Diversity and Interactions of Wood-Inhabiting Fungi and Beetles after Deadwood Enrichment

• Published: November 24, 2015
• http://dx.doi.org/10.1371/journal.pone.0143566

Abstract

Freshly cut beech deadwood was enriched in the canopy and on the ground in three cultural landscapes in Germany (Swabian Alb, Hainich-Dün, Schorfheide-Chorin) in order to analyse the diversity, distribution and interaction of wood-inhabiting fungi and beetles. After two years of wood decay 83 MOTUs (Molecular Operational Taxonomic Units) from 28 wood samples were identified. Flight Interception Traps (FITs) installed adjacent to the deadwood enrichments captured 29.465 beetles which were sorted to 566 species. Geographical ‘region’ was the main factor determining both beetle and fungal assemblages. The proportions of species occurring in all regions were low. Statistic models suggest that assemblages of both taxa differed between stratum and management praxis but their strength varied among regions. Fungal assemblages in Hainich-Dün, for which the data was most comprehensive, discriminated unmanaged from extensively managed and age-class forests (even-aged timber management) while canopy communities differed not from those near the ground. In contrast, the beetle assemblages at the same sites showed the opposite pattern. We pursued an approach in the search for fungus-beetle associations by computing cross correlations and visualize significant links in a network graph. These correlations can be used to formulate hypotheses on mutualistic relationships for example in respect to beetles acting as vectors of fungal spores.

Figures

Citation: Floren A, Krüger D, Müller T, Dittrich M, Rudloff R, Hoppe B, et al. (2015) Diversity and Interactions of Wood-Inhabiting Fungi and Beetles after Deadwood Enrichment. PLoS ONE 10(11): e0143566. doi:10.1371/journal.pone.0143566

Editor: Petr Karlovsky, Georg-August-University Goettingen, GERMANY

Received: August 14, 2015; Accepted: November 8, 2015; Published: November 24, 2015

Copyright: © 2015 Floren et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Data Availability: MOTU reference sequences are available from the International Nucleotide Sequence Database Collaboration portals or the DNA Data Bank of Japan under accessions LC015665–LC015745.

Funding: The work has been funded by the DFG Priority Program 1374 "Infrastructure-Biodiversity- Exploratories" (grants LI 150/22-1 and KR 3587/3-2) and also supported through the Helmholtz Interdisciplinary Graduate School for Environmental Research (HIGRADE). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Deadwood is an important habitat and structural component in forest ecosystems developing often into biodiversity hotspots. It provides shelter and nutrition to various organisms, primarily fungi and saproxylic insects [1–3]. Wood-inhabiting fungi are key players in forest ecosystems due to their ability of decomposing wood, recycling nutrients and initiating a successional dynamic for saproxylic arthropods [4,5]. Many studies have focused on the effects of resource availability for fungal and beetle communities [6,7] and how communities are affected by anthropogenic disturbance [8–10]. The amount and quality of deadwood have been shown to be crucial for saproxylic organisms [11–13]. As deadwood availability is greatly influenced by forest management type the interrelation of these factors and their impacts on biodiversity and ecosystem functioning has become a major topic in research [14,15].

Recent findings indicate that wood-inhabiting fungi can discriminate forest types [16,17]. This is remarkable because spores are usually assumed to be dispersed easily in forests although studies suggest that some wood-inhabiting fungi might actually be dispersal limited [4,18]. This raises questions about the mechanisms determining the spatial distribution of fungi. Recent research hints towards the role of arthropods as vectors for fungal spores [19]. For example, investigations indicated that bark beetles facilitate the establishment of wood-inhabiting fungi [20,21]. Although the role of zoochory has been considered low besides for mutualistic relationships [22,23,24] more and more studies indicate that vectoring insects can influence fungal community composition [19,20]. However, examples of effective insect vectors refer mostly to economically important associations like those between bark beetles (Scolytidae) or plant wasps (Symphyta) and their fungal associates [25,26]. The role of saproxylic arthropods in the process of wood decay is more controversially discussed [27]. Saproxylic arthropods are mainly considered to mechanically reduce wood to small pieces extending the surface area and allowing microorganisms to decompose woody material more easily [28]. Fungal spore transport might be of greater importance in this context by influencing fungal community composition and thereby also the effectivity of wood decomposition [5,19,29]. Apart from the importance the arthropods play for the colonisation of wood-decaying fungi priority effects during the colonisation of fungi might also lead to the establishment of differently structured fungi communities thus influencing the succession of saproxylic arthropods [30]. Other fungus-beetle relationships could be even more sophisticated. For example, fungal volatiles may also attract beetle species influencing beetle community composition [31]. Such relationships are little investigated topics in research.

Our research aims to narrow this gap of knowledge by analysing how wood-inhabiting fungi and beetle assemblages respond to local habitat conditions and to what extent both groups show similar patterns in vertical stratification (ground–canopy) as suggested in earlier investigations [32,33]. We also test for the effects of forest management on assemblage composition and ask how sensitive taxa respond to changing environmental conditions. Finally, we use the abundance data for a cross-correlation in order to search for possible indications of fungus-beetle associations. In this context, our study can be only seen as a precursor step for a subsequent detailed screening for species interactions.

