•Four paired 1m2 plots on Aleppo pine and Holm oak were monitored from 2010 till 2014.•Total rainfall was 2721mm and 4 events were larger than 100mm.•Aleppo pine covered soils yield six times more ...runoff than Holm oak.•Sediment concentration was 4.9gl−1 in Aleppo pine and 2.6gl−1 in Holm oak.•Soil erosion rate was ten times higher in Aleppo pine than in Holm oak.
Afforestation aims to recover the vegetation cover, and restore natural ecosystems. The plant species selected for restoration will determine species richness and the fate of the ecosystem. Research focussing on the impact of vegetation recovery on soil quality are abundant, especially on fire affected land and where rehabilitation, afforestation and restoration projects were carried out. However, little is known about how different plants species affect soil erosion and water losses, which are key factors that will impact the fate of the afforested land. Aleppo pine (Pinus halepensis M.) is the species commonly used for afforestation in the Mediterranean and is very successful when natural recovery takes place, however, the original forests were composed of Holm oaks (Quercus ilex subsp. rotundifolia L.). There is little information about the hydrological and erosional impact of this change of vegetation cover stimulated by a millennia old forest use in the Mediterranean, and a century old afforestation policies and natural recovery as a consequence of land abandonment. To get insights in the effect of plant species on runoff generation and soil erosion, individual trees should be selected. Plots of 1 m2 are necessary to identify homogeneous patches, and were installed under Aleppo pine (4 plots) and Holm oaks (4 plots) in a 30(34)-years old plant cover recovered after a forest fire that took place in 1979. A raingauge was installed in the study site to characterize the rainfall. The soil erosion plots were built with metal borders and each plot drained to a collector (gutter) and a 60L container to store the surface runoff. Runoff was measured after each rainfall event and sediment concentration was determined by desiccation. Results show that Aleppo pine covered soils yield six times more runoff (232mm, 8.31%) than Holm oaks (40mm, 1.4%) during the experimental period of 2010–2014, when rainfall amount 2,721.1mm. Runoff sediment concentration was higher in the Aleppo pine plots (4.9gl−1) than in the Holm oaks plots (2.6gl−1). Soil erosion rate was ten times higher in Aleppo pine (2.6Mgha−1 y−1) than in Holm oaks (0.26Mgha−1 y−1).
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•VIs revealed differences in needle phenology among Aleppo pine ecotypes.•P. halepensis sub-humid ecotypes showed earlier needle phenology.•Potential trade-offs between fire- and drought-related ...traits.•Lack of intra-specific differences in litter flammability of Aleppo pine.
Pinus halepensis Mill. is a conifer typical of Mediterranean pinewoods adapted to drought and fire. Although the timing of seasonal events in P. halepensis is strongly associated with these stressors and other environmental factors, needle phenology and litter flammability are insufficiently characterized at the intraspecific level. These traits can be informative of the existence of locally adapted populations across the species’ distribution range, and remote sensing approaches are promising tools to infer phenological changes in forest trees. In this study, we investigated intraspecific differentiation of P. halepensis related to needle phenology at the onset of the fire season (May-June) through vegetation indexes (VIs) obtained from unmanned aerial vehicles. We collected drone images using multispectral and RGB sensors for 56 adult populations of P. halepensis categorized into five ecotypes growing in two common gardens located in Spain under contrasting conditions (dry-continental versus wet-coastal). In the dry trial, we additionally monitored the temporal variation of RGB-derived indexes using two flights spaced over a one-month period. We also performed four consecutive ground measurements of needle pigments and fuel moisture content and obtained litter flammability traits for a subset of populations. Most in situ measurements and flammability traits did not show population differentiation. Regarding RGB-derived VIs, we did not detect obvious temporal patterns which differed among populations. However, we observed greener canopies in June than in May, which are indicative of the pace of current-year needle development. We also deduced an earlier phenology (i.e., earlier current-year needle unfolding) in the dry-continental trial. Ecotypic differentiation was found for some vegetation indexes related to needle unfolding (i.e., TCARI/OSAVI) and old needle senescence (i.e., PRSI). These differences were generally consistent across trials and time, and fundamentally indicated that sub-humid ecotypes typical of the eastern Mediterranean showed earlier needle unfolding and old needle senescence than semiarid ecotypes thriving in western continental Mediterranean areas. The intraspecific divergence observed in early season phenology is potentially related to the existence of contrasting life-history strategies present at the intraspecific level for the species. In particular, some semi-arid ecotypes, which are known to optimize the trade-off between carbon gain and water loss, exhibited an early old needle senescence (high likelihood of crown fire development) coupled with a late needle unfolding (conservative water use). These results indicate a possible trade-off between drought and fire resistance for the species, which suggest the importance of considering the intraspecific characteristics of Aleppo pine in forest management actions.
