Deadwood Decomposition Research Articles

Quantitative and qualitative attributes of dead wood in dominated by Carpinus betulus L. forests in Kaniv Nature Reserve

The article presents the quantitative and qualitative attributes of dead wood in forests dominated by Carpinus betulus L. in Kaniv Nature Reserve. The study was conducted in 130–140-year natural common hornbeam forests on two permanent sample plots of 0.24 ha each by identifying and measuring all components of standing and lying (fallen) dead wood. It was found that wood detritus has an average volume of 39.8 m3/ha consists of standing dead trees (23.1%) and fallen dead wood (76.9%). The species composition is dominated by common hornbeam (96.5%), and the share of Norway maple (Acer platanoides L.) is low (3.5%). Wood of II (13.2 m3/ha, 33.1%) and III (12.2 m3/ha, 30.7%) classes of destruction predominates. Standing dead wood is formed by only one tree species — common hornbeam and has an average volume of 9.2 m3/ha. It is represented mainly by standing broken trees. The volume of standing dead wood is dominated by wood detritus of the II stage of decomposition (95.7%). Fallen dead wood is formed by two tree species — common hornbeam (95.4%) and Norway maple (4.6%), has an average volume of 30.6 m3/ha. It is represented by whole uprooted and broken fallen trees (trunks), fragments of fallen trees (trunks) and rough branches. Lying dead wood is represented by detritus of all five classes of decomposition, but wood of III (12.2 m3/ha, 39.9%) and IV (9.6 m3/ha, 31.4%) classes predominates. The volume of fallen dead wood is mainly formed by components with an average diameter of 10.1–30.0 cm (75.7%). The diversity of fractions and components, structural features, sizes and stages of decomposition of dead wood can be important in the formation of potential habitats and substrates for a number of species of living organisms.

Warming effects on wood decomposition depend on fungal assembly history

Abstract Climate warming has the potential to drive changes in fungal community development and dead wood decomposition, but our understanding of this process is obscured by complex interactions between temperature and multiple other factors. A pivotal factor driving decay dynamics is fungal assembly history, yet its response to elevated temperature is poorly understood. We investigated the combined effect of warming and assembly history on community composition, respiration and decomposition using experimental communities of wood‐decaying fungi on spruce wood. Assembly histories were assigned to microcosms under normal and elevated temperatures in a factorial design. Both temperature and assembly history influenced wood mass loss and respiration. Temperature was the most important factor, but the effects of warming on decomposition varied greatly with fungal assembly history. Depending on which fungal species colonized first, warming of 5°C increased wood mass loss by 7%–57% after 9 months. The large variation in decomposition response to warming resulted from differential responses in the growth of initial colonizers (pre‐inoculated) and their competitive ability, resulting in different decomposer communities. Synthesis. Our study demonstrates that temperature and assembly history jointly determine deadwood decomposition and fungal community composition under controlled laboratory conditions. Further investigations are needed to confirm these results under natural conditions. Nevertheless, our findings highlight the importance of considering interactions between priority effects and climate factors to understand forest carbon feedbacks in the context of climate change.

Effect of Deadwood Decomposition on the Restoration of Soil Cover in Landslide Areas of the Karpaty Mountains, Poland

Disturbances play an essential role in the shaping of temporal and spatial heterogeneity in natural community structures. The aim of this study was to provide an assessment of the deadwood influence on the chemical and biochemical properties of soils in a landslide area. The samples used to determine soil properties were collected from the entire landslide area, with locations distributed on a regular grid (50 × 50 m). The soil samples were collected from directly under the logs, and background soil samples were taken 1 m from the deadwood logs. The effect of the deadwood decomposition process was visible in the total organic carbon (C) and nitrogen (N) content and microbial activity of the soil. An increase in the enzyme activity and microbial biomass of the soil from directly beneath the deadwood was noted. In this study, it was found that a greater stock of deadwood was present in the accumulation zone, which resulted in a stronger effect of the released components on the soil cover. In order to restore landslide soils, microbial activity can be effectively stimulated by leaving deadwood on the landslide surface.

