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At least 361 records · Page 20Linked to original sources
PubMed2005

Winter photosynthesis by saplings of evergreen broad-leaved trees in a deciduous temperate forest.

* Here we investigated photosynthetic traits of evergreen species under a deciduous canopy in a temperate forest and revealed the importance of CO2 assimilation during winter for annual CO2 assimilation. * Saplings were shaded by the canopy trees from spring through to autumn, but were less shaded during the winter months. Photosynthetic rates at light saturation (Aarea) were lower during winter than during the growing season. Aarea was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus during the winter, but differed little during summer and autumn. * Estimated daily CO2 assimilation (Aday) was higher during the winter than during the growing season in Camellia, Ilex and Photinia but was higher than that during the growing season only at the beginning and end of winter in Castanopsis, Cleyera and Quercus. Aday was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus but differed little among them during the growing season. * These results reveal the importance of winter CO2 assimilation for the growth of Camellia, Ilex and Photinia. Furthermore, differences in annual CO2 assimilation among species are strongly modified by species-specific photosynthetic traits during the winter under deciduous canopy trees.

Carbon Dioxide↗
PubMed2000

Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions.

The seasonal pattern of terpene content and emission by seven Mediterranean woody species was studied under field conditions. Emission rates were normalized at 30°C and 1000 μmol·m·s PFD (photosynthetic photon flux density). Bupleurum fruticosum, Pinus halepensis, and Cistus albidus stored large amounts of terpenes (0.01-1.77% [dry matter]) with maximum values in autumn and minimum values in spring. They emitted large amounts of terpenes (2-40 μg·g DM·h), but with no clear seasonal trend except for Cistus albidus, which had maximum values in spring and minimum values in autumn. The nonstoring species Arbutus unedo, Erica arborea, Quercus coccifera and Quercus ilex also emitted large amounts of terpenes (0-40 μg·g DM·h) and also tended to present maximum emission rates in spring, although this trend was significant only for A. unedo. At the seasonal scale, emission rates did not follow changes in photosynthetic rates; instead, they mostly followed changes in temperature. From autumn to spring, the least volatile monoterpenes such as limonene were emitted at highest rates, whereas the most volatile monoterpenes such as α-pinene and β-pinene were the most emitted in summer. The monoterpene emission rates represented a greater percentage of the photosynthetic carbon fixation in summer (from 0.51% in Arbutus unedo to 5.64% in Quercus coccifera) than in the rest of the seasons. All these seasonality trends must be considered when inventorying and modeling annual emission rates in Mediterranean ecosystems.

Journal Article↗
PubMedDate not supplied

Comparative analysis of phenolic acids in mistletoe plants from various hosts.

Phenolic acids present in mistletoe plants collected from various hosts were analysed with the use of HPLC. The following numbers of compounds were found in the mistletoe plant material gathered from respective hosts: Sorbus aucuparia- 12 compounds; Acer plantanoides--14 compounds: Malus domestica, Pyrus communis and Populus nigra--13 compounds each; Quercus robur--15 compounds. Altogether 21 phenolic acids were chromatographically identified in the tested material. The compounds were either free or combined as esters or glycosides. Comparative chromatography revealed qualitative differences in the investigated compounds between the various plant materials. For example o-coumaric acid was only found in mistletoe hosted by Quercus robur. Digallic acid was only found in the plant material hosted by Acer plantanoides. Qualitative and quantitative composition of mistletoes hosted by Malus domestica and Pyrus communis showed considerable similarities as far as phenolic acids were concerned. Moreover. vanillic acid. absent in all other batches of plant material, seemed to be characteristic of the above mistletoes. Quantitative HPLC analysis demonstrated a considerable content of salicylic acid (39.55 mg%) in mistletoe hosted by Sorbus aucuparia. Apart from the above material, this compound was only present in small quantities in plants hosted by Populus nigra (15.63 mg%) and Quercus robur (2.63 mg%).

Chromatography, High Pressure Liquid↗
PubMed2005

[Understory vegetation composition and main woody population niche of artificial masson pine forest in south subtropical area].

