Dead Wood Density Research Articles

Assessing Deadwood Carbon Stock within the National Parks of Indonesia

The preservation of national parks has emerged as a significant component of Indonesia’s climate mitigation efforts, primarily due to its substantial carbon stocks. However, little is known about the potential carbon stored in deadwoods within these areas. This study aims to estimate fallen deadwood carbon stocks in four national parks in Indonesia. The results show that the density of deadwood in study areas ranges from 0.26 – 0.79 g cm-3. Deadwood volume varies between 247.37 – 388.50 cm3. Bukit Tigapuluh National Park has the highest fallen deadwood biomass and carbon stock, accounting for 261.35 and 122.83 tons ha-1, respectively, followed by Sebangau National Park (187.41 and 88.08 tons ha-1), Kutai National Park (139.91 and 65.76 tons ha-1) and Lore Lindu National Park (87.90 and 41.32 tons ha-1). This study also found that large deadwood with diameters of >7.5 cm contributes to more than 80% of the total deadwood carbon stock. Understanding the carbon stock stored in deadwood within national park areas is crucial for refining estimates of potential avoided greenhouse gas emissions resulting from the conservation of national park forests.

Harmonization and variation of deadwood density and carbon concentration in different stages of decay of the most important Central European tree species

Coarse woody debris (CWD) is a major component of the ecosystem carbon (C) balance. The estimation of C storage in CWD is an important element of the German greenhouse gas (GHG) reporting of forests, which is mainly based on the German National Forest Inventory. The deadwood C stock is calculated based on deadwood volume and, according to deadwood density (DD) and carbon concentration (CC) for each decay class (DC). Yet, the data basis of DD and CC per DC for above-ground CWD is still insufficient since there are very few country-specific measurements. Values from literature provide a first approximation for national-level estimates. However, different DC systems often prevent the use of DD and CC of other countries. Therefore, we developed a conversion method for harmonization of these data with the German four-class system. Following this, we conducted a meta-analysis to calculate mean DD and CC values for the main Central European tree species and to assess their variation. Significantly lower DDs were observed with increasing DC, except for beech between DC 3 and 4. Compared to spruce and pine, DD of beech CWD was significantly higher, overall as well as in DC 1 and 2. Species became similar in DD in advanced decay stages. A maximum of 92% of the variation in DD could be explained mainly by DC, CWD type, tree species and their interaction. DD values were mostly higher than current values in GHG reporting. CC increased with increasing DC in spruce and pine and was higher than in beech CWD, where no variation was detected. About 86% of the variation in CC could be explained mainly by DC, tree species and their interactive effect. The default value of 50% employed by the Intergovernmental Panel on Climate Change might under- (spruce, pine) and/or overestimate (spruce, pine, beech) the real CC depending on DC by up to 3.4 (pine) and/or 4.2% (beech). Based on our calculated mean DD and CC values, the accuracy of C stock assessment in deadwood as part of the GHG reporting for Germany can be substantially improved.

Translocation of deadwood in ecological compensation: A novel way to compensate for habitat loss

Restoration of degraded habitat is frequently used in ecological compensation. However, ecological restoration suffers from innate problems of long delivery times of features shown to be good proxies for biodiversity, e.g., large dead trees. We tested a possible way to circumvent this problem; the translocation of hard-to-come deadwood substrates from an impact area to a compensation area. Following translocation, deadwood density in the compensation area was locally equivalent to the impact area, around 20 m3 ha−1, a threshold for supporting high biodiversity of rare and red-listed species. However, deadwood composition differed between the impact and compensation area, showing a need to include more deadwood types, e.g., late decomposition deadwood, in the translocation scheme. To guide future compensation efforts, the cost for translocation at different spatial scales was calculated. We conclude that translocation of deadwood could provide a cost-efficient new tool for ecological compensation/restoration but that the method needs refinement.

