GIS-Based Assessment of Soil Chemical and Physical Properties as a Basis for Land Reclamation in Toshka Area, Aswan, EGYPT

The accurate assessment of soil properties is a crucial factor for composing and implementing reclamation plans. The main objective of this study was to evaluate soil chemical and physical properties and calculate the chemical and fertility index for assisting land reclamation in Toshka area. The Toshka area is located between latitudes 31°32'N and 31°36'N and longitudes 32°40'E and 32°60'E. GIS was used to select 16 sites. The results revealed the soil has undesirable characteristics. The soil pH ranged from slightly alkaline to moderately alkaline. Furthermore, it was characterized as saline (with a ECe of 4.65 - 11.45 dS⋅m−1) and moderately calcareous soil (with CaCO3 at 11.85% - 17.20%). The soil had a low soil organic matter content which did not exceed 0.18%. The soil was dominated by a sandy loam texture (62.50%) followed by a sandy clay loam texture (18.75%). The bulk density, total soil porosity and saturated hydraulic conductivity values varied with 1.38 - 1.55 Mg⋅cm−3, 41.85% - 48.45% and 1.20 - 3.34 cm⋅h−1, respectively. The chemical index ranged from low to moderate quality. The correlations between the parameters osculated between negative and positive. Therefore, the soil may be reclaimed if the soil properties are improved and crop selection is optimized for this soil.

Effect of fire severity on physical and biochemical soil properties in Zagros oak(Quercus brantii Lindl.)forests in Iran

Fire affects the physical and chemical properties and soil biological activity of natural ecosystems. This study was conducted in the Miyan Tang region, Ilam Province in western Iran. The study site was 110 hectares, where we sampled soils in areas that were classified by fire severity： low （LS）, high （HS） and medium severity （MS）, and unburned （UB）, which served as the control. In each severity class, 25 transect points were randomly selected for measurement. Around each transect plot center, 3 soil samples were selected randomly and soils collected from the 0 to 20 cm depth were combined into a composite sample that was used in laboratory analysis to represent conditions at that point. Plots in the UB and LS fire classes had similar soil conditions and had higher values of factors such as saturated moisture, organic carbon, carbon dioxide, and silt and clay content. In contrast, plots in the HS and MS fire severity classes were clustered in the positive direction along the first axis that represented gradients in soil acidity, electrical conductivity, cation exchange capacity, accessible phosphorus, accessible potassium, bulk density, and sand. Soil attributes were similar in areas of HS and MS fire severity classes, whereas soil conditions in the LS class and UB controls were most similar. Fire in the LS areas either did not significantly alter the physicalchemical soil properties and microbial basal respiration, or soils were able to recover quickly after being burned.

Effects of Different Nitrogen Applications on Soil Physical, Chemical Properties and Yield in Maize (<i>Zea mays</i>L.)

Application of nitrogen (N) fertilizer is one of the most important approaches on improving maize grain yield. However, as is known to all, overuse N fertilizer not only leads to decline of N use efficiency and maize yield, but also leads to potential risk to environment pollution. This experiment was conducted to determine the effects of N fertilizer applications with nine different treatments on soil physical-chemical characters and maize grain yield using hybrid variety Zhengdan 958 in 2011 and 2012. Results indicated that the soil bulk densities of T2 (CK) and T1 were the lowest compared to other treatments in 2011 and 2012, respectively, whereas the soil bulk density of T5 in 2011 and T3 in 2012 were higher than other treatments. The soil porosity and field capacity of T5 in 2011 and T3 in 2012 were lower than other treatments, but those of CK in 2011 and T1 in 2012 were higher than other treatments. The pH values of T3 to T7 were lower than other treatments. These results indicated that the soil bulk densities were increased, whereas the soil porosity, field capacity and values pH were decreased by N application at different stages. N application could increase the N contents of leaf and stem, whereas less or excess N application should not significant improve maize yield. Although the soil organic matter and total N contents of T3 were the highest in both 2011 and 2012, the yield of T4 is the highest in both 2011 and 2012. The application amount, period and times of N fertilizer were important to maize yield.

