Soil Biology & Biochemistry最新文献

{"title":"Do chromogenic assays of soil enzyme activities need buffers? More disadvantages than advantages of modified universal buffer in the para-nitrophenyl-based assay of phosphomonoesterase and β-glucosidase activities","authors":"Chongyang Li ,&nbsp;Jordon Wade ,&nbsp;Kelly Vollbracht ,&nbsp;Diane G. Hooper ,&nbsp;Skye A. Wills ,&nbsp;Andrew J. Margenot","doi":"10.1016/j.soilbio.2024.109704","DOIUrl":"10.1016/j.soilbio.2024.109704","url":null,"abstract":"<div><div>Buffers are commonly employed in soil enzyme activity assays to maintain a constant pH during the assay incubation, but soils are already buffered and buffer can alter apparent V_max and K_m. To test for potential artifacts of buffer on soil enzyme activities, we selected 32 soils to furnish a broad range of physicochemical characteristics and assayed soil β-glucosidase (BG) and phosphomonoesterase (PME) activities at varied substrate concentrations in water or in modified universal buffer (MUB). The pH of assays differed by up to 1.6 units from the measured soil pH (1:2, m/v in water), but MUB did not maintain pH any better than water. Compared to water, MUB generally suppressed activities (by ≈31%), apparent V_max (by ≈32%) and K_m (by ≈52%) of PME, but yielded similar activities (by ≈4% difference) and apparent V_max (by ≈9% difference) for BG. Soils with higher pH tended to have larger degree of PME actvity suppression by MUB compared to water. Based on the best practice of using a substrate concentration that is 5 × K_m to approximate substrate saturation of the enzyme, the median substrate requirement to assay PME across the 32 soils was ≈50 mM g⁻¹ in water and 25 mM g⁻¹ in MUB. Regardless of assay matrix, the commonly employed PME substrate concentration of 10 mM g⁻¹ (e.g., Tabatabai, 1994) is insufficient for accurate activity assays (i.e., activities assayed at V_max). In contrast, for BG assays the commonly used <em>p</em>NP-linked substrate concentration of 10 mM g⁻¹ appears appropriate for most soils with a median substrate requirement of ≈4 mM g⁻¹ in water and ≈6 mM g⁻¹ in MUB. Our results support previous propositions that buffers are unnecessary for assaying soil enzyme activities and may alter apparent kinetic parameters (K_m, V_max). Potential soil- and enzyme-specific substrate requirements should be determined <em>a priori</em> to ensure accurate measurements of enzyme activities in soils.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109704"},"PeriodicalIF":9.8,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888323","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In pursuit of soil P mineralization: A review and synthesis of radioisotopic labeling techniques","authors":"Chongyang Li ,&nbsp;Jordon Wade ,&nbsp;Andrew J. Margenot","doi":"10.1016/j.soilbio.2024.109701","DOIUrl":"10.1016/j.soilbio.2024.109701","url":null,"abstract":"<div><div>Predicting soil phosphorus (P) bioavailability requires an understanding of organic P mineralization (P_min) but assessing P_min rates is challenging. Recent advances in radioisotopic P labeling enable estimates of P_min rates in soil. However, there is yet no standardization of radioisotopic dilution methods, potentially compromising comparison of results among studies. We conducted a systematic literature search to (1) synthesize the varying procedures among different studies, (2) compare the soil P_min results obtained via the two most commonly used approaches, isotope exchangeable kinetics (IEK) and isotope pool dilution (IPD), and (3) address the methodological advantages and limitations of IEK and IPD. We identified and analyzed 98 studies, and found large discrepancies in study-specific radioisotope spike level, soil incubation period and extraction methods used to estimate the soil available P pool. On average, a spike level of 10–20 kBq g⁻¹ soil was used among studies but empirical assessments are required to confirm that this assumed range of spike level is sufficient to measure exchangeable P. We found that incubation duration should be ≤ 14 d because there is an increasing possibility of measuring declining cumulative gross P_min values beyond 14 d, even though a reduced cumulative pool with increasing time is theoretically impossible. Gross P_min rates were lower by IPD compared to IEK. However, 18 studies reported undetectable gross P_min, possibly due to the unverified but widely made assumption that biotic and abiotic process rates are additive. The complexity of the methodological issues may necessitate a more nuanced approach to select a method based on trade-offs. To address the methodological issues identified in this review, a greater quantity and quality of observations need to be collected (e.g., well-designed experiments, data quality assurance such as quenching correction).