•Forest management have positive and negative effects on soil C stocks and GHG fluxes.•Intensive thinning and harvesting decrease soil C stock.•Coniferous tree species and fertilization increase soil ...C stock.•On drained peatlands, loss of soil C can be reduced by elevated water level.•Further understanding on soil C stabilization process and microbial processes needed.
The global forest carbon (C) stock is estimated at 662 Gt of which 45% is in soil organic matter. Thus, comprehensive understanding of the effects of forest management practices on forest soil C stock and greenhouse gas (GHG) fluxes is needed for the development of effective forest-based climate change mitigation strategies. To improve this understanding, we synthesized peer-reviewed literature on forest management practices that can mitigate climate change by increasing soil C stocks and reducing GHG emissions. We further identified soil processes that affect soil GHG balance and discussed how models represent forest management effects on soil in GHG inventories and scenario analyses to address forest climate change mitigation potential.
Forest management effects depend strongly on the specific practice and land type. Intensive timber harvesting with removal of harvest residues/stumps results in a reduction in soil C stock, while high stocking density and enhanced productivity by fertilization or dominance of coniferous species increase soil C stock. Nitrogen fertilization increases the soil C stock and N2O emissions while decreasing the CH4 sink. Peatland hydrology management is a major driver of the GHG emissions of the peatland forests, with lower water level corresponding to higher CO2 emissions. Furthermore, the global warming potential of all GHG emissions (CO2, CH4 and N2O) together can be ten-fold higher after clear-cutting than in peatlands with standing trees.
The climate change mitigation potential of forest soils, as estimated by modelling approaches, accounts for stand biomass driven effects and climate factors that affect the decomposition rate. A future challenge is to account for the effects of soil preparation and other management that affects soil processes by changing soil temperature, soil moisture, soil nutrient balance, microbial community structure and processes, hydrology and soil oxygen concentration in the models. We recommend that soil monitoring and modelling focus on linking processes of soil C stabilization with the functioning of soil microbiota.
The priming effect is a pivotal mechanism for microbial regulation of soil C cycling; however, the microbial mechanisms underlying priming effects remain elusive. Here, we combined an isotopic ...approach with metagenomic sequencing to investigate priming effects at five forest sites along an elevational gradient. Positive priming effects were found across the Quercus aliena var. acutiserrata (low elevation), Q. wutaishanica (low-mid elevation), Betula albosinensis (mid elevation), Abies fargesii Franch (mid-high elevation), and Larix chinensis Beissn (high elevation) forest sites. A significant positive correlation was found between the abundance of microbial C decomposition genes and priming effects (p < 0.05). Further analysis revealed that the microbial functional genes for breaking down stable C (lignin, lipids, and chitin) predominately drove the positive priming effects. Moreover, we found strong correlations between the relative abundance of eight near-complete bacterial genome bins and the priming effect. Five out of the eight genomes were associated with the Proteobacteria, indicating their predominant role in priming effects. Our results revealed that SOM quality (soil organic C, total nitrogen, and ratio of alkyl-C to O-alkyl-C), and soil environment (pH and bulk density) were the major drivers of the priming effect in forest soils as they regulated the abundance of microbial decomposition genes. In conclusion, the present study investigated the metagenomic basis of the priming effect, highlighting the importance of bacteria in association with substrate and environmental factors for C decomposition in forest soils.
•Positive priming effects were found in forest sites, the magnitude declined with elevation.•Microbial functional genes for breaking down the stable C drive the positive priming effects.•Soil substrates and soil environment drive of priming effect by regulating microbial genes.