Dynamic feedbacks among tree functional traits, termite populations and deadwood turnover

Abstract Changes in the composition of plant functional traits may affect ecosystem processes through influencing trophic interactions. Bottom‐up control by plant species through food availability to animals may vary with time. However, such dynamics and their consequences for deadwood turnover are poorly known for detrital food webs. We introduce a dynamic conceptual model of the feedback of tree functional traits, (deadwood‐feeding) termite populations and deadwood decomposition. We hypothesized that tree functional diversity (in terms of a wood resource economic spectrum [WES]) supports the sustenance of termite populations via complementary food supplied through time, as deadwood varies in traits both initially across species and because of different decomposition rates. Simultaneously, driven by this temporal dynamics of food quality, the consumption of deadwood by termites should hypothetically sustain deadwood turnover in a functionally diverse forest over time. We tested our hypothesis through an 18‐month termite‐exclusion decomposition experiment by incubating coarse (i.e. 5 cm diameter) deadwood of 34 woody species in two subtropical forests in East China. One site still sustained a healthy population of pangolins as the keystone termite predator, whereas another had lost its pangolins due to hunting and illegal wildlife trade. The results supported our hypothesis: in the first 12 months, termites amplified the positive linear relationship between % wood mass loss and initial wood quality (WES). In contrast, between 12 and 18 months, termite‐mediated consumption, and associated wood mass loss, showed a humpback relation with the initial WES. This shift in termite preference of deadwood species along the WES reflects complementary food availability to termites through time. Synthesis. Our findings imply that tree functional composition, with variation in deadwood quality through decomposition time, can help to sustain termite populations and thereby forest carbon turnover. Future studies need to test whether and how our conceptual model may apply to other detrital systems and food webs. In general, food web research would benefit from a stronger focus on temporal patterns for better understanding the interactions of basal resource functional traits and consumers on ecosystem functions.

Carbon flux and forest dynamics: Increased deadwood decomposition in tropical rainforest tree-fall canopy gaps.

Tree mortality rates are increasing within tropical rainforests as a result of global environmental change. When trees die, gaps are created in forest canopies and carbon is transferred from the living to deadwood pools. However, little is known about the effect of tree-fall canopy gaps on the activity of decomposer communities and the rate of deadwood decay in forests. This means that the accuracy of regional and global carbon budgets is uncertain, especially given ongoing changes to the structure of rainforest ecosystems. Therefore, to determine the effect of canopy openings on wood decay rates and regional carbon flux, we carried out the first assessment of deadwood mass loss within canopy gaps in old-growth rainforest. We used replicated canopy gaps paired with closed canopy sites in combination with macroinvertebrate accessible and inaccessible woodblocks to experimentally partition the relative contribution of microbes vs. termites to decomposition within contrasting understorey conditions. We show that over a 12month period, wood mass loss increased by 63% in canopy gaps compared with closed canopy sites and that this increase was driven by termites. Using LiDAR data to quantify the proportion of canopy openings in the study region, we modelled the effect of observed changes in decomposition within gaps on regional carbon flux. Overall, we estimate that this accelerated decomposition increases regional wood decay rate by up to 18.2%, corresponding to a flux increase of 0.27MgCha-1 year-1 that is not currently accounted for in regional carbon budgets. These results provide the first insights into how small-scale disturbances in rainforests can generate hotspots for decomposer activity and carbon fluxes. In doing so, we show that including canopy gap dynamics and their impacts on wood decomposition in forest ecosystems can help improve the predictive accuracy of the carbon cycle in land surface models.

Complementary Roles of Wood-Inhabiting Fungi and Bacteria Facilitate Deadwood Decomposition.

