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At least 163 records · Page 9Linked to original sources
PubMed2006

Hydraulic compensation in northern Rocky Mountain conifers: does successional position and life history matter?

As trees grow tall and the resistance of the hydraulic pathway increases, water supply to foliage may decrease forcing stomata to close and CO2 uptake to decline. Several structural (e.g. biomass allocation) and physiological adjustments, however, may partially or fully compensate for such hydraulic constraints and prevent limitations on CO2 uptake and growth. The degree to which trees compensate for hydraulic constraints as they grow tall may depend on the costs and benefits associated with hydraulic compensation according to their ecology and life history. Because later successional Rocky Mountain conifers are more shade tolerant, optimization of CO2 uptake as trees grow tall and shade increases may confer greater benefits than in earlier successional species. If so, higher compensation for hydraulic constraints is expected in later successional species relative to co-occurring earlier successional species. I have examined height-related changes of crown stomatal conductance on a leaf area basis (G(LA)) and leaf to sapwood ratios (A(L):A(S)) for five conifer species in the northern Rocky Mountains. Species were arranged in pairs, each pair consisting of an early and late successional species. For high elevations I used, respectively, whitebark pine (Pinus albicaulis) and subalpine fir (Abies lasiocarpa); for mid-elevations, western larch (Larix occidentalis) and Douglas-fir (Pseudotsuga menziesii); for lower elevations, ponderosa pine (Pinus ponderosa) and Douglas-fir. A(L):A(S) either decreased (subalpine fir, ponderosa pine), remained constant (Douglas-fir, western larch) or increased (whitebark pine) with tree height. As hypothesized, earlier successional species (ponderosa pine, whitebark pine and western larch) exhibited significantly stronger decreases of G(LA) with tree height relative to their later successional pairs (Douglas-fir and subalpine fir), which fully compensated for height-related hydraulic constraints on G(LA). A life history approach that takes into account the optimization of size- and species-specific ecological functions may also help researchers better understand biomass allocation and hydraulic function in trees.

Adaptation, Physiological↗
PubMed2006

Modification of wood with isopropyl glycidyl ether and its effects on decay resistance and light stability.

China fir (Cunninghamia lanceolata var. lanceolata) and maple (Acer sp.) wood were etherified with isopropyl glycidyl ether and the decay resistance and light stability of the modified wood were assessed. CP/MAS (13)C NMR and FT-IR analyses indicated that new ether bonds containing isopropyl groups formed after reacting wood with isopropyl glycidyl ether. Modified wood samples were very resistant to decay when exposed to brown-rot fungus Laetiporus sulphureus or white-rot fungus Lenzites betulina for 60 days in the soil-block test. The isopropyl glycidyl ether treatment of wood was effective in decreasing formation of phenoxyl radicals upon UV irradiation and thus protecting wood from photodiscoloration.

Acer↗
PubMed2004

Trichloroacetic acid in Norway spruce/soil-system. II. Distribution and degradation in the plant.

Independently from its origin, trichloroacetic acid (TCA) as a phytotoxic substance affects coniferous trees. Its uptake, distribution and degradation were thus investigated in the Norway spruce/soil-system using 14C labeling. TCA is distributed in the tree mainly by the transpiration stream. As in soil, TCA seems to be degraded microbially, presumably by phyllosphere microorganisms in spruce needles. Indication of TCA biodegradation in trees is shown using both antibiotics and axenic plants.

Anti-Bacterial Agents↗
PubMed2004

Biflavonoids from Brazilian pine Araucaria angustifolia as potentials protective agents against DNA damage and lipoperoxidation.