Variation of deadwood density by decay class in pure and mixed Oriental spruce stands in Northeastern Black Sea

Variation of deadwood density by decay class in pure and mixed Oriental spruce stands in Northeastern Black Sea

A Standardized Field Method and Habitat Suitability Model to Assess Reintroduction Sites for Alligator Snapping Turtles

Head-start programs have been established to aid in the recovery of Macrochelys temmincki (Alligator Snapping Turtle) throughout the Mississippi River drainage. As the success of the breeding programs increase, additional release sites are needed where suitable habitat persists for reintroduction of Alligator Snapping Turtles, but methods to evaluate habitat suitability remain loosely defined. We developed a standardized field survey and habitat suitability model that can be used to assess and prioritize potential reintroduction sites. We measured important habitat features in the field and indexed them using a simple model that translated continuous data to an ordinal scoring system, resulting in an overall site-suitability score. We developed the model using 2 potential measurements of submerged deadwood density and determined habitat suitability among 17 sites in Kansas, Oklahoma, and Mississippi where Alligator Snapping Turtles were absent, present, and reintroduced. The model using side-scan sonar correctly predicted the presence of good habitat at sites where wild and reintroduced populations of Alligator Snapping Turtles were present, and scores were significantly related to Alligator Snapping Turtle abundance.

Deadwood density, C stocks and their controlling factors in a beech-silver fir mixed virgin European forest

Deadwood is a fundamental structural and functional component of forests, with a crucial role in supporting forest biodiversity, nutrient and carbon cycling. Precise deadwood density estimates and its relation to environmental factors are necessary to evaluate the biomass and carbon stocked in this component. In this study, we estimated dry deadwood density for two different tree species, silver fir (Abies alba) and European beech (Fagus sylvatica) and for three snags and five logs decomposition classes in a virgin mixed beech-fir forest in the Southern Carpathians. The goal was to assess how deadwood density is influenced by different abiotic (moisture, elevation, slope, aspect) and wood-related factors (rottenness, position along the piece, contact with the soil).For snags, the mean dry density showed a reduced variability within decomposition classes (484–326 kg.m−3 for beech and 374–319 kg.m−3 for fir), compared to the logs (486–139 kg.m−3 for beech and 359–161 kg.m−3 for fir). While the mass moisture varied slowly in the first three decay classes (around 60–80 %), it increased sharply in the last two decay classes of logs (>140 % in the fourth class and > 350 % in the last one). The rottenness increased with the decay class in a similar way for both species. The contact of logs with the soil influenced positively the moisture, but the position of the sampling within the piece did not play any significant role in the variability of density. Based on density estimates per decay classes we estimated that the carbon (C) stored in deadwood varied greatly among the 21 plots from 0.36 to 41.16 MgC ha−1, with a mean value of 15.96 ± 2.36 (±SE) MgC ha−1.Our study suggests that volume-based calculations might yield biased quantitative estimates of C stored in deadwood unless a local estimate of dead wood density corrected per species and decomposition class is applied. Moreover, the use of an averaged value of dry density instead of value for each decay class may result in an overestimation of 22% on the estimation of C stock. Thus, our study emphasises the importance of considering decay class-specific values in future inventories of C stocks in other forests and for other species. Furthermore, it could serve as a methodological basis for more specific research designed to uncover the potential influence of different forest management practices on dry deadwood density.

A simple concept for estimating deadwood carbon in forests

Deadwood in forests is becoming an important topic globally for forest management and carbon markets. While deadwood volume is now routinely assessed by forest inventories and can be even monitored using remote sensing, data about deadwood carbon and density depending on the extent of decay is scarce. We propose a simple concept for estimating deadwood carbon using data from a pilot study in selected coniferous and broadleaf forests covering different climate zones in Austria. We measured deadwood volume and decay classes and calculated deadwood density and carbon fraction from destructive field samples. We found that decay reduces deadwood density significantly, while carbon fraction increases moderately with decay. Partitioning the explained variation confirmed that size and site parameters are more important for explaining deadwood carbon fraction than for deadwood density. These patterns were consistent for coniferous and broadleaf tree species. We also show how to estimate deadwood carbon stocks using standard forest inventory measurements or country statistics, without information on decay classes. We found differences in decay classes of standing versus lying deadwood, and our proposed method allows considering this in large-scale deadwood carbon assessments. We highlight research gaps and missing deadwood information, to provide more accurate carbon assessments of deadwood.

