Effect of animal browse protection and fertilizer application on the establishment of planted Nuttall oak seedlings

For establishment to be successful, planted oak must emerge above vegetative competition and browse level. A 3 year study was established in 2000 in a cutover bottomland hardwood forest in west Alabama to examine the influences of seedling browse protection and fertilizer use on growth of Nuttall oak (Quercus nuttallii Palm.) seedlings. The treatments included: control, 1.2 m tall wire tree shelter, and 1.2 m tall plastic tree shelter. Fertilizer (20–10–5) was applied to one-half of all seedlings at planting. Competing vegetation was controlled around all seedlings with mulch mats and herbicide. Fertilization did not affect height growth or successful establishment after 3 years. Four percent of protected seedlings (plastic and wire tree shelters combined) were browsed compared to 95% of control seedlings. After 3 years, plastic tree shelters were the most effective treatment for promoting height growth and successful seedling establishment of Nuttal oak seedlings (193 cm, 92.71% compared to 120 cm, 68.75% and 52 cm, 8.33% for wire tree shelter, and control seedlings, respectively). Animal browse protection is deemed essential for successful seedling establishment in southern bottomland forests where deer density is high (density estimated at 27 km⁻² in vicinity of study area).     

Visible Ozone Injury on Forest Trees in Great Smoky Mountains National Park, USA

During the summer of 1991 ozone injury trend plots in Great Smoky Mountains National Park, USA, consisting of mature black cherry, sassafras and yellow-poplar were established near three ozone monitors, ranging in elevation from 597-1265 m. Beginning in mid-August 1991-1993, three exposed branches each from the upper- and mid- to lower-crown of each tree were collected and evaluated for ozone injury. Of the trees examined, 63%, 52% and 36% exhibited some amount of foliar injury in 1991, 1992 and 1993, respectively. Ozone injury across species was the greatest at Cove Mountain in all three years of the study. Overall, across sites and years, 11, 12 and 11% of all leaves examined exhibited visible injury for black cherry, sassfras and yellow-poplar, respectively. The percentage of injured leaves per branch was greater in the mid- to lower-canopy for black cherry, across all sites. Trees for each species that exhibited the greatest or least amounts of visible injury did so in all three years of the study, indicating a differential sensitivity within each species population. No significant ozone exposure-tree response relationships were observed with any variable tested. These data indicate that ozone concentrations are high enough to cause visible symptoms to selected trees within Great Smoky Mountains National Park, USA.     

Lead Accumulation in Quercus Nigra and Q. Velutina near Smelting Facilities in Alabama,U.S.A.

Lead is very toxic and if ingested cancause severe health problems to both animals andhumans. To determine if lead accumulation in treescould provide a direct pathway to enter the foodchain, oaks (Q. nigra or Q. velutina)growing near two lead smelting facilities in Alabama,U.S.A., were analyzed for lead in acorns, leaves and treecores. A relatively pristine site was used as acontrol. Lead was not detected in acorns collected atany site, and was only found in tree cores from thesites near smelters. Significant increases in treecore lead from 1975–1995 were detected at the activesmelter site. Results were different from the inactivesmelter site; lead increased in tree cores until thesmelter ceased operation, then decreased afterclosing. Soil lead decreased linearly with distancefrom both smelters. In addition, a significantpositive relationship was observed between leaf andsoil lead at the site with the active smelter, andmay be the result of both translocation via treeroots, and foliar absorption of deposited lead ionsinto the leaf structure.     

The influence of acid precipitation and ozone on nitrogen nutrition of young loblolly pine

Field grown loblolly pine (Pinus taeda L.) seedlings from two half-sibling families were exposed to three levels of acid precipitation and four levels of O₃ in open top chambers at Auburn, AL. At the end of one growing season, dry weight and total N accumulation of seedlings was directly related. to rainfall acidity, possibly indicating a fertilizer response in the N deficient soil. Increasing O₃ levels elicited an increase in N content of permanent tissues that was not related to a dry weight response. The origin of this N was believed to be increased internal translocation associated with enhanced premature needle senescence observed at higher O₃ levels.     

Model estimates of net primary productivity,evapotranspiration, and water use efficiency in the terrestrial ecosystems of the southern United States during 1895–2007

