Surface mould growth on wooden claddings – effects of transient wetting,relative humidity,temperature and material properties

ABSTRACT

Effects of climatic factors and material properties on the development of surface mould growth on wooden claddings were investigated in a laboratory experiment. Specimens of aspen (Populus tremula), Siberian larch (Larix Sibirica), American white oak (Querqus alba), Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and thermally modified pine were incubated in eight climatic chambers at specified wetting periods (2 or 4?h per day), relative humidity (58–86%) and temperature conditions (10–27°C). Surface mould growth was assessed weekly for 13 weeks, and the results were evaluated statistically using Generalized Estimating Equations logistic regression models. All tested climatic factors had significant effects on the mould growth, and there were significant differences between the materials. The ranking of the materials varied with temperature and over time. Aspen, pine sapwood and oak were overall most susceptible to mould growth, and thermally modified pine least susceptible. There were significant differences between sapwood and heartwood for pine and spruce. The effect of density was tested on the spruce heartwood material, but was not found to be significant. The results can be used to further develop prediction models for mould growth on wooden claddings.     

Shape stability of laminated veneer products – An experimental study of the influence on distortion of some material and process parameters

Abstract

A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. In this study, we have examined the influence of different UF-adhesive systems, adhesive distribution, and veneer properties such as species, moisture content, and fibre orientation. Two different species were studied: beech (Fagus silvatica L.) and birch (Betula pubescens Ehrh.). Distortion was determined directly after moulding and after storage in a changing relative humidity. The aim of the work was to study how the above-mentioned material and process parameters influence the distortion. The results show that the material and process parameters and the storage in a changing relative humidity had a clear impact on distortion. Fibre orientation, differences in moisture content between veneers, and the moisture gradient in the final product are identified in this study as being the most important parameters influencing the distortion and shape stability of laminated veneer products.     

Influence of moisture content on estimating Young’s modulus of full-scale timber using stress wave velocity

The effect of moisture content on the stress wave propagation velocity was investigated in order to estimate the Young’s modulus of full-scale timbers in an air-drying state using the measurement of stress wave propagation velocity above the fiber saturation point. Using Japanese cedar lumber, the velocity and the density under high-moisture condition and air-drying states were measured respectively; after measuring the modulus of elasticity in an air-drying state, the moisture content of each condition was measured. By performing numerical analysis on these data, the relationship between the moisture content and the rate of change of velocity of full-scale timbers was derived. This relationship was used to estimate the Young’s modulus of the timber in the air-drying state from the velocity in high-moisture condition. First, the velocity and the Young’s modulus in an air-drying state were estimated accurately from its density, moisture content and velocity under high-moisture condition. In cases where the density could not be measured, using the database of mechanical properties with the Monte Carlo simulation method, the Young’s modulus of the full-scale timber in an air-drying state might be estimated within 20% accuracy from its moisture content and velocity under high-moisture condition.     

Influence of local stand basal area on density and growth of regeneration in uneven‐aged Picea abies stands

In single‐tree selection, trees removed by harvest or lost through mortality are replaced by ingrowth from the seedling/sapling bank. Because the level of ingrowth is governed not only by the recruitment rate of new seedlings, but also by mortality and growth rates within the seedling/sapling stratum, knowledge of how these processes are related to the tree stratum is important for successful application of single‐tree selection. Therefore, Norway spruce (Picea abies (L.) Karst.) regeneration (0.1 m ≤ height ≤ 2.0 m) was measured on seventy 100 m² circular subplots at each of two sites in central and northern Sweden. Both sites had previously been selectively logged, but the time elapsed since the last harvest was at least 30 yrs. Basal area of trees of at least 2 m height within three different radii from the subplot centres was measured. Measurements on regeneration included height and leader length. Influence of local stand basal area on density and growth of regeneration was analysed by ordinary least‐squares linear regression for each of four height intervals. Regeneration was significantly aggregated at both sites, but number of Norway spruce seedlings and saplings per circular subplot was not correlated to local stand basal area. Out of 36 regressions, only eight showed a significantly (p < 0.05) negative correlation between seedling and sapling height growth and local stand basal area. In five of these cases, removal of one point (subplot) made p > 0.05. The results suggest that density and growth of Norway spruce regeneration in selectively logged uneven‐aged Norway spruce stands is affected more by ground conditions than by local stand basal area.     

