Lake Fluctuations, Plant Productivity, and Long-Term Variability in High-Elevation Tropical Andean Ecosystems

CARILLA, J; GRAU, HR; PAOLINI, L; MORALES, MS

ARCTIC ANTARCTIC AND ALPINE RESEARCH

INST ARCTIC ALPINE RES

Lugar: Boulder, USA; Año: 2013 vol. 45 p. 179 - 189

1523-0430

Environmental trends and ecosystems´ ranges of variability are little known in tropical very high elevation Andean ecosystems (above 4400 masl). We combined satellite image analyses and dendrochronological methods to quantify assess changes in water balance and plant productivity of subtropical high-elevation Andean ecosystems in northern Argentina and southern Bolivia through assessments of lake level fluctuation combined with instrumental climatic records at lower elevation. To assess the relationships between water balance and two indices of plant productivity: tree ring width of the treelet Polylepis tarapacana and seasonal patterns of vegetation ?greenness? (EVI) derived from satellite images. Between 1985 and 2009, inter-annual lake fluctuations were positively correlated with interannual variations in regional precipitation and de Martonne?s aridity index, showing a decreasing trend in moisture availability during the analyzed period. Increases in lake size were positively correlated with radial growth of P. tarapacana, and with MODIS-derived annual indices of EVI (an index of vegetation ?greenness?) phenology between 2001 - 2010; thus indicating that water balance has a significant effect on ecosystem functioning related to regional scale atmospheric circulation. A long term tree ring chronology indicated that tree growth during the last 2-3recent decades waswere the ones with lower thangrowing of the last 150 years; and are were comparable to what growth patterns occurred between 1775 and 1825; thus suggesting if current climatic trends continue, long term ranges of variability in ecosystem functioning will be exceeded