</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109701"},"PeriodicalIF":9.8,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in microbial carbon cycling functions along rice cultivation chronosequences in saline-alkali soils","authors":"Shangqi Xu ,&nbsp;Meng Na ,&nbsp;Yongjie Huang ,&nbsp;Jie Zhang ,&nbsp;Jihai Zhou ,&nbsp;Lu-Jun Li","doi":"10.1016/j.soilbio.2024.109699","DOIUrl":"10.1016/j.soilbio.2024.109699","url":null,"abstract":"<div><div>Saline-alkali soils are widely distributed worldwide and pose significant threats to food security and environmental safety. Rice cultivation is an effective strategy for ameliorating saline-alkali soils, increasing grain productivity, promoting soil organic carbon (SOC) accumulation and sustaining soil health in the Songnen Plain of Northeast China. This study investigated changes in microbial carbon cycling functions along rice cultivation chronosequences at two saline-alkali sites, Daan and Qianan. Rice cultivation improved soil health of the saline-alkali soils by neutralizing the pH and increasing the SOC content. Initial soil nutrient levels differed significantly at the two sites, but the nutrient dynamics were consistent, e.g., available nitrogen (AN) gradually increased, while available phosphorus (AP) initially increased and then decreased during rice cultivation. The diversity of carbon cycling genes increased with the duration of rice cultivation, while the relative abundance of genes associated with carbon decomposition decreased, which could promote carbon accumulation. These changes were primarily driven by the reduction in soil pH, followed by nutrient availability. Interestingly, at the Daan site, where AP and AN levels were relatively low, these nutrients significantly influenced carbon cycling genes. Conversely, at the Qianan site, where AP and AN levels were higher, there was less impact of nutrients than SOC on carbon cycling genes. This suggests that nutrient stoichiometry may be regulating carbon cycling genes. The soil succession process can be divided into two stages: less than 15 years of rice cultivation and more than 15 years. With longer-term rice cultivation, first the nitrogen limitation and then the phosphorus availability constrained microbial carbon cycling functions, and nutrient availability became more important than the soil pH effect. The soil nutrient and pH dynamics, together with flooding conditions in rice paddies, may limit microbial carbon decomposition, thereby promoting SOC accumulation in saline-alkali soils.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109699"},"PeriodicalIF":9.8,"publicationDate":"2024-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trait-based modeling of microbial interactions and carbon turnover in the rhizosphere","authors":"Ahmet Kürşad Sırcan ,&nbsp;Thilo Streck ,&nbsp;Andrea Schnepf ,&nbsp;Mona Giraud ,&nbsp;Adrian Lattacher ,&nbsp;Ellen Kandeler ,&nbsp;Christian Poll ,&nbsp;Holger Pagel","doi":"10.1016/j.soilbio.2024.109698","DOIUrl":"10.1016/j.soilbio.2024.109698","url":null,"abstract":"<div><div>Understanding the feedback mechanisms between roots and soil, and their effects on microbial communities, is crucial for predicting carbon cycling processes in agroecosystems. Process-based modeling is a valuable tool for quantifying biogeochemical processes and identifying regulatory mechanisms in the rhizosphere. A novel one-dimensional axisymmetric rhizosphere model is used to simulate the spatially resolved dynamics of microorganisms and soil organic matter turnover around a single root segment. The model accounts for two functional groups with different life history strategies (copiotrophs and oligotrophs), reflecting trade-offs in functional microbial traits related to substrate utilization and microbial metabolism. It considers differences in the accessibility of soil organic matter by including the microbial utilization of low and high molecular weight organic carbon compounds (LMW-OC, HMW-OC). The model was conditioned using Bayesian inference with constraint-based parameter sampling, which enabled the identification of parameter sets resulting in plausible model predictions in agreement with experimental evidence.</div><div>Mimicking the behavior of growing roots, the model assumed 15 days of rhizodeposition for LMW-OC. The simulations show a decreasing pattern of dissolved LMW-OC away from the root surface. We observed a dominance of copiotrophs close to the root surface (0–0.1 mm). Spatial patterns of functional microbial groups persisted after rhizodeposition ended, indicating a legacy effect of rhizodeposition on microbial communities, particularly on oligotrophic activity. Simulated microbial biomass exhibits a very rapid change within 0–0.2 mm away from the root surface, which points to the importance of resolving soil properties and states at sub-millimeter resolution. Microbial-explicit rhizosphere modeling thus facilitates elucidating spatiotemporal patterns of microorganisms and carbon turnover in the rhizosphere. The identified legacy effect of rhizodeposition on soil microorganisms might be leveraged for rhizosphere-based carbon stabilization strategies in agroecosystems.