Influence of Ammoniacal Copper Quaternary treatments on mechanical properties of blue-stained Lodgepole Pine wood

Three concentrations （2.8%, 2.0%, 1.2%） of Ammoniacal Copper Quaternary （ACQ） was selected to treat Lodgepole pine wood for evaluating ACQ treatment on mechanical properties of blue-stained wood. The bending modules of elasticity （MOE）, modules of rupture （MOR）, toughness and shearing strength parallel to grain on tangential surface, are tested according to the criteria GB1927-1943-91. Non-treated sample were also tested according to the same procedure. The results showed that the three groups specimen impregnated by different concentrations of ACQ solution met the AWPA standard 2003 of America （UC4A 6.4g/cm^3）. There were significant difference of toughness between treated wood and non-treated wood （p=0.01）, but there were no statistically significant differences among three concentrations in terms of toughness, and toughness of treated wood was approximately 20% lower than non-treated. MOR, MOE as well as sheafing strength parallel to grain were found to be not significantly different between treated wood and non-treated one, and there were no statistically significant difference among three concentrations of ACQ too. Toughness, MOR, MOE and sheafing strength parallel to grain increased with decrease of concentration of ACQ, but they were hardly affected by ACQ preservatives.     

Influence of Raw Material and Mat-forming on Physical-mechanical Properties of Panels

China is one of the major production countries forwood-based panel products, and its production wasranked in the second place in the world in 2003. Onthe other hand, however, China is also a country withshortage of forest resources. As the main raw material,wood supply is becoming a serious problem with thefast growing of panel production. Fortunately, thereare plenty of agricultural residues in China, and thisgives the possibility to use agri-based fibers instead ofwood. Many wood-based pane…     

Influence of drought and salt stress on the growth of young Populus nigra ‘Italica’ plants and associated mycorrhizal fungi and non-mycorrhizal fungal endophytes

New Forests - Populus nigra ‘Italica’ (Lombardy poplar) is a breeding cultivar of black poplar, widely used as a street tree or windbreak, often exposed to salinity and limited water...     

Outdoor winter storage of container stock on raised pallets—effects on root zone temperatures and seedling growth

Containerized seedlings of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) were overwintered on the ground and above ground on pallets. Soil temperatures in elevated containers were lower and showed greater fluctuation than containers on the ground. The lowest temperatures (‐15 to ‐16°C) were observed in containers stored on pallets with little or no snow cover during the winter. Temperatures in the edge rows of containers were lower than interior bed soil temperatures. Lower temperatures were also observed in the top than in the bottom of the container. The storage on pallets resulted in reduced shoot and root growth. Although insulation preventing air movements beneath the container units improved soil temperature conditions and subsequent seedling growth, the best result was obtained when seedlings were stored directly on the ground surface.     

Physical-Mechanical Properties of Sympodial Bamboo and Influence on Architecture Material Manufacture

Bambooisoneofimportantreproduciblefast-growingforestresources.Itisattributedtoitsrapidgrowthrateandhighyield,andcanbeoflong-termutilizationwithonlyonceplantationandreasonablemanagement.Comparedwithwood,bamboohasgoodstrength,elasticityandhighstiffness.ForalongtimeitisusedasoneofimportantstructuralmaterialsinChinaandothercountriesinbamboo-producedregionsoftheworld.Intraditionalbamboostructuralutilization,thebamboologsareuseddirectly.Butasthelargevariationindiameterandcharacter,theyareusedonlyin…     

Effect of resin‐top disease caused by Peridermium pini on the volume and value of Pinus sylvestris saw timber and pulpwood

The role of the resin‐top disease caused by Peridermium pini in volume and value losses to Scots pine (Pinus sylvestris L.) was surveyed in two heavily infected stands in northern Finland. Of the Scots pines, 26% were infected by the disease. Peridermium pini caused 2% volume losses to saw timber trees and 3% volume losses to pulpwood trees in the stem‐lesion class and 10% and 14% in the dead‐top class, respectively. The disease caused saw timber volume losses to saw timber trees of 34% and 22% in the stem‐lesion and dead‐top class, respectively. However, saw timber volume losses increased the pulpwood volume in both disease classes. The disease reduced the marketing value of saw timber trees and pulpwood trees by 18% and 3% in the stem‐lesion class and by 15% and 14% in the dead‐top class.     

