As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious so...As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious soil and water loss; however, the characteristics of rain splash erosion in those regions are still unclear. The objectives of the study are to ana-lyze the characteristics of splash erosion on loess soil, red soil, purple soil and black soil, and to discuss the relationship between splash erosion and soil properties. Soil samples spatially distributed in the abovementioned regions were col-lected and underwent simulated rainfalls at a high intensity of 1.2mm/min, lasting for 5, 10, 15, and 20min, respectively. Rain splash and soil crust development were analyzed. It shows that black soil sample from Heilongjiang Province corre-sponds to the minimum splash erosion amount because it has high aggregate content, aggregate stability and organic mat-ter content. Loess soil sample from Inner Mongolia corresponds to the maximum splash erosion amount because it has high content of sand particles. Loess soil sample from Shanxi Province has relatively lower splash erosion amount be-cause it has high silt particle content and low aggregate stability easily to be disrupted under rainfalls with high intensity. Although aggregate contents of red soil and purple soil samples from Hubei and Guangdong provinces are high, the sta-bility is weak and prone to be disrupted, so the splash erosion amount is medium. Splash rate which fluctuates over time is observed because soil crust development follows a cycling processes of formation and disruption. In addition, there are two locations of soil crust development, one appears at the surface, and the other occurs at the subsurface.展开更多
Negative effect of precipitation on plant photosynthesis was investigated in this work. Stomatal conductance, transpiration rate and net photosynthetic rate were measured before and after each precipitation event, res...Negative effect of precipitation on plant photosynthesis was investigated in this work. Stomatal conductance, transpiration rate and net photosynthetic rate were measured before and after each precipitation event, respectively, and the corresponding precipitation was recorded as well. Moreover, plant dry matter accumulation was counted at the end of our entire experiment. The results show that precipitation fully demonstrates its negative effect on plant photosynthesis under the condition of without water shortage. Although it has not been proved, leaf shape seems to be associated with this effect. Broad-leaved species are less influenced than coniferous and lanceleaf species no matter on the length of variation time or changes in variation values. The different situation among three broad-leaved species seems to illustrate that the effect is also related to the size of single leaf area. The correlation between precipitation and photosynthetic rate variation is analogous to the relationship between precipitation and splash erosion, and in the view of the relationship between plant photosynthetic characteristics and dry mass accumulation, it can be thought that it can reflect the negative impact of precipitation on plant growth by making use of splash erosion. Therefore, a section was added in the traditional plant biomass estimation algorithms by using eco-physiological models, and this was proved to enhance the accuracy of traditional estimation from preliminary verifications.展开更多
Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion ...Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion may be exacerbated or mitigated by ongoing land use/cover change.To estimate the effects of various land use and management systems on splash erosion in the humid tropics,we measured the actual splash erosion under natural rainfall conditions in a tropical rainforest(TR),rubber monoculture(RM),and four rubber agroforestry ecosystems in Xishuangbanna,Southwestern China.The average cumulative splash mass in the RM was 48.7 times higher compared to that in the TR,indicating that the replacement of TR by RM results in severe splash erosion.In the rubber agroforestry systems,the throughfall kinetic energy and splash mass were 34-76%and 86-97%lower,respectively,than that in the RM,indicating that intercropping crops with rubber trees can effectively alleviate erosive power of throughfall and thus splash erosion.Under all land use regimes,in the plots where the litter layer was removed,splash erosion was significantly(2.0-12.1 times)higher and more spatially heterogeneous than in those with litter cover.This highlighted the key role of the forest litter layer in protecting the soil from raindrop detachment.In the study area,the actual splash erosion was strongly correlated with the conditions of precipitation(amount and intensity(I10)of rainfall)and the vegetation structure(especially the crown base height,leaf area index,and canopy cover),but weakly correlated with the soil properties.Given the importance of near-ground intercrops(height<5 m)for improving the vegetation structure,surface cover,and soil conditions,the intercropping of Camellia sinensis and Theobroma cacao with rubber trees is a promising approach for controlling splash erosion and also has benefits on the sus-tainable development of rubber plantation.展开更多
