The conservation requirements of an endangered hoverfly, Hammerschmidtia ferruginea (Diptera, Syrphidae) in the British Isles

The saprophagous larva of the endangered hoverfly, Hammerschmidtia ferruginea (Fallén, 1817) (Diptera, Syrphidae) develops in wet, decaying sap under the bark of dead trees and branches of aspen, Populus tremula L. (Saliaceae). However this breeding site is transient: wet decay builds up patchily over 1.5–2 years of the tree or branch dying and lasts for a further 1–3 years before the bark falls off. Between 1990 and 2006, H. ferruginea swung through a cycle of abundance when the number of localities where it was detected dropped from 13 to 5 and back to 8. Fluctuations in amounts of dead wood caused by winds and storms probably explain this population swing. When there are few dead trees and branches, H. ferruginea breeds in sap flows on live P. tremula trees and populations are maintained but at low levels. To prevent local extinctions during periods when fallen wood is scarce, breeding habitat can be supplemented by felling trees and branches. Fallen wood with wet decaying sap is also important as an assembly site for mate selection. Adult food plants include flowers of bird cherry Prunus padus, rowan Sorbus aucuparia and hawthorn Crategus monogyna. Adults were recorded dispersing up to 1 km but are probably able to move further than this.     

Modeling decay rates of dead wood in a neotropical forest

Variation of dead wood decay rates among tropical trees remains one source of uncertainty in global models of the carbon cycle. Taking advantage of a broad forest plot network surveyed for tree mortality over a 23-year period, we measured the remaining fraction of boles from 367 dead trees from 26 neotropical species widely varying in wood density (0.23–1.24 g cm⁻³) and tree circumference at death time (31.5–272.0 cm). We modeled decay rates within a Bayesian framework assuming a first order differential equation to model the decomposition process and tested for the effects of forest management (selective logging vs. unexploited), of mode of death (standing vs. downed) and of topographical levels (bottomlands vs. hillsides vs. hilltops) on wood decay rates. The general decay model predicts the observed remaining fraction of dead wood (R ² = 60%) with only two biological predictors: tree circumference at death time and wood specific density. Neither selective logging nor local topography had a differential effect on wood decay rates. Including the mode of death into the model revealed that standing dead trees decomposed faster than downed dead trees, but the gain of model accuracy remains rather marginal. Overall, these results suggest that the release of carbon from tropical dead trees to the atmosphere can be simply estimated using tree circumference at death time and wood density.     

Edge effects on moisture reduce wood decomposition rate in a temperate forest

Forests around the world are increasingly fragmented, and edge effects on forest microclimates have the potential to affect ecosystem functions such as carbon and nutrient cycling. Edges tend to be drier and warmer due to the effects of insolation, wind, and evapotranspiration and these gradients can penetrate hundreds of metres into the forest. Litter decomposition is a key component of the carbon cycle, which is largely controlled by saprotrophic fungi that respond to variation in temperature and moisture. However, the impact of forest fragmentation on litter decay is poorly understood. Here, we investigate edge effects on the decay of wood in a temperate forest using an experimental approach, whereby mass loss in wood blocks placed along 100 m transects from the forest edge to core was monitored over 2 years. Decomposition rate increased with distance from the edge, and was correlated with increasing humidity and moisture content of the decaying wood, such that the decay constant at 100 m was nearly twice that at the edge. Mean air temperature decreased slightly with distance from the edge. The variation in decay constant due to edge effects was larger than that expected from any reasonable estimates of climatic variation, based on a published regional model. We modelled the influence of edge effects on the decay constant at the landscape scale using functions for forest area within different distances from edge across the UK. We found that taking edge effects into account would decrease the decay rate by nearly one quarter, compared with estimates that assumed no edge effect.     

Community structure of polypores (Basidiomycota) in Andean alder wood in Argentina: Functional groups among wood‐decay fungi?

