Early Stages Of Decay Research Articles

Litter Decomposition and Nutrient Dynamics in Fire-Affected Larch Forests in the Russian Far East

Russian boreal forests hold a considerable carbon (C) stock and are subjected to frequent surface fires that unbalance C storage and ecosystem function. Although postfire ecological changes aboveground are well understood, biological C flows (e.g., decomposition in the postfire period) remain unclear. We present the results of a long-term field litterbag experiment on needle litter decomposition in typical Larix gmelinii boreal forests in the Russian Far East. For 3 years, we measured mass loss, C and nitrogen (N) concentrations, lignin and manganese dynamics, respiration intensity and enzyme activity in decaying needles, and environmental conditions (temperature and litter moisture). The decomposition rate at 850 days was 0.435 and 0.213 yr−1 in a control forest and in a forest 15 years after a surface fire, respectively. Early stages of needle decay did not differ among sites, whereas decomposition slowed in later stages in burned forest relative to the control (p < 0.01). This was supported by hampered respiration, slow lignin accumulation in decaying needles, and low peroxidase activity in burned forest. We found no direct N release, and decaying litter immobilization was more pronounced in the control forest. In the later stages, we revealed restrained mass loss and associated C release from larch litter in burned forest. Slow and delayed N release may alter organic matter accumulation, the N cycle, and regeneration of the fire-disturbed larch ecosystem. Our investigations highlight hampered C flow from aboveground litter to soil humus even decades after surface fire in a larch ecosystem. Given the climate-induced increase of fire activity, C retained in the litter layer represents a pool that is more vulnerable to the next fire event.

Latitudinal Patterns of the Early Stages of Woody Debris Decay in the Forest Zone of West Siberia

Latitudinal Patterns of the Early Stages of Woody Debris Decay in the Forest Zone of West Siberia

Assessment of volatile metabolites for in situ detection of fungal decay in wooden structures

Although incipient fungal decay of wood may be difficult to detect in early stages, it causes a significant decrease in wood strength. Developing a reliable non-destructive identification method of decay to overcome wood replacement costs is necessary. This study examined mass losses and compression strength decrease of a softwood, spruce pine (Pinus glabra), and a hardwood, quaking aspen (Populus tremuloides), exposed to two brown rot (Gloeophyllum trabeum and Postia placenta) and two white rot (Trametes versicolor and Irpex lacteus) fungi, and identified fungal volatile organic compounds (VOCs) collected over 12 weeks of decay. Principal component analysis (PCA) of VOCs spectra differentiated volatiles emitted from sound wood and wood exposed to fungi. Volatile compounds from two fungal species revealed distinctive patterns of early and late decay stages in each wood species. The overall distinct volatile patterns of fungal decay showed promising results for development of non-destructive identification of incipient decay in wooden building structures.

Anatomical characterization of wood decay patterns in Hevea brasiliensis and Pinus merkusii caused by white-rot fungi: Polyporus arcularius and Pycnoporus sanguineus

Biological pulping is an environmentally friendly process for making pulp and paper whereby the wood raw material is pre-treated with selective delignifying white-rot fungi. Therefore, the purpose of this study is to determine the decay patterns of white-rot fungi Polyporus arcularius and Pycnoporus sanguineus, as well as its ability to decay Hevea brasiliensis (as hardwood) and Pinus merkusii (as softwood) by observing the anatomical characteristics. Fungal attack testing on wood was carried out by the Kolle-flask method with a variation of 6, 9, and 12 weeks incubation time. The structure of wood cells was analyzed using wood incision method, followed by a combination of safranin-picro aniline blue and safranin-astra blue, and maceration method. The results showed that H. brasiliensis wood has a higher percentage of weight loss than P. merkusii wood. Wood attacked by P. sanguineus showed a higher weight loss compared to the P. arcularius. The decay pattern of P. sanguineus infected wood was concluded as selective delignification in P. merkusii and simultaneous delignification in H. brasiliensis while those infected with P. arcularius both performed simultaneous delignification. In the early stages of decay, selective delignification is characterized by the formation of intercellular space due to degradation of lignin in the middle lamella, while simultaneous delignification is characterized by cell wall thinning. The anatomical structure of H. brasiliensis attacked by the white-rot fungi showed differences with P.merkusii, whereby the ray cells of P.merkusii wood was more degraded than in H. brasiliensis.