Material and Methods

Study sites

Research was performed in three distant regions of Germany that were established within the “Biodiversity Exploratories” project [34]. These were the UNESCO Biosphere Reserve Swabian Alb (Alb) in South-West Germany, the Hainich-Dün exploratory containing the UNESCO World Heritage at Hainich Mountains and adjacent areas such as the Dün Mountains in Central Germany (Hainich) and the UNESCO Biosphere Reserve Schorfheide-Chorin (Chorin) in North-East Germany (S1 Fig). Distance between each region from South to North is approximately 300 km. All regions are further characterized by different representative soil types (Schwabian Alb: Cambisol/Leptosol; Hainch-Dün: Luvisol/Stagnosol; Schorfheide-Chorin: Cambisol). In each region several beech forests managed with differing intensities were selected. Three types of land use intensity were distinguished, 1) forests left unmanaged for 20–70 years (unm), 2) forests from which only individual trees or small groups are harvested resulting in an uneven age-structure (ext) without further invasive management activities in order to restore structurally more complex beech stands and 3) age-class forests (acf) which are characterised by uniform tree species composition, forest structure and site conditions. The latter forests are managed for efficient timber extraction in 60 to 100 years intervals. Altitudes vary between 600–860 m a.s.l. in the Alb, 290–550 m in Hainich and 3–140 m in Chorin. Annual mean precipitation is between 700–1000 mm in the Alb and 500–800mm in the other areas while the range of mean temperature lies between 6–8.5°C. Landscapes consist of a small-scale mosaic of grasslands and forests with European beech (Fagus sylvatica) as economically most important deciduous tree species. Within these landscapes a total of 16 forest plots were selected (S2 Fig) which were separated from each other by several kilometres of open land or other forests.

Deadwood enrichment

Deadwood was artificially enriched in the canopy and near the ground of a single study tree in each forest plot in 2009 (S2 Fig). All wood was taken from a single freshly felled forest stand of each of the three areas to keep the experimental set up, like existing endophytic fungi, as comparable as possible. Sterilisation of the freshly cut deadwood was not possible due to the amounts used in the experiment. At the time of this investigation the deadwood had been left decomposing already for two years. The experimental set-up was based on the assumption that amounts of deadwood are too low to sustain functionally diverse communities of saproxylic arthropods. It has been extensively described in Floren et al. [32] so that we provide only basic information here. The enrichment experiment used three log sizes (diameters 1–5 cm, 6–10 cm, 11–20 cm). In the canopy, bundles of dead-wood were fixed at the trunk with wire mesh and steel rope at 22 m, 18 m and 16 m height (smallest size on top and largest size below). Each size of deadwood contained about 0.2 m3 so that the total amount was 1.2 m3 per tree. In addition, three stacks of cut wood (each 1 m3) of the same three sizes were piled up on the ground beneath the study trees. Such large quantities were used to overcome resource limitation. Logs were placed on a wooden underlay to delay soil fungi from colonising. FITs were installed next to each deadwood bundle to continuously sample arthropods in a jar mounted at the bottom of each FIT. A 1.5% cuprum-sulphate solution was used as killing and conserving liquid. All traps were installed in February 2011 and emptied monthly from April to the end of September. Beetles from the two individual trees per plot were pooled for the analysis.

Collection of beetles and deadwood drill samples for identification of fungi

The following recordings aim at documenting the importance of colonizing arthropods and wood-inhabiting fungi during the decomposition of deadwood. Beetles were collected close to the deadwood that was artificially enriched in the canopy and near the ground of a single study tree in each forest plot in 2009 (S2 Fig). At the time of this investigation the deadwood had been left decomposing already for two years. Wood-inhabiting fungi were detected by molecular methods from drill samples obtained from the same logs that follow a procedure which is described in detail in [35]. Briefly, in 2011 wood chips from the deadwood logs of the experiment were sampled using an electronic drill machine. One drill core each was sampled from the large sized wood stack. To avoid contamination between samples, the wood auger was flamed and wiped with ethanol between each core. The wood samples were kept on dry ice and later stored at -80°C upon return to the lab.

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Behavior of the brown-rot fungus Gloeophyllum trabeum on thermally-modified Eucalyptus grandis wood

Floresta Ambient. vol.20 no.3 Seropédica July/Sept. 2013  Epub Sep 24, 2013

Comportamento do fungo de podridão pardaGloeophyllum trabeum na madeira de Eucalyptus grandis modificada termicamente

Fred Willians Calonego^I; Meire Cristina Nogueira de Andrade^II; Djanira Rodrigues Negrão^III; Cinthia Dias Rocha^I; Marli Teixeira de Almeida Minhoni^III; João Vicente Latorraca^IV; Elias Taylor Durgante Severo^I
IDepartamento de Ciência Florestal, Universidade Estadual Paulista - UNESP, Botucatu/SP, Brasil  

^IICentro de Ciências Exatas e Sociais Aplicadas, Universidade do Sagrado Coração - USC, Bauru/SP, Brasil  

^IIIDepartamento de Produção Vegetal, Universidade Estadual Paulista - UNESP, Botucatu/SP, Brasil  