Abstract The polypores (Aphyllophorales s.l., Basidiomycota) are very effective wood decayers. Different species differ in their capacity to decay wood; therefore, many functionally different species can be found decaying different substrate conditions (decay stages and log diameter). This study aimed to describe the structure of the wood‐decay polypore communities that occur on different states of wood of the Andean alder (Alnus acuminata) within Argentina and to identify groups of polypore species that share the same substrate condition, and thus might have a similar functional role in the decay processes. We found 16 polypore species, among which Trametes versicolor, Bjerkandera adusta and Trametes cubensis were dominant species, showing the highest relative frequency in alder wood. Species richness was lower on trunks of living trees and higher on dead branches. Based on preferential occurrence on different wood conditions, a cluster analysis distinguished three groups, each of them containing one of the three dominant species. This corresponds to the situation of other groups of organisms, where each functional type consists of a dominant species that accounts for most of the ‘function’ and several subordinate species with similar functions. Albeit preliminary, our results provide a formal classification of wood‐decay fungi into functional types.     

The utilization of dead wood resources by woodpeckers in Britain

Dead wood is important for woodpeckers, providing foraging, roost and nest-sites. In this paper, data from long-term studies of woodpeckers and dead wood in oakwoods in southern England are used to examine the dead wood requirements of the three British resident woodpecker species. Both Great Dendrocopos major and Lesser Spotted Woodpeckers Dendrocopos minor select dead trees for nest-sites although the former is able to nest in living trees too. On the other hand a smaller fraction of Lesser Spotted Woodpecker nests are in living trees. Green Woodpecker Picus viridis shows no selection for dead nesting trees. Hence the smallest woodpecker species appears to be most dependent on dead and decaying trees for nest-sites. Great and Lesser Spotted Woodpeckers show no preference for foraging on dead trees although they both make use of dead branches on living trees. Lesser Spotted Woodpeckers forage on smaller branches higher in the tree than Great Spotted Woodpeckers. There has been a trend for increasing dead wood resources in the study woods with both dead wood on the ground and standing dead trees (snags) increasing in the last 20 years. The levels of dead wood are shown to be the result of continual processes of creation and decay. Around 0.5% of oak Quercus spp., Ash Fraxinus excelsior and Hornbeam Carpinus betulus and 3.4% of the birch Betula spp. trees die each year in the woods resulting in a continuity of new dead snags and fallen trees. There is a high turnover of standing dead snags of oak and birch with 95% and 80% annual survival, respectively. Snags are only suitable for nesting Great Spotted Woodpeckers for a few years after their creation. It is suggested that these stand and dead wood dynamics are likely to provide habitats more favourable for the Great Spotted than the Lesser Spotted Woodpecker.     

Distribution of Myxomycetes on coarse woody debris of <Emphasis Type="Italic">Pinus densiflora</Emphasis> at different decay stages in secondary forests of western Japan

The relationship between myxomycete species and the decay stage of wood of Pinus densiflora coarse woody debris was investigated in warm temperate secondary forests of western Japan. The number of species and species diversity of the myxomycete community reached the maximum on moderately decayed wood. The 25 dominant species recorded from 8 or more samples of the total 1530 samples were arranged in order of the succession index corresponding to the stage of decay. Species on slightly decayed hard pine wood were characterized by Stemonitis splendens, Enerthenema papillatum, and Physarum viride, whereas species of Cribrariaceae were found on brittle decayed soft wood increasing abundance according to the decay stages. Most of the species occurred where there was sufficient moisture preserved in the environment of the decaying wood, although S. splendens specifically emerged in low-moisture environments. Because the myxomycete species had preference to different decay stages of wood, it appears that they change sequentially during myxomycete community succession on dead pine wood according to the progression of decay.     

Antrodia gossypium,Phlebiopsis gigantea and Heterobasidion parviporum: in vitro growth and Norway spruce wood block decay

