Effects of Soil Texture on the Growth of Young Apple Trees and Soil Microbial Community Structure Under Replanted Conditions

A two-year field experiment was carried out in order to study the occurrence degree and mechanism of apple replant disease(ARD)in the apple orchards with different soil textures.So we can adopt appropriate controlmeasures according to the severity of ARD.Healthy two-year-old seedlings with consistent growth were selected,of which the root stock was T337 and the scion was Yanfu 3.There were significant differences in biomass between methyl bromide fumigation and replanted treatments,and the difference was the largest in clay loam,followed by sandy loam,and loam,which verified ARD in clay loam was most serious,followed by sandy loam and loam.Based on high-throughput sequencing of fungi in soil samples,fungal richness and diversity were the highest in clay loam,followed by sandy loam,and loam.The relative abundance of Fusarium in SX,SL,FX,FL,WX and WL was 7.33%,19.32%,2.70%,4.24%,10.71%and 23.87%,respectively.Based on Real-time quantitative analysis,there were significant differences in the number of Fusarium oxysporum and Fusarium solani between methyl bromide fumigation and replanted treatments,i.e.,clay loam>sandy loam>loam.Fusarium was the main pathogen causing ARD.This shows that ARD is the most serious under replanted clay loam condition.High-throughput sequencing technology was used to prove the difference in Fusarium was one of the important reasons for ARD under different soil textures.This technology provides a new idea for the prevention and control of ARD.

Water and salt movement in different soil textures under various negative irrigating pressures

supported by the National High-Tech R＆D Program of China （2013AA102901）

Effect of Soil Texture on Starch Accumulation and Activities of Key Enzymes of Starch Synthesis in the Kernel of ZM 9023

Three kinds of soil texture （clay-loam, mid-loam, and sand-loam soil） were used to study the effects of soil texture on starch accumulating rate and the changes in activities of the key enzymes of starch synthesis in the kernel during grain filling in high gluten content wheat ZM 9023, under conditions of pond culture. The content of starch and its components were measured according to the method of double-wave length described by Bao （1996）. ADP-glucose pyrophosphorylase （AGPP） activity was tested according to the method described by Doehlert et al. （1988）. Soluble starch synthase （SSS） and starch branching enzyme （SBE） activities were tested according to the method described by Nakamura et al. （1989）. The amylose, amylopectin, and total starch accumulating rate in the kernel of ZM 9023 were found to be a single-peak curve in three different soil textures during grain filling, and peaked 20, 15, and 15 d after anthesis, respectively. The activities of the enzymes, AGPP, SSS, and SBE, in the kernel of ZM 9023 had a single-peaked curve, which peaked 20, 15, and 15 d after anthesis, respectively. The activities of the above three enzymes of ZM 9023 were higher in the sand-loam soil. The accumulating peak of amylose formed later compared to that of amylopectin. The sand-loam soil could help high gluten content cultivars to synthesize starch.

Safety-efficiency trade-offs in the cotton xylem：acclimatization to different soil textures

The acclimatization of plant xylem to altered environmental conditions has attracted considerable attention from researchers over several decades. Plants growing in natural environments must seek a balance between water uptake and the water loss of leaves from evaporation. Thus, the adaptation of xylem to different soil textures is important in maintaining plant water balance. In this study, we investigated the xylem changes of cotton（Gossypium herbaceum L.） xylem in sandy, clay and mixed soils. Results showed that soil texture had a significant effect on xylem vessel diameter and length of stems and roots. Compared with G. herbaceum growing in the clay soil, those plants growing in the sandy soil developed narrower and shorter xylem vessels in their roots, and had a higher percentage of narrow vessels in their stems. These changes resulted in a safer（i.e. less vulnerable to cavitation）, but less-efficient water transport system when soil water availability was low, supporting the hydraulic safety versus efficiency trade-off hypothesis. Furthermore, in sandy and mixed soils, the root： shoot ratio of G. herbaceum increased twofold, which ensures the same efficiency of leaves. In summary, our finding indicates that the morphological plasticity of xylem structure in G. herbaceum has a major role in the acclimatization of this plant species to different soil textures.

