•Whether CWD has a positive effect on C sequestration in forest soils remains to be debated.•We need a comparison of the role of C from CWD and from leafy litter in soil C stabilization.•To elucidate ...the contribution of CWD to stable soil C we need to trace individual compounds.•Management of CWD should also focus on increasing sequestration in stable C pools.
Worldwide, forests have absorbed around 30% of global anthropogenic emissions of carbon dioxide (CO2) annually, thereby acting as important carbon (C) sinks. It is proposed that leaving large fragments of dead wood, coarse woody debris (CWD), in forest ecosystems may contribute to the forest C sink strength. CWD may take years to centuries to degrade completely, and non-respired C from CWD may enter the forest soil directly or in the form of dissolved organic C. Although aboveground decomposition of CWD has been studied frequently, little is known about the relative size, composition and fate of different C fluxes from CWD to soils under various substrate-specific and environmental conditions. Thus, the exact contribution of C from CWD to C sequestration within forest soils is poorly understood and quantified, although understanding CWD degradation and stabilization processes is essential for effective forest C sink management. This review aims at providing insight into these processes on the interface of forest ecology and soil science, and identifies knowledge gaps that are critical to our understanding of the effects of CWD on the forest soil C sink. It may be seen as a “call-to-action” crossing disciplinary boundaries, which proposes the use of compound-specific analytical studies and manipulation studies to elucidate C fluxes from CWD. Carbon fluxes from decaying CWD can vary considerably due to interspecific and intraspecific differences in composition and different environmental conditions. These variations in C fluxes need to be studied in detail and related to recent advances in soil C sequestration research. Outcomes of this review show that the presence of CWD may enhance the abundance and diversity of the microbial community and constitute additional fluxes of C into the mineral soil by augmented leaching of dissolved organic carbon (DOC). Leached DOC and residues from organic matter (OM) from later decay stages have been shown to be relatively enriched in complex and microbial-derived compounds, which may also be true for CWD-derived OM. Emerging knowledge on soil C stabilization indicates that such complex compounds may be sorbed preferentially to the mineral soil. Moreover, increased abundance and diversity of decomposer organisms may increase the amount of substrate C being diverted into microbial biomass, which may contribute to stable C pools in the forest soil.
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•Mass loss of logs of 13 tree species over 9.8 years is best described by a linear or a sigmoidal model.•Logs of diffuse-porous angiosperms decay faster than ring-porous angiosperms ...and gymnosperms.•Logs of the same tree species exhibit large variability in mass loss across 29 forest sites.•Mass loss is highest in the region with higher temperature, dry and nutrient-poor soils.•Forest structure including deadwood stock in the neighborhood had little influence on mass loss.
Deadwood provides important ecological and biogeochemical functions in forest ecosystems. These functions rely on tree species-specific decay dynamics, but only few studies investigated how exogenous parameters affected the decay of deadwood at the regional scale. Here, we explore the influence of climate, soil traits and forest structure on decay dynamics and mass loss of logs of 13 tree species in 29 plots across three regions in Germany. This long-term experiment (BELongDead) comprises 1,066 logs of 9 angiosperms and 4 gymnosperms and covers a decay time of almost 10 years. Mass loss of logs was relatively high for the temperate climate with partly different half-lives ranging from 6 to 13 years (mean 8.9 ± 2.2 years). Diffuse-porous angiosperms lost 70 ± 13 % of their initial mass, followed by gymnosperms (49 ± 16 %) and ring-porous angiosperms (46 ± 12 %) within the study period. We applied three different mathematical models to fit mass loss in time and found that a linear model is most appropriate for 10 tree species. A sigmoidal model best described the mass loss of Fraxinus, Quercus and Pinus logs. A multivariate analysis revealed a significant effect of soil, temperature and precipitation on mass loss at the plot level. Mass loss increased with decreasing soil nutrient content, possibly as a result of enhanced bidirectional element translocations between nutrient-poor soils and logs by fungal hyphae. Temperature had a positive effect on mass loss, whereas increasing precipitation and soil moisture were negatively related to mass loss. The region with warmer, moderately humid climate and unfavourable soil properties led to overall higher mass loss (66 ± 4 %) whereas the other two regions were indifferent (both 57 ± 3 %). Forest structure, including canopy cover, share of coniferous trees and the stock of deadwood in the vicinity of the logs explained only a small part of the variability in mass loss. High variability within individual tree species suggests that other factors such as organismic diversity and microbial activity have stronger impact on the decay process at the regional scale than exogenous factors.
