Land-use practices (coppices and dehesas) and management intensity modulate responses of Holm oak growth to drought

Last decades increase in reported events of drought-induced tree mortality evidences how climate-change is transforming forest ecosystems all over the world. The parallel increase in human pressure over the land is also causing major changes in forest functioning but it remains unclear how these two driving forces interact between them. We combined tree-ring data with aboveground cover, leaf area index (LAI), soil variables, and the standardized precipitation evapotranspiration index (SPEI) as water availability indicator to disentangle the existence of linkages between contrasting Holm oak (Quercus ilex L. subsp. ballota [Desf.] Samp) land-use practices and its drought-induced decline and mortality. We selected ten sites covering different soil and climatic gradients, land-use practices (i.e., declining dehesas, DH; declining coppices, FRd; and healthy coppices, FRh), and tree vigour classes (i.e., living, affected, and dead trees) in Spain. DH sites presented lower tree coverage, soil water holding capacity and soil pH than coppice (FR) sites. Dead Holm oaks from DH sites were younger than living ones, whereas dead trees from FRd sites were smaller and showed lower growth rates than living ones. We also found that conservation of traditional land-use practices in FR sites, resulting in less understorey cover but more soil erosion (less nutrients and microbial biomass and more bare soil), may positively affect the growth plasticity and sensitivity to drought of Holm oak trees by alleviating inter-specific competition, but in detriment of vegetation cover and soil health. Further studies should evaluate whether what holds true for FRh sites regarding the maintenance of traditional land-use practices might also apply for healthy DH. In the face of drier and hotter scenarios, our results add robust evidences on how the modulation of the intensity of the traditional uses could be a useful tool to optimize ecosystem services in Mediterranean systems highly vulnerable to climate change. © 2020This research was funded by the Spanish Government projects VERONICA (CGL2013-527 42271-P) and IBERYCA (CGL2017-84723-P). Additionally, it was also supported by the Basque Government through the BERC 2018-2021 program, and by the Spanish Ministry of Science, Innovation and Universities through the BC3 María de Maeztu excellence accreditation (MDM-2017-0714). Ana-Maria Hereş was financially supported by the projects NATIvE (PN-III-P1-1.1-PD-2016-0583) and REASONING (PN-III-P1-1.1-TE-2019-1099), both funded by the Romanian Ministry of National Education and by the Romanian Ministry of Research and Innovation through UEFISCDI ( link ). A. Gazol acknowledges funding by project RTI2018-096884-B-C31 (Spanish Ministry of Science). We thank Daniel García Angulo, Miguel Fernandez, David López Quiroga, Bárbara Carvalho, Matheus Lopes Souza, and Mario Díaz for their priceless support during the field campaigns and the laboratory work

Legacies of past forest management determine current responses to severe drought events of conifer species in the Romanian Carpathians

Worldwide increases in droughts- and heat-waves-associated tree mortality events are destabilizing the future of many forests and the ecosystem services they provide. Along with climate, understanding the impact of the legacies of past forest management is key to better explain current responses of different tree species to climate change. We studied tree mortality events that peaked in 2012 affecting one native (silver fir; growing within its natural distribution range) and two introduced (black pine and Scots; growing outside their natural distribution range) conifer species from the Romanian Carpathians. The three conifers were compared in terms of mortality events, growth trends, growth resilience to severe drought events, climate-growth relationships, and regeneration patterns. The mortality rates of the three species were found to be associated with severe drought events. Nevertheless, the native silver fir seems to undergo a self-thinning process, while the future of the remaining living black pine and Scots pine trees is uncertain as they register significant negative growth trends. Overall, the native silver fir showed a higher resilience to severe drought events than the two introduced pine species. Furthermore, and unlike the native silver fir, black pine and Scots pine species do not successfully regenerate. A high diversity of native broadleaf species sprouts and develops instead under them suggesting that we might be witnessing a process of ecological succession, with broadleaves recovering their habitats. As native species seem to perform better in terms of resilience and regeneration than introduced species, the overall effect of the black pine and Scots pine mortality might be compensated. Legacies of past forest management should be taken into account in order to better understand current responses of different tree species to ongoing climate change. © 2020 Elsevier B.V.We thank the Forest District staff of Sacele, Kronstadt, Rasnov, Teliu, Codlea, and Intorsura Buzaului for all their support and for giving us access to the Forest Management Plans. This work was financed by the NATIvE ( PN-III-P1-1.1-PD-2016-0583 ) and TreeMoris ( PN-II-RU-TE-2014-4-0791 ) projects through UEFISCDI (link; Romanian Ministry of Education and Research ) and supported by the BERC 2018-2021 ( Basque Government ), and BC3 María de Maeztu Excellence Accreditation 2018-2022, Ref. MDM-2017-0714 ( Spanish Ministry of Science, Innovation and Universities ). We also thank Antonio Gazol for interesting discussions on the study and Ionela-Mirela Medrea, Andrei Apafaian, Maria Băluţ, and Florin Dinulică for assistance during field and laboratory campaigns. Silver fir, black pine, and Scots pine figures included in the graphical abstract are reproduced with the authorization of the designer Luiza Anamaria Pop (©2020) who drew the three conifer species and processed the drawings in Adobe Illustrator® CS5 (v. 15.0.0)

