Decomposable Groups Research Articles

Characteristic modules and Gorenstein (co-)homological dimension of groups

In this paper, we examine the Gorenstein dimension of modules over the group algebra kG of a group G with coefficients in a commutative ring k. As a Gorenstein analogue of the classical case, we bound this dimension in terms of the Gorenstein dimension of the underlying k-module and the Gorenstein dimension of G over k. Our method is based on the notion of a characteristic module for G, introduced by the second author, and uses the stability properties of the Gorenstein categories. We also examine the class of hierarchically decomposable groups defined by Kropholler and use the module of bounded Z-valued functions on such a group G to characterize the Gorenstein flat ZG-modules, in terms of flat modules, and the Gorenstein injective ZG-modules, in terms of injective modules (by complete analogy with the characterization of Gorenstein projective ZG-modules, in terms of projective modules, obtained by Dembegioti and the second author). It follows that, for a group G in Kropholler's class, (a) any Gorenstein projective ZG-module is Gorenstein flat and (b) a ZG-module is Gorenstein flat if its Pontryagin dual module is Gorenstein injective.

Plant invasion down under: exploring the below-ground impact of invasive plant species on soil properties and invertebrate communities in the Central Plateau of New Zealand

AbstractThe impacts of invasive plants on arthropod communities are often reported to be negative and have predominantly been explored aboveground, but there is a paucity of information regarding what happens belowground. To address this gap, we compared soil properties and soil fauna communities associated with two native plant species (Leptospermum scoparium—mānuka and Chionochloa rubra—red tussock) and two invasive species (non-N-fixing Calluna vulgaris—European heather and N-fixing Cytisus scoparius—Scotch broom) in the Central Plateau of New Zealand. We expected that (1) at individual plant level soil properties would be different under invasive and native plant species, with higher soil nutrient concentrations under invasive species, especially N-fixing broom; (2) total abundance of soil fauna would be higher under invasive plant species, as generally positive impact of invasive plants on soil invertebrates is indicated in the literature; (3) invasive plants, and especially N-fixing broom, will be associated with greater abundances of soil decomposer groups. We found that soil properties and soil fauna assemblages did not cluster by plant invasive status as initially predicted. At individual plant level, there was similarity in soil conditions between mānuka and broom, and between red tussock and heather. The invasive N-fixer (broom) had positive effects on soil N availability, with higher N pool and lower C/N ratio in soil under this species. There were no consistent differences in total soil fauna abundance between invasive and native plants. Broom and mānuka were associated with higher abundances of Collembola, Oligochaeta and Diplopoda; heather and red tussock had higher abundances of Hymenoptera and Hemiptera. Significantly more Oligochaeta and Collembola under broom matched the prediction of invasive plants (and especially N-fixing invasives) being associated with greater abundances of decomposers. However, another important decomposer group—oribatid mites—did not show the same tendency. These results evidence that simplified generalizations regarding the impacts of invasive plants are unlikely to be justified, since the ecological effects of plant invasions are complex and do not always follow the same pattern. Therefore, we need to take into consideration the ecological context and the traits of individual plant species and target organisms in an unbiased manner to fully understand the impacts of plant invasions.

Molecular phylogeny and morphology reveal a new Hymenochaete species (Hymenochaetaceae, Basidiomycota) from China

Wood-inhabiting fungi play an essential role in forest ecosystems as an important group of decomposers, which are found in living trees, dead standing trees, decorticated trunks, fallen branches, as well as manufactured wood. A new wood-inhabiting fungus Hymenochaete sinensis, belonging to the family Hymenochaetaceae, is described and illustrated based on the morphological characteristics and molecular data. Hymenochaete sinensis sp. nov. is characterized by annual, resupinate basidiomata with aurantium to coconut brown to brownish black hymenial surface, a monomitic hyphal system having the simple-septate with distinctly thick-walled generative hyphae, and ellipsoid to broadly ellipsoid basidiospores measuring as 4–5 × 2.5–3.5 µm. The phylogenetic analyses based on ITS+nLSU rDNA sequences confirmed that the new species belongs to the genus Hymenochaete. The ITS phylogenetic tree revealed that the new taxon is closely related to species of Hymenochaete longispora and H. quercicola.

