Discoloration following bark stripping wounds on Fraxinus excelsior

A total of 101 Fraxinus excelsior trees 8–32 cm in d.b.h. with bark stripping wounds caused by Alces alces and Cervus elaphus in Lithuania were cut, dissected and examined. The injuries ranged in age from 5 to 18 years, when the trees were 22–40 years old and were in the size range 6–24 cm d.b.h. For 5-10 years old wounds, the mean length of associated wood discoloration was 804 × 201 cm, while in 16–18 years old wounds it was 912 × 144 cm. There was no correlation between wound age and extent of discoloration in the stems examined (r = 0.11). Tree d.b.h. and wound size (initial width × length) were correlated with the extent of discoloration (r = 0.43 and r = 0.20, respectively). The presence of complete wound occlusion had no significant effect on the length of columns of discoloration associated with wounds of 10 or more years old. The average occlusion rate during the first 10 years was 128 × 28 mm or 13 mm/year, correlating positively with the radial increment (r = 0.42). Amongst a total of 500 F. excelsior trees with wounds, 29 trees (5.8%) bore basidiomycete fruiting bodies. Most common was Phellinus punctatus, found on 12 (2.4%) stems, followed by Coniophora puteana (1.6%), Peniophora limitata (0.4%) and Datronia mollis (0.4%). Fungi most commonly isolated from discoloured wood were ascomycetes Phaeoacremonium rubrigenum, Phialophora malorum, Hypoxylon rubiginosum, Coniothyrium sporulosum, Libertella spp., Ophiostoma sp., and basidiomycetes Ischnoderma benzoinum, Ischnoderma resinosum, Tyromyces sp.     

Healing ability and diameter growth of lime-trees (<Emphasis Type="Italic">Tilia begonifolia</Emphasis> Stev.) following logging wounds

Lime-trees (Tilia begonifolia Stev.) have countless ecological and economical values in the northern forests of Iran. Bole wounds on residual trees are commonly caused by logging. The healing ability of bole wounds and the effect of bole wounds on diameter growth in lime-trees were assessed in a natural mixed uneven-age stand. The susceptibility to decay in relation to the wound severity was also evaluated. Condition and location of lime-trees before and after selective logging were determined through systematic plot sampling. The position of each lime-tree was identified on a topographical map using the global positioning system. After 10 years from wound occurrence, tree and wound characteristics were also re-measured. Overall, 68 stems (9.7 stem ha^?1) of lime-trees were found in the sampled area, 25 stems (36.8%) were damaged in the form of bole wound, and 43 stems (63.2%) were undamaged. Statistical differences between wounded or non-wounded lime-trees in terms of diameter and height were not found. Most of the wounds occurred at the height of < 1 m; the average wound size was 370.5 cm². Wound severity was related to wound size and wound position. Wound width healing rate was 6.2 mm year^?1. The wound shape was found to be a healing factor as the healing rate by width was higher than that by length. Healed wounds were only 12, 60% of bole wounds resulted in decay. Diameter growth of wounded trees was 43.5% lower than undamaged trees. The average annual diameter growth decreased by increasing wound severity. The results indicated the lime-tree is a very sensitive species to damage caused by logging (bole wound). Single-tree selection cutting needs more careful logging operations to reduce damage on residual lime-trees in order to safeguard this species, valuable in ecologic and economic terms.     

The Development of Stain in Wounded Sitka Spruce Stems

In order to investigate the severity of staining in woundedSitka spruce stems, the vertical extent of two categories ofstain (based on colour and termed ‘light’ and ‘heavy’)was measured in stems at two sites in south Scotland. Data wereobtained from 98 wounds most of which were between 8 and 14years old and most of which had been caused by Red deer. Theupward extent of stain and its rate of upward spread were positivelycorrelated with wound surface area and length. Most stain wasof the light type which, although it was associated with nearlyall wounds, usually constituted an insignificant defect anddid not commonly extend for more than 1 m ahve wounds. Heavystain occurred above less than half of all wounds studied butwas common above wounds exceeding 300 cm² surface area. Forall wounds, the mean value for the upward extent of heavy stainwas 16.1 cm with a mean rate of spread of 1.9 cm y^–1.However, for wounds exceeding 300 cm² surface area, the valueswere 51.7 cm and 5.5 cm y^–1. These results suggest that,although there is an important effect of wound size on the typeand extent of stain, wounds of the type studied are unlikelyto lead to severe stain and decay in Sitka spruce over a periodof 8–14 years. The results are discussed in relation toother studies on wound staining in conifers.     

