PARENT SESSION
Poster Session #19: Nutrient Cycling.
Tuesday, August 7, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
41
Landscape-level drivers of variation in plant nutrient status in disturbed dry tropical forests of Southern Yucatan.
Foster, David1, Lawrence, Deborah2, White, Kimberly2, 1 2
ABSTRACT- Our goal was to understand the controls on tissue nutrient quality in trees of a human-dominated landscape. We investigated the effect of forest age, cultivation history, and regional differences in soils and precipitation on leaf nitrogen and phosphorus. We studied 28 secondary forests (2-25 yrs since last cultivated) and 8 mature forests. The sample represents three distinct precipitation regimes (890, 1140, 1420 mm yr-1). In each stand, composite soil samples (0-15 cm deep) were collected, along with live leaf tissue of 5-6 species (matched across sites). Soil samples were analyzed for texture and nutrient content; leaves for N and P. Soil texture, and cations did not vary substantially by region, but soil organic matter (SOM) increased (10-9-13.3%) with precipitation. Preliminary data suggest that leaf [N] and [P] were greater in the wettest region. SOM increased significantly with age (p<0.002), but tissue N and P tended to decrease with age. Both SOM and leaf nutrient content declined with number of cycles of shifting cultivation (p<0.01) and cultivation history (p<0.01). Regional differences in leaf nutrient content appear linked to the effect of precipitation on SOM. Likewise, declines in SOM with increasing cultivation intensity limit the nutrient content of leaves. Declining tissue quality may be responsible for declining litter production with increasing cultivation intensity observed in related studies (Lawrence and Foster, 2001). Continued shifting cultivation may decrease forest productivity in the future.
KEY WORDS: none