Soil Biogeochemical Properties Research Articles

Effects of Stockpiling on Topsoil Biogeochemistry for Semiarid Mine Reclamation

Stockpiling and storage of topsoil for use in reclamation and revegetation are common practices for many mining operations. However, stockpiling can lead to significant changes in topsoil physical and biogeochemical properties that may be detrimental to reclamation. The objective of this research was to assess the effect of long-term stockpiling on soil biogeochemical properties in a semiarid region. We hypothesized that soil properties would change systematically with depth reflecting a shift to anaerobic conditions and resulting in a general decrease in soil health. To address this hypothesis, boreholes > 20-m deep were drilled into a 14-year-old topsoil stockpile at a copper mine in Arizona and samples collected every ~ 75 cm. Samples were analyzed for soil DNA biomass, texture, general agronomic properties, mineral composition, oxalate and dithionite extraction of active mineral phases, and total elemental composition. Depth profiles revealed non-systematic changes in biogeochemical variables with depth, including variation in soil DNA biomass, organic matter (OM), extractable nitrate (NO3-N) and ammonium (NH4-N) nitrogen, plant-available manganese (Mn) and iron (Fe), and oxalate-extractable Mn and Fe. Differences in biogeochemical properties were associated with zones of variable redox state mediated by OM content and layer depth. Anaerobic zones were observed at depths greater than 4 m where OM > 1%, and aerobic zones were observed at depths up to 15 m where OM < 1%. This study demonstrates the importance of stockpile composition on biogeochemical processes during storage and contributes to improved understanding of topsoil management as a resource for reclamation of degraded mine lands in semiarid environments.

Assessment of soil quality degradation impacted by topsoil stockpiling of a surface mining operation in a Tropical climate.

Topsoil stripping and storage are primarily carried out before mining, yet the main problem of returning this stockpile post-mining is the decline in soil quality. This study investigated the impact of varying storage durations on soil biogeochemical properties and the presence of heavy metals in stockpiled topsoils of four different ages (3, 8, 13, and 18 years) compared to a native forest at the Newmont Ghana Gold Limited, Ghana. Soil samples were collected on the various stockpiles to evaluate soil pH, total nitrogen, organic carbon, nitrate and ammonium nitrogen, exchangeable cations, bacterial population, and microbial biomass carbon (MBC), Fe, Pb, Cd, Cu, and Zn. Our findings revealed that prolonged storage duration considerably diminishes soil quality relative to the natural forest. Notably, MBC significantly decreased from 49.00 mg C kg-1 soil in the 3-year-old stockpile to 39.00 mg C kg-1 soil in the 8-year-old stockpile. However, MBC increased dramatically from 12.82% to 49.49% in the 13- and 18-year-old stockpiles respectively. The bacteria population decreased by 15.01%, 40.00%, and 40.90% when the storage age increased from 3- to 8-, 13-, and 18-year-old stockpiles. All the stockpiles recorded higher contamination factors, pollution load indexes, and Igeo indexes for measured heavy metals except Cd. The increase in stockpile ages beyond 3 years resulted in an increased deterioration index compared with the natural forest. The principal component analysis revealed that MBC, bacteria, NO3- -N, fungi, and earthworm populations were the most sensitive soil indicators affected by stockpiling. The decline in stockpile quality may significantly hamper reclamation efforts, necessitating that land managers and mining firms consider stockpile age, nutrient content and biological indicators for effective restoration. Additionally, amendment applications to 8 years and above stockpiles could optimize nutrient availability, facilitating ecosystem restoration.

Thermal desorption remediation effects on soil biogeochemical properties and plant performance: Global Meta-analysis

Soil contamination remains a global problem, and numerous studies have been published for investigating soil remediation. Thermal desorption remediation (TDR) can significantly reduce the contaminants in the soil within a short time and consequently has been used worldwide. However, the soil properties respond to TDR differently and are dependent on the experimental set-up. The causative mechanisms of these differences are yet to be fully elucidated. A statistical meta-analysis was thus undertaken to evaluate the TDR treatment effects on soil properties and plant performance. This review pointed out that soil clay was reduced by 54.2%, while soil sand content was enhanced by 15.2% after TDR. This might be due to the release of cementing agents from clay minerals that resulted in the formation of soil aggregates. Soil electrical conductivity enhanced by 69.5% after TDR, which might be due to the heating-induced loss of structural hydroxyl groups and the consequent liberation of ions. The treatment of TDR leads to the reduction of plant germination rate, length, and biomass by 19.4%, 44.8%, and 20.2%, respectively, compared to that of control soil. This might be due to the residue of contaminants and the loss of soil fertility during the thermal process that inhibited plant germination and growth. Soil pH and sulfate content increased with heating temperature increased, while soil enzyme activities decreased with thermal temperature increased. Overall, the results suggested that TDR treatment has inhibited plant growth as well as ecological restoration.

