Cork Oak Forests Research Articles

Dynamic height growth model for Spanish and Tunisian cork oak (Quercus suber L.) forests

Seven simple and advanced dynamic polymorphic functions were considered to develop a dominant height growth model for Spanish and Tunisian cork oak forests. Data from 115 stem analyses performed in two regions in each country were used to fit the equations. Parameter estimates were obtained using the Dummy variable method. Both numerical, graphical and biological consistency were used to compare alternative models. The dynamic equation finally selected was derived from the Hossfeld model by considering the shape parameter to be related to site productivity. An analysis of the dominant height growth patterns between the two countries indicated that the same dominant height growth model was valid for both countries. This dominant height growth model allows estimation of dominant height with a level of reliability of at least 83% from an age of 15 years for a prediction interval of less than 40 years.

Effects of a low severity prescribed fire on water-soluble elements in ash from a cork oak ( Quercus suber) forest located in the northeast of the Iberian Peninsula

Wildfire is the major disturbance in Mediterranean forests. Prescribed fire can be an alternative to reduce the amount of fuel and hence decrease the wildfire risk. However the effects of prescribed fire must be studied, especially on ash properties, because ash is an important nutrient source for ecosystem recovery. The aim of this study is to determine the effects of a low severity prescribed fire on water-soluble elements in ash including pH, electrical conductivity (EC), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), aluminum (Al), manganese (Mn), iron (Fe), zinc (Zn), silica (SiO 2) and total sulphur (TS). A prescribed fire was conducted in a cork oak ( Quercus suber) (Q.S) forest located in the northeast part of the Iberian Peninsula. Samples were collected from a flat plot of 40×70 m mainly composed of Q.S and Quercus robur (Q.R) trees. In order to understand the effects of the prescribed fire on the soluble elements in ash, we conducted our data analysis on three data groups: all samples, only Q.S samples and only Q.R samples. All three sample groups exhibited a significant increase in pH, EC ( p<0.001), water-soluble Ca, Mg, Na, SiO 2 and TS and a decrease in water-soluble Mn, Fe and Zn. Differences were identified between oak species for water-soluble K, Al and Fe. In Q.S samples we registered a significant increase in the first two elements p<0.001 and p<0.01, respectively, and a non-significant impact in the third, at p<0.05. In Q.R data we identified a non-significant impact on water-soluble K and Al and a significant decrease in water-soluble Fe ( p<0.05). These differences are probably due to vegetation characteristics and burn severity. The fire induced a higher variability in the ash soluble elements, especially in Q.S samples, that at some points burned with higher severity. The increase of pH, EC, Ca, Mg, Na and K will improve soil fertility, mainly in the study area where soils are acidic. The application of this low severity prescribed fire will improve soil nutrient status without causing soil degradation and thus is considered to be a good management strategy.

Usage patterns of Mediterranean agro-forest habitat components by wood mice Apodemus sylvaticus

Sixteen wood mice Apodemus sylvaticus were radio-tracked in a Mediterranean cork oak agro-forestry-system to describe their spatial distribution and organisation as well as their use of different habitat components. Our study, the first to analyse these features of wood mouse spatial ecology in Mediterranean agro-forestry environments using radio-tracking, showed a high variability in home ranges sizes reaching a mean values of 1.124 ± 0.925 ha (mean ± sd), with no inter-sexual differences (8 males and 8 females tracked in March and June 2008). The extent to which different habitat components were used by wood mice varied significantly (− N ln λ = 22.837, P < 0.0001, n = 6): while cork oak forests without understory were selected by both sexes equally in core areas (− N ln λ = 32.361, P < 0.0001, n = 6), we also found evidence for a female-driven selection for home ranges to be located in olive groves (− N ln λ = 59.949, P < 0.0001, n = 6), and movements to be set within cork oak forests with understory (− N ln λ = 15.091, P < 0.05, n = 6). This habitat preference appears to result from the need of females to ensure access to sufficient food resources, the need of males to ensure access to females, and the need of both sexes for cover protection from predators. Moreover, we also show that the use of arboreal strata, most probably to access food, may also be an important factor to consider in analysing habitat use by wood mice. Implications of the recent evolution of this agro-silvo-pastoral system to the species ecology are emphasized.

