Soil organic carbon (SOC) stocks in forest floors and in mineral and peat forest soils were estimated at the European scale. The assessment was based on measured C concentration, bulk density, coarse ...fragments and effective soil depth data originating from 4914 plots in 22 EU countries belonging to the UN/ECE ICP Forests 16×16km Level I network. Plots were sampled and analysed according to harmonized methods during the 2nd European Forest Soil Condition Survey. Using continuous carbon density depth functions, we estimated SOC stocks to 30-cm and 1-m depth, and stratified these stocks according to 22 WRB Reference Soil Groups (RSGs) and 8 humus forms to provide European scale benchmark values. Average SOC stocks amounted to 22.1tCha−1 in forest floors, 108tCha−1 in mineral soils and 578tCha−1 in peat soils, to 1m depth. Relative to 1-m stocks, the vertical SOC distribution confirmed global patterns reported for forest soils: ~50% of SOC was stored in the upper 20cm, and ~55–65% in the upper 30cm of soil. Assuming 163Mha of European forest cover and by using various scaling up procedures, we estimated total stocks at 3.50–3.94Gt C in forest floors and 21.4–22.7Gt C in mineral and peat soils down to 1-m, which is ~40% more than commonly published. The most useful predictors and stratifiers for C stocks were humus form and tree species for the forest floor, RSG for mineral soils and parent material for peat soils.
This dataset will be further explored, predominantly for validation of soil C models, resampling and comparison with legacy and future forest SOC inventories.
•Benchmark SOC stocks were quantified for 8 humus forms and 22 reference soil groups.•EU forests store ~3.7Gt C in forest floors and ~22Gt C in soils down to 1m depth.•Proportional vertical SOC distribution in EU forest soils confirms a global pattern.•European forests store about 2.5 times more C in soils than in tree biomass.
Trees contribute to bedrock weathering in a variety of ways. However, evaluating their full impact is complicated by a lack of direct observation of unexposed root systems of individual trees, ...especially when the scale of the analysis goes down to the level of microbiomes. In the present study, we investigated the contribution of tree root systems to bioweathering and soil production at the macro- and microscale. Soil profiles developed under trees on granite bedrock were investigated in two parts of the Sudety Mountains, SW Poland: the Rudawy Janowickie Mountains, and the Stołowe Mountains. Soil profiles were gradually excavated and soil samples collected from pre-defined positions of the root zone: 1) bulk soil, 2) rhizosphere, 3) cracks, 4) topsoil, and 5) control positions. In total, we analyzed 103 samples for soil chemistry and microbiological activity. In addition, we analyzed 19 samples using XRF (X-ray Fluorescence). Four parent rock samples, in the form of thin-sections, were the subject of mineralogical evaluation. Soil analyses included: total organic carbon (C) and nitrogen (N) content, soil pHH2O, soluble iron (Fed), and aluminum (Ald), non-crystalline (amorphous) iron (Feox), and aluminum (Alox). For microbiological analyses, we used a Biolog (EcoPlate) system to determine the functional diversity of soil microorganisms. We evaluated the results on soil chemistry and microbiological activity statistically by principal component analysis (PCA) and redundancy analysis (RDA). Differences between soil sampling positions were assessed using a non-parametric Kruskal-Wallis (K-W) rank sum test and a post-hoc pairwise Dunn test.
Trees developed different root architectures, likely shaped by the depth to bedrock and its pre-existing net of fractures and fissures. Tree roots were able to enter bedrock cracks at one study site (at Pstrążna, Stołowe Mountains). The soil profile was too deep for root system penetration at the second study site (Mt Jańska, Rudawy Janowickie Mountains, RJM). The rhizospheric soil along the roots had significantly different chemical properties compared to non-rhizospheric soil types. At Mt. Jańska, soil differed from the crack soil in terms of Alox (pHolm-adj. < 0.0006) and Feox (pHolm-adj. < 0.004), and from the bulk soil (pHolm-adj. < 0.02) and topsoil (pHolm-adj. < 0.007). In addition, at Pstrążna, the soil differed from the control soil in terms of C (pHolm-adj. < 0.009) and soil pHH2O (pHolm-adj. < 0.0008) and from the topsoil in terms of soil pHH2O. The highest metabolic activity was in cracks at Mt. Jańska and in control samples from Pstrążna. In general, the spatial distribution of soil microbial activity, and the weathering that results from that portion of the soil biome, is spatially heterogeneous and appears to be partially determined by the interaction of root growth and bedrock fracture patterns.