Relationships between almost completely decomposable abelian groups and their multiplication groups

Let [Formula: see text] be the class of Abelian block-rigid almost completely decomposable groups of ring type with cyclic regulator quotient. In this paper, we study relationships between the above groups [Formula: see text] and their multiplication groups Mult [Formula: see text]. It is proved that groups from [Formula: see text] are determined by their multiplication groups. For a rigid group [Formula: see text], the isomorphism problem is solved: we describe multiplications from [Formula: see text] that define isomorphic rings on [Formula: see text]. We also describe Abelian groups that are realized as the multiplication group of some group in [Formula: see text]. We describe groups in [Formula: see text] that are isomorphic to their multiplication groups.

Are there different trophic niches of enchytraeids? A stable isotopic (δ13C, δ15N) evidence

Enchytraeids, also known as pot worms, represent one of the least studied groups of soil mesofauna. These organisms can be found throughout the globe from coasts to deserts reaching high densities and biomass, but their specific roles within the soil food web remain a stark knowledge gap. Enchytraeid species are involved in belowground trophic interactions, which could be distinguished by their morphological characteristics and ecological traits. To quantify this, we analyzed stable isotopes δ13C and δ15N in 16 enchytraeid species across various biomes and habitats in European Russia. Their isotopic niches were compared with different potential food sources and other soil invertebrates. We found that the total δ13C and δ15N range by across single enchytraeid samples reached 8 and 11‰, and isotopic niche of species depends on soil stratification and is reflected in the chaeta number per bundle, and, to a lesser extent, on the size or genera identity. These findings enabled us to split enchytraeids into three guilds within the functional group of secondary decomposers: (i) epigeic – that include litter-dwelling species that predominantly feed on plant material but also can ingest microorganisms; (ii) epi-endogeic – inhabiting upper humified soil and F-litter horizons, and feed primarily on various saprotrophic microorganisms; (iii) endogeic – consuming old processed humified and dissolved organic matter in lower H-horizon and even mineral A-horizons beneath. Our results are an important step forward in integrating enchytraeids into the next-generation food web models, not as a single black box, but as multiple blocks delivering different functions.

Enchytraeids in imported soil and organic deposits in Pyramiden, an abandoned mining town on Spitsbergen in the High Arctic

In Arctic soils, potworms (Clitellata: Enchytraeidae) are a particularly important decomposer group. There are relatively many faunistic records from the Svalbard archipelago, in particular its main island Spitsbergen, but few ecological studies on enchytraeids. With climate change and increasing tourism, the introduction and subsequent spreading of exotic species might pose a threat to native biotic communities. In Pyramiden, a Russian (formerly Soviet) coal mining settlement on Spitsbergen abandoned in 1998, Chernozem soil from southern Russia or Ukraine had been imported in 1983 to create lawns. Today the long central lawn presents an environmental gradient: on one end rather shallow humus-rich soil is fertilized by a sea bird colony on an adjacent building, the central part has a rich organic horizon topping humus-rich mineral soil, whereas on the other end humus-rich soil is covered by deposited mineral soil. In August 2018, we sampled this gradient to study the enchytraeid assemblage. Additional samples were also taken within frames with a vigorous grass turf in front of residential houses and in a vegetated heap of decomposing organic material (mostly woodchips). The objectives were to see (1) if and how the differences between habitats would be reflected by changes of the enchytraeid assemblages and (2) if there were any potentially introduced species. Almost 3700 specimens were identified and 9 species were recorded, which is high for habitats of the High Arctic. One species, Enchytraeus buchholzi s.l., had been recorded before in the archipelago only once, also in imported soil. This small-bodied euryoecious r-strategist is abundant in agricultural and other disturbed soils. Molecular barcoding and comparison with sequences from Central Europe showed close resemblance to several specimens, which makes an introduction with the transferred Chernozem highly probable. Most enchytraeids were concentrated in the upper 3 cm of soil (even if mineral), only in the organic deposits vertical distribution was rather even down to 12 cm depth. Numbers in the organic deposits were exceedingly high (ca 417,000 individuals/m2) and E. buchholzi s.l. represented ca 90 % of all specimens. Ordination (NMDS) showed all habitats to host rather distinct assemblages. Spearman's rank correlation showed significant positive correlation of species richness with conductivity and total nitrogen and of abundance with phosphorous and potassium contents in aqueous solution.

