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Resin extraction from Pinus pinaster (maritime pine) trees was an important economic activity for most of the 20th century in Mediterranean forests, until the decrease in resin prices that led to their abandonment in the 1960s-1970s. Reduced tree growth is often observed after long periods of resin tapping, but it is unknown how these formerly tapped stands respond to recent climate warming and aridification. We sampled three historically tapped maritime pine stands in Teruel, eastern Spain, to understand differential growth and responses to climate in resin tapped and non-tapped trees. Using dendrochronological methods, we compared tree growth trends and responses to climate in tapped and non-tapped trees. Overall, tree growth was higher in resin tapped trees than in non-tapped trees, which were generally younger. However, tree growth decreased over time, increasing the negative effects of late spring temperatures, summer drought and reduced summer precipitation, with increased sensitivity to drought in tapped than non-tapped trees. Among tapped trees, those with larger wound area grew more than those less tapped, and were more sensitive to drought, particularly after the 80 s. Our results suggest that the legacy effects of previous management can constrain tree responses to climate change by increasing the sensitivity of tree growth to drought.

IntroductionPlantations located outside the species distribution area represent natural experiments to assess tree tolerance to climate variability. Climate change amplifies warming-related drought stress but also leads to more climate extremes. MethodsWe studied plantations of the European larch (Larix decidua), a conifer native to central and eastern Europe, in northern Spain. We used climate, drought and tree-ring data from four larch plantations including wet (Valgañón, site V; Santurde, site S), intermediate (Ribavellosa, site R) and dry (Santa Marina, site M) sites. We aimed to benchmark the larch tolerance to climate and drought stress by analysing the relationships between radial growth increment (hereafter growth), climate data (temperature, precipitation, radiation) and a drought index. ResultsBasal area increment (BAI) was the lowest in the driest site M (5.2 cm2 yr-1; period 1988–2022), followed by site R (7.5 cm2 yr-1), with the youngest and oldest and trees being planted in M (35 years) and R (150 years) sites. BAI peaked in the wettest sites (V; 10.4 cm2 yr-1; S, 10.8 cm2 yr-1). We detected a sharp BAI reduction (30% of the regional mean) in 2001 when springto-summer conditions were very dry. In the wettest V and S sites, larch growth positively responded to current March and June-July radiation, but negatively to March precipitation. In the R site, high April precipitation enhanced growth. In the driest M site, warm conditions in the late prior winter and current spring improved growth, but warm-sunny conditions in July and dry-sunny conditions in August reduced it. Larch growth positively responded to spring-summer wet conditions considering short (1-6 months) and long (9-24 months) time scales in dry (site M) and wet-intermediate (sites S and R) sites, respectively.DiscussionLarch growth is vulnerable to drought stress in dry slow-growing plantations, but also to extreme spring wet-cloudy events followed by dry-hot conditions in wet fast-growing plantations.

Fibropapillomatosis (FP) is an emerging neoplastic disease associated with chelonid herpesvirus 5 (ChHV5; Scutavirus chelonidalpha 5) that affects all species of marine turtles worldwide, mainly green turtles (Chelonia mydas) at coastal feeding sites. This report describes the case of a juvenile green turtle stranded alive on the coast of Veracruz, Mexico that presented 41 lesions suggestive of FP distributed on the eyes, neck, front flippers, axillary/inguinal regions and plastron. Morphologically, the lesions varied in size, shape and appearance of the surface. A tumour was collected and analysed by histopathology revealing a benign neoplasm with fibropapilloma characteristics (dermal and epidermal proliferation) and cytopathic effects consistent with herpesvirus infection, such as ballooning, reticular, and vacuolar degeneration, cell necrosis, eosinophilic intranuclear inclusion bodies, and inflammatory cell infiltration. The tumour tested positive for ChHV5 through conventional PCR targeting the UL30, UL18, UL22, and UL27 genes. Phylogenetic analysis of the DNA Polymerase (UL30) placed the Veracruz variant in the Western Atlantic/Eastern Caribbean cluster along with sequences from Florida, Colombia, Barbados, and Brazil. Additional identification of the CMA1.1 DNA mitochondrial haplotype for this individual supports the connectivity between green turtles from the northern and southern regions of the Gulf of Mexico (GoM) and the Caribbean. It also suggests a potential risk route for ChHV5 infection. This report details the first case of FP linked to ChHV5 in Veracruz and the southwestern GoM. Further research on FP and ChHV5 in these areas is crucial due to their role as habitats for five sea turtle species across various life stages. [ABSTRACT FROM AUTHOR]

Abstract Increased winter and early spring temperatures due to climate change can enhance forest productivity due to earlier growth onset in temperate regions. However, drought‐prone forests can be highly vulnerable to the combined effect of high summer temperatures and water stress. Understanding how water stress and rising temperatures along the growing season control tree growth in co‐occurring species with contrasting drought tolerances is key to project climate change effects on forest dynamics. Here, we evaluated the interactive effect of seasonal temperature and water availability on annual radial growth and climate–growth instability over six decades (1951–2015) in three pine species with contrasting drought tolerances (Pinus pinaster, Pinus nigra, and Pinus sylvestris). For this, we retrospectively observed radial tree growth using dendroecological methods and evaluated seasonal temperature and water availability effects by using linear mixed models. Early growing season temperature and water availability had a positive effect on tree growth, but the positive effect of late season temperature was modulated by water availability. Moving time‐window analyses revealed temporal instability in climate–growth relationships. Since the 1980s, pine species showed a higher growth sensitivity to both seasonal temperatures and annual water availability. Furthermore, growth reductions were more pronounced due to increased summer temperatures and reduced precipitation. Our results were similar for the three studied pine species despite their contrasting tolerance to drought. Overall, climate warming effects on pine growth are contingent upon water availability in Mediterranean continental forests. Synchronization among species, climate–growth instability, and negative growth trends suggests an increased vulnerability to drought of Mediterranean pine species in response to ongoing climate change.

