PARENT SESSION
Poster Session # 13: Biogeochemistry, Photosynthesis, and Respiration.
Tuesday, August 5 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Changes in soil phosphorus following shifting cultivation in the Yucatan Peninsula.
Diekmann, Lucy*,1, Lawrence, Deborah1, 1 University of Virginia, Charlottesville, VA, USA
ABSTRACT- Phosphorus is a limiting nutrient in the dry tropical forests of the Americas. Following forest conversion, phosphorus impoverishment is a leading cause of declining soil fertility. Typically reduced phosphorus availability results from the transformation of available to unavailable phosphorus rather than net losses from the system. To determine the cumulative effect of shifting cultivation on soil phosphorus dynamics in a repeatedly disturbed ecosystem, we studied 24 sites that represent a cultivation history gradient around El Refugio, an ejido in the southern Yucatan Peninsula. These sites ranged in age from recently abandoned agricultural fields to mature forest (undisturbed for >50 yrs.) and had undergone from 0-6 cultivation-fallow cycles. The cultivation history of each site was found through interviews with local farmers. Using a sequential chemical extraction, we determined the size and availability of soil phosphorus pools during shifting cultivation. Preliminary results in an ongoing study showed no significant difference in total phosphorus between stands that had undergone one or two cultivation cycles and were less than 6 yrs. old. However, the range of soil phosphorus in these stands (0.13-0.15 mg P/g) is only 69% of total phosphorus in mature forests. Our results suggest that repeated anthropogenic disturbance in these forests has a significant effect on soil phosphorus. Phosphorus transformations influence forest resilience following disturbance, making an understanding of soil phosphorus dynamics in a habitually disturbed ecosystem essential to developing sustainable agricultural and forestry practices in the dry tropics.
Key words: phosphorus, land-use change, tropical forests, soil