Multifractal characteristics and spatial variability of soil particle-size distribution in different land use patterns in a small catchment of the Three Gorges Reservoir Region,China

Characterizing soil particle-size distribution is a key measure towards soil property.The purpose of this study was to evaluate the multifractal characteristics of soil particle-size distribution among different land-use from a purple soil catchment and to generalize the spatial variation trend of multifractal parameters across the catchment.A total of 84 soil samples were collected from four kinds of land use patterns(dry land,orchard,paddy,and forest)in an agricultural catchment in the Three Gorges Reservoir Region,China.The multifractal analysis method was applied to quantitatively characterize the soil particle size distribution.Six soil particle size distribution(PSD)multifractal parameters(D(0),D(1),D(2),(35)a(q),(35)f[a(q)],α(0))were computed.Additionally,a geostatistical analysis was employed to reveal the spatial differentiation and map the spatial distribution of these parameters.Evident multifractal characteristics were found.The trend of generalized dimension spectrum of four land use patterns was basically consistent with the range of 0.8 to 2.0.However,orchard showed the largest monotonic decline,while the forest demonstrated the smallest decrease.D(0)of the four land use patterns were ranked as:dry land<orchard<forest<paddy,the order of D(1)was:dry land<paddy<orchard<forest,D(2)presented a rand-size relationship as dry land<forest<paddy<orchard.Furthermore,all land-use patterns presented asΔf[α(q)]<0.The rand-size relationship ofα(0)was same as D(0).The best-fitting model for D(0),D(1),D(2)andΔf[α(q)]was spherical model,forΔα(q)was gaussian model,and forα(0)was exponential model with structure variance ratio was 1.03%,49.83%,0.84%,1.48%,22.20%and 10.60%,respectively.The results showed that soil particles of each land use pattern were distributed unevenly.The multifractal parameters under different land use have significant differences,except forΔα(q).Differences in the composition of soil particles lead to differences in the multifractal properties even though they belong to the same soil texture.Farming behavior may refine particles and enhance the heterogeneity of soil particle distribution.Our results provide an effective reference for quantifying the impact of human activities on soil system in the Three Gorges Reservoir region.

The Characteristics of Soil Nutrients in Terracing Land under Different Land Use Patterns in Three Gorges Reservoir Area

In this study,taking the typical terracing land in Wushan County of Chongqing Municipality for example,we study the distribution of soil nutrients in the terracing land under different land use patterns in Three Gorges Reservoir Area. We conduct field survey and sampling on three different land use patterns( cash crop land,food crop land and abandoned land),and do the indoor experimental analysis of soil nutrient indicators. The results indicate that there is significant or very significant impact on soil nutrients under different land use patterns. The content of soil organic matter declines in sequence from abandoned land,food crop land to cash crop land; the content of soil N declines in sequence from cash crop land,abandoned land to food crop land; the content of soil P declines in sequence from cash crop land,food crop land to abandoned land; the content of soil K declines in sequence from abandoned land,cash crop land to food crop land. The result is in close relation to land use patterns,human cultivation activity,land disturbance and application of fertilizer.

Fractal features of soil profiles under different land use patterns on the Loess Plateau, China

Fractal theory is becoming an increasingly useful tool to describe soil structure dynamics for a better understanding of the performance of soil systems. Changes in land use patterns significantly affect soil physical, chemical and biological properties. However, limited information is available on the fractal characteristics of deep soil layers under different land use patterns. In this study, the fractal dimensions of particle size distribution（PSD） and micro-aggregates in the 0–500 cm soil profile and soil anti-erodibility in the 0–10 cm soil profile for 10 typical land use patterns were investigated in the Zhifanggou Watershed on the Loess Plateau, China. The 10 typical land use patterns were： slope cropland, two terraced croplands, check-dam cropland, woodland, two shrublands, orchard, artificial and natural grasslands. The results showed that the fractal dimensions of PSD and micro-aggregates were all significantly influenced by soil depths, land use patterns and their interaction. The plantations of shrubland, woodland and natural grassland increased the amount of larger micro-aggregates, and decreased the fractal dimensions of micro-aggregates in the 0–40 cm soil profile. And they also improved the aggregate state and aggregate degree and decreased dispersion rate in the 0–10 cm soil profile. The results indicated that fractal theory can be used to characterize soil structure under different land use patterns and fractal dimensions of micro-aggregates were more effective in this regard. The natural grassland may be the best choice for improving soil structure in the study area.

