Managing forests for resilience under increasing aridity: the case of Iberian dry-edge pine forests

Abstract

Abstract Context. Mediterranean dry-edge pine forests maintain key ecosystem functions and supply services but are jeopardized by climate change. In the past, forest management has successfully balanced these demands but resilience under increasing aridity remains uncertain. Objectives. To assess landscape forest resilience under increasing aridity and three policy-management scenarios implying tradeoffs in ecosystem services supply: i) “business as usual”, based on the current harvesting regime; ii) "conservation", aiming to preserve forest stock; and iii) "productivity" oriented to yield maintenance. Methods. The study site is part of a large-homogeneous pine-covered landscape covering sandy flatlands in Central Spain. We parameterized and tested an analytical size-structured forest dynamics model with last century historical management records. Results. Management regimes shaped forest landscape structure: conservation-oriented management resulted in more developed forests with larger trees and a heterogeneous landscape structure, while yield-oriented management resulted in smaller, structurally more homogeneous forests. Under “business as usual scenario", both forest stock and yield decreased with aridity, indicating that current management is not sustainable in the long term. Forest stock preservation required an increase in tree harvestable size and a reduction of wood extraction. Yield maintenance required a drastic decrease of tree harvestable size and an increase in harvest rates, but it was unsustainable at high aridity levels. Conclusions. Forest and landscape structure play a key role in reducing dry-edge forest vulnerability in response to increasing aridity. Adaptive management can play a key role in preventing the forests from crossing a tipping point over a degraded alternate state and ensuring long-term ecosystem service supply.