ALBERT

Beschreibung: Aim: We investigate the effects of the environmental and geographical processes driving growth resilience and recovery in response to drought inMediterraneanPinus pinasterforests. We explicitly consider how intra-specific variability modulates growth resilience to drought. Location: western Mediterranean basin Methods: We analyzed tree rings froma large network of 48 forests (836 trees) encompassing wide ecological and climatic gradients and including six provenances. To characterize the major constraints of P. pinaster growth under extremely dry conditions, we simulated growth responses to temperature and soil moisture using a process-based growth model coupled with the quantification of climate-growth relationships.Then, we related growth-resilience indices to provenance and site variables considering different drought events. Results: P. pinaster displayed strong variation in growth resilience across its distributional range, but common patterns were found within each provenance. Post-drought resilience increased with elevation and drier conditions but decreased with spring precipitation. Trees from dry sites were less resistant to drought but recovered faster than trees from wet sites. Main conclusions: Resilience strategies differed among tree provenances: wet forests showed higher growth resistance to drought, while dry forests presentedfaster growthrecovery, suggesting different impacts of climate warming on forest productivity.We detected geographicallystructured resilience patterns corresponding to different provenances,confirming high intra-specific variability in response to drought. This information should be included in species distribution models to simulate forest responses toclimate warming and forecasted aridification.

Beschreibung: Coccoliths, calcite plates produced by the marine phytoplankton coccolithophores, have previously shown a large array of carbon and oxygen stable isotope fractionations (termed “vital effects”), correlated to cell size and hypothesized to reflect the varying importance of active carbon acquisition strategies. Culture studies show a reduced range of vital effects between large and small coccolithophores under high CO2, consistent with previous observations of a smaller range of interspecific vital effects in Paleocene coccoliths. We present new fossil data examining coccolithophore vital effects over three key Cenozoic intervals reflecting changing climate and atmospheric partial pressure of CO2 (pCO2). Oxygen and carbon stable isotopes of size-separated coccolith fractions dominated by different species from well preserved Paleocene-Eocene thermal maximum (PETM, ~56 Ma) samples show reduced interspecific differences within the greenhouse boundary conditions of the PETM. Conversely, isotope data from the Plio-Pleistocene transition (PPT; 3.5-2 Ma) and the last glacial maximum (LGM; ~22 ka) show persistent vital effects of ~2 per mil. PPT and LGM data show a clear positive trend between coccolith (cell) size and isotopic enrichment in coccolith carbonate, as seen in laboratory cultures. On geological timescales, the degree of expression of vital effects in coccoliths appears to be insensitive topCO2 changes over the range ~350 ppm (Pliocene) to ~180 ppm (LGM). The modern array of coccolith vital effects arose after the PETM but before the late Pliocene and may reflect the operation of more diverse carbon acquisition strategies in coccolithophores in response to decreasing Cenozoic pCO2.