Forests accumulate and store large amounts of carbon (C), and a substantial fraction of this stock is contained in deadwood. This transient pool is subject to decomposition by deadwood-associated organisms, and in this process it contributes to CO2 emissions. Although fungi and bacteria are known to colonize deadwood, little is known about the microbial processes that mediate carbon and nitrogen (N) cycling in deadwood. In this study, using a combination of metagenomics, metatranscriptomics, and nutrient flux measurements, we demonstrate that the decomposition of deadwood reflects the complementary roles played by fungi and bacteria. Fungi were found to dominate the decomposition of deadwood and particularly its recalcitrant fractions, while several bacterial taxa participate in N accumulation in deadwood through N fixation, being dependent on fungal activity with respect to deadwood colonization and C supply. Conversely, bacterial N fixation helps to decrease the constraints of deadwood decomposition for fungi. Both the CO2 efflux and N accumulation that are a result of a joint action of deadwood bacteria and fungi may be significant for nutrient cycling at ecosystem levels. Especially in boreal forests with low N stocks, deadwood retention may help to improve the nutritional status and fertility of soils.IMPORTANCE Wood represents a globally important stock of C, and its mineralization importantly contributes to the global C cycle. Microorganisms play a key role in deadwood decomposition, since they possess enzymatic tools for the degradation of recalcitrant plant polymers. The present paradigm is that fungi accomplish degradation while commensalist bacteria exploit the products of fungal extracellular enzymatic cleavage, but this assumption was never backed by the analysis of microbial roles in deadwood. This study clearly identifies the roles of fungi and bacteria in the microbiome and demonstrates the importance of bacteria and their N fixation for the nutrient balance in deadwood as well as fluxes at the ecosystem level. Deadwood decomposition is shown as a process where fungi and bacteria play defined, complementary roles.

Fauna Community Convergence During Decomposition of Deadwood Across Tree Species and Forests

Natural forests contain a large amount of deadwood, which is a key contributor to biodiversity, especially by providing dynamic habitats and resources for a huge variety of invertebrates. However, for managing forest biodiversity we need to better understand what drives the dynamics of invertebrate communities in deadwood. We hypothesized that the invertebrate communities in logs will converge from initial to middle decomposition stage among tree species and forest stands as the differentiating role of bark diminishes and xylem traits converge during decay. We investigated invertebrate communities in decomposing logs of ten tree species over 4 years in the “tree cemetery” LOGLIFE experiment in two contrasting forests in the Netherlands. The predominant faunal groups studied were Annelida (earthworms), Isopoda (woodlice), Chilopoda (centipedes), Diplopoda (millipedes), Diptera (flies, midges) and Coleoptera (beetles). We demonstrated that (1) tree species, decay stages and incubation forests all had effects on the invertebrate communities; (2) community compositions of fauna in logs first were very dissimilar and then became more similar among tree species through the decay years; and (3) this converging pattern of faunal community dynamics also manifested itself, both across and within given tree species, between two contrasting forests over decomposition time. Thus, invertebrate communities generally converged during deadwood decay, which adds fundamental insights into the role of interacting drivers of community succession. These findings also highlight that, both within and among forests, more functionally different tree species and logs in different decay stages, will support relatively high biodiversity of invertebrate communities; these patterns may inform forest management strategies aimed at maximizing biodiversity.

Decomposition of black pine (Pinus nigra J. F. Arnold) deadwood and its impact on forest soil components

