Martina Pollastrini | Università degli Studi di Firenze (University of Florence) (original) (raw)
Papers by Martina Pollastrini
The ICP-Forest program for the monitoring of forest conditions includes the assessment of ozone s... more The ICP-Forest program for the monitoring of forest conditions includes the assessment of ozone symptoms in the European forests. This contribute to discussion points out the problems related to the recognition of such symptoms, with a special focus on the difficulties to extend the results obtained in experimental conditions to woody plant species growing in the field. Non specific symptoms (such as reddening, yellowing, early senescence and leaf loss), and the concurrent action of modifying factors (high light, drought, nutrient deficiency, pest attack and fungi) make the recognition elusive. In these cases, the action of ozone cannot be proven or excluded with “ad hoc” experiments. Apparently “good” bioindicators (Rubus sp. Cornus sp. pl., Prunus sp. pl., Viburnum sp. pl. etc.) are not suitable to assess the impact of ozone on vegetation. Symptoms are not necessarily related to the ozone dose taken up by stomata, and don’t are reliable indicator for biomass and productivity losse...
Agrochimica -Pisa-
The current ecological condition of cities in respect to the surrounding countryside (higher temp... more The current ecological condition of cities in respect to the surrounding countryside (higher temperatures and CO 2 levels, drought, photochemical pressure and particulate matter pollutants), may anticipate the effects of climate change at a broader scale. However, the condition of urban trees can be exacerbated by some specific factors within cities, such as mismanagement and the direct impact of human activities. The acclimation and adaptation strategies shown by urban tree species may be similar to those already known for climate change, including the substitution of the current tree species with better adapted genotypes (native or not native) and the adoption of techniques aimed at improving stress resistance. In this paper, we review the main ecological factors affecting the physiology of urban trees, with a special reference to Mediterranean conditions. We summarise the criteria to select the most suitable trees, such as pheno-typing and the identification of functional traits ...
Plant Biology, 2014
Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kalte... more Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kaltenborn, Germany, and Satakunta, Finland) within a forest diversity experiment. Trees at Satakunta, planted in 1999, form a stratified canopy, while in Kaltenborn the trees are 7 years old, with no apparent canopy connection among broadleaf species. The following ChlF parameters from measured OJIP transient curves were examined: F V /F M (a proxy for maximum quantum yield); Ψ Eo (a proxy for efficiency in transferring an electron from reduced QA to the electron transport chain); I-P phase (a proxy for efficiency of reducing final acceptors beyond PSI); and PI tot (total performance index for potential energy conservation from photons absorbed by PSII to reduction of PSI end acceptors). At Satakunta F V /F M and Ψ Eo in Betula pendula were higher in monocultures and lower in mixed plots, perhaps due to increasing light availability in mixed plots, which can induce photoinhibition. The opposite trend was observed in Picea abies, which was shaded in mixed plots. At Kaltenborn F V /F M decreased in Fagus sylvatica and P. abies in mixed plots due to competition both above-and belowground. At Satakunta LMA increased in B. pendula leaves with increasing species richness. Leaf area of ten leaves was reduced in F. sylvatica in mixed plots at Kaltenborn. By up-scaling the overall fluorescence response to plot level (PI tot_plot ), a significant positive correlation with tree diversity was found at Kaltenborn, but not at Satakunta. This could suggest that competition/facilitation processes in mixed stands play a significant role in the early stages of forest establishment, but then tend to be compensated in more mature stands.
The aim of this educational review is to provide practical information on the hardware, methodolo... more The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who
have some experience with the application of Chl a fluorescence but are still in the process of discovering what it
all means and how it can be used. Topics discussed are
(among other things) the kind of information that can be
obtained using different fluorescence techniques, the
interpretation of Chl a fluorescence signals, specific
applications of these techniques, and practical advice on
different subjects, such as on the length of dark adaptation
before measurement of the Chl a fluorescence transient.
Recent research has shown that interactions between species with different functional traits can ... more Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (d 13 C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the d 13 C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and wateruse of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species.
Forest@ - Rivista di Selvicoltura ed Ecologia Forestale, 2012
La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'e... more La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'erosione genetica, può rappresentare una seria minaccia per il funzionamento degli ecosistemi . In quest'ottica, le domande che si pongono agli scienziati, ai gestori ed ai politici sono: quanto è importante la biodiversità per garantire la funzionalità degli ecosistemi? Quali sono le conseguenze ecologiche del suo declino?
Tree physiology, Jan 27, 2015
The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina... more The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina was detected in Italian coastal pine forests (Pinus pinea L.) in addition to the common native species Heterobasidion annosum (Fries) Brefeld. High levels of tropospheric ozone (O3) as an atmospheric pollutant are usually experienced in Mediterranean pine forests. To explore the effect of interaction between the two Heterobasidion species and ozone pollution on P. pinea, an open-top chamber (OTC) experiment was carried out. Five-year-old P. pinea seedlings were inoculated with the fungal species considered (H. irregulare, H. annosum and mock-inoculation as control), and then exposed in charcoal-filtered open-top chambers (CF-OTC) and non-filtered ozone-enriched chambers (NF+) from July to the first week of August 2010 at the experimental facilities of Curno (North Italy). Fungal inoculation effects in an ozone-enriched environment were assessed as: (i) the length of the inoculation lesi...
Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in ... more Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in the field by field teams working on the same project. In the first exercise (2007, Passo Pura, Ampezzo, Udine, Northern Italy) the operators took measurements on the same leaf areas (maintaining fixed leaf clips); in the second (2009, Monterotondo Marittimo, Grosseto, Central Italy) the teams worked independently, but addressing a common research question. The results of the first exercise showed that: (a) F V /F M was stable and had little variation among teams and instruments; (b) the results from the different teams correlated well; (c) the most suitable parameters of fast kinetics analysis are those measured on the normalized fluorescence transients. In the second exercise, when the teams worked independently, the results were much more variable and the correlations between measurements of different operators were weak. These results suggest that field chlorophyll a fluorescence measurements taken by different teams/operators can be comparable only if particular care is taken to the internal variability of the samples and a standardized sampling strategy is applied. A statistically sound representation of a population can be then reached.
The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populu... more The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populus maximowiczii Henry X P. × berolinensis Dippel -Oxford clone) in an open top chamber experiment carried out at the Curno facilities (Northern Italy). Chlorophyll (Chl) a fluorescence parameters (from both modulated and direct fluorescence) were assessed at different hours of the day (predawn, morning, midday, afternoon, and evening), from June to August 2008. This paper compares the results from predawn (PD, before sunrise) and afternoon (AN, in full sunlight) measurements, in order to evaluate the role of high sunlight as a factor influencing responses to ozone stress. Sunlight affected the maximum quantum yield of primary photochemistry (decrease of F v /F m ) thus indicating photoinhibition. The effective quantum yield (Φ PSII ) and the photochemical quenching (q P ) were enhanced in the afternoon with respect to the predawn, whereas the nonphotochemical quenching (NPQ) was reduced. The effect of ozone was detected with fluorescence on well watered plants in the first week of July, before the onset of visible symptoms. As far as F v /F m are concerned, the differences between ozone-treated and control plants were statistically significant in the predawn, but not in the afternoon. Ozone exerted only minor effects on drought exposed plants because of the reduced stomatal ozone uptake, but effects on the IP phase of the fluorescence transient were observed also in drought-stressed plants. Abbreviations: ABS -absorption energy flux; AN -afternoon; AOT40 -accumulated ozone above the threshold of 40 ppb; CF -charcoal filtered chambers; D -nonwatered plants (dry); DM -dry mass; ET -energy flux for electron; F 0 -minimal fluorescence of the dark-adapted state; F 0 ' -minimal fluorescence of the light-adapted state; F m -maximal fluorescence of the darkadapted state; F m ' -maximal fluorescence of the light-adapted state; FM -fresh mass; F v -total variable fluorescence (F m -F 0 ); F v /F m (= φ Po ) -maximum quantum yield of primary photochemistry in the dark-adapted state; F v ' /F m ' -PSII maximum efficiency in the light-adapted state; g s -stomatal conductance to water vapour; IP phase -[ΔV IP = 1 -V I ] -indicates the amplitude of the IP phase, i.e. the efficiency of electron transport around the PSI to reduce the final acceptors of the electron transport chain; J step -[Ψ Eo = 1 -V J ], expresses the efficiency with which a trapped exciton can move an electron into the electron transport chain from Q A to the intersystem electron acceptors; K band -relative variable fluorescence at 300 μs; L band -relative variable fluorescence at 100 μs; NF -not filtered chambers; NPQ -nonphotochemical quenching; OEC -oxygen-evolving complex; OTC -open top chamber; PAR -photosynthetically active radiation; PD -predawn; PI tot -Performance Index total, i.e. the performance index for energy conservation from photons absorbed by PSII to the reduction flux of PSI end acceptors; P N -net photosynthetic rate; PSI -photosystem I; PSII -photosystem II; q P -photochemical quenching; R -rainfall; RC -reaction center; RE -energy flux for the reduction of end acceptors; RH -relative humidity; RWC -relative water content; SM -satured fresh mass; T -temperature; TR -trapping capacity; V t -variable fluorescence at time t; W -well watered plants; Φ PSII -actual quantum yield of PSII, or PSII operating efficiency; Ψ w -water potential.
Recent research has shown that interactions between species with different functional traits can ... more Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (d 13 C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the d 13 C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and wateruse of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species.
La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'e... more La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'erosione genetica, può rappresentare una seria minaccia per il funzionamento degli ecosistemi . In quest'ottica, le domande che si pongono agli scienziati, ai gestori ed ai politici sono: quanto è importante la biodiversità per garantire la funzionalità degli ecosistemi? Quali sono le conseguenze ecologiche del suo declino?
