退耕地三倍体毛白杨林地土壤抗蚀性研究

以未退耕的陡坡耕地作对比,对退耕还林4a后三倍体毛白杨林地两种不同的草本层模式进行的土壤抗蚀性研究表明,两种模式林地内土壤的水稳性团聚体含量在上、中、下层和未退耕地总量差别不大,但林地上层和中层大粒级水稳性团聚体含量明显高于未退耕地;人工草林地有机质比自然草林地略高,但不明显,未退耕地则由于人为增施农家肥而高于林地;以微团聚体含量为基础的各项抗蚀指标,虽一定程度上也表明了林地的抗蚀性高于未退耕地,但不如以水稳性团聚体含量为基础的明显。     

紫色土团聚体抗蚀特征研究

从水稳性、力稳性和化学稳定性3方面研究了紫色土团聚体稳定性和抗蚀性特征及内在机理,结果表明:不同利用方式土壤>3mm,>1mm,>0.25mm水稳性团聚体的含量均表现为荒草地>林地>园地>耕地,结构破坏率表现为耕地>园地>林地>荒草地;力稳性参数"原始稳定性"表现出荒草地>林地>园地>耕地,"崩解速率"表现为耕地>园地>林地>荒草地,不同利用方式土壤团聚体力稳性表现为荒草地>林地>园地>耕地;蓬莱镇组、遂宁组和沙溪庙组3种母质发育的土壤,遂宁组母质发育土壤抗蚀性最强,不同利用方式抗蚀强弱表现为荒草地>林地>园地>耕地;土壤有机质和粘粒含量显著地影响土壤团聚体的"原始稳定性"和"崩解速率",是影响土壤团聚体抗蚀性的主要内在因素。     

紫色土区植物篱篱前淤积带与篱下土坎土壤抗蚀性研究

为探究紫色土坡地植物篱篱前淤积带与篱下土坎土壤抗蚀性的差异及变化规律,选取遂宁市水土保持试验站10°新银合欢植物篱小区(T1)、10°和15°香根草植物篱小区(T2和T3)进行研究。研究小区布设有上、中、下坡篱带,分别采集篱前淤积带和篱下土坎(下坡无)的表土样,测定有机质含量、水稳性团聚体和微团聚体组成,运用主成分分析法对土壤抗蚀性进行分析。结果表明:同一篱带,土壤有机质含量、团聚度和团聚状况均是篱前淤积带高于篱下土坎,土壤水稳性团聚体含量和抗蚀性综合指数则反之,篱下土坎的抗蚀性综合指数是篱前淤积带的1.48～3.17倍;同一小区,篱前淤积带土壤有机质含量、团聚度和团聚状况均表现为下坡中坡上坡,篱下土坎为中坡上坡,而土壤水稳定性和抗蚀性综合指数在坡位间则无显著性差异;同坡度下,香根草植物篱小区土壤有机质含量、团聚度、团聚状况和水稳定性均高于新银合欢植物篱小区;坡度越大,香根草植物篱小区土壤有机质含量、团聚状况和水稳定性表现越差;主成分分析发现,水稳性团聚类指标能较好地反映紫色土坡地土壤抗蚀性能的强弱,研究小区土壤抗蚀能力表现为T2T1T3。     

桂西北喀斯特地区不同土地利用类型土壤抗蚀性研究

土壤抗蚀性是反映土壤抵抗侵蚀能力的重要参数之一,是土壤侵蚀研究的重要内容。本文选取土壤有机质、水稳性团聚体、团聚体结构破坏率、团聚状况、团聚度、分散率和<0.05 mm粉黏粒含量等7个指标,通过单因素方差分析及主成分分析,探讨了桂西北喀斯特地区5种不同土地利用类型土壤抗蚀性的差异。结果表明:原生林和次生林土壤有机质含量显著(P<0.05)高于撂荒地、坡耕地和人工林,撂荒地土壤有机质含量较坡耕地和人工林高,但差异不显著。原生林、次生林及撂荒地土壤>0.25 mm水稳性团聚体总量及团聚状况显著高于坡耕地及人工林,但其土壤团聚体结构破坏率及分散率显著低于坡耕地;人工林土壤团聚体结构破坏率显著高于次生林,但与原生林、撂荒地和坡耕地差异不显著;人工林土壤分散率则与坡耕地类似,显著低于原生林、次生林及撂荒地;原生林、次生林土壤团聚度与撂荒地、坡耕地差异不显著,但显著高于人工林;次生林、撂荒地及人工林<0.05 mm粉黏粒含量与原生林、坡耕地差异不显著,但坡耕地土壤<0.05 mm粉黏粒含量显著高于原生林。由主成分分析综合评分得到土壤抗蚀性强弱顺序为:原生林>次生林>撂荒地>坡耕地>人工林。因此,喀斯特地区人为干扰严重降低了土壤的抗蚀性,耕地通过撂荒方式能够提高土壤抗蚀性。     

