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Quercus Robur L. (quercus + robur_l)
Selected AbstractsHost shifting by Operophtera brumata into novel environments leads to population differentiation in life-history traitsECOLOGICAL ENTOMOLOGY, Issue 5 2003Adam J. Vanbergen Abstract., 1. Operophtera brumata L. (Lepidoptera: Geometridae), a polyphagous herbivore usually associated with deciduous trees such as oak Quercus robur L., has expanded its host range to include the evergreen species heather Calluna vulgaris (L.) Hull and, most recently, Sitka spruce Picea sitchensis (Bong.) Carrière. 2. Phenology, morphology, and survival of O. brumata were measured at several life-history stages in populations from the three different host plant communities sampled from a range of geographical locations. The data were used to test for population differences, reflecting the marked differences in host-plant secondary chemistry, growth form, and site factors such as climate. The hypothesis that spruce-feeding populations originated from populations feeding on moorland, commonly sites of coniferous afforestation, was also tested. 3. Altitude, not host plant species, was the major influence on the timing of adult emergence. An effect of insect population independent of altitude was found, implying that additional unidentified factors contribute to this phenological variation. Larval survival and adult size varied between populations reared on different host plant species. Survival of larvae was affected negatively when reared on the novel host plant, Sitka spruce, versus the natal plant (oak or heather) but oak and heather-sourced insects did not differ in survivorship on Sitka spruce. 4. Host range extension into novel environments has resulted in population differentiation to the local climate, demonstrating that host shifts pose challenges to the herbivore population greater than those offered by the host plant alone. The hypothesis that Sitka spruce feeding populations have arisen predominantly from moorland feeding populations was not supported. [source] Nitrate leaching from three afforestation chronosequences on former arable land in DenmarkGLOBAL CHANGE BIOLOGY, Issue 6 2007KARIN HANSEN Abstract In regions dominated by agricultural activities, nitrogen (N) is recognized as a major pollutant in aquatic environments. In north-western Europe, afforestation of agricultural land is part of a strategy to improve water quality. In Denmark, former arable land has been afforested during the past 40,50 years. This study evaluated the effect of afforestation of former arable land on nitrate leaching, based on three afforestation chronosequences. Precipitation, canopy throughfall and soil water were collected and soil moisture was monitored at two Danish locations, Vestskoven (nutrient-rich, medium deposition) and Gejlvang (nutrient-poor, high deposition). Afforestation was performed using Norway spruce [Picea abies (Karst.) L.] and common oak (Quercus robur L.) at Vestskoven and Norway spruce at Gejlvang. The results suggest that afforestation of former arable land initially leads to lower nitrate leaching than that occurring under the former agricultural land use, and largely below the standard of 50 mg NO,3 L,1 for groundwater to be utilized as drinking water. Nitrate concentrations became almost negligible in forest stands of 5,20 years of age. However, after canopy closure (>20 years) nitrate concentrations below the root zone and nitrate leaching tended to increase. This was attributed to increased N deposition with increasing canopy development and decreased N demand once the most N-rich biomass compartments had been built up. Nitrate leaching started to increase at a throughfall deposition level of about 10 kg N ha,1 yr,1. Compared with nutrient-poor sandy soils, nutrient-rich clayey soils appeared more vulnerable to disturbance of the N cycle and to increased N deposition, leading to N saturation and enhanced nitrate leaching. In approximately the first 35 years after afforestation, nitrate leaching below the root zone was generally higher below oak than below Norway spruce. [source] Realized gene flow within mixed stands of Quercus robur L. and Q. petraea (Matt.) L. revealed at the stage of naturally established seedlingMOLECULAR ECOLOGY, Issue 10 2010I. J. CHYBICKI Abstract The estimates of contemporary gene flow assessed based on naturally established seedlings provide information much needed for understanding the abilities of forest tree populations to persist under global changes through migration and/or adaptation facilitated by gene exchange among populations. Here, we investigated pollen- and seed-mediated gene flow in two mixed-oak forest stands (consisting of Quercus robur L. and Q. petraea [Matt.] Liebl.). The gene flow parameters were estimated based on microsatellite multilocus genotypes of seedlings and adults and their spatial locations within the sample plots using models that attempt to reconstruct the genealogy of the seedling cohorts. Pollen and seed dispersal were modelled using the standard seedling neighbourhood model and a modification,the 2-component seedling neighbourhood model, with the later allowing separation of the dispersal process into local and long-distance components. The 2-component model fitted the data substantially better than the standard model and provided estimates of mean seed and pollen dispersal distances accounting for long-distance propagule dispersal. The mean distance of effective pollen dispersal was found to be 298 and 463 m, depending on the stand, while the mean distance of effective seed dispersal was only 8.8 and 15.6 m, which is consistent with wind pollination and primarily seed dispersal by gravity in Quercus. Some differences observed between the two stands could be attributed to the differences in the stand structure of the adult populations and the existing understory vegetation. Such a mixture of relatively limited seed dispersal with occasional long distance gene flow seems to be an efficient strategy for colonizing new habitats with subsequent local adaptation, while maintaining genetic diversity within populations. [source] | ||||||||||