Amount Of Dead Wood Research Articles

Disentangling the importance of space and host tree for the beta-diversity of beetles, fungi, and bacteria: Lessons from a large dead-wood experiment

Forestry in Europe changed the tree species composition and reduced dead-wood amount and heterogeneity, and therefore negatively affected saproxylic diversity. Efficient conservation requires knowledge about the importance of the relevant diversity drivers across taxa. We examined the relative importance of space vs. host for saproxylic diversity at a spatial extend of 600 km in Germany. Further, we disentangled effects of among regions, forest stands, host clades, and tree species on saproxylic diversity. This allows inferences for spatial- and host tree-related conservation strategies. Beetle, fungal sporocarp, molecular-derived fungal, and bacterial communities were studied in a large nested dead-wood experiment comprising 11 tree species. We used multiplicative diversity partitioning to assess the diversity of rare, typical, and dominant species. The beta-diversity of beetles and fungal sporocarps was equally explained by space and host, but that of molecular fungi and bacteria mainly by the host. Across taxa, beta-diversity was higher among forest stands than among regions. However, for beetles and fungal sporocarps, differences among regions were also important. Host tree clade and host tree species were important for beetle and host clade for fungal sporocarp beta-diversity. Host tree species was more important than host clade for the beta-diversity of molecular fungi and bacteria. The divergent response of different taxa to space and host calls into question the use of a simple spatially-centered or host-centered strategy. Instead, a high dead-wood tree species diversity on a broad spatial coverage at the national scale in temperate European forests is necessary to maintain rare and abundant species.

Forest management impact on soil organic carbon: A paired-plot study in primeval and managed European beech forests

Forest soils have been recognized as important reservoirs of older stable carbon (C) in the biosphere and thus play a key role in the global C cycle. While much research has addressed the consequences of forest conversion and forest use on soil organic carbon (SOC) stocks, some controversies remain as to whether primary forest soils store significantly more SOC than soils in managed forests. Here, we explore the effect of forest management on SOC stocks in European beech (Fagus sylvatica) forests through a paired-plot study in nearby primeval and managed forests in the western Carpathians, testing the hypotheses that primeval forests store significantly more SOC especially in the topsoil and that larger biomass and deadwood amounts are important drivers. The three primeval forests stored on average 15 % more SOC (∼1.8 kg C m−2) in the organic layers and mineral soil to 50 cm depth than the managed forests prior to harvest (difference marginally significant at p = 0.09). Contrary to expectation, the difference was significant in the subsoil (30–50 cm depth) but not in the topsoil. Consequently, the primeval forests had a greater proportion of their SOC pool located in the subsoil than the managed forests. Despite considerably larger wood biomass and deadwood amounts in the primeval forests, SOC pools were neither related to biomass nor deadwood mass. PCA and correlation analyses revealed a prominent negative effect of the availability of Ca, Mg, K and P on SOC stocks, suggesting that clear-cutting has slightly (but significantly) increased nutrient supply in the managed forests, likely stimulating soil biological activity and reducing SOC storage in comparison to the primeval forests. We conclude that the primeval forest reference is important for assessing forest management effects on SOC storage, and that a long history of management likely has significantly reduced the SOC stocks of Central European beech forests.

Aesthetic preferences for deadwood in forest landscape: A case study in Italy

In the last decades, the structural and functional role of standing dead trees and lying deadwood in forests has been widely recognized by scientific community and forest managers. However, a large amount of deadwood in forests can have negative impacts on recreational forests by reducing the aesthetic value and site attractiveness. The aims of the present study are to investigate whether deadwood in forests is truly perceived negatively by people and whether socio-demographic characteristics influence the respondents’ perception. To achieve these aims, the study was implemented by submitting an online questionnaire to a sample of 1292 Italian citizens. The results show that 73.4% of respondents have previous knowledge of the concept of deadwood in forests, while 26.6% have never heard this concept. For most of the respondents, standing dead trees and lying deadwood have a negative aesthetic effect on the landscape (52.2% and 42.9%), while for only 7.5% and 23.0% of respondents standing dead trees and lying deadwood have a positive effect on forest landscape. The results show that for all six forest stands proposed (Old European beech coppice, Mediterranean maquis, Norway spruce high forest, simple sweet Chestnut coppice, European beech high forest, black pine high forest) the respondents prefer the situation without deadwood. Finally, the results show that deadwood – both standing dead trees and lying deadwood – in forests is on average more appreciated by male (rather than female), young people (rather than old people), and people with a low level of education (rather than people with a high level of education).

