Growth phenology adjusts to seasonal changes in water availability in coexisting evergreen and deciduous mediterranean oaks

Different leaf(evergreen vs.deciduous habit)and xylem(diffuse-vs.ring-porous wood)traits represent contrasting strategies to face seasonal changes in water availability and temperature.However,how contrasting leaf and xylem habits of coexisting tree species affect stem wood formation and tree-ring development remains poorly understood.Here,we investigated the spatio-temporal patterns of wood formation in two deciduous oaks(Quercus faginea and Quercus petraea)and two evergreen oaks(Quercus ilex and Quercus suber)coexisting in seasonally dry Mediterranean forests along an aridity gradient in Spain.We hypothesized that growth responses to drought and intra-and inter-annual growth patterns would differ between functional groups.We simulated intra-and interannual growth using a modified version of the Vaganov-Shashkin(VS)process-based,growth model.The VS model simulations were used to estimate growth changes under a high emission scenario(RCP 8.5)for the current distribution of the study oak species and to forecast their future performance under warm(4.8℃)conditions in the Iberian Peninsula.Our simulations indicate that climate warming would induce a shortening of the ringgrowth season and a reduction of radial growth in evergreen and deciduous Mediterranean oaks,particularly in dry sites from southern and eastern Iberia currently occupied by Q.ilex and Q.faginea.Evergreen oaks may better recover after dry periods than deciduous oaks by resuming growth after the summer drought.Low soil water availability in spring would be more detrimental to growth of deciduous oaks.Process-based growth models should be refined and validated to better forecast changes in tree growth as a function of climate.

Twenty years of population dynamics in European beech-oak forest at their rear range margin anticipate changes in its structure and composition

There is an increasing interest in restoring degraded forests,which occupy half of the forest areas.Among the forms of restoration,passive restoration,which involves the elimination of degrading factors and the free evolution of natural dynamics by applying minimal or no management,is gaining attention.Natural dynamics is difficult to predict due to the influence of multiple interacting factors such as climatic and edaphic conditions,composition and abundance of species,and the successional character of these species.Here,we study the natural dynamics of a mixed forest located in central Spain,which maintained an open forest structure,due to intensive use,until grazing and cutting were banned in the 1960s.The most frequent woody species in this forest are Fagus sylvatica,Quercus petraea,Quercus pyrenaica,Ilex aquifolium,Sorbus aucuparia,Sorbus aria and Prunus avium,with contrasting shade and drought tolerance.These species are common in temperate European deciduous forest and are found here near their southern distribution limit,except for Q.pyrenaica.In order to analyze forest dynamics and composition,three inventories were carried out in 1994,2005 and 2015.Our results show that,despite the Mediterranean influence,the natural dynamics of this forest has been mainly determined by different levels of shade tolerance.After the abandonment of grazing and cutting,Q.pyrenaica expanded rapidly due to its lower shade tolerance,whereas after canopy closure and forest densification,shade-tolerant species gained ground,particularly F.sylvatica,despite its lower drought and late-frost tolerance.If the current dynamics continue,F.sylvatica will overtake the rest of the species,which will be relegated to sites with shallow soils and steep slopes.Simultaneously,all the multi-centennial beech trees,which are undergoing a rapid mortality and decline process,will disappear.

Early life investment in antlers and body growth reflects adult performance in roe deer population under supplementary feeding conditions

Recent research has challenged the idea that cervid antlers are such costly traits,supporting the assertion early-life antler investment is an honest signal of adult phenotypic quality.However,inferences were made based on antler measurements while growing(velvet)and thus,studies on fully-formed clean antlers are needed to avoid possible bias caused by the inter-individual variation in antler growth phenology.We studied a semi-captive population of European roe deer inhabiting a sub-Mediterranean area(Valsemana research station)and living under optimal conditions(ad libitum food supply and veterinary care).Based on repeated measurements taken from 146 individuals,we assessed whether allocation to secondary sexual traits during early life affected body mass or antler development during adulthood.Furthermore,we evaluated which body measurements better predicted future male quality.Additionally,using 488 individuals,we described age-class-specific variation in male body measurements and assessed the decline in antler size between adult and senescent stages(i.e.magnitude of senescence).Results agree with the assertion that there is no negative effect of a high investment in antler during early life on adult antler size or body mass,but we suggest the use of clean antlers as a more robust and reliable measure.The variables that better predicted body mass during adulthood were yearling body mass and body size at 6 months.Antler score between 10 and 18 months resulted in the best indicator of adult antler size.Finally,we support the idea that the magnitude of senescence in antler size is smaller in environments with higher resource availability during winter.

A Regulatory Module Controlling CA-Mediated Endosperm Cell Expansion Is Critical for Seed Germination in Arabidopsis

A key component of seed germination is the interplay of mechanical forces governing embryo growth and the surrounding restraining endosperm tissue.Endosperm cell separation is therefore thought to play a critical role in the control of this developmental transition.Here we demonstrate that in Arabidopsis thaliana seeds,endosperm cell expansion is a key component of germination.Endosperm cells expand to accommodate embryo growth prior to germination.We show that this is an actively regulated process supported by spatiotemporal control of the cell expansion gene EXPANSIN 2 (EXPA2).The NAC transcription factors NAC25 and NACIL were identified as upstream regulators of EXPA2 expression,gibbereliinmediated endosperm expansion,and seed germination.The DELLA protein RGL2 repressed activation of the EXPA2 promoter by NAC25/NACIL.Taken together,our findings uncover a key role of the GA/ DELLA-NAC25/NACIL-EXPA2 network in regulating endosperm cell expansion to control the seed-toseedling transition.