Nanostructural Analysis of Enzymatic and Non-enzymatic Brown Rot Fungal Deconstruction of the Lignocellulose Cell Wall†.

Brown rot (BR) decay mechanisms employ carbohydrate-active enzymes (CAZymes) as well as a unique non-enzymatic chelator-mediated Fenton (CMF) chemistry to deconstruct lignocellulosic materials. Unlike white rot fungi, BR fungi lack peroxidases for lignin deconstruction, and also lack some endoglucanase/cellobiohydrolase activities. The role that the CMF mechanism plays in “opening up” the wood cell wall structure in advance of enzymatic action, and any interaction between CMF constituents and the selective CAZyme suite that BRs possess, is still unclear. Expression patterns for CMF redox metabolites and lytic polysaccharide monooxygenase (LPMO–AA9 family) genes showed that some LPMO isozymes were upregulated with genes associated with CMF at early stages of brown rot by Gloeophyllum trabeum. In the structural studies, wood decayed by the G. trabeum was compared to CMF-treated wood, or CMF-treated wood followed by treatment with either the early-upregulated LPMO or a commercial CAZyme cocktail. Structural modification of decayed/treated wood was characterized using small angle neutron scattering. CMF treatment produced neutron scattering patterns similar to that of the BR decay indicating that both systems enlarged the nanopore structure of wood cell walls to permit enzyme access. Enzymatic deconstruction of cellulose or lignin in raw wood samples was not achieved via CAZyme cocktail or LPMO enzyme action alone. CMF treatment resulted in depolymerization of crystalline cellulose as attack progressed from the outer regions of individual crystallites. Multiple pulses of CMF treatment on raw wood showed a progressive increase in the spacing between the cellulose elementary fibrils (EFs), indicating the CMF eroded the matrix outside the EF bundles, leading to less tightly packed EFs. Peracetic acid delignification treatment enhanced subsequent CMF treatment effects, and allowed both enzyme systems to further increase spacing of the EFs. Moreover, even after a single pulse of CMF treatment, both enzymes were apparently able to penetrate the cell wall to further increase EF spacing. The data suggest the potential for the early-upregulated LPMO enzyme to work in association with CMF chemistry, suggesting that G. trabeum may have adopted mechanisms to integrate non-enzymatic and enzymatic chemistries together during early stages of brown rot decay.

Macrofungi on large decaying spruce trunks in a Central European old-growth forest: what factors affect their species richness and composition?

Species richness and composition of macrofungi on huge fallen trunks of spruce (Picea abies) were monitored at a model old-growth forest locality, Boubinský prales virgin forest (Czech Republic). Using detailed survey of all macrofungal groups based on fruit bodies, 168 species were recorded on 33 trunks with a diameter of 100–150 cm, which is a very high species richness. Individual trunks were inhabited by 6–32 species. The number of species per trunk was positively correlated with increasing tree cover, medium decay stages, and decreasing altitude. The species-richest groups were resupinate fungi with annual basidiomata and fleshy saprotrophic fungi. Species composition on particular trunks was significantly influenced by percentage of bark cover, altitude, and decay stage and to a lesser degree also by percentage of trunk contact with the soil and cover of mosses, trees, and shrubs. Resupinate fungi and fleshy saprotrophs were distributed along the entire decay gradient. Most polypores prevailed in early decay stages. Mycorrhizal agarics were associated with the latest stages. The presence of dominant species Fomitopsis pinicola had a low effect on the composition of other fungal species on the same trunk, whereas Phellinus nigrolimitatus had a significant effect. The monitoring revealed 71% of species known at the locality from spruce, and 45 species new to the locality, especially those with inconspicuous fruit bodies. The previously published field survey was more efficient for capturing rare species with larger fruit bodies. Both methods should be combined during mycobiota inventories.

Where to look for basidiomata of Phellinidium pouzarii (Fungi, Hymenochaetaceae), a rare European polypore of montane old-growth forests with fir (Abies)?

