Abstract. The saturated hydraulic conductivity (Ksat) is a key soil hydraulic property governing agricultural production. However, the influence of the conversion from the conventional tillage (CT) to conservation tillage (CS; including no tillage, NT, and reduced tillage, RT) on the Ksat of soils is not well understood and still debated. In this study, we applied a global meta-analysis method to synthesize 227 paired observations for soil Ksat from 69 published studies and investigated factors influencing the effects of conversion to CS on Ksat. Results showed that soil layer, conservation tillage type, soil texture type, and cropping system management did not have significant effects on the influence of conversion to CS on Ksat. When the Ksat was measured by the rainfall simulator, the conversion to CS significantly (p<0.05) increased the surface and subsurface soil Ksat by 41.7 % and 36.9 %, respectively. In addition, the subsurface Ksat also tended to increase under CS practices when the Ksat was measured by a tension disc infiltrometer. However, when the Ksat was measured by a hood infiltrometer, ring infiltrometer, constant/falling head, and Guelph permeameter, the conversion to CS had no significant effects on the Ksat. It is observed that, when the conversion period was less than 15 years, the Ksat under CS showed a greater increase for a longer conversion period. Climatic and topographic factors, including the mean annual temperature (MAT) and the mean annual precipitation (MAP), were statistically related to the responses of Ksat to tillage conversion at the global scale. Quadratic polynomials can describe the relationships between them. These findings suggested that quantifying the effects of tillage conversion on soil Ksat needed to consider experimental conditions, especially the measurement technique and conversion period.
{"title":"Effects of environmental factors on the influence of tillage conversion on saturated soil hydraulic conductivity obtained with different methodologies: a global meta-analysis","authors":"K. Liao, Juan Feng, X. Lai, Q. Zhu","doi":"10.5194/soil-8-309-2022","DOIUrl":"https://doi.org/10.5194/soil-8-309-2022","url":null,"abstract":"Abstract. The saturated hydraulic conductivity (Ksat) is a key\u0000soil hydraulic property governing agricultural production. However, the influence of the conversion from the conventional tillage (CT) to conservation tillage (CS; including no tillage, NT, and reduced tillage, RT) on the Ksat of soils is not well understood and still debated. In this study, we applied a global meta-analysis method to synthesize 227 paired\u0000observations for soil Ksat from 69 published studies and investigated factors influencing the effects of conversion to CS on Ksat. Results showed that soil layer, conservation tillage type, soil texture type, and cropping system management did not have significant effects on the influence of conversion to CS on Ksat. When the Ksat was measured by the rainfall simulator, the conversion to CS significantly (p<0.05) increased the\u0000surface and subsurface soil Ksat by 41.7 % and 36.9 %, respectively. In addition, the subsurface Ksat also tended to increase under CS practices when the Ksat was measured by a tension disc infiltrometer. However, when the Ksat was measured by a hood infiltrometer, ring infiltrometer, constant/falling head, and Guelph permeameter, the conversion to CS had no significant effects on the Ksat. It is observed that, when the conversion period was less than 15 years, the Ksat under CS showed a greater increase for a longer conversion period. Climatic and topographic factors, including the mean annual temperature (MAT) and the mean annual precipitation (MAP), were statistically related to the responses of Ksat to tillage conversion at the global scale. Quadratic polynomials can describe the relationships between them. These findings suggested that quantifying the effects of tillage conversion on soil Ksat needed to\u0000consider experimental conditions, especially the measurement technique and conversion period.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79450072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Understanding the relationship between soil microbial taxonomic compositions and functional profiles is essential for predicting ecosystem functions under various environmental disturbances. However, even though microbial communities are sensitive to disturbance, ecosystem functions remain relatively stable, as soil microbes are likely to be functionally redundant. Microbial functional redundancy may be more associated with “broad” functions carried out by a wide range of microbes than with “narrow” functions in which specific microorganisms specialize. Thus, a comprehensive study to evaluate how microbial taxonomic compositions correlate with broad and narrow functional profiles is necessary. Here, we evaluated soil metagenomes worldwide to assess whether functional and taxonomic diversities differ significantly between the five broad and the five narrow functions that we chose. Our results revealed that, compared with the five broad functions, soil microbes capable of performing the five narrow functions were more taxonomically diverse, and thus their functional diversity was more dependent on taxonomic diversity, implying lower levels of functional redundancy in narrow functions. Co-occurrence networks indicated that microorganisms conducting broad functions were positively related, but microbes specializing in narrow functions were interacting mostly negatively. Our study provides strong evidence to support our hypothesis that functional redundancy is significantly different between broad and narrow functions in soil microbes, as the association of functional diversity with taxonomy was greater in the five narrow than in the five broad functions.