Background: Plasticity in response to environmental drivers can help trees cope with droughts. However, our understanding of the importance of plasticity and physiological adjustments in trees under global change is limited. Methods: We used the International Tree-Ring Data Bank (ITRDB) to examine 20th century growth responses in conifer trees during (resistance) and following (resilience) years of severe soil and atmospheric droughts occurring in isolation or as compound events. Growth resilience indices were calculated using observed growth divided by expected growth to avoid spurious correlations, in which the expected values were obtained by the autoregressive moving average (ARIMA) model. We used high atmospheric vapour pressure deficit (VPD) to select years of atmospheric drought and low annual values of the Standardized Precipitation-Evapotranspiration Index (SPEI) to select years with soil drought. We acquired the sensitivities (i.e., the slopes of the relationships) by fitting the resilience indices as a function of environmental drivers, and assessed how these sensitivities changed over time for different types of drought events using linear mixed models. We also checked whether plasticity in growth responses was sufficient to prevent long-term trends of growth reductions during or after severe droughts. We acknowledge that by focusing on the response of surviving trees from the ITRDB we are potentially biasing our results towards higher resilience, as stand level responses (e.g., mortality) may result in lowered competition after the disturbance event. Results: Sensitivities of resilience to VPD and SPEI changed throughout the 20th century, with the directions of these changes often reversing in the second half of the century. For the 1961–2010 period, changing sensitivities had positive effects on resilience, especially following years of high-VPD and compound events, avoiding growth losses that would have occurred if sensitivities had remained constant. Despite sensitivity changes, resilience was still lower at the end of the 20th century compared to the beginning of the century. Conclusions: Future adjustments to low-SPEI and high-VPD events are likely to continue to compensate for the trends in climate only partially, leading to further generalized reductions in tree growth of conifers. An improved understanding of these plastic adjustments and their limits, as well as potential compensatory processes at the stand level, is needed to project forest responses to climate change.

Understanding how plants survive drought and cold is increasingly important as plants worldwide experience dieback with drought in moist places and grow taller with warming in cold ones. Crucial in plant climate adaptation are the diameters of water-transporting conduits. Sampling 537 species across climate zones dominated by angiosperms, we find that plant size is unambiguously the main driver of conduit diameter variation. And because taller plants have wider conduits, and wider conduits within species are more vulnerable to conduction-blocking embolisms, taller conspecifics should be more vulnerable than shorter ones, a prediction we confirm with a plantation experiment. As a result, maximum plant size should be short under drought and cold, which cause embolism, or increase if these pressures relax. That conduit diameter and embolism vulnerability are inseparably related to plant size helps explain why factors that interact with conduit diameter, such as drought or warming, are altering plant heights worldwide.

Ongoing climatic change is threatening the survival of drought-sensitive tree species, such as silver fir (Abies alba). Drought-induced dieback had been previously explored in this conifer, although the role played by tree-level genetic diversity and its relationship with growth patterns and soil microsite conditions remained elusive. We used double digest restriction-site-associated DNA sequencing (ddRADseq) to describe different genetic characteristics of five silver fir forests in the Spanish Pyrenees, including declining and non-declining trees. Single nucleotide polymorphisms (SNPs) were used to investigate the relationships between genetics, dieback, intraspecific trait variation (functional dendrophenotypic traits and leaf traits), local bioclimatic conditions, and rhizosphere soil properties. While there were no noticeable genetic differences between declining and non-declining trees, genome–environment associations with selection signatures were abundant, suggesting a strong influence of climate, soil physicochemical properties, and soil microbial diversity on local adaptation. These results provide novel insights into how genetics and diverse environmental factors are interrelated and highlight the need to incorporate genetic data into silver fir forest dieback studies to gain a better understanding of local adaptation.

Abstract Background Equatorward, rear-edge tree populations are natural monitors to estimate species vulnerability to climate change. According to biogeographical theory, exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations. However, the ecological and biogeographical margins can mismatch due to the impact of ecological factors (topography, soils) or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited. Methods We tested these ideas in six tree species, three angiosperms (Fagus sylvatica, Quercus robur, Quercus petraea) and three gymnosperms (Abies alba, Pinus sylvestris and Pinus uncinata) by comparing rear-edge tree populations subjected to different degrees of aridity. We used dendrochronology to compare the radial-growth patterns of these species in northern, intermediate, and southern tree populations at the continental rear edge. Results and conclusions We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F. sylvatica, P. sylvestris, and A. alba. This was also observed in species from cool-wet sites (P. uncinata and Q. robur), despite their limited responsiveness to drought. However, in the case of Q. petraea the intermediate population showed the strongest relationship to drought. For drought-sensitive species as F. sylvatica and P. sylvestris, southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer. We found a trend of enhanced vulnerability to drought in these two species. The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge. Nevertheless, the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q. petraea. In widespread species showing enhanced vulnerability to drought, as F. sylvatica and P. sylvestris, increased vulnerability to climate warming in their rear edges is forecasted. Therefore, we encourage the monitoring and conservation of such marginal tree populations.