Seasonal dynamics of vegetation indices as a criterion for grouping grassland typologies

Andreise Moreira,Carolina Bremm,Tatiana Mora Kuplich,Denise Cybis Fontana

doi:10.1590/1678-992x-2017-0173

Abstract

This study aimed to characterize the average seasonal pattern of the vegetation in southern grassland in Brazil, and the variability found in the time series of vegetation indices. It also sought to identify similarities in the seasonal pattern of different grassland typologies. Moderate Resolution Imaging Spectroradiometer (MODIS), Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) images from Feb to Dec, 2000 to 2014 were analyzed for ten regions. The grassland typologies studied showed EVI and NDVI profiles consistent with the seasonal dynamics of grassland vegetation under the influence of a subtropical climate, with highest values in the indices during the warm seasons of the year (spring and summer) and lowest in the colder seasons (autumn and winter). Considering the values of EVI and NDVI, grassland typologies were allocated to four groups with similar temporal profiles. Among the groups formed from the EVI index it is possible to identify differences between grassland typologies during the autumn and winter, while the NDVI showed differences only in winter as compared to the other seasons.

Highlights

Characterized by the occurrence of repetitive biological events and its relationship to variations in abiotic and biotic environments (Lieth, 1974; Vanschaik et al, 1993), phenology is used as an ecological parameter for monitoring the growing season of plants and reflects the relationship of plant growth to the environment (Zhang et al, 2003)
This study aimed to characterize the average seasonal pattern of the vegetation in southern grassland in Brazil, and the variability found in the time series of vegetation indices
The monitoring of the season, which includes the periods of growth and senescence, can be performed through temporal series of spectral vegetation indices obtained by orbital sensors, such as the EVI (Enhanced Vegetation Index) and the NDVI (Normalized Difference Vegetation Index) Moderate Resolution Imaging Spectroradiometer (MODIS) (Huete et al, 2002; Zhang et al, 2003; Soudani et al, 2012)

Summary

Introduction

Characterized by the occurrence of repetitive biological events and its relationship to variations in abiotic and biotic environments (Lieth, 1974; Vanschaik et al, 1993), phenology is used as an ecological parameter for monitoring the growing season (seasonal) of plants and reflects the relationship of plant growth to the environment (Zhang et al, 2003). Grassland vegetation consists of dominant ecosystems in many countries and it is paramount to preserve water resources and carbon accumulation in the soil. It serves as fodder source for pastoral activity and offers scenic attractions with major tourism potential, among other environmental services (Pillar et al, 2012). It is estimated that 54 % of the original grassland vegetation has been converted to agriculture, forestry, or urbanization, and only 0.33 % of the grasslands are currently protected in conservation units (Overbeck et al, 2007; Overbeck et al, 2013)

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