Monday, August 6, 2007

PS 3-44: Applying the Dahlem Desertification Paradigm (DDP) to assess key supporting ecosystem services in a coupled human-ecological system: A case study in La Amapola, Mexico

Mónica Ribeiro Palacios1, Elisabeth Huber-Sannwald1, Javier E. Garcia de Alba Verduzco1, Humberto Reyes Hernandez2, and James F. Reynolds3. (1) Instituto Potosino de Investigacion Cientifica y Tecnologica, (2) Universidad Autonoma de San Luis Potosi, (3) Duke University

Desertification is a critical environmental problem in global drylands. In México, livestock production, subsistence farming, and long periods of drought have led to severe land degradation in large areas of its drylands. This has provoked long-term declines in soil carbon stocks and fertility, which are considered to be key ecosystem services supporting both ecosystem functioning and sustainable livelihoods in coupled human-ecological systems. The DDP is an integrated framework to explore simultaneously the environmental, economic and social dimensions of desertification. We present a case study in the rural community La Amapola in the Central Plateau of México, where we analyzed the complex interactions and feedbacks between human activities (livestock production, rain-fed agriculture), topography and the spatial distribution of soil carbon and fertility by implementing the DDP. We identified key socioeconomic drivers for goat, corn and bean production; and using a landscape-scale sampling approach, we examined differences in soil organic carbon (C), total soil nitrogen (N) and organic matter (SOM) at five sites in three dominant land use types (rangeland, crop fields, oak-pine forest). The long-term grazing and cropping history is reflected in greatly reduced soil C and N stocks in rangelands and agricultural fields, which are over 60 % lower than in forests (P<0.0001). Crop fields in the valley bottom have greater C, N and SOM stocks than uphill rangelands (P<0.001). However, overriding differences in soil fertility among croplands are associated with land tenure policies, which allow only some households access to government subsidy programs (use of tractors and irrigation). Hence, certain management practices and preferences by some households to grow monocultures impacts soil C stocks and fertility. We propose options for adaptive carbon management as a long-term strategy for the restoration of key supporting ecosystem services in La Amapola.