Aleppo Pine Forests Research Articles

Positive coupling between growth and reproduction in young post-fire Aleppo pines depends on climate and site conditions

In fire- and drought-prone Mediterranean forests tree growth and regeneration depend on the moisture regime between fires. Therefore, post-fire tree regeneration will depend on moisture conditions and how they are altered by fire recurrence and climate warming. Aleppo pine forests are the most abundant Circum-Mediterranean ecosystems subjected to frequent wildfires and summer droughts. Because both stressors constrain their reproduction and growth patterns across diverse ecological conditions, these forests represent a suitable system to test how moisture availability drives post-fire regeneration. Aleppo pine is an obligate seeder species that reproduces at an early age after fire. Such precocious behaviour poses the question as to whether post-fire regeneration depends on moisture conditions and the coupling between female cone production and growth. Here, we evaluate if female cone production and radial growth are linked at the tree level in post-fire Aleppo pines by comparing a dry v. a very dry site and considering stands with three different tree densities in south-eastern Spain. We found that trees with higher basal areas produced more female cones and this positive association intensified as the water balance improved. Aleppo pines from the very dry site were more precocious in reproductive terms than pines of the same age from the dry site, but long-term cone production was lower at the very dry site. Lower tree density enhances the resilience of xeric post-fire Aleppo pine forests, in growth and reproduction terms, but this effect can be reversed by droughts. Overall, a more positive water balance improves post-fire regeneration by enhancing growth and cone production. Thus, silvicultural treatments such as thinning should be applied by taking into account the post-fire water balance to maximise growth and cone production in Aleppo pine stands. Our findings illustrate how climate warming could hamper post-fire tree regeneration by aggravating drought stress.

Seed and Cone Production Patterns from Seventy-Nine Provenances of Pinus halepensis Mill. Across Tunisia Forests

Pinus halepensis Mill. is an important tree species in the Mediterranean Basin. In Tunisia, there is an increasing interest in its seed production due to their impact on the socio-economical life of the Tunisian population, forest regeneration (seedling production) and biodiversity maintenance. Adaptative strategies were developed to fire recurrence by early cone production and seed storage in the serotinuous cones. Tunisia's native forests were investigated to examine the impact of four bioclimatic zones on Aleppo pine cone and seed production. Stand characteristics and average tree size measurements were studied with simple and multiple regression analyses for explaining their influences in seed and cone production and characteristics. Results showed a positive relationship between the accumulated rainfall and the geographical variables to the number of cones and its seeds content. Density had a strong adverse effect on the average tree's cone crop and seed yield. The cone production and the total seed mass were positively correlated with tree dimensions, but diameter at breast height and crown height were the most explanatory variables. Several environmental factors substantially increased the production of cones and seeds. The results could help foresters to decide better locations of cone and seed production according to density in Aleppo pine forests.

Identification of windows of emergence and seedling establishment in a pine Mediterranean forest under controlled disturbances

The regeneration phase is a critical step in plant population dynamics, but is still incompletely understood owing to the intricacy and complexity of the factors concerned. We investigated the role played by pine emergence, survival and growth in the recruitment process of a Mediterranean pine forest under disturbances of various intensities. Disturbances were produced by site treatments including mechanical chopping, soil scarification, and controlled fire of low or high intensity. Pine seedling emergence, survival, dimensions and the relative cover of bare soil, grasses and shrub were monitored on 5801-m2 plots over 6 years in a mature Aleppo pine forest (Pinus halepensis Mill.).Seedlings did not emerge continuously and regularly with time, but mostly in bursts, which were particularly marked in the rainy autumnal seasons. This specific pattern defined a ‘window’ of emergence characterised by the length of time during which seedlings emerged, the number of emerged seedlings and the shape of the window. Survival and growth decreased from the youngest cohort to the oldest cohort. Emergence, survival and growth did not respond in the same way to treatments and soil surface conditions. In particular, scarification treatments were most favourable to emergence, whereas the high-intensity controlled fire treatment was most beneficial to survival. Shrub cover was detrimental to emergence, but positively influenced survival and growth.We conclude that environmental factors controlling survival, emergence and growth processes differ, and that their importance varies over time. A detailed understanding of the processes involved in seedling recruitment can be helpful for selecting the types and intensities of the controlled disturbances to be applied to successfully regenerate forest stands.

