Soil fertility and forest structure influence tree carbon stocks.However,it remains unclear how tree mycorrhizal types affect these relationships.This study addressed the question of how aboveground and belowground tr...Soil fertility and forest structure influence tree carbon stocks.However,it remains unclear how tree mycorrhizal types affect these relationships.This study addressed the question of how aboveground and belowground tree carbon stocks in soils with different mycorrhizal types are affected by soil fertility and forest structure.Tree demographic data were used from a 21.12-ha study area collected over a ten-year period(2009-2019),covering 43species of woody plants and more than 50,000 individuals.Relationships between tree carbon stock,soil fertility and forest structure(stand density,diameter variation,species diversity and spatial distribution)were examined,as well as whether these relationships differed between arbuscular mycorrhiza and ectomycorrhizal mycorrhiza groups in a typical temperate conifer and broad-leaved mixed forest.We found that total tree carbon stock was positively impacted by variations in stand density and tree diameter but negatively influenced by soil fertility,tree species diversity and uniform angle index.Soil fertility promoted carbon stock of trees associated with arbuscular mycorrhiza(AM)but inhibited the carbon stock of trees with ectomycorrhizal mycorrhiza fungi(EcM).Carbon stock of AM trees was mainly influenced by soil fertility,while carbon stock of EcM trees was influenced by stand density.Our findings show that mycorrhizae types mediate the impact of stand structure and soil fertility on tree carbon stocks and provides new evidence on how forest tree carbon stocks may be enhanced based on the types of mycorrhizal associations.Tree species with different mycorrhizal types can be managed in different ways.展开更多
The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil...The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil foundations can prolong the structure's natural vibration period and enhance its seismic response.We develops a soilstructure interaction system model and a comparative rigid foundation model using the finite element software LS-DYNA to investigate the impact of SSI on the dynamic characteristics and seismic response of stone structures.The results indicate that the SSI effect alters stone structures'dynamic properties and seismic response.This alteration is evident in the extended natural vibration period,which reduces overall stiffness,increases interstory displacement angles,and slightly decreases the acceleration response.Under both SSI and FIX systems,the structural failure mode is characterized by the external collapse of the second-story stone walls,which causes the roof stone slabs to lose support and fall,leading to overall collapse.The FIX system demonstrates better structural integrity and stability with slower crack development.In contrast,the SSI system exhibits cracks that appear earlier and develop more rapidly,causing more severe damage.The research findings provide a theoretical basis for the seismic reinforcement of existing stone structures on soft soil foundations.展开更多
In this paper,a two-layer hierarchical structure of optimization and control for polypropylene grade transition was raised to overcome process uncertain disturbances that led to the large deviation between the open-lo...In this paper,a two-layer hierarchical structure of optimization and control for polypropylene grade transition was raised to overcome process uncertain disturbances that led to the large deviation between the open-loop reference trajectory and the actual process.In the upper layer,the variant time scale based control vector parametric methods(VTS-CVP) was used for dynamic optimization of transition reference trajectory,while nonlinear model predictive controller(NMPC) based on closed-loop subspace and piece-wise linear(SSARX-PWL) model in the lower layer was tracking to the reference trajectory from the upper layer for overcoming high-frequency disturbances.Besides,mechanism about trajectory deviation detection and optimal trajectory updating online were introduced to ensure a smooth transition for the entire process.The proposed method was validated with the real data from an industrial double-loop propylene polymerization reaction process with developed dynamic mechanism mathematical model.展开更多
The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidate...The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later stage due to the abundance of lichens and mosses. But, the speed of natural succession was so slow that the community-building species was still the first dominant species after 42 years, except that its dominant degree decreased just slightly. However, successive speed and trend were affected by water, vegetation coverage, terrain, time and soil physico-chemical properties as well, especially Mn content in the soil appeared to have a threshold effect.展开更多
A 112 m×8 m sample pot which includes 14 sub-plots was set up along the slope in Hongshi Forestry Farm of Baihe Forestry Bureau (127°55′E, 42°30′ N), Jilin Province in August 2002. Community structure...A 112 m×8 m sample pot which includes 14 sub-plots was set up along the slope in Hongshi Forestry Farm of Baihe Forestry Bureau (127°55′E, 42°30′ N), Jilin Province in August 2002. Community structure, soil moisture contents at 0–10 cm and 10–20 cm in depth, water content of litter as well as the contents of C, N and P of litter, living leaves and branches in the broad-leaved/Korean pine (Pinus korraiensis) forest were measured in each sub-plot on different slope positions. The analytical results showed that there existed an obvious soil moisture gradient along the slope: upper slope <middle slope< lower slope. The difference in soil moisture contents on different positions of slope led to a change of the stand structure of the braod-leaved/Korean pine forest. The proportion ofQuercus mongolica gradually increased with the decrease of