{"title":"Lower functional redundancy in “narrow” than “broad” functions in global soil metagenomics","authors":"Huaihai Chen, Kayan Ma, Yu Huang, Qi Fu, Ying Qiu, Jiajiang Lin, C. Schadt, Hao Chen","doi":"10.5194/soil-8-297-2022","DOIUrl":"https://doi.org/10.5194/soil-8-297-2022","url":null,"abstract":"Abstract. Understanding the relationship between soil microbial taxonomic compositions\u0000and functional profiles is essential for predicting ecosystem functions\u0000under various environmental disturbances. However, even though microbial\u0000communities are sensitive to disturbance, ecosystem functions remain\u0000relatively stable, as soil microbes are likely to be functionally redundant.\u0000Microbial functional redundancy may be more associated with “broad”\u0000functions carried out by a wide range of microbes than with “narrow”\u0000functions in which specific microorganisms specialize. Thus, a comprehensive\u0000study to evaluate how microbial taxonomic compositions correlate with\u0000broad and narrow functional profiles is necessary. Here, we\u0000evaluated soil metagenomes worldwide to assess whether functional and\u0000taxonomic diversities differ significantly between the five broad and\u0000the five narrow functions that we chose. Our results revealed that,\u0000compared with the five broad functions, soil microbes capable of\u0000performing the five narrow functions were more taxonomically diverse,\u0000and thus their functional diversity was more dependent on taxonomic\u0000diversity, implying lower levels of functional redundancy in narrow\u0000functions. Co-occurrence networks indicated that microorganisms conducting\u0000broad functions were positively related, but microbes specializing\u0000in narrow functions were interacting mostly negatively. Our study provides\u0000strong evidence to support our hypothesis that functional redundancy is\u0000significantly different between broad and narrow functions in soil\u0000microbes, as the association of functional diversity with taxonomy was\u0000greater in the five narrow than in the five broad functions.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89926591","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Schlüter, Tim Roussety, Lena Rohe, V. Guliyev, E. Blagodatskaya, Thomas Reitz
Abstract. Land use is known to exert a dominant impact on a range of essential soil functions like water retention, carbon sequestration, organic matter cycling and plant growth. At the same time, land use management is known to have a strong influence on soil structure, e.g., through bioturbation, tillage and compaction. However, it is often unclear whether the differences in soil structure are the actual cause of the differences in soil functions or if they only co-occur. This impact of land use (conventional and organic farming, intensive and extensive meadow, extensive pasture) on the relationship between soil structure and short-term carbon mineralization was investigated at the Global Change Exploratory Facility, in Bad Lauchstädt, Germany. Intact topsoil cores (upper 10 cm, n=75) were sampled from all land use types at the early growing season. Soil structure and microbial activity were measured using X-ray-computed tomography and respirometry, respectively. Differences in microstructural properties between land uses were small in comparison to the variation within land uses. The most striking difference between land uses was larger macropore diameters in grassland soils due to the presence of large biopores that are periodically destroyed in croplands. Grasslands had larger amounts of particulate organic matter (POM), including root biomass, and also greater microbial activity than croplands, both in terms of basal respiration and rate of carbon mineralization during growth. Basal respiration among soil cores varied by more than 1 order of magnitude (0.08–1.42 µg CO2-C h−1 g−1 soil) and was best explained by POM mass (R2=0.53, p<0.001). Predictive power was only slightly improved by considering all bulk, microstructure and microbial properties jointly. The predictive power of image-derived microstructural properties was low, because aeration did not limit carbon mineralization and was sustained by pores smaller than the image resolution limit (<30 µm). The frequently postulated dependency of basal respiration on soil moisture was not evident even though some cores were apparently water limited, as it was likely disguised by the co-limitation of POM mass. This finding was interpreted in regards to the microbial hotspots which form on decomposing plant residues and which are decoupled from water limitation in bulk soil. The rate of glucose mineralization during growth was explained well by substrate-induced respiration (R2=0.84) prior to growth, which in turn correlated with total microbial biomass, basal respiration and POM mass, and was not affected by pore metrics. These findings stress that soil structure had little relevance in predicting carbon mineralization in well-aerated soil, as mineralization appeared to by predominantly driven by the decomposition of plant residues in intact soil. Land use therefore affects carbon mineralization in well-aerated soil mainly in the amount and quality of labile carbon.