Short communication: Variation of deadwood density by decay class in Douglas fir (Pseudotsuga menziesii (Mirbel) Franco) stands in Italy

Aim of the study: To estimate fresh and basic density values of Douglas fir deadwood for the five decay classes used in the National Forest Inventories (NFIs).
 Area of study: Rincine forest in Tuscany region (Italy).
 Material and methods: 140 samples of Douglas fir deadwood (28 for each decay class; 14 of which were collected in summer and 14 in winter) were collected and analysed in the laboratory. The samples were weighed fresh, then placed in the oven for 3 days at 60°C. Afterwards the samples were weighed dried. The laboratory data were used to estimate moisture content (%), fresh and basic density by decay class.
 Main results: The results showed that the trend of basal density decreased from 1st to 5th decay class (0.43 g cm-3, 0.39 g cm-3, 0.37 g cm-3, 0.29 g cm-3 and 0.20 g cm-3). An average basic density of 0.34 g cm-3 could be used in future studies concerning the estimation of C-stock in Douglas fir deadwood.
 Research highlights: The moisture content of all decay classes of lying deadwood is influenced by the season (winter vs. summer) and consistent with the local climate regime.

Spruce (Picea abies L.) planting leads post-clearcut bird assemblages to a novel successional pathway\u2014a comparative study in hemiboreal mixed forests

Key messageBird assemblages in planted spruce (Picea abies L.) forests were compositionally distinct from those in naturally regenerated mixed stands. Despite rapid stand development on productive soils, even-aged silviculture cannot host most old-forest species. However, their habitat quality could be supported in landscape mosaics with retention forestry and set-asides.ContextThe most productive forest lands have naturally the richest bird assemblages but tend to be also most intensively managed. Sustainable solutions to this conflict are unclear.AimTo assess bird assemblages and their successional dynamics in planted Norway spruce (Picea abies L.) stands compared to naturally developing stands.MethodsWe mapped breeding bird assemblages in forty 5-ha plots on highly productive soils in Estonia. The plots included sets of naturally regenerated and planted stands, and (as successional endpoints) clear-cuts and old stands.ResultsPlanted stands had fewer bird species and pairs than naturally regenerated stands; the latter having a species composition resembling late-successional deciduous-dominated stands. Importantly, the species composition in mature spruce plantations converged toward the composition observed in late-successional conifer-dominated stands. Downed dead wood, stand age, deciduous trees, and stock density were the most significant stand characteristics shaping bird assemblages.ConclusionThe habitat value of established spruce plantations can be primarily improved by allowing for some deciduous trees and gaps with deciduous undergrowth. At the landscape scale, the bird diversity of even-aged systems would be enhanced by multi-scale applications of retention forestry—from retention trees to old-growth set-asides.

Variation in Downed Deadwood Density, Biomass, and Moisture during Decomposition in a Natural Temperate Forest

Deadwood is a resource of water, nutrients, and carbon, as well as an important driving factor of spatial pedocomplexity and hillslope processes in forested landscapes. The applicability of existing relevant studies in mountain forests in Central Europe is limited by the low number of data, absence of precise dating, and short time periods studied. Here, we aimed to assess the decomposition pathway in terms of changes and variability in the physical characteristics of deadwood (wood density, biomass, and moisture) during the decomposition process, and to describe differences in decomposition rate. The research was carried out in the Žofínský Primeval Forest, one of the oldest forest reserves in Europe. Samples were taken from sapwood of downed logs of the three main tree species: Fagus sylvatica L., Abies alba Mill., and Picea abies (L.) Karst. The time since the death of each downed log was obtained using tree censuses repeated since 1975 and dendrochronology. The maximal time since the death of a log was species-specific, and ranged from 61–76 years. The rate of change (slope) of moisture content along the time since death in a linear regression model was the highest for F. sylvatica (b = 3.94) compared to A. alba (b = 2.21) and P. abies (b = 1.93). An exponential model showing the dependence of biomass loss on time since death revealed that F. sylvatica stems with a diameter of 50–90 cm had the shortest decomposition rate—51 years—followed by P. abies (71 years) and A. alba (72 years). Our findings can be used in geochemical models of element cycles in temperate old-growth forests, the prediction of deadwood dynamics and changes in related biodiversity, and in refining management recommendations.