^IVDepartamento de Produtos Florestais, Universidade Federal Rural do Rio de Janeiro - UFRRJ, Seropédica/RJ, Brasil

Autor(es) para correspondência

ABSTRACT

In this study, we aimed evaluate the behavior of the brown-rot fungus Gloeophylum trabeum and white-rot fungus Pycnoporus sanguineus on thermally-modified Eucalyptus grandis wood. To this end, boards from five-year-eleven-month-old E. grandis trees, taken from the Duratex-SA company stock, were thermally-modified between 180 ºC and 220 ºC in the Laboratory of Wood Drying and Preservation at Universidade Estadual Paulista - UNESP, Botucatu, Sao Paulo state Brazil. Samples of each treatment were tested according to the ASTM D-2017 (2008) technical norm. The accelerated decay caused by the brown-rot fungus G. trabeum was compared with the decay caused by the white-rot fungus P. sanguineus, studied by Calonego et al. (2010). The results showed that (1) brown-rot fungus caused greater decay than white-rot fungus; and (2) the increase in temperature from 180 to 220 ºC caused reductions between 28.2% and 70.0% in the weight loss of E. grandis samples incubated with G. trabeum.

Keywords: decay resistance, G. trabeum, heat-treated wood, eucalypts, rot fungi.

RESUMO

O objetivo deste estudo foi avaliar o comportamento do fungo de podridão parda Gloeophylum trabeum e do fungo de podridão branca Pycnoporus sanguineus sobre a madeira de Eucalyptus grandis modificada termicamente. Tábuas de árvores de E. grandis com cinco anos e 11 meses de idade, da empresa Duratex-SA, foram modificadas termicamente entre 180 ºC e 220 ºC no Laboratório de Secagem e Preservação de Madeiras da UNESP, Botucatu-SP, Brasil. Corpos de prova de cada tratamento foram testados, de acordo com a norma técnica ASTM D-2017 (2008). O apodrecimento acelerado causado pelo fungo de podridão parda G. trabeum foi comparado com o do fungo de podridão branca P. sanguineus, estudado por Calonego et al. (2010). Os resultados mostraram que (1) o apodrecimento causado pelo fungo de podridão parda foi maior que o de podridão branca e (2) o aumento da temperature de 180 para 220 ºC ocasionou reduções de 28,2% a 70,0% na perda de massa dos corpos de prova de E. grandis incubados com o G. trabeum.
Palavras-chave: resistência ao apodrecimento, G. trabeum, madeira tratada termicamente, eucalipto, fungos apodrecedores.

1. INTRODUCTION

The mechanism of wood degradation differs fundamentally between brown and white rot fungi. In general, the brown-rot fungi selectively removes cellulose and hemicelluloses compounds, whereas the white-rot fungi causes degradation of all cell wood components (Oliveira et al., 1986; Barreal, 1998). However, the white-rot fungus Pycnoporus sanguineus (L.) Murrill is a good producer of phenoloxidase, and preferentially degrades lignin (Esposito et al., 1993).

According to Oliveira et al. (1986), Barreal (1998) and Kleman-Leyer et al. (1992), the white-rot fungus attacks the surfaces of the microfibrils resulting in a progressive erosion of the polymers of wood. Yet, the brown-rot fungus completely cleaves the amorphous regions of the cellulose microfibrils, and subsequently, promotes significant loss in wood weight because of degradation in the crystalline region of the cellulose. At advanced stages of decay, the structural polysaccharides are quantitatively removed, and a modified lignin residue remains.

In general, the brown-rot fungi, including the species Gloeophyllum trabeum (Pers.) Murrill, produce extracellular hydrogen peroxide (H₂O₂) and oxalic acid (H₂C₂O₂), which react with the iron ions present in lignocelluloses materials. The hydroxyl radicals produced by the Fenton's reaction were suggested to explain the cleavage of long chain cellulose molecules into small fragments. Thus, there is an increase of porosity of the cell wall allowing penetration of cellulolytic enzymes, which increase the decay on wood (Goodell et al., 1997; Xu & Goodell, 2001; Arantes & Milagres, 2009; Watanabe et al., 2010; Aguiar & Ferraz, 2011). Dutton et al. (1993) showed that the brown-rot fungi secrete large amounts of oxalate in culture medium reducing the pH of the substrate compared with the white-rot fungi, which do not reduce the pH of medium.

In evaluating the natural biological resistance of Aspidosperma desmanthum, Parinari excelsa, Mouriri callocarpa, Marmaroxylon racemosum, Peltogyne paniculata and Astronium sp. woods to the brown-rot fungus G. trabeum and white-rot fungus Pycnoporus sanguineus, it was founded that the decay caused by brown-rot fungus was greater. The woods studied presented weight loss between 1.97% and 12.2% when decayed to G. trabeum, and between 0.05% and 3.21% to P. sanguineus after accelerated decay test of 6 weeks (Alves et al., 2006).

According to Andrade et al. (2012), Eucalyptus grandis wood then exposed to the white-rot fungi Ganoderma applanatum (Pers.) Pat., P. sanguineus, Lentinula edodes (Berk.) Pegler, and Pleurotus sajor-caju (Fr.) Singer for 8 weeks, presented weight loss of 34.0%, 29.0%, 27.5%, and 13.0%, respectively.