摘要众所周知，土地利用对一系列基本土壤功能(如保水、固碳、有机物循环和植物生长)产生主导影响。与此同时，已知土地利用管理对土壤结构有很强的影响，例如通过生物扰动、耕作和压实。然而，土壤结构的差异是否是土壤功能差异的实际原因，或者它们只是共同发生的，通常是不清楚的。位于德国Bad Lauchstädt的全球变化探索设施研究了土地利用(传统和有机农业、集约和粗放草甸、粗放牧场)对土壤结构和短期碳矿化之间关系的影响。在生长早期，从所有土地利用类型取样完整的表土岩心(上部10 cm, n=75)。分别使用x射线计算机断层扫描和呼吸测量法测量土壤结构和微生物活性。与土地利用内部的变化相比，不同土地利用之间微观结构特性的差异很小。不同土地利用方式之间最显著的差异是草地土壤的大孔直径更大，这是由于在农田中存在周期性破坏的大生物孔。在生长过程中的基础呼吸和碳矿化速率方面，草地的颗粒物有机质(POM)(包括根系生物量)和微生物活性均高于农田。土壤芯间的基础呼吸变化超过1个数量级(0.08-1.42µg CO2-C h - 1 g - 1土壤)，最好用POM质量来解释(R2=0.53, p<0.001)。综合考虑所有的体积、微观结构和微生物特性，预测能力仅略有提高。由于曝气不限制碳矿化，并且是由小于图像分辨率极限(<30µm)的孔隙维持的，因此图像衍生的微观结构性质的预测能力较低。通常假定的基础呼吸对土壤水分的依赖并不明显，即使一些核心显然是水限制的，因为它可能被POM质量的共同限制所掩盖。这一发现被解释为微生物热点是在分解植物残留物上形成的，并且与散装土壤中的水分限制脱钩。生长过程中的葡萄糖矿化速率可以用生长前底物诱导的呼吸(R2=0.84)很好地解释，这反过来又与总微生物生物量、基础呼吸和POM质量相关，而不受孔隙率的影响。这些发现强调，土壤结构与预测通风良好的土壤中的碳矿化关系不大，因为矿化似乎主要是由完整土壤中植物残留物的分解驱动的。因此，土地利用对通气良好土壤中碳矿化的影响主要表现在活性碳的数量和质量上。
{"title":"Land use impact on carbon mineralization in well aerated soils is mainly explained by variations of particulate organic matter rather than of soil structure","authors":"S. Schlüter, Tim Roussety, Lena Rohe, V. Guliyev, E. Blagodatskaya, Thomas Reitz","doi":"10.5194/soil-8-253-2022","DOIUrl":"https://doi.org/10.5194/soil-8-253-2022","url":null,"abstract":"Abstract. Land use is known to exert a dominant impact on a range of\u0000essential soil functions like water retention, carbon sequestration, organic\u0000matter cycling and plant growth. At the same time, land use management is\u0000known to have a strong influence on soil structure, e.g., through\u0000bioturbation, tillage and compaction. However, it is often unclear whether\u0000the differences in soil structure are the actual cause of the differences in soil\u0000functions or if they only co-occur. This impact of land use (conventional and organic farming, intensive and\u0000extensive meadow, extensive pasture) on the relationship between soil\u0000structure and short-term carbon mineralization was investigated at the\u0000Global Change Exploratory Facility, in Bad Lauchstädt, Germany. Intact\u0000topsoil cores (upper 10 cm, n=75) were sampled from all land use types at\u0000the early growing season. Soil structure and microbial activity were\u0000measured using X-ray-computed tomography and respirometry, respectively. Differences in microstructural properties between land uses were small in\u0000comparison to the variation within land uses. The most striking difference\u0000between land uses was larger macropore diameters in grassland soils due to\u0000the presence of large biopores that are periodically destroyed in croplands.\u0000Grasslands had larger amounts of particulate organic matter (POM), including\u0000root biomass, and also greater microbial activity than croplands, both in\u0000terms of basal respiration and rate of carbon mineralization during growth.\u0000Basal respiration among soil cores varied by more than 1 order of\u0000magnitude (0.08–1.42 µg CO2-C h−1 g−1 soil) and was\u0000best explained by POM mass (R2=0.53, p<0.001).\u0000Predictive power was only slightly improved by considering all bulk, microstructure\u0000and microbial properties jointly. The predictive power of image-derived\u0000microstructural properties was low, because aeration did not limit carbon\u0000mineralization and was sustained by pores smaller than the image resolution\u0000limit (<30 µm). The frequently postulated dependency of\u0000basal respiration on soil moisture was not evident even though some cores\u0000were apparently water limited, as it was likely disguised by the\u0000co-limitation of POM mass. This finding was interpreted in regards to the microbial\u0000hotspots which form on decomposing plant residues and which are decoupled\u0000from water limitation in bulk soil. The rate of glucose mineralization\u0000during growth was explained well by substrate-induced respiration\u0000(R2=0.84) prior to growth, which in turn correlated with total\u0000microbial biomass, basal respiration and POM mass, and was not affected by pore\u0000metrics. These findings stress that soil structure had little relevance in predicting\u0000carbon mineralization in well-aerated soil, as mineralization appeared to by\u0000predominantly driven by the decomposition of plant residues in intact soil.\u0000Land use therefore affects carbon mineralization in well-aerated soil mainly\u0000in the amount and quality of labile carbon.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88254497","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Araya, Jeffrey P. Mitchell, J. Hopmans, T. Ghezzehei
Abstract. We studied the long-term impact of contrasting tillage and cover cropping systems on soil structure and hydraulic properties. Complete water retention and conductivity curves for the top (0–5 cm) and subsurface (20–25 cm) soils were characterized and contrasted. Dynamic water storage and retention were evaluated using numerical simulations in HYDRUS-2D software. Compared with standard-till (ST) and no-cover-crop (NO) systems, soils under no-till (NT) and cover cropping (CC) systems showed improved soil structure in terms of pore size distribution (PSD). Changes in hydraulic conductivity (K) under these systems led to an increased infiltration rate and water retention. However, NT and CC plots had lower water content at field capacity (33 kPa suction) and lower plant-available water (PAW) compared with ST and NO plots. Numerical simulations, however, showed that NT and CC plots have higher water storage (albeit marginal in magnitude) and water availability following irrigation. Because the numerical simulations considered retention and conductivity functions simultaneously and dynamically through time, they allow the capture of hydraulic states that are arguably more relevant to crops. The study concludes that the long-term practices of NT and CC systems were beneficial in terms of changes to the PSD. NT and CC systems also marginally improved soil water conductivity and storage at the plot scale.
