Effect of slope position on leaf and fine root C,N and P stoichiometry and rhizosphere soil properties in Tectona grandis plantations

Little is known about C-N-P stoichiometries and content in teak(Tectona grandis)plantations in South China,which are mostly sited on hilly areas with lateritic soil,and the effect of slope position on the accumulation of these elements in trees and rhizosphere soils.Here we analyzed the C,N,P content and stoichiometry in leaves,fine roots and rhizosphere soils of trees on the upper and lower slopes of a 12-year-old teak plantation.The Kraft classification system of tree status was used to sample dominant,subdominant and mean trees at each slope position.The results showed that the C,N and P contents in leaves were higher than in fine roots and rhizosphere soils.The lowest C/N,C/P and N/P ratios were found in rhizosphere soils,and the C/N and C/P ratios in fine roots were higher than in leaves.Nutrient accumulation in leaves,fine roots and rhizosphere soils were significantly influenced by slope position and tree class with their interaction mainly showing a greater effect on rhizosphere soils.Leaf C content and C/N ratio,fine root C and P contents,and C/N and C/P ratios all increased distinctly with declining slope position.The contents of organic matter(SOM),ammonium(NH4+-N),nitrate-nitrogen(NO3--N)and available potassium(AK)in rhizosphere soils were mainly enriched on upper slopes,but exchange calcium(ECa),available phosphorus(AP),and pH were relatively lower.Variations in the C,N and P stoichiometries in trees were mainly attributed to the differences in rhizosphere soil properties.N and P contents showed significant positive linear relationships between leaf and rhizosphere soil,and C content negative linear correlation among leaves,fine roots and rhizosphere soils.Chemical properties of rhizosphere soils,particularly C/N and NH4+-N,had significant effects on the leaf nutrients in trees on the upper slope.Correspondingly,rhizosphere soil properties mainly influenced fine root nutrients on the lower slope,and soil AK was the major influencing factor.Overall,these results offer new insights for the sustainability and management of teak plantations in hilly areas.

The Use of Mineral Nutrients for Biomass Production by Young Birch Stands and Stands Vitality in Different Forest Growing Conditions

The data of field studies about mineral nutrient content in the biomass components of young birch stands （9-15 years old） in different forest growing conditions and soil types have been analyzed. In forest growing conditions on fertile soils （ASG, TSC and SP） the total amount of biomass produced by young birch stands divides into fractions as follows： stem wood 51.8%-59.5%; branch wood 9.8%-12.4%; foliage 5.7%-6.8%; stump wood and roots 25%-30%. In forest types on lean soils （TP） the same indices are 32.3%-41.8%, 18.2%-24.2%, 13.2%-16.1% and 26.8%-27.4%, respectively. The stand performance closely correlates with the basic nutrient （P, N, K, C and Mg） availability in forest soils. In lean typicpodzol soils （TP） the content of mineral nutrients is no higher than 20%-48% of that in more fertile soils （ASG, TSC and SP）. In young birch stands the take-up of mineral nutrients from 0-40 cm soil layer for developing the above-ground biomass makes a fairly small proportion of the total： up to 4.8%-6.2% for P; 4.9%-12.2% for N; 1.1%-4.1% for K; 11.6% for Ca; 0.8%-7.7% for Mg; in leaner soils the same indices are P 0.1%-0.4%, N 1%-1.5%, K 0.2%-0.6%, Ca 0.1%-0.9%, Mg 0.1%-0.8%, respectively. The analyses of pest damages in young birch stands confirm a hypothesis that the degree of pest damage depends on the stand vitality as described by the site index.