Dead wood is initially a nitrogen (N) poor substrate, where the N content increases with decay, partly due to biological N2 fixation, but the drivers of the N accumulation are poorly known. We ...quantified the rate of N2 fixation in decaying Norway spruce logs of different decay stages and studied the potential regulators of the N2-fixation activity. The average rate for acetylene reduction in the decaying wood was 7.5 nmol ethylene g−1d−1, which corresponds to 52.9 μg N kg−1d−1. The number of nifH copies (g−1 dry matter) was higher at the later decay stages, but no correlation between the copy number and the in vitro N2 fixation rate was found. All recovered nifH sequences were assigned to the order Rhizobiales, and therein mostly (60%) to methane oxidizing genera. We confirm that nitrogen fixing methanotrophs are present in all the wood decay phases and suggest that their interaction between methane producing organisms in decaying wood should be further studied.
•N2 fixing bacteria are active in decaying wood.•The number of nifH copies was higher at later decay stages.•No correlation between nifH copy number and in vitro N2 fixation rate was found.•60% of the nifH sequences were assigned to methane oxidizing bacteria.
•Enrichment of deadwood and canopy gaps during logging operations promote beetle diversity in production forests.•Higher abundance, species number and species richness of both saproxylic and ...non-saproxylic beetles were found in gaps.•Beetle species number and richness, but not abundance, was higher in stands with snags, logs and/or stumps.•Although stumps are immediately highly attractive, snags and logs provide longer-lasting deadwood resources.
Conservation tools to enrich habitat diversity in the widely distributed homogeneous production forests include stumps as logging residues but also the intentional creation of logs or snags, as well as varying canopy conditions. While an open canopy has been shown to foster forest biodiversity, the impact of different deadwood types at stand scale is less clear, which is crucial since this is the most relevant scale for silvicultural decisions. In this study, we experimentally manipulated canopy conditions (open vs. closed) and created deadwood (stumps, logs, snags) in different combinations in five mature European beech (Fagus sylvatica L.) forests to test the potential of active manipulations to increase the diversity of beetles, one of the most diverse insect orders in temperate forests. We estimated abundance, species number and species richness (controlled for abundance) of saproxylic (i.e., deadwood-dependent) and non-saproxylic beetles using flight-interception traps and analyzed species assemblages within the first 3 years of the experiment. Using generalized linear mixed effect models we found a 33.7 % and 43.4 % higher abundance as well as a 26.1 % and 23.5 % higher species number under open canopies for saproxylic and non-saproxylic beetles respectively, accompanied by a higher species richness of both groups. Stands with deadwood had a 38.6 % and 32.7 % higher species number followed by higher species richness of saproxylic and non-saproxylic beetles compared to stands without manipulation but manipulations did not affect beetle abundances. We identified sampling year, followed by canopy condition and deadwood type (in addition to an overall higher impact of spatial distance between stands and sites) by applying multiple regression analyses as most important to explain species assemblages of both beetle groups. Saproxylic abundance and species number in stump treatments were initially high but decreased over 3 years, while treatments containing snags and logs resulted in an increase in both abundance and species number over time. These temporal trends were mediated by canopy cover. Our findings provide three major insights for biodiversity-orientated management in mature beech forests: First, opening the canopy increases the stand-scale abundance, species number, and species richness of saproxylic and non-saproxylic beetles. Second, while stumps are attractive for saproxylics shortly after the logging operation, snags and logs provide longer-lasting deadwood resources, thus underlining longer sustainability of snag and log enrichment for forest biodiversity. Third, deadwood enrichment at the stand scale promotes not only deadwood-dependent but also other beetle species.