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109698"},"PeriodicalIF":9.8,"publicationDate":"2024-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate outweighs fertiliser effects on soil phoD-harbouring communities in agroecosystems","authors":"Lin Xu ,&nbsp;Yongping Kou ,&nbsp;Qian Mao ,&nbsp;Xiangzhen Li ,&nbsp;Chaonan Li ,&nbsp;Bo Tu ,&nbsp;Jiabao Li ,&nbsp;Lihua Tu ,&nbsp;Lixia Wang ,&nbsp;Hongwei Xu ,&nbsp;Chengming You ,&nbsp;Han Li ,&nbsp;Sining Liu ,&nbsp;Li Zhang ,&nbsp;Bo Tan ,&nbsp;Jiao Li ,&nbsp;Yaling Yuan ,&nbsp;Kai Wei ,&nbsp;Zhenfeng Xu","doi":"10.1016/j.soilbio.2024.109697","DOIUrl":"10.1016/j.soilbio.2024.109697","url":null,"abstract":"<div><div>Alkaline phosphatase (<em>phoD</em>) gene-encoding bacterial (<em>phoD</em>-harbouring) communities are crucial for organic phosphorus (P) mineralisation in agroecosystems. However, the relative contributions of natural factors (e.g., climate) and anthropogenic influences (e.g., fertilisation) to these communities remain unclear, particularly at large spatial scales. To address this, we analysed <em>phoD</em> amplicon sequence data from 290 samples across 15 independent cropland studies, spanning diverse climatic zones and soil types from central to eastern Asia. Our results reveal that climatic factors exert stronger effects than fertiliser regimes on soil <em>phoD</em>-harbouring communities. Specifically, the richness of soil <em>phoD</em>-harbouring communities decreased by approximately three times as mean annual precipitation increased from 160 mm to 1800 mm, and mean annual temperature rose from 9 °C to 18 °C. Compared to the control, chemical nitrogen (N) + P + organic fertiliser doubled richness, while the control's richness was 10 times higher than that of chemical N + P + potassium fertiliser. Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria were the most dominant <em>phoD</em>-harbouring taxa, collectively accounting for 65.3% of the relative abundance. Precipitation explained up to 96.3% of the variance in community composition, while fertiliser regimes explained approximately 40%. Notably, excessive potassium fertilisation was linked to reduced richness and abundance of dominant <em>phoD</em>-harbouring taxa, potentially limiting the availability of plant-accessible P. This suggests that the amount of potassium fertiliser should be carefully considered in future agricultural practices, as it may reduce plant-available P by inhibiting soil <em>phoD</em>-harbouring communities.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109697"},"PeriodicalIF":9.8,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drivers of soil fauna communities along a successional gradient in upper andean tropical forests","authors":"Camilo Castillo-Avila ,&nbsp;Dennis Castillo-Figueroa ,&nbsp;Juan M. Posada","doi":"10.1016/j.soilbio.2024.109692","DOIUrl":"10.1016/j.soilbio.2024.109692","url":null,"abstract":"<div><div>Soils harbor more than half of Earth's biodiversity, with soil fauna representing one of the most diverse groups. However, understanding the drivers influencing their biodiversity remains limited. Upper Andean tropical forests are among Earth's most biodiverse ecosystems, but have undergone large-scale historical transformations, resulting in landscapes with different forest successional stages. In this study, we aimed to analyze soil fauna communities along a successional gradient in Colombia's Eastern Andean forests and identify key microclimatic, soil, and forest structural drivers. We collected soil fauna from 168 samples (30 × 30 × 5 cm), in dry and wet seasons, in 14 permanent plots (20 × 20 m) located in four sites. Data on microclimate, nutrients, productivity, plant diversity, and litter functional richness were gathered from these permanent plots. We observed significant soil fauna biodiversity turnover among Andean montane forest sites, mirroring the distinctive floristic composition between them. We also found that soil fauna richness and abundance increased with succession, attributed to higher productivity and more suitable microclimatic conditions in old-growth forests. Our findings suggest that the primary driver of soil fauna richness in tropical mountain Andean forests is the amount of energy (i.e, forest productivity), while soil fauna abundance is mainly influenced by thermal conditions. Additionally, factors framed within the physiological tolerance hypothesis (i.e., calcium, aluminum) and within the habitat heterogeneity hypothesis (i.e., litter functional richness, plant diversity) also play a role, albeit to a lesser extent. This study emphasizes the importance of examining forest recovery including soil fauna groups to understand successional patterns in tropical mountain forests.