Search

The health of Mediterranean forests is seriously threatened by the effects of progressive climate change. Frequent droughts and heat waves induce heavy stress and favor the ignition of large wildfires causing decline in tree growth and mortality. Although trees are often able to survive the impact of fire thanks to their adaptive traits, partial injuries, such as crown defoliation, could compromise their physiology and resilience amplifying pre-existing climatic/site-specific stresses.Expanding knowledge on the physiological and mechanistic dynamics of burned forests in areas prone to multi-stress conditions is crucial to identify the most resilient species capable of countering future rates of climate change.In this context, our research aimed to understand the resilience of Pinus pinaster Aiton plantations located in the Vesuvius National Park, a particularly warm and dry area of southern Italy, affected by a large wildfire in 2017, which led to a progressive defoliation of trees in the post-fire years, reaching 50% in 2020. We selected different study sites along a wildfire severity gradient (control, low and medium burning intensity) and we applied a multi-parametric approach studying in the post-fire years (2017-2020): tree growth, intrinsic water use efficiency of the trees, morphological traits and needle nutrients in foliage, as well as the forest soil properties.Morpho-anatomical analyses of foliage showed that although the burned stands suffered severe defoliation, resilience reactions already started in burned trees during weeks following wildfire, with the formation of larger but also more xeromorphic and defensive foliage (i.e. needles with higher linear weight and increased percentage area of resin ducts) than at the control site. On another hand, the needle nutrient content indicated for all sites severe deficiencies of main macro and micro-nutrients (especially N, P, K). Accordingly, soil analyzes highlighted a forest soil particularly poor in nutrients, and in burned sites the fire seems to have worsened the dystrophy by burning the nutrient pool in topsoil humus layer. Finally, the stem growth never recovered: tree-growth was steadily in decline in the burned versus control sites in the post fire years. Similarly, the intrinsic water use efficiency was reduced in burned stands indicating higher transpiration costs for assimilated carbon. The higher conductance, confirmed by the increase in the density of the stomatal lines found in needles, suggested the need of the burned trees to attempt a higher carbon uptake and counteract the carbon starvation in the stem triggered by the crown reduction.Our results suggest that the studied burned stands are unlikely to recover their pre-fire performance. Carbon starvation will be difficult to reverse due to carbon retention in foliage to form new, heavier, and more defensive needles, also given the foliar nitrogen concentrations below deficiency level, further impeding assimilation. Therefore, the forest ecosystem reached a high vulnerability, not as a direct consequence of forest wildfire but due to the synergic effect of several stress factors: poor soil nutritional condition (exacerbated by the wildfire), an environment prone to drought stress and partial defoliation due to the fire (that lowered the tree photosynthetic capacity).

Over the years, remote sensing and spectroscopy have contributed significantly to vegetation monitoring, primarily to understand the interaction of plants with solar radiation. However, due to spatial and temporal heterogeneity, light availability below and within tree canopies is challenging to estimate or time-consuming. Therefore, it is essential to know the structure of the tree canopy through vertical light transmission profiles, which will allow estimating plant development, biophysical properties throughout the canopy and the seasonal phenology of the species.Currently, technologies based on the Internet of Things (IoT) are constituted as efficient and low-cost tools for monitoring forest ecology at the individual and species levels. A device applied to ecology and based on IoT is the "TreeTalker" (TT +), which allows measuring in semi-real time, in addition to water transport in trees, diametrical growth, the spectral transmittance of light through the canopy in 12 spectral bands, using spectrometers in the visible range (VIS) between 450 – 650 nm and 610 – 860 nm in the near-infrared (NIR). These parameters are acquired and stored by each TT+ every hour, sent to a node (TT-Cloud), and transmitted and stored on a server.In this context, our study integrates remote sensing data and those obtained through IoT to evaluate the variability of the spectral response at the population level in forest species: Quercus cerris, Fagus Sylvatica and Pinus pinaster. Cloud computing was used through Google Earth Engine (GEE) to extract multitemporal values from the Sentinel 2 satellite and its subsequent integration with data from the TreeTalker spectrometer, devices installed in trees of 05 plots located in central and southern Italy, precisely in the Rocarespampani sector in Viterbo, Vesuvio National Park and Matese Regional Park in Campania Region.Preliminary results show the ability of the TT+ spectrometer to store daily information at different wavelengths during the year. The spectral response of the near-infrared (NIR) bands is the most susceptible to foliage changes for deciduous species, mainly in the summer and spring seasons. In the case of visible bands (VIS), it is more susceptible to energy input in coniferous species and in the winter and autumn seasons. Finally, a higher correlation was obtained between the NIR bands of Sentinel 2 and TT+, mainly for the deciduous species Q. cerris and F. Sylvatica.The seasonal assessment of the species will be continued during the following years at local and regional scales to understand their responses to climate change. Also, light transmission through the forest canopy will contribute to identifying and complementing knowledge of forest-climate interactions, allowing a more detailed understanding of the ecophysiological parameters of forest vegetation and phenological changes at the species and ecosystem level.

