Characterization of main sulfur source of wood-degrading basidiomycetes by S K-edge X-ray absorption near edge spectroscopy (XANES)

The main wood degraders in aerobic terrestrial ecosystems belong to the white- and brown-rot fungi, where their biomass can be created on wood decay only. However, total sulfur (S) concentration in wood is very low and only little is known about the different sulfur compounds in wood today. Sulfur-starved brown-rot fungi Gloeophyllum trabeum and Oligoporus placenta were incubated on sterilized pine wood blocks whereas Lentinus cyathiformis and the white-rot fungi Trametes versicolor were incubated on sterilized beech wood blocks. After 19 weeks of incubation, the S oxidation status was analyzed in wood, in degraded wood, and in biomass of wood-degrading fungi by synchrotron based S K-edge XANES, and total S and sulfate were quantified. Total sulfur and sulfate content in pine wood blocks were approximately 50 and 1 ??g g⁻¹, respectively, while in beech wood approximately 100 and 20 ??g g⁻¹ were found, respectively. Sulfur in beech was dominated by sulfate-esters. In contrast, pine wood also contained larger amounts of reduced S. Three out of four selected fungi caused a reduction of the S oxidation state in wood from oxidized S (sulfate-ester, sulfate) to intermediate S (sulfonate, sulfoxide) or reduced S (thiols, e.g., proteins, peptides, enzyme cofactors). Only O. placenta shifted thiol to sulfonate. Growth experiments of these fungi on selective minimal media showed that in particular cysteine (thiol), sulfonates, and sulfate enhanced total mycelium growth. Consequently, wood-degrading fungi were able to utilize a large variety of different wood S sources for growth but preferentially transformed in vivo sulfate-esters and thiol into biomass structures.     

Biological Processing of Pine Logs for Pulp and Paper Production with Phlebiopsis gigantea

Phlebiopsis gigantea (=Phanerochaete gigantea) is a white rot fungus that rapidly colonizes cut stumps, stems, and branches of pine. Two laboratory and several field studies showed that inoculation of red pine logs, Pinus resinosa, with P. gigantea reduced the pitch content of wood, facilitated bark removal, modified wood cells, and controlled detrimental sapstain. Isolations from inoculated logs revealed up to 100 and 80% colonization of the sapwood by P. gigantea after 8 weeks in the field and 32 days in the laboratory, respectively. Logs colonized by P. gigantea in both the laboratory and field showed a 9 to 71% reduction in pitch content, as well as a significant enhancement of bark removal. Examination with Simons' stain of refined wood fibers from inoculated logs revealed an increase in cell wall porosity. Blue stain fungi that cause dark discoloration of the sapwood were inhibited by inoculation with P. gigantea. These studies demonstrate that biological processing of logs with P. gigantea can result in substantial benefits to the pulp and papermaking process.     

Fungal decay resistance and durability of organosilicon-treated wood

The potential use of organosilicons as protective agents against basidiomycetes attack of wood used in outdoor applications was investigated using Scots pine sapwood and beech specimens. Both mini-blocks and EN 113 specimens were subjected to brown-rot and white-rot fungi. A dose–response could be observed showing that with higher weight percentage gain of the organosilicon, the resistance (i.e., efficacy) against fungi increased. At relatively low weight percentage gains, which are assumed to be economically feasible, Scots pine could be partly protected against decay by Postia placenta and Coniophora puteana and beech could be partly protected against decay by C. puteana and Trametes versicolor. Full protection was achieved by some silicons for Scots pine sapwood against C. puteana and for beech against T. versicolor. The most promising products were a solvent-based mixture of the alkoxysilanes methyltrimethoxysilane (MTM) and octyltriethoxysilane (OTES) and a water-based micro-emulsion of polydimethylsiloxane (PDMS) and triethoxysilane (TES) when applied above 20 and 30% weight gain for Scots pine and above 30 and 40% weight gain for beech. A water-based mixture of dimethylmethylhydrogen siloxane (DMS) and N-octyltriethoxysilane (n-OTES) was able to protect beech at weight gains above 30%.     