Stem traits, compartments and tree species affect fungal communities on decaying wood.

SummaryDead wood quantity and quality is important for forest biodiversity, by determining wood‐inhabiting fungal assemblages. We therefore evaluated how fungal communities were regulated by stem traits and compartments (i.e. bark, outer‐ and inner wood) of 14 common temperate tree species. Fresh logs were incubated in a common garden experiment in a forest site in the Netherlands. After 1 and 4 years of decay, the fungal composition of different compartments was assessed using Internal Transcribed Spacer amplicon sequencing. We found that fungal alpha diversity differed significantly across tree species and stem compartments, with bark showing significantly higher fungal diversity than wood. Gymnosperms and Angiosperms hold different fungal communities, and distinct fungi were found between inner wood and other compartments. Stem traits showed significant afterlife effects on fungal communities; traits associated with accessibility (e.g. conduit diameter), stem chemistry (e.g. C, N, lignin) and physical defence (e.g. density) were important factors shaping fungal community structure in decaying stems. Overall, stem traits vary substantially across stem compartments and tree species, thus regulating fungal communities and the long‐term carbon dynamics of dead trees.

Windthrown elements: a key point improving microsite amelioration and browsing protection to transplanted seedlings

Mountain forest dynamics and ecosystems services are critically influenced by disturbances, in particular storm events. After extensive disturbance, the large amount of deadwood lying on ground and the necessity for restoring the forest cover with natural regeneration are two critical issues to be dealt with. Salvage logging is the most common post-disturbance management strategy, but it does not consider the strategic role of coarse woody debris (CWD) in favoring regeneration establishment and survival. The aim of this study is to analyze how CWDcontributes to creating favorable microsites for regeneration, increasing seedling establishment probability, after a large windthrow in the eastern Italian Alps. We focused on two different facilitative mechanisms provided by CWD, microsite amelioration and seedling protection, by planting a set of seedlings in the surroundings of deadwood elements. The former mechanism was analyzed by measuring temperature and SWC (Soil Water Content) locally, while for the latter we recorded evidence of browsing at the end of the season. For each trial, we established control sites in empty areas nearby with no CWD presence in order to infer its contribution. The results show that north-facing microsites on south-exposed slopes offer significantly lower temperature and fewer water stress for saplings, in comparison to south-facing microsites. More in general, saplings on deadwood-mitigated microsites are less exposed to desiccation, which mitigates the transplanting shock and facilitates the establishment. Moreover, the presence of lying deadwood increases roughness and, as a consequence, the cost for browsers to reach the seedlings. Using a coefficient expressing this increment, we underline the significant protective effect of CWD against deer browsing. The results of our study highlight the importance of deadwood in providing favorable regeneration microsites, enhancing the probability of sapling establishment and survival, protecting them from deer browsing.

Forest dieback in a protected area triggers the return of the primeval forest specialist Peltis grossa (Coleoptera, Trogossitidae)