Deadwood decomposition is a complex and dynamic process with large implications for biogeochemical cycling of carbon (C) and nitrogen (N) in forest soil and litter. Moreover, it affects functional and structural diversity of fungal and bacterial communities in these components. Mesocosms with deadwood blocks at progressive decay classes were set in a black pine forest and incubated for 28 months in the field with the aim to assess the impact of deadwood decomposition on i) CO2, CH4 and N2O fluxes; ii) C and N pools and allocation among deadwood, litter and soil; iii) the fungal and bacterial structural diversity and activity.CO2, CH4 and N2O fluxes from deadwood were monitored throughout the field incubation; deadwood biomass loss and decay rate for each decay class were calculated. The stock of C and N, enzyme activities, fungal and bacterial communities in deadwood, litter fractions (fresh, fragmented and humified) and soil at two depths were measured.Emissions of CO2 and CH4 increased over the deadwood decomposition advancement and the decay reached the maximum rates in the last decomposition classes. N2O fluxes were low and showed either production (prevalent in the first year) or consumption. Independent of the decay class, 20% of C stored in deadwood was lost as CO2 in the atmosphere, whereas 32% was transferred to the fragmented and humified litter fractions in the last decay class. A corresponding increase of cellulose and hemicellulose degrading enzymes was found in deadwood, also favored by substrates accessibility through fragmentation and successional changes in fungal and bacterial communities.Deadwood, litter fractions and soil components were clearly distinguished in terms of chemical and microbiological properties and activities. Fragmented and humified litter fractions were the only components responsive to the advanced stage of deadwood decomposition, being directly affected by the physical redistribution of fragmented organic matter.

Tissue type and location within forest together regulate decay trajectories of Abies faxoniana logs at early and mid-decay stage

Deadwood decomposition plays a crucial role in global carbon and nutrient cycles. Factors controlling deadwood decomposition at local scales could also have strong effects at broader scales. We tested how trait variation within stems (i.e. tissue types) and forest habitat heterogeneity (i.e. location within forest) together influence the deadwood decay trajectory and decay rate. We conducted an in situ decomposition experiment of Abies faxoniana logs in an alpine forest on the eastern Qinghai-Tibetan Plateau, decomposing logs from a series of decay classes I-III (on a 5-class scale) for five years on the forest floor in canopy gap, gap edge and under closed canopy (each sized 25 ± 3 × 25 ± 3 m). We found strong differences in density and chemical composition between tissue types at least across decay classes I-III, which revealed the distinct contribution of each tissue type to carbon and nutrient cycling. There were remarkable interactions of tissue types and locations within forest. We found bark always decomposed faster than wood, while heartwood can decompose faster than sapwood in canopy edge and canopy gap. Locations within forest influenced the best fit decay model and decay rate of bark and sapwood in the same way, while it had no corresponding effects for heartwood decay dynamics. The largest difference in T0.25 and T0.4 (time to 25% and 40% mass loss) between locations were 1.52 and 3.21 (bark), 19.41 and 37.61 (wood overall), 31.82 and 60.15 (sapwood), and 12.86 and 22.84 (heartwood), respectively. We also found that pH was significantly negatively related with sapwood and heartwood mass loss, demonstrating that pH can potentially be applied to evaluate sapwood and heartwood mass loss when density correction is difficult to achieve at least at early to mid-decay stages. However, whether pH is a powerful predictor of decomposition trajectory across more species and biomes remains to be tested. We strongly recommend that further model predictions of coarse log decay include radial positions within stem and locations within forest as factors to increase the reliability of carbon budget estimates.

Fungal communities and their association with nitrogen-fixing bacteria affect early decomposition of Norway spruce deadwood

Deadwood decomposition is relevant in nature and wood inhabiting fungi (WIF) are its main decomposers. However, climate influence on WIF community and their interactions with bacteria are poorly understood. Therefore, we set up an in-field mesocosm experiment in the Italian Alps and monitored the effect of slope exposure (north- vs. south-facing slope) on the decomposition of Picea abies wood blocks and their microbiome over two years. Unlike fungal richness and diversity, we observed compositional and functional differences in the WIF communities as a function of exposure. Wood-degrading operational taxonomic units (OTUs) such as Mycena, and mycorrhizal and endophytic OTUs were characteristic of the south-facing slope. On the north-facing one, Mucoromycota, primarily Mucor, were abundant and mixotrophic basidiomycetes with limited lignin-degrading capacities had a higher prevalence compared to the southern slope. The colder, more humid conditions and prolonged snow-coverage at north exposure likely influenced the development of the wood-degrading microbial communities. Networks between WIF and N2-fixing bacteria were composed of higher numbers of interacting microbial units and showed denser connections at the south-facing slope. The association of WIF to N2-fixing Burkholderiales and Rhizobiales could have provided additional competitive advantages, especially for early wood colonization.