Isothiazolinone inhibition of soil microbial activity persists despite biocide dissipation

Soil microbial growth and activity are generally assumed to recover rapidly after dissipation of organic toxicants. We studied the effects of four readily degradable isothiazolinone biocides (benzisothiazolinone, BIT; methylisothiazolinone, MIT; octylisothiazolinone, OIT; 4,5-dichloro-2-octyl-isothiazolinone, DCOIT) on bacterial growth, fungal growth, basal respiration, and substrate-induced respiration in controlled soil microcosm experiments. Bacterial growth followed by fungal growth were the two most sensitive endpoints during the first two days. Significant dissipation of biocides occurred within just 8 h and 94–100% had dissipated after 40 days except for DCOIT tested at a high concentration (50 mg kg−1, 54% remaining after 40 d). Despite biocide dissipation, all isothiazolinones inhibited bacterial growth for >7 days, whereas fungal growth and substrate-induced respiration were inhibited for up to 40 days. Bacterial growth recovery after 40 days was linked to development of bacterial community tolerance for DCOIT, but not for the other less persistent isothiazolinones. Our study is the first to report on toxic effects of isothiazolinones on soil microbial growth and demonstrates that inhibitory effects of isothiazolinones on soil microbial growth and activity (especially fungal growth and substrate-induced respiration) persisted even long after biocide dissipation, indicating “legacy effects” and retarded recovery of soil microbial functions. We propose that retarded recovery of fungal, relative to bacterial, growth may be a general phenomenon during the dissipation of toxicants in contaminated soils and that it may be explained by intrinsic differences between bacterial and fungal biology in soil and by competitive interactions between these two dominant groups of soil microbial decomposers.

Macrofungal Diversity of Brahakshetra Community Forest, Ghorahi, Dang, Nepal

Fungi are a diverse group of organisms ranging from microscopic to macroscopic mushrooms. Being a major group of decomposers, they are essential for the survival of other organisms in the ecosystem and important for the degradation of organic matter. The main aim of this study was to study the macrofungal diversity of Brahakshetra Community Forest, Ghorahi, Dang. The forest is mainly dominated by Shorea robusta and other associated species. The study was made from June to September 2020. The sampling was done by using a 10×10m quadrate in a line transect and each plot was divided into 5×5m quadrats and samples were collected during the rainy season from different habitats of the forest. Mushrooms were photographed in their natural habitat and preserved in dry and liquid preservation. The specimens were identified by examining their macroscopic and microscopic features, and also by using references from standard literature and websites. In the study, a total of 66 species were recorded under 30 genera belonging to 21 families, and 8 orders. Among them, 65 belong to basidiomycetes and 1 belongs to Ascomycetes. Agaricales was found as the largest order followed by Russulales and Boletales. The diversity indices, the Shannon Weiner index and Simpson diversity index were found to be 3.59 and 0.93 respectively. The result of this study concludes that the Brahakshetra Community Forest was rich in macrofungal diversity, especially ectomycorrhizal. There were positive trends between species richness of macrofungi and environmental variables, i.e., tree canopy, soil pH, soil moisture, and leaf litter which means species increased with increasing these environmental variables.