AbstractForest set‐aside is a commonly employed conservation strategy, but large‐scale disturbances regularly evoke discussions on its utility for biodiversity conservation in former production forests. In this study, we reconstructed the return of a primeval forest specialist, the beetle Peltis grossa (Linnaeus, 1758) of the family Trogossitidae, to two national parks after more than a century of absence. To illuminate historical processes and the role of potential refuges and species' size, we compared the beetle's current distribution collected in a large‐scale citizen science approach, with historical data and the current distribution of two closely related, smaller species. We quantified deadwood preferences and investigated the effect of benign neglect versus salvage‐logging management practices on P. grossa abundances. Our findings support the view that P. grossa survived in the southern Bohemian Forest, which enabled its recolonization of the landscapes. However, a build‐up of the population was dependent upon a massive supply of deadwood by bark beetles within the refuge area. In a large area in the north of the study region that >20 years ago contained ample amounts of deadwood, forest succession outpaced colonization by P. grossa. The current probability of the species' presence decreased with distance to the presumed refuge area from 70% to 5% at 40 km. In the present core distribution area of P. grossa, salvage logging reduced its abundance by the factor 20. These results provide three important lessons on the potential of natural disturbances as a biodiversity restoration tool in forest set‐asides: First, large supply of deadwood by disturbance can trigger the return of locally extinct primeval forest specialists. Second, the species must survive within a critical distance (for P. grossa < 10–40 km). Third, salvage logging significantly reduces the population densities of forest specialists by reducing habitat amount.

Climate-induced forest dieback drives compositional changes in insect communities that are more pronounced for rare species

Species richness, abundance and biomass of insects have recently undergone marked declines in Europe. We metabarcoded 211 Malaise-trap samples to investigate whether drought-induced forest dieback and subsequent salvage logging had an impact on ca. 3000 species of flying insects in silver fir Pyrenean forests. While forest dieback had no measurable impact on species richness, there were significant changes in community composition that were consistent with those observed during natural forest succession. Importantly, most observed changes were driven by rare species. Variation was explained primarily by canopy openness at the local scale, and the tree-related microhabitat diversity and deadwood amount at landscape scales. The levels of salvage logging in our study did not explain compositional changes. We conclude that forest dieback drives changes in species assemblages that mimic natural forest succession, and markedly increases the risk of catastrophic loss of rare species through homogenization of environmental conditions.

Surviving trees and deadwood moderate changes in soil fungal communities and associated functioning after natural forest disturbance and salvage logging

Temperate forests are increasingly subject to natural disturbance by stand replacing windthrows or bark-beetle attacks. Forests are commonly salvage logged after disturbance, whereby substantial parts of biological legacies, such as surviving trees and deadwood, are removed. Despite increasing concerns about the ecological consequences of salvage logging operations, our knowledge on the effects on the soil microbiome and associated functioning remains limited.Here, we studied soil fungal communities, decomposition processes, and soil organic matter dynamics in 21 intact or disturbed, temperate Norway spruce stands about one decade after they were damaged by windthrow or bark-beetle attacks. Disturbed stands comprised different post-disturbance management, i.e. deadwood retention and salvage logged plots. We used high-throughput sequencing and ergosterol measurements to explore fungal communities and biomass, and enzyme assays to study decomposition processes.Disturbance shifted soil fungal communities from ectomycorrhizal to saprotrophic dominated assemblages. Fungal biomass declined with decreasing tree abundance after disturbance. Activities of organic matter degrading enzymes declined by ca. 30–80% after disturbance. The relative abundance of ectomycorrhizal fungi was positively related to enzymatic activities. Tree biomass parameters and amounts of deadwood retained were positively related to fungal biomass, certain ectomycorrhizal taxa, and relative ectomycorrhizal fungal abundance among disturbed stands, which, in turn, was associated with higher enzymatic activities.Our findings demonstrate a significant response of soil fungal communities to natural forest disturbance and salvage logging, with consequences for decomposition and soil organic matter dynamics. We conclude that the retention of surviving trees and deadwood as biological legacies attenuated associated changes to a significant extent, highlighting their importance for the preservation of ectomycorrhizal fungi and the maintenance of decomposition processes after disturbance.