Photoprotective compounds as early markers to predict holm oak crown defoliation in declining Mediterranean savannahs

This research was mainly funded by the Spanish Government through the IBERYCA project (CGL2017-84723-P) and its associated FPI scholarship BES-2014-067971 (to M.E.-V.). It was further supported by the BC3 María de Maeztu excellence accreditation (MDM-2017-0714; the Spanish Government) and by the BERC 2018-2021 and the UPV/EHU-GV IT-1018-16 program (Basque Government). Additionally, this research was further supported through the ‘Juan de la Cierva program’ (the Spanish Government to M.V.; (IJCI-2017-34640).) and two projects funded by the Romanian Ministry of Education and Research through UEFISCDI (NATIvE, PN-III-P1-1.1-PD- 2016-0583 and REASONING, PN-III-P1-1.1-TE-2019-1099 to A.-M.H.)

Alteration of the tree–soil microbial system triggers a feedback loop that boosts holm oak decline

In anthropic savanna ecosystems from the Iberian Peninsula (i.e. dehesa), complex interactions between climate change, pathogen outbreaks and human land use are presumed to be behind the observed increase in holm oak decline. These environmental disturbances alter the plant–soil microbial continuum, which can destabilize the ecological balance that sustains tree health. Yet, little is known about the underlying mechanisms, particularly the directions and nature of the causal–effect relationships between plants and soil microbial communities. In this study, we aimed to determine the role of plant–soil feedbacks in climate-induced holm oak decline in the Iberian dehesa. Using a gradient of holm oak health, we reconstructed key soil biogeochemical cycles mediated by soil microbial communities. We used quantitative microbial element cycling (QMEC), a functional gene-array-based high-throughput technique to assess microbial functional potential in carbon, nitrogen, phosphorus and sulphur cycling. The onset of holm oak decline was positively related to the increase in relative abundance of soil microbial functional genes associated with denitrification and phosphorus mineralization (i.e. nirS3, ppx and pqqC; parameter value: 0.21, 0.23 and 0.4; p < 0.05). Structural equation model (χ2 = 32.26, p-value = 0.73), moreover, showed a negative association between these functional genes and soil nutrient availability (i.e. mainly mineral nitrogen and phosphate). Particularly, the holm oak crown health was mainly determined by the abundance of phosphate (parameter value = 0.27; p-value < 0.05) and organic phosphorus (parameter value = −0.37; p-value < 0.5). Hence, we propose a potential tree–soil feedback loop, in which the decline of holm oak promotes changes in the soil environment that triggers changes in key microbial-mediated metabolic pathways related to the net loss of soil nitrogen and phosphorus mineral forms. The shortage of essential nutrients, in turn, affects the ability of the trees to withstand the environmental stressors to which they are exposed. Read the free Plain Language Summary for this article on the Journal blog. © 2023 The Authors. Functional Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.This research has been mainly funded by the Spanish Government through the IBERYCA project (CGL2017‐84723‐P), its associated FPI scholarship BES‐2014‐067971 (ME‐V), the SMARTSOIL (PID2020‐113244GB‐C21) and SMARTHEALTH (PID2020‐113244GA‐C22) projects (both funded by MCIN/AEI/10.13039/501100011033). It has been further supported by the BC3 María de Maeztu excellence accreditation (MDM‐2017‐0714; the Spanish Government), by the BERC 2018–2021 and by the UPV/EHU‐GV IT‐1648‐22 (from the Basque Government). Additionally, this research was further supported through the grant Holistic management practices, modelling and monitoring for European forest soils—HoliSoils (EU Horizon 2020 Grant Agreement No 101000289) and the ‘Juan de la Cierva programme’ (MV; IJCI‐2017‐34640; the Spanish Government). We acknowledge the Nutrilab‐URJC (Mostoles, Spain) laboratory services for the soil chemical analyses and SGIker of UPV/EHU (Leioa, Spain) for the technical and staff support for the high‐throughput quantitative‐PCR analysis. We also thank the private owners of the dehesas for facilitating our access to their properties. We are thankful to Celia López‐Carrasco Fernández and the ‘Consejería de Agricultura, Medioambiente y Desarrollo rural de la Junta de Castilla‐La Mancha’ for all the logistical support. The ‘Tree’ icon by Hey Rabbit illustrator, from thenounproject.com were used to design the Graphical abstract. Open Access funding provided by the Univer