护坡人工混凝土壤不同粒级团聚体分布特征及其抗蚀性研究

为了定量评价人工混凝土壤生态护坡基材的抗蚀性,室内测定了其团聚体分布特征和各抗蚀性指标,并与立地条件相似的自然土壤进行了对照分析。结果表明:与自然土壤相比,人工混凝土壤中 > 0.25 mm机械稳定性团聚体含量、> 0.25 mm水稳性团聚体含量R_0.25、平均重量直径MWD、几何平均直径GWD与有机质含量均显著提升,可蚀性因子K、结构破坏率PAD、分形维数D与分散率均显著降低;同时,抗蚀性主成分值提高了2.53倍。这均证实人工混凝土壤团聚状况和团聚度有所改善,抗蚀性较自然土壤有较大的提升。相关性分析表明 > 0.25 mm水稳性大团聚体含量R_0.25和有机质含量与其他抗蚀性指标之间均存在极显著的相关性。综合分析可知,由于添加了水泥和天然有机物料,人工混凝土壤的水稳性大团聚体含量和有机质含量明显提升,因此导致其稳定性与抗蚀性显著优于原材料之一的自然土壤。     

岩溶区不同土地利用方式土壤抗蚀性分析

采用土壤微团聚体类、水稳性团聚体类及有机质含量作为指标,通过主成分分析方法,对重庆市中梁山不同土地利用方式表层土壤抗蚀性进行了研究。结果表明：〉0.25mm水稳性团聚体含量及破坏率、〉0.5mm水稳性团聚体含量及破坏率、平均重量直径和有机质含量是评价土壤抗蚀性的最佳4指标;土壤抗蚀性强弱顺序为：灌丛地〉草地〉竹林地〉坡耕地,退耕还林、还草有利于提高土壤抗蚀性;运用微团聚体类指标和水稳性团聚体类及有机质指标分别进行土壤抗蚀性评价时,得到相反的结论;土壤水稳性团聚体类指标评价结果与主成分分析结果一致,这与研究区特殊的成土过程和脆弱的生态环境有关;耕作侵蚀使坡耕地土壤主要性质产生坡面分异,进而产生土壤抗蚀性的坡面分异。坡耕地不同部位土壤抗蚀性强弱为：上部〉下部〉底部〉顶部,这与土壤水稳性团聚体含量坡面分异一致,证明水稳性团聚体类指标可以较好地反映土壤抗蚀性特性。     

不同巨桉人工林土壤分形特征及抗蚀性分析

为探讨耕地退耕成人工巨桉林后对土壤团粒结构及土壤抗蚀性能产生的影响,在野外调查与室内分析的基础上,选择4.5年生巨桉纯林、巨桉+果树、巨桉+粮食作物土壤作为研究对象,农耕地作为对照,研究了不同巨桉人工林下水稳性团聚体分形维数的变化特征,分析了分形维数与土壤养分状况、土壤结构稳定性以及土壤抗蚀性能的关系。结果表明,4种模式土壤分形维数介于2.142~2.296;在0~15 cm土层分形维数表现为耕地林果林粮纯林,纯林和农耕地之间差异显著,其他3种模式之间差异不显著;在15~30 cm土层分形维数表现为耕地纯林林粮林果,4种模式之间差异不显著。分形维数与土壤有机质含量、大团聚体含量呈显著和极显著负相关;与土壤平均重量直径、水稳性指数有负相关趋势;与土壤体积质量、微团聚体含量呈极显著正相关。说明土壤分形维数越小,土壤有机质、大团聚体含量越高,土壤平均重量直径、水稳性指数越大,土壤体积质量、微团聚体含量越低,土壤结构越稳定,抗蚀力越强。因此,团聚体的分形维数值能反映土壤性质的变化,通过对土壤分形维数特征的研究可以定量揭示不同巨桉模式下土壤抗侵蚀的能力。     

