Aboveground macrodetritivores and belowground soil processes: Insights on species redundancy

The literature pertaining to N immobilization indicates that ammonium is immobilized in preference to nitrate. Our previous research in an alkaline clay soil has indicated substantial immobilization of nitrate. To verify the preference for immobilization of nitrate or ammonium by the microbial biomass in this and other soil types, the immobilization of ammonium and nitrate from applications of ammonium sulfate and potassium nitrate following the addition of cotton crop stubble was monitored in six soils. The preference for ammonium or nitrate immobilization was highly correlated with each soil's pH, C/N ratio and its nitrification capacity. Nitrate was immobilized in preference to ammonium in neutral and alkaline soils; ammonium was preferentially immobilized in acid soils. No assimilation of nitrate (or nitrification) occurred in the most acid soil. Similarly, little assimilation of ammonium occurred in the most alkaline soil. Two physiological pathways, the nitrate assimilation pathway and the ammonium assimilation pathway, appear to operate concurrently; the dominance of one pathway over the other is indicated by soil pH. The addition of a nitrification inhibitor to an alkaline soil enhanced the immobilization of ammonium. Recovery of 15N confirmed that N was not denitrified, but was biologically immobilized. The immobilization of 1 5 ~ and the apparent immobilization of N were similar in magnitude. The identification of preferential nitrate immobilization has profound biological significance for the cycling of N in alkaline soils.

Changes of isopod assemblages along an urban–suburban–rural gradient in Hungary

In the Carei Plain natural reserve we identified 15 terrestrial isopod species: Haplophthalmus mengii, Haplophthalmus danicus, Hyloniscus riparius, Hyloniscus transsylvanicus, Plathyarthrus hoffmannseggii, Cylisticus convexus, Porcellionides pruinosus, Protracheoniscus politus, Trachelipus arcuatus, Trachelipus nodulosus, Trachelipus rathkii, Porcellium collicola, Porcellio scaber, Armadillidium vulgare and Armadillidium versicolor. The highest species diversity is found in wetlands, while the lowest is in plantations and forests. On the Carei Plain, there are some terrestrial isopods that are normally connected with higher altitudes. Moreover, some sylvan species are present in the open wetlands. Unlike marshes, sand dunes present anthropophilic and invasive species. The diversity of the terrestrial isopods from the Carei Plain protected area is high due to the habitats? diversity and the history of this area. Thus, the composition of the terrestrial isopod communities from the area underlines its distinct particularities, emphasizing the necessity of preserving the natural habitats.

The humidity reactions of Oniscus asellus, Porcellio scaber and Armadillidium vulgare have been analysed and compared. The mechanism whereby the three species collect in moist air is twofold, Consisting of (a) hygrokinesis, or decrease in activity and speed in moist air, and (b) of more frequent turnings in space, retaining them in the areas of greater humidity. These mechanisms are most clearly expressed in Oniscus asellus and least in Armadillidium vulgare. This sequence may be correlated with the resistance to desiccation of the three species, which is greatest in Armadillidium vulgare, and greater in Porcellio scaber than in Oniscus asellus. It is suggested that the humidity reactions of isopods are controlled by water loss by evaporation from the whole body. A correlation between hygrokinesis and thigmokinesis was observed in Porcellio scaber. There appears to be a reversal from negative to positive phototaxis in Oniscus asellus, correlated with the water loss by evaporation. The humidity reactions, low thigmokinesis and negative phototaxis combine to retain the isopods in damp, dark habitats.

