Effects of root architecture, physical tree characteristics, and soil shear strength on maximum resistive bending moment for overturning Salix babylonica and Juglans ailanthifolia

Effects of root architecture, physical tree characteristics, and soil shear strength on overturning moment due to flooding were investigated using Salix babylonica and Juglans ailanthifolia, exotic and invasive plants in Japanese rivers. Tree-pulling experiments that simulated flood action were conducted, and the resulting damage was examined to assess the effects of physical tree characteristics and root architecture on the maximum resistive bending moment (M _max) for overturning. In situ soil shear strength tests were conducted to measure soil strength parameters. The effects of species differences on the M _max were examined by analyzing root architecture. S. babylonica has a heart-root system that produces a greater overturning moment due to the strong root anchorage and the large amount of substrate that must be mobilized during overturning. J. ailanthifolia has a plate-root system that produces a smaller overturning moment. However, trees with the plate-root system may withstand overturning better due to an increased root:shoot ratio. The results of the study show that the M _max of a tree for overturning had significant (P < 0.05) correlations with a tree’s physical characteristics, including height (H), trunk diameter at breast height (D _bh), D _bh², height multiplied by the second power of D _bh (trunk volume index H × D _bh²), and root–soil plate depth (R _d), and root–soil plate radius (R _r). Considering the strategy of J. ailanthifolia to increase the root:shoot ratio for anchoring in the substrate, the trunk volume index (H × D _bh²) is a better parameter than D _bh² because it indirectly involves the difference in below-ground volume and surface area. Different soil cohesion values were found at different experimental sites, and the average M _max for overturning each species decreased linearly with increasing soil cohesion.     

刺槐根系对深层土壤水分的影响

对黄土高原主要造林树种刺槐根系及其林地土壤水分进行调查和监测,结果表明,在阴坡立地上,刺槐细根在距树干2.0 m范围内的水平分布无明显差异,最大分布深度均为2.0 m;而阳坡立地上刺槐细根在距树干0.5 m处的垂直分布深度可达2.0 m,且阴坡立地上细根密度特征值明显大于阳坡.根系对土壤深层水分的影响范围因不同立地条件下根系分布空间差异而不同,在阳坡立地上,刺槐根系对深层土壤水分的影响深度可达2.7 m处的土层,而在阴坡立地上,这种影响范围可达3.3 m处的土层.     

土层厚度对刺槐旱季水分状况和生长的影响

该研究测定了旱季和雨季刺槐(Robinia pseudoacacia)林不同土层厚度的土壤含水量, 刺槐的树高、胸径、小枝凌晨水势、叶片碳稳定同位素组成(δ¹³C)、叶面积、比叶重和气体交换指标; 分析了刺槐旱季和雨季的水分状况和土层厚度之间的关系; 通过刺槐对季节性干旱胁迫的反应, 估计华北石质山区不同土层厚度土壤水分对刺槐的承载能力; 并求证近年来该地区刺槐衰败和水分因素的关系。结果显示: 随着土层厚度减小, 旱季土壤含水量下降、凌晨小枝水势降低; 气孔导度和最大光合速率都减小, 而瞬时水分利用效率增加, 雨季上述指标无显著性差异, 旱季土壤含水量只有雨季的60%左右。随着土层变薄, 刺槐叶片δ¹³C增高, 叶面积减小, 比叶重增加; 刺槐树高和胸径减小。以上结果表明: 刺槐在不同季节下的水分状况综合反映土壤的供水能力, 土层浅薄导致土壤水分承载力不足, 致使刺槐在旱季受到较严重的水分胁迫, 这可能是刺槐出现衰败的重要原因。     

Effects of tree characteristics and substrate condition on critical breaking moment of trees due to heavy flooding