两种有机添加物对岩石边坡植被恢复人工土壤抗蚀性的影响

分别选取鸡粪有机肥和泥炭土作为岩石边坡植被恢复人工土壤的有机添加物,通过常规工程措施进行原料混配和人工土壤喷射.以研究草本植被成坪期内其对人工土壤抗蚀性的改良效果.运用水稳性团聚体含量、团聚度、分散率等指标,对人工土壤抗蚀性能进行分析,结果表明:(1)两种有机添加物对于提高人工土壤抗蚀性均有显著作用;(2)鸡粪有机肥组各处理水稳性团聚体含量、团聚度和分散率3项指标几乎都显著优于泥炭土组对应处理(P＜0.05),鸡粪有机肥改善人工土壤抗蚀性效果显著优于泥炭土;(3)各指标相关性分析表明,鸡粪有机肥组有机质含量与团聚度、分散率和分散系数3个指标相关性显著,而泥炭土组有机质含量与所有指标相关性均不显著.(4)回归分析表明,相对于泥炭土,在人工土壤配比设计阶段,通过添加鸡粪有机肥能够更好地对人工土壤抗蚀性能进行预控.(5)在本研究中原料土壤·鸡粪有机肥(质量比)为2.41～2.94时,人工土壤抗蚀性能效果最好.     

两种巨桉人工林地土壤抗蚀性的比较研究

[目的]揭示巨桉人工林组培苗和实生苗两种起源对土壤抗蚀性的影响。[方法]利用S形采样法在样地内采集多个样点,按上(0—10cm),中(10—20cm),下(20—30cm)三层分别利用环刀和塑料盒采集原状土壤,测定不同层次土壤容重、非毛管孔隙度、毛管孔隙度、总孔隙度、渗透速率、水稳性团聚体含量等。[结果](1)随着土壤深度增加,两种巨桉林地土壤容重呈现递增趋势,而总孔隙度和通气孔隙度呈递减趋势。组培巨桉林土壤容重低于实生苗巨桉林地,而土壤总孔隙度、通气孔隙度高于显著实生苗巨桉林地(p0.05);(2)随着土壤深度增加,两种巨桉林地土壤水稳性指数、抗蚀指数、团聚状况、团聚度和结构系数呈现下降趋势,水稳性指数和抗蚀指数达到显著水平(p0.05),而分散率和分散系数呈现升高趋势。组培巨桉林地不同土层的抗蚀指数和结构系数均高于实生苗巨桉林地,但分散系数均显著低于实生苗巨桉林地(p0.05);(3)随着土壤深度增加,两种巨桉林地土壤各粒径水稳性团聚体含量和平均重量直径(MWD)呈现出下降趋势,土壤结构体破坏率呈现上升趋势。组培苗巨桉林地不同土层各粒径(5mm;5~2mm;0.5~0.25mm;0.5mm;0.25mm)水稳性团聚体含量和MWD均高于实生苗林地,而结构体破坏率、2~1mm和1~0.5mm水稳性团聚体含量均低于实生苗巨桉林地。[结论]组培巨桉人工林的土壤抗蚀性更佳。     

喀斯特高原峡谷区不同植被类型的土壤抗蚀性

[目的]对喀斯特高原峡谷区不同植被类型土壤抗蚀性的变化特征进行分析,为该区水土保持和脆弱生态系统的恢复工作提供科学支撑。[方法]以喀斯特高原峡谷区5种植被类型土壤为研究对象,选取常用的11个理化指标,运用主成分分析法进行最佳指标筛选及土壤抗蚀性评价。[结果]与耕地相比,其他植被类型土壤抗蚀性均明显增强;土壤团聚状况和水稳性大团聚体含量显著增加(p≤0.05);土壤黏粒含量有增加趋势,差异不显著(p0.05);土壤分散率和团聚体破坏率显著减小(p≤0.05)。主成分分析结果表明,黏粒含量、结构性颗粒指数、分散率、团聚状况、水稳性大团聚体含量和团聚体破坏率是评价该研究区土壤抗蚀性的最佳指标;土壤抗蚀性强弱顺序为:林地林草间作地荒草地退耕还草地耕地。[结论]楸树林自然恢复模式下土壤抗蚀性最优,建议该区域增加楸树林的面积,提高土壤抗蚀性,促进区域生态恢复和增强水土保持功能。     