Bacterial,nutrients and heavy metal ions pollution assessment along the eastern coastal area of the United Arab Emirates

A program to monitor nutrients and heavy metal ions concentrations in addition to selected bacterial communities counts was carried out at three sites along the eastern coast of the United Arab Emirates on the Gulf of Oman. Total saprophytic bacteria (TSB), salt tolerant saprophytic bacteria (STSB), Gram-negative bacteria (GNB), total coliform (TC), and faecal coliform bacteria (FC) were enumerated. The concentrations of heavy metal ions including Mn, Fe, Pb, Cd, Zn, Cr, Ni, Co and Cu were determined by atomic absorption spectrometry. Bacterial counts had a distinct pattern with peaks in mid spring (May) and in autumn (October). The TSB, STSB and the GNB ranges fluctuated between, 3.3 × 10⁴ to 4 × 10⁵, 1.8 × 10⁴ to 2.5 × 10⁵ and 0.7 × 10⁴ to 1.3 × 10⁵ colony forming units (CFU) ml^–1, respectively. Total and faecal coliform bacteria fluctuated depending on several factors including the presence of nearby recreation and commercial areas, but were at no time consistently high.Bacillus, Pseudomonas, Staphylococcus, Micrococcus and Alteromonas, were the predominant bacterial genera in these waters. Major nutrients and trace heavy metal ions concentrations were within the normal ranges for sea water with occasional sharp fluctuations in some sites. It was generally concluded that the area is slightly polluted.     

Woody tissue maintenance respiration of four conifers in contrasting climates

We estimate maintenance respiration for boles of four temperate conifers (ponderosa pine, western hemlock, red pine, and slash pine) from CO₂ efflux measurements in autumn, when construction respiration is low or negligible. Maintenance respiration of stems was linearly related to sapwood volume for all species; at 10°C, respiration per unit sapwood volume ranged from 4.8 to 8.3 mol CO₂ m^–3 s^–1. For all sites combined, respiration increased exponentially with temperature (Q ₁₀ =1.7, r ²=0.78). We estimate that maintenance respiration of aboveground woody tissues of these conifers consumes 52–162 g C m^–2 y^–1, or 5–13% of net daytime carbon assimilation annually. The fraction of annual net daytime carbon fixation used for stem maintenance respiration increased linearly with the average annual temperature of the site.     

Airborne concentrations of bacteria and fungi in Thailand border market

Thailand border market is where the local Thais, Cambodians, Laotians, and Burmeses exchange their goods and culture at the border checkpoints. It is considered to be the source of aerial disease transmission especially for foreigners because it is always very crowded with people from all walks of life. Unhealthy air quality makes this area high risk of spread of airborne diseases. This study assessed airborne concentrations of bacteria and fungi in a border market to improve exposure estimates and develop efficient control strategies to reduce health risk. The density and distribution of airborne bacteria and fungi were investigated in the Chong Chom border market in Surin Province, Thailand. Eighteen air sampling sites were taken from outdoors and various work environments including indoor footpaths, wooden handicraft shops, electronic shops, the secondhand clothing shops, and fruit market areas. Exposed Petri plate method and liquid impinger sampler were used for sampling at the breathing zone, 1.5 m above the floor level, during weekend and holiday. Meteorological factors such as relative humidity, temperature, and light intensity were collected by portable data logger. The relative humidity was 67–73%, and temperature 29–33°C, and light varied between 18 and 270 Lux m⁻². Gram-positive and Gram-negative bacteria were found at a mean value of 10⁴ CFU m⁻³, and airborne fungi of 10³ CFU m⁻³ were recorded. The highest concentration of culturable airborne microorganisms was found along the indoor footpath (9.62 × 10⁴ CFU m⁻³ and 750.00 CFU/plate/h for impingement and sedimentation methods, respectively), the fruit market area (7.86 × 10⁴ CFU m⁻³ and 592.42 CFU/plate/h for impingement and sedimentation methods, respectively), and the secondhand clothing shop (4.59 × 10³ CFU m⁻³ and 335.42 CFU/plate/h for impingement and sedimentation methods, respectively) for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The lowest concentration of Gram-positive bacteria, Gram-negative bacteria, and fungi was found only at the outdoor area at 1.53 × 10⁴ CFU m⁻³, 0.93 × 10⁴ CFU m⁻³ and 0.80 × 10³ CFU m⁻³ by means of impingement method and 136.67 CFU/plate/h, 69.25 CFU/plate/h, and 62.00 CFU/plate/h by means of sedimentation methods for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The most frequently present airborne bacteria were identified as Bacillus, Corynebacteria, Diplococcus, Micrococcus, Acinetobacter, Alcaligenes, Enterobacter, and spore former rods. Acremonium, Aspergillus, Cladosporium, Penicillium, and Sporotrichum were the most frequently found aerosol fungi genera. The distribution of airborne microorganisms correlated with relative humidity and light factors based on principal component analysis. In conclusion, the border market is a potential source of aerial disease transmission and a various hazards of bioaerosols for workers, consumers, sellers, and tourists. The bioaerosol concentration exceeded the standard of occupational exposure limit. Many major indicators of allergenic and toxigenic airborne bacteria and fungi, Acinetobacter, Enterobacter, Pseudomonas, Cladosporium, Alternaria, Aspergillus, and Penicillium, were found in the various market environments.     