Characterization of an Area Polluted by Copper and Zinc:the Relation between Soil Texture,Mineralogy and Pollutant Concentration

Twenty-four soil samples were collected at three depths from an approximately 2.5 acre contaminated site in southern Piedmont （Italy） and then analyzed. The main soil parameters determined were： pH, Cation Exchange Capacity （CEC）, particle size distribution, total organic carbon （TOC） content and retained metal concentration. The mineral phases were identified by X-Ray Powder Diffraction （XRPD）. All of the samples contained Zn and Cu resulting from industrial contamination during the last century, and those obtained at depths of 20-40 cm consistently showed the highest levels. To determine which size fraction was most active in the retention process, the samples were separated into four fractions （≤2 mm, ≤63 0m, ≤30 0m and ≤2 μm） and the amount of pollutant measured in each. It was found that metal retention was the highest in the clayey fraction, whose clay minerals were identified by XRPD after K＋ and Mg2＋ saturation, glycerol treatment and heating to 550℃. The clayey fraction was also the richest in TOC, and a direct correlation between TOC amount and metal retention was observed.

Relating thermal conductivity of soil skeleton with soil texture by the concept of“local thermal conductivity fluctuation”

The thermal conductivity of the soil skeletonλ;is an essential parameter from the point of view of the correct assessment of soil overall/effective conductivity.This work introduces the concept of“local thermal conductivity fluctuation”which characterizes the microscale variation of conductivity within the solid phase.It is proposed to link the“local fluctuation”of thermal conductivityλwith the soil texture-the information that is available at the scale of engineering applications.It was possible to relate the skeleton thermal conductivity with the grain size distribution of the soil.Finally,based on a large series of numerical simulations,the paper provides four triangle diagrams(at different organic matter contents:0%,2%,4%and 6%)relating the value ofλ;with volume fraction of individual soil separates.This result is extremely important from the practical point of view.One can quickly evaluateλ;value provided that information on the grain size distribution and organic matter content is available.

In-situ soil texture classification and physical clay content measurement based on multi-source information fusion

Soil texture is one of the most important soil characteristics that affect soil properties.Rapid acquisition of soil texture information is of great significance for accurate farmland management.Traditional soil texture analysis methods are relatively complicated and cannot meet the requirements of temporal and spatial resolution.This research introduced a self-developed vehicle-mounted in-situ soil texture detection system,which can predict the type of soil texture and the particle composition of the texture,and obtain real-time data during the measurement process without preprocessing the soil samples.The detection system is mainly composed of a conductivity measuring device,a camera,an auxiliary mechanical structure,and a control system.The soil electrical conductivity(ECa)and the texture features extracted from the surface image were input into the embedded model to realize real-time texture analysis.In order to find the best model suitable for the detection system,measurements were carried out in three test fields in Northeast and North China to compare the performance of different models applied to the detection system.The results showed that for soil texture classification,ExtraTrees performed best,with Precision,Recall,and F1 all being 0.82.For particle content of soil texture prediction,the R2 of ExtraTrees was 0.77,and RMSE and MAPE were 74.72 and 39.58.It was observed that ECa,Moment of inertia,and Entropy had larger weights in the drawn model influence weight map,and they are the main contributors to predicting soil texture.These results showed the potential of the vehicle-mounted in-situ soil texture detection system,which can provide a basis for fast,cost-effective,and efficient soil texture analysis.

Estimating the Texture of Purple Soils Using Vis-NIR Spectroscopy and Optimized Conversion Models

