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Holm Oak (holm + oak)

Distribution by Scientific Domains

Life Sciences	71%

Selected Abstracts

Physiological responses of cork oak and holm oak to infection by fungal pathogens involved in oak decline

FOREST PATHOLOGY, Issue 4 2009
B. T. Linaldeddu
Summary The aim of this research was to study the changes in net photosynthesis and stomatal conductance values in 3-year-old cork oak and holm oak seedlings growing in natural conditions and inoculated with Apiognomonia quercina, Biscogniauxia mediterranea, Botryosphaeria corticola and Pleurophoma cava. Throughout the 4-month experimental period, the evolution of visual external symptoms and the values of physiological variables were periodically recorded. All pathogens caused stem lesions around the infection point; however, the lesions caused by B. corticola were longer in both oak species. On cork oak seedlings, all pathogens induced a significant and gradual reduction in net photosynthesis and stomatal conductance values, whereas other physiological disturbances were induced only by B. corticola infections on holm oak seedlings. [source]

Seasonal and spatial mortality patterns of holm oak seedlings in a reforested soil infected with Phytophthora cinnamomi

FOREST PATHOLOGY, Issue 6 2005
M. C. Rodríguez-Molina
Summary The viability of 1-year-old holm oak (Quercus ilex) seedlings in a soil naturally infected with Phytophthora cinnamomi was studied during 2 consecutive years in a plot located in south-western Spain. In both years, total mortality during autumn and winter was not noticeable (<2.1%). In spring, mortality levels were higher (8.3,4.6%), especially the first year. A steep increase in total mortality occurred in summer, both in the first (11.4%) and second (24.2%) year, but mortality attributable to P. cinnamomi was 1.9 and 7.6%, respectively. Thus, 2 years after planting, total cumulative mortality was 43.4%, and that attributable to P. cinnamomi 9.6% (i.e. 22.1% of total mortality). Fungus-derived mortality followed a spatially aggregated pattern in the reforestation plot, suggesting a clustered distribution of the inoculum in the soil. Furthermore, mortality by P. cinnamomi was also associated with nearness of infected adult trees in the plot. Results obtained are discussed in the framework of seasonal water deficit, P. cinnamomi damage, weed competition and sanitation techniques to be used in declined holm oak stands in Spain. Résumé La viabilité de semis de chênes verts d'un an dans un sol naturellement infecté par P. cinnamomi a été suivie pendant deux années consécutives dans une parcelle du sud-ouest de l'Espagne. La mortalité en automne et hiver a été négligeable (<2.1%) au cours des deux années. La mortalité a été plus forte au printemps (8.3 ,4.6%), particulièrement la première année. Un pic de mortalité a été observé pendant l'été, aussi bien la première (11.4%) que la deuxième année (24.2%) mais la mortalité attribuable àP. cinnamomi n'est que de 1.9% et 7.6% respectivement. Deux ans après plantation, la mortalité cumulée est de 43.4%, dont 9.6% attribuable àP. cinnamomi (22% de la mortalité totale). La mortalité associée à l'agent pathogène présente une agrégation spatiale dans la parcelle reboisée, suggérant une distribution en agrégats de l'inoculum dans le sol. De plus cette mortalité est associée à la proximitéà des arbres infectés dans la parcelle. Les résultats sont discutés dans la perspective du déficit hydrique estival, des dégâts causés par P. cinnamomi, de la compétition herbacée et des techniques sanitaires à utiliser dans les peuplements dépérissants de chênes verts en Espagne. Zusammenfassung Während zwei aufeinander folgenden Jahren wurde die Überlebensrate von einjährigen Steineichen (Quercus ilex)-Sämlingen in einem natürlich mit Phytophthora cinnamomi infizierten Boden auf einer Versuchsfläche in Süd-West-Spanien untersucht. In beiden Jahren war die Mortalität im Herbst und Winter sehr gering (<2.1%). Im Frühling lag die Absterberate besonders im ersten Jahr höher (8,3,4,6%). Im Sommer stieg die Gesamtmortalität stark an, im ersten Jahr betrug sie 11,4%, im zweiten Jahr 24,2%, jedoch lagen die P. cinnamomi zuzuordnenden Raten bei nur 1,9 bzw. 7,6%. Somit lag die Gesamtmortalität zwei Jahre nach der Pflanzung bei 43,4%, die P. cinnamomi zuzuordnende Mortalität bei 9,6% (d.h. 22,1% der abgestorbenen Pflanzen). Die pilzbedingte Mortalität war in der Aufforstungsfläche räumlich aggregiert, was auf eine klumpige Verteilung des Inokulums im Boden schliessen lässt. Zudem war die Mortalität durch P. cinnamomi mit der Nähe zu infizierten adulten Bäumen assoziiert. Diese Ergebnisse werden in Zusammenhang mit jahreszeitlichem Wassermangel, Schäden durch P. cinnamomi, Konkurrenz durch Unkräuter und mögliche phytosanitäre Massnahmen an Standorten mit absterbenden Steineichen diskutiert. [source]

A global change-induced biome shift in the Montseny mountains (NE Spain)