To elucidate tree breakage conditions with different breaking mechanisms, i.e., moment by drag force, local scour, and degradation of the substrate around trees, field surveys were conducted after a flood event (September 2007 flood due to Typhoon 9) in the Tamagawa River, Japan. Trees in a river have two main breaking mechanisms during a flood event, moment by fluid force and erosion of the substrate. Moment by fluid force causes two breaking phenomena, trunk damage (bending, breakage) and overturning. Trunk bending or breakage can be expressed as a function of d ^c , where d is the trunk diameter at breast height and the power c equals 3 for trunk bending or breakage, and approximately 2 for overturning. Smaller diameter trees experienced trunk breakage, but larger trees were overturned. The range for these two breaking patterns changes with the substrate condition. If severe scouring has occurred, the threshold for overturning moment can be quite small. Tree overturning occurred mostly on the bank side of the gravel bar; however, some trees, especially Robinia pseudo acacia and Morus bombycis, were overturned if the substrate was a thin deposited soil or silt layer on gravel. The roots were anchored in the small-particle deposited layer in that case. As for the erosion of the substrate, the tree-breaking patterns can be classified into three types depending on the relationship between the nondimensionalized bed shear stress of d ₅₀ and d ₈₄, the representative grain diameters at which 50 and 84% of the volume of the material, respectively, is finer. The nondimensionalized shear stress of d ₈₄ is an important parameter for discussing the rehabilitation of the gravel bed bar. The boundary region for tree overturning can be changed by the effects of plant cover and debris attachment.     

根系分泌物C∶N对刺槐林地土壤理化特征和土壤呼吸的影响

为探究根系分泌物C∶N对土壤养分循环及微生物活性的影响,本研究以黄土高原人工刺槐林为对象,在生境条件基本一致的15、25、35、45 a刺槐林地取原位土壤,通过模拟不同C∶N的根系分泌物(只添加N、C∶N=10、C∶N=50、C∶N=100和只添加C)添加至土壤,以去离子水作为对照,分析根系分泌物C∶N对土壤碳、氮、磷、pH值等理化特征和土壤呼吸的影响。结果表明: 1)有机碳含量与根系分泌物C∶N呈正相关,根系分泌物C∶N=10时土壤有机碳(SOC)分解较快,高根系分泌物C∶N(C∶N=100)能延缓SOC分解,而只添加C处理对SOC无显著影响。2)不同C∶N根系分泌物处理对全氮的影响不明显,碳添加能促进微生物对铵态氮的吸收,氮添加能促进铵态氮的硝化,随着根系分泌物C∶N增加,土壤中铵态氮含量下降。3)氮添加会导致土壤pH值下降,增加土壤全磷含量。4)刺槐林地土壤呼吸值与根系分泌物C∶N呈正相关,随着C∶N增加,根系分泌物对25和35 a人工刺槐林土壤呼吸的促进作用更显著。综上,根系分泌物C∶N值越高,对人工刺槐林土壤呼吸的促进作用越显著。研究结果进一步加深了对森林根系-土壤-微生物互作过程的认识。     

Effects of Robinia pseudoacacia on the undergrowth of herbaceous plants and soil properties in the Loess Plateau of China

刺槐对黄土高原林下草本植物及土壤性质的影响 外来物种刺槐(Robinia pseudoacacia)的引入会对林下草本植物、土壤性质及二者之间的相互关系产 生一定影响,且这种影响可能与植被带有关。然而,在黄土高原较大面积范围内,关于刺槐对林下草本植物和土壤影响的研究依然很少。我们以黄土高原草原带、森林草原带和森林带作为研究区,选择了两种冠层植物类型：刺槐林分和相邻的原生植被。我们测定了5个叶片功能性状：叶片碳含量、叶片氮含量、叶片磷含量、比叶面积和叶组织密度,并计算了群落功能多样性、物种多样性和群落加权性状值。研究结果表明,(1)与原生植被相比,3个植被带内林下草本植物群落的叶氮、叶磷和比叶面积的群落加权性状值均显著提高,而叶碳和叶组织密度的群落加权性状值显著降低。(2)物种多样性、功能多样性和群落生物量在草原带内呈下降趋势,在森林带内呈上升趋势,在森林草原带内差异不显著。(3)与原生植被相比,土壤有机碳和土壤全氮仅在森林带内显著减少。(4)林下草本植物群落特性与土壤之间的关系是受刺槐和植被带所依赖的。总的来说,刺槐对林下草本植物和土壤性质的影响与植被带密切相关。该研究结果对黄土高原人工植被恢复与重建的规划具有重要指导意义。     

