scholarly journals The Dry and the Wet Case: Tree Growth Response in Climatologically Contrasting Years on the Island of Corsica

Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1175
Author(s):  
Martin Häusser ◽  
Sonja Szymczak ◽  
Isabel Knerr ◽  
Jörg Bendix ◽  
Emilie Garel ◽  
...  
Keyword(s):  
Tree Growth ◽  
Elevation Gradient ◽  
Western Mediterranean ◽  
Growth Patterns ◽  
Mountain Range ◽  
High Plasticity ◽  
Substantial Impact ◽  
Western Mediterranean Basin ◽  
Novel Approach ◽  
The Impact

Stem radial variations of Corsican Black pine (Pinus nigra Arnold subsp. laricio Maire) and Maritime pine (Pinus pinaster Aiton) were monitored to quantify the impact of two meteorologically contrasting consecutive years. On the French island of Corsica, in the western Mediterranean basin, the year 2017 was extremely dry, while 2018 was exceptionally wet. We attached electric band dendrometers to 36 pines along an east–west transect, spanning the central mountain range, and set up automated weather stations at all five sites, ranging from 10 m asl to 1600 m asl. Stem radial variations (SRV) were separated into irreversible growth (GRO) and tree water deficit (TWD) periods. During the drought of 2017, the most severe tree water deficits occurred in the western part of the island, whereas trees at higher elevations were more affected than at lower elevations. A prolonged decrease of SRV, even close to the tree line, suggests bimodal growth and reveals high plasticity of growth patterns in both Corsican pines. Stem radial variations correlated significantly with precipitation and temperature. The positive correlations of GRO with precipitation and the negative correlations of TWD with temperature imply that high evapotranspiration led to the intense period of TWD in 2017. A novel approach was used to further investigate the growth/climate relationship by including synoptic-scale pressure situations. This revealed that an elevation gradient in GRO per weather pattern was only present in the wet year and that even rarely occurring weather patterns can have a substantial impact on tree growth. This novel approach provides a more comprehensive insight into meteorological drivers of tree growth patterns by incorporating different scales of the climatic system.

scholarly journals Divergent Growth Responses to Warming between Stand-Grown and Open-Grown Trees in a Dryland Montane Forest in Northwestern China

Forests ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 1133 ◽  
Author(s):  
Lei Zhang ◽  
Hao Shi ◽  
Pengtao Yu ◽  
Yanhui Wang ◽  
Shufen Pan ◽  
...  
Keyword(s):  
Climate Change ◽  
Tree Growth ◽  
Elevation Gradient ◽  
Montane Forest ◽  
Growth Patterns ◽  
Forest Growth ◽  
Northwestern China ◽  
Growth Responses ◽  
Internal Factors ◽  
High Elevations

Dryland montane forests conserve water for people living in the fluvial plains. The fate of these forests under climate warming is strongly affected by local environmental factors. The question remains of how internal factors contribute to climate change impacts on forest growth in these regions. Here, we investigated tree ring records for similar-aged stand-grown trees and their neighboring open-grown trees at elevation in a dryland montane forest (Picea crassifolia Kom.) in northwestern China. The growth rate of open-grown trees is much higher than their neighboring stand-grown trees across the entire elevation gradient, and the lower the altitude, the greater the difference. Open-grown trees at different elevations showed similar growth patterns, as tree growth at all sites was accelerated over time. In contrast, growth patterns of stand-grown trees were divergent at different altitudes, as growth at high elevations (3100–3300 m a.s.l.) was accelerated, whereas growth at low elevations (2700–2900 m a.s.l.) became stable after the year 1990. Analysis of growth–climate relationships indicated that warming promoted open-grown tree growth across the entire altitude gradient, and also stand-grown tree growth at high elevations, but negatively affected the growth of stand-grown trees at low elevations. Water scarcity can be exacerbated by competition within forests, inhibiting the warming-induced benefits on tree growth. Moving window correlation analysis suggested the negative effect of warming on tree growth at low elevations was diminished after the late 1990s, as the drought stress was alleviated. Our research shows the divergent growth responses to warming of stand-grown and open-grown trees along elevation. It reveals effects of internal factors in determining tree growth response to warming and holds the potential to aid forest management and ecosystem models in responding to climate change.