Using Relationships Between Vegetation and Surface Soil Biogeochemical Properties to Assess Regional Soil Carbon Inventories for South Baffin Island, Nunavut, Canada

AbstractAs Arctic regions warm rapidly, it is unclear whether high‐latitude soil carbon (C) will decrease or increase. Predicting future dynamics of Arctic soil C stocks requires a better understanding of the quantities and controls of soil C. We explore the relationship between vegetation and surface soil C in an understudied region of the Arctic: Baffin Island, Nunavut, Canada. We combined soil C data for three vegetation types—polar desert, mesic tundra, and wet meadow—with a vegetation classification to upscale soil C stocks. Surface soil C differed significantly across vegetation types, and interactions existed between vegetation type and soil depth. Polar desert soils were consistently mineral, with relatively thin organic layers, low percent C, and high bulk density. Mesic soils exhibited an organic‐rich epipedon overlying mineral soil. Wet meadows were consistently organic soil with low bulk density and high percent C. For the top 20 cm, polar desert contained the least soil C (2.17 ± 0.48 kg m−2); mesic tundra had intermediate C (8.92 ± 0.74 kg m−2); wet meadow stored the most C (13.07 ± 0.69 kg m−2). Extrapolating to the top 30 cm, our results suggest that approximately 44 Tg C is stored in the study region with a mean landscape soil C stock of 2.75 kg m−2 for non‐water areas. Combining vegetation mapping with local soil C stocks considerably narrows the range of estimates from other upscaling approaches (27–189 Tg) for soil C on South Baffin Island.

Intercropping prairie cordgrass with kura clover had little effect on soil biogeochemistry

AbstractIntercropping kura clover (Trifolium ambiguum) (KC) with prairie cordgrass (Spartina pectinata) (PCG) has great potential for biofuel feedstock on marginal lands. This study evaluated the impacts of 10‐year PCG‐KC intercropping and PCG monoculture fertilized with different nitrogen (N) rates of granular urea (five treatments: PCG‐KC, PCG‐0N, PCG‐75N, PCG‐150N, and PCG‐225N) on soil biogeochemical properties: (i) in the surface soil (0‐ to 10‐cm depth) at three different sampling times during the crop growing season: spring (April, pre‐emergence), summer (June, active growth), and fall (November, post‐harvest); and (ii) at different soil depths (0–5, 5–15, 15–30, 30–45, and 45–60 cm) (only total carbon (C) and N) in fall 2021. All soil biogeochemical parameters were higher during summer as compared to spring and/or fall, except urease activity, ammonium‐N, microbial biomass C and N, and fluorescein diacetate (FDA). On average over the sampling times, PCG‐KC had significantly higher β‐glucosidase activity and hot‐water extractable organic N than PCG‐0N; but no significant difference between PCG‐KC and N‐fertilized PCG. Cold‐water extractable organic N was significantly lower than the highest N rate, but not significantly different from PCG‐0N and lower N rate treatments. Urease activity under PCG‐KC treatment was double that of PCG‐0N and PCG‐75N; FDA was higher in PCG‐KC than all monocultures. No treatment effect was found on soil total C and N, except that they decreased with depth. Overall, intercropping PCG‐KC showed some benefits in terms of promoting soil biogeochemical properties during crop growth periods, having lower residual reactive N in the soil, and maintaining biomass yield and quality on marginal lands.