The lethal effects of gamma irradiation on larvae of the Huhu beetle, Prionoplus reticularis: a potential quarantine treatment for New Zealand export pine trees

Gamma irradiation was investigated as a possible method for disinfestation of huhu beetle larvae, Prionoplus reticularis White, in Pinus radiataD. Don. Larvae of four representative size classes were irradiated at six doses, and the lethal dose (LD₉₉) calculated from mortality data 3 days and 10 days post treatment. All larval size classes showed a similar sensitivity to gamma irradiation and required 3677 Gray (Gy) and 2476 Gy for a LD₉₉ 3 and 10 days post-treatment, respectively. The penetration of gamma irradiation into pine wood was found to be lowest in freshly cut logs, and decreased linearly at a rate of 0.698 Gy mm^–1 of wood. The penetration was greatest in wood that had been stored for 2 years, and decreased 0.512 Gy mm^–1 of wood. These results are likely to be correlated with wood moisture content. Gamma irradiation appears to be a potential alternative method to fumigation for quarantine treatment of P. reticularis.     

Air biocontamination in a variety of agricultural industry environments in Egypt: a pilot study

Inhalation of airborne microorganisms and organic dust is an occupational concern among workers in agricultural industries. Airborne microorganisms and particulate matter samples were collected from poultry house, flourmill, textile, and food industry sites by use of liquid impinger and gravimetric samplers. Particulate matter concentrations were recorded at median concentrations of 1.56, 1.92, 4.39, and 0.7 mg/m³ in the occupied poultry house, textile, flourmill, and food indoor working environments, respectively. The highest median particulate matter concentration (27.9 mg/m³) was detected at the flourmill’s stack site. The highest median indoor concentration of culturable airborne bacteria (6.23 × 10⁵ CFU/m³) was found at the occupied poultry-house site and the lowest concentration (4.6 × 10³ CFU/m³) was found at the food industry site. The highest median indoor concentration of culturable airborne fungi (3.15 × 10⁴ CFU/m³) was found at the flourmill site whereas the lowest (1.24 × 10³ CFU/m³) was found at the textile industry site. Bacillus and Staphylococcus were the predominant Gram-positive bacteria whereas Acinetobacter and Klebsiella were the predominant Gram-negative bacteria. Escherichia coli and Salmonella were only detected in the indoor air at the poultry house site. Aspergillus flavus, Aspergillus niger, Penicillium, and yeast were the predominant fungal types at flourmill, textile, food industry, and poultry house, respectively. Workers were continuously exposed to airborne microorganisms at a median value of 10⁴ CFU/m³ in all the industries studied.     