Responses of microbial activities and soil physical-chemical properties to the successional process of biological soil crusts in the Gurbantunggut Desert,Xinjiang

Biological soil crusts （BSCs） are capable of modifying nutrient availability to favor the establishment of biogeochemical cycles. Microbial activities serve as critical roles for both carbon and nutrient transformation in BSCs. However, little is known about microbial activities and physical-chemical properties of BSCs in the Gurbantunggut Desert, Xinjiang, China. In the present research, a sampling line with 1-m wide and 20-m long was set up in each of five typical interdune areas selected randomly in the Gurbantunggut Desert. Within each sampling line, samples of bare sand sheet, algal crusts, lichen crusts and moss crusts were randomly collected at the depth of 0-2 cm. Varia- tions of microalgal biomass, microbial biomass, enzyme activities and soil physical-chemical properties in different succession of BSCs were analyzed. The relationships between microalgal biomass, microbial biomass, enzymatic activities and soil physical-chemical properties were explored by stepwise regression. Our results indicate that micro- algal biomass, microbial biomass and most of enzyme activities increased as the BSCs developed and their highest values occurred in lichen or moss crusts. Except for total K, the contents of most soil nutrients （organic C, total N, total P, available N, available P and available K） were the lowest in the bare sand sheet and significantly increased with the BSCs development, reaching their highest values in moss crusts. However, pH values significantly decreased as the BSCs developed. Significant and positive correlations were observed between chlorophyll a and microbial biomass C. Total P and N were positively associated with chlorophyll a and microbial biomass C, whereas there was a significant and negative correlation between microbial biomass and available P. The growth of cyanobacteria and microorganism contributed C and N in the soil, which offered substrates for enzyme activities thus increasing enzyme activities. Probably, improvement in enzyme activities increased soil fertility and promoted the growth of cyanobacteria, eukary- otic algae and heterotrophic microorganism, with the accelerating succession of BSCs. The present research found that microalgal-microbial biomass and enzyme activities played important roles on the contents of nutrients in the successional stages of BSCs and helped us to understand developmental mechanism in the succession of BSCs.

Robinia pseudoacacia leaves improve soil physical and chemical properties

The role of the leaves of Robinia pseudoacacia L., which is widely distributed in the arid lands, on improving soil physical and chemical properties was analyzed at various incubation periods. The incubated soils added with 0, 25, 50 and 75 g Robinia pseudoacacia leaves were tested after consecutive incubation intervals of 6, 8 and 10 months and the different soil parameters were measured. The results showed the increases in organic matter (OM), extractable K, cation exchange capacity (CEC), aggregate stability and water holding capacity, but the decreases in pH value and bulk density after 6 months’ incubation. The gradual decrease in change rates of soil properties indicated less microbial population and organic residual mineralization under acidic conditions, which were resulted from fast decomposition of leaves after the first 6 months incubation. The increases in soil organic matter content, extractable K, CEC, aggregate stability and water holding capacity and the decreases in soil pH and bulk density provide favorable conditions for crop’s growth.

Effects of Crude Oil Contamination on Soil Physical and Chemical Properties in Momoge Wetland of China

Large oilfields are often coincidentally located in major river deltas and wetlands,and potentially damage the structure,function and ecosystem service values of wetlands during oil exploration.In the present study,the effects of crude oil contamination during oil exploration on soil physical and chemical properties were investigated in marshes of the Momoge National Nature Reserve in Jilin Province,China.The concentrations of total petroleum hydrocarbons in the marsh soil near the oil wells are significantly higher than those in the adjacent control marsh.Soil water contents in oil-contaminated marshes are negatively correlated with soil temperature and are significantly lower than those in the control area,especially in fall.Crude oil contamination significantly increases the soil pH up to8.0,and reduces available phosphorus concentrations in the soil.The concentrations of total organic carbon are significantly different among sampling sites.Therefore,crude oil contamination could potentially alkalinize marsh soils,adversely affect soil fertility and physical properties,and cause deterioration of the marshes in the Momoge National Nature Reserve.Phyto-remediation by planting Calamagrostis angustifolia has the potential to simultaneously restore and remediate the petroleum hydrocarbon-contaminated wetlands.Crude oil contamination affects the soil physical and chemical properties,so developing an effective restoration program in the Momoge wetland is neccesary.