scholarly journals Tree growth is more limited by drought in rear-edge forests most of the times

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
J. Julio Camarero ◽  
Antonio Gazol ◽  
Gabriel Sangüesa-Barreda ◽  
Marta Vergarechea ◽  
Raquel Alfaro-Sánchez ◽  
...  
Keyword(s):  
Tree Growth ◽  
Tree Species ◽  
Large Scale ◽  
Abies Alba ◽  
Growth Patterns ◽  
Widespread Species ◽  
Growth Variability ◽  
Rear Edge ◽  
Species Vulnerability ◽  
The Impact

Abstract Background Equatorward, rear-edge tree populations are natural monitors to estimate species vulnerability to climate change. According to biogeographical theory, exposition to drought events increases with increasing aridity towards the equator and the growth of southern tree populations will be more vulnerable to drought than in central populations. However, the ecological and biogeographical margins can mismatch due to the impact of ecological factors (topography, soils) or tree-species acclimation that can blur large-scale geographical imprints in trees responses to drought making northern populations more drought limited. Methods We tested these ideas in six tree species, three angiosperms (Fagus sylvatica, Quercus robur, Quercus petraea) and three gymnosperms (Abies alba, Pinus sylvestris and Pinus uncinata) by comparing rear-edge tree populations subjected to different degrees of aridity. We used dendrochronology to compare the radial-growth patterns of these species in northern, intermediate, and southern tree populations at the continental rear edge. Results and conclusions We found marked variations in growth variability between species with coherent patterns of stronger drought signals in the tree-ring series of the southern populations of F. sylvatica, P. sylvestris, and A. alba. This was also observed in species from cool-wet sites (P. uncinata and Q. robur), despite their limited responsiveness to drought. However, in the case of Q. petraea the intermediate population showed the strongest relationship to drought. For drought-sensitive species as F. sylvatica and P. sylvestris, southern populations presented more variable growth which was enhanced by cool-wet conditions from late spring to summer. We found a trend of enhanced vulnerability to drought in these two species. The response of tree growth to drought has a marked biogeographical component characterized by increased drought sensitivity in southern populations even within the species distribution rear edge. Nevertheless, the relationship between tree growth and drought varied between species suggesting that biogeographical and ecological limits do not always overlap as in the case of Q. petraea. In widespread species showing enhanced vulnerability to drought, as F. sylvatica and P. sylvestris, increased vulnerability to climate warming in their rear edges is forecasted. Therefore, we encourage the monitoring and conservation of such marginal tree populations.

scholarly journals Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

2012 ◽  
Vol 9 (9) ◽  
pp. 12845-12894 ◽  
Author(s):  
M. Stabholz ◽  
X. Durrieu de Madron ◽  
M. Canals ◽  
A. Khripounoff ◽  
I. Taupier-Letage ◽  
...  
Keyword(s):  
Western Mediterranean ◽  
Open Ocean ◽  
Outer Margin ◽  
Nepheloid Layer ◽  
Mooring Lines ◽  
Gulf Of Lions ◽  
Western Mediterranean Basin ◽  
Particle Fluxes ◽  
The Impact ◽  
Ocean Convection

Abstract. The deep outer margin of the Gulf of Lions and the adjacent basin, in the Western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the Western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e. temperature and salinity), currents, and particle fluxes was monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350 m-depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW–SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION"), located at 42° 02.5′ N and 4° 41′ E, at 2350 m-depth, show that open-ocean convection reached mid-water depth (≈ 1000 m-depth) during winter 2007–2008, and reached the seabed (≈ 2350 m-depth) during winter 2008–2009. Horizontal currents were unusually strong with speeds up to 39 cm s−1 during winter 2008–2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008–2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5%, were abnormally low (≤ 1%) during winter 2008–2009 and approached those observed in surface sediments (≈ 0.6%). Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization of sediments in the deep outer margin and the basin, with a subsequent alteration of the seabed likely impacting the functioning of the deep-sea ecosystem.