Nutrients in litterfall,forest floor and mineral soils in two adjacent forest ecosystems in Greece

The fluxes of masses and the nutrients Ca,Mg,K,N,P and S were determined in the litterfall of two adjacent forest ecosystems of Hungarian oak(Quercus frainetto L.)and European beech(Fagus sylvatica L.)in a mountainous area of northeastern Greece in 2010–2015.The foliar litterfall for both species reached about 70%of the total litterfall,and was significantly higher from the other two fractions(woody and rest litterfall).The fluxes of masses and nutrients were compared between ecosystems for each fraction separately.Only one significant statistical difference was found,that of K in the woody litterfall.In addition,the stocks of masses and nutrients were calculated in the forest floors and mineral soils of the two ecosystems.Likewise,the stocks of nutrients in the forest floors and mineral soils were compared between ecosystems.In the L horizon of the forest floors,statistical differences,as a result of species effect,were found for the stocks of Ca and N.In the FH horizons,the masses and all the nutrient stocks differed significantly,as the beech plot had much higher quantities of organic matter and nutrients.These higher quantities were probably due to low soil temperatures(microclimate)and high acidity in the beech plot(species effect)that slowed down decomposition.In the mineral soils,the propagation of random error derived from random errors of the individual soil layers was an important factor in the statistical comparisons.Because of the soil acidity in the beech plot,the stocks of exchangeable base cations were significantly higher in the oak plot,whereas the other nutrient stocks did not differ.

Nutrient Release Characteristics of Vinyl Chloride-Vinyl acetate Copolymers Coated SlowRelease Nitrogen Fertilizer and Its Effect on Soil Mineral Nitrogen

[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.

Growth and mineral nutrient analysis of teak (Tectona grandis) grown on acidic soils in south China

Teak （Tectona grandis L.f.） is widely planted in the world due to its high market demand, economic, ecological and social value. Its plantations have mostly been established and expanded into sites that are acidic to severely acidic in southern China. But, there are no available and specific evidence-based nutrient management techniques. To better recognize and understand the relationship between teak tree growth and nutrient content in the foliage and soil and establish nutrient norms are critical to optimally manage these young plantations. We studied the foliar nutrient and soil chemistry in 19 representative teak plantations aged 5-8 years. Regression analysis indicated that the mean annual increment of teak volume was linearly and positively correlated with foliar N, Ca, Fe and B concentrations, with soil base saturation percentage, available P and Zn concentrations, and negatively correlated with soil Al concentration. Only if the Ca and Mg contents in soil were enhanced, could the increase in soil base saturation percentage benefit teak growth. A revised classification of low-and high-yielding stands was established by using a sorting method of principal components over 6 foliar macro and 8 micro elements in a Diagnosis and Recommendation Integrated System （DRIS）. Specific DRIS norms for teak plantations in acid soils were derived. The nutrient balance of N, P, K Ca, Mg, Zn, B with Fe or A1, Ca with Mg, and Fe with AI provided a key to promote the growth of teak in acid soils. Meanwhile, soil Zn was also found as a primary trace element that affected teak growth in this study.

Pedo-Transfer Functions to Estimate Kinetic Parameters for Anaerobic Soil Nitrogen Mineralization

Knowledge of potential anaerobic soil N mineralization is important for nitrogen fertilizer application. Instead of time-consuming laboratory incubation, we attempt to use pedo-transfer functions (PTFs) approach to get this information. 27 soil samples with various soil depths were collected from paddy field, woodland and tea field in subtropical central China, anaerobically incubated at 35°C for 7 weeks to determine N mineralization, which was fitted by a modified double exponential model with two parameters (the fraction of active N pool (f) and mineralization rate constant (k) for active N pool). The PTFs for parameters were developed from significant soil properties using multiple stepwise regression method. Parameter f (range: 1.59% - 10.4%, mean: 5.2%) was mainly correlated with soil total N (TN), organic C (SOC), sand and silt particle contents (r = -0.59 - 0.69, p k (range: 0.027 - 0.155 d-1, mean: 0.97 d-1) was significantly related to TN, SOC, clay content, C to N ratio and pH (r = -0.6 - 0.71, p f (R2 = 0.72, p TN and pH) for parameter k (R2 = 0.61, p < 0.01). The developed PTFs, integrating various land uses and soil depths, suggest that basic soil properties are helpful for estimation of anaerobic soil N mineralization.