The biological durability of wood can be increased by impregnation with chemical products, but in general, this technique is not positively regarded. Thus, increasing the biological durability of wood by thermal modification is considered to be more acceptable (Homan et al., 2000).

In general, thermal treatments expose the timber to temperatures approaching 200 ºC for several hours, and change the chemical composition of wood. The equilibrium moisture content of wood and the availability of food (hemicelluloses) to fungi are reduced, new molecules that act as fungicides are produced, and there is a cross-linking between the lignin and the polymer from the thermal degradation of cellulose, making the recognition of the substrate by fungi difficult (Weiland & Guyonnet, 2003; Hakkou et al., 2006; Calonego et al., 2010, 2012; Severo et al., 2012).

In the accelerated decay test of Pinus pinaster untreated wood and wood that was thermally-modified at 230-260 ºC, and then exposed to the brown-rot fungus Poria placenta (Fr.) Cooke for 16 weeks, a weight loss of 17.13% and 9.76%, respectively, was verified. The respective weight losses of untreated and treated Fagus sylvatica were approximately 22.92% and 5.94% (Weiland & Guyonnet, 2003).

In tests of untreated Pinus radiata, Pinus syslvestris, Pseudotsuga menziesii and Picea abies woods exposed to the white-rot fungus C. versicolor and brown-rot fungus C. puteana, weight losses of 9% and 26%, 4% and 12%, 1% and 9%, and 12% and 19%, respectively, were observed. When the same woods were thermally-treated and exposed to the same rot fungi, weight loss was always less than 4% (Millitz & Tjeerdsma, 2001).

Momohara et al. (2003) thermally-modified Cryptomerica japonica heartwood at 150 ºC for 24 hours and concluded that the weight loss caused by the brown-rot fungus Fomitopsis palustris (Berk. & M.A. Curtis) Gilb. & Ryvarden, for 8 weeks in accelerated laboratory tests, was 30% in untreated wood and 10% in thermally-treated wood.

In the accelerated decay test of untreated Eucalyptus grandis wood and wood that was thermally-modified at 180º, 200º and 220 ºC, and then exposed to the white-rot fungus P. sanguineus for 12 weeks, a weight loss of 34.32%, 28.95%, 23.81% and 6.05%, respectively, was observed (Calonego et al., 2010).

However, there is little information about the effects of thermal treatment on the technological properties of Eucalyptus wood (Unsal & Ayrilmis, 2005).

Thus, the aim of this study was to evaluate the behavior of the brown-rot fungus G. trabeum and white-rot fungus P. sanguineus on thermally-modified E. grandis wood.

2. MATERIAL AND METHODS

In this study, we utilized wood from five-year-eleven-month-old Eucalyptus grandis trees from the Rio Claro Farm, managed by the Duratex-SA company, located in Lençóis Paulista, Sao Paulo state, Brazil. Six trees were randomly selected from inside the 2.2-ha stand. After felling, the trees were sectioned into 6.0-m logs. The first log from each tree with diameter between 20 and 22 cm was cut into flat saw boards. The boards that contained the pith were cut into 34-mm thick pieces for this study. Subsequently, all of the boards were dried from 75.7% to 10.0% moisture content in a dry kiln with capacity for approximately 2.5 m³ of wood.

2.1. Thermal treatments of boards
The six dried boards were planed to 32-mm thick and cut into smaller pieces measuring 0.60 m in length. Regions with cracks and knots were discarded. One of these smaller pieces was kept in its original condition (untreated wood), and the other pieces were reserved for the thermal treatments (thermally-modified wood).

The material was placed in a thermal modification oven with programmable control. The treatment proceeded in steps from an initial temperature of 100 ºC to 180 ºC, and then to 200 ºC and 220 ºC over a period of 2.5 hours, according to the application of patent developed by Severo & Calonego (2009). Following the end of the thermal treatment, the oven was turned off and the wood pieces were kept inside. The pieces were allowed to cool naturally.

2.2. Accelerated laboratory tests of decay resistance of wood
The test to assess the attack of brown-rot fungus on the thermally-modified Eucalyptus grandis wood was conducted according to the standards presented in ASTM D-2017 (2008) norm. This procedure was performed simultaneously in the material inoculated with the white-rot fungus P. sanguineus studied by Calonego et al. (2010).

The samples were cut to create wood perfectly oriented in relation to the three anatomical planes (radial, tangential and longitudinal), and were approximately 40 mm from the pith of each piece of wood. The samples were sawn into test blocks measuring 25 by 25 by 9 mm in size, with the 9 mm dimension in the grain direction.

Although the ASTM D-2017 (2008) standard show that the necessary number of samples to characterize the decay resistance of wood is six, eighteen samples obtained from six boards were used to characterize each treatment (untreated wood and three other thermally-modified woods), totaling seventy-two samples by fungus tested.

In preparation for the test, the wood samples were dried in a drying oven at 103 ± 2 ºC, until constant weight was reseached. As recommended by the ASTM D-1413 (2007) norm, the initial oven-dry weight (WI) of each test block was determined.

