Phosphorus availability may shape plant–microorganism–soil interactions in forest ecosystems. Our aim was to quantify the interactions between soil P availability and P nutrition strategies of ...European beech (Fagus sylvatica) forests. We assumed that plants and microorganisms of P-rich forests carry over mineral-bound P into the biogeochemical P cycle (acquiring strategy). In contrast, P-poor ecosystems establish tight P cycles to sustain their P demand (recycling strategy). We tested if this conceptual model on supply-controlled P nutrition strategies was consistent with data from five European beech forest ecosystems with different parent materials (geosequence), covering a wide range of total soil P stocks (160–900 g P m⁻²; <1 m depth). We analyzed numerous soil chemical and biological properties. Especially P-rich beech ecosystems accumulated P in topsoil horizons in moderately labile forms. Forest floor turnover rates decreased with decreasing total P stocks (from 1/5 to 1/40 per year) while ratios between organic carbon and organic phosphorus (C: Porg) increased from 110 to 984 (A horizons). High proportions of fine-root biomass in forest floors seemed to favor tight P recycling. Phosphorus in fine-root biomass increased relative to microbial P with decreasing P stocks. Concomitantly, phosphodi-esterase activity decreased, which might explain increasing proportions of diester-P remaining in the soil organic matter. With decreasing P supply indicator values for P acquisition decreased and those for recycling increased, implying adjustment of plant–microorganism–soil feedbacks to soil P availability. Intense recycling improves the P use efficiency of beech forests.
Full text
Available for:
BFBNIB, DOBA, EMUNI, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NMLJ, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Biochar and biochar–compost did not reduce available Cu in a temperate vineyard.•Compost and biochar–compost did not affect Cu phytoextraction by cover crops.•Compost and biochar–compost ...significantly increased microbial abundance and activity.•Treatments significantly changed microbial community structure in soil.
The use of copper (Cu) fungicides in agriculture has led to Cu accumulation in European topsoils. This study is the first to investigate the in situ efficacy of biochar and biochar–compost as Cu immobilizers, reducing Cu uptake by plants and increasing microbial abundance and activity, in a temperate vineyard topsoil (0–10cm). After application of biochar, compost and biochar–compost in April 2011, plant and soil samples were taken in November 2011, April 2012, August 2012, and November 2012. Similar amounts of exchangeable Cu fractions (CuDTPA) in all treatments showed that there was no significant effect on Cu immobilization in soil. In contrast, cover crops grown between vine rows were observed to take up a significant amount of Cu (38.7mg Cu kg−1), reducing soil Cu concentrations over time. Treatments with biochar and/or compost initially increased total carbon, with compost and biochar–compost additionally increasing extractable organic carbon in soil. Compost and biochar–compost significantly increased microbial biomass, phospholipid fatty acids (PLFAs), enzyme activities (phosphatase, arylsulfatase) and bacterial taxa abundances (Actinobacteria, α-Proteobacteria, β-Proteobacteria, Firmicutes, Gemmatimonadetes). A high abundance of gram+ Actinobacteria in all treatments suggested that they are adapted to heavy metals, likely due to their specific cell membrane structures. Additionally, each treatment was characterized by a specific microbial community composition. Compost and biochar–compost increased the relative abundance of Firmicutes, while control and biochar increased Acidobacteria,Gemmatimonadetes and Actinobacteria. In conclusion, biochar and/or compost were not viable Cu remediation options, but compost and biochar–compost provided ecosystem services by reinforcing the microbial community.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The anecic earthworm
Lumbricus terrestris L. is known to strongly affect organic matter transformation and soil development in temperate ecosystems. Processes in the gut of the earthworm play an ...important role where sand grains contribute to the grinding of leaf litter in the muscular gizzard. To investigate effects of sand and litter availability and earthworm gut passage on carbon and nitrogen mineralisation two experiments were set up, one with beech forest soil and beech litter, the other with arable soil and rye litter, thereby exploring the effects of agricultural management and litter type on mobilisation and stabilisation of organic matter.