Succession of Soil Acidity Quality and its Influence on Soil Phosphorus Types

Succession rules of soil acidity quality of larch plantations in first rotation at different development stages, succession rules of soil acidity quality of young stand of larch plantations in second rotation and the relationship between soil acidity and various forms of organic phosphorus and inorganic phosphorus were studied in mountainous area of eastern part of Northeastern China. The results showed that active acidity (pH value) inrhizosphere soil decreased continually with stand age increasing from young stand, half-mature stand, near mature stand to mature stand, but active acidity (pH value) in non-rhizosphere soil, exchange acidity, exchangeable aluminium, total hydrolytic acidity, and the ratio of exchange acidity and total hydrolytic acidity in rhizosphere soil and in non-rhizosphere soil increased apparently; total organic P, moderately resistant organic P, and highly resistant organic P in soil decreased at all age stages in larch plantations when soil acidity added. For rhizosphere soil of     

Effect of planting density on plant growth and camptothecin content of Camptotheca acuminata seedlings

C. acuminata seedlings cultivated in greenhouse were transplanted into the fields with 5 designed planting densities (11, 16, 25, 44 and 100 plants·m⁻²) in May of 2004 and were harvested in the middle of September of 2004. The seedling growth indexes including plant height and crown width, biomass allocation, camptothecin (CPT) content and CPT yield of different organs (young leaf, old leaf, stem, and root) were studied. For the 5 selected planting densities, the plant biomass, height, crown width, and total leaf area ofC. acuminata seedlings all showed highest values at the planting density of 25 plants·m⁻². CPT content in young leaves was higher than that in other organs of seedlings and presented an obvious change with the variation of planting densities and with the highest value at density of 100 plants·m⁻², while for other organs no significant variation in CPT content was found with change of planting density. The accumulation of CPT was enhanced significantly at the planting density of 25 plants·m⁻². It is concluded that for the purpose to get raw materials with more CPT fromC. acuminata, the optimal planting density ofC. acuminata seedlings should be designed as 25 plants·m⁻². Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 3970086) and Heilongjiang Province Foundation for Distinguished Youth Scholars (JC-02-11) Biography: Wei Huan-yong (1978-), male, Graduate in College of Life Sciences, Northeast Forestry University, Harbin 150040, P. R. China. Responsible editor: Zhu Hong     

Effects of phosphorus and potassium addition on growth and nodula- tion of Dalbergia sissoo in the nursery

A study was conducted to test the influence of different inorganic fertilizers （phosphorous and potassium） on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combinations of P, K fertilizers were incorporated with the nutrient-deficient natural forest soils, and then amended with cowdung （soil： cowdung = 3：1）. Nodulation status （nodule number, shape, fresh weight, dry weight and color） in the roots and the plant growth parameters （length of shoot and root, collar diameter, fresh and dry weight of shoot and root） were recorded 60 days after seeds sowing. Nodulation status and growth of the plants varied significantly （P〈0.05） in the soils amended with fertilizers in comparison to the control. The highest nodule number （62）, fresh （0.50 g） and dry （0.07 g） weights were recorded with the dose of PK at the rate of 160 kg/hm2. Nodule shape and color also varied widely in different treatments. In case of plant growth parameters, shoot and root length, collar diameter, fresh and dry weight of the plants took on a significant difference （P〈0.05） among various combination of fertilizers. From the study, it is revealed that PK at the rate of 160 kg/hm^2 fertilizer with soil and cowdung mixture （soil： eowdung = 3：1） is recommended for optimum growth and nodule formation of D. sissoo in degraded soils at a nursery level.     

Freezing temperatures in the root zone—effects on growth of containerized Pinus sylvestris and Picea abies seedlings

Roots of 1‐year‐old containerized seedlings of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) were experimentally frozen in December. The seedlings were then grown for 3 weeks in a growth chamber and evaluated with regard to root growth capacity (RGC) and shoot elongation. The subsequent RGC of Scots pine declined as root zone temperatures were lowered from ‐6°C to ‐11°C and from ‐11°C to ‐16°C. Almost no root growth was observed after exposure to ‐20°C. Shoot growth was also negatively affected by low root temperatures but less than root growth. Low root temperatures did not affect Norway spruce as much as Scots pine, although root and shoot growth of Norway spruce were reduced after exposure to the lowest test temperatures (‐16°C and ‐20°C). The length of exposure, ranging between 1 and 8 hours had no effect on subsequent growth.     