Plant invasion alters soil phosphorus cycling on tropical coral islands: Insights from Wollastonia biflora and Chromolaena odorata invasions

Plants may modify soil biogeochemical properties that facilitate their invasion of new sites which may be mediated by soil microorganisms. We compared microbially-mediated soil phosphorus (P) cycling among sites with different degrees of invasion by Wollastonia biflora and Chromolaena odorata on two coral islands. Wollastonia biflora and C. odorata outcompeted all native species and invested more P in leaves (45–136% more than the native species). We found a decrease in the proportion of HCl–P and organic P, and a corresponding increase in the proportion of labile inorganic P (Pi) of the soil total P concentrations following plant invasion. Leaf P concentrations in invasive species were positively correlated with the proportion of labile Pi, suggesting that HCl–P and organic P were the major P sources for invasive plants, and that plant invasion increased soil P-cycling rates as a result of root carboxylate release (evidenced by greater leaf manganese concentrations) and enhanced soil alkaline phosphatase activity. The latter was confirmed by an increased soil phoD gene abundance after plant invasion. Soil P availability was elevated after plant invasion which was associated with increases in the release of root carboxylates and microbial activities that are involved in mobilization of HCl–P and mineralization of organic P, respectively, especially in the wet season. This, in turn, strongly increased leaf P concentrations of invasive species to sustain rapid plant growth, and presumably depriving competitors of P. These novel insights into soil P cycling through the enrichment of a specific soil microbial community and root carboxylate release in invaded ecosystems enhance our understanding of plant invasion mechanisms on coral islands.

Soil pH Variability in Mangu, Bokkos and Pankshin Local Government Areas of Plateau State

This paper investigates soil pH variability in three local government areas (LGAs) in Plateau State, Nigeria: Bokkos, Mangu, and Pankshin. Soil pH is a crucial factor influencing soil biogeochemical properties, which in turn affect crop yield, soil nutrient levels, and microbial activity. The study utilized Stratified Random Sampling to collect soil samples, and employed IDW (Inverse Distance Weighted) interpolation for analysis. The results revealed a pH range of 4.5 to 7.07, categorized into five classes: very strongly acidic (4.5 - 5.05), strongly acidic (5.05 - 5.35), moderately acidic (5.35 - 5.58), slightly acidic (5.58 - 5.83), and neutral (5.83 - 7.07). Slightly acidic and moderately acidic soils were predominant across the entire study area, covering 1643.96 Km² and 1444.41 Km² respectively. Noteworthy variations in pH were observed between the LGAs, with Bokkos and Mangu exhibiting more acidic soils, while Pankshin had soils tending towards neutrality. These variations were attributed to the local topography and geology. The pH variations also play a significant role in determining suitable crops for cultivation. Bokkos and Mangu are conducive for extensive farming of maize and Irish potatoes, while Pankshin is better suited for millet and sorghum cultivation. Given the global implications of events like the Russia-Ukrainian war on food supply, the study recommends that relevant government agencies identify areas with similar soil characteristics and invest in extensive cultivation of crops well-suited to those soils. This could contribute significantly to enhancing food security on a global scale]

Understory vegetation removal significantly affected soil biogeochemical properties in forest ecosystems

Understory vegetation plays a crucial role in mediating the natural development of forest ecosystems. The removal of understory vegetation, as a common forest management practice, may have a significant impact on soil properties. However, a global perspective on how understory removal might affect soil biogeochemical properties is still lacking. To fill this knowledge gap, we performed a meta-analysis with 2059 observations collected from 71 peer reviewed publications to evaluate the effects of understory vegetation removal on soil carbon (C), nitrogen (N), phosphorus (P), potassium (K), and microbial biomass. We found that (1) removal of the understory significantly increased soil nitrates (NO3−) concentration by 6.5 %, but decreased the stocks of C and N, the concentrations of N, available K (AK) and microbial biomass C (MBC), and fine root biomass by 19.4, 15.1, 7.9, 19.9, 13.5 and 32.2%, respectively; (2) mycorrhizal association significantly mediated understory removal effects on soil organic C (SOC) and dissolved organic C (DOC) concentrations, and soil pH, while canopy type had a significant impact on the effects of understory removal on soil K, AK, NO3−, MBC concentrations, C:N ratio, and soil pH; (3) soil depth had a negative impact on the effects of understory removal on SOC, AK, ammonium nitrogen (NH4+) concentrations, and soil moisture; and (4) mycorrhizal association, soil depth, slope, forest stand age, elevation, and MAT were the most important moderator variables. Our results suggest that the removal of understory vegetation generally have negative effects on soil biogeochemical properties, and that managing understory vegetation is important for promoting the healthy development of forest ecosystems.

