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IOBC-WPRS Bulletin Vol. 127, 2017


IOBC-WPRS Bulletin Vol. 127, 2017

Working Group "Integrated Protection in Oak Forests"
Proceedings of the Meeting at Cordoba (Spain), 23 - 27 October, 2016
Edited by: Pino Angelo Ruiu, Maria Esperanza Sanchez and Mohamed Lahbib Ben Jamâa
ISBN 978-92-9067-312-5 [X + 244 pp]


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Infestation of Platypus cylindrus F. (Coleoptera: Curculionidae) in Tunisian cork oak forests
Amani Bellahirech, Luis Bonifacio, Edmundo Sousa, Mohamed Lahbib Ben Jamâa

Abstract: Platypus cylindrus F. has been considered one of the main causes of cork oak trees decline and mortality in Portugal, in Morocco and recently in Algeria. However, in Tunisia, the insect behaves as secondary, attacking only weakened or dead trees. The aim of this work is to establish a synthesis of knowledge concerning the infestation and biology of the pinhole borer in Tunisia and to clarify the the relations between P. cylindrus and cork oak trees in Tunisian forests. The methodology is based on investigation, carried between 2010 and 2011, in the Tunisian cork oak region, complemented with literature reviews of previous works. The results showed that the insect distribution follows the distribution of host trees and P. cylindrus is active in spring and summer, between May and July. Observations indicate that the insect attacks appear to be more related to inappropriate cork removal than to tree phytosanitary status.


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Carpophagous insects of holm oak in southern Spain and their susceptibility to Beauveria bassiana native isolates
Hani K. Aldebis, Ángel Romero, Adel Hatem and Enrique Vargas-Osuna

Abstract: The carpophagous insects Curculio elephas, Cydia fagiglandana and Cydia splendana are cause of damage to the Quercus trees in southern Spain. We have investigated the insecticidal activity of Beauveria bassiana isolated from these carpophagous insects, on larvae of their respective natural hosts, as well as their cross activity. In addition, the activity of an isolate obtained from the lepidopteran defoliator Phycita sp. was evaluated on these carpophagous species.


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Effect of the defoliations of Lymantria dispar on the cork growth
Mohamed Lahbib Ben Jamâa & Sofiane Mnara

Abstract: The gypsy moth, Lymantria dispar, is the most important defoliator of the cork oak forests in North Africa. The moth larvae can cause partial or total defoliation of oak stands. This study aims to estimate the impact of defoliations on cork growth. Three areas that suffered increasing defoliation rates in two consecutive years and a control area without defoliation have been identified and 30 trees randomly selected in each. From each tree, 4 cork stops were collected at 1.30 m above the ground from every cardinal direction (480 stops).
Results showed that cork growth did not vary significantly between cardinal directions but was severely affected by defoliation. The cork production losses were estimated based on the diameter class of tree trunks and defoliation index. The loss was minimal (not exceeding 13%) in cork oaks of small diameters (less than 50 cm) and higher when tree diameters were beyond 50 cm. Loss reached about 30% for trees having 50-60 cm in diameter and having suffered a partial or total defoliation. For cork oaks having 60-70 cm in diameter, cork loss reached about 30% after partial defoliation and more than 50% after total defoliation. Finally, for trees whose diameter exceeds 70 cm, cork loss exceeds already 60% after partial defoliation.


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Infestation and bio-ecology of Phyllonorycter messaniella (Zeller) (Lepidoptera, Gracillariidae) in zen oak forests in northwestern Tunisia
Yaussra Mannai, Olfa Ezzine, Saïd Nouira et Mohamed Lahbib Ben Jamâa

Abstract: The oak leafminer, Phyllonorycter messaniella, is a common defoliator in Europe where its damage usually remains occasional and limited. This insect has been observed for the first time in northwestern oak forests of Tunisia in 2012. The study, which was the first performed on this pest in Tunisia, aimed at acquiring a set of data on the pest bioecology in two zen oak forests, Mzara and Ain Zena. The rate of infestation of leaves with mines was high in Mzara (41.5%), whereas it was low in Ain Zena (17.6% of infested leaves). The number of collected larvae was higher in Mzara than in Ain Zena with 187 and 66 larvae, respectively. The average length of the collected pupae was 7.8 mm. The average duration of the pupal stage was 12 days. Characteristics of the developmental instars of larva, pupa and adult stages of the oak leafminer are also described.


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Infestation of Quercus coccifera by Phyllonorycter messaniella (Zeller, 1846) (Lepidoptera, Gracillariidae) in Tunisia
Olfa Ezzine, Sameh Mhamdi, Sonia Hammami, Samir Dhahri and Mohamed Lahbib Ben Jamâa

Abstract: Phyllonorycter messaniella is a leafminer that infests numerous plants, mainly on deciduous oaks. In Tunisia, this leafminer was observed for the first time in 2013 on the kermes oak, Quercus coccifera, in north-eastern Tunisia. The aim of this work is to study the pest infestation on the kermes oak and the insect behavior. The study was done in spring 2015 in 4 stations in Jebel Abderrahmane. Host-plant infestation was evaluated by counting the number of infested leaves on 30 kermes oak trees in each station. Large and small diameters of host-plants were measured to calculate the average diameter (Dm). Infested leaves were collected, scanned, and the leaf area was calculated using the Image J Launcher software. Beni Oulid was the most infested station with a mean of 5 infested leaves/tree, whereas Ftahiz was the least infested with 1.73 infested leaves/tree. In small leaves, infestation was observed on the entire leaf. In Beni Oulid, the average crown diameter (Dm) was 145.68 cm, on a leaf area of 5.19 cm2, the leafminer can burrow 1.09 cm2. In Delhiza, with Dm = 114.5 cm, 0.90 cm2 of 2.88 cm2 was defoliated. In Ftahiz, with Dm = 113.8 cm, 0.82 cm2 of 3.20 cm2 of the leaf area was defoliated. In Guitoun, Dm = 122.1 cm, 1.28 cm2 of 3.63 cm2 was defoliated. More studies on host plants of P. messaniella will be carried out.


