Direct effects of elevated carbon dioxide on forest tree productivity

This paper provides an introduction to the book on forests and climatic change. A brief overview is given on the different sections included as well as the concepts covered in each: climate change, forestry and the science-policy interface; forestry options for contributing to climate change mitigation; adaptation regarding the impacts of climate change on forests; and policies within national and international frameworks <br/

Diurnal changes in photosynthetic parameters of Populus tremuloides, modulated by elevated concentrations of CO2 and/or O3 and daily climatic variation

The diurnal changes in light-saturated photosynthesis (Pn) under elevated CO2 and/or O3 in relation to stomatal conductance (gs), water potential, intercellular [CO2], leaf temperature and vapour-pressure difference between leaf and air (VPDL) were studied at the Aspen FACE site. Two aspen (Populus tremuloides Michx.) clones differing in their sensitivity to ozone were measured. The depression in Pn was found after 10:00 h. The midday decline in Pn corresponded with both decreased gs and decreased Rubisco carboxylation efficiency, Vcmax. As a result of increasing VPDL, gs decreased. Elevated [CO2] resulted in more pronounced midday decline in Pn compared to ambient concentrations. Moreover, this decline was more pronounced under combined treatment compared to elevated CO2 treatment. The positive impact of CO2 on Pn was relatively more pronounced in days with environmental stress but relatively less pronounced during midday depression. The negative impact of ozone tended to decrease in both cases. © 2009 Elsevier Ltd

Acute O \u3c inf\u3e 3 damage on first year coppice sprouts of aspen and maple sprouts in an open-air experiment

We studied the effect of high ozone (O 3) concentration (110-490 nmol mol -1) on regenerating aspen (Populus tremuloides) and maple (Acer saccharum) trees at an open-air O 3 pollution experiment near Rhinelander WI USA. This study is the first of its kind to examine the effects of acute O 3 exposure on aspen and maple sprouts after the parent trees, which were grown under elevated O 3 and/or CO 2 for 12 years, were harvested. Acute O 3 damage was not uniform within the crowns of aspen suckers; it was most severe in the mature, fully expanded photosynthesizing leaves. Young expanding leaves showed no visible signs of acute O 3 damage contrary to expectations. Stomatal conductance played a primary role in the severity of acute O 3 damage as it directly controlled O 3 uptake. Maple sprouts, which had lower stomatal conductance, smaller stomatal aperture, higher stomatal density and larger leaf surface area, were tolerant of acute O 3 exposure. Moreover, elevated CO 2 did not ameliorate the adverse effects of acute O 3 dose on aspen and maple sprouts, in contrast to its ability to counteract the effects of long-term chronic exposure to lower O 3 levels. © 2011 The Royal Society of Chemistry

Carbon gain and bud physiology in Populus tremuloides and Betula papyrifera grown under long-term exposure to elevated concentrations of CO2 and O3

Paper birch (Betula papyrifera Marsh.) and three trembling aspen clones (Populus tremuloides Michx.) were studied to determine if alterations in carbon gain in response to an elevated concentration of CO2 ([CO2]) or O3 ([O3]) or a com- bination of both affected bud size and carbohydrate composi- tion in autumn, and early leaf development in the following spring. The trees were measured for gas exchange, leaf size, date of leaf abscission, size and biochemical characteristics of the overwintering buds and early leaf development during the 8th–9th year of free-air CO2 and O3 exposure at the Aspen FACE site located near Rhinelander, WI. Net photosynthesis was enhanced 49–73% by elevated [CO2], and decreased 13–30% by elevated [O3]. Elevated [CO2] delayed, and ele- vated [O3] tended to accelerate, leaf abscission in autumn. Ele- vated [CO2] increased the ratio of monosaccharides to di- and oligosaccharides in aspen buds, which may indicate a lag in cold acclimation. The total carbon concentration in over- wintering buds was unaffected by the treatments, although ele- vated [O3] decreased the amount of starch by 16% in birch buds, and reduced the size of aspen buds, which may be related to the delayed leaf development in aspen during the spring. Ele- vated [CO2] generally ameliorated the effects of elevated [O3]. Our results show that both elevated [CO2] and elevated [O3] have the potential to alter carbon metabolism of overwintering buds. These changes may cause carry-over effects during the next growing season

Evaluation of insecticidal and anti-hookworm activities of crude extracts and isolates from dichapetalum madagascariense stem bark

The constituents of the roots of Dichapetalum madagascariense have been investigated for their anti-tumour and anti-proliferative activities on some cancer cell lines and anti-parasitic activities against some causative pathogens of selected neglected tropical diseases. The most active constituents were the dichapetalins. To investigate the constituents of the stem bark of the plant for potential insecticidal and anti-hookworm activities, chromatographic separation of the stem bark extracts gave four commonly occurring triterpenoids; friedelan-3β-ol (1), friedelan-3-one (2), the relatively rare triterpenoid zeylanol (3), β-sitosterol (4) and stigmasterol (5), which was obtained as a mixture with (4). This is the first report of the presence of zeylanol (3) in D. madagascariense. Activity against the maize weevil, Sitophilus zeamais gave LD50 values (µg/mL) of 0.48 (compound 1), 0.56 (2), 0.52 (mixture of 1 and 2), and 0.98 (mixture of 4 and 5). Crude extract-treated maize grains at doses ≥ 2 g per 100 g grain provided the most effective protection to maize against hidden eggs and immature stages of S. zeamais compared to complete protection at the highest dosage (10 g/100 g grain). The IC50 of tested compounds against human hookworm Necator americanus showed lower potencies (0.64-1.33 µg/µL) than the standard, albendazole (0.0024 µg/µL). This study has established the presence of zeylanol (3) in D. madagascariense and shown that the insecticidal activity of the tested compounds and extracts against S. zeamais could provide some protection against maize grains but at levels that are uneconomical for incorporation into sustainable pest management programmes. Anti-hookworm activities obtained may serve as leads for further optimization and development in the anthelmintic drug discovery efforts. &nbsp