Soil texture is an indicator of soil physical structure which delivers many ecological functions of soils such as thermal regime, plant growth, and soil quality. However, traditional methods for soil texture measurement are time-consuming and labor-intensive. This study attempts to explore an indirect method for rapid estimating the texture of three subgroups of purple soils (i.e. calcareous, neutral, and acidic). 190 topsoil (0 - 10 cm) samples were collected from sloping croplands in Tongnan and Beibei Districts of Chongqing Municipality in China. Vis-NIR spectrum was measured and processed, and stepwise multiple linear regression (SMLR), partial least squares regression (PLSR), and back propagation neural network (BPNN) models were constructed to inform the soil texture. The clay fractions ranged from 4.40% to 27.12% while sand fractions ranged from 0.34% to 36.57%, hereby soil samples encompass three textural classes (i.e. silt, silt loam, and silty clay loam). For the original spectrum, the texture of calcareous and neutral purple soils was not significantly correlated with spectral reflectance and linear models (SMLR and PLSR) exhibited low prediction accuracy. The correlation coefficients and the goodness-of-fits between soil texture and the transformed spectra of all soil groups increased by continuum-removal (CR), first-order differential (R'), and second-order differential (R") transformations. Among them, the R" had the best performance in terms of improving the correlation coefficients and the goodness-of-fits. For the calcareous purple soil, the SMLR exceeds PLSR and BPNN with a higher coefficient of determination (R2) and the ratio of performance to inter-quartile distance (RPIQ) values and lower root mean square error of validation (RMSEV), but for the neutral and acidic purple soils, the PLSR model has a better prediction accuracy. In summary, the linear methods (SMLR and PLSR) are more reliable in estimating the texture of the three purple soil groups when using Vis-NIR spectroscopy inversion.

Parkland trees on smallholder farms ameliorate soil physical-chemical properties in the semi-arid area of Tigray,Ethiopia

Proposed agroforestry options should begin with the species that farmers are most familiar with,which would be the native multipurpose trees that have evolved under smallholder farms and socioeconomic conditions.The African birch(Anogeissus leiocarpa(DC.)Guill.&Perr.)and pink jacaranda(Stereospermum kunthianum Cham.)trees are the dominant species in the agroforestry parkland system in the drylands of Tigray,Ethiopia.Smallholder farmers highly value these trees for their multifunctional uses including timber,firewood,charcoal,medicine,etc.These trees also could improve soil fertility.However,the amount of soil physical and chemical properties enhanced by the two species must be determined to maintain the sustainable conservation of the species in the parklands and to scale up to similar agroecological systems.Hence,we selected twelve isolated trees,six from each species that had similar dendrometric characteristics and were growing in similar environmental conditions.We divided the canopy cover of each tree into three radial distances:mid-canopy,canopy edge,and canopy gap(control).At each distance,we took soil samples from three different depths.We collected 216 soil samples(half disturbed and the other half undisturbed)from each canopy position and soil depth.Bulk density(BD),soil moisture content(SMC),soil organic carbon(SOC),total nitrogen(TN),available phosphorus(AP),available potassium(AK),p H,electrical conductivity(EC),and cation exchange capacity(CEC)were analysed.Results revealed that soil physical and chemical properties significantly improved except for soil texture and EC under both species,CEC under A.leiocarpus,and soil p H under S.kunthianum,all the studied soils were improved under both species canopy as compared with canopy gap.SMC,TN,AP,and AK under canopy of these trees were respectively 24.1%,11.1%,55.0%,and 9.3% higher than those soils under control.The two parkland agroforestry species significantly enhanced soil fertility near the canopy of topsoil through improving soil physical and chemical properties.These two species were recommended in the drylands with similar agro-ecological systems.

Influence of soil texture on the process of subsurface drainage in saturated-unsaturated zones

This study addressed the problem of low drainage efficiency or even no drainage in subsurface drainage systems buried in saturated-unsaturated zones above the water table.An indoor experiment on infiltration under ponded conditions in a homogeneous soil column was performed to study the effects of soil texture on the soil wetting front morphology,soil infiltration rate,drainage efficiency of the subsurface drainage pipe,vertical distribution of soil water content and salinity along the soil column.The results showed that the drainage process of subsurface drainage pipes above the water table was quite different from that of subsurface drainage pipes below the water table.When a subsurface drainage pipe was located in sandy soil,the migration of soil water toward the bottom of the drainage pipe was significant,and the water could not be discharged into the pipe.When the drainage pipe was located in loamy clay,the movement of soil water towards the bottom of the pipe was retarded,and the water could be discharged into the pipe.During the drainage process,the drainage of the pipe can produce nonequilibrium flow in the soil,and the continuity of the nonequilibrium flow can be affected by the hydraulic conductivity of the soil above the pipe,which can result in discontinuous drainage and low drainage efficiency.The water holding capacity,permeability and aeration of soil are important factors that affect the drainage under unsaturated conditions.Eliminating the hysteresis effect and capillary barrier around the drainage pipe and adjusting water holding capacity,the permeability and aeration of soil structure through a new subsurface drainage structure may enhance the drainage efficiency of subsurface drainage pipes in saturated-unsaturated zones.