Soil microbial resource limitation along a subarctic ecotone from birch forest to tundra heath

Soil microorganisms regulate the decomposition of organic matter. However, microbial activities can also be rate-limited by the resource in lowest supply. Arctic ecosystems are being exposed to pronounced climate warming, with arctic greening, treeline advance and shrubification resulting in increased plant-derived carbon (C) inputs to soils, and faster rates of decomposition releasing mineral nutrients, potentially shifting the limiting factor for microbial growth. Here we used a “space-for-time” approach across a subarctic ecotone (birch forest, tree line, shrub and tundra sites). N and P fertilization treatments were also applied in the field, to test whether changes in resource limitation could be induced through nutrient loading of soils. In these soils, we measured the responses of bacterial and fungal growth as well as soil respiration to full factorial additions of C, nitrogen (N) and phosphorus (P) (“limiting factor assays”: LFA) to infer how the limiting factor for microbial growth would be affected by future climate change. We found that bacteria were triple-limited by C, N and P, while fungi were co-limited by C and N, with no shift in the limiting factor for bacterial or fungal growth across the ecotone. However, bacterial responses to the LFA were stronger in the tundra, showing 9-fold stronger increases in response to LFA-CNP addition compared to that in the forest. In contrast, fungal responses to the LFA were stronger in the forest, showing a 120% higher growth in response to LFA-CN addition, with no detectable response to LFA-CN addition in the tundra. These contrasting results suggested competitive interactions for resources between the two decomposer groups. Fertilization in the field shifted the bacterial resource limitation, but had no effect on the limiting factor for fungal growth. Together, our findings suggest that resource limitations for soil microorganisms will not change due to future warming, but rather affect degrees of fungal-to-bacterial dominance.

Fully Inert Subgroups of Completely Decomposable Groups with Homogeneous Components of Finite Rank

Fully Inert Subgroups of Completely Decomposable Groups with Homogeneous Components of Finite Rank

A trait-based framework for dung beetle functional ecology.

Traits are key for understanding the environmental responses and ecological roles of organisms. Trait approaches to functional ecology are well established for plants, whereas consistent frameworks for animal groups are less developed. Here we suggest a framework for the study of the functional ecology of animals from a trait-based response-effect approach, using dung beetles as model system. Dung beetles are a key group of decomposers that are important for many ecosystem processes. The lack of a trait-based framework tailored to this group has limited the use of traits in dung beetle functional ecology. We review which dung beetle traits respond to the environment and affect ecosystem processes, covering the wide range of spatial, temporal and biological scales at which they are involved. Dung beetles show trait-based responses to variation in temperature, water, soil properties, trophic resources, light, vegetation structure, competition, predation and parasitism. Dung beetles' influence on ecosystem processes includes trait-mediated effects on nutrient cycling, bioturbation, plant growth, seed dispersal, other dung-based organisms and parasite transmission, as well as some cases of pollination and predation. We identify 66 dung beetle traits that are either response or effect traits, or both, pertaining to six main categories: morphology, feeding, reproduction, physiology, activity and movement. Several traits pertain to more than one category, in particular dung relocation behaviour during nesting or feeding. We also identify 136 trait-response and 77 trait-effect relationships in dung beetles. No response to environmental stressors nor effect over ecological processes were related with traits of a single category. This highlights the interrelationship between the traits shaping body-plans, the multi-functionality of traits, and their role linking responses to the environment and effects on the ecosystem. Despite current developments in dung beetle functional ecology, many knowledge gaps remain, and there are biases towards certain traits, functions, taxonomic groups and regions. Our framework provides the foundations for the thorough development of trait-based dung beetle ecology. It also serves as an example framework for other taxa.

Drivers of community assembly change during succession in wood-decomposing beetle communities.

