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The (w)hole story: Facilitation of dead wood fauna by bark beetles?
... Strong intra-and inter-specific interactions are therefore expected to be important for community assembly in such a restricted space. While facilitation between species has been proposed as a key driver of soil animal co-existence in deadwood (Zuo et al., 2016b), there is scarce evidence to substantiate the causal mechanisms. The challenge may stem from disentangling the dual functionality (i.e., food and habitat) of deadwood for soil animals (Fujii et al., 2020(Fujii et al., , 2023, complicating the separation of facilitated habitat and food aspects of deadwood resources. ...
... The challenge may stem from disentangling the dual functionality (i.e., food and habitat) of deadwood for soil animals (Fujii et al., 2020(Fujii et al., , 2023, complicating the separation of facilitated habitat and food aspects of deadwood resources. For example, studies have shown wood and bark boring beetles facilitate other invertebrate groups by helping them unlock deadwood resources (Sydenham et al., 2016;Zuo et al., 2016b;Priest et al., 2021). However, their involvement in the process may entail two mutually non-exclusive interactions (i.e., habitat creation and food quality improvement) with the beneficiaries (Brin and Bouget, 2018). ...
... Aligned with our second hypothesis, we found that the abundance of isopods was positively correlated with the number of wood holes, independently of deadwood host species (Fig. 4a and b), as was previously shown for bark beetles and their bark holes and galleries (Zuo et al., 2016b). This suggests that there is a sequence from facilitation of invertebrates including isopods by bark beetles followed by facilitation by wood-boring beetles. ...
... Recent studies have demonstrated the role of caterpillars, gall-inducing insects, and bark and wood-boring beetles as facilitators for arthropods (Vieira and Romero 2013, Harvey et al. 2016, Satoh et al. 2016, Sydenham et al. 2016, Wetzel et al. 2016, Zuo et al. 2016, Raath et al. 2017. Particularly, when adult wood-boring beetles emerge from tree hosts, they leave behind cavities where their larvae develop, thus promoting new habitats for other species to occupy (Buse et al. 2008, Zuo et al. 2016. ...
... Recent studies have demonstrated the role of caterpillars, gall-inducing insects, and bark and wood-boring beetles as facilitators for arthropods (Vieira and Romero 2013, Harvey et al. 2016, Satoh et al. 2016, Sydenham et al. 2016, Wetzel et al. 2016, Zuo et al. 2016, Raath et al. 2017. Particularly, when adult wood-boring beetles emerge from tree hosts, they leave behind cavities where their larvae develop, thus promoting new habitats for other species to occupy (Buse et al. 2008, Zuo et al. 2016. Some groups of insects like ants and bees can take advantage of the abandoned beetle cavities in the wood for nesting (Satoh et al. 2016, Sydenham et al. 2016). ...
... Some groups of insects like ants and bees can take advantage of the abandoned beetle cavities in the wood for nesting (Satoh et al. 2016, Sydenham et al. 2016). However, little is known about the role of wood-boring beetles promoting new habitats for arthropod communities (but see Zuo et al. 2016). ...
The twig-girdler beetle Oncideres albomarginata chamela (Chemsak and Giesbert) (Cerambycidae: Lamiinae) detaches branches of Spondias purpurea L. (Sapindales: Anacardiaceae) that fall on the forest floor or remain suspended on vegetation. Many wood-boring beetles also oviposit in these branches and larval development creates cavities that are abandoned when the adults emerge. The objective of this study was to evaluate the role of wood-boring beetles as facilitators by creating new habitats for arthropods, and test for vertical stratification and temporal variation of arthropods associated with S. purpurea branches that were previously engineered by O. albomarginata chamela in a tropical dry forest (TDF) in Jalisco, Mexico. In order to determine the effects of vertical strata and seasons on branch colonization by arthropods, we placed 60 branches on the forest floor (ground stratum) and 60 were placed in trees (vegetation stratum) from February to April (dry season), and from August to October 2016 (rainy season), for 240 branch samples in total. We collected 8,008 arthropods, which included 7,753 ants (14 species) and 255 nonsocial arthropods (80 species) from 13 different orders. We observed a greater arthropod abundance in the branches in the vegetation stratum in the dry season compared with the rainy season, whereas the richness and abundance of arthropods in the ground stratum were greater in the rainy season compared with the dry season. We concluded that wood-boring beetles are important habitat facilitators for arthropods, and that the vertical position of branches and the seasonal variations in TDFs differently affect the colonization of the abandoned cavities by arthropods.
... than in other trees after one year and the abundance in the logs of the two species decreased through the decomposition year. In the case of Picea, this pattern may be partly explained by facilitation: Zuo et al. (2016b) demonstrated how entrance and exit holes and feeding/ breeding galleries of bark beetles (Dryocoetes autographus and Hylastes cunicularius, in the bark of P. abies promoted the abundance of earthworms in the bark during early decay. Moreover, the relatively fast early-stage decomposition of both Populus species (Chang et al., 2020) manifested itself partly by the bark coming loose from the wood faster than in the other genera in the experiment (observations by the authors). ...
... For instance, they can regulate deadwood decomposition by interactions with the fungal hyphae, micro-organisms and the deadwood organic matter. Earthworms also interact with other invertebrates (Zuo et al., 2016b), many of which are themselves important for wood decomposition (Ulyshen, 2016), soil biodiversity and other soil functions, adding more ways by which wood decomposition may influence soil properties via earthworms. Given the likely important role of earthworms in forest carbon and nutrient cycling, including wood decomposition, their communities in dead trees, and interactions with other organisms there, could play an important role in the diversity and functioning of the whole temperate forest ecosystem. ...
... Weakened plants are particularly attractive to bark-and wood-borers, which are considered habitat modifiers (McPherson et al., 2008;Kirkendall et al., 2015;Novais et al., 2018;Toffin et al., 2018). These insect feeding guilds allow arthropod colonisation of newly constructed habitats (Buse et al., 2008;Zuo et al., 2016). Intraspecific variation in features of these habitats may affect the diversity of associated invertebrates (Crawford et al., 2007;Crutsinger et al., 2009;Whitham et al., 2012). ...
... Intraspecific variation in features of these habitats may affect the diversity of associated invertebrates (Crawford et al., 2007;Crutsinger et al., 2009;Whitham et al., 2012). For example, variation in size and density of galleries built by wood-borer beetles (Scolytinae) in Norway spruce logs affect the abundance of colonising chilopods and diplopods (Zuo et al., 2016). ...
Parasitic plants and herbivores show similarities in their interactions with host plants. Herbivore‐induced resistance/susceptibility in plants can scale up to the arthropod community. Similar evidence regarding parasitic plants is scarce. We evaluated the indirect effects initiated by the mistletoe Tristerix aphyllus on the arthropod community of the cactus Echinopsis chiloensis in the Chilean coastal desert. Field observations suggested that a stem‐borer beetle bores more brood chambers in mistletoe‐parasitised cacti than in non‐parasitised cacti, and that arthropods colonise these chambers.
We compared tissue toughness, chamber density and morphology in mistletoe‐parasitised and non‐parasitised cacti. We also compared richness, total abundance, abundance per taxa, diversity and composition of the colonising arthropod community.
Parasitised cacti showed a 14% reduction in tissue toughness. Chamber density in parasitised cacti was four times greater and chambers were larger: 35% more volume, an entrance‐opening area 30% greater, and twice the area of the maximum‐width section. Arthropod species richness and diversity were higher in chambers of parasitised cacti. Arthropod community composition was different in chambers of parasitised and non‐parasitised cacti. Thus, spiders and moths were more abundant in parasitised cacti, and pseudoscorpions, scolopendras, ants and flies were exclusively present there, while non‐parasitised cacti had no exclusive taxa.
Mistletoe infection results in a richer, more diverse and distinct arthropod community on its cactus host, which occurs through induced susceptibility to stem‐borers whose brood chambers are colonised by arthropods. Tristerix aphyllus could be a key‐stone species in these arid ecosystems, where arthropod diversity is relatively low.
... (Photo: B. Wermelinger) decomposition of wood. They thus initiate an entire succession of many other woodinhabiting and purely saprophagous insects, fungi, and even vertebrates Zuo et al. 2016). Bark beetles are also an essential food source for specialized predatory and parasitic insects as well as for woodpeckers (Wegensteiner et al. 2015). ...
Ecosystem services are the benefits people obtain from ecosystems. Disturbances can have multiple, often negative, effects on ecosystem services. Primary production is temporarily reduced by disturbances, while water and nutrient cycles are stimulated by disturbances. Consequently, the production of plant biomass (wood, animal fodder) may be temporarily decreased. In the context of climate regulation, disturbances reduce carbon storage (warming effect) but simultaneously increase albedo (cooling effect). Furthermore, disturbances reduce the protection function of forests against natural hazards. The way disturbances affect cultural services, such as the recreational function of ecosystems, depends on the subjective perception of people.KeywordsFire
Wind
Bark beetles
Drought
Supporting services
Provisioning services
Regulating services
Cultural services
... They were also found to build suitable habitats for other insects (e.g. Zuo et al., 2016), contributing to habitat provision. Finally, TSAIs can be food for either terrestrial organisms predating along the shoreline or subsidies for aquatic organisms when they fall into the water, adding carbon, nitrogen and phosphorus to the dry or wet part of the IRES habitat continuum, and thus affect respective assemblage • Recycling of organic matter • Aeration of soil due to digging • Biological control of pests in crops planted adjacent to river channels • Provision of food to aquatic and terrestrial consumers, contributing to both aquatic and terrestrial food webs How does the habitat continuum model apply to other regions of the world? ...
Intermittent rivers and ephemeral streams (IRES), which cease flow and/or dry at some point, are the most abundant waterways on earth, and are found on every continent. They can support a diverse, and often abundant, terrestrial and semi-aquatic invertebrate (TSAI) fauna, which has been poorly explored due to its position at the fringe between aquatic and terrestrial disciplines. TSAIs can inhabit a variety of habitat types, including the shoreline, the surface of exposed gravel bars, unsaturated gravels, dry riverbeds, riparian zones, and floodplains. Much less is known about the species composition and ecological roles of TSAIs of IRES than their aquatic counterparts, with TSAIs being largely overlooked in conceptual models, legislation, policy, and ecological monitoring. Herein we review the TSAI literature that has increased substantially over the last decade and present conceptual models describing how TSAIs respond to hydrological changes in IRES. Then, we test these models with data collected during wet and dry phases in IRES from Australia and France. These generic models can be utilised by water managers and policy makers, ensuring that both wet and dry phases are considered in the management and protection of IRES. IRES should be viewed as a habitat continuum through time, with taxa from a pool of aquatic, semi-aquatic and terrestrial invertebrates inhabiting at any hydrological stage. We call for collaboration among terrestrial and aquatic ecologists to explore these invertebrates and ecosystems further.
... The bark is recognized as an important barrier to the colonization of living as well as dead trees by insects and fungi (Zuo et al., 2016b;Boddy et al., 2017;Dossa et al., 2018). Removing bark partially or completely increases species richness of wood saprotrophs in decomposing Norway spruce (Hagge et al., 2019). ...
