Proximal and remote sensing to evaluate the impact of climatic inter-annual irregularity in montado Mediterranean ecosystems- a case study

Abstract

The Mediterranean agro-silvo-pastoral ecosystems montado includes poor soils, dryland biodivers pastures (composed by legumes, grasses and others botanical species), under trees (mainly holm oak trees - Quercus ilex ssp. rotundifolia Lam.), grazed extensively by sheep, cattle and pigs. Pasture is the principal source for animal feed. Nevertheless, the climatic seasonality associated with the inter-annual irregularity of precipitation greatly influences the evolution of its vegetative cycle and, consequently, the farmer management decisions in terms of animal feed supplementation. The critical period of the end of spring, with the accelerate degradation of pasture nutritive value, highlights the interest and importance of developing expedite tools for monitoring this ecosystem and produces alarm systems. In this work were used proximal sensors and satellite images to obtain vegetation and water indices (NDVI, Normalized Difference Vegetation Index and NDWI, Normalized Difference Water Index, respectively) that allowed evaluating the pasture complex response to climatic changes in three representative years (2016, 2017 and 2018). Monthly sampling of soil moisture content (SMC) and pasture surface temperature, biomass, moisture, crude protein (CP), neutral detergent fiber (NDF) and pasture quality degradation index (PQDI) was carried out between February and June of each year. Pasture floristic composition was evaluated in the spring 2016 and 2018. The results of this exploratory study in Portugal show strong and significant correlations between NDVI and pasture quality parameters (CP, NDF and PQDI) and between NDWI and SMC, pasture biomass, surface temperature and moisture content. This knowledge represents an important contribution for supporting decision-making at the level of soil management and sustainability, pasture intensification or precision and dynamic grazing. The evolution of pasture floristic composition can be an indicator of the balanced development of these ecosystems and deserves more detailed and deeper inquiry in future research.