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•Roots of living trees contribute to soil production in granite bedrock.•Tree roots change soil properties and form a highly biologically active rhizosphere.•In the long-term perspective, trees modify the soil formation trajectory.•Granite properties control the impact of bioweathering on soil-forming processes.•Microbiota adds to the complexity of bioweathering under trees.
•We explored the effects of several characteristics on forest soil carbon (C) stocks.•We analyzed the effects of these characteristics using generalized additive models.•The FF content positively ...affected C stocks in sandy soils (80–100% sand)•The effect of elevation was most evident from 300 to 1000 m above sea level.•C stocks were lowest in soil pHH2O range 4.5–5.5.
Data from forest inventories provide information on C stocks under various tree species. However, based on the literature, the effects of tree species can be insignificant due to variation caused by the influence of site-related factors. The aim of this study was to explore the effects of soil texture, pHH2O, elevation, and dominant tree species on soil carbon (C) stocks in forest soils of Poland using data mining. Data were obtained from 468 investigation sites, spread over the entire area of Poland, representing forest sites with five dominant tree species (Scots pine, Norway spruce, Silver fir, deciduous oak and European beech), different elevations (lowlands, uplands, and mountains) and variable soil texture. We analyzed the effects of these characteristics using generalized additive models (GAM). Total soil-profile (up to 100 cm) C stocks (on average 26 t ha−1 in the organic horizon and 66 t ha−1 in the mineral soil) in forest soils of Poland were slightly lower than those reported previously for European forests. Simple ANOVA results implied that soils of pine stands contained significantly less stored C than soil under the other coniferous species (spruce and fir) and under deciduous oak and beech. The GAM analysis enabled quantification of the overall contribution of variables to variation in C stocks, namely fine-fraction (FF; silt and clay) content (15%), pHH2O (13%), altitude (8%), and dominant tree species (3%). The FF content positively affected C stocks (up to 10 t C ha−1 particularly in sandy soils (80–100% sand). The effect of elevation was most evident in the organic horizon and 0–10 cm mineral layer, which resulted in an increase of ∼40 t C ha−1 from 300 to 1000 m above sea level. The GAM analysis also showed that in all horizons the C stocks were lowest in soil pHH2O range 4.5–5.5. Decreased pHH2O or increased pHH2O resulted in an increase of 10–40 t C ha−1 in C stocks. Tree species alone explained about 3% of variation in C stocks, but a large portion of the effects of pHH2O may be attributable to the dominant tree species.