Scarce population genetic differentiation but substantial spatiotemporal phenotypic variation of water‑use efficiency in Pinus sylvestris at its western distribution range

Water and carbon fluxes in forests are largely related to leaf gas exchange physiology varying across spatiotemporal scales and modulated by plant responses to environmental cues. We quantified the relevance of genetic and phenotypic variation of intrinsic water-use efficiency (WUEi, ratio of net photosynthesis to stomatal conductance of water) in Pinus sylvestris L. growing in the Iberian Peninsula as inferred from tree-ring carbon isotopes. Inter-population genetic variation, evaluated in a provenance trial comprising Spanish and German populations, was low and relevant only at continental scale. In contrast, phenotypic variation, evaluated in natural stands (at spatial level) and by tree-ring chronologies (at temporal inter-annual level), was important and ten- and threefold larger than the population genetic variance, respectively. These results points to preponderance of plastic responses dominating variability in WUEi for this species. Spatial phenotypic variation in WUEi correlated negatively with soil depth (r = − 0.66; p < 0.01), while temporal phenotypic variation was mainly driven by summer precipitation. At the spatial level, WUEi could be scaled-up to ecosystem-level WUE derived from remote sensing data by accounting for soil water-holding capacity (r = 0.63; p < 0.01). This outcome demonstrates a direct influence of the variation of leaf-level WUEi on ecosystem water and carbon balance differentiation. Our findings highlight the contrasting importance of genetic variation (negligible) and plastic responses in WUEi (large, with changes of up to 33% among sites) on determining carbon and water budgets at stand and ecosystem scales in a widespread conifer such as Pinus sylvestris.This work was supported by the Spanish Government [MINECO Grant Number AGL2015-68274-C3-3-R] and the Russian Science Foundation (Project Number 14-14-00219-P, mathematical approach). We acknowledge P. Sopeña and M.J. Pau for technical assistance and V. Muñoz, M. Sala and A. Teixidó for field sampling

Early-Warning Signals of Individual Tree Mortality Based on Annual Radial Growth

Tree mortality is a key driver of forest dynamics and its occurrence is projected to increase in the future due to climate change. Despite recent advances in our understanding of the physiological mechanisms leading to death, we still lack robust indicators of mortality risk that could be applied at the individual tree scale. Here, we build on a previous contribution exploring the differences in growth level between trees that died and survived a given mortality event to assess whether changes in temporal autocorrelation, variance, and synchrony in time-series of annual radial growth data can be used as early warning signals of mortality risk. Taking advantage of a unique global ring-width database of 3065 dead trees and 4389 living trees growing together at 198 sites (belonging to 36 gymnosperm and angiosperm species), we analyzed temporal changes in autocorrelation, variance, and synchrony before tree death (diachronic analysis), and also compared these metrics between trees that died and trees that survived a given mortality event (synchronic analysis). Changes in autocorrelation were a poor indicator of mortality risk. However, we found a gradual increase in inter- annual growth variability and a decrease in growth synchrony in the last similar to 20 years before mortality of gymnosperms, irrespective of the cause of mortality. These changes could be associated with drought-induced alterations in carbon economy and allocation patterns. In angiosperms, we did not find any consistent changes in any metric. Such lack of any signal might be explained by the relatively high capacity of angiosperms to recover after a stress-induced growth decline. Our analysis provides a robust method for estimating early-warning signals of tree mortality based on annual growth data. In addition to the frequently reported decrease in growth rates, an increase in inter-annual growth variability and a decrease in growth synchrony may be powerful predictors of gymnosperm mortality risk, but not necessarily so for angiosperms.Peer reviewe

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Habitat Fragmentation can Modulate Drought Effects on the Plant-soil-microbial System in Mediterranean Holm Oak (Quercus ilex) Forests

© 2015, Springer Science+Business Media New York. Ecological transformations derived from habitat fragmentation have led to increased threats to above-ground biodiversity. However, the impacts of forest fragmentation on soils and their microbial communities are not well understood. We examined the effects of contrasting fragment sizes on the structure and functioning of soil microbial communities from holm oak forest patches in two bioclimatically different regions of Spain. We used a microcosm approach to simulate the annual summer drought cycle and first autumn rainfall (rewetting), evaluating the functional response of a plant-soil-microbial system. Forest fragment size had a significant effect on physicochemical characteristics and microbial functioning of soils, although the diversity and structure of microbial communities were not affected. The response of our plant-soil-microbial systems to drought was strongly modulated by the bioclimatic conditions and the fragment size from where the soils were obtained. Decreasing fragment size modulated the effects of drought by improving local environmental conditions with higher water and nutrient availability. However, this modulation was stronger for plant-soil-microbial systems built with soils from the northern region (colder and wetter) than for those built with soils from the southern region (warmer and drier) suggesting that the responsiveness of the soil-plant-microbial system to habitat fragmentation was strongly dependent on both the physicochemical characteristics of soils and the historical adaptation of soil microbial communities to specific bioclimatic conditions. This interaction challenges our understanding of future global change scenarios in Mediterranean ecosystems involving drier conditions and increased frequency of forest fragmentation

