Although most ecologists agree that both top-down and bottom-up forces (predation and resource limitation, respectively) act in concert to influence populations of herbivores, it has proven difficult to estimate the relative contributions of such forces in terrestrial systems. Using a combination of time-series analysis of population counts recorded over 16 years and experimental data, we prese...

The ability of metalaxyl-M, phosphonic acid in the form of phosphonate, and copper hydroxide to inhibit different stages in the life cycle of Phytophthora ramorum , the causal agent of sudden oak death (SOD), was tested in vitro using 12 isolates from the North American forest lineage. In addition, experiments were conducted in planta to study the ability of phosphonic acid injections and metal...

Acute Oak Decline (AOD) is complex syndrome affecting Britain’s keystone native oak species, (Quercus robur L. and Q. petraea (Matt.) Liebl.), in some cases causing mortality within five years of symptom development. The most distinguishable weeping stem lesions, from which four species bacteria have been isolated: Brenneria goodwinii, Gibbsiella quercinecans, Lonsdalea britannica Rahnella vict...

Old hollow trees have declined in Europe and many saproxylic (i.e. wood-dwelling) invertebrates living on them are threatened. The aim of this study was to investigate to what extent artificial habitats can be exploited by saproxylic beetles. To mimic the conditions in tree hollows, we constructed wooden boxes filled with different combinations of substrates like oak saw dust, oak leaves, a dea...

In southern nurseries, hardwood seedlings often grow so large that they are difficult to lift and plant. In a study at the Southern Hardwoods Laboratory, maleic hydrazide (MH) was tested as a means of halting height growth when seedlings reach suitable size. Seeds of green ash (Fraxinus pennsylvanica Marsh.) and Shumard oak (Quercus shumardii Buckl.) were nursery sown during the summer of 1961....

Oak trees play a vital role in the ecosystem of the Wasatch Mountains of Utah, providing both food and shelter for numerous organisms. Most of the Wasatch Oaks are Quercus gambelii (deciduous scrub oaks), shedding their leaves during the harsh high elevation winters. There are several unexpected evergreen oaks which appear to be hybrids of the Wasatch scrub oaks and the evergreen oak, Quercus t...

Plants of one evergreen oak (Quercus ilex) and three deciduous oaks (Q. faginea, with small leaves; Q. pyrenaica and Q. robur, with large leaves) were exposed both to filtered air and to enhanced ozone levels in Open-Top Chambers. Q. faginea and Q. pyrenaica were studied for the first time. Based on visible injury, gas exchange, chlorophyll content and biomass responses, Q. pyrenaica was the mo...

A previously unknown Phytophthora was recovered more than 60 times from evergreen hybrid azalea leaves collected during surveys for the sudden oak death pathogen Phytophthora ramorum in California and Tennessee. The novel Phytophthora was discovered when genomic DNA from this species cross-reacted with the ITS-based diagnostic PCR primers used to screen plants for the presence of P. ramorum. Th...

herbivory is observed in different forms, one of these forms leading to gall production. among gall–inducing insects, oak gall wasps (hymenoptera: cynipidae) are found on the oak trees producing galls on certain parts of the host. in this survey, oak gall wasps were collected from oak forests in west azerbaijan in spring (2010). the occurred galls on oak trees (in spring) were collected from su...

Isoprene is synthesized and emitted in large amounts by a number of plant species, especially oak (Quercus sp.) and aspen (Populus sp.) trees. It has been suggested that isoprene improves thermotolerance by helping photosynthesis cope with high temperature. However, the evidence for the thermotolerance hypothesis is indirect and one of three methods used to support this hypothesis has recently ...