▪ Abstract We explore empirical and theoretical evidence for the functional significance of plant-litter diversity and the extraordinary high diversity of decomposer organisms in the process of litter decomposition and the consequences for biogeochemical cycles. Potential mechanisms for the frequently observed litter-diversity effects on mass loss and nitrogen dynamics include fungi-driven nutrient transfer among litter species, inhibition or stimulation of microorganisms by specific litter compounds, and positive feedback of soil fauna due to greater habitat and food diversity. Theory predicts positive effects of microbial diversity that result from functional niche complementarity, but the few existing experiments provide conflicting results. Microbial succession with shifting enzymatic capabilities enhances decomposition, whereas antagonistic interactions among fungi that compete for similar resources slow litter decay. Soil-fauna diversity manipulations indicate that the number of trophic levels, spec...

Biodiversity and Litter Decomposition in Terrestrial Ecosystems

Regulation of soil organic matter dynamics and microbial activityin the drilosphere and the role of interactionswith other edaphic functional domains

Previous studies on biodiversity and soil food web composition have mentioned plant species identity, as well as plant species diversity as the main factors affecting the abundance and diversity of soil organisms. However, most studies have been carried out under limitations of time, space, or appropriate controls. In order to further examine the relation between plant species diversity and the soil food web, we conducted a three-year semi-field experiment in which eight plant species (4 forb and 4 grass species) were grown in monocultures and mixtures of two, four and eight plant species. In addition there were communities with 16 plant species. We analyzed the abundance and identity of the nematodes in soil and roots, including feeding groups from various trophic levels (primary and secondary consumers, carnivores, and omnivores) in the soil food web. Plant species diversity and plant identity affected the diversity of nematodes. The effect of plant diversity was attributed to the complementarity in resource quality of the component plant species rather than to an increase in total resource quantity. The nematode diversity varied more between the different plant species than between different levels of plant species diversity, so that plant identity is more important than plant diversity. Nevertheless the nematode diversity in plant mixtures

Plant species identity and diversity effects on different trophic levels of nematodes in the soil food web

http://www.srs.fs.usda.gov/pubs/ja/ja_wallenstein001.pdf

Nitrogen fertilization decreases forest soil fungal and bacterial biomass in three long-term experiments

FORUM is a lighter channel of communication between readers and contributors; it aims to stimulate discussion and debate, particularly by presenting new ideas and by suggesting alternative interpretations to the more formal research papers published in ECOGRAPHY and elsewhere A lighter prose is encouraged and no summary is required Contributions should be concise and to the point, with a relatively short bibliography Formal research papers, however short, will not be considered

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0587.2000.tb00294.x

The structure of oribatid mite communities (Acari, Oribatida): patterns, mechanisms and implications for future research

Scheu, S., Albers, D., Alphei, J., Buryn, R., Klages, U., Migge, S., Platner, C. andSalamon, J.-A. 2003. The soil fauna community in pure and mixed stands of beechand spruce of different age: trophic structure and structuring forces. – Oikos 101:225–238.This study investigates the response of the soil fauna community to replacement ofbeech by spruce or by mixed stands of beech and spruce. Stands of different age wereinvestigated in a factorial design with the factors tree species (beech and spruce) andstand age (30 and 120 years). The input of leaf/needle litter did not differ signiﬁcantlybetween the study sites. By contrast, the amount of organic matter in upper soillayers (L/F, H/Ah) of spruce forests strongly exceeded that of beech forests particu-larly in mature stands. The increase in organic matter in spruce stands was notassociated by an increase in the amount of microbial biomass. Biomass of eight(bacterivorous, fungivorous and omnivorous nematodes, enchytraeids, earthworms,isopodes, mycetophilid and cecidomyiid Diptera) of the twelve microbi-detritivoroussoil animal groups studied was signiﬁcantly increased in beech forests; only that ofone group (elaterid beetles) was increased in spruce forests and three groups did notrespond signiﬁcantly (collembolans, oribatid mites, sciarid Diptera). This indicatesthat in the forests studied neither habitat space (amount of organic matter in L/FandH/Ah layers) nor the amount of microbial biomass controlled microbi-detritivores.Rather, the quality of litter materials and the concentration of microbial biomasstherein appeared to be most important. Herbivores and predators also were favouredby beech: the biomass of one (rhizophagous nematodes) of the three herbivorousgroups studied were signiﬁcantly increased in beech stands and none in spruce stands;the biomass of four (predatory nematodes, centipedes, carabid and cantharid beetles)of the seven carnivorous groups studied were increased in beech stands, none inspruce stands. Generally, the biomass ratio between prey and predators was at aminimum in mature beech and mixed stands indicating more intense top-downcontrol in these forests. Overall, the study documents that replacement of beech byspruce strongly alters the soil food web. Mixed stands were more similar to sprucestands in respect to the biomass of soil animal groups but predator–prey interactionsappeared to be more similar in mature beech and mixed stands. Differences betweentree species usually were more pronounced in 120 compared to 30 years old standsindicating that the development of stand characteristics is slow.

The soil fauna community in pure and mixed stands of beech and spruce of different age: trophic structure and structuring forces

Middens of the earthworm Lumbricus terrestris (Lumbricidae): microhabitats for micro- and mesofauna in forest soil

To investigate the importance of the availability of food resources for soil micro- and mesofauna, carbon (as glucose) and nutrients (nitrogen as NH4NO3; phosphorus as NaH2PO4) were added separately and in combination to experimental plots in a beechwood on limestone (Gottinger Wald) for 15 months The aim of the study was to increase the amount of resources (microorganisms) for the soil micro- and mesofauna and to observe changes in their density, ie to evaluate the strength of bottom-up forces Furthermore, we wanted to investigate changes in the density of animals which feed on micro- and mesofauna, ie predacious animals including Gamasina, Uropodina and predatory Nematoda In the litter layer the density of all animal groups studied was not significantly affected by experimental manipulations In the soil animal groups responded differently but not parallel to the amount of respective food resources The density of oribatid and uropodid mites declined in the C only treatment and the decline in oribatid mites was more pronounced when C and P were added in combination Collembolan density also declined in the CP treatment In contrast, Nematoda and Protozoa increased in density after the addition of C, N or P The number of amoebae increased when P was added and this increase was most pronounced in the CP treatment Flagellate density increased slightly in C treatment but the increase was stronger in CN, CP and CNP treatments Gamasina did not respond significantly to experimental manipulations The results point to a differential response of soil animal groups to an increased supply of food resources We assume that the responses were strongly influenced by indirect effects caused by the increased number and biomass of earthworms in C treatments Presumably, high density and biomass of earthworms stimulated populations of Nematoda, Amoebae and Flagellata while it detrimentally affected collembolans and particularly oribatid mites It is concluded that in the forest studied litter consumption, bioturbation and mucus excretion by earthworms negatively affects the habitable space of collembolans and oribatid mites but improves habitat conditions for microfauna by increasing the water content Therefore, earthworm effects may superimpose bottom-up forces confirming that earthworms are important ecosystem engineers in mull forest soils

Romuald Buryn

Papers

The soil fauna community in pure and mixed stands of beech and spruce of different age: trophic structure and structuring forces

Middens of the earthworm Lumbricus terrestris (Lumbricidae): microhabitats for micro- and mesofauna in forest soil

Indirect effects of carbon and nutrient amendments on the soil meso- and microfauna of a beechwood