Mapping the vertical distribution of maize roots in China in relation to climate and soil texture

Aims Optimizing water and fertilizer management for crops requires an understanding of root distribution.Maize(Zea mays L.)is currently the most widely planted cereal crop in China,yet the vertical dis-tribution of maize roots across different regions remains unknown.The aims of this work were(i)to quantify the effects of climate and soil texture on the vertical distribution of maize roots,and(ii)to show the depth distribution of root biomass in China.Methods We used data of maize root biomass from 11 Chinese ecological stations with discontinuous observations from 2004 to 2014 to fit the regression coefficientβfor an asymptotic equation Y=1-βd,where d is the soil depth and Y is the proportion of root biomass from the surface to depth d.A statistical model was then developed to quantify the effects of climate and soil texture on the fittedβval-ues.Using the statistical model,we map the depth distribution of maize root biomass in China.Important Findings Maize root biomass in the 0-100 cm soil depth varied by an order of magnitude at different stations,from 64 to 268 g m−2.Maize planted in sandy soils and/or maize with high accumu-lated temperature for development had higher root biomass and deeper rooting systems.The fittedβvalues ranged from 0.785 to 0.977,which can be modeled by an integration of the accu-mulated temperature during the maize growing period and the soil clay and sand fractions(R2=0.66,n=50,P<0.001).Up to 82%of maize planting regions in China showed shallower rooting systems where more than 90%and 95%of the root bio-mass occurred in the top 20 and 30 cm soil layers,respectively.Deeper rooting systems occurred in some temperate arid and temperate semi-arid regions,with less than 80%of the root bio-mass in the top 20 cm soil.Our findings highlighted the vertical distribution of maize roots,and underlined the spatial variability in the vertical distribution of roots across China’s planting areas of maize.

The response of soil organic carbon to climate and soil texture in China

Soil organic carbon(SOC)plays an essential role in the carbon cycle and global warming mitigation,and it varies spatially in relation to other soil and environmental properties.But the national distributions and the impact mechanisms of SOC remain debated in China.Therefore,how soil texture and climate factors affect the SOC content and the regional differences in SOC content were explored by analyzing 7857 surface soil samples with different land-use.The results showed that the SOC content in China,with a mean value of 11.20 g·kg^(-1),increased gradually from north to south.The SOC content of arable land in each geographical area was lower than in grassland and forest-land.Although temperature also played a specific role in the SOC content,precipitation was the most critical climate factor.The SOC content was positively correlated with the silt and clay content.The lower the temperature,the greater the effect of environmental factors on SOC.In contrast,the higher the temperature,the more significant impact of soil texture on SOC.The regional difference in SOC highlights the importance of soil responses to climate change.Tempera-ture and soil texture should be explicitly considered when predicting potential future carbon cycle and sequestration.

Soil Chemical Property Changes over Time from Struvite Compared to Other Fertilizer-Phosphorus Sources in Multiple Soils

Studies have shown that phosphorus (P) recovered from wastewater as the mineral struvite [MgNH4PO4·6(H2O)] may be a viable alternative fertilizer-P source. This study aimed to compare the effectiveness of electrochemically precipitated struvite (ECST), reclaimed from synthetic wastewater, to other commercial fertilizer-P sources in cultivated soils from Arkansas [AR;silt loam (SiL) and loam (L)], Missouri (MO;SiL), and Nebraska [NE;SiL and sandy loam (SL)]. A plant-less, moist-soil incubation experiment, including ECST, chemically precipitated struvite (CPST), monoammonium phosphate (MAP), triple superphosphate (TSP), and an unamended control (UC), was conducted to quantify soil pH, nitrate (NO3-N), ammonium (NH4-N), and Mehlich-3 (M3)-P, -Ca, -Mg, and -Fe concentrations at 0.5, 1, 2, 4, and 6 months. All measured soil properties differed (P ·kg-1 for AR-L-TSP after 1 month and NE-SiL-MAP after 6 months, respectively. Soil M3-P ranged from -29.6 mg·kg-1 in the AR-L-UC after 1 month to 429 mg·kg-1 AR-SiL-TSP after 0.5 months. Results showed that, over time, ECST had comparable pH and soil NO3-N, NH4-N, and M3-P, -Ca, -Mg, and -Fe behavior compared to CPST, MAP, and TSP across various soil textures.