Post-fire hillslope log debris dams for runoff and erosion mitigation in the semiarid Ebro Basin

The hydrologic effects of hillslope log debris dams were analyzed in areas of the Castejón Mountains (semiarid Ebro Basin, NE-Spain) affected by a wildfire. Four experimental sites showing differences in the soil composition (calcareous and gypseous) and the aspect of the steep slopes (north and south facing) were selected. All of the experimental sites were located along planar hillslopes, where Aleppo pine forest had burned in 2009, in the four sites per triplicate. Runoff and sediment yields were measured for two consecutive years (2012, 2013) after the construction of log dams on partially re-vegetated sites in 2011.In 2012, log dam installation significantly decreased soil erosion from 8.51Mgha−1year−1 to 0.76Mgha−1year−1, with a log dam performance of approximately 90% being obtained. Similarly, the log dams caused a significant reduction of runoff, from 6.9 to 3.3mmyear−1, presenting a performance of 52%. Both differences decreased one year later. Approximately 75% of the soil loss from 2012 was collected in only one clean-out period, when rainfall was almost half of annual rainfall. The quality of the eroded sediments and water runoff was related to the composition of the Ah horizon. Log dams reduced soil erosion in three of the four sites tested during the first year. However, in the second year, only one site showed statistically significant differences, which was the site with the greatest amount of bare soil. These findings indicate that in semi-arid areas, post-fire active restoration measures are still active four years after a fire on south-facing slopes with poor soils and slow ground cover recovery.

Biogeochemical indicators of elevated nitrogen deposition in semiarid Mediterranean ecosystems.

Nitrogen (N) deposition has doubled the natural N inputs received by ecosystems through biological N fixation and is currently a global problem that is affecting the Mediterranean regions. We evaluated the existing relationships between increased atmospheric N deposition and biogeochemical indicators related to soil chemical factors and cryptogam species across semiarid central, southern, and eastern Spain. The cryptogam species studied were the biocrust-forming species Pleurochaete squarrosa (moss) and Cladonia foliacea (lichen). Sampling sites were chosen in Quercus coccifera (kermes oak) shrublands and Pinus halepensis (Aleppo pine) forests to cover a range of inorganic N deposition representative of the levels found in the Iberian Peninsula (between 4.4 and 8.1 kg N ha(-1) year(-1)). We extended the ambient N deposition gradient by including experimental plots to which N had been added for 3 years at rates of 10, 20, and 50 kg N ha(-1) year(-1). Overall, N deposition (extant plus simulated) increased soil inorganic N availability and caused soil acidification. Nitrogen deposition increased phosphomonoesterase (PME) enzyme activity and PME/nitrate reductase (NR) ratio in both species, whereas the NR activity was reduced only in the moss. Responses of PME and NR activities were attributed to an induced N to phosphorus imbalance and to N saturation, respectively. When only considering the ambient N deposition, soil organic C and N contents were positively related to N deposition, a response driven by pine forests. The PME/NR ratios of the moss were better predictors of N deposition rates than PME or NR activities alone in shrublands, whereas no correlation between N deposition and the lichen physiology was observed. We conclude that integrative physiological measurements, such as PME/NR ratios, measured on sensitive species such as P. squarrosa, can provide useful data for national-scale biomonitoring programs, whereas soil acidification and soil C and N storage could be useful as additional corroborating ecosystem indicators of chronic N pollution.

Response strategies of the main forest types to climatic anomalies across Croatian biogeographic regions inferred from FAPAR remote sensing data