Effect of soil microorganisms on the growth of roots in rice seedlings

Abstract

Root system of rice seedlings grown on nutrient solution inoculated with soil microorganisms were examined morphologically in comparison with those obtained under sterile condition. In the presence of soil microorganisms, primary roots increased in their number and decreased in the total length. Inoculated plants had more secondary roots equipped with tertiary roots. In addition, longer root hairs developed densely on primary and secondary roots of the inoculated seedlings.

Anatomical examination of the primary roots revealed that the number and width of cortical layers, as well as the length and width of the cortical cells, were increased by the effect of microorganisms. Microbial effect on outer morphology of rice roots, consequently, was estimated to have been induced from the alteration in histological and cytological activities including the activation of the periclinal divisions of the epidermal cells, the inactivation of the transverse divisions of the cortical cells and the activation of the elongation of cortical cells.     

水、氮供应和土壤空间所引起的根系生理特性变化

在限制根系生长的胁迫条件下.,研究了补充和不补充供应水、氮对玉米根系生理特性及养分吸收的影响。结果表明.,正常生长条件下.,水、氮供应促进了根系生长.,增加了根系吸收总面积、活跃吸收面积和TTC还原量.,促进了根系对养分的吸收.,从而提高了产量.;限制根系生长.,水分的作用与正常条件下相同.,氮素的作用则受控于土壤水分。补充灌水增强了氮肥作用.,供氮促进了根系生长.,改善了根系生理特性.,减少了限制根系生长所引起的不良影响.;不补充灌水限制了氮肥作用的发挥.,供氮导致了根系生物量和生理特性下降.,加重了限制根系生长的不良影响。     

Partial replacement of chemical fertilizer by manure affects maize root traits in North China Plain

In order to achieve high yields and environmental friendliness simultaneously, the replacement of chemical fertilizers by manure has become a research hotspot in recent years. Roots absorb nitrogen, participate in its assimilation and contribute to the cereal's dry matter accumulation. A 5-year filed experiment in the North China Plain was initiated to assess the response of root morphology and distribution of summer maize (Zea mays L.) to fertilizer application and contribution to crop yield. The treatments included CK (unfertilized control), NPK (inorganic nitrogen/phosphorus/potassium fertilizer) and NPKM (manure + 70% NPK). We determined the root biomass, root diameter, root length density (RLD) of three diameters (>0.8 mm, 1stRLD; 0.2–0.8 mm, 2ndRLD; <0.2 mm, 3rdRLD) and the soil chemical properties at 60 cm with 10 cm increments. At 40–60 cm, NPKM significantly decreased the root diameter than NPK. Fertilization showed no effect on total RLD, 1stRLD, 2ndRLD and 3rdRLD for a 60-cm soil profile. At 40–50 cm, the NPKM increased the RLD compared to NPK, mainly by increasing the 2ndRLD and 3rdRLD. Under CK and NPK, root lengths of 0–20 cm made up 62% and 57% of the total root length, respectively. Under NPKM, root lengths of 40–60 cm made up 46% of the total root length. Our results indicate that maize yield was preserved after replacing 30% of N fertilizer with manure, presumably depending on the change of root vertical distribution pattern and increase of the fine root length in deeper soil.     

The role of phosphorus sources on root diameter,root length and root dry matter of barley (Hordeum vulgare L.)

Roots are the main plant organs that supply nutrients, water, hormones and physical support for the plant. Phosphorus (P) is one of the most limiting and important elements in root growth and crop production. The aims of this study were to investigate the effects of different sources of phosphorus treatments on root growth (root length, diameter and dry matter) of barley. The two glasshouse pot experiments results showed that under P deficiency, the weight of dry root significantly decreased and the total root length of whole plant significantly increased with decrease of root diameter. Our results suggested that soil fertility and root structure are widely recognized as important role of the soil community and plant growth, the root structure and root extension can directly and indirectly affected by soil fertility and specially P nutrient of the soil. Accordingly, root characteristics can determine the circumstance of plant growth and crop production.     