A biflavonoid fraction (BFF) obtained from Araucaria angustifolia needles was effective to quench singlet oxygen (1O2), to protect plasmid DNA against single strand break (ssb) caused by 1O2 or Fenton reaction and to inhibit Fenton or UV radiation-induced lipoperoxidation in phosphatidylcholine liposomes. The activity of the biflavonoid fraction (BFF) was compared with quercetin, rutin (flavonoids), ginkgetin, amentoflavone (biflavonoids), alpha-tocopherol and Trolox. The BFF displayed a higher quenching rate constant compared to flavonoids and biflavonoids and protected against ssb induced by 1O2. Although the BFF was not as efficient as either flavonoids, alpha-tocopherol or Trolox in protection against ssb induced by Fenton-reaction or lipoperoxidation, these scavenging properties suggest that BFF is still an excellent candidate for successful employment as an antioxidant and photoprotector.

Brazil↗
PubMed2006

Benzoic acid allopyranosides from the bark of Pseudolarix kaempferi.

Two benzoic acid allopyranosides, pseudolaroside A and pseudolaroside B, along with seven known compounds were isolated from the bark of Pseudolarix kaempferi. Their structures were determined by analysis of HR-ESI-MS, 1D and 2D NMR spectroscopic data, chemical analysis and comparison to the literature data.

Benzoic Acid↗
PubMed2006

Linking patterns and processes of species diversification in the cone flies Strobilomyia (Diptera: Anthomyiidae).

Phytophagous insects provide useful models for the study of ecological speciation. Much attention has been paid to host shifts, whereas situations where closely related lineages of insects use the same plant during different time periods have been relatively neglected in previous studies of insect diversification. Flies of the genus Strobilomyia are major pests of conifers in Eurasia and North America. They are specialized feeders in cones and seeds of Abies (fir), Larix (larch) ,and Picea (spruce). This close association is accompanied by a large number of sympatric Strobilomyia species coexisting within each tree genus. We constructed a molecular phylogeny with a 1320 base-pair fragment of mitochondrial DNA that demonstrated contrasting patterns of speciation in larch cone flies, as opposed to spruce and fir cone flies; this despite their comparable geographic distributions and similar resource quality of the host. Species diversity is the highest on larch, and speciation is primarily driven by within-host phenological shifts, followed by allopatric speciation during geographical expansion. By contrast, fewer species exploit spruce and fir, and within-host phenological shifts did not occur. This study illustrates within-host adaptive radiation through phenological shifts, a neglected mode of sympatric speciation.

Animals↗
PubMed2002

Biological activity of soil organic matter mobilized by root exudates.

In order to study the biological activity of soil organic matter mobilized by agrarian (Zea mays: cultivars Mytos and Samantha) and forest (Picea abies Karst. and Pinus sylvestris L.) root exudates, two different soils, an Eutric Cambisol (EC) and a Rendzic Leptosol (RL), were considered. Soil organic matter extracts were obtained by treating the soils with water (control) or plant root exudates. The extracts were characterized by hormone-like activities and gas chromatographic/mass spectrometric (GC/MS) measurements. Their effects on the nitrogen metabolism in maize seedlings were evaluated. The nitrogen organification in the maize seedlings has been greatly stimulated by all the organic acid extracts from the agrarian soil, while the extracts from the forest soil had no influence upon the metabolism; this indicated a probable link between the plant and the environment. The different biological activities of the extracts are discussed.

Gas Chromatography-Mass Spectrometry↗
PubMed2002

Trichloroacetic acid in the environment.

