水肥耦合对欧美108杨幼林表土层细根形态及分布的影响

采用根钻法对水肥耦合条件下(地表滴灌和随水施肥)欧美108杨幼林(Populus×euramericana cv.‘Guariento’)林地0—30 cm表土层细根形态及分布进行了系统研究。田间试验设计3个灌溉水平(灌溉土壤水势起始阈值为-75、-50、-25 k Pa)和3个养分水平(施N150、300、450 g株-1a-1),组合成9个水肥耦合处理,另设1个对照处理(CK)。研究结果表明:(1)垂直方向上,10个处理下欧美108杨幼林细根生物量、表面积、体积和根长密度均随着土壤深度的增加而递减(且多数处理达到显著水平),而比根长则在低水和中水处理下表现出0—10 cm土层显著小于10—20 cm和20—30 cm土层,在高水和CK处理下各土层之间差异不显著(P0.05)。从表征细根分布特征的多数指标来看,水肥耦合没有改变欧美108杨幼林细根的垂直分布格局,其细根主要分布在0—10cm土层,该层生物量和根长密度分别是10—20 cm土层的1.25—5.05倍和1.05—2.05倍、分别是20—30 cm土层的2.8—13.06倍和1.99—4.99倍。(2)欧美108杨幼林细根生物量、根长密度、表面积和体积均表现出:低肥量下的3个滴灌水平处理均与CK无显著差异,中肥和高肥量下的6个处理均显著大于CK,尤其高水高肥处理促进细根生长的效果最显著,其3个土层细根生物量较CK分别显著提高了316%、386%和442%,根长密度较CK分别显著提高了345%、176%、132%(P0.05);各处理比根长均随着滴灌和施肥量的增加而减小。(3)同一滴灌水平下各土层细根生物量随施肥量变化的回归方程拟合具有较高R2(0.702—0.891),P0.0001,而同一施肥水平下各土层细根生物量随滴灌量变化的回归方程拟合度较低,说明欧美108杨幼林细根的趋肥性强于向水性,故在对其水肥经营管理中应该将施肥措施放在首位。     

滴灌水氮耦合对欧美108杨林木生长和土壤氮素的影响

采用地表滴灌技术,田间设计9个水氮耦合处理,以不灌溉不施肥为对照(CK),9个耦合处理由3个灌溉水平(灌溉土壤水势起始阈值为-75、-50、-25 kPa)和3个施N水平(150、300、450 g·tree^-1·a^-1)组合,于2012和2013年2个生长季的滴灌水氮耦合措施后,研究耦合措施对欧美108杨林木胸径、树高和蓄积量的年增量及0～60 cm土层全氮含量的影响.结果表明: 水氮耦合措施可显著促进108杨林木生长并有效提高林地生产力,耦合措施第一年,9个耦合处理中高水高肥处理(土壤水势-25 kPa+施N量450 g·tree^-1·a^-1)使108杨蓄积年增量达到11.54 m³·hm^-2·a^-1,相比CK的8.01 m³·hm^-2·a^-1提高了44.1%,耦合措施第二年,中水高肥处理(土壤水势-50 kPa+施N量450 g·tree^-1·a^-1)使108杨蓄积年增量达到27.85 m³·hm^-2·a^-1,较CK的20.48 m³·hm^-2·a^-1提高36.0%.连续的水氮耦合措施显著提高了林地0～20 cm土层全N含量,耦合措施第一和第二年高水高肥处理各土层全N含量分别比CK高出12.3%～59.4%和71.1%～81.1%.108杨胸径和树高增量与土壤全N含量呈显著正相关,施N水平和水氮交互作用对林木生长和土壤全N含量具有显著的影响,而灌溉水平的影响不显著.综合表明,滴灌水氮耦合措施可通过改善林地土壤肥力,尤其是浅土层全氮含量来有效促进林木生长并提高林地生产力.     