Three different sand concentrations were tested in the forest soil: without, with 25% and with 50% sand (dry weight). In the arable soil only treatments without and with 25% sand were established. The soil was taken from a beech forest on limestone and from a long-term agricultural experiment. Earthworms were fed fragmentised beech or rye litter (<4 mm), or were kept without litter. Earthworm casts produced during 65 days were placed in microcosms and incubated at 20 °C for 280 days. CO
2 production and mineral nitrogen in leaching water were measured at regular intervals. Earthworms lost more mass in arable than in forest soil; even though in arable soil the earthworms produced two times more casts. Litter availability reduced burrow construction. Casts were more enriched in carbon and nitrogen if litter was available. Leaching of N
min from casts of
L. terrestris strongly exceeded that of the corresponding soil treatments in the arable soil but not in the forest soil. In earthworm casts decomposition of rye litter was strongly increased, in particular early in the experiment. In contrast, the decomposition of beech litter was reduced initially and stimulated later. The addition of sand stimulated carbon mineralisation in both organic matter in soil and enclosed in earthworm casts. In soils with high clay content (forest soil) the stimulating effect of sand was less pronounced than in soils with low clay content (arable soil). Overall, except in earthworm casts of the forest soil without litter, cumulative CO
2 production exceeded that in the corresponding soil suggesting that in earthworm casts mobilisation rather than stabilisation processes prevail.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
As a key component of the carbon cycle, soil CO2 efflux (SCE) is increasingly studied to improve our mechanistic understanding of the important carbon flux. Predicting ecosystem responses to climate ...change often depends on extrapolation of current relationships between ecosystem processes and their climatic drivers to conditions not yet experienced by the ecosystem. This raises the question of to what extent these relationships remain unaltered beyond the current climate window for which observations are available to constrain the relationships. Here, we evaluate whether current responses of SCE to fluctuations in soil temperature and soil water content can be used to predict SCE under altered rainfall patterns. Of these 58 experiments for which we gathered SCE data, 20 were discarded because either too few data were available or inconsistencies precluded their incorporation in the analyses. The 38 remaining experiments were used to test the hypothesis that a model parameterized with data from the control plots (using soil temperature and water content as predictor variables) could adequately predict SCE measured in the manipulated treatment. Only for 7 of these 38 experiments was this hypothesis rejected. Importantly, these were the experiments with the most reliable data sets, i.e., those providing high=frequency measurements of SCE. Regression tree analysis demonstrated that our hypothesis could be rejected only for experiments with measurement intervals of less than 11 days, and was not rejected for any of the 24 experiments with larger measurement intervals. This highlights the importance of high-frequency measurements when studying effects of altered precipitation on SCE, probably because infrequent measurement schemes have insufficient capacity to detect shifts in the climate dependencies of SCE. Hence, the most justified answer to the question of whether current moisture responses of SCE can be extrapolated to predict SCE under altered precipitation regimes is "no" - as based on the most reliable data sets available. We strongly recommend that future experiments focus more strongly on establishing response functions across a broader range of precipitation regimes and soil moisture conditions. Such experiments should make accurate measurements of water availability, should conduct high-frequency SCE measurements, and should consider both instantaneous responses and the potential legacy effects of climate extremes. This is important, because with the novel approach presented here, we demonstrated that, at least for some ecosystems, current moisture responses could not be extrapolated to predict SCE under altered rainfall conditions.
In this Brief Communications Arising Reply, the affiliation for author P. H. Templer was incorrectly listed as 'Department of Ecology & Evolutionary Biology, University of California Irvine, Irvine, ...California 92697, USA' instead of 'Department of Biology, Boston University, Boston, Massachusetts 02215, USA'. This has been corrected online.
Full text
Available for:
KISLJ, NUK, SBMB, UL, UM, UPUK
Earthworms play an important role in organic matter processing and nutrient cycling in temperate ecosystems. It is known that earthworms preferentially ingest sand grains mixed with organic material ...and it has been suggested that the mixture of sand and organic material during the gut passage may play an important role in litter degradation and nutrient release, which may accelerate assimilation of nutrients by earthworms and likely enhance plant growth. In a greenhouse experiment, we investigated the effect of the anecic earthworm species
Lumbricus terrestris and the endogeic earthworm species
Octolasion tyrtaeum separately and in combination on carbon and nitrogen mobilisation from surface applied rye litter labelled with
13C and
15N. By mixing arable soil with 25% sand, we investigated the effect of the availability of sand. To quantify the mobilisation of
15N, three rye seedlings were planted in each microcosm and analysed for isotope signature after 3 months of incubation. Mobilisation of
13C was quantified by analysing the incorporation of label into the soil and earthworm tissue.
Irrespective of the addition of sand the biomass of
L. terrestris decreased during the experiment, whereas that of
O. tyrtaeum increased in single species treatment and slightly decreased in the combined treatment with
L. terrestris. The concentration of
13C decreased while that of
15N increased in the tissue of both earthworm species, with the effect being more pronounced in
L. terrestris for
13C and in
O. tyrtaeum for
15N. Both earthworm species increased shoot biomass, with the effect of
L. terrestris (+80%) exceeding that of
O. tyrtaeum (+28%) and maximum plant biomass in the combined treatment (+92%). Earthworms did not affect the
15N concentration of rye plants, but sand significantly increased
15N concentration of plants, presumably due to improving soil structure. Overall, the incorporation of
13C into the soil was low and was significantly increased in presence of sand, with the highest enrichment in treatments without earthworms.