基于地理信息系统的植物根系分析方法

简便、快速、准确的根长测量和根系分级方法,在不同灌溉方式对作物生长影响的对比研究等方面具有重要意义.该文提出了一种利用地理信息系统技术,测量根长并对根系进行分级的方法.通过与目前常用的直接测量法、网格交叉法进行比较,发现该方法测量精度高、速度快,而且简单易用.     

两个氮素利用率不同的水稻品种根系形态及生理特性的差异

The variation in nitrogen (N) uptake by rice has been widely studied but differences in rice root morphology that may contribute to this variation are not completely understood. Field and greenhouse experiments were carried out to study N accumulation, root dry weights, total root lengths, root surface areas, and root bleeding rates of two rice cultivars, Elio with low N-use efficiency and Nanguang with high N-use efficiency. Low (1 mmol N L^-1) and high (5 mmol N L^-1) N applications were established in the greenhouse experiment, and the N rates were 0, 120, and 240 kg ha^-1 in the field experiments at Jiangning and Jiangpu farms, Nanjing, China. The results showed that the N accumulation, root dry weight, total root length, and root surface area increased with an increase in N application. At the heading stage, N accumulation in the shoots and roots of Nanguang was greater than that of Elio in the field experiments and that of Elio at 5 mmol N L^-1 in the greenhouse experiment. After the heading stage, N accumulation was higher for Nanguang at both 1 and 5 mmol N L^-1 in the greenhouse experiment. The total root length and root surface area were significantly different between the two cultivars. Over the range of the fertilizer application rates, the root lengths of Nanguang at Jiangning Farm were 49%-61% greater at booting and 26%-39% greater at heading than those of Elio, and at Jiangpu Farm they were 22%-42% and 26%-38% greater, respectively. Nanguang had a greater root bleeding rate than Elio. It was concluded that the N-use efficiency of the two rice cultivars studied depended to a great extent on the root morphological parameters and root physiological characteristics at different growth stages.     

Measurement of root diameter in field-grown crops under a microscope without washing

The variation in the root diameter of field-grown crops was directly measured under a microscope by manually removing soil particles from roots without washing the roots. The frequency of the root diameter at the mode (about 10 μm, mainly of root hairs) was higher in wheat and maize (about 60%) than in soybean and sugar beet (about 30%), and it was the lowest in potato (21%). The diameter of 88 to 97% of the roots larger than 20 μm ranged from 21 to 160 μm. The finer the roots, the higher was the frequency, except for potato roots in which the frequency of roots with a diameter of 21 to 40, 41 to 80, and 81 to 160 μm was about 30%. Since fine roots and root hairs account for the largest proportion of the crop root system, they should appropriately be quantified whenever morphological and physiological aspects of roots are analyzed.     