The influence of black locust (Robinia pseudoacacia) flower and leaf fall on soil phosphate

To investigate the influence of black locust (Robinia pseudoacacia) flower and leaf fall on soil phosphate, we monitored litterfall, litter decomposition, and soil membrane phosphate in a R. pseudoacacia forest on Mt. Ilzasan, Seoul, Korea. R. pseudoacacia flower litter was 30–50% of total litter production in May and the flowers decomposed rapidly. More than 11% of R. pseudoacacia leaf litter decomposed from February to May, while that of Quercus spp. decomposed very little. Fast decomposition of R. pseudoacacia flower and leaf litter significantly increased membrane phosphate in the soil. The rapid nutrient-cycling of R. pseudoacacia through flower litterfall and rapid decomposition benefits the plant itself in the growing season when nutrients demand is increasing. Rapid nutrient-cycling might be a strategy that helps R. pseudoacacia to persist in poor soil environments.     

不同林龄刺槐叶片养分重吸收特征及其对土壤养分有效性的响应

为揭示丘陵沟壑区刺槐的养分重吸收特征及其驱动因素,研究该区不同林龄刺槐叶片全氮和全磷的浓度,以及土壤有机碳、全氮、全磷、铵态氮、硝态氮和速效磷浓度及其化学计量,分析了叶片氮磷重吸收效率与土壤养分特性之间的关系。结果表明: 植物和土壤的养分随林龄增长发生显著变化,而土壤总磷和速效磷浓度较低。氮重吸收效率随林分生长先增加后降低,范围为48.2%～54.0%,平均为48.5%;磷重吸收效率则显著增加,范围为45.2%～49.4%,平均为46.9%。氮重吸收效率与土壤氮素和氮磷比呈负向响应,而磷重吸收效率与氮磷比呈显著正相关,与土壤速效磷呈负相关。表明土壤养分有效性的变化负向驱动养分重吸收效率。由于该生境中刺槐林的固氮效应及磷限制,叶片养分重吸收策略对土壤氮磷比响应强烈。     

不同土壤水分下刺槐和油松的生理特征

在适宜土壤水分(70%θf)、中度干旱(55%θf)和严重干旱(40%θf)3种土壤水分条件下研究了黄土高原常见造林树种刺槐(Robinia pseudoacacia L.)和油松(Pinus tabulaeformis Carr.)的生长及水分利用特性.结果表明:干旱胁迫使2树种的成活率、干物质累积和光合速率均显著下降.在适宜水分下刺槐的单叶水分利用率(WUE)最高,严重干旱下最低.刺槐和油松的枝条快速生长期主要集中在3-6月,在中度干旱条件,2个树种均可良好生长;在严重干旱下2个树种的生长均受到显著抑制,但刺槐受影响较大,油松受影响较小.在3种土壤水分条件下刺槐耗水量、生物量及水分利用率均显著高于油松.2树种在中度干旱下的总WUE最高,严重干旱下最低.刺槐属于高耗水树种,油松属于低耗水树种,油松的耐旱性强于刺槐.研究结果表明,刺槐在黄土高原缺水地区不适宜大面积栽植,只能用于水分条件较好的立地条件下造林.油松应尽可能在含水量较高的阴坡或沟坡地带造林.     