Records of Phellinidium pouzarii from 13 localities in seven European countries were analyzed as for the microhabitat parameters at sites of basidiomata occurrence. The dataset consisted of 45 records out of them 37% were on artificial microhabitats – cut surfaces of fallen fir (Abies) trunks, and 61% on natural positions, mostly lateral and bottom sides of trunks lying on the soil. In the latter case the basidiomata often were very large and thick, forming irregular 'pies' or horizontal strips up to 150 cm long and 5 cm thick. A newly revealed microhabitat is a naked wood of fracture surfaces of fallen trunks broken to several parts. In this case, basidiomata were small, having the area of several cm 2 and thickness of up to 5 mm. Detailed information on parameters of selected trunks helped to reveal that P. pouzarii basidiomata occur both several years after trunk fall and up to 4 decades after trunk death. Basidiomata grow on decorticated wood from early decay stages to the late ones (with maximum records in the medium stages) and they can persist for at least one decade on the same trunk. A distribution map showing currently known European localities was compiled. A record from Romania is published here for the first time. Phellinidium pouzarii has a clear island pattern of occurrence. It is limited to well-preserved montane old-growth forests with fir at the elevations 710–1100 m a. s. l., in all cases protected as nature reserves.

An evolutionary signal to fungal succession during plant litter decay.

ABSTRACTEcologists have frequently observed a pattern of fungal succession during litter decomposition, wherein different fungal taxa dominate different stages of decay in individual ecosystems. However, it is unclear which biological features of fungi give rise to this pattern. We tested a longstanding hypothesis that fungal succession depends on the evolutionary history of species, such that different fungal phyla prefer different decay stages. To test this hypothesis, we performed a meta-analysis across studies in 22 different ecosystem types to synthesize fungal decomposer abundances at early, middle and late stages of plant litter decay. Fungal phyla varied in relative abundance throughout decay, with fungi in the Ascomycota reaching highest relative abundance during early stages of decay (P < 0.001) and fungi in the Zygomycota reaching highest relative abundance during late stages of decay (P < 0.001). The best multiple regression model to explain variation in abundance of these fungal phyla during decay included decay stage, as well as plant litter type and climate factors. Most variation in decay-stage preference of fungal taxa was observed at basal taxonomic levels (phylum and class) rather than finer taxonomic levels (e.g. genus). For many finer-scale taxonomic groups and functional groups of fungi, plant litter type and climate factors were better correlates with relative abundance than decay stage per se, suggesting that the patchiness of fungal community composition in space is related to both resource and climate niches of different fungal taxa. Our study indicates that decomposer fungal succession is partially rooted in fungal decomposers’ deep evolutionary history, traceable to the divergence among phyla.

Electric resistance tomography and stress wave tomography for decay detection in trees-a comparison study.

BackgroundTo ensure the safety of trees, two NDT (nondestructive testing) techniques, electric resistance tomography and stress wave tomography, were employed to quantitatively detect and characterize the internal decay of standing trees. Comparisons between those two techniques were done to make full use of the individual capability for decay detection.MethodsEighty trees (40 Manchurian ash and 40 Populus simonii) were detected, then wood increment cores were obtained from each cross disc trial. The Dt, which was defined as the value determined by the mass loss ratio of each wood core, was regarded as the true severity of decay. Using ordinary least-squares regression to analyze the relationship between Dt and De (De was defined as the severity of decay determined by electric resistance tomography) and between Dt and Ds (Ds was defined as the severity of decay determined by stress wave tomography).ResultsThe results showed that both methods could estimate the severity of decay in trees. In terms of different stages of decay, when Dt < 30%, De had a strong positive correlation with Dt (R2 = 0.677, P < 0.01), while, when Dt ≥ 30%, Ds had a significant positive correlation relationship with Dt (R2 = 0.645, P < 0.01).ConclusionElectric resistance tomography was better than stress wave tomography for testing in the early stages of decay, while stress wave tomography can be used effectively in the late stage of decay. It is suggested that each technique can be used in the practice of internal decay testing of standing trees based on decay stages and operating conditions.

Saproxylic Diptera assemblages in a temperate deciduous forest: implications for community assembly.

Saproxylic insects, those associated directly or indirectly with decaying wood for all or part of their life cycle, compose a large proportion of forest organisms. Flies (Diptera) are often the most abundant and species-rich group of insects in forest microhabitats, yet most work to date on saproxylic insect diversity and ecology has focused on beetles (Coleoptera). We compared saproxylic Diptera assemblages reared from two tree species (sugar maple and American beech) at two stages of decay (early/young and advanced/old) for a total of 20 logs in an eastern Canadian Nearctic old-growth forest. We found that communities are distinct within both species type and decay stage of wood. Early decay stage wood is more variable in community composition than later decay stage; however, as the age of the decaying wood increases, the abundance of Diptera increases significantly. Most indicator species are discernible in later decay stage and wood type. We venture to suggest that stochastic and deterministic processes may play a role in driving Diptera communities in temperate deciduous forests. To retain the highest saproxylic Diptera diversity in a forest, a variety of decaying wood types at different stages of decomposition is necessary.