Black locust coppice stands homogenize soil diazotrophic communities by reducing soil net nitrogen mineralization

Background:Black locust(BL,Robinia pseudoacacia)is considered a promising tree species for reforestation due to its great ability to fix nitrogen.However,after two or three coppice-harvesting rotations,the productivity of BL declines.Whether soil microbial communities are affected and how these groups correlate with the nitrogen mineralization process across multi-generation stands remains unclear.Methods:We investigated the composition and structure of free-living nitrogen-fixing microorganisms(diazotrophs)by sequencing the marker gene nifH and compared these results to levels of soil nitrogen mineralization in the bulk soil and rhizosphere in black locust plantations on Mount Tai,China.Results:The results showed multi-generation BL coppice plantations decreased the total soil nitrogen(N),soil phosphorus(P),soil microbial biomass N(MBN),soil microbial biomass C(MBC),soil nitrification rate(Rn),soil ammonification rate(Ra),and net soil N mineralization rate(Rm),but significantly increased the concentration of soil NH_(4þ)-N to maintain sufficient NO_(3)^(-)N.The dominant species in bulk soil and rhizosphere changed from Rhodopseudomonas(22.62%and 15.76%),unclassified_c_Alphaproteobacteria(22.37%and 29.28%),unclassified_o_Rhizobiales(15.40%and 13.31%),Bradyrhizobium(12.00%and 11.74%)in seedling plantations to Bradyrhizobium(45.95%and 47.86%)and Rhodopseudomonas(43.56%and 41.84%)in coppice plantations,respectively.Mantel test and Redundancy analysis(RDA)revealed that Rn,Ra,and Rm were the most important factors shaping the diazotrophic communities.Conclusions:Our results suggest that the multi-generation BL coppice plantation can homogenize soil diazotrophic communities,which is mainly regulated by the available N loss caused by nitrogen mineralization.Strengthening the management technology of coppice plantations will provide more beneficial external consumption.

Fire alters the availability of soil nutrients and accelerates growth of Eucalyptus grandis in Zambia

Fire has been used to prepare land during tree plantation establishment for many years but uncertainty about how ecosystems respond to prescribed burning makes it difficult to predict the effects of fire on soil nutrients.The aim of this study was to determine the effect of burning accumulated forest residues(slash)on soil chemical properties and how trees respond.We analyzed 40 burned and unburned sites and compared growth of Eucalyptus grandis W.Hill ex Maiden between sites.Soil pH increased by 39%after fire,suggesting reduced soil acidity and increased liming.Total nitrogen increased by 100%;other nutrients(Ca^2+,Mg^2+and K^+)also increased.Increase in nutrients had a significant effect on the growth of E.grandis;larger and taller trees were associated more with burned than unburned sites.This study provides evidence that burning accumulated slash during land preparation prior to plantation establishment alters soil nutrient status and enhances the growth of E.grandis.

Potential of Soil Fertility Management to Improve Essential Mineral Nutrient Concentrations in Vegetables in Dodoma and Kilombero, Tanzania

Collective efforts to fight mineral nutrient malnutrition in humans require consideration of soil fertility management practices (SFMP) in vegetable production. This study aimed at establishing the relationship between SFMP and vegetable nutrient concentration for human health in farming systems of Tanzania. Soil and vegetable samples collected from vegetable growing areas in Kilombero and Dodoma were analyzed for chemical properties and mineral nutrient concentration. Descriptive statistics, analysis of variance and correlation analysis were employed. The results showed that soil pH in Kilombero ranged from 6.04 to 6.8 and in Dodoma ranged from 6.23 to 8.58. The organic C was low, ranged from 0.10% to 1.87%. All soils studied had sufficient Zn (0.45 to 29.3 mg/kg), Cu (0.71 to 3.23 mg/kg), Fe (3.70 to 171.7 mg/kg) and Mn (2.84 to 41.38 mg/kg). Zinc concentration in all vegetables ranged from 12.57 to 134.54 mg/kg, 14% of vegetables had low Zn (<20 mg/kg) for human health. The Cu concentration in vegetables ranged from 0.07 to 52.37 mg/kg, and vegetables from Kilombero had very low Cu (<0.10 mg/kg) for plant and human nutrition. Vegetable Fe and Mn concentration ranged from 152.95 to 1780 mg/kg and 35.10 to 321.82 mg/kg, respectively. The SFMP used did not affect mineral micronutrients concentration in vegetables, but affected soil Zn, Cu, Fe and Mn concentrations. Soil pH, Zn, and CEC correlated with vegetable Cu, K, Mg, Zn, P and Fe concentrations, and differed among soils. Therefore, soil properties differed with SFMP, and both determined mineral concentrations in vegetables for human health.