Responses of dissolved organic carbon to freeze–thaw cycles associated with the changes in microbial activity and soil structure

Abstract. Arctic warming accelerates snowmelt, exposing soil surfaces with shallow or no snow cover to freeze–thaw cycles (FTCs) more frequently in early spring and late autumn. FTCs influence Arctic soil C dynamics by increasing or decreasing the amount of dissolved organic carbon (DOC); however, mechanism-based explanations of DOC changes that consider other soil biogeochemical properties are limited. To understand the effects of FTCs on Arctic soil responses, we designed microcosms with surface organic soils from Alaska and investigated several soil biogeochemical changes for seven successive temperature fluctuations of freezing at −9.0 ± 0.3 ∘C and thawing at 6.2 ± 0.3 ∘C for 12 h each. FTCs significantly changed the following soil variables: soil CO2 production (CO2), DOC and total dissolved nitrogen (TDN) contents, two DOC quality indices (SUVA254 and A365 / A254), microaggregate (53–250 µm) distribution, and small-sized mesopore (0.2–10 µm) proportion. Multivariate statistical analyses indicated that the FTCs improved soil structure at the scale of microaggregates and small-sized mesopores, facilitating DOC decomposition by soil microbes and changes in DOC quantity and quality by FTCs. This study showed that FTCs increased soil CO2 production, indicating that FTCs affected DOC characteristics without negatively impacting microbial activity. Soil microaggregation enhanced by FTCs and the subsequent increase in microbial activity and small-sized pore proportion could promote DOC decomposition, decreasing the DOC quantity. This study provides a mechanism-based interpretation of how FTCs alter DOC characteristics of the organic soil in the active layer by incorporating structural changes and microbial responses, improving our understanding of Arctic soil C dynamics.

The core microbiota as a predictor of soil functional traits promotes soil nutrient cycling and wheat production in dryland farming

Abstract Host plants and the microbiota living in the rhizosphere are interdependent, mutually reinforced and mutually beneficial but the assembly, functions and microbial interactions of the host‐associated microbiota are still unclear. Herein, winter wheat was selected as a test plant to explore the assembly process of total bacteria from bulk soil (BS) and rhizosphere soil (RS), and phoD‐harbouring bacteria in RS at a long‐term (14 years) trial site. We also identified core microbes that are potentially relevant to soil carbon (C), nitrogen (N) and phosphorus (P) cycling genes and soil biogeochemical properties, and investigated the relationships between soil variables, functional genes and wheat productivity. The results showed that the microhabitat of the plant, rather than P fertilizer input, was the main factor affecting the microbial diversity, composition and co‐occurrence networks. The BS bacterial community was driven by deterministic processes but the RS and phoD bacterial communities were dominated by stochastic processes. The influence of deterministic processes decreased with increasing soil nutrient content. A core microbial community consisted of 10 OTUs in different microhabitats and was significantly related to soil functional genes and properties. In the rhizosphere soil, significant correlations were found between soil variables, soil functional bacteria and genes, and crop productivity. Synthesis and applications. This study provides empirical evidence that the assembly process of the microbial community is governed by environmental factors in various soil environments and provides new perspectives on the sustainable improvement of crop productivity. Read the free Plain Language Summary for this article on the Journal blog.

Vegetation as a key driver of the distribution of microbial generalists that in turn shapes the overall microbial community structure in the low Arctic tundra

Understanding the variability of microbial niches and their interaction with abiotic and biotic factors in the Arctic can provide valuable insights into microbial adaptations to extreme environments. This study investigates the structure and diversity of soil bacterial communities obtained from sites with varying vegetation coverage and soil biogeochemical properties in the low Arctic tundra and explores how bacteria interact under different environmental parameters. Our findings reveal differences in bacterial composition and abundance among three bacterial niche breadths (specialists, common taxa, and generalists). Co-occurrence network analysis revealed Rhizobiales and Ktedonobacterales as keystone taxa that connect and support other microbes in the habitat. Low-elevation indicators, such as vascular plants and moisture content, were correlated with two out of three generalist modular hubs and were linked to a large proportion of generalists’ distribution (18%). Structural equation modeling revealed that generalists’ distribution, which influenced the remaining microbial communities, was mainly regulated by vegetation coverage as well as other abiotic and biotic factors. These results suggest that elevation-dependent environmental factors directly influence microbial community structure and module formation through the regulation of generalists’ distribution. Furthermore, the distribution of generalists was mainly affected by macroenvironment filtering, whereas the distribution of specialists was mainly affected by microenvironment filtering (species-engineered microbial niche construction). In summary, our findings highlight the strong top–down control exerted by vegetation on generalists’ distribution, which in turn shapes the overall microbial community structure in the low Arctic tundra.