Morphology and General Characteristics of Bacteriophages Infectious to Robinia pseudoacacia Mesorhizobia

Four phages infectious to Mesorhizobium strains were identified in soil samples taken from local Robinia pseudoacacia stands. Based on their polyhedral heads and short noncontractile tails, three of the phages, Mlo30, Mam12, and Mam20, were assigned to group C of Bradley’s classification, the Podoviridae family, while phage Mlo1, with its elongated hexagonal head and a long flexible tail represented subgroup B2 bacteriophages, the Siphoviridae family. The phages were homogeneous in respect of their virulence, as they only lysed Mesorhizobium strains, but did not affect strains of Rhizobium or Bradyrhizobium. On the basis of one-step growth experiments, the average virus yield was calculated as approximately 10–25 phage particles for phages Mlo30, Mam12 and Mam20, and as many as 100–120 for phage Mlo1. The rate of phage adsorption to heat-treated cells showed differences in the nature of their receptors, which seemed to be thermal sensitive, thermal resistant, or a combination of the two. Only the receptor for phage Mlo30 was likely to be an LPS molecule, which was supported by a neutralization test. The smooth LPS with O-antigenic chains of the phage-sensitive M. loti strain completely reduced the bactericidal activity of virions at a concentration of 1 μg/ml. The molecular weights of phage DNAs estimated from restriction endonuclease cleavage patterns were in the range from ~39 kb for group C phages to ~80 kb for B2.     

不同光环境对麻栎和刺槐幼苗生长和光合特征的影响

通过搭建遮阳棚设置3个光照强度,模拟森林幼苗生长的林缘、林窗和林下光环境,研究麻栎和刺槐幼苗形态结构、光合特性、生物量积累及其分配对不同光照强度的响应。结果表明,极度弱光环境限制了幼苗的株高、基径、总叶面积、冠面积、叶面积指数和总叶数等形态指标的增长,与全光环境相比,适度遮荫有利于幼苗的形态生长,光照对麻栎形态的异速生长曲线影响较小,刺槐较麻栎的曲线变化更明显一些,弱光降低了异速生长指数。随遮荫程度的增加,麻栎的净光合速率、蒸腾速率、气孔导度逐渐降低,刺槐的净光合速率则在适度遮荫下最大,两者的光能利用效率均显著增大,水分利用效率先升后降。随光照强度的减弱,麻栎各器官的生物量积累降低,叶面积比率的增加和根冠比的减少有利于增加光能的捕获,而刺槐的生物量积累和分配则在适度遮荫下达到最优;各叶绿素含量均显著上升,而叶绿素a/b则逐渐下降。麻栎和刺槐显示出不同的生存策略和光利用策略,在一定程度上可以揭示它们在阔叶林群落中不同的演替地位。     

黄土高原半干旱和半湿润地区刺槐林地生物量与土壤干燥化效应的模拟

 黄土高原人工刺槐(Robinia pseudoacacia)林地深层土壤干燥化现象普遍发生, 日益严峻地威胁着人工植被建设成效。分析和比较半干旱和半湿润地区刺槐林地生物量演变趋势、深层土壤干燥化发生规律和区域分布特征差异, 能够为黄土高原因地制宜地营造刺槐林提供科学依据。在WinEPIC模型气象、土壤和作物参数数据库组建与模拟精度验证的基础上, 应用WinEPIC模型模拟研究了1957–2001年黄土高原半湿润地区洛川和长武、半干旱地区延安和固原等地1–45年生刺槐林地生物量演变规律和深层土壤干燥化效应。结果表明: 洛川、长武、延安和固原的刺槐林地连年净生产力模拟值在5–8年生时达到最大值后, 随着降水量年际波动呈现出明显的波动性降低趋势, 其平均值分别为5.33 × 10³、4.56 × 10³、4.03 × 10³和3.35 ×10³ kg·hm^–2·a^–1; 1–7年生刺槐林地年耗水量高于同期年降水量, 导致林地0–10 m土层土壤强烈干燥化, 洛川、长武、延安和固原刺槐林地年均土壤干燥化速率分别为164.3、165.7、187.1和190.0 mm·a^–1, 8–45年生刺槐林地有效含水量在0–250 mm的较低水平上随降水量变化而波动; 1–9年生刺槐林地0–10 m土层土壤湿度剖面分布变化剧烈, 土壤湿度逐年降低且土壤干层逐年加厚, 7–9年生时土壤干层厚度已经超过10 m, 8–45年生刺槐林地2–10 m土层土壤湿度保持相对稳定的干燥化状态; 洛川和长武刺槐林地水分生产力较高且相对稳定, 刺槐林地生长期可以超过45年; 而延安和固原刺槐林地水分生产力较低且稳定性差, 刺槐林稳定生长期不超过40年。     