Nutrient characteristics in rhizosphere of pure and mixed plantations of Manchur ian walnut and Dahurian larch

A comparison study was made for the characteristics of pH value, orga nic matter content, nutrient element N, P and K contents in rhizosphere soils of pure and mixed plantations of Manchurian walnut and Dahurian larch and in bulk soils. The results show that the pH values of rhizosphere soil for all the plant ations except the pure walnut stand, which was slightly higher, were lower than those of bulk soils, while the organic matter contents in the rhizosphere soil f or all the plantations except the mixed plantation, which was slightly lower, we re higher than that in bulk soil. There exists a relative nitrogen accumulation in the rhizosphere and the extent to which the nitrogen accumulates is closely r elated to tree species and mixed pattern. As far as the total P and K contents a re considered, there exists a deficient tendency in rhizosphere in comparison wi th bulk soil. The element N, P and K are all mobilized in the rhizosphere of the pure or mixed plantation, characterized by the higher contents of the available N, P and K in the rhizosphere. The available N content in the rhizosphere of th e larch in mixed plantation was obviously higher than that of its pure plantatio n, whereas the available P and K contents in the rhizosphere of walnut in the mi xed plantation, on the other hand, were significantly higher than those of its p ure plantation.

外源添加L-脯氨酸对棉花黄萎病发生及其根际土壤微生物群落的影响

【目的】根系分泌物是植物与土壤微生物进行互作的信号媒介,对于植物病害发生和植株生长均具有重要调控功能。论文旨在明确棉花根系分泌物L-脯氨酸抵御棉花黄萎病发生的微生态机制,揭示L-脯氨酸介导的根际微生物与棉花黄萎病发生的互作关系,为构建生物防治土传病害的有益菌群提供新视角。【方法】通过温室盆栽试验,以外源添加不同浓度的L-脯氨酸(0、50、100、200和400 mmol·L^(-1))为试验处理,采用实时荧光定量PCR(real-time qPCR)和宏基因组测序技术分别测定不同处理的土壤中大丽轮枝菌(Verticillium dahliae)DNA拷贝数量和土壤微生物群落结构及功能,采用主成分分析比较不同处理的根际土壤微生物群落结构,利用冗余分析研究土壤养分因子与微生物群落结构的相关性,利用斯皮尔曼相关分析研究微生物群落结构功能代谢途径的相关性。【结果】与空白对照相比,低浓度(50 mmol·L^(-1))L-脯氨酸处理不能够减轻棉花黄萎病的发生,高浓度(100、200和400 mmol·L^(-1))L-脯氨酸处理的病情指数分别下降22.51%、60.23%和64.23%。qPCR结果表明,L-脯氨酸处理不能够显著降低土壤中大丽轮枝菌拷贝数量。宏基因组测序分析表明,L-脯氨酸处理后细菌多样性Shannon指数显著增加,真菌多样性Shannon指数呈下降趋势。在属水平上,L-脯氨酸处理后类诺卡氏菌属(Nocardioides)、溶杆菌属(Lysobacter)、节杆菌属(Arthrobacter)、Phycicoccus、假单胞菌属(Pseudomonas)和毛霉菌属(Mucor)的相对丰度呈上升趋势。线性判别分析表明,除浓度为100 mmol·L^(-1)的L-脯氨酸外,外源添加L-脯氨酸处理后根际土壤微生物KEGG通路的富集情况发生改变。冗余分析表明,细菌群落组成受pH、电导率、硝态氮、铵态氮和有机质显著影响,而真菌群落组成与铵态氮存在显著相关性。Spearman相关分析表明,细菌的KEGG代谢通路与pH、有机质、铵态氮含量呈负相关关系,而与电导率和硝态氮呈正相关关系;真菌的大部分KEGG代谢通路与土壤养分的相关性较差。【结论】外源添加适量L-脯氨酸通过改变土壤细菌群落结构和功能,增加有益微生物的相对丰度,从而影响棉花黄萎病的发生,但其不能够改变病原菌数量。同时,根际细菌群落组成和功能均与土壤养分存在相关性。