Deadwood may alter the chemical and microbial properties of forest soils. However, it is unclear how downed deadwood (logs) of different tree species affect nutrients, microbial activity and biomass ...in different forest soils and regions. We investigated the effect of logs on underlying soils after 8 years of decomposition in an experiment consisting of 13 log tree species replicated at 30 forest sites across three German regions with distinct climate and geology. Soils beneath logs were compared to soils without recognizable influence of deadwood (control) 8 m away. Carbon, nitrogen, phosphorous and calcium concentrations increased by 5–18% in the soils under logs, whereas soil potassium, magnesium, iron, manganese and aluminum were not or slightly negatively affected by logs. Soils beneath logs exhibited 33%, 18% and 54% higher carbon mineralization, microbial biomass and ergosterol (component of fungal cell membranes) contents, respectively. Despite major differences in decay rates, the effect on soil properties hardly differed among the 13 log tree species. The effect of logs on microbial and chemical soil parameters increased with decreasing concentration of carbon, nitrogen, phosphorous and pH in the prevailing forest soils. Consequently, the strongest effects of logs on soil parameters occurred in plots with low soil nutrient contents and low soil pH. Our results suggest that logs of all tree species primarily increase the microbial activity and nutrient contents of acidic and nutrient-poor soils.
A motile, Gram-stain-negative, rod-shaped bacterium, designated G-4-1-14
T
, was obtained from forest soil sampled at Gwanggyo mountain, Gyeonggi-do, Republic of Korea. Cells were colourless, ...aerobic, grew optimally at 28–35 °C and hydrolysed DNA and casein. Phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain G-4-1-14
T
formed a lineage within the genus
Zoogloea
. The closest members were
Zoogloea resiniphila
ATCC 70068
T
(98.6 % sequence similarity),
Zoogloea caeni
EMB43
T
(98.2 %),
Zoogloea oryzae
A-7
T
(97.7 %),
Zoogloea ramigera
IAM 12136
T
(96.9 %) and
Zoogloea oleivorans
Buc
T
(96.2 %). The major respiratory quinone was ubiquinone-8 and the principal polar lipids were phosphatidylethanolamine, phosphatidyl-
N
-methylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The predominant cellular fatty acids were summed feature 3 (iso-C
15 :0
2-OH/C
16 : 1
ω
7
c
) and C
16 : 0
. The DNA G+C content was 65.9 mol%. The average nucleotide identity and digital DNA–DNA hybridization relatedness values between strain G-4-1-14
T
and other type strains were ≤81.6 and ≤24.9 %, respectively, which are below the species demarcation thresholds. Based on the results of phenotypic, phylogenetic and genomic analyses, strain G-4-1-14
T
represents a novel species in the genus
Zoogloea
, for which the name
Zoogloea dura
sp. nov. is proposed. The type strain is G-4-1-14
T
(=KACC 21618
T
=NBRC 114358
T
). In addition, we propose emendation of the genus
Zoogloea
and the species
Zoogloea oryzae
and
Zoogloea ramigera
.
Background and aims Nanoparticles and colloids affect the mobilisation and availability of phosphorus for plants and microorganisms in soils. We aimed to give a description of colloid sizes and ...composition from forest soil profiles and to evaluate the size-related quality of colloids for P fixation. Methods We investigated the size-dependent elemental composition and the P content of water-dispersible colloids (WDC) isolated from five German (beech-dominated) forest soil profiles of varying bulk soil P content by field-flow fractionation (FFF) coupled to various detectors. Results Three size fractions of WDC were separated: (i) nanoparticles <25 nm (NP) rich in Corg, (ii) fine colloids (25 nm–240 nm; FC) composed mainly of Corg, Fe and Al, probably as associations of Fe- and Al- (hydr)oxides and organic matter, and (iii) medium-sized colloids (240 nm–500 nm; MC), rich in Fe, AI and Si, indicating the presence of phyllosilicates. The P concentration in the overall WDC was up to 16 times higher compared to the bulk soil. The NP content decreased with increasing soil depth while the FC and MC showed a local maximum in the mineral topsoil due to soil acidification, although variant distributions in the subsoil were observed. NP were of great relevance for P binding in the organic surface layers, whereas FC- and MC-associated P dominated in the Ah horizon. Conclusion The nanoparticles and colloids appeared to be of high relevance as P carriers in the forest surface soils studied, regardless of the bulk soil P content.