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Larvae mortality of Orgyia trigotephras Boisduval, 1829 (Lep.: Erebidae, Lymantriinae) in Tunisia
Sonia Hammami, Olfa Ezzine, Samir Dhahri, Claire Villemant, Stefan Schmidt & Mohamed Lahbib Ben Jamâa

Abstract: Phytophagous insects feed on a plant or on a part of the plant. This choice is not only based on the nutritional content of the host plant, but also on the intensity of predation and parasitism. This work carried out in spring 2013 (mid-April, early June), aims to study the importance of larval parasitoids of Orgyia (Clethrogyna) trigotephras (Lepidoptera: Lymantriinae) in two sites Jebel Abederrahmane (North-East, Cap-Bon) and Sejnane (North-West, Bizerte) on two host-plants Quercus coccifera and Pistacia lentiscus. A total of 761 larvae of O. trigotephras of different instars were collected on both host-plants. In the laboratory, the caterpillars were individually placed in Petri dishes and reared on young foliage of Q. coccifera. Daily monitoring, allowed larvae mortality and parasitoids emergence. Morphological and molecular analyzes identified five parasitoids: Agrothereutes tunetanus (Hym.: Ichneumonidae) and Eupelmus seculatus (Hym.: Eupelmidae) where observed only on P. lentiscus in Jebel Abederrahmane. Microplictis nr sofron (Hym.: Braconidae) observed on both host-plants in Jebel Abederrahmane. An unidentified Eulophidae observed on Q. coccifera in Jebel Abederrahmane and on P. lentiscus in Sejnane. The tachinid observed in the two sites, on both host-plants in Jebel Abederrahmane and only on Q. coccifera in Sejnane. Overall mortality (parasitism and other factors) is higher in Jebel Abederrahmane (79.62%) than in Sejnane (20.37%). Parasitism rate reached 33% (206/623) in Jebel Abderrahmane and 39% (55/138) in Sejnane. It is also important to follow the dynamics of populations of parasitoids of larvae of O. trigotephras over the years and for the other stages of development of the insect.


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Diversité des Encyrtinae (Hymenoptera: Chalcidoidea, Encyrtidae) collectés par pièges Malaise au sein de la forêt de la Maâmora au Maroc
Khadija Kissayi, Souâd Benhalima & Ahmed Douaik

Abstract: The objective of this study is to characterize different parameters of the biodiversity of the Encyrtinae subfamily (parasitoids) collected by Malaise traps within the oak cork of Maâmora. The specimens were sampled once a week at three locations between June 2012 and May 2014. Quantitative analyzes identified 13 species and 12 genera belonging to 8 tribes. In addition, new data of genera and species were recorded for the first time in Morocco. The tribes containing a largest number of species are Aphicini and Habrolepidini (3). Metaphycus is the only genus represented by more than one species (2). Richness was estimated using nonparametric estimators: Chao 2, Jackknife 1 and Jackknife 2 with values of 48.4, 21.8 and 30.5, respectively. Diversity was calculated using the Shannon index, the equitability index and the Simpson index, and has the value 1.41, 0.55 and 0.54, respectively.


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Identification key to Q. ilex, Q. suber and Q. coccifera oak galls and relation with oak species from Quercus sections (Hym.: Cynipidae)
Juli Pujade-Villar & Claire Villemant

Abstract: Throughout the history of cynipids, 50 species that make galls on evergreen Quercus trees (Q. ilex, Q. coccifera and Q. suber) have been cited. All studied species belong to Cynipini (4 genera) and Synergini (2 genera). A total of 23 species (27 morph-galls) have been proved to be present in these hosts; the rest are either erroneous identifications or are pending confirmation. Most of them can be identified through the gall structure, without obtaining adults. The aim of this study is to present the identification key of galls in order to recognize the 23 species present in Q. ilex (14 species), Q. coccifera (10 species) and Q. suber (8 species), grouped into 6 genera (4 gall formers and 2 inquilines). Some aspects of their life cycle and some curious distributions are exposed. All galls are illustrated. A special mention to the inquiline species capable of deforming Cynipini galls is also given.


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Potential natural enemy complex of Lymantria dispar L. in the eastern Andalucía
Gloria López-Pantoja, Antonia M. Paramio, Sebastiana Malia and Israel Sánchez-Osorio

Abstract: Cork oak (Quercus suber L.) is the dominant tree species across a fourth of the dehesa surface in Andalucía (Southern Spain), with the gipsy moth (Lymantria dispar L.) being the major cork oak defoliator all over its geographical range. The main purpose of this work was to study the entomological diversity in two areas of Andalucía (Cádiz and Granada provinces; Spain) with different infestation levels by L. dispar, focusing on orders that include potential candidate natural enemies of this defoliator. For this purpose 10 experimental plots were studied: eight plots in 2010 (four plots per province) and two plots in 2011 (located in Cádiz). We also wanted to determine the influence of the infestation level by L. dispar on both the abundance and diversity of potential natural enemies of this defoliator. For this purpose the four studied plots of each researching area in 2010 were located as follows: two plots in highly infested stands by L. dispar and other two plots in stands low infested by this lepidopteran species. In each plot we installed two trap types: pitfall (8 traps per tree; 10 trees randomly selected per plot), and cross-vane transparent intercept traps (10 traps per plot, hung from the same trees where pitfall traps were installed). The orders Coleoptera, Diptera, Hemiptera and Hymenoptera were represented with altogether 125 families. Among them, 13 families were considered as candidates to contain potential natural enemies of L. dispar, with Carabidae (Coleoptera) being the most represented family among potential predating insects (accounting for 17 candidate morphospecies), whiles three Hymenoptera families (Braconidae, Encyrtidae and Ichneumonidae) accounted for ~ 59% of the identified candidate parasitoid morphospecies. When the whole candidate natural enemy complex was considered, the insect abundance per tree was significantly higher in low infested plots than that of highly infested plots (68.1 ± 3.9 and 49.1 ± 5 specimens, respectively).