Fungi are the main decomposers of litter and wood, driving carboin and nutrient cycles. Despite a large number of studies, fungal community composition is remarkably difficult to predict. In the present study, we explore the importance of secondary metabolites and nutrient content in wood and bark as determinants of fungal community composition. We used aspen (Populus tremula) logs of similar size, from one location, and measured concentrations of carbon, nitrogen and secondary metabolites in bark and wood sampled shortly after felling. Fungal DNA was extracted from logs directly after felling and after two seasons of decomposition, and the fungal communities were assessed using DNA-metabarcoding. Concentrations of metabolites varied considerably between individual trees, and we also observed significant differences within single trees. Plant metabolites and nitrogen concentrations significantly affected fungal community composition. For the overall fungal communities and for wood saprotrophic fungi, the explanatory power of wood and bark metabolites was highest in logs decomposed over two seasons. In recently felled trees however, concentration of metabolites had a stronger effect on plant pathogens and endophytes. We conclude that secondary metabolites represent an overlooked, but important niche dimension for fungal communities in both functional sapwood and dead wood.
... This pattern could be explained by their close association with the range of suitable wood availability (Grove, 2002;Hulcr et al., 2008), and not leaves. Therefore, wood diameter and air moisture content seem to be better predictors of their diversity , since they feed and spend much of their lives inside the bark, with little interaction with the external environment (Wood, 1982;Zuo et al., 2016). Here, it is important to emphasize that although Lepidoptera like the Symphita larvae are very important representatives of chewing herbivorous insect guild, they were not considered in our results especially due to the limitations of sampling traps (see Schmidt, 2016;Rosa et al., 2019;Skvarla et al., 2021). ...
... This pattern could be explained by their close association with the range of suitable wood availability (Grove, 2002;Hulcr et al., 2008), and not leaves. Therefore, wood diameter and air moisture content seem to be better predictors of their diversity , since they feed and spend much of their lives inside the bark, with little interaction with the external environment (Wood, 1982;Zuo et al., 2016). Here, it is important to emphasize that although Lepidoptera like the Symphita larvae are very important representatives of chewing herbivorous insect guild, they were not considered in our results especially due to the limitations of sampling traps (see Schmidt, 2016;Rosa et al., 2019;Skvarla et al., 2021). ...
Insects make up the bulk of terrestrial diversity and about half of insect species are herbivores that have direct relationships with their host plants and are the basis of the entire food chain, on which wildlife and humanity depend. Some herbivorous insect traits, such as their spatio-temporal distribution, are especially relevant in the current scenario of global changes, which are more pronounced in high elevation areas, helping to improve the effectiveness of conservation actions. Here we evaluated the influence that different spatiotemporal scales have on three free-feeding herbivorous insect guilds (fluid-feeding, leaf-chewing, and xylophagous insects) in montane forest islands immersed in a grassland-dominated matrix (campo rupestre). We assessed whether species turnover or nestedness was the main component determining both spatial and temporal species composition variation (β-diversity) of the herbivorous insect community. We also checked the temporal effect on herbivorous insect guilds composition between vertical strata. We sampled herbivorous insects during two summers and two winters in 14 forest islands of different sizes and shapes in a natural mountainous fragment located in southeastern Brazil. A total of 6597 herbivorous insects representing 557 morphospecies were sampled, 290 of which were fluid-feeding, 147 leaf-chewing and 120 xylophagous insects. We found a main contribution of time scale in the organization of the herbivorous insect composition sampled in this study, mainly by turnover, with small differences among guilds. Additionally, we could see that climate determined the local variation of species, corroborating that we have a highly variable always-green system over space and time where the understory community varies less in comparison to the canopy community. Our findings suggest that long-term ecological research on herbivorous community structure in relation to climatic variation is a key element for future investigations, which can be decisive for the conservation Frontiers in Forests and Global Change | www.frontiersin.org 1 October 2021 | Volume 4 | Article 709403 Kuchenbecker et al. Distribution Herbivorous Insects Forest Islands of herbivorous insect communities. We also suggest that the effects of anthropogenic pressures must be monitored in this system, since these forest islands may serve as warming refuges in a fragmented landscape holding an invaluable diversity of species that, without these old-growth forest reservoirs, would be doomed to disappear.
... Several insects modify plant structures to complete their life cycle, such as leafroller caterpillars, gall-inducing insects, bark, and woodboring beetles. These new habitats might persist on plants and can be later used as shelter by other arthropods in a facilitative interaction process (Vieira and Romero 2013, Zuo et al. 2016, Novais et al. 2018. Particularly, ants can take advantage of the abandoned shelters made by other insects for nesting, such as wood-boring beetle abandoned cavities (Tschinkel 2002, Satoh et al. 2016, Novais et al. 2017, senescent galls (Fernandes et al. 1988, Mehltreter et al. 2003, Almeida et al. 2014, Santos et al. 2017, and empty cocoons (Raath et al. 2017). ...
In ant–plant mutualistic interactions, plants provide shelter (domatia) and/or food to ants and in exchange, and ants provide protection against herbivores. After plant tissue senescence, ants are expected to abandon dead domatia, leaving these empty spaces available for other arthropods. In this study, we tested for the role of the mutualistic interaction between Cordia alliodora and Azteca pittieri in promoting
new habitats for arthropods through abandoned dead domatia. We predicted that species richness, abundance, and colonization frequency of secondary arthropods would be greater in dead branch domatia (dead domatia) compared with live branch domatia (live domatia). During March 2019, we selected 38 C. alliodora trees in a Mexican tropical dry forest. For each tree, we collected five live and five dead domatia, for 380 domatia in total. We found six morphospecies of secondary arthropods colonizing live domatia,
while 42 were present in dead domatia. Ants were the most species-rich group (10 species) in abandoned dead domatia and utilized them as nesting sites (25 nests). Secondary arthropod species richness, abundance, and colonization frequency were greater in dead domatia compared with live domatia. We concluded that the Azteca–Cordia mutualistic interaction is an important habitat facilitator by promoting new habitats for arthropods through abandoned dead domatia.
... A more complete survey of earthworms in the beech-dominated forests would sensibly utilize the method proposed by Ashwood et al. (2019) which fully accounts for dead wood in forests when estimating earthworm population density and biomass. Researchers have now come to understand that many epigeic and even endogeic earthworms will exploit resources below the bark of dead wood when conditions allow (Zou et al. 2016(Zou et al. , 2018. ...
This work relates data from field sampling of Eisenia lucens and from laboratory-based culture. Field sampling used soil sorting and vermifuge extraction and took place in beech-dominated forests of southwest Poland. Initial work derived population estimates from four sub-communities of the forest looking for seasonal dynamics and later work employed targeted sampling in summer within rotting wood to obtain live specimens for laboratory culture. A preliminary examination within and below rotten wood during winter was also undertaken. In the laboratory, clitellate earthworms were kept at 20 °C, the substrate changed every 6 months, and the population examined. Cocoons were incubated individually at 15 °C, with number of hatchlings per cocoon and the mass of each determined. Hatchlings were grown at 15 °C in field-collected wood and compared with growth in a 1:1 volume ratio of wood and horse manure. Further hatchlings were fed with horse manure only (at 10 °C) and after 19 weeks, half were transferred to 15 °C. In the field, mature individuals varied significantly (p < 0.01) in biomass between 2 sampling sites where found, with an overall mean density across sites of 4.14 ± 3.53 m⁻² with a mean biomass of 2.21 ± 1.93 g m⁻². Numbers in soil varied over the sampling period, with a suggestion that this species moves from mineral soil to organic-rich dead wood as conditions permit. In summer, all life stages were recovered from rotting wood above the mineral soil. Sampling in winter found cocoons in rotting wood below snow. These hatched rapidly (within 2 weeks) when taken to the laboratory. Laboratory culture allowed maintenance of a population for 2 years. Mean cocoon mass was 50.6 mg with a mean of 2.9 hatchlings per cocoon and hatchling mass was inversely proportional to number per cocoon. Growth with 50% horse manure was significantly greater (p < 0.001) than with wood. Increased temperature from 10 to 15 °C brought more significantly (p < 0.05) rapid growth. To culture this species through its life cycle, a natural substrate is needed, but then it is necessary to acclimate the animals to something more easily obtainable. More work is needed from field sampling to fully understand the seasonal dynamics of this species, which utilises different parts of the soil profile throughout the year.
... Sie gehören zu den Pionierinsekten, die geschwächte lebende oder frisch abgestorbene Nadelbäume besiedeln, ihre Rinde lösen und damit den Abbau des Holzes einleiten. Sie initiieren damit eine ganze Sukzession von vielen weiteren xylobionten, rein saprophagen Insekten, Pilzen bis hin zu Wirbeltieren (Müller et al. 2008, Beudert et al. 2015, Zuo et al. 2016. Borkenkäfer sind auch eine wesentliche Nahrungsgrundlage spezialisierter räuberischer und parasitischer Insekten sowie von Spechten (Wegensteiner et al. 2015). ...
Borkenkäfer sind wichtige Komponenten in der natürlichen Dynamik von Nadelwäldern. In Europa hat vor allem der Buchdrucker (Ips typographus) das Potenzial, grossflächigen Befall zu verursachen und damit als ökologische Störung zu wirken. Nach vorausgehenden Störungen wie Windwurf oder Trockenheit kann er seine Populationsdichten so weit erhöhen, dass er auch vitale Bäume erfolgreich befallen und eine selbsterhaltende Dynamik entwickeln kann. Der weitere Verlauf einer solchen Massenvermehrung auf lebenden Bäumen ist vor allem durch die Temperatur und die Disposition der Wirtsbäume gegeben. Borkenkäferbefall erzeugt wichtige neue Habitate, bedeutet aber häufig auch ökonomische Schäden.
... Le bois mort est un compartiment important des écosystèmes forestiers. Il intervient dans la structure et le fonctionnement des écosystèmes forestiers mais aussi dans les cycles biogéochimiques (Fahey et al., 1991 ;Keenan, 1993;Samuelsson et al., 1994;Goodburn et Lorimer, 1998 ;Floudas et al., 2012 ;Zuo et al., 2016). Peu d'auteurs ont orienté leurs études vers le suivi de la dynamique de décomposition des débris ligneux végétaux et de la proportion de chaque classe de débris ligneux végétaux (Stone et al., 1998 ;Yan et al., 2006). ...
