scholarly journals Cavitation Limits the Recovery of Gas Exchange after Severe Drought Stress in Holm Oak (Quercus ilex L.)

Forests ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 443 ◽  
Author(s):  
José Peguero-Pina ◽  
Óscar Mendoza-Herrer ◽  
Eustaquio Gil-Pelegrín ◽  
Domingo Sancho-Knapik
Keyword(s):  
Drought Stress ◽  
Quercus Ilex ◽  
Stomatal Closure ◽  
Maximum Velocity ◽  
Holm Oak ◽  
Severe Drought ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Partial Recovery ◽  
Xylem Embolism

Holm oak (Quercus ilex L.) is a Mediterranean species that can withstand intense summer drought through a high resistance to cavitation far beyond the stomatal closure. Besides stomatal limitations, both mesophyll and biochemical limitations to CO2 uptake could increase in holm oak under drought. However, no studies have addressed how hydraulic and non-hydraulic factors may limit the recovery of photosynthesis when re-watering after inducing 50% loss of hydraulic conductivity. We measured photosynthetic traits, xylem embolism, and abscisic acid (ABA) in holm oak with increasing levels of drought stress and seven days after plant re-watering. Drought stress caused a sharp decrease in net CO2 assimilation (AN), stomatal and mesophyll conductance (gs and gm), and maximum velocity of carboxylation (Vcmax). The stomatal closure could be mediated by the rapid increase found in ABA. The high level of xylem embolism explained the strong down-regulation of gs even after re-watering. Therefore, only a partial recovery of AN was observed, in spite of non-hydraulic factors not limiting the recovery of AN, because i/ABA strongly decreased after re-watering, and ii/gm and Vcmax recovered their original values. Therefore, the hydraulic-stomatal limitation model would be involved in the partial recovery of AN, in order to prevent extensive xylem embolism under subsequent drought events that could compromise holm oak survival.

Leaf morphology, photochemistry and water status changes in resprouting Quercus ilex during drought

2005 ◽  
Vol 32 (2) ◽  
pp. 117 ◽  
Author(s):  
Karen Peña-Rojas ◽  
Xavier Aranda ◽  
Richard Joffre ◽  
Isabel Fleck
Keyword(s):  
Drought Stress ◽  
Quercus Ilex ◽  
Structural Characteristics ◽  
Water Status ◽  
Stomatal Closure ◽  
Severe Drought ◽  
Clear Cut ◽  
Leaf Mass Area ◽  
Relative Water ◽  
Moderate Drought

Functional and morphological (structural) characteristics of Quercus ilex L. leaves under drought stress were studied in the forest and in a nursery. We compared undisturbed individuals (controls) with resprouts emerging after clear-cut or excision. When soil water availability was high, gas-exchange was similar in resprouts and controls, despite higher midday leaf water potential, midday leaf hydration and relative water content (RWC). In moderate drought, stomatal closure was found to limit photosynthesis in controls, and in severe drought non-stomatal limitations of photosynthesis were also greater than in resprouts. Leaf structure and chemical composition changed under drought stress. Leaves tended to be smaller in controls with increasing drought, and resprouts had larger leaves and lower leaf mass area (LMA). The relationship between nitrogen (N) content and LMA implied lower N investment in photosynthetic components in controls, which could be responsible for their increased non-stomatal limitation of photosynthesis. Changes were more apparent in leaf density (D) and thickness (T), components of LMA. Decreases in D were related to reductions in cell wall components: hemicellulose, cellulose and lignin. In resprouts, reduced D and leaf T accounted for the higher mesophyll conductance (gmes) to CO2 measured.

scholarly journals Summer drought stress: differential effects on cane anatomy and non-structural carbohydrate content in overwintering Cabernet Sauvignon and Syrah vines

2019 ◽  
Vol 13 ◽  
pp. 03007 ◽  
Author(s):  
Rachele Falchi ◽  
Elisa Petrussa ◽  
Marco Zancani ◽  
Valentino Casolo ◽  
Paola Beraldo ◽  
...  
Keyword(s):  
Water Stress ◽  
Drought Stress ◽  
Biochemical Characterization ◽  
Carbon Allocation ◽  
Starch Accumulation ◽  
Cabernet Sauvignon ◽  
Severe Drought ◽  
Summer Drought ◽  
Long Term Effects ◽  
Experimental Conditions