Croatia is positioned in the transitional zone of South-eastern Europe and the Mediterranean, a region with frequent occurrence of severe droughts and dry spells, which makes it particularly vulnerable to the impact of climate change. It distends across three main European biogeographical regions – Continental, Alpine and Mediterranean – and therefore has a very high level of forest diversity comprised of 11 out of 14 European forest types. This makes it very convenient to study the exposure of main European forest types to extreme climatic events in the southern limits of their species distribution range. This study provides an assessment of responses of forest vegetation under episodes of climatic anomalies consisting of the most severe historical dry and warm spells in 2000 and 2003, together with the extremely rainy season in 2005 across Croatian territory. The question of interest in this study was to reveal how the existing forest types across the territorial gradient respond to highly expressed extreme climatic variations and to infer some clues about related adaptive strategies. The regional scale approach was applied which previously performed structural delineation of forest cover into eleven main forest groups or bioclimates and were examined considering functional differences. Responses of eleven bioclimatic types were analyzed by time series (1998–2005) of monthly FAPAR (The Fraction of Absorbed Photosynthetic Active Radiation) coverage with a spatial resolution of 1.2km, freely available from JRC FAPAR project. To quantify and differentiate the vegetation response in the considered years we adopted indices of resilience (resistance, recovery, resilience and relative resilience). We also provided a modified approach by applying these indices on a seasonal scale to examine the relationship between variations of phenology and ecosystem responses. The results confirmed the modification of seasonality of photosynthetic activity in relation to the altitudinal and spatial gradient. At the intra-seasonal scale, we distinguished specific opportunistic behavior of the common beech and oak forest types to alternating climatic conditions. Beech forest types show a very high ability to shift their phenology to earlier spring warming as a consequence of global warming. However, continental and Mediterranean oak forest types and in particular Aleppo pine and holm oak forests showed a higher increase of FAPAR during rainy events. The revealed capability of some tree species to better exploit rainfall in very wet periodic episodes has to be further evaluated in drawing conclusions about the overall resilience of forests under future climate change scenarios.

The influence of short-interval recurrent forest fires on the abundance of Aleppo pine (Pinus halepensis Mill.) on Mount Carmel, Israel

The increasing number of fires, fire size, and decreasing fire recurrence intervals are major environmental factors in Mediterranean-type ecosystems, and are known to affect Aleppo pine (Pinus halepensis) forests. The fact that in the Mediterranean basin most fires are man-made increases the danger of fires recurring at short intervals. P. halepensis is a lowland Mediterranean species with a disjunct east-Mediterranean population in Israel and Jordan, with the Mount Carmel population as one of the few native pine forests in Israel.Here we assess the effect of recurrent fires on the regeneration and spatial distribution of P. halepensis, as reflected by the number of trees at 18 sites, according to the number of previous fires and the time elapsed since the last fire. At each site, 100×1m−2 squares were randomly placed to record numbers of trees. Results indicate that in most cases the number of pines per unit area is inversely proportional to the number of fires. For example, tree density in sites that were last burnt during the spring of 2005, varied between 1.2treesm−2 (single-fire), and 0.25 and 0.39treesm−2 in two- and three-fire sites, respectively, while in the unburnt control sites pine density was 0.46treesm−2. The effect of recurrent fires, however, was particularly evident when the time interval between two successive fires was shorter than 20years – the time needed for P. halepensis trees to mature and produce an adequate canopy seed bank. Apparently, not only the number of fires, but also the fire season has a major effect on regeneration dynamics. Although frequent recurrent fires reduce the number of pines at the site, their total elimination from any site never occurred, demonstrating the resilience of this species and its accommodation to short-interval recurrent fires. These results are crucial for establishing post-fire management programmes in fire-prone Mediterranean ecosystems.

At What Depth Are The Properties of a Gypseous Forest Topsoil Affected By Burning?

AbstractWildfires represent one of the main factors of land degradation in Mediterranean environments having negative effects to several ecosystem services. In this work, the fire‐induced changes associated with depth (O horizon and Ah at 0–1, 1–2 and 2–3 cm depths) were studied in a gypseous soil under Aleppo pine forest. Topsoil monoliths were burned in an outdoor combustion tunnel simulating a fire of moderate intensity. In the O horizon, burning caused an immediate and significant decrease in water repellency (WR), total organic carbon (TOC) and pyrolyzed carbon (PyC) and an increase in total inorganic carbon. The Ah horizon was also significantly affected by fire, but mainly in its first shallower centimetre and with a different direction according to soil properties: TOC, gypsum, WR and PyC decreased, whereas soil aggregate stability and pH increased. Soil burning not only involved the loss of the pre‐fire organic matter content of the O horizon and the upper centimetre of the Ah horizon but also decreased their relative abundance of markers of resins, lignin and polysaccharides. Moreover, the soil burning exerted the cracking of alkylic long‐chain molecular series, some of them until the 2 cm Ah depth. The reduction of organic lipophilic molecules in the upper soil centimetre may be related to the fire‐induced decreases in WR. Moderate burning of the studied gypseous ochric horizon does not modify any of the properties studied at depths greater than 2 cm. Copyright © 2013 John Wiley & Sons, Ltd.