•We investigated small-scale variability of soil pH under pine and oak stands.•Data indicated a strong influence of former windthrows on spatial structure of pH.•Data confirmed that nearby pine tree ...pH depression was also present.•Stripped pattern of soil pH remaining after soil preparation was found in pine stands.•Variations in pH are controlled by the saturation of soil with Al, not base cations.
This study was conducted to investigate the factors affecting small-scale variability of soil pHCaCl2 under homogeneous pine forest monocultures and seed-regenerated oak stands, with particular emphasis on the effects of soil disturbances (windthrows, soil preparation) and tree positions on spatial variability of soil pHCaCl2. We also attempted to explain the mechanism controlling this small scale spatial variability in terms of soil cation exchange properties. Investigations were conducted in forested areas of Southern Poland. Six 20 × 20 m plots were laid out in homogeneous, mature (40–80 years) pine (three plots) and oak (three plots) stands. Soil samples were collected from the top 10 cm of mineral soil in regular 1 m × 1 m grid, what gives 441 samples per plot. Semivariogram analyses indicated a strong influence of former windthrows (mound-pit soil disturbances) on spatial structure of soil pHCaCl2, particularly in soil under oak stands. Moreover, we found that under oak trees soil pHCaCl2 increased with increasing distance from the tree, confirming the presence of so called near tree pHCaCl2 depression. This suggests that the characteristics of mound material are largely a result of the apparent single-tree influence on soil pHCaCl2. Data from pine stands also confirmed that nearby planted tree pHCaCl2 depression was also present; however, variograms characteristics and maps of pHCaCl2 may be proof for stripped pattern of soil pHCaCl2 remaining after soil preparation. Analysis of the cation exchange properties of the soils revealed that variations in soil pHCaCl2 is related to the saturation of soil with Al (i.e., soil having higher pHCaCl2 has less adsorbed H+ replaced by Al3+), while base cations (Ca2+, K+, Mg2+) had no effect, implying that in trees vicinity soil has lower degree of saturation with Al3+.
Iron (Fe) minerals play an important role in carbon (C) and nutrient dynamics in redox fluctuating soils. We explored how the frequency of redox oscillations influence Fe reduction rates and C ...content in Puerto Rican soils. We hypothesized that iron reduction rates would be faster during short oscillation periods than in longer oscillation periods. Surface soils from an upland valley in a humid tropical forest were exposed to systematic redox oscillations over 49 days. The oxidation events were triggered by the introduction of air (21% O₂), maintaining the time ratio under oxic or anoxic conditions at 1:6 (τox/τanox). After preconditioning the soil to fluctuating redox conditions for 1 month, we imposed 280- and 70-h (or 11.67- and 2.5-day) redox oscillations, measuring FeII every few days. We found that by the end of the experiment, Fe reduction rates were higher in the short oscillation period (τox = 10 h, τanox = 60 h) than in the long oscillation period (τox = 40 h, τanox = 240 h). Carbon and nitrogen loss however was similar for both treatments. These results suggest the characteristics of redox fluctuations can alter rates of Fe reduction and potentially influence ecosystem processes that depend on iron behavior.
The ratio of carbon-to-nutrient in forest floors is usually much higher than the ratio of carbon-to-nutrient that soil microorganisms require for their nutrition. In order to understand how this ...mismatch affects carbon (C) cycling, we investigated the respiration rate per unit soil microbial biomass – the metabolic quotient (qCO2) – in relation to the soil carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratio in temperate forests. For this purpose, cores of beech, spruce, and mixed spruce-beech forest soils were cut into slices of 1 cm from the litter layer down to 5 cm in the mineral soil, and the relationship between the qCO2 and the soil C:N and the soil C:P ratio was analyzed. We found that the qCO2 was positively correlated with soil C:N ratio in spruce soils (R = 0.72), and with the soil C:P ratio in beech (R = 0.93), spruce (R = 0.80) and mixed forest soils (R = 0.96). We also observed a close correlation between the qCO2 and the soil C concentration in all three forest types. Yet, the qCO2 decreased less with depth than the C concentration in all three forest types, suggesting that the change in qCO2 is not only controlled by the soil C concentration. We conclude that microorganisms increase their respiration rate per unit biomass with increasing soil C:P ratio and C concentration, which adjusts the substrate to their nutritional demands in terms of stoichiometry.