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Indirect infection of Curculio elephas Gyll. larvae with the fungus Beauveria bassiana (Balsamo) Vuill.
Anna Cerboneschi, Clizia Sechi

Abstract: The entomopathogenic fungus Beauveria bassiana (Balsamo) Vuill. (Deuteromycotyna, Hyphomycetes) was tested in laboratory experiments against larvae of Curculio elephas recovered from acorns of Quercus suber L. harvested in a cork-oak stand located in North-Sardinia.
The larvae were indirectly infected by contact with sand treated with two suspensions with different concentrations of conidia. The data regarding the mortality of contaminated larvae, detected after two weeks of incubation, confirm the results obtained, in previous tests, by direct immersion of larvae in the conidial suspensions. These results showed the efficaciousness of the fungal antagonist towards the larvae of Sardinian population of C. elephas and provide additional information to carry out field application tests.


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The gypsy moth control by assisted spreading of Entomophaga maimaiga in oak forests in Serbia in the period 2011-2014
Mara Tabakovic-Tosic

Abstract: Entomophaga maimaiga was isolated and described as the natural enemy of the gypsy moth in Japan, some parts of China and the Russian Far East, where it causes the periodical epizootics. It is not native entomopathogenic fungus in Europe. It was introduced for the first time in Bulgaria, in 1999. Recent data suggest that E. maimaiga is getting spread in Europe. Since the presence of E. maimaiga, in Central Serbia had already been determined, at 97 selected plots situated in: Belgrade, Valjevo, Krusevac, Kraljevo, Vrnjacka Banja, Blace, Prokuplje, Kursumlija and Negotin regions. In spring and autumn of 2012 and 2013 the assisted spread of E. maimaiga was perfomed, through the introduction of the infectious inoculum in the oak forests. E. maimaiga was dealt with fungus, which is particularly susceptible to the weather and the global warming conditions and the great drought, a special preparation of inoculum was made. In the following year the mass epizootic of the gypsy moth caterpillars occurred, which implies that E. maimaiga caused the decline of the gypsy moth population. The detailed microscope survey showed the presence of numerous conidiospores and azygospores of the E. maimaiga in 83.8% of collected cadavers.


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Forest decline and xylophagous pests on Quercus woods in South Apulia Region
Eustachio Tarasco, Monica Oreste, Cezary Tkaczuk and Rudolf Wegensteiner

Abstract: In the heel of Italy, the southern part of Apulia Region called Salento, some oak woods have been affected in recent years by severe desiccation and gradual decline. The strong desiccation can be attributed to various causes, such as xylophagous pests and presence of plant pathogens, in conjunction with abiotic factors as sudden lowering of the water table. In particular the encountered xylophagous pests belong mainly to bark beetles (Scolytinae), longhorn beetles (Cerambycidae) and jewel beetles (Buprestidae), with some of the collected insects infected by entomopathogenic fungi. The present study shows the phytosanitary situation of these oak woods with a detailed examination of xylophagous attacks.


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New aspects about the epidemiology of oomycetes causing Quercus suber root rot in Spain
Mario González, María Socorro Serrano and María Esperanza Sánchez

Abstract: Phytophthora cinnamomi and Pythium spiculum are the main pathogens causing root rot on Quercus suber in the Iberian Peninsula, although the environmental conditions favoring root infections by each pathogen seem to be different. The present work analysed the competition level between both species under two dry soil conditions: moderate drought (51% ≥ θs ≥ 38%) and extreme drought (30% ≥ θs ≥ 20%) in comparison with previous results obtained in wet soil conditions. Cork oak seedlings were inoculated with resting spores (chlamydospores of Py. spiculum and/or oospores of P. cinnamomi) from both pathogens alone or mixed. Eight plants (replicates) per water regime and inoculum were grown in infested or uninfested (control) fertilized peat and incubated in an acclimatised greenhouse. Severity of foliar symptoms (yellowing, wilting and/or defoliation) was weekly evaluated, and the percentage of root necrosis assessed at the end of the experiments. Phytophthora cinnamomi and Py. spiculum showed a similar moderate virulence at moderate drought in comparison with control plants, which also showed some root damage not associated with oomycete infections. In contrast, only Py. spiculum caused a significant root necrosis in extreme drought, even considering that control plants also showed a high level of root damage in absence of pathogens. These results suggest that Py. spiculum could be better adapted than P. cinnamomi to terrestrial habitats, becoming less dependent on wet soil conditions. In conclusion, P. cinnamomi and Py. spiculum are able to cause root rot on Q. suber in a wide range of soil humidity. Then, independently of variations in soil water content, oaks growing in infested soils would be in high risk of disease.


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Water and nutrient status of oaks and their relationship with canopy defoliation
María Teresa Hidalgo Fernández, José Ramón Leal, María Dolores Carbonero, Alma María García, María Luisa Sillero et Pilar Fernández Rebollo

Abstract: The Andalusian Network on Forest Ecosystem Health (SEDA network) evaluates each year the status of forest health in more than 400 permanent plots. The water status is one of the most important indicators of oaks health. Water Content (WC) and Relative Water Content (RWC) are the most common indices used to evaluate the water status of tree leaves. The aim of this work was to assess the relationship between water and nutrient status of tree and canopy defoliation. WC, RWC and macronutrient concentrations of leaves were assessed through spectral indices. RWC varies positively related with K concentration of leaf. WC was negatively related with N concentration and positively with K and P concentrations. Tree canopy defoliation increased with increasing RWC and decreased when trees showed high N leaf concentration. Mean water status of tree within a plot was mainly determined by site factors and weather factors. The results suggest the knowledge of the water and nutrient status of tree will allow a better understanding and interpretation of the canopy defoliation and their relationship with changes in environmental conditions and management practices.