Tree leaves are interfaces between the whole organism and the environment. Leaves display a serie... more Tree leaves are interfaces between the whole organism and the environment. Leaves display a series of attributes that are linked to specific functions (functional leaf traits-FLT) and/or show responses to biotic and abiotic stress factors (stress response traits, SRT), which can be subdivided into: (a) morphological traits; (b) chemical traits; (c) physiological traits; (d) symptoms. The analysis of FLT is a useful tool for tree species and provenance phenotyping, due to the adaptation of trees to environmental stress. Additionally, FLT can be used as response factor in long term and large spatial scales surveys of forest conditions. Despite these potential benefits of leaf traits in the assessment of ecosystem health and functioning, leaf sampling in forests is time-consuming and costly, especially in forests with a complex vertical and horizontal structure and in remote forest areas. Once a foliar sample has been collected, many different analyses can be carried out; however, analyses should be technically simple and able to be performed within one day following the leaf collection (i.e., on fresh samples), or after air-drying the leaves themselves (analysis of dried specimens). This paper reports the results of leaf sampling and foliar analyses carried out in previous research projects and revises the current state-of-the-art. The leaf traits that are easily obtainable from leaf sampling are listed, together with the operational procedures necessary for their measurement, described in a standardized protocol. Their ecological and functional relevance is discussed in relation to their potential information (as indicators of climatic stress, drought, air and soil pollution, tree light-use and competition, plant nutritional status, health and general plant stress conditions). Finally, this review provides suggestions for the elaboration and reporting of data, and proposes some guidelines to improve the effectiveness of foliar analysis in the assessment of forest ecosystem health, properties and functioning.
An open-top chamber experiment has been carried out at the facilities of Curno (North Italy), in ... more An open-top chamber experiment has been carried out at the facilities of Curno (North Italy), in June-August 2009, to assess the response to ozone in two poplar clones Populus maximowiczii Henry × P. berolinensis Dippel (Oxford clone, OX), and Populus nigra "Jean Pourtet" (JP) in concomitance of severe drought events. Three different water regimes were applied: W -Well Watered Control: field capacity; D1 -Drought Treatment 1: field capacity until begin July, then reduced water availability (plants were then subjected to severe drought events); D2 -Drought Treatment 2: constant water shortage (plants were then subjected to severe drought events). Leaf water potential, gas exchange and chlorophyll fluorescence (JIP-test) were assessed every 2 weeks; growth parameters and stable isotope composition (ı 13 C and ı 18 O) were measured at the end of the experiment. The main results were: (i) drought, but not ozone, reduced photosynthesis and growth and increased ı 13 C; (ii) the two clones showed different strategies to cope with ozone stress: JP shed the damaged leaves, whereas OX maintained their leaves ozone provoked the loss of leaves in W plants of the JP clone; (iii) in the D1 plants the response to drought provokes an additional effects with the effect of ozone absorbed before the severe drought events; (iv) D2 plants did not respond to ozone until the last event, when a clear synergistic effect between the two stressors was observed. We conclude that ozone had different effects in relation to the way the drought stress was applied. These results are discussed for their ecological consequence on vegetation in field conditions.
Increasingly severe droughts are expected to negatively impact forest functioning in the future, ... more Increasingly severe droughts are expected to negatively impact forest functioning in the future, especially in the Mediterranean region. Favoring mixed species stands has been advocated as a compromise between wood production and biodiversity conservation, but whether such management practices would allow forest ecosystems to acclimate to future climate conditions remains to be addressed. We tested whether the transpiration of Quercus cerris (Qc) and Quercus petraea (Qp) during droughts differ when they grow in pure or mixed forests. We measured sap flux density (F D ) and leaf carbon isotope composition (d 13 C), as a proxy for intrinsic water use efficiency (WUE int ), in pure and mixed Qc and/or Qp forest plots in Italy during the summer 2012. Qc and Qp showed a drop in F D of 41% and 52% respectively during the summer drought independently of the mixtures, but with different seasonal trends. Qp transpiration response to soil drought did not differ between pure and mixed plots. In contrast, Qc transpiration was reduced by 56% in mixed plots at the maximum of the drought and only by 31% in the pure plot. Furthermore, we observed higher WUE int for Qc in the mixed plot and no change for Qp, supporting the higher water stress intensity in the mixed plot for Qc. Our study illustrated the negative impact of Qp on Qc when these species compete for water resources. We suggest that managing for mixed stands in the Mediterranean region might, in some cases, increase the detrimental effect of drought on species functioning.
Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in ... more Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in the field by field teams working on the same project. In the first exercise (2007, Passo Pura, Ampezzo, Udine, Northern Italy) the operators took measurements on the same leaf areas (maintaining fixed leaf clips); in the second (2009, Monterotondo Marittimo, Grosseto, Central Italy) the teams worked independently, but addressing a common research question. The results of the first exercise showed that: (a) F V /F M was stable and had little variation among teams and instruments; (b) the results from the different teams correlated well; (c) the most suitable parameters of fast kinetics analysis are those measured on the normalized fluorescence transients. In the second exercise, when the teams worked independently, the results were much more variable and the correlations between measurements of different operators were weak. These results suggest that field chlorophyll a fluorescence measurements taken by different teams/operators can be comparable only if particular care is taken to the internal variability of the samples and a standardized sampling strategy is applied. A statistically sound representation of a population can be then reached.
Plant Physiology and Biochemistry, 2014
Nine short-term independent studies were carried out with two M-PEA units on several plant specie... more Nine short-term independent studies were carried out with two M-PEA units on several plant species differing in their functional traits (woody evergreen, woody deciduous, herbaceous) and exposed to different kind of abiotic stress (drought, salt, ozone, UV radiation). Aim of the study is to check the consistency of plant responses, assessed through three sets of simultaneously measured signals: Prompt Fluorescence (PF), Delayed Fluorescence (DF) and Modulated Reflectance of 820 nm light (MR). The decrease of F V /F M and F 0 , the increase of V J and V I were the most common responses related to PF parameters. The decrease of v ox and v red as well the increase of MR min were common response of MR. DF showed species-treatment specific behaviours. The Principal Component Analysis (PCA) suggests that the combination of PF and MR parameters represents a powerful tool for plant stress phenotyping, whereas MR parameters are linked to physiological strategies, related to different functional groups, to cope with stress factors.