The ongoing climate change, with altered precipitation regimes and altered evaporative demand due to the increase in temperature are affecting hydrological conditions in most forest sites in Europe. This change has strong consequences on the distribution, composition and ecological functioning of forest species . Fagus sylvatica is one of the most important species in Europe, spanning from southern Scandinavia to the Mediterranean region. Species distribution models forecast a reduction of the area of distribution of F. sylvatica in Italy under the climate change scenarios. The hydraulic behaviour and transpiration responses of the beech to climate conditions have been studied in central Europe. However, this has been scarcely addressed in the southernmost part of its distribution area, where this knowledge might be critical in understanding the physiological responses of this species to climate change, and then its capability to persist in the area.This study aims to understand the responses of the transpiration of a Fagus sylvatica forest to meteorological variables in the southern Apennines (Matese Regional Park, Italy). The forest stand has been continuously monitored for 2 years with the TreeTalker devices, that record sap flux data at an hourly scale, along with several microenvironmental parameters. The monitoring period encompasses the droughty 2022 year, with high temperatures and precipitations well below the average.The forest stand studied varies its sap flux in response to the environmental conditions, by reducing its transpiration in late summer, when VPD is high, but water availability is low. This conservative hydraulic behaviour seems to protect the trees from immediate damage due to drought periods, as no tree mortality has been observed. These results suggest that even if in the past Fagus sylvatica has been considered an anisohydric species, the southern ecotypes show a more isohydric behaviour than expected. The prosecution of this monitoring might provide further information about long-term trends in the ecophysiology of this forest.

Forest fires are becoming more intense and recurring due to climate change and are increasingly threatening the integrity and functionality of forests worldwide. Trees’ resilience is closely influenced not only by direct fire damages, but also by pre-existing climate stress conditions, such as high temperatures and water deficit. Fire wounds and extreme climate events can impair plant physiology triggering tree mortality in the medium and long term. Therefore, understanding the links between fire, climate and tree health is essential to anticipate the impacts of global warming and to plan climate-adapted forest management strategies. In this context, our research aims to study the post-fire effects on a Pinus pinaster Aiton forest growing in Vesuvius National Park, a particularly drought prone area in Southern Italy, comparing plants with severe damage to the canopy with non-defoliated trees. We combined inter-annual analyses of dendrochronology, carbon and oxygen isotope composition in tree rings, and intra-annual monitoring of xylogenesis to explore the effects on tree-growth, ecophysiological processes and wood formation dynamics. The tree-ring approach showed that crown damage compromised the photosynthetic activity of burned trees, with a decrease in tree-growth in the medium term compared to control trees. Moreover, the xylogenesis analysis demonstrated a delay in phenology and a lower xylem productivity and plasticity of the defoliated trees, as well as the negative influence of hot and dry months on cambial production. Our findings suggested that although maritime pine can survive severe forest fires in the short term, a severe crown defoliation and prolonged drought conditions can compromise the species' eco-physiological functions reducing the chances to regain the pre-disturbance productivity rates.