Influence of forest stand age on soil water repellency and hydraulic conductivity in the Mediterranean environment

The hydrological response of forest soil in the Mediterranean environment is characterised by high runoff and erosion rates, mainly due to low infiltration and high repellency of soils. However, little literature exists about the effects of forest ages on soil water repellency (SWR) and hydraulic conductivity (SHC). This study evaluates these hydrological parameters in five Pinus nigra Arn ssp. Salzmannii stands of different ages in Central-Eastern Spain; one of these stands, unmanaged, was chosen as reference system. SWR (measured in terms of water drop penetration time, WDPT) and SHC as well as the main physico-chemical properties and surface characteristics of soils were surveyed in forty-five plots. Water infiltration was higher in the older stands (including the older and unmanaged forest) and lower (by over 60%) in the more recent pine forests. Four of the studied stands did not show water repellency; only the more recent plantation showed a slight SWR. The differences in SHC among the forest ages were mainly driven by the organic matter (OM) and nutrient contents of the soils as well as by the bulk density and quantity of dead wood. SWR was similar among the plots (despite significantly differences in WDPTs), although having variable OM contents. Considering these differences in soil properties, SHC and SWR were simply predicted for each forest stand using on dbRDA models and the following soil properties: (i) OM and total nitrogen contents of soil (for SHC and SWR); (ii) dead wood and bulk density (for SHC); and (iii) clay content and the percentage of bare soil (for SWR). Overall, this study has showed that, when a new forest stand is planted, decreases in water infiltration, with subsequent increases in runoff generation capacity) of the soils, can be expected. Conversely, no water repellency is likely to affect new pine plantations.

Dead wood carbon density for the main tree species in the Lithuanian hemiboreal forest

Aboveground dead wood has a range of important ecological functions, including carbon (C) storage. According to the Intergovernmental Panel on Climate Change guidelines for National Greenhouse Gas Inventories established on the basis of the United Nations Framework Convention on Climate Change and the Kyoto Protocol, Lithuania is encouraged to quantify C pools in forests, including C in living biomass, soil and dead wood. The aim of this study was to assess species-specific dead wood density (DWD) and carbon content (CC) per decay class for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) H. Karst.), silver birch or downy birch (Betula pendula Roth or Betula pubescens Ehrh.), European aspen (Populus tremula L.), grey alder (Alnus incana (L.) Moench), black alder (Alnus glutinosa (L.) Gaertn.), common oak (Quercus robur L.) and European ash (Fraxinus excelsior L.), as the main representative hemiboreal forest tree species. The study findings revealed that mean DWD significantly decreased, while mean CC slightly increased during the wood decomposition process, which led to carbon density (CD) reduction over five decay classes. The mean CC showed little variation among the eight tree species and ranged between 47 and 54%. The lower CDs in the dead wood of decay classes 1 and 2 were more associated with coniferous than deciduous species. The estimated CD significantly decreased in all species with increasing decay class. Dead wood at decay class 5 of Scots pine, silver or downy birch, European ash and common oak had the highest CD, followed by Norway spruce and grey alder, and the lowest CDs were obtained for European aspen and black alder.

