1. Dead wood is a habitat for numerous fungal species, many of which are important agents of decomposition. Previous studies suggested that wood-inhabiting fungal communities are affected by climate, ...availability of dead wood in the surrounding landscape and characteristics of the colonized dead-wood object (e.g. host tree species). These findings indicate that different filters structure fungal communities at different scales, but how these factors individually drive fungal fruiting diversity on dead-wood objects is unknown. 2. We conducted an orthogonal experiment comprising 180 plots (0.1 ha) in a random block design and measured fungal fruit body richness and community composition on 720 dead-wood objects over the first 4 years of succession. The experiment allowed us to disentangle the effects of the host (beech and fir; logs and branches) and the environment (microclimate: sunny and shady plots; local dead wood: amount and heterogeneity of dead wood added to plot). 3. Variance partitioning revealed that the host was more important than the environment for the diversity of wood-inhabiting fungi. A more detailed model revealed that host tree species had the highest independent effect on richness and community composition of fruiting species of fungi. Host size had significant but low independent effects on richness and community composition of fruiting species. Canopy openness significantly affected the community composition of fruiting species. By contrast, neither local amount nor heterogeneity of dead wood significantly affected the fungal diversity measures. 4. Synthesis. Our study identified host tree species as a more important driver of the diversity of wood-inhabiting fungi than the environment, which suggests a hostcentred filter of this diversity in the early phase of the decomposition process. For the conservation of wood-inhabiting fungi, a high variety of host species in various microclimates is more important than the availability of dead wood at the stand level.
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The habitat-amount hypothesis challenges traditional concepts that explain species richness within habitats, such as the habitat-patch hypothesis, where species number is a function of patch size and ...patch isolation. It posits that effects of patch size and patch isolation are driven by effects of sample area, and thus that the number of species at a site is basically a function of the total habitat amount surrounding this site. We tested the habitat-amount hypothesis for saproxylic beetles and their habitat of dead wood by using an experiment comprising 190 plots with manipulated patch sizes situated in a forested region with a high variation in habitat amount (i.e., density of dead trees in the surrounding landscape). Although dead wood is a spatio-temporally dynamic habitat, saproxylic insects have life cycles shorter than the time needed for habitat turnover and they closely track their resource. Patch size was manipulated by adding various amounts of downed dead wood to the plots (∼800 m3 in total); dead trees in the surrounding landscape (∼240 km2) were identified using airborne laser scanning (light detection and ranging). Over 3 yr, 477 saproxylic species (101,416 individuals) were recorded. Considering 20–1,000 m radii around the patches, local landscapes were identified as having a radius of 40–120 m. Both patch size and habitat amount in the local landscapes independently affected species numbers without a significant interaction effect, hence refuting the island effect. Species accumulation curves relative to cumulative patch size were not consistent with either the habitat-patch hypothesis or the habitat-amount hypothesis: several small dead-wood patches held more species than a single large patch with an amount of dead wood equal to the sum of that of the small patches. Our results indicate that conservation of saproxylic beetles in forested regions should primarily focus on increasing the overall amount of dead wood without considering its spatial arrangement. This means dead wood should be added wherever possible including in local landscapes with low or high dead-wood amounts. For species that have disappeared from most forests owing to anthropogenic habitat degradation, this should, however, be complemented by specific conservation measures pursued within their extant distributional ranges.
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Resource availability and habitat heterogeneity are principle drivers of biodiversity, but their individual roles often remain unclear since both factors are usually correlated. The biodiversity of ...species dependent on dead wood could be driven by either resource availability represented by dead‐wood amount or habitat heterogeneity characterized by dead‐wood diversity or both. Understanding their roles is crucial for improving evidence‐based conservation strategies for saproxylic species in managed forests. To disentangle the effects of dead‐wood amount and dead‐wood diversity on biodiversity relative to canopy openness (microclimate), we experimentally exposed different amounts of logs and branches of two different tree species representing a gradient of dead‐wood diversity in 190 sunny and shady forest plots. During the 3 years after exposing dead wood, we sampled saproxylic beetles, which are together with fungi the most diverse and important taxonomic group involved in decomposition of wood. The composition of saproxylic beetle assemblages differed clearly between shady and sunny forest plots, with higher richness in sunny plots. Both dead‐wood amount and dead‐wood diversity positively and independently affected species richness of saproxylic beetles, but these effects were mediated by canopy openness. In sunny forest, species richness increased with increasing amount of dead wood, whereas in shady forest, dead‐wood diversity was the prevailing factor. The stepwise analysis of abundance and species richness, however, indicated that effects of both factors supported only the habitat‐heterogeneity hypothesis, as the positive effect of high amounts of dead wood could be explained by cryptic variability of dead‐wood quality within single objects. Synthesis and applications. As canopy openness and habitat heterogeneity seem to be the major drivers of saproxylic beetle diversity in temperate forests, we recommend that managers aim to increase the heterogeneity of dead‐wood substrates under both sunny and shady forest conditions. Intentional opening of the canopy should be considered in anthropogenically homogenized, dense forests. Specifically in temperate mixed montane forests, dead wood should be provided in the form of large logs in sunny habitats and a high diversity of different dead‐wood substrates should be retained or created in shady forests.