Estimation of canopy fuel characteristics of Aleppo pine (Pinus halepensis Mill.) forests in Greece based on common stand parameters

Canopy fuel characteristics that influence the initiation and spread of crown fires were measured in forty representative Aleppo pine (Pinus halepensis Mill.) stands in Greece. Aleppo pine canopy fuels are characterized by low canopy base height (CBH) (2.0–6.5 m), while available canopy fuel load (CFL) (0.63–1.82 kg/m2) and canopy bulk density (CBD) (0.07–0.22 kg/m3) values are similar to those of other conifers worldwide. Regression equations for the estimation of canopy fuels were developed based on common stand parameters. Stand basal area was the best-fitted predictor for the estimation of CFL and CBD at stand level, explaining 77 and 74 % of the observed variation, respectively. Regression analysis failed to provide any significant estimates for the CBH. Prediction of canopy fuel characteristics based on stand basal area can be useful in fuel management and fire prevention planning since it and can be easily incorporated into existing forest inventory systems and can be used for the Kyoto protocol requirements of carbon changes in Aleppo pine forests located in Greek sites.

Predicting time-windows for full recovery of postfire regenerating Pinus halepensis Mill. forests after a future wildfire

A regeneration predictor (RP) has been elaborated to forecast the minimal inter-fire period, required for full recovery (assumed at 1,000 mature stems ha−1, a typical value for a dense pine forest) of an even-aged, postfire regenerating Pinus halepensis population after a subsequent wildfire, in the future. The study has been conducted in three Aleppo pine forests of northern Euboea Island, Greece. Postfire field surveys of sapling growth, sapling density and reproductive dynamics (cone-bearing population fraction, annual cone and seed production per sapling, canopy seed bank build-up) were carried out for three, consecutive growing seasons (years). Additional postfire parameters, with values estimated from literature data, have been also included in order to devise the RP. In the cases of the three populations studied, the application of this RP provides time-windows for full recovery after a recurrent fire, as short as 10–15, 8–11 and 7–11 years, respectively (values corresponding to best and worst scenarios). It is suggested that in even-aged, postfire regenerating Aleppo pine populations, the minimal inter-fire period required for full recovery can be predicted by monitoring a few selected variables, namely (a) sapling density, (b) vegetative to reproductive shift dynamics, and (c) cones/sapling and germinable seeds/cone, for at least 2 years (either consecutive or 2–3 years apart) at a postfire age of 7–12 years.

Changes in water repellency, aggregation and organic matter of a mollic horizon burned in laboratory: Soil depth affected by fire

High variability in the literature is reported on the soil depth affected by forest fires because many factors are involved. We study the fire-induced changes on properties related to soil erodibility as water repellency (WR), soil aggregate stability (SAS) and organic matter at topsoil centimeter-scale (O horizon, and Ah horizon at 1, 2 and 3cm depth). In order to achieve this aim, topsoil monoliths (Rendzic Phaeozem) were sampled from an Aleppo pine forest, with no recent history of forest fires and burned in an outdoor combustion tunnel.Fire caused an immediate and significant decrease in WR, total organic carbon (TOC) and pyrolyzed carbon (PyC) in the O horizon. The Ah horizon was also affected by burning but only up to 2cm soil depth and with a different intensity according to the soil property: TOC was not significantly affected; WR and PyC decreased up to the upper centimeter and SAS up to 2cm Ah horizon depth. Soil burning involved the loss of 2/3 of the pre-fire TOC of the O horizon and 1/3 of the TOC of the upper centimeter of the Ah horizon. Fire also modified the structural composition of organic matter, an effect that was apparent again only above 2cm depth. Specifically the relative abundance of typical vegetation markers (terpenes, resinic acids) and lignin markers (methoxyphenols) decreased. Fire fragmented the long-chain molecules of the alkylic series (n-alkanes, alkenes, fatty acids and methylated fatty acids). This observation, together with a conspicuous reduction in the amount of organic molecules with functional groups in the upper centimeters of the soil monoliths, may be related to the fire-induced decreases in WR and SAS. In conclusion, moderate burning of a mollic horizon in the laboratory produced changes in the hydrophobicity, aggregation, and organic matter only up to 2cm depth.