Vineyard productivity and grape quality are strictly linked with the pedoclimatic characteristics (e.g. soil and climate) as well as with cultivation techniques (e.g. canopy and soil management, plant nutrition). Each grapevine cultivar is characterized by specific morpho-physiological traits which determine the ability to cope with stressors. The knowledge of the plasticity of such traits is needed to forecast how vineyards would respond to climate changes. Indeed, viticulture in some areas of the Mediterranean basin, is facing sustainability problems due increase in severe and prolonged drought periods, responsible for reduction in yield and grape quality. Although to achieve quality and/or geographical indication labels, the Italian legislation imposes rainfed cultivation for grapevine, the need for irrigation introduction and management in the vineyard is becoming more and more evident. For designing the best strategies for water use in the vineyard, it is fundamental to gain knowledge on hydraulics of the specific cultivar in its pedoclimatic context. The application of dendro-sciences techniques, based on the fine study of anatomical and isotopic traits of tree-rings in the vine main stem and of their relations with environmental parameters, can help reconstructing the past plant’s eco-physiological behaviour. Here we report the results of one of the activities carried out within the GREASE project, funded by the Campania Region through the Rural Development Programme 2014-2020, in the framework of improving grapevine productivity, resource use efficiency and resilience for the sustainable management of vineyards.The study was conducted in a vineyard of Vitis vinifera L. subsp. vinifera ‘Greco’ at the premises of Feudi di San Gregorio farm, in southern Italy (Avellino). In this study, we aimed to analyse the relations between anatomical and isotopic wood traits with climate parameters in tree-ring series from vines of two age classes which were subjected to a change in pruning technique in the past years. Wood cores and stem disks were sampled and tree-rings were dated according to dendro-chronological techniques. Then semi-thin sections of the tree-ring series were cut and analysed through light and fluorescence microscopy. Digital image analysis allowed the quantification of wood anatomical traits linked with hydraulic conductivity and vulnerability to embolism. The tree-ring series were then dissected to prepare samples for the determination of d13C and evaluate intrinsic water use efficiency. The overall wood anatomical and stable isotope parameters were analysed together with climatic data through multivariate statistical analysis.The application of dendro-sciences technique proved to be useful to reconstruct how vines have used the water resources before and after the changing in the pruning technique. Understanding how the vine has reacted to past environmental variability and changes in cultivation factors can help forecasting how it will behave under the different climate change scenarios.

Climate-induced forest mortality is a critical issue in the Mediterranean basin, with major consequences for the functioning of these key ecosystems. Indeed, in Mediterranean ecosystems, where water stress is already the most limiting factor for tree performance, climatic changes are expected to entail an increase in water deficit. In this context, annual growth rings can provide short- (e.g., years) and long-term (e.g., decades) information on how trees respond to drought events. With climate change, Pinus pinaster and Pinus pinea L. are expected to reduce their distribution range in the region, being displaced at low altitudes by more drought tolerant taxa such as sub Mediterranean Quercus spp.This study aims was to assess the physiological response of Pinus and Quercus species growing in the Vesuvio National park, located in Southern Italy and where an increase of temperature and drought events has been recorded in the recent years. Our preliminary results underlined the importance of temperature on the tree ring width of all the analyses species. The high temperatures can cause a change in the constant kinetics of the RuBisCo, leading to a consequent decrease in carboxylation rate and thus to a reduction in tree growth. On the other hand, also precipitation seemed to affect the growth of the sampled trees: indeed, in all the chronologies a reduction in growth was found after particular dry years: for example, the low rainfall in 1999 (455 mm/year) determined a drastic decline in growth in 2000 in all the species. In addition to the climatic factors, competition can also play an important role in the growth rate: dendrochronological analyzes have highlighted how stand specific properties (i.e. density, structure and composition) can influence individual tree responses to drought events. The knowledge of those researches should be integrated into sustainable forest management strategies to minimize the potential impacts of climate change on forest ecosystems.