Aboveground Deadwood Biomass and Composition Along Elevation and Land-Use Gradients at Mount Kilimanjaro

Deadwood is an important structural and functional component of forest ecosystems and biodiversity. As deadwood can make up large portions of the total aboveground biomass, it plays an important role in the terrestrial carbon (C) cycle. Nevertheless, in tropical ecosystems and especially in Africa, quantitative studies on this topic remain scarce. We conducted an aboveground deadwood inventory along two environmental gradients—elevation and land use— at Mt. Kilimanjaro, Tanzania. We used a huge elevation gradient (3690 m) along the southern slope of the mountain to investigate how deadwood is accumulated across different climate and vegetation zones. We also compared habitats that differed from natural forsts in land-use intensity and disturbance history to assess anthropogenic influence on deadwood accumulation. In our inventory we distinguished coarse woody debris (CWD) from fine woody debris (FWD). Furthermore, we calculated the C and nitrogen (N) content of deadwood and how the C/N ratio varied with decomposition stages and elevation. Total amounts of aboveground deadwood ranged from 0.07 ± 0.04 to 73.78 ± 36.26 Mg ha–1 (Mean ± 1 SE). Across the elevation gradient, total deadwood accumulation was highest at mid-elevations and reached a near-zero minimum at very low and very high altitudes. This unimodal pattern was mainly driven by the corresponding amount of live aboveground biomass and the combined effects of decomposer communities and climate. Land-use conversion from natural forests into traditional homegardens and commercial plantations, in addition to frequent burning, significantly reduced deadwood biomass, but not past selective logging after 30 years of recovery time. Furthermore, we found that deadwood C content increased with altitude. Our study shows that environmental gradients, especially temperature and precipitation, as well as different anthropogenic disturbances can have considerable effects on both the quantity and composition of deadwood in tropical forests.

Evidence of the association between deadwood and forest recreational site choices

The level of biodiversity is in decline, also in forests. As more natural structures are known to safeguard biodiversity, changes in forest management, including higher amounts of deadwood, may help reverse the decline. However, this could lead to trade-offs between forest ecosystem services, and forest recreation might be negatively affected by the presence of more natural forest structures, especially deadwood. So far, only a few studies have investigated the influence of deadwood on recreation in larger forest areas and on a national or regional scale. To better understand the possible impact, we analysed how higher amounts and different forms of deadwood would affect site preferences for recreation employing an online survey based on a representative sample in Bavaria, Germany (N = 1462). A choice experiment comprising different forest alternatives with varying degrees of deadwood showed that the amount of deadwood does not influence respondents' choice of recreation sites. However, deadwood quality attributes, i.e. structural variety and advanced decomposition positively impacted site choices. Latent class models revealed both observed and unobserved taste heterogeneity. Deadwood was, however, not an essential attribute for the forest site-selection, while infrastructure facilities or good paths/accessibility were more important. The results show that no significant trade-offs between forest recreation and deadwood enrichment exist. At the same time, respondents showed solid preferences for improving habitats for rare and endangered species in forests, indicating that biodiversity is significant to them. As the preferences for a mixture of standing and lying structures also coincide with conservation ecology research, we conclude that conflicts between recreationists and increased occurrence of deadwood to promote biodiversity are not that severe as often assumed by forest managers.

Influence of tree hollow characteristics and forest structure on saproxylic beetle diversity in tree hollows in managed forests in a regional comparison.

Tree hollows are among the rarest habitats in today's Central European managed forests but are considered key structures for high biodiversity in forests. To analyze and compare the effects of tree hollow characteristics and forest structure on diversity of saproxylic beetles in tree hollows in differently structured managed forests, we examined between 41 and 50 tree hollows in beech trees in each of three state forest management districts in Germany. During the two‐year study, we collected 283 saproxylic beetle species (5880 individuals; 22% threatened species), using emergence traps. At small spatial scales, the size of hollow entrance and the number of surrounding microhabitat structures positively influenced beetle diversity, while the stage of wood mould decomposition had a negative influence, across all three forest districts. We utilized forest inventory data to analyze the effects of forest structure in radii of 50–500 m around tree hollows on saproxylic beetle diversity in the hollows. At these larger spatial scales, the three forest management districts differed remarkably regarding the parameters that influenced saproxylic beetle diversity in tree hollows. In Ebrach, characterized by mostly deciduous trees, the amount of dead wood positively influenced beetle diversity. In the mostly coniferous Fichtelberg forest district, with highly isolated tree hollows, in contrast, only the proportion of beech trees around the focal tree hollows showed a positive influence on beetle diversity. In Kelheim, characterized by mixed forest stands, there were no significant relationships between forest structure and beetle diversity in tree hollows. In this study, the same local tree hollow parameters influenced saproxylic beetle diversity in all three study regions, while parameters of forest structure at larger spatial scales differed in their importance, depending on tree‐species composition.