{"title":"Long-term impact of cover crop and reduced disturbance tillage on soil pore size distribution and soil water storage","authors":"S. Araya, Jeffrey P. Mitchell, J. Hopmans, T. Ghezzehei","doi":"10.5194/soil-8-177-2022","DOIUrl":"https://doi.org/10.5194/soil-8-177-2022","url":null,"abstract":"Abstract. We studied the long-term impact of contrasting tillage\u0000and cover cropping systems on soil structure and hydraulic properties.\u0000Complete water retention and conductivity curves for the top (0–5 cm) and\u0000subsurface (20–25 cm) soils were characterized and contrasted. Dynamic\u0000water storage and retention were evaluated using numerical simulations in\u0000HYDRUS-2D software. Compared with standard-till (ST) and no-cover-crop (NO)\u0000systems, soils under no-till (NT) and cover cropping (CC) systems showed\u0000improved soil structure in terms of pore size distribution (PSD). Changes in\u0000hydraulic conductivity (K) under these systems led to an increased infiltration\u0000rate and water retention. However, NT and CC plots had lower water content\u0000at field capacity (33 kPa suction) and lower plant-available water (PAW)\u0000compared with ST and NO plots. Numerical simulations, however, showed that NT\u0000and CC plots have higher water storage (albeit marginal in magnitude) and\u0000water availability following irrigation. Because the numerical simulations\u0000considered retention and conductivity functions simultaneously and\u0000dynamically through time, they allow the capture of hydraulic states that\u0000are arguably more relevant to crops. The study concludes that the long-term\u0000practices of NT and CC systems were beneficial in terms of changes to the\u0000PSD. NT and CC systems also marginally improved soil water\u0000conductivity and storage at the plot scale.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78123282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Roberta Pulcher, E. Balugani, M. Ventura, N. Greggio, D. Marazza
Abstract. Biochar production and application as soil amendment is a promising carbon (C)-negative technology to increase soil C sequestration and mitigate climate change. However, there is a lack of knowledge about biochar degradation rate in soil and its effects on native soil organic carbon (SOC), mainly due to the absence of long-term experiments performed in field conditions. The aim of this work was to investigate the long-term degradation rate of biochar in an 8-year field experiment in a poplar short-rotation coppice plantation in Piedmont (Italy), and to modify the RothC model to assess and predict how biochar influences soil C dynamics. The RothC model was modified by including two biochar pools, labile (4 % of the total biochar mass) and recalcitrant (96 %), and the priming effect of biochar on SOC. The model was calibrated and validated using data from the field experiment. The results confirm that biochar degradation can be faster in field conditions in comparison to laboratory experiments; nevertheless, it can contribute to a substantial increase in the soil C stock in the long term. Moreover, this study shows that the modified RothC model was able to simulate the dynamics of biochar and SOC degradation in soils in field conditions in the long term, at least in the specific conditions examined.
{"title":"Inclusion of biochar in a C dynamics model based on observations from an 8-year field experiment","authors":"Roberta Pulcher, E. Balugani, M. Ventura, N. Greggio, D. Marazza","doi":"10.5194/soil-8-199-2022","DOIUrl":"https://doi.org/10.5194/soil-8-199-2022","url":null,"abstract":"Abstract. Biochar production and application as soil amendment is a\u0000promising carbon (C)-negative technology to increase soil C sequestration\u0000and mitigate climate change. However, there is a lack of knowledge about\u0000biochar degradation rate in soil and its effects on native soil organic\u0000carbon (SOC), mainly due to the absence of long-term experiments performed\u0000in field conditions. The aim of this work was to investigate the long-term\u0000degradation rate of biochar in an 8-year field experiment in a poplar\u0000short-rotation coppice plantation in Piedmont (Italy), and to modify the\u0000RothC model to assess and predict how biochar influences soil C dynamics.\u0000The RothC model was modified by including two biochar pools, labile (4 %\u0000of the total biochar mass) and recalcitrant (96 %), and the priming effect\u0000of biochar on SOC. The model was calibrated and validated using data from\u0000the field experiment. The results confirm that biochar degradation can be\u0000faster in field conditions in comparison to laboratory experiments;\u0000nevertheless, it can contribute to a substantial increase in the soil C stock\u0000in the long term. Moreover, this study shows that the modified RothC model\u0000was able to simulate the dynamics of biochar and SOC degradation in soils in\u0000field conditions in the long term, at least in the specific conditions\u0000examined.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"140 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86664212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Ortner, M. Seidel, Sebastian Semella, T. Udelhoven, Michael Vohland, S. Thiele-Bruhn
Abstract. Soil organic matter (SOM) is an indispensable component of terrestrial ecosystems. Soil organic carbon (SOC) dynamics are influenced by a number of well-known abiotic factors such as clay content, soil pH, or pedogenic oxides. These parameters interact with each other and vary in their influence on SOC depending on local conditions. To investigate the latter, the dependence of SOC accumulation on parameters and parameter combinations was statistically assessed that vary on a local scale depending on parent material, soil texture class, and land use. To this end, topsoils were sampled from arable and grassland sites in south-western Germany in four regions with different soil parent material. Principal component analysis (PCA) revealed a distinct clustering of data according to parent material and soil texture that varied largely between the local sampling regions, while land use explained PCA results only to a small extent. The PCA clusters were differentiated into total clusters that contain the entire dataset or major proportions of it and local clusters representing only a smaller part of the dataset. All clusters were analysed for the relationships between SOC concentrations (SOC %) and mineral-phase parameters in order to assess specific parameter combinations explaining SOC and its labile fractions hot