Vegetation phenology in the Argentinean Wet Chaco: Assessing seasonality and precipitation dependence through NDVI MODIS time series (2000–2018)

Abstract

Plant phenology, that is, the timing of plant growth and development, is sensitive to climate and land-use changes. Despite its importance in the context of global change, little is known about the plant phenology of subtropical regions. In the Argentinean Wet Chaco region, which is currently under high pressure due to land-use intensification, the phenology patterns of its natural land covers are remarkably understudied. This important aspect of vegetation functioning can be effectively monitored through indices based on satellite imagery, such as the Normalized Difference Vegetation Index (NDVI). Thus, in this work, we used the NDVI from MODIS imagery to analyse plant phenology in the Argentinean Wet Chaco and discuss its implications in the current context of global change. NDVI time series were analysed for the period 2000–2018 for the following plant categories: riparian forest, forest islet, dense and open palm savanna and flooding grassland. Their seasonality and precipitation marginal response (PMR) were also assessed. The riparian forest presented the highest NDVI annual mean values and lowest PMR, followed by the forest islet. The flooding grassland presented the highest seasonality and palm savannas the highest precipitation dependence, with even higher PMR values in drier years. Climate change models predict an increase in precipitation in the region. If this occurs, palm savannas and flooding grasslands could present a more stable phenology. This would imply better conditions for cattle grazing and would, thus, reinforce the current land-use pressure. On the contrary, this increase in precipitation would not have an impact over the photosynthetic activity of both types of forest, since our results suggest that this parameter is not limited by rainfall. In the current context of climate change and land-use intensification, the results obtained provide key knowledge for a better use, management and conservation of the environments of the Argentinean Wet Chaco. Abstract in Spanish is available with online material.