In recent years there has been an increasing concern about the wood in debris flows and floodwaters, which results in extensive destruction of properties and infrastructures along river courses. In ...order to prevent the damage, appropriate installment of measures to control the outflow of the wood is necessary, with a reliable budget of coarse woody debris underpinned by solid understanding of its behavior. This study presents the budget for the Tottabetsu River catchment (153.4 km2) in Eastern Hokkaido for a record high rainfall brought by Typhoon No. 10 in August 2016. There were no control measures for woody debris in the river before the event. The budget was estimated by the combination of field investigation, an analysis of airborne LiDAR data obtained before and after the event, and an interpretation of a series of aerial photograph images. The storm intensively eroded riverbeds and banks, producing a large amount of woody debris. The wood, some of which remained jammed or captured in sediment deposits along the course after the event, was originated from both hillslopes and riparian forests. The outflow was estimated at 58,000 m3 from the Tottabetsu River in total, which was 70% of the inflow into the course. Dividing the catchment into units based on stream order, the proportion of the outflow of the wood ranged from 0.90 to 1.00 for the mountainous and from 0.17 to 0.86 for the alluvial parts. The outflow was positively correlated with catchment sediment yield for each unit. The outcomes in this study will help plan the control measures of coarse woody debris through the channel network, not only for the Tottabetsu River but also elsewhere with a range of catchment sizes.
Saproxylic species from different taxonomic groups often occur only on certain types of deadwood with specific qualitative characteristics. The various types of deadwood are very dynamic elements of ...forest ecosystems, associated with many site and stand features, as well as with the type of forest management. Using a pool of 29,098 sample plots spread across Poland, we analyzed 30 different deadwood types defined on the basis of three characteristics: position (standing, lying), degree of decomposition, and size. Statistical hurdle models were used to assess changes in the volume of individual deadwood types based on a broad range of independent variables. Depending on the type of management, terrain, site fertility, stand volume, tree density, and stand age, the models revealed substantial differences in the volume of different deadwood types, ranging from 0 to approx. 4 m3 ha−1. It was found that the volume of most deadwood types (except for a few, mostly with diameters under 15 cm) increases with stand age or stand volume. In managed forests at all stages of stand development there is a deficiency of thick deadwood. Both standing and lying deadwood at different decay stages is available continuously, irrespective of the values of individual independent variables, but considerable differences exist. While most lying deadwood exhibits higher levels of decomposition, in standing deadwood the proportions of different decay stages are strongly associated with tree diameter at breast height. The developed models make it possible to predict the volume of individual deadwood types for a broad range of independent variables. The current work presents several examples, with the results showing extremely complex relationships between deadwood diversity and site and stand features at every stage of forest development, with continuous changes in the volume and proportions of different deadwood types. In general, at the landscape level Polish forests contain both standing and lying deadwood at all decay stages in more or less equal proportions. However, in forest management one should pay special attention to the dimensions of retained deadwood. The absence of thick deadwood is particularly conspicuous in lowland managed forests.
•The total deadwood volume consists of many deadwood types with very different characteristics.•Statistical models based on stand features describe the diversity of dead wood with high accuracy.•The diversity of the deadwood changes with the age of the stand, the method of management and habitat conditions.•Some types of deadwood are not found in all forests, especially thick deadwood is completely removed.•Management of deadwood resources should be largely based on its diversity.
•Coarse woody debris of Scots pine hosts abundant and diverse mycobiota.•The Illumina technology proved to be very effective in detection of fungi.•Fungal communities in coarse dead wood are huge ...complexes with many previously undifferentiated taxa.•Sanitary cutting, commercial thinning and timber harvesting cause an increase in abundance of fungi and richness of fungal communities in decayed dead wood.•Faster decomposition of wood decreases the abundance and diversity of fungi.
Abundance of fungi and richness of fungal communities were studied in coarse wood debris of Scots pine in stands that were unmanaged or managed (by sanitary cutting, commercial thinning and timber harvesting) in an 85-year-old Scots pine forest in western Poland, in June 2014. Samples consisted of 20 × 20 × 20 cm pieces of logs, fallen branches and stumps, in the 1st, 2nd and 3rd decay classes. Fungal communities were analysed using high throughput Illumina MiSeq sequencing of fungal rDNA internal transcribed spacer. From a total of 80 076 OTUs from 34 samples, 58 436 (72.98%) were of culturable fungi and 21 640 (27.02%) were of non-culturable fungi and other organisms. Fungi from Glomeromycota, Zygomycota, Ascomycota and Basidiomycota were detected. In the unmanaged stand the frequency of Glomeromycota was 0–0.2%, of Zygomycota 0.01–0.29%, of Ascomycota 30.47–79.08%, of Basidiomycota 1.56–16.45%, and of non-culturable fungi 7.28–65.51%. In the managed stand the frequency of Glomeromycota was 0–0.12%, of Zygomycota 0.04–1.48%, of Ascomycota 52.25–68.33%, of Basidiomycota 8.01–18.05%, and of non-culturable fungi 10.54–26.09%. Fungal communities in coarse dead wood were shown to be huge complexes which include many previously undifferentiated taxa that often occupy specific ecological niches. Samples were colonized by at least 260 taxa of fungi. Fungi were most abundant and fungal communities most species-rich in the managed stand and in the initial stages of wood decay. Known wood-decay species were most abundant in the less decayed wood. Management practice influenced density and diversity of fungal communities in decayed wood. Illumina technology proved to be more effective in detection of fungi than analysis based on fungal morphology in culture or Sanger DNA sequencing.