间套种模式对喀斯特地区核桃根际土壤养分和微生态环境的影响

为探究喀斯特地区间套种核桃对根际土壤养分及微生态环境的影响,该研究以桂西北喀斯特地区间套种核桃-桑树(H-SS)、核桃-十大功劳(H-SD)、核桃-玉米(H-YM)以及核桃单种(H-D)的核桃根际和非根际土壤为试验对象,基于室内化学实验和Illumina Miseq PE300高通量测序技术,分析不同种植模式下核桃根际与非根际土壤理化性质和微生物特征。结果表明:(1)不同模式核桃根际土壤对全氮(TN)、全磷(TP)、全钾(TK)、速效磷(AP)、土壤有机碳(SOC)和交换性钙主要表现为不同程度的富集作用,对速效氮(AN)有亏缺现象。H-SS对TN、TP和SOC富集作用明显,H-YM富集AP、速效钾(AK)和交换性钙的效果最佳。(2)蔗糖酶活性、微生物量碳、氮及细菌均出现明显的根际效应,H-YM的蔗糖酶活性、磷酸酶活性和微生物量碳最高,但间套种模式降低了微生物量氮和细菌的根际效应。(3)3种间套种模式下根际土壤细菌Shannon指数均高于核桃单种。(4)根际土壤微生物多样性主要受养分影响,非根际主要受酶活性影响。综上认为,间套种能够提高根际养分富集率、增强土壤酶活性、促进微生物增殖。此中,H-SS根际土壤对TN、TP和SOC的富集作用明显,其土壤细菌含量也最高;H-YM根际土壤富集AP、AK和交换性钙的效果更佳。在实际生产中可根据当地经营习俗选择桑树或玉米进行间套种。

与玉米间作促进苍术根际养分吸收利用的原因

与玉米间作能够缓解苍术连作障碍,而养分条件变化是关键因素之一。为探究苍术||玉米间作对苍术根际养分吸收利用的影响,本研究开展了为期2年的苍术||玉米间作根际不同分隔处理的田间试验,共设置了4种处理:苍术单作(A)、苍术||玉米间作不隔膜(AI)、苍术||玉米间作隔尼龙膜(AN)和苍术||玉米间作隔塑料膜(AP),分别测定了苍术生物量和4种挥发油成分含量,苍术根茎氮磷钾含量,根际土壤pH、有机质和土壤养分因子含量。结果发现,AI和AN处理的苍术根茎鲜重均高于A和AP,且AI与A和AP的差异达显著水平(P<0.05)。苍术4种挥发油含量均表现为AI和AN高于A和AP,其中AI的β-桉叶醇含量分别比A和AP显著高128.4%和205.6%(P<0.05),AI和AN的苍术素含量比A和AP显著提高75.0%~875.0%(P<0.05);相比A和AP,AI和AN的苍术根茎4种挥发油成分总含量显著提高82.8%~210.3%(P<0.05),表明苍术||玉米间作的地下根际互作对促进苍术根茎生物量和挥发油积累有重要作用。AI和AN比A和AP苍术根际土壤pH下降0.4%~6.3%、土壤有机质含量提高13.5%~48.1%;AI的苍术根际土壤碱解氮含量分别比A和AP显著提高32.8%和36.2%(P<0.05),AN的速效钾含量分别显著提高51.5%和46.7%(P<0.05)。相关性分析发现,苍术酮主要与苍术根茎氮磷钾含量和根际土壤氮磷钾含量呈正相关,而苍术素主要与根茎钾含量呈正相关。与A和AP相比,AI苍术磷吸收效率分别提高23.4%和30.0%(P<0.05);AI和AN的氮和钾利用效率比A显著提高131.3%~222.2%(P<0.05)。综上可知,苍术||玉米间作体系中,与无根际互作(A和AP)相比,地下根际互作效应(AI和AN)可提高苍术根际酸化水平,活化土壤氮磷钾,促进苍术根茎养分吸收利用,进而提高苍术产量,同时影响苍术根茎挥发油积累。本研究揭示了苍术||玉米间作地下根际作用是促进苍术根际养分吸收利用的重要因素,为药用植物生态多样性种植模式推广提供重要参考。

