Trends and ENSO/AAO Driven Variability in NDVI Derived Productivity and Phenology alongside the Andes Mountains

Willem Van Leeuwen,Marcelo Miranda,Francisco Meza,Kyle Hartfield

doi:10.3390/rs5031177

Willem Van Leeuwen, Marcelo Miranda + Show 2 more

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https://doi.org/10.3390/rs5031177

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Abstract

Increasing water use and droughts, along with climate variability and land use change, have seriously altered vegetation growth patterns and ecosystem response in several regions alongside the Andes Mountains. Thirty years of the new generation biweekly normalized difference vegetation index (NDVI3g) time series data show significant land cover specific trends and variability in annual productivity and land surface phenological response. Productivity is represented by the growing season mean NDVI values (July to June). Arid and semi-arid and sub humid vegetation types (Atacama desert, Chaco and Patagonia) across Argentina, northern Chile, northwest Uruguay and southeast Bolivia show negative trends in productivity, while some temperate forest and agricultural areas in Chile and sub humid and humid areas in Brazil, Bolivia and Peru show positive trends in productivity. The start (SOS) and length (LOS) of the growing season results show large variability and regional hot spots where later SOS often coincides with reduced productivity. A longer growing season is generally found for some locations in the south of Chile (sub-antarctic forest) and Argentina (Patagonia steppe), while central Argentina (Pampa-mixed grasslands and agriculture) has a shorter LOS. Some of the areas have significant shifts in SOS and LOS of one to several months. The seasonal Multivariate ENSO Indicator (MEI) and the Antarctic Oscillation (AAO) index have a significant impact on vegetation productivity and phenology in southeastern and northeastern Argentina (Patagonia and Pampa), central and southern Chile (mixed shrubland, temperate and sub-antarctic forest), and Paraguay (Chaco).

Highlights

The Millennium Ecosystem Assessment [1] illustrates how South American ecosystem services are governed by high biodiversity, productive land cover, a variety of land use changes, and by desertification that is taking place in some areas
This research provided new baselines and characteristics of South America’s of productivity and phenological trends and the impact of climate indicators. Both positive and negative trends were observed for Chaco and Patagonia
Land use and climate variability and change were related to the observed productivity and phenology trends and pattern

Summary

Introduction

The Millennium Ecosystem Assessment [1] illustrates how South American ecosystem services are governed by high biodiversity, productive land cover, a variety of land use changes, and by desertification that is taking place in some areas. Vegetation productivity has been estimated by using NDVI time series data [2,3,4]. Long term NDVI times series have been used to analyze trends [5,6,7,8,9] and responses of vegetation to environmental variables such as climate [6,10,11,12,13]. The Intergovernmental Panel on Climate Change (IPCC) indicated that phenology, the timing of recurring biological events in response to the environment, is a relatively simple measure or proxy for climate change and variability [19]. Land surface phenology, is defined as “the seasonal pattern of variation in vegetated land surfaces observed from remote sensing” [20], is key to many earth surface processes and impacts carbon and hydrological processes as well as societies and economies [21]

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