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1.
本研究结合近年来国内外土壤动物的相关研究,基于前人研究的成果,在概述土壤动物多样性的基础上,详细介绍了如蚯蚓、蚂蚁和线虫、弹尾虫等不同种类且具代表性土壤动物的生态功能,以及与各环境因子如何产生相互作用关系。尽管国内外很多学者已对土壤动物多样性有诸多研究,但其生态功能及自身与不同环境因子相互影响以及如何作用还鲜有报道。故笔者归纳了土壤动物多样性、生态功能以及与自然环境因子（如大气氮(N)沉降、植被类型、土壤环境等）和人为干扰（如开垦、火烧等）因子影响下的相互作用机理,并讨论了土壤动物生态功能以及未来研究热点等,以期为更好地理解陆地生态系统中土壤动物如何在地下生态过程中发挥作用提供依据。  相似文献   

2.
通过长期定位试验,研究不同施肥处理对河北省低平原区土壤有机质、不同氮形态含量及作物产量的影响,旨在为该区冬小麦–夏玉米轮作系统秸秆全量还田下土壤肥力和作物产量的提高提供理论依据。结果表明,经过36个小麦玉米轮作周期的不同施肥处理后,与不施肥处理（CK）相比,施肥可以提高土壤有机质和全氮含量,且随化肥施用量的增加而逐渐增加。在化肥施用量≤N 360kg/hm2+P2O5 240kg/hm2时,秸秆还田较不还田可显著提高土壤有机质和全氮含量,在化肥施用量为N 540kg/hm2+P2O5 360kg/hm2时,增加速度减缓。与CK相比,长期施肥提高了土壤碱解氮和硝态氮含量,而对土壤铵态氮含量没有显著影响。单施化肥时,表层土壤碱解氮和硝态氮含量随氮肥施用量的增加而增加;在秸秆还田下,N360+P240+S9000处理表层土壤碱解氮和硝态氮含量最高。施肥显著提高了作物产量,单施化肥处理,小麦、玉米产量均随施肥量的增加而逐渐增加;秸秆还田条件下,小麦产量在化肥施用量≤N 360kg/hm2+P2O5 240kg/hm2时较单独施用化肥的处理增产。由以上结果可知,长期施肥可提高土壤肥力,增加土壤有机质和全氮含量,适宜的氮肥施用量配合秸秆还田可固持土壤有机碳和全氮,过量氮肥不利于土壤有机质的累积。长期单施化肥或化肥配合秸秆还田均可提高土壤碱解氮和硝态氮含量,对土壤铵态氮含量无显著影响。长期施肥可提高作物产量,在秸秆还田条件下,化肥施用量为N 360kg/hm2+P2O5 240kg/hm2时,增产效果较好。  相似文献   

3.
夏玉米产量及茎秆抗倒伏性状对不同肥料滴灌配施的响应   总被引：2，自引：0，他引：2  
为探索密植玉米群体茎秆质量改善,抗倒伏能力提高的技术途径和措施,大田滴灌条件下研究了不同肥料配施对夏玉米生长发育及与茎秆质量、抗倒伏相关的农学性状和力学性状的影响。试验设置5个肥料配施处理:仅施氮肥(N)、氮配施磷肥(N+P)、氮配施钾肥(N+K)、氮配施4种微肥(N+4M)、氮配施磷钾和4种微肥(N+P+K+4M),并以传统施肥方式(全部肥料一次性底施)为对照(CK)。结果表明,与传统施肥相比,滴灌配施钾肥显著增加了玉米干物质积累量和籽粒产量,各器官干物质积累分配模式也得以优化,同时控制株高和重心高度、缩短基部节间、增加基部节间的直径、干质量从而使单位长度干质量显著增加。玉米茎秆的抗弯曲力、穿刺强度、机械强度以及抗倒伏指数与株高、重心高度和基部节间长呈负相关或(极)显著负相关,而与植株干鲜质量以及基部节间直径、干质量和单位长度干质量呈正相关或(极)显著正相关。滴灌条件下不同肥料配施玉米茎秆的抗弯曲力、穿刺强度、机械强度显著以及抗倒伏指数都高于或者显著高于传统施肥方式,尤其是配施钾肥处理效果最为明显,这可为该地区玉米密植抗倒高产提供理论依据。  相似文献   