soil moisture content and that of other major tree species in the broad-leaved/Korean pine forest gradually decreased or disappeared. The dynamic of soil moisture contents in the litter layer was as same as that in mineral soils. The decomposition rates of the litter on different slope positions were different and the dry weights of existent litter varied significantly. The soil nutrients in the litter on the lower slope was richer than that on the upper slope due to the different stand structure on the different slope positions. The moisture content and nutrient contents of soil had effects on the composition, decomposition, and the nutrient release of litter, thus affecting stands growth and stand structure and finally leading to the change of ecosystem. Key words Soil moisture gradient - nutrient - Stand structure - Broad-leaved/Korean pine forest CLC number S718.5 Document code A Foundation item: This study was supported by the NKBRSF (G1999043407-1), Tackle Key Problem of Science and technology of China (2001BA510B-07), Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-406, SCXZD0101), NKTRDP (2001BA510B-07. 2002BA516A20).Biography: WANG Yan (1970-), female, Ph. D, associate professorResponsible editor: Song Funan展开更多
Based on the vertical stratification type of vegetation in the 48 plots （15m×15 m） in Hetian Town, Changting County, Fujian Province, this study was conduct ed to determine the overall vegetation fractional cov...Based on the vertical stratification type of vegetation in the 48 plots （15m×15 m） in Hetian Town, Changting County, Fujian Province, this study was conduct ed to determine the overall vegetation fractional coverage （VFC）, litter thickness, soi particle size distribution and nutrient content at different vertical level, analyze the correlations between vegetation characters and soil properties, and compare the dif ferences in the VFC, litter thickness, soil particle size distribution and nutrient con- tent among different erosion degrees and vertical structure types. The result., showed that the VFC and litter thickness were all negatively related to erosion de gree; they were positively related to soil organic matter content, total nitrogen con- tent and total phosphorus content, but not significantly correlated with soil tota potassium content. When the VFC was higher than 50% and litter thickness wa.＇ higher than 20 ram, the water and soil could be effectively conserved; and the plan litter showed better water and soil conservation effect than the upper vegetation o~ canopy layer. In the vertical structure types of different vegetations, the forest-shrub grass, forest-shrub, shrub-grass and pure grass all could promote vegetation growth improve soil structure and maintain soil fertility.展开更多
[Objective] This comparative experiment was to explore the soil loss con- trol effects under cultivation combination of different soil and vegetation types, and to provide scientific basis for the upcoming pilot proje...[Objective] This comparative experiment was to explore the soil loss con- trol effects under cultivation combination of different soil and vegetation types, and to provide scientific basis for the upcoming pilot project of ecological recovery. [Method] Both the rudiment of water locomotion functioned by micro-landscape structures and different spatial combinations of various landscape constituents are considered, thus, the combination of multi-soil type, crop species and site conditions is designed in three different experimental sites. [Result] Soil loss estimates in experiments in South Wello significantly depended on various soil type, slope, vegetation and type of con- servation structure; grass cover tremendously reduces soil loss; legume cultivation performed better than cereal cultivation in soil loss control. [Conclusion] By conduct- ing the data analysis of the experiment, a scientific reference is proposed to the agri- culture planting and protective mode for the alleviation of water and soil loss in Amhara Region, Ethiopia.展开更多
The research progress of soil loss under the dual structure of southwest karst is systematically studied. The results show that the research of the soil erosion in karst mountainous area started late, and the basic re...The research progress of soil loss under the dual structure of southwest karst is systematically studied. The results show that the research of the soil erosion in karst mountainous area started late, and the basic research is lagging. Most of the existing research results focus on the present situation, causes and control measures of surface erosion. The view of underground soil loss in the context of karst diploid structure has been recognized by most scholars. However, limited to the research methods and the lack of observational data, the way of underground soil loss, the amount of loss and its harm are still unclear. Therefore, seeking the necessary technical means to carry out the necessary field observation from the way and process of loss is the focus of the study of soil loss under karst structure in the future.展开更多
Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. ...Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.展开更多
Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on so...Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on soil microorganisms. The impacts of Eucalyptus successive rotations on soil microbial communities were evaluated by comparing phospholipid fatty acid （PLFA） abundances, compositions, and enzyme activities of native Pinus massoniana plantations and adjacent 1st, 2nd, 3rd, 4th generation Eucalyptus plantations. The conversion from P. massoniana to Eucalyptus plantations significantly decreased soil microbial community size and enzyme activities, and increased microbial physiological stress. However, the PLFA abundances formed ＂U＂ shaped quadratic functions with Eucalyptus plantation age. Alternatively, physiological stress biomarkers, the ratios of monounsaturated to saturated fatty acid and Gram＋ to Gram- bacteria, formed ＂∩＂ shaped quadratic functions, and the ratio of cy17：0 to 16： 1ω7c decreased with plantation age. The activities of phenol oxidase, peroxidase, and acid phosphatase increased with Eucalyptus plantation age, while the cellobiobydrolase activity formed ＂U＂ shaped quadratic functions. Soil N：P, alkaline hydrolytic nitrogen, soil organic carbon, and understory cover largely explained the variation in PLFA profiles while soil N：P, alkaline hydrolytic nitrogen, and understory cover explained most of the variability in enzyme activity. In conclusion, soil microbial structure and function under Eucalyptus plantations were strongly impacted by plantation age. Most of the changes could be explained by altered soil resource availability and understory cover associated with successive planting of Eucalyptus. Our results highlight the importance of plantation age for assessing the impacts of plantation conversion as well as the importance of reducing disturbance for plantation management.展开更多
Biolog, 16S rRNA gene denaturing gradient gel electrophoresis （DGGE）, and phospholipid fatty acid （PLFA） analyses were used to assess soil microbial community characteristics in a chronosequence of tea garden syst...Biolog, 16S rRNA gene denaturing gradient gel electrophoresis （DGGE）, and phospholipid fatty acid （PLFA） analyses were used to assess soil microbial community characteristics in a chronosequence of tea garden systems （8-, 50-, and 90- year-old tea gardens）, an adjacent wasteland, and a 90-year-old forest. Biolog analysis showed that the average well color development （AWCD） of all carbon sources and the functional diversity based on the Shannon index decreased （P 〈 0.05） in the following order： wasteland 〉 forest 〉 tea garden. For the DCCE analysis, the genetic diversity based on the Shannon index was significantly lower in the tea garden soils than in the wasteland. However, compared to the 90-year-old forest, the tea garden soils showed significantly higher genetic diversity. PLFA analysis showed that the ratio of Gram positive bacteria to Cram negative bacteria was significantly higher in the tea garden soils than in the wasteland, and the highest value was found in the 90-year-old forest. Both the fungal PLFA and the ratio of fungi to bacteria were significantly higher in the three tea garden soils than in the wasteland and forest, indicating that fungal PLFA was significantly affected by land-use change. Based on cluster analysis of the soil microbial community structure, all three analytical methods showed that land-use change had a greater effect on soil microbial community structure than tea garden age.展开更多
The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understa...The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.展开更多
An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for t...An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for the dynamic analysis, and compared with a 3D finite element （FE） model. Two commercial software packages are used for dynamic analysis considering the soilpile-structure interaction （SPSI）. Stiffness and damping of the pile foundation are generated from a computer program, and then input into the FE model. To examine the SPSI thoroughly, three cases for the soil, piles and superstructure are considered and compared. In the first case, the interaction is fully taken into account, that is, both the superstructure and soil-pile system are flexible. In the second case, the superstructure is flexible but fixed to a rigid base, with no deformation in the base （no SSI）. In the third case, the dynamic soil-pile interaction is taken into account, but the table top structure is assumed to be rigid. From the comparison beteen the results of these three cases some conclusions are made, which could be helpful for engineering practice.展开更多
The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile fo...The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile foundation for different conditions:(1) rigid base,i.e.no deformation in the foundation:(2) linear soil-pile system;and (3) nonlinear soil-pile system. The effects of pile foundation displacements on the behavior of tall building are investigated,and compared with the behavior of buildings supported on shallow foundation.With a model of non-reflective boundary between the near field and far field, Novak's method of soil-pile interaction is improved.The computation method for vibration of pile foundations and DYNAN computer program are introduced comprehensively.A series of dynamic experiments have been done on full-scale piles, including single pile and group,linear vibration and nonlinear vibration,to verify the validity of boundary zone model.展开更多
It has been well documented that natural normally-consolidated marine soils are generally subjected to the effects of soil structure. The interpretation of the resistance of soil structure is an important issue in the...It has been well documented that natural normally-consolidated marine soils are generally subjected to the effects of soil structure. The interpretation of the resistance of soil structure is an important issue in the theory study and engineering practice of ocean engineering and geotechnical engineering. It is traditionally considered that the resistance of soil structure gradually disappears with increasing stress level when the applied stress is beyond the consolidation yield stress. In this study, however, it is found that this traditional interpretation of the resistance of soil structure can not explain the strength behavior of natural marine deposits with a normally-consolidated stress history. A new interpretation of the resistance of soil structure is proposed based on the strength behavior. In the preyield state, the undrained strength of natural marine deposits is composed of two components: one developed by the applied stress and the other developed by the resistance of soil structure. When the applied stress is beyond the consolidation yield stress, the strength behavior is independent of the resistance of soil structure.展开更多