Litter chemistry influences decomposition through activity of specific microbial functional guilds

AbstractNiche differentiation among species is a key mechanism by which biodiversity may be linked to ecosystem function. We tested a set of widely invoked hypotheses about the extent of niche differentiation in one of the most diverse communities on Earth, decomposer microorganisms, by measuring their response to changes in three abundant litter resources: lignin, cellulose, and nitrogen (N). To do this, we used the model system Arabidopsis thaliana to manipulate lignin, cellulose, and N availability and then used high‐throughput sequencing to measure the response of microbial communities during decay. Resequencing the decomposer communities after incubation of decomposed litter with pure substrates showed that groups of species had unique substrate use profiles, such that species organized into functional “guilds” of decomposers that were associated with individual litter chemicals. Low concentrations of lignin, cellulose, or N in the litter caused unique shifts in decomposer community composition after 1 yr of decay. Low cellulose plants had low levels of fungi in all decomposer guilds, low lignin plants had high levels of fungi in all decomposer guilds, and low N plants had low levels of fungi in decomposer guilds associated with sucrose and lignin. The relative abundance of decomposer guilds correlated with the total loss of individual litter chemicals during litter decay in the field. In addition, N fertilization shifted decomposer communities during both the early and later stages of decay to those dominated by decomposers in the cellulose guild. Our results contrast the assumption that major carbon (C) and N degradation mechanisms are uniform across whole decomposer communities and instead suggest that decomposition arises from complementarity among groups of metabolically distinct taxa.

Forest management strategy affects saproxylic beetle assemblages: A comparison of even and uneven-aged silviculture using direct and indirect sampling.

Management of forest for wood production has altered ecosystem structures and processes and led to habitat loss and species extinctions, worldwide. Deadwood is a key resource supporting forest biodiversity, and commonly declines following forest management. However, different forest management methods affect dead wood differently. For example, uneven-aged silviculture maintains an age-stratified forest with ongoing dead wood production, while even-aged silviculture breaks forest continuity, leading to long periods without large trees. We asked how deadwood-dependent beetles respond to different silvicultural practices and if their responses depend on deadwood volume, and beetles preference for decay stages of deadwood. We compared beetle assemblages in five boreal forest types with different management strategies: clearcutting and thinning (both representing even-aged silviculture), selective felling (representing uneven-aged silviculture), reference and old growth forest (both uneven-aged controls without a recent history [~50 years] of management, but the latter with high conservation values). We collected beetles using window traps and by sieving the bark from experimental logs (bolts). Beetle assemblages on clear-cuts differed from all other stand types, regardless of trapping method or decay stage preference. Thinning differed from reference stands, indicating incomplete recovery after clear-cutting, while selective felling differed only from clear-cuts. In contrast to our predictions, early and late successional species responded similarly to different silvicultural practices. However, there were indications of marginal assemblage differences both between thinned stands and selective felling and between thinned and old growth stands (p = 0.10). The stand volume of early decay stage wood influenced assemblage composition of early, but not late successional species. Uneven-aged silviculture maintained species assemblages similar to those of the reference and old growth stands and might therefore be a better management option when considering biodiversity conservation.

Diffusion Equations for Early Stages of Solid Solutions Decay Based on the Markovian Theory of Random Walk

Examination was made of the early stages of binodal or spinodal solid solutions decay connected with the growth of local zones of concentration fluctuations. The theory of Markovian process of random walk of the individual atoms describes how particle transport with short diffusion paths causes the growth of these zones. The resulting equation predicts the growth and transformation of initial zones of concentration fluctuations into growing clusters with surface boundary or formation of the quasiperiodic concentration distribution inherent in spinodal decomposition.