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Coarse woody debris (CWD) is an important pool of carbon in forest ecosystems and is present in all strata as fallen, standing or suspended CWD. However, there are relatively few decomposition ...studies of CWD in tropical forests compared with temperate forests, and research on suspended CWD in particular has largely not been attempted. Termites are important decomposers in tropical ecosystems yet their role relative to microbial decomposers and the importance of the vertical location of CWD has rarely been considered. For the first time, we examined the relative contribution of macro-invertebrates (predominantly termites) and microbes to the decay of suspended and ground-placed (fallen) CWD in lowland, tropical rainforest. We set up wood baits (Pinus radiata) with and without termite access, and measured wood mass loss after 1 year. Mass loss of groundplaced CWD assays was over four times greater than suspended CWD assays. Termite decomposition was vertically stratified with termites having a large relative contribution to the decomposition of ground-placed CWD and a negligible contribution to the decomposition of suspended CWD. In contrast, the effect of microbes on decomposition was low and not vertically stratified. Although our results support the findings of temperate studies in that decomposition of CWD is dependent on its physical location, we show that in tropical rainforests this is predominantly due to greater termite decomposition on the forest floor. Suspended CWD remains an important carbon sink due to slow microbial decay until it falls to the forest floor where it is more accessible to termites.
•Species-specific dead wood basic density (DWBD) means by decay class are provided.•Decay class-specific conversion factors yielded 11.1%–26.6% lower estimate in national dead wood C pool.•Majority ...of studied tree species followed a steady decline pattern of relative wood density.•Genus-specific DWBD meta-means by decay class are available for use in the lack of local DWBD data.
Dead wood (DW) is an important forest carbon (C) pool for which the reporting of C stock changes within the National Greenhouse Gas Inventory Report (NIR) is mandatory. The use of DW volume-to-carbon conversion factors by decay classes, i.e. DW basic density (DWBD) and C fraction (CF), or C density (CD) as their product, facilitates more accurate estimates of DW C stocks and C stock changes.
We present DW conversion factors, namely DWBD, CF, and CD, by decay classes for six broadleaf (Quercus robur L., Carpinus betulus L., Alnus glutinosa Garnet., Fraxinus angustifolia Vahl., Fagus sylvatica L., and Quercus ilex L.) and four conifer (Abies alba Mill., Picea abies (L.) Karst., Pinus nigra Arnold and Pinus pinaster Aiton) tree species from Continental, Alpine and Mediterranean biogeographical regions of Croatia. For each tree species DW logs (diameter from 5 to 30 cm) were visually categorized into four decay classes and nine discs per decay class were sampled. In addition, three healthy trees of each species were felled down at the same location for estimating the basic density of fresh wood (BWD, decay class 0) and calculation of species-specific relative density reduction patterns. In total, 390 discs were sampled and analysed in the laboratory.
Our results show that broadleaves, on average, have higher DWBD than conifers (p < 0.05) for decay classes 0–3, but for decay class 4 no difference (p < 0.05) was observed between these two tree species groups. Unlike for DWBD, CF showed no trend with decay class, but a difference (p < 0.05) in the average CF was found between broadleaves and conifers with the mean (s.e.) of 47.65% (0.12%) and 50.67% (0.23%), respectively. The application of decay class-specific CD by forest land use strata used in the Croatian NIR yielded 11.1% − 26.6% lower DW C pool estimates, compared to the current ones calculated using BWDs and default CF.
DWBD data from our study was compared with DWBD data from the literature. We observed good agreement between national species-specific DWBD and global genus-specific DWBD for the great majority of investigated tree genera and decay classes. Therefore, we combined our results with the published data to provide a global DWBD meta-means with confidence intervals by decay classes for eight tree genera. Our results suggest that in the absence of local or national DWBD data, the use of genus-specific DWBD meta-means is justified.
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Aim
European temperate forests have lost dead wood and the associated biodiversity owing to intensive management over centuries. Nowadays, some of these forests are being restored by enrichment with ...dead wood, but mostly only at stand scales. Here, we investigated effects of a seminal dead‐wood enrichment strategy on saproxylic organisms at the landscape scale.
Location
Temperate European beech forest in southern Germany.
Methods
In a before–after control–impact design, we compared assemblages and gamma diversities of saproxylic organisms in strictly protected old‐growth forest areas (reserves) and historically moderately and intensively managed forest areas before and a decade after starting a landscape‐wide strategy of dead‐wood enrichment.