This paper studied the characteristics of the natural understory vegetation in the artificial masson pine forest replanted after Chinese fir cut for 13 years. The results indicated that there were 100 species of understory vegetation, including 74 species of shrub or small arbor, accounting for 74.0% of the total species, belonging to 41 faculties and 63 categories, and 26 herbs belonging to 14 faculties and 23 categories. The tropical and subtropical elements were dominant in the vegetation, while the temperate ones were scare. The species diversity and richness were decreased after masson pine regenerated from Chinese fir. The analysis of important value showed that the main species of shrub or small arbor were Tinomiscium tonkinensis, Mycetia longiflora, Evodia lepta, Paederia scandens, Mussaenda pubuscens, Actinodaphne pilosa and Quercus glauca, and those of herb were Cyrtococcum patens, Blechnunm orientale, Dicranopteris dichotoma, Adiantum flabellulatum, Adiantum edgeworthii and Pteris semipinnata. The biomass of the vegetation in different slope positions was decreased in order of upside> downside > middle part. There was a significantly positive correlation between the niche breath and the important value of main woody population. The important values of woody populations were higher than those of the others, and their niche breadths were also larger, which meant that they were more adaptable to the habitat. The niche overlaps of six population counterparts Tinomiscium tonkinensis-Mycetia longiflora, Tinomiscium tonkinensis-Evodia lepta, Mussaenda pubuscens-Maesa japonica, Quercus glauca-Aphananthe aspera, Actinodaphne pilosa-Saraca chinensis and Evodia lepta-Quercus glaucathese were very large, which could offer information for the restoration and reconstruction in selecting natural vegetation. The large niche overlaps of major woody population counterparts suggested their similar utilization of natural resources.

Biodiversity↗
PubMed2005

Ozone exposure induces the activation of leaf senescence-related processes and morphological and growth changes in seedlings of Mediterranean tree species.

Four Mediterranean tree taxa, Quercus ilex subsp. ilex, Quercus ilex subsp. ballota, Olea europaea cv. vulgaris and Ceratonia siliqua, were exposed to different ozone (O(3)) concentrations in open top chambers (OTCs) during 2 years. Three treatments were applied: charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus 40 ppb(v) of O(3) (NF +). The photochemical maximal efficiency, Fv/Fm, decreased in NF + plants during the second year of exposure, especially during the most stressful Mediterranean seasons (winter and summer). An increase of delta(13)C was found in three of the four studied species during the first year of exposure. This finding was only maintained in C. siliqua during the second year. Decreases in the chlorophyll content were detected during the first year of fumigations in all the species studied, but not during the second year. The NF + treatment induced changes in foliar anatomical characteristics, especially in leaf mass per area (LMA) and spongy parenchyma thickness, which increased in some species. A reduction in N content and an increase in delta(15)N were found in all species during the second year when exposed in the NF + OTCs, suggesting a change in their retranslocation pattern linked to an acceleration of leaf senescence, as also indicated by the above mentioned biochemical and anatomical foliar changes. The two Q. ilex subspecies were the most sensitive species since the changes in N concentration, delta(15)N, chlorophyll, leaf area, LMA and biomass occurred at ambient O(3) concentrations. However, C. siliqua was the most responsive species (29% biomass reduction) when exposed to the NF + treatment, followed by the two Q. ilex subspecies (14-20%) and O. europaea (no significant reduction). Ozone resistance of the latter species was linked to some plant traits such as chlorophyll concentrations, or spongy parenchyma thickness.

Biomass↗
PubMed2005

The effects of extracts from anti-diarrheic Thai medicinal plants on the in vitro growth of the intestinal protozoa parasite: Blastocystis hominis.