GLOBAL CHANGE BIOLOGY, Issue 2 2003
Josep Peñuelas
Abstract Shifts in plant species and biome distribution in response to warming have been described in past climate changes. However, reported evidence of such shifts under current climate change is still scarce. By comparing current and 1945 vegetation distribution in the Montseny mountains (Catalonia, NE Spain), we report here a progressive replacement of cold-temperate ecosystems by Mediterranean ecosystems. Beech (Fagus sylvatica) forest has shifted altitudinally upwards by ca. 70 m at the highest altitudes (1600,1700 m). Both the beech forests and the heather (Calluna vulgaris) heathlands are being replaced by holm oak (Quercus ilex) forest at medium altitudes (800,1400 m). This beech replacement has been observed to occur through a progressive isolation and degradation of beech stands. In ,isolated' (small and surrounded by holm oaks) beech stands, beech trees are 30% more defoliated, beech recruitment is 41% lower, and holm oak recruitment is three times higher than in ,continental' (large and continuous) beech stands. The progressively warmer conditions, complemented by the land use changes (mainly the cessation of traditional land management) are the apparent causes, providing a paradigmatic example of global change affecting distributions of plant species and biomes. [source]

Spatial pattern of Quercus ilex and Quercus pubescens recruitment in Pinus halepensis dominated woodlands

JOURNAL OF VEGETATION SCIENCE, Issue 4 2000
T.R. Lookingbill
Abstract. European Mediterranean landscapes have undergone changes in structure in recent years as a result of widespread agricultural land abandonment and cessation of silvicultural regimes. Studies concerning the regeneration dynamics of dominant forest species have become critical to the prediction of future landscape trends in these changing forest stands. Quercus ilex (holm oak) and Q. pubescens (downy oak) are considered to be the terminal point of secondary succession in extensive areas of the Mediterranean region. Recent studies, however, have suggested the existence of recruitment bottlenecks in oak genet populations as a result of current management regimes. In this study, we present evidence of the successful establishment of Q. ilex and Q. pubescens in Pinus halepensis (Aleppo pine) woodlands. We investigate the distribution patterns and spatial relationships among oak recruits and resident pines. Established P. halepensis is randomly distributed throughout the study area. Oak seedlings are positively associated with pine trees, suggesting that P. halepensis individuals provide safe sites for oak genet recruitment. We show that spatial patterns of recruitment are in agreement with the general model of spatial segregation described for other Mediterranean plant communities, with seeder species colonizing large openings after disturbance, followed by a more aggregated recruitment of resprouter species. [source]

Phylogeographical variation of chloroplast DNA in holm oak (Quercus ilex L.)

MOLECULAR ECOLOGY, Issue 11 2002
R. Lumaret
Abstract Variation in the lengths of restriction fragments (RFLPs) of the whole chloroplast DNA molecule was studied in 174 populations of Quercus ilex L. sampled over the entire distribution of this evergreen and mainly Mediterranean oak species. By using five endonucleases, 323 distinct fragments were obtained. From the 29 and 17 cpDNA changes identified as site and length mutations, respectively, 25 distinct chlorotypes were distinguished, mapped and treated cladistically with a parsimony analysis, using as an outgroup Q. alnifolia Poech, a closely related evergreen oak species endemic to Cyprus where Q. ilex does not grow. The predominant role of Q. ilex as maternal parent in hybridization with other species was reflected by the occurrence of a single very specific lineage of related chlorotypes, the most ancestral and recent ones being located in the southeastern and in the northwestern parts of the species' geographical distribution, respectively. The lineage was constituted of two clusters of chlorotypes observed in the ,ilex' morphotyped populations of the Balkan and Italian Peninsulas (including the contiguous French Riviera), respectively. A third cluster was divided into two subclusters identified in the ,rotundifolia' morphotyped populations of North Africa, and of Iberia and the adjacent French regions, respectively. Postglacial colonization probably started from three distinct southerly refugia located in each of the three European peninsulas, and a contact area between the Italian and the Iberian migration routes was identified in the Rhône valley (France). Chlorotypes identical or related to those of the Iberian cluster were identified in the populations from Catalonia and the French Languedoc region, which showed intermediate morphotypes, and in the French Atlantic populations which possessed the ,ilex' morphotype, suggesting the occurrence of adaptive morphological changes in the northern part of the species' distribution. [source]

RUNOFF PRODUCTION AND EROSION PROCESSES ON A DEHESA IN WESTERN SPAIN,

GEOGRAPHICAL REVIEW, Issue 3 2002
ANTONIO CEBALLOS
ABSTRACT. Runoff generation and soil erosion were investigated at the Guadalperalón experimental watershed (western Spain), within the land-use system known as dehesa, or open, managed evergreen forests. Season and type of surface were found to control runoff and soil-loss rates. Five soil units were selected as representative of surface types found in the study area: hillslope grass, bottom grass, tree cover, sheep trails, and shrub cover. Measurements were made in various conditions with simulated rainfall to gain an idea of the annual variation in runoff and soil loss. Important seasonal differences were noted due to surface cover and moisture content of soil, but erosion rates were determined primarily by runoff. Surfaces covered with grass and shrubs always showed less erosion; surfaces covered with holm oaks showed higher runoff rates, due to the hydrophobic character of the soils. Concentrations of runoff sediment during the simulations confirmed that erosion rates at the study site depended directly on the sediment available on the soil surface. [source]