Deposition of ammonia to the forest floor under spruce and beech at the Höglwald site

Laboratory and field measurements of the flux of ammonia to forest floor canopies of spruce and beech stands at the Höglwald site in southern Bavaria are reported. Measurements were performed with an open chamber method. A linearity between ammonia concentration and ammonia flux from the atmosphere to the ground floor canopy was detected. Deposition of ammonia showed no saturation even at air concentrations up to 50 g NH₃ m^–3 air. Temperature, water content and the moss layer of the ground floor canopy had a minor influence on the deposition velocity in laboratory experiments. Deposition velocity of ammonia was higher to the spruce (1.3 cm s^–1), and limed spruce ground floor canopy (1.17 cm s^–1) compared to the beech stand (0.79 cm s^–1). In field studies, a diurnal course of the deposition velocity was detected with highest velocities in midday and minor during night times, but not in the climatic chamber. The flux of ammonia to the ground floor canopy was estimated of app. 10 kg N ha^–1 yr^–1 for the soil under spruce, 9 kg N ha^–1 yr^–1 for the limed spruce and 6 kg N ha^–1yr^–1 for the soil under beech. The fluxes are interpreted as fluxes from the atmosphere to the ground canopies of the stands.     

Comparative durability of untreated wood in use above ground

Cross-brace units constructed of 10 different softwoods and nine different hardwoods were exposed on a test fence in Wisconsin for up to 22 years. Sapwood was included for all species and heartwood for some. The objective of this study was to determine the above-ground longevity of these woods against decay. The wood was classified into above-ground decay resistance groups. The longevity spans apply only to structural components similar in cross-sectional size to the test units used in this study. Millwork and fencing components may fit into this category. Woods estimated to last more than 20 years above ground, and thus classified as most resistant, included the heartwood of Douglas-fir, western white pine, redwood, Eucalyptus sp., red and white oak, lodgepole pine, ponderosa pine, western red cedar, and the sapwood of redwood, white oak, and red oak. No woods fell into the nonresistant class ( 7 years expected average life). The remaining woods were classified moderately resistant or resistant based upon service lives of 8 to 13 and 14 to 19 years, respectively.     

Evaluation of bio-aerosols at an animal feed manufacturing industry: A case study

Both total and biological particles (totalculturable bacteria, Gram negative bacteria,mold and actinomycetes) were measured at ananimal feed manufacturing industry. Suspendedparticle concentration ranged from 1.72 to2.3 mg m^–3 with a mean value of1.97 mg m^–3. Airborne microorganisms weredetected in lower concentrations than thoseassociated with suspended dust andfeed-materials. Bacterial concentrations weretwo to three times higher than concentrationsof mold and actinomycetes. Bacterialconcentrations averaged4.86 × 10³ cfu m^–3; 2.6 × 10⁴cfu m^–3 and 3.96 × 10⁷ cfu g^–1 inair, associated with suspended dust andfeed-materials, respectively, whereas moldconcentrations averaged 7.33 × 10²cfu m^–3; 1.97 × 10³ cfu m^–3 and7 × 10⁵ cfu g^–1 of the correspondingenvironments, respectively. Enterobacterspp and Klebsiella spp were the mostabundant Gram negative bacteria, whereas Bacillus species. were the most dominant Grampositive bacteria. Aspergllius niger,other Aspergillus species and Penicillium were the dominant mold isolates.Acremonium was only detected in feedmaterials, whereas Aspergillus fumigatuswas only detected in air. The animal feedindustry environment has a significantbio-contamination and many of microorganismsimplicated in respiratory problems weredetected in this environment.     