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The role of difference genotypes of Brassica carinata and Brassica juncea as biofumigant crops in contrasting ecosystems
José Ramón Leal Murillo, María Dolores Carbonero, Alma M. García, María Teresa Hidalgo, Sara Obregón, Antonio De Haro and Pilar Fernández-Rebollo

Abstract: This study analyzed the production of plant tissues (above and below ground) and the concentration and profile of glucosinolates of two genotypes of B. carinata A. Braun and B. juncea L. Brassica genotypes were grown in two locations of south Andalusia with different weather and soils (dehesa – oak open woodland – and valley), during two campaigns (2013 and 2014). Samples were taken in full bloom, at the time of incorporation of the plant tissues into the soil. The genotypes of both species tested have shown different productions between locations and years. Total plant production was higher in valley than in dehesa. In dehesa, production was low in the first year, due to a deficient initial plant establishment. Above-ground biomass ranged between 25-8 T DM/ha in valley and between 6-0.2 T DM/ha in dehesa. Below-ground biomass ranged between 9-3 T DM/ha and 1.7-0.1 T DM/ha in valley and dehesa respectively. Genotypes of B. juncea reached higher production than those of B. carinata in dehesa, and similar values in the valley. In both areas, sinigrin was the main glucosinolate in aerial and root tissues. Total sinigrin that can be incorporated into soil was estimated around 270-50 kg DM/ha in valley and 39-0.5 kg DM/ha in dehesa. The results pointed out that B. juncea can play a better role as a biofumigant plant against P. cinnamomi than B. carinata, especially in dehesa area.


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Effects of limestone amendments in the response of holm oak infected by Phytophthora cinnamomi
José Ramón Leal Murillo, María Dolores Carbonero, Alma M. García, María Teresa Hidalgo, Macarena Férriz, María S. Serrano and Pilar Fernández-Rebollo

Abstract: The aim of this work was to evaluate the effects of two limestone amendments in the response of infected holm oaks in field conditions. An experiment with different types of limestone amendments (CaCO3 and CaSO4) was carried out in two dehesas farms – open oak woodland – with oak root rot caused by Phytophthora cinnamomi in Huelva province (Andalusia, Spain). We evaluated the change of soil parameters (pH, exchangeable Ca and K), water and nutrient concentrations of holm oak leaves, shoot growth and the evolution of tree canopy defoliation. Limestone amendments have effectively increased the concentration of soil exchangeable Ca, especially with CaCO3 application. The increase of Ca in soil has shifted exchangeable K. In the short term, CaCO3 amendment increased soil pH while CaSO4 reduced it. Tree shoot growth was similar between limestone amendments and did not differ to the control trees. Additionally, no significant differences in nutrient concentrations of leaves were found. CaCO3 amendment increased the water concentration of leaves. Compared with control trees, limestone amendments slowed down the defoliation of the canopy in the first year after treatment but kept increasing the second year. Results obtained indicate that limestone amendments may attenuate the disease symptoms but their effects are ephemeral and are related to weather condition.


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Quantification of phosphite ions in treated cork oak trees
María Angeles Romero, Javier Perales, María Socorro Serrano, Mario González, María Esperanza Sánchez

Abstract: Since 2013, the use of potassium phosphite products has been prohibited in Spain when registered as fertilizers, so other phosphite-based products but registered as pesticides need to be tested for use in oak-rangelands for Phytophthora cinnamomi management. In autumn 2014, an experimental plot with Quercus suber trees affected by the root rot disease were established in a site in Huelva (southern Spain). Sixty trees were selected in the site and classified according to their defoliation class (0 = < 10% defoliation, 1 = 11-25%, 2 = 26-50%). Ten trees per class were treated with Fosetyl-Al by trunk injections at the manufacturer recommended dose (4% phosphite ion), remaining the other 10 trees as untreated controls. Three months after treatments (spring 2015), leaves and root samples were taken and analysed to assess their phosphite-ion content following the methodology described in Stasikowski et al. (2013). The phosphite concentration in root water extracts was estimated by comparison of the intensity of the grey-black precipitate obtained with a standard scale of rising concentrations of phosphite (0.1-50 mM). Values of phosphite ion detected in cork oak leaves varied between 0.1 and 21.5 mM, raising 5.2 to 22.6 mM in roots. A significant and positive correlation (Pearson test) between concentration in leaves and roots was found. ANOVA analysis showed significant differences in phosphite concentration depending on defoliation class in cork oak leaves, being significantly higher for the highest defoliation class (LSD test, α = 0.05). Phosphite concentration in roots also increased with increasing defoliation class, but differences were not significant. We conclude that the active matter applied (same quantity independently of defoliation class) would be equivalently distributed through roots and foliage present in the tree, less abundant as defoliation is higher. A new sampling and phosphite quantification will reveal whether concentrations and correlations found are maintained some years later. Preventive effect on cork oak disease development will be evaluated in the medium-long term.


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The occurrence of Phytophthora cinnamomi in southern Spain: Presence – absence records and potential distribution area
Oliver Gutiérrez-Hernández, María Esperanza Sánchez, Cristina Ramo, Jonatan Eloy Sánchez-Solana, Luis-Ventura García

Abstract: Phytophthora cinnamomi is an alien species, which causes root rot and decline in cork oak (Quercus suber) and holm oak (Quercus ilex) native forests and agroecosystems in the Iberian Peninsula. However, there is little reliable and accessible data on the presence and absence of this soil borne pathogen in Spain. For this reason, we applied the Environmental Niche Models to predict the potential distribution of P. cinnamomi in Andalusia (southern Spain). Firstly, we developed a georeferenced database about presence-absence records of P. cinnamomi in the study area based on published data and from our research projects. Secondly, we developed a set of environmental variables at a resolution of 250 meters. Thirdly, the inferential approach was based on the regression methods using presence-absence data, and the machine learning algorithms using presence-background data, and evaluated the models using ROC/AUC. Finally, we ensembled the best models to mapping the results in one consensus model. The result showed a large potential distribution area of P. cinnamomi in Andalusia, from one-third to one-half of the region and connected areas.