Effects of land use patterns on slope soil water in the semiarid Loess Plateau,China

Land use patterns(LUPs)are the form in which various land use types are combined spatially,evidently impacting soil water.However,the influence mechanism by which LUPs form remains unclear.In this study,the soil water content(SWC)in the 0–160-cm soil depth was observed in shrubland(SL),mature forestland(MF),grassland(GL)and young forestland(YF)sites on four slopes with different LUPs in the Yangjuangou catchment of the Chinese Loess Plateau.The SWC in SL-YF-SL(13.28%)was significantly greater than that in YF-MF(9.93%),MF-GL-YF(10.38%)and SL-MF(10.83%)and was temporally stable during the study period.The spatial distribution of SWC along the slope differed among the four LUPs.Vegetation characteristics and soil texture mainly determined the spatial variations in SWC in the shallow soil layers(0–40 cm),while topographic factors were the determinants in the deep soil layers(60–160 cm)as well as in the entire soil profile(0–160 cm).The significance of SWC differences among the various land use patterns increased with decreasing precipitation during the growing seasons.YF-MF(77.8 mm)and SL-YF-GL(73.9 mm)required more rainwater than SL-MF(68.2 mm)and MF-GL-MF(67.5 mm)to compensate for the loss of soil water on the monthly scale during the rainy season.Therefore,vegetation restoration should consider land use patterns on hillslopes for soil water conservation.

Effects of land use patterns on soil aggregate stability in Sichuan Basin,China

Soil aggregate stability as a key indicator of soil structure, is a product of interactions between soil environment, management practices, and land use patterns. The objective of this study was to analyze the impact of various land use patterns on soil aggregate stability in Sichuan Basin of southwestern China. The dry- and water-stable aggregate size distributions were determined by manual dry sieving procedure and Yoder＇s wet sieving procedure, respectively, while microaggregates and its mechanical and chemical stabilities by Kachisky＇s method, oscillator method, and citrate-dithionate （C-D） reagent method, separately. The results indicated that fractal dimension and surface fractal dimension were useful indicators to reflect soil aggregate distribution. Land use patterns have an obvious influence on soil aggregate stability. In the study area, water stability, mechanical stability, and chemical stability followed the sequence, Barren land 〉 forestland 〉 orchard 〉 cropland, and the original stability and collapse velocity were sensitive to soil properties and soil structure. The difference of aggregate stability under different land use patterns is mainly due to the intensity of human disturbance and cultivation. Improper land use patterns will lead to breakdown of unstable aggregates, producing finer and more-easily transportable particles and microaggregates. In the future, inappropriate cultivation and land use patterns should be changed to protect soil structure, to improve soil aggregate stability and soil fertility in Sichuan Basin.

The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

Due to relatively strong human activities in the hilly area of Loess Plateau, the natural vegetation has been destroyed, and landscape pattern based on agricultural land matrix was land use mosaic composing of shrub land, grassland, woodland and orchard. This pattern has an important effect on soil moisture and soil nutrients. The Danangou catchment, a typical small catchment, was selected to study the effects of land use and its patterns on soil moisture and nutrients in this paper. The results are as follows: The comparisons of soil moisture among seven land uses for wet year and dry year were performed: (1) the average of soil moisture content for whole catchment was 12.11% in wet year, while it was 9.37% in dry year; (2) soil moisture among seven land uses was significantly different in dry year, but not in wet year; (3) from wet year to dry year, the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasing type; (4) the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope, while complicated distribution of soil moisture was observed in multiple land uses along slope. The relationships between soil nutrients and land uses and landscape positions were analysed: (1) five nutrient contents of soil organic matter (SOM), total N (TN), available N (AN), total P (TP) and available P (AP) in hilly area were lower than that in other areas. SOM content was less than 1%, TN content less than 0.07%, and TP content between 0.05% and 0.06%; (2) SOM and TN contents in woodland, shrub land and grassland were significantly higher than that in fallow land and cropland, and higher level in soil fertility was found in crop-fruit intercropping land among croplands; (3) soil nutrient distribution and responses to landscape positions were variable depending on slope and the location of land use types.