Microbial nitrogen (N) immobilization, which typically results in soil N retention but based on the balance of gross N immobilization over gross N production, affects the fate of the anthropogenic reactive N. However, global patterns and drivers of soil gross immobilization of ammonium (INH4 ) and nitrate (INO3 ) are still only tentatively known. Here, we provide a comprehensive analysis considering gross N production rates, soil properties, and climate and their interactions for a deeper understanding of the patterns and drivers of INH4 and INO3 . By compiling and analyzing 1966 observations from 274 15 N-labelled studies, we found a global average of INH4 and INO3 of 7.41 ± 0.72 and 2.03 ± 0.30 mg N kg-1 day-1 with a ratio of INO3 to INH4 (INO3 :INH4 ) of 0.79 ± 0.11. Soil INH4 and INO3 increased with increasing soil gross N mineralization (GNM) and nitrification (GN), microbial biomass, organic carbon, and total N and decreasing soil bulk density. Our analysis revealed that GNM and GN were the main stimulators for INH4 and INO3 , respectively. The structural equation modeling showed that higher soil microbial biomass, total N, pH, and precipitation stimulate INH4 and INO3 through enhancing GNM and GN. However, higher temperature and soil bulk density suppress INH4 and INO3 by reducing microbial biomass and total N. Soil INH4 varied with terrestrial ecosystems, being greater in grasslands and forests, which have higher rates of GNM, than in croplands. The highest INO3 :INH4 was observed in croplands, which had higher rates of GN. The global average of GN to INH4 was 2.86 ± 0.31, manifesting a high potential risk of N loss. We highlight that anthropogenic activities that influence soil properties and gross N production rates likely interact with future climate changes and land uses to affect soil N immobilization and, eventually, the fate of the anthropogenic reactive N.

It has been documented that some species of terrestrial isopods in the genera Porcellio and Armadillidium engage in turn alternation (TA) to maintain a straight path while exploring new terrains, escaping inhospitable conditions, or avoiding predators. Within Porcellio, such studies are most often conducted with Porcellio scaber (Latreille, 1804) or Porcellio laevis (Latreille, 1804), leaving the extent of TA in other species of Porcellio unexplored. Consequently, TA behavior is often assumed in other genera of isopods, despite the lack of documentation. Therefore, the current study investigated TA in Porcellio spinicornis (Say, 1818) and Trachelipus rathkii (Brandt, 1833) using a commonly employed multiple T-maze. Both P. spinicornis and T. rathkii were found to TA at frequencies significantly above random chance. The data also showed a marginal interaction between group and sex, such that T. rathkii females, but not males, and P. spinicornis males, but not females, significantly TA. The current study provides the first documentation of TA in Porcellio spinicornis and extends this behavior to the genus Trachelipus - broadening our understanding of TA behavior across isopod taxa. Furthermore, the data suggests that TA may follow a pattern of sex-specific selection that could differ among species of terrestrial isopods. Further studies on TA across a broader range of isopod species and genera may reveal important ecological and evolutionary patterns.

Soil gross nitrogen (N) transformations are crucial for assessing forest N status. Although there is evidence suggesting that the N cycle is open in the karst forest, southwest China, process‐based investigation of gross soil N transformations is limited. In the current study, gross soil N transformations were investigated using 15N isotope dilution and 15N tracer techniques in a typical karst forest with calcareous soil (Calcareous lithosols) in comparison with an adjacent nonkarst forest with red soil (Haplic acrisol).The gross rates of N mineralization, nitrification, dissimilatory nitrate reduction to ammonium (DNRA), and nitrate immobilization were significantly greater in the karst forest. Ammonium immobilization was comparable to gross N mineralization, so that ammonium could be efficiently conserved in the nonkarst forest. Meanwhile, the produced nitrate was mostly retained via DNRA and nitrate immobilization. This resulted in a negligible net nitrate production in the nonkarst forest. In contrast, ammonium immobilization rate only accounted for half of gross N mineralization rate in the karst forest. The nitrate retention capacity is relatively low, with 41.6 ± 4.2% of the produced nitrate being retained via DNRA and nitrate immobilization. Due to relatively low nitrate retention capacity, nitrate was accumulated in the karst forest soil. Our results indicate that the nonkarst forest with red soil holds a very conservative N cycle, but the N cycle in the karst forest is leaky.

A survey between 2004 and 2010 yielded 2434 individuals of seven terrestrial isopod species – Cylisticus convexus, Oniscus asellus, Trachelipus rathkii, Porcellio scaber, Porcellio spinicornis, Porcellium conspersum, along Ligidium hypnorum – along the Curonian Spit and in various woodlands in Lithuania. The data on the Lithuanian fauna of all terrestrial isopods are presented for the first time. Isopod richness was the highest in woody habitats (dune pine forests and old mixed forests) where common European and Holarctic species (O. asellus, P. scaber, and T. rathkii) formed the majority of isopod assemblages. Additionally, more specialized isopods (L. hypnorum, P. conspersum) were also found in mixed and deciduous forests. Porcellio scaber and T. rathkii, the species tolerating human and natural disturbances, were the only isopods found in sand dunes at the coast. The article includes a detailed list of Isopoda occurrences and the numbers of individuals captured. 2004–2010 metais Kursių nerijoje ir įvai...