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Soil-borne pathogens limit Quercus suber regeneration in Mediterranean forests
Jara Domínguez-Begines, Francisco Alcocer, Luis Ventura García, Ana Pozuelos, Maria Esperanza Sánchez, Lorena Gómez-Aparicio

Abstract: In the Iberian Peninsula, evergreen Quercus species are suffering a severe adult tree mortality caused by the exotic soil-borne pathogen Phytophthora cinnamomi. Nevertheless, the effect of this pathogen on oak regeneration has been poorly investigated under field conditions. In this work, we experimentally assess the role of P. cinnamomi as a limiting factor of Q. suber seedling recruitment under field and controlled conditions. A seed sowing experiment was conducted in declining Q. suber forests at Los Alcornocales Natural Park (SW Spain). Q. suber acorns were sown with and without fungicide in 3 different sites (49 sowing points per site), and their emergence and survival were monitored monthly during 18 months. We also conducted a greenhouse experiment where Q. suber seedlings were sowed in soils collected under 4 types of adult trees: healthy, defoliated and dead Q. suber and under Olea europaea (the coexisting tree species). Half of the seedlings were treated with a fungicide monthly during 4 months. At the end of the experiment, aboveground biomass was weighed in all the seedlings. In the field experiment, the application of fungicide increased Q. suber emergence and survival. In the greenhouse experiment, the fungicide increased seedling aboveground biomass in all type of soils. Overall, our results experimentally demonstrate that P. cinnamomi has negative effects on the performance of Q. suber seedlings in declining Mediterranean forests. Soil-borne pathogens should therefore be added to the list of factors (e.g. seed predation, summer drought) that limit the natural regeneration of Q. suber.


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Role of Phytophthora species in the lack of seedling recruitment in Mediterranean cork oak forests
Bruno Scanu, Lucia Maddau, Antonio Franceschini

Abstract: Oak forests are far the most important ecosystems in the Mediterranean regions. However, their sustainability is under threat due to severe decline process, climate change and lack of natural regeneration. The oomycetes Phytophthora spp. have been associated with oak decline, with P. cinnamomi being the most widespread species. Besides killing adult trees, Phytophthora can in turn act as damping-off pathogen affecting the natural regeneration. This study aimed to explore the diversity of Phytophthora species occurring in Sardinian oak forests (Italy) and to investigate the variation in early survival of oak seedlings to Phytophthora infections. Soil and root samples underneath oak trees and from seedlings showing symptoms of Phytophthora infection were baited using fresh oak leaves. Several Phytophthora species were isolated and identified based on morphology and DNA sequence analyses. The susceptibility of germinated acorns to Phytophthora infections was tested by immerging growing taproot in a zoospore suspension. Although at different rates, Phytophthora species were able to cause a significant reduction of root development. In the field, the lack of seedling recruitment was assessed in 1 m2 plots selected in Phytophthora infested and disease-free sites. The results of this study provide new insights in the aetiology of oak decline and lack of seedling recruitment. The ecological implications of these findings are discussed.


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Phytophthora species associated with cork oak decline in a Mediterranean forest in western Algeria
Hadjer Smahi, Latifa Belhoucine-Guezouli, Antonio Franceschini, Bruno Scanu

Abstract: Oak decline has been a serious problem in Mediterranean countries since the beginning of the twentieth century. The invasive pathogen P. cinnamomi has been associated with intense mortality of oak trees in the Iberian Peninsula, southern France and Italy. Although oak decline has been reported also in North Africa, P. cinnamomi was never recovered in any of the surveyed stands, and tree decline has been associated with other diseases, pests, climate and human intervention. The aim of this work was to investigate the occurrence of Phytophthora species and their possible involvement in the decline of cork oak trees in Algeria. A declining cork oak forest located along the Mediterranean northwest coast was surveyed between 2015-2016. Symptomatic trees showed thinning and crown dieback, withering of leaves and death. Root rot and extensive loss of both lateral small woody roots and fine roots were observed. To isolate Phytophthora, roots and soil samples collected from 18 declining and 8 asymptomatic cork oak trees were baited using fresh cork oak leaves. Isolations were made on SMA, a selective medium for Phytophthora spp. Isolates were identified using morphological analysis and DNA-based techniques. Phytophtora cinnamomi was the most frequent species isolated and three other Phytophthora species identified as P. gonapodyides, P. multivora and P. quercina were detected. Comparative aggressiveness of these Phytophthora species was assessed on 3-month-old seedlings of Quercus afares, Q. canariensis, Q. ilex and Q. suber. This is the first study looking at the diversity of Phytophthora pathogens in Algerian oak forests.


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Studies on the infestation by Phytophthora spp. affecting oak seedling production in forest nurseries in Sardinia (Italy)
Salvatore Seddaiu, Clizia Sechi, Antonio Franceschini, Bruno Scanu

Abstract: Quercus ilex and Q. suber are the main forest species grown in Sardinia nurseries. Between 2013 and 2016, seedlings of both oak species were sampled to detect Phytophthora species, one of the most important groups of pathogens in nursery environment. Root and soil samples were collected from both asymptomatic and symptomatic potted plants in two forest nurseries located in North Sardinia. In addition, potting soil and irrigation water were sampled. Isolations from soil and plant materials were made with fresh oak leaves as baits and using Synthetic Mucor Agar (SMA), a selective medium for Phytophthora. Isolates were identified based on a combination of morphological and DNA sequencing analyses. In total, three known Phytophthora species were detected. Phytophthora cinnamomi was the species with the highest detection rates, followed by P. cryptogea and P. plurivora, and a new species currently under taxonomic description. The overall percentage of samples positive for Phytophthora isolation averaged 80%. At one nursery, 100% of the sampled seedlings were positive, with most of the plants remaining asymptomatic. The high level of Phytophthora infestation rate has seriously compromised the production of oak seedlings in these nurseries. Best management practices for reducing the risk of introduction and dispersal of Phytophthora spp. outside nurseries need to be undertaken.