Environmental and Experimental Botany, 2014
Increasing temperatures and drought risks through climate change are expected to have several con... more Increasing temperatures and drought risks through climate change are expected to have several consequences for European forests. Adaptive strategies may include: (i) persistence of the current forest types, thanks to the acclimatization to local conditions and to phenotypic plasticity of the populations; (ii) evolution, or local adaptation, i.e., change in genotype (frequencies) within the same species due to environmental pressure. It is favored by large within population diversity and (when possible) gene flow among populations; (iii) migration and substitution of species; and (iv) extinction of populations with low ecological plasticity, especially at the edges of their distribution or in the case of isolated (relict) populations. Because of the economic and ecological relevance of forests, it is of fundamental importance to apply appropriate forest management to make forests able to cope with the new environmental conditions. This may include changes in the composition and structure of forest stands, selection of adapted provenances of the most important European tree species or, if this is regarded as insufficient, assisted migration (i.e., the use of species suitable for the future climatic conditions) and, alternatively, substitution of native with non native species. The intraspecific (genetic and phenotypic) variability at a given site has been proven to be often higher than the variability among sites. Species with a large distribution range are supposed to have a wide variety of genotypes, allowing them to be adapted to different environmental conditions. Genetic variability and phenotypic plasticity are the key factors for the identification of useful tree genotypes for future forestation programs. Adaptation to drought, i.e., the probably most important future abiotic risk factor for forestry, can be reflected in variation of key functional traits (FT), at morphological, physiological and phenological level. FT utilized to screen for adapted genotypes in common gardens and provenance trials include growth, survival, leaf flushing and senescence, foliar features as leaf mass per area and nitrogen content, water use efficiency (e.g., estimated by analysis of the stable carbon isotopes, d 13 C) chlorophyll content, photosystem II functioning, and photosynthetic capacity under water shortage. Current modeled simulation of future forest distribution suggests the expansion of forests at the highest latitudes and altitudes, alongside with a reduction in the hottest and driest Mediterranean regions of South Europe. The general expectations, however, may be disproved especially at a regional level, by factors unexpected or not well known, such as possible extreme climatic events and increased roles of parasites/diseases (with negative effects), or high capacity of forest persistence or adaptation (with positive effects). Natural migration and species substitution can be hampered by co-factors of climate change, such as forest fragmentation and increased frequency and intensity of forest fires.
Water Air Soil Pollut, 2013
An experiment in open-top chambers was carried out in summer 2008 in Curno (northern Italy) in or... more An experiment in open-top chambers was carried out in summer 2008 in Curno (northern Italy) in order to study the effects of ozone and drought stress on net photosynthesis, growth and stable isotope partitioning on cuttings of an ozone-sensitive poplar clone (Oxford). The biomass (as dry weight) of stems, leaves and roots was assessed five times during the growing season on a set of plants intended for destructive measurements (set 1). Another set of plants (set 2) was used for repeated measurements (net photosynthesis) and then destroyed at the end of the experiment. The dry weight of the stems in set 1 plants was calculated using allometric relations. The results showed that drought stress had a strong effect on all the parameters assessed. Ozone did not have any effect on biomass allocation in woody stems and stable isotope composition but reduced root/shoot ratios and caused loss of leaves during the growing season. The loss of leaves in the lower part of the crown was partly recovered with the emission of new young leaves in the upper part, thus restoring the overall photosynthetic apparatus. We conclude that the metabolic costs suffered to repair damage and support growth, and the reduction in starch reserves in the roots can compromise growth and the capacity to cope with stress factors in subsequent years.
Proceedings of the National Academy of Sciences of the United States of America, Jan 14, 2014
Climate models predict an increase in the intensity and frequency of drought episodes in the Nort... more Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ(13)CS). Δδ(13)CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the...
The ICP-Forest program for the monitoring of forest conditions includes the assessment of ozone s... more The ICP-Forest program for the monitoring of forest conditions includes the assessment of ozone symptoms in the European forests. This contribute to discussion points out the problems related to the recognition of such symptoms, with a special focus on the difficulties to extend the results obtained in experimental conditions to woody plant species growing in the field. Non specific symptoms (such as reddening, yellowing, early senescence and leaf loss), and the concurrent action of modifying factors (high light, drought, nutrient deficiency, pest attack and fungi) make the recognition elusive. In these cases, the action of ozone cannot be proven or excluded with “ad hoc” experiments. Apparently “good” bioindicators (Rubus sp. Cornus sp. pl., Prunus sp. pl., Viburnum sp. pl. etc.) are not suitable to assess the impact of ozone on vegetation. Symptoms are not necessarily related to the ozone dose taken up by stomata, and don’t are reliable indicator for biomass and productivity losse...
