Impact of subterranean fungus-growing termites (Isoptera, Macrotermitiane) on chosen soil properties in a West African savanna

Fungus-growing termites (Isoptera, Macrotermitinae) play an important role in tropical ecosystems in modifying soil physical properties. Most of the literature regarding the impact of termites on soil properties refers to termite epigeous mounds. In spite of their abundance and activity in African savannas, few studies deal with the properties of underground nest structures (fungus-comb chambers) built by subterranean Macrotermitinae termites. We tested whether these termites significantly modify the soil physico-chemical properties within their nests in a humid tropical savanna and whether these effects are different for two termite species with differing building behaviour. Termite-worked soil material was collected from fungus-comb chamber walls of two widespread species: Ancistrotermes cavithorax, which builds diffuse and ephemeral nests and Odontotermes nr pauperans, which most often builds concentrated and permanent nests for a comparatively much longer period of time. Neither species influenced soil pH but both significantly modified soil texture and C-N content in their nest structures. A strong impact on clay-particle size was also detected but no significant differences in clay mineralogy. Thus Odontotermes has a greater effect on soil properties, that could be explained by its building behaviour and the concentration in space of its nest units. Therefore, spatial pattern and life-span of fungus-comb chambers should be an important parameter to be considered in the functional role of subterranean Macrotermitinae termites in the savanna.     

埃塞俄比亚罗毕高原含铬雏形土地区凋落物饲喂的白蚁(Macrotermes spp)的化学性质及其生化活动的研究

Termite(Macrotermes spp.) mounds are complex biological habitats originated by the termite activity and possessing peculiar physical, chemical and biochemical properties. In this study we examined the concentration of nutrients and the biochemical activity of abandoned soil and mounds colonized by termites of the genera Macrotermes located in the Borana District, Ethiopia. To elucidate the magnitude and persistence of the termite-induced effects, we also studied an abandoned mound, previously colonized by termites of the same genera formed on the same soil. Results confirmed that termite-colonized mounds are ‘hot spots' of nutrient concentration and microbial activity in tropical soils. This is due to the termite driven litter input and decomposition. The abandoned mounds showed higher microbial biomass and activity and displayed a nutrient redistribution and a greater microbial activity than the adjacent soils. These findings allowed us to hypothesize a model of nutrient cycling in colonized soils and a partition of the relative roles of termites and soil microorganisms in nutrient location and turnover in tropical soils. These results may be also useful for the optimal management of termite-colonized soils.     

Impacts of habitat disturbance on termites and soil water storage in a tropical Australian savanna

This study examines changes in the abundance and diversity of soil macroinvertebrate taxa and soil water storage across different disturbance treatments in a tropical savanna woodland in northern Australia. Nine plots representing three habitat disturbance treatments (uncleared savanna woodland; 25-year-old regrowth following past clearing; cleared areas) were sampled for macrofauna using soil pits in April 2003. Sub-surface soil moisture (0-0.4 m) was measured at 0.1 m intervals over the 2002/2003 wet season. Termites represented 55% of total individuals sampled. Abundance of soil macrofauna was greatest in uncleared plots and lowest in cleared plots, with the latter treatment also having the lowest taxon diversity. Mean abundances of termites, earthworms and ants were greatest in uncleared treatment plots. Five termite species from four genera were present, with Microcerotermes nervosus constituting 47% of termite species identified. Of the wood-, grass- and polyphagous-feeding termites present, wood-feeding species were restricted to uncleared treatment plots and grass-feeders to regrowth treatment plots. A shift in termite nesting habits from epigeal to hypogeal was observed from uncleared to cleared treatments. Soil water storage was lowest in the dry season and highest during the monsoon, and varied significantly across habitat disturbance treatments at the start and end of the wet season. Cleared plots were least effective in the capture of the first wet season rains, and uncleared treatment plots showed the greatest capacity to retain soil water during the transition from wet to dry season. The negative effects of habitat disturbance on soil water storage may have been partially mediated by the observed changes in soil macrofauna, especially termites.     

Use of RAPD markers for the study of microbial community similarity from termite mounds and tropical soils

In this study, we test the use of the RAPD (Random Amplified Polymorphic DNA) molecular markers as a way to estimate the similarity of the microbial communities in various termite mounds and soils. In tropical ecosystems, termite activities induce changes in the chemical and physical properties of soil. The question then arises as to whether or not termites affect the presence of natural microbial communities. Successful 16S rDNA amplifications provided evidence of the occurrence of bacterial DNA in termite constructions including both soil feeder and fungus grower materials. A phenetic dendrogram using the similarity distance calculated from pairwise data including 88 polymorphic RAPD markers was reconstructed and bootstrap scores mapped. The microbial communities of the mounds of the four soil-feeding termites were clustered in the same clade, while those of the mounds of the fungus-growing species were distinct like those of control soils. Microbial changes in nests result from termite building behavior, depending on whether they include feces in their constructions for soil-feeders or use saliva as particle cement for fungus-growers. It is argued that RAPDs are useful markers to detect differences in microbial community structure not only between termitaries and control soils but also between mounds of soil-feeders.     

Effects of termites on the physical and chemical properties of the acid sandy soils of southern Nigeria

Abstract

This study was aimed at characterizing the effects of the activity of termites of the genus Nasutitermes on the physico‐chemical properties of the acid sandy soils of southern Nigeria. Selected morphological properties of the termite mounds were measured in the field. Outside portions of the termite mound and surface (0–15 cm) soil were collected and analyzed for some physical and chemical properties. Results obtained showed a density of 112 mounds ha^‐1 with average height of 0.85 m. There were significantly higher proportions of clay, silt, and organic carbon, and higher pH, exchangeable potassium (K), calcium (Ca), magnesium (Mg), available phosphorus (P), effective cation exchange capacity and base saturation in the mounds of the Nasutitermes than in the surrounding topsoil. Mounds of Nasutitermes termites, if returned to the soil, could improve the properties of the soil in areas where termites occur in large numbers.     

Effect of gut transit and mound deposit on soil organic matter transformations in the soil feeding termite: A review

Even if termites are often considered as a pest due to the damage they cause to agriculture and architecture, they contribute to the soil humification process in the tropics. This impact on the soil organic matter humification process is due to the most important feeding habit in terms of species diversity, the soil feeding termites (∼1 200 species). Unlike other termites, their diet is not based on lignocellulosic plant degradation, but on the consumption of the mineral-containing horizons for the acquisition of nutrients. They are mostly distributed in humid forest or savannah equatorial zone. High structure and compartment with steep radial and axial gradients of O₂, H₂ and pH characterize their gut and create a patchy biotope. Furthermore, the humic compounds ingested are submitted, during a sequential transit, to different chemical (alkaline hydrolysis) and microbial degradation processes (fermentation, anaerobic respiration and mineralization). During this gut transit, the soil organic matter is strongly modified in terms of nature (organic matter concentration, fulvic and humic acid ratio) and organization (formation of organo-mineral complexes with clay). The soil organic matter ingested is further included as faeces in the nest and the galleries which, as a whole, constitutes the termitosphere. Compared to the control soil, the soil organic matter in the termitosphere is more stable and protected from the intense mineralization, which occurs in the tropics. These shifts of the organic matter into long turnover pool generated by the termite gut transit and deposition in the termitosphere indicate that besides the earthworm, the soil feeding termite has a positive impact on the overall organic matter cycling in the tropics.     

Effect of termites and mulch on the physical rehabilitation of structurally crusted soils in the Sahel

The effectiveness of mulch and termite activity in the rehabilitation of the physical properties of crusted soil was studied in northern Burkina Faso (Province de Bam). A split plot design was used with three replications each being on one soil type. The soil types were Ferric Lixisol, Haplic Lixisol and Chromic Cambisol. The main factor was termite activity, and to this end dieldrin (0·50 kg a.i. ha⁻¹) was used to create plots without termite activity next to plots with termite activity. The subplots consisted of Pennisetum pedicellatum mulch, wood Pterocarpus lucens mulch and composite (wood+straw) mulch, applied at rates of 3, 6 and 4 t ha⁻¹, respectively. Two years after establishing the experiment, the combined effect of termite and mulch on the change in physical properties of the soil was measured. The parameters used for this assessment were porosity, saturated hydraulic conductivity and soil resistance to cone penetration. Soil water content was also measured. Termite activity was found to increase soil porosity, soil saturated hydraulic conductivity, improve soil water status and reduce soil bulk density and soil resistance to cone penetration. The only difference between bare plots and mulched plots without termites was in water content. This indicates that the mechanism whereby mulch improves the physical properties of crusted soil is mainly based on soil biology processes and to a limited extent on protecting soil against weather impact. © 1997 John Wiley & Sons, Ltd.     

Transformation and mineralization of 14C-labeled cellulose, peptidoglycan, and protein by the soil-feeding termite Cubitermes orthognathus

 We performed feeding trials with the soil-feeding termite Cubitermes orthognathus using soil spiked by uniformly ¹⁴C-labeled preparations of cellulose, peptidoglycan, protein, and bacterial cells (Bacillus megaterium and Escherichia coli). When incubated in soil for 8 days in the absence of termites, cellulose and peptidoglycan showed low mineralization rates (0.5% and 0.2%, respectively). However, when termites were present, their mineralization rates strongly increased (21.6% and 30.6%, respectively). The mineralization rate of protein was 12.4% in the control soils and increased to 36.2% in the presence of termites. Mineralization of bacterial cells in control soils occurred in two phases (rapid mineralization during the first 4–5 days and stabilization thereafter). When termites were present, the rates of mineralization of bacterial cells increased and the stabilization phase was abolished. In all cases, radiolabel accumulated in the termites and the solubility of the labeled compounds located in the gut increased strongly. Mineralization was accompanied by transformation of residual carbon from the humic acid fraction to the fulvic acid fraction during gut passage. High-performance gel permeation chromatography demonstrated a strong shift in the size distribution of the residual carbon from high-molecular-weight towards low-molecular-weight molecules in the gut of termites and an accumulation of small molecules in the termite bodies. The present study provides strong evidence that structural polysaccharides of plants and bacteria and microbial biomass are carbon and energy sources for soil-feeding termites. Received: 29 May 2000     

Modification of soils in Nigerian savanna by soil-feeding Cubitermes (isoptera,termitidae)

Soil-feeding termites ingest humified, organic-rich soil. The soil faeces are used for nest construction and mounds of two species of Cubitermes contained more soil, clay, exchangeable Ca and Mg, available P, total N and organic C than adjacent topsoil. Available P increased by 1.4–6.0 times. Mounds of a plant-debris feeding termite, Trinervitermes, contained significantly more of these fractions, with the exception of available P, than adjacent topsoil. The modification of Trinervitermes mounds by Cubitermes resulted in a 2-fold increase in available P, whereas organic C remained the same and N increased by 1.5-times. The relatively large increase in available P resulting from soil feeding termites could be attributed to the high pH regime in their hind-guts.     

Naphthalene production by microorganisms associated with termites: Evidence from a microcosm experiment

There have been several reports published which suggest that it is possible that the polycyclic aromatic hydrocarbons (PAHs) naphthalene (NAPH), phenanthrene (PHEN) and perylene (PERY) in tropical environments have a biological source. This source might be related to the activity of termites or their associated microorganisms. We aimed to provide direct evidence for the biological production of NAPH, PHEN and PERY by conducting microcosm experiments in the State of Tocantins, Brazil, in which termite nests (with or without termites) were placed in an enclosed environment in which we controlled all PAH fluxes and monitored changes of PAH stocks. The experiments were carried out with termites from a tropical floodplain forest environment at the Estação Canguçu (Ilha do Bananal) in the State of Tocantins, Brazil. We set up the following treatments: live nest of Nasutitermes cf. minor using PAH-poor wood as food (LNW), live nest of Nasutitermes cf. minor using PAH-poor corn as food (LNC), termite nest without live termites called dead nest (DNC) and dead nest with additional treatment by a combined fungicide/bactericide (FDN) in several replicates. In LNW, LNC, and DNC, there were mean increases of 43%, 21%, and 46% in NAPH stock after 20 d while the stocks of the 20 other PAHs studied did not change or even decreased. In contrast, FDN lost 20% of the NAPH stock after 20 d of the microcosm experiment because of dissipation and lack of microbial synthesis of new NAPH. In LNW and LNC, low-molecular weight PAHs (acenaphthylene to chrysene) were significantly lost at a mean percentage which was strongly correlated with the octanol-water partitioning coefficient (K_OW, r = 0.78). This was not the case in DNC and FDN. There were no indications that in the studied termite nests PHEN and PERY were produced. Our microcosm experiments suggest that NAPH can be produced by fungi and bacteria in termite mounds while all other low-molecular weight PAHs are degraded in microcosms with live termite nests. PAH degradation seems to be enhanced by the combined activity of termites and microorganisms.     

Effect of termites on clay minerals in tropical soils: fungus-growing termites as weathering agents

Termites of the subfamily Macrotermitinae play an important role in tropical ecosystems: they modify the soil's physical properties and thereby make food available for other organisms. Clay is important in the architecture of Macrotermitinae termite nests, and it has been postulated that termites could modify the mineralogical properties of some clays. We have tested this hypothesis of clay transformation by termites in the laboratory under controlled conditions, using Odontotermes nr. pauperans termite species, one of the main fungus‐growing species at Lamto Research Station (Côte d'Ivoire). Soil handled by termites in nest building was saturated with SrCl₂, glycol or KCl and afterwards heated at 250°C for X‐ray diffraction analyses. Termite handling led to an increase in the expandable layers of the component clay minerals. Heating and saturation by potassium of modified clays did not close the newly formed expandable clay layers. However, differences occurred between parts of the constructions built by termites, and the clays can be ranked according to their degree of alteration in the following order: unhandled soils < galleries < chamber walls. Consequently, termites can be seen as weathering agents of clay minerals, as previously shown for micro‐organisms and plants.     

Biological Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in the Amazonian Rain Forest

Hazardous polycyclic aromatic hydrocarbons (PAHs) widely occur in the environment and are believed to be mainly anthropogenic. Here we present strong indications for large biological sources of the PAHs naphthalene, perylene, and possibly also phenanthrene in the Amazonian basin. Termite nests, plant wood, and soils were sampled. Naphthalene is detected in plant wood and is accumulated in the nests of termites from the genus Nasutitermes. Perylene is found in all studied termite nests including six different genera. Phenanthrene occurs at substantial concentrations in wood, soil, and termite nests.     

Chemical,physical and micromorphological properties of termite mounds and adjacent soils along a toposequence in Zona da Mata,Minas Gerais State,Brazil

Little is known about the effects of neotropical mound-building termites in soil chemical and physical properties. The influence of soil termite activity on soil characteristics was studied by assessing chemical, physical and micromorphological properties of a toposequence of Latosols (Oxisols). Soil samples were collected from the walls and inner parts of termite mounds and also from adjacent soil. A high diversity of termite genera was found in the mounds along the toposequence, together with the inquiline termites and other soil-dwelling arthropods. Chemical analyses showed that pH and the contents of organic C and N, P, Ca and Mg were significantly higher in termite mounds compared with adjacent areas, with an inverse trend for Al content. Significant differences in pH and exchangeable Al were observed between soil and mound across the slopes. The mound density across the landscape was higher at the upper slope segment, followed by the hill top, middle slope and lower slope segments. Considering a lifespan of 30 years and dimensions of termite mounds found in the toposequence we conclude that the textural and chemical uniformity of Latosols may be increased, following the pedobiological turnover during mound building, with local rates varying from 2.1 to 7.5 m³ ha^− 1.     

Diversity of macro-detritivores in dead wood is influenced by tree species,decay stage and environment

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.     

