Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of ...Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of cracks in root-soil complex in different growth periods under dry-wet cycles,the alfalfa root-loess complex was in-vestigated during different growth periods under different dry-wet cycles,and a dry-wet cycle experiment was conducted.The crack rate,relative area,average width,total length,and the cracks fractal dimension in the root-soil complex were extracted;the crack development characteristics of plain soil were analyzed under the PG-DwC(dry-wet cycle caused by plant water management during plant growth period),as well as the crack development characteristics of root-soil complex under PG-DWC and EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain);the effects of plant roots and dry-wet cycles on soil cracks were discussed.The results showed that the average crack width,crack rate,relative crack area,and total crack length of the alfalfa root-loess complex were higher than those of the plain soil during PG-DWC.The result indicated that compared with plain soil during PG-DWC,the presence of plant roots in alfalfa root-soil complex in the same growth period promoted the cracks development to some extent.The alfalfa root-soil complex crack parameters during different growth periods were relatively stable during PG-DWC(O dry-wet cycle).During EC-DWC(1,3,and 5 dry-wet cycles),the alfalfa root-loess complex crack parameters increased with the number of dry-wet cycles during different growth periods.Unlike PG-DWC,the EC-DWC accelerated crack development,and the degree of crack development increased with the number of dry-wet cycles.The existence of plant roots promoted crack development and expansion in the root-soil complex to a certain extent,and the dry-wet cycle certainly promoted crack development and expansion in the root-soil complex.This result contradicts the im-provement in the root-soil complex's macro-mechanical properties during plant growth,due to differences in the mechanical properties of roots and soil.The research results will provide reference for the root soil complex crack development law and the design of slope protection by vegetation.展开更多
Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strengt...Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.展开更多
The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,E...The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.展开更多
【目的】研究不同栽培模式下多花黄精健株和根腐病病株根际土壤细菌群落多样性差异,为土壤微生态调控和多花黄精根腐病的绿色防治提供理论依据。【方法】通过Illumina Mi Seq高通量测序技术对林下和大田栽培的多花黄精健株和根腐病病株...【目的】研究不同栽培模式下多花黄精健株和根腐病病株根际土壤细菌群落多样性差异,为土壤微生态调控和多花黄精根腐病的绿色防治提供理论依据。【方法】通过Illumina Mi Seq高通量测序技术对林下和大田栽培的多花黄精健株和根腐病病株根际土壤细菌群落结构及多样性进行分析,并对土壤细菌群落进行功能预测。【结果】与健株相比,多花黄精病株根际土壤细菌数量下降,但其多样性增加。不同栽培模式下多花黄精健株与病株根际土壤细菌的优势菌门为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteriota)和放线菌门(Actinobacteriota),优势菌属为鞘氨醇单胞菌属(Sphingomonas)和芽单胞菌属(Gemmatimonas)。变形菌门和放线菌门在健株根际土壤中的相对丰度高于病株(大田4年生样品除外),而酸杆菌门相反。鞘氨醇单胞菌属在多花黄精病株根际土壤中的相对丰度高于健株。通过土壤微生物群落功能预测发现,具有新陈代谢功能的土壤细菌群落占比最大,但健株与病株的土壤细菌群落功能无明显差异。【结论】不同栽培模式下多花黄精健株和病株根际土壤细菌群落结构和多样性差异较大,植株根际土壤细菌减少可能是多花黄精患根腐病的重要原因之一。展开更多
基金the Key Research and Development Project of Ningxia Hui Autonomous Region(No.2023BEG02072)for their financial support.