森林根际土壤细菌的分离、鉴定及生物活性筛选

【目的】从无量山国家级自然保护区森林根际土壤发掘具有多种生物活性的功能菌株,探究其开发应用潜力。【方法】采集无量山地区25个区域植物的根际土壤,采用选择培养基,分离鉴定磷酸盐溶解、固氮、溶锌和拮抗等活性菌株,进一步测定菌株分泌铁载体、ACC脱氨酶和吲哚乙酸等生物活性,并验证促番茄种子发芽和生长效果。【结果】分离鉴定得到解磷菌70株,固氮菌27株,解钾菌8株,拮抗镰刀菌的菌株51株。其中,YIM B08401和YIM B08402形态学结合生理生化特性和16S rDNA序列测序,鉴定为白色伯克霍尔德氏菌(Burkholderia alba)和青岛假单胞菌(Pseudomonas qingdaonensis),两个菌株均具有磷酸盐溶解、固氮、溶锌和分泌铁载体的活性,最大可溶性磷含量为(455.63±59.65)mg/L和(878.95±64.78)mg/L;两株菌的促种子发芽试验结果接近,施加稀释10倍、10^(2)倍和10^(3)倍的发酵上清液后,发芽率都维持在82%-93%,明显高于对照组的56%和49%,施加菌株发酵液的处理组相较于空白对照组的长度都有显著增加。盆栽实验证明,两株菌株促生效果最明显的处理组在地上部长度、鲜重、干重、茎粗、根长、根鲜重、根干重方面的数据都显著优于对照组,YIM B08401的上述指标相对于对照组分别显著增加了89%、495%、268%、62%、53%、385%和469%,YIM B08402的上述指标相对于对照组分别显著增加了118%、528%、477%、55%、37%、413%和747%。此外,菌株YIM B08401还具有拮抗病原菌和分泌ACC脱氨酶活性,YIM B08402则还具有分泌吲哚乙酸的活性。【结论】无量山森林根际土壤蕴含具有多种生物活性的功能菌株,白色伯克霍尔德氏菌(B. alba, YIM B08401)和青岛假单胞菌(P. qingdaonensis, YIM B08402)具备开发为新型微生物肥料的应用潜力。

腐植酸尿素对土壤矿质氮含量及生菜品质的影响

为探究腐植酸尿素对蔬菜品质的影响,以半结球生菜为指示作物,设CK(不施氮肥)、T1(常规尿素)、T2(腐植酸尿素)、T3(商品有机肥)4个处理,测定根际和非根际土壤铵态氮、硝态氮含量及变化,以及生菜硝酸盐、草酸、亚硝酸盐、可溶性总糖、维生素C含量等品质指标,采用隶属函数法评价腐植酸尿素对生菜品质的综合影响。结果表明,与非根际土壤结果一致,腐植酸尿素处理的平均根际土壤矿质氮(铵态氮+硝态氮)含量(w)为137.77 mg·kg^(-1),高于其他处理,且以硝态氮为主。随着种植茬数增加,腐植酸尿素处理的土壤铵态氮、硝态氮富集率由正转负。腐植酸尿素处理的生菜可食部分鲜质量显著高于常规尿素处理。土壤铵态氮含量与可食部分鲜质量呈显著正相关,蔬菜硝酸盐含量与土壤硝态氮含量呈显著正相关。综上所述,腐植酸尿素有利于高品质蔬菜生产,但其对土壤铵态氮、硝态氮的调控机制仍需进一步研究。