The results indicate that the availability of sand does not increase effects of earthworms on litter degradation, nutrient release and plant growth. Rather, independent of soil sand content earthworms increase plant growth, whereas the presence of sand itself enhances the uptake of nitrogen from plant litter and the incorporation of litter carbon into the soil.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► The addition of easily available C strongly decreases decomposition rates of plant litter. ► Possible mechanisms of negative priming are preferential utilization and catabolic repression. ► ...Disrupting of the mycelial connection decreases decomposition rates of N-poor litter. ► Disruption of mycelial connection does not necessary decrease the net N input into the litter.
The translocation of nutrients by networks of fungal hyphae is an important mechanism controlling decomposition rates of plant residues. We performed a 15-month long field experiment aiming to assess the effects of the C and N availability and the role of the mycelial connection between litter and underlying mineral soil on the decomposition rates and levels of enzyme activities in plant litter. Litterbags containing either N-rich litter of alder (
Alnus glutinosa) or N-poor litter of aspen (
Populus tremula) were exposed on top of A-horizon of forest soil. The experiment was set up in a full-factorial design with litter species, C and N availability, and presence of mycelial connection as factors. Labile C and N were added as sucrose and ammonium nitrate solutions in four combinations: −C−N, +C−N, −C+N and +C+N. To disrupt the mycelial connection between litter and soil half of the litterbags were slightly moved, whereas others were left untouched. All experimental manipulations were performed every ten days during snow-free period. At the natural levels of C and N availability, N-poor aspen litter, but not N-rich alder litter, accumulated significant amounts of N. The addition of easily available C decreased the activity of xylanase and phenoloxidase and reduced litter decomposition rates of aspen litter; in alder litter similar but less pronounced trends were also observed. The severance of the mycelial connection between plant litter and underlying soil generally decreased xylanase activity and decomposition rates of the N-limited litter, likely due to the reduced presence of basidiomycete fungi in the litterbags. This effect was not observed, if the N-limitation was artificially relieved by the addition of easily available N, likely due to the increased activity of bacteria and microfungi.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The present study tests whether soil management (tillage and fertilizer) modified the small-scale abundance and function of soil microorganisms in response to changes in organic matter quantity and ...quality. The experimental field, located in the coastal hills of Marche (central Italy), was planted in rotation with Triticum durum in winter and Zea mais in summer. Soil samples were collected in the maize-field soil, in conventional and no-tillage (NT) systems, and in fertilized and unfertilized soil. We analysed total organic C (TOC), total nitrogen (TN) microbial biomass C (MBC), enzymes involved in C- (β-glucosidase, α-glucosidase, β-cellobiohydrolase, β-xylosidase), N- (leucine-aminopeptidase and N-acetyl-β-glucosaminidase), P- (acid phosphatase) and S-cycling (arylsulphatase), as well as functional diversity in the bulk soil, coarse sand, fine sand, silt and clay fractions. Micro-scale investigations revealed great microbial abundance in smaller fractions because of protection offered by microaggregates, whereas the distribution of enzymes reflected the availability of their corresponding substrates. No-tillage treatment significantly increased organic input, mainly in the coarser fractions, enhancing enzyme activities and the functional diversity of the microbial community. This effect was even larger in the absence of fertilizer. At the particle-size level of resolution, adding fertilizer stimulated nutrient cycling. Our results confirmed the hypothesis that no-tillage enlarges the content of particulate organic matter in the coarse sand fraction and stimulates microbial decomposition. In the smaller fractions the enlarged microbial pool and increased soil organic matter with small C/N ratio under NT confirm that this management practice is effective in increasing soil C sequestration capacity.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Factors determining C turnover and microbial succession at the small scale are crucial for understanding C cycling in soils. We performed a microcosm experiment to study how soil moisture affects ...temporal patterns of C turnover in the detritusphere. Four treatments were applied to small soil cores with two different water contents (matric potential of −0.0063 and −0.0316MPa) and with or without addition of 13C labelled rye residues (δ13C=299‰), which were placed on top. Microcosms were sampled after 3, 7, 14, 28, 56 and 84 days and soil cores were separated into layers with increasing distance to the litter. Gradients in soil organic carbon, dissolved organic carbon, extracellular enzyme activity and microbial biomass were detected over a distance of 3mm from the litter layer. At the end of the incubation, 35.6% of litter C remained on the surface of soils at −0.0063MPa, whereas 41.7% remained on soils at −0.0316MPa. Most of the lost litter C was mineralised to CO2, with 47.9% and 43.4% at −0.0063 and −0.0316MPa, respectively. In both treatments about 6% were detected as newly formed soil organic carbon. During the initial phase of litter decomposition, bacteria dominated the mineralisation of easily available litter substrates. After 14 days fungi depolymerised more complex litter compounds, thereby producing new soluble substrates, which diffused into the soil. This pattern of differential substrate usage was paralleled by a lag phase of 3 days and a subsequent increase in enzyme activities. Increased soil water content accelerated the transport of soluble substrates, which influenced the temporal patterns of microbial growth and activity. Our results underline the importance of considering the interaction of soil microorganisms and physical processes at the small scale for the understanding of C cycling in soils.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF
