Pub Date : 2024-07-08DOI: 10.5194/egusphere-2024-1833
Ruizhe Wang, Xia Hu
Abstract. Seasonal freeze‒thaw (FT) processes alter soil formation and causes changes in soil structure in alpine ecosystems. Soil aggregates are basic soil structural units and play a crucial role in soil organic carbon (SOC) protection and microbial habitation. However, the impact of seasonal FT processes on pore structure and its impact on SOC fractions have been overlooked. This study characterized the pore structure and SOC fractions of aggregates during the unstable freezing period (UFP), stable frozen period (SFP), unstable thawing period (UTP) and stable thawed period (STP) in typical alpine ecosystems via the dry sieving procedure, X-ray computed tomography (CT) scanning and elemental analysis. The results showed that pore characteristics of 0.25–2 mm aggregates were more vulnerable to seasonal FT processes than that of > 2 mm aggregates. The freezing process promoted the formation of > 80 μm pores of aggregates. The total organic carbon (TOC), particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) contents of macroaggregates were high in the stable frozen period and low in unstable thawing period, demonstrating that freezing process enhanced SOC accumulation while early stage of thawing led to SOC loss. The vertical distribution of SOC of aggregates was more uniform in stable frozen period than in other periods. Pore equivalent diameter was the most important structural characteristic influencing SOC contents of aggregates. In the freezing period, the importance of pore structure in regulating SOC protection was more obvious and pore structure inhibited SOC loss by promoted the formation of >80 μm pores. In the thawing period, pores of 15–30 μm inhibited SOC protection. Our results are valuable for evaluating potential changes in alpine soil carbon sinks under global warming.
{"title":"Freeze-thaw processes correspond to the protection-loss of soil organic carbon through regulating pore structure of aggregates in alpine ecosystems","authors":"Ruizhe Wang, Xia Hu","doi":"10.5194/egusphere-2024-1833","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1833","url":null,"abstract":"<strong>Abstract.</strong> Seasonal freeze‒thaw (FT) processes alter soil formation and causes changes in soil structure in alpine ecosystems. Soil aggregates are basic soil structural units and play a crucial role in soil organic carbon (SOC) protection and microbial habitation. However, the impact of seasonal FT processes on pore structure and its impact on SOC fractions have been overlooked. This study characterized the pore structure and SOC fractions of aggregates during the unstable freezing period (UFP), stable frozen period (SFP), unstable thawing period (UTP) and stable thawed period (STP) in typical alpine ecosystems via the dry sieving procedure, X-ray computed tomography (CT) scanning and elemental analysis. The results showed that pore characteristics of 0.25–2 mm aggregates were more vulnerable to seasonal FT processes than that of > 2 mm aggregates. The freezing process promoted the formation of > 80 μm pores of aggregates. The total organic carbon (TOC), particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) contents of macroaggregates were high in the stable frozen period and low in unstable thawing period, demonstrating that freezing process enhanced SOC accumulation while early stage of thawing led to SOC loss. The vertical distribution of SOC of aggregates was more uniform in stable frozen period than in other periods. Pore equivalent diameter was the most important structural characteristic influencing SOC contents of aggregates. In the freezing period, the importance of pore structure in regulating SOC protection was more obvious and pore structure inhibited SOC loss by promoted the formation of >80 μm pores. In the thawing period, pores of 15–30 μm inhibited SOC protection. Our results are valuable for evaluating potential changes in alpine soil carbon sinks under global warming.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"81 5 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141557166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-05DOI: 10.5194/soil-10-467-2024
Maximiliano González-Sosa, Carlos A. Sierra, J. Andrés Quincke, Walter E. Baethgen, Susan Trumbore, M. Virginia Pravia
Abstract. Integrated crop–pasture rotational systems can store larger soil organic carbon (SOC) stocks in the topsoil (0–20 cm) than continuous grain cropping. The aim of this study was to identify if the main determinant for this difference may be the avoidance of old C losses in integrated systems or the higher rate of new C incorporation associated with higher C input rates. We analyzed the temporal changes of 0–20 cm SOC stocks in two agricultural treatments of different intensity (continuous annual grain cropping and crop–pasture rotational system) in a 60-year experiment in Colonia, Uruguay. We incorporated this information into a process of building and parameterizing SOC compartmental dynamical models, including data from SOC physical fractionation (particulate organic matter, POM > 53 µm > mineral-associated organic matter, MAOM), radiocarbon in bulk soil, and CO2 incubation efflux. This modeling process provided information about C outflow rates from pools of different stability, C stabilization dynamics, and the age distribution and transit times of C. The differences between the two agricultural systems were mainly determined by the dynamics of the slow-cycling pool (∼MAOM). The outflow rate from this compartment was between 3.68 and 5.19 times higher in continuous cropping than in the integrated system, varying according to the historical period of the experiment considered. The avoidance of old C losses in the integrated crop–pasture rotational system resulted in a mean age of the slow-cycling pool (∼MAOM) of over 600 years, with only 8.8 % of the C in this compartment incorporated during the experiment period (after 1963) and more than 85 % older than 100 years old in this agricultural system. Moreover, half of the C inputs to both agricultural systems leave the soil in approximately 1 year due to high decomposition rates of the fast-cycling pool (∼POM). Our results show that the high capacity to preserve old C of integrated crop–pasture systems is the key for SOC preservation of this sustainable intensification strategy, while their high capacity to incorporate new C into the soil may play a second role. Maintaining high rates of C inputs and relatively high stocks of labile C appear to be a prerequisite for maintaining low outflow rates of the MAOM pool.