Effects of uprooting tree on herbaceous species diversity, woody species regeneration status and soil physical characteristics in a temperate mixed forest of Iran

We conducted a study to examine the pattem of develop- ment of herbaceous plant species, woody species regeneration and soil physical characteristics after tree uprooting in 20-ha areas of Experimen- tal Forest Station of Tarbiat Modares University located in a temperate forest of Mazandaran province in the north of Iran. Soil bulk density, soil texture and moisture from pit and mound （PM） were measured in the laboratory. Results show that the soil bulk density was most in soil deeper layers at mound top, and the soil moisture content was most in soil deeper layers at Pit bottom. Our study supports that the mi- cro-topography of PM （pit and mound） topography will create a mosaic of environmental conditions. This environmental heterogeneity could be responsible for the diversity of herbaceous plant species and regeneration of woody species. It is recommend that the fallen trees with PM structure should remain in the protected area without clearing as the best option for forest restoration. This information can be useful for forest management that attempts to emulate natural processes.

Eucalyptus grandis plantations:effects of management on soil carbon,nutrient contents and yields

The expansion of fast-growing tree plantations is a worldwide process,with consequences on soil fertility and soil carbon storage.Disparate results were found on the effects of afforestation with Eucalyptus on soil carbon and other nutrient contents.These discrepancies are usually caused by differences in climate,land use history,soil texture as well as by management related factors such as plantation age,number of rotations,method of establishment(plantation or coppice),harvest residue management and soil preparation.We studied the effect of plantation age,number of rotations,and method of establishment on soils and plant nutrient concentrations in Eucalyptus grandis plantations in NE Argentina on different textured soils.We also determined if yields changed with nutrient variations in soils,and compared soils under plantations to soils under grasslands they replaced.Thirty-one E.grandis stands of different ages,number of rotations and method of establishment were evaluated as well as eight grassland sites.Levels of carbon,nitrogen,phosphorus,potassium,calcium and magnesium were determined for soils and plants.Soil carbon and nitrogen decreased over the number of rotations and were more pronounced in soils with 50-60%sand than soils with>75%sand.Coppice stands showed higher soil carbon and nitrogen levels than plantations,suggesting a negative effect of site preparation before planting on soil nutrient conservation,especially in fine-textured soils.Foliar nutrient concentrations did not follow the trends observed for soil nutrients nor did they reflect nutrient limitations.There was no evidence of decreased yields over successive rotations.Soil carbon and nitrogen contents decrease when grasslands are replaced by E.grandis plantations,and therefore a yield limitation may occur in a medium to long-term frame,especially in stands re-established for short-rotation management.Harvest residue management and site preparation must be specifically designed for improving soil nutrient management.

Responses of Amygdalus pedunculata Pall.in the sandy and loamy soils to water stress

Amygdalus pedunculata Pall.is a major species that is widely planted in afforested soils with different textures in the transitional zone between Mu Us Desert and Loess Plateau,China.However,the responses of A.pedunculata to increasing intensity of water stress in different textural soils are not clear.Here,we conducted a soil column experiment to evaluate the effects of different textures(sandy and loamy)on water consumption,water use efficiency(WUE),biomass accumulation and ecological adaptability of A.pedunculata under increasing water stress,i.e.,90%(±5%)FC(field capacity),75%(±5%)FC,60%(±5%)FC,45%(±5%)FC and 30%(±5%)FC in 2018.A.pedunculata grown in the sandy soil with the lowest(30%FC)and highest(90%FC)water contents had respectively 21.3%-37.0%and 4.4%-20.4%less transpiration than those with other water treatments(45%-75%FC).In contrast,A.pedunculata transpiration in the loamy soil decreased with decreasing water content.The magnitude of decrease in transpiration increased with increasing level of water deficit(45%and 30%FC).Mean daily and cumulative transpirations of the plant were significantly lower in the sandy soil than in the loamy soil under good water condition(90%FC),but the reverse was noted under water deficit treatments(45%and 30%FC).Plant height,stem diameter and total biomass initially increased with decreasing water content from 90%to 75%FC and then declined under severe water deficit conditions(45%and 30%FC)in the sandy soil.However,these plant parameters decreased with decreasing water content in the loamy soil.WUE in the sandy soil was 7.8%-12.3%higher than that in the loamy soil,which initially increased with decreasing water content from 90%to 75%FC and then declined under water deficit conditions(45%and 30%FC).The study showed that plant transpiration,biomass production and WUE responded differentially to increasing intensity of water stress in the sandy and loamy soils.The contrasting responses of A.pedunculata to water stress in different textural soils can guide future revegetation programs in the northern region of Chinese Loess Plateau by considering plant adaptability to varying soil and water conditions.