The structure of the ＂black soil＂ in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage （CT） practices. In this study, micro- morphological observation and im...The structure of the ＂black soil＂ in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage （CT） practices. In this study, micro- morphological observation and image analysis of soil thin sections were conducted to evaluate the impacts of 21 years （1986-2007） of no tillage （NT） on soil structure as compared to CT in an experiment near Gongzhuling City, Jilin Province. Soil organic matter （SOM）, wet aggregate stability and saturated hydraulic conductivity （Ks） were also analyzed. Total SOM was not significantly affected by tillage systems, but fresher SOM was observed in the surface layer under NT. The aggregates under NT showed different hierarchies in the form of crumbs, and the mean weight diameter （MWD） of NT was significant higher than that of CT in the surface layer. Platy and blocky aggregates were frequently observed in the lower layers under CT practice. The compound pore structure with intertwined intra- and inter- aggregates pores under NT was well developed in a layer from 0-5 cm to 20-25 era. While under CT system, more inter-aggregate pores and fewer intra- aggregate pores were observed, and planes and channels were frequently found in the 20-25 cm layer, where maeroporosity decreased significantly and a plow pan was evident. The Ks values of NT weresignificantly lower at o-5 cm but significantly higher at 20-95 cm compared with CT, which showed the same trend with macroporosity. These results confirmed that long-term CT practice fragmented the tillage layer soil and compacted the lower layer soil and formed a plow pan. While long-term NT practice in the black soil region favored soil aggregation and a stable porous soil structure was formed, which are important to the water infiltration and prevent soil erosion.展开更多
The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese...The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese （Ⅳ） oxide） were used herein. After adding antimony （Ⅲ） oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe Kedge, and Mn K-edge. The results indicated that manganese （Ⅳ） oxide played an important role in the oxidation of Sb（Ⅲ）; however iron （Ⅲ） hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure （XANES） measurement with an interval of I rain of one of the artificial soil samples （SiO2 ＋ MnO2 ＋ Sb2O3）, a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ±0.04 hr-1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn（Ⅳ） in natural soils, the oxidation process of Sb（Ⅲ） might be relatively slow and require more time to convert Sb（Ⅲ） to Sb（V）.展开更多
The penetration depth of torpedo anchor in two-layered soil bed was experimentally investigated. A total of 177 experimental data were obtained in laboratory by varying the undrained shear strength of the two-layered ...The penetration depth of torpedo anchor in two-layered soil bed was experimentally investigated. A total of 177 experimental data were obtained in laboratory by varying the undrained shear strength of the two-layered soil and the thickness of the top soil layer. The geometric parameters of the anchor and the soil properties(the liquid limit, plastic limit, specific gravity, undrained shear strength, density, and water content) were measured. Based on the energy analysis and present test data, an empirical formula to predict the penetration depth of torpedo anchor in two-layered soil bed was proposed. The proposed formula was extensively validated by laboratory and field data of previous researchers. The results were in good agreement with those obtained for two-layered and single-layered soil bed.Finally, a sensitivity analysis on the parameters in the formula was performed.展开更多
This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures(aboveground vegetation cover, surface litter layer and underground roots), plant diversity, ...This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures(aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features(i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales(i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation.展开更多
基金supported by the Science and Technology Project of the Department of Transportation of Heilongjiang Province(HJK2023B024-3)the National Key R&D Program of China(2023YFF1304001-01)。
文摘Soil fertility and forest structure influence tree carbon stocks.However,it remains unclear how tree mycorrhizal types affect these relationships.This study addressed the question of how aboveground and belowground tree carbon stocks in soils with different mycorrhizal types are affected by soil fertility and forest structure.Tree demographic data were used from a 21.12-ha study area collected over a ten-year period(2009-2019),covering 43species of woody plants and more than 50,000 individuals.Relationships between tree carbon stock,soil fertility and forest structure(stand density,diameter variation,species diversity and spatial distribution)were examined,as well as whether these relationships differed between arbuscular mycorrhiza and ectomycorrhizal mycorrhiza groups in a typical temperate conifer and broad-leaved mixed forest.We found that total tree carbon stock was positively impacted by variations in stand density and tree diameter but negatively influenced by soil fertility,tree species diversity and uniform angle index.Soil fertility promoted carbon stock of trees associated with arbuscular mycorrhiza(AM)but inhibited the carbon stock of trees with ectomycorrhizal mycorrhiza fungi(EcM).Carbon stock of AM trees was mainly influenced by soil fertility,while carbon stock of EcM trees was influenced by stand density.Our findings show that mycorrhizae types mediate the impact of stand structure and soil fertility on tree carbon stocks and provides new evidence on how forest tree carbon stocks may be enhanced based on the types of mycorrhizal associations.Tree species with different mycorrhizal types can be managed in different ways.