{"title":"High capacity of integrated crop–pasture systems to preserve old soil carbon evaluated in a 60-year-old experiment","authors":"Maximiliano González-Sosa, Carlos A. Sierra, J. Andrés Quincke, Walter E. Baethgen, Susan Trumbore, M. Virginia Pravia","doi":"10.5194/soil-10-467-2024","DOIUrl":"https://doi.org/10.5194/soil-10-467-2024","url":null,"abstract":"Abstract. Integrated crop–pasture rotational systems can store larger soil organic carbon (SOC) stocks in the topsoil (0–20 cm) than continuous grain cropping. The aim of this study was to identify if the main determinant for this difference may be the avoidance of old C losses in integrated systems or the higher rate of new C incorporation associated with higher C input rates. We analyzed the temporal changes of 0–20 cm SOC stocks in two agricultural treatments of different intensity (continuous annual grain cropping and crop–pasture rotational system) in a 60-year experiment in Colonia, Uruguay. We incorporated this information into a process of building and parameterizing SOC compartmental dynamical models, including data from SOC physical fractionation (particulate organic matter, POM > 53 µm > mineral-associated organic matter, MAOM), radiocarbon in bulk soil, and CO2 incubation efflux. This modeling process provided information about C outflow rates from pools of different stability, C stabilization dynamics, and the age distribution and transit times of C. The differences between the two agricultural systems were mainly determined by the dynamics of the slow-cycling pool (∼MAOM). The outflow rate from this compartment was between 3.68 and 5.19 times higher in continuous cropping than in the integrated system, varying according to the historical period of the experiment considered. The avoidance of old C losses in the integrated crop–pasture rotational system resulted in a mean age of the slow-cycling pool (∼MAOM) of over 600 years, with only 8.8 % of the C in this compartment incorporated during the experiment period (after 1963) and more than 85 % older than 100 years old in this agricultural system. Moreover, half of the C inputs to both agricultural systems leave the soil in approximately 1 year due to high decomposition rates of the fast-cycling pool (∼POM). Our results show that the high capacity to preserve old C of integrated crop–pasture systems is the key for SOC preservation of this sustainable intensification strategy, while their high capacity to incorporate new C into the soil may play a second role. Maintaining high rates of C inputs and relatively high stocks of labile C appear to be a prerequisite for maintaining low outflow rates of the MAOM pool.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"66 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141545771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.5194/soil-10-451-2024
Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, Zhe H. Weng
Abstract. A substantial carbon (C) debt has been accrued due to long-term cropping for global food production emitting carbon dioxide from soil. However, the factors regulating the persistence of soil organic C (SOC) remain unclear, with this hindering our ability to develop effective land management strategies to sequester organic C in soil. Using a Ferralsol from semi-arid subtropical Australia, alteration of bulk C contents and fractions due to long-term land use change (up to 72 years) was examined with a focus on understanding whether SOC lost due to cropping could be restored by subsequent conversion back to pasture or plantation. It was found that use of soil from cropping for 72 years resulted in the loss of >70 % of both C and N contents. Although conversion of cropped soil to pasture or plantation for up to 39 years resulted in an increase in both C and N, the C contents of all soil fractions were not restored to the original values observed under remnant vegetation. The loss of C with cropping was most pronounced from the particulate organic matter fraction, whilst in contrast, the portion of the C that bound strongly to the soil mineral particles (i.e. the mineral-associated fraction) was most resilient. Indeed, aliphatic C was enriched in the fine fraction of mineral-associated organic matter (<53 µm). Our findings were further confirmed using Synchrotron-based micro-spectroscopic analyses of intact microaggregates, which highlighted that binding of C to soil mineral particles is critical to SOC persistence in disturbed soil. The results of the present study extend our conceptual understanding of C dynamics and behaviour at the fine scale where C is stabilized and accrued, but it is clear that restoring C in soils in semi-arid landscapes of subtropical regions poses a challenge.