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109692"},"PeriodicalIF":9.8,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the diversity of nematode antagonists in an agricultural soil, and their steerability by root-knot nematode density and cover crops","authors":"Sara G. Cazzaniga ,&nbsp;Philippe Belliard ,&nbsp;Joris van Steenbrugge ,&nbsp;Sven van den Elsen ,&nbsp;Carin Lombaers ,&nbsp;Johnny Visser ,&nbsp;Leendert Molendijk ,&nbsp;Jose G. Macia-Vicente ,&nbsp;Joeke Postma ,&nbsp;Liesje Mommer ,&nbsp;Johannes Helder","doi":"10.1016/j.soilbio.2024.109693","DOIUrl":"10.1016/j.soilbio.2024.109693","url":null,"abstract":"<div><div>Plant-parasitic nematodes are harmful pathogens for many agricultural crops. Within this category, root-knot nematodes (RKN, <em>Meloidogyne</em> spp.) are worldwide regarded as the most impactful because of their wide geographical distribution and their polyphagous nature. Host plant resistances against RKN have been successfully introduced in a few crops only. As the use of nematicides is becoming increasingly restricted because of environmental and human health concerns, there is a need for alternative strategies to control RKN. One such approach is the stimulation of local nematode antagonists. We investigated this in an experimental field setting with two main variables: density of the Columbia root-knot nematode <em>Meloidogyne chitwoodi</em>, and the type of cover crop. For each of the three <em>M. chitwoodi</em> densities, the effects of ten cover crop treatments were tested on both the resident (DNA) and the active (RNA) fractions of the bacterial and fungal communities. In our analyses, we focused on changes in the abundance of plant-parasitic nematode antagonists. From the eight bacterial and 26 fungal genera known from global literature to harbour potential antagonists of plant-parasitic nematodes, we detected respectively five and 14 genera in our agricultural field. Among the bacterial genera, four genera were shown to comprise bacterial species for which nematode antagonism has been documented. The fungal genera included facultative nematode parasites (<em>e.g</em>., <em>Arthrobotrys</em> spp.), endophytes strengthening host defences (<em>e.g</em>., <em>Acremonium</em> spp.), as well as multiple obligatory nematophagous species. This study revealed that conventionally managed arable fields may harbour an unexpectedly high diversity of nematode antagonists. Multiple antagonists were stimulated by cover crops in a cover crop-specific manner, and, to a lesser extent, by increased RKN densities. The richness in putative nematode antagonists did not translate into <em>M. chitwoodi</em> suppression, and currently we are investigating whether this relates to the facultative nematophagous lifestyle of most of these antagonists.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109693"},"PeriodicalIF":9.8,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Depth-dependent regulations of soil priming effects along a 2000 km grassland transect","authors":"Yunlong Hu ,&nbsp;Jiguang Feng ,&nbsp;Shuai Zhang ,&nbsp;Zhongkui Luo ,&nbsp;Biao Zhu","doi":"10.1016/j.soilbio.2024.109696","DOIUrl":"10.1016/j.soilbio.2024.109696","url":null,"abstract":"<div><div>Global change may change plant carbon input, which may in turn accelerate or retard the mineralization of soil organic matter (SOM), a phenomenon known as priming effect. However, deep soil priming effect on large geographic scale is poorly understood, hindering a complete understanding of the response of whole-soil carbon dynamics to plant carbon input. Across a 2000 km grassland transect in Inner Mongolia, China, this study showed that soil priming effects at 0–200 cm depth varied systematically with climate and soil properties. The intensity of priming effect varied with depth. Averaged across 10 sites along the transect, glucose addition increased native SOM decomposition by 5.1% in surface soil (0–10 cm), while decreased it by 12.9% and 25.7% in middle (30–50 cm) and deep (150–200 cm) soils, respectively. Interestingly, the regulating factors of priming at different depths were significantly different. The priming effect in surface soil was primarily regulated by SOM stability represented by content of soil minerals and (clay + silt) %, whereas that in middle soil was mainly regulated by soil substrates, SOM stability and soil pH, and that in deep soil was mainly controlled by soil substrates. This study demonstrates distinct controls of the priming effect across soil depths at the regional scale, and contributes to improving our understanding of how whole-soil carbon dynamics respond to global change.