What is unmanaged forest and how does it sustain biodiversity in landscapes with a long history of intensive forestry?

Abstract A recent paper by Schall et al. (2020) concluded that beech forests managed in even‐aged (EA) rotation systems were more efficient than unmanaged (UNM) forest and forest managed in uneven‐aged (UEA) selective cutting systems in supporting landscape‐scale biodiversity in Germany. The authors based their conclusion on a comprehensive multitaxon survey and a promising resampling model for assessing gamma diversity at landscape scale. Here, we challenge their conclusions and evaluate the importance of UNM forests for conservation of forest biodiversity. The average amount of dead wood reported from EA stands (27.8 m3/ha) was almost 30% higher than reported from UNM stands (21.6 m3/ha) in the study. Averages from long UNM temperate forests in Europe are typically six to seven times higher (131–157 m3/ha). We therefore conclude the UNM studied stands to reflect legacies of former management, and to be poorly representative of UNM forests. Data from our own studies, including long UNM beech stands in Denmark, demonstrate how this shortcoming seriously undermines the general validity of the presented results to conservation of forest biodiversity. Synthesis and applications. Preservation and restoration of intact forest ecosystems remains essential to biodiversity conservation. We show that the findings of Schall et al. (2020) do not contradict this important notion. Schall and colleagues identified UEA management systems as potentially inferior to more traditional EA management systems for conserving forest biodiversity at the landscape scale. The paper also provides insight into the limited short‐term conservation value of simply abandoning forest management in intensively managed landscapes. Based on this, we call for discarding the current orthodox view of non‐intervention when new forest reserves are created in temperate Europe. Active reinforcement of natural disturbance regimes and active habitat creation may lead to faster recovery of natural stand structure and forest biodiversity.

Animal diversity in beech forests – An analysis of 30 years of intense faunistic research in Hessian strict forest reserves

Under natural conditions beech forest would be the most widespread habitat in Central Europe. Therefore the knowledge of this vegetation type, including the animal communities dwelling there, as well as the mechanisms forming these communities are of high interest for biodiversity research and conservation in Central Europe. However, historically, Central European beech forests were thought to harbor only relatively few species. Here, faunistic data of five beech forest reserves, which were generated as part of the Hessian strict forest reserves program, are analyzed to investigate diversity patterns of Hessian beech forests of low mountain ranges. We focus on species-level data from six organism groups: Aculeata, Araneae, Coleoptera, Heteroptera, Lumbricidae, and Macrolepidoptera. We show that with 2552 forest-dwelling species from these organism groups an unexpectedly high number of species was found in Hessian beech forests, and that a higher species richness can be expected in these groups. Observed species diversity ranges from 1245 to 1556 forest dwelling species in the five individual forest reserves. Overall, 36 % of the forest dwelling species of the considered species groups known from Germany were found with all applied methods in the forest reserves. Different forest reserves share 40–50 % of the species, representing 50–70 % of the species of the individual reserves, indicating high levels of regional and habitat-structure based differentiation. Only 21 % of the species are found in all five reserves. The low percentage of species found in all five reserves is, in addition to differing local conditions, probably a result of the communities being composed of few highly abundant and many rare species, leading to a high percentage of species only found by chance in our surveys. We also observe differences in community heterogeneity among the five reserves. Patterns differ between organism groups, clearly indicating that a focus on single taxa or a single indicator group falls short of revealing meaningful patterns. In spider communities, beta diversity is linked to the spatial distance between traps. In other organism groups community heterogeneity within reserves rather depends on structural heterogeneity. Species richness was associated with percentage of reserve area not covered with the most dominant habitat type, the deadwood amount, and with survey year. Being the potential natural vegetation of Germany and considering the unexpectedly high diversity of their associated fauna, beech forests bear a great conservation value. However, their widespread occurrence and dominance is likely to push them out of focus of conservation efforts. Yet protecting diverse and richly structured beech forests can contribute greatly to preserving the native arthropod fauna and should play a central role in biodiversity conservation efforts in Central Europe.