{"title":"The influence of land use and management on the behaviour and persistence of soil organic carbon in a subtropical Ferralsol","authors":"Laura Hondroudakis, Peter M. Kopittke, Ram C. Dalal, Meghan Barnard, Zhe H. Weng","doi":"10.5194/soil-10-451-2024","DOIUrl":"https://doi.org/10.5194/soil-10-451-2024","url":null,"abstract":"Abstract. A substantial carbon (C) debt has been accrued due to long-term cropping for global food production emitting carbon dioxide from soil. However, the factors regulating the persistence of soil organic C (SOC) remain unclear, with this hindering our ability to develop effective land management strategies to sequester organic C in soil. Using a Ferralsol from semi-arid subtropical Australia, alteration of bulk C contents and fractions due to long-term land use change (up to 72 years) was examined with a focus on understanding whether SOC lost due to cropping could be restored by subsequent conversion back to pasture or plantation. It was found that use of soil from cropping for 72 years resulted in the loss of >70 % of both C and N contents. Although conversion of cropped soil to pasture or plantation for up to 39 years resulted in an increase in both C and N, the C contents of all soil fractions were not restored to the original values observed under remnant vegetation. The loss of C with cropping was most pronounced from the particulate organic matter fraction, whilst in contrast, the portion of the C that bound strongly to the soil mineral particles (i.e. the mineral-associated fraction) was most resilient. Indeed, aliphatic C was enriched in the fine fraction of mineral-associated organic matter (<53 µm). Our findings were further confirmed using Synchrotron-based micro-spectroscopic analyses of intact microaggregates, which highlighted that binding of C to soil mineral particles is critical to SOC persistence in disturbed soil. The results of the present study extend our conceptual understanding of C dynamics and behaviour at the fine scale where C is stabilized and accrued, but it is clear that restoring C in soils in semi-arid landscapes of subtropical regions poses a challenge.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"79 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-04DOI: 10.5194/egusphere-2024-1587
Alberto Carrera, Luca Peruzzo, Matteo Longo, Giorgio Cassiani, Francesco Morari
Abstract. Monitoring soil structure is of paramount importance due to its key role in the critical zone as the foundation of terrestrial life. Variations in the arrangement of soil components significantly influence its hydro-mechanical properties, and therefore its impact on the surrounding ecosystem. In this context, soil compaction resulting from inappropriate agricultural practices not only affects soil ecological functions, but also decreases the water-use efficiency of plants by reducing porosity and increasing water loss through superficial runoff and enhanced evaporation. In this study, we compared the ability of electric and electromagnetic geophysical methods, i.e. Electrical Resistivity Tomography and Frequency-domain Electromagnetic Method, to assess the effects of compaction on agricultural soil. The objective was to highlight the electro-magnetic response caused by both heavy plastic soil deformations generated by a super-heavy vehicle and the more common tractor tramlines. DC-current prospecting has finer spatial resolution and allows a tomographic approach, requiring higher logistic demands and the need for ground galvanic contact. On the other hand, contactless electromagnetic induction methods can be quickly used to define the distribution of electrical conductivity in the shallow subsoil in an easier way. Results, validated with traditional soil characterization techniques (i.e. penetration resistance, bulk density and volumetric water content on collected samples), show the pros & cons of both techniques and how differences in their spatial resolution heavily influence the ability to characterize compacted areas with good confidence. This work aims at contributing to the methodological optimization of agro-geophysical acquisitions and data processing, in order to obtain accurate soil models through a non-invasive approach.
{"title":"Electromagnetic and DC-current geophysics for soil compaction assessment","authors":"Alberto Carrera, Luca Peruzzo, Matteo Longo, Giorgio Cassiani, Francesco Morari","doi":"10.5194/egusphere-2024-1587","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1587","url":null,"abstract":"<strong>Abstract.</strong> Monitoring soil structure is of paramount importance due to its key role in the critical zone as the foundation of terrestrial life. Variations in the arrangement of soil components significantly influence its hydro-mechanical properties, and therefore its impact on the surrounding ecosystem. In this context, soil compaction resulting from inappropriate agricultural practices not only affects soil ecological functions, but also decreases the water-use efficiency of plants by reducing porosity and increasing water loss through superficial runoff and enhanced evaporation. In this study, we compared the ability of electric and electromagnetic geophysical methods, i.e. Electrical Resistivity Tomography and Frequency-domain Electromagnetic Method, to assess the effects of compaction on agricultural soil. The objective was to highlight the electro-magnetic response caused by both heavy plastic soil deformations generated by a super-heavy vehicle and the more common tractor tramlines. DC-current prospecting has finer spatial resolution and allows a tomographic approach, requiring higher logistic demands and the need for ground galvanic contact. On the other hand, contactless electromagnetic induction methods can be quickly used to define the distribution of electrical conductivity in the shallow subsoil in an easier way. Results, validated with traditional soil characterization techniques (i.e. penetration resistance, bulk density and volumetric water content on collected samples), show the pros & cons of both techniques and how differences in their spatial resolution heavily influence the ability to characterize compacted areas with good confidence. This work aims at contributing to the methodological optimization of agro-geophysical acquisitions and data processing, in order to obtain accurate soil models through a non-invasive approach.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"29 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141521724","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), which are two primary components of the soil carbon (C) reservoir, have different physical and chemical properties as well as biochemical turnover rates. Microbial necromass entombment is a primary mechanism for MAOC formation from fast-decaying plant substrates, whereas POC is typically considered the product of structural litter via physical fragmentation. However, emerging evidence shows that microbial by-products derived from labile C substrates can enter the POC pool. To date, it is still unclear to what extent dissolved C can enter the POC pool and how it affects the subsequent long-term soil organic carbon (SOC) storage. Our study here, through a 13C-labeling experiment in 10 soils from 5 grassland sites as well as a modeling analysis, showed that up to 12.29 % of isotope-labeled glucose C (i.e., dissolved C) was detected in the POC pool. In addition, the glucose-derived POC was correlated with 13C-MBC (microbial biomass carbon) and the fraction of clay and silt, suggesting that the flow of dissolved C to POC is dependent on interactions between soil physical and microbial processes. The modeling analysis showed that ignoring the C flow from MBC to POC significantly underestimated soil C sequestration by up to 53.52 % across the 10 soils. The results emphasize that the soil mineral-regulated microbial process, besides the plant structural residues, is a significant contributor to POC, acting as a vital component in SOC dynamics.