Polypore Communities and Their Substrate Characteristics in Atlantic Forest Fragments in Southeast Brazil

Anthropogenic environmental changes have resulted in biodiversity crisis. Although tropical rainforests are one of the global biodiversity hotspots, their biodiversity is still poorly known. Especially fungi are poorly represented in national Red Lists and conservation plans, despite their important role in ecosystem functioning. We studied wood-inhabiting fungi (polypores) in four areas within two Atlantic rainforest fragments in Southeast Brazil. Our aim was to investigate fungal substrate characteristics and community composition. Deadwood amount ranged from 27 to 82 m3/ha among the four study areas and altogether we recorded 53 polypore species. More species were observed in intermediate and late decay stages than in early decay stages, but other deadwood variables did not explain the occurrence of polypores. Similarity in polypore community composition within and among the areas was low. Dissimilarity originated mostly from species turnover from a transect and area to another, and no nestedness in species occurrence pattern was detected. Hence, the observed dissimilarity in community composition was probably a result of heterogeneity in forest composition and structure, instead of environmental gradients or substrate limitations. These results corroborate previous polypore studies from the Atlantic forest in that tropical polypores are specialists toward particular decay stages. To develop ecologically effective conservation program for tropical polypores, more studies are needed on their distribution and abundance globally.

Temporal evolution of near‐surface chlorophyll over cyclonic eddy lifecycles in the southeastern Pacific

AbstractTemporal evolution of near‐surface chlorophyll (CHL) associated with mesoscale eddies over entire eddy lifespan is complicated. Based on satellite measurements and a reanalysis data set, we identify and quantify major temporal and spatial CHL responses in cyclonic eddies in the southeastern Pacific, and explore the associated mechanisms. Only few temporal CHL variations can be directly linked to the four primary mechanisms: “eddy pumping,” “eddy trapping,” “eddy stirring,” and “eddy‐induced Ekman pumping.” About 80% of the temporal CHL variations are too complex to be explained by a single mechanism. Five characteristic CHL responses, including classic dipoles (CD), positive‐dominant dipoles (PD), negative‐dominant dipoles (ND), positive monopoles (PM), and negative monopoles (NM) are identified using the self‐organizing map (SOM). CD, a dominant response induced primarily by “eddy stirring,” has a continued increasing of frequency of occurrence with time, although its contribution to the total CHL variability remains low. As the secondary prominent response, NM has two peaks of frequency of occurrence at eddy formation and maturation stages, mainly accounted by “eddy trapping” after eddy breakup and “eddy‐induced Ekman pumping,” respectively. The sum of frequency of occurrence of PD and PM are comparable to that of NM. The initial positive CHL at eddy formation stage is associated with “eddy trapping.” The significant positive CHL increase from the eddy intensification to early decay stage is mainly attributed to “eddy pumping.” Although the frequency of occurrence of ND is the smallest, its contribution to negative CHL anomalies is unnegligible.

Necrophilous Insect Dynamics at Small Vertebrate Carrion in a Temperate Eucalypt Woodland.

Insects associated with carrion are critical to the decomposition process and nutrient cycling in ecosystems. Yet the communities of insects associated with carrion vary between locations, and detailed case studies are necessary for identifying differences and similarities among contrasting habitats. In this study, we examined temporal changes in the crawling insect community collected from rabbit carcasses placed in contrasting grassland and tree habitats in southeastern Australia. We collected 18,400 adult insects, including 22 species of fly, 57 species of beetle, and 37 species of ant. We found significant effects of habitat type and time, but not their interaction, on the composition of the entire insect community. Several ant species showed early and rapid colonization and highest abundances during early stages of decay, including Iridomyrmex purpureus (Smith, 1858) under trees, and Iridomyrmex rufoniger (Lowne, 1865) and Rhytidoponera metallica (Smith, 1858) in grassland. We found that most fly species showed highest abundance during active decay, but Chrysomya varipes (Macquart 1851) was more abundant under trees than in grassland during this time. Beetles peaked during active or advanced decay stages, with Saprinus and Omorgus the most abundant genera. Our study demonstrates that strong replication of contrasting environmental treatments can reveal new information on habitat preferences of important carrion insect species. The numerical dominance of ants early in decomposition has implications for insect community structure via potential competitive interactions with flies, and should be more rigorously examined in future carrion studies.