Les forêts tropicales humides du bassin du Congo sont encore mal connues dans leur fonctionnement bien que leurs rôles dans l'atténuation du climat aient été rapportés depuis quelques décennies. Dans le but d'améliorer la connaissance du fonctionnement des forêts tropicales pluvieuses dans le bassin du Congo, une étude sur la décomposition des gros débris ligneux a été effectuée au nord de la République du Congo, dans le département de la Likouala. Quatorze parcelles carrées de 50 m * 50 m dont dix parcelles dans les forêts primaires et quatre dans les forêts dégradées (3 dans les forêts secondaires et 1 dans une zone agro forestière) ont été installées. La méthode utilisée a consisté à inventorier des bois morts couchés au sol et à déterminer leurs degrés de décomposition en utilisant un métal tranchant. Suivant le niveau de pénétration du métal dans le bois mort, nous avons défini les différentes classes de décomposition I, II, III et IV. Les résultats de cette étude montrent que la classe de décomposition la plus importante dans les trois types forestiers est la classe II avec des proportions de 38,34% dans les forêts primaires de 35,84% dans les forêts secondaires et de 45,83% en agroforesterie (p < 0,05). Les données collectées sur le terrain (paramètres climatiques, type de décomposeurs biotiques) ont montré que l'humidité du sol et les champignons participent activement à la décomposition du bois mort. ABSTRACT The wet tropical forests of the Congo basin are still very badly known in their functioning although their roles in the attenuation of the climate were reported since some decades. With the aim of improving knowledge on the functioning of tropical rain forests in the Congo basin, a study on the decomposition of the coarse woody debris was carried out in the north of Republic of Congo in the Department of Likouala. Fourteen square plots of 50 m * 50 m with ten plots in primary forests and four in degraded forests (3 in secondary forests and 1 in an agroforestry area) were installed. The method used consisted of an inventory of all deadwood lying on the ground and the determination of their levels of decomposition. Following the level of penetration of metal in the vegetable woody debris, four classes of woody debris were defined I, II, III and IV. The results of this study showed that the class of the most significant decomposition in the three forest types is class 2 with proportions of 38,34% in the primary forests, of 35,84% in the secondary forests and of S. A. IFO et al. / Int. J. Biol. Chem. Sci. 12(2): 837-849, 2018 838 45,83% in the agroforestery area (p < 0.05). Data collected on the ground (climatic parameters, biotic agent) revealed soil moisture and fungi are actively explained the decomposition of woody debris.
... A last example comes from an experiment on Picea abies logs where holes and galleries made by bark beetles facilitated the entrance of other beetles and other deadwood fauna (Isopoda, Diplopoda, and Annelida) (Zuo et al. 2016). The positive influence of the surface area of inner bark consumed by bark beetles on the abundance of invertebrates was even more important in the nutrient-rich site compare with the nutrient-poor site. ...
A better understanding of biotic interactions in species-rich saproxylic insect communities can provide essential information for biodiversity conservation and ecosystem functioning enhancement. Evidence in the literature mainly relates to beetle species, in particular scolytines, at tree—or even smaller—spatial scales and mostly refers to antagonistic interactions. We here present an overview of competition, predation/parasitism and facilitation among saproxylic insects. We first underline segregation patterns between wood consumers, resulting from competition processes, such as spatial and temporal resource partitioning, competitive displacement via interference and even enemy-mediated “apparent competition.” Considering natural history facts about prey-predator and host-parasitoid relationships, we then emphasize processes regulating the pressure of top-down influences on prey/host population dynamics. Facilitative interactions, including mechanisms of habitat location, creation, and improvement, are thereafter considered. The implications of some findings for pest management strategies (biocontrol, semiochemical-based methods) and for ecosystem functioning (deadwood decomposition) are highlighted meanwhile. Approaches based on life-history traits or indirect mediated interactions finally move the focus from the responses of paired species to multispecific community-level changes. Ecological network analysis should help increase our understanding of biotic interactions and investigate the consequences of environmental changes for those interactions and ecosystem functioning.
... The table shows the standardized effect sizes (SES values) and permutation-based P-values for five community wide association indices: CU, C-Score; SCU, standardized C-score; JAC, Jaccard index; SOR, Sorensen index; BCD, Bray-Curtis dissimilarity index. Zuo et al. 2016), little is known about how these different interactions affect the structure of saproxylic insect assemblages. This study analyzed, for the first time, non-random patterns of aggregation and segregation between species pairs and trophic guilds in tree hollows of Q. pyrenaica trees from Iberian Mediterranean forests using an exhaustive collecting method that allows us to work with species abundance and to lower the possible bias of richness estimations. ...
Tree hollows are complex microhabitats in which a variety of abiotic and biotic factors shape the community assembly of saproxylic insects. Detecting non-random species co-occurrence patterns is a fundamental goal in ecology in order to understand the assembly mechanisms of communities. We study association patterns of species of Coleoptera and Diptera (Syrphidae), belonging to different trophic guilds, on 72 tree hollows at a local and regional scale in three protected areas in Mediterranean forests using a fixed-fixed null model. Our matrix-level analysis shows a tendency for segregation in species association (species exclusion) at the regional and site levels. However, the high complexity of tree-hollow habitats, offering different resources for a more or less specialized fauna, makes it difficult to prove competition interactions. Indeed, pairwise analysis shows a dominance of non-random aggregation patterns (species coexistence) at the local and regional levels. Both aggregation and segregation of non-random patterns were more common among species from different trophic guilds than within the same guilds, with predators being a common denominator for a high percentage of the inter-guild pairs. Our results suggest that predation and facilitation interactions, together with habitat segregation, are the main factors shaping tree-hollow assemblages, while competition seems to be less important. We conclude that species interactions take an important part of the process of assemblage structuration and special attention should be paid to 'ecosystem engineers' and threatened species in the conservation of tree hollow assemblages.
... The degradation of a tree (here Fagus sylvatica) is a long-term process, influenced by the position of the tree: A. laying dead tree and B. standing dead tree (Photo: Sönke Hardersen). (Zuo et al., 2016). It thus seems likely that also other early colonizers of deadwood, espacially large ones such as Aegosoma scabricorne, are key species for initiating the degradation of dead wood, because this species creates large emergence holes, up to 20 mm in their longer dimension (Foit et al., 2016). ...
Forests are storing vast amounts of carbon and every tree will at some point become part of the soil, if not harvested or washed into the sea. The degradation of trees is a long-term process as the structural compounds of wood are extremely difficult to break down. A complex community of invertebrates, fungi and micro-organisms is needed to decompose the wood and beetles that penetrate the bark are critical to the initiation of this process, also because they directly inoculate the wood with a characteristic community of fungi and bacteria. A particular type of wood decay are trunk cavities with wood mould in living trees. Saproxylic insects play an important role also in this process. In managed forests the majority of wood is harvested and very little is left to become dead wood and to finally be incorporated into the soil. The paucity of dead wood has important implications for forest biodiversity and for soil organic matter.
... Similarly, bark and wood-boring insects, create suitable habitats for other insects (e.g. Zuo et al. 2016), and have been shown to facilitate colonization by fungi, thus indirectly accelerating the decomposition of woody debris (Strid et al. 2014, Ulyshen et al. 2016. It is therefore important to understand which ecological functions performed by herbivores can in fact result in regulating services, and how they interact with supporting and provisioning services. ...
Insects play a key role in the regulation and dynamics of many ecosystem services (ES).
However, this role is often assumed, with limited or no experimental quantification of its real
value. We examined publication trends in the research on ES provided by insects, ascertaining
which ES and taxa have been more intensively investigated, and which methodologies have
been used, with particular emphasis on experimental approaches. We first performed a
systematic literature search to identify which ES have been attributed to insects. Then we
classified the references retrieved according to the ES, taxonomic group and ecosystem
studied, as well as to the method applied to quantify each ES (in four categories: no
quantification, proxies, direct quantification and experiments). Pollination, biological control,
food provisioning, and recycling organic matter are the most studied ES. However, the
majority of papers do not specify the ES under consideration, and from those that do, most do
not quantify the ES provided. From the rest, a large number of publications use proxies as
indicators for ES, assuming or inferring their provision through indirect measurements such as
species abundances, species density, species richness, diversity indices, or the number of
functional groups. Pollinators, predators, parasitoids, herbivores, and decomposers are the
most commonly studied functional groups, while Hymenoptera, Coleoptera, and Diptera are
the most studied taxa. Experimental studies are relatively scarce and they mainly focus on
biological control, pollination, and decomposition performed in agroecosystems. These results
suggest that our current knowledge on the ES provided by insects is relatively scarce and
biased, and show gaps in the least-studied functional and taxonomic groups. An ambitious
research agenda to improve the empirical and experimental evidence of the role played by
insects in ES provision is essential to fully assess synergies between functional ecology,
community ecology, and biodiversity conservation under current global changes.
... To experimentally test the colonization of empty detached branches by the ant community, we utilized flagging tapes to attach four branches of different diameters in trees under the canopy of 15 individuals of S. purpurea distant from each other by at least 30 m. Each of the four branches was located in four trees, without canopy connection, at a height ranging from 1.5 to 2.0 m for two months, sufficient time for invertebrate community colonization (Zuo et al. 2016). In April and October 2016, we collected all branches, immediately placed them in individual bags of fine mesh, and transported them to the laboratory. ...
Oncideres albomarginata chamela (Cerambycidae: Lamiinae) is a stem-boring beetle that
girdles branches of Spondias purpurea (Anacardiaceae) for oviposition. Many beetles
opportunistically oviposit in these branches and larvae create cavities that are abandoned when
the adults emerge. Our objective was to evaluate the role of wood-boring beetles in promoting
ant nest cavities mediated by a twig-girdler engineer. We collected 120 abandoned branches
that had been detached by O. albomarginata chamela, in a tropical dry forest, in Jalisco,
Mexico. Sixty abandoned branches were placed in trees from February to April, and another
sixty from August to October 2016. In order to test the effects of nest characteristics on ant
species, we measured the diameter of each branch and the diameter of the ant nest entrance as
explanatory variables, whereas the size of ant species was used as response variable. We
found 49 nests of arboreal ants from 14 species. The body size of the ants nesting in the
abandoned branches was positively correlated with the diameter of the nest entrance. Ants used abandoned branches mainly as polydomic nests. Our result confirms that ants
partitioning resources according to the size of entrance holes made by wood-boring beetles in
dead wood. Polydomic nests have been reported as a strategy to promote the colonization of
new nesting sites and the reduction of intraspecific competition. We conclude that the
ecosystem engineering carried out by the twig-girdler O. albomarginata chamela had
extended effects on the arboreal ant community, that takes advantage of the cavities
abandoned by wood-boring beetles for nesting, especially for polydomic nests.
... Deadwood is an important structural and functional component of forest ecosystems, acting as a temporal store of plant nutrients and water, and providing shelter and nutrition to various organisms, primarily fungi and saproxylic insects (Floudas et al., 2012;Harmon et al., 1986;Zuo et al., 2016). Moreover, deadwood represents a global carbon store estimated to be in the range of 73 ± 6 Pg (Pan et al., 2011), making its decomposition dynamics a determinant of the soil carbon balance and forest productivity (Bradford et al., 2014). ...