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

The stationary and non-stationary character of the silver fir, black pine and Scots pine tree-growth-climate relationships

Tree-growth-climate relationships are usually assumed to have a stationary character, i.e., continuous and/or time-independent, along the lifetime of the trees. The fact that non-stationarity, i.e., discontinuous and/or time-variable, is more likely to actually be their general rule, has been often neglected in dendrochronology. Nine silver fir, black pine and Scots pine residual ring-width index chronologies (RWIresidual) and five precipitation- and temperature-derived seasonal climatic variables, covering the 20th century and the beginning of the 21st one, were used in this study. Heat map analyses based on rolling window correlations, using corrected p-values in order to deal with the type I errors (i.e., the multiple testing or comparison problem) and reduce them, were conducted to evaluate the evolution and stability of tree-growth-climate relationships along the lifetime of the trees, i.e., their stationary and/or non-stationary character. The obtained results showed that stationary tree-growth-climate relationships were well conserved within trees belonging to a given genus: positive effects, both at young and mature stages, of Twinter (winter temperature) on the Abies trees and of Psprsum(t) (spring-summer precipitation of the current-to-growth year) on the Pinus trees. Non-stationary tree-growth-climate relationships were instead species- and site-dependent and stopped in the 1970s/1980s/1990s. Growth decoupling from seasonal climatic variables was linked in many cases with climatic anomalies but the obtained results did not yield a general rule in this regard. Heat map analyses based on rolling window correlations proved to be a powerful statistical tool in disentangling between the stationary and/or non-stationary character of the tree-growth-climate relationships. Summarizing, this study puts into perspective the critical aspect of looking at the stationary and/or non-stationary character of the tree-growth-climate relationships if we want to better predict the impact of climate change on the future forest tree growth and dynamics based on past tree-growth-climate relationshipsWe thank the Forest District staff of Sacele, Kronstadt, Rasnov, Teliu, Codlea and Intorsura Buzaului for all their support during the fieldwork and for allowing us to access their Forest Management Plans. This work was supported by different projects granted by the Romanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI – UEFISCDI: PN-II-RU-TE-2014-4-0791 (TREEMORIS), PN-III-P1-1.1-PD-2016-0583 (NATIvE), PN-III-P1-1.1-TE-2019-1099 (REASONING) and PN-III-P4-ID-PCE-2020-2696 (DeWooD). This work was also supported by the BERC 2018-2021 (Basque Government) and by the BC3 María de Maeztu Excellence Accreditation 2018-2022, Ref. MDM-2017-0714 (Spanish Ministry of Science, Innovation and Universities). JMPM acknowledges funding support from the SEPE (Spanish National Employment Service), the Junta de Castilla y León and the European Regional Development Fund (grant CLU-2019-03). We very much appreciate all the critical help that we received during the field and laboratory campaigns from Ionela-Mirela Medrea, Andrei Apafaian, Cosmin Zgremţia, Maria Băluţ and Florin Dinulică. The designer Luiza Anamaria Pop (©2020) drew the silver fir, black pine and Scots pine figures that appear in the graphical abstract and processed them in Adobe Illustrator® CS5 (v. 15.0.0). These figures are reproduced with her permission. We thank the Forest District staff of Sacele, Kronstadt, Rasnov, Teliu, Codlea and Intorsura Buzaului for all their support during the fieldwork and for allowing us to access their Forest Management Plans. This work was supported by different projects granted by the Romanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI – UEFISCDI: PN-II-RU-TE-2014-4-0791 (TREEMORIS), PN-III-P1-1.1-PD-2016-0583 (NATIvE), PN-III-P1-1.1-TE-2019-1099 (REASONING) and PN-III-P4-ID-PCE-2020-2696 (DeWooD). This work was also supported by the BERC 2018-2021 (Basque Government) and by the BC3 María de Maeztu Excellence Accreditation 2018-2022, Ref. MDM-2017-0714 (Spanish Ministry of Science, Innovation and Universities). JMPM acknowledges funding support from the SEPE (Spanish National Employment Service), the Junta de Castilla y León and the European Regional Development Fund (grant CLU-2019-03). We very much appreciate all the critical help that we received during the field and laboratory campaigns from Ionela-Mirela Medrea, Andrei Apafaian, Cosmin Zgremţia, Maria Băluţ and Florin Dinulică. The designer Luiza Anamaria Pop (©2020) drew the silver fir, black pine and Scots pine figures that appear in the graphical abstract and processed them in Adobe Illustrator® CS5 (v. 15.0.0). These figures are reproduced with her permission