Influence of volcanic ash deposits on the radial growth of trees in Central Mexico: the case of Parícutin volcano

The impact of volcanic eruptions on humans and infrastructure has been significant and widely documented. However, the impact on forests covered by ash or tephra has not been as widely known or documented. This research evaluated the ashfall effects of the 1943–1952 Parícutin eruption on the radial growth of trees located near the top and flanks of the Tancítaro stratovolcano, ca.10 km southwest of the Parícutin volcano. We carried a dendrochronological sampling out in a temperate forest dominated by Pinus hartwegii and Abies religiosa trees. A ring-width chronology was built with 68 increment cores from 47 trees showed two statistically significant suppression events. The first event occurred from 1943 to 1946; it was caused by falling ash of the eruptive columns from Parícutin during the first 6 months of its eruption (February–June 1943). The second event occurred from 1818 to 1823, and it is attributed to the 1818 eruption of Volcán de Colima. The 1943–1946 suppression event observed in the tree rings demonstrates that trees are useful as palaeoenvironmental archives to evaluate the influence of volcanic eruptions in recent centuries in the Trans-Mexican Volcanic Belt. Our results indicate that falling ash immediately impacted the growth of trees in intertropical mountain zones of the Michoacan state located in the Michoacán-Guanajuato Volcanic Field. Such impact means that future eruptions may cause damage to crops and trees at the local and regional levels. Our findings contribute to evaluating volcanic hazards and risks in areas with active volcanoes and monogenetic volcanic fields.

     

Effects of sludge on germination and initial growth performance of Leucaena leucocephala seedlings in the nursery

A study was carried out to determine the influence of different types of sludges （municipal, industrial and residential） on field germination, growth and nodulation of L. leucocephala seedlings in the nursery. Before sowing of seeds, different combinations of sludges were incorporated with the nutrient deficient natural forest soils. Field germination, nodulation status and physical growth parameters of seedlings （shoot and root length, vigor index, collar diameter, leaf number, fresh and dry weight of shoot and root and total dry biomass increment） were recorded after three and six months of seed sowing. Field germination, nodulation status and growth parameters were varied significantly in the soil amended with sludges in comparison to control. The highest number of nodule was recorded from soil amended with residential sludge （ 1：1 ） and highest fresh and dry nodule weight was also found from the same combination in both three and six month old seedlings. In case of growth parameters, the highest growth was recorded from soil and residential sludge （ 1：1 ） combination compared to control. From the study, it can be recommended that soil amended with residential sludge （ 1：1 ） provide better field germination, growth and nodule formation of L. leucocephala in degraded soil.     

Investigation on physical and mechanical properties of pulp–plastic composites from bagasse

High-density polyethylene (HDPE), bagasse fibers treated by four pulping processes (AS-AQ (alkaline sulfite anthraquinone), SODA-AQ (soda anthraquinone), MEA (monoethanolamine) and chemical–mechanical pulping (CMP)), three levels of nano-SiO₂ (0, 2, and 5?wt%), and maleic anhydride polyethylene as coupling agent were used to produce pulp–plastic composites (PPCs) by injection molding. The physical and mechanical properties of corresponding composites were evaluated according to ASTM standards. The results showed that compared to untreated bagasse/HDPE composite, the addition of bagasse pulp fibers increased significantly the mechanical properties such as tensile strength and modulus, flexural strength and modulus, and hardness. The chemical pulps-reinforced composites showed better mechanical strengths than that of CMP-reinforced composites, but in some properties, CMP pulp composites have comparable results to the chemical pulp-reinforced composites. Natural fibers (untreated and treated) increased water absorption and thickness swelling of composites compared to pure HDPE. The addition of nano-SiO₂ particles showed both increasing and decreasing trends on physical and mechanical properties ofPPCs.     

Allelopathic effects of Lantana camara on germination and growth behavior of some agricultural crops in Bangladesh

An experiment was conducted to understand the growth inhibitory effects of aqueous extracts derived from Lantana camara L. （a globally recognized invasive alien weed） on six popular agricultural crops of Bangladesh. The test was conducted in sterilized petridishes with a photoperiod of 24 hours and an average temperature of 29℃. The effect of different concentrations ofL. camara leaf extracts were recorded and compared with control （i.e., distil water）. Result showed different concentrations of aqueous leaf extracts caused significant inhibitory effect on germination, root and shoot elongation and development of lateral roots of receptor crops. Bioassays also indicated that the inhibitory effect was proportional to the concentrations of the extracts and higher concentration had the stronger inhibitory effect whereas the lower concentration showed stimulatory effect in some cases. The inhibitory effect was much pronounced in root and lateral root development rather than shoot and germination.