Altitudinal treelines of the southern Andes near 40°S1

In the southern Andes near 40degreesS, altitudinal treelines are dominated by Nothofagus pumilio, a broadleaf deciduous angiosperm in the beech family (Fagaceae). Treeline elevations, ranging from 1100 to 1500 in a.s.l., are influenced by regional climate and volcanism. At the local scale, disturbance influences treeline elevation, ecotone length, and vegetation productivity. Decadal and interannual variation in climate related to El Nino-Southern Oscillation (ENSO) significantly affected radial growth of krummholz trees and seedling demography: however, climate-treeline relations were complex. Radial growth of krummholz trees and seedling demography responded differently to climate variation. These relations differed between climate regions and were unstable through time. We conclude that inter-annual variations in climate, such as those associated with ENSO, will be critical for successful reproduction and growth of Nothofagus pumilio at treeline in the Andes under the influence of global warming.