water-extractable C (HWEC) and microbial biomass C (MBC). Analyses were focused on soil parameters that are known as possible predictors for the occurrence and stabilization of SOC (e.g. fine silt plus clay and pedogenic oxides). Regarding the total clusters, we found significant relationships, by bivariate models, between SOC, its labile fractions HWEC and MBC, and the applied predictors. However, partly low explained variances indicated the limited suitability of bivariate models. Hence, mixed-effect models were used to identify specific parameter combinations that significantly explain SOC and its labile fractions of the different clusters. Comparing measured and mixed-effect-model-predicted SOC values revealed acceptable to very good regression coefficients (R2=0.41–0.91) and low to acceptable root mean square error (RMSE = 0.20 %–0.42 %). Thereby, the predictors and predictor combinations clearly differed between models obtained for the whole dataset and the different cluster groups. At a local scale, site-specific combinations of parameters explained the variability of organic carbon notably better, while the application of total models to local clusters resulted in less explained variance and a higher RMSE. Independently of that, the explained variance by marginal fixed effects decreased in the order SOC > HWEC > MBC, showing that labile fractions depend less on soil properties but presumably more on processes such as organic carbon input and turnover in soil.
{"title":"Content of soil organic carbon and labile fractions depend on local combinations of mineral-phase characteristics","authors":"M. Ortner, M. Seidel, Sebastian Semella, T. Udelhoven, Michael Vohland, S. Thiele-Bruhn","doi":"10.5194/soil-8-113-2022","DOIUrl":"https://doi.org/10.5194/soil-8-113-2022","url":null,"abstract":"Abstract. Soil organic matter (SOM) is an indispensable component of\u0000terrestrial ecosystems. Soil organic carbon (SOC) dynamics are influenced by\u0000a number of well-known abiotic factors such as clay content, soil pH, or pedogenic oxides. These parameters interact with each other and vary in\u0000their influence on SOC depending on local conditions. To investigate the\u0000latter, the dependence of SOC accumulation on parameters and parameter\u0000combinations was statistically assessed that vary on a local scale depending\u0000on parent material, soil texture class, and land use. To this end, topsoils were sampled from arable and grassland sites in south-western Germany in four regions with different soil parent material. Principal component analysis\u0000(PCA) revealed a distinct clustering of data according to parent material\u0000and soil texture that varied largely between the local sampling regions,\u0000while land use explained PCA results only to a small extent. The PCA\u0000clusters were differentiated into total clusters that contain the entire\u0000dataset or major proportions of it and local clusters representing only a\u0000smaller part of the dataset. All clusters were analysed for the relationships between SOC concentrations (SOC %) and mineral-phase parameters in order to assess specific parameter combinations explaining SOC\u0000and its labile fractions hot water-extractable C (HWEC) and microbial biomass C (MBC). Analyses were focused on soil parameters that are known as possible predictors for the occurrence and stabilization of SOC (e.g. fine\u0000silt plus clay and pedogenic oxides). Regarding the total clusters, we found\u0000significant relationships, by bivariate models, between SOC, its labile\u0000fractions HWEC and MBC, and the applied predictors. However, partly low explained variances indicated the limited suitability of bivariate models. Hence, mixed-effect models were used to identify specific parameter combinations that significantly explain SOC and its labile fractions of the different\u0000clusters. Comparing measured and mixed-effect-model-predicted SOC values revealed acceptable to very good regression coefficients (R2=0.41–0.91)\u0000and low to acceptable root mean square error (RMSE = 0.20 %–0.42 %).\u0000Thereby, the predictors and predictor combinations clearly differed between\u0000models obtained for the whole dataset and the different cluster groups. At a local scale, site-specific combinations of parameters explained the variability of organic carbon notably better, while the application of total\u0000models to local clusters resulted in less explained variance and a higher\u0000RMSE. Independently of that, the explained variance by marginal fixed effects decreased in the order SOC > HWEC > MBC,\u0000showing that labile fractions depend less on soil properties but presumably\u0000more on processes such as organic carbon input and turnover in soil.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"1212 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76127813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. M. S. Ndour, C. Hatté, W. Achouak, T. Heulin, L. Cournac
Abstract. Rhizosheath size varies significantly with crop genotype, and root exudation is one among its driving factors. Unravelling the relationships between rhizosheath formation, root exudation and soil carbon dynamics may bring interesting perspectives in terms of crop breeding towards sustainable agriculture. Here we grew four pearl millet (C4 plant type: δ13C of −12.8 ‰, F14C = 1.012) inbred lines showing contrasting rhizosheath sizes in a C3 soil type (organic matter with δ13C of −22.3 ‰, F14C = 1.045). We sampled the root-adhering soil (RAS) and bulk soil after 28 d of growth under a semi-controlled condition. The soil organic carbon (SOC) content and δ13C and F14C of soil samples were measured and the plant-derived C amount and Clost / Cnew ratio in the RAS were calculated. The results showed a significant increase in δ13C in the RAS of the four pearl millet lines compared to the control soil, suggesting that this approach was able to detect plant C input into the soil at an early stage of pearl millet growth. The concentration of plant-derived C in the RAS did not vary significantly between pearl millet lines, but the absolute amount of plant-derived C varied significantly when we considered the RAS mass of these different lines. Using a conceptual model and data from the two carbon isotopes' measurements, we evidenced a priming effect for all pearl millet lines. Importantly, the priming effect amplitude (Clost / Cnew ratio) was higher for the small rhizosheath (low-aggregation) line than for the large rhizosheath (high-aggregation) ones, indicating a better C sequestration potential of the latter.