Fire Alters Soil Properties and Vegetation in a Coniferous–Broadleaf Mixed Forest in Central China

Fire is the predominant natural disturbance that influences the community structure as well as ecosystem function in forests. This study was conducted to examine the soil properties, loss of aboveground biomass, and understory plant community in response to an anthropogenic fire in a coniferous (Pinus massoniana Lamb.) and broadleaf (Quercus acutissima Carruth.) mixed forest in a subtropical–temperate climatic transition zone in Central China. The results showed that soil pH, NO3−-N concentration, and microbial biomass carbon (C) increased three months after the fire; however, there were no significant differences in soil organic C, total nitrogen (N), NH4+-N concentration, or microbial biomass N between the burned and unburned observed plots. The total aboveground biomass was 39.0% lower in the burned than unburned plots four weeks after fire. Direct biomass combustion (19.15 t ha−1, including understory shrubs and litters) was lower than dead wood biomass loss (23.69 t ha−1) caused by the fire. The declining trends of tree mortality with increasing diameter at breast height for both pine and oak trees suggest that small trees are more likely to die during and after fires due to the thinner bark of small trees and tree and branch fall. In addition, burning significantly stimulated the density of shrub (160.9%) and herb (88.0%), but it also affected the richness of shrub and herb compared with that in the unburned plots two months after the fire. The rapid recovery of understory plants after fires suggest that the diversity of understory species could benefit from low-severity fires. Our findings highlight that the decomposition of dead wood and understory community recovery should be considered for offsetting C emissions after fires for further research.

The effect of forest management practices on deadwood resources and structure in protected and managed montane forests during tree-stand reconstruction after dieback of Norway spruce

Forest management practices can not only influence the amount of deadwood but also the proportions of particular elements. The goal of the present paper was to compare the amount, number of logs, stumps and snags and their dendrometrical parameters between the protected and managed forests in the Karkonosze Mts after a huge dieback of Picea abies. A massive decline of Norway spruce has been observed since the 1980s. The protected forests belong to Karkonosze National Park and the managed forests are situated in its buffer zone. In total, 1336 elements of coarse woody debris (CWD) were included in the study. They were distributed on 180 study plots (10 m × 10 m) that were randomly selected. Among the deadwood elements, spruce Picea abies dominated (80.3%) followed by beech Fagus sylvatica (14.3%). Logs were more numerous in the protected forest (57.3%) than in the managed forests (42.7%). Snags and stumps were more frequent – 56.9% and 52.8%, respectively, in the managed forests than in the protected forests – 43.1% and 47.2%, respectively. The mean volume of CWD was ca 114 m3 ha-1 in the protected forests whereas ca 70 m3 ha-1 was in managed forests.The mean number of stumps per study plot was higher in the managed forests. The mean volume and mean area of logs were higher in the protected forest as was the mean volume and diameter at breast height, whereas the height of the snags was higher in the managed forests. In terms of differences in the decomposition of deadwood between the two types of forests, the mean weighted degree of decay on a five-degree scale amounted to 2.9 in the protected forests and 2.7 in the managed forests. A larger amount of deadwood as well as a greater volume and surface area are very important for nature conservation because deadwood can function as a niche for many saproxylobiont organisms. The forest management practices and especially the weak conditions of spruce lead to a larger number of snags in a managed forest due to the reconstruction of tree-stands and the removal of deadwood by foresters.