Effects of soil faunal activity and woody shrubs on water infiltration rates in a semi-arid fallow of Senegal

The effects of soil faunal activity on the physical properties of the soils of a 2-year-old fallow in the sahelian zone of Senegal were studied. Factors studied included the presence or absence of woody shrubs and the effect of protection of plots from grazing and removal of fuel wood. The experimental design included a control in which termite activity was excluded by treating the soil with the persistent insecticide dieldrin.In both the protected and unprotected area of the experiment, termite burrowing activity (as measured by the number of entrance holes per square-metre) and water infiltration rates were significantly (ca. 80%) lower in termite exclusion plots than in plots not treated with insecticide 2 years after initial treatment. In protected plots where termites were present, there was a significant increase in infiltration rates in the part where woody shrubs were removed. In unprotected plots, by contrast, the presence of shrubs significantly increased infiltration rates, whether or not termites were present.Burrowing activity of earthworms was greater in the protected than in the unprotected area, and in the unprotected area burrowing in dieldrin treated plots was significantly increased by almost 65%. Activity of ants appeared to be little affected by the different treatments. The results demonstrate that the presence of healthy soil faunal populations was important in the infiltration of water in fallow soils and that protection from grazing and human activity improves faunal activity and water infiltration.     

Soil genesis and heterogeneity of phosphorus forms and carbon below mounds inhabited by primary and secondary termites

Termite activities are known to significantly influence small-scale soil properties in tropical savannas. The lateral and vertical extent of the alterations to the nest's surrounding, and particularly resulting impacts on diagnostic soil horizons remain largely unresolved until today. We examined the effects of mound-building termites on soil genesis and constitutive chemical soil properties in and below their nests. Two transects to a soil depth of 100 cm were dug below three younger mounds of Cornitermes silvestrii (the primary nest builder), three older mounds in which C. silvestrii had died out and which were secondarily colonized mainly by Nasutitermes kemneri, and three reference sites in the Brazilian Cerrado. The samples were characterized by standard procedures for soil classification; in addition, phosphorus extractions were conducted on selected samples using NaHCO₃ for labile P forms, and concentrated HCl for stable P forms. This data set was then used to build calibration models for the prediction of labile and stable inorganic (P_i) and organic (P_o) P forms, as well as for contents of organic carbon (OC), for the remaining samples applying mid-infrared spectroscopy in combination with partial least squares regression (MIRS-PLSR). We can show that the termite influence on the soil was sufficiently large to change diagnostic characteristics of the soils under termite mounds. The MIRS-PLSR predictions were suitable for quantifying organic carbon and most of the labile and stable phosphorus fractions. They showed an enrichment of OC, NaHCO₃-P_o and NaHCO₃-P_i contents in nests inhabited by primary and secondary termites by factors of 1.6–2.0 and 1.4–1.5, respectively. The soils surrounding the nests had higher contents of OC and NaHCO₃-P under both nest types vertically down to 30 cm below the lower nest border, and OC and NaHCO₃-P_i contents were elevated at minimum to a lateral distance of 60 cm away from the nest border. As the pattern of HCl_conc-P_i, which comprised 95% of total P, showed no variations, we conclude that the higher NaHCO₃-P_i amount was formed in termite nests by changing the availability of the more stable HCl_conc-P_i. In contrast to the contents, the OC and NaHCO₃-P stocks below the mounds inhabited by primary termites were comparable to those inhabited by secondary ones, because the bulk density of the secondarily inhabited nests was elevated. This was due to a transport of clay-rich material from the subsurface argic horizons into the nests. Here, the secondary termites even reverted the lessivation observed in the reference soils and under mounds inhabited by primary termites, thus causing the soil types to change from Alisols and Acrisols to the properties of Umbrisols.     

Tree species-mediated spatial patchiness of the composition of microbial community and physicochemical properties in the topsoils of a tropical montane forest

To evaluate the importance of plant-soil feedbacks in forest ecosystems, it is fundamental to understand the spatial range within which plant species control soil physicochemical and microbial properties. We investigated the spatial pattern of soil properties associated with canopy trees in a tropical montane forest on Mt. Kianbalu, Borneo. We analyzed soil physicochemical properties and microbial communities (biomarker lipid abundance) as a function of soil depth and distance from the tree trunk of a conifer (Dacrydium gracilis) or a broadleaf tree (Lithocarpus clementianus). The concentration of condensed tannins and fungi-to-bacteria were higher beneath Dacrydium than beneath Lithocarpus. Furthermore, carbon-degrading enzyme activities were lower beneath Dacrydium. These effects of the tree species were more distinct on soil properties beneath the tree crown than on those outside the tree crown. These effects appeared to be largely due to differences in litter chemistry, and the distinct set of soil properties formed corresponding to the above canopy crown. In conclusion, the species-rich forest on the tropical mountain contains spatially distinct units of soil properties associated with canopy trees, and this spatial pattern can influence ecosystem dynamics in the forest through plant-soil feedback effects.     