基金jointly sponsored by Fujian Province construction science and technology development research project(2023-B-07,2023-K-47,2022-K-118)。
文摘The coastal region of Fujian contains numerous existing stone masonry structures,many of which are constructed on soft soil sites.Previous studies have shown that the soil-structure interaction(SSI)effect on soft soil foundations can prolong the structure's natural vibration period and enhance its seismic response.We develops a soilstructure interaction system model and a comparative rigid foundation model using the finite element software LS-DYNA to investigate the impact of SSI on the dynamic characteristics and seismic response of stone structures.The results indicate that the SSI effect alters stone structures'dynamic properties and seismic response.This alteration is evident in the extended natural vibration period,which reduces overall stiffness,increases interstory displacement angles,and slightly decreases the acceleration response.Under both SSI and FIX systems,the structural failure mode is characterized by the external collapse of the second-story stone walls,which causes the roof stone slabs to lose support and fall,leading to overall collapse.The FIX system demonstrates better structural integrity and stability with slower crack development.In contrast,the SSI system exhibits cracks that appear earlier and develop more rapidly,causing more severe damage.The research findings provide a theoretical basis for the seismic reinforcement of existing stone structures on soft soil foundations.
基金Supported by the Electronic Information Industry Development Foundation of China(20140806)the National Natural Science Foundation of China(61374121,61134007)
文摘In this paper,a two-layer hierarchical structure of optimization and control for polypropylene grade transition was raised to overcome process uncertain disturbances that led to the large deviation between the open-loop reference trajectory and the actual process.In the upper layer,the variant time scale based control vector parametric methods(VTS-CVP) was used for dynamic optimization of transition reference trajectory,while nonlinear model predictive controller(NMPC) based on closed-loop subspace and piece-wise linear(SSARX-PWL) model in the lower layer was tracking to the reference trajectory from the upper layer for overcoming high-frequency disturbances.Besides,mechanism about trajectory deviation detection and optimal trajectory updating online were introduced to ensure a smooth transition for the entire process.The proposed method was validated with the real data from an industrial double-loop propylene polymerization reaction process with developed dynamic mechanism mathematical model.
文摘The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later stage due to the abundance of lichens and mosses. But, the speed of natural succession was so slow that the community-building species was still the first dominant species after 42 years, except that its dominant degree decreased just slightly. However, successive speed and trend were affected by water, vegetation coverage, terrain, time and soil physico-chemical properties as well, especially Mn content in the soil appeared to have a threshold effect.
基金This study was supported by the NKBRSF (G1999043407-1) Tackle Key Problem of Science and technology of China (2001BA510B-07) Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-406SCXZD0101)NKTRDP (2001BA510B
文摘A 112 m×8 m sample pot which includes 14 sub-plots was set up along the slope in Hongshi Forestry Farm of Baihe Forestry Bureau (127°55′E, 42°30′ N), Jilin Province in August 2002. Community structure, soil moisture contents at 0–10 cm and 10–20 cm in depth, water content of litter as well as the contents of C, N and P of litter, living leaves and branches in the broad-leaved/Korean pine (Pinus korraiensis) forest were measured in each sub-plot on different slope positions. The analytical results showed that there existed an obvious soil moisture gradient along the slope: upper slope <middle slope< lower slope. The difference in soil moisture contents on different positions of slope led to a change of the stand structure of the braod-leaved/Korean pine forest. The proportion ofQuercus mongolica gradually increased with the decrease of soil moisture content and that of other major tree species in the broad-leaved/Korean pine forest gradually decreased or disappeared. The dynamic of soil moisture contents in the litter layer was as same as that in mineral soils. The decomposition rates of the litter on different slope positions were different and the dry weights of existent litter varied significantly. The soil nutrients in the litter on the lower slope was richer than that on the upper slope due to the different stand structure on the different slope positions. The moisture content and nutrient contents of soil had effects on the composition, decomposition, and the nutrient release of litter, thus affecting stands growth and stand structure and finally leading to the change of ecosystem. Key words Soil moisture gradient - nutrient - Stand structure - Broad-leaved/Korean pine forest CLC number S718.5 Document code A Foundation item: This study was supported by the NKBRSF (G1999043407-1), Tackle Key Problem of Science and technology of China (2001BA510B-07), Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-406, SCXZD0101), NKTRDP (2001BA510B-07. 2002BA516A20).Biography: WANG Yan (1970-), female, Ph. D, associate professorResponsible editor: Song Funan
基金Supported by National Natural Science Foundation of China(4157141541071281)+1 种基金Natural Science Foundation of Jiangsu Province(BK20131078)"Qinglan Project"of Jiangsu Province~~
文摘Based on the vertical stratification type of vegetation in the 48 plots （15m×15 m） in Hetian Town, Changting County, Fujian Province, this study was conduct ed to determine the overall vegetation fractional coverage （VFC）, litter thickness, soi particle size distribution and nutrient content at different vertical level, analyze the correlations between vegetation characters and soil properties, and compare the dif ferences in the VFC, litter thickness, soil particle size distribution and nutrient con- tent among different erosion degrees and vertical structure types. The result., showed that the VFC and litter thickness were all negatively related to erosion de gree; they were positively related to soil organic matter content, total nitrogen con- tent and total phosphorus content, but not significantly correlated with soil tota potassium content. When the VFC was higher than 50% and litter thickness wa.＇ higher than 20 ram, the water and soil could be effectively conserved; and the plan litter showed better water and soil conservation effect than the upper vegetation o~ canopy layer. In the vertical structure types of different vegetations, the forest-shrub grass, forest-shrub, shrub-grass and pure grass all could promote vegetation growth improve soil structure and maintain soil fertility.