•The qCO2 (respiration rate per unit microbial biomass) increased with soil C:N ratio in spruce soils.•The qCO2 increased with soil C:P ratio in beech, spruce, and mixed forest soils.•Microorganisms adjust the substrate to their nutritional demands in terms of C:N:P stoichiometry.
We investigated the interactions among pH, Al solubility and Al–soil organic matter (SOM) complexation to test the hypothesis that competition between Al and H ions for cation binding sites on soil ...organic matter (SOM) determines soil pH and Al solubility in acidic forest soils in the northeastern U.S. Samples from five soil horizons in 39 forested watersheds across the northeastern U.S. were used with two Al complexation models to test the hypothesis. Our results indicated that Al solubility increases with soil depth when pH is less than 4.5 and the ratio of the fractions of organically bound Al and H(NAl/NH) or the ratio of organically bound Al to total organic carbon (Alorg/C) remains roughly constant within each horizon. Both the NAl/NH and the Alorg/C ratios are effective measures of the ratio of sites bound to Al and H in Al–SOM complexation models. The log-linear relationship pAlKCl-p(Alorg/C)=0.75×pHKCl-1.56 (r=0.86,P<.0001) can be used to describe Al–pH relationships in Oie, Oa, Bh and Bs1 horizon samples from across the region. The competition between H+ and Al3+ for binding to SOM affects soil pH and Al solubility to a greater degree in Oa and Bs1 horizons than in Oie and E horizons. Our data are consistent with the conceptual model that portrays the Al–pH relationship in acid forest soils as a balance between organic acidity and alkalinity produced through the weathering of aluminosilicate minerals.
•pH, Al solubility and Al–SOM complexes control acid–base chemistry in forest soils.•Two Al binding/solubility models were tested with data from the northeastern USA.•The effects of Al saturation must be considered in the Al–SOM complexation models.•Al–H competition controls pH and Al solubility in Oa and upper mineral horizons.•Base cations compete with exchangeable H ions to regulate pH in Oi/Oe horizons.
The leaching of P from the upper 20cm of forest topsoils influences nutrient (re-)cycling and the redistribution of available phosphate and organic P forms. However, the effective leaching of ...colloids and associated P forms from forest topsoils was so far sparsely investigated. We demonstrated through irrigation experiments with undisturbed mesocosm soil columns, that significant proportions of P leached from acidic forest topsoils were associated with natural colloids. These colloids had a maximum size of 400nm. By means of Field-flow fractionation the leached soil colloids could be separated into three size fractions. The size and composition was comparable to colloids present in acidic forest streams known from literature. The composition of leached colloids of the three size classes was dominated by organic carbon. Furthermore, these colloids contained large concentrations of P which amounted between 12 and 91% of the totally leached P depending on the type of the forest soil. The fraction of other elements leached with colloids ranged between 1% and 25% (Fe: 1–25%; Corg: 3–17%; Al: <4%; Si, Ca, Mn: all <2%). The proportion of colloid–associated P decreased with increasing total P leaching. Leaching of total and colloid-associated P from the forest surface soil did not increase with increasing bulk soil P concentrations and were also not related to tree species. The present study highlighted that colloid-facilitated P leaching can be of higher relevance for the P leaching from forest surface soils than dissolved P and should not be neglected in soil water flux studies.
Display omitted
•Natural colloids up to a size of 400nm leached from forest topsoil columns.•Leached colloids were dominated by soil organic matter.•Large proportions of P leached from loamy soils were bound to colloids.•The fraction of P bound to colloids decreased with rising P leachate concentrations.
PDF