Bacterial diversity and community composition changes in paddy soils that have different parent materials and fertility levels

Parent materials and the fertility levels of paddy soils are highly variable in subtropical China.Bacterial diversity and community composition play pivotal roles in soil ecosystem processes and functions.However,the effects of parent material and fertility on bacterial diversity and community composition in paddy soils are unclear.The key soil factors driving the changes in bacterial diversity,community composition,and the specific bacterial species in soils that are derived from different parent materials and have differing fertility levels are unknown.Soil samples were collected from paddy fields in two areas with different parent materials(quaternary red clay or tertiary sandstone)and two levels of fertility(high or low).The variations in bacterial diversity indices and communities were evaluated by 454 pyrosequencing which targeted the V4–V5 region of the 16S rRNA gene.The effects of parent material and fertility on bacterial diversity and community composition were clarified by a two-way ANOVA and a two-way PERMANOVA.A principal coordinate analysis(PCoA),a redundancy analysis(RDA),and multivariate regression trees(MRT)were used to assess changes in the studied variables and identify the factors affecting bacterial community composition.Co-occurrence network analysis was performed to find correlations between bacterial genera and specific soil properties,and a statistical analysis of metagenomic profiles(STAMP)was used to determine bacterial genus abundance differences between the soil samples.The contributions made by parent material and soil fertility to changes in the bacterial diversity indices were comparable,but soil fertility accounted for a larger part of the shift in bacterial community composition than the parent material.Soil properties,especially soil texture,were strongly associated with bacterial diversity.The RDA showed that soil organic carbon(SOC)was the primary factor influencing bacterial community composition.A key threshold for SOC(25.5 g kg^(–1))separated low fertility soils from high fertility soils.The network analysis implied that bacterial interactions tended towards cooperation and that copiotrophic bacteria became dominant when the soil environment improved.The STAMP revealed that copiotrophic bacteria,such as Massilia and Rhodanobacter,were more abundant in the high fertility soils,while oligotrophic bacteria,such as Anaerolinea,were dominant in low fertility soils.The results showed that soil texture played a role in bacterial diversity,but nutrients,especially SOC,shaped bacterial community composition in paddy soils with different parent materials and fertility levels.

Factors determining soil water heterogeneity on the Chinese Loess Plateau as based on an empirical mode decomposition method