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A review of integrated control of Phytophthora root rot in oak rangeland ecosystems
María Socorro Serrano, Pedro Ríos, Mario González, María Ángeles Romero, Pilar Fernández and María Esperanza Sánchez

Abstract: The root rot caused by Phytophthora cinnamomi is the most devastating disease affecting cork and holm oak trees in the southern Iberian Peninsula. Every year thousands of trees are killed, with severe ecological and economic consequences. Over the last 10 years, different control strategies have been developed, and they can be integrated for disease management. Firstly, cultural actions may be applied in healthy areas to minimize pathogen arrival, but also in infected areas to reduce its spreading, such as soil drainage, livestock load and soil tillage limitation, as well as reducing movement of farm machinery and other vehicles. Other cultural methods are focused on reducing the viable inoculum density in the soil, including the soil application of calcium amendments, especially CaSO4 and CaCO3, which are able to reduce the infectivity of P. cinnamomi. In the same way, the cultivation of susceptible species (Lupinus luteus) that favour the multiplication of the pathogen (production of zoospores and chlamydospores) should be avoided. Biofumigation using Brassica spp. with high content in Sinigrin, like B. juncea or B. carinata, shows a suppressive effect on P. cinnamomi resistance spores survival. The use of oak morphotypes resistant to the pathogen appears very limited; however, hybridization with some species could be used in breeding programs as showed for natural hybrid Q. ilex-Q. faginea, which exhibit low levels of root symptoms and only in artificial inoculations. Finally, chemical control actions based on inducing resistance, such as the application of systemic phosphonate fungicides by trunk injection or the increase of Ca2+ content in the tree, could be also applied.


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Litterfall production and seasonal variations in leaf area index of cork oak stand in the forest Ain Snoussi (Northwestern Tunisia)
Kaouther Ben Yahia, Sameh Mhamdi, Hatem Chaar, Souleima Bahri, Kamel Soudani, Brahim Hasnaoui

Abstract: Although it is used as an index of primary production, studies relating to litter falls from cork oak are scarce in Tunisia. Thus the understanding of its dynamics is a prerequisite for the study of energy flows (through canopy structure, LAI) and the nutrient cycle in a Mediterranean forest ecosystem based on cork oak. The objective of the study is to quantify the litter falls, their monthly variations and compare them with their foliar index (LAI). In a 1 ha plot in the forest of Ain Snoussi, where the three arborescent (cork oak), shrub (Arbutus unedo) and herbaceous (Briza maxima) strata exist, leaf fall has been determined at 35 square traps, of 1 m² of surface, placed systematically every 15 m, under the trees to 10 cm above the ground. Pick-up was monthly from January 2010 to September 2011. The LAI (Leaf area index) of the stand was estimated by hemispheric photography systematically every 10 m in the year 2011, one to two times per season. The results showed that litter fall occurred throughout the year with a spring peak (May). This fall varied from year to year. It was in the order of 389.422 ± 34.7 g/m²/year in 2010, whereas in 2011 it was 300.51 ± 35.041 g/m² over a 9-month period of measurements. The most important fractions were mainly the leaves of cork oak, canary oak, Arbutus unedo and Myrtus communis, the main species of shrub. The foliar contribution was on the order of 83% of the total biomass. The seasonal variation of LAI showed that this functional parameter evolved according to the season. It was low at the end of winter, increased in spring when leaf fall was maximal, reached its maximum value in summer when the fall was minimal and then decreased in autumn.


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Research of an allelopathic effect of Acacia mearnsii (De Wild.) and Eucalyptus camaldulensis (Dehn) on the growth of Quercus suber (L.)
Imene Boudiaf, M. Souelmi, Arifa Beddiar

Abstract: The biological invasion by exotic plants is one of the biggest threats of biodiversity extinction. The success of some invasive species has been linked to the release of allelochemical compounds that affect the native plants growth. The aim of this study is to investigate the allelopathic effect of Acacia mearnsii (De Wild.) invasive species in cork oak forests of the El Kala’s National Park (North-East of Algeria) and the Eucalyptus camaldulensis (Dehn) on cork oak (Quercus suber L.) growth. The allelopathic potential of different concentrations of solution extracts of the leaves, pods, and litter of A. mearnsii and E. camaldulensis leaves was tested on the growth of Q. suber (L.). The primary results show a remarkable negative effect of aqueous extracts (A. mearnsii leaves, E. camaldulensis leaves and litter) on the root’s growth of the cork oak seedlings as well as the ectomycorrhizal (ECM): Control of cork oak represented by 47.8% mycorrhizal rate compared with eucalyptus with 1.4% followed by litter and acacia, respectively, with 1.6% and 5.4% mycorhization rate.


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Phenological response to drought in Quercus ilex: thinning as mitigation tool
Maria Dolores Carbonero, Jean Marc Ourcival, Jean Marc Limousin, Richard Joffre

Abstract: Mediterranean forests will be greatly affected by climate change, which is expected to have changes in the timing of some phenological events. In this context, management practices could improve ecosystem resilience to disturbances. This study tested the response of an experimental drought on holm oak phenology and how thinning could mitigate its effects. The study was performed in the Puechabon Forest (Southern France) using 4 experimental treatments on 120 m² plots: control (C), thinning (T, -30% basal area), drought (D, -30% precipitation) and drought + thinning (DT). Plots are part of the Experimentation in Ecosystem Research European infrastructure. We analyzed development of Quercus ilex leaves in spring over 2003-2013 period. Phenology was affected by the treatment, being C plot the earliest, DT plot the latest and T and D plots reached intermediate values. Regarding the phenophases length, we only found differences for the last one (expanding leaves and enduring) reaching drought plots (D and DT) the lowest values. Moreover, synchrony was highest for drought plots (D and DT). These phenological differences amongst treatments, could affect growth and acorn production with important ecological consequences.


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Assessing oak replacement in dehesa system through in-plot analysis
Pilar Fernández-Rebollo, A. García, B. Abellanas, R. Mata, J. L. Gómez, J. R. Leal

Abstract: Dehesa is the most extended agrosilvopastoral system in south Spain and Holm oak the main tree species. Continuous grazing combined with other practices such as cultivation and burning, is associated with failures in oak recruitment and hence, in the long term, with loss of tree canopy cover. The aim of this paper is to analyze the evolution of holm oak density in dehesas in the last decades through in-plot dynamic analysis. Using aerial photographs from 1977 and 2011, we have compared tree canopy cover and density in 200 plots of 1 ha within 16 dehesa-farms of Andalucía (South of Spain). Overall, tree density has reached similar values for both dates, 32 trees/ha, but we found significant differences between regions and farms. In areas with a denser tree canopy cover in 1977, holm oak density has decreased significantly whilst it increased in those with previous low tree canopy. On the other hand, tree canopy cover has experienced an increase in this period, from 29% to 34%. This increase was also observable at regional and farm levels. The widespread increase in coverage has been mainly due to the growth of existing trees and, secondly, to the incorporation of new trees. The annual rate of tree loss is 0.23 trees/ha. These results indicate that tree density of Andalusian dehesas has remained constant over the last 40 years through a tradeoff driven by farmers between tree loss and recruitment.