Grapevines store non-structural carbohydrates (NSC) during late summer to sustain plant development at the onset of the following spring’s growth. Starch is the main stored carbohydrate, found in the wood-ray parenchyma of roots and canes. Although the relationship between hydraulic and plant photosynthetic performance is well-recognized, little research has been done on the long-term effects of drought in grapevines adopting different strategies to cope with water stress (i.e. isohydric and anisohydric). We performed our study by exposing two different grape cultivars (Syrah and Cabernet Sauvignon) to a short but severe drought stress, at two stages of the growing season (July and September). No marked differences in the physiological and hydraulic responses of the two varieties were found, probably due to our experimental conditions. However, anatomical and biochemical characterization of overwintering canes pointed out several interesting outcomes. We found a significant and parallel increase of starch and medullar ray number in both cultivars exposed to early water stress. We hypothesize that stressed vines limited their carbon allocation to growth, while shifting it to starch accumulation, with a most evident effect in the period of intense photosynthetic activity. We also speculate that a different aptitude to osmotic adjustment may underlay variation in starch increase and the specific involvement of bark NSC in the two cultivars.

scholarly journals The impact of drought on total ozone flux in a mountain Norway spruce forest

2020 ◽  
Vol 66 (No. 7) ◽  
pp. 280-278 ◽  
Author(s):  
Thomas Agyei ◽  
Stanislav Juráň ◽  
Kojo Kwakye Ofori-Amanfo ◽  
Ladislav Šigut ◽  
Otmar Urban ◽  
...  
Keyword(s):  
Norway Spruce ◽  
Stomatal Closure ◽  
Severe Drought ◽  
Summer Drought ◽  
Spruce Forest ◽  
Soil Humidity ◽  
Drought Period ◽  
The Impact ◽  
Mild Drought ◽  
Norway Spruce Forest

In order to understand the impact of summer drought on dry deposition of tropospheric ozone (O<sub>3</sub>), we compared severe and mild drought periods of summer 2018 in a mountain Norway spruce forest at Bílý Kříž, Beskydy Mts. An eddy covariance technique was applied to measure diurnal courses of the ecosystem O<sub>3</sub> and CO<sub>2</sub> fluxes. Low O<sub>3</sub> deposition was recorded in the morning and evening, while the highest CO<sub>2</sub> and O<sub><sup>3</sup></sub> fluxes were recorded during the central hours of the day. Total O<sub>3</sub> deposition during severe drought (soil humidity 13%) was significantly higher than the deposition during the mild drought period (soil humidity 19%). Our data indicate that high vapour pressure deficit and low soil humidity during severe drought led to the stomatal closure, while non-stomatal O<sub>3</sub> deposition, associated with chemical reactions of O<sub>3</sub> with NO and volatile organic compounds, are responsible for higher total O<sub>3</sub> deposition during the severe drought period. Therefore, we assume that under severe drought stomatal O<sub>3</sub> uptake decreases but non-stomatal depositions to forest ecosystems substantially increase.

Contrasting functional strategies following severe drought in two Mediterranean oaks with different leaf habit: Quercus faginea and Quercus ilex subsp. rotundifolia

2020 ◽  
Author(s):  
David Alonso-Forn ◽  
José Javier Peguero-Pina ◽  
Juan Pedro Ferrio ◽  
Maurizio Mencuccini ◽  
Óscar Mendoza-Herrer ◽  
...  
Keyword(s):  
Life Span ◽  
Quercus Ilex ◽  
Soil Water Potential ◽  
Leaf Life Span ◽  
Severe Drought ◽  
Summer Drought ◽  
Drought Period ◽  
Quercus Faginea ◽  
Leaf Habit ◽  
Mediterranean Oaks

Abstract Nowadays, evergreen sclerophyllous and winter-deciduous malacophyllous oaks with different paleogeographical origins coexist under Mediterranean-type climates, such as the mixed forests of the evergreen Quercus ilex subsp. rotundifolia Lam. and the winter-deciduous Quercus faginea Lam. Both Mediterranean oaks constitute two examples of contrasting leaf habit, so it could be expected that they would have different functional strategies to cope with summer drought. In this study, we analysed photosynthetic, photochemical and hydraulic traits of different organs for Q. faginea and Q. ilex subsp. rotundifolia under well-watered conditions and subjected to very severe drought. The coordinated response between photosynthetic and hydraulic traits explained the higher photosynthetic capacity of Q. faginea under well-watered conditions, which compensated its shorter leaf life span at the expense of higher water consumption. The progressive imposition of water stress evidenced that both types of Mediterranean oaks displayed different functional strategies to cope with water limitations. Specifically, the decrease in mesophyll conductance associated with edaphic drought seems to be the main factor explaining the differences found in the dynamics of net CO2 assimilation throughout the drought period. The sharp decline in photosynthetic traits of Q. faginea was coupled with a strong decrease in shoot hydraulic conductance in response to drought. This fact probably avoided extensive xylem embolism in the stems (i.e., ‘vulnerability segmentation’), which enabled new leaf development after drought period in Q. faginea. By contrast, leaves of Q. ilex subsp. rotundifolia showed effective photoprotective mechanisms and high resistance to drought-induced cavitation, which would be related with the longer leaf life span of the evergreen Mediterranean oaks. The co-occurrence of both types of Mediterranean oaks could be related to edaphic conditions that ensure the maintenance of soil water potential above critical values for Q. faginea, which can be severely affected by soil degradation and climate change.