The soil-block test was prepared in 725 mL cylindrical culture bottles using 300 g of soil with a water holding capacity of 29%. After filling the bottles with distilled water, a feeder strip of Pinus sp. was added. Subsequently, the bottles were sterilized at 121 ±1 ºC for 1 hour.

The culture bottles were then inoculated with the brown-rot fungus G. trabeum (collected from mycology collection of the INPA, Manaus, Amazonas state, Brazil, and identified as ID 408).
After sterilization, the test blocks were placed in the culture bottles with the cross-section face of the feeder strip facing down. The culture bottles were incubated in an incubation chamber in the dark to promote the growth of the fungus at 26.7 ± 1 ºC and 70 ± 4% relative humidity for 12 weeks.
At the end of the exposure period, the test blocks were removed from the culture bottles and any surface fungus growth was carefully brushed off. The blocks were then dried in drying oven at 103 ± 2 ºC once again until constant weight was reseached. This weight was determined as the final oven-dry weight (WF) of each test block.

The percent weight losses in the individual test blocks from before and after exposure to the decay fungi were then calculated. The percent weight losses in the test blocks provide a measure of the relative decay susceptibility of the untreated and thermally-modified Eucalyptus grandis wood.

3. RESULTS AND DISCUSSION

The weight loss data of Eucalyptus grandis wood caused by the action of the brown-rot fungus G. trabeum was normally distributed and analysis of variance with a randomized block design was therefore used, taking into account the thermal treatments, as well as Tukey's test at 5% significance level for the comparison of the means.
The values for the amount of weight loss in untreated Eucalyptus grandis wood, found in Table 1, were 50.33% and 34.32% for the samples incubated with the brown-rot and white-rot fungi, respectively.

These results are similar to those cited by Andrade et al. (2012), who characterized the biological resistance of Eucalyptus grandis wood and concluded that material inoculated with the white-rot fungus P. sanguineus showed a weight loss of 29.0%, after 8 weeks in the accelerated test decay.
However, as shown in Table 1, the resistance of E. grandis wood to the brown-rot fungus G. trabeum was smaller than to the white-rot fungus studied by Calonego et al. (2010). According to Dutton et al. (1993), these variations were expected because the brown-rot fungi secrete large amounts of oxalate in culture medium, reducing the pH of the substrate during growth, and the amount of oxalate produced by white-rot fungi was not enough to reduce the pH of the medium during growth.

Several authors have reported that the brown-rot fungus G. trabeum produce extracellular hydrogen peroxide (H₂O₂) and oxalic acid (H₂C₂O₂), which react with the iron ions present in lignocellulosic materials by the Fenton's reaction and cause the cleavage of long chain cellulose molecules into small fragments. Thus, there is an increase of porosity of the cell wall allowing penetration of cellulolytic enzymes which increase the decay on wood (Goodell et al., 1997; Xu & Goodell, 2001; Arantes & Milagres, 2009; Watanabe et al., 2010; Aguiar & Ferraz, 2011).

These explanations are in agreement with Alves et al. (2006), who evaluated the natural biological resistance of various tropical woods to the brown-rot fungus G. trabeum and white-rot fungus P. sanguineus and concluded that the decay caused by brown-rot fungus was greater.
However, the objective of this study was also to evaluate the resistance of thermally-modified E. grandis wood to brown-rot fungus in comparison with white-rot fungus.
The visual features of samples submitted to the action of the brown-rot and white-rot fungi are shown in Figure 1, and the values for the amount of weight loss and the average moisture content of E. grandis wood are presented in Table 1.

These evaluations indicated that although the thermal treatment reduced some of the mechanical properties of wood (Calonego et al., 2012), there was a significant improvement in the decay resistance of Eucalyptus grandiswood by the increase in treatment temperatures. These results were expected because Homan et al. (2000), Millitz & Tjeerdsma (2001), Momohara et al. (2003), Weiland & Guyonnet (2003), Hakkou et al. (2006), and Calonego et al. (2010) found that thermal treatment at high temperatures increased the decay resistance of wood of other species and/or other fungi.
The decrease in weight loss caused by decay fungi (see Table 1) has already been explained by several authors, among them Weiland & Guyonnet (2003), Hakkou et al. (2006), Calonego et al. (2010) and Severo et al. (2012), because of changes in the chemical composition of wood, mainly the unavailability of food (hemicelluloses) to the fungi, the production of new molecules that act as fungicides, and the cross-linking between lignin and the polymer from the thermally degraded cellulose.

Verifying the effects of the thermal treatment on the decay caused by the white-rot fungus P. sanguineus and by the brown-rot fungus G. trabeum, it was possible to verify that the decay caused by brown-rot fungus was greater in all temperatures of thermal treatment.
These results can be explained by the ability of brown-rot fungi to secrete hydroxide complexes and oxalic acid able to cleave long chain cellulose molecules into small fragments, increasing the porosity of the cell wall, the penetration of cellulolytic enzymes, and the decay of wood (Goodell et al., 1997; Xu & Goodell, 2001; Arantes & Milagres, 2009; Watanabe et al., 2010; Aguiar & Ferraz, 2011).