The patterns of successional change of decomposer communities is unique in that resource availability predictably decreases as decomposition proceeds. Saproxylic (i.e. deadwood-dependent) beetles are a highly diverse and functionally important decomposer group, and their community composition is affected by both deadwood characteristics and other environmental factors. Understanding how communities change with faunal succession through the decomposition process is important as this process influences terrestrial carbon dynamics. Here, we evaluate how beta-diversity of saproxylic beetle communities change with succession, as well as the effects of different major drivers of beta-diversity, such as deadwood tree species, spatial distance between locations, climate and forest structure. We studied spatial beta-diversity (i.e. dissimilarity of species composition between deadwood logs in the same year) of saproxylic beetle communities over 8 years of wood decomposition. Our study included 379 experimental deadwood logs comprising 13 different tree species in 30 forest stands in Germany. We hypothesized that the effects of tree species dissimilarity, measured by phylogenetic distance, and climate on beta-diversity decrease over time, while the effects of spatial distance between logs and forest structure increase. Observed beta-diversity of saproxylic beetle communities increased over time, whereas standardized effects sizes (SES; based on null models) of beta-diversity decreased indicating higher beta-diversity than expected during early years. Beta-diversity increased with increasing phylogenetic distance between tree species and spatial distance among regions, and to a lesser extent with spatial distance within regions and differences in climate and forest structure. Whereas effects of space, climate and forest structure were constant over time, the effect of phylogenetic distance decreased. Our results show that the strength of the different drivers of saproxylic beetle community beta-diversity changes along deadwood succession. Beta-diversity of early decay communities was strongly associated with differences among tree species. Although this effect decreased over time, beta-diversity remained high throughout succession. Possible explanations for this pattern include differences in decomposition rates and fungal communities between logs or the priority effect of early successional communities. Our results suggest that saproxylic beetle diversity can be enhanced by promoting forests with diverse tree communities and structures.

Decomposable groups with exactly two nonlinear non-faithful irreducible characters

In [Finite solvable groups with exactly two nonlinear non-faithful irreducible characters, J. Algebra Appl. 18(5) (2019) 1950091], the first author studied directly indecomposable, solvable groups with exactly two nonlinear non-faithful irreducible characters. In this paper, we study the decomposable case and give a classification of decomposable groups possessing exactly two nonlinear non-faithful irreducible characters. In particular, nilpotent groups with this property are also classified.

Faunistic analysis of longhorn beetles (Cerambycidae: Coleoptera) in Cerrado and Atlantic Forest areas: biodiversity hotspots of Brazil

ABSTRACT We analysed the diversity of Cerambycidae in three phytophysiognomies, one of Cerrado (cerradão) and two of Atlantic Forest (freshwater swamp forest and semideciduous seasonal forest) within the Municipal Botanical Garden of Bauru (central São Paulo State, Brazil), a relevant preservation area. Ceramybycidae, one of the most diverse beetle families, are important bioindicators due to their intimate relationship with their host plants. They have great ecological importance as one of the major groups of decomposers. Despite having a crucial role in forest ecosystems, detailed faunistic studies of the family are scarce. Sampling of adult Cerambycidae was conducted with malaise traps from October 2019 to September 2020. In total, we collected 69 species, mostly belonging to Cerambycinae and Lamiinae. Isomerida vittata (Pascoe, 1858) was the most abundant species. Species accumulation curves show sufficient sampling effort. We found higher abundances during the spring–summer period, indicating a seasonal distribution pattern. A comparison of species composition among the three areas showed that cerradão and semideciduous seasonal forest are more similar; a lower similarity was calculated between freshwater swamp forest and semideciduous seasonal forest. Diversity profiles show that the cerradão is the most diverse area and freshwater swamp forests have the highest evenness. Our study is one of the few survey studies of Cerambycidae in large remnant areas of the Cerrado and Atlantic Forest and provides primary data on this taxon which may help to develop future conservation policies.

Temporal diversity patterns for fungi and mites associated with decaying Sporobolus pumilus (Spartina patens) in the Minas Basin, Nova Scotia

Coastal salt marshes provide many ecosystem services; however, little is known of the biology of decomposer taxa in these systems. This study employed aboveground and belowground litterbags to characterize the fungal and mite communities associated with the dominant salt marsh grass, Sporobolus pumilus, in the Minas Basin, Nova Scotia. Decomposition rates of aboveground and belowground tissues and environmental variables were quantified to contextualize temporal patterns in community composition. Aboveground litterbag mass loss peaked in July and decreased consistently over succeeding months, which positively correlated with fungal richness. Fungal and mite richness displayed inverse relationships over time, with mites gradually increasing in diversity before peaking in November, suggesting the presence of a complex detrital network where mites and fungi respond to different and possibly unrelated environmental cues. This study offers a first look at temporal community dynamics of two neglected groups of decomposers associated with S. pumilus in Canada.