Wildfire effects on nutrients and organic carbon of a Rendzic Phaeozem in NE Spain: Changes at cm-scale topsoil

Soil organic carbon and nutrient content are analysed at topsoil cm-scale in a Rendzic Phaeozem from an Aleppo pine forest in semiarid Central Ebro Basin (NE-Spain). Soil depth affected by a severe wildfire is studied immediately after burning and a year later, trying to differentiate the heat shock and the ash/charcoal deposition effects. One week after the wildfire, soil organic carbon content (SOC) on burned topsoil decreases significantly at 0–1cm soil depth. Wildfire degrades polysaccharides and proteins and eliminates, or at least reduces, biogenic compound markers, derived from lignin and lipids, but only above 2cm soil depth. A characteristic cracking in the alkane series, as well as the presence of pyrogenic polycyclic aromatic hydrocarbons are also observed in the burned 1st cm topsoil. Below 2cm the fire has little or no effect in soil organic matter molecular assemblage. Calcium, magnesium, potassium, ammonium, nitrate and phosphorous increased significantly a week after the fire, in the first cm soil depth. These modifications detected immediately after the fire (SOC decrease and nutrient increase) are related to the heat released during the severe wildfire. One year after the wildfire, SOC in the 1st cm of burned topsoil regain the same level to that observed in unburned sites, which could be a consequence of burned residues and black ash incorporation and even new inputs on soil surface derived from the reblooming processes, which starts after the fire. With the exception of nitrates whose concentration is higher in burned plots than the control ones within 0–3cm of soil depth studied, nutrient concentration relatively decreased one year after the wildfire. Despite this decrease, fire effect (memory) still remains at the 1st cm topsoil, with many nutrients having comparatively high concentration in the burned soils under semiarid climate.

Resin Tapping History of an Aleppo Pine Forest in Central Greece

The resin tapping history of an Aleppo pine (Pinus halepensis ssp halepensis) forest in Northern Evia, Central Greece was investigated by standard dendrochronological methods. Cross-sections disks of tapped and non-tapped trees were taken from a representative, concerning structure and management, Aleppo pine stand. The identification of resin tapping scars in the cross-sections, combined with tree-rings dating, provided information about tapping methods applied, number and width of tapping faces, tree diameter on the time of tapping commencement and tapping duration. The measurement of tree ring width and the proportion of latewood of tapped and non-tapped trees showed a reduction in the average tree-ring width by 14.1% and in the proportion of latewood by 6% caused by tapping. Tree-ring examination showed that tapping causes severe anomalies in wood like deformations, callous tissues and discoloration. The above information is a helpful tool for the management and study of the Greek resin tapping methods of Aleppo pine forests.

A GIS-based integrated approach predicts accurately post-fire Aleppo pine regeneration at regional scale

This study investigates post-fire natural regeneration of Aleppo pine (Pinus halepensis) forests at Ilia region (Peloponnesus, Greece) following the catastrophic fire of 2007. The objective of this study is the prediction of P. halepensis post-fire regeneration at a regional scale through an integrated geographic information systems (GIS) model as a basis for post-fire management plans. The model was developed in three interconnected stages: (1) field data collection, (2) development of two prediction models (based on interpolation of field data and multi-criteria evaluation (MCE) that combined factors known to affect regeneration), and (3) combination of applied models using Bayesian statistics. Post-fire pine regeneration presented high variation among the studied plots. Redundancy analysis revealed the positive effect of fallen branches and a negative correlation with altitude. Both modeling approaches (geostatistical and MCE) predicted the post-fire pine regeneration with high accuracy. A very significant correlation (r = 0.834, p < 0.01) was found between the combined final model and the actual number of counted seedlings, illustrating that less than 10 % of the studied area corresponds to sites of very low post-fire pine regeneration. The combination of GIS models increased the prediction success of different levels of pine regeneration. Low-altitude areas with low grass cover overlying tertiary deposits were proved the most suitable for pine regeneration, while stands developing on limestone proved least suitable. The proposed methodology provides management authorities with a sound tool to quickly assess Aleppo pine post-fire regeneration potential.