4. CONCLUSIONS

This study shows that the decay caused by brown-rot fungus was greater than that caused by white-rot fungus. However, in verifying the effects of thermal modification on the decay resistance of E. grandis wood, it was possible to conclude that there was a decrease between 28.2 % and 70.0 % in the weight loss of wood exposed to the brown-rot fungus Gloeophylum trabeum.

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Hakkou M, Pétrissans M, El Bakali I, Gérardin P, Zoulalian A. Investigations of the reasons for fungal durability of heat-treated beech wood. Polymer Degradation and Stability 2006;91(2):393-397. http://dx.doi.org/10.1016/j.polymdegradstab.2005.04.042      [ Links ]
Homan W, Tjeerdsma B, Beckers E, Jorissen A. Structural and other properties of modified wood. In: World Conference on Timber Engineering; 2000; British Columbia. British Columbia; 2000. 8 p.         [ Links ]
Kleman-Leyer K, Agosin E, Conner AH, Kirk TK. Changes in molecular size distribution of cellulose during attack by white rot and brown rot fungi. Applied and Environmental Microbiology 1992;58(4):1266-1270. PMid:16348694PMCid:PMC195585.         [ Links ]
Millitz H, Tjeerdsma B. Heat treatment of wood by the PLATO-process. In: Special Seminar: Environmental Optimisation of Wood Protection; 2001; Antibes, France. Antibes; 2001. p. 27-38        [ Links ]
Momohara I, Ohmura W, Kato H, Kubojima Y. Effect of high-temperature treatment on wood durability against the Brown-rot fungus, Fomitopsis palustris, and the termite, Coptotermes formosanus. In: International IUFRO Wood Drying Conference; 2003. p. 284-287        [ Links ]
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Severo ETD, Calonego FW. Processo de modificação térmica, por irradiação de calor, para a melhora da estabilidade dimensional e da durabilidade biológica de madeira sólida. Patente n. BR PI0902/38-8A2; 2009.         [ Links ]
Severo ETD, Calonego FW, Sansígolo CA. Physical and chemical changes in juvenile and mature woods of Pinus elliottii var. elliottii by thermal modification. European Journal of Wood and Wood Products - Holz als Roh- und Werkstoff 2012;70(5):741-747. http://dx.doi.org/10.1007/s00107-012-0611-1       [ Links ]
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 Autor(es) para correspondência: 
Fred Willians Calonego
Programa de Pós-graduação em Ciência Florestal, Departamento de Ciência Florestal, Faculdade de Ciências Agronômicas - FCA, Universidade Estadual Paulista - UNESP
Fazenda Experimental Lageado, s/n, CP 237
CEP 18610-307, Botucatu, SP, Brasil
e-mail: fwcalonego@ig.com.br
Received: 06/18/2013
Accepted: 08/01/2013
CAPES PNPD-02405/09-1

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Reasons Why Power Walking Is Healthier Than Jogging

Both power walking and jogging produce good health benefits. For people already in good shape who can handle the joint-pounding abuse jogging can cause, jogging might be the better overall exercise, according to the University of Rochester Medical Center. However, not everyone can handle the jarring and pounding that often accompanies jogging. Power walking is the healthier exercise for most people for several reasons.

Power walking provides many health benefits. Photo Credit Ryan McVay/Photodisc/Getty Images.

Easier on the Joints

Between walking and jogging, the former is easier on the knees, hips, heels, shins and back. Jogging can cause shin splints, runner's knee or hamstring strains. You don't have to worry as much about injuries with power walking as you do with jogging, and you get almost the same benefits from walking as you do from jogging. Power walking can strengthen your bones, help your cardiovascular system and tone your muscles.

Burns More Fat

Fat burning occurs with longer duration exercises. The key to burning fat is to engage in an activity at a steady pace for a long duration. The longer you can keep the same pace and intensity the more fat you burn. You are likely to maintain a fast walking pace for a longer time than you can maintain a steady jogging pace.

What Jogging Entails

"Webster's New World College Dictionary, Fourth Edition" states that to jog is "to move along at a slow, steady, jolting pace or trot." A pace slower than 6 mph is considered jogging. It is a more intensive form of movement than walking, but it is not as intense as running and doesn't bring the same benefits. According to the University of Rochester Medical Center, any increase in bone mass from jogging inexplicably tops out at 25 to 30 miles a week. "For women," the center notes on its website, "overtraining may lead to the female athlete triad, a combination of eating disorders, halting of menstrual periods, and a weakening of the bones."

Power Walking Vs. Walking

Power walking is not the same as taking a stroll around your neighborhood after dinner. It is a specific exercise that requires a certain form and intensity level. You must keep up a brisk pace. You should still be able to converse while power walking, but you won't be able to sing. You should have good posture by standing tall and by holding the tummy muscles in. Squeezing the buttocks gives that area an extra workout. You can also swivel your hips some as you walk because that helps to burn more calories, fitness trainer Nicki Waterman told MailOnline.

www.livestrong.com

Inexpensive Ways to Get Rid of Deep Wrinkles Around the Mouth

Overview

You don't have to pay for expensive professional treatments to reduce the appearance of deep wrinkles around your mouth. You can make a few lifestyle changes or try natural or over-the-counter remedies to get rid of deep skin wrinkles. The treatments may take a bit of effort, but you'll save money and avoid time-consuming and possibly painful visits to the dermatologist.