4.
探讨不同土壤改良措施对土壤物理性质、养分、微生物和甘蔗产量的影响,对机械压实后酸性土壤改良策略的制定具有较为重要的意义。本研究设置添加松土精(B2)、添加生物菌肥(B3)、添加有机肥(B4)、添加生石灰(B5)4种土壤改良处理,以不添加土壤改良剂作为对照(B1),连续2个作物季对蔗地土壤物理性质、养分、微生物和甘蔗产量构成等指标进行研究。结果表明, B4处理可显著降低土壤容重、紧实度、贯入阻力和抗剪强度,提高土壤总孔隙度、通气孔隙度和毛孔孔隙度,其固相容积率显著低于对照,液相容积率显著高于对照,土壤有机质含量、全氮含量得到显著提升, B2、B3处理紧实度和总孔隙度降低,土壤物理性状得到一定改善, B5处理土壤pH值显著提升,土壤酸性得到改善, B3、B5处理土壤有效磷含量得到显著提升。4种土壤改良措施土壤细菌和真菌Shannon指数、Chao1指数和ACE指数均高于对照,均能提升土壤耕层细菌和真菌的物种多样性和物种丰富度,降低土壤细菌中Proteobacteria (变形菌门)和Acidobacteria (酸杆菌门)的相对丰度、真菌中Basidiomycota (担子菌门)的相对丰度,增加细菌中Actinobacteria (放线菌)和Chloroflexi (绿弯菌门)的相对丰度、真菌中Ascomycota (子囊菌门)的相对丰度,并改变其他真菌群落组成。4种土壤改良措施均可不同程度地提高成熟期甘蔗有效茎数和单茎重,从而增加甘蔗产量;效果以添加有机肥最好,生物菌肥其次。本研究为筛选适合改良和培肥机械压实酸性土壤措施,提高甘蔗产量提供了科学依据。  相似文献   

5.
不同氮利用效率基因型水稻茎秆特性比较   总被引：12，自引：5，他引：7  
选用低产氮低效型、高产氮中效型和高产氮高效型具有代表性的6个粳稻品种,在各基因型各自最适氮素水平下,研究了茎秆力学特性、物理特性和化学成分含量的差异及其与氮效率的关系。结果表明：(1)较之低产类型品种,高产类型品种茎秆基部N1节间变短、N6节间变长,株高有所增加;茎粗、茎壁厚、茎鞘干重均极显著增加;茎鞘的K、Si含量极显著增加,N含量显著降低。由于茎秆物理性状的改善及化学成分的差异导致茎秆综合抗折力明显提高,倒伏指数降低。(2)同为高生产力类型品种,因氮效率的差异茎秆形态生理特征表现不同。较之高产氮中效类型,高产氮高效类型水稻品种茎秆N4、N5节间变长;茎秆粗度略有降低,但茎壁厚增加,表现茎秆干重增加,充实度加强;茎鞘的K含量无明显变化,但Si含量显著降低,N含量也呈降低趋势。对于高产品种,适当增加N4、N5节间长度以改善叶片配置,适当降低茎粗而提高壁厚和充实度以保证茎秆抗折力和输导能力,适当降低茎鞘Si含量以促进氮素的转移,有利于进一步提高氮肥利用率。  相似文献   

6.
黄河源区河漫滩湿地退化过程土壤的变化特征   总被引：1，自引：0，他引：1  
笔者从黄河源区河漫滩湿地地理地形指标和土壤指标出发,分析和研究黄河源区河漫滩湿地退化过程中土壤变化特征。结果表明：黄河源区河漫滩湿地不同退化阶段土壤的酸碱值大于pH 7 时,pH随退化程度加剧有明显减少;随着退化梯度的加剧,土壤含水量减少,草土比也逐渐减小;黄河源区河漫滩湿地退化土壤为松砂土,黄河源区河漫滩湿地随着退化程度的加剧小于0.01 mm物理黏粒含量基本上呈现减少的趋势;黄河源区河漫滩湿地主要养分在垂直方向上都表现出上层高于下层的规律,土壤有机质和全氮随着湿地退化都呈现了逐渐减少的规律。多重比较的结果,全N、全K和有机质,在退化阶段5 与阶段1、阶段2、阶段3 和阶段4 之间差异显著(P＜0.05),阶段1、阶段2、阶段3 和阶段4 之间差异不显著;碱解N在退化阶段2 与阶段5 之间差异显著(P＜0.05),阶段1、阶段3 和阶段4 之间差异不显著;全P、速效P和速效K在河漫滩湿地退化过程中差异虽未达到显著水平,但随着退化进展,速效P是呈现出减少趋势,全P和速效K呈现出增加趋势。  相似文献   