The activities of n-hexane, dichloromethane and methanol extracts from five anti-diarrheic Thai medicinal plants, Acacia catechu (Fabaceae) resin, Amaranthus spinosus (Amaranthaceae) whole plant, Brucea javanica (Simaroubaceae) seed, Piper longum (Piperaceae) fruit and Quercus infectoria (Fagaceae) nut gall were tested against the in vitro growth of fresh isolates of the intestinal protozoan parasite, Blastocystis hominis. The extracts at concentrations that ranged from 62.5 to 2000 microg/mL, were incubated with several isolates of Blastocystis hominis for 48 h. The activities were classified as killed, inhibited, moderately inhibited and not-inhibited. Dichloromethane and methanol extracts from the Brucea javanica seed and a methanol extract from Quercus infectoria nut gall showed the highest activity. At a concentration of 2000 microg/mL, the three extracts killed 82, 75 and 67% of the Blastocystis hominis samples tested and inhibited 94, 100 and 76% of them, respectively. Metronidazole, used as a reference antiprotozoan drug, at a concentration of 40 microg/mL, killed 97% of the Blastocystis hominis isolates and inhibited all samples tested at concentrations that ranged from 1.25 to 20 microg/mL.

Animals↗
PubMed2006

The use of compost in afforestation of Mediterranean areas: Effects on soil properties and young tree seedlings.

In Mediterranean frequently burnt areas, fire and erosion result in the decrease of soil fertility, so afforestation is a major concern. We carried out an in situ experiment of compost amendment to improve survival and growth of planted tree seedlings. One-year-tree seedlings of native species (Quercus ilex, Pinus halepensis and Pinus pinea) were planted on a frequently burnt calcareous site. Three rates of fresh co-composted sewage sludge and greenwastes (control without compost, 20 and 40 kg m(-2) of compost) were incorporated into the soil at each seedling stem. Changes of soil properties and tree development were studied during 3 years (2001-2003) and 2 years (2002-2003) respectively. The compost improved survival of Quercus ilex and Pinus pinea seedlings in severe drought conditions, but had no effect on Pinus halepensis. For all species seedling length and radial growth and NPK nutrition were increased for both rates of amendment. Amendment improved soil fertility, but available P concentration increased 13 fold in the neighbouring soil of seedlings amended at the maximal rate compared to control. However, amendment did not significantly increase concentrations of Cd, Cr, Ni and Pb in soils or tree seedlings. It increased Cu and Zn total and available concentrations in soils, while foliar Cu and Zn concentrations in the seedlings remained similar in all plots. Compost can efficiently help afforestation of dry soils with low organic matter content. However, sewage sludge concentrations in P, and to a lesser extent in Cu and Zn, limit rates of application that can be applied without environmental hazard.

Agriculture↗
PubMed2005

Response of the nitrogen isotopic composition of tree-rings following tree-clearing and land-use change.

Clear-cutting of forests affects the nitrogen cycle and the nitrogen isotopic composition of bioavailable ammonium and nitrate in the soil. Here, we have used nitrogen isotopic variations of tree-rings in red oak (Quercus rubra) and white oak (Quercus alba) as indicators of changes in the nitrogen cycle on a local scale. The delta15N values of late-wood from trees at two remnant forest stands in Ontario, Canada, that underwent large-scale tree-clearing and permanent land-use change at different times were measured. Trees from the perimeter of each stand record a marked 1.5-2.5 per thousand increase in the delta15N values of their tree-rings relative to the values in trees from the center of the stand, with the shift synchronous with the tree-clearing and land-use change. This shift was most likely due to increased rates of nitrification and nitrate leaching in the soil as a result of tree-clearing combined with permanent changes in hydrology and probable fertilizer use accompanying the change in land-use. Nitrogen concentration in tree-rings was not affected bytree-clearing and the associated change in land-use. These results indicate that changes in nitrogen cycling in forest ecosystems, whether due to climate change, land-use change, or other environmental changes (increased O3, other atmospheric pollutants, insects, etc.), can be faithfully monitored with nitrogen isotopic compositions of tree-rings and that dendrogeochemical analysis can be incorporated into studies of the effects of long-term anthropogenic effects on forest ecosystems.

Analysis of Variance↗
PubMed2002

Extractives content in cooperage oak wood during natural seasoning and toasting; influence of tree species, geographic location, and single-tree effects.