Distribution of deadwood and other forest structural indicators relevant for bird conservation in Natura 2000 special protection areas in Poland

Numerous bird species, often rare or endangered, rely on the presence of standing and downed deadwood for shelter, nesting, and foraging. Habitat quality was evaluated on the basis of deadwood volume, the density of large standing deadwood, and the space filling index (SFI). The SFI reflects the degree of space filling of the bottom layers taking into account tree trunks, seedlings, saplings, ground vegetation, stumps, and downed deadwood. Analysis encompassed all special protection areas (SPAs) in Poland (a total of 107 SPAs containing 7974 sample plots monitored under the National Forest Inventory). An additional in-depth analysis was conducted for 30 SPAs with the greatest share of forest habitats. The studied indicators varied substantially both between and within individual SPAs, with deadwood volume ranging from 1.3 to 50.5 m3 ha−1 (mean of 9.0 m3 ha−1) and the density of large standing deadwood (diameter at breast height ≥ 30 cm) from 0.1 to 16.0 ind ha−1 (mean of 2.2 ind ha−1). These values were relatively low compared to the density of living trees with corresponding dimensions (111 ind ha−1). SFI analysis indicated high or very high space filling of the bottom forest layers on 14–56% of sample plots in a given SPA. The presence of deadwood was found to be significantly positively affected by SPA location in the mountains, a greater proportion of sites with higher fertility, a greater share of forest area under strict protection, as well as higher stand volume within a given SPA. The correlation between deadwood volume and the density of birds (primary and secondary cavity nesters) in individual SPAs was positive (R = 0.60). As compared to lowland areas, SPAs in mountain areas are generally characterized by high stand volumes, a greater density of large living trees, and a greater amount of diverse deadwood. In those areas conservation measures should involve continuous monitoring and diagnosing of any problems associated with the populations of individual bird species; focused efforts should be implemented to support those species that exhibit unfavorable population trends. In most lowland SPAs measures aimed at the improvement of site conditions for birds must be more extensive than in the mountains, with a low abundance of dead trees (especially large ones). These parameters can be improved by retaining some senescent stands in managed forests until their natural death and implementing a strict protection regime in areas of high conservation value.

Assessing Forest Structural and Topographic Effects on Habitat Productivity for the Endangered Apennine Brown Bear

Any forest management potentially affects the availability and quality of resources for forest-dwelling wildlife populations, including endangered species. One such species is the Apennine brown bear, a small and unique population living in the central Apennines of Italy. The conservation of this relict bear population is hampered by the lack of knowledge of the fine-scale relationships between productivity of key foods and forest structure, as this prevents the design and implementation of effective forest management plans. To address this issue, we sampled the main structural stand attributes within the bear’s range and used multivariate generalized linear mixed models in a Bayesian framework to relate forest structural attributes to proxies of productivity of key bear foods. We found that hard mast was positively associated with both forest typology and high forest system, but negatively related to both the time elapsed since the last forest utilization and the amount of deadwood. The availability of soft-mast producing species was positively related to past forestry practices but negatively associated with steep slopes historically managed with high tree densities and a low silvicultural disturbance. Our findings also suggest that herb cover was negatively affected by terrain steepness and basal area, while herb productivity was positively affected by northern and southern exposure. Additionally, richness of forest ants was associated with forests characterized by low volume and high density. Our findings confirm that the productivity of natural bear foods is strongly affected by forest structural and topographical characteristics and are relevant as preliminary information for forest management practices to support the long-term conservation of Apennine bears.