Although slope aspect determines the amount of solar irradiation, with implications on the functioning of forest ecosystems, little is known yet about how this affects the aboveground deadwood decomposition dynamics. Therefore, we set up a climosequence case study to evaluate the impact of slope exposure (north- vs. south-facing sites) on the physico-chemical and microbiological properties of Picea abies coarse woody debris (CWD) at different stages of natural decay (decay classes, DCls 1–5) in an Italian Alpine setting. Variations in bacterial, fungal and archaeal abundances were assessed by real-time PCR in the extra- and intracellular DNA fractions (eDNA vs. iDNA) of the total deadwood DNA pool. Physico-chemical wood properties (macro- and micronutrients; lignin and cellulose content; 3D structure via X-ray microtomography) were also performed along with the determination of key enzymatic activities involved in the main nutrient cycles. Overall, higher microbial abundances were registered in Picea abies CWD samples at the cooler, more acidic and moister north-facing site, which are favourable conditions especially for fungal wood decomposers. This thermal signal (N > S) was more evident for the advanced decay stages (DCls 4 and 5), being wood pH the most determinant factor for discriminating between both slopes. We also found that the impact of exposure was enzyme-specific and strongly dependent on the decay class, except for those enzymes involved in the P cycle. In addition, the eDNA/iDNA ratio provided a simple yet powerful index of microbial activity in terms of exposure, with lower values at the north-facing slope indicative of a higher microbial activity. This is in line with the more pronounced physical wood damage detected at this slope by the X-ray microtomography. A higher microbial activity at the cooler north-facing site rather seems surprising – a circumstance that probably is not due to temperature itself but due to increased moisture availability at this slope.
... Some species dig nests in the soil, but most are specialists in using pre-existing cavities in the ground, among rocks or in pithy stems and galls (Eickwort et al. 1981). Pre-existing cavities are also found in dead wood, such as old galleries of wood-dwelling beetles, which are important nest spaces in forest ecosystems (Zuo et al. 2016). ...
Studies on the nesting biology of cavity nesting hymenoptera (bees and wasps) have stimulated many questions related to the behavior, life cycle, trophic niche, and sex ratio to better understanding of the life history of insects. Leafcutting bees are common insects, and many are important and efficient pollinators of crops and other plants. We studied the nesting biology of Megachile (Moureapis) maculata in a montane semi-deciduous forest in Brazil using trap nests in order to improve the knowledge of aspects of the natural history of this important pollinator group. During 27 months, 87 nests were collected with an average of seven brood cells per nest. Most of the nests were in cavities of 0.9 cm in diameter (77%), and the number of brood cells ranged from 1 to 11. Absence of seasonality in nesting behavior suggests a multivoltine species. The total mortality rate was 26%, with the cuckoo bee Coelyoxis (Acrocoelioxys) sp. being the main natural enemy attacking 15% of brood cells. The sex ratio is clearly male-biased (1:0.42). Females and their brood cells were larger than males and their brood cells, which may suggest an imbalance in the energetic cost of each sex. The success of this bee species in colonizing trap nests makes it an interesting potential opportunity to use this species for pollination of cultivated Asteraceae plant species, like sunflower.
... Detritivores may also directly fragment CWD and increase its accessibility to other decomposers (biological fragmentation) (Harmon et al., 1986). Bark beetles for instance puncture the outer bark and engrave galleries in the inner bark and wood, thereby facilitating the invasions of other invertebrates (Zuo et al., 2016). ...
Worldwide, forests have absorbed around 30% of global anthropogenic emissions of carbon dioxide (CO2) annually, thereby acting as important carbon (C) sinks. It is proposed that leaving large fragments of dead wood, coarse woody debris (CWD), in forest ecosystems may contribute to the forest C sink strength. CWD may take years to centuries to degrade completely, and non-respired C from CWD may enter the forest soil directly or in the form of dissolved organic C. Although aboveground decomposition of CWD has been studied frequently, little is known about the relative size, composition and fate of different C fluxes from CWD to soils under various substrate-specific and environmental conditions. Thus, the exact contribution of C from CWD to C sequestration within forest soils is poorly understood and quantified, although understanding CWD degradation and stabilization processes is essential for effective forest C sink management. This review aims at providing insight into these processes on the interface of forest ecology and soil science, and identifies knowledge gaps that are critical to our understanding of the effects of CWD on the forest soil C sink. It may be seen as a “call-to-action” crossing disciplinary boundaries, which proposes the use of compound-specific analytical studies and manipulation studies to elucidate C fluxes from CWD. Carbon fluxes from decaying CWD can vary considerably due to interspecific and intraspecific differences in composition and different environmental conditions. These variations in C fluxes need to be studied in detail and related to recent advances in soil C sequestration research. Outcomes of this review show that the presence of CWD may enhance the abundance and diversity of the microbial community and constitute additional fluxes of C into the mineral soil by augmented leaching of dissolved organic carbon (DOC). Leached DOC and residues from organic matter (OM) from later decay stages have been shown to be relatively enriched in complex and microbial-derived compounds, which may also be true for CWD-derived OM. Emerging knowledge on soil C stabilization indicates that such complex compounds may be sorbed preferentially to the mineral soil. Moreover, increased abundance and diversity of decomposer organisms may increase the amount of substrate C being diverted into microbial biomass, which may contribute to stable C pools in the forest soil.
... We expect that, with the progression of decay, invertebrates will interact more strongly with each other negatively (e.g. competition, predation), while it is unknown whether and how facilitative effects seen during early decomposition (Zuo et al. 2016a) play a role later on; these factors will make community assembly in dead wood less predictable. At later decomposition stage, variation in wood traits will become more important than bark traits, partly because much of the bark will have fallen off, but especially because wood-specialized decomposers, such as wood-boring beetles, will colonize the wood. ...
1. Dead tree trunks have significant ecosystem functions related to biodiversity and biogeochemical cycles. When lying on the soil surface, they are colonized by an array of invertebrate fauna, but what determines their community composition is still unclear.
2. We apply community assembly theory to colonization of tree logs by invertebrates. During early decomposition, the attached bark is critically important as an environment filter for community assembly through habitat provision. Specifically, we hypothesized that the more dissimilar bark traits were between tree species, the more their faunal community compositions would differ.
3. We tested this hypothesis by investigating the effects of bark traits on the invertebrate communities in the early-decomposing logs of 11 common, temperate tree species placed in the ‘common garden’ experiment LOGLIFE. Bark traits included bark looseness, fissure index, outer bark thickness, ratio of inner to outer bark thickness, punch resistance, water storage capacity and bark pH. The predominant faunal groups studied were Annelida, Isopoda, Chilopoda, Diplopoda, Diptera and Coleoptera.
4. Our results showed (i) strong interspecific differences in bark traits, (ii) that bark traits related to environmental buffering had profound effects on the abundance of specific invertebrate groups, and (iii) the higher the overall bark trait dissimilarity between tree species, the more dissimilar these tree species were in faunal community composition, and the higher was the joint invertebrate family richness.
5. A suite of bark traits together has fundamental afterlife effects on invertebrate community assembly, strongly filtering the colonizing invertebrates in early-decomposing logs, driving variation in their community composition and diversity. Our findings indicate that bark trait dissimilarity among tree species in forest stands is likely a better indicator of early-phase dead trunk fauna diversity than tree species diversity per se<br/
Bark beetles are important components of the natural dynamics of coniferous forests. In Europe, the European spruce bark beetle (Ips typographus) in particular has the potential to cause extensive infestations and thus can act as an ecological disturbance. After disturbances such as windthrow or drought, this beetle can increase its population density to such an extent that it is able to successfully colonize vigorous trees. The further development of mass infestations of living trees mainly depends on temperature and the susceptibility of the host trees. From an ecological viewpoint, bark beetles contribute to the natural dynamics of forest ecosystems and create valuable new habitats for many organisms. Socio-economically, however, bark beetle outbreaks often lead to extensive damage.KeywordsClimate changeDamageDynamicsEcological significanceEuropean spruce bark beetleHost treeInfestationMountain pine beetleOutbreakScolytinae
Revealing the ecological consequences of bark multifunctionality and its underlying traits has become a relatively new but essential focus in plant ecology. Although the enormous differences between the most crucial bark layers, that is, inner and outer bark, in structure and functions have been widely recognized, the overall bark has been regarded as a homogenous tissue in most bark‐related studies. This has led to poor knowledge on the functional independence, specialized contributions and possible linkages of inner and outer bark traits across tree species when further evaluating the crucial ecosystem functions that bark provides, especially in driving variation in bark decomposition.
To fill this research gap, we used a ‘common garden experiment’ on deadwood of six gymnosperms in a temperate forest in the Netherlands over 4 years of decomposition. We evaluated the differences and associations between the inner and outer bark in initial functional traits, decomposition rates and afterlife effects of traits in driving in situ bark decomposition across tree species at the earlier decomposition stage.
We report four main findings: (1) inner and outer bark traits varied significantly and were not coordinated across tree species; (2) correspondingly, the decomposition of the inner and outer bark were asynchronous and not coordinated across species and inner bark generally decomposed faster than outer bark; (3) the strong predictive traits driving bark decomposability were bark layer‐specific, with several inner bark traits controlling inner bark decomposition rates but outer bark decomposability being poorly predicted by outer bark traits and (4) besides being controlled by inner bark traits, inner bark decomposition was also indirectly regulated by several functional traits and the structure‐related trait spectrum of outer bark.
Synthesis. This is the first study that has linked functional traits, decomposability and afterlife effects of the inner and outer bark within the bark quantitatively. We highlight the significance of separating functional traits and ecological consequences of the inner and outer bark in research in bark ecology and deadwood dynamics, rather than erroneously considering bark as a homogeneous tissue. Such research will help to better evaluate the function‐oriented contribution of bark to the turnover of forest carbon and biogeochemical cycles from local to global scale.
Popularnonaukowa monigrafia zagadnień związanych z bilansem, rolą i ochroną martwych drzew w w ekosystemach, głównie (ale nie tylko) leśnych. Przedstawia m. in. zagadnienia:
Co to jest drewno. Jakich rozmiarów dorastają i jak długo żyją drzewa?
Pochodzenie, bilans i cechy martwego drewna, w lasach, poza lasem: w parkach, zadrzewieniach i innych środowiskach; w wodach. Martwe drewno na żywym drzewie – Mikrosiedliska nadrzewne. Znikający krajobraz ekotonów leśnych i lasów pastwiskowych.
Etapy i konsekwencje zamierania drzew. Jak martwe drzewa „ożywają”: kolonizacja martwych drzew i martwego drewna
Zamierające i martwe drewno jako środowisko życia. Organizmy zwiąane z martwym drewnem.
Funkcje ekosystemowe martwego drewna: Leśne „paliwo”, magazynowanie materii organicznej, akumulacja węgla i azotu, magazynowanie wody, rola martwych drzew w odnowieniu lasu, ochrona przed erozją, rola w procesach glebowych, rola w ciekach.
Rola martwego drewna w ochronie lasu i ochronie przyrody. Rola w leśnictwie i świadomość leśników. Martwe drewno jako składnik chronionych ekosystemów i wskaźnik ich stanu. Ochrona gatunkowa zwiążanych z martwym drewnem zwierząt, roślin i grzybów, w tym gatunków reliktowych.
Rozległe zaburzenia – niechciany dar przyrody?
Martwe drewno a zagadnienia bezpieczeństwa.
Martwe drewno w nauce i gospodarce.
Metody jakościowej i ilościowej oceny martwego drewna.