The chemical composition of cooperage oak wood is highly variable, depending upon the tree species (Quercus robur L. versus Quercus petraea Liebl.), its geographic location, and the single-tree effect. In the process of cask-making, natural seasoning and toasting contribute strongly to the modification of the oak wood chemical composition and therefore influence wine cooperaging. HPLC and GC quantification of ellagitannins and volatile compounds such as whiskey-lactones, eugenol, and vanillin over a sample set of 61 pedunculate oaks and 72 sessile oaks originating from six different forests showed that natural drying leads to a decrease of the ellagitannins and total extractives content level and a quasi constant level of the volatile compounds. Toasting (medium type) drastically enhanced the loss of ellagitannins and the gain in volatile compounds. Statistical treatment showed that the species effect remained significant throughout the process of drying and toasting, but not the provenance. The poor correlation with ring width of extractives levels measured on fresh timber remained unchanged as did the single-tree effect, with high variability found for all chemical parameters. These results provide further evidence that cooperage oak selection should not be based solely on the wood grain or the provenance but rather on a species-provenance combination.

Benzaldehydes↗
PubMed2003

Changes in amine concentrations during aging of red wine in oak barrels.

This investigation studied the evolution of amines in red wines made with Merlot variety, during aging in American oak barrels (Quercus alba) and in French oak barrels (Quercus sessilis) from the Allier and Nevers regions. From the results obtained it was observed that the evolutions of the amines were similar in all three types of oak woods. Histamine and tyramine were produced at the beginning of the aging process, although they were not accumulated in the wines, probably due to their degradation. Putrescine was the most abundant amine in the wines; its concentration increased to an important extent during aging as it did not undergo degradation. The concentration of cadaverine increased slightly at the first stage of aging and, like putrescine, did not degrade at all. The volatile amines showed slight variations during aging, although in no cases were high accumulations observed in the wines. Dimethylamine and isobutylamine were degraded during storage in the barrels.

Biogenic Amines↗
PubMed2002

Influence of odor from wood-decaying fungi on host selection behavior of deathwatch beetle, Xestobium rufovillosum.

Adult females of Xestobium rufovillosum de Geer demonstrated anemotactic orientation when exposed to an odor plume containing volatiles generated by wood-decaying fungi (Coriolus versicolor, Donkioporia expansa) and decayed oak wood (Quercus petraea, Quercus robur). They did not orient towards undecayed oak wood, beech (Fagus sylvatica), or pine wood (Pinus sylvestris). Although all insects tested showed anemotactic orientation, responses were nonlinear with respect to insect age. Adult females more readily oriented upwind when they were between 10 and 16 days old. Oviposition choice bioassays showed that ovipositing females would preferentially oviposit on extract-treated cellulose paper discs that had been treated with various strains of the wood-decaying fungus, Donkioporia expansa. HPLC-fractionated mycelial extracts were attractive to ovipositing deathwatch beetles, whereas HPLC-fractionated fungal broth extracts were repellent to ovipositing females. The implications of these results are discussed in the context of timber pest management in historically important buildings.

Animals↗
PubMed2003

Cynipid gall-wasp communities correlate with oak chemistry.

Host-plant association data, gathered from field surveys conducted throughout Florida and from the literature, were used to identify the specificity of cynipid gall inducers to one or more of six Quercus species that occur at Archbold Biological Station, Lake Placid, Florida, USA, including the red oaks Q. laevis, Q. myrtifolia, and Q. inopina, and the white oaks Q. chapmanii, Q. geminata, and Q. minima. Quercus myrtifolia had the highest cynipid richness and diversity (37 cynipid species, Shannon H' = 3.61, Simpson's D = 0.97), followed by Q. chapmanii, Q. laevis, Q. inopina, Q. geminata, and finally Q. minima (10 species, H' = 2.30, D = 0.90). All cynipid species showed strong fidelity to a particular host plant or a restricted set of host plants. An ordination of gall-wasp host associations indicated that the cynipid communities of each oak species were distinct and specific to a given oak species. Leaf samples taken from each oak species were analyzed for condensed and hydrolyzable tannins, total phenolics, lignin, cellulose and hemicellulose, nitrogen, and carbon. All of these chemical traits, with the exception of carbon, differed by oak species, and the differences were strongly correlated with the axes of the cynipid-species ordination. These results suggest that gall-wasp occurrence is influenced by oak chemistry and imply that experimental studies of cynipid gall inducers that examine host-plant chemistry and female oviposition choice and larval performance will yield useful insights.