A woman is applying moisturizer to her skin. Photo Credit sdeva/iStock/Getty Images.

Lifestyle Changes

MayoClinic.com states that smoking can create deep wrinkles around your mouth and speed up your skin's natural aging process. Stop smoking to prevent deep wrinkles from forming or getting worse. Sun exposure can also lead to wrinkles around your mouth. If you go out in the sun, apply sunblock to your face to prevent the sun's ultraviolet rays from worsening your wrinkles or creating new wrinkles around your mouth.

Home Remedies

Purchase grape seed extract at any health food store and use the extract topically to treat your deep facial wrinkles. Grape seed extract has natural antioxidant properties and can help restore elasticity to your wrinkled skin. Massage the grape seed extract into your deep wrinkles daily to keep your skin looking young.

Topical Treatments

Choose an over-the-counter anti-wrinkle cream to treat the deep wrinkles around your mouth. Over-the-counter creams can be more affordable than prescription medications or professional treatments. MayoClinic.com states that some wrinkle creams can reduce the appearance of facial wrinkles. Look for topical creams that contain beneficial ingredients that reduce deep wrinkles such as retinol, alpha hydroxy acids, coenzyme Q10 or kinetin. Don't think you have to spend a lot to get the best wrinkle cream. Inexpensive wrinkle creams can be just as helpful in reducing wrinkles as more expensive creams.

Exercises

One of the most affordable ways to get rid of deep wrinkles around your mouth is to perform face-tightening exercises. The Genius Beauty website recommends standing in front of the mirror and performing facial exercises for 15 minutes every day to reduce the appearance of wrinkles. Start by stretching your mouth as wide as you can, as if saying "cheese." Hold the position for two seconds, then pucker your lips together tightly so that your lips almost touch your nose. Hold this pose for two seconds, then stretch your mouth back into the "cheese" position. After two seconds, stretch your lips forward and down, as if saying the word "go." Hold for two seconds, then relax. Repeat the entire routine 20 times.

www.livestrong.com

Wild Lettuce and Anxiety

You've probably experienced anxious feelings at times, such as when you've been exposed to a stressful or fearful situation. In fact, anxiety is a normal human response to stress and fear. However, persistent symptoms of anxiety without an easily identifiable cause may be an indication of anxiety disorder. While anxiety is often treated with psychotherapy or medication, certain natural remedies, such as wild lettuce, may also provide benefits. As with any dietary supplement, inform your doctor if you plan to use wild lettuce.

Wild lettuce may help symptoms of anxiety. Photo Credit Dynamic Graphics/Creatas/Getty Images.

About Wild Lettuce

Wild lettuce, also known as Lactuca virosa, bitter lettuce or lettuce opium, is an herbal medication used by herbalists and alternative healers for a variety of purported benefits. In their book, "The Essential Guide to Herbal Safety," authors Simon Mills and Kerry Bone state that wild lettuce has sedative properties. Some believe that wild lettuce has psychoactive properties, although these claims are largely anecdotal. Mills and Borne point out that the presence of a psychoactive constituent in wild lettuce has been suggested but not confirmed. According to Hoag Memorial Hospital Presbyterian, wild lettuce is sometimes used to treat insomnia, restlessness and hyperactivity in children. Because of its sedative effects, wild lettuce may be useful for reducing symptoms of anxiety, although there is little scientific evidence to support this claim.

Anxiety Facts

Anxiety is a common mental health problem around the world. In fact, in the United States alone, an estimated 40 million American adults suffer from anxiety disorders each year, according to the National Institute of Mental Health. While there are several types of anxiety disorders, they share common symptoms, such as chronic worry, fear and tension, irritability, sleep problems, appetite changes, panic and unexplained aches and pains. Anxiety disorders need to be diagnosed by a qualified mental health professional. Treatment methods usually include some form of psychotherapy and, in some cases, medication. Some people wish to avoid the unpleasant side effects of medication and seek alternative and natural treatments. However, the benefits of many alternative remedies, such as wild lettuce, are largely anecdotal and not backed up by scientific research.

Clinical Evidence

There is a dearth of clinical evidence regarding wild lettuce's benefits for anxiety and anxiety disorders. Anecdotal evidence suggests that wild lettuce may help improve symptoms of insomnia, one of the key symptoms of anxiety disorders. However, a clinical review published in 2005 in the "Journal of Clinical Sleep Medicine" states that while wild lettuce has been used for insomnia, its efficacy has not been evaluated. A few studies have evaluated the analgesic and sedative properties of lactucin and its derivatives, components found in wild lettuce. One study, published in the September 2006 issue of the "Journal of Ethnopharmacology," showed that lactucin and lactucopicrin produced pain-relieving and sedative-like effects in laboratory rats. However, due to the lack of clinical evidence evaluating wild lettuce's benefits for anxiety in humans, more research studies are needed.