Post‐fire soil extracellular enzyme activities in subtropical–warm temperate climate transitional forests

AbstractWildfire impacts on soil microbial community structure and functional activity have attracted a growing attention because of the higher sensitivity of soil microbes to wildfire. Soil extracellular enzymes play pivotal roles in biogeochemical processes, such as mediating carbon (C) and nutrient cycling. However, little is known about how post‐fire changes in soil biogeochemical properties and microbial community composition affect soil extracellular enzyme activities. This study explored the responses and regulating factors of C‐, nitrogen‐(N), and phosphorus‐(P) acquiring extracellular enzyme activities across a wildfire chronosequence (i.e., 1, 6, 13, and 50 years after fire) in subtropical–temperate ecotonal forests in Central China. The activities of C‐(β‐glucosidase), N‐(N‐acetylglucosaminidase), and P‐(acid phosphatase) acquiring enzymes declined with time post‐fire, with the highest values one‐year post‐fire. The response of C‐acquiring enzyme activity to fire was positively correlated with bacterial biomass, suggesting that microbial compositions were related to post‐fire changes in extracellular enzyme decomposition. The response of N‐acquiring enzyme activity to fire was positively correlated with soil P availability, while P‐acquiring enzyme activity was positively correlated with soil N availability. Overall, soil extracellular enzyme activity declined with time post‐fire, suggesting wildfire may reduce microbial demand for nutrients over time. Future research is needed to elucidate fire impacts on microbial processes for nutrient‐microbial‐enzyme linkages.

Co-Responses of Soil Organic Carbon Pool and Biogeochemistry to Different Long-Term Fertilization Practices in Paddy Fields

Long-term application of soil organic amendments (SOA) can improve the formation of soil organic carbon (SOC) pool as well as soil fertility and health of paddy lands. However, the effects of SOA may vary with the input amount and its characteristics. In this work, a descriptive field research was conducted during one cropping season to investigate the responses of various SOC fractions to different long-term fertilization practices in rice fields and their relationships with soil biogeochemical properties and the emission of greenhouse gases (GHG). The field sites included two conventional paddies applied with chemical fertilizer (CF) or CF + rice straw (RS) and six organic agriculture paddies applied with oilseed cake manure (OCM) + wheat straw (WS), cow manure (CM) + WS, or CM + RS. The two paddy soils treated with CM + RS had significantly higher concentrations of recalcitrant to labile C forms, such as loss-on-ignition C (LOIC; 56-73 g kg-1), Walkley-Black C (WBC; 20-25 g kg-1), permanganate oxidizable C (POXC; 835-853 mg kg-1), and microbial biomass carbon (MBC; 133-141 mg kg-1), than soils treated with other SOA. Likewise, long-term application of CM + RS seemed to be the best for regulating soil fertility parameters, such as ammonium (11-141 mg kg-1); phosphate (61-106 mg kg-1); and soluble Ca, K, and Mg (7-10, 0.5-1.2, and 1.9-3.8 mg kg-1, respectively), although the results varied with the location and soil properties of rice fields. Additionally, the two paddy sites had the largest cumulative methane emission (754-762 kg ha-1), seemingly attributed to increased microbial biomass and labile C fractions. The significant correlations of most SOC fractions with soil microbial biomass, trophic factors, and methane emissions were confirmed with multivariate data analysis. It was also possible to infer that long-term SOA application, especially with CM + RS, enhanced interaction in belowground paddy fields, contributing to soil fertility and rice production sustainability. Based on our findings, we suggest the need for analysis of various types of SOC fractions to efficiently manage soil fertility and quality of paddy fields, C sequestration, and GHG emissions.

Effects of geological conditions and atmospheric deposition on soil biogeochemical properties in Japanese forested ecosystems revealed by Sr isotope analysis

Effects of geological conditions and atmospheric deposition on soil biogeochemical properties in Japanese forested ecosystems revealed by Sr isotope analysis

Variation in Hydraulic Properties of Forest Soils in Temperate Climate Zones

The structure of forests in temperate climates has been changing to ensure the resilience of trees. This change affects the local water balance. Knowledge of soil hydraulic properties (SHP) is essential to assess the water cycle in ecosystems. There is little knowledge about the impact of tree species on SHP and the water balance. Based on a compilation of 539 related studies we aimed at identifying the effects of tree species and age on SHP in temperate climates. However, most studies concentrated on soil biogeochemical properties, whereas only 256 studies focused on SHP. The literature presents no standard methods for assessing SHP and there is no knowledge of their variations in forests. We present a systematic overview of the current state of knowledge on variations in SHP based on forest type in temperate climates. We identify the gaps and weaknesses in the literature and the difficulties of evaluating the reviewed studies. More studies following standardised methodologies are needed to create a robust database for each forest type and soil texture. It would improve the assessment of the forest water balance through calibrated plot/site-scale process models. Such a database does not yet exist, but it would greatly improve the management and development of future forest ecosystems.