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•Adaptive silviculture must be assessed regarding its effects on water.•Soil water dynamics and drainage were greatly modulated by the antecedent soil water content (ASW).•ASW was significantly ...enhanced with thinning, although site/climate conditions were also important.•Run-off was negligible in both sites and not affected by the thinning treatment.•Thinning improved the elasticity of soil water and drainage, making them less vulnerable to drought.
Water is the key element that modulates the provision of goods and services together with global/climate stressors affecting semiarid forests. In this sense, there is a need to improve the understanding and quantification of forest and water relationships as affected by forest management. This work addresses this issue by comparing net rainfall (Pn) redistribution into different belowground hydrological processes (BHP) in two forest types after a thinning treatment: a holm oak coppice (HU) and a post-fire Aleppo pine regeneration (CAL). The relative contribution (RI) of forest structure, antecedent soil moisture (θst), rainfall and meteorological conditions on the BHP was assessed through boosted regression trees models. In both sites, the RI of the forest structure itself was limited (<10%). However, θst, which clearly increased significantly with thinning, received an average RI of 29%. Surface and subsurface lateral flows showed values <1% of gross rainfall (Pg) in either site and were not significantly affected by thinning. On the other hand, soil moisture and drainage were affected by the thinning treatment, although with different extent depending on the site: in the drier site (CAL), the increased Pn in the thinning was mainly allocated into increased soil water content, with very limited improvement in drainage (<10 mm/year); in contrast, in the wetter continental site of HU, drainage to deeper soil layers was the most remarkable effect of thinning (50 mm/year higher than in control), given the higher θst and hence the lower soil water storage available. Thinning also improved the response of BHP during drought, making these processes more elastic and less vulnerable to climatic extremes. The results presented here complement those previously reported on rainfall partitioning in these sites and all together provide a comprehensive understanding of the short-term effect (3–4 years) of water-oriented silviculture in Quercus ilex and Pinus halepensis low-biomass semiarid forests. Questions such as the long-term effects of thinning remain open for these ecosystems.
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•High predictability of ecotypic plastic responses in P. halepensis for tree growth.•Standing genetic variation, and not plasticity, dominates ecotypic growth patterns.•Mesic populations from the ...eastern Mediterranean show general adaptation.•Less reactive ecotypes to improved conditions have high survival but low growth.
The combined effects of local adaptation and phenotypic plasticity influencing plant performance are relevant to understand the capacity for genetic responses to climate change. Pinus halepensis is a native species of low- to mid-elevation Mediterranean forests with a high ecological value in drought-prone areas. Thus, it is of utmost importance to determine its adaptive structure for key traits such as growth or survival. Here, we analyse a highly unbalanced dataset collated from different common-garden networks that cover the distribution range of the species. A total of 82 range-wide populations were evaluated in nine Mediterranean trials located in Israel, Italy and Spain. A climate classification of populations allowed for the definition of six different groups, or ecotypes, which showed contrasting performances for tree height and survival at age 15. The effects of ecotypic differentiation and among-ecotypes genetic variation in plasticity were disentangled by fitting stability models accounting for interaction and heteroscedasticity in genotype-by-environment tables. For growth, a Finlay–Wilkinson model suggested high predictability of ecotypic plastic responses in P. halepensis, as described by different linear reaction norms. However, differences in mean height of ca. 15% among ecotypes dominated intra-specific patterns of tree growth across trials, pointing to preponderance of genotypic adaptation over differential ecotypic plasticity in this species. For survival, ecotypic differences were approximately constant across trials, suggesting lack of genotype-by-environment effects. Sub-humid cool climate populations from the eastern Mediterranean (e.g., Greek populations) showed general adaptation and high sensitivity to improved growing conditions, as opposed to populations from the driest ecological extreme of the species (e.g., south Spain and Maghreb populations), which exhibited specific adaptation to harsh environments. Altogether, our results indicate a general adaptive syndrome by which less reactive ecotypes to ameliorated conditions (e.g., non-water-limited) would be associated with high survival rates and low growth. The reported ecotypic differentiation constitutes the basis for tailoring intra-specific responses to climate and disentangling the relationship between adaptive variation and resilience towards climatic warming for this exemplary Mediterranean pine.