有机肥配施生物质炭对根际/非根际土壤氮赋存形态的影响

阐明化肥和有机肥配施生物质炭对根际/非根际土壤养分和氮赋存形态的影响,有助于农田氮的高效利用及科学管理。采用盆栽试验方法,设置不施肥(CK)、单施化肥(CF)、施有机肥(M)、化肥配施生物质炭(CFB)、有机肥配施生物质炭(MB)、新鲜有机肥配施生物质炭(FMB)6个处理,通过测定根际及非根际土壤养分含量和土壤氮赋存形态,阐明不同施肥处理对氮形态转化的影响。结果表明:与CK处理相比,MB处理提高非根际及根际土壤pH 0.32和0.28个单位,FMB处理提高根际土壤pH 0.63个单位;MB和FMB处理分别提高根际土壤有机质含量25.4%和84.9%,同时显著提高根际土壤全氮含量25.4%和50.9%,表现出明显的根际效应。施肥能显著提高土壤离子交换态氮(IEF-N)含量,以CF和CFB处理的效果最好。施用有机肥和生物质炭能显著提高土壤碳酸盐结合态氮(CF-N)含量,以M和MB处理效果最好,且CF-N存在根际富集效应。配施生物质炭(CFB、MB和FMB)处理能促进土壤非可转化态氮(NTF-N)向铁锰氧化物结合态氮(IMOF-N)和有机硫化物结合态氮(OSF-N)这两种活性更高的氮形态转化,其中IMOF-N和OSF-N分别占可转化态氮的35.9%~61.7%和26.7%~46.6%,是根际及非根际土壤可转化态氮(TF-N)的主要成分。因此,有机肥配施生物质炭是改善根际及非根际土壤养分和调控氮转化有效的方式。

不同刈割时间对南北疆油莎豆根际土壤养分和盐基离子含量的影响

【目的】探究不同刈割时间对南北疆油莎豆(Cyperus esculentus)根际土壤养分和盐基离子的影响。【方法】2021年5月15日在南疆莎车县北疆阜康市种植油莎豆,分别于播种后第78、91、106和124天采集油莎豆根际土壤样品进行养分和盐基离子分析测定。【结果】采样点和刈割时间显著影响了油莎豆根际土壤的pH(P<0.05);采样点和刈割时间的交互作用显著影响了油莎豆根际土壤的pH、全氮、全磷和全钾含量(P<0.05),对油莎豆根际土壤的离子含量均没有显著影响。北疆油莎豆根际土壤的全氮、全钾、速效磷和速效钾含量显著高于南疆(P<0.05),但北疆的阳离子(钠离子、钾离子、钙离子和镁离子)含量显著低于南疆(P<0.05)。在北疆地区,油莎豆根际土壤的pH与速效钾和氯离子含量呈显著负相关关系(P<0.05),与碳酸氢根离子含量呈显著正相关关系(P<0.05)。在南疆地区,油莎豆根际土壤的pH与速效钾含量呈显著负相关关系(P<0.05),与氯离子和钠离子含量呈正相关关系。【结论】刈割改变了南北疆种植油莎豆根际土壤全钾、速效钾和速效磷含量及pH值,改变了北疆油莎豆根际土壤氯离子含量,但刈割时间和采样点(北疆)的交互作用对土壤全氮和全磷的影响最大,为实际生产中在新疆区域推广种植油莎豆提供理论依据。

氮添加对华北落叶松根际与非养分的影响

[目的]大气氮沉降对森林根际与非根际土壤养分有重要影响。华北地区是我国氮沉降高值区之一,然而目前关于氮沉降对该地区森林土壤养分影响的阈值及其是否引起其它养分限制还不清楚。[方法]本研究以河北省木兰林场国有林场的华北落叶松人工林为研究对象,通过多水平氮添加实验(0、5、10、20、40、80、160 kg N·ha^(-1)·yr^(-1)),分析氮添加对根际和非根际土壤在全量养分、速效养分及其生态化学计量的差异影响,旨在揭示氮添加对华北落叶松人工林根际效应的影响。[结果]研究表明:1)根际土壤有机碳(SOC)、总氮(TN)、硝态氮(NO_(3)^(-)-N)和有效氮(AN)含量随氮添加水平呈上升趋势,且都在氮添加为80 kg N·ha^(-1)·yr^(-1)时达到最高值,与对照组相比增加了39.55%、36.27%、56.69%、44.02%。2)非根际土壤NO_(3)^(-)-N在氮添加为160 kg N·ha^(-1)·yr^(-1)时达到最大,与对照组存在显著性差异,不同氮添加水平下SOC、TN、TP含量等均无显著变化。3)随着氮添加水平的增加,根际土壤的C∶P、N∶P呈上升趋势,非根际土壤的C∶P、N∶P呈下降趋势。4)相对于对照组,氮添加后土壤SOC、TN、NO_(3)^(-)-N、AN、AP、C∶P、N∶P的根际效应呈增加趋势。[结论]本研究表明,氮添加会增强根际效应,提高华北落叶松人工林根际土壤SOC、TN、NO_(3)^(-)-N、AN的含量,且阈值均在80 kg N·ha^(-1)·yr^(-1),而且氮添加会改变土壤磷元素平衡,华北落叶松人工林生长未来可能会面临土壤磷限制。本研究可为大气氮沉降或施肥措施下华北落叶松人工林的养分调控提供理论和科学依据。