Animals↗
PubMed2003

Crown condition surveys in Italian forests: issues in reporting findings.

This study examines defoliation and discoloration findings collected throughout the Italian Level I network between 1997 and 2000. Prior to this period no Quality Assurance procedures had been implemented, so that earlier findings cannot be considered reliable. The aim of the study is to compare different indices used in reporting findings, in order to determine the full potential and limitations of each. In international surveys, findings are normally expressed in terms of individual trees presenting a defoliation level greater than 25%; this criterion, however, has been challenged since it is not based on scientific evidence. By analysing the distribution of defoliationvalues (grouped in 5% classes) relating to the main species (Fagus sylvatica, Quercus pubescens, Quercus cerris, Picea abies), the study examines the behaviour of statistical indices such as the median, the mode and the mean. Instead of using the traditional 25% threshold to determine the part of the population with the highest defoliation values, a procedure is suggested whereby a different threshold can be determined for each species. It is established based on the 90 degrees percentile of cumulative defoliation values recorded over the four-year period. Each index used to report findings possesses its own information potential, and the findings may at times appear contradictory. The use of a combined defoliation and discoloration index (Ilce = Lacking Crown Equivalent Index) is also proposed, but the results obtained do not differ in substance from the results relating to defoliation alone. The functional limitations of this index are due mainly to the way the data are collected: for this reason suggestions are made on how to improve the procedure in future surveys.

Air Pollutants↗
PubMed2005

Modeled regional climate change and California endemic oak ranges.

In the coming century, anthropogenic climate change will threaten the persistence of restricted endemic species, complicating conservation planning. Although most efforts to quantify potential shifts in species' ranges use global climate model (GCM) output, regional climate model (RCM) output may be better suited to predicting shifts by restricted species, particularly in regions with complex topography or other regionally important climate-forcing factors. Using a RCM-based future climate scenario, we found that potential ranges of two California endemic oaks, Quercus douglasii and Quercus lobata, shrink considerably (to 59% and 54% of modern potential range sizes, respectively) and shift northward. This result is markedly different from that obtained by using a comparable GCM-based scenario, under which these species retain 81% and 73% of their modern potential range sizes, respectively. The difference between RCM- and GCM-based scenarios is due to greater warming and larger precipitation decreases during the growing season predicted by the RCM in these species' potential ranges. Based on the modeled regional climate change, <50% of protected land area currently containing these species is expected to contain them under a future midrange "business-as-usual" path of greenhouse gas emissions.

California↗
PubMed2002

Potential impact of global warming on deciduous oak dieback caused by ambrosia fungus Raffaelea sp. carried by ambrosia beetle Platypus quercivorus (Coleoptera: Platypodidae) in Japan.

Deciduous oak dieback in Japan has been known since the 1930s, but in the last ten years epidemics have intensified and spread to the island's western coastal areas. The symbiotic ambrosia fungus Raffaelea sp. is the causal agent of oak dieback, and is vectored by Platypus quercivorus (Murayama). This is the first example of an ambrosia beetle fungus that kills vigorous trees. Mortality of Quercus crispula was approximately 40% but much lower for associated species of Fagaceae, even though each species had a similar number of beetle attacks. It is likely that other oaks resistant to the fungus evolved under a stable relationship between the tree, fungus and beetle during a long evolutionary process. Quercus crispula was probably not part of this coevolution. This hypothesis was supported by the fact that P. quercivorus showed the least preference for Q. crispula yet exhibited highest reproductive success in this species. Therefore, P. quercivorus could spread more rapidly in stands with a high composition of Q. crispula. The present oak dieback epidemic in Japan probably resulted from the warmer climate that occurred from the late 1980s which made possible the fateful encounter of P. quercivorus with Q. cripsula by allowing the beetle to extend its distribution to more northerly latitudes and higher altitudes. Future global warming will possibly accelerate the overlapping of the distributions of P. quercivorus and Q. crispula with the result that oak dieback in Q. crispula will become more prevalent in Japan.