Определяемость вполне разложимой группы ранга 3 её группой автоморфизмов

In the work of Vildanov, Gaidak, and Timoshenko, all completely decomposable groups of rank 2 were found that are defined by their automorphism group in the class of all completely decomposable groups. In this article, a similar problem is solved for groups of rank 3. It is shown that a completely decomposable group of rank 3 is determined by its automorphism group if and only if it is a direct sum of three almost divisible summands of rank 1, two of which are isomorphic to each other and embed into the third . Contribution of the authors: the authors contributed equally to this article. The authors declare no conflicts of interests.

Вполне инертные подгруппы вполне разложимых групп, имеющие однородные компоненты конечного ранга

Вполне инертные подгруппы вполне разложимых групп, имеющие однородные компоненты конечного ранга

The contribution of insects to global forest deadwood decomposition.

The amount of carbon stored in deadwood is equivalent to about 8 per cent of the global forest carbon stocks1. The decomposition of deadwood is largely governed by climate2-5 with decomposer groups-such as microorganisms and insects-contributing to variations in the decomposition rates2,6,7. At the global scale, the contribution of insects to the decomposition of deadwood and carbon release remains poorly understood7. Here we present a field experiment of wood decomposition across 55 forest sites and 6 continents. We find that the deadwood decomposition rates increase with temperature, and the strongest temperature effect is found at high precipitation levels. Precipitation affects the decomposition rates negatively at low temperatures and positively at high temperatures. As a net effect-including the direct consumption by insects and indirect effects through interactions with microorganisms-insects accelerate the decomposition in tropical forests (3.9% median mass loss per year). In temperate and boreal forests, we find weak positive and negative effects with a median mass loss of 0.9 per cent and -0.1 per cent per year, respectively. Furthermore, we apply the experimentally derived decomposition function to a global map of deadwood carbon synthesized from empirical and remote-sensing data, obtaining an estimate of 10.9 ± 3.2 petagram of carbon per year released from deadwood globally, with 93 per cent originating from tropical forests. Globally, the net effect of insects may account for 29 per cent of the carbon flux from deadwood, which suggests a functional importance of insects in the decomposition of deadwood and the carbon cycle.

Using plant litter decomposition as an indicator of ecosystem response to soil contamination

The inventory and remediation of contaminated sites have emerged as top environmental priorities worldwide. A large body of evidence has accumulated to show how soil contamination affects biological communities and ecological processes. This knowledge has yet to be used for the development of indicators of soil quality that are meaningful to end-users and are easy to implement in soil quality assessment schemes. In this study, we used quantifiable measures of litter decomposition, a key biophysical process, as indicators of the ecological impact of soil contamination by trace metals and hydrocarbons. We conducted a litterbag experiment with coarse and fine mesh bags to compare highly vs. minimally contaminated sites within eight locations representative of a wide array of environmental conditions and types of pollution. Contrary to the common assumption that soil contamination hampers soil functions, idiosyncratic responses were detected for litter decomposition rate and decomposer activity metrics. A negative relationship between detritivore and microbial responses to soil contamination indicates that wherever the activity of one group of decomposers is reduced, increase in activity of the other group may ensure litter decomposition to proceed at rate similar or higher than baseline rate. This finding may indicate that compensatory dynamics in soil communities is important in determining ecosystem stability against chemical stressors. As litter decomposition may inform on the capacity of terrestrial ecosystems to cope with soil contamination, it may be a useful complement to chemical soil analyses in routine soil quality assessment schemes.

Root presence modifies the long‐term decomposition dynamics of fungal necromass and the associated microbial communities in a boreal forest

Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated β-glucosidase activity was highest at 6months, while leucine aminopeptidase peptidase was highest at 18months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal necromass decomposition, but resulted in higher amounts of fungal necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial necromass turnover with time.