Synergetic effect of complex soil amendments to improve soil quality and alleviate toxicity of heavy metal(loid)s in contaminated arable soil: toward securing crop food safety and productivity.

Globally, various types of soil amendments have been used to improve the fertility and quality of soils in agricultural lands. In heavy metal(loid) (HM)-contaminated land, the soil amendments can also act as an immobilizing agent, thereby detoxifying HMs. A pot experiment was conducted to investigate the effects of three different complex amendments, including T1 (gypsum + peat moss + steel slag; GPMSS), T2 (GPMSS + lime), and T3 (GPMSS + lime + sulfate), on biogeochemical properties of the HM-contaminated arable soils, including Soil A and Soil B, and the magnitude of HM uptake by Chinese cabbage (Brassica rapa L.) for 6weeks. All the examined complex amendments improved soils' physical and biological properties by increasing the water-stable aggregate (WSA) ratio by 18-54% and dehydrogenase activity (DHA) by 300-1333mg triphenyl formazan (TPF) kg-1 24h-1 in comparison to control soils. The concentrations of HMs accumulated in B. rapa appeared to decrease tremendously, attributed to effectively immobilizing the HMs in soils by incorporating complex amendments mediated by soil pH, dissolved organic carbon (DOC), and complexation with the components of amendments. All these positive changes in soil properties resulted in the elevation of B. rapa productivity. For instance, T1 treatment induced an increase of plant dry weight (DW) by 3.7-3.9 times compared to the controls. Suppose there are no typical differences in the efficiency among the treatments. In that case, our findings still suggest that using complex amendments for the HM-contaminated arable soils would be beneficial by bringing a synergetic effect on improving soil biogeochemical properties and alleviating HM toxicity, which eventually can enhance plant growth performance.

Effect of nitrogen fertilization on central tendency and spatial heterogeneity of soil moisture, pH and dissolved organic carbon and nitrogen in two bioenergy croplands#

AbstractBackgroundSoil moisture, pH, dissolved organic carbon and nitrogen (DOC, DON) are important soil biogeochemical properties in switchgrass (SG) and gamagrass (GG) croplands. Yet their spatiotemporal patterns under nitrogen (N) fertilization have not been studied.AimsThe objective of this study is to investigate the main and interactive effects of N fertilization and bioenergy crop type on central tendencies and spatial heterogeneity of soil moisture, pH, DOC and DON.MethodsBased on a 3‐year long fertilization experiment in Middle Tennessee, USA, 288 samples of top horizon soils (0–15 cm) under three fertilization treatments in SG and GG croplands were collected. The fertilization treatments were no N input (NN), low N input (LN: 84 kg N ha−1 in urea) and high N input (HN: 168 kg N ha−1 in urea). Soil moisture, pH, DOC and DON were quantified. And their within‐plot variations and spatial distributions were achieved via descriptive and geostatistical methods.ResultsRelative to NN, LN significantly increased DOC content in SG cropland. LN also elevated within‐plot spatial heterogeneity of soil moisture, pH, DOC and DON in both croplands though GG showed more evident spatial heterogeneity than SG. Despite the pronounced patterns described above, great plot to plot variations were also revealed in each treatment.ConclusionThis study informs the generally low sensitivity of spatiotemporal responses in soil biogeochemical features to fertilizer amendments in bioenergy croplands. However, the significantly positive responses of DOC under low fertilizer input informed the best practice of optimizing agricultural nutrient amendment.