文摘Repeated wet swelling and dry shrinkage of soil leads to the gradual occurrence of cracks and the formation of a complex fracture network.In order to study the development characteristics and quantitative analysis of cracks in root-soil complex in different growth periods under dry-wet cycles,the alfalfa root-loess complex was in-vestigated during different growth periods under different dry-wet cycles,and a dry-wet cycle experiment was conducted.The crack rate,relative area,average width,total length,and the cracks fractal dimension in the root-soil complex were extracted;the crack development characteristics of plain soil were analyzed under the PG-DwC(dry-wet cycle caused by plant water management during plant growth period),as well as the crack development characteristics of root-soil complex under PG-DWC and EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain);the effects of plant roots and dry-wet cycles on soil cracks were discussed.The results showed that the average crack width,crack rate,relative crack area,and total crack length of the alfalfa root-loess complex were higher than those of the plain soil during PG-DWC.The result indicated that compared with plain soil during PG-DWC,the presence of plant roots in alfalfa root-soil complex in the same growth period promoted the cracks development to some extent.The alfalfa root-soil complex crack parameters during different growth periods were relatively stable during PG-DWC(O dry-wet cycle).During EC-DWC(1,3,and 5 dry-wet cycles),the alfalfa root-loess complex crack parameters increased with the number of dry-wet cycles during different growth periods.Unlike PG-DWC,the EC-DWC accelerated crack development,and the degree of crack development increased with the number of dry-wet cycles.The existence of plant roots promoted crack development and expansion in the root-soil complex to a certain extent,and the dry-wet cycle certainly promoted crack development and expansion in the root-soil complex.This result contradicts the im-provement in the root-soil complex's macro-mechanical properties during plant growth,due to differences in the mechanical properties of roots and soil.The research results will provide reference for the root soil complex crack development law and the design of slope protection by vegetation.
基金received the Key Research and Development Project of Ningxia Hui Autonomous Region(2022BEG03052,2023BEG02072).
文摘Triaxial compression tests were conducted on the alfalfa root-loess complex at different growthperiods obtained through artificial planting.The research focused on analyzing the time variation law of the shear strength index and deformation index of the alfalfa root-loess complex under dry-wet cycles.Additionally,the time effect of the shear strength index of the alfalfa root-loess complex under dry-wet cycles was analyzed and its prediction model was proposed.The results show that the PG-DWC(dry-wet cycle caused by plant water management during plant growth period)causes the peak strength of plain soil to change in a"V"shape with the increase of growth period,and the peak strength of alfalfa root-loess complex is higher than that of plain soil at the same growth period.The deterioration of the peak strength of alfalfa root-loess complex in the same growth period is aggravated with the increase of drying and wetting cycles.Compared with the 0 days growth period,the effective cohesion of alfalfa root-loess complex under different dry-wet cycles maximum increase rate is at the 180 days,which are 33.88%,46.05%,30.12%and 216.02%,respectively.When the number of dry-wet cycles is constant,the effective cohesion of the alfalfa root-loess complex overall increases with the growth period.However,it gradually decreases comparedwith the previous growth period,and the minimum increase rate are all at the 180 days.For the same growth period,the effective cohesion of the alfalfa root-loess complex decreases with the increase of the number of dry-wet cycles.This indicates that EC-DWC(the dry-wet cycles caused by extreme natural conditions such as continuous rain)have a detrimental effect on the time effect of the shear strength of the alfalfa root-loess complex.Finally,based on the formula of total deterioration,a prediction model for the shear strength of the alfalfa root-loess complex under dry-wet cycles was proposed,which exhibits high prediction accuracy.The research results provide useful guidance for the understanding of mechanical behavior and structural damage evolution of root-soil composite.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23090402)the National Natural Science Foundation of China(Nos.41790442,41825018)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)。
文摘The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.
文摘【目的】研究不同栽培模式下多花黄精健株和根腐病病株根际土壤细菌群落多样性差异,为土壤微生态调控和多花黄精根腐病的绿色防治提供理论依据。【方法】通过Illumina Mi Seq高通量测序技术对林下和大田栽培的多花黄精健株和根腐病病株根际土壤细菌群落结构及多样性进行分析,并对土壤细菌群落进行功能预测。【结果】与健株相比,多花黄精病株根际土壤细菌数量下降,但其多样性增加。不同栽培模式下多花黄精健株与病株根际土壤细菌的优势菌门为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteriota)和放线菌门(Actinobacteriota),优势菌属为鞘氨醇单胞菌属(Sphingomonas)和芽单胞菌属(Gemmatimonas)。变形菌门和放线菌门在健株根际土壤中的相对丰度高于病株(大田4年生样品除外),而酸杆菌门相反。鞘氨醇单胞菌属在多花黄精病株根际土壤中的相对丰度高于健株。通过土壤微生物群落功能预测发现,具有新陈代谢功能的土壤细菌群落占比最大,但健株与病株的土壤细菌群落功能无明显差异。【结论】不同栽培模式下多花黄精健株和病株根际土壤细菌群落结构和多样性差异较大,植株根际土壤细菌减少可能是多花黄精患根腐病的重要原因之一。