Present land use and cover patterns and their development potential in North Ningxia

With the objectives to acquire the fundamental dat a of the territorial resource, understand the impacts of human activit ies on the land use and cover patterns and evaluate the potential of the future exploitation, an intensive land cover classification with an accuracy of 93% has been completed for North Ningxia by remote sen sing technique based on the adoption of a combination method composed o f texture training, maximum likelihood classification and post-processing such as re-allocation and aggregation. This classification result was incorporated with the contemporaneous socio-economic and meteorological d ata for cross-sectional regression modelling to reveal the spatial dete rminants of the land cover patterns and understand the human-environmen tal relationships. A tentative evaluation on the potential of soil exp loitation in the near future was carried out in combination with our land use and cover change detection results aiming at supplying some useful references for the central and local governments in their sustainable l and use planning.

Changes in Transformation of Soil Organic C and Functional Diversity of Soil Microbial Community Under Different Land Uses

Changes in soil biological and biochemical properties under different land uses in the subtropical region of China were investigated in order to develop rational cultivation and fertilization management. A small watershed of subtropical region of China was selected for this study. Land uses covered paddy fields, vegetable farming, fruit trees, upland crops, bamboo stands, and forestry. Soil biological and biochemical properties included soil organic C and nutrient contents, mineralization of soil organic C, and soil microbial biomass and community functional diversity. Soil organic C and total N contents, microbial biomass C and N, and respiration intensity under different land uses were changed in the following order： paddy fields （and vegetable farming） 〉 bamboo stands 〉 fruit trccs （and upland）. The top surface （0-15 cm） paddy fields （and vegetable farming） were 76.4 and 80.8% higher in soil organic C and total N contents than fruit trees （and upland） soils, respectively. Subsurface paddy soils （15-30 cm） were 59.8 and 67.3% higher in organic C and total N than upland soils, respectively. Soil microbial C, N and respiration intensity in paddy soils （0-15 cm） were 6.36, 3.63 and 3.20 times those in fruit tree （and upland） soils respectively. Soil microbial metabolic quotient was in the order： fruit trees （and upland） 〉 forestry 〉 paddy fields. Metabolic quotient in paddy soils was only 47.7% of that in fruit tree （and upland） soils. Rates of soil organic C mineralization during incubation changed in the order： paddy fields 〉 bamboo stands 〉 fruit trees （and upland） and soil bacteria population： paddy fields 〉 fruit trees （and upland） 〉 forestry. No significant difference was found for fungi and actinomycetes populations. BIOLOG analysis indicated a changing order of paddy fields 〉 fruit trees （and upland） 〉 forestry in values of the average well cell development （AWCD） and functional diversity indexes of microbial community. Results also showed that the conversion from paddy fields to vegetable farming for 5 years resulted in a dramatic increase in soil available phosphorus content while insignificant changes in soil organic C and total N content due to a large inputs of phosphate fertilizers. This conversion caused 53, 41.5, and 41.3% decreases in soil microbial biomass C, N, and respiration intensity, respectively, while 23.6% increase in metabolic quotient and a decrease in soil organic C mineralization rate. Moreover, soil bacteria and actinomycetes populations were increased slightly, while fungi population increased dramatically. Functional diversity indexes of soil microbial community decreased significantly. It was concluded that land uses in the subtropical region of China strongly affected soil biological and biochemical properties. Soil organic C and nutrient contents, mineralization of organic C and functional diversity of microbial community in paddy fields were higher than those in upland and forestry. Overuse of chemical fertilizers in paddy fields with high fertility might degrade soil biological properties and biochemical function, resulting in deterioration of soil biological quality.