Soil fertility in forestry systems has usually been constrained to soil nutrients, with little attention to soil morphological attributes and physical properties. Our hypothesis was that soil ...physical properties and morphological attributes are more closely related with commercial forest growth than soil chemical fertility. The objective of the study was to analyze the influence of soil properties, in different soil types, on dendrometric variables and productivity of clonal E. saligna and seminal E. dunnii, both widely employed in commercial plantations managed for pulp and lumber production in southern Brazil. On inventory plots with two Eucalyptus species, namely Eucalyptus saligna (clone 32864) and seminal E. dunnii, we evaluated morphological attributes and physical and chemical properties of 17 soils (Ultisols and Entisols), and the dendrometric variables tree height, tree dominant height (h100) and diameter at breast height (DBH), all measured in 7-years old plantations. Eucalyptus growth was variable and influenced by profile attributes and soil properties, but correlations between h100 and soil properties were weak (r < 0.7) and usually not significant. Tree height and DBH were not affected by Eucalyptus species, soil type and their interaction. Overall, DBH ranged from 77.98 to 304.30 mm, with an average value of 183.23 mm. By contrast, tree h100 was affected by Eucalyptus species and soil type, but not by their interaction. Trees of E. saligna (23.4 m) were taller than E. dunnii (22.1 m), while among soil types Ultisols had the tallest (23.4 m) and Entisols the shortest trees (22 m). Chemical properties were more variable in surface soil layers, whereas physical properties mainly differentiated subsurface soil layers. The lowest dominant height resulted from the interaction between the lowest field capacity and plant available water capacity and the smaller depth of Entisols' soil profile. Contrary to our hypothesis, most soil properties/attributes were not significantly correlated with dominant tree height. Neither soil physical, morphological properties nor soil chemical fertility are determinants to forest growth when these parameters are not at critical limits for forest growth, particularly with absence of extreme edaphoclimatic conditions such as low rainfall or high temperatures. Associations among soil morphological attributes, physical properties and edaphoclimatic variables should be validated in future studies to better understand their effect of forest productivity in subtropical environments.
•Tree height and tree diameter were not affected by genetic material and soil type.•Genetic material and soil type influenced tree dominant height (h100).•For h100, E. saligna > E. dunnii, and Ultisols > Entisols.•Low depth and water retention explains the lowest h100 for Entisols.•Morphological and soil properties and edaphoclimatic interactions must be considered.
Fungi are the agents primarily responsible for the transformation of plant-derived carbon in terrestrial ecosystems. However, little is known of their responses to the seasonal changes in resource ...availability in deciduous forests, including photosynthate allocation below ground and seasonal inputs of fresh litter.
Vertical stratification of and seasonal changes in fungal abundance, activity and community composition were investigated in the litter, organic and upper mineral soils of a temperate Quercus petraea forest using ergosterol and extracellular enzyme assays and amplicon 454-pyrosequencing of the rDNA-ITS region.
Fungal activity, biomass and diversity decreased substantially with soil depth. The highest enzyme activities were detected in winter, especially in litter, where these activities were followed by a peak in fungal biomass during spring. The litter community exhibited more profound seasonal changes than did the community in the deeper horizons. In the litter, saprotrophic genera reached their seasonal maxima in autumn, but summer typically saw the highest abundance of ectomycorrhizal taxa. Although the composition of the litter community changes over the course of the year, the mineral soil shows changes in biomass.
The fungal community is affected by season. Litter decomposition and phytosynthate allocation represent important factors contributing to the observed variations.
Extracellular lignocellulose-degrading enzymes are responsible for the transformation of organic matter in hardwood forest soils. The spatial variability on a 12
×
12
m plot and vertical distribution ...(0–8
cm) of the ligninolytic enzymes laccase and Mn-peroxidase, the polysaccharide-specific hydrolytic enzymes endoglucanase, endoxylanase, cellobiohydrolase, 1,4-β-glucosidase, 1,4-β-xylosidase and 1,4-β-
N-acetylglucosaminidase and the phosphorus-mineralizing acid phosphatase were studied in a
Quercus petraea forest soil profile. Activities of all tested enzymes exhibited high spatial variability in the L and H horizons. Acid phosphatase and 1,4-β-
N-acetylglucosaminidase exhibited low variability in both horizons, while the variability of Mn-peroxidase activity in the L horizon, and endoxylanase and cellobiohydrolase activities in the H horizon were very high. The L horizon contained 4× more microbial biomass (based on PLFA) and 7× fungal biomass (based on ergosterol content) than the H horizon. The L horizon also contained relatively more fungi-specific and less actinomycete-specific PLFA. There were no significant correlations between enzyme activities and total microbial biomass. In the L horizon cellulose and hemicellulose-degrading enzymes correlated with each other and also with 1,4-β-
N-acetylglucosaminidase and acid phosphatase activities. Laccase, Mn-peroxidase and acid phosphatase activities correlated in the H horizon. The soil profile showed a gradient of pH, organic carbon and humic compound content, microbial biomass and enzyme activities, all decreasing with soil depth. Ligninolytic enzymes showed preferential localization in the upper part of the H horizon. Differences in enzyme activities were accompanied by differences in the microbial community composition where the relative amount of fungal biomass decreased and actinomycete biomass increased with soil depth. The results also showed that the vertical gradients occur at a small scale: the upper and lower parts of the H horizon only 1
cm apart were significantly different with respect to seven out of nine activities, microbial biomass content and community composition.