基金Supported by FAO of the United Nations under South-South Cooperation Program in Ethiopia(SSC/SPFS-FAO-ETHIOPIA-CHINA)~~
文摘[Objective] This comparative experiment was to explore the soil loss con- trol effects under cultivation combination of different soil and vegetation types, and to provide scientific basis for the upcoming pilot project of ecological recovery. [Method] Both the rudiment of water locomotion functioned by micro-landscape structures and different spatial combinations of various landscape constituents are considered, thus, the combination of multi-soil type, crop species and site conditions is designed in three different experimental sites. [Result] Soil loss estimates in experiments in South Wello significantly depended on various soil type, slope, vegetation and type of con- servation structure; grass cover tremendously reduces soil loss; legume cultivation performed better than cereal cultivation in soil loss control. [Conclusion] By conduct- ing the data analysis of the experiment, a scientific reference is proposed to the agri- culture planting and protective mode for the alleviation of water and soil loss in Amhara Region, Ethiopia.
基金Supported by the National Science&Technology Pillar Program during the Twelfth FiveYear Plan Period of China(2012BAD05B06)the Fund Program for Science and Technology of Guizhou in 2012(Qiankehe Code J LKS[2012]No.27~~
文摘The research progress of soil loss under the dual structure of southwest karst is systematically studied. The results show that the research of the soil erosion in karst mountainous area started late, and the basic research is lagging. Most of the existing research results focus on the present situation, causes and control measures of surface erosion. The view of underground soil loss in the context of karst diploid structure has been recognized by most scholars. However, limited to the research methods and the lack of observational data, the way of underground soil loss, the amount of loss and its harm are still unclear. Therefore, seeking the necessary technical means to carry out the necessary field observation from the way and process of loss is the focus of the study of soil loss under karst structure in the future.
基金Projects(51478484,51308551,51678571)supported by the National Natural Science Foundation of ChinaProject(2016zzts063)supported by Fundamental Research Funds for the Central Universities,China
文摘Expansive soil is sensitive to dry and wet environment change. And the volume deformation and inflation pressure of expansive soil may induce to cause the deformation failure of roadbed or many other adverse effects. Aimed at a high-speed railway engineering practice in the newly built Yun-Gui high-speed railway expansive soil section in China, indoor vibration test on a full-scaled new cutting subgrade model is carried out. Based on the established track-subgrade-foundation of expansive soil system dynamic model test platform, dynamic behavior of new cutting subgrade structure under train loads coupling with extreme service environment(dry, raining, and groundwater level rising) is analyzed comparatively. The results show that the subgrade dynamic response is significantly influenced by service conditions and the dynamic response of subgrade gradually becomes stable with the increasing vibration times under various service environment conditions. The vertical dynamic soil stress is related with the depth in an approximate exponential function, and the curves of vertical dynamic soil stress present a "Z" shape distribution along transverse distance. The peak value of dynamic soil stress appears below the rail, and it increases more obviously near the roadbed surface. However, the peak value of dynamic soil stress is little affected outside 5.0 m of center line. The vibration velocity and acceleration are in a quadratic curve with an increase in depth, and the raining and groundwater level rising increase both the vibration velocity and the acceleration. The vertical deformations at different depths are differently affected by service environment in roadbed. The deformation of roadbed increases sharply when the water gets in the foundation of expansive soil, and more than 60% of the total deformation of roadbed occurs in expansive soil foundation. The laid waterproofing and drainage structure layer, which weakens the dynamic stress and improves the track regularity, presents a positive effect on the control deformation of roadbed surface. An improved empirical formula is then proposed to predict the dynamic stress of ballasted tracks subgrade of expansive soil.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Science (No.KZCX2-EW-QN406)the National Natural Science Foundation of China (No.31170425,40871130)
文摘Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on soil microorganisms. The impacts of Eucalyptus successive rotations on soil microbial communities were evaluated by comparing phospholipid fatty acid （PLFA） abundances, compositions, and enzyme activities of native Pinus massoniana plantations and adjacent 1st, 2nd, 3rd, 4th generation Eucalyptus plantations. The conversion from P. massoniana to Eucalyptus plantations significantly decreased soil microbial community size and enzyme activities, and increased microbial physiological stress. However, the PLFA abundances formed ＂U＂ shaped quadratic functions with Eucalyptus plantation age. Alternatively, physiological stress biomarkers, the ratios of monounsaturated to saturated fatty acid and Gram＋ to Gram- bacteria, formed ＂∩＂ shaped quadratic functions, and the ratio of cy17：0 to 16： 1ω7c decreased with plantation age. The activities of phenol oxidase, peroxidase, and acid phosphatase increased with Eucalyptus plantation age, while the cellobiobydrolase activity formed ＂U＂ shaped quadratic functions. Soil N：P, alkaline hydrolytic nitrogen, soil organic carbon, and understory cover largely explained the variation in PLFA profiles while soil N：P, alkaline hydrolytic nitrogen, and understory cover explained most of the variability in enzyme activity. In conclusion, soil microbial structure and function under Eucalyptus plantations were strongly impacted by plantation age. Most of the changes could be explained by altered soil resource availability and understory cover associated with successive planting of Eucalyptus. Our results highlight the importance of plantation age for assessing the impacts of plantation conversion as well as the importance of reducing disturbance for plantation management.