Soil interparticle forces can pose important effects on soil aggregate stability and rainfall splash erosion.Meanwhile,these interparticle forces are strongly influenced by specific ion effects.In this study,we applie...Soil interparticle forces can pose important effects on soil aggregate stability and rainfall splash erosion.Meanwhile,these interparticle forces are strongly influenced by specific ion effects.In this study,we applied three monovalent cations(Li^(+),Na^(+),and K^(+))with various concentrations to investigate the influence of specific ion effects on aggregate stability and splash erosion via pipette and rainfall simulation methods.The specific ion effects on soil interparticle forces were quantitatively evaluated by introducing cationic non-classical polarization.The results showed that aggregate stability and splash erosion had strong ion specificity.Aggregate breaking strength and splash erosion rate at the same salt concentration followed the sequence as Li^(+)>Na^(+)>K^(+).With decreasing salt concentration,the difference in aggregate breaking strength or splash erosion rate between different cation systems increased initially(1–10^(-2)mol L^(–1))and later was nearly invariable(10^(–2)–10^(–4)mol L^(–1)).The experimental results were well quantitatively explained by soil interparticle forces considering cationic non-classical polarization.Furthermore,both aggregate breaking strength and splash erosion rate of three cations revealed a strong positive linear relation with net force subjected to cationic non-classical polarization(R^(2)=0.81,R^(2)=0.81).These results demonstrated that different non-classical polarization of cations resulted in different soil interparticle forces,and thus led to differences in aggregate stability and splash erosion.Our study provides valuable information to deeply understand the mechanisms of rainfall splash erosion.展开更多
The average annual rainfall was close to the average for the Jornada Experimental Range basin (225 mm<span style="white-space:nowrap;">∙</span>y<sup><span style="white-spa...The average annual rainfall was close to the average for the Jornada Experimental Range basin (225 mm<span style="white-space:nowrap;">∙</span>y<sup><span style="white-space:nowrap;">−</span>1</sup>). Decomposition of leaf litter bags on the soil surface was a function of the rainfall at the site and of soil texture. Sites with the highest splash erosion and infiltration (highest sand content) had the highest decomposition rates. There was no evidence that run-off, run-on processes had an effect on the decomposition of surface litter. Root decomposition was only different at one of the tarbush sites (p > 0.001) and that difference was primarily due to soil texture and spatial distribution of rainfall. High concentration of the clay-silt fraction resulted in differences in mass loss of surface litter at grassland, dry-lakes, and tarbush sites. One site at each of these was different from the other two sites because they are between 8 and 20 km from the other two sites.展开更多
Effective soil particle size composition can more realistically reflect the particle size sorting process of erosion.To reveal the individual contributions of rainfall intensity and slope to splash erosion,and to dist...Effective soil particle size composition can more realistically reflect the particle size sorting process of erosion.To reveal the individual contributions of rainfall intensity and slope to splash erosion,and to distinguish the enrichment ratio of each size and the critical size in splash,loessial soil collected on the Loess Plateau in May 2019 was tested under different rainfall intensities(60,84,108,132,156 mm h^(-1))and slopes(0°,5°,10°,15°,20°).The results demonstrated that 99%of splash mass was concentrated in 0–0.4 m.Rainfall intensity was the major factor for splash according to the raindrop generation mode by rainfall simulator nozzles.The contributions of rainfall intensity to splash erosion were 82.72%and 93.24%,respectively in upslope and downslope direction.The mass percentages of effective clay and effective silt were positively correlated with rainfall intensity,while the mass percentages of effective very fine sand and effective fine sand were negatively correlated with rainfall intensity.Opposite to effective very fine sand,the mass percentages of effective clay significantly decreased with increasing distance.Rainfall intensity had significant effects on enrichment ratios,positively for effective clay and effective silt and negatively for effective very fine sand and effective fine sand.The critical effective particle size in splash for loessial soil was 50μm.展开更多
This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect...This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.展开更多
基金Under the auspices of National Natural Science Foundation of China ( No. 40471084)Innovation Program of Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences (No. 066U0104SZ)State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau (No. 10501-173)
文摘As the first event of soil erosion, rain splash erosion supplies materials for subsequent transportation and en-trainment. The Loess Plateau, the southern hilly region and the Northeast China are subject to serious soil and water loss; however, the characteristics of rain splash erosion in those regions are still unclear. The objectives of the study are to ana-lyze the characteristics of splash erosion on loess soil, red soil, purple soil and black soil, and to discuss the relationship between splash erosion and soil properties. Soil samples spatially distributed in the abovementioned regions were col-lected and underwent simulated rainfalls at a high intensity of 1.2mm/min, lasting for 5, 10, 15, and 20min, respectively. Rain splash and soil crust development were analyzed. It shows that black soil sample from Heilongjiang Province corre-sponds to the minimum splash erosion amount because it has high aggregate content, aggregate stability and organic mat-ter content. Loess soil sample from Inner Mongolia corresponds to the maximum splash erosion amount because it has high content of sand particles. Loess soil sample from Shanxi Province has relatively lower splash erosion amount be-cause it has high silt particle content and low aggregate stability easily to be disrupted under rainfalls with high intensity. Although aggregate contents of red soil and purple soil samples from Hubei and Guangdong provinces are high, the sta-bility is weak and prone to be disrupted, so the splash erosion amount is medium. Splash rate which fluctuates over time is observed because soil crust development follows a cycling processes of formation and disruption. In addition, there are two locations of soil crust development, one appears at the surface, and the other occurs at the subsurface.