黄土高原剌槐水土保持林防护成熟与更新研究

在分析乔木水土保持林防护机理的基础上 ,通过对渭北黄土高原剌槐水土保持林调查、分析 ,确定该区剌槐水土保持林在常规密度下的初始防护成熟龄为 11～ 16年 (平均为 12年 ) ;最大防护成熟龄为 2 5年 ;更新龄为 4 2年 ;防护成熟期 (更新龄与初始防护成熟龄之差 )为2 6～ 31年。以防护成熟龄为基础 ,确定剌槐水土保持林的三个经营阶段 :成熟前期、防护成熟期和更新期。这些结果将为水土保持林的合理经营提供参考。     

Effects of black locust (Robinia pseudoacacia) on soil properties in the loessial gully region of the Loess Plateau, China

Black locust (Robinia pseudoacacia) has been widely planted in the Loess Plateau for soil and water conservation. The effects of black locust on soil properties has significant role in land use and ecosystem management. However, this beneficial effect has been little studied in the Loess Plateau. The soil properties below black locust and native grass growing in Nanxiaohe and Wangdonggou watersheds, located in the loessial gully region of the Loess Plateau, were studied for changes in soil properties after establishment of black locust. The black locust significantly increased soil cation exchange capacity, organic carbon, total nitrogen, nitrate, and carbon:nitrogen and carbon:phosphorus (P) ratios, as well as some enzymes like alkaline phosphatase and invertase in 0–20 cm or 0–80 cm depths of soil compared to the native grassland in Nanxiaohe and Wangdonggou watersheds. However, the effects on ammonium, total P, and extractable P and potassium were not consistent in both watersheds. There were more obvious differences in soil properties between black locust land and grassland for Nanxiaohe watershed than for Wangdonggou watershed, suggesting that the effects of black locust on most soil properties increase with black locust age. The results indicate that black locust has potential to improve soil properties in the loessial gully region of the Loess Plateau and the improvements were greater in long-term than middle-term black locust stands.     

生长不同植物的刺槐树洞附生土中真菌群落组成的初步调查研究

树洞是陆地生态系统特殊生境之一,目前对其研究报道不多。基于高通量测序,我们调查分析了贵州城市绿地一些生长有不同植物的刺槐树洞附生土样中真菌群落的组成。研究结果显示,在属水平上,植物为排风藤Solanum cathayanum、女贞Ligustrum lucidum、小藜Chenopodium serotinum、中国绣球Hydrangea chinensis、苦苣Cichorium endivia及牛膝Achyranthes bidentata的刺槐树洞附生土,其真菌群落优势属分别为绿僵菌属Metarhizium、粗糙孔菌属Trechispora、Fungi下一未鉴定属、团壳菌科Boliniaceae中一未定属、久浩酵母属Guehomyces及丛赤壳科Nectriaceae中一未定属,各优势属的相对多度分别为57.67%、42.96%、30.60%、86.45%、33.15%及12.26%。此外,样本中还存在许多昆虫及人类潜在病原菌和独特的真菌资源,值得进一步探索。     

刺槐,国槐根际土壤生化成分及其对伴生杨树营养的影响

分析了杨树、刺槐和国槐的根面与根际土壤中的游离氨基酸及植物生长素ＩＡＡ,测定了不同处理小区中杨树叶片的营养状况（Ｎ、Ｐ、Ｋ和叶绿素含量）以及净光合速率和气孔阻力．结果表明,刺槐、国愧和杨树根面氨基酸组成和数量有很大差别;３个树种根际土壤中氨基酸含量显著低于根面．３个树种根面和根际土壤中ＩＡＡ含量为刺槐＞国槐＞杨树．混交豆科树种后,杨树叶片营养状况有所改善,净光合速率明显提高,气孔阻力有所降低．     

