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 R²_test = 0.68 were obtained using Spec-lab data, mean R²_test 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 R²_test = 0.64 and mean RPD_test = 1.73. The mean values of R²_test = 0.50 and RPD_test = 1.54 using Sentinel-2 BOA reflectance were marginally better than the values obtained with Spec-field (mean R²_test = 0.48, mean RPD_test = 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.

Land use change (LUC) is identified as one of the main drivers of soil erosion in the Mediterranean. However, very little information exists regarding the relationship between land use and erosion over longer time periods and on regional scales. We quantified the LUC in Southern Spain between 1956 and 2018, examining its effect on soil erosion and assessing the mitigation role of the permanent grassland (PG). The land use influence on erosion is represented by the RUSLE's C-factor, which was modelled using the Monte Carlo Method (MCM) based on historical LUC. Moreover, future LUC scenarios by 2038 were developed by binary logistic model (scFS) and by a complete conversion of PG to cropland (scPC), permanent crop (scPP) and forest and natural (scFP). Historically, Southern Spain has experienced an impressive intensification of its agricultural system. While soil loss variation is noted within the classes, no big variation is observed in cumulative erosion on a regional scale. The underlying reasons for this resilience are multifold, but mainly attributed to the fact that a small fraction of the total surface (20%), dominates total erosion (67%). The C-factor decrease in this area displays a LUC towards forest and natural area, suggesting an agriculture abandonment. On the other hand, the agricultural intensification that has taken place in the remainder of the area, contributes much less to overall soil erosion. Future LUC scenarios illustrate the importance of PG for erosion mitigation. scFS scenario does not project major changes. However, scCP and scPP, show an abrupt increase in regional erosion by 13% and 14%, while scFP shows a negligible reduction of erosion close to 0%. This allows to quantify the erosion mitigation offered by maintaining the PG and should be taken into account for future agricultural policy.

Sustainability and functioning of silvopastoral ecosystems are being threatened by the forecasted warmer and drier environments in the Mediterranean region. Scattered trees of these ecosystems could potentially mitigate the impact of climate change on herbaceous plant community but this issue has not yet tested experimentally. We carried out a field manipulative experiment of increased temperature (+2-3 °C) using Open Top Chambers and rainfall reduction (30%) through rain-exclusion shelters to evaluate how net primary productivity and digestibility respond to climate change over three consecutive years, and to test whether scattered trees could buffer the effects of higher aridity in Mediterranean dehesas. First, we observed that herbaceous communities located beneath tree canopy were less productive (351 g/m²) than in open grassland (493 g/m²) but had a higher digestibility (44% and 41%, respectively), likely promoted by tree shade and the higher soil fertility of this habitat. Second, both habitats responded similarly to climate change in terms of net primary productivity, with a 33% increase under warming and a 13% decrease under reduced rainfall. In contrast, biomass digestibility decreased under increased temperatures (-7.5%), since warming enhanced the fiber and lignin content and decreased the crude protein content of aerial biomass. This warming-induced effect on biomass digestibility only occurred in open grasslands, suggesting a buffering role of trees in mitigating the impact of climate change. Third, warming did not only affect these ecosystem processes in a direct way but also indirectly via changes in plant functional composition. Our findings suggest that climate change will alter both the quantity and quality of pasture production, with expected warmer conditions increasing net primary productivity but at the expense of reducing digestibility. This negative effect of warming on digestibility might be mitigated by scattered trees, highlighting the importance of implementing strategies and suitable management to control tree density in these ecosystems.

This study presents an evaluation of soil organic carbon (SOC) and stock (SOC_stock) for the whole rooting depth (60 cm), spaced 55 months in two adjacent olive orchards with similar conditions but different tree densities: (i) intensive, planted in 1996 at 310 tree ha⁻¹; (ii) superintensive, planted in 2000 at 1850 tree ha⁻¹. This was carried out to test the hypothesis that olive orchards at different plant densities will have different rates of accumulation of SOC in the whole soil rooting depth. SOC increased significantly in the superintensive orchard during the 55-month period, from 1.1 to 1.6% in the lane area, and from 1.2 to 1.7% in the tree area (average 0–60 cm), with a significant increase in SOC_stock from 4.7 to 6.1 kg m⁻². In the intensive orchard, there was not a significant increase in SOC_stock in 0–60 cm, average of 4.06 and 4.16 kg m⁻² in 2013 and 2018, respectively. Results indicate a potential for a significant increase in SOC and SOC_stock in olive orchards at higher tree densities when combined with temporary cover crops and mulch of chopped pruning residues. The increase is associated with an increase in SOC, mainly at a 0–15 cm depth. Results also point to the need for improve our monitoring capabilities to detect moderate increases in SOC.

Incorporating trees into agricultural systems, including grasslands, increases the soil organic carbon sequestration and contributes to climate change mitigation. Site preparation for tree establishment is a common practice that can involve a variety of techniques and agricultural implements such as subsoiling. This study aimed to evaluate the long-term effects of subsoiling on soil organic carbon (SOC) concentrations and stocks in a Mediterranean grassland afforested with holm oaks 22 years ago and now converted into a Dehesa agroforestry system. The study was conducted in a dehesa farm in Southwest Spain. Soil samples were taken at six depths under 10 tree canopies within and outside the original subsoiling line. Subsoiling significantly decreased SOC concentration. Mean SOC concentration in the first 20 cm was 30% lower at the subsoiling line. SOC stocks for the first 60 cm were 2660 g m⁻² within the subsoiling line and 4320 g m⁻² outside the line. There was a clear reduction in SOC concentration and stock with increasing depth. Root abundance and deeper rooting increased with subsoiling but did not translate into sufficient carbon accumulation in the soil, which is moderate even after 22 years. This study reveals that, in the long term, there is a trade-off in CO₂ sequestration between tree planting and soil subsoiling, highlighting the need for further research into the potential benefits and detriments of subsoiling.