Wound occlusion and decay in Picea abies stems

In forest stands, Picea abies is commonly subjected to logging and bark stripping injuries. Most mechanical wounds do not exceed 300 cm², but their pathological consequences are unclear. The aim of the study was to estimate the rate of wound occlusion and the probability of decay in P. abies stems in relation to initial wound size and wounding season. The study included forty-five stems with 1-, 2-, 3-, 4- and 5-cm-wide by 15-cm-long wounds (15–75 cm²), and eighty-three stems with 15-cm-wide by 20-cm-long wounds (300 cm²), made either in January or in August. After 19–21 years, each wound was assessed for occlusion rate and the presence of decay. All 1- to 2-cm-wide wounds were occluded, compared to 58–70% of the 3- to 4-cm-wide wounds, 25% of the 5-cm-wide wounds, and 0% of the 15-cm-wide wounds. On average, it took 3.6, 5.5, 10.4, 12.7 and 14.7 years to occlude wounds ranging in size from 1- to 5-cm-wide, respectively. After 21 years, the observed size of wounds comprising an initial area of 300 cm² ranged between 14 and 481 cm². Wounding season and stem DBH had no impact on wound healing. Wound decay incidence correlated positively with the initial width of injury (r = 0.925; P < 0.05). All 1- to 2-cm-wide wounds lacked any decay, while the proportions of decay among 3-, 4-, 5- and 15-cm-wide wounds were 58.3, 50.0, 83.3 and 100%, respectively. Length of decay comprised 35–225 cm. Consequently, wounds on P. abies stems greater than 5 cm width are unlikely to be occluded and more prone to decay development.     

Fungi in bark peeling wounds of Picea abies in central Sweden

A total of 210 Norway spruce trees with stem wounds resulting from bark peeling by moose (Alces alces) were examined in three 45–50-year-old stands that contained 20-30% of damaged trees. Injured stems were between 8 and 40 cm diameter at breast height (d.b.h.) and showed 1 to 23-year-old wounds. Wounds varied in size from 2 to 4815 cm². The size of injury correlated negatively with the age of the injury (r=-0.24; p=0.004), and positive correlation was established between the age of the injury and d.b.h. of the wounded tree (r=0.50; p=0.0001). Each wound was sampled once using an increment borer and fungi were isolated. Among basidiomycetes, Stereum sanguinolentum was the most common (isolated from 26.7% of the damaged stems). Other common species were Cylindrobasidium evolvens (23.8%), Amylostereum areolatum (5.2%), A. chailletii (0.5%), Heterobasidion annosum (5.2%), Peni-ophorapithya (1.4%), Sistotrema brinkmannii (1.0%). The ascomycete Nectria fuckeliana was the most common among all fungi (present in 35.7% of bark peeling wounds). The frequency of S. sanguinolentum infection correlated positively with the age of the injury (r=0.27; p=0.001) and the opposite relationship was revealed for C. evolvens (r=?0.30; p=0.0001). Furthermore, C. evolvens infection correlated positively with the wound size (r=0.30; p=0.0001) and negatively with the tree d.b.h. (r=?0.20; p=0.004). A positive correlation was found between tree d. b. h. and the occurrence in stems of H. annosum (r=0.23; p=0.001 and N. fuckeliana (r=0.23; p=0.0006). The spruce bark beetle Dendroctonus micans attacked 14.8% of wounded trees. Presence in stems of N. fuckeliana was associated significantly with the D. micans attack (r=0.190; p =0.006; χ² test: p=0.01). Except for a negative correlation between infections of S. sanguinolentum and H. annosum (r=-0.140; p=0.04), no significant relationship between fungal species was found.     