Stand, tree and crown variables affecting cone crop and seed yield of Aleppo pine forests in different bioclimatic regions of Tunisia

In Tunisia, the Aleppo pine seed has a great importance, since in the last decades human consumption has risen considerable. Thus its regeneration and seed production capacities are important factors to take into account to reach the necessities of the country. To study the production of cones and seeds of Aleppo pine, Tunisia’s native Aleppo pine forests were surveyed in summer 2006, using 79 plots (40 × 25 m: 1,000 m²) spread over four bioclimatic zones. Standard tree characteristics, crown dimensions and cone/seed variables were measured from an average tree of each plot(i.e. a total of 79 trees). Recorded data were submitted to simple and multiple regression analyses for explaining the variability in crown volume and crown surface, cone number and seed yield per average tree. Results showed a negative correlation between the stand density, crown characteristics and number of cones and seeds harvested from the average tree. For crown volume and surface, age, stand density, tree height, diameter at breast height, crown diameterand crown height were important explanatory variables under multiple regression analyses. For cone number per tree, only the age, stand density and total height were the most determinant variables. Matures cone number per tree and cone mass per tree were the most informative parameters for the total seed yields per tree. Finally, forest managers should know that crown size affects cone and seed crop of the Aleppo pine individual tree grown in Tunisia, but has no effects on seed number per cone and seed mass per cone.

Aleppo pine forests of northern and western Peloponnisos (southern Greece): Plant communities and diversity

Mature Aleppo pine forests of northern and western Peloponnisos (Achaia and Ilia prefectures) were studied. The studied forests lie in hilly areas and consist of Pinus halepensis ssp. halepensis trees with an understorey of evergreen sclerophyllous shrubs. Three syntaxonomical vegetation units were identified: Oleo europaeae-Pistacietum lentisci pinetosum halepensis of the Oleo-Ceratonion alliance belonging to the thermomediterranean vegetation belt; sub-association Arbuto andrachnes-Quercetum ilicis pinetosum halepensis of the Quercion ilicis alliance belonging to the mesomediterranean vegetation belt and described here for the first time and, finally, the P. halepensis facies of the Arbutus unedo–Erica arborea community of the Quercion ilicis alliance. The above-mentioned vegetation units differ in terms of the floristic composition of the shrub and herb layers, floristic diversity, altitudinal distribution and potential succession.

Geographical variation on cone and seed production of natural Pinus halepensis Mill. forests in Tunisia

Aleppo pine ( Pinus halepensis Mill.) is found in discontinuous bands along the Mediterranean Basin, usually at low elevations and in dry climates. This study was conducted to relate bioclimatic zones and geographic distribution with representative individual tree of populations for cone number and weight from the driest to the wettest Aleppo pine forest zones. Epidometric values were recorded in all sample stands in the monitoring plots set in 79 native populations from the Algerian border to the eastern coast of Tunisia, representing a wide range from each region in northern Africa. Simple and multiple regressions were performed on the data. Results showed that the canopy seed bank increased according to elevation, latitudinal and longitudinal gradients. The simple regression analysis showed a latitudinal effect positively relating increasing latitude to greater cone crop. Similarly, longitudinal and elevation variations were related to significant differences in cone dimensions. Higher average seed mass was related to populations located westwards or at higher elevation. The multiple regression analysis indicated that the longitudinal variations were the most determinant geo-positional factors in Aleppo pine cone dimensions and average seed mass in natural Aleppo pine forests in Tunisia.