„Drugie Zycie Drzewa”, autorstwa J.M. Gutowskiego, A. Bobca, P. Pawlaczyka i K. Zuba ukazało się po raz pierwszy w 2004 r. Obecne II wydanie (2022 r.) jest znacznie zmienione i rozbudowane, stosownie do obecnej wiedzy na temat ekologicznej roli martwych drzew. Wiedza ta przez 18 lat jakie minęły od I wydania, wzrosła niepomiernie: w 2021 r. internetowe wyszukiwarki literatury naukowej znajdowały ok. 40 tys. publikacji na ten temat. Blisko połowa z nich pochodzi z ostatniego dziesięciolecia.
Do autorów II wydania dołączyli: Michał Ciach i Anna Kujawa. W szczególności szeroko zostały opisane zagadnienia związane z rolą tzw. drzew biocenotycznych i mikrosiedlisk nadrzewnych w lasach. Zupełnie nową treść i jakość uzyskały rozdziały opisujące grzyby, porosty i śluzowce oraz ich związki z martwym drewnem. O nowe zagadnienia i treści został rozszerzony rozdział „Martwe drewno w ochronie lasu i ochronie przyrody”, który zaktualizowano też do obecnego stanu prawnego. Znacznie szerzej przedstawiono rolę martwego drewna w wodach. Zaktualizowano oraz uzupełniono, przede wszystkim o nową literaturę, również pozostałe rozdziały publikacji. Znacznie rozbudowano materiał ilustracyjny. Nowe wydanie liczy ponad 340 stron, dodatkowo na większym formacie, co oznacza ok. dwukrotnie większą objętość od wydania I.
Książka w wersji elektronicznej (pdf) jest dostępna także na stronach wydawcy (The book is available at the publisher website): https://www.wwf.pl/sites/default/files/2022-03/drugie-zycie-drzewa-03-2022.pdf
Background
Land clearing generates coarse woody debris (CWD), much of which ultimately becomes atmospheric CO2. Schemes for greenhouse gas accounting must consider the contribution from land clearing, but the timing of the contribution will have large uncertainty, due to a paucity of knowledge about the rate of CWD disappearance. To better understand above-ground CWD disappearance following a land clearing event—through the actions of microorganisms, invertebrates, wildfire, or deliberate burning—we combined statistical modelling with an archive of semi-quantitative observations (units of CWD %), made within Queensland, Australia.
Results
Using a generalised additive mixed-effects model (median absolute error = 14.7%), we found that CWD disappearance was strongly influenced by the: (i) number of years elapsed since clearing; (ii) clearing method; (iii) bioregion (effectively a climate-by-tree species interaction); and (iv) the number of times burned. Years-since-clearing had a strongly non-linear effect on the rate of CWD disappearance. The data suggested that disappearance was reverse-sigmoidal, with little change in CWD apparent for the first three years after clearing. In typical conditions for Queensland, the model predicted that it will take 38 years for 95% of CWD to disappear, following a land clearing event; however, accounting for uncertainty in the data and model, this value could be as few as 5 years, or > 100 years. In contrast, due to an assumption about the propensity of land managers to burn CWD, the official method used to assess Australia’s greenhouse gas emissions predicted that 95% of CWD will disappear in < 1 year.
Conclusions
In Queensland, the CWD generated by land clearing typically takes 38 years to disappear. This ultimately implies that a key assumption of Australia’s official greenhouse gas reporting—i.e. that 98% of CWD is burned soon after a clearing event—does not adequately account for delayed CO2 emissions.
Bark beetle (Coleoptera: Curculionidae: Scolytinae) outbreaks can be spectacular, killing trees across hundreds to thousands of hectares or more of forest land. As bark beetles are a natural disturbance agent, it is hypothesized that ecosystems are adapted to such periodic disturbances. Under climate change, however, these beetle outbreaks have become more severe, persistent, and chronic on many landscapes, bringing into question the long-term resilience of these forests and the biota that depend on them. Our chapter objective is to review and generalize the effects of bark beetle outbreaks on flora, fauna, and soil microbiota across diverse landscapes worldwide. Through loss of canopy trees, there is an increase in forest gaps and dead organic material that alters resource availability for many organisms. As organisms respond to altered resources, they may create feedback loops to themselves and their environment. Tree regeneration dynamics may set the stage for dominance by the same or different canopy species, retriggering, advancing, or otherwise altering successional trajectories. Herbs and shrubs often become more abundant and diverse under postbark beetle outbreaks due to increased light, water, and nutrient availability. Faunal species that rely on open habitat conditions and greater availability of newly available resources (e.g., coarse woody debris, bark beetles as prey items, and understory plant release) tend to benefit from bark beetle outbreaks; vice versa for other species; and variable responses are indicated for other species. Both positive and negative impacts on red-listed or endangered species have been reported. Ectomycorrhizal and saprophytic fungi, respectively, tend to decrease and increase after bark beetle outbreaks. There may be an increase in soil bacteria with different bacterial species dominant in beetle-killed trees. Responses of biota are therefore species-specific, and there are winners and losers in systems based on habitat alterations and life-history requirements. Longer-term and comprehensive studies of cascading, interacting, and simultaneous ecological impacts for multitaxa are recommended for maintaining the resilience of these disturbed landscapes under climate change.
Most people meet insects with fear and disgust but this reputation is largely unfounded, as few insects pose health risks. In fact, many are beneficial and their absence would adversely affect human life; thus insect conservation is important but unpopular. We have begun addressing these concerns as part of a broader effort to establish an ongoing outreach partnership between graduate students at the University of Kansas and the Girl Scouts of Northeast Kansas/Northwest Missouri. To explore ways to advocate for insect conservation, we held an insect collecting activity at a Girl Scout summer camp and surveyed changes in attitudes towards insects afterwards. This activity positively changed reactions to insect encounters and increased confidence in identifying harmful insects but did not strongly reduce fears or increase curiosity towards insects. Beyond these proximate results, this project highlights the potential of Girl Scout troops as targets for informal science education that can benefit both academics and the broader community.
Natural forests contain a large amount of deadwood, which is a key contributor to biodiversity, especially by providing dynamic habitats and resources for a huge variety of invertebrates. However, for managing forest biodiversity we need to better understand what drives the dynamics of invertebrate communities in deadwood. We hypothesized that the invertebrate communities in logs will converge from initial to middle decomposition stage among tree species and forest stands as the differentiating role of bark diminishes and xylem traits converge during decay. We investigated invertebrate communities in decomposing logs of ten tree species over 4 years in the “tree cemetery” LOGLIFE experiment in two contrasting forests in the Netherlands. The predominant faunal groups studied were Annelida (earthworms), Isopoda (woodlice), Chilopoda (centipedes), Diplopoda (millipedes), Diptera (flies, midges) and Coleoptera (beetles). We demonstrated that (1) tree species, decay stages and incubation forests all had effects on the invertebrate communities; (2) community compositions of fauna in logs first were very dissimilar and then became more similar among tree species through the decay years; and (3) this converging pattern of faunal community dynamics also manifested itself, both across and within given tree species, between two contrasting forests over decomposition time. Thus, invertebrate communities generally converged during deadwood decay, which adds fundamental insights into the role of interacting drivers of community succession. These findings also highlight that, both within and among forests, more functionally different tree species and logs in different decay stages, will support relatively high biodiversity of invertebrate communities; these patterns may inform forest management strategies aimed at maximizing biodiversity.
Dead wood availability and the variability in dead wood quality, i.e. tree species and decay stages, are often low in managed forests, which negatively affects biodiversity of invertebrate species. Leaving more (coarse) dead wood can increase invertebrate richness, but it remains unclear how many and which combinations of tree taxa and decay stages are required to optimize niche heterogeneity in managed forests. We investigated the diversity of the main arthropod groups associated with dead wood, i.e. millipedes, centipedes, isopods and beetles, through the first four years of decomposition of logs of twenty common temperate tree species placed in the “common garden” experiment LOGLIFE. We hypothesized that (1) invertebrate richness for combinations of a given number of tree species would be promoted by mixing both tree species and decay period and that (2) invertebrate richness increases up to a saturation point with more tree species at different decay stages added. We also hypothesized that (3) an increase in phylogenetic distance among the tree species in combinations would promote their overall invertebrate diversity. We found that the better combinations, in terms of invertebrate richness, after one and two years of decay, but not after four years, consisted of a mix of gymnosperms and angiosperms, indicating that variation in tree species is especially important during the initial decomposition period. The best combinations in terms of invertebrate richness consisted of at least one tree species from each decay period, indicating that also variation in the decay stage of the tree is important to promote invertebrate diversity. We observed that at least four wood types were required to approach the 95% saturation point for species richness. The third hypothesis, that dissimilarity in phylogenetic position could be a predictive tool for increasing invertebrate richness in combinations of tree species, was not supported by our results. Thus, in order to maintain diversity of dead wood invertebrates in forests we recommend not only to provide richness in tree species, but also to plant particular combinations of trees (preferably angiosperm-gymnosperm combinations) that differ in the invertebrate communities they typically host and to temporally spread the logging of trees. This way the logging residues cover different resources and habitats at each moment in time, which is likely to result in a large diversity of dead wood invertebrates.
Woody debris (WD) represents a globally significant carbon stock and its decomposition returns nutrients to the soil while providing habitat to microbes, plants and animals. Understanding what drives WD decomposition is therefore important.
WD decomposition rates differ greatly among species. However, the role of bark in the process remains poorly known.
We ask how, and how much, interspecific variation in bark functional traits related to growth and protection have afterlife effects on the decomposition of wood, partly mediated by animals. We examine the roles of bark cover and bark traits throughout the wood decomposition process.
Synthesis . We find that: (1) bark effects on WD decomposition are species‐ and wood size‐specific, (2) bark can enhance coarser WD decomposition but slows twig decomposition in some species, and (3) bark acts as an environmental filter to faunal assemblages in the early stage of wood decomposition.
We highlight the need to account for bark effects on WD decomposition and offer an important complementary contribution to including woody species identity effects in biogeochemical and climate‐change models via species bark traits.
The diversity and habitat requirements of invertebrates associated with dead wood have been the subjects of hundreds of studies in recent years but we still know very little about the ecological or economic importance of these organisms. The purpose of this review is to examine whether, how and to what extent invertebrates affect wood decomposition in terrestrial ecosystems. Three broad conclusions can be reached from the available literature. First, wood decomposition is largely driven by microbial activity but invertebrates also play a significant role in both temperate and tropical environments. Primary mechanisms include enzymatic digestion (involving both endogenous enzymes and those produced by endo- and ectosymbionts), substrate alteration (tunnelling and fragmentation), biotic interactions and nitrogen fertilization (i.e. promoting nitrogen fixation by endosymbiotic and free-living bacteria). Second, the effects of individual invertebrate taxa or functional groups can be accelerative or inhibitory but the cumulative effect of the entire community is generally to accelerate wood decomposition, at least during the early stages of the process (most studies are limited to the first 2–3 years). Although methodological differences and design limitations preclude meta-analysis, studies aimed at quantifying the contributions of invertebrates to wood decomposition commonly attribute 10–20% of wood loss to these organisms. Finally, some taxa appear to be particularly influential with respect to promoting wood decomposition. These include large wood-boring beetles (Coleoptera) and termites (Termitoidae), especially fungus-farming macrotermitines. The presence or absence of these species may be more consequential than species richness and the influence of invertebrates is likely to vary biogeographically.