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109696"},"PeriodicalIF":9.8,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence of the need for crop-specific N2O emission factors","authors":"Akeem T. Shorunke,&nbsp;Bobbi L. Helgason,&nbsp;Richard E. Farrell","doi":"10.1016/j.soilbio.2024.109694","DOIUrl":"10.1016/j.soilbio.2024.109694","url":null,"abstract":"<div><div>Crop residues are an important source of N for subsequent crops and contribute to cropping system nitrous oxide (N₂O) emissions. Oilseed residues, particularly canola (<em>Brassica napus</em> L.), can instigate higher N₂O emissions compared to pulse and wheat crop residues but the reason for this disproportionate emission response is unknown. To determine the quantity and source of N₂O emissions, we conducted an incubation experiment (84 d) using ¹⁵N and ¹³C labelled residues of canola, wheat, flax, pea and investigated key N-cycling gene abundances, microbial abundance and community structure using PLFA and soil C and N dynamics. Residue addition of all types significantly increased microbial abundance and abundances of denitrification and nitrification genes. Canola residue resulted in significantly greater <em>nosZI</em> abundance. Lower incorporation of canola residue ¹³C into PLFA and higher ¹³CO₂ emissions suggests that canola residue C was used less efficiently (i.e., less for growth and more for respiration), depleting O₂ and stimulating denitrification. The magnitude of N₂O emission from residue-amended soils was significantly higher (<em>p</em> &lt; 0.05) than the unamended control soil and differed with residue type: canola &gt; pea = wheat &gt; flax &gt; control. The canola residue emission factor was 1.56% of residue N – significantly higher than that of wheat (0.99%), pea (0.95%) and flax (0.18%). This higher canola emission factor resulted from greater residue-derived (1.47%) N₂O as well as residue-induced (0.65%) soil emissions. The combined use of stable isotope tracing of ¹⁵N₂O and ¹³CO₂ and microbial characterization quantified differences in residue-derived N₂O emissions from common crops that were linked to differences in microbial abundance, community structure and activity.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109694"},"PeriodicalIF":9.8,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Increase in mineral-associated organic carbon does not offset the decrease in particulate organic carbon under long-term nitrogen enrichment in a steppe ecosystem","authors":"Li Liu ,&nbsp;Junjie Yang ,&nbsp;Jing Wang ,&nbsp;Qiang Yu ,&nbsp;Cunzheng Wei ,&nbsp;Liangchao Jiang ,&nbsp;Jianhui Huang ,&nbsp;Yunhai Zhang ,&nbsp;Yong Jiang ,&nbsp;Haiyang Zhang ,&nbsp;Xingguo Han","doi":"10.1016/j.soilbio.2024.109695","DOIUrl":"10.1016/j.soilbio.2024.109695","url":null,"abstract":"<div><div>Nitrogen (N) deposition significantly impacts ecosystem carbon (C) cycling. However, most experimental N deposition studies applied N fertilizers in low-frequency, typically once or twice per year during the growing season. Few studies have been conducted to investigate the effects of high-frequency N deposition at varying rates on the formation and stability of soil organic carbon (SOC). Additionally, the effects of N addition on the two SOC fractions — particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) — and the underlying mechanisms are not well understood. To address these gaps, we conducted a long-term N addition experiment in a typical steppe ecosystem in Inner Mongolia, China, beginning in 2008. The N addition rates ranged from 0 to 50 g N m⁻² yr⁻¹, with a high frequency of N additions (once a month, 12 additions per year). After a decade of N addition, we observed a consistent decrease in SOC (by 3.9 ± 0.51 %) and POC (by 17.5 ± 2.31 %) and an increase in MAOC (by 5.8 ± 1.68 %) compared to the control treatment (i.e., the treatment without N addition). The decline in POC was attributed to stimulated microbial decomposition due to improved quality of particulate organic matter and increased priming effect from SOC. The increase in MAOC was associated with enhanced mineral protection, resulting from increased solubility of iron/aluminum (Fe/Al) that are reactive in directly adsorbing SOC molecules to form stable metal-SOC complexes. However, this increase in MAOC does not offset the decrease in POC, leading to an overall decrease in SOC under N enrichment. This study reveals the crucial roles of microbial decomposition and mineral protection in determining SOC fractions in <em>N</em>-enriched steppe ecosystems.</div></div>","PeriodicalId":21888,"journal":{"name":"Soil Biology & Biochemistry","volume":"202 ","pages":"Article 109695"},"PeriodicalIF":9.8,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142823362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}