Agrochimica -Pisa-
The current ecological condition of cities in respect to the surrounding countryside (higher temp... more The current ecological condition of cities in respect to the surrounding countryside (higher temperatures and CO 2 levels, drought, photochemical pressure and particulate matter pollutants), may anticipate the effects of climate change at a broader scale. However, the condition of urban trees can be exacerbated by some specific factors within cities, such as mismanagement and the direct impact of human activities. The acclimation and adaptation strategies shown by urban tree species may be similar to those already known for climate change, including the substitution of the current tree species with better adapted genotypes (native or not native) and the adoption of techniques aimed at improving stress resistance. In this paper, we review the main ecological factors affecting the physiology of urban trees, with a special reference to Mediterranean conditions. We summarise the criteria to select the most suitable trees, such as pheno-typing and the identification of functional traits ...
Plant Biology, 2014
Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kalte... more Chlorophyll a fluorescence (ChlF) and leaf morphology were assessed in two sites in Europe (Kaltenborn, Germany, and Satakunta, Finland) within a forest diversity experiment. Trees at Satakunta, planted in 1999, form a stratified canopy, while in Kaltenborn the trees are 7 years old, with no apparent canopy connection among broadleaf species. The following ChlF parameters from measured OJIP transient curves were examined: F V /F M (a proxy for maximum quantum yield); Ψ Eo (a proxy for efficiency in transferring an electron from reduced QA to the electron transport chain); I-P phase (a proxy for efficiency of reducing final acceptors beyond PSI); and PI tot (total performance index for potential energy conservation from photons absorbed by PSII to reduction of PSI end acceptors). At Satakunta F V /F M and Ψ Eo in Betula pendula were higher in monocultures and lower in mixed plots, perhaps due to increasing light availability in mixed plots, which can induce photoinhibition. The opposite trend was observed in Picea abies, which was shaded in mixed plots. At Kaltenborn F V /F M decreased in Fagus sylvatica and P. abies in mixed plots due to competition both above-and belowground. At Satakunta LMA increased in B. pendula leaves with increasing species richness. Leaf area of ten leaves was reduced in F. sylvatica in mixed plots at Kaltenborn. By up-scaling the overall fluorescence response to plot level (PI tot_plot ), a significant positive correlation with tree diversity was found at Kaltenborn, but not at Satakunta. This could suggest that competition/facilitation processes in mixed stands play a significant role in the early stages of forest establishment, but then tend to be compensated in more mature stands.
The aim of this educational review is to provide practical information on the hardware, methodolo... more The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who
have some experience with the application of Chl a fluorescence but are still in the process of discovering what it
all means and how it can be used. Topics discussed are
(among other things) the kind of information that can be
obtained using different fluorescence techniques, the
interpretation of Chl a fluorescence signals, specific
applications of these techniques, and practical advice on
different subjects, such as on the length of dark adaptation
before measurement of the Chl a fluorescence transient.
Recent research has shown that interactions between species with different functional traits can ... more Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (d 13 C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the d 13 C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and wateruse of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species.
Forest@ - Rivista di Selvicoltura ed Ecologia Forestale, 2012
La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'e... more La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'erosione genetica, può rappresentare una seria minaccia per il funzionamento degli ecosistemi . In quest'ottica, le domande che si pongono agli scienziati, ai gestori ed ai politici sono: quanto è importante la biodiversità per garantire la funzionalità degli ecosistemi? Quali sono le conseguenze ecologiche del suo declino?
Tree physiology, Jan 27, 2015
The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina... more The presence of the American root-rot disease fungus Heterobasidion irregulare Garbel. & Otrosina was detected in Italian coastal pine forests (Pinus pinea L.) in addition to the common native species Heterobasidion annosum (Fries) Brefeld. High levels of tropospheric ozone (O3) as an atmospheric pollutant are usually experienced in Mediterranean pine forests. To explore the effect of interaction between the two Heterobasidion species and ozone pollution on P. pinea, an open-top chamber (OTC) experiment was carried out. Five-year-old P. pinea seedlings were inoculated with the fungal species considered (H. irregulare, H. annosum and mock-inoculation as control), and then exposed in charcoal-filtered open-top chambers (CF-OTC) and non-filtered ozone-enriched chambers (NF+) from July to the first week of August 2010 at the experimental facilities of Curno (North Italy). Fungal inoculation effects in an ozone-enriched environment were assessed as: (i) the length of the inoculation lesi...
Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in ... more Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in the field by field teams working on the same project. In the first exercise (2007, Passo Pura, Ampezzo, Udine, Northern Italy) the operators took measurements on the same leaf areas (maintaining fixed leaf clips); in the second (2009, Monterotondo Marittimo, Grosseto, Central Italy) the teams worked independently, but addressing a common research question. The results of the first exercise showed that: (a) F V /F M was stable and had little variation among teams and instruments; (b) the results from the different teams correlated well; (c) the most suitable parameters of fast kinetics analysis are those measured on the normalized fluorescence transients. In the second exercise, when the teams worked independently, the results were much more variable and the correlations between measurements of different operators were weak. These results suggest that field chlorophyll a fluorescence measurements taken by different teams/operators can be comparable only if particular care is taken to the internal variability of the samples and a standardized sampling strategy is applied. A statistically sound representation of a population can be then reached.