In forest ecosystems, trees represent the major primary producers and affect the chemical composition and microbial processes in the ecosystem via specific litter chemistry and rhizodeposition. ...Effects of trees on the abundance of soil microorganisms have been previously observed but the extent to which trees affect the composition of microbial communities remains unknown. Here we analyse the factors affecting the composition of bacterial and fungal communities in forest litter and soil under seven tree species studied at twenty-eight spatially independent sites of similar age developed on the same initial substrate. Microbial communities differed between litter and soil. Bacterial communities were more diverse than fungal communities, especially in litter, and exhibited higher evenness. Eighty percent of the bacterial sequences belonged to the 200–250 most dominant operational taxonomic units (OTUs), and 80% of the fungal sequences were composed of only 23–28 OTUs. The effect of tree species on the microbial-community composition was significant in both litter and soil for fungi as well as bacteria. In bacteria, the tree effect was likely partly mediated by litter and soil pH. Fungal taxa showed a greater tendency to be tree-specific: 35–37% of the dominant fungal OTUs but only 0–3% of the bacterial OTUs were restricted to 1 or 2 trees, and 15–45% of the fungi and 80% of the bacteria were common under 6 or 7 trees. Microbial taxa were demonstrated to associate with less trees than would be expected based on the patterns of their abundance in samples and the tree identity thus affects their occurrence. The numbers of observed dominant fungal OTUs in the study area increased faster with an increasing numbers of trees, indicating high β-diversity. Although the proportion of the arbuscular mycorrhizal and ectomycorrhizal fungi differed among trees, the tree-specific fungal taxa were both root-symbiotic and saprotrophic. The effect of trees on the composition of microbial community was demonstrated to be stronger than other soil properties and to explain a large proportion of variation in community composition, especially in fungi.
•Forest trees affect community composition of bacteria and fungi in soil and litter.•More fungi than bacteria are tree-specific, especially in the litter.•Effects of trees on bacteria are likely mediated by litter or soil pH.•Both root-symbiotic and saprotrophic fungi are tree-specific.•Litter and soils under different trees are dominated by different fungi.
The activities of extracellular enzymes that participate in the decomposition of litter and organic matter in forest soils depend on, among other factors, temperature and soil moisture content and ...also reflect the quality of litter, which changes dramatically after a short litterfall period. Here, we explored the effects of soil temperature and seasonality on the sizes of extracellular enzyme pools and activities in a temperate hardwood forest soil with dominant Quercus petraea (cambisol, mean annual temperature 9.3 °C). We hypothesized that the most significant variation of enzyme activity would occur in the litter, which faces greater variations in temperature, moisture content and chemical quality during the season, which decrease with soil depth. The site exhibited relatively large seasonal temperature differences and moderate changes in soil moisture content. Enzyme activity, microbial biomass, soil moisture content, temperature and pH were monitored for three years in the litter (L), organic horizon (O) and upper mineral horizon (Ah). Enzyme activity in vitro strongly increased with temperature until 20–25 °C, the highest temperatures recorded in situ. While no significant differences in the pools of most extracellular enzymes and in the content of microbial biomass were found among the seasons, enzyme activity typically increased during the warm period of the year, especially in the O and Ah horizons. Approximately 63%, 64%, and 69% of total annual activity was recorded during the warm period of the year in the L, O, and Ah horizons, respectively. Significant positive correlations were observed between soil moisture content and fungal biomass, but not bacterial biomass, indicating a decrease of the fungal/bacterial biomass ratio under dry conditions. The effect of moisture on enzyme activities was not significant except for endoxylanase in the litter. If soil temperature rises as predicted due to global climate change, enzyme activity is predicted to rise substantially in this ecosystem, especially in winter, when decomposition is not limited by drought and fresh litter that can decompose rapidly is present.