Microbial communities associated with decomposing deadwood of downy birch in a natural forest in Khibiny Mountains (Kola Peninsula, Russian Federation)

Deadwood plays an important role in the forest ecosystems, providing nutrients and habitat for a wide range of organisms, preventing soil erosion, and improving carbon storage. Microorganisms are primary agents in wood decomposition. The aim of the present research is to describe the changes in diversity, structure and abundance of microbial communities over downy birch lying deadwood decomposition in a boreal forest under natural conditions. This study also included investigations on the potential involvement of deadwood in climate change.The decomposition of deadwood was visually assessed using a five-class system. The microbial community diversity and composition were assessed with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting. Real time PCR was used to evaluate the absolute and relative microbial abundance. The potential involvement of deadwood in climate change was assessed by in situ-measuring of the carbon dioxide (CO2) emissions from downy birch lying deadwood and from soil.The results obtained indicate that deadwood represents a substrate whose physico-chemical and microbiological property change with time. Higher diversity of fungi, bacteria, and archaea were recorded in the decay class 5. Conversely, actinobacteria showed the lowest values of diversity in decay class 5. We observed a succession of dominant microbial taxa over the decomposition progress. Overall, the abundance of each microbial group increases with the advance of decomposition. Among the estimated physico-chemical properties, nitrogen content, that increased with decay, and pH were the most important candidate drivers of microbial community composition and abundance. CO2 emissions were recorded higher in the decay class 5 and in soil of plots with the highest amount of lying deadwood.Bacteria dominated the microbial community and may play a more important role in the late stages of wood decomposition conversely to fungi and actinobacteria that are assumed to be primary involved in early stages of wood colonization. Archaea are shown to be an integral and dynamic component of decaying wood biota. The presence of large amounts of deadwood may affect greenhouse gas (GHG) emissions, especially in the event of an increase in temperatures that could reduce the carbon (C) sink capacity of the boreal forests.

Impact of deadwood decomposition on soil organic carbon sequestration in Estonian and Polish forests

Key messageThe deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests. In warmer conditions (Poland), the deadwood decomposition process had a higher rate than in cooler Estonian forests. Soil organic matter fractions analysis can be used to assess the stability and turnover of organic carbon between deadwood and soil in different experimental localities.ContextDeadwood is an important element of properly functioning forest ecosystem and plays a very important role in the maintenance of biodiversity, soil fertility, and carbon sequestration.AimsThe main aim was to estimate how decomposition of deadwood of different tree species with different decomposition rates affects soil organic carbon sequestration in Estonian and Polish forests.MethodsThe investigation was carried out in six forests in Poland (51° N) and Estonia (58° N). The study localities differ in their mean annual air temperature (of 2 °C) and the length of the growing season (of 1 month). The deadwood logs of Norway spruce (Picea abies (L.) Karst.), common aspen (Populus tremula L.), and silver birch (Betula pendula Roth) were included in the research. Logs in three stages of decomposition (III–V) were selected for the analysis.ResultsThere were differences in the stock of soil organic carbon in two experimental localities. There was a higher soil carbon content under logs and in their direct vicinity in Polish forests compared to those in the cooler climate of Estonia. Considerable differences in the amount of soil organic matter were found. The light fraction constituted the greatest quantitative component of organic matter of soils associated with deadwood.ConclusionA higher carbon content in surface soil horizons as an effect of deadwood decomposition was determined for the Polish (temperate) forests. More decomposed deadwood affected soil organic matter stabilization more strongly than less decayed deadwood. This relationship was clearer in Polish forests. Higher temperatures and longer growing periods primarily influenced the increase of soil organic matter free light fraction concentrations directly under and in close proximity to logs of the studied species. The slower release of deadwood decomposition products was noted in Estonian (hemiboreal) forests. The soil organic matter mineral fraction increased under aspen and spruce logs at advanced decomposition in Poland.

Tree species identity determines wood decomposition via microclimatic effects.