Diversification of Pinus halepensis forests by sowing Quercus ilex and Quercus pubescens acorns: testing the effects of different vegetation and soil treatments

The goal of this study was to develop management strategies favouring establishment and survival of holm oak (Quercus ilex L.) and downy oak (Quercus pubescens Willd.)—two species co-occurring in Southern France—in mature Allepo pine forests (Pinus halepensis Mill subsp. halepensis). An experimental design was assessed in a partially cut mature stand of Aleppo pine in which five soil and vegetation treatments—chopping, chopping followed by scarification in one or two directions, prescribed burning, control—and two slash treatments (presence/absence) were applied. A total of 1,600 sowing points, each composed of 3 Q. ilex or Q. pubescens acorns, were installed in the different treatments in November of two consecutive years at 6 and 18 months, after the end of treatments. Survival was monitored 3 and 2 years after sowing, soil surface at the sowing points was characterized at different dates, and predawn leaf water potentials were measured during the dry season. High mortality occurred after the first summer, but survival after 1 year was 2.3–5.2 higher in Q. ilex than in Q. pubescens, confirming that Q. ilex was better adapted to the drier parts of the Mediterranean area. Survival was significantly influenced by the treatments, but there was a variable response between the two sowing years under most of the treatments. Only intense fire proved the most beneficial treatment for seedling survival in both years. The micro-local soil cover conditions induced by the treatments played a major role in explaining oak survival. In particular, grass cover (mainly Brachypodium retusum) proved to be largely unfavourable to seedling survival and growth, and this detrimental effect was also confirmed by lower predawn leaf water potential values with increasing grass cover. Acorn introduction designed to diversify mature Aleppo pine forest after soil and vegetation treatments therefore has to be considered for treatments that most efficiently impair the pre-existing competing grass cover such as prescribed high-intensity fire treatment.

Saproxylic beetle assemblages in the Mediterranean region: Impact of forest management on richness and structure

Forests cover almost 30% of the Mediterranean region today, yet forest management activities have influenced structure and composition of both natural and planted forests. To date no study has been conducted to evaluate the impact of forest management on saproxylic beetle assemblages, although it is known that the Mediterranean is a biodiversity hotspot with a long-lasting human pressure on natural habitats. We provide an overview of saproxylic beetle assemblages of three forest types (mature Pinus halepensis forests, mature Pinus brutia forests, young Quercus calliprinos forests) in the East Mediterranean region using a one-year sample from 12 forest plots located in the north of Israel. The studied forest types differed in forest structure, but we found no significant difference in saproxylic beetle species richness. Aleppo pine forests showed the largest number of saproxylic beetle species. Forests dominated by P. brutia, a non-native tree species in Israel, show the lowest species number of all three forest types. Species composition differs substantially between oak and pine forests. A third of the species found either in P. halepensis or in Q. calliprinos forests being unique to these habitats, while a smaller proportion of unique beetle species is found in P. brutia forests. Several beetle species that were found both in oak and pine plots in our study develop exclusively on broadleaved shrubs or trees. This may be explained by the small distances between the studied pine trees and oaks in their proximity. Biodiversity in pine forests can be increased when these are mixed with broad-leaved trees, e.g. oaks in the understorey layer, as can be observed the natural regrowth in most of the planted pine stands in our research area. There is some evidence from other studies that older successional stages of oak forests are likely to host more species overall than the mature pine forests studied here. In order to enhance structural diversity foresters should allow for aging of single trees or stands, regardless of the tree species.

Effects of fire frequency on nutrient levels in soils of Aleppo pine forests in southern France

El fuego juega un papel importante en la evolución de los ecosistemas Mediterráneos. En el presente trabajo se estudian los efectos de incendios repetidos en suelo bajo Pinus halepensis. La zona de estudio estaba situada en Montpellier (sureste de Francia) y el clima es mediterráneo. Se seleccionan y muestrearon 30 muestras de suelo (10 quemadas en 1981, 10 quemadas en 1996 y 10 quemadas en julio de 1981 y requemadas en septiembre de 1996). Diez suelos se muestrearon en una zona no quemada situada en la proximidad de la zona quemada. Se muestrearon los primeros 5 cm del suelo (horizonte 1) y hasta 10 cm (horizonte 2). Las mayores diferencias se apreciaron en los suelos quemados en 1996, en comparación con los otros suelos. También se detectaron aumento del contenido de materia orgánica en el suelo quemado, así como N y P disponible en el horizonte 2. Los niveles de calcio también fueron mayores en los suelos quemados, que en el control, sin embargo no se observaron diferencias significativas en los valores de Mg y K. Los valores de pH no cambian después del paso del fuego y la conductividad eléctrica disminuye en el horizonte 1 de suelos quemados. Los cationes de cambio son similares a los del suelo control.