Effects of Land Use on Heavy Metal Accumulation in Soils and Sources Analysis

Heavy metal accumulation and its influential factors were studied in the different land use soils, which would provide a theoretical basis for controlling the content of heavy metals in soils. To identify the effects of land use on the accumulation of heavy metals in soils, 148 soil samples were collected from four land use patterns including greenhouse field, uncovered vegetable field, maize field, and forest field in Siping area of Jilin Province, China, and Cr, Ni, Cu, As, Cd, Pb, and Zn contents of those samples were determined with ICP and ICP-Mass. The result showed that there was a rather large difference in effects of the accumulation of Cr, Ni, Cu, As, Cd, and Zn in soils under different land use patterns, except Pb. Based on the assessment which compared with background concentrations in soil, the higher accumulation of heavy metals was found in greenhouse and uncovered vegetable field, much less in maize field and forest field. The mean contents of heavy metals in soils from high to low were arranged in order of greenhouse field, uncovered vegetable field, maize field, and forest field. Cd and Cu had relatively serious accumulation in soils compared to Cr, Ni, As, and Zn. The mean content of Cd in greenhouse field was 0.467 mg kg-x,which exceeded the grade II of the Chinese Soil Quality Criterion GB15618-1995 （6.5 〈pH〈7.5） for Cd standard of 0.3 mg kg^-1, while it was 5.2 times of Cd standard in the forest fields. The mean contents ofCr, Ni, Cu, As, Pb, and Zn in soils under four land use patterns were lower than the grade II of the Chinese Soil Quality Criterion. Compared with the soil cultivated years, the agricultural chemical compounds and manures application, especially the quality and quantity of applied fertilizer was one of the main reasons for leading to different accumulation of heavy metals in soils under the studied land use patterns. The accumulation of heavy metals, such as Cr, Ni, Cu, As, Cd, and Zn in soils was significantly affected by land use patterns, among them the accumulation of heavy metals in greenhouse soils was higher than others. It is suggested that the application of chemical fertilizer, organic fertilizer, and pesticides with high contents of heavy metals should be avoided to prevent the accumulation of heavy metal and keep high quality soils for sustainable use.

The effects of land use on runoff and soil nutrient losses in a gully catchment of the hilly areas:implications for erosion control

Serious soil erosion is one of the major issues threatening sustainable land use in semiarid areas, especially in the Loess Plateau of China. Understanding the effects of land use on soil and water loss is important for sustainable land use strategy. Two sub-catchments： catchment A （CA） and catchment B （CB） with distinct land uses were selected to measure soil moisture, runoff and soil nutrient loss in Da Nangou catchment of the Loess Plateau of China. The effects of land use patterns on runoff and nutrient losses were analyzed based on soil moisture pattern by kriging and soil nutrients using multiple regression model. The results indicated that there were significant differences in runoff yield and soil nutrient losses between the two sub-catchments. With similar land uses, the CA produced an average sediment yield of 49 kg ha^-1 and 22.27 kg ha^-1 during two storm events. Meanwhile, there was almost no runoff in the CB with dissimilar land uses during the same events. Buffer zones should be established to re-absorb runoff and to trap sediments in catchment with similar land use structure such as the CA. Moreover, land use management strategy aiming to increase the infiltration threshold of hydrological response units could decrease the frequency of runoff occurrence on a slope and catchment scale.

Research Advances of Effects of Land Use Pattern on Greenhouse Gas Fluxes in Grassland Ecosystem

The grassland is the largest terrestrial ecosystem in China,and greenhouse gas fluxes such as CO2,CH4 and N2O play an important role in the global climate change. The differences in grazing,cultivation and management measures will affect greenhouse gas emissions in grassland ecosystem. Studies suggest that reclamation will lead to increased CO2 fluxes,and fertilization will lead to increased N2 O fluxes; no grazing in summer can reduce greenhouse gas emissions,but impacts of grazing and management measures on greenhouse gas fluxes have not yet reached the same conclusion. The different results may be related to local natural conditions,management measures and research methods. Future research should be focused on unity and standardization in these areas,making the results scientific and comparable,and finally providing the basis for emission reduction of greenhouse gases in grassland ecosystem.