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Effect of the synergistic use of a nurse plant, Lavandula stoechas L., and mycorrhizae on the growth of cork oak plants in nurseries
Hana Ksentini, Arifa Beddiar, Amel Meddad-Hamza

Abstract: Some plants of the cortege floristic of the cork oak, such as the case of the lavender in this study may be favorable to the juvenile growth of cork oak. Thus, plants nurses facilitate the ecological restoration of forest areas degraded greatly, mycotrophic, which can ensure the restoration of mycorrhizal power of soil, thus favoring the good development of the plant cover. The objective of this present study was to evaluate the synergistic effect produced by the presence of plant nurse (Lavandula stoechas L.) and the inoculation of mycorrhizae (Ectovit and Symbivit) on the growth of cork oak. For this purpose, a test of controlled mycorrhization in the nursery has been realized on a twenty plants of this plant grown in polyethylene bag in the presence or absence of lavender (Lavandula stoechas L.) based on plant of cork oak and 10 plants of lavender per bag. The substrate is a soil came from the cork oak forest of Brabtia (Northeastern Algeria), whose condition is well degraded. Non-inoculated controls with and without lavender were provided. After 12 months of growth, the statistical study according to the LSD test showed that cork oak inoculated and not in the presence of lavender had the highest rates of mycorrhization, respectively, 49.59% and 43.66% the same for the total biomass such as 25.02 g and 19.55 g compared to the treatments in absence of lavender as 15.63 g and 12.59 g.


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Forest fire spread model with non-universal dynamical critical behavior
Khadidja Khelloufi, Yamina Baara, J. P.Clerc, B. Porterie and N. Zekri

Abstract: The critical behavior of spread dynamics is examined using forest fire model. The model is characterized by long-range interactions due to flame radiation and a weighting process induced by the ignition energy of the combustibles. It is found that the rate of spread critical exponents depend on the local interaction as well as the weighting parameter indicatinga non-universal phase transition.


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Dielectric analyses of a shrub leaf for the modelling of forest fire
Khadidja Khelloufi, Yamina Baara, Nouredine Zekri, Cláudia Pinto, Domingos Xavier Viegas

Abstract: Most Mediterranean regions face a high risk to forest fires, estimation and anticipation of this risk modeled as a stochastic propagation process reproduces well some fire properties. Our model needs information on different types of vegetation including their bio-physical properties behavior associated to combustion. In this work, an experimental study to analyze the structure of a leaf of Laurel shrub at different biological stages is presented; it allows following the structural exchanges induced on the leaf by the effect of increasing temperature for a better understanding of the pyrolysis phenomenon and to determine accurately the chemical parameters such as activation energy and time associated to each reaction caused by temperature increase. The results obtained provide information on the process of thermal degradation caused by fire. The evolution of the leaf impedance as a function of the applied frequency characterizes the moisture loss in plant species during pyrolysis. The dielectric response confirms our proposition to the equivalent circuit of the leaf of vegetation as a composite of liquid and solid parts.


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Current state and dendrometric study of cork oak (Quercus suber) from National Park of Theniet El Had area of Tissemsilt (North West Algeria)
Bouazza Khaldia, Oumeldjilali Naggar, Mohamed Zedek, Abdelkader Dellal

Abstract: The cork oak forests of Theniet-El-Had Wilaya Tissemssilt (west of Algéria) form an integral part of the territory of the National Park. They are situated mainly in the south side of the park to a maximum altitude of 1575 m. This work consists of a study on the current state of the cork oak forests abandoned for decades. The methodology is to install during 2012 circular plots of 5 acres surface. In total 23 units are installed environmental samples exposure, altitude, topography and slope) and dendrometric (circumference, total height) are harvested. The trees have an average height rarely exceeding 8 m and an average thickness of 0.70 m. The stands have a very low regeneration and irregular structure characterized by a poor distribution of stems, the result of a long absence of appropriate silvicultural treatments. In addition almost 80% of inventoried stems are not harvested (the last operation dates back to 1994). The rehabilitation of the cork oak forests of Theniet El Had based on a thorough knowledge on tree growth factor and its variability (typology of stands and fertility index) and cork’s productivity.


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Characterization of floral diversity in oak forests of western Algerian region
Zaira Souidi et Malika Moumou

The objective of our study is to present the richness, spatial distribution of the shrub and the structure of the main tree species in five oak Algerian western regions. The methodological approach is based on a survey of plant species followed by a floristic analysis of 6 squares in each forest. The results obtained show a fairly low phytodiversity in the forests studied. Species richness was 36 species, 19 genera and 16 families on average for each station in 66 floristic surveys made. There is the influence of altitude, exposure and climate and anthropogenic factors on the structure and distribution of vegetation.


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Behavior monitoring varietal of three origins of cork oak in western Algeria in soilless cultivation
Zaira Souidi et Malika Moumou

Abstract: Our work aims to compare three origins of cork oak Algerian western region, forest Bissa from wilaya of Chlef, Hafir forest from Tlemcen and Nesmoth forest from Mascara. The methodology is based on soilless culture of cork oak acorns nursery for three origins and monitoring of some morphological and physiological indicators. The plants were also exposed to different levels of heat stress. The results show that the average size of the plants, the average number of leaves and the average length of seedling germination vary according to the region studied. Biometric study acorns and monitoring the growth of young plants has noted a maximum height of seedling stems of 14 cm after 64 days. Monitoring the germination of acorns shows that the tassels of Hafir forest represent the highest rate (32%) compared with acorns Bissa forest (20%) and Nesmoth (13%). The study of these different indicators, especially the stomatal density and stomatal conductance, can allow us to better differentiate the effect of varieties of each region.