Polymerase chain reaction-amplified and sequenced isolates of Antrodia gossypium, Phlebiopsis gigantea and Heterobasidion parviporum from decaying Norway spruce wood blocks after three and six months, which exhibited linear growth, were investigated. P. gigantea strains showed the fastest growth, whereas A. gossypium growth was five times slower. The differences between the mean daily increment of A. gossypium and the other examined isolates (except Hp2) were statistically significant. There were also significant differences in wood decay between densities over time. These results were confirmed by the decay acceleration index (DAI) and decay activity index, which were positively correlated with wood density regardless of the fungus species. The registered P. gigantea strains (Rotstop and PG Suspension) exhibited a strong decomposition ability (28% after six months); the weight loss caused by A. gossypium after six months of decay (15.2%) was similar to the results of P. gigantea (GB) after just three months (13.2%). All tested H. parviporum isolates showed rather rapid growth and equally strong wood decay (20–25%) compared to those of P. gigantea. DAI showed that A. gossypium may significantly contribute to wood decomposition over time, particularly in less dense wood samples. The use of both saprotrophs as biological agents against root pathogens is discussed.     

Relationships among wood‐boring beetles,fungi, and the decomposition of forest biomass

A prevailing paradigm in forest ecology is that wood‐boring beetles facilitate wood decay and carbon cycling, but empirical tests have yielded mixed results. We experimentally determined the effects of wood borers on fungal community assembly and wood decay within pine trunks in the southeastern United States. Pine trunks were made either beetle‐accessible or inaccessible. Fungal communities were compared using culturing and high‐throughput amplicon sequencing (HTAS) of DNA and RNA. Prior to beetle infestation, living pines had diverse fungal endophyte communities. Endophytes were displaced by beetle‐associated fungi in beetle‐accessible trees, whereas some endophytes persisted as saprotrophs in beetle‐excluded trees. Beetles increased fungal diversity several fold. Over forty taxa of Ascomycota were significantly associated with beetles, but beetles were not consistently associated with any known wood‐decaying fungi. Instead, increasing ambrosia beetle infestations caused reduced decay, consistent with previous in vitro experiments that showed beetle‐associated fungi reduce decay rates by competing with decay fungi. No effect of bark‐inhabiting beetles on decay was detected. Platypodines carried significantly more fungal taxa than scolytines. Molecular results were validated by synthetic and biological mock communities and were consistent across methodologies. RNA sequencing confirmed that beetle‐associated fungi were biologically active in the wood. Metabarcode sequencing of the LSU/28S marker recovered important fungal symbionts that were missed by ITS2, though community‐level effects were similar between markers. In contrast to the current paradigm, our results indicate ambrosia beetles introduce diverse fungal communities that do not extensively decay wood, but instead reduce decay rates by competing with wood decay fungi.     

Spatial pattern of downed logs and wood‐decaying fungi in an old‐growth Picea abies forest

Abstract. Since many wood‐living forest species are influenced by the dynamics of coarse woody debris (CWD), information about the spatial pattern of CWD under natural conditions is essential to understand species distributions. In this study we examined the spatial pattern of downed logs and wood‐decaying fungi in an old‐growth boreal Picea abies forest in northwestern Sweden that is governed by gap‐phase dynamics. The spatial pattern of wood‐decaying fungi was studied to draw conclusions about species dispersal abilities. A total of 684 logs with a diameter > 10 cm were mapped and analysed with Ripley's K‐function. The distribution of all logs taken together displayed a significant aggregated pattern up to 45 m. The different decay stages also deviated from random expectations. Fairly fresh logs and logs in the middle decay stage were clumped up to about 25 and 35 m respectively, and late decayed logs aggregated up to 95 m. Logs with diameters from 10–29 cm were aggregated up to 25 m, whereas logs ≥30 cm diameter were randomly distributed. The result suggests that gap‐dynamics do have an impact on the spatial pattern of the CWD, creating fine‐scale clumping. The random distribution of large logs may result from the slightly regular spacing of large living trees. The spatial patterns of 16 species (n > 20) of wood‐decaying fungi were analysed with Ripley's K‐function. Three patterns were aggregated, for Gloeophyllum sepiarium, Coniophora olivacea and Vesiculomyces citrinus. These results indicate that the distribution of most species at the stand level is generally not influenced by dispersal limitations.     