The long way back: Development of Central European mountain forests towards old‐growth conditions after cessation of management

AbstractQuestionsPrimary forests fulfil important roles in preserving biodiversity, storing carbon and increasing ecological understanding. Yet, they have become very rare in Europe. An important policy goal is thus to increase the share of naturally developing forests by creating protected areas in formerly managed forests. Here, we investigated: (a) if and how such forests return to conditions similar to old‐growth; and (b) whether recently observed stand‐replacing natural disturbances in combination with climate change set them onto an alternative developmental pathway.LocationDürrenstein Wilderness Area (IUCN Cat. Ib) in the Austrian Alps, containing the Rothwald, one of the last primary forest remnants of Central Europe.MethodsWe built a chronosequence of 87 plots, spanning 220 years of forest development after the cessation of management, and compared them to old‐growth forests. We analysed the recovery of nine attributes of forest composition, structure and functioning. To evaluate stand‐level development of these attributes after recent natural disturbance and climate change, we additionally used a process‐based simulation model.ResultsOld‐growth forests showed a wide range of variability across investigated attributes. Forests converged to old‐growth conditions after management ceased, with seven out of the nine attributes falling within the range of old‐growth at the end of our chronosequence. The variation in tree diameters and the downed amount of deadwood were, however, still significantly lower than in old‐growth forests after 220 years of unmanaged stand development. Simulations did not indicate an alternative developmental pathway of recently disturbed stands.ConclusionsWhile a full return to old‐growth conditions can take centuries, a number of important forest attributes recover quickly, indicating that protecting formerly managed forests is a valuable strategy to enrich forest landscapes. Our results indicate that the mountain forests of Central Europe have high ecological resilience, developing towards old‐growth conditions after both past management and current natural disturbance.

Effects of Forestry Intensification and Conservation on Green Infrastructures: A Spatio-Temporal Evaluation in Sweden

There is a rivalry between policies on intensification of forest management to meet the demands of a growing bioeconomy, and policies on green infrastructure functionality. Evaluation of the net effects of different policy instruments on real-world outcomes is crucial. First, we present data on final felling rates in wood production landscapes and stand age distribution dynamic in two case study regions, and changes in dead wood amounts in Sweden. Second, the growth of formally protected areas was compiled and changes in functional connectivity analysed in these regions, and the development of dead wood and green tree retention in Sweden was described. The case studies were the counties Dalarna and Jämtland (77,000 km2) representing an expanding frontier of boreal forest transformation. In the wood production landscape, official final felling rates averaged 0.84%/year, extending the regional timber frontier. The amount of forest <60 years old increased from 27–34% in 1955 to 60–65% in 2017. The amounts of dead wood, a key forest naturalness indicator, declined from 1994 to 2016 in north Sweden, and increased in the south, albeit both at levels far below evidence-based biodiversity targets. Formal forest protection grew rapidly in the two counties from 1968 to 2020 but reached only 4% of productive forests. From 2000 to 2019, habitat network functionality for old Scots pine declined by 15–41%, and Norway spruce by 15–88%. There were mixed trends for dead wood and tree retention at the stand scale. The net result of the continued transformation of near-natural forest remnants and conservation efforts was negative at the regional and landscape levels, but partly positive at the stand scale. However, at all three scales, habitat amounts were far below critical thresholds for the maintenance of viable populations of species, let alone ecological integrity. Collaboration among stakeholder categories should reject opinionated narratives, and instead rely on evidence-based knowledge about green infrastructure pressures, responses, and states.

From mixtures to monocultures: Bird assemblage responses along a production forest conifer-broadleaf gradient

Increasing the prevalence of broadleaf trees in conifer-dominated production forests is a recommended means of improving habitat availability for broadleaf and mixed-forest species. The implications for biodiversity are often measured by contrasting broadleaf-conifer mixtures with conifer-dominated stands. However, few studies include broadleaf-dominated stands in these assessments. Here we contrasted the bird assemblages of even-aged production forests along a mixture gradient from Norway spruce (Picea abies) dominated, to birch (Betula spp.) dominated stands in southern Sweden. We conducted point count surveys of bird individuals exhibiting breeding behaviour within 30 stands varying from <0.5% to over 98.5% broadleaf by basal area. A total of 355 birds were detected, comprising 36 bird species, seven of which are classified as near threatened by the Swedish Red-list. Our results indicate i) a distinct shift in bird community composition linked to the percentage of broadleaf trees at stand and landscape scales, ii) significantly higher bird species richness, evenness, and abundance in stands with a higher proportion of birch, iii) higher bird abundance in birch-dominated stands than in mixtures, and iv) shifts in bird species guilds as related to stand basal area, the amount of shrubs in the understory, and quantities of dead wood. All of these results have implications for the ways in which production forest management could be altered to enhance avian diversity, and we discuss these with respect to the use of broadleaf versus mixed-species stands.