The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populu... more The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populus maximowiczii Henry X P. × berolinensis Dippel -Oxford clone) in an open top chamber experiment carried out at the Curno facilities (Northern Italy). Chlorophyll (Chl) a fluorescence parameters (from both modulated and direct fluorescence) were assessed at different hours of the day (predawn, morning, midday, afternoon, and evening), from June to August 2008. This paper compares the results from predawn (PD, before sunrise) and afternoon (AN, in full sunlight) measurements, in order to evaluate the role of high sunlight as a factor influencing responses to ozone stress. Sunlight affected the maximum quantum yield of primary photochemistry (decrease of F v /F m ) thus indicating photoinhibition. The effective quantum yield (Φ PSII ) and the photochemical quenching (q P ) were enhanced in the afternoon with respect to the predawn, whereas the nonphotochemical quenching (NPQ) was reduced. The effect of ozone was detected with fluorescence on well watered plants in the first week of July, before the onset of visible symptoms. As far as F v /F m are concerned, the differences between ozone-treated and control plants were statistically significant in the predawn, but not in the afternoon. Ozone exerted only minor effects on drought exposed plants because of the reduced stomatal ozone uptake, but effects on the IP phase of the fluorescence transient were observed also in drought-stressed plants. Abbreviations: ABS -absorption energy flux; AN -afternoon; AOT40 -accumulated ozone above the threshold of 40 ppb; CF -charcoal filtered chambers; D -nonwatered plants (dry); DM -dry mass; ET -energy flux for electron; F 0 -minimal fluorescence of the dark-adapted state; F 0 ' -minimal fluorescence of the light-adapted state; F m -maximal fluorescence of the darkadapted state; F m ' -maximal fluorescence of the light-adapted state; FM -fresh mass; F v -total variable fluorescence (F m -F 0 ); F v /F m (= φ Po ) -maximum quantum yield of primary photochemistry in the dark-adapted state; F v ' /F m ' -PSII maximum efficiency in the light-adapted state; g s -stomatal conductance to water vapour; IP phase -[ΔV IP = 1 -V I ] -indicates the amplitude of the IP phase, i.e. the efficiency of electron transport around the PSI to reduce the final acceptors of the electron transport chain; J step -[Ψ Eo = 1 -V J ], expresses the efficiency with which a trapped exciton can move an electron into the electron transport chain from Q A to the intersystem electron acceptors; K band -relative variable fluorescence at 300 μs; L band -relative variable fluorescence at 100 μs; NF -not filtered chambers; NPQ -nonphotochemical quenching; OEC -oxygen-evolving complex; OTC -open top chamber; PAR -photosynthetically active radiation; PD -predawn; PI tot -Performance Index total, i.e. the performance index for energy conservation from photons absorbed by PSII to the reduction flux of PSI end acceptors; P N -net photosynthetic rate; PSI -photosystem I; PSII -photosystem II; q P -photochemical quenching; R -rainfall; RC -reaction center; RE -energy flux for the reduction of end acceptors; RH -relative humidity; RWC -relative water content; SM -satured fresh mass; T -temperature; TR -trapping capacity; V t -variable fluorescence at time t; W -well watered plants; Φ PSII -actual quantum yield of PSII, or PSII operating efficiency; Ψ w -water potential.
Recent research has shown that interactions between species with different functional traits can ... more Recent research has shown that interactions between species with different functional traits can promote forest ecosystem processes. In the context of climate change, understanding whether species interactions in mixed-species ecosystems can improve the adaptation of these ecosystems to extreme climatic events is crucial to developing new management strategies. In this study, we investigated the impact of species interactions on the sap flux density of three Mediterranean tree species (Quercus faginea, Pinus nigra and Pinus sylvestris) during a summer drought. Measurements of foliar carbon isotopic composition (d 13 C) were also conducted on the same trees. The decline in transpiration during drought was the greatest for P. sylvestris and the least pronounced for Q. faginea. For P. nigra and Q. faginea, the decrease in transpiration as the drought progressed was lower when these species where interacting with another tree species, particularly with P. sylvestris. In contrast, the decrease for P. sylvestris was higher when this species was interacting with another species. Differing drought effects were consistent with the d 13 C values. We showed that the identity of the species present in the direct neighbourhood of a given tree can differentially influence water availability and wateruse of these three co-existing Mediterranean tree species during a summer drought. Our findings suggest that species interactions play an important role in modulating the response of tree species to drought. Favouring tree species diversity in this region does not seem to be systematically beneficial in terms of soil water availability and water-use for all the interacting species.
La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'e... more La perdita di biodiversità attualmente in atto in molti sistemi naturali, oltre a costituire un'erosione genetica, può rappresentare una seria minaccia per il funzionamento degli ecosistemi . In quest'ottica, le domande che si pongono agli scienziati, ai gestori ed ai politici sono: quanto è importante la biodiversità per garantire la funzionalità degli ecosistemi? Quali sono le conseguenze ecologiche del suo declino?