Treatment of wounds on Acer rubrum with Trichoderma viride1

Wounds on 90 Acer rubrum trees were inoculated with Trichoderma viride in July and August 1973 to determine the effect of the fungus on the development of decay. The trees were 45 years old and 15 cm diam at 1.4 m aboveground. Each tree had 12 wounds, 1.4 cm in diam and 5 cm deep. After a year 28 trees were harvested and isolations were made from the discolored, and decayed wood associated with each wound. Trichoderma viride was reisolated from all wounds that were inoculated with it. Hymenomycetes were isolated frequently from decayed wood associated with wounds not inoculated with T. viride. No Hymenomycetes were isolated from wounds inoculated with T. viride.     

Impact of bark wounds on sapwood in Norway spruce and silver fir

Bark wounds by damage during harvesting are a serious problem in forestry due to fungi infection and wood deterioration. This paper presents results of an investigation about the influence of the wounds on the internal structure of such injured stems. In an experiment, bark wounds were artificially created at the stem base of Norway spruce [Picea abies (L.) Karst.] and silver fir (Abies alba Mill.). 2 years later, the injured stems along with undamaged controls were cut and the trunk portion below breast height subjected to computer tomographic (CT) analysis. Analysis of the CT-images revealed a substantial impact of wounding on sapwood properties in spruce: directly adjacent to the wound surface in all examined trees, a large disturbance zone was detected affecting on average 17% of the potential sapwood area. With increasing distance from the wound, the size of this disturbance zone diminished, but was still detectable in all trees at breast height ca. 1 m above the bark wound.     

Discoloured wood of aspen caused by increment boring

Decay resulting from increment borings varies with tree species. Trembling aspen (Populus tremuloidcs Michx.) in Newfoundland is seriously affected by this particular wound. Three years after 20 trees had been bored, none had healed probably because of a pronounced split of the bark. The wood discoloration extended horizontally to about 2 cm on each side and vertically half metre above and below the wound. Peniophora polygonia (Pers. ex Fr.) Bourd. et Galz. was the most common fungus isolated while Polyporus adustus Willd. ex Fr. and several imperfect fungi and bacteria were also present.     

Contribution of active defense responses in the limitation of fungal spread in the sapwood of living sugi (Cryptomeria japonica) tree

The participation of active defense responses in the limitation of fungal spread in the sapwood of living sugi tree was determined. Isolates ofGuignardia cryptomeriae were inoculated to living trees, fresh logs, frozen and thawed logs and autoclaved logs, and the spread of wood discoloration and fungal hyphae was assessed. In autoclaved logs and freeze-treated logs, wood discoloration and reaction zone formation were not observed, and fungal hyphae of both of virulent and avirulent isolates grew rapidly in the wood. In fresh logs, wood discoloration and the formation of a pale reaction zone and transition zone were observed. Virulent isolates spread rapidly, but the spread of avirulent isolates was inhibited. In living trees, wood discoloration was observed and reaction zones were formed at lesion margins. These results indicated that constitutive defense mechanisms had no effect on the spread of both of virulent and avirulent isolates, and that active defense responses were important in the limitation of spread of fungal hyphae, hence in the limitation of wood discoloration. Further, it appeared that avirulent, but not virulent, races ofG. cryptomeriae were easily inhibited even by weak host responses. This study was presented at 105th and 106th Annual Meeting of the Japanese Forestry Society.     

Factors influencing infection of Acacia mearnsii by the wilt pathogen Ceratocystis albifundus in South Africa

It is well known that species of Ceratocystis, which cause canker and wilt diseases on trees, require wounds for infection. In this regard, a number of physical and environmental factors influence the success of wound colonization by these fungi. The aim of this study was to consider the influence of wound age, stem diameter and colonization of wounds by Ophiostoma quercus on the success of infection by Ceratocystis albifundus, an important wilt pathogen of Acacia mearnsii in southern and eastern Africa, under field conditions. This was performed by doing controlled inoculations on Acacia mearnsii trees, of different diameters, with C. albifundus at different time intervals after wounding and after pre‐inoculation of wounds with O. quercus at the time of wounding. The success of infection by C. albifundus decreased significantly from 8 h after wounding and was higher on stems of greater diameter. Pre‐infection of wounds by O. quercus reduced the infection success of C. albifundus. The overall results showed that managing wounds created during forestry operations by treating wounds with naturally occurring, non‐virulent fungi, such as O. quercus, could reduce the prevalence of infections by C. albifundus.     

