Investigating the potential of Sentinel-2 configuration to predict the quality of Mediterranean permanent grasslands in open woodlands.

The assessment of pasture quality in permanent grasslands is essential for their conservation and management, as it can contribute to making real-time decisions for livestock management. In this study, we assessed the potential of Sentinel-2 configuration to predict forage quality in high diverse Mediterranean permanent grasslands of open woodlands. We evaluated the performance of Partial Least Squares Regression (PLS) models to predict crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and enzyme digestibility of organic matter (EDOM) by using three different reflectance datasets: (i) laboratory measurements of reflectance of dry and ground pasture samples re-sampled to Sentinel-2 configuration (Spec-lab) (ii) field in-situ measurements of grasslands canopy reflectance resampled to Sentinel-2 configuration (Spec-field); (iii) and Bottom Of Atmosphere Sentinel-2 imagery. For the three reflectance datasets, the models to predict CP content showed moderate performance and predictive ability. Mean R2test = 0.68 were obtained using Spec-lab data, mean R2test decreased by 0.11 with Spec-field and by 0.18 when Sentinel-2 reflectance was used. Statistics for NDF showed worse predictions than those obtained for CP: predictions produced with Spec-lab showed mean R2test = 0.64 and mean RPDtest = 1.73. The mean values of R2test = 0.50 and RPDtest = 1.54 using Sentinel-2 BOA reflectance were marginally better than the values obtained with Spec-field (mean R2test = 0.48, mean RPDtest = 1.43). For ADF and EDOM, only predictions made with Spec-lab produced acceptable results. Bands from the red-edge region, especially band 5, and the SWIR regions showed the highest contribution to estimating CP and NDF. Bands 2, blue and 4, red also seem to be important. The implementation of field spectroscopy in combination with Sentinel-2 imagery proved to be feasible to produce forage quality maps and to develop larger datasets. This study contributes to increasing knowledge of the potential and applicability of Sentinel-2 to predict the quality of Mediterranean permanent grasslands in open woodlands.

Spatio-temporal analysis of oak decline process in open woodlands: A case study in SW Spain.

This study aims to characterize at landscape level the spatio-temporal dynamics of a massive oak decline that is occurring in dehesas ecosystems. We are looking at possibilities of matching with Phytophthora disease behavior, a harmful disease detected in the studied area, in order to interpret its implications within the context of the disease management. Spatial locations of affected trees from 2001, 2009 and 2016 identified through photointerpretation were analyzed with the inhomogeneous Ripley's K-function to assess their spatial pattern. Multivariate Adaptive Regression Splines (MARS), a non-parametric data mining method, was used to investigate the influence of a range of landscape descriptors of different nature on the proneness to oak decline, using the location of affected trees in comparison with that of healthy spots (points randomly extracted from areas covered by healthy trees). Affected trees showed a strong clustering pattern that decreased over time. The reported spatial patterns align with the hypothesis of Phytophthora cinnamomi Rands. being the main cause of oak decline in Mediterranean forests. Location of affected trees detected in different years was found to be spatially related, suggesting the implication of a contagion process. MARS models from 2001, 2009 and 2016 reported Area Under the Curve (AUC) values of 0.707, 0.671 and 0.651, respectively. Slope was the most influential landscape descriptor across the three years, with distance to afforestations being the second for 2001 and 2009. Landscape descriptors linked to human factors and soil water content seem to influence oak decline caused by Phytophthora cinnamomi at landscape level. Afforestations carried out as part of the afforestation subsidy program promoted by the European Commission in 1992 could have acted as an initial source of Phytophthora cinnamomi infection. These findings together with the consideration of the spatial and temporal scale of the spreading are essential when planning the management of oak decline in open woodlands.