Variation in Deadwood Microsites in Areas Designated under the Habitats Directive (Natura 2000)

The continuing decline in biodiversity presents a major environmental protection challenge. The conservation of sufficiently extensive and diverse habitats requires an array of coordinated actions, often involving large areas. While a set of conservation objectives have been defined for the Natura 2000 network, no universal methods of accomplishing them have been specified, and so they must be designed by individual Member States. Deadwood volume and the density of large deadwood pieces are widely used for evaluating the quality of forest habitat types designated under the Habitats Directive. In the present study, data from 5557 sample plots were used to evaluate the mean values of the two deadwood indicators as well as the ratio of deadwood volume to living tree volume for each of the 13 habitat types in Poland. In addition, a logistic regression model was constructed to evaluate the effects of terrain, site, and tree stand characteristics as well as protection type on deadwood volume in Natura 2000 areas. Mean deadwood volume varied greatly between habitat types, with the lowest values found for Central European lichen Scots pine forests (91T0–2.5 m3 ha−1) and Old acidophilous oak woods (9190–4.4 m3 ha−1), and the highest for Riparian mixed forests (91F0–43.1 m3 ha−1) and Acidophilous Picea forests of the montane to alpine levels (9410–55.4 m3 ha−1). The ratio of deadwood volume to living tree volume ranged from approx. 1%–17%. Additionally, the presence of large deadwood differed among habitat types: in some, there were no deadwood pieces with a diameter of ≥50 cm, while their maximum density was 6.1 pieces ha−1. The logistic regression model showed that the likelihood of a habitat type to have a ‘favorable conservation status’ as defined by deadwood abundance (a threshold of at least 20 m3 ha−1 according to Polish manuals on habitat type evaluation) increased with sample plot elevation, site fertility, and moisture, as well as stand age and volume. Positive effects were also observed for forests under strict and active protection versus managed forests. Planned efforts are necessary to enhance the quality of habitats with insufficient deadwood, especially in managed forests. Special attention should be given to areas that are readily accessible due to gentle terrain and low site moisture. Furthermore, younger stands on less fertile sites may require intervention to promote deadwood accumulation. We recommend retaining a certain proportion of mature stands until natural death and decomposition. Increasing the density of large deadwood is currently one of the most pressing conservation needs in most habitat types.

Mangrove blue carbon stocks and dynamics are controlled by hydrogeomorphic settings and land‐use change

Globally, carbon‐rich mangrove forests are deforested and degraded due to land‐use and land‐cover change (LULCC). The impact of mangrove deforestation on carbon emissions has been reported on a global scale; however, uncertainty remains at subnational scales due to geographical variability and field data limitations. We present an assessment of blue carbon storage at five mangrove sites across West Papua Province, Indonesia, a region that supports 10% of the world's mangrove area. The sites are representative of contrasting hydrogeomorphic settings and also capture change over a 25‐years LULCC chronosequence. Field‐based assessments were conducted across 255 plots covering undisturbed and LULCC‐affected mangroves (0‐, 5‐, 10‐, 15‐ and 25‐year‐old post‐harvest or regenerating forests as well as 15‐year‐old aquaculture ponds). Undisturbed mangroves stored total ecosystem carbon stocks of 182–2,730 (mean ± SD: 1,087 ± 584) Mg C/ha, with the large variation driven by hydrogeomorphic settings. The highest carbon stocks were found in estuarine interior (EI) mangroves, followed by open coast interior, open coast fringe and EI forests. Forest harvesting did not significantly affect soil carbon stocks, despite an elevated dead wood density relative to undisturbed forests, but it did remove nearly all live biomass. Aquaculture conversion removed 60% of soil carbon stock and 85% of live biomass carbon stock, relative to reference sites. By contrast, mangroves left to regenerate for more than 25 years reached the same level of biomass carbon compared to undisturbed forests, with annual biomass accumulation rates of 3.6 ± 1.1 Mg C ha−1 year−1. This study shows that hydrogeomorphic setting controls natural dynamics of mangrove blue carbon stocks, while long‐term land‐use changes affect carbon loss and gain to a substantial degree. Therefore, current land‐based climate policies must incorporate landscape and land‐use characteristics, and their related carbon management consequences, for more effective emissions reduction targets and restoration outcomes.