Damage to residual stands from thinning with short-span tower yarders: Re-examination of wounds after five years

The current status of wounds on residual trees was investigated and compared with the wound status from five years ago when the stands were thinned and logged. Wound status was defined according to the four levels of severity based on appearance. Several damaged trees were cut for inspection of the wounded areas. Most wounds of a lighter severity level had already healed by occlusion and were no longer evident. Wounds reflecting heavy damage but had healed, were smaller in the horizontal dimension, or width, than those not yet healed. Slight wounds, but with a current status reflecting persistent damage were smaller in the vertical dimension, or length. An inspection of wound sections revealed the development of discoloration in the wood. Only the slight wounds that healed early had no or small discolored areas. The width of discolored areas of wounds in which cambium was still exposed was greater than the original width of the wound. In conclusion, wound width rather than length significantly affects healing or occlusion of wounds.     

Long‐term survival and non‐vector spread of the pinewood nematode,Bursaphelenchus xylophilus,via wood chips

The pinewood nematode, Bursaphelenchus xylophilus, is the causal agent of pine wilt disease and is transmitted to new host trees by beetles of the genus Monochamus. The increasing interest in imported wood chips from North America for paper production and energy purposes and the corresponding phytosanitary risk of non‐vector transmission of B. xylophilus has been discussed since 1984, the year of the first interception of B. xylophilus in wood chips in the European Union. The long‐term survival of B. xylophilus in wood chips and its non‐vector spread from infested wood chips to non‐infested trees were studied. Pinus sylvestris logs were inoculated with a suspension of B. xylophilus to produce infested wood chips. During the long‐term storage test, B. xylophilus in P. sylvestris wood chips were examined. Four variants, including sealed and openly stored wood chips at both 15°C and 25°C, were studied. For the test of non‐vector spread, B. xylophilus ‐infested wood chips were placed on three‐ to four‐year‐old P. sylvestris saplings under different conditions. Bursaphelenchus xylophilus survived for more than 1 year at both temperatures in the sealed wood chips, which was significantly longer than for the openly stored variant at 25°C. Temperature, tree condition and wood chip location all influenced non‐vector spread through wood chips. Of the 480 trees that were in contact with infested wood chips and showed clear symptoms of pine wilt disease, B. xylophilus were extracted from 42 pines at 25°C and one pine at 15°C. The highest B. xylophilus infestation rates resulting in clear pine wilt disease symptoms (75%) were found in infested wood chips directly attached to stem‐wounded trees at 25°C. However, more variants exhibited B. xylophilus infestation at this temperature; trees with stem or root injuries plus direct contact with infested wood chips to the wounded part were primarily affected. Moreover, non‐vector spread was also detected in stem‐ and root‐injured pines without any direct contact with infested wood chips. Our results confirmed that B. xylophilus can survive for long periods in wood chips and can be transmitted from infested wood chips to damaged trees, but the likelihood of such PWN establishment should be low compared to spread through vectors. These findings must be considered in the pest risk analysis of B. xylophilus, and studies using outdoor trials should be carried out to complete this pest risk analysis.     

Clonal propagation of Pterocarpus santalinoides L'Hér. ex DC.: the effect of substrate,cutting type,genotype and auxin

Pterocarpus santalinoides is a multipurpose tree species, native to Africa and South America. However, excessive pruning for fodder is jeopardising its seed production leading to poor regeneration in the Sahel region. Efficient vegetative propagation techniques may overcome this concern. To address this issue, four experiments were conducted to determine the effects of substrate (Experiment 1), cutting type (Experiments 2 and 3), genotype (Experiment 4) and auxins (Experiments 1, 2, and 4) on rooting ability in a non-mist propagating unit in Mali. Among the four tested substrates, no significant differences were found in rooting parameters, including the percentage of rooted cuttings, the number of roots and secondary roots per rooted cutting, and the length of the longest root per rooted cutting. Semi-hardwood cuttings rooted significantly better than softwood cuttings with a higher percentage of rooted cuttings (31.7?±?6.5% vs. 9.2?±?2.7%), greater number of roots (8.2?±?4.8 vs 1.5?±?0.7), greater number of secondary roots (16.7?±?4.2 vs 4.6?±?1.8) and longer root length (17.8?±?12.0?cm vs 2.3?±?1.0?cm) per rooted cutting. In addition, one-node cuttings cut below the second and third nodes, respectively, had the highest rooting success (88% and 90%, respectively) followed by cuttings cut below the fourth node (68%) and the first node (62%). Significant differences in the percentage of rooted cuttings were found among 12 randomly selected genotypes with rooting varying from 2% to 75%.The results also showed that auxin application, especially IBA, had a significant effect on rooting success, the number of roots and secondary roots per rooted cutting. Single-node cuttings, and cuttings of 10?cm length with multiple softwood and semi-hardwood nodes, can be used with or without auxin treatment for successful clonal propagation of P. santalinoides. The results of the present study indicated that P. santalinoides is amenable to clonal propagation using low-cost propagators and sand-based rooting media.     

Wood‐rotting basidiomycetes are a minor component of fungal communities associated with Acacia hybrid trees grown for sawlogs in South Vietnam

Acacia hybrid (Acacia mangium × Acacia auriculiformis) clones are widely planted in Vietnam with a total of approximately 400,000 ha to meet the demand for pulpwood, sawn timber and wood chip exports. Silvicultural techniques such as pruning and thinning have been applied to improve productivity and sawlog quality of Acacia hybrid plantations. However, those techniques may also create opportunities for wood decay fungi to enter the Acacia hybrid stems through wounds and cause stem defects that reduce sawlog quality and the value of the plantation. The presence of fungal decay agents in Acacia hybrid trees was examined in two Vietnamese plantations. In July 2011, just prior to a second thinning, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Phan Truong Hai for the isolation of fungi. In July 2012, approximately 18 months after pruning and thinning treatments, discoloured wood samples were taken from a three‐year‐old Acacia hybrid plantation at Nghia Trung for the isolation of fungi. DNA sequencing of the rDNA ITS identified the isolates. In May 2015, approximately 4 years after thinning and fertilizer treatments, discoloured and decayed wood samples were taken from the above (7‐year‐old) Acacia hybrid plantation at Phan Truong Hai for fungal identification. DNA was extracted directly from discoloured and decayed wood samples and fungal rDNA ITS amplicons sequenced on a Roche 454 sequencer. The results showed that silvicultural treatments did not affect the fungal communities associated with discoloured and decayed wood of Acacia hybrid plantation at Phan Truong Hai. A total of 135 fungal species or OTUs (operational taxonomic units) were identified, including 82 members of Ascomycota and 52 Basidiomycota.     

Logging activity and tree regeneration in an Amazonian forest

We studied the effect of experimental logging of 4 ha plots on the regeneration of tree species in a forest 90 km north of Manaus, Amazonas, Brazil. Logging resulted in a total reduction in live wood volume of 44–107 m³ ha⁻¹, although only 63% of this volume was felled, and only 43% removed from the plots. The density of established regeneration (trees and shrubs with diameter at breast height ≤10 cm, and height ≥200 cm) was greater in logged plots than in control plots when measured 3 and 7–8 years after logging. Species richness was also significantly higher in logged plots than in controls. We registered 139 species per 1000 stems, 7–8 years after logging, 143 species per 1000 stems, 3 years after logging, and 136 species per 1000 stems in control plots. Overall species composition was significantly affected by the intensity of logging damage in the plots after 7–8 years, and control plots were significantly different from plots logged 3 years previously. However, changes were not great in relation to natural variation within the forest. Most species increased in density after logging (mean=17%), and the number of individuals belonging to species with commercial value on the local market was 15% greater in logged plots than in control plots. The total potential value of the regeneration, based on the value of wood per m³ (when adult) of the individuals, was 23% higher in logged plots than in control plots, though this difference was not statistically significant. Therefore, enrichment planting is not necessary to maintain either the biodiversity, or potential economic value for wood production, of this forest.     

Response of maple sapwood to injury and infection

In sapwood challenge experiments in Acer rubrum, columns of discolouration initiated by wounding and inoculation with pioneer fungi (Cephalosporium sp., Phialophora sp.) were similar in size to untreated wounds. Inoculation with decay fungi (Pleurotus ostreatus, Trametes versicolor) produced larger columns of wound-initiated discolouration. The removal of bark around a bore wound caused a significantly larger column to form compared to the sum of the columns inititiated by separate wounds. Stage-I discoloured wood, not associated with obviously rotted wood, had concentrations of mobile cations and soluble phenols similar to sapwood. Stage-II discoloured wood, spatially associated with rotted wood, was frequently bounded by a chemically distinct boundary layer and the discoloured wood contained significantly greater concentrations of mobile cations and soluble phenols than stage-I discoloured wood.     

Stem-rot damage and the progress of causal fungi in old-aged Japanese larch trees at the foot of Mt. Fuji

Damage caused by stem-rot and the progress of the causal fungi in old-aged Japanese larch (Larix kaempferi (Lamb.) Carr.) was investigated at the foot of Mt. Fuji. Stem-rot was found in 75% of 108 trees investigated, and volume of rot was 6% of the total wood volume in the forest investigated. Stem-rot damage was much greater than the damage by butt-rot.Stereum sanguinolentum (Alb. and Schw. ex Fr.) Fr. infected larch trees at the greatest incidence (49.4%). However,Porodaedalea chrysoloma (Fr.) Imaz. caused the most volume loss to the trees.S. sanguinolentum infected larch stems mainly through stem wounds, and decay caused by the fungus progressed 9.75×10² cm³/year on average.P. chrysoloma infected larch stems mainly through dead branches and wounds, and the average rate of decay progress for the fungus was 2.74×10³ cm³/year.     

A rapid staining‐assisted wood sampling method for PCR‐based detection of pine wood nematode Bursaphelenchus xylophilus in Pinus massoniana wood tissue

For reasons of unequal distribution of more than one nematode species in wood, and limited availability of wood samples required for the PCR‐based method for detecting pinewood nematodes in wood tissue of Pinus massoniana, a rapid staining‐assisted wood sampling method aiding PCR‐based detection of the pine wood nematode Bursaphelenchus xylophilus (Bx) in small wood samples of P. massoniana was developed in this study. This comprised a series of new techniques: sampling, mass estimations of nematodes using staining techniques, and lowest limit Bx nematode mass determination for PCR detection. The procedure was undertaken on three adjoining 5‐mg wood cross‐sections, of 0.5 × 0.5 × 0.015 cm dimension, that were cut from a wood sample of 0.5 × 0.5 × 0.5 cm initially, then the larger wood sample was stained by acid fuchsin, from which two 5‐mg wood cross‐sections (that adjoined the three 5‐mg wood cross‐sections, mentioned above) were cut. Nematode‐staining‐spots (NSSs) in each of the two stained sections were counted under a microscope at 100× magnification. If there were eight or more NSSs present, the adjoining three sections were used for PCR assays. The B. xylophilus– specific amplicon of 403 bp ( DQ855275 ) was generated by PCR assay from 100.00% of 5‐mg wood cross‐sections that contained more than eight Bx NSSs by the PCR assay. The entire sampling procedure took only 10 min indicating that it is suitable for the fast estimation of nematode numbers in the wood of P. massonina as the prelimary sample selections for other more expensive Bx‐detection methods such as PCR assay.     

Pre-commercial thinning,birch admixture and sprout management in planted Norway spruce stands in South Sweden

Early management of the regenerated seedlings shapes the future stand properties. To address these issues, pre-commercial thinning (PCT) and control treatments were applied to planted Norway spruce (Picea abies L. Karst) and naturally regenerated birch (Betula pendula Roth., Betula pubescens Ehrh.) stands in forest experiments in southern Sweden (lat. 56–57?N) containing 1.1–5.5?m tall saplings. The treatments were retention of 1000 or 2000?stems?ha^?1 of Norway spruce, with no birch or birch at 1000?stems?ha^?1. Treatments were replicated with and without annual removal of birch sprouts from stumps. The periodic annual increment (PAI) over five years was calculated for total stand volume and individual trees. The mean PAI of dominant trees was significantly higher both following all PCT treatments than controls, and following low rather than high-density PCT. Birch retention did not affect growth of the dominant trees but PAI was lower in plots with uncontrolled sprouting. The PAI of birch was significantly higher in low-density Norway spruce plots than in control plots and the high-density plots. The treatment response was significant even in stands with initial heights of only 1–2?m.