{"title":"Dissolved carbon flow to particulate organic carbon enhances soil carbon sequestration","authors":"Qintana Si, Kangli Chen, Bin Wei, Yaowen Zhang, Xun Sun, Junyi Liang","doi":"10.5194/soil-10-441-2024","DOIUrl":"https://doi.org/10.5194/soil-10-441-2024","url":null,"abstract":"Abstract. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), which are two primary components of the soil carbon (C) reservoir, have different physical and chemical properties as well as biochemical turnover rates. Microbial necromass entombment is a primary mechanism for MAOC formation from fast-decaying plant substrates, whereas POC is typically considered the product of structural litter via physical fragmentation. However, emerging evidence shows that microbial by-products derived from labile C substrates can enter the POC pool. To date, it is still unclear to what extent dissolved C can enter the POC pool and how it affects the subsequent long-term soil organic carbon (SOC) storage. Our study here, through a 13C-labeling experiment in 10 soils from 5 grassland sites as well as a modeling analysis, showed that up to 12.29 % of isotope-labeled glucose C (i.e., dissolved C) was detected in the POC pool. In addition, the glucose-derived POC was correlated with 13C-MBC (microbial biomass carbon) and the fraction of clay and silt, suggesting that the flow of dissolved C to POC is dependent on interactions between soil physical and microbial processes. The modeling analysis showed that ignoring the C flow from MBC to POC significantly underestimated soil C sequestration by up to 53.52 % across the 10 soils. The results emphasize that the soil mineral-regulated microbial process, besides the plant structural residues, is a significant contributor to POC, acting as a vital component in SOC dynamics.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"24 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141489492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-21DOI: 10.5194/soil-10-425-2024
Jorge Prieto-Rubio, José L. Garrido, Julio M. Alcántara, Concepción Azcón-Aguilar, Ana Rincón, Álvaro López-García
Abstract. Soil functioning is intrinsically related to the structure of associated biological communities. This link is barely understood in the multispecies context of soil microbial communities, which often requires complex analytical approaches to discern structural and functional roles of microbial taxa inhabiting the soil. To investigate these ecological properties, we characterized the assembly and soil functioning contribution of ectomycorrhizal (ECM) fungal communities through co-occurrence network analysis. Co-occurrence networks were inferred from ECM root tips of Cistus albidus, Quercus faginea and Q. ilex on a regional scale, in Mediterranean mixed forests. Soil enzymatic activities related to carbon and nutrient cycling were also measured, and soil functionality outcomes related to ECM fungal network structure were evaluated on the community to taxon levels. Network complexity relied on habitat characteristics and seasonality, and it was linked to different dominant ECM fungal lineages across habitats. Soil enzymatic activities were habitat-dependent, driven by host plant identity and fungi with reduced structuring roles in the co-occurrence network (mainly within Thelephorales, Sebacinales and Pezizales). ECM fungal co-occurrence network structure and functioning were highly context-dependent, pointing to divergent regional fungal species pools according to their niche preferences. As increased network complexity was not related to greater soil functionality, functional redundancy might be operating in Mediterranean forest soils. The revealed differentiation between structural and functional roles of ECM fungi adds new insights into the understanding of soil fungal community assembly and its functionality in ecosystems.