Differences of raw cork quality in productive cork oak woods in Sicily in relation to stand density

Differences of raw cork quality, in terms of thickness and porosity, were observed in productive cork oak ( Quercus suber L.) stands in the Nebrodi and Iblei mountains of Sicily in relation to stand density. Five study areas were chosen across a range of different stand density satisfying specific sampling requirements among two managed cork oak woods.Analysis of variance using Fisher–Snedecor‘s F test ( p < 0.05) were used to identify statistically significant differences of cork quality and sylvicultural, dendrometric and cork stripping parameters between study areas within each stand. Relationships between cork quality and sylvicultural and dendrometric parameters were also tested using Pearson's correlation coefficient ( r). Results shown that sylvicultural practices are a key factor influencing cork quality: statistically significant differences in cork thickness and crown area were observed between areas at different stand density; positive correlations were found between cork thickness and crown area in lower density study areas favouring a significant vegetative activity; negative correlations were found between parameters of cork stripping (cork stripping coefficient, cork stripping surface, maximum height of cork stripping) and cork thickness. No correlations were found between cork porosity and dendrometric or sylvicultural parameters, demonstrating the probable genetic origin of cork porosity. Results shown that cork quality parameters and stand attributes may be used in sustainable management models of cork oak forests.

Variation of endophytic cork oak-associated fungal communities in relation to plant health and water stress

The main objective of this study was to obtain more comprehensive knowledge about the effect of water stress on endophytic fungal communities in asymptomatic and declining cork oak trees. Six asymptomatic and six declining cork oak trees were randomly selected in a natural cork oak forest located in Sardinia, Italy. In February 2003, the soil around three asymptomatic and three declining trees was covered with a circular plastic film to reduce rain water supply with the intention to induce water stress. The remaining six trees served as controls. Predawn xylematic water potential (PWP) was used as water status indicator and measured seasonally. Between July 2003 and June 2004, fungal endophytes were isolated every 2–4 months from twigs, branches and woody tissues. Significant differences in PWP between covered and control trees were detected mainly in autumn. Gas exchange was greatest in asymptomatic control plants. All tissues were colonized by endophytic fungi. Nineteen fungal species were isolated from 1620 plant fragments. Biscogniauxia mediterranea was the most frequently isolated fungus. Its isolation frequency was significantly higher in declining covered trees than in control trees (p < 0.05). Presence of this fungus in asymptomatic control trees was significantly higher in winter than in summer. Water stress seems to reduce species diversity of the endophytic mycobiota in cork oak and to promote proliferation of some potentially pathogenic endophytes.

Coping with invasive alien species: the Argentine ant and the insectivorous bird assemblage of Mediterranean oak forests

Cork oak forests invaded by the Argentine ant Linepithema humile have a lower abundance and biomass of arthropod prey for birds than uninvaded forests. We studied whether the biomass of breeding insectivorous birds was also lower in invaded areas. We explored this and other possible effects of the ant invasion on the bird community by censusing birds in transects located in four invaded and four uninvaded forest sites in Catalonia (NE Spain) for 3 years. Redundancy analysis showed only slight differences in the community composition between forests. Two insectivorous species, Luscinia megarhynchos and Fringilla coelebs, tended to be less abundant in invaded areas although two others, Phylloscopus bonelli and Sylvia melanocephala, showed the opposite trend. Overall, the differences in prey biomass between invaded and uninvaded areas did not entail a biomass shift in the guild of insectivorous birds, regardless of whether they were shrub or canopy foragers. The main role of the habitat structure in determining bird densities and food resources being non-limiting in the studied forests are two possible non-exclusive explanations for this inconsistency. At today’s levels, the Argentine ant invasion does not appear to have greatly determined the insectivorous bird assemblage of the forests evaluated.

ORIGIN AND IDENTIFICATION OF THE POLYPHENOLS OF CORK OAK ACORNS ATTACKED BY CARPOPHAGOUS INSECTS

The Algerian cork oak forest is constituted with numerous essences, essentially the cork oak (Quercus suber) which establishes an ecosystem very rich in terms of biovariety. The called acorn ballot characteristic fruit of the genus Quercus forms in the year, its shape and its size vary according to trees. This reproductive organ is constituted with an embryo surrounded with a tissue containing materials of reserves (the albumen) and protected by a more or less thick and impervious integument. The acorn is classified in the category of girdles kick out which is the object of numerous attacks of insects. We extracted acorns of cork oak infested by carpophagous insects using organic solvents as the acetone, the chloroform, the ethanol and also extract by water. The dosage of the total polyphenols realized by Folin-Ciacolteau's method allowed to show that phenolic composition is important for all the used solvents, it is the ethanol which extracts most of polyphenols (154,8 mg GAE/g dry weight), it seems clear that among the used solvents, the chloroform is the least effective solvent (44,6 mg GAE/g dry weight). Dosage, quantification and identification of the polyphenolic contents was realized by coupling chromatography in gas phase/spectrometry of mass (GC/MS). Chromatographic profile and spectre show that the compound adults are going molecules from 18 to 29 carbons. We identified besides polyphenols with 28 and 29 carbons, acids, alcohols and aldehyds.