Heartwood and sapwood development within maritime pine (<Emphasis Type="Italic">Pinus pinaster </Emphasis>Ait.) stems

Heartwood and sapwood development in maritime pine (Pinus pinaster Ait.) is reported based on 35 trees randomly sampled in four sites in Portugal. It was possible to model the number of heartwood rings with cambial age. The heartwood initiation age was estimated to be 13 years and the rate of sapwood transformation into heartwood was 0.5 and 0.7 rings year^–1 for ages below and above 55 years, respectively. Reconstruction of heartwood volume inside the tree stem was made by visual identification by image analysis in longitudinal boards along the sawn surfaces. This volume was integrated into the 3D models of logs and stems developed for this species representing the external shape and internal knots. Heartwood either follows the stem profile or shows a maximum value at 3.8 m in height, on average, while sapwood width is greater at the stem base and after 3 m remains almost constant up the stem. Up to 50% of tree height heartwood represents 17% of stem volume, in 83-year-old trees and 12–13% in 42 to 55-year-old trees. Tree variables such as stem diameter, DBH and tree total height were found to correlate significantly with the heartwood content.     

Pine stumps act as hotspots for seedling regeneration after pine dieback in a mixed natural forest dominated by <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>

Over the past few decades, rural forest ecosystems in Japan have experienced dynamic vegetation changes due to forest dieback and changes in land use, leading to the loss of local species populations and biodiversity. The aim of this study was to evaluate the importance of pine (Pinus densiflora) stumps and logs for tree seedling regeneration in a mixed natural forest in Kyoto Prefecture, Japan, that had previously experienced severe pine dieback, and to determine which factors most greatly affect seedling establishment. Seedlings of 17 tree species were recorded on pine stumps and logs in later stages of decay, among which Chamaecyparis obtusa and Rhododendron reticulatum were most dominant. Both of these species had a greater density on pine stumps than on logs or soil, despite stumps covering less than 0.5% of the study area. In addition, the seedling densities of both species were positively associated with moss cover on coarse woody debris, but negatively associated with wood pH. Brown rot in the sapwood and heartwood, which occurred more frequently in stumps than in logs, also positively associated with the seedling densities of both species. Predictive modelling showed that C. obtusa seedlings exhibited a stronger response to pH in stumps than in logs. Therefore, since brown-rotted wood is acidic due to fungal decay activities, brown-rotted pine stumps may present hotspots of C. obtusa seedling regeneration at the study site.     

The relationship between wood litter infall and relative abundance and feeding activity of subterranean termites Reticulitermes spp. in three southeastern coastal plain habitats

We estimated the densities of termites in dead wood using a point-quarter technique in four habitats: pine plantations subject to control burning and unburned, lowland hardwood forest, and turkey oak woodland. The burned pine plantation had the highest estimated termite density, 13×10⁶·ha^-1 unburned pine plantation and lowland hardwood had estimated densities of 2.6×10⁶·ha^-1 and 2.2×10⁶·ha^-1, respectively, and the turkey oak woodland had an estimated densities of 61.9×10³·ha^-1. There were varying percentages of Reticulitermes flavipes and R. virginicus in the various habitats. There was nearly linear increase in percentage of pine blocks attacked by termites in the pine and hardwood forests and by the end of the growing season, nearly all had been channelized by termites. In the turkey oak habitat 70% of the pine blocks were channelized. Termites removed between 3% and 12% of the original mass of over one-fourth of the pine blocks during the growing season.Wood litter in fall was highest in the lowland hardwood forest: 2869 kg·ha^-1·yr^-1. Wood litter input in the long leaf pine plantation, 792 kg·ha^-1·yr^-1 was nearly equivalent to the three year average wood litter in fall in a Danish oak forest.     

Dietary‐driven variation effects on the symbiotic flagellate protist communities of the subterranean termite Reticulitermes grassei Clément