{"title":"Ectomycorrhizal fungal network complexity determines soil multi-enzymatic activity","authors":"Jorge Prieto-Rubio, José L. Garrido, Julio M. Alcántara, Concepción Azcón-Aguilar, Ana Rincón, Álvaro López-García","doi":"10.5194/soil-10-425-2024","DOIUrl":"https://doi.org/10.5194/soil-10-425-2024","url":null,"abstract":"Abstract. Soil functioning is intrinsically related to the structure of associated biological communities. This link is barely understood in the multispecies context of soil microbial communities, which often requires complex analytical approaches to discern structural and functional roles of microbial taxa inhabiting the soil. To investigate these ecological properties, we characterized the assembly and soil functioning contribution of ectomycorrhizal (ECM) fungal communities through co-occurrence network analysis. Co-occurrence networks were inferred from ECM root tips of Cistus albidus, Quercus faginea and Q. ilex on a regional scale, in Mediterranean mixed forests. Soil enzymatic activities related to carbon and nutrient cycling were also measured, and soil functionality outcomes related to ECM fungal network structure were evaluated on the community to taxon levels. Network complexity relied on habitat characteristics and seasonality, and it was linked to different dominant ECM fungal lineages across habitats. Soil enzymatic activities were habitat-dependent, driven by host plant identity and fungi with reduced structuring roles in the co-occurrence network (mainly within Thelephorales, Sebacinales and Pezizales). ECM fungal co-occurrence network structure and functioning were highly context-dependent, pointing to divergent regional fungal species pools according to their niche preferences. As increased network complexity was not related to greater soil functionality, functional redundancy might be operating in Mediterranean forest soils. The revealed differentiation between structural and functional roles of ECM fungi adds new insights into the understanding of soil fungal community assembly and its functionality in ecosystems.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"7 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141435839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-12DOI: 10.5194/soil-10-381-2024
Esko Karvinen, Leif Backman, Leena Järvi, Liisa Kulmala
Abstract. As an increasing share of the human population is being clustered in cities, urban areas have swiftly become the epicentres of anthropogenic carbon (C) emissions. Understanding different parts of the biogenic C cycle in urban ecosystems is needed in order to assess the potential to enhance their C stocks as a cost-efficient means to balance the C emissions and mitigate climate change. Here, we conducted a field measurement campaign over three consecutive growing seasons to examine soil respiration carbon dioxide (CO2) fluxes and soil organic carbon (SOC) stocks at four measurement sites in Helsinki, representing different types of tree-covered urban green space commonly found in northern European cities. We expected to find variation in the main drivers of soil respiration – soil temperature, soil moisture, and SOC – as a result of the heterogeneity of urban landscape and that this variation would be reflected in the measured soil respiration rates. In the end, we could see fairly constant statistically significant differences between the sites in terms of soil temperature but only sporadic and seemingly momentary differences in soil moisture and soil respiration. There were also statistically significant differences in SOC stocks: the highest SOC stock was found in inactively managed deciduous urban forest and the lowest under managed streetside lawn with common linden trees. We studied the impacts of the urban heat island (UHI) effect and irrigation on heterotrophic soil respiration with process-based model simulations and found that the variation created by the UHI is relatively minor compared to the increase associated with active irrigation, especially during dry summers. We conclude that, within our study area, the observed variation in soil temperature alone was not enough to cause variation in soil respiration rates between the studied green space types, perhaps because the soil moisture conditions were uniform. Thus, irrigation could potentially be a key factor in altering the soil respiration dynamics in urban green space both within the urban area and in comparison to non-urban ecosystems.
{"title":"Soil respiration across a variety of tree-covered urban green spaces in Helsinki, Finland","authors":"Esko Karvinen, Leif Backman, Leena Järvi, Liisa Kulmala","doi":"10.5194/soil-10-381-2024","DOIUrl":"https://doi.org/10.5194/soil-10-381-2024","url":null,"abstract":"Abstract. As an increasing share of the human population is being clustered in cities, urban areas have swiftly become the epicentres of anthropogenic carbon (C) emissions. Understanding different parts of the biogenic C cycle in urban ecosystems is needed in order to assess the potential to enhance their C stocks as a cost-efficient means to balance the C emissions and mitigate climate change. Here, we conducted a field measurement campaign over three consecutive growing seasons to examine soil respiration carbon dioxide (CO2) fluxes and soil organic carbon (SOC) stocks at four measurement sites in Helsinki, representing different types of tree-covered urban green space commonly found in northern European cities. We expected to find variation in the main drivers of soil respiration – soil temperature, soil moisture, and SOC – as a result of the heterogeneity of urban landscape and that this variation would be reflected in the measured soil respiration rates. In the end, we could see fairly constant statistically significant differences between the sites in terms of soil temperature but only sporadic and seemingly momentary differences in soil moisture and soil respiration. There were also statistically significant differences in SOC stocks: the highest SOC stock was found in inactively managed deciduous urban forest and the lowest under managed streetside lawn with common linden trees. We studied the impacts of the urban heat island (UHI) effect and irrigation on heterotrophic soil respiration with process-based model simulations and found that the variation created by the UHI is relatively minor compared to the increase associated with active irrigation, especially during dry summers. We conclude that, within our study area, the observed variation in soil temperature alone was not enough to cause variation in soil respiration rates between the studied green space types, perhaps because the soil moisture conditions were uniform. Thus, irrigation could potentially be a key factor in altering the soil respiration dynamics in urban green space both within the urban area and in comparison to non-urban ecosystems.