Foraging behavior of the Eurasian Three-toed Woodpecker (Picoides tridactylus) and its implications for ecological restoration and sustainable boreal forest management

Several studies have shown that the Three-toed Woodpecker (Picoides tridactylus) is strongly favored by large-scale disturbances, including forest fires. However, natural disturbances have largely disappeared from European boreal forests because of modern forestry practices and fire suppression. We currently lack knowledge on the foraging activity and resource use of the Eurasian Three-toed Woodpecker, especially in burned forests, and this restricts our ability to develop strategies for sustainable forest management and ecological restoration aiming at improving the situation of this woodpecker and associated species. In order to fill this knowledge gap, we studied the characteristics of selected foraging substrates and the foraging behavior of the Three-toed Woodpecker during the breeding season in unburned forests and forests that have been subjected to prescribed burning. We used instantaneous sampling duringtwo consecutive springs (2016-2017), where we observed the woodpeckers’ foraging behavior during a total of 977 minutes in burned forest and 962 minutes in unburned forests. The preferred foraging substrate for Three-toed Woodpeckers in both burned and unburned forests can be characterized as freshly dead trees with a DBH > 15 cm. However, data on time spent foraging on different substrates suggest that also substrates in the 5-15 DBH range and living trees are important. Additionally, prescribed burnings led to less pronounced selection of tree species, which suggest that fire may reduce differences in abundance of saproxylic insect prey between tree species. This information on substrate selection and foraging time provide complementary knowledge and thus should be used simultaneously when management strategies for improved woodpecker habitat are developed. Our results suggest that both prescribed burning and protecting forests with high density and diversity of dead wood provides habitat opportunities for Three-toed Woodpeckers and using both in management may maximize conservation outcome

Deadwood in the oak forests of the Left Bank Forest-steppe of Ukraine

Abstract Deadwood is an important component of forest ecosystems, and difference in the deadwood carbon stock depends on many variables including forest management. The aim of our study was to determine the patterns of formation of deadwood stocks in oak (Quercus robur L.) forests in the Left Bank Forest-steppe of Ukraine. As an outcome of the research, the data on deadwood parameters were obtained. The growth characteristics and coarse woody debris (CWD) characteristics were measured on intensive monitoring and inventory plots. Assessment of morphometric parameters of the CWD in oak stands was carried out by measuring diameters at top and bottom cut and length; to determine the carbon content, deadwood density was used. The distribution of deadwood by tree species, sizes and stages of decomposition was defined. The stock of dead trees (snags) in oak forest is 15.2 m3/ha and that of logs is 21.5 m3/ha. The carbon accumulation in oak forest stands in the Left Bank Forest-steppe of Ukraine was 3.4 and 4.5 t C/ha in dead trees and logs, respectively. The dynamics of deadwood stocks according to the results of repeated observations was given.

Habitat heterogeneity affects predation of European pine sawfly cocoons.

Habitat heterogeneity is thought to affect top‐down control of herbivorous insects and contribute to population stability by providing a more attractive microhabitat for natural enemies, potentially leading to reduced population fluctuations. Identifying the parameters that contribute to habitat heterogeneity promoting top‐down control of herbivorous insects by natural enemies could facilitate appropriate management decisions, resulting in a decreased risk of pest insect outbreaks because of a higher level of predation. In our study, we measured the top‐down pressure exerted by small mammals on the cocoons of a notorious pest insect in pine forests, the European pine sawfly (Neodiprion sertifer), which is known to be regulated by small mammal predation. The forest stands used differed in heterogeneity measured in terms of differences in tree diversity and density, understory vegetation height, presence/absence, and density of dead wood. We found higher predation in more dense spots within forest stands. Further, the effect of dead wood on sawfly cocoon predation depended on the pine proportion in forest stands. The addition of dead wood in a manipulation experiment had a slight positive effect on cocoon predation, while dead wood removal caused a clear decrease in predation rate, and the decrease was more pronounced when the proportion of pine increased. Our results show that habitat heterogeneity affects predation by generalist predators on herbivorous insects. This knowledge could be applied to reduce the risk of insect outbreaks by applying management methods that increase heterogeneity in perennial systems such as forests and orchards, thus decreasing the levels of insect damage.