Effect of Change of Forest Carbon Storage on Net Carbon Dioxide Balance of Wood Use for Energy in Japan

This study analyzed the net carbon dioxide (CO₂) emission reductions between 2005 and 2050 by using wood for energy under various scenarios of forest management and energy conversion technology in Japan, considering both CO₂ emission reductions from replacement of fossil fuels and changes in carbon storage in forests. According to our model, wood production for energy results in a significant reduction of carbon storage levels in forests (by 46% to 77% in 2050 from the 2005 level). Thus, the net CO₂ emission reduction when wood is used for energy becomes drastically smaller. Conventional tree production for energy increases net CO₂ emissions relative to preserving forests, but fast‐growing tree production may reduce net CO₂ emissions more than preserving forests does. When wood from fast‐growing trees is used to generate electricity with gas turbines, displacing natural gas, the net CO₂ emission reduction from the combination of fast‐growing trees and electricity generation with gas turbines is about 58% of the CO₂ emission reduction from electricity generation from gas turbines alone in 2050, and an energy conversion efficiency of around 20% or more is required to obtain net reductions over the entire period until 2050. When wood is used to produce bioethanol, displacing gasoline, net reductions are realized after 2030, provided that heat energy is recovered from residues from ethanol production. These results show the importance of considering the change in carbon storage when estimating the net CO₂ emission reduction effect of the wood use for energy.     

When does dead wood turn into a substrate for spruce replacement?

Question: How many years must elapse for freshly fallen Picea abies stems to be transformed into a substrate for P. abies recruitment? Location: Natural sub‐alpine spruce forest, 1200–1300 m a.s.l., western Carpathians, Poland. Methods: Coarse woody debris (CWD) was measured on nine plots with a total area of 4.3 ha. All individuals of P. abies regeneration growing on dead wood were counted and their age was estimated. Decay rate of logs was determined using dendrochronological cross‐dating of samples from logs in different decay stages. Results: Although CWD covered only 4% of the forest floor, 43% of the saplings were growing on decaying logs and stumps. The highest abundance of P. abies recruitment occurs on logs 30–60 years after tree death, when wood is in decay stages no. 4–7 (on an 8 degree decay scale). However, much earlier colonization is possible. The first seedlings may germinate on a log during the second decade after tree death and survive for decades. Their slow growth is possibly due to the gradual progressive decomposition of wood. Conclusions: This study confirms the importance of decaying wood for P. abies recruitment. The decaying logs exhibit continuous and favourable conditions for the germination of P. abies seeds throughout their decay process. Logs, irrespective of their decay stage and age, are colonized by young seedlings. This recruitment bank is constantly renewed.     

Nutritional dynamics during the development of xylophagous beetles related to changes in the stoichiometry of 11 elements

The present study examines the adaptive strategy used by wood‐boring beetles to compensate for the lack of nutrients in dead wood. The contents of nutritional elements in growing wood‐boring beetles (Stictoleptura rubra L. and Chalcophora mariana Dejean) are compared with the elemental composition of decaying dead wood (pine stumps), showing changes during the beetles' ontogenetic (i.e. larval) development. The stoichiometric ratios of C and other nutritional elements (N, P, K, Na, Ca, Mg, Fe, Zn, Mn and Cu) are investigated to identify the most important nutrients for larval development. The degree of nutritional mismatch that is encountered by the beetle larvae changes dramatically over 3–4 years of simultaneous larval growth and wood decay. Excluding C, the relative contents of nutritional elements increase substantially in decaying wood, whereas the opposite tendency is found in larvae, most likely because of carbon deposition in fat. The elements limiting larval development because of their scarcity in dead wood are N, P, K, Na, Mg, Zn and Cu. Fungal activity (i.e. the transport of nutrients from the surrounding environment to decaying stumps) can explain the observed mitigation of the original mismatch, although prolongation of the larval development time is still necessary to compensate for the scarcity of some of the required elements in food.     

Resistance of Scots pine wood to Brown-rot fungi after long-term forest fertilization

The susceptibility of Scots pine (Pinus sylvestris L.) sap- and heartwood against the wood decaying brown-rot fungus (Coniophora puteana) was investigated after long-term forest fertilization at three different sites in central Finland. Different wood properties: wood extractives, wood chemistry, and wood anatomy were used to explain sap- and heartwood decay. Scots pine sapwood was more susceptible to decay than its heartwood. In one site, sapwood seemed to be more resistant to wood decay after forest fertilization whereas the susceptibility of heartwood increased. Significant changes in the sapwood chemistry were found between treatment and sites, however, no relationship between wood chemistry and wood decay was observed in the factor analysis. The results of this study show that there was an inconsistent relationship between decay susceptibility and fertilization and the measured physical and chemical attributes of the wood were not consistently correlated with the decay rate.     