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"10 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141309195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-12DOI: 10.5194/soil-10-407-2024
Maria Regina Gmach, Martin Anders Bolinder, Lorenzo Menichetti, Thomas Kätterer, Heide Spiegel, Olle Åkesson, Jürgen Kurt Friedel, Andreas Surböck, Agnes Schweinzer, Taru Sandén
Abstract. Litter decomposition is an important factor affecting local and global C cycles. It is known that decomposition through soil microbial activity in ecosystems is mainly influenced by soil type and climatic conditions. However, for agroecosystems, there remains a need for a better understanding of how management practices influence litter decomposition. This study examined the effect of different management practices on decomposition at 29 sites with long-term (mean duration of 38 years) field experiments (LTEs) using the Tea Bag Index (TBI) protocol with standard litter (rooibos and green tea) developed by Keuskamp et al. (2013). The objective was to determine if the TBI decomposition rate (k) and stabilization factor (S) are sensitive enough to detect differences in litter decomposition between management practices as well as how they interact with edaphic factors, crop type and local climatic conditions. Tea bags were buried and collected after ∼90 d at 16 Austrian and 13 Swedish sites. The treatments in the Austrian LTEs focused on mineral and organic fertilizer application, tillage systems and crop residue management, whereas those in Sweden addressed cropping systems, mineral fertilizer application and tillage systems. The results for Austria showed that the incorporation of crop residue and high-N fertilizer application increased k, compared with crop residue removal and low or no N application, respectively. Minimum tillage had significantly higher k compared with reduced and conventional tillage. In Sweden, fertilized plots showed higher S than non-fertilized plots and high-N fertilizer had the highest k. Growing spring cereal led to higher k than forage crops. Random forest regressions for Austria and Sweden jointly showed that k and S were mainly governed by climatic conditions, which explained more than 70 % of their variation. However, under similar climatic conditions, management practices strongly influenced decomposition dynamics. It would be appropriate to apply the TBI approach to a more large-scale network using LTEs for agroecosystems, in order to improve the index's usefulness as an indicator of the effect of management practices on litter decomposition dynamics, particularly linking it with the potential for C storage.
摘要垃圾分解是影响当地和全球碳循环的一个重要因素。众所周知，生态系统中通过土壤微生物活动进行的分解主要受土壤类型和气候条件的影响。然而，对于农业生态系统来说，仍然需要更好地了解管理方法如何影响垃圾的分解。本研究采用 Keuskamp 等人（2013 年）开发的茶袋指数（TBI）方案，在 29 个地点进行了长期（平均持续时间为 38 年）现场实验（LTE），考察了不同管理方法对腐烂的影响。目的是确定茶袋指数分解率（k）和稳定因子（S）是否足够灵敏，以检测不同管理方法下垃圾分解的差异，以及它们如何与环境因素、作物类型和当地气候条件相互作用。在奥地利的 16 个地点和瑞典的 13 个地点埋设茶叶袋，并在 90 天后收集茶叶袋。奥地利长效试验的处理侧重于矿物肥料和有机肥料的施用、耕作制度和作物残留物管理，而瑞典的处理侧重于耕作制度、矿物肥料的施用和耕作制度。奥地利的研究结果表明，与清除作物秸秆、低氮或不氮施肥相比，作物秸秆沤肥和高氮施肥分别增加了 k。与减少耕作和传统耕作相比，少耕的 K 值明显更高。在瑞典，施肥地块的 S 值高于非施肥地块，高氮肥的 k 值最高。对奥地利和瑞典的随机森林回归共同表明，k 和 S 主要受气候条件的影响，气候条件解释了其 70% 以上的变化。然而，在相似的气候条件下，管理方法对分解动态有很大影响。为了提高该指数作为管理措施对废弃物分解动态影响的指标的实用性，尤其是将其与碳储存潜力联系起来，最好能将 TBI 方法应用到使用农业生态系统 LTE 的更大规模的网络中。
{"title":"Evaluating the Tea Bag Index approach for different management practices in agroecosystems using long-term field experiments in Austria and Sweden","authors":"Maria Regina Gmach, Martin Anders Bolinder, Lorenzo Menichetti, Thomas Kätterer, Heide Spiegel, Olle Åkesson, Jürgen Kurt Friedel, Andreas Surböck, Agnes Schweinzer, Taru Sandén","doi":"10.5194/soil-10-407-2024","DOIUrl":"https://doi.org/10.5194/soil-10-407-2024","url":null,"abstract":"Abstract. Litter decomposition is an important factor affecting local and global C cycles. It is known that decomposition through soil microbial activity in ecosystems is mainly influenced by soil type and climatic conditions. However, for agroecosystems, there remains a need for a better understanding of how management practices influence litter decomposition. This study examined the effect of different management practices on decomposition at 29 sites with long-term (mean duration of 38 years) field experiments (LTEs) using the Tea Bag Index (TBI) protocol with standard litter (rooibos and green tea) developed by Keuskamp et al. (2013). The objective was to determine if the TBI decomposition rate (k) and stabilization factor (S) are sensitive enough to detect differences in litter decomposition between management practices as well as how they interact with edaphic factors, crop type and local climatic conditions. Tea bags were buried and collected after ∼90 d at 16 Austrian and 13 Swedish sites. The treatments in the Austrian LTEs focused on mineral and organic fertilizer application, tillage systems and crop residue management, whereas those in Sweden addressed cropping systems, mineral fertilizer application and tillage systems. The results for Austria showed that the incorporation of crop residue and high-N fertilizer application increased k, compared with crop residue removal and low or no N application, respectively. Minimum tillage had significantly higher k compared with reduced and conventional tillage. In Sweden, fertilized plots showed higher S than non-fertilized plots and high-N fertilizer had the highest k. Growing spring cereal led to higher k than forage crops. Random forest regressions for Austria and Sweden jointly showed that k and S were mainly governed by climatic conditions, which explained more than 70 % of their variation. However, under similar climatic conditions, management practices strongly influenced decomposition dynamics. It would be appropriate to apply the TBI approach to a more large-scale network using LTEs for agroecosystems, in order to improve the index's usefulness as an indicator of the effect of management practices on litter decomposition dynamics, particularly linking it with the potential for C storage.