► Activity of enzymes in temperate forest soil increased with temperature. ► The enzyme pools and activities decreased down the soil profile. ► Microbial biomass increased with soil moisture content but not with temperature. ► Enzyme activities were higher in summer then in winter. ► If temperature increases, enzymatic decomposition is predicted to rise, especially in winter.
•Tree species influence the amount of labile and stable organic matter fractions.•Amount of labile and stable organic matter fractions vary vertically in soil profiles.•Fractional composition of SOM ...is influenced by DOC.•Lime and maples significantly enhance stabilization of mineral-associated fraction.
The species composition of a forest stand has a significant impact on the biophysicochemical properties of soil. The aim of our research was to determine the relationship between the fractional composition of soil organic matter (SOM) and the composition of leachates from soil influenced by various tree species. In our research, we assumed that the fractions of SOM are strongly positively correlated with dissolved organic carbon (DOC), nitrogen and the ionic composition of leachates. Our study was conducted in a common garden experiment with eight different tree species. The research included the analysis of vertical variability in the composition of SOM fraction in relation to the leachates composition. The research covered the organic horizon (O), humus mineral horizon (A) and enrichment horizon (B). Our findings confirmed the differentiated impact of the studied tree species on the amount of light and the heavy fraction − mineral associated fraction of SOM. The species composition of the forest stand significantly influenced the amount of released DOC, as well as pH values and the content of selected cations and anions in the leachates from various genetic soil horizons. The amounts of C and N in the SOM fraction and the ionic composition of the leachates change with the depth. C and N of the labile and stable fractions were strongly positively correlated with the amount of DOC and N in the leachates. In order to initiate the stabilization of organic matter, it is worth using deciduous species such as Norway maple, sycamore maple and small-leaved lime. The results of our research may find practical application in planning the species composition of a tree stand, especially under changing climate conditions.
Forest soils represent important terrestrial carbon (C) pools, where C is primarily fixed in plant biomass and then is incorporated in the biomass of fungi and bacteria. Although classical concepts ...assume that fungi are the main decomposers of the recalcitrant organic matter within plant and microbial biomass, whereas bacteria are considered to mostly utilize simpler compounds, recent studies have shown that fungi and bacteria overlap in substrate utilization. Here, we studied the microbial contribution to the recycling of dead biomass by analyzing the bacterial and fungal communities in soil microcosms supplemented with 13C-labeled biomass of plant, fungal, and bacterial origin using a combination of DNA-stable isotope probing and metagenomics. Both fungi and bacteria contributed actively to the degradation of complex components of plant and microbial biomass. Specific families of carbohydrate-active enzymes (CAZyme) were involved in the degradation of each biomass type. Moreover, the analysis of five bacterial metagenome-assembled genomes indicated the key role of some bacterial genera in the degradation of plant biomass (Cytophaga and Asticcacaulis) and microbial biomass (Herminiimonas). The enzymatic systems utilized by bacteria are highly complex and complementary but also highly diverse among taxa. The results confirm the importance of bacteria, in addition to fungi, as decomposers of complex organic matter in forest soils.
•Both fungi and bacteria actively degrade complex plant and microbial biomass.•The pool of CAZymes was distinct in fungi and bacteria.•Fungal communities encode more specific CAZymes that degrade plant biomass.•Bacterial communities are richer in CAZymes that target microbial biomass.•Bacteria use structurally variable but complementary enzymatic systems.
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