Analysis of the Engineering Restoration Effect of Abandoned Yongledian Quarry in Beijing City Based on Soil Physical and Chemical Properties

The improvement of the soil physical and chemical properties is the most important foundation for mine ecological restoration.The experiment is aimed at undisturbed area,restored area,and damaged area of abandoned Yongledian Quarry in Beijing.Through determination and analysis of soil physical and chemical properties,it shows that there are significant differences in the composite effects of soil physical and chemical properties between restored area,and undisturbed area,damaged area,and engineering restoration effectively improves the composite effects of soil physical and chemical properties in the restored area.The single factor hypothesis test shows that soil pH value,organic matter,alkali-hydrolyzable nitrogen,and total nitrogen traits are the key targets to be restored in this mining area.

Soil Physical and Chemical Properties of Pure Pinus massoniana and Its Mixed Forests in Different Ages in Southern Guangxi

Six forest stands of 59,34 and 24 year-old Pinus massoniana forests and their mixed forests were selected at the Experimental Center of Tropical Forestry of Chinese Academy of Forestry,and 20 m × 20 m plot was set up and soil samples were taken from 0-60 cm soil layers,to analyze the changes of soil nutrient content under different forest stands and forest ages. The results showed that soil moisture and the bulk density in the mesophytic forest land were higher than those of other forest lands. The highest soil porosity value was observed in the early forest land. Soil p H of different forest was 4. 45-4. 75,indicating the variation was small. Besides,it indicated that the mixed forest was more able to increase the soil fertility than the pure forest because that the variation of soil acidity,organic matter content and total P and K in 34 and24 year-old mixed forests were higher than those in pure forests of the same year old. However,the content of soil available P and K decreased with the increase of soil depth,and varied in terms of forest ages. From the changes of soil indicators in different forest lands,soil nutrients in the 34 year-old P. massoniana forest was superior to that of other forest stands.

Effect of Different Cultivation Practices on Soil Physical and Chemical Properties for Greenhouse Vegetables under Long-Term Continuous Cropping

Five kinds of greenhouse vegetables( eggplant,loofah,tomato,cucumber and pepper) were selected in summer uprooting stage from greenhouse in Shouguang area,Shandong Province. Total nitrogen,ammonium nitrogen,nitrate nitrogen,available phosphorus,available potassium,organic matter content and p H,EC value of three soil layers were measured,respectively. The results showed that the total nitrogen,ammonium nitrogen,nitrate nitrogen,available phosphorus and available potassium in the soil were mainly accumulated in the upper soil,which made the soil acidification trend,because different farmers adopted different cultivation practices for different greenhouse vegetables in Shouguang region,but there was no significant effect on soil EC value. The input of ammonium nitrogen and nitrate nitrogen and other related fertilizers to greenhouse cucumber was higher than that of other greenhouse vegetables,but the amount of available potassium fertilizer and organic matter input to greenhouse tomato under different cultivation practices was lower than other greenhouse vegetables. In Shouguang area,the input of organic matter into greenhouse vegetables should be increased by increasing the proportion of manure input to increase the content of soil organic carbon,so as to achieve the balance of carbon and nitrogen ratio,and to provide a scientific basis for the establishment of an evaluation system for the environmental benefits brought about by chemical fertilizer reduction in greenhouse vegetables in Shouguang area.