The increasing irregularity in precipitation patterns and frequency of extreme drought events in the Mediterranean area is challenging the sustainability of grapevine production, especially in some areas of southern Italy. Here, being the grapevine mostly rainfed-cultivated, there is a strong demand for cultivation techniques aiming to improve water use efficiency and water stress tolerance.Pruning techniques and training system can have an effect on the hydraulic architecture of vines, thus on their hydraulic behavior that is strictly coordinated with photosynthetic efficiency and ultimately contribute to determine yield and grape quality.In this study, we aimed to evaluate whether and to what extent a change in pruning technique can influence the efficiency and safety of water flow in vines. In order to pursue this objective, we combined the dendro-sciences approach, analysing tree-ring width and anatomical features of vines subjected to an abrupt change in the pruning technique. The study was conducted within the GREASE project, funded by the Campania Region through the Rural Development Programme 2014-2020, within the framework of the optimization of agricultural practices for improving grapevine resources-use efficiency for the sustainable management of vineyards.The study was conducted in a vineyard of Vitis vinifera L. subsp. vinifera ‘Greco’ (Feudi di San Gregorio farm) located in southern Italy (Avellino) at a site where the pruning technique was changed in 2004 following the method by Simonit & Sirch (Simonit 2014 Manuale di potatura della vite Ed IA; Sun et al 2008 Am J Bot 95:1498-1505). This method applies pruning cuts oriented in a way to drive vine natural tendency in the branching, to reduce injuries stress, in order to modulate the hydraulic pathway to reduce resistances to flow. Wood cores were extracted by the vines trunk, tree-rings were dated and widths were measured according to dendro-chronological techniques using WinDENDRO software. Then the cores were subjected to thin sectioning to obtain tree-ring series that were analysed through microscopy and subjected to digital image analysis. Wood anatomical traits, linked with hydraulic conductivity and vulnerability, were quantified in each year. The tree-ring series were then annually separated and d13C was measured in each year, in order to obtain information on intrinsic water use efficiency. The overall wood anatomical and stable isotope parameters were integrated to reconstruct and interpret past eco-physiological vine behaviour in response to the change in pruning technique also taking into account the inter-annual environmental variability.The analysis of wood anatomical functional traits linked with carbon stable isotopes of grapevine tree-ring series confirmed that vineyard management technique can severely affect the vine water use, thus affecting plant growth, productivity and ultimately plant ability to adapt to changing environmental conditions.All these interactions and their effects on water use should be taken into account when designing management practices in vineyards for sustainable production.

Forests play a key role in mitigating greenhouse gases and fighting climate change. However, numerous environmental stressors threaten the integrity and ecological functionalities of forests. In recent decades, the increase of drought events and fires occurrence is negatively influencing forest health, causing dieback events and higher rates of mortality, especially in the Mediterranean environments.Studying the mechanisms of plants in response to these events and relating them to the duration and intensity of stress can be the key to understand the vulnerability and sensitivity at individual and regional scale. Currently, most of the available studies are severely limited in time and space, providing information with a relatively poor temporal resolution.In this context, our research aims to examine the effects of these events on the ecophysiology of Pinus pinaster Aiton, a very common conifer species in the Mediterranean environment, through the use of the innovative TreeTalker device (TT+). This instrument is able to monitor multiple physiological and environmental parameters of the tree such as sap flow, the amount of light absorbed by the canopy, meteorological information etc. The study is conducted in Southern Italy, more precisely at the Vesuvius National Park, affected in recent years by severe drought conditions and where a large wildfire occurred in July 2017. To evaluate the incidence of stress conditions, during the spring of 2020, 10 TT+ devices were installed in a pine stand affected by fire (Burned Site -BS) and 10 TT+ devices in a second stand called Control Site (CS) in which plants were not affected by the 2017 fire.The preliminary monitoring data show interesting information about the hydraulic and stomatal strategies implemented by the trees on both stands according to the variation of the climatic conditions. While in the spring a rather regular sap flow trend was observed in both stands, during the summer months (July, August and good part of September), the trees show a reduction in their stomatal activity during the hottest hours of the day (11 am -15 pm), predictably as a mean to avoid episodes of xylem cavitation and to contrast the high temperatures. In the autumn months of October and November, however, vegetative activity has continued uninterrupted although a considerable decrease in hydraulic flow was registered. Finally, from the data collected it emerges that the severe reduction of the crown suffered by the plants of the BS has determined a lower absorption capacity of photosynthetic light, exposing these individuals to a greater possibility of carbon starvation.The monitoring activities will continue for the next few years, allowing to understand better the eco-physiological dynamics leading the individuals of this species to overcome or succumb to stress events and/or extreme climatic conditions.