Tree hollows offer an ideal niche for saproxylic insects in mature Mediterranean forests, where Diptera and Coleoptera are the richest groups. Co-occurrence is frequently observed among many species of both groups in these microhabitats, and some of these species have been considered to facilitate the presence of other species by acting as ecosystem engineers. One of the systems that is found in Mediterranean tree hollows is formed by cetonid (Coleoptera: Cetoniidae) and syrphid (Diptera: Syrphidae) larvae. Here, cetonid larvae feed on wood and litter and produce a substrate that is easier to decompose. To assess the possible role of these larvae as facilitating agents for the saproxylic guild, we studied whether the presence of saprophagous Syrphidae inside tree hollows is associated with the activity of cetonid larvae. Furthermore, in laboratory conditions, we tested whether cetonid larvae activity can improve the development and fitness of the saprophagous syrphid species. Our results show that "cetonid activity" was the variable that best explained the presence of saprophagous syrphid species in natural conditions. Myathropa florea (L., 1758) was one of the species most influenced by this activity. The laboratory experiment gave similar results, demonstrating that an enriched substrate with Cetonia aurataeformis Curti, 1913 larval feces improves syrphid larval growth rate and fitness of adults (measured as longer wing length) of M. florea.
Old-growth forests are important stores for carbon as they may accumulate C for centuries. The alteration of biomass and soil carbon pools across the development stages of a forest dynamics cycle has rarely been quantified. We studied the above- and belowground C stocks in the five forest development stages (regeneration to decay stage) of a montane spruce (Picea abies) forest of the northern German Harz Mountains, one of Central Europe’s few forests where the natural forest dynamics have not been disturbed by man for several centuries. The over-mature and decay stages had the largest total (up to 480 Mg C ha−1) and aboveground biomass carbon pools (200 Mg C ha−1) with biomass C stored in dead wood in the decay stage. The soil C pool (220–275 Mg C ha−1, 0–60 cm) was two to three times larger than in temperate lowland spruce forests and remained invariant across the forest dynamics cycle. On the landscape level, taking into account the frequency of the five forest development stages, the total carbon pool was approximately 420 Mg C ha−1. The results evidence the high significance of over-mature and decaying stages of temperate mountain forests not only for conserving specialized forest organisms but also for their large carbon storage potential.
Coarse woody debris (CWD) is an important component of temperate stream and forest ecosystems. This chapter reviews the rates at which CWD is added and removed from ecosystems, the biomass found in streams and forests, and many functions that CWD serves. CWD is added to ecosystems by numerous mechanisms, including wind, fire, insect attack, pathogens, competition, and geomorphic processes. Despite the many long-term studies on tree mortality, there are few published rates of CWD input on mass-area-1 time-1 basis. CWD is significantly transformed physically and chemically. Movement of CWD, especially in streams, is also an important but poorly documented mechanism whereby CWD is lost from ecosystems. Many factors control the rate at which CWD decomposes, including temperature, moisture, internal gas composition of CWD, substrate quality, size of CWD, and types of organisms involved. However, the importance of many of these factors has yet to be established in field experiments. CWD performs many functions in ecosystems, serving as autotrophic and heterotrophic habitat and strongly influencing geomorphic processes, especially in streams. It is also a major component of nutrient cycles in many ecosystems and is an important functional component of stream and forest ecosystems.
In contrast to many other biotic forces, such as competition and predation, the role played by habitat modification by plants and sessile animals in natural communities has not been given the experimental attention it deserves. To test the hypothesis that habitat modification by seaweed canopies can have direct positive effects on rocky intertidal communities, the authors quantified habitat amelioration by Ascophyllum nodosum canopies and its consequences on understory organisms in the Gulf of Maine, USA. At the upper and lower elevational borders of the algal canopy, the authors examined the recruitment, growth, and survivorship of common benthic organisms in canopy removal, and shaded canopy removal plots intended to mimic canopy habitat modifications. The algal canopy greatly reduced potential physical stresses, particularly at high tidal heights. Maximum daily rock temperatures were 5--10 C lower and evaporative water loss was in order of magnitude less under the canopy than in canopy removal plots. The response of understory organisms to canopy removal, however, was species specific and somewhat idiosyncratic. Nonetheless, in general, at the high intertidal border of the canopy the recruitment, growth, and survival of understory organisms were enhanced by the canopy, whereas at the low intertidal border canopy effects were negative or neutral. nearly half of the interactions the authors studied were positive in the high zone.
The focus of this study was to investigate the role of tree dimension and associated bark structures for high structural complexity and high natural biodiversity in forest ecosystems. Two-hundred and ninety-one Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirbel) Franco) trees in two regions of the US Pacific Northwest were investigated for the relationship between tree diameter and bark thickness (measured as bark fissure depth) and the relationships of both to bark microhabitats and signs of bark use. Our results emphasize the habitat function of tree bark of large-diameter Douglas-fir trees. Many bark microhabitat types and their total abundance significantly increased with increasing tree diameter and bark thickness. These were bark pockets with and without decaying substrate, bowls in the bark, and signs of bark use, e.g., small holes from woodpecker drillings and large insects, large bark excavations from woodpeckers, spider funnel webs, natural cavities at the stem base without decay, and the occurrence of herb vegetation at the tree base. In forest monitoring, tree diameter may be a good indicator of the number of bark microhabitats and of bark thickness because it is strongly related to both of these variables. However, because of the high variability of bark thickness in large-diameter trees, we suggest monitoring bark fissure depth if an ecological evaluation of Douglas-fir forests is needed.
* 1Endemic populations of the bark beetle Dendroctonus ponderosae attack weakened lodgepole pine (Pinus contorta var. latifolia) trees that are often previously infested by other bark beetle species, such as Pseudips mexicanus. * 2The effect of interactions on D. ponderosae was assessed by examining host selection and productivity of D. ponderosae in trees containing P. mexicanus and trees infested solely by D. ponderosae. * 3The findings obtained show that D. ponderosae attacked hosts previously occupied by P. mexicanus at greater densities, and offspring emerged earlier compared with hosts infested by D. ponderosae alone. Additionally, D. ponderosae larvae in P. mexicanus-infested trees were found to require a significantly lower amount of resource to complete development with no loss in size. * 4The presence of P. mexicanus may affect host condition, improving the subcortical environment for endemic D. ponderosae, ultimately aiding in population maintenance at low levels. Hosts in this state should be preferentially attacked by D. ponderosae.
Dead wood provides a huge terrestrial carbon stock and a habitat to wide-ranging organisms during its decay. Our brief review highlights that, in order to understand environmental change impacts on these functions, we need to quantify the contributions of different interacting biotic and abiotic drivers to wood decomposition. LOGLIFE is a new long-term 'common-garden' experiment to disentangle the effects of species' wood traits and site-related environmental drivers on wood decomposition dynamics and its associated diversity of microbial and invertebrate communities. This experiment is firmly rooted in pioneering experiments under the directorship of Terry Callaghan at Abisko Research Station, Sweden. LOGLIFE features two contrasting forest sites in the Netherlands, each hosting a similar set of coarse logs and branches of 10 tree species. LOGLIFE welcomes other researchers to test further questions concerning coarse wood decay that will also help to optimise forest management in view of carbon sequestration and biodiversity conservation.
Dead wood is a habitat for many insects and other small animals, some of which may be rare or endangered and in need of effective protection. In this paper, saproxylic beetle assemblages associated with different host trees in the subtropical forests in southwestern China were investigated. A total of 277 species (1 439 specimens) in 36 beetle families were collected from 117 dead wood samples, of which 101 samples were identified and respectively belonged to 12 tree genera. The number of saproxylic beetle species varied greatly among logs of different tree genera, with the highest diversity on logs of Juglans. Generally, broad-leaved trees had a higher richness and abundance of saproxylic species than coniferous trees. Cluster analysis revealed that assemblages from broad-leaved tree genera were generally similar (except for Betula) and assemblages from coniferous trees formed another distinct cluster. The subsequent indicator analysis proposed that there are different characteristic species for different cluster groups of host tree genera. In our study, log diameter has no positive influence on beetle species density. Conversely, comparisons of individual-based rarefaction curves suggested that beetle species richness was highest in the small diameter class both in coniferous and broad-leaved tree genera. With increased wood decay, proportion of habitat specialists (saproxylic beetles living on one tree genus) decreased, whereas proportion of habitat generalists (living on more than three tree genera) increased. The beetle species density was found to be higher in early stages, and decreased in later stages as well. A negative influence of altitude on saproxylic beetle species richness and abundance was detected. It was indicated that different tree genera and altitudes possibly display cross effects in modulating the altitudinal distribution and host preference of the beetles.
1. The complex structure of tree bark reflects its many functions, which include structural support as well as defence against fire, pests and pathogens. Thick bark, however, might limit respiration by the living tissues of the trunk. Nevertheless, little research has addressed community-level variation in bark thickness, and to the best of our knowledge, no one has tested multiple hypotheses to explain variation in bark thickness.
2. We conducted an extensive survey of bark thickness within and among species of trees in the tropical rain forests of French Guiana. Trunk bark thickness increased by 1·2 mm per 10 cm increase in stem diameter, and varied widely at all taxonomic levels. Mean trunk bark thickness was 4·5 mm (range: 0·5–29 mm), which was less that found in two Amazonian rain forests in previous studies. This survey of bark thickness should be of use for forest management since tree survival through fire is strongly predicted by bark thickness.
3. We combined the survey data with multiple datasets to test several functional hypotheses proposed to explain variation in bark thickness. We found bark to provide an average of 10% of the flexural rigidity of tree stems, which was substantially less than that found in the only other study of bark stiffness. Bark thickness was uncorrelated with species’ association with fire-prone habitats, suggesting that the influence of fire on bark thickness does not extend into moist Forests. There was also little evidence that bark thickness is affected by its function as a defence against herbivory. Nor was there evidence that thick bark limits trunk respiration.
4. A re-analysis of previously collected anatomical data indicated that variation in rhytidome (non-conducting outer bark) thickness explains much of the variation in overall bark thickness. As rhytidome is primarily involved in protecting the living tissues of the trunk, we suggest that bark thickness is driven mostly by its defensive function.
5. Functional explanations for the variation in bark thickness were not clear-cut. Nevertheless, this study provides a foundation for further investigation of the functional bases of bark in tropical trees.