Impact of Short Term Irrigation with Different Water Types on Some Chemical and Physical Soil Properties

The concern of this study is determine the quality of soil when irrigation used treated water and wastewater in comparison with soil irrigated with tap water on some chemical and physical soil properties. The experiment components were three trials carried out under greenhouse conditions, 10 pots for each trial. The first trial irrigated with tap water, the second trial irrigated by treated water and the third trial irrigated with wastewater. The experiment conducted to study the impact of water types on some soil physical and chemical properties. The experiment included important analysis for water and soil before and after irrigation. The results showed that the values for electrical conductivity (EC) were 0.850, 308 and 324 μs/cm for the treated soil with tap water, treated water and wastewater, respectively. The variation of pH values seems to be approximately constant between the different of water used. The percent of organic matter (OM) in soils receiving treated water and wastewater 4.7% and 5.2% respectively were higher than values in soil treated with tap water 3%. The same trend was in organic carbon (OC) in soils receiving treated water and wastewater 58.5% and 89% respectively, while soil treated with tap water showed the lowest value 27.7%. Soil particle density (SPD) increased significantly in both water treatments were the values was 2 g/cm3 in tap water but increased value 2.8 g/cm3 and 3.3 g/cm3 in treated water and wastewater used respectively. The Bulk Density (BD) values range 1.1 g/cm3 in soil irrigated with tap water 1.5 g/cm3 in soil irrigated with treated water and 1.85 g/cm3 in soil irrigated with treated water. The results of soil analysis before and after planting showed that most of the values increased for the physical and chemical soil properties.

Effects of Long-term Site-specific Fertilization on Soil Physical and Chemical Properties and Nutrients in Dry Farmland

In order to investigate the variation in soil physical and chemical properties and nutrients in the mountainous areas in southern Ningxia, and to provide a theoretical basis for fertilization management in local farmland, the soil p H, total salt content,crop root length, root weight, soil organic matter, available nitrogen, total nitrogen, total phosphorous and total potassium in different fertilization treatments were measured from 2010 to 2016. Multiple comparisons of the data were performed using Duncan's new multiple range test. The results indicated that in the 0-20 cm soil layer, soil p H value and total salt content changed in different patterns, and varied greatly from 2010 to 2016(P<0.05). The changes of both root length and root weight of millet over time fitted S-shaped curves. The root length and root weight in the four fertilization treatments(Treatment 2 to Treatment5) increased faster than those in the control(Treatment 1). The soil organic matter content in all the five treatments gradually increased from 2010 to 2016. The content of alkaline hydrolyzable nitrogen in soil rapidly increased in the first two to three years of the experiment, followed by a slow increase or decrease in 2013, and then raised rapidly again from 2014 to 2016.The soil total nitrogen content varied significantly from 2010 to 2016. The total phosphorus content in soil changed in a different pattern from that of total nitrogen content. The seven-year field trails revealed that soil p H, total salt content, root length, root weight and soil nutrient all changed with the increase of fertilizer level, and that long-term fertilization is of significance for maintaining soil fertility, improving soil quality and reducing soil salinization.

The Effect of Some Soil Physical and Chemical Properties on Soil Aggregate Stability in Different Locations in Sulaimani and Halabja Governorate

Some soil properties were studied in relation soil aggregate along a climatologically region and different crop land use in the Northeast of Sulaimani City/Kurdistan Region of Iraq. Five locations were selected along these regions ranging from semiarid to sub-humid climatologically conditions. The soil physical, chemical properties, aggregate stability and size distribution were analyzed. A mean-weight-diameter (MWD) value was determined on 5 soils, which was the sum of the percentage of soil on each sieve (6, 3, 1.5, 0.75, 0.375 and 0.125 mm). The results of the measurements could evaluated with linear correlation coefficients for the relationships between aggregate stability (MWD) and soil physical and chemical properties of the different crop land use. The correlation coefficient for the relationship between aggregate stability and organic matter was highly significant (P < 0.0l%) which is in agreement with the findings of [1]. Generally large aggregates (large 6, 3, 3 - 1.5 mm) were present in highest proportions in the most semiarid of the studied areas. Aggregates 0.75 - 0.125 mm were positively correlated to fine, very fine sand and silt fractions and to organic matter. Stability of aggregates showed a positive correlation with clay content and organic matter content, while the carbonate content was strongly correlated with aggregate stability. The land use history affecting soil overlaps the pattern of climatological situations and cultivated crop lands and has to be taken into account. Aggregate size distribution and stability can be used as indicator of soil conservation and productivity.

