Relations between the NDVI variability and the interannual growth in Anarthrophyllum rigidum in the shrubs steppes of Patagonia

SRUR, ANA M.; VILLALBA, RICARDO; BALDI, GERMÁN

Vancouver

Congreso; First American Dendrochronology Conference - AmeriDendro 2008; 2008

The Normalized Difference Vegetation Index (NDVI) is a linear indicator of absorbed photosynthetic active radiation, and therefore, it represents a measure of carbon flux across ecosystems. The annual bands of growth in woody species are a useful tool for monitoring environmental changes and ecosystem dynamics at different temporal and spatial scales. We combined temporal series of NDVI and growth rings to document changes in productivity and ecosystems in xeric regions of Patagonia. Our objective was to determine the temporal relationships between NDVI and the radial growth of Anarthrophyllum rigidum in the shrubby steppes across Patagonia. Anarthrophyllum rigidum (Mata guanaco o Pataguilla) is a shrub native of Patagonia. Cross-sections were collected at 16 sites located from southern Mendoza to Santa Cruz, Argentina. Across of the spatial distribution of Anarthrophyllum rigidum, there is a strong relationship between the annual integral of the NDVI and the total annual precipitation. The values of NDVI during de period 1982 to 1999 were provided by the program LechuSA (Land Ecosystem Change Utility for South America, http//lechusa.unsl.edu.ar). The growth rings reflect the CO2 uptake in the ecosystems during the season of growth (December to March); which is coincident with the seasonal peak of NDVI in the area. For the sampling sites in the southern range of the Anarthrophyllum rigidum distribution, the relationship between radial growth and NDVI also includes April and May suggesting a delay in the growth ring formation in the southern sites.