We used a laboratory assay to partition the effects of predation and intraspecific competition on the establishment, mating success, and brood development of an endophytic herbivore. We selected a system in which the same predator feeds both exophytically and endophytically on the same prey, to evaluate the role of herbivore feeding guild on predator numerical and functional responses. The bark beetle, Ips pini (Coleoptera: Scolytidae) reproduces within the stems of conifers. Males establish mating chambers under the bark, produce aggregation pheromones, and are subsequently joined by females that construct ovipositional galleries. Thanasimus dubius (Coleoptera: Cleridae) adults prey on adults alighting on the bark surface. T. dubius females then oviposit at the bark beetles' entrance sites, and their larvae prey on developing bark beetle larvae within the tree. We imposed a controlled 3Ƿ factorial design of prey and predator adult densities on red pine logs. Both predation and competition decreased I. pini reproduction. However, the per capita effect of predation was greater than competition, with one adult T. dubius reducing herbivore reproduction by an equivalent amount as four to five competing males and their harems. Increased densities of adult T. dubius on the plant surface reduced the number of prey captured per predator. Total predation on adults and larvae was similar. However, adult T. dubius on the plant surface ate approximately 18-35 times more I. pini per day than did their endophytic larvae. Within the plant, cannibalism among T. dubius, low herbivore densities, limited feeding times, and presumably the complex gallery architecture of I. pini reduced the number of predator progeny. The progeny of I. pini showed even sex ratios in the absence of predators, but were female biased when predators were present. We quantified a relatively narrow set of predator and prey densities that can generate replacement rates greater than one for this predator that specializes on endophytic herbivores. We attribute some of the benefits of an endophytic lifestyle not only to escape from generalist predators, but also to relatively low functional and numerical responses of adapted predators.
Investigations of the role of competition, predation and abiotic stress in shaping natural communities were a staple for previous generations of ecologists and are still popular themes. However, more recent experimental research has uncovered the largely unanticipated, yet striking influence of facilitation (i.e. positive species interactions) on the organization of terrestrial and aquatic communities. Modern ecological concepts and theories were well established a decade before the current renaissance of interest in facilitation began, and thus do not consider the importance of a wide variety of facilitative interactions. It is time to bring ecological theory up to date by including facilitation. This process will not be painless because it will fundamentally change many basic predictions and will challenge some of our most cherished paradigms. But, ultimately, revising ecological theory will lead to a more accurate and inclusive understanding of natural communities.
Data were analysed on the volume of dead wood in 86 beech forest reserves, covering most of the range of European beech forests. The mean volume was 130 m3/ha and the variation among reserves was high, ranging from almost nil to 550 m3/ha. The volume depended significantly on forest type, age since reserve establishment and volume of living wood. More dead wood was found in montane (rather than lowland/submontane) reserves, longer-established reserves (time since designation) and reserves with higher volumes of living wood.On average, fallen dead wood contributed more to the total dead wood volume than standing dead wood. The percentage of dead wood that was standing was almost twice as high in montane than in lowland/submontane forest reserves (45% versus 25%). The volume of dead wood at selected sites changed considerably over time. The fluctuations were significantly higher in lowland/submontane than montane reserves, possibly connected with differences in the disturbance regimes and especially damage caused by windstorms. In NW Europe, the blow down of formerly managed, even-aged stands led to extraordinary high volumes of dead wood shortly after reserve establishment.The implications for forest management and biodiversity conservation are discussed. An increase in dead wood volumes must be carried out in accordance with the local/regional forest type and disturbance regime. Thus, in order to fulfil the requirements of as many wood-depending organisms as possible, it is important to preserve not only larger amounts of dead wood, but also dead wood of different types and dimensions as well as securing a long-term continuity of dead wood.
Facilitative or positive, interactions are encounters between organisms that benefitat least one of the participants and cause harm to neither. Such interactions are considered "mutualisms" when both species derive benefit from the interaction. Positive interactions are ubiquitous: they may lie at the root of such divese evolutionary phenomena as the origin of eukaryotic cells, the radiation of flowering plants, and the flourishing of coral reefs. Although a few ecologists have long recognised the importance of positive interactions in stressful environments (e.g.Clements 1916; Addicott 1984), ecological research on positive interactions is still far less common than that on other forms of interactions among species (Bronstein 1994a, Bruno & Bertness 2000). Consequently, positive interactions are rarely factored into models or even into thinking about about factors impacting populations and communities. Recent empirical work and the conceptual models derived from this work (e.g. Bertness & Callaway 1994; Bruno & Bertness 2000) have helped to refocus attention on the role of positive interactions among species, however, and the scientists are beginning to better appreciate the importance of those interactions in the structuring of ecological communities.
Physical ecosystem engineers are organisms that directly or indirectly control the availability of resources ot other organisms by causing physical state changes in biotic or abiotic materials. Physical ecosystem engineering by organisms is the physical modification, maintenance, or creation of habitats. Ecological effects of engineers on many other species occur in virtually all ecosystems because the physical state changes directly create non-food resources such as living space, directly control abiotic resources, and indirectly modulate abiotic forces that, in turn, affect resource use by other organisms. Trophic interactions and resource competition do not constitute engineering. Engineering can have significant or trivial effects on other species, may involve the physical structure of an organism (like a tree) or structures made by an organism(like a beaver dam), and can but does not invariably, have feedback effects on the engineer. We argue that engineering has both negative and positive effects on species richness and abundances at a small scales, but the net effects are probably positive at larger scales encompassing engineered and non-engineered environments in ecological and evolution space and time. Models of the population dynaimcs of the engineers suggest that the engineer/habitat equilibrium is often, but not always, locally stable and may show long-term cycles, with potential ramifications for community and ecosystem stability. As yet, data adequate to parameterise such a model do not exist for any engineer species. Because engineers control flow of energy and materials but do not have to participate in these flows, energy, mass and stoichiometry do not appear to be useful in predicting which engineers have big effects. Empirical observations suggest some potential generalisations about which species will be important engineers in which ecosystems. We point out some of the obvious, and not so obvious, ways in which engineering and trophic relations interact, and we call for greater research on physical ecosystem engineers, their impacts, and their interface with trophic relations.
Ecosystem engineering may influence community structure and biodiversity by controlling the availability of resources and/or habitats used by other organisms. Insect herbivores may act as ecosystem engineers but there is still poor understanding of the role of these insects structuring arthropod communities.
We evaluated the effect of ecosystem engineering by the stem-borer Oncideres albomarginata chamela on the arthropod community of a tropical dry forest for three consecutive years. The results showed that ecosystem engineering by O. albomarginata chamela had strong positive effects on the colonization, abundance, species richness and composition of the associated arthropod community, and it occurred mainly through the creation of a habitat with high availability of oviposition sites for secondary colonizers. These effects cascade upward to higher trophic levels. Overall, ecosystem engineering by O. albomarginata chamela was responsible for nearly 95% of the abundance of secondary colonizers and 82% of the species richness.
Our results suggest that ecosystem engineering by O. albomarginata chamela is a keystone process structuring an arthropod community composed by xylovores, predators and parasitoids. This study is the first to empirically demonstrate the effect of the ecosystem engineering by stem-boring insects on important attributes of arthropod communities. The results of this study have important implications for conservation.
Trunk hollows with wood mould harbour a rich invertebrate fauna with many threatened species, and it has been suggested that the beetle Osmoderma eremita (Coleoptera, Scarabaeidae) is a keystone species in this community. We estimated the amount of nitrogen and phosphorus in wood mould and compared the coarse fraction which constitutes frass of O. eremita with the finer fraction of wood mould, and found that the nutrient richness was higher in frass. O. eremita larvae have a fermentation chamber that harbours nitrogen fixing bacteria. As the levels of absorbable nitrogen are a limiting factor in insect growth, an increase in nutrient richness is one of several possible explanations why the species richness of saproxylic beetles is higher in hollow oaks where O. eremita is present in relation to similar trees where the beetle is absent.
Conifers are long-lived organisms, and part of their success is due to their potent defense mechanisms. This review focuses on bark defenses, a front line against organisms trying to reach the nutrient-rich phloem. A major breach of the bark can lead to tree death, as evidenced by the millions of trees killed every year by specialized bark-invading insects. Different defense strategies have arisen in conifer lineages, but the general strategy is one of overlapping constitutive mechanical and chemical defenses overlaid with the capacity to up-regulate additional defenses. The defense strategy incorporates a graded response from 'repel', through 'defend' and 'kill', to 'compartmentalize', depending upon the advance of the invading organism. Using a combination of toxic and polymer chemistry, anatomical structures and their placement, and inducible defenses, conifers have evolved bark defense mechanisms that work against a variety of pests. However, these can be overcome by strategies including aggregation pheromones of bark beetles and introduction of virulent phytopathogens. The defense structures and chemicals in conifer bark are reviewed and questions about their coevolution with bark beetles are discussed.
For more than 10 years, ecologists have been discussing the concept of ecosystem engineering (i.e., nontrophic interactions of an organism that alters the physical state of its environment and affects other species). In conservation biology, the functional role of species is of interest because persistence of some species may be necessary for maintaining an entire assemblage with many threatened species. The great capricorn (Cerambyx cerdo), an endangered beetle listed in the European Union's Habitats Directive, has suffered a dramatic decline in the number of populations and in population sizes in Central Europe over the last century. The damage caused by C. cerdo larvae on sound oak trees has considerable effects on the physiological characteristics of these trees. We investigated the impacts of these effects on the species richness and heterogeneity of the saproxylic beetle assemblage on oaks. We compared the catches made with flight interception traps on 10 oaks colonized and 10 oaks uncolonized by C. cerdo in a study area in Lower Saxony (Germany). Our results revealed a significantly more species-rich assemblage on the trees colonized by C. cerdo. Colonized trees also harbored more red-listed beetle species. Our results suggest that an endangered beetle species can alter its own habitat to create favorable habitat conditions for other threatened beetle species. Efforts to preserve C. cerdo therefore have a positive effect on an entire assemblage of insects, including other highly endangered species. On the basis of the impact C. cerdo seems to have on the saproxylic beetle assemblage, reintroductions might be considered in regions where the species has become extinct.
Over a ten year period, 1988--1998, over 300 woodlands were visited throughout Scotland and 2061 records of saproxylic Diptera obtained. Of these 1574 were records of early stages; 258 species in 32 families were encountered; 206 species were reared of which 53 were red-listed, 9 were new to Britain and 10 were new to science. Most records came from native boreal trees such as Betula pubescens, Pinus sylvestris and Populus tremula. However, few saproxylic Diptera were specific to tree species, exceptions were 6 red-listed species associated with P. tremula and 5 red-listed species with P. sylvestris. In contrast, most saproxylic Diptera were specific to microhabitat or breeding site. The most important microhabitats were decaying sap under bark and decaying sapwood. Most red-listed species are restricted to Strathspey and north-east Scotland where relatively large stands of native boreal trees exist.
Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks.
Diplopoda (millipedes) and Isopoda (woodlice) are among the most abundant macro-detritivores in temperate forests. These key regulators of plant litter decomposition are influenced by habitat and substrate quality, including that of dead wood. Dead wood provides shelter and resources to macro-detritivores, but the relative effects of tree species, wood decay stage, forest environment and their interactions on macro-detritivore communities are poorly known. To unravel these effects, we combined a reciprocal field incubation experiment and direct field sampling to compare the Diplopoda and Isopoda communities in logs of silver birch (Betula pendula) and Norway spruce (Picea abies) in two contrasting sites in terms of soil texture, pH, fertility and microclimate. We found: (1) a curvilinear relationship between wood decay stage and abundance of Diplopoda and Isopoda, by using wood density as a measure for the decay stage; (2) the pH of dead wood was a good predictor of wood decay stage in a site with pH close to neutrality but not in an acidic site; (3) Diplopoda and Isopoda community composition on different tree species converged during the decay process, consequently tree species are more important in the substrate selection of macro-detritivores at the beginning of their dead wood decomposition; (4) tree species, the growing environment of the trees and the decomposition environment of the logs strongly determined Diplopoda and Isopoda community composition in dead wood, these drivers of macro-detritivore communities interacted with each other and with the wood decay stage. Thus, when trying to understand and predict future patterns of macro-detritivore diversity under regimes of changing land-use and climate, these interactions should be taken into account. An important next step will be to quantify the feedback of macro-detritivore community composition to dead wood decomposition itself. This feedback may be better understood from the combination of (1) the complex interactions of tree species, wood decay stage and forest environment on the macro-detritivore community and (2) the functional traits of these macro-detritivore species. A better knowledge about these feedbacks can help in predicting carbon storage and nutrient cycling functions of dead wood in forests differing or changing in tree species composition and abiotic environment.