The importance of large-diameter trees to the creation of snag and deadwood biomass

BackgroundBaseline levels of tree mortality can, over time, contribute to high snag densities and high levels of deadwood (down woody debris) if fire is infrequent and decomposition is slow. Deadwood can be important for tree recruitment, and it plays a major role in terrestrial carbon cycling, but deadwood is rarely examined in a spatially explicit context.MethodsBetween 2011 and 2019, we annually tracked all trees and snags ≥1 cm in diameter and mapped all pieces of deadwood ≥10 cm diameter and ≥1 m in length in 25.6 ha of Tsuga heterophylla / Pseudotsuga menziesii forest. We analyzed the amount, biomass, and spatial distribution of deadwood, and we assessed how various causes of mortality that contributed uniquely to deadwood creation.ResultsCompared to aboveground woody live biomass of 481 Mg ha−1 (from trees ≥10 cm diameter), snag biomass was 74 Mg ha−1 and deadwood biomass was 109 Mg ha−1 (from boles ≥10 cm diameter). Biomass from large-diameter trees (≥60 cm) accounted for 85%, 88%, and 58%, of trees, snags, and deadwood, respectively. Total aboveground woody live and dead biomass was 668 Mg ha−1. The annual production of downed wood (≥10 cm diameter) from tree boles averaged 4 Mg ha−1 yr−1. Woody debris was spatially heterogeneous, varying more than two orders of magnitude from 4 to 587 Mg ha−1 at the scale of 20 m × 20 m quadrats. Almost all causes of deadwood creation varied in importance between large-diameter trees and small-diameter trees. Biomass of standing stems and deadwood had weak inverse distributions, reflecting the long period of time required for trees to reach large diameters following antecedent tree mortalities and the centennial scale time required for deadwood decomposition.ConclusionOld-growth forests contain large stores of biomass in living trees, as well as in snag and deadwood biomass pools that are stable long after tree death. Ignoring biomass (or carbon) in deadwood pools can lead to substantial underestimations of sequestration and stability.

Deadwood volumes matter in epixylic bryophyte conservation, but precipitation limits the establishment of substrate-specific communities

Deadwood is a habitat for numerous biota and serves as an indicator of forest biodiversity. Bryophytes significantly contribute to deadwood communities and epixylic bryophytes are particularly threatened. Additional to deadwood volumes, their occurrence depends on climatic conditions. However, the interactive effects of deadwood and climate on epixylic bryophytes have hardly been assessed. Here, we analyse these effects based on 8 143 bryophyte specimens collected on 510 logs in 51 Austrian forests. We found that annual precipitation sum and deadwood volume explained 67%, 90%, and 82% of the variation in moss, liverwort and total species richness, respectively. Segmented regression indicated several breakpoints in these relationships, especially at c. 60 m3/ha of deadwood and 900 mm, respectively 1700 mm of annual precipitation. Epixylic bryophyte diversity increased strongly up to the deadwood threshold, but only moderately with still higher volumes. Nine hundred mm of annual precipitation was a macroclimatic limit for deadwood-specific bryophyte species. Below this value, obligate epixylic bryophytes were lost and liverworts were rare, even at sites with high deadwood amounts. At the wettest sites, the overall number of species decreased while deadwood-specific specialists further increased in number. The close tie of epixylic bryophytes to macroclimate may constrain the efficiency of deadwood management measures and suggests considerable impacts of climate change. A drier and warmer climate will probably decrease species richness and change the composition of epixylic bryophyte communities, with the most characteristic species, especially liverworts, facing the highest risk.