The ability of subterranean termites to digest lignocellulose relies not only on their digestive tract physiology, but also on the symbiotic relationships established with flagellate protists and bacteria. The objective of this work was to test the possible effect of different cellulose‐based diets on the community structure (species richness and other diversity metrics) of the flagellate protists of the subterranean termite Reticulitermes grassei. Termites belonging to the same colony were subjected to six different diets (natural diet, maritime pine wood, European beech, thermally modified European beech, cellulose powder and starvation), and their flagellate protist community was evaluated after the trials. All non‐treated sound woods produced similar flagellate protist communities that were more diverse and of high evenness (low dominance). On the contrary, flagellate protist communities from cellulose‐fed termites and starving termites were considered to be significantly different from all non‐treated woods; they were less diverse and some morphotypes became dominant as a consequence of flagellate protist communities having suffered major adaptations to these diets. The flagellate protist communities of untreated beech and thermally modified beech‐fed termites were considered to be significantly different in terms of abundance and morphotype diversity. This may be caused by a decrease in lignocellulose quality available for termites and from an interference of thermally treated wood with the chemical stability of the termite hindgut. Our study suggests that as a consequence of the strong division of labour among these protists to accomplish the intricate process of lignocellulose digestion, termite symbiotic flagellate protist communities are a dynamic assemblage able to adapt to different conditions and diets. This study is important for the community‐level alteration approach, and it is the first study to investigate the effects of thermally modified wood on the flagellate protist communities of subterranean termites.     

Exposure of agricultural workers to airborne microorganisms and endotoxin during handling of various vegetable products

Airborne concentrations of viablemicroorganisms and bacterial endotoxin were determinedduring 10 intramural agricultural activities includinghandling or processing of 6 kinds of vegetableproducts: grain, hay, horticulture seeds, herbs, flaxand potatoes. The median values of the concentrationof total viable microorganisms (bacteria + fungi)were within a range from 43.2 × 10³ CFU/m³at potato processing to 1240.0 × 10³ CFU/m³in small granaries, exceeding in 9 out of 10 cases thelevel of 10⁵ CFU/m³ suggested as aoccupational exposure limit (OEL). Many of theisolated bacteria and fungi were reported asallergenic and/or immunotoxic agents. The medianvalues of the endotoxin concentration ranged from0.0125 g/m³ at handling hay to54.9 g/m³ at crushing grain, exceeding in 5out of 7 cases the suggested OEL of0.1 g/m³. The high levels of exposure toairborne microorganisms and endotoxin found by thisstudy indicate a potential risk of occupationalrespiratory disorders among agricultural workers, mostly in those handling grain.     

Evaluation of ACQ-D treated Chinese fir and Mongolian Scots pine with different post-treatments after 20 months of exposure

The field test of alkaline copper quat-type D (ACQ-D) treated Chinese fir (Cunninghamia lanceolata Hook.) and Mongolian Scots pine (Pinus sylvestris Linn. var. mongolica Litv.) stakes after different post-treatments was performed in two test plots (Chengdu and Guangzhou, China). The ACQ-D treatments used two concentration levels (0.5 and 1.1%) and four different post-treatments: air drying for 1 month (AD), conditioning at 70 °C and 80% relative humidity for 24 h (HC), oven drying at 110 °C for 24 h (DO) and boiling in water for 15 h (HW). The decay and termite ratings of the stakes after 6 and 20 months of exposure were recorded according to the method described in AWPA standard E07-07. The copper retention and compression strength parallel to grain before and after exposure were also compared. The results showed that Chinese fir had slightly better natural durability than Mongolian Scots pine but the untreated sapwood stakes for both wood species were mostly destroyed after 20 months exposure. After ACQ-D treatment, the sapwood of both wood species showed much better biological performance. Among the four post-treatments, HC exhibited the best performance by showing excellent biological resistance, less copper depletion and a slight reduction in compression strength after 20 months outdoor exposure. While the performance of the other post-treated stakes were impaired heavily in some cases in terms of wood species, test plots and the concentration levels of ACQ-D solutions. Furthermore, the study confirms that ACQ-D treated plantation-grown Chinese fir could be used for outdoor above ground and ground-contact applications.     