The abundance of terrestrial isopods (Isopoda: Oniscidea) was evaluated along an urban-suburban-rural gradient. We tested two hypotheses regarding the response of species: (i) habitat specialist hypothesis, according to which the abundance of the forest specialists would increase, while the abundance of the urban environment specialist isopods would decrease along the urban-rural gradient, and (ii) opportunistic species hypothesis (abundance of the generalist species would increase by increasing level of urbanization). The abundance of the forest specialist isopod Trachelipus ratzeburgii increased significantly along the studied gradient. An opposite tendency was observed for the abundance of the urban environment specialist isopod Porcellio scaber, as it was significantly higher in the urban area than in the suburban and rural sites. One generalist species (Trachelipus rathkii) gained dominance in the urban area, while other two generalists (Armadillidium vulgare and Porcellium collicola) showed no significant changes in abundance along the gradient.

This study aimed to resolve the taxonomy of cassid gastropods from the upper Eocene Ocala Limestone based on specimens collected from Florida Museum of Natural History locality AL004. In 1890, Dall described a specimen from this formation, collected in a nearby county as Phalium globosum (subfamily Phaliinae). However, further collection of cassids from AL004 suggested the presence of more than one morphologically distinct taxon. Eocene cassids are particularly interesting because that is presumably the time when cassids experienced rapid diversification, which has implications for the evolutionary history of echinoid-cassid predator–prey interactions. Based on 75 specimens from AL004, it appears that the specimens interpreted as belonging to two or more morphologically distinct taxa are more likely members of a single species with extreme morphological variability, redescribed here as Semicassis globosum. Results of morphometric analyses using nine qualitatively defined cassid morphotaxa (subfamily Phaliinae) suggest that S. globosum is characterised by high intraspecific variability in shell morphology that may reflect high ecophenotypic variability or elevated intraspecific genetic variability. This study highlights the challenges associated with delineating species status using low numbers of specimens, as a dearth of diagnostic material may lead to taxonomic “over-splitting,” thereby resulting in an inflated estimate of biodiversity.

Soil gross mineral N production and consumption processes are crucial regulators of plant productivity and N loss from croplands. Substituting synthetic fertilizers by integrating legumes in cultivation systems is common in organic farming, but research on its long-term impact on dynamics of gross soil N transformation and associated environmental N loss is scarce. In particular, studies at a temporal resolution that allows for a mechanistic understanding of long-term effects of organic farming are missing. Therefore, we determined gross N turnover rates of ammonification, nitrification, and ammonium and nitrate immobilization at monthly temporal resolution during a full green rye-maize cropping sequence. Measurements were carried out at sites with same pedo-climatic background but organic farming (OF) and integrated farming (IF) history. During green rye growing, N turnover rates for OF and IF were low and not significantly different, likely owing to low temperatures. During silage maize growing, IF exhibited significantly higher average N turnover rates of 1.86, 4.46, and 5.57 mg N kg⁻1 dry soil d⁻1 for gross ammonification, ammonium immobilization, and nitrate immobilization, respectively, compared to OF values of 1.11, 1.80, and 2.90 mg N kg⁻1 dry soil d⁻1. The significantly higher N turnover rates were likely due to higher soil organic C, N and microbial biomass which result from different long-term management practices. Especially the increased immobilization potential on the IF site contributed to significantly lower area-scaled N₂O emissions (1.45 vs. 4.36 kg N ha⁻1) during periods of high nitrification. This shows that for low SOC soils, integrated farming history with high C return enhances soil N cycling and reduces the risk of N losses in the form of N2O emission.

