Abstract

VEGA-ARAYA, Mauricio  and  ALVARADO-BARRANTES, Ricardo. Time Series Analysis of Biophysical Variables in Four Ecoregions of Guanacaste, Costa Rica. Ciencias Ambientales [online]. 2019, vol.53, n.2, pp.60-96. ISSN 2215-3896.  http://dx.doi.org/10.15359/rca.53-2.4.

In this work, the analysis of the Leaf Area Index (LAI), the Fraction of Observed Photosinthetically Active Radiation (fPAR), and the Normalized Difference Vegetation Index (NDVI) is presented for four ecoregions in the Guanacaste province. These biophysical variables are key elements for understanding the phenological processes of the ecosystems under the climate change frame. Nowadays, the usage of data coming from remote sensors are the primary source for the estimation of environmental and vegetation variables at different levels (local, regional and global). The data come from the Moderate Resolution Imaging Spectroradiometer (MODIS). The analysis is based on the decomposition of each series in three components: stationarity, trend and residuals. The analysis was performed using the Earth Engine platform with a time resolution of 16 days and a pixel size of 500 m. Trends for fPAR, LAI and NDVI are very similar for three ecoregions, which suggests that it will not be necessary to perform independent analysis for these variables in the future. On the other hand, the ecoregions show internal homogeneity, but heterogeneity among them; however, seasonal moist forest and Pacific dry forest have very similar maximum and minimum values in their trends. Thus, it seems that the decomposition of the series in trend and stationarity brings good inside for monitoring changes, but also it is a valuable tool for relating biophysical variables and their productivity with other climatic elements, such as ENOS effect.

Keywords : Leaf Area Index; Fraction of Observed Photosynthetically Active Radiation; NDVI; bioclimate.

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