Seasonal trends in photosynthesis and electron transport during the Mediterranean summer drought in leaves of deciduous oaks

Almond willow (Salix triandra L.) is a valuable basket species that is used to create plantings for various purposes. He occupies a special place in the system of the genus Salix. He can be used as a model object to identify patterns of morphogenesis of shoots. Object of research: model inbred population of almond willow in culture. Subject of research: seasonal dynamics of internode length on annual shoots of three-year-old seedlings willow of almond willow. The purpose of the research: to identify the seasonal dynamics of the length of internodes on annual shoots of almond willow against the background of a sharp change in early summer drought by cold rainy weather. Empirical methods for obtaining initial data: comparative-morphological. The obtained data were processed using the methods of analysis of dynamics series. It is found that seasonal trends in the dynamics of internode length are described by second-order regression equations with varying reliability. The configuration and topology of nonlinear seasonal trends are determined by individual differences between seedlings. The dynamics of deviations of internode length from seasonal trends correlates with the dynamics of hydrothermic conditions. Deviations in the length of internodes from seasonal trends are cyclical. The empirical series of deviations of the internode length from seasonal trends with high reliability are approximated by the sums of harmonic oscillations. The maximum contribution to the cyclical deviations of the internode length from seasonal trends is made by the rhythm with a period of fluctuations of 54 days. On most shoots, the influence of rhythms with a period of fluctuations of 36 and 27 days can be traced. Short-period rhythms detected on different shoots are irregular. In most observations, the specific rhythms of seasonal dynamics of internode length are determined by differences between shoots. The identified rhythms do not depend on hydrothermic conditions, on the length of shoots, on the length of internodes, or on seasonal trends in the dynamics of internode length. The hypothesis that the relationship between the dynamics of deviations in the length of internodes from seasonal trends and the dynamics of hydrothermic conditions is random is substantiated. Cyclicity deviations of internode length from seasonal trends are determined by endogenous rhythms of development.

Download Full-text

The effect of summer drought on vegetation structure in the mediterranean climate region of Australia

Plant Response to Stress ◽

10.1007/978-3-642-70868-8_43 ◽

1987 ◽

pp. 625-639 ◽

Cited By ~ 7

Author(s):

R. L. Specht

Keyword(s):

Vegetation Structure ◽

Mediterranean Climate ◽

Summer Drought ◽

Climate Region ◽

The Mediterranean

Download Full-text

Saharan Hot and Dry Sirocco Winds Drive Extreme Fire Events in Mediterranean Tunisia (North Africa)

Atmosphere ◽

10.3390/atmos11060590 ◽

2020 ◽

Vol 11 (6) ◽

pp. 590 ◽

Cited By ~ 1

Author(s):

Chiraz Belhadj-Khedher ◽

Taoufik El-Melki ◽

Florent Mouillot

Keyword(s):

Mediterranean Basin ◽

Heat Waves ◽

Fire Hazard ◽

Weather Conditions ◽

Burned Area ◽

Summer Drought ◽

Climate Conditions ◽

The Mediterranean ◽

The Mediterranean Basin ◽

Extreme Fire

With hot and dry summers, the Mediterranean basin is affected by recurrent fires. While drought is the major driver of the seasonal and inter-annual fire distribution in its northern and mildest climate conditions, some extreme fire events are also linked to extreme winds or heat waves. The southern part of the Mediterranean basin is located at the driest range of the Mediterranean bioclimate and is influenced by Saharan atmospheric circulations, leading to extreme hot and dry episodes, called Sirocco, and potentially acting as a major contributor to fire hazard. The recently created fire database for Tunisia was used to investigate the ±10-day pre- and post-fire timeframe of daily weather conditions associated with fire events over the 1985–2006 period. Positive anomalies in minimum and maximum temperatures, negative anomalies in air relative humidity, and a preferential south-eastern wind during fire events were identified, which were characteristic of Sirocco winds. +7 °C anomalies in air temperature and −30% in relative air humidity were the critical thresholds for the most extreme fire conditions. In addition, meteorological anomalies started two days before fire events and lasted for three days after for large fires >400 ha, which suggests that the duration of the Sirocco event is linked with fire duration and final fire size. Lastly, the yearly number of intense Sirocco events better explained the inter-annual variability of burned area over the 1950–2006 period than summer drought based on Standardized Precipitation Evaporation Index (SPEI) indices.

Download Full-text

Trends and extremes of drought indices throughout the 20th century in the Mediterranean

Natural Hazards and Earth System Science ◽

10.5194/nhess-11-33-2011 ◽

2011 ◽

Vol 11 (1) ◽

pp. 33-51 ◽

Cited By ~ 161

Author(s):

P. M. Sousa ◽

R. M. Trigo ◽

P. Aizpurua ◽

R. Nieto ◽

L. Gimeno ◽

...