Evaluation of soil moisture stress parameterizations in MEGAN model against MOFLUX field data and satellite observations of formaldehyde from OMI 

2021 ◽  
Author(s):  
Beata Opacka ◽  
Trissevgeni Stavrakou ◽  
Jean-François Müller ◽  
Maite Bauwens ◽  
Diego Miralles ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Drought Stress ◽  
Transport Model ◽  
Moisture Stress ◽  
Atmospheric Composition ◽  
Severe Drought ◽  
Summer Drought ◽  
Soil Moisture Stress ◽  
Community Land Model ◽  
Flux Measurements

&lt;p&gt;Biogenic volatile organic compounds (BVOCs) are emitted globally at about 1,100 Tg per year, with almost half of the share entailed by isoprene. Isoprene is highly reactive in the atmosphere, and its degradation impacts the atmospheric composition through the generation of ozone (in presence of NOx typical of polluted areas) and secondary organic aerosols, which both pose a risk to human health. Extreme weather conditions like heatwaves and droughts can substantially affect the emissions of isoprene in ways that are largely unknown. This limited knowledge is owed to the scarcity of isoprene flux measurements under drought stress conditions. The Missouri Ozarks AmeriFlux (MOFLUX) site is located in a high isoprene-emitting oak-hickory forested region with recurring drought occurrences. Until today, it is the only site with isoprene flux measurements that capture drought behaviour.&lt;/p&gt;&lt;p&gt;In this study, we use the state-of-the-art MEGAN biogenic emission model (Guenther et al., 2006; 2012) coupled with the canopy model MOHYCAN (M&amp;#252;ller et al., 2008) to estimate isoprene emissions and evaluate two different parameterizations of the soil moisture stress factor (&amp;#947;&lt;sub&gt;SM&lt;/sub&gt;): (a) the one used in MEGANv2.1, which consists of a simple dependence on soil water content and the permanent wilting point with inputs either from ERA-Interim or the GLEAMv3 reanalysis (Martens et al., 2017), and (b) the parameterization available in MEGANv3 (Jiang et al., 2018), which considers the physiological effects of drought stress on plant photosynthesis as defined in the Community Land Model (CLM4.5), which embeds the MEGAN model. &amp;#160;The effect of &amp;#947;&lt;sub&gt;SM&lt;/sub&gt;&amp;#160;on isoprene estimates is assessed against measurements of isoprene fluxes at the MOFLUX field site collected during the mild summer drought in 2011 (Potosnak et al., 2014) and the severe drought in 2012 (Seco et al., 2015). Based on the comparisons at the MOFLUX site, we perform an optimization of the empirical parameters of the MEGANv2.1 soil moisture stress parameterization. In addition, the parameterization is further evaluated using spaceborne formaldehyde (HCHO) columns observed by the OMI sounder. To this end, we perform multiyear simulations (2005-2016) of atmospheric composition with the IMAGES global chemistry-transport model (M&amp;#252;ller et al., 2019) using isoprene emission datasets obtained for several variants of the parameterization. We evaluate the resulting HCHO column distributions and their interannual variability against OMI HCHO columns over drought-prone regions.&lt;/p&gt;&lt;p&gt;This work is conducted in the frame of the ALBERI project, funded by the Belgian Science Policy Office through the STEREO III programme.&lt;/p&gt;

scholarly journals Grafting cv. Grechetto Gentile Vines to New M4 Rootstock Improves Leaf Gas Exchange and Water Status as Compared to Commercial 1103P Rootstock

Agronomy ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 708 ◽  
Author(s):  
Tommaso Frioni ◽  
Arianna Biagioni ◽  
Cecilia Squeri ◽  
Sergio Tombesi ◽  
Matteo Gatti ◽  
...  
Keyword(s):  
Water Stress ◽  
Gas Exchange ◽  
Water Use ◽  
Leaf Gas Exchange ◽  
Water Status ◽  
Stomatal Closure ◽  
Leaf Water ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Drought Tolerant

