PARENT SESSION
Oral Session #5: Ecosystem processes: Decomposition and litter. Presiding: K. Lajtha.
Monday, August 6, 2001. 8:00 AM to 12:15 PM. Hall of Ideas E.
Litter nutrient dynamics in secondary dry tropical forests of the Southern Yucatan.
Read, Larissa1, Lawrence, Deborah 1, Foster, David2, 1 2
ABSTRACT- Nutrient and water availability are the main factors limiting primary productivity in the dry tropical forests of the Americas. How nutrient cycling changes following forest conversion may significantly impact the ability of forests to recover from human disturbance. To investigate such changes at a regional scale, we investigated litter nutrient dynamics along a seasonal, a successional, and a precipitation gradient in the Southern Yucatan Peninsula. Our goal was to examine changes in litter chemistry in secondary forests during succession and to characterize these dynamics over a regional precipitation gradient and a seasonal timescale. Litter was harvested monthly during 1999 from 28 secondary forests recovering from shifting cultivation of maize, plus 8 mature forests. As expected, litter P and N decline with forest age. Average P content of litter from the southern, wettest region is 0.83mgP/g, almost twice the P content in litter samples from the drier central and northern regions (0.42-0.45mgP/g, p<0.0001 ANOVA). Preliminary results indicate that litter N ranges from 1.1% to 1.7%, with higher values in the southern region. Preliminary values of litter C range from 40-44%, with little seasonal variation. However, minima in both P and N content from all regions are pronouncedly timed with peak litterfall, suggesting nutrient retranslocation during periods of stress. Our results suggest that persistent human disturbance in these forests has important effects on their nutrient cycling during recovery.
KEY WORDS: tropical forests, land-use change, nutrient dynamics