Keyword(s):

20Th Century ◽

Extreme Values ◽

Statistical Significance ◽

Drought Indices ◽

Summer Drought ◽

Monthly Precipitation ◽

Central Mediterranean ◽

Annual Variability ◽

Drought Conditions ◽

The Mediterranean

Abstract. Average monthly precipitation, the original Palmer Drought Severity Index (PDSI) and a recent adaptation to Europe, the Self Calibrated PDSI (scPDSI) have been used here to analyse the spatial and temporal evolution of drought conditions in the Mediterranean during the 20th century. Monthly, seasonal and annual trends were computed for the period 1901–2000 and also for the first and second halves of this period. The statistical significance of trends was obtained with a modified version of the Mann-Kendall test that accounts for serial auto-correlation. The results show a clear trend towards drier conditions during the 20th century in most western and central Mediterranean regions, with the exceptions of northwestern Iberia and most of Turkey that reveal an increase of moisture availability. A Generalized Extreme Values (GEV) analysis was applied to the maximum and minimum regional values of scPDSI, with results pointing towards a significant decline of absolute extreme values in central areas (Italy and Balkans) and a less clear picture emerging in western (Iberia) and eastern (Turkey) realms. The inter-annual variability of the scPDSI index series is shown to be more realistic than the corresponding PDSI version, fitting better the drought episodes sequence and magnitude described in the literature for each sub-region. We assess the decadal and inter-annual variability of the scPDSI for each sub-domain and evaluate the role played by the major teleconnection patterns, and by several sea surface temperature (SST) anomalies. The main driver of scPDSI in western and central Mediterranean areas is the winter North Atlantic Oscillation (NAO) pattern that is also relevant during the following spring and summer seasons with anti-correlation values below −0.60. The second most important mode corresponds to the Scandinavian Pattern that is significantly associated to the scPDSI between winter and summer over central Mediterranean (correlation values around 0.50). Finally, the teleconnection and SST analysis has allowed us to calibrate a stepwise regression model, enabling the forecasting of summer drought conditions six months in advance. The final model obtained is capable of reproducing the observed scPDSI time series fairly well, with a correlation coefficient of 0.79 (0.77 after cross-validation) and a significant gain over climatology (SSc=59%), while the corresponding result against persistence is more modest (SSp6=11%).

Download Full-text

Seasonal trends in energy contents and storage substances of the Mediterranean species Dittrichia viscosa and Thymelaea tartonraira

Environmental and Experimental Botany ◽

10.1016/s0098-8472(97)00022-1 ◽

1998 ◽

Vol 39 (1) ◽

pp. 21-31 ◽

Cited By ~ 12

Author(s):

M.S Meletiou-Christou ◽

G P. Banilas ◽

S Diamantoglou

Keyword(s):

Mediterranean Species ◽

Seasonal Trends ◽

Dittrichia Viscosa ◽

The Mediterranean ◽

And Storage

Download Full-text

Wood Anatomy of Capparis Spinosa from an Ecological Perspective

IAWA Journal ◽

10.1163/22941932-90001567 ◽

1999 ◽

Vol 20 (4) ◽

pp. 419-429 ◽

Cited By ~ 17

Author(s):

G.K. Psaras ◽

I. Sofroniou

Keyword(s):

Wood Anatomy ◽

Adaptive Strategy ◽

Ecological Perspective ◽

Summer Drought ◽

Anatomical Features ◽

Vessel Elements ◽

Capparis Spinosa ◽

The Mediterranean ◽

Perforation Plates ◽

Xylem Conduits

Root and stern wood of the Mediterranean summergreen Capparis spinosa L. was studied. Wood anatomical features favour high hydraulic conductivity, which is necessary for maintaining the high midday stomatal conductance and rates of photosynthesis observed in this plant. Xylem conduits of both stern and root consist of wide and short vessel elements with simple perforation plates. Vessel grouping in the stern secures xylem safety against cavitations. The plant would be highly vulnerable to cavitations due to freezing conditions, although these are rare during the Mediterranean winter. Thus, the anatomical features of the plant, which does not seem to suffer from water stress though growing entirely during the Mediterranean summer drought, are compatible with its adaptive strategy. The significant amount of minerals found in the root vessels, and the abundant starch grains of the wood might be involved in a possible osmotic shifting of water in the xylem.