Influence of Cognettia sphagnetorum (Enchytraeidae) on birch growth and microbial activity, composition and biomass in soil with or without wood ash

In this laboratory study using microcosms with seedlings of silver birch (Betula pendula), we explored whether Cognettia sphagnetorum (Enchytraeidae) can retain its important role of accelerating decomposition processes in soils and stimulating primary production under disturbance. We established systems with or without wood ash amendment (first-order disturbance) in the soil, either in the presence or absence of C. sphagnetorum. To test whether the systems treated with wood ash are more sensitive to an additional disturbance than the ash-free systems, the microcosms were later on disturbed by drought. To determine the influence of two disturbances on the enchytraeids and populations of other fauna, and the possible changes in the system functioning, measurements were made of the growth of birch seedlings, foliar N concentration, composition and biomass of soil microbial communities and leaching of N and dissolved organic carbon from the microcosms. Both wood ash application and drought exerted a clear negative influence on the populations of C. sphagnetorum. However, populations of this species were very resilient and recovered rapidly after drought in the ash-free soils. In the ash-free soils C. sphagnetorum tended to improve birch growth, increased the N content of the birch leaves, and decreased the root to shoot ratio. However, in the ash-treated soils enchytraeids had negative effects on these parameters. C. sphagnetorum impacted on neither N and C leaching nor soil microbes, whereas wood ash decreased microbial biomasses and changed their community structure (as determined by phospholipid fatty acids method and denaturing gel electrophoresis) and substrate utilisation potential (Biolog method). It was concluded that C. sphagnetorum can retain its influential role under varying environmental conditions, but that the stimulating or retarding effects of this species on system functioning can be context dependent.     

Termites promote soil carbon and nitrogen depletion: Results from an in situ macrofauna exclusion experiment,Peru

We present results from one of the first in situ soil termite exclusion experiments using translocated soil that was not colonised by termites prior to the experiment. Macrofauna were excluded or included using fine (0.3 mm) and coarse (5 mm) mesh, respectively. We found that termites were the most dominant macrofauna in the macrofauna-included samples throughout the sampling period. Additionally, C and N depletion rates were consistently higher in samples with macrofauna than without macrofauna despite the seasonal decline of termites at the start of the wet season. This suggests that the presence of termites in soil promotes C and N depletion that may be linked to the passage of soil through the termite gut and the affect termites have on bioturbation and nutrient distribution.     

Physical activation of biochar and its meaning for soil fertility and nutrient leaching – a greenhouse experiment

The slow alteration of the surface of charred biomass (biochar) over time may contribute to an improved nutrient retention and thus fertility of tropical soils. Here, we investigated soils from temperate climates and investigated whether a technical steam activation of biochar could accelerate its positive effects on nutrient retention and uptake by plants relative to nonactivated biochar. To this aim, we performed microcosm experiments with sandy or silty soil, mixed with 2.0, 7.5 and 15.0 g/kg soil of fine (<2 mm) or coarse‐sized (2–10 mm) biochar from beech wood (Fagus sp.). After initial fertilizer (NPK), ashes and excess nutrients were leached with water, and the microcosms were planted for 142 days with Italian Ryegrass (Lolium multiflorum ssp. italicum). Thereafter, leachate, soil and plant samples were analysed for their nutrient contents. The results showed that biochar additions of ≤15 g/kg soil left elevated contents of available P and N in the surface soil but reduced their uptake into the plants. As a result, total biomass production was unchanged. Different particle size and application amounts influenced these findings only marginally. Nitrate leaching was enhanced in the sandy soil (+41% for nitrate, but reduced in the silty soil ?17%) and P was immobilized. Hence, the fertility of the temperate soils under study was only marginally affected by pure biochar amendments. Steam activation, however, almost doubled the positive effects of biochars in all instances, thus being an interesting option for future biochar applications.