Relationship between land use and user’s behavior along the street:A case study of Da Nang City,Viet Nam

Human activities on street spaces are affected by both physical and non-physical settings on streets.These two aspects are primarily impacted by land use which results in the uneven distribution of different activities on streets.This research investigates land use patterns and their characteristics in association to user’s behaviors.By using mixed qualitative and quantitative research methods,e.g.,place-centered behavioral map,observation,visual encounter surveys,machine learning,the relationship between user’s behavior and land use characteristics along the street is unveiled.All user behaviors along both types of streets were classified into six main categories,with 26 subcategories.The observation results show that the residential use of land along the street was transformed into the commercial use for various types of shophouses based on the resident’s ideas.There is a great correlation between land use and user’s activities.These findings give support to authorities to manage urban streets and develop a sustainable policy for improving street spaces.Further,this research contributes useful information to urban designers and planners in creating a successful street space that is appropriate for the Vietnam Community.

Evaluation, simulation, and optimization of land use spatial patterns for high-quality development: A case study of Zhengzhou city, China

High-intensity land use and resource overloaded-induced regional land use spatial pattern(LUSP)are essential and challenging for high-quality development.The empirical studies have shown that a scientific land uses spatial layout,and the supporting system should be based on a historical perspective and require better considering the double influence between the current characteristics and future dynamics.This study proposes a comprehensive framework that integrates the resource environment carrying capacity(RECC)and land use change(LUC)to investigate strategies for optimizing the spatial pattern of land use for high-quality development.China’s Zhengzhou city was the subject of a case study whose datasets include remote sensing,spatial monitoring,statistics,and open sources.Three significant results emerged from the analysis:(1)The RECC has significant spatial differentiation but does not follow a specific spatial law,and regions with relatively perfect ecosystems may not necessarily have better RECC.(2)From 2020 to 2030,the construction land and farmland will fluctuate wildly,with the former increasing by 346.21 km^(2) and the latter decreasing by 295.98 km^(2).(3)The study area is divided into five zones,including resource conservation,ecological carrying,living core,suitable construction,and grain supply zones,and each one has its LUSP optimization orientation.This uneven distribution of RECC reflects functional defects in the development and utilization of LUSP.In addition,the increase in construction land and the sharp decline of farmland pose potential threats to the sustainable development of the study area.Hence,these two elements cannot be ignored in the future high-quality development process.The findings indicate that the LUSP optimization based on dual dimensions of RECC and LUC is more realistic than a single-dimension solution,exhibiting the LUSP optimization’s effectiveness and applicability.

Response of CH_4 emission of paddy fields to land management practices at a microcosmic cultivation scale in China

The terrestrial ecosystem may be either a source or a sink of CH_4 in rice paddies, depending, to a great extent, on the change of ecosystem types and land use patterns. CH_4 emission fluxes from paddy fields under 4 cultivation patterns (conventional plain culture of rice(T1), no-tillage and ridge culture of rice(T2), no-tillage and ridge culture of rice and wheat (T3), and rice-wheat rotation(T4)) were measured with the closed chamber technique in 1996 and 1998 in Chongqing, China. The results showed that differences existed in CH_4 emission from paddy fields under these land management practices. In 1996 and 1998, CH_4 emission was 71 48% and 78 82%(T2), 65 93% and 57 18%(T3), and 61 53% and 34 22%(T4) of that in T1 during the rice growing season. During the non-rice growing season, CH_4 emission from rice fields was 76 23% in T2 and 38 69% in T1 The accumulated annual CH_4 emission in T2, T3 and T4 in 1996 decreased by 33 53%, 63 30% and 65 73%, respectively, as compared with that in T1 In 1998, the accumulated annual CH_4 emission in T1, T2, T3 and T4 was 116 96 g/m^2, 68 44 g/m^2, 19 70 g/m^2 and 11 80 g/m^2, respectively. Changes in soil physical and chemical properties, in thermal and moisture conditions in the soil and in rice plant growth induced by different land use patterns were the dominant causes for the difference in CH_4 emission observed. The relative contribution of various influencing factors to CH_4 emission from paddy fields differed significantly under different land use patterns. However, the general trend was that chlorophyll content in rice leaves, air temperature and temperature at the 5 cm soil layer play a major role in CH_4 emission from paddy fields and the effects of illumination, relative humidity and water layer depth in the paddy field and CH_4 concentration in the crop canopy were relatively non-significant. Such conservative land use patterns as no-tillage and ridge culture of rice with or without rotation with wheat are thought to be beneficial to reducing CH_4 emission from paddy fields and are, therefore, recommended as a significant solution to the problems of global(climatic) change.