{"title":"Rhizodeposition efficiency of pearl millet genotypes assessed on a short growing period by carbon isotopes (δ13C and F14C)","authors":"P. M. S. Ndour, C. Hatté, W. Achouak, T. Heulin, L. Cournac","doi":"10.5194/soil-8-49-2022","DOIUrl":"https://doi.org/10.5194/soil-8-49-2022","url":null,"abstract":"Abstract. Rhizosheath size varies significantly with crop genotype,\u0000and root exudation is one among its driving factors. Unravelling the\u0000relationships between rhizosheath formation, root exudation and soil carbon\u0000dynamics may bring interesting perspectives in terms of crop breeding\u0000towards sustainable agriculture. Here we grew four pearl millet (C4\u0000plant type: δ13C of −12.8 ‰, F14C = 1.012) inbred lines showing contrasting rhizosheath sizes in a C3 soil\u0000type (organic matter with δ13C of −22.3 ‰,\u0000F14C = 1.045). We sampled the root-adhering soil (RAS) and bulk soil\u0000after 28 d of growth under a semi-controlled condition. The soil organic carbon (SOC) content and δ13C and F14C of soil samples were measured and the plant-derived C amount and Clost / Cnew ratio in the RAS were calculated. The results showed a significant increase in δ13C in the RAS of the four pearl millet lines compared to the control\u0000soil, suggesting that this approach was able to detect plant C input into the soil at an early stage of pearl millet growth. The concentration of\u0000plant-derived C in the RAS did not vary significantly between pearl millet\u0000lines, but the absolute amount of plant-derived C varied significantly when\u0000we considered the RAS mass of these different lines. Using a conceptual\u0000model and data from the two carbon isotopes' measurements, we evidenced a priming effect for all pearl millet lines. Importantly, the priming effect amplitude (Clost / Cnew ratio) was higher for the small rhizosheath\u0000(low-aggregation) line than for the large rhizosheath (high-aggregation)\u0000ones, indicating a better C sequestration potential of the latter.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"118 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79404683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Rath, N. Bogie, L. Deiss, S. Parikh, D. Wang, S. Ying, N. Tautges, A. Berhe, T. Ghezzehei, K. Scow
Abstract. Subsoil carbon (C) stocks are a prime target for efforts to increase soil C storage for climate change mitigation. However, subsoil C dynamics are not well understood, especially in soils under long-term intensive agricultural management. We compared subsoil C storage and soil organic matter (SOM) composition in tomato–corn rotations after 25 years of differing C and nutrient management in the California Central Valley: CONV (mineral fertilizer), CONV+WCC (mineral fertilizer and cover crops), and ORG (composted poultry manure and cover crops). The cover crop mix used in these systems is a mix of oat (Avena sativa L.), faba bean (Vicia faba L.), and hairy vetch (Vicia villosa Roth). Our results showed a ∼19 Mg ha−1 increase in soil organic C (SOC) stocks down to 1 m under ORG systems, no significant SOC increases under CONV+WCC or CONV systems, and an increased abundance of carboxyl-rich C in the subsoil (60–100 cm) horizons of ORG and CONV+WCC systems. Our results show the potential for increased subsoil C storage with compost and cover crop amendments in tilled agricultural systems and identify potential pathways for increasing C transport and storage in subsoil layers.