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"2014 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141309056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Soil colloidal particles are the most active components of all, and they also vary in elemental composition and environmental behaviors with the particle size. The purposes of the present study are to clarify how particle size affects the physiochemical properties and aggregation kinetics of soil colloids, and to further reveal the underlying mechanisms. Soil colloidal particles from two alkaline soils—Lou soil and cinnamon soil were subdivided into three ranges: d < 2 μm, d < 1 μm and d < 100 nm. The organic and inorganic carbon contents, clay mineralogy, surface electrochemical properties, including surface functional groups and zeta potentials, were characterized. Through time-resolved light scattering technique, the aggregation kinetics of soil colloidal fractions were investigated, and their critical coagulation concentrations (CCCs) were determined. With decreasing colloidal particle diameter, the total carbon content, organic carbon, organic functional groups content and illite content all increased. The absolute zeta potential values and the charge variability decreased with decreasing particle diameter. The CCC values of Lou soil and cinnamon soil colloids followed the descending order of d < 100 nm, d < 1 μm, d < 2 μm. Compared with the course factions (d < 1 μm and d < 2 μm), soil nanoparticles were more abundant in organic carbon and more stable clay minerals (d < 100 nm), thus they exhibited strongest colloidal suspension stability. The differences in organic matter contents and clay mineralogy are the fundamental reasons for the differences in colloidal suspension stability behind the size effects of Lou soil and cinnamon soil colloids. The present study revealed the size effects of two alkaline soil colloids on carbon content, clay minerals, surface properties and suspension stability, emphasizing that soil nanoparticles are prone to be more stably dispersed instead of being aggregated. These findings can provide references for in-depth understanding of the environmental behaviors of the heterogeneous soil organic-mineral complexes.
{"title":"Effect of colloidal particle size on physicochemical properties and aggregation behaviors of two alkaline soils","authors":"Yuyang Yan, Xinran Zhang, Chenyang Xu, Junjun Liu, Feinan Hu, Zengchao Geng","doi":"10.5194/egusphere-2024-1266","DOIUrl":"https://doi.org/10.5194/egusphere-2024-1266","url":null,"abstract":"<strong>Abstract.</strong> Soil colloidal particles are the most active components of all, and they also vary in elemental composition and environmental behaviors with the particle size. The purposes of the present study are to clarify how particle size affects the physiochemical properties and aggregation kinetics of soil colloids, and to further reveal the underlying mechanisms. Soil colloidal particles from two alkaline soils—Lou soil and cinnamon soil were subdivided into three ranges: <em>d</em> < 2 μm, <em>d</em> < 1 μm and <em>d</em> < 100 nm. The organic and inorganic carbon contents, clay mineralogy, surface electrochemical properties, including surface functional groups and zeta potentials, were characterized. Through time-resolved light scattering technique, the aggregation kinetics of soil colloidal fractions were investigated, and their critical coagulation concentrations (CCCs) were determined. With decreasing colloidal particle diameter, the total carbon content, organic carbon, organic functional groups content and illite content all increased. The absolute zeta potential values and the charge variability decreased with decreasing particle diameter. The CCC values of Lou soil and cinnamon soil colloids followed the descending order of <em>d </em>< 100 nm, <em>d </em>< 1 μm, <em>d</em> < 2 μm. Compared with the course factions (<em>d </em>< 1 μm and <em>d</em> < 2 μm), soil nanoparticles were more abundant in organic carbon and more stable clay minerals (<em>d </em>< 100 nm), thus they exhibited strongest colloidal suspension stability. The differences in organic matter contents and clay mineralogy are the fundamental reasons for the differences in colloidal suspension stability behind the size effects of Lou soil and cinnamon soil colloids. The present study revealed the size effects of two alkaline soil colloids on carbon content, clay minerals, surface properties and suspension stability, emphasizing that soil nanoparticles are prone to be more stably dispersed instead of being aggregated. These findings can provide references for in-depth understanding of the environmental behaviors of the heterogeneous soil organic-mineral complexes.","PeriodicalId":48610,"journal":{"name":"Soil","volume":"8 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141304532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-06-06DOI: 10.5194/soil-10-367-2024
Laura Sereni, Julie-Maï Paris, Isabelle Lamy, Bertrand Guenet