Survey of subterranean termites (Isoptera: Rhinotermitidae) in a managed silvicultural plantation in Portugal, using a line-intersection method (LIS)

Subterranean termites (Reticulitermes grassei) were surveyed over successive seasons in a managed eucalyptus plantation in southeastern Portugal for 26 months. Termite activity in seven diameter categories of lying dead wood was investigated by a modified line intersection method (LIS). Each item sampled was inspected and assessed for termite attack and for general (i.e. fungal) decay status using standard protocols. Line intersection is quantitative to the extent that it can link foraging and decay parameters to woody biovolume. It was found that termites selected items with larger diameter, the observed trend showing an exponential character with greater termite attack as diameter increased. Attack by termites was positively associated with prior decay by fungi. A clear positive relationship was shown between rainfall and total woody biovolume containing live termites, underlining the importance of moisture for termite activity. Subterranean termites appeared to be important wood decomposers in the woodland studied, with an average of 30% of lying dead wood branches showing signs of termite attack.     

Optimization of sampling procedures for DNA‐based diagnosis of wood decay fungi in standing trees

Aims: To develop fast and reliable sampling procedures for DNA‐based diagnosis of wood decay fungi in standing trees. Methods and Results: A total of 250 trees were tested for the presence of a suite of wood decay fungi by collecting wood frass obtained by drilling each tree once with a 4‐mm‐diameter, 43‐cm‐long bit. We identified at least one of 11 target wood decay fungi in 56 trees through multiplex PCR assays. The presence of target wood decay taxa was further investigated in these 56 trees, by analysing independently wood from each of six drillings. Results were then compared with those obtained using sampling schemes differing in terms of number and position of drillings. Samples of 1–4 drillings were either analysed separately, and the results were combined, or pooled together before analysis was performed. In comparison with taxa identified by the analysis of six drillings, diagnostic efficiency ranged from 56·6% for the scheme based on a single drill to 96·8% for the scheme based on four drillings analysed separately. Both schemes significantly differ (P < 0·05) from those based on two and three drillings, whose efficiency was 72·6% and 83·9%, respectively. Diagnostic efficiency of pooled samples was comparable to that of samples analysed separately. Conclusions: Highest diagnostic efficiency was obtained by analysing wood from four drillings. It is advisable to pool samples deriving from different drillings to reduce laboratory costs. Significance and Impact of the Study: Fast and reliable sampling procedures make DNA‐based diagnosis more suitable for tree inspection procedures.     

Sequence of bryophytes and lichens in relation to substrate variables of decaying coniferous wood in Northern Sweden

Söderström, L. 1988. Sequence of bryophytes and lichens in relation to substrate variables of decaying coniferous wood in Northern Sweden. - Nord. J. Bot. 8: 89–97. Copenhagen. ISSN 0107–055X.
The species sequence on decaying logs during the decay period has been investigated in a forest in Northern Sweden. The species present can be divided, by means of a weighted average technique, into four groups, facultative epiphytes, early and late epixylics, and ground flora species.
Species sequence on several variables reflecting the wood decay, was measured for 25 species. Wood texture (degree of surface erosion) was the most important variable in separating species. Logs high above ground had very few species, probably due to low moisture content. Log diameter was important and several species did not occur, or only rarely occurred, on small logs. Small logs are more rapidly overgrown by ground flora species and very few reach late decay stages before being overgrown. Larger logs also have greater waterholding capacity which facilitates growth of many species sensitive to drought.     

Decomposition of standing dead trees in the southern Appalachian Mountains

Summary Decomposition of standing dead trees that were killed by fire was examined for 10 species in the Great Smoky Mountains National Park. The decrease in wood density as fire age increased was used to estimate decomposition rates. Quercus prinus had the fastest decay rate (11% yr^-1) while Pinus virginiana had the slowest decay rate (3.6% yr^-1) for standing dead wood. Decay rates were intermediate between those reported in western USA and tropics for wood.     