{"title":"Synergy between compost and cover crops in a Mediterranean row crop system leads to increased subsoil carbon storage","authors":"D. Rath, N. Bogie, L. Deiss, S. Parikh, D. Wang, S. Ying, N. Tautges, A. Berhe, T. Ghezzehei, K. Scow","doi":"10.5194/soil-8-59-2022","DOIUrl":"https://doi.org/10.5194/soil-8-59-2022","url":null,"abstract":"Abstract. Subsoil carbon (C) stocks are a prime target for efforts to increase soil C storage for climate change mitigation. However, subsoil C dynamics are not well understood, especially in soils under long-term intensive agricultural management. We compared subsoil C storage and soil organic matter (SOM) composition in tomato–corn rotations after 25 years of differing C and nutrient management in the California Central Valley: CONV (mineral fertilizer), CONV+WCC (mineral fertilizer and cover crops), and ORG (composted poultry manure and cover crops). The cover crop mix used in these systems is a mix of oat (Avena sativa L.), faba bean (Vicia faba L.), and hairy vetch (Vicia villosa Roth). Our results showed a ∼19 Mg ha−1 increase in soil organic C (SOC) stocks down to 1 m under ORG systems, no significant SOC increases under CONV+WCC or CONV systems, and an increased abundance of carboxyl-rich C in the subsoil (60–100 cm) horizons of ORG and CONV+WCC systems. Our results show the potential for increased subsoil C storage with compost and cover crop amendments in tilled agricultural systems and identify potential pathways for increasing C transport and storage in subsoil layers.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81051284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Frkova, C. Pistocchi, Y. Vystavna, K. Čapková, J. Doležal, F. Tamburini
Abstract. At the early stages of pedogenesis, the dynamics of phosphorus (P) in soils are controlled by microbial communities, the physicochemical properties of the soil and the environmental conditions. While various microorganisms involved in carrying out biogeochemical processes have been identified, little is known about the actual contribution of microbial processes, such as organic P hydrolysis and microbial P turnover, to P cycling. We thus focused on processes driven by microbes and how they affect the size and cycling of organic and inorganic soil P pools along a soil chronosequence in the Chamser Kangri glacier forefield (Western Himalayas). The rapid retreat of the glacier allowed us to study the early stages of soil formation under a cold arid climate. Biological P transformations were studied with the help of the isotopic composition of oxygen (O) in phosphate (δ18OP) coupled to sequential P fractionation performed on soil samples (0–5 cm depth) from four sites of different age spanning 0 to 100–150 years. The P bound to Ca, i.e., 1 M HCl-extractable P, still represented 95 % of the total P stock after approximately 100 years of soil development. Its isotopic composition was similar to the parent material at the most developed site. Primary phosphate minerals, possibly apatite, mostly comprised this pool. The δ18OP of the available P and the NaOH-extractable inorganic P instead differed from that of the parent material, suggesting that these pools underwent biological turnover. The δ18OP of the available P was mostly controlled by the microbial P, suggesting fast exchanges occurred between these two pools possibly fostered by repeated freezing–thawing and drying–rewetting cycles. The release of P from organic P becomes increasingly important with soil age, constituting one-third of the P flux to available P at the oldest site. Accordingly, the lighter isotopic composition of the P bound to Fe and Al oxides at the oldest site indicated that this pool contained phosphate released by organic P mineralization. Compared to previous studies on early pedogenesis under alpine or cold climate, our findings suggest a much slower decrease of the P-bearing primary minerals during the first 100 years of soil development under extreme conditions. However, they provide evidence that, by driving short-term P dynamics, microbes play an important role in controlling the redistribution of primary P into inorganic and organic soil P pools.
{"title":"Phosphorus dynamics during early soil development in a cold desert: insights from oxygen isotopes in phosphate","authors":"Z. Frkova, C. Pistocchi, Y. Vystavna, K. Čapková, J. Doležal, F. Tamburini","doi":"10.5194/soil-8-1-2022","DOIUrl":"https://doi.org/10.5194/soil-8-1-2022","url":null,"abstract":"Abstract. At the early stages of pedogenesis, the dynamics of phosphorus (P)\u0000in soils are controlled by microbial communities, the physicochemical\u0000properties of the soil and the environmental conditions. While various\u0000microorganisms involved in carrying out biogeochemical processes have been\u0000identified, little is known about the actual contribution of microbial\u0000processes, such as organic P hydrolysis and microbial P turnover, to P\u0000cycling. We thus focused on processes driven by microbes and how they affect\u0000the size and cycling of organic and inorganic soil P pools along a soil\u0000chronosequence in the Chamser Kangri glacier forefield (Western Himalayas).\u0000The rapid retreat of the glacier allowed us to study the early stages of\u0000soil formation under a cold arid climate. Biological P transformations were\u0000studied with the help of the isotopic composition of oxygen (O) in phosphate\u0000(δ18OP) coupled to sequential P fractionation performed on\u0000soil samples (0–5 cm depth) from four sites of different age spanning 0 to\u0000100–150 years. The P bound to Ca, i.e., 1 M HCl-extractable P,\u0000still represented 95 % of the total P stock after approximately 100 years of soil\u0000development. Its isotopic composition was similar to the parent material at\u0000the most developed site. Primary phosphate minerals, possibly apatite,\u0000mostly comprised this pool. The δ18OP of the available P\u0000and the NaOH-extractable inorganic P instead differed from that of the\u0000parent material, suggesting that these pools underwent biological turnover.