scholarly journals Assessing the impact of SSTs on a simulated medicane using ensemble simulations

2018 ◽  
Author(s):  
Robin Noyelle ◽  
Uwe Ulbrich ◽  
Nico Becker ◽  
Edmund P. Meredith
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Tyrrhenian Sea ◽  
Western Mediterranean Basin ◽  
Minor Influence ◽  
Climate Model Simulations ◽  
Upper Level ◽  
A Minor ◽  
The Impact

Abstract. The sensitivity of the October 1996 medicane in the western Mediterranean basin to sea surface temperatures (SSTs) is investigated via 24-member ensembles of regional climate model simulations. Eleven ensembles are created by uniformly changing SSTs in a range of −4 K to +6 K from the observed field, with a 1 K step. By using a modified phase space diagram and a simple compositing method, it is shown that the SST state has a minor influence on the tracks of the cyclones, but a strong influence on their intensities. Increased SSTs lead to greater probabilities of tropical transitions, to stronger low- and upper-level warm cores, and to lower pressure minima. The tropical transition occurs sooner and lasts longer, which enables a greater number of transitioning cyclones to survive landfall over Sardinia and to re-intensify in the Tyrrhenian Sea. The results demonstrate that SSTs influence the intensity of fluxes from the sea, which leads to greater convective activity before the storms reach their maturity. These results suggest that the processes at steady-state for medicanes are very similar to tropical cyclones.

scholarly journals Tree Rings Reveal the Impact of Soil Temperature on Larch Growth in the Forest-Steppe of Siberia

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1765
Author(s):  
Liliana V. Belokopytova ◽  
Dina F. Zhirnova ◽  
David M. Meko ◽  
Elena A. Babushkina ◽  
Eugene A. Vaganov ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Tree Ring ◽  
Air Temperature ◽  
Tree Growth ◽  
Ring Width ◽  
Forest Steppe ◽  
Growth Data ◽  
Maximum Correlation ◽  
Substantial Impact ◽  
The Impact

Dendroclimatology has focused mainly on the tree growth response to atmospheric variables. However, the roots of trees directly sense the “underground climate,” which can be expected to be no less important to tree growth. Data from two meteorological stations approximately 140 km apart in southern Siberia were applied to characterize the spatiotemporal dynamics of soil temperature and the statistical relationships of soil temperature to the aboveground climate and tree-ring width (TRW) chronologies of Larix sibirica Ledeb. from three forest–steppe stands. Correlation analysis revealed a depth-dependent delay in the maximum correlation of TRW with soil temperature. Temperatures of both the air and soil (depths 20–80 cm) were shown to have strong and temporally stable correlations between stations. The maximum air temperature is inferred to have the most substantial impact during July–September (R = −0.46–−0.64) and early winter (R = 0.39–0.52). Tree-ring indices reached a maximum correlation with soil temperature at a depth of 40 cm (R = −0.49–−0.59 at 40 cm) during April–August. High correlations are favored by similar soil characteristics at meteorological stations and tree-ring sites. Cluster analysis of climate correlations for individual trees based on the K-means revealed groupings of trees driven by microsite conditions, competition, and age. The results support a possible advantage of soil temperature over air temperature for dendroclimatic analysis of larch growth in semiarid conditions during specific seasons.

Multiplatform analysis of a large anticyclonic eddy in the Algero-Provencal basin in 2019

2020 ◽  
Author(s):  
Aida Alvera-Azcárate ◽  
Alexander Barth ◽  
Charles Troupin ◽  
Jean-Marie Beckers ◽  
Hayley Evers-King ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Cold Water ◽  
Remote Sensing Data ◽  
Western Mediterranean ◽  
Anticyclonic Eddy ◽  
Model Data ◽  
Multiple Sources ◽  
In Situ Data ◽  
Western Mediterranean Basin ◽  
The Impact