•We monitored 2744 retention trees individually for 20 years after timber harvests.•Retention tree mortality was high initially, but low after 4 years.•Retention level and prescribed burning affected ...the availability of deadwood.•Higher retention level promotes the volume and diversity of deadwood.•Low retention levels impose a trade-off between deadwood volume and continuity.
Deadwood is essential for species diversity in forests. Forest management has led to the shortage of deadwood in managed forests and, consequently, to the decline of biodiversity. Prescribed burning and tree retention during harvests may promote deadwood formation, but the long-term effectiveness of these methods is not known. We examined patterns of tree mortality and deadwood dynamics following tree retention and prescribed burning in Finnish boreal forests in a large-scale replicated field experiment with two factors: retention level (10 or 50 m3/ha) and burning (burned or unburned). We monitored 2744 trees individually for 20 years. Deadwood input was initially high after the treatments, since nearly all retention trees on the burned sites and about one third of the trees on the unburned sites died within four years. For the rest of the monitoring period, deadwood input was much lower since the mortality rate of retention trees decreased to a level similar to the background mortality rate. After 20 years from the treatments, deadwood volume varied from about 40 m3/ha on the burned sites with 50 m3/ha retention to about 5 m3/ha on the unburned sites with 10 m3/ha retention. Prescribed burning altered deadwood composition e.g. via the complete mortality of fire-susceptible tree species. Still, deadwood diversity was mainly affected by retention level. Lastly, prescribed burning generated high numbers of snags, which fell rather quickly, with an estimated maximal longevity of 49 years. We conclude that the combination of a high retention level and prescribed burning produces high volumes of diverse deadwood, and thereby has the potential to support the conservation of deadwood-associated biodiversity in managed forests. However, the stand-scale continuity of deadwood throughout the forestry rotation period is still uncertain. The application of management methods should be adjusted at the landscape level to ensure the continuity of deadwood habitats.
•We synthesize the measurement and dynamics of dead wood carbon and decomposition.•Many protocols exist for inventorying standing dead trees and downed woody debris.•Research needs are presented to ...promote the accurate quantification of dead wood.•Issues presented here are hindered by unknowns of future global change scenarios.
The amount and dynamics of forest dead wood (both standing and downed) has been quantified by a variety of approaches throughout the forest science and ecology literature. Differences in the sampling and quantification of dead wood can lead to differences in our understanding of forests and their role in the sequestration and emissions of CO2, as well as in developing appropriate strategies for achieving dead wood-related objectives, including biodiversity protection, and procurement of forest bioenergy feedstocks. A thorough understanding of the various methods available for quantifying dead wood stores and decomposition is critical for comparing studies and drawing valid conclusions. General assessments of forest dead wood are conducted by numerous countries as a part of their national forest inventories, while detailed experiments that employ field-based and modeling methods to understand woody debris patterns and processes have greatly advanced our understanding of dead wood dynamics. We review methods for quantifying dead wood in forest ecosystems, with an emphasis on biomass and carbon attributes. These methods encompass various sampling protocols for inventorying standing dead trees and downed woody debris, and an assortment of approaches for forecasting wood decomposition through time. Recent research has provided insight on dead wood attributes related to biomass and carbon content, through the use of structural reduction factors and robust modeling approaches, both of which have improved our understanding of dead wood dynamics. Our review, while emphasizing temperate forests, identifies key research needs and knowledge which at present impede our ability to accurately characterize dead wood populations. In sum, we synthesize the current literature on the measurement and dynamics of forest dead wood carbon stores and decomposition as a baseline for researchers and natural resource managers concerned about forest dead wood patterns and processes.
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