\u0000The δ18OP of the available P was mostly controlled by the\u0000microbial P, suggesting fast exchanges occurred between these two pools\u0000possibly fostered by repeated freezing–thawing and drying–rewetting cycles.\u0000The release of P from organic P becomes increasingly important with soil\u0000age, constituting one-third of the P flux to available P at the oldest site.\u0000Accordingly, the lighter isotopic composition of the P bound to Fe and Al\u0000oxides at the oldest site indicated that this pool contained phosphate\u0000released by organic P mineralization. Compared to previous studies on early\u0000pedogenesis under alpine or cold climate, our findings suggest a much slower\u0000decrease of the P-bearing primary minerals during the first 100 years of\u0000soil development under extreme conditions. However, they provide evidence\u0000that, by driving short-term P dynamics, microbes play an important role in\u0000controlling the redistribution of primary P into inorganic and organic soil\u0000P pools.\u0000","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82364321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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 : 2022-01-01DOI: 10.1137/1.9781611977073.111
Dominik Kempa, Barna Saha
Lempel-Ziv (LZ77) compression is the most commonly used lossless compression algorithm. The basic idea is to greedily break the input string into blocks (called "phrases"), every time forming as a phrase the longest prefix of the unprocessed part that has an earlier occurrence. In 2010, Kreft and Navarro introduced a variant of LZ77 called LZ-End, that additionally requires the previous occurrence of each phrase to end at the boundary of an already existing phrase. Due to its excellent practical performance as a compression algorithm and a compressed index, they conjectured that it achieves a compression that can be provably upper-bounded in terms of the LZ77 size. Despite the recent progress in understanding such relation for other compression algorithms (e.g., the run-length encoded Burrows-Wheeler transform), no such result is known for LZ-End. We prove that for any string of length , the number of phrases in the LZ-End parsing satisfies , where is the number of phrases in the LZ77 parsing. This is the first non-trivial upper bound on the size of LZ-End parsing in terms of LZ77, and it puts LZ-End among the strongest dictionary compressors. Using our techniques we also derive bounds for other variants of LZ-End and with respect to other compression measures. Our second contribution is a data structure that implements random access queries to the text in space and time. This is the first linear-size structure on LZ-End that efficiently implements such queries. All previous data structures either incur a logarithmic penalty in the space or have slow queries. We also show how to extend these techniques to support longest-common-extension (LCE) queries.
{"title":"An Upper Bound and Linear-Space Queries on the LZ-End Parsing.","authors":"Dominik Kempa, Barna Saha","doi":"10.1137/1.9781611977073.111","DOIUrl":"10.1137/1.9781611977073.111","url":null,"abstract":"<p><p>Lempel-Ziv (LZ77) compression is the most commonly used lossless compression algorithm. The basic idea is to greedily break the input string into blocks (called \"phrases\"), every time forming as a phrase the longest prefix of the unprocessed part that has an earlier occurrence. In 2010, Kreft and Navarro introduced a variant of LZ77 called LZ-End, that additionally requires the previous occurrence of each phrase to end at the boundary of an already existing phrase. Due to its excellent practical performance as a compression algorithm and a compressed index, they conjectured that it achieves a compression that can be provably upper-bounded in terms of the LZ77 size. Despite the recent progress in understanding such relation for other compression algorithms (e.g., the run-length encoded Burrows-Wheeler transform), no such result is known for LZ-End. We prove that for any string of length <math><mi>n</mi></math>, the number <math><msub><mrow><mi>z</mi></mrow><mrow><mi>e</mi></mrow></msub></math> of phrases in the LZ-End parsing satisfies <math><msub><mrow><mi>z</mi></mrow><mrow><mi>e</mi></mrow></msub><mo>=</mo><mi>𝒪</mi><mfenced><mrow><mi>z</mi><msup><mrow><mi>l</mi><mi>o</mi><mi>g</mi></mrow><mrow><mn>2</mn></mrow></msup><mo></mo><mi>n</mi></mrow></mfenced></math>, where <math><mi>z</mi></math> is the number of phrases in the LZ77 parsing. This is the first non-trivial upper bound on the size of LZ-End parsing in terms of LZ77, and it puts LZ-End among the strongest dictionary compressors. Using our techniques we also derive bounds for other variants of LZ-End and with respect to other compression measures. Our second contribution is a data structure that implements random access queries to the text in <math><mi>𝒪</mi><mfenced><mrow><msub><mrow><mi>z</mi></mrow><mrow><mi>e</mi></mrow></msub></mrow></mfenced></math> space and <math><mi>𝒪</mi><mo>(</mo><mi>p</mi><mi>o</mi><mi>l</mi><mi>y</mi><mi>l</mi><mi>o</mi><mi>g</mi><mo></mo><mi>n</mi><mo>)</mo></math> time. This is the first linear-size structure on LZ-End that efficiently implements such queries. All previous data structures either incur a logarithmic penalty in the space or have slow queries. We also show how to extend these techniques to support longest-common-extension (LCE) queries.</p>","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"144 1","pages":"2847-2866"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11145761/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83791180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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