EVALUATION OF ANTIOXIDANT ACTIVITY, ANTIMICROBIAL AND FUNGICIDAL EFFECT OF ORGANIC EXTRACTS OF CORK OAK ACORNS INFESTED BY CARPOPHAGOUS INSECTS

ISHS International Symposium on Medicinal and Aromatic Plants - SIPAM2009 EVALUATION OF ANTIOXIDANT ACTIVITY, ANTIMICROBIAL AND FUNGICIDAL EFFECT OF ORGANIC EXTRACTS OF CORK OAK ACORNS INFESTED BY CARPOPHAGOUS INSECTS

A contribute to the knowledge of the climatophilous cork—oak woodlands from Iberian southwest

This work results as an in—depth study of climatophilous cork—oak woodlands from Iberian southwest, by the necessity to profound the knowledge of this West—Mediterrenean vegetal formations, particularly in the most atlantic territories. Accordingly, we describe a new cork—oak forest association subhumid to humid, thermomediterranean, siliceous, from « Marianico—Monchiquense » sector as a climatophilous serie, named Lavandulo viridis—Quercetum suberis new ass. Their floristic, ecologic and dynamic particularities are exposed. It's also presented a comparison with the rest of the cork—oak communities described to the Querco rotundifoliae—Oleion sylvestris Barbéro, Quézel & Rivas- Martínez in Rivas-Martínez, Costa & Izco 1986 alliance. Finally, some considerations are made about the conservation status of these sclerophyllous formations and highlighted the most important management policies that aim to protect, recover and increase the value of cork—oak forests.

Ecology and habitats of Serapias perez-chiscanoi (Orchidaceae) near Vila Nova da Baronia (Lower Alentejo, Portugal)

We present the results of the ecology and variation in habitat of the orchid Serapias perez-chiscanoi Acedo, based on field studies between 2002 and 2007. The study area lies in the proximity of the small village of Vila Nova de Baronia, which is situated in the Lower Alentejo province (Portugal). The following climatophilous series of cork oak forest were identified: Asparago aphylli-Querceto suberis sigmetum and their subsequent stages: Phillyreo angustifoliae-Arbutetum unedonis, Halimio ocymoidis-Ericetum umbellatae and/or the community of Ulex australis subsp. welwitschianus and Cistus ladanifer and Trifolio cherleri-Plantaginetum bellardii. Typical communities of wet soils (Junco pygmaei-Isoetetum velati, Periballio laevis-Illecebretum verticillati, Loto hispidi- Chaetopogonetum fasciculati) and saturated soils (Myosotido stoloniferae-Ranunculetum omiophylli and the Juncus bulbosus and Myosotis lusitanica community) were found in depressions.S.perez-chiscanoi was found in the following plant communities: Junco pygmaei-Isoetetum velati, Loto hispidi-Chaetopogonetum fasciculati, Gaudinio fragilis-Agrostietum castellanae, and the community of Ulex australis subsp. Welwitschianus and Cistus ladanifer.