基金the National Natural Science Foundation of China (Nos.30671207 and 40371063).
文摘Biolog, 16S rRNA gene denaturing gradient gel electrophoresis （DGGE）, and phospholipid fatty acid （PLFA） analyses were used to assess soil microbial community characteristics in a chronosequence of tea garden systems （8-, 50-, and 90- year-old tea gardens）, an adjacent wasteland, and a 90-year-old forest. Biolog analysis showed that the average well color development （AWCD） of all carbon sources and the functional diversity based on the Shannon index decreased （P 〈 0.05） in the following order： wasteland 〉 forest 〉 tea garden. For the DCCE analysis, the genetic diversity based on the Shannon index was significantly lower in the tea garden soils than in the wasteland. However, compared to the 90-year-old forest, the tea garden soils showed significantly higher genetic diversity. PLFA analysis showed that the ratio of Gram positive bacteria to Cram negative bacteria was significantly higher in the tea garden soils than in the wasteland, and the highest value was found in the 90-year-old forest. Both the fungal PLFA and the ratio of fungi to bacteria were significantly higher in the three tea garden soils than in the wasteland and forest, indicating that fungal PLFA was significantly affected by land-use change. Based on cluster analysis of the soil microbial community structure, all three analytical methods showed that land-use change had a greater effect on soil microbial community structure than tea garden age.
基金supported by the Strategic Technology Project of Chinese Academy of Sciences(XDA05060300)the Science and Technology Research and Development Program of Shaanxi ProvinceChina(2011KJXX63)
文摘The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.
文摘An investigation of soil-pile-structure interaction is carried out, based on a large reciprocating compressor installed on an elevated concrete foundation （table top structure）. A practical method is described for the dynamic analysis, and compared with a 3D finite element （FE） model. Two commercial software packages are used for dynamic analysis considering the soilpile-structure interaction （SPSI）. Stiffness and damping of the pile foundation are generated from a computer program, and then input into the FE model. To examine the SPSI thoroughly, three cases for the soil, piles and superstructure are considered and compared. In the first case, the interaction is fully taken into account, that is, both the superstructure and soil-pile system are flexible. In the second case, the superstructure is flexible but fixed to a rigid base, with no deformation in the base （no SSI）. In the third case, the dynamic soil-pile interaction is taken into account, but the table top structure is assumed to be rigid. From the comparison beteen the results of these three cases some conclusions are made, which could be helpful for engineering practice.
文摘The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile foundation for different conditions:(1) rigid base,i.e.no deformation in the foundation:(2) linear soil-pile system;and (3) nonlinear soil-pile system. The effects of pile foundation displacements on the behavior of tall building are investigated,and compared with the behavior of buildings supported on shallow foundation.With a model of non-reflective boundary between the near field and far field, Novak's method of soil-pile interaction is improved.The computation method for vibration of pile foundations and DYNAN computer program are introduced comprehensively.A series of dynamic experiments have been done on full-scale piles, including single pile and group,linear vibration and nonlinear vibration,to verify the validity of boundary zone model.
文摘It has been well documented that natural normally-consolidated marine soils are generally subjected to the effects of soil structure. The interpretation of the resistance of soil structure is an important issue in the theory study and engineering practice of ocean engineering and geotechnical engineering. It is traditionally considered that the resistance of soil structure gradually disappears with increasing stress level when the applied stress is beyond the consolidation yield stress. In this study, however, it is found that this traditional interpretation of the resistance of soil structure can not explain the strength behavior of natural marine deposits with a normally-consolidated stress history. A new interpretation of the resistance of soil structure is proposed based on the strength behavior. In the preyield state, the undrained strength of natural marine deposits is composed of two components: one developed by the applied stress and the other developed by the resistance of soil structure. When the applied stress is beyond the consolidation yield stress, the strength behavior is independent of the resistance of soil structure.