7.
The prefabricated pile,driven in soft clay,can squeeze the soil laterally in a certain scope around the pile,and the void ratio is reduced significantly;consequently,the shear bearing capacity is raised.But the soil parameter,which is used to estimate the capacity of pile,is reduced according to the soil state before the pile was driven.Then,a certain difference appears when the pile is working.The calculation result usually is partial to conservative.This paper analyzes the squeezing mechanism of the pile using the theory of cylindrical cavities expansion.And a formula,which is used to estimate the increment of shear bearing capacity of soil around the pile when excess pore water pressure from pile driving distributes completely,is presented based on the unique relation between the shear bearing capacity and the density of the soil.This formula can be used to estimate the final ultimate-bearing capacity of the pile.The calculated results by the proposed formula are in good agreement with those of the site measurement.  相似文献   

8.
Bearing capacity behavior of roll forming filling screw pile (screw pile for short) is investigated through numerical calculation and static load test. The influence of pile-type parameters, such as width of thread tooth and thread pitch, on the ultimate bearing capacity of crew pile is studied; furthermore, the bearing capacity behavior of screw pile and that of pile with the same diameter are compared and analyzed through static load test. The results show that the ultimate bearing capacity of screw pile is a bit higher than that of pile with the same outside diameter; width of thread tooth has a distinct effect on ultimate bearing capacity which increases with the increment of width of thread tooth. When the screw pile is tested under light load, the resistance on pile side is distributed along screw pile, and tip resistance is small, but the resistance rises considerably with load increasing. Besides, the design formula of bearing capacity of screw pile is proposed.  相似文献   

9.
The effectiveness of equivalent strip model calculating the horizontal ultimate bearing capacity of multi-story steel plate shear walls(SPSW)by using the software SAP2000 to make Pushover analysis was demonstrated by comparing the simulated values with results from experimental studies performed by different researchers.The effect of different slenderness ratios on the ultimate bearing capacity of four-story single-span SPSW and four-story three-span dual steel shear walls system subjected to the inverse triangular load was obtained by the verified analytical model,which was compared with the performance of corresponding bare frames.The slenderness ratio of 250~300 is suggested for the design of SPSW.  相似文献   

10.
Four series stud push-out specimens were conducted to study static mechanical behavior when stud shear connectors of composite beams were corroded. Firstly, the studs were manually rapidly corroded by electrochemical methods, and then a static load test was performed on them. Test results show that when corrosion occurs at stud rod especially close to combined surface, the ultimate bearing capacity reduces most by 18%, slip under the same load increases, and slip relative to the ultimate load reduces most by 12%. When corrosion occurs at the large end of stud, it has little effect on ultimate bearing capacity of push-out specimens, but deformation performance of stud shear connectors is affected seriously.  相似文献   

11.
不同加载方式SIP墙体的抗剪性能   总被引：1，自引：0，他引：1  
以3种不同的单向加载方式对以木质OSB覆面的SIP墙体进行侧向加载实验,对比分析3种加载方式下SIP墙体的破坏形式及这3种加载方式对墙体抗剪性能参数的影响,结果表明:3种加载方式得到的墙体的抗剪性能指标有所差异,其中,采用ISO22452加载协议,即对墙体施加持续增加载荷的加载方式所得到的极限承载力最大、极限位移和延性系数居中,分别为46.06 kN、71.83 mm、3.31;采用ASTM E72-05加载时极限承载力居中、极限位移及延性系数最大,分别为:40.66 kN、76.97 mm、4.07。采用ASTM E564-06加载,即对墙体施加阶段载荷并使阶段目标载荷持续作用一段时间的方式,所得到的极限承载力、极限位移及延性系数最小,分别为37.73 kN、54.92 mm、2.91;3种加载方式对墙体破坏形式的影响不大。  相似文献   