Tree leaves are interfaces between the whole organism and the environment. Leaves display a serie... more Tree leaves are interfaces between the whole organism and the environment. Leaves display a series of attributes that are linked to specific functions (functional leaf traits-FLT) and/or show responses to biotic and abiotic stress factors (stress response traits, SRT), which can be subdivided into: (a) morphological traits; (b) chemical traits; (c) physiological traits; (d) symptoms. The analysis of FLT is a useful tool for tree species and provenance phenotyping, due to the adaptation of trees to environmental stress. Additionally, FLT can be used as response factor in long term and large spatial scales surveys of forest conditions. Despite these potential benefits of leaf traits in the assessment of ecosystem health and functioning, leaf sampling in forests is time-consuming and costly, especially in forests with a complex vertical and horizontal structure and in remote forest areas. Once a foliar sample has been collected, many different analyses can be carried out; however, analyses should be technically simple and able to be performed within one day following the leaf collection (i.e., on fresh samples), or after air-drying the leaves themselves (analysis of dried specimens). This paper reports the results of leaf sampling and foliar analyses carried out in previous research projects and revises the current state-of-the-art. The leaf traits that are easily obtainable from leaf sampling are listed, together with the operational procedures necessary for their measurement, described in a standardized protocol. Their ecological and functional relevance is discussed in relation to their potential information (as indicators of climatic stress, drought, air and soil pollution, tree light-use and competition, plant nutritional status, health and general plant stress conditions). Finally, this review provides suggestions for the elaboration and reporting of data, and proposes some guidelines to improve the effectiveness of foliar analysis in the assessment of forest ecosystem health, properties and functioning.
An open-top chamber experiment has been carried out at the facilities of Curno (North Italy), in ... more An open-top chamber experiment has been carried out at the facilities of Curno (North Italy), in June-August 2009, to assess the response to ozone in two poplar clones Populus maximowiczii Henry × P. berolinensis Dippel (Oxford clone, OX), and Populus nigra "Jean Pourtet" (JP) in concomitance of severe drought events. Three different water regimes were applied: W -Well Watered Control: field capacity; D1 -Drought Treatment 1: field capacity until begin July, then reduced water availability (plants were then subjected to severe drought events); D2 -Drought Treatment 2: constant water shortage (plants were then subjected to severe drought events). Leaf water potential, gas exchange and chlorophyll fluorescence (JIP-test) were assessed every 2 weeks; growth parameters and stable isotope composition (ı 13 C and ı 18 O) were measured at the end of the experiment. The main results were: (i) drought, but not ozone, reduced photosynthesis and growth and increased ı 13 C; (ii) the two clones showed different strategies to cope with ozone stress: JP shed the damaged leaves, whereas OX maintained their leaves ozone provoked the loss of leaves in W plants of the JP clone; (iii) in the D1 plants the response to drought provokes an additional effects with the effect of ozone absorbed before the severe drought events; (iv) D2 plants did not respond to ozone until the last event, when a clear synergistic effect between the two stressors was observed. We conclude that ozone had different effects in relation to the way the drought stress was applied. These results are discussed for their ecological consequence on vegetation in field conditions.
Increasingly severe droughts are expected to negatively impact forest functioning in the future, ... more Increasingly severe droughts are expected to negatively impact forest functioning in the future, especially in the Mediterranean region. Favoring mixed species stands has been advocated as a compromise between wood production and biodiversity conservation, but whether such management practices would allow forest ecosystems to acclimate to future climate conditions remains to be addressed. We tested whether the transpiration of Quercus cerris (Qc) and Quercus petraea (Qp) during droughts differ when they grow in pure or mixed forests. We measured sap flux density (F D ) and leaf carbon isotope composition (d 13 C), as a proxy for intrinsic water use efficiency (WUE int ), in pure and mixed Qc and/or Qp forest plots in Italy during the summer 2012. Qc and Qp showed a drop in F D of 41% and 52% respectively during the summer drought independently of the mixtures, but with different seasonal trends. Qp transpiration response to soil drought did not differ between pure and mixed plots. In contrast, Qc transpiration was reduced by 56% in mixed plots at the maximum of the drought and only by 31% in the pure plot. Furthermore, we observed higher WUE int for Qc in the mixed plot and no change for Qp, supporting the higher water stress intensity in the mixed plot for Qc. Our study illustrated the negative impact of Qp on Qc when these species compete for water resources. We suggest that managing for mixed stands in the Mediterranean region might, in some cases, increase the detrimental effect of drought on species functioning.
Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in ... more Two field exercises were carried out to compare chlorophyll a fluorescence measurements taken in the field by field teams working on the same project. In the first exercise (2007, Passo Pura, Ampezzo, Udine, Northern Italy) the operators took measurements on the same leaf areas (maintaining fixed leaf clips); in the second (2009, Monterotondo Marittimo, Grosseto, Central Italy) the teams worked independently, but addressing a common research question. The results of the first exercise showed that: (a) F V /F M was stable and had little variation among teams and instruments; (b) the results from the different teams correlated well; (c) the most suitable parameters of fast kinetics analysis are those measured on the normalized fluorescence transients. In the second exercise, when the teams worked independently, the results were much more variable and the correlations between measurements of different operators were weak. These results suggest that field chlorophyll a fluorescence measurements taken by different teams/operators can be comparable only if particular care is taken to the internal variability of the samples and a standardized sampling strategy is applied. A statistically sound representation of a population can be then reached.