The effects of global change on ecosystem productivity and water resources in the southern United States (SUS), a traditionally ‘water-rich’ region and the ‘timber basket’ of the country, are not well quantified. We carried out several simulation experiments to quantify ecosystem net primary productivity (NPP), evapotranspiration (ET) and water use efficiency (WUE) (i.e., NPP/ET) in the SUS by employing an integrated process-based ecosystem model (Dynamic Land Ecosystem Model, DLEM). The results indicated that the average ET in the SUS was 710 mm during 1895–2007. As a whole, the annual ET increased and decreased slightly during the first and second half of the study period, respectively. The mean regional total NPP was 1.18 Pg C/yr (525.2 g C/m²/yr) during 1895–2007. NPP increased consistently from 1895 to 2007 with a rate of 2.5 Tg C/yr or 1.10 g C/m²/yr, representing a 27% increase. The average WUE was about 0.71 g C/kg H₂O and increased about 25% from 1895 to 2007. The rather stable ET might explain the resulting increase in WUE. The average WUE of different biomes followed an order of: forest (0.93 g C/kg H₂O) > wetland (0.75 g C/kg H₂O) > grassland (0.58 g C/kg H₂O) > cropland (0.54 g C/kg H₂O) > shrubland (0.45 g C/kg H₂O). WUE of cropland increased the fastest (by 30%), followed by shrubland (17%) and grassland (9%), while WUE of forest and wetland changed little from the period of 1895–1950 to the period of 1951–2007. NPP, ET and WUE showed substantial inter-annual and spatial variability, which was induced by the non-uniform distribution patterns and change rates of environmental factors across the SUS. We concluded that an accurate projection of the regional impact of climate change on carbon and water resources must consider the spatial variability of ecosystem water use efficiency across biomes as well as the interactions among all stresses, especially land-use and land-cover change and climate.     

Mature Black Cherry Used as a Bioindicator of Ozone Injury

Incidence and severity of foliar symptoms due to ambient ozone exposures were documented on mature black cherry (Prunus serotina) in two National Parks [Great Smoky Mountains National Park (GRSM) and Shenandoah National Park (SHEN)] in the Appalachian Mountains of the eastern USA during the summer of 1991-1993. Three plots in each park containing 30 trees each (Big Meadows in SHEN had 60 trees) with 90 and 120 trees total trees were evaluated in GRSM and SHEN, respectively. Plots were established at different elevations adjacent to ozone monitoring stations. Samples of foliage were collected and three exposed branches from the upper- crown and three branches from the mid-to-lower crown were examined for symptoms of foliar ozone injury. Incidence was greatest in 1991 at both locations; 60% and 45% for GRSM and SHEN, respectively. In 1992 and 1993, incidence was very similar in both parks, with approximately 33% of the trees affected. Black cherry at the highest elevations exhibited the greatest amount of symptoms in both parks all three years of the study. These sites also exhibited the highest ozone concentrations. In addition, the percent of trees injured by ozone was positively correlated with SUM06 and W126. These results along with forest surveys and open-top chamber studies indicate that black cherry may be a reliable bioindicator of foliar injury due to ambient ozone.     

Tree shelters and weed control: Effects on protection,survival and growth of cherrybark oak seedlings planted on a cutover site

In the southern USA oaks (Quercusspp.) are often favored by forest owners havingmultiple objectives for forest ownership as oaksprovide mast for wildlife, are consideredaesthetically pleasing, and are valuable for timberproducts. Regeneration and early seedling growth isa concern to those forest owners interested insustaining oaks as a component of their forests. Theeffects of tree shelters and herbaceous weed controlon second-year seedling survival, browse by deer andrabbits, and seedling growth of hand-plantedcherrybark oak (Quercus pagoda Raf.) wereexamined. The study was established on a cutovermixed pine-hardwood forest in Alabama. Fourtreatments were: weed control only, tree shelter only,tree shelter with weed control, and a controlconsisting of a seedling without a tree shelter orweed control. No significant difference in seedlingsurvival was found among the treatments after twoyears. Tree shelters were effective in preventingbrowsing. No seedlings in the tree-shelter-onlytreatment were browsed. There was no significant,difference, however, in the percentage of seedlingsbrowsed between the control treatment and the weedcontrol treatment. The use of tree shelters with weedcontrol was the most effective treatment for promoting2-year ground-line diameter, height, and stem volumegrowth.     

Nutritive Quality of Highbush Blackberry (Rubus argutus) Exposed to Tropospheric Ozone

Numerous studies have examined the impacts of ground level O₃ on plants that are important for human consumption, but native species that are important for wildlife have received less scrutiny. During May–August 2004 we examined the effects of O₃ on biomass production and nutritive quality of highbush blackberry (Rubus argutus Link), an important forage for white-tailed deer (Odocoileus virginianus Zimmerman) and other herbivorous mammals. Plants were fumigated in open-top chambers with three levels of O₃ in a randomized-block experiment with three replicates of each treatment. Our three experimental treatments were carbon-filtered air, characteristic of clean air quality; nonfiltered air, representative of air quality in Auburn, AL; and air with double (2×) the ambient concentration of O₃. Although biomass production was not influenced by O₃ exposure, nutritive quality of plants was associated negatively with O₃ concentration. Specifically, neutral detergent fiber was greater and relative feed value was less in plants exposed to elevated levels of O₃. Similarly, in vitro dry matter digestibility tended to be less in plants exposed to elevated O₃. Nutritive quality of regrowth vegetation followed a similar pattern, where neutral detergent fiber was greater and relative feed value was less in plants exposed to elevated levels of O₃. These data suggest that elevated levels of ground level O₃ could have implications for diet selection of herbivorous mammals.