Effects of arbuscular mycorrhizal fungi on calorific value and contents of carbon and ash in Robinia pseudoacacia

该试验以根内球囊霉(Glomus intraradices)和地表球囊霉(G. versiforme)为接种剂, 研究了丛枝菌根真菌对刺槐(Robinia pseudoacacia)生物量、热值、含碳量、灰分、能量积累和碳素积累的影响。结果表明, 接种根内球囊霉和地表球囊霉对提高刺槐生物量、热值、能量积累和碳素积累都起到了重要作用。接种根内球囊霉和地表球囊霉后刺槐的总生物量比对照分别增加了89.61%和91.34%, 能量积累分别比对照增加102.20%和94.19%, 碳素积累分别比对照增加93.30%和77.21%; 同时发现刺槐的能量和碳主要分布在根系和叶, 而茎中能量和碳所占的比例较小。接种根内球囊霉提高了刺槐的干重热值, 其根、茎、叶的干重热值分别比对照增加7.72%、8.94%和8.41%; 接种地表球囊霉也显著(p < 0.05)提高了刺槐的干重热值, 但其效果低于根内球囊霉。接种根内球囊霉显著(p < 0.05)提高了刺槐根的含碳量, 对茎和叶的含碳量影响不明显。接种根内球囊霉和地表球囊霉都显著(p < 0.05)提高了刺槐茎和叶的去灰分热值。     

刺槐树洞悬土可培养真菌群落组成及其多样性分析

结合形态特征与分子鉴定,分析贵州贵阳花溪刺槐"树洞悬土"和其对应地下土样中可培养真菌的群落组成。结果表明,树洞悬土中共分离得到真菌7属19种315株,其中普通青霉Penicillium commune为优势种,相对多度为81.11%;地下土壤共分离到真菌6属18种156株,优势种也是普通青霉,但相对多度仅为24.93%。树洞悬土中的真菌数量明显高于地下土,并且二者在真菌种群的多样性水平上也存在一定差异,树洞悬土的Shannon-Wiener多样性指数H=0.8291,Simpson优势度指数D=0.3373,Pielou均匀度指数J=0.2815,Margalef丰富度指数R=1.3300,均低于地下土。同时在树洞悬土中分离到一些独特真菌,如小克银汉霉Cunninghamella elegans、帚状刺壳霉Chaetopyrena penicillata和雪白腐殖霉Humicola nivea。刺槐树洞悬土和对应地下土壤真菌群落的相似性较低(Cj=0.2300)。     

摘叶造成的碳限制对刺槐碳素分配和水力学特性的影响

以3年生刺槐（Robinia pseudoacacia Linn.）为研究对象,通过对其进行连续3次摘叶造成严重碳限制,检测摘叶后刺槐的生物量分配、叶片形态和不同部位的非结构性碳（NSC）浓度,同时检测其根压和根系导水率、枝条水势和导水率损失值（PLC）及茎的抗栓塞能力,研究摘叶造成的碳限制对刺槐碳素分配和水力学特性的影响。结果显示,摘叶显著降低了刺槐不同部位的生物量,其中细根生物量降低程度最大;摘叶还造成了刺槐不同部位NSC浓度显著降低,茎韧皮部、茎木质部、根韧皮部和根木质部的NSC浓度分别为对照的29.6%、20.2%、10.2%和8.7%,且根部NSC的降低程度显著高于茎;碳限制显著降低了刺槐苗木的根压和根系导水率,增加了枝条凌晨和正午的PLC,降低了其抗栓塞能力。研究结果表明摘叶造成的碳限制改变了刺槐的碳素分配模式,限制了碳素向根的分配,抑制细根的发生,进而限制根的水分吸收能力,加重枝条栓塞程度,同时还会导致枝条抗栓塞能力下降,从而降低植物水分输导的安全性。