Ecosystem engineers play fundamental ecological roles by modifying habitats in ways that affect a multitude of other species and by creating refugia with novel microclimates. We hypothesize that burrow-creating organisms may facilitate climate change adaptation by providing refugia from extreme and fluctuating temperatures found aboveground. We support this hypothesis by showing that large burrow-dwelling tortoises, Gopherus polyphemus, likely depend upon burrows for thermoregulation. By exploiting the varied thermal conditions within burrows, tortoises avoided lethal temperatures and extreme fluctuations in body temperature, maintained moderate and stable body temperatures on hot days, and maintained relatively warm temperatures overnight. Climate change is predicted to increase maximum air temperatures throughout the geographic range of this species, with impacts most severe in Florida, US, where the range of future conditions could be above that of current maxima. This implies that environmental temperatures will be above lethal thermal limits more often, highlighting the importance of refugia from extreme conditions. Large burrowing animals (e.g. aardvarks, pocket gophers, rabbits, seabirds, tortoises, wombats) are widely distributed globally and could provide similar thermal refugia for countless commensal taxa. Burrows and the animals that create them are in urgent need of conservation, which will help ensure the widespread availability of refugia that offer protection from extreme temperatures under climate change.
I. II. III. IV. V. VI. VII. VIII. References SUMMARY: Models describing the biotic drivers that create and maintain biological diversity within trophic levels have focused primarily on negative interactions (i.e. competition), leaving marginal room for positive interactions (i.e. facilitation). We show facilitation to be a ubiquitous driver of biodiversity by first noting that all species use resources and thus change the local biotic or abiotic conditions, altering the available multidimensional niches. This can cause a shift in local species composition, which can cause an increase in beta, and sometimes alpha, diversity. We show that these increases are ubiquitous across ecosystems. These positive effects on diversity occur via a broad host of disparate direct and indirect mechanisms. We identify and unify several of these facilitative mechanisms and discuss why it has been easy to underappreciate the importance of facilitation. We show that net positive effects have a long history of being considered ecologically or evolutionarily unstable, and we present recent evidence of its potential stability. Facilitation goes well beyond the common case of stress amelioration and it probably gains importance as community complexity increases. While biodiversity is, in part, created by species exploiting many niches, many niches are available to exploit only because species create them.
Publisher Summary
This chapter reviews the rates at which Coarse Woody Debris (CWD) is added and removed from ecosystems, the biomass found in streams and forests, and many functions that CWD serves. CWD is an important component of temperate stream and forest ecosystems and is added to the ecosystem by numerous mechanisms, including wind, fire, insect attack, pathogens, competition, and geomorphic processes. Many factors control the rate at which CWD decomposes, including temperature, moisture, the internal gas composition of CWD, substrate quality, the size of the CWD, and the types of organisms involved. The mass of CWD in an ecosystem ideally represents the balance between addition and loss. In reality, slow decomposition rates and erratic variations in input of CWD cause the CWD mass to deviate markedly from steady-state projections. Many differences correspond to forest type, with deciduous-dominated systems having generally lower biomass than conifer-dominated systems. Stream size also influences CWD mass in lotic ecosystems, while successional stage dramatically influences CWD mass in boat aquatic and terrestrial settings. This chapter reviews many of these functions and concludes that CWD is an important functional component of stream and forest ecosystems. Better scientific understanding of these functions and the natural factors influencing CWD dynamics should lead to more enlightened management practices.
1. Once neglected, the role of facilitative interactions in plant communities has received considerable attention in the last two decades, and is now widely recognized. It is timely to consider the progress made by research in this field. 2. We review the development of plant facilitation research, focusing on the history of the field, the relationship between plant-plant interactions and environmental severity gradients, and attempts to integrate facilitation into mainstream ecological theory. We then consider future directions for facilitation research. 3. With respect to our fundamental understanding of plant facilitation, clarification of the relationship between interactions and environmental gradients is central for further progress, and necessitates the design and implementation of experiments that move beyond the clear limitations of previous studies. 4. There is substantial scope for exploring indirect facilitative effects in plant communities, including their impacts on diversity and evolution, and future studies should connect the degree of non-transitivity in plant competitive networks to community diversity and facilitative promotion of species coexistence, and explore how the role of indirect facilitation varies with environmental severity. 5. Certain ecological modelling approaches (e.g. individual-based modelling), although thus far largely neglected, provide highly useful tools for exploring these fundamental processes. 6. Evolutionary responses might result from facilitative interactions, and consideration of facilitation might lead to re-assessment of the evolution of plant growth forms. 7. Improved understanding of facilitation processes has direct relevance for the development of tools for ecosystem restoration, and for improving our understanding of the response of plant species and communities to environmental change drivers. 8. Attempts to apply our developing ecological knowledge would benefit from explicit recognition of the potential role of facilitative plant-plant interactions in the design and interpretation of studies from the fields of restoration and global change ecology. 9. Synthesis: Plant facilitation research provides new insights into classic ecological theory and pressing environmental issues. Awareness and understanding of facilitation should be part of the basic ecological knowledge of all plant ecologists.
Wood represents the defining feature of forest systems, and often the carbon in woody debris has a long residence time. Globally, coarse dead wood contains 36–72 Pg C, and understanding what controls the fate of this C is important for predicting C cycle responses to global change. The fate of a piece of wood may include one or more of the following: microbial decomposition, combustion, consumption by insects, and physical degradation. The probability of each fate is a function of both the abiotic environment and the wood traits of the species. The wood produced by different species varies substantially in chemical, micro- and macro-morphological traits; many of these characteristics of living species have ‘afterlife’ effects on the fate and turnover rate of dead wood. The colonization of dead wood by microbes and their activity depends on a large suite of wood chemical and anatomical traits, as well as whole-plant traits such as stem-diameter distributions. Fire consumption is driven by a slightly narrower range of traits with little dependence on wood anatomy. Wood turnover due to insects mainly depends on wood density and secondary chemistry. Physical degradation is a relatively minor loss pathway for most systems, which depends on wood chemistry and environmental conditions. We conclude that information about the traits of woody plants could be extremely useful for modeling and predicting rates of wood turnover across ecosystems. We demonstrate how this trait-based approach is currently limited by oversimplified treatment of dead wood pools in several leading global C models and by a lack of quantitative empirical data linking woody plant traits with the probability and rate of each turnover pathway. Explicitly including plant traits and woody debris pools in global vegetation climate models would improve predictions of wood turnover and its feedback to climate.
Experimental evidence for positive interactions, or facilitation, among plants has increased markedly during the last 10 years.
Experiments documenting facilitation have been conducted in many diverse ecological systems, which suggests that positive
interactions may be fundamental processes in plant communities. Here, I review the evidence for facilitation, the mechanisms
by which facilitation operates, and the effects facilitation has on community structure. Facilitative mechanisms may act simultaneously
with resource competition or allelopathy, and the overall effect of one species on another may be the product of multiple,
complex interactions. Positive interactions may also determine community spatial patterns, permit coexistence, enhance diversity
and productivity, and drive community dynamics. Once viewed as anecdotal and idiosyncratic, facilitation is now contributing
to a more complete understanding of community structure and dynamics.
The role of lignin as a physical defence against Dendroctonus micans was investigated in laboratory feeding experiments. The effect of lignin is dose-dependent, reducing larval survival, growth rate, and weight, as well as affecting gallery construction. Adults lay fewer eggs in lignified bark and also tend to construct abnormal galleries. The distribution of lignin in trees suggests a role in defence against bark beetles that feed in the thicker bark on the lower bole.
In the mainland Nordic countries and the Baltic States, the delineation and set-aside of woodland key habitats (WKHs) has been one important approach to conserving biodiversity outside traditional protected areas. Though the specifics of the key habitat concept differ from country to country, the intent is to set aside forest areas that (1) exhibit a low degree of exploitation, (2) host or potentially host red-listed species, and/or (3) contain old-growth characteristics (e.g. dead wood, large old trees) or other qualities considered valuable for maintaining biodiversity. However, it is still uncertain to what extent WKHs actually retain quantities and qualities of coarse woody debris (CWD) that are characteristic of old-growth forests. The Biodiversity Monitoring Programme (BMP) recently conducted a detailed inventory of 491 WKHs across Sweden, providing a large dataset with which to evaluate the effectiveness of the WKH program with respect to CWD. In the present study we analyze the BMP data and compare CWD volume and composition between WKHs, mature managed (stand age 81–120 years), overmature managed (age 121–140 years), and published findings from old-growth forests. The national average volume of CWD (standing and downed combined, m3/ha) was higher in WKHs (19.5) than the mature managed (9.3) and the overmature managed forest (12.2), yet was markedly lower than that reported from old-growth forests. CWD volumes in spruce-dominated WKHs had been reduced by 50–63% in the southern and middle boreal regions to 43–64% in the northern boreal region when compared to old-growth forests. In general, CWD amount, variability and quality were greater within WKHs in the boreal regions as opposed to the nemoral and boreonemoral regions in the south of Sweden. The majority of the WKHs (64%) contained key elements (very large and/or decayed dead wood known to be crucial habitat for many threatened wood-dependent species). Considering that these structures are largely absent from managed forests, WKHs have better retained some of the important features of old-growth forests when compared to the surrounding managed forest. WKHs are therefore valuable habitats for dead wood dependent species and representative focal areas for continued and future forest restoration and landscape planning. Our results confirm that large sun-exposed and burned dead wood are underrepresented CWD components within WKHs and emphasize the need to broaden the WKH definition to include locations containing these structures.
Facilitation as a ubiquitous driver of biodiversity
- E J Mcintire
- A Fajardo
McIntire, E.J., Fajardo, A., 2014. Facilitation as a ubiquitous driver of biodiversity.
New Phytologist 201, 403e416.
Insects of Eastern Spruces, Fir and Hemlock
- A Rose
- O Lindquist
- P Syme
Rose, A., Lindquist, O., Syme, P., 1994. Insects of Eastern Spruces, Fir and Hemlock.
Canadian Forest Service, Ottawa, ON.
Verspreidingsatlas Nederlandse landpissebedden, duizendpoten en miljoenpoten (Isopoda, Chilopoda, Diplopoda) (EIS Nederland
- M P Berg
- M Soesbergen
- D Tempelman
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