2023 Issues

Birgit Lang, Bibiana Betancur-Corredor & David J. Russell

 

Abstract

Soil organisms and their interactions play a key role in various ecosystem processes and functions, such as the provision of nutrients. The main actors in nitrogen transformation processes are microorganisms, but earthworms affect these processes as their activity results in changes of the microhabitat and microbial community. Studies have shown that nitrogen content is higher in earthworm casts than in bulk soil, and that earthworm invasion affects soil mineral nitrogen. However, we still lack a quantitative synthesis of earthworm effects on soil nitrogen in bulk soil that integrates the influence of potential controlling factors (i.e., soil properties, climatic conditions and experimental parameters). Here, we investigated the impact of earthworms on soil ammonium (NH₄⁺), nitrate (NO₃^–) and total mineral nitrogen (ammonium + nitrate, N_min) using meta-analytic techniques. Earthworms generally increased NO₃^– (+ 88%) and N_min (+ 63%), but did not affect NH₄⁺. We assume that earthworms affect total mineral nitrogen mainly by their impact on NO₃^–. Endogeic and epigeic earthworms significantly increased NO₃^– and N_min, whereas no clear effect of anecic earthworms was found. This result is presumably caused by diverse effects of the different ecological groups on the microbial community composition. Our results for mixed ecological groups (i.e., anecic + endogeic earthworms) reveal potentially antagonistic effects of ecological groups. The impact of earthworm presence on NO₃^– and N_min increased when experiments lasted longer than one week. The effect of earthworms on NH₄⁺, NO₃^– or N_min was not influenced by earthworm abundance and biomass, soil organic carbon, soil C/N ratio, litter C/N ratio, the initial amount of NH₄⁺, NO₃^– or N_min, total soil nitrogen or temperature. However, as data availability or replication across factor categories was low for some of these moderators, the non-significant results should be interpreted with caution. Also, we could not investigate interactions among the controlling factors due to paucity of data. Our study thus reveals important knowledge gaps regarding earthworm effects on soil nitrogen. Overall, our results highlight the importance of earthworms for soil nitrogen cycling and strengthen the call for soil-functional models to incorporate soil faunal effects.

Keywords
Ecological groups | inorganic nitrogen | mineralization | nitrogen cycle | soil functions

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DOI 10.25674/so95iss1id308

Tobias Mainda

 

Abstract

A new species of the genus Megalopinus Eichelbaum, 1915 from the Huachuca Mountains in Arizona, U.S.A., Megalopinus lingafelteri spec. nov., is described and illustrated. It is the northernmost member of the Megalopinus peploides (Sharp, 1886) species group. Its habitat is illustrated, comparing it to presumptive closely related species.

Keywords
Rove beetles | new species | Huachuca Mountains | Madrean region | biodiversity

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DOI 10.25674/so95iss1id309

Johannes Frisch & Raden Pramesa Narakusumo

 

Abstract

This contribution deals with the genus Scopaeus Erichson, 1839 (Coleoptera, Staphylinidae, Paederinae) in Indonesia with a focus on the fauna of the Mount Halimun-Salak National Park, Jawa Barat. Nineteen new species are described: Scopaeus anuliflagellatus Frisch, spec. nov., S. batukaruensis Frisch, spec. nov., S. bipectenatus Frisch, spec. nov., S. bipennicillatus Frisch, spec. nov., S. crassipunctatus Frisch, spec. nov., S. cuspidatus Frisch, spec. nov., S. cuspilobatus Frisch, spec. nov., S. diversilobatus Frisch, spec. nov., S. grandis Frisch, spec. nov., S. halimunsalakensis Frisch, spec. nov., S. heronifer Frisch, spec. nov., S. posoanus Frisch, spec. nov., S. pulcher Frisch, spec. nov., S. riedeli Frisch, spec. nov., S. spiraliflagellatus Frisch, spec. nov., S. sulawesianus Frisch, spec. nov., S. tortuosiflagellatus Frisch, spec. nov., S. uncinatus Frisch, spec. nov. and S. velifer Frisch, spec. nov.. Based on type revisions, S. borneensis Cameron, 1941, S. elegantulus Cameron, 1930, S. jacobsoni Cameron, 1930, S. javanus Cameron, 1936, S. mixtus Cameron, 1941 and S. niger Cameron, 1918 are redescribed. Lectotypes are designated for S. javanus and S. niger. New distribution data from Indonesia are presented for S. filiformis Wollaston, 1867, S. limbatus Kraatz, 1859, S. nitidulus Motschulsky, 1858, S. sundaensis Frisch, 2005, S. testaceus Motschulsky, 1858, S. unifasciatus Fauvel, 1889 and S. wunderlei Frisch, 2003. Scopaeus dilutus Motschulsky, 1858, S. fusculus Motschulsky, 1858, S. micros Kraatz, 1859, S. procerus Kraatz, 1859, S. subfasciatus Kraatz, 1859 and S. velutinus Motschulsky, 1858 are excluded from the fauna of Indonesia owing to unproven records or misidentification. A catalogue of the Scopaeus species of Indonesia including their known distribution at the province level is given.