Airborne dust,bacteria, actinomycetes and fungi at a flourmill

A study was carried out on suspended dust, bacterial and fungal aerosols in a four-storey flourmill building located in Giza, Egypt. Airborne microorganisms were quantitatively isolated using liquid impinger and gravimetric samplers during the period from March 2004 to February 2005. Suspended dust varied from 1.96 to 16.3 mg m⁻³ and 0.69 to 1.8 mg m⁻³ in the indoor and outdoor environments, respectively. Suspended dust was significantly greater (P < 0.05) at bran package, double roller, purifiers and flour storage units in comparison to the outdoor reference site. The dust levels exceed the occupational exposure limit (OEL) of 0.5 mg m⁻³ for flour dust. Airborne microbial counts were found at median values, between sampling locations, ranged from 0 to >10⁴ CFU m⁻³. Gram-negative bacteria were found in small numbers (0–10² CFU m⁻³). The highest concentration of actinomycetes (>10³ CFU m⁻³) was detected in the storage unit. Airborne fungal counts were found at the median values, between sampling locations, varied from 10³ to 10⁴ CFU m⁻³. The counts of airborne bacteria and fungi were significantly greater (P < 0.05) at the purifiers and double roller mill units in comparison to the outdoor reference site using the liquid impinger sampler. Microbial levels associated with bulk deposited dust averaged between 10⁵ and 10⁶ CFU g⁻¹. Alcaligenes (5.4%) Pseudomonas (3.87%) and Enterobacter (3.1%) were the predominant Gram-negative species while Bacillus (29.4%) and Micrococci (13.9%) were the major components of Gram-positive bacteria. Aspergillus and Penicillium were the predominant fungal types indoor whereas Cladosporium (35.2%) and Aspergillus species (22.2%) were the predominant fungal types outdoor. A number of allergenic and toxigenic bioaerosols were found in the flourmill workplace.     

Growth promotion of Prunus rootstocks by root treatment with specific bacterial strains

A collection of bacterial strains obtained from a wide-range origin was screened for ability to promote growth in two types of Prunus rootstocks in a commercial nursery. Only few strains promoted growth significantly and consistently, and a strong specificity for the rootstock cultivar was observed. Irrigation of plants with Pseudomonas fluorescens EPS282 and Pantoea agglomerans EPS427 significantly increased plant height and root weight of the plum Marianna 2624 and the peach–almond hybrid GF-677, respectively. Plant height showed a higher rate of growth in early stages of development (2.6–3.5 times the non-treated controls), but the effect decreased with plant age. However, in aged plants growth promotion was more significant on root weight (1.9 times the non-treated controls) than on plant height. The efficacy of growth promotion and the persistence of strains in the root environment were dependent on the bacterial inoculum concentration applied. Increases in root development were maximum at inoculum concentrations of up to 8 log₁₀ CFU ml^–1 (ca 10 log₁₀ CFU L^–1 of potting mix). Population levels at the optimum inoculum concentration were around 7 log₁₀ CFU g f.w.^–1 root material at early stages of development and decreased to 4 log₁₀ CFU g f.w.^–1 after several months of development. The best plant growth-promoting strains were very diverse in secondary metabolite production and antagonistic ability against several plant pathogens.     

Dead wood biomass and turnover time,measured by radiocarbon,along a subalpine elevation gradient

Dead wood biomass can be a substantial fraction of stored carbon in forest ecosystems, and coarse woody debris (CWD) decay rates may be sensitive to climate warming. We used an elevation gradient in Colorado Rocky Mountain subalpine forest to examine climate and species effects on dead wood biomass, and on CWD decay rate. Using a new radiocarbon approach, we determined that the turnover time of lodgepole pine CWD (340±130 years) was roughly half as long in a site with 2.5–3°C warmer air temperature, as that of pine (630±400 years) or Engelmann spruce CWD (800±960 and 650±410 years) in cooler sites. Across all sites and both species, CWD age ranged from 2 to 600 years, and turnover time was 580±180 years. Total standing and fallen dead wood biomass ranged from 4.7±0.2 to 54±1 Mg ha^–1, and from 2.8 to 60% of aboveground live tree biomass. Dead wood biomass increased 75 kg ha^–1 per meter gain in elevation and decreased 13 Mg ha^–1 for every degree C increase in mean air temperature. Differences in biomass and decay rates along the elevation gradient suggest that climate warming will lead to a loss of dead wood carbon from subalpine forest.Electronic Supplementary Material Supplementary material is available for this article at