Oribatid mite (Arachnida: Oribatida) coenoses from SW Sardinia

Oribatid mite communities were investigated at five sites in SW Sardinia (Carbonia-Iglesias and Medio Campidano provinces) in three representative habitat types: holm oak (Quercus ilex) forest, cork oak (Quercus suber) forest and pineland (Pinus radiata and P. pinaster). A total of 1,180 oribatid mite specimens, belonging to 67 different species, were extracted from soil samples. Significant differences in species diversity, abundance and Berger-Parker index of dominance were found among the different vegetation types throughout the sampling period, and non-metric multidimensional scaling (n-MDS) ordination confirmed a clear separation between the three coenoses, showing how oribatid assemblages are significantly affected by habitat evolution. The faunistic knowledge of the oribatid mites of Sardinia is rather poor, the present research represents one of the first contributions for the main Sardinian island. Besides a majority of eurytopic and widespread species representing the main part of the edaphic communities in Mediterranean landscapes, some rare and characteristic species are recorded. They are remnants of the original populations of Sardinia and the western part of the Italian peninsula, resulting from the complex tectonic events that formed the western Mediterranean basin. Among these, Belorchestes gebennicus Grandjean, 1957 (Zetorchestidae), Microppia minus longisetosa Subías &amp; Rodriguez, 1988, and Pluritrichoppia insolita Subías &amp; Arillo, 1989 (Oppiidae) had never been collected in Italy, single individuals of Oxyoppioides and Thamnacarus probably belong to undescribed species, while Brachychthonius hirtus Moritz, 1976 (Brachychthoniidae), Mongaillardia aeoliana (Bernini, 1979) (Amerobelbidae), Berniniella aeoliana (Bernini, 1973), Lauroppia similifallax Subías &amp; Minguez, 1986, Ramusella (Ramusella) gyrata (Mahunka &amp; Paoletti, 1984) (Oppiidae) and Ophidiotrichus oglasae Bernini, 1975 (Oribatellidae) are new to the Sardinian fauna.

An approach to cork oak forest management planning: a case study in southwestern Portugal

This paper presents results of research aiming at the development of tools that may enhance cork oak (Quercus suber L.) forest management planning. Specifically, it proposes an hierarchical approach that encompasses the spatial classification of a cork oak forest and the temporal scheduling of cork harvests. The use of both geographical information systems and operations research techniques is addressed. Emphasis is on the achievement of cork even flow objectives. Results from an application to a case study in the Charneca Pliocénica of Ribatejo in southern Portugal encompassing a cork oak forest extending over 4.8 thousand ha are discussed. They suggest that the proposed approach is capable of effective spatial classification of cork oak management units. They further suggest that it may be used to select optimal cork even flow scheduling strategies. Results also show that the proposed approach may lead to a substantial increase in net present value when compared to traditional approaches to cork oak forest management planning.

Assessing the relative fire proneness of different forest types in Portugal

We have assessed the fire proneness of the main forest types in Portugal classified according to the main species, using three different approaches: the use of resource selection ratios applied to burned patches, the proportion of randomly located plots that were burned and the proportion of burned National Forest Inventory plots. The results allowed ranking fire proneness according to the following decreasing order: maritime pine forests, eucalyptus forests, unspecified broadleaf forests, unspecified conifer forests, cork oak forests, chestnut forests, holm oak forests and stone pine forests. In order to understand the obtained results we have assessed the structure of the different forest types using the percent cover of seven vegetation layers (C1–C7), a Tree Dominance Index, a Height Index and a Cover Index (IC). Structural variables and stand composition were used to predict fire probability according to binary logistic modelling. Only four structural variables and stand composition provided significant results, the latter being the most important variable for explaining fire probability. These models were used to predict fire probability for different stand types as a function of IC.

Stone marten (Martes foina) habitat in a Mediterranean ecosystem: effects of scale, sex, and interspecific interactions

Mediterranean ecosystems are inherently patchy, challenging habitat-use behavior. Certain mammalian carnivores take advantage of this patchiness by a strategy of habitat complementation/supplementation, which is invariant to the scale of analysis. To test if the same behavior is adopted by the stone marten, we used a combined data set of capture and radio-tracking data at three scales of analysis (1-m, 25-m, and 452-m radius plots). We used compositional analysis to test if there were sex-specific differences in foraging and resting habitat use of stone martens and if these patterns were affected by the presence of other mesocarnivores. Our results showed that stone martens are found both in rural and forested landscapes. Foraging and resting activities occurred far from roads in large and complex patches of cork oak woodlands, riparian vegetation, orchards, and pastureland. Use varied with the scale of analysis and the sex. At smaller scales, females use pastures for foraging and orchards for resting, whereas riparian vegetation and sparse cork oak forests influenced this use at larger scales. Males, on the other hand, were more consistent across scales, using riparian areas and dense cork oak woodlands for foraging and pastures for resting. Stone martens shared the same areas with other coexisting mesocarnivores. Stone martens use cork oak woodlands and complement/supplement this use with other land cover types. The consistent use of cork oak woodlands across scales emphasizes the importance of this land cover to the preservation of functional Mediterranean ecosystems in southern Portugal.