Keywords
Taxonomy | distribution | Java | Sulawesi | Halimun-Salak National Park

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DOI 10.25674/so95iss1id311

Léa Rosine Djoussi Nde, Elias Nchiwan Nukenine & Hartmut Koehler

 

Abstract

Soil degradation and desertification negatively affect agricultural productivity. It affects 46 % of Africa’s land area, where agriculture sustains over 50 % of the economy in many countries. Microarthropod communities’ abundance and composition are important components for soil health and quality assessment. Unfortunately, there is a dearth of information on microarthropods in central Africa in general and Cameroon in particular. We, thus, evaluated the population dynamics of Acari and Collembola as influenced by season, maize cultivation and fertilization in the high Guinean savanna agro-ecological zone (HGSAZ) of Cameroon. The abundances of Acari groups (Oribatida, Gamasina, Uropodina, Prostigmata, Astigmata) and Collembola were recorded. They were extracted from a field trial consisting of three plots of maize and one savanna plot that was established at Dang (Ngaoundéré 3, Adamawa region) in May of 2017 and 2018. The first plot received dead organic matter (DOM) while the second was treated with chemical fertilizer (NPK 20:10:10 at the rate of 8.75g/m²). The third plot received no external input and served as a control. The adjacent grassy savanna was the out-of-field control. Results revealed that microarthropods were more abundant in the rainy than dry season. Overall, abundances of 16 tsd. ind./m² for Acari and 8 tsd. ind./m² for Collembola were recorded in the savanna control. In the experimental field with maize cultivation, the highest abundances of Acari (20 tsd. ind./m²) and Collembola (7 tsd. ind./m²) were recorded in the plot that received dead organic matter (DOM), while the control plot without DOM (10 tsd. ind./m² for Acari and 2 tsd. ind./m² for Collembola) and the plot with chemical fertilizer (8 tsd. ind./m² for Acari and 8 tsd. ind./m² for Collembola) had the lowest abundances. Therefore, application of NPK and removal of DOM from cultivated areas have negative effects on soil microarthropods, and could result in very high costs for farmers to maintain soil fertility. In contrast, mulches are safe, simple and easily accessible to local farmers, promote soil biota and have a positive influence on soil structure and microclimate. Further, knowledge from the present study may contribute to the improvement of soil health and quality and boost agricultural productivity in the HGSAZ of Cameroon.

Keywords
Acari | Collembola | dead organic matter | NPK fertilizer | maize

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DOI 10.25674/so95iss1id301

Walter Sudhaus 

 

Abstract

Eleven years after publication, the catalogue on ‘Rhabditidae’ is herewith continued, presenting for subsequently described species information including synonyms, type locality and type habitat. Of the seven genus taxa proposed since 2011, five were judged to be synonymous, and of the 120 species described as new, 11 were suggested to be synonymous. The 109 new valid species are distributed across 25 genus taxa which each represent a side branch of the phylogenetic tree. Diagnostic features are mentioned for the new genera Auanema and Tokorhabditis. The increase in the number of nominal species mainly concerns Caenorhabditis (40 new species), Oscheius (12 new species) and Pellioditis (15 new species). New species were recruited mainly from India (29), Central and South America (17), Europe (15), Africa (9) and China (7 species). A list of nomina nuda is also given.

Keywords
Caenorhabditis | Heterorhabditis | Phasmarhabditis | Psychodorhabditis | gastropod-pathogenic

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DOI 10.25674/so95iss1id312