Suppositions that the trichloroacetic acid (TCA, CCl3C(O)OH) found in nature was a consequence solely of the use of chlorinated hydrocarbon solvents prompted this critical review of the literature on its environmental fluxes and occurrences. TCA is widely distributed in forest soils (where it was rarely used as an herbicide) and measurements suggest a soil flux of 160 000 tonnes yr(-1) in European forests alone. TCA is also produced during oxidative water treatment and the global flux could amount to 55 000 tonnes yr(-1) (from pulp and paper manufacture, potable water and cooling water treatments). By contrast, the yields of TCA from chlorinated hydrocarbon solvents are small: from tetrachloroethene 13 600 tonnes yr(-1) and from 1,1,1-trichloroethane 4300 tonnes yr(-1) on a global basis, at the atmospheric burdens and removal rates typical of the late 1990s. TCA is ubiquitous in rainwater and snow. Its concentrations are highly variable and the variations cannot be connected with location or date. However, there is no significant difference between the concentrations found in Chile and in eastern Canada (by the same analysts), or between Malawi and western Canada, or between Antarctica and Switzerland, nor any significant difference globally between the concentrations in cloud, rain and snow (although local enhancement in fog water has been shown). TCA is present in old ice and firn. At the deepest levels, the firn was deposited early in the 19th century, well before the possibility of contamination by industrial production of reactive chlorine, implying a non-industrial background. This proposition is supported by plume measurements from pulp mills in Finland. TCA is ubiquitous in soils; concentrations are very variable but there are some indications that soils under coniferous trees contain higher amounts. The concentrations of TCA found in plant tissue are region-specific and may also be plant-specific, to the extent that conifers seem to contain more than other species. TCA is removed from the environment naturally. There is abundant evidence that soil microorganisms dehalogenate TCA and it is lost from within spruce needles with a half-life of 10 days. There is also recent evidence of an abiotic aqueous decarboxylation mechanism with a half-life of 22 days. The supposedly widespread effects of TCA in conifer needles are not shown in controlled experiments. At concentrations in the needles of Scots pine similar to those observed in needles in forest trees, changes consequent on TCA treatment of field laboratory specimens were almost all insignificant.

Caustics↗
PubMed2001

The fate of 137Cs in coniferous forests following the application of wood-ash.

In the future, it may become common practice in Swedish forestry to recycle wood-ash, a waste product of the combustion of bio-fuel. As a consequence of the Chernobyl radioactive fallout in 1986, large areas of central Sweden were contaminated. Application of recycled wood-ash, originating from contaminated areas, to a previously uncontaminated forest, risks an increase in the concentration of radioactive 137Cs. We measured 137Cs radioactivity in different parts of coniferous forests in seven field experiments. Measurements of radioactivity were made 5-8 years after an application of wood-ash equivalent to 3000 kg ha(-1). The sites, in a north-south transect across Sweden, have a background radioactivity ranging from 0 to 40 kBq m(-2), the higher levels are mainly a result of the Chernobyl fall-out. Depending on its origin, the radioactivity of the applied wood-ash ranged from 0.0 to 4.8 kBq kg(-1), corresponding to 0.0-1.44 kBq m(-2). In autumn 1999, samples were taken from the soil, field vegetation, needles and twigs and the levels of 137Cs determined. In addition, soil samples were analysed for extractable K. The highest 137Cs concentration was found in the soil. At six of the seven sites there were no statistically significant effects of wood-ash application on 137Cs activity. This was despite the fact that the wood-ash had, in one case, added the same amount of radioactivity as the background. However, at one site with intermediate 137Cs deposition (10-20 kBq m(-2)), there was a statistically significant decrease in 137Cs radioactivity in the soil, needles and twigs from the plots treated with wood-ash. The decrease in radioactivity was partly due to the fact that one of the main constituents of wood-ash is K, which is antagonistic to 137Cs. Based on our results, it appears that application of wood-ash containing 137Cs does not necessarily increase the 137Cs radioactivity in plants and soil. However, some of the observed effects could be a result of the low number of replicates used in this study.

Cesium Radioisotopes↗
PubMed2002

Nitrate reductase activity in some subarctic species and UV influence in the foliage of Betula pendula Roth. seedlings.