Difference in Soil Biogeochemical Properties of Agricultural Highland by Topographical Characteristic and Soil Management

In agricultural highland, soil properties change over time due to soil management methods, soil erosion, and cultivation. The objective of this study was to investigate the differences in soil properties according to land management in agricultural highland. As a result of the soil analysis, Anbandegi, Maebongsan, Yeongwol, and Jeongseon, located near the top of the mountain, had low bulk densities, and organic matter, CEC, exchangeable cation, water stable aggregation rate, and dehydrogenase activity, were relatively higher than those of Daegwallyeong and Punch bowl. In the Daegwallyeong and Punch bowl, saprolite soil was periodically piled to replace eroded top-soil, and as a result, soil characteristics differed significantly from those located near the top of the mountain. In the principal component analysis result, organic matter showed the largest eigenvalue in PC1, and pH was selected as PC2. The distribution of soil clusters by sampling point was PC1, and Daegwallyeong and Punch bowl were classified differently from highland areas near the top of the mountain, and coastal basins and Daegwallyeong were classified by PC2. In conclusion, highland soil showed different soil properties for each region, which was the result of differences according to the soil management methods. And considering the relationship between soil characteristics, it was confirmed that organic matter was the most important factor in the soil management methods. Coefficients of each variable for PC1 and PC2 through the PCA of agricultural highland soils.

Chronological changes in soil biogeochemical properties of the glacier foreland of Midtre Lovénbreen, Svalbard, attributed to soil-forming factors

Glacier forelands provide an excellent opportunity to investigate vegetation succession and soil development along the chronosequence; however, there are few studies on soil biogeochemical changes from environmental factors, aside from time. This study aimed to investigate soil development and biogeochemical changes in the glacier foreland of Midtre Lovénbreen, Svalbard, by considering various factors, including time. Eighteen vegetation and soil variables were measured at 38 different sampling sites of varying soil age, depth, and glacio-fluvial activity. Soil organic matter (SOM) was quantitatively measured, and the compositional changes in SOM were determined following size-density fractionation. In the topsoil, the soil organic carbon (SOC) and total nitrogen (N) content was found to increase along the soil chronosequence and were highly correlated with vegetation-associated variables. These findings suggest that plant-derived material was the main driver of the light fraction of SOM accumulation in the topsoil. The heavy fractions of SOM were composed of microbially transformed organic compounds, eventually contributing to SOM stabilization within short 90-yr deglaciation under harsh climatic conditions. In addition to time, the soil vertical profiles showed that other environmental parameters, also affected the soil biogeochemical properties. The high total phosphorous (P) content and electrical conductivity in the topsoil were attributed to unweathered subglacial materials and a considerable amount of inorganic ions from subglacial meltwater. The high P and magnesium content in the subsoil were attributed to parent materials, while the high sodium and potassium content in the surface soil were a result of sea-salt deposition. Glacio-fluvial runoff hampered ecosystem development by inhibiting vegetation development and SOM accumulation. This study emphasizes the importance of considering various soil-forming factors, including parent/subglacial materials, aeolian deposition, and glacio-fluvial runoff, as well as soil age, to obtain a comprehensive understanding of the ecosystem development in glacier forelands.

Deforestation-free land-use change and organic matter-centered management improve the C footprint of oil palm expansion.

In recent decades, mounting evidence has indicated that the expansion of oil palm (OP) plantations at the expense of tropical forest has had a far pernicious effect on ecosystem aspects. While various deforestation‐free strategies have been proposed to enhance OP sustainability, field‐based evidence still need to be consolidated, in particular with respect to savanna regions where OP expansion has recently occurred and that present large area with potential for OP cultivation. Here we show that the common management practice creating within the plantation the so‐called management zones explained nearly five times more variability of soil biogeochemical properties than the savanna land‐use change per se. We also found that clayey‐soil savanna conversion into OP increased total ecosystem C stocks by 40 ± 13 Mg C ha−1 during a full OP cultivation cycle, which was due to the higher OP‐derived C accumulated in the biomass and in the soil as compared to the loss of savanna‐derived C. In addition, application of organic residues in specific management zones enhanced the accumulation of soil organic carbon by up to 1.9 Mg ha−1 year−1 over the full cycle. Within plantation, zones subjected to organic amendments sustained similar soil microbial activity as in neighboring savannas. Our findings represent an empirical proof‐of‐concept that the conversion of non‐forested land in parallel with organic matter‐oriented management strategies can enhance OP agroecosystems C sink capacity while promoting microbe‐mediated soil functioning. Nonetheless, savannas are unique and threatened ecosystems that support a vast biodiversity. Therefore, we suggest to give priority attention to conservation of natural savannas and direct more research toward the impacts of the conversion and subsequent management of degraded savannas.