Nitrogen (N) is an important nutrient for re-vegetation during ecosystem restoration, but the effects of cover restoration on soil N transformations are not fully understood. This study was conducted to investigate N transformations in soils with different cover restoration ages in Eastern China. Soil samples were collected from four degraded and subsequently restored lands with restoration ages of 7, 17, 23, and 35 years along with an adjacent control of degraded land. A 15N tracing technique was used to quantify gross N transformation rates. Compared with degraded land, soil organic carbon (SOC) and total N (TN) increased by 1.60–3.97 and 2.49–5.36 times in restoration land. Cover restoration increased ammonium and nitrate immobilization, and dissimilatory nitrate reduction to ammonium (DNRA) by 0.56–0.96, 0.34–2.10, and 0.79–3.45 times, respectively, indicating that restoration was beneficial for N retention. There were positive correlations between SOC content and ammonium and nitrate immobilization and DNRA, indicating that the increase in soil N retention capacity may be ascribed to increasing SOC concentrations. The stimulating effect of SOC on ammonium immobilization was greater than its effect on organic N mineralization, so while SOC and TN increased, inorganic N supply did not increase. Autotrophic and heterotrophic nitrification increased with increasing SOC and TN concentrations. Notably, heterotrophic nitrification was an important source of NO3−−N production, accounting for 47–67% of NO3−−N production among all restoration ages. The capacity of N retention was improved by cover restoration, leading to an increase in soil organic carbon and total N over time, but inorganic N supply capacity did not change with cover restoration age.

The influence of microclimate on foraging and sheltering behaviours of terrestrial isopods: Implications for soil carbon dynamics under climate change

The present study contains the results of a study on terrestrial isopod (Crustacea: Isopoda: Oniscidea) samples collected by pitfall traps from five different habitats during four different months in different seasons (late spring, early summer, early autumn, and late autumn) during 2012. All sampling plots were located in Kaunas city. As a result, three species were identified: Trachelipus rathkii (Brandt, 1833), Porcellio scaber (Latreille, 1804), and Oniscus asellus (Linnaeus, 1758). All species found had previously been known from Lithuania. T. rathkii, a eurytopic species, dominated in all studied habitats. Low species richness and diversity might be due to a selective nature of the sampling method. Abundance (surface activity) showed a seasonal pattern. The sample size of the superdominant T. rathkii allowed calculating a temporal sex ratio for this species: females dominated in all habitats and in almost all periods.

Since any given trait of an organism is considered to represent either an adaptation to the environment or a phylogenetic constraint, most physiological gut characteristics should be adaptive in terms of optimizing digestion and utilization of the respective food source. Among the Crustacea, the taxon Oniscidea (Isopoda) is the only suborder that includes, and essentially consists of, species inhabiting terrestrial environments, feeding on food sources different from those of most other Crustacea (i.e., terrestrial leaf litter). Microelectrodes were used to assay physiological characteristics of the gut lumen from representatives of four families of terrestrial isopods: Trichoniscus pusillus (Trichoniscidae), Oniscus asellus (Oniscidae), Porcellio scaber (Porcellionidae), and Trachelipus rathkii (Trachelipodidae). Microsensor measurements of oxygen pressure (Clark-type oxygen microelectrodes) revealed that O2-consuming processes inside the gut lumen created steep radial oxygen gradients. Although all guts were oxic in the periphery, the radial center of the posterior hindgut was micro-oxic or even anoxic in the adults of the larger species. The entire gut lumen of all examined species was strongly oxidizing (Pt microelectrodes; apparent redox potential, Eh: +600-700 mV). Such conditions would allow for the coexistence of aerobic and anaerobic microorganisms, with both oxidative and fermentative activities contributing to digestion. Although bacterial O2 consumption was also observed in the midgut glands (hepatopancreas), they remained entirely oxic, probably owing to their large surface-to-volume ratio and high oxygen fluxes across the hepatopancreatic epithelium into the gland lumen. Measurements with pH microelectrodes (LIX-type) showed a slight pH gradient from acidic conditions in the anterior hindgut to neutral conditions in the posterior hindgut of O. asellus, P. scaber and T. rathkii. By contrast, the pH in the hindgut lumen of T. pusillus was almost constant. We discuss to what extent these physiological characteristics may be adaptive to the digestion of terrestrial food sources that are rich in lignocellulose.