PARENT SESSION
Oral Session 2 / Sesion Orales 2: Production Systems / Sistemas de Produccion
Moderated by: Gross, Kay,
Thursday, January 12 / Jueves, 12 de Enero, 8:30 am - 12:30 pm, Salon Uxmal, Level 1, Holiday Inn
Is shifting cultivation in southern Mexico sustainable?
Lawrence, Deborah*,1, Eaton, James1, Read, Larissa2, 1 University of Virginia, Charlottesville, VA, USA2 Intermountain Support Office, National Park Service, Lakewood, CO, USA
ABSTRACT- Within the last century, and increasing in the last 30 years, people from other parts of Mexico have migrated to the dry forests of the southern Yucatan peninsula region, seeking land and opportunity. Most rely on shifting cultivation of corn (milpa) for subsistence, with little or no chemical inputs. How does the cycling of carbon and nutrients change with shifting cultivation? As currently practiced, can the system sustain productivity? Using secondary forest biomass and carbon stocks as a proxy for productive potential, we examined the effect of repeated shifting cultivation on productivity. We studied 53 plots along gradients of forest age, cultivation history, and annual precipitation in Campeche and Quintana Roo, Mexico. Live aboveground biomass, litterfall, coarse woody debris, fine woody debris, forest floor litter, and soils were sampled. Carbon stocks in all forest components, except fine woody debris, were significantly affected by forest age. Even after 25 years of fallow (far longer than is typical), soil carbon was only 90% of that in montanas; aboveground live biomass was only 62% of that in montanas. In addition, carbon in live aboveground biomass and coarse woody debris declined 38% and 85%, respectively, from the first to the third cycle of shifting cultivation. Lower inputs of organic matter to soils may contribute to an observed decline in available soil phosphorus over multiple cycles. Litterfall nutrient dynamics suggest that phosphorus is limiting when primary limitation by water is alleviated. Thus, declining phosphorus may feedback to reduce future agricultural and forest productivity.
SPANISH ABSTRACT- .