12.
According to the theory of truss-arch model, the shear mechanism of reinforced concrete beam was analyzed, and formula of shear bearing capacity was proposed. In this formula, softening effect of concrete and the arch function were taken into account, and the coefficients in the formula were amended with experimental data. When the performance difference between the structural material and the original material is huge, the code formula of shear bearing capacity calculation is inapplicable. After the computation, the ratio of the results calculated by truss-arch model theory formula and the results calculated by the current code formula was close to 1, and the standard deviation coefficient and coefficient of variation were smaller than those of standard formula results, and the results calculated by truss-arch model formula were in good agreement with the experimental results. The collected experimental data was calculated with the shear capacity formula in ACI318-08, and the calculation results showed that United States building code was more conservative than the standard of China. The results indicate that the shear bearing capacity formula based on truss-arch model can be used for computation of shear bearing capacity of reinforced concrete beams.  相似文献   

13.
For the convenience of industrialized production and site operation,specification design of PPCRP (precast prestressed concrete ribbed panels) is discussed. In order to obtain ultimate bearing capacity,bending rigidity and crack resistance,four PPCRP with two types of spans are studied,and the results show that PPCRP can satisfy the requirements of bearing capacity in construction phase and can serve as stay-in place formwork. To verify the mechanical property,shear behavior on contact interface of composite member and moment redistribution factor of continuous composite member,two single-span composite members and one two-span continuous composite member are studied. It is indicated that computational method for bearing capacity of composite member can be the same as cast-in-situ concrete slab. Besides,section strain analysis for composite member in two-loading is conducted,which suggests that thickness of bottom board can be used as calculated height with the consideration of two-loading.  相似文献   

14.
In order to study the mechanical behaviors of irregular joints in rigid steel frames which had been used in large scale power plant, 6 specimens in 1/4 scale of the prototype model were designed according to different axial compression ratio and section height ratio of beams and were tested under low cyclic reversed loading.Based on the failure law of specimens, the main factors that affect the bearing capacity of the irregular joints were analyzed.By the division of panel zone, the calculating formula was put forward according to mechanical principles.It is found that the difference between calculating results and experimental results is about 18%.And the proposed method for calculating the irregular joints in rigid steel frames is feasible.  相似文献   

15.
The calculation on working resistances of supports has been one of key research questions for coal faces with sublevel caving. Based on experimental results of mechanical property of top-coal, it is the top-coal failure strength meeting Mohr-Coulomb Theory that is summed up. According to force characteristic of top-coal body in coal face with sublevel caving, using strain-equivalent principle of Damage Mechanics, the authors set up bearing mechanical model for top-coal body within face width. From the top-coal bearing capacity point of view, the interaction relationship between supports and top-coal body is studied. Theoretical calculation formula on working resistance of supports is deduced. Ground press behaviors which working with resistances of supports are increased with top-coal strength increment were better explained with this model. The conclusions have a definite direction value for calculating working resistances of supports in coal faces with sublevel caving.  相似文献   

16.
影响基础上拔承载能力的因素包括地基土物理力学参数及基础尺寸参数,而确定混凝土方量最小、基础上拔承载力最大的基础参数配比是基础优化设计的关键。以戈壁滩碎石土地基中的原状土扩底基础为研究对象,采用正交设计方法,以立柱直径、深宽比、扩展角为影响因素,以基础上拔承载力为分析指标,设计出9组尺寸的足尺基础。通过现场试验,获得了各试验基础的荷载位移曲线和上拔承载力值,提出了采用渐变率的概念表征荷载位移曲线的非线性变化特征,通过分析发现基础荷载位移曲线渐变率与承载能力呈负相关。结合正交试验分析结果,得出立柱直径、深宽比、扩展角3个因素中对碎石土地基原状土扩底基础抗拔承载能力的影响程度由大到小依次为深宽比、立柱直径、扩展角,表明在戈壁滩碎石土地基基础的工程设计中增加深宽比能提高基础抗拔承载能力。  相似文献   

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