Soil water is a critical resource,and as such is the focus of considerable physical research.Characterization of the distribution and spatial variability of soil water content(SWC)offers important agronomic and environmental information.Estimation of non-stationary and non-linear SWC distribution at different scales is a research challenge.Based on this context,we performed a case study on the Chinese Loess Plateau,with objectives of investigating spatial variability of SWC and soil properties(i.e.,soil particle composition,organic matter and bulk density),and determining multi-scale correlations between SWC and soil properties.A total of 86 in situ sampling sites were selected and 516 soil samples(0–60 cm depth with an interval of 10 cm)were collected in May and June of 2019 along the Yangling-Wugong-Qianxian transect,with a length of 25.5 km,in a typical wheat-corn rotation region of the Chinese Loess Plateau.Classical statistics and empirical mode decomposition(EMD)method were applied to evaluate characteristics of the overall and scale-specific spatial variation of SWC,and to explore scale-specific correlations between SWC and soil properties.Results showed that the spatial variability of SWC along the Yangling-Wugong-Qianxian transect was medium to weak,with a variability coefficient range of 0.06–0.18,and it was gradually decreased as scale increased.We categorized the overall SWC for each soil layer under an intrinsic mode function(IMF)number based on the scale of occurrence,and found that the component IMF1 exhibited the largest contribution rates of 36.45%–56.70%.Additionally,by using EMD method,we categorized the general variation of SWC under different numbers of IMFs according to occurrence scale,and the results showed that the calculated scales among SWC for each soil layer increased in correspondence with higher IMF numbers.Approximately 78.00%of the total variance of SWC was extracted in IMF1 and IMF2.Generally,soil texture was the dominant control on SWC,and the influence of the three types of soil properties(soil particle composition,organic matter and bulk density)was more prominent at larger scales along the sampling transect.The influential factors of soil water spatial distribution can be identified and ranked on the basis of the decomposed signal from the current approach,thereby providing critical information for other researchers and natural resource managers.

Coastal afforestation effects on soil properties at Hatiya in Bangladesh

An exploratory study was conducted in the coastal plantation （12- and 17-year-old Sonneratia apetala） of Char Alim and Char Piya and on their adjacent barren lands at Char Rehania and Char Nurul Islam in Hatiya of Noakhali district, in Bangladesh to determine afforestation effects on soil properties. At soil depths of 0-10, 10-30 and 30-40 cm across three different land strips viz. inland, middle and sea side in 12- and 17-year-old keora （Sonneratia apetala） plantations, soil moisture, particle density, organic matter and C, total N, pH, available P, K, Na, Ca and Mg were significantly （p≤0.05, p≤0.01, p≤0.001） higher, and soil salinity significantly （p〈0.001） lower than that in their adjacent barren lands. Soil moisture, particle density, organic matter and C, total N, pH, soil salinity, available P, K, Na, Ca and Mg of surface soil in Char Alim plantation at inland were 31.09%, 2.24 g.cm^-3, 2.41%, 4.14%, 0.58%, 7.07, 0.09 dS＇cm^-1, 28.06 mg.L^-1, 0.50 mg-L^- 1 11.5 mg-L^-1, 3.30 mg·L^-1 and 2.7 mmol.kg^-1, respectively. Their corresponding values for the same depth and land position at adjacent Char Rehania barren land were 16.69%, 1.25g.cm^-3, 0.43%, 0.74%, 0.25%, 6.57, 0.13 dS.cm^-1, 13.07mg-L^-1, 0.30 mg.L^-1, 1.4 mg.L^-1, 0.30 mmol·kg^-1 and 0.50 mg.L^-1, respectively. Soil moisture, particle density, organic matter and C, total N, pH, available P, K and Ca decreased, and soil salinity, available Na and Mg increased from inland towards sea side in the plantations. Although soil texture did not differ in most soil depths between plantation and adjacent barren land, proportion of sand particle was significantly （p≤0.01） lower and silt particle significantly （p〈0.001） in the plantations higher than that in their adjacent barren lands. In the study, evaluation of all the parameters was also done for the other pair of lands.

Study on soil water characteristics of tobacco fields based on canonical correlation analysis

In order to identify the principal factors influencing soil water characteristics （SWC） and evaluate SWC effectively, the multivariate-statistical canonical correlation analysis （CCA） method was used to study and analyze the correlation between SWC and soil physical and chemical properties. Twenty-two soil samples were taken from 11 main tobacco-growing areas in Guizhou Province in China and the soil water characteristic curves （SWCC） and basic physical and chemical properties of the soil samples were determined. The results show that： （1） The soil bulk density, soil total porosity and soil capillary porosity have significant effects on SWC of tobacco fiels. Bulk density and total porosity are positively correlated with soil water retention characteristics （SWRC）, and soil capillary porosity is positively correlated with soil water supply characteristics （SWSC）. （2） Soil samples from different soil layers at the same soil sampling point show similarity or consistency in SWC. Inadequate soil water supply capability and imbalance between SWRC and SWSC are problems of tobacco soil. （3） The SWC of loamy clay are generally superior to those of silty clay loam.