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.

Decomposition along a precipitation gradient in Patagonia: species-rainfall interactions.

Austin, Amy¹, Sala, Osvaldo¹, ¹

ABSTRACT- We conducted a decomposition experiment with reciprocal placement of plant litter in four sites along an IGBP precipitation gradient ranging from 170 mm to 800 mm mean annual precipitation (MAP) in the Patagonian region of temperate Argentina. Over a distance of less than 40 kilometers moving east to west, vegetation shifts from a shrub-grass steppe to a closed-canopy southern beech forest. We collected newly senesced litter in fall (April-May) and placed litter of dominant species from each site in decomposition bags at all sites in Patagonia in early spring (October) of the following year. In addition, all litter types of both leaf and structural material of dominant species were placed in an independent mesic site. Precipitation of litter origin was positively related to decomposition for leaf litter (k=0.004*MAP-0.1593, r²= 0.77) and negatively correlated to decomposition rates for structural material (k=0.7561-0.0008*MAP, r²=0.90). After two years in Patagonia, there was not a systematic effect of rainfall on litter decomposition, with patterns of mass loss varying depending on the species. Moreover, for some litter types, there was site specificity of decomposition, where litter in its site of origin decomposed faster independent of climatic effects. Factors such as radiation interception or microbial community affinity for particular litter quality may play a role in addition to climate in determining decomposition rates in these water-limited ecosystems.

KEY WORDS: decomposition, Patagonia, precipitation gradient, species characteristics