Central Yucatan Peninsula. The analysis compares two 25 km2 study sites, differing by dominant land-cover class: (1) crops and (2) early to mid-late successional forest intermixed with less intensive, smallholder cultivated crops. Two vegetation indices were compared. NDVI provided a higher accuracy (83%) for distinguishing forest succession than the Boyd ratio (67%). Change trajectories from 1988 to 2005 show a distinct difference in study site land area converted from early successional forest to crops vs. mid-late successional forest to crops, suggesting that fallow periods are longer in the forest-dominated study site. The observed spatio-temporal variation in land-cover conversion in the milpa landscape, particularly forest fallow duration and total forest cover, deserves further investigation regarding the drivers of change in forest cover and shifting cultivation practices.