Nutrients return from leaves and litterfall in a mediterranean cork oak (Quercus suber L.) forest in southwestern Spain

Nutrients return from leaves and litterfall in a mediterranean cork oak (Quercus suber L.) forest in southwestern Spain

A new soil-dwelling palpigrade species from Northern Italy (Palpigradi: Eukoeneniidae)

Among the 27 palpigrade species recorded in Europe so far, 23 occur in caves or narrow subterranean voids. Eukoenenia gallii n. sp. from a cork oak forest on the Italian Riviera (Liguria) is added to the small group of edaphic European palpigrades. E. gallii is not closely related to the common soil-dweller E. mirabilis (Grassi &amp; Calandruccio, 1885), but to E. subangusta (Silvestri, 1903). Body shape and proportions make the new species look extremely edaphomorphic. All instars are described and illustrated with light micrographs of diagnostic traits.

Nutrients return from leaves and litterfall in a mediterranean cork oak (Quercus suber L.) forest in southwestern Spain

The knowledge of the cycle of nutrients is fundamental for the correct comprehension of the tree–soil relationship and for an adequate forest management. In order to analyse the nutrients return from leaves and litterfall in a Mediterranean cork oak forest in southwestern Spain, 12 trees were randomly selected and litterfall collected for 2 years. Samples were taken monthly and separated in different fractions (leaves, twigs, catkins, acorns and miscellaneous), then leaves nutrients were analyzed. Simultaneously, we analyzed the nutrient content of living leaves from the same trees in each season during 1 year. The analyzed nutrients were C, N, P, K, Ca, Mg, Fe, Mn, S, Cu, Zn and Mo. Annual patterns of each nutrient in fallen leaves were characterized and compared with seasonal values of these nutrients in living leaves. Leaves fall has two annual maximum, first and most important in spring around April coinciding with renewal of foliar cover and second around October. Main concentration patterns of N, P and K are related with phenological patterns, in consequence minimum concentration in leaves fall were obtained in periods of growing and maximum litterfall. Concentrations of Ca, Fe and Mn increase with the age of the leaves and maximum concentrations were obtained before periods of maximum litterfall while concentrations of Cu, Mo and Mg stay stable. Seasonal analysis of nutrients in living leaves collected from the same trees in four different periods of the year allowed to corroborate the patterns of leaves fall and the probable osmotic function of K.

Landscape dynamics in endangered cork oak woodlands in Southwestern Portugal (1958–2005)

Cork oak landscape dynamics were assessed over a 47-year period (1958–2005) in an endangered region of southwest Portugal using a GIS approach. The area of cork oak woodlands was maintained during this period, but shifts due to land abandonment were evident leading to transformation of cork oak agriculture areas into woodlands and of cork oak woodlands into shrublands (average yearly change rates of 0.6 and 0.1%, respectively). The multi-temporal landscape analyses showed that expansion and regression rates of cork oak forests were similar (15 and 16 ha year−1, respectively). The main factor determining oak woodlands expansion and regression was related to land-use changes, but slope, aspect and soil type were also significant factors. The substitution of agriculture lands and oak woodlands by shrublands has a determining role in periods of disturbance and recovery of these Mediterranean ecosystems.

Factors affecting post-fire crown regeneration in cork oak (Quercus suber L.) trees

Cork oak (Quercus suber) forests are acknowledged for their biodiversity and economic (mainly cork production) values. Wildfires are one of the main threats contributing to cork oak decline in the Mediterranean Basin, and one major question that managers face after fire in cork oak stands is whether the burned trees should be coppiced or not. This decision can be based on the degree of expected crown regeneration assessed immediately after fire. In this study we carried out a post-fire assessment of the degree of crown recovery in 858 trees being exploited for cork production in southern Portugal, 1.5 years after a wildfire. Using logistic regression, we modelled good or poor crown recovery probability as a function of tree and stand variables. The main variables influencing the likelihood of good or poor crown regeneration were bark thickness, charring height, aspect and tree diameter. We also developed management models, including simpler but easier to measure variables, which had a lower predictive power but can be used to help managers to identify, immediately after fire, trees that will likely show good crown regeneration, and trees that will likely die or show poor regeneration (and thus, potential candidates for trunk coppicing).

What to take into account to develop cork weight models?: review and statistical considerations

In this paper we present a critical revision of the published cork yield models at tree and stand level with the aim of underlying the different issues that need to be taken into account in such models. After stressing the importance of this kind of models in the management of cork oak forests, the review focuses in their statistical aspects, from the variables that are used, functional forms, fitting methods and variable selection to the analysis of the initial hypothesis and validation.