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Cette étude présente l'entomofaune trouvée dans la pinède de pin d'Alep de Draa El Aoud, dans la commune de Méchéria (Sud-Ouest Algérien). Plantée en 1975 sur 1000 ha, cette pinède a subi un net ...recul, puisqu'elle a totalement disparu sur 28 des 50 parcelles qui la portaient initialement. Son dépérissement est en outre très avancé sur 18 autres parcelles. Un échantillonnage des scolytes a été réalisé dans les années 2018-2019 sur 65 sujets, vivants mais très affectés, répartis sur les parcelles en dépérissement. Des mesures dendrométriques (hauteur et diamètre), un inventaire des insectes et le dénombrement des trous de scolytes à 1,30 m au dessus du sol, ont été effectués. L'analyse des résultats ne montre pas de relation entre le nombre de trous de scolytes et la hauteur ou le diamètre des arbres. Cinq ravageurs appartenant à quatre familles ont été identifiés : - Thaumetopoea pityocampa (Denis et Schiffermuller, 1775), la processionnaire du pin, - trois xylophages : Orthotomicus erosus W., Orthotomicus proximus E. et Colydium elongatum (Fabricius, 1787) - enfin, Arhopalus ferus (Mulsant, 1839), une espèce connue pour être saproxylophage à tendance pyrophile. La mise en évidence d'Arhopalus ferus dans la région, constitue une première. Il a en outre été constaté qu'il pouvait attaquer le bois encore vivant. L'action de ces ravageurs, qui vient se surajouter aux effets d'un milieu difficile, en particulier par son climat semi-aride, participe à mettre en péril la survie de la pinède.
This study presents the entomofauna found in the Aleppo pine forest of Draa El Aoud, in the commune of Méchéria (southwestern Algeria). Planted in 1975 over an area of 1,000 ha, this pine forest has suffered a sharp decline, having completely disappeared from 28 of the 50 plots where it was originally planted. Another 18 plots are at an advanced stage of decline. In 2018-2019, bark beetles sampling was conducted on 65 living but severely affected trees spread across the declining plots. Dendrometric measurements (height and diameter), an insect inventory and a count of bark beetles holes at 1.30 m above ground level were carried out. Analysis of the results showed no relationship between the number of bark beetles holes and tree height or diameter. Five pests belonging to four families were identified: - Thaumetopoea pityocampa (Denis et Schiffermuller, 1775), the pine processionary, - three xylophages: Orthotomicus erosus W., Orthotomicus proximus E. and Colydium elongatum (Fabricius, 1787) - finally, Arhopalus ferus (Mulsant, 1839), a known saproxylophage species with pyrophilic tendencies. The discovery of Arhopalus ferus in the region is a first. It has also been found to attack living wood. The action of these pests, which comes on top of the effects of a difficult environment, in particular its semi-arid climate, is helping to endanger the survival of the pine forest.Translated with DeepL.com (free version)
•We studied Pinus halepensis resilience to drought across its distribution range.•Drought intensity reduced tree growth resistance but hardly affected its resilience.•Preceding and following ...conditions are of crucial importance in explaining resilience.•The magnitude of response to drought strongly increased with site aridity.
Severe droughts limit tree growth and forest productivity worldwide, a phenomenon which is expected to aggravate over the next decades. However, how drought intensity and climatic conditions before and after drought events modulate tree growth resilience remains unclear, especially when considering the range-wide phenotypic variability of a tree species.
We gathered 4632 Aleppo pine (Pinus halepensis Mill.) tree-ring width series from 281 sites located in 11 countries across the Mediterranean basin, representing the entire geographic and bioclimatic range of the species. For each site and year of the period 1950–2020, we quantified tree-growth resilience and its two components, resistance and recovery, to account for the impact of drought and the capacity to recover from it. Relative drought intensity of each year was assessed using SPEI (Standardized Precipitation Evapotranspiration Index), a climatic water deficit index. Generalized additive mixed models were used to explore the non-linear relationships between resilience and its two components and drought intensity, preceding and following years climatic conditions.
We found that P. halepensis radial growth was highly dependent on the SPEI from September of the previous year to June of the current year. Trees growing under more arid bioclimates showed higher inter-annual growth variability and were more sensitive to drought, resulting in an increased response magnitude to pre-, during and post-drought conditions. In contrast to our expectations, drought intensity only slightly affected resilience, which was rather negatively affected by favorable preceding conditions and improved by favorable following conditions.
Resilience and its components are highly dependent on preceding and following years climatic conditions, which should always be taken into account when studying growth response to drought. With the observed and predicted increase in drought frequency, duration and intensity, favorable conditions following drought episodes may become rare, thus threatening the future acclimation capacity of P. halepensis in its current distribution.
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L’étude menée sur 230 placettes temporaires de Pin d’Alep (Pinus halepensis Mill.) dans l’Aurès (Algérie) a pour objectif de construire deux tables de production pour deux itinéraires sylvicoles ...différents. Quatre classes de fertilité ont été définies avec des hauteurs dominantes à 70 ans de 19,50 m, 16,50 m, 13,50 m et 10,50 m, respectivement. Les effets de l’itinéraire sylvicole ne changent pas la production totale de bois en volume mais modifient la répartition des catégories de diamètre avec une proportion de gros bois de plus en plus élevée, ce qui permet une meilleure valorisation économique des peuplements.