Dead wood basic density, and the concentration of carbon and nitrogen for main tree species in managed hemiboreal forests

Forest ecosystems are an important carbon (C) pool, and the decomposition of dead wood plays a key role in its C cycle. Based on the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, IPCC Guidelines for National Greenhouse Gas Inventories were established. Nations that have signed the agreements are encouraged to quantify C pools and fluxes in their forests, including its proportion occurring as dead wood. There are significant differences in density and C concentration of dead wood among tree species. In managed hemiboreal forests of Estonia the dead wood density, and C and N concentration changes in different decay classes for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), silver and downy birch (Betula pendula Roth. and Betula pubescens Ehrh.), black alder (Alnus glutinosa (L.) Gaertn.), grey alder (Alnus incana (L.) Moench.) and European aspen (Populus tremula L.) have been assessed. All together 548 sample discs taken from logs (measurements were restricted to fallen dead trees only) were collected. The results revealed a decrease in mean dead wood density with progressing decay state for all studied tree species. Pine, spruce and grey alder had the smallest wood density reduction with progressing decay state, retaining 37%, 30%, and 36% of initial density, respectively. Other broadleaved tree species (birch, black alder and aspen) had the greatest density reduction during decomposition, retaining 24%, 23%, and 16% of initial density, respectively. For all studied tree species there were no significant differences of wood density between sites with different moisture conditions (dry, medium or wet areas). In case of pine, spruce and birch the C concentrations were significantly affected by the decay class, while in case of both alders and aspen the C concentrations were not significantly affected by changes in decay classes. For all the assessed tree species the N concentration in dead wood was increasing with increasing decay class.

Carbon storage in old-growth forests of the Mid-Atlantic: toward better understanding the eastern forest carbon sink.

Few old-growth stands remain in the matrix of secondary forests that dominates the eastern North American landscape. These remnant stands offer insight on the potential carbon (C) storage capacity of now-recovering secondary forests. We surveyed the remaining old-growth forests on sites characteristic of the general Mid-Atlantic United States and estimated the size of multiple components of forest C storage. Within and between old-growth stands, variability in C density is high and related to overstory tree species composition. The sites contain 219 ± 46 Mg C/ha (mean ± SD), including live and dead aboveground biomass, leaf litter, and the soil O horizon, with over 20% stored in downed wood and snags. Stands dominated by tulip poplar (Liriodendron tulipifera) store the most live biomass, while the mixed oak (Quercus spp.) stands overall store more dead wood. Total C density is 30% higher (154 Mg C/ha), and dead wood C density is 1800% higher (46 Mg C/ha) in the old-growth forests than in the surrounding younger forests (120 and 5 Mg C/ha, respectively). The high density of dead wood in old growth relative to secondary forests reflects a stark difference in historical land use and, possibly, the legacy of the local disturbance (e.g., disease) history. Our results demonstrate the potential for dead wood to maintain the sink capacity of secondary forests for many decades to come.

Wildfire and drought dynamics destabilize carbon stores of fire-suppressed forests.

Widespread fire suppression and thinning have altered the structure and composition of many forests in the western United States, making them more susceptible to the synergy of large-scale drought and fire events. We examine how these changes affect carbon storage and stability compared to historic fire-adapted conditions. We modeled carbon dynamics under possible drought and fire conditions over a 300-year simulation period in two mixed-conifer conditions common in the western United States: (1) pine-dominated with an active fire regime and (2) fir-dominated, fire suppressed forests. Fir-dominated stands, with higher live- and dead-wood density, had much lower carbon stability as drought and fire frequency increased compared to pine-dominated forest. Carbon instability resulted from species (i.e., fir's greater susceptibility to drought and fire) and stand (i.e., high density of smaller trees) conditions that develop in the absence of active management. Our modeling suggests restoring historic species composition and active fire regimes can significantly increase carbon stability in fire-suppressed, mixed-conifer forests. Long-term management of forest carbon should consider the relative resilience of stand structure and composition to possible increases in disturbance frequency and intensity under changing climate.