Improvements of marine clay slurries using chemicale-physical combined method(CPCM)

In this paper, the effectiveness, applicability and validity of chemicalephysical combined methods（CPCMs） for treatment of marine clay （MC） slurries were evaluated. The method CPCM1 combineschemical stabilization and vacuum preloading （VP）, while CPCM2 is similar to CPCM1 but includes boththe application of surcharge and use of geo-bags to provide confinement during surcharge preloading.The key advantage of CPCM2 using geo-bags is that the surcharge can be immediately applied on thechemically stabilized slurries. Two types of geo-bags were investigated under simulated land filling anddyke conditions, respectively. The test results show that the shear strength （cu） of treated slurry byCPCM2 is generally much higher than that by CPCM1. Besides, the use of CPCM2 can significantly reducethe treatment time due to the short drainage paths created by geo-bags. Overall, CPCM2 allows fasterconsolidation and higher preloading that help to achieve higher mechanical properties of the stabilizedslurry. There are consistent relationships between cU and water content of slurries treated by CPCM2.Several important observations were also made based on comparisons of experimental data. 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Effects of land uses on soil physic-chemical properties and erodibility in collapsing-gully alluvial fan of Anxi County,China

the National Key Technologies R＆D Program of China during the 12th Five-Year Plan period （2011BAD31B00）

Effects of Different Farming Methods and Their Effects on Soil Physicochemical Properties of Guilin Maojian Tea Gardens

In order to further optimize the cultivation and agronomic technology of Guilin Maojian tea gardens, the effects, efficiencies and costs of different farming methods and their effects on the physiochemical properties of tea garden soil were studied through the modification of the test sites with the non-farming land as the control. The results showed that human farming, mini-tiller farming and crawler tractor farming could improve the physical and chemical properties of soil. After farming, the soil had good water retention but low moisture content compared to the control group, while the soil bulk density and hardness value were significantly lower than those of the control, and the porosity of soil was significantly higher than that of contrast. With the passage of time, soil bulk density and hardness value gradually increased after farming, while the porosity of soil decreased gradually. There were great differences in the effects, efficiencies and costs of different farming methods. Crawler tractor had the best and most stable farming effect, and the operation efficiency was 10 times that of human farming while the cost was only 0.39 times of human farming. Therefore, it was feasible to adopt mini-tiller or crawler tractor to carry out mechanical farming of Guilin Maojian tea garden, which provided theoretical references for the soil property improvement using mechanical farming and was favorable for promoting the popularization of farming machines and the acceleration of mechanization of tea gardens. But for tea plantations that are intended to be mechanized, apart from the mechanical and technical personnel to be configured in place, the site conditions, planting modes and mechanical way reservation of tea garden should be planned accordingly. It is recommended to select flat or gentle slope for reclamation, and preference is given to non-sexual tea tree varieties with big line spacing over 180 cm long. Moreover, the main road construction should be more than 3.0 m, and trunk road 2.0 m or above. And isolation ditch and drain should be set between the tea garden and the surrounding mountain forests and farmland.

Impact of Seasons on Soil Physico-Chemical Properties and Tea Yields Based on Enriched Sheep Manure Used in Kericho, Kenya