低钾胁迫下不同耐低钾玉米品种 (系) 开花后根系生长和结构的变化

  【目的】  土壤缺钾常引起植株早衰,严重影响玉米产量。从玉米开花后根系形态、结构和活性等参数的变化,研究低钾胁迫下玉米早衰的机理。  【方法】  以耐低钾玉米自交系90-21-3和钾敏感玉米自交系D937为试材,进行池栽试验。设置天然低钾土壤 (低钾,–K) 和正常供钾 (CK,+K) 两个处理,分别于玉米开花后测定根系形态、结构和活性等参数。  【结果】  与正常供钾处理相比,低钾处理降低了90-21-3和D937根系中钾素含量,抑制了根系的生长,破坏了根系结构,引起根系活力降低。低钾胁迫下,90-21-3的第一层节根数目和根系干重分别显著降低了20.37%和42.24%,D937分别显著降低了39.06%和59.64%;90-21-3的第二层节根数目和干重分别显著降低了23.40%和39.30%,D937分别显著降低了36.67%和59.86%。随着玉米的生长,低钾胁迫下90-21-3和D937的根系活力以及第一层和第二层根的长度、表面积、体积和侧根长度整体均呈现降低趋势,D937降低幅度大于90-21-3,根平均直径整体逐渐增加。低钾胁迫下90-21-3根系解剖结构完整,外皮层和内皮层完整,大、小导管形状规则,结构清晰可见;D937根系解剖结构受破坏严重,外皮层和内皮层结构被破坏,导管形状不规则,大、小导管结构模糊甚至消失。与正常供钾相比,低钾胁迫下90-21-3的大导管直径、小导管直径、大导管面积和小导管面积分别降低了11.15%、14.37%、21.07%和30.21%;D937分别显著降低了33.99%、22.86%、56.43%和40.55%。  【结论】  低钾胁迫显著降低了玉米开花后根系的生长和结构的稳定性。与耐低钾玉米自交系 (90-21-3) 相比,钾敏感自交系 (D937) 在低钾胁迫下大面积皮层结构遭到严重破坏,内皮层结构不完整,导管形状不规则,大导管周围的小导管结构模糊,甚至消失,质膜透性高,影响养分和水分的吸收利用。而耐低钾玉米90-21-3在生育后期能够维持较大根系体积、根系活力以及输导组织,增强低钾胁迫下根系对外界钾素的吸收和运移能力,延缓根系衰老。     

贺兰山3种乔木单根及根土复合体力学特性

为研究和比较贺兰山山杨、青海云杉、油松单根和根土复合体的力学特性,通过单根拉伸、三轴压缩、饱和渗透试验测定了3种乔木单根和根土复合体的力学参数及土水特征曲线。结果表明:3种乔木单根力学特性存在显著差异,且直径对单根的力学特性有显著影响。单根最大拉力与直径成幂函数相关,随直径增大而增大;单根抗拉强度、杨氏模量与直径成对数函数相关,随直径增大而减小。山杨单根平均最大拉力(0.38kN)青海云杉(0.25kN)油松(0.17kN);山杨单根平均抗拉强度(33.39 MPa)青海云杉(27.79MPa)油松(18.45MPa);山杨单根平均杨氏模量(0.17GPa)青海云杉(0.12GPa)油松(0.11GPa)。3种乔木根土复合体的黏聚力、弹性模量存在显著差异,但摩擦角没有显著差异(平均值30.48°)。山杨根土复合体的黏聚力(10.65kPa)青海云杉(8.97kPa)油松(7.13kPa);山杨根土复合体的弹性模量(2.17 MPa)青海云杉(2.52 MPa)油松(4.21 MPa)。3种乔木根土复合体的土水特征曲线、渗透函数曲线都存在极显著差异,山杨根土复合体的渗透能力油松青海云杉。研究结果对于评价山杨、青海云杉、油松稳定边坡能力和建立贺兰山边坡稳定性分析数值模型都具有重要参考价值。     

灌木根系几何特性对拉拔力影响的试验研究

[目的]探究灌木根系几何特性对拉拔力的影响,为边坡防护植物物种的选择与植物价值的充分利用提供理论参考。[方法]以红叶石楠为例,通过对多根系形态的灌木根系进行室外拉拔试验,研究不同含水率、根系形态、二级侧根等情况对根土间相互作用力的影响。[结果]Y型根系和水平根系最大拉拔力随土壤含水率的增加呈对数和指数函数减小,而主直根系最大拉拔力随土壤含水率的增加呈先增大后减小的趋势,最优含水率在17.5%左右;Y型根系的最大拉拔力随Y型根系夹角的增加逐渐增大,而根系全段激活时间随根系夹角的增加呈现先减小后增大的趋势,在夹角为75°时最容易被激活;Y型根系及主直根系的最大拉拔力均随二级侧根数的增加呈线性增加,且主直根系最大拉拔力的增加趋势大于Y型根系。主直根系在土壤含水率为10%,20%,25%时,拉拔曲线呈拉拔硬化型,含水率为15%时,拉拔曲线呈拉拔软化型;水平根系和Y型根系在含水率为15%,17.5%时,拉拔曲线呈拉拔硬化型,含水率为20%,22.5%,25%时,拉拔曲线呈拉拔软化型。[结论]根系形态与含水率是影响根系拉拔力的关键因素,根系形态越复杂,拉拔力越大;含水率越高,拉拔曲线逐渐由硬化向软化型转变。