Factors affecting fall down rates of dead aspen (Populus tremuloides) biomass following severe drought in west‐central Canada

Increases in mortality of trembling aspen (Populus tremuloides Michx.) have been recorded across large areas of western North America following recent periods of exceptionally severe drought. The resultant increase in standing, dead tree biomass represents a significant potential source of carbon emissions to the atmosphere, but the timing of emissions is partially driven by dead‐wood dynamics which include the fall down and breakage of dead aspen stems. The rate at which dead trees fall to the ground also strongly influences the period over which forest dieback episodes can be detected by aerial surveys or satellite remote sensing observations. Over a 12‐year period (2000–2012), we monitored the annual status of 1010 aspen trees that died during and following a severe regional drought within 25 study areas across west‐central Canada. Observations of stem fall down and breakage (snapping) were used to estimate woody biomass transfer from standing to downed dead wood as a function of years since tree death. For the region as a whole, we estimated that >80% of standing dead aspen biomass had fallen after 10 years. Overall, the rate of fall down was minimal during the year following stem death, but thereafter fall rates followed a negative exponential equation with k = 0.20 per year. However, there was high between‐site variation in the rate of fall down (k = 0.08–0.37 per year). The analysis showed that fall down rates were positively correlated with stand age, site windiness, and the incidence of decay fungi (Phellinus tremulae (Bond.) Bond. and Boris.) and wood‐boring insects. These factors are thus likely to influence the rate of carbon emissions from dead trees following periods of climate‐related forest die‐off episodes.     

谷蠹感染的小麦储存环境中二氧化碳浓度变化研究

在25℃和密闭条件下测定了谷蠹Rhyzopertha dominica(F.)密度分别为0、2、5、10和20头/kg的小麦储存环境中二氧化碳浓度的变化情况。主要结果为:含水量为12%的小麦,未感染谷蠹成虫时,在180d内二氧化碳浓度从0.048%增加到1.157%;以2头/kg密度感染后,同样时间内二氧化碳浓度从0.048%上升到9.910%。害虫密度增加,产生的二氧化碳浓度都相应地增高,但二氧化碳的浓度与害虫密度不是相应地成比例升高。感染不同害虫密度的粮食,二氧化碳浓度随时间的延长呈"S"型曲线增长。这些结果表明,小麦感染谷蠹后在很短时间后即可检测到储存环境中二氧化碳浓度显著增加,二氧化碳浓度的变化与虫口密度相关。同样害虫密度时,储存时间延长,二氧化碳浓度呈"S"型曲线增加。一定条件下可通过检测二氧化碳浓度反映粮情和虫情变化。     

Dendrochronological assessment of the time since death of dead wood in an old growth Magellan's beech forest,Navarino Island (Chile)

The present study investigated the relationship between time since death and the morphological characteristics of fallen dead trees in a Nothofagus betuloides forest stand located on the island of Navarino (Chile). In this unmanaged forest, there were 399 m³ ha^?1 of dead wood, which represented about half of the living tree volume. At the investigation site, 18 living trees were selected and increment cores were collected from them to build master ring‐width chronologies. Cross sections were also collected from 48 fallen dead trees. The samples collected were then assigned to observable decay classes and their death date was determined dendrochronologically. Cross‐dating techniques were used and it was found that the fallen dead trees cross‐dated significantly with standard chronologies. A year of death was successfully determined for 75% of the sampled fallen dead trees. However, this study demonstrated that, in the standard classification, the transition rate from one class of decay to another was highly variable. Furthermore, the inconsistencies found in the decay rates of the fallen dead trees demonstrated that the existing decay classification schemes were unsuitable for this type of forest stand and that the relationship between qualitatively assessed decay classes and the time since death of trees in this extreme environment was rather weak. In addition, the analysis of the time since death, in this old growth forest, was indicative of the persistence of dead wood on the forest floor in austral cold ecosystems and of its contribution to long‐term carbon storage.