Carbon and nitrogen stocks in dead wood of tropical lowland forests as dependent on wood decay stages and land-use intensity

Rapid transformation of natural forests into other land-use systems in the lowlands of Sumatra, Indonesia, strongly reduces total aboveground biomass and affects nutrient cycling. However, the consequences of this conversion for C and N stocks of dead wood remains poorly understood particularly in natural forests and jungle rubber. This study examined the differences in dead wood abundance, and C, N and lignin concentrations of three decay stages of dead wood as well as the stocks of these chemical components stored in dead wood. Standing and fallen dead wood was determined as coarse woody debris with diameter ≥ 10 cm and classified into three decay stages of wood. Mass of dead wood was estimated using allometric equation. Total C and N stocks in dead wood in the natural forests (4.5 t C ha -1 , 0.05 t N ha -1 , respectively) were three times higher than those in the jungle rubber (1.5 t C ha -1 , 0.02 t N ha -1 , respectively). The stocks of C and N at early and advanced wood decay stages in the natural forests were also higher than those in the jungle rubber. The decay stages showed pronounced differences in concentrations of chemical components. With advancing stage of wood decay, N concentration increased and C/N ratio decreased, while concentrations of C and lignin were variable. The distribution of dead wood mass and stocks of C, and lignin were found to be higher in the early decay than those in the advanced decay stage. Higher input of dead wood in natural forests indicated a higher importance of dead wood decay in natural forests than in jungle rubber systems. Thus, replacing natural forests with jungle rubber strongly reduces total C and N stocks which might have a marked negative effect on the ecosystems' nutrient turnover and cyle.

Dental sealants

Have you ever noticed how uneven the chewing surfaces are on your back teeth? That’s because these teeth (your molars) have pits and grooves. Though these pits and grooves help grind food, they also can make it easier for cavities to develop. Cavities occur when acid breaks down the hard, protective enamel surface of the tooth. Plaque is a thin film of bacteria that coats everyone’s teeth all the time. When you eat, the bacteria in plaque produce the acids that can break down tooth enamel. Brushing your teeth and cleaning between them helps remove the plaque and food particles that can cause this breakdown, so these are 2 important things that you can do to reduce your risk of developing decay. However, it is difficult to clean inside the pits and grooves on your molars with a toothbrush. Luckily, sealants can protect your teeth from decay by filling in those pits and grooves, keeping food and plaque out. Sealants may even stop very early stages of tooth decay from going on to form a cavity.1Wright J.T. Crall J.J. Fontana M. et al.Evidence-based clinical practice guideline for the use of pit-and-fissure sealants: a report of the American Dental Association and the American Academy of Pediatric Dentistry.JADA. 2016; 147: 672-682Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar, 2Goepferd S.J. Olberding P. The effect of sealing white spot lesions on lesion progression in vitro.Pediatr Dent. 1989; 11: 14-16PubMed Google Scholar Usually, sealants are made of a special type of plastic, although sometimes other dental materials may be used. The sealant is applied in a thin coat to the chewing surfaces of your molars. It covers the deep pits and grooves that put you at risk of developing tooth decay. “This coverage makes sealants one of the most effective interventions available for prevention of tooth decay,” according to Dr. Alonso Carrasco-Labra, director of the American Dental Association’s Center for Evidence-Based Dentistry. With the exception of an allergy that may exist, there are no known side effects to sealants. Children and adults both can benefit from sealants. The earlier in life they are applied, the greater protection sealants offer, but it’s never too late to protect any chewing surface that is free from tooth decay with sealants. Sealants are a good investment for anyone, as they can save time and money down the road because you won’t need to treat tooth decay.1Wright J.T. Crall J.J. Fontana M. et al.Evidence-based clinical practice guideline for the use of pit-and-fissure sealants: a report of the American Dental Association and the American Academy of Pediatric Dentistry.JADA. 2016; 147: 672-682Abstract Full Text Full Text PDF PubMed Scopus (125) Google Scholar, 3Dasanayake A.P. Li Y. Kirk K. Bronstein J. Childers N.K. Restorative cost savings related to dental sealants in Alabama Medicaid children.Pediatr Dent. 2003; 25: 572-576PubMed Google Scholar However, you should check with your insurance carrier to be sure that sealants are covered under your policy. The dental professional who applies your sealant will need to start with a clean and dry surface. To make sure the sealant forms a strong bond with the tooth, the tooth’s chewing surface will be roughened with a special gel. Then, the gel is wiped off, and the surface of the tooth is dried once more. Finally, the sealant is applied to the tooth. When applied, sealants have the consistency of a gel or paste and then harden into a strong, protective coating. Some sealants require intense light to harden, so your dentist or dental hygienist may shine a light on the molar surface. Sealants are very durable, and in most cases, hold up for several years. Everyone is different, however, and sometimes sealants need to be reapplied. Your dentist will check them at every visit. Nothing takes the place of good oral care. Your daily routine should include brushing your teeth for 2 minutes, twice a day. Use a soft-bristled toothbrush and a toothpaste (or gel) with fluoride that have the ADA Seal of Acceptance. Flossing goes hand in hand with brushing. Once a day, you should floss or clean between your teeth. This can be done with dental floss or another product made specifically to clean between the teeth, such as prethreaded flossers, tiny brushes that reach between the teeth, water flossers, or wooden plaque removers. Cleaning between your teeth once a day helps remove plaque from between your teeth—another area your toothbrush can't reach. In addition, you should see your dentist on a regular basis for professional cleanings. Treatments such as topical fluoride, provided by your dentist when needed, also can be important in keeping your teeth cavity-free. Sealants are easy to apply and, along with good daily care and regular visits to your dentist, they can be part of a complete dental health plan.

