Suchergebnisse

1. Climate warming increases vulnerability to drought in Mediterranean water-limited forests. However, we still lack knowledge of the long-term physiological responses of coexisting pine species in these forests regarding their ability to cope with warming-induced drought stress. 2. We investigated spatiotemporal patterns of tree performance for five isohydric pines with partially overlapping ecological niches in the eastern Iberian Peninsula along an altitudinal gradient: Pinus halepensis = Pinus pinaster ≤ Pinus nigra ≤ Pinus sylvestris ≤ Pinus uncinata. 3. Using indexed tree-ring widths (TRWi), we assessed the changes in the temporal coherence of radial growth (growth synchrony, âC) over the period 1902-2011 across three elevation belts: low ≈1100 m; mid = 1615 m; high = 2020 m. We also examined by mixed modelling whether TRWi showed an increased coupling with leaf-level gas exchange (inferred from indexed carbon isotope discrimination, Δ13Ci) by enhanced stomatal regulation in response to an amplified regional drought stress. 4. Increasingly negative annual water balances (decrease in annual precipitation minus evapotranspiration = −4·8 mm year−1; 1970-2011) prompted more synchronous growth of coexisting pines between low- and mid-elevation belts, with âC rising from 0·25 ± 0·04 (1902-1951) to 0·62 ± 0·05 (1962-2011). This effect was coupled with tighter stomatal regulation at mid-elevation as indicated by high correlations between TRWi and Δ13Ci (>0·60 from the mid-1970s onwards) which resembled those found at low elevation. Simultaneously, TRWi vs. Δ13Ci uncoupling occurred at the high-elevation belt across species. 5.Weaker growth-climate relationships as elevation increased highlighted the major role of the altitude-dependent thermal gradient in growth responsiveness to drought; however, an intensified Δ13Ci response to spring water availability across elevation belts observed from mid-1970s onwards suggested regional shifts in tree physiological activity linked to earlier seasonal drought impacts. Warming-induced drought stress is spreading to higher altitudes in Iberian pinewoods as multispecies growth is linked to progressively tighter stomatal control of water losses reflected in wood Δ13C. ; T.A.S. and J.P.F acknowledge ERANET-Mundus (European Commission, Grant agreement 20112573) and the Ramón y Cajal program (RYC-2008-02050) respectively. A.A.K. benefitted from a visiting grant (University of Lleida). This study was supported by projects AGL2015-68274-C3-3-R (MINECO/FEDER) and 2014 SGR1141 (Catalan Government). We acknowledge P. Sopeña and M.J. Pau for technical assistance and G. Sangüesa-Barreda for field sampling.

Fungi provide important forest ecosystem services worldwide. In Mediterranean pine forests, predicted warmer and drier conditions could lead to a decline in mushroom yields. Climate is a key factor regulating both tree growth and fungal yields, particularly in drought-prone Mediterranean ecosystems. However, the responses of forest growth and mushroom production to climate depend on the differences among tree and fungal species and functional groups (e.g., mycorrhizal vs. saprotrophic), forest types, as well as depending on site conditions. Here we investigate how climatic conditions drive seasonal wood formation (earlywood −EW− and latewood −LW− production) and mycorrhizal mushroom production, to disentangle if growth and fungal yields are related. This assessment was done in Mediterranean forests dominated by four pine species in two areas located in Catalonia (NE Spain) representing mesic and xeric conditions and encompassing wide ecological gradients. The data consisted of 7-year to 13-year long inventories of mushroom production. EW production was favoured by cold and wet climate conditions during the previous fall and winter, and during the current spring and summer. LW production was enhanced by warm and humid conditions from spring to early fall. Mushroom yield was improved by wet late-summer and fall conditions, mainly in the most xeric area. This study confirms the ample differences found in tree growth and fungal production along ecological and climatic gradients. Clear relationships between mycorrhizal fungal yields and tree growth were mostly observed in specific sites characterized by severe summer drought. Specifically, latewood production seems to be the tree-ring variable most tightly linked to mycorrhizal fungal yield in drought-prone areas. ; This study was partially funded by the research projects AGL2012-40035-C03-01 and AGL2015-66001-C3-1-R (Ministerio de Economía y Competitividad of Spain, Secretaría de Estado de Investigación, Desarrollo e Innovación), by the European project "StarTree—Multipurpose trees and non-wood forest products: a challenge and opportunity" under grant agreement No. 311919. Irantzu Primicia work was supported by a STSM Grant from the COST Action FP1203 (European Non-Wood Forest Products). Sergio de Miguel's work was supported by the European Union's Horizon 2020 research and innovation programme within the framework of the MultiFUNGtionality Marie Skłodowska-Curie Individual Fellowship (IF-EF) under grant agreement No 655815.

The Périgord black truffle is an exclusive culinary delicacy, but its Mediterranean harvests have declined, despite cultivation efforts since the 1970s. The role of long-term irrigation, symbiotic fungus-host interaction, and microbial belowground progression remain poorly understood, because generally too short experimental settings miss the necessary degree of real world complexity and reliable information from truffle orchards is limited. Here, we conduct the first dendrochronological and wood anatomical assessment of 295 holm oaks, which have been growing under different irrigation intensities in the world's largest truffle orchard in Spain. The relationships between different climatic variables (monthly temperature means and precipitation totals) and dendro-parameters (ring width, vessel count and vessel size) of the oak hosts are utilized to disentangle direct and indirect drivers of truffle fruit body production. Irrigation at medium - instead of high - intensity is most beneficial for oak growth. Non-irrigated trees reveal overall lower stem increments. Warmer temperatures from February to April and wetter conditions from May to July enhance host vitality and possibly also its interplay with fungi symbionts via increased fine root production and mycorrhizal colonization. Adequately irrigated Mediterranean orchards may counteract some of the drought-induced natural truffle decline, and help stabilizing rural tourism, regional agriculture and global markets. ; Supported by the WSL-internal DITREC project, the Ernst Göhner Foundation, the ClimFun project of the Norwegian RC (No. 225043), the project AGL2012-40035-C03 (Government of Spain), the project Micosylva+ (Interreg IVB SUDOE SOE3/P2/E533), the Government of Castilla y León, ARAID, the project Xilva (CGL2011-26654, Economy and Competitiveness Ministry), as well as the Operational Program of Education for Competitiveness of Ministry of Education, Youth and Sports of the Czech Republic (No. CZ.1.07/2.3.00/20.0248).