Download Full-text

Evaluation of modern and mid-Holocene seasonal precipitation of the Mediterranean and northern Africa in the CMIP5 simulations

Climate of the Past ◽

10.5194/cp-10-551-2014 ◽

2014 ◽

Vol 10 (2) ◽

pp. 551-568 ◽

Cited By ~ 43

Author(s):

A. Perez-Sanz ◽

G. Li ◽

P. González-Sampériz ◽

S. P. Harrison

Keyword(s):

Coupled Model ◽

Summer Rainfall ◽

Northern Africa ◽

Zone Model ◽

Summer Drought ◽

Equatorial Zone ◽

Spring Precipitation ◽

Precipitation Regimes ◽

Northward Expansion ◽

The Mediterranean

Abstract. We analyse the spatial expression of seasonal climates of the Mediterranean and northern Africa in pre-industrial (piControl) and mid-Holocene (midHolocene, 6 yr BP) simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Modern observations show four distinct precipitation regimes characterized by differences in the seasonal distribution and total amount of precipitation: an equatorial band characterized by a double peak in rainfall, the monsoon zone characterized by summer rainfall, the desert characterized by low seasonality and total precipitation, and the Mediterranean zone characterized by summer drought. Most models correctly simulate the position of the Mediterranean and the equatorial climates in the piControl simulations, but overestimate the extent of monsoon influence and underestimate the extent of desert. However, most models fail to reproduce the amount of precipitation in each zone. Model biases in the simulated magnitude of precipitation are unrelated to whether the models reproduce the correct spatial patterns of each regime. In the midHolocene, the models simulate a reduction in winter rainfall in the equatorial zone, and a northward expansion of the monsoon with a significant increase in summer and autumn rainfall. Precipitation is slightly increased in the desert, mainly in summer and autumn, with northward expansion of the monsoon. Changes in the Mediterranean are small, although there is an increase in spring precipitation consistent with palaeo-observations of increased growing-season rainfall. Comparison with reconstructions shows most models underestimate the mid-Holocene changes in annual precipitation, except in the equatorial zone. Biases in the piControl have only a limited influence on midHolocene anomalies in ocean–atmosphere models; carbon-cycle models show no relationship between piControl bias and midHolocene anomalies. Biases in the prediction of the midHolocene monsoon expansion are unrelated to how well the models simulate changes in Mediterranean climate.

Download Full-text

Hydrogen peroxide is involved in the acclimation of the Mediterranean shrub, Cistus albidus L., to summer drought

Journal of Experimental Botany ◽

10.1093/jxb/ern274 ◽

2008 ◽

Vol 60 (1) ◽

pp. 107-120 ◽

Cited By ~ 58

Author(s):

T. Jubany-Mari ◽

S. Munne-Bosch ◽

M. Lopez-Carbonell ◽

L. Alegre

Keyword(s):

Hydrogen Peroxide ◽

Summer Drought ◽

Cistus Albidus ◽

The Mediterranean ◽

Mediterranean Shrub

Download Full-text

The European 2015 drought from a climatological perspective

Hydrology and Earth System Sciences ◽

10.5194/hess-21-1397-2017 ◽

2017 ◽

Vol 21 (3) ◽

pp. 1397-1419 ◽

Cited By ~ 87

Author(s):

Monica Ionita ◽

Lena M. Tallaksen ◽

Daniel G. Kingston ◽

James H. Stagge ◽

Gregor Laaha ◽

...

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Geopotential Height ◽

Western Europe ◽

North Atlantic Ocean ◽

Western Mediterranean ◽

Daily Maximum ◽

Summer Drought ◽

Drought Conditions ◽

The Mediterranean

Abstract. The summer drought of 2015 affected a large portion of continental Europe and was one of the most severe droughts in the region since summer 2003. The summer of 2015 was characterized by exceptionally high temperatures in many parts of central and eastern Europe, with daily maximum temperatures 2 °C higher than the seasonal mean (1971–2000) over most of western Europe, and more than 3 °C higher in the east. It was the hottest and climatologically driest summer over the 1950–2015 study period for an area stretching from the eastern Czech Republic to Ukraine. For Europe, as a whole, it is among the six hottest and driest summers since 1950. High evapotranspiration rates combined with a lack of precipitation affected soil moisture and vegetation and led to record low river flows in several major rivers, even beyond the drought-hit region. The 2015 drought developed rather rapidly over the Iberian Peninsula, France, southern Benelux and central Germany in May and reached peak intensity and spatial extent by August, affecting especially the eastern part of Europe. Over the summer period, there were four heat wave episodes, all associated with persistent blocking events. Upper-level atmospheric circulation over Europe was characterized by positive 500 hPa geopotential height anomalies flanked by a large negative anomaly to the north and west (i.e., over the central North Atlantic Ocean extending to northern Fennoscandia) and another center of positive geopotential height anomalies over Greenland and northern Canada. Simultaneously, the summer sea surface temperatures (SSTs) were characterized by large negative anomalies in the central North Atlantic Ocean and large positive anomalies in the Mediterranean basin. Composite analysis shows that the western Mediterranean SST is strongly related to the occurrence of dry and hot summers over the last 66 years (especially over the eastern part of Europe). The lagged relationship between the Mediterranean SST and summer drought conditions established in this study can provide valuable skill for the prediction of drought conditions over Europe on interannual to decadal timescales.

Download Full-text