Experimental verification of an orthotropic finite element model for numerical simulations of ultrasonic testing of wood poles

Ultraso nic testing is a non-destructive and non-invasive method which has been used for internal condition assessment of wood poles in electric transmission and distribution lines. The reliability of this method of evaluation relies on a good understanding of propagation of ultrasonic waves in wood. However, a full-waveform analysis in ultrasonic testing is rarely performed in practice because of difficulties in establishing realistic values for the elastic parameters, modeling the material damping and characterizing the dynamic response of an ultrasonic transmitter. In this paper, a calibrated orthotropic finite element model for numerical simulations of ultrasonic testing of a sound red pine pole is presented. In the calibrated model, the dynamic modulus of elasticity in the radial and tangential directions, Poisson’s ratio and damping ratios are estimated from ultrasonic testing; whereas the dynamic modulus of elasticity in the longitudinal direction is estimated from transverse-vibration testing. The measured response of an ultrasonic transmitter to a one-cycle sinusoidal pulse of 50 kHz is used as dynamic excitation and introduced in the numerical model as displacement-time history. Results of the first arrival of compression waves and the frequency response magnitude computed at three receiver locations are in good agreement with the obtained ones from ultrasonic testing. The calibrated orthotropic finite element model will be used for a better understanding of propagation of surface and compression waves in ultrasonic testing for the detection of early stages of decay in wood poles.

Effects of riparian buffer width on wood loading in headwater streams after repeated forest thinning

Forested riparian buffer zones are used in conjunction with upland forest management, in part, to provide for the recruitment for large wood to streams. Small headwater streams account for the majority of stream networks in many forested regions. Yet, our understanding of how riparian buffer width influences wood dynamics in headwater streams is relatively less developed compared to larger fish-bearing streams. The effects of riparian buffer width on instream wood loading after thinning can be difficult to discern due to the influence of basin characteristics and reach-scale geomorphology on wood recruitment, breakage and redistribution. We assessed the relationships between instream wood loading, geomorphology and riparian buffer width in small headwater streams after upland thinning. Then we examined the distances between pieces of stream wood and their sources, or the distance from which wood volumes were recruited to these streams. Data were collected along 34 stream reaches at six different sites in a replicated field experiment, comparing three no-harvest streamside buffer treatments (∼6-m, 15-mminimum, and ∼70-m widths). At each site, second-growth forests were thinned first to 200trees per ha [tph] and ∼10years later to 85tph, alongside an unthinned reference unit (∼400tph). We measured wood loading (m3/100m) four times: (1) prior to thinning; (2) year 5 post-1st thinning; (3) immediately prior to the 2nd thinning; and (4) year 1 post-2nd thinning. The majority of wood volume was in late stages of decay, most likely biological legacies from the previous forest stand, and distributed along the streambank. Surprisingly, wood volume in early stages of decay was higher in stream reaches with a narrow 6-m buffer than in stream reaches with larger 15- and 70-m buffers and the unthinned reference units. Additionally, wood volume increased with drainage basin area. Only 45% of wood in late stages of decay could be associated with a particular source. Yet, 82% and 85% of sourced wood in early and late stages of decay, respectively, originated from within 15m of streams. Expected continue low rates will likely result in declining volumes of wood in late stages of decay. Thinning and directional felling of logs into to streams could be used to augment wood volumes in the near term, and accelerate the development of large-diameter logs for future inputs. However, the relationship between instream wood loading and basin area suggests that instream wood loading depends on management across the entire watershed.