Results
Before enrichment with dead wood, the gamma diversity of saproxylic organisms in historically intensively managed forest stands was significantly lower than in reserves and historically moderately managed forest stands; this difference disappeared after 10 years of dead‐wood enrichment. The species composition of beetles in forest stands of the three historical management intensities differed before the enrichment strategy, but a decade thereafter, the species compositions of previously intensively logged and forest reserve plots were similar. However, the differences in fungal species composition between historical management categories before and after 10 years of enrichment persisted.
Main conclusions
Our results demonstrate that intentional enrichment of dead wood at the landscape scale is a powerful tool for rapidly restoring saproxylic beetle communities and for restoring wood‐inhabiting fungal communities, which need longer than a decade for complete restoration. We propose that a strategy of area‐wide active restoration combined with some permanent strict refuges is a promising means of promoting the biodiversity of age‐long intensively managed Central European beech forests.
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Aim: Climate change is expected to have major impacts on terrestrial biodiversity at all ecosystem levels, including reductions in species-level distribution and abundance. We aim to test the extent ...to which land use management, such as setting-aside forest from production, could reduce climate-induced biodiversity impacts for specialist species over large geographical gradients. Location: Sweden. Methods: We applied ensembles of species distribution models based on citizen science data for six species of red-listed old-forest indicator fungi confined to spruce dead wood. We tested the effect on species habitat suitabilities of alternative climate change scenarios and varying amounts of forest set-aside from production over the coming century. Results: With 3.6% of forest area set-aside from production and assuming no climate change, overall habitat suitabilities for all six species were projected to increase in response to maturing spruce in set-aside forest. However, overall habitat suitabilities for all six species were projected to decline under climate change scenario RCP4.5 (intermediate-low emissions), with even greater declines projected under RCP 8.5 (high emissions). Increasing the amount of forest set-aside to 16% resulted in significant increases in overall habitat suitability, with one species showing an increase. A further increase to 32% forest set-aside resulted in considerably more positive trends, with three of six species increasing. Main conclusions: There is interspecific variation in the importance of future macroclimate and resource availability on species occurrence. However, large-scale conservation measures, such as increasing resource availability through setting aside forest from production, could reduce future negative effects from climate change, and early investment in conservation is likely to reduce the future negative impacts of climate change on specialist species.
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Standing dead trees (snags) decompose more slowly than downed dead wood and provide critical habitat for many species. The rate at which snags fall therefore influences forest carbon dynamics and ...biodiversity. Fall rates correlate strongly with mean annual temperature, presumably because warmer climates facilitate faster wood decomposition and hence degradation of the structural stability of standing wood. These faster decomposition rates coincide with turnover from fungal-dominated wood decomposer communities in cooler forests to codomination by fungi and termites in warmer regions. A key question for projecting forest dynamics is therefore whether temperature effects on wood decomposition arise primarily because warmer conditions facilitate faster decomposer metabolism, or are also influenced indirectly by belowground community turnover (e.g., termites exert additional influence beyond fungal-plus-bacterial mediated decomposition). To test between these possibilities, we simulate standing dead trees with untreated wooden posts and follow them in the field across 5 yr at 12 sites, before measuring buried, soil–air interface and aerial post sections to quantify wood decomposition and organism activities. High termite activities at the warmer sites are associated with rates of postfall that are three times higher than at the cooler sites. Termites primarily consume buried wood, with decomposition rates greatest where termite activities are highest. However, where higher microbial and termite activities co-occur, they appear to compensate for one another first, and then to slow decomposition rates at their highest activities, suggestive of interference competition. If the range of microbial and termite codomination of wood decomposer communities expands under climate warming, our data suggest that expansion will accelerate snag fall with consequent effects on forest carbon cycling and biodiversity in forests previously dominated by microbial decomposers.
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Veteranisation is a promising management technique for dead wood creation at sites where dead wood, and ancient and veteran tree abundance is limited; it aims to replicate the microhabitats ...associated with ancient and veteran trees in younger trees by controlled physical damage of woody tissues. Five veteranisation treatments were applied, using a chainsaw, to healthy branches within the crowns of three mature oak trees. Treatments consisted of variations of cambium girdling, lopping, and lopping with girdling in combination; in addition, two branches that had died naturally were selected from each tree for comparison. Veteranised branches were harvested after 14 months. The fungal community composition was determined in different parts of the branch and their 3-dimensional structure mapped in representative branches. Stereum gausapatum was the most frequently isolated basidiomycete from veteranised branches, which occurred in all treatment types. The most commonly isolated ascomycete of veteranised branches was Ophiostoma quercus, which caused distinctive pockets of discoloured wood and was associated with half girdle treatments. There were significant differences in fungal species composition between veteranised branches and branches that had died naturally. This compositional difference may influence the development of later stage fungal communities, managers must consider these community compositional differences when prescribing veteranisation.
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The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks
. The decomposition of deadwood is largely governed by climate
with decomposer groups-such ...as microorganisms and insects-contributing to variations in the decomposition rates
. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood
. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect-including the direct consumption by insects and indirect effects through interactions with microorganisms-insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and -0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle.
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