Tea (Camellia sinensis (L) O. Kuntze) is a perennial crop grown for beverage consumption. Its production is the leading foreign exchange earner in Kenya contributing about 26% foreign exchange and 4% GDP. Nitrogen (N), Phosphorus (P) and potassium (K) are the recommended nutrients for tea production. However, their continuous use has been reported to have negative effect on soil physico-chemical properties and health. Sheep manure has been recommended in tea production for its soil pH buffering effect and increased tea yields. However, effects of sheep manure enriched with inorganic fertilizer on tea soils and yield have not been conclusively investigated. This study was established at KALRO—Tea Research Institute Kericho in Timbilil estate to determine the impact of seasonal variation on soil pysico-chemical properties and yields on enriched sheep manure used. Randomized complete block design (RCBD) experimental design was adopted with 14 treatments replicated thrice. The treatments were: control with no fertilizer use, NPK at 180 Kgs N/ha/yr, sheep manure only and two enriched sheep manure ratios of 4:1 and 8:1 which translates to a mixture of (4:1) 4 parts of sheep manure and 1 part of D.A.P inorganic fertilizer. Same applied to 8:1 ratio, respectively at rates of 60, 120, 180 and 240 Kgs N/ha once per year. Data were subjected to ANOVA in GenStat statistical package and means separated by Duncan’s multiple range tests at P ≤ 0.05 significance level. Results obtained showed that soil physico-chemical properties and tea yields were influenced significantly (P ≤ 0.05) by treatments applied. Soil available water and organic matter were higher on enriched sheep manure 4:1 at 240 rate used while soil porosity and bulk density were not significantly affected. Total N and P, increased with enriched sheep manure ratio of 4:1 at 240 rate while K+, Ca2+, Mg2+, Mn and pH increased with sole application of sheep manure at rate 180 and enriched sheep manure 8:1 at 180 rate. Tea yields increased with enriched sheep manure 4:1 ratios at the rates of 240. The findings recommend enriched sheep manure 4:1 ratio at 240 rates to be adopted by tea farmers within Kericho region. Further studies involving different geographical locations are proposed.

Effect of chemical and organic fertilization on soil carbon and nitrogen accumulation in a newly cultivated farmland

Increased food demand from the rapidly growing human population has caused intensive land transition from desert to farmland in arid regions of northwest China. In this developing ecosystem, the optimized fertilization strategies are becoming an urgent need for sustainable crop productivity, efficient resources use, together with the delivery of ecosystems services including soil carbon（C） and nitrogen（N） accumulation. Through a 7-year field experiment with 9 fertilization treatments in a newly cultivated farmland, we tested whether different fertilizations had significant influences on soil C and N accumulation in this developing ecosystem, and also investigated possible mechanisms for this influence. The results showed that applying organic manure in cultivated farmland significantly increased the soil C and N accumulation rates; this influence was greater when it was combined with chemical fertilizer, accumulating 2.01 t C and 0.11 t N ha^（–1） yr^（–1） in the most successful fertilization treatment. These high rates of C and N accumulation were found associated with increased input of C and N, although the relationship between the N accumulation rate and N input was not significant. The improved soil physical properties was observed under only organic manure and integrated fertilization treatments, and the significant relationship between soil C or N and soil physical properties were also found in this study. The results suggest that in newly cultivated farmland, long term organic manure and integrated fertilization can yield significant benefits for soil C and N accumulation, and deliver additional influence on physical properties.

Extended wet sieving method for determination of complete particle size distribution of general soils

The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional method and presents an extended wet sieving method.The extended method uses both the steel sieves and the nylon filter cloth sieves.The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm,0.038 mm,0.014 mm,0.012 mm,0.0063 mm,0.004 mm,0.003 mm,0.002 mm,and 0.001 mm,respectively.The extended method uses five steps to separate the general soil into many material sub-groups of gravel,sand,silt and clay with known particle size ranges.The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups.The extended method is demonstrated with a general soil of completely decomposed granite(CDG)in Hong Kong,China.The silt and clay materials with different particle size ranges are further examined,checked and verified using stereomicroscopic observation,physical and chemical property tests.The results further confirm the correctness of the extended wet sieving method.