Empirical evidence suggests that the rich set of ecosystem functions and nature's contributions to people provided by forests depends on tree diversity. Biodiversity–ecosystem functioning research revealed that not only species richness per se but also other facets of tree diversity, such as tree identity, have to be considered to understand the underlying mechanisms. One important ecosystem function in forests is the decomposition of deadwood that plays a vital role in carbon and nutrient cycling and is assumed to be determined by above‐ and belowground interactions. However, the actual influence of tree diversity on wood decay in forests remains inconclusive. Recent studies suggest an important role of microclimate and advocate a systematical consideration of small‐scale environmental conditions. We studied the influence of tree species richness, tree species identity, and microclimatic conditions on wood decomposition in a 12‐year‐old tree diversity experiment in Germany, containing six native species within a tree species richness gradient. We assessed wood mass loss, soil microbial properties, and soil surface temperature in high temporal resolution. Our study shows a significant influence of tree species identity on all three variables. The presence of Scots pine strongly increased wood mass loss, while the presence of Norway spruce decreased it. This could be attributed to structural differences in the litter layer that were modifying the capability of plots to hold the soil surface temperature at night, consequently leading to enhanced decomposition rates in plots with higher nighttime surface temperatures. Therefore, our study confirmed the critical role of microclimate for wood decomposition in forests and showed that soil microbial properties alone were not sufficient to predict wood decay. We conclude that tree diversity effects on ecosystem functions may include different biodiversity facets, such as tree identity, tree traits, and functional and structural diversity, in influencing the abiotic and biotic soil properties.

A comparison of C:N:P stoichiometry in soil and deadwood at an advanced decomposition stage

The aim of this study is to compare the C/N/P stoichiometry of deadwood among four tree species at different stages of decomposition. The way in which the relative concentrations of these elements in the soil are directly impacted by deadwood decomposition is also explored. First, hornbeam, alder, aspen and fir logs in different decomposition stages (III, IV and V) were selected and sampled. Second, the concentration and stoichiometry of carbon, nitrogen and phosphorous were established. Marked differences in C/N/P stoichiometry were observed between deadwood in an advanced decomposition stage and the soil immediately under the log. The average C/N/P ratio of soil under the influence of deadwood was narrower compared to the C/N/P ratio of deadwood. The C/N/P ratio of studied soils was similar to the expected C/N/P ratio of organic soils or humus. The results indicate that stage of decomposition and tree species have an impact on the elemental stoichiometry of the soil. Thus, C/N/P stoichiometry is a useful indicator of the intensity of nutrient flux from deadwood to the soil.

Carbon flux from decomposing wood and its dependency on temperature, wood N2 fixation rate, moisture and fungal composition in a Norway spruce forest.

Globally 40–70 Pg of carbon (C) are stored in coarse woody debris on the forest floor. Climate change may reduce the function of this stock as a C sink in the future due to increasing temperature. However, current knowledge on the drivers of wood decomposition is inadequate for detailed predictions. To define the factors that control wood respiration rate of Norway spruce and to produce a model that adequately describes the decomposition process of this species as a function of time, we used an unprecedentedly diverse analytical approach, which included measurements of respiration, fungal community sequencing, N2 fixation rate, nifH copy number, 14C‐dating as well as N%, δ13C and C% values of wood. Our results suggest that climate change will accelerate C flux from deadwood in boreal conditions, due to the observed strong temperature dependency of deadwood respiration. At the research site, the annual C flux from deadwood would increase by 27% from the current 117 g C/kg wood with the projected climate warming (RCP4.5). The second most important control on respiration rate was the stage of wood decomposition; at early stages of decomposition low nitrogen content and low wood moisture limited fungal activity while reduced wood resource quality decreased the respiration rate at the final stages of decomposition. Wood decomposition process was best described by a Sigmoidal model, where after 116 years of wood decomposition mass loss of 95% was reached. Our results on deadwood decomposition are important for C budget calculations in ecosystem and climate change models. We observed for the first time that the temperature dependency of N2 fixation, which has a major role at providing N for wood‐inhabiting fungi, was not constant but varied between wood density classes due to source supply and wood quality. This has significant consequences on projecting N2 fixation rates for deadwood in changing climate.