Animals↗
PubMed2004

Should models of disease dynamics in herbivorous insects include the effects of variability in host-plant foliage quality?

Interactions between insects and their baculovirus pathogens are often described using simple disease models. Baculoviruses, however, are transmitted when insects consume virus-contaminated foliage, and foliage variability, whether within or between host-plant species, can affect viral infectiousness. Insect-baculovirus interactions may thus be embedded in a tritrophic interaction with the insect's host plant, but disease models include only the host and the pathogen. We tested these models by measuring the transmission of a baculovirus of gypsy moths (Lymantria dispar) on red oak (Quercus rubra) and white oak (Quercus alba) in the field in six experiments over four years. In all experiments, there were only weak effects of host-tree species, and in only one did the best-fitting model include tree species effects. These weak effects of foliage variability on transmission were not due to a lack of foliage variability on viral infectiousness, because when larvae were force-fed virus-contaminated foliage, infection rates were higher on white oak. Our results suggest that feeding behavior plays an important role in baculovirus transmission and that models can usefully describe baculovirus dynamics even without including foliage variability. Our work provides a clear example of how two-species models are sometimes sufficient to describe what appear to be tritrophic interactions.

Animals↗
PubMed2004

Photoinhibition and drought in Mediterranean woody saplings: scaling effects and interactions in sun and shade phenotypes.

Interacting effects of high light and drought on the performance of sun and shade phenotypes were experimentally undertaken following survival, chlorophyll fluorescence and gas exchange in 2-year-old saplings of four Mediterranean trees (Quercus ilex and Q. coccifera as water-saving species, and Pistacia lentiscus and P. terebinthus as water-spending species). Half of the saplings were grown in full sunlight and the other half in the shade (6% sunlight). Half of each combination of species-phenotype was exposed to high light during a simulated late-summer drought. Light absorptance and gas exchange were scaled up to the whole plant with the 3-D geometrical model, Y-Plant. Quercus species were more plastic and tolerated high light and water stress better than Pistacia species, surviving longer and in drier soils, and exhibiting a less pronounced photoinhibition. There was no evidence of disadvantage for shade phenotypes under high light with increasing drought. By contrast, shade phenotypes survived longer despite larger initial decreases in photochemical efficiency and higher sensitivity to drought than sun phenotypes. The enhanced control of transpiration during drought in water-saving versus water-spending species (and also in shade versus sun phenotypes in three out of the four species) allowed extended survival. Photoinhibition reduced whole crown carbon gain in high light by c. 3% and affected significantly more the shaded leaves of a given plant (reducing their carbon gain by up to 7%) than those exposed to direct sunlight. Despite this apparently minor impact, whole plant carbon gain reduction by photoinhibition negatively correlated with survival and drought tolerance. The implications for succession and forest regeneration in arid environments, particularly under a global change scenario, are discussed.

Adaptation, Physiological↗
PubMed2006

How periodic growth pattern and source/sink relations affect root growth in oak tree seedlings.

Seedlings of Quercus pubescens were grown in root boxes to study the growth pattern of the root system in relation to shoot development. Shoot growth was typically rhythmic. Root elongation was also periodic, in contrast to several previous reports on other Quercus species. Both taproot and lateral root elongation were depressed during expansion of the second leaf flush, with a more pronounced response of lateral root growth. Apical diameter of the taproot followed comparable but less prominent trends than taproot elongation. Modifying source/sink relationships through various defoliation treatments altered the root growth pattern. Ablation of source organs (mature leaves or cotyledons) amplified the decrease in root growth concomitant with leaf expansion. Root growth recovery was even more difficult when both cotyledons and mature leaves had been removed. Ablation of sink aerial organs (young leaves) initially suppressed competition for growth between the shoot and the root, and then caused a gradual decrease in lateral root growth. Antagonism between maximum leaf expansion and root growth reduction during the second flush, and various responses of seedlings with modified source/sink relationships, raise an hypothesis of mutual competition for carbohydrates. The gradual decrease in lateral root growth after ablation of young leaves suggests a long-term carbohydrate limitation, or auxin limitation as auxin sources have been removed.

Biomass↗