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Impact of the drought stress on the morphometric of the seedlings of Quercus suber L. of the west of Algeria
Malika Moumou, Zahira Souidi et Assia Letreuch-Belarouci

Abstract: Our study deals with the effect of water deprives imposed on hydroponic crops of oak trees (Quercus suber L.) taken from the west region of Algeria. The application of the various water stresses consisted in suspending the watering of the plants from the 6th week after sowing. The test was carried out on 450 Q. suber, the samples’ plants obtained by seedlings from mature acorns taken from three oak forests in western Algeria. Each plant was analyzed for growth, morphology, and physiology. Samples’ growth measurement was performed before and during stress such as weight leaf area and lengths which are the key to compare between origin. The results obtained from the calculated growth indices (RGR, LMF, SMF, RS, LAR) lead us to conclude that there are different ecotypes of the species Q. suber. This is due mainly to the marked polymorphism of this species, to adaptive characteristics of this species to the conditions of climate change resulting in response of functions of leaves and roots.


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Study of the structure and growth factors of stands of cork oak (Quercus suber) from National Park of Theniet El Had (North West Algeria)
Oumeldjilali Naggar, Tarek Rachid Bouhraoua

Abstract: The study of cork oak from the national park of Teniet El Had aims to identify the structure of the stands and the spatial distribution of the stems. So, 30 rectangular plots of 5 a were installed during the year 2013 distributed uniformly in the forest. The spacing of the stems and crowns shows that the area of the cork oak crown decreases in the mixed stands relative to the total height which increases. This is due to competition imposed by other species (Cedrus atlantica, Quercus fagenea). Moreover, in pure stands where the density is less important, the diameter of the crown increases and the total height becomes less important.


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Results of the use of shelters in cork oak (Quercus suber L.) reforestation in Sardinia
Pino Angelo Ruiu, Agostino Pintus

Abstract: The artificial reforestations using Quercus suber L. are widely distributed in Sardinia and the authors have previously conducted a series of studies in a reforestation of Q. suber L., established in 2001, by using individual protection shelters of different types and heights. Results were positive; the shelters reduced the mortality and favoured the growth of seedlings.
In autumn 2006, the individual protections were removed without any modification of the experimental plots in order to follow the evolution of the seedlings; the data for the period 2006-2012 were analysed in this paper. Pluviometric data showed that the trend of rainfall was nearly always higher than the historical average, with some years particularly rainy. The data analysis shows that the control seedlings, grown without individual protection shelters, continue to have a significantly higher mortality. The greater height values were observed in plants protected by shelters of 60 cm. After protection removing, the seedlings protected by shelters of 120 cm, have suffered from 2007 to 2009 stunting. The increase in diameter was higher in seedlings grown with Tubex 60 and Arboplus 60, while control plants exhibited the lowest growths, confirming the results obtained in 2006. The ipso-diametric ratio decreased in all the modalities, in particular for plants protected by shelters of 120 cm, highlighting the achievement of a balance between growth in height and in diameter. The use of individual protection shelters, originally created to avoid damage by animals, has demonstrated its effectiveness in reducing seedling mortality and improving their development, especially when using shelters of 60 cm.


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Plant biodiversity investigation in a Sardinian deciduous oak woods grazed by cattle
Pino Angelo Ruiu, Giuseppino Pira, Maria Sitzia, Gianmarco Marrosu

Abstract: Oak woods, pure or mixed, are the most common wooded formations in Sardinia covering over 20% of Sardinian territory. They have a very high environmental and economic value thanks because of the cork production and their inclusion as pasture in livestock farming system. Numerous studies were conducted on the relationship between forest preservation and pasture management have showed the compatibility of a moderate cattle grazing with the forest conservation. However, researches focused on the grazing effect on forest biodiversity are still insufficient. The aims of this work were to evaluate the relationship between cattle grazing in a silvo-pastoral system and forestry conservation and to analyse its influence on flora biodiversity. The research was carried out between 2011 and 2015 at the experimental oak forest of Agris Sardegna, located in the North-West of Sardinia. Inside the experimental oak forest covering about 70 ha and dominated by Downy Oak (Quercus pubescens L.), were identified 5 circular sample areas (1256 m2), representative of the total areas. Within each circular area the botanical species composition of the herbaceous sward was established and the diameter and height of trees were performed. This study was conducted annually, in June, according to the phytopastoral method of Daget and Poissonet (1971). A total number of species and their abundance was determined. The grazing value and the indices Piélou’s evenness, Shannon-Wiener for the biodiversity were assessed. The results seem to confirm low intensity cattle grazing compatibility with the maintenance of forest cover and botanic biodiversity.


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Impacts of salinization and eutrophication on soil functioning in Quercus suber forests (Doñana National Park, SW Spain)
María T. Domínguez, María S. Serrano, Eduardo Gutiérrez, Beatriz R. González-Domínguez, José M. Ávila, Miguel Román-Écija, Adela Moreno, Luis V. García

Abstract: Soil salinization and eutrophication are two major threats of soil degradation in the Mediterranean basin, which may have a large impact in the functioning of Mediterranean forest systems. Cork oak forests at Doñana National Park (SW Spain) are affected by soil salinisation and eutrophication, due to the presence of large colonies of wading birds, which supply the soil with high amounts of detritus, resulting in a decline in tree health status. We analysed soil physico-chemical properties, microbial activity (biomass and basal respiration) and composition (T-RFLP: terminal restriction fragment length polymorphisms) of soil microbial communities along a bird influence gradient in these declining forests during two contrasting seasons (autumn and summer). Bird influence resulted in remarkable alterations in the physico-chemical properties of the soil, particularly in increased salinity, and increases in available soil phosphorus, nitrate, ammonium and dissolved organic carbon (DOC). In contrast to our expectations, microbial biomass and respiration increased in those saline soils, due to increases in DOC promoting microbial growth. Increased soil phosphorus had some influence on soil fungal diversity both in autumn and summer, while bacterial communities were only affected by guano deposition in the summer season. Bacterial richness and diversity decreased along the avian intensity gradient in the dry season, while archaeal diversity increased. In conclusion, the presence of large colonies of wading birds at Doñana National Park clearly influences biogeochemical cycles in this declining ecosystem, which obligates to a greater consideration of soil processes in conservation priorities.


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