Graduation date: 1996

No description available.

Shifting cultivation is considered to be a key cause of deforestation in the tropics as agriculturalists transform the rain forest into cropland and later allow for its regeneration through fallowing. Forest fallows strongly influence the ecological and economic potential of shifting cultivation, yet, secondary forest management among shifting cultivators remains poorly understood. This study focuses on secondary forest management among peasant households in a land-abundant ejido, near the Calakmul Biosphere Reserve of Mexico. Data were gathered through in-depth household interviews and field visits with 44 households, accounting for more than 450 fields. Striking differences were found in fallowing practices in Nuevo Becal. The holding of secondary forest is related to access to male labour, wealth in land-assets, household age, and the holding of pasture. Fallow length at the plot level is associated with household age, land holding size and the manner in which land is acquired. Fallow periods tend to be longer for cycles begun from primary forest and appear to have become longer over time. This study demonstrates the importance of the microdynamics that influence differential land use decisions among households under apparently similar environmental and macroeconomic conditions.

No description available.

Wild plant resources are harvested and managed by people in a variety of land-uses but few studies examine the interactions of landscape dynamics and the use and availability of wild plant resources. I address this question using a case study of common property lands with a history of community forestry and traditional shifting cultivation. Specifically I ask: What is the perceived importance of plant resources obtained in agricultural and forest environments? Have forest and agricultural land-use/land covers changed? How do landscape changes, and in particular shorter fallow times, influence the availability and use of plant resources? / The perceived importance of wild plant resources was studied using free-listing and ranking exercises with focus groups of men and women. Remote sensing and interviews served to analyse landscape dynamics (1976-2000) and to identify local forest conservation regulations. The impact of shorter fallow times on the availability of forage and firewood in agricultural fields was assessed by sampling 26 fields derived from short to long fallows, while a household survey served to characterize patterns of firewood collection. / Men attributed highest importance to commercial forest products, while resources most valued by women were domestic resources obtained in a variety of environments. High rates of forest retention were observed; conservation was focused on forests with high densities of commercial products. The agricultural zones shifted from a mosaic of diverse successional stages to a homogeneous landscape dominated by younger fallows and shorter fallow periods; these changes led to reductions in the availability of firewood and some forage species. Firewood collection was related to accessibility; areas with the least amount of firewood available (short-fallow cycles and low forest cover) experienced the highest collection pressure. / The findings demonstrate that indigenous territories can be very dynamic, even when rates of forest conservation are high, and that changes in land-use and landscape structure have important implications for the availability and use of wild plant resources. A conceptual model linking landscape dynamics to wild plant use is proposed and the significance of the results for community-based conservation initiatives is discussed.