基金Project(TD2011-01)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(20133050)supported by the China Scholarship Council
文摘Negative effect of precipitation on plant photosynthesis was investigated in this work. Stomatal conductance, transpiration rate and net photosynthetic rate were measured before and after each precipitation event, respectively, and the corresponding precipitation was recorded as well. Moreover, plant dry matter accumulation was counted at the end of our entire experiment. The results show that precipitation fully demonstrates its negative effect on plant photosynthesis under the condition of without water shortage. Although it has not been proved, leaf shape seems to be associated with this effect. Broad-leaved species are less influenced than coniferous and lanceleaf species no matter on the length of variation time or changes in variation values. The different situation among three broad-leaved species seems to illustrate that the effect is also related to the size of single leaf area. The correlation between precipitation and photosynthetic rate variation is analogous to the relationship between precipitation and splash erosion, and in the view of the relationship between plant photosynthetic characteristics and dry mass accumulation, it can be thought that it can reflect the negative impact of precipitation on plant growth by making use of splash erosion. Therefore, a section was added in the traditional plant biomass estimation algorithms by using eco-physiological models, and this was proved to enhance the accuracy of traditional estimation from preliminary verifications.
基金supported by Yunnan Fundamental Research Projects(grant NO.202101AT070056 and 202101AS070010)the National Natural Science Foundation of China(32101380,32171557,and 31570622)the Youth Innovation Promotion Association CAS(2021397).
文摘Soil erosion by water is known to be a major driver of land degradation.Splash erosion is the initial stage of water erosion and directly contributes to the detachment of soil particles on sloping land.Splash erosion may be exacerbated or mitigated by ongoing land use/cover change.To estimate the effects of various land use and management systems on splash erosion in the humid tropics,we measured the actual splash erosion under natural rainfall conditions in a tropical rainforest(TR),rubber monoculture(RM),and four rubber agroforestry ecosystems in Xishuangbanna,Southwestern China.The average cumulative splash mass in the RM was 48.7 times higher compared to that in the TR,indicating that the replacement of TR by RM results in severe splash erosion.In the rubber agroforestry systems,the throughfall kinetic energy and splash mass were 34-76%and 86-97%lower,respectively,than that in the RM,indicating that intercropping crops with rubber trees can effectively alleviate erosive power of throughfall and thus splash erosion.Under all land use regimes,in the plots where the litter layer was removed,splash erosion was significantly(2.0-12.1 times)higher and more spatially heterogeneous than in those with litter cover.This highlighted the key role of the forest litter layer in protecting the soil from raindrop detachment.In the study area,the actual splash erosion was strongly correlated with the conditions of precipitation(amount and intensity(I10)of rainfall)and the vegetation structure(especially the crown base height,leaf area index,and canopy cover),but weakly correlated with the soil properties.Given the importance of near-ground intercrops(height<5 m)for improving the vegetation structure,surface cover,and soil conditions,the intercropping of Camellia sinensis and Theobroma cacao with rubber trees is a promising approach for controlling splash erosion and also has benefits on the sus-tainable development of rubber plantation.