Nitrate reductase (NR) activity was studied in the foliage of five subarctic species: mature trees of European white birch (Betula pubescens Erch. S.S.), Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies L. Karst), Ericaceous shrub bilberry (Vaccinium myrtillus L.), naturally growing in a forest, and seed-grown silver birch (Betula pendula Roth.) seedlings in an ultraviolet (UV) exclusion field experiment at the Pallas-Ounastunturi National Park in Finnish Lapland (68 degrees N). Mean NR activity ranged from 0 in bilberry to 1477 (S.D. = 277.7) and 1910 (S.D. = 785.4) nmol g(-1) DW h(-1) in mature trees of European white birch and silver birch seedlings, respectively. Significant differences due to UV exclosure treatments were determined for the NR activity of silver birch seedlings (F = 3.62, P= 0.025*) after three growing seasons (191 days) of UV exclusion. The ambient and control silver birch seedlings had or tended to have higher NR activity than those grown under UV exclusion. No relationship was found between the foliage NR activity and total nitrogen content, which ranged from 0.61 to 1.35% per seedling. The present study suggests large differences in NR activity between the species and the induction of NR activity in silver birch seedlings due to ambient UV radiation.

Adaptation, Physiological↗
PubMed2002

Sulphur migration in the soil-plant system contaminated by deposits from nickel industry: a field manipulation.

Sulphur migration in the soil-plant system was studied in a field experiment carried out in the spruce-pine forest 70 km SE from the 'Severonickel' smelting plant on the Kola Peninsula. In the experiment, dry particle deposits collected from filters of smokestacks in different departments of 'Severonickel' were applied on the study plots and on gravity lysimeters in quantities simulating estimated actual annual emissions in the area within 2-5 km from the smelter. In the present paper, the effects of two types of deposits consisting mostly of water-soluble sulphates of copper and nickel are described ("Cu-contaminant": Cu-55%, Ni-3.8%, SO4-25%; "Ni-contaminant": Ni-20%, Cu-5%, SO4--65%). Soil, plant tissue and penetration water were analysed during 3 years after the treatment. Extractable sulphur distribution in the soil-plant system showed downward movement after 1 year and upward movement after 3 years. The trend was more pronounced in the site treated with Ni-contaminant.

Biological Availability↗
PubMed2003

Antifungal diterpenoids of Pseudolarix kaempferi, and their structure-activity relationship study.

The in vitro antifungal activities of 19 structurally diversified analogues of pseudolaric acids tested against the major pathogenic fungus Candida albicans has led to the establishment of a very clear structure-activity relationship of pseudolaric acids derivatives. Pseudolaric acid A was first found to be a potent antifungal component comparable with pseudolaric acid B. Among the tested 19 diterpenoids, pseudolaric acids A2 (1), B2 (3), B3 (4) and methyl pseudolarate A2 (2) are new isolates of the root bark of Pseudolarix kaempferi, and their structures were elucidated mainly by 2D-NMR techniques and chemical methods. Compounds 12-19 were first semi-synthesized by efficient routines from pseudolaric acid B.

Animals↗
PubMed2005

Airborne fungal colonisation of coarse woody debris in North Temperate Picea abies forest: impact of season and local spatial scale.

Coarse woody debris is important for mycodiversity in forest ecosystems, but its availability in managed stands is reduced. Leaving dead wood during felling is suggested as an option to sustain and restore the diversity. However, little is known what fungi would colonise freshly cut wood left on managed sites, and how the colonisation process is influenced by ecological factors. During summer and autumn, 120 freshly cut Picea abies stem sections over 8 cm in diameter were placed upright in mapped locations over two discrete plots separated by 100 m in a north-temperate forest. After seven weeks the sections were collected, and isolation and identification of fungi was done from their upper surfaces. In all 943 fungal strains were isolated, representing 97 species. Species richness in the summer survey was 42.5% higher than during the autumn survey. Low species similarity characterized the different seasons (Sorensen indices: S(S) = 0.36 and S(N) = 0.34) and for 21 species (22%) observation frequency was significantly affected by season. As a result, community structures in summer and autumn differed notably (z-test; P < 0.001). Species richness between the two plots differed by less than 10%, but there were 64 species (66%) found only in one of them, thus qualitative similarity was low (S(S) = 0.49). Quantitative similarity was higher (S(N) = 0.63), indicating that the dominant species colonised wood to a similar extent in both areas. Fungal community structure differed significantly among the two plots (z-test; P < 0.001). Our data showed that freshly cut CWD contributed to mycodiversity in managed north-temperate forest, providing habitats for numerous individuals from over 100 species. The fungal community within a single stand differed markedly both across small distances and over the seasons. In order to sustain and enhance mycodiversity in managed stands. coarse wood should always be left during harvesting. This study also demonstrates the importance of molecular identification and ITS sequence databases for exploring fungal diversity in natural communities.