M4 is a relatively new rootstock that was selected for increased resilience of vineyards across hot regions where meteorological drought is often coupled to water scarcity. However, M4 has thus far been tested only against water-stress sensitive rootstocks. Against this backdrop, the aim of the present work is to examine the water status and gas exchange performances of vines grafted to M4 in comparison to those of vines grafted to a commercial stock that is drought-tolerant, 1103 Paulsen (1103P), under a progressive water deficit followed by re-watering. This study was undertaken on Grechetto Gentile, a cultivar that is renowned for its rather conservative water use (near-isohydric behavior). While fifty percent of both grafts were fully irrigated (WW), the remaining underwent progressive water stress by means of suspending irrigation (WS). Soil and leaf water status, as well as leaf gas exchanges, along with chlorophyll fluorescence, were followed daily from 1 day pre-stress (DOY 176) until re-watering (DOY 184). Final leaf area per vine, divided in main and lateral contribution, was also assessed. While 1103P grafted vines manifested higher water use under WW conditions, progressive stress evidenced a faster water depletion by 1103P, which also maintained slightly more negative midday leaf water potential (Ψleaf) as compared to M4 grafted plants. Daily gas exchange readings, as well as diurnal assessment performed at the peak of stress (DOY 183), also showed increased leaf assimilation rates (A) and water use efficiency (WUE) in vines grafted on M4, which were also less susceptible to photosynthetic downregulation. Dynamic of stomatal closure targeted at 90% reduction of leaf stomatal conductance showed a similar behavior among rootstocks since the above threshold was reached by both at Ψleaf of about −1.11 MPa. The same fractional reduction in leaf A was reached by vines grafted on M4 at a Ψleaf of −1.28 MPa vs. −1.10 MPa measured in 1103P, meaning that using M4 as a rootstock will postpone full stomatal closure. While mechanisms involved in improved CO2 uptake in M4-grafted vines under moderate-to-severe stress are still unclear, our data support the hypothesis that M4 might outscore the performance of a commercial drought-tolerant genotype (1103P) and can be profitably used as a tool to improve the resilience of vines to summer drought.

Do volatile organic compound emissions of Tunisian cork oak populations originating from contrasting climatic conditions differ in their responses to summer drought?

2008 ◽  
Vol 38 (12) ◽  
pp. 2965-2975 ◽  
Author(s):  
Michael Staudt ◽  
Amel Ennajah ◽  
Florent Mouillot ◽  
Richard Joffre
Keyword(s):  
Organic Compound ◽  
Gas Exchange ◽  
Volatile Organic Compound ◽  
Photochemical Efficiency ◽  
Photosynthetic Parameters ◽  
Severe Drought ◽  
Summer Drought ◽  
Partial Recovery ◽  
Volatile Organic ◽  
Volatile Organic Compound Emissions

The intrinsic variability of volatile organic compound emissions and photosynthetic parameters in response to two drying cycles was investigated on Quercus suber L. saplings originating from three Tunisian populations native to contrasting climates. Emissions mainly included monoterpenes plus traces of sesquiterpenes and methylsalicylate that steadily decreased during the experiment unrelated to treatments. Instead, monoterpene emissions increased by 30% during a first moderate drought and remained enhanced after rewatering, while CO2–H2O gas exchange was reduced by 30%. A second severe drought decreased monoterpene emissions to about two third of controls, strongly inhibited gas exchange and photochemical efficiency, and caused a partial loss of chlorophyll. Rewatering led to only partial recovery of emissions and photosynthetic parameters of stressed plants whose biomasses and leaf nitrogen and chlorophyll contents were lower than in control plants. There was no clear difference among populations in volatile organic compound emissions or photosynthetic parameters. However, the population inhabiting the most arid region had intrinsically smaller leaves with lower specific leaf masses and higher drought-related leaf losses than populations native to less arid climates. These results indicate an adaptive shift from stress-tolerating towards stress-avoiding ecotypes under arid climates involving mainly morphological adaptations without apparent differentiation in volatile organic compound production, probably because of its high phenological plasticity.

scholarly journals Parameterization of the Stomatal Component of the DO3SE Model for Mediterranean Evergreen Broadleaf Species