Messages clés :• Deux tables de production ont été construites pour le Pin d’Alep en Algérie.• Ces tables intègrent deux itinéraires sylvicoles.• Selon l’itinéraire choisi, la valorisation économique est différente.
The assessment of fire effects in Aleppo pine forests is crucial for guiding the recovery of burned areas. This study presents a methodology using UAV-LiDAR data to quantify malleability in three ...burned areas (1970, 1995, 2008) through the statistical analysis of tree height and Profile Area Change (PAC) metrics. Significant differences in vegetation height (99th percentile) among the three fires, with specific maximum absolute differences (D) depending on the fire year, have been identified. Positive PAC values in 2008 indicate deeper LiDAR penetration, resulting in lower regeneration, while values close to 0 in 1970 suggest more uniform regeneration. The use of LiDAR metrics and uni-temporal sampling between burned sectors and controls aids in understanding community resilience and identifying recovery stages in P. halepensis forests.
•A buffering effect on T, VPD, RH was noted for the overstory and the understory.•This effect was more pronounced in summer due to a stronger shading effect.•Shrub influence on T, RH, VPD was higher ...in low pine cover and in open conditions.•Soil moisture was reduced in the presence of a developed shrub layer.
Forest cover creates a specific microclimate by buffering most environmental variables. If the influence of the overstory on microclimatic variables has been well studied, the role of the understory has received less attention. In this study we investigated how the shrub layer modifies solar radiation, air temperature (T), relative air humidity (RH), vapor pressure deficit (VPD) and soil moisture under different thinning treatments in an Aleppo pine forest (Pinus halepensis Mill.). Microclimatic variables were measured along a vegetation cover gradient made up of three pine densities (dense, medium, low) and open conditions, with or without the presence of shrubs. The results were analyzed with a focus on the summer period which represents a major bottleneck for plant development in the Mediterranean area.
Average T and VPD values increased with decreasing vegetation cover (+1.38 °C and +0.21 kPa for the whole year) while RH decreased (-2.34%). Along the same gradient, daily amplitude of T, RH, VPD increased while the buffering capacity decreased. These patterns were more pronounced during the summer period compared to the whole year and were primarily driven by overstory transmittance. However, the shrub layer played a significant role in the low pine cover treatment where it was developed and in open conditions. Soil water content in the forest area was higher under low pine cover without shrubs than it was in the other treatments, though differences were less marked during summer drought episodes. In open conditions, soil moisture was always significantly lower beneath the shrub canopy than outside it. Despite a reduction in soil moisture, shrubs may represent safe sites for woody seedling development in sparse pine forests and in treeless areas by buffering the microclimate during the summer period.
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•Local site factors control Aleppo pine seedling density more than fire severity.•Minimum temperature can help classify populations and predict their regeneration.•Prefire forest ...structure predicts hyperdense regeneration after fire.•Hyperdense regeneration is not expected with prefire stand density < 100 trees/ha.•Soil depth and bedrock predict hyperdense regeneration after fire.
Postfire Pinus halepensis (Aleppo pine) regeneration is often hyperdense. The overstocked stands created by this hyperdense regeneration considerably increase the risk of biotic and abiotic disturbances, especially fires, by increasing the potential for widespread forest losses. Our aim was to understand the relation between prefire site factors (climate, geographical position, topography, soil), prefire forest structure variables and fire severity with regeneration density after fire. We specifically wondered: (1) what are the general drivers of natural regeneration in these forests after fire?; (2) what are the necessary prefire conditions for establishing Aleppo pine hyperdense regenerations (>4,000 plants/ha)? To answer these questions, we sampled 147 plots in 15 wildfires located in the Comunitat Valenciana, which were representative of Aleppo pine Mediterranean forests. We used full and partial redundancy analyses (RDAs) for variance partitioning, and a decision tree analysis to look for the key site factors that drive regeneration density after fire. We found that all the site factors measured in the study explained 34.4 % of total variation in regeneration density. Prefire site factors and fire severity together explained 28.4 % of total variability, while the measured postfire factors explained only 7.5 %. Forest structure and climate explained 8.3 % and 6.7 % of variation, respectively. Five specific site factors drove regeneration density after fire: average minimum temperature, tree density before fire, resprouting shrubs coverage before fire, soil depth and bedrock type. The conclusions of this study were: (i) the average minimum temperature was the main significant variable that classified regeneration density and split data into three significant groups of Aleppo pine burned sites; (ii) the prefire forest structure (overstorey density and understorey coverage) controls regeneration density at colder burned sites, but soil depth and bedrock can be more important at warmer sites; (iii) fire severity relates positively to pine regeneration density, but negatively to resprouting vegetation coverage after fire; (iv) overstocked stands are not expected if prefire stand density is below 100 trees/ha at colder burned sites. These results may facilitate the planning of forest management and restoration actions because it may be used to identify those areas more likely to regenerate overstocked stands when faced with a changing fire regime.
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