Plant Physiology and Biochemistry, 2014
Nine short-term independent studies were carried out with two M-PEA units on several plant specie... more Nine short-term independent studies were carried out with two M-PEA units on several plant species differing in their functional traits (woody evergreen, woody deciduous, herbaceous) and exposed to different kind of abiotic stress (drought, salt, ozone, UV radiation). Aim of the study is to check the consistency of plant responses, assessed through three sets of simultaneously measured signals: Prompt Fluorescence (PF), Delayed Fluorescence (DF) and Modulated Reflectance of 820 nm light (MR). The decrease of F V /F M and F 0 , the increase of V J and V I were the most common responses related to PF parameters. The decrease of v ox and v red as well the increase of MR min were common response of MR. DF showed species-treatment specific behaviours. The Principal Component Analysis (PCA) suggests that the combination of PF and MR parameters represents a powerful tool for plant stress phenotyping, whereas MR parameters are linked to physiological strategies, related to different functional groups, to cope with stress factors.
Environmental and Experimental Botany, 2014
Increasing temperatures and drought risks through climate change are expected to have several con... more Increasing temperatures and drought risks through climate change are expected to have several consequences for European forests. Adaptive strategies may include: (i) persistence of the current forest types, thanks to the acclimatization to local conditions and to phenotypic plasticity of the populations; (ii) evolution, or local adaptation, i.e., change in genotype (frequencies) within the same species due to environmental pressure. It is favored by large within population diversity and (when possible) gene flow among populations; (iii) migration and substitution of species; and (iv) extinction of populations with low ecological plasticity, especially at the edges of their distribution or in the case of isolated (relict) populations. Because of the economic and ecological relevance of forests, it is of fundamental importance to apply appropriate forest management to make forests able to cope with the new environmental conditions. This may include changes in the composition and structure of forest stands, selection of adapted provenances of the most important European tree species or, if this is regarded as insufficient, assisted migration (i.e., the use of species suitable for the future climatic conditions) and, alternatively, substitution of native with non native species. The intraspecific (genetic and phenotypic) variability at a given site has been proven to be often higher than the variability among sites. Species with a large distribution range are supposed to have a wide variety of genotypes, allowing them to be adapted to different environmental conditions. Genetic variability and phenotypic plasticity are the key factors for the identification of useful tree genotypes for future forestation programs. Adaptation to drought, i.e., the probably most important future abiotic risk factor for forestry, can be reflected in variation of key functional traits (FT), at morphological, physiological and phenological level. FT utilized to screen for adapted genotypes in common gardens and provenance trials include growth, survival, leaf flushing and senescence, foliar features as leaf mass per area and nitrogen content, water use efficiency (e.g., estimated by analysis of the stable carbon isotopes, d 13 C) chlorophyll content, photosystem II functioning, and photosynthetic capacity under water shortage. Current modeled simulation of future forest distribution suggests the expansion of forests at the highest latitudes and altitudes, alongside with a reduction in the hottest and driest Mediterranean regions of South Europe. The general expectations, however, may be disproved especially at a regional level, by factors unexpected or not well known, such as possible extreme climatic events and increased roles of parasites/diseases (with negative effects), or high capacity of forest persistence or adaptation (with positive effects). Natural migration and species substitution can be hampered by co-factors of climate change, such as forest fragmentation and increased frequency and intensity of forest fires.
Water Air Soil Pollut, 2013
An experiment in open-top chambers was carried out in summer 2008 in Curno (northern Italy) in or... more An experiment in open-top chambers was carried out in summer 2008 in Curno (northern Italy) in order to study the effects of ozone and drought stress on net photosynthesis, growth and stable isotope partitioning on cuttings of an ozone-sensitive poplar clone (Oxford). The biomass (as dry weight) of stems, leaves and roots was assessed five times during the growing season on a set of plants intended for destructive measurements (set 1). Another set of plants (set 2) was used for repeated measurements (net photosynthesis) and then destroyed at the end of the experiment. The dry weight of the stems in set 1 plants was calculated using allometric relations. The results showed that drought stress had a strong effect on all the parameters assessed. Ozone did not have any effect on biomass allocation in woody stems and stable isotope composition but reduced root/shoot ratios and caused loss of leaves during the growing season. The loss of leaves in the lower part of the crown was partly recovered with the emission of new young leaves in the upper part, thus restoring the overall photosynthetic apparatus. We conclude that the metabolic costs suffered to repair damage and support growth, and the reduction in starch reserves in the roots can compromise growth and the capacity to cope with stress factors in subsequent years.
Proceedings of the National Academy of Sciences of the United States of America, Jan 14, 2014
Climate models predict an increase in the intensity and frequency of drought episodes in the Nort... more Climate models predict an increase in the intensity and frequency of drought episodes in the Northern Hemisphere. Among terrestrial ecosystems, forests will be profoundly impacted by drier climatic conditions, with drastic consequences for the functions and services they supply. Simultaneously, biodiversity is known to support a wide range of forest ecosystem functions and services. However, whether biodiversity also improves the resistance of these ecosystems to drought remains unclear. We compared soil drought exposure levels in a total of 160 forest stands within five major forest types across Europe along a gradient of tree species diversity. We assessed soil drought exposure in each forest stand by calculating the stand-level increase in carbon isotope composition of late wood from a wet to a dry year (Δδ(13)CS). Δδ(13)CS exhibited a negative linear relationship with tree species diversity in two forest types, suggesting that species interactions in these forests diminished the...