2007 ◽  
Vol 7 ◽  
pp. 119-127 ◽  
Author(s):  
Roccío Alonso ◽  
Susana Elvira ◽  
María J. Sanz ◽  
Lisa Emberson ◽  
Benjamín S. Gimeno
Keyword(s):  
Quercus Ilex ◽  
Measured Data ◽  
Holm Oak ◽  
Accurate Estimation ◽  
Soil Parameters ◽  
Summer Drought ◽  
Moisture Deficit ◽  
Broadleaf Species ◽  
Mapping Exercise ◽  
Good Agreement

An ozone (O3) deposition model (DO3SE) is currently used in Europe to define the areas where O3concentrations lead to absorbed O3doses that exceed the flux-based critical levels above which phytotoxic effects would be likely recorded. This mapping exercise relies mostly on the accurate estimation of O3flux through plant stomata. However, the present parameterization of the modulation of stomatal conductance (gs) behavior by different environmental variables needs further adjustment if O3phytotoxicity is to be assessed accurately at regional or continental scales. A new parameterization of the model is proposed for Holm oak (Quercus ilex), a tree species that has been selected as a surrogate for all Mediterranean evergreen broadleaf species. This parameterization was based on a literature review, and was calibrated and validated using experimentally measured data of gsand several atmospheric and soil parameters recorded at three sites of the Iberian Peninsula experiencing long summer drought, and very cold and dry winter air (El Pardo and Miraflores) or milder conditions (Tietar). A fairly good agreement was found between modeled and measured data (R2= 0.64) at Tietar. However, a reasonable performance (R2= 0.47–0.62) of the model was only achieved at the most continental sites when gsand soil moisture deficit relationships were considered. The influence of root depth on gsestimation is discussed and recommendations are made to build up separate parameterizations for continental and marine-influenced Holm oak sites in the future.

Evaluating the effect of the 2018 drought on the NEE in the Sorø beech forest by means of trend analysis and mechanistic canopy modelling of GPP.

2020 ◽  
Author(s):  
Kim Pilegaard ◽  
Andreas Ibrom
Keyword(s):  
Water Content ◽  
Linear Trend ◽  
Heavy Rain ◽  
Beech Forest ◽  
Seasonal Development ◽  
Severe Drought ◽  
Summer Drought ◽  
Co2 Uptake ◽  
Data Set ◽  
Flux Data

&lt;p&gt;Denmark experienced a severe drought in 2018 lasting from the beginning of May to the end of August with very little rain during this period. The influence of drought on the net ecosystem CO&lt;sub&gt;2&lt;/sub&gt; exchange (NEE) was analysed at the Danish ICOS DK-Soroe site (a mature beech forest). The site has a very long continuous flux data set starting in June 1996. The annual NEE of the site has been increasing over the years, mainly due to a prolonged growing season in the autumn and CO&lt;sub&gt;2&lt;/sub&gt; fertilisation (Pilegaard et al., 2011).&lt;/p&gt;&lt;p&gt;The effect of the summer drought in 2018 was analysed by means of linear trend estimation based on monthly trends during 1996-2017. The observed monthly NEE in 2018 was compared to the predicted values from the monthly time series.&lt;/p&gt;&lt;p&gt;The analysis showed an increased NEE in May and June and a strongly reduced NEE in July and August. Overall, the NEE was reduced 25% compared to the predicted value.&lt;/p&gt;&lt;p&gt;The increased NEE in May and June can be explained by the benefit for the photosynthesis of the trees of the increased light and temperature, while there was still a sufficient water content in the soil. By the end of June, the low water content in the soil affected the NEE, and despite some heavy rain in the beginning of August, the NEE only recovered by September.&lt;/p&gt;&lt;p&gt;We used the flux data set together with a mechanistic canopy model to examine the tree physiological nature of the photosynthesis limitation. The results showed that stomatal limitation alone was not able to explain the large reduction of GPP during the drought. Based on these findings, we extended the approach and show the seasonal development of drought induced GPP limitation contrasting stomatal and biochemical photosynthesis limitations.&lt;/p&gt;&lt;p&gt;The effects on NEE and energy partitioning during the 2018 summer drought are compared to previous years with (less severe) summer drought.&amp;#160;&lt;/p&gt;&lt;p&gt;Reference:&lt;/p&gt;&lt;p&gt;Kim Pilegaard, Andreas Ibrom, Michael S. Courtney, Poul Hummelsh&amp;#248;j, Niels Otto Jensen. Increasing net CO2 uptake by a Danish beech forest during the period from 1996 to 2009. Agricultural and Forest Meteorology 151 (2011) 934&amp;#8211;946.&lt;/p&gt;&lt;p&gt;Acknowledgement:&lt;/p&gt;&lt;p&gt;The study was based on data from ICOS/DK.&lt;/p&gt;

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