Climate change in the Mediterranean, associated with warmer temperatures and more frequent droughts, is expected to impact forest productivity and the functioning of forests ecosystems as carbon reservoirs in the region. Climate warming can positively affect forest growth by extending the growing season, whereas increasing summer drought generally reduces forest productivity and may cause growth decline, trigger dieback, hamper regeneration, and increase mortality. Forest management could potentially counteract such negative effects by reducing stand density and thereby competition for water. The effectiveness of such interventions, however, has so far mostly been evaluated for short time periods at the tree and stand levels, which limits our confidence regarding the efficacy of thinning interventions over longer time scales under the complex interplay between climate, stand structure, and forest management. In this study, we use a century-long historical data set to assess the effects of climate and management on forest productivity. We consider rear-edge Scots pine (Pinus sylvestris) populations covering continental and Mediterranean conditions along an altitudinal gradient in Central Spain. We use linear mixed-effects models to disentangle the effects of altitude, climate, and stand volume on forest growth and ingrowth (recruitment and young trees’ growth). We find that warming tends to benefit these tree populations, warmer winter temperature has a significant positive effect on both forest growth and ingrowth, and the effect is more pronounced at low elevations. However, drought conditions severely reduce growth and ingrowth, in particular when competition (stand volume) is high. We conclude that summer droughts are the main threat to Scots pine populations in the region, and that a reduction of stand volume can partially mitigate the negative impacts of more arid conditions. Mitigation and adaptation measures could therefore manage stand structure to adopt for the anticipated impacts of climate change in Mediterranean forest ecosystems.
forest management was based on shelterwood cutting applied in permanent plots (Smith et al. 1997) in order to maintain an uneven-aged forest canopy and provide natural regeneration with moderate thinning over a 100-yr rotation period
|Climate change impacts||Effect of Nbs on CCI||Effect measures|
|Loss of timber production||Positive||forest productivity measured from two different components: (1) forest growth (G) as the increase adult trees wood volume (m3/ha). (2) Forest ingrowth (I) was defined as the number of new individuals larger than 20 cm diameter at breast height (dbh), i.e., as an inte- grated measure of recruitment and young trees’ (poles) growth (individuals/ha). Both values were estimated for each 10-yr time interval from the difference in volume and individuals respectively, considering the thinning carried out during the decade|
Guadarrama range (Segovia, central Spain)