<p>A large anticyclonic eddy formed in April 2019 in the Algero-Provencal basin between Mallorca and Sardinia, and lasted until November 2019. While mesoscale activity is usually high in this part of the Mediterranean basin, the formation of such large (about 150 km in diameter) and long-lived eddies is not common. The eddy formed from a filament originated in the Algerian coast and was visible in multiple sources of satellite data, including sea surface temperature and ocean colour from Sentinel-3, until summer. Because of the warming of the surface layer, during summer months the eddy remained as a subsurface structure, evidenced by the sea level anomaly derived from altimetry data. A surface signal developed again in November, and the eddy finally dissipated in December 2019. According to CMEMS model data, in its strongest period the eddy reached about 300 m in depth, and during its sub-surface period the center was located at about 100 m depth. While at the surface the temperature signal was very clear, model data suggest the salinity anomaly was stronger than temperature, especially at depth. Such large and long-lived eddies have an impact in the basin currents, specifically in the transport of cold water from the northern to the southern part of the western Mediterranean basin, influencing the ecosystem there. The impact of the presence of this eddy, its long duration and the additional mesoscale and submesoscale activity that originated in its surroundings are investigated using a combination of remote sensing data, in situ data and model data.</p>

scholarly journals How Do Mediterranean Pine Trees Respond to Drought and Precipitation Events along an Elevation Gradient?

Forests ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 758 ◽  
Author(s):  
Sonja Szymczak ◽  
Martin Häusser ◽  
Emilie Garel ◽  
Sébastien Santoni ◽  
Frédéric Huneau ◽  
...  
Keyword(s):  
Tree Growth ◽  
Elevation Gradient ◽  
Growth Patterns ◽  
Precipitation Event ◽  
Cold Environments ◽  
Pine Trees ◽  
The Mediterranean ◽  
Mediterranean Pine ◽  
Study Sites ◽  
Precipitation Events

Drought is a major factor limiting tree growth and plant vitality. In the Mediterranean region, the length and intensity of drought stress strongly varies with altitude and site conditions. We used electronic dendrometers to analyze the response of two native pine species to drought and precipitation events. The five study sites were located along an elevation gradient on the Mediterranean island of Corsica (France). Positive stem increment in the raw dendrometer measurements was separated into radial stem growth and stem swelling/shrinkage in order to determine which part of the trees’ response to climate signals can be attributed to growth. Precipitation events of at least 5 mm and dry periods of at least seven consecutive days without precipitation were determined over a period of two years. Seasonal dynamics of stem circumference changes were highly variable among the five study sites. At higher elevations, seasonal tree growth showed patterns characteristic for cold environments, while low-elevation sites showed bimodal growth patterns characteristic of drought prone areas. The response to precipitation events was uniform and occurred within the first six hours after the beginning of a precipitation event. The majority of stem circumference increases were caused by radial growth, not by stem swelling due to water uptake. Growth-induced stem circumference increase occurred at three of the five sites even during dry periods, which could be attributed to stored water reserves within the trees or the soils. Trees at sites with soils of low water-holding capacity were most vulnerable to dry periods.

scholarly journals African dust outbreaks over the western Mediterranean basin: 11 year characterization of atmospheric circulation patterns and dust source areas

2014 ◽  
Vol 14 (5) ◽  
pp. 5495-5533 ◽  
Author(s):  
P. Salvador ◽  
S. Alonso ◽  
J. Pey ◽  
B. Artíñano ◽  
J. J. de Bustos ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Mediterranean Basin ◽  
Circulation Pattern ◽  
Western Mediterranean ◽  
Atmospheric Circulation Patterns ◽  
African Dust ◽  
Western Mediterranean Basin ◽  
Circulation Patterns ◽  
Impact Index ◽  
The Impact