基金funded by the National Science and Technology Supporting Programs of China under Grants No. 2006BAD15B01 and 2006BAD02A14
文摘The structure of the ＂black soil＂ in Northeast China has been greatly deteriorated by long-term intensive conventional mouldboard plow tillage （CT） practices. In this study, micro- morphological observation and image analysis of soil thin sections were conducted to evaluate the impacts of 21 years （1986-2007） of no tillage （NT） on soil structure as compared to CT in an experiment near Gongzhuling City, Jilin Province. Soil organic matter （SOM）, wet aggregate stability and saturated hydraulic conductivity （Ks） were also analyzed. Total SOM was not significantly affected by tillage systems, but fresher SOM was observed in the surface layer under NT. The aggregates under NT showed different hierarchies in the form of crumbs, and the mean weight diameter （MWD） of NT was significant higher than that of CT in the surface layer. Platy and blocky aggregates were frequently observed in the lower layers under CT practice. The compound pore structure with intertwined intra- and inter- aggregates pores under NT was well developed in a layer from 0-5 cm to 20-25 era. While under CT system, more inter-aggregate pores and fewer intra- aggregate pores were observed, and planes and channels were frequently found in the 20-25 cm layer, where maeroporosity decreased significantly and a plow pan was evident. The Ks values of NT weresignificantly lower at o-5 cm but significantly higher at 20-95 cm compared with CT, which showed the same trend with macroporosity. These results confirmed that long-term CT practice fragmented the tillage layer soil and compacted the lower layer soil and formed a plow pan. While long-term NT practice in the black soil region favored soil aggregation and a stable porous soil structure was formed, which are important to the water infiltration and prevent soil erosion.
基金XAFS measurements were carried out at Photon Factory,Tsukuba,Japan(Nos.2014G066,2016G086).
文摘The oxidation of antimony （Ⅲ） in soils was studied using X-ray absorption fine structure （XAFS） spectra. An andosol soft sample and artificial soil samples （SiO2 blended with iron （Ⅲ） hydroxide and manganese （Ⅳ） oxide） were used herein. After adding antimony （Ⅲ） oxide to all soil samples, the oxidation process was observed by recording the XAFS spectra of Sb K-edge, Fe Kedge, and Mn K-edge. The results indicated that manganese （Ⅳ） oxide played an important role in the oxidation of Sb（Ⅲ）; however iron （Ⅲ） hydroxide was not directly related to the reaction. During a 2-hr continuous Sb K-edge X-ray absorption near edge structure （XANES） measurement with an interval of I rain of one of the artificial soil samples （SiO2 ＋ MnO2 ＋ Sb2O3）, a pseudo-first-order reaction was determined with an average estimated rate of 0.52 ±0.04 hr-1. Compared to the lower oxidation rate of andosol, it is suggested that because of the low concentration of Mn（Ⅳ） in natural soils, the oxidation process of Sb（Ⅲ） might be relatively slow and require more time to convert Sb（Ⅲ） to Sb（V）.
基金financially supported by the Ministry of Education of China(Grant No.6141A02022337)
文摘The penetration depth of torpedo anchor in two-layered soil bed was experimentally investigated. A total of 177 experimental data were obtained in laboratory by varying the undrained shear strength of the two-layered soil and the thickness of the top soil layer. The geometric parameters of the anchor and the soil properties(the liquid limit, plastic limit, specific gravity, undrained shear strength, density, and water content) were measured. Based on the energy analysis and present test data, an empirical formula to predict the penetration depth of torpedo anchor in two-layered soil bed was proposed. The proposed formula was extensively validated by laboratory and field data of previous researchers. The results were in good agreement with those obtained for two-layered and single-layered soil bed.Finally, a sensitivity analysis on the parameters in the formula was performed.
基金National Natural Science Foundation of China,No.41390464National Key Research and Development Program,No.2016YFC0501602Youth Innovation Promotion Association CAS,No.2016040
文摘This review summarizes the effects of vegetation on runoff and soil loss in three dimensions: vertical vegetation structures(aboveground vegetation cover, surface litter layer and underground roots), plant diversity, vegetation patterns and their scale characteristics. Quantitative relationships between vegetation factors with runoff and soil loss are described. A framework for describing relationships involving vegetation, erosion and scale is proposed. The relative importance of each vegetation dimension for various erosion processes changes across scales. With the development of erosion features(i.e., splash, interrill, rill and gully), the main factor of vertical vegetation structures in controlling runoff and soil loss changes from aboveground biomass to roots. Plant diversity levels are correlated with vertical vegetation structures and play a key role at small scales, while vegetation patterns also maintain a critical function across scales(i.e., patch, slope, catchment and basin/region). Several topics for future study are proposed in this review, such as to determine efficient vegetation architectures for ecological restoration, to consider the dynamics of vegetation patterns, and to identify the interactions involving the three dimensions of vegetation.
