Human well-being depends on forest ecosystem services (ES), yet these benefits are increasingly threatened in Mediterranean regions by climate change and land-use pressures. In Portugal, forests cover about 36% of the mainland, yet ES assessments are fragmented across individual services and land-use types. This study develops an ES assessment approach based on the CICES framework to define ES at the management-unit scale, establishing a baseline for a 582 ha landscape in the Middle Tagus region. The study area represents a Mediterranean forest management area, dominated by eucalyptus (65%), cork oak (9%), stone pine (4%), maritime pine (3%), and a riparian forest of alders and willows (2%) classified as high conservation value. The region has a sub-humid mesothermal climate with severe summer water deficits. Five CICES-based indicators were selected: wood production, carbon (C) stock, water regulation, water quality, and biodiversity maintenance.

Field campaigns in 2024/2025 combined forest inventory, soil sampling for C assessment, eDNA-based biodiversity analysis, and hydrological monitoring. Forest inventories used National Forest Inventory allometric equations to estimate biomass in plots for major land uses. Litter and soil sampling (0–30 cm) evaluated organic C stocks, eDNA samples from air, vegetation, and water were collected and analyzed. Water monitoring was conducted through a hydrometric station located at the catchment outlet and with monthly water quality sampling.

Results show that managed forests are highly productive and significant C reservoirs. Regarding provisioning services, mean annual increment of even-aged forests ranged from 0.6 m³ ha⁻¹year⁻¹ (cork oak) to 14.5 m³ ha⁻¹ year⁻¹ (first-rotation eucalyptus) and uneven-aged cork oak stands had an annual increment of 0.6 m³ ha⁻¹year⁻¹. Considering regulatory ecosystem services, aboveground and belowground C stocks in biomass reached 117 t. ha⁻¹ in eucalyptus, and C storage varied from 5 to 28 t.ha⁻¹ over five years across land uses. Soil organic C averaged 35 ± 12 t.ha⁻¹.

The biodiversity assessment revealed a highly diverse community of over 630 taxa, dominated by invertebrates (85%). Riparian area was a biodiversity hotspot (262 taxa, 163 unique), while stone pine (62 unique taxa) and cork oak (47 unique taxa) also contributed. Notably, plantation stands shared substantial biodiversity with native systems, and eucalyptus areas supported relevant proportions of pollinator insects, suggesting that production cycles do not necessarily hinder ecological richness.

These results suggest that managed production forests, mainly if management is made at landscape level, can simultaneously deliver high productivity, significant C storage, and substantial biodiversity, challenging conventional trade-offs between provisioning and regulating services. The proposed framework provides a practical basis for integrating ES into forest management. However, high costs and technical complexity of baseline assessments remain a barrier to adoption, limiting access to C markets and PES schemes. This highlights the need for scalable, cost-efficient monitoring solutions.

Acknowledgments: This study was funded under the Mobilizing Agenda “TransForm – Digital transformation of the forest sector towards a resilient and low-carbon economy,” supported by the PRR (Recovery and Resilience Plan) and the European Union’s NextGenerationEU funds.