武夷山不同种植模式下茶园土壤理化性质和酶活性的季节变化特征

土壤酶活性是表征土壤肥力水平和养分转化的重要指标,揭示种植模式和季节变化对茶园土壤酶活性影响,阐明影响茶园土壤酶活性变化的主要环境因子,为合理评估有机茶种植的土壤生态效应提供理论依据。结合野外调查和室内分析方法,以武夷山茶区3种类型样地,即林地(FD)、常规茶园(CT)和有机茶园(OT)为研究对象,测定了参与土壤碳、氮和磷循环的6种酶活性,研究不同种植模式下土壤酶活性的季节变化规律及影响因子。结果显示,与林地土壤相比,常规种植模式茶园土壤铵态氮、全磷、有效磷和有效钾含量显著增加,土壤全钾和pH显著降低;相比常规茶园,有机茶园土壤有机质和全氮含量显著增加,土壤全磷、有效磷、全钾和速效钾含量显著降低,土壤pH有所增加,土壤养分比例更为协调。种植模式和季节及其交互作用对土壤脲酶和过氧化氢酶活性影响显著。与林地土壤相比,常规茶园土壤脲酶、多酚氧化酶、过氧化氢酶和酸性磷酸酶活性下降了12.05%~63.55%,有机茶园土壤脲酶显著提高了324.95%,种植模式并未改变土壤硝酸还原酶活性。总体而言,夏秋季节(5月和8月)土壤脲酶、多酚氧化酶、蔗糖酶和酸性磷酸酶活性明显高于冬春季节(11月和2月),土壤硝酸还原酶和过氧化氢酶活性在春季最高。置换多元方差分析结果显示,种植模式对土壤整体理化性质的影响远大于季节变化。冗余分析结果显示,土壤环境因子解释了土壤酶活性变异的77.03%,土壤有机质、全氮、铵态氮、全磷、有效磷、全钾、有效钾和pH对土壤酶活性有显著或极显著的影响。综上所述,林地转变为茶园对土壤理化性质和酶活性产生显著影响,常规种植导致茶园土壤速效磷钾积累,土壤酶活性降低,有机种植提高了土壤酶活性,增强了土壤碳氮养分供应能力,具有良好的生态环境效应。

凋落物输入变化对黄河三角洲柽柳人工林土壤有机碳及其组分的影响

为探究凋落物输入变化对土壤有机碳库的影响,明确凋落物对森林生态系统土壤碳循环的作用,以黄河三角洲滨海盐碱地柽柳人工林为研究对象,通过设置添加凋落物(LA)、去除凋落物(LR)和对照(CK)3种处理方法,分析凋落物不同输入变化对土壤理化性质、土壤有机碳及其组分的影响。结果表明:凋落物添加和去除处理影响土壤理化性质的变化,与对照相比,添加凋落物降低了土壤密度和含盐量,增加了土壤含水量和养分(全氮、全磷、全钾),而去除凋落物则相反。3种处理对土壤有机碳(SOC)及其储量以及活性有机碳组分的影响一致,均表现为LA处理影响最大,LR处理影响最小,其中LA处理比CK增加了SOC质量分数及储量,但增加不显著;LR处理则显著降低了SOC质量分数及其储量,土层深度(d)0<d≤10 cm土层,LR处理比CK处理的SOC质量分数及其储量分别显著降低了34.93%、12.66%,10 cm<d≤20 cm土层,LR处理比CK处理的SOC质量分数及其储量分别显著降低了24.27%、16.13%。LA处理的土壤SOC及可溶性有机碳(DOC)、易氧化有机碳(EOC)、微生物量碳(MBC)质量分数均出现明显的表聚现象,而LR处理影响则不显著,且DOC和MBC则出现随土层深度增加而增大的趋势。土壤惰性有机碳(ROC)质量分数在不同土层间存在差异,0<d≤10 cm土层,各处理表现为LA>CK>LR,10 cm<d≤20 cm土层,各处理则表现为CK>LA>LR,而在CK和LR处理出现随土层增加而增加的趋势,偏于向土层下方积累。土壤密度(BD)与SOC及其各组分呈负相关,而土壤含水量(WC)、全氮、全磷与SOC及EOC、MBC、DOC质量分数呈极显著正相关(P<0.01)。因此,不同处理方式及不同土层深度的土壤密度、全氮质量分数和土壤含水量是影响SOC及组分变化的主要环境因子。