Considerations

While wild lettuce may improve symptoms of anxiety, you should not use wild lettuce or any dietary supplement as a replacement for conventional medical care. According to Hoag Memorial Hospital Presbyterian, serious side effects, such as slow breathing, loss of consciousness and even death, can occur if you take too much wild lettuce. Other side effects may include hives, chest pain and breathing difficulties. As with any dietary supplement, inform your doctor if you plan to use wild lettuce, especially if you have a medical condition or take any prescription or over-the-counter medication or herbal supplements.

www.livestrong.com

Healthy Lunch Wraps That Make You Lose Weight

When you are trying to lose weight and avoid high-calorie fast food, wraps are options that you can pack and carry with you for lunch. By choosing your ingredients carefully and varying your choices, you can use lunch wraps to help you lose weight and prevent boredom on your diet. Remember that what you eat with your wrap and during other daily meals affects your weight loss just as much as your wrap.

A lean protein and vegetable wrap can be a healthy lunch for weight loss. Photo Credit Howard Shooter/Dorling Kindersley RF/Getty Images.

Think About Lean Proteins

The filling for your wrap should include a source of lean protein, such as cooked chicken breast, turkey breast, tofu, canned tuna or beans. Low-fat or fat-free cheese is a source of protein and calcium. Protein is a filling nutrient that can help you lose weight because it slows the emptying of food from your stomach and delays the onset of hunger, according to Harvard University. Avoid fatty meats and full-fat cheese because they are high in cholesterol-raising saturated fat and calories.

Fill Up on Vegetables

Eating more vegetables can help you lose weight because they are low in calories and high in fiber, according to the Centers for Disease Control and Prevention. Add sprouts and cucumber slices to a wrap with garbanzo beans and fat-free yogurt, or add lettuce and tomatoes to a classic turkey wrap. Cooked vegetables, such as grilled eggplant and zucchini, go well with low-fat cheese. Fruit is also high-fiber and relatively low-calorie, and you can try a wrap filled with black beans and mango or papaya, or chicken breast with diced pears.

Be Creative with Fillings and Toppings

Leftovers can be healthy, low-calorie fillings or lunch wraps. Make a salad with diced leftover cooked chicken breast, romaine lettuce, raspberries and low-fat vinaigrette, and stuff it into a wrap. Another combination with leftovers is cooked fish with shredded cabbage and cilantro. Full-fat spreads and dressings, such as mayonnaise, butter, ranch dip and honey mustard sauce, can add unnecessary calories to your lunch wraps. Instead, use lower-calorie options, such as fat-free plain yogurt, salsa and yellow or Dijon mustard.

Other Considerations

A smaller wrap is lower in calories and better for weight loss than a larger one. Also, choose a whole-wheat or other whole-grain wrap because regularly substituting whole grains for refined options can help you control your weight, according to the the publication "Dietary Guidelines for Americans, 2010." You can reduce the calorie content of your wrap by using a lettuce leaf instead of a tortilla. To further support weight loss, have fruit and vegetables to round out your lunch instead of unhealthy high-calorie sides, such as cookies and chips.

www.livestrong.com

The Best of Woodwork: 20 Lessons in the Pursuit of Mastery

THE WOODWORKING DESIGN COLLECTION - ONLY 69 LEFT !

Format: Magazine Single Issue 

The Pursuit of Mastery

One of the many pleasures of working wood is the realization, every so often, that your game is improving. This awareness may be the result of something big, like a newly finished piece that draws praise from others and approval even from your own critical eye. Or it may be prompted by something much subtler—a joint that comes together clean, tight and without fuss; a gossamer shaving that lifts off the wood and floats to the floor; a speckless, drip-free coat of varnish that you just laid down. Whatever the instance, it marks a moment on your way toward mastering your craft.

But what does that mean, to master a craft? And more, how do you pursue this mastery? Well, for one thing, though it may be a goal, mastery is not really some end point. It's more akin to a journey with numerous stages along the way. A concept popularly linked to this journey is the "10,000 hour rule," a shorthand way of saying that, whatever else mastery may require, practice and more practice is a fundamental and unending part of it. In a craft as complex as woodwork, where the material is so variable and the ways of handling it so diverse, 10,000 hours represents more like a good start on your way. And of course, it's not just a matter of putting in the hours on your own. Trial-and-error can be slow, and will only get you so far, sometimes even in the wrong direction. There are numerous tools and techniques that require some form of instruction or guidance to direct your hours in the shop. 

Finally, in addition to practice and instruction there is one more factor, perhaps the most elusive in the pursuit of mastery. Hard to describe but definitely recognizable, it is a quality of artistry or vision that informs and elevates the work. Vision can't be taught, but it can be experienced, and these encounters are a vital part of the process. 

Woodwork magazine was founded with the goal of exploring the vast territory of this field, providing instruction and inspiration in the pursuit of mastery. For this book, I have drawn on material from the years when I was editor of the magazine, and it is presented in three sections. The first profiles four artists, each with a unique vision of working wood, and each with a different path taken to get to his or her level of mastery. The second section takes the reader beyond the basics, expanding and fine-tuning tool use and techniques, and concludes with a tour de force demonstration by a master craftsman. Reflections on art and craft, and encounters with the creative process form the core of the third section. Taken together, these three elements are the heart of what Woodwork has to offer. I hope they serve you well as guideposts on your journey. 

John Lavine
Guest Editor

SKU	WWBKZ11
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