Soil biochemical properties and stabilisation of soil organic matter in relation to deadwood of different species.

Despite the increasing number of studies on deadwood, we still have limited knowledge of its dynamics. The aim of this study was to examine the effect of deadwood on the biochemical properties of soil and stabilisation of soil organic matter (SOM). The investigation was carried out in the Czarna Rózga Reserve in Central Poland. The logs of four tree species at different stages of decomposition (III, IV and V) were selected for the analysis. Three replicate logs were sampled for each combination of decay classes, and the soil samples were collected from directly under the logs and from 1 m away from the logs. In this way, changes to the chemical and biochemical properties of the wood were determined. The SOM was physically fractioned. As the rate of deadwood decomposition increases, its biochemical activity increases and its chemical properties change. The biochemical activity, especially the soil's enzyme activity, was stimulated under highly decayed deadwood. The effects of deadwood are visible in SOM fractions, particularly in the content of the light fraction of SOM.

Saproxylic biodiversity and decomposition rate decrease with small-scale isolation of tree hollows

Biodiversity is fundamental for ecosystem functioning, but little is known about how function responds to biodiversity loss following habitat disturbance in natural systems. Due to the global decay of veteran trees, many associated saproxylic (i.e. deadwood-dependent) insects are considered threatened. Nevertheless, the role of habitat spatial configuration on saproxylic insect biodiversity and dead wood decomposition is poorly understood. We performed a six-year landscape-scale colonization experiment on saproxylic beetles inhabiting hollow oaks, using boxes filled with wood mould as standardized habitat patches. We placed boxes either on a hollow tree or on another tree 61–324 m from the hollows, thereby creating two habitat isolation levels. We quantified wood mould decay and biodiversity in the boxes, measuring species richness, total abundances and community-weighted mean of body mass (CWM) as an index of community functional composition. Isolation had a persistent negative effect on primary consumer biodiversity, but it only impaired decay at the beginning of the experiment. All effects were independent of landscape-level (500-m radius) habitat amount surrounding the boxes. Wood mould decay was mediated by CWM of primary consumers. Therefore function was driven by the body masses of the dominant primary consumer species but not by species numbers (richness) or individual numbers (abundance). Our experiment shows that small-scale habitat isolation leads to biodiversity loss and reduced function and indicates that habitats created by conservation efforts will be used by more saproxylic species if located within sites with a high density of veteran trees.

Determinants of Deadwood-Inhabiting Fungal Communities in Temperate Forests: Molecular Evidence From a Large Scale Deadwood Decomposition Experiment.

Despite the important role of wood-inhabiting fungi (WIF) in deadwood decomposition, our knowledge of the factors shaping the dynamics of their species richness and community composition is scarce. This is due to limitations regarding the resolution of classical methods used for characterizing WIF communities and to a lack of well-replicated long-term experiments with sufficient numbers of tree species. Here, we used a large scale experiment with logs of 11 tree species at an early stage of decomposition, distributed across three regions of Germany, to identify the factors shaping WIF community composition and Operational Taxonomic Unit (OTU) richness using next generation sequencing. We found that tree species identity was the most significant factor, corresponding to (P < 0.001) and explaining 10% (representing 48% of the explainable variance) of the overall WIF community composition. The next important group of variables were wood-physicochemical properties, of which wood pH was the only factor that consistently corresponded to WIF community composition. For overall WIF richness patterns, we found that approximately 20% of the total variance was explained by wood N content, location, tree species identity and wood density. It is noteworthy that the importance of determinants of WIF community composition and richness appeared to depend greatly on tree species group (broadleaved vs. coniferous) and it differed between the fungal phyla Ascomycota and Basidiomycota.