Abstract. The occurrence of African dust outbreaks over the western Mediterranean basin were identified on an 11 year period (2001–2011). PM10 daily data from nine regional background air quality monitoring sites across the study area were compiled and the net dust load transported during each event was estimated. Then, the main atmospheric circulation patterns causing the transport of African air masses, were characterized by mean of an objective classification methodology of atmospheric variables fields. Next, the potential source areas of mineral dust, associated to each circulation pattern were identified by trajectory statistical methods. Finally, an impact index was calculated to estimate the incidence of the African dust outbreaks produced during each circulation pattern, on the levels of dust load in PM10 concentrations recorded in the different regions. Our results indicate that the values of the impact index and the areas affected by African dust, strongly depended on the atmospheric circulation pattern. Four circulation types were obtained by the classification procedure. Two of them (CT-1 and CT-4) occurred predominantly during the warm season, bringing dust from areas of Algeria, Tunisia, Western Sahara, western Libya and Mauritania. African dust outbreaks produced during the CT-4 were the most frequent across the period of study, generating the highest impact index over southern, central and eastern regions of the Iberian Peninsula as well as over the Balearic Islands. Conversely, the events caused by the CT-1 encompassed the highest impact index over the western areas of the Iberian Peninsula. The two remaining circulation types (CT-2 and CT-3) were more frequently observed during the spring season. The prevailing flows generated by these two atmospheric circulation patterns, carried mineral dust from areas of Algeria, Tunisia and Western Sahara, giving rise to higher values of the impact index from eastern to western areas of the western Mediterranean basin.

scholarly journals Assessing the impact of sea surface temperatures on a simulated medicane using ensemble simulations

2019 ◽  
Vol 19 (4) ◽  
pp. 941-955 ◽  
Author(s):  
Robin Noyelle ◽  
Uwe Ulbrich ◽  
Nico Becker ◽  
Edmund P. Meredith
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Western Mediterranean ◽  
Sea Surface ◽  
Tyrrhenian Sea ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Western Mediterranean Basin ◽  
A Minor ◽  
The Impact

Abstract. The sensitivity of the October 1996 Medicane in the western Mediterranean basin to sea surface temperatures (SSTs) is investigated with a regional climate model via ensemble sensitivity simulations. For 11 SST states, ranging from −4 K below to +6 K above the observed SST field (in 1 K steps), 24-member ensembles of the medicane are simulated. By using a modified phase space diagram and a simple compositing method, it is shown that the SST state has a minor influence on the tracks of the cyclones but a strong influence on their intensities. Increased SSTs lead to greater probabilities of tropical transitions, to stronger lower- and upper-level warm cores and to lower pressure minima. The tropical transition occurs sooner and lasts longer, which enables a greater number of transitioning cyclones to survive landfall over Sardinia and re-intensify in the Tyrrhenian Sea. The results demonstrate that SSTs influence the intensity of fluxes from the sea, which leads to greater convective activity before the storms reach their maturity. These results suggest that the processes at steady state for medicanes are very similar to tropical cyclones.

scholarly journals The radiative impact of desert dust on orographic rain in the Cevennes–Vivarais area: a case study from HyMeX

2015 ◽  
Vol 15 (16) ◽  
pp. 22451-22492
Author(s):  
C. Flamant ◽  
J.-P. Chaboureau ◽  
P. Chazette ◽  
P. Di Girolamo ◽  
T. Bourrianne ◽  
...  
Keyword(s):  
Mesoscale Model ◽  
Convective Available Potential Energy ◽  
Heavy Precipitation ◽  
Western Mediterranean ◽  
Target Area ◽  
Radiative Effect ◽  
Western Mediterranean Basin ◽  
Radiative Impact ◽  
The Mediterranean ◽  
The Impact

Abstract. The study is focused on Intensive Observation Period (IOP) 14 of the Hydrology Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October and was dedicated to the study of orographic rain in the Cevennes Vivarais (CV) target area. During this IOP a dense dust plume originating from North Africa (Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the Western Mediterranean basin. The impact of this dust plume, the biggest event observed during the 2 month long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high resolution simulations from the convection permitting mesoscale model Meso-NH validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4 day simulation reproduced realistically the temporal and spatial variability (incl. vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg-1 increase of most unstable convective available potential energy (and up to +900 J kg-1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h accumulated rainfall in the dusty simulation.

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