Air Microbiology↗
PubMed2001

Persistence of the insecticide Dimilin 45 ODC on conifer forest foliage in an Atlantic-climate ecosystem.

The oil formulation of diflubenzuron (Dimilin 45 ODC) persisted for 10-12 weeks on the foliage of a conifer forest in an Atlantic-climate ecosystem. Within 22-30 days following treatment, 55-80% of the insecticide had been removed from the foliage. During this period, the concentration of diflubenzuron was higher than 370 ng g(-1). Aerial application at 56.3 g of Al ha(-1) resulted in deposition levels of the insecticide ranging from 867.5 to 1824.4 ng g(-1), depending upon forest characteristics. The results showed that aerial application is only a suitable technique for the treatment of forest areas with dense foliage and/or high tree density and no more than 15% of tree-free area. The only metabolite detected was 2,6-difluorobenzamide, and this persisted on foliage until the first rainfalls occurred. An empirical mathematical correlation was found to express the influence of meteorological variables--rainfall, solar radiation and temperature--on the persistence of the insecticide. These results suggested that degradation of diflubenzuron on foliage could be due to photodegradation. Some recommendations were made to optimize the deposition of the insecticide on foliage and to minimize its persistence and the off-site spray drift.

Diflubenzuron↗
PubMed2002

Five new diterpenoids from Pseudolarix kaempferi.

Five new diterpenoids, pseudolaric acids F (1), G (2), and H (3), 2',3'-dihydroxy-1'-propoxypseudolarate B (4), and 6'-O-acetylpseudolaric acid B O-beta-D-glucopyranoside (5), along with nine known diterpenoids, pseudolaric acids A, B, and C(1), deacetylpseudolaric acid C(2), deacetylpseudolaric acid A, methyl pseudolarate A, methyl pseudolarate B, pseudolaric acid A-O-beta-D-glucopyranoside, and pseudolaric acid B-O-beta-D-glucopyranoside, were isolated from the root bark of Pseudolarix kaempferi. Their structures and stereochemistry were elucidated mainly by spectral data, especially 2D NMR techniques.

Chromatography, Thin Layer↗
PubMed2005

Diterpenoid, steroid, and triterpenoid agonists of liver X receptors from diversified terrestrial plants and marine sources.

It has been demonstrated that liver X receptors (LXR) play a significant role in cholesterol homeostasis. Agonists of LXR are expected to increase cellular cholesterol efflux, lower LDL, and raise HDL levels. Screening of a natural product library of plant extracts using a LXR-SPA binding assay and bioassay-guided fractionation of a number of plant and marine gorgonian extracts led to the isolation of a number of active compounds. These included acanthoic acid (1) and alcohol (2), viperidone (3), polycarpol (4), rosacea acid (5), a cycloartane derivative (6), a new cycloartane analogue (7), betulinic acid (8), and gorgostane derivatives (9, 10, and 11). Of these compounds, 1, 4, and 11 exhibited potent binding affinity for alpha-receptor with IC(50) values of 0.25, 0.12, and 0.07 microM, respectively. Functionally they also showed strong coactivator association stimulation for LXRalpha receptor with EC50 values of 0.18, 0.03, and 0.05 microM, respectively. They also exhibited 15-, 8-, and 13-fold induction of the alpha-receptor in a transactivation assay in HEK-293 cells, respectively. In general these compounds were selective for the LXR alpha-receptor over the beta-receptor in all assays and were much better stimulators of the alpha-receptor than the endogenous steroid ligands.

Animals↗