Abstract. Contaminant inputs to soil are highly dependent on anthropogenic activities, while contaminant retention, mobility, and availability are highly dependent on soil properties. The knowledge of partitioning between soil solid and solution phases is necessary to estimate whether deposited amounts of contaminants will be either transported with runoff or accumulated. Besides, runoff is expected to change during the next century due to changes in climate and in rainfall patterns. In this study, we aimed to estimate at the European scale the areas with a potential risk due to contaminant leaching (LP). We also defined, in the same way, the surface areas where limited copper (Cu) leaching occurred, leading to potential accumulation (AP) areas. We focused on Cu widely used in agriculture either in a mineral form or in association with organic fertilizers, resulting in high spatial variations in the deposited and incorporated amounts in soils, as well as in European policies of application. We developed a method using both Cu partition coefficients (Kf) between total and dissolved Cu forms and runoff simulation results for historical and future climates. The calculation of Kf with pedo-transfer functions allowed us to avoid any uncertainties due to past management or future depositions that may affect total Cu concentrations. Areas with a high potential risk of leaching or of accumulation were estimated over the 21st century by comparing Kf and runoff to their respective European medians. Thus, at three distinct times, we considered a grid cell to be at risk of LP if its Kf was low compared to the European median and if its runoff was high compared to the European median of the time. Similarly, a grid cell was considered to be at risk of AP if its Kf was high and its runoff was low compared to its respective European median of the time. To deal with uncertainties in climate change scenarios and the associated model prediction, we performed our study with two atmospheric greenhouse gas representative concentration pathways (RCPs), defined according to climate change associated with a large set of socio-economic scenarios found in the literature. We used two land surface models (ORCHIDEE and LPJmL, given soil hydrologic properties) and two global circulation models (ESM2m and CM5a, given rainfall forecasts). Our results show that, for historical scenarios, 6.4 ± 0.1 % (median, median deviation) and 6.7 ± 1.1 % of the grid cells of the European land surfaces experience LP and AP, respectively. Interestingly, we simulate a constant surface area with LP and AP for around 13 % of the grid cells, which is consistent with an increase in AP and a decrease in LP. Despite large variations in LP and AP extents, depending on the land surface model used for estimations, the two trends were more pronounced with RCP 6.0 than with RCP 2.6, highlighting the global risk of combined climate change and contamination and the need for more local and seasonal assessment
{"title":"Estimations of soil metal accumulation or leaching potentials under climate change scenarios: the example of copper on a European scale","authors":"Laura Sereni, Julie-Maï Paris, Isabelle Lamy, Bertrand Guenet","doi":"10.5194/soil-10-367-2024","DOIUrl":"https://doi.org/10.5194/soil-10-367-2024","url":null,"abstract":"Abstract. Contaminant inputs to soil are highly dependent on anthropogenic activities, while contaminant retention, mobility, and availability are highly dependent on soil properties. The knowledge of partitioning between soil solid and solution phases is necessary to estimate whether deposited amounts of contaminants will be either transported with runoff or accumulated. Besides, runoff is expected to change during the next century due to changes in climate and in rainfall patterns. In this study, we aimed to estimate at the European scale the areas with a potential risk due to contaminant leaching (LP). We also defined, in the same way, the surface areas where limited copper (Cu) leaching occurred, leading to potential accumulation (AP) areas. We focused on Cu widely used in agriculture either in a mineral form or in association with organic fertilizers, resulting in high spatial variations in the deposited and incorporated amounts in soils, as well as in European policies of application. We developed a method using both Cu partition coefficients (Kf) between total and dissolved Cu forms and runoff simulation results for historical and future climates. The calculation of Kf with pedo-transfer functions allowed us to avoid any uncertainties due to past management or future depositions that may affect total Cu concentrations. Areas with a high potential risk of leaching or of accumulation were estimated over the 21st century by comparing Kf and runoff to their respective European medians. Thus, at three distinct times, we considered a grid cell to be at risk of LP if its Kf was low compared to the European median and if its runoff was high compared to the European median of the time. Similarly, a grid cell was considered to be at risk of AP if its Kf was high and its runoff was low compared to its respective European median of the time. To deal with uncertainties in climate change scenarios and the associated model prediction, we performed our study with two atmospheric greenhouse gas representative concentration pathways (RCPs), defined according to climate change associated with a large set of socio-economic scenarios found in the literature. We used two land surface models (ORCHIDEE and LPJmL, given soil hydrologic properties) and two global circulation models (ESM2m and CM5a, given rainfall forecasts). Our results show that, for historical scenarios, 6.4 ± 0.1 % (median, median deviation) and 6.7 ± 1.1 % of the grid cells of the European land surfaces experience LP and AP, respectively. Interestingly, we simulate a constant surface area with LP and AP for around 13 % of the grid cells, which is consistent with an increase in AP and a decrease in LP. Despite large variations in LP and AP extents, depending on the land surface model used for estimations, the two trends were more pronounced with RCP 6.0 than with RCP 2.6, highlighting the global risk of combined climate change and contamination and the need for more local and seasonal assessment","PeriodicalId":48610,"journal":{"name":"Soil","volume":"14 1","pages":""},"PeriodicalIF":6.8,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141264751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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