紫花苜蓿/甜高粱间作对根际土壤特性及微生物群落特征的影响

为探究紫花苜蓿/甜高粱间作体系对根际土壤微生态环境的影响,改善土壤结构、维持良好的土壤微生态环境和实现土地生态保护提供理论依据,本研究以紫花苜蓿和甜高粱为对象,对其连续3年单作和间作种植下的结瘤固氮特性、根际土壤养分、土壤酶活性以及种植第3年的土壤微生物群落特征及其之间的相互关系进行研究。结果表明:紫花苜蓿/甜高粱间作系统内的变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和芽孢杆菌属(Bacillus)为主要优势菌群,且与单作相比,间作有效提高了根际土壤中的拟杆菌门、变形菌门、放线菌门(Actinobacteria)和Gp6相对丰度,显著提高了甜高粱根际土壤有机质含量、有效磷含量、脲酶活性和蔗糖酶活性(P<0.05),显著提高了紫花苜蓿固氮酶活性和单株固氮潜力(P<0.05),同时显著降低了间作中2种牧草的根际土壤pH值(P<0.05)。间作紫花苜蓿根际土壤碱性磷酸酶和蔗糖酶的活性随着年份的增加逐年提升,同时3种种植模式下根际土壤pH值均随年份的增加显著降低(P<0.05)。相关性分析发现,4个根际土壤酶与碱解氮、速效钾和有机质呈极显著正相关(P<0.01);变形菌门和拟杆菌门与pH值呈极显著负相关,与碱解氮呈极显著正相关,而酸杆菌门(Acidobacteria)和疣微菌门(Verrucomicrobia)与pH值呈极显著正相关,与碱解氮呈极显著负相关(P<0.01)。因此,紫花苜蓿/甜高粱间作可以改善根际土壤结构,提高土壤微生物活性。

川黄檗不同树龄矿质元素含量及其与根际土壤因子的相关性分析

【目的】探究川黄檗不同树龄各部位和根际土壤中矿质元素含量变化规律,以及矿质元素和土壤因子相关性,以期为川黄檗幼龄林营养诊断、科学施肥提供依据。【方法】以川黄檗1~3年生苗木为试材,对不同部位(叶、当年生枝和根)和根际土壤中矿质元素含量及其变化规律进行研究,并分析了根际土壤与不同部位间以及各部位中矿质元素间的相关性,进而评价不同部位对土壤中矿质营养元素的富集能力。【结果】1)不同树龄和不同部位矿质元素含量具有一定的差异,且随着树龄的增加,叶中N、Ca、Cu和Zn,当年生枝中P和Cu以及根中Mg含量显著下降(P<0.05)。2)不同树龄根际土壤矿质元素含量差异显著(P<0.05),随着树龄增加,Ca、Mn和Zn含量显著增加(P<0.05),Fe含量显著下降(P<0.05);元素含量大小为:N>K>Ca>Fe>P>Mn>Mg>Cu>Zn。3)川黄檗对根际土壤中矿质元素的富集能力不同,对Ca、Mg的富集能力较强,对N、P和K的富集能力居中,对Fe、Mn和Cu的富集能力较低。4)叶中K与P,当年生枝及根中的N与K间均存在显著正相关(P<0.05),各部位N与多种元素相关性显著(P<0.05);土壤中元素与叶、根中多种元素显著相关(P<0.05)。【结论】川黄檗幼龄林不同生长年限各部位及土壤中矿质元素含量呈现不同的变化规律,各部位元素之间及与土壤中矿质元素既有协同作用又有拮抗作用,不同部位对矿质营养元素具有不同的富集能力。依据研究结果,川黄檗幼龄林施肥时应该注意补充叶中N、Ca、Cu和Zn,同时合理搭配P和Mg等元素,注意用量的协调,保证植株营养均衡。