Tree planting on abandoned agricultural land could both restore the soil quality and increase the productivity of economically valuable woody species. Here, we assess the impact of mixed-species tree plantations on soil quality at a site in Central Italy where tree intercropping systems were established 20 years ago on a former agricultural land. These intercropping systems include two species of economic interest, Populus alba and Juglans regia, and one of three different nurse trees, i.e., Alnus cordata, Elaeagnus umbellata, both of which are N-fixing species, and Corylus avellana. We measured tree growth and compared how soil organic matter, soil extracellular enzymes, and nematodes of different feeding groups varied among the intercropping systems and relative to a conventional agricultural field. Our results indicate that tree plantation led to an increase in soil carbon and nitrogen, and enhanced enzyme activities, compared with the agricultural land. The proportion of nematode feeding groups was heterogeneous, but predators were absent from the agricultural soil. Multivariate analysis of soil properties, enzymatic activity, nematodes, and tree growth point to the importance of the presence N-fixing species, as the presence of A. cordata was linked to higher soil quality, and E. umbellata to growth of the associated valuable woody species. Our findings indicate that intercropping tree species provide a tool for both restoring fertility and improving soil quality.

In the Mediterranean Basin, fire incidence has increased dramatically during the past decades and fire is expected to become more severe in the future due to climate change. The effects of fires on forest ecosystems can last several years: the survival of fire-injured trees depend not only on the adaptive traits of individual species, but also on the ability of trees to tolerate post-fire environmental constraints.Several trees, although initially resisting the strong heat injury caused by the high temperatures of the flames, can reduce their vigor and finally die after a few years after fire, due to serious damage at the canopy level or due to the difficult conditions arising in the surrounding stands. The study of long-term trends of the eco-physiological processes in plants subjected to fire are of fundamental importance in planning management actions and restoration strategies of burned areas.In this context, our research aims to identify and understand the impacts that post-fire conditions can have on the growth and eco-physiology of Pinus pinaster Aiton, through the study of a forest stand hit by a devastating fire that affected the Vesuvius National Park, in Southern Italy, in July 2017. This study combines the dendrochronological analyses with the monitoring of xylogenesis, supported by the measurements in continuum of the eco-physiological parameters of the individual plants through the use of the innovative TreeTalker device.The results of the dendrochronological analyses showed that, at the end of 2018, despite the strong stress suffered and a significant decrease in growth, the plants showed a very limited mortality rate: only 2-10% of the individuals reduced their vigor. However, preliminary data on xyologenesis, collected from spring 2019 to nowadays, suggest how, after two years, the fire of 2017 is still influencing the cambium activity of individual plants: the productivity and the differentiation kinetics of xylem cells are strongly influenced by the damages suffered at the canopy level.The monitoring activities will continue for the next few years in order to identify the recovery times of the plant to return to normal vital functions, as well as, eventually, understand the eco-physiological processes that lead to a reduction in productivity or even to death.

Thinning intensity is an important factor affecting forest structure and density and influencing tree growth. The main objective of the study is to evaluate how the different intensity of thinning can influence, in the short and long term, the productivity and intrinsic water use efficiency (WUEi) of Quercus robur L., a widespread European species. Three thinning types of different intensity were applied in 14-year mixed plantation of Quercus robur L. growing with Alnus glutinosa (L) Gaertn., a N-fixing species, with an initial density of 625 trees/ha. A multidisciplinary approach was applied, coupling the tree-ring analyses with the measurements of stable isotopes of carbon and oxygen. Findings highlighted how the different conditions of light and competition, determined by the type and intensity of thinning, triggered different responses of Q. robur species in terms of growth and WUEi. Data suggested that the moderate selective thinning (31% reduction of total biomass) was not able to reduce the high competition for resources among individuals: this condition negatively influenced the trees growth. The presence of the N-fixing species, left after the thinning, was not able to counteract the negative effect of competition. A negative effect on productivity was recorded with the geometric thinning (62% reduction of total biomass). Indeed, this treatment resulted in an increase of asymmetry of the canopy (0.90 vs 0.83, respectively in pre- and post-thinning period), due to the partial crown competition from one side and with a consequent limitation of the photosynthetic activity of the trees. Finally, the very high selective thinning (75% reduction of total biomass) resulted to be the most appropriate management practice, as it guarantees positive effects both in terms of growth and intrinsic water use efficiency. The post thinning conditions determined high photosynthesis rates, an increase of productivity and a limited water loss.