Vertical distribution characteristics of soil organic carbon content in Caohai wetland ecosystem of Guizhou plateau, China

We selected four kinds of land use types from Caohai wetlands of Guizhou plateau（a total number of 32 soil profiles） to study the distribution characteristics of organic carbon content in soil. With different ways of land use, the organic carbon content of soil profiles and organic carbon density show the tendency of decreasing firstly and then increasing from top to bottom. With the increase of depth, the vertical difference becomes smaller first and then starts increasing. Land reclamation reduces the soil organic carbon content and density, changing its distribution structure in topsoil. The average content of organic carbon in Caohai wetlands are as follows： lake bed silt [ marsh wetland [ farmland [ woodland, the average organic carbon content of lake bed silt, marsh wetland,farmland and woodland are 16.40, 2.94, 1.81 and 1.08 %,respectively. Land reclamation reduces the organic carbon content of soil, therefore the conversion of cultivated lands to wetlands and the increase of forest coverage will help to fix the organic carbon in soil and increase its reserves.

Regional Differences and Characteristics of Soil Organic Carbon Density Between Dry Land and Paddy Field in China

Study on the regional characteristics of soil organic carbon （SOC） density in farmland will not only contribute greatly to the technique of soil productivity enhancement, but also give evidences of technique selection and policy making for carbon sequestration in soils. Based on the second national soil survey of China, the situation of SOC density in the plow layer of farmland was analyzed under different land use patterns. Results showed that SOC density in the plow layer was about 3.15 kg m^-2 in average ranging from 0.81 to 12.68 kg m^-2. The highest density was found in the southeastern region with an average of 3.63 kg ma, while the lowest occurring in the northwestern region with an average of 3.00 kg m^-2. The variation coefficient of SOC density in the plow layer of farmland was 57%, which was 35% lower than that of non-farmland soils. Compared to SOC density in the dry land, SOC density in paddy soils was 13% higher with a lower variation coefficient between different regions. In addition, the relationships between the climatic factors （annual average temperature and precipitation） and SOC density were lower in farmland than those in non-farmland soils, as well as lower in paddy soils than those in dry land of farmland. These results suggest that anthropogenic disturbances have great impacts on SOC density in farmland soils, especially in paddy soils, indicating that Chinese rice cropping may contribute greatly to the SOC stability and sequestration in paddy field.

Impacts of regional land-use patterns on ecosystem services in the typical agro-pastoral ecotone of northern China

A comprehensive understanding of the spatial-temporal evolution and driving forces on ecosystem services(ES)is essential for the agro-pastoral ecotone’s ecological security in northern China.However,the land-use pattern(LULC)agglomeration with spatial differentiation in the pastoral and agricultural areas has been rarely concerned.Taking distinct LULC(1980-2018)in Chifeng as an example,we compared four crucial categories of ESs with InVEST.Using SEM,we further contrasted the effects of several variables on regional ES variations in pastoral-dominated(North)and agriculture-dominated(South)regions,respectively.Results revealed the conversion between forest and grassland oriented the LULC transformation in the North.In contrast,human-activitiy-oriented land tended to occupy environmentally sensitive places in the South.Similar ES variations were supplied with the North outperforming the South when soil conservation was omitted.As for the impacts of regional ES variations,the natural and LULC policies both showed positive effects,whereas the anthropogenic factors showed positive in the North,which was negative in the South.Therefore,the ecologicallymaintained-dominant and ecologically-restored-dominant strategies should be separately adopted in the North and South.Our study provided appropriate regional ecological management suggestions for balancing the LULC-driven conflicts between ecological protection and regional development.