基金supported by the National Natural Science Foundation of China(41977024,41601236)the Fundamental Research Funds for the Central Universities(2452019078).
文摘Soil interparticle forces can pose important effects on soil aggregate stability and rainfall splash erosion.Meanwhile,these interparticle forces are strongly influenced by specific ion effects.In this study,we applied three monovalent cations(Li^(+),Na^(+),and K^(+))with various concentrations to investigate the influence of specific ion effects on aggregate stability and splash erosion via pipette and rainfall simulation methods.The specific ion effects on soil interparticle forces were quantitatively evaluated by introducing cationic non-classical polarization.The results showed that aggregate stability and splash erosion had strong ion specificity.Aggregate breaking strength and splash erosion rate at the same salt concentration followed the sequence as Li^(+)>Na^(+)>K^(+).With decreasing salt concentration,the difference in aggregate breaking strength or splash erosion rate between different cation systems increased initially(1–10^(-2)mol L^(–1))and later was nearly invariable(10^(–2)–10^(–4)mol L^(–1)).The experimental results were well quantitatively explained by soil interparticle forces considering cationic non-classical polarization.Furthermore,both aggregate breaking strength and splash erosion rate of three cations revealed a strong positive linear relation with net force subjected to cationic non-classical polarization(R^(2)=0.81,R^(2)=0.81).These results demonstrated that different non-classical polarization of cations resulted in different soil interparticle forces,and thus led to differences in aggregate stability and splash erosion.Our study provides valuable information to deeply understand the mechanisms of rainfall splash erosion.
文摘The average annual rainfall was close to the average for the Jornada Experimental Range basin (225 mm<span style="white-space:nowrap;">∙</span>y<sup><span style="white-space:nowrap;">−</span>1</sup>). Decomposition of leaf litter bags on the soil surface was a function of the rainfall at the site and of soil texture. Sites with the highest splash erosion and infiltration (highest sand content) had the highest decomposition rates. There was no evidence that run-off, run-on processes had an effect on the decomposition of surface litter. Root decomposition was only different at one of the tarbush sites (p > 0.001) and that difference was primarily due to soil texture and spatial distribution of rainfall. High concentration of the clay-silt fraction resulted in differences in mass loss of surface litter at grassland, dry-lakes, and tarbush sites. One site at each of these was different from the other two sites because they are between 8 and 20 km from the other two sites.
基金Natural Science Foundation of China,No.42077058,No.41601282,No.41867015Young Talent Fund of University Association for Science and Technology in Shaanxi,China,No.20210705+1 种基金Fundamental Research Funds for Central Universities,No.GK202309005Shaanxi Provincial Key Research and Development Program,No.2021ZDLSF05-02。
文摘Effective soil particle size composition can more realistically reflect the particle size sorting process of erosion.To reveal the individual contributions of rainfall intensity and slope to splash erosion,and to distinguish the enrichment ratio of each size and the critical size in splash,loessial soil collected on the Loess Plateau in May 2019 was tested under different rainfall intensities(60,84,108,132,156 mm h^(-1))and slopes(0°,5°,10°,15°,20°).The results demonstrated that 99%of splash mass was concentrated in 0–0.4 m.Rainfall intensity was the major factor for splash according to the raindrop generation mode by rainfall simulator nozzles.The contributions of rainfall intensity to splash erosion were 82.72%and 93.24%,respectively in upslope and downslope direction.The mass percentages of effective clay and effective silt were positively correlated with rainfall intensity,while the mass percentages of effective very fine sand and effective fine sand were negatively correlated with rainfall intensity.Opposite to effective very fine sand,the mass percentages of effective clay significantly decreased with increasing distance.Rainfall intensity had significant effects on enrichment ratios,positively for effective clay and effective silt and negatively for effective very fine sand and effective fine sand.The critical effective particle size in splash for loessial soil was 50μm.
基金Supported by the National Natural Science Foundation of China (NSFC) (No. 41101019)the Fundamental Research Funds for the Central Universities of Chinathe State Key Laboratory of Earth Surface Processes and Resource Ecology of China (No. 2011-KF-09)
文摘This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and iden-tified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influ-encing surface crust formation;depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and the crust reformed with long-term rainfall.In conclusion,this study showed that soil micromorphological studies were a useful method for evaluating soil crust formation.