The Italian TREETALKER NETWORK (ITT-Net) aims to respond to one of the grand societal challenges: the impact of climate changes on forests ecosystem services and forest dieback. The comprehension of the link between these phenomena requires to complement the most classical approaches with a new monitoring paradigm based on large scale, single tree, high frequency and long-term monitoring tree physiology, which, at present, is limited by the still elevated costs of multi-sensor devices, their energy demand and maintenance not always suitable for monitoring in remote areas. The ITT-Net network will be a unique and unprecedented worldwide example of real time, large scale, high frequency and long-term monitoring of tree physiological parameters. By spring 2020, as part of a national funded project (PRIN) the network will have set 37 sites from the north-east Alps to Sicily where a new low cost, multisensor technology “the TreeTalker®” equipped to measure tree radial growth, sap flow, transmitted light spectral components related to foliage dieback and physiology and plant stability (developed by Nature 4.0), will monitor over 600 individual trees. A radio LoRa protocol for data transmission and access to cloud services will allow to transmit in real time high frequency data on the WEB cloud with a unique IoT identifier to a common database where big data analysis will be performed to explore the causal dependency of climate events and environmental disturbances with tree functionality and resilience.With this new network, we aim to create a new knowledge, introducing a massive data observation and analysis, about the frequency, intensity and dynamical patterns of climate anomalies perturbation on plant physiological response dynamics in order to: 1) characterize the space of “normal or safe tree operation mode” during average climatic conditions; 2) identify the non-linear tree responses beyond the safe operation mode, induced by extreme events, and the tipping points; 3) test the possibility to use a high frequency continuous monitoring system to identify early warning signals of tree stress which might allow to follow tree dynamics under climate change in real time at a resolution and accuracy that cannot always be provided through forest inventories or remote sensing technologies.To have an overview of the ITT Network you can visit www.globaltreetalker.org

The effect of fire severity on Pinus pinaster growth and ecophysiological responses was evaluated in four burned sites of Vesuvio National Park, Southern Italy. After the wildfire of 2017, when over 1300 hectares of vegetation, mainly P. pinaster woods, were destroyed, four sites were selected according to the different degree of fire severity and a multidisciplinary approach based on tree rings, stable isotopes and percentage of crown scorched or consumed was applied. All the sampled trees in the burned sites showed a decrease in tree growth in 2017, in particular in the latewood at high-severity site. The dendrochronology analyses showed that several individuals experienced and endured higher fire severity in the past compared to 2017 fire. Further delta C-13 and delta O-18 underlined the ecophysiological responses and recovery mechanisms of P. pinaster, suggesting a drastic reduction of photosynthetic and stomata activity in the year of the fire. Our findings demonstrated that P. pinaster growth reduction is strictly linked to the percentage of crown scorch and that even trees with high level of crown scorched could survive. In all the burned sites the high temperatures and the time of exposure to the flames were not sufficient to determine the death of the cambium and all the trees were able to complete the 2017 seasonal wood formation. This data can contribute to define guidelines to managers making post-fire silvicultural operations in pine forest stands in the Mediterranean Basin.

Using a gravity model for trade, this work analyzes the factors influencing the patterns of international hazardous waste flows, relying on newly available data reported in the E-PRTR (European Pollutant Release and Transfer Registry) for EU-OECD countries over the period 2007 to 2014. Exploiting a consolidated empirical framework (Kellenberg, 2012), we test two empirical hypotheses: firstly, we explicitly assess if, according to the pollution heaven hypothesis (PHH), the relative levels of environmental policies across countries are an important determinant of hazardous waste trade, and secondly, we test if technological specialization, proxied here by a technology-specific patent stock, can be considered as a pull factor capable to influence the patterns of international trade of hazardous waste.