黄土高原4种植被类型的细根生物量和年生产量

细根(≤2 mm)在陆地生态系统净初级生产力的分配中占有重要地位,在碳循环和水土保持方面具有重要意义. 本文采用土钻法和内生长法,以黄土高原刺槐人工林、落叶灌木、退耕草地和沙蒿群落4种主要植被类型为对象,研究0～40 cm土层细根生物量、垂直分布和细根年生产量. 结果表明： 细根生物量与纬度呈线性负相关. 4种植被类型0～40 cm土层细根生物量的大小顺序为落叶灌木(220 g·m^-2)>刺槐人工林(163 g·m^-2)≈退耕草地(162 g·m^-2)>沙蒿群落(79 g·m^-2). 退耕草地直径≤1 mm细根生物量占直径≤2 mm总细根生物量的74.1%,在4种植被类型中最高;4种植被类型细根生物量随着土层深度的增加而减少,最大值均出现在0～10 cm土层. 退耕草地0～10 cm土层细根生物量占0～40 cm土层总细根生物量的44.1%,显著高于其他3种植被类型;细根年生产量与纬度呈线性负相关. 4种植被类型0～40 cm土层细根年生产量大小顺序为退耕草地(315 g·m^-2·a^-1)>落叶灌木(249 g·m^-2·a^-1)>刺槐人工林(219 g·m^-2·a^-1)>沙蒿群落(115 g·m^-2·a^-1),其中退耕草地显著高于其他3种植被类型. 退耕草地0～10 cm土层细根生产量占0～40 cm土层总细根生产量的40.4%,在4种植被类型中最高. 退耕草地细根周转时间为0.51 a,低于其他3种植被类型.     

毛竹细根分布特征研究

为了解毛竹(Phyllostachys edulis)细根的分布规律,对不同水平距离和土层深度0~1 mm和1~2 mm细根的生物量、比根长、组织密度和根长密度进行了分析。结果表明,随着毛竹年龄的增加,细根生物量和根长密度先上升后降低,根组织密度先降低后升高,比根长呈降低的趋势。细根生物量和根长密度以距竹秆60 cm处最大,根组织密度以20 cm处最大,比根长在40 cm处最大,但他们在距竹秆不同距离间的差异不显著。细根生物量以10~20 cm土层最大,根组织密度以20~30 cm土层最大,细根生物量、比根长、组织密度和根长密度在不同土层间的差异不显著。与1~2 mm细根相比,0~1 mm细根生物量和根组织密度更小,比根长和根长密度更大。因此,毛竹年龄对细根生长具有显著的影响,1年生毛竹有最大的比根长和较大的根组织密度,具有更强的资源利用率。毛竹细根在一定的土层范围内呈均匀分布状态,可更有效地利用特定区域的水肥资源。     

杉木成熟林细根形态与功能特征的海拔梯度变异特点

为探究植物对环境变化的适应策略,在安徽省金寨县天马国家自然保护区,以不同海拔高度(750、850、1000、1150 m)杉木(Cunninghamia lanceolata)成熟林为对象,采用土钻法获取土壤细根样品,分别测定了不同海拔不同土层(0—10 cm、10—20 cm、20—30 cm)土壤细根生物量、形态特征参数和碳氮含量。结果表明:(1)随海拔梯度增加,0—30 cm土层细根生物量、根长密度、比根长、表面积密度、体积密度均呈先减少后增加趋势,在海拔750 m生物量最大,其余指标在海拔1150 m最大;随土层深度增加,同一海拔细根生物量、根长密度、表面积密度、体积密度均呈减少趋势。(2)随海拔梯度增加,0—30 cm土层细根C和N含量呈先增加后减少趋势,C/N比呈先减少后增加再减少趋势;随土层深度增加,同一海拔细根C含量呈先减少后增加趋势,N含量呈降低趋势,C/N比呈上升趋势。(3)细根N含量与生物量、根长密度和体积密度显著正相关,C/N比与生物量、根长密度、表面积密度和体积密度极显著负相关。(4)土壤水分对细根生物量及其形态指标影响显著。     

漓江水陆交错带典型立地根系分布与土壤性质的关系

研究根系与土壤关系是发掘河岸带生态退化等问题内在原因的重要途径。在漓江流域水陆交错带选取缓坡、陡坡、江心洲、人工岸坡4种典型立地类型,对不同土层深度的根长密度、根系生物量、比根长,以及根系特征与土壤有机质、全氮、有效磷的关系进行了研究,旨在为漓江流域生态修复过程中植被恢复、植被配置、快速绿化材料选取提供科学依据。结果表明:(1)同一立地类型0—10 cm土层和10—20 cm土层比根长差异性不显著。0—10 cm到10—20 cm土层,各立地类型根长密度和根系生物量密度均减小,但不同立地类型根长密度和根系生物量密度的差异程度逐渐缩小,表明地形、地表植物类型及生长状况对根长密度分布的影响也随土层深度的增加而逐渐减小。细根根长和生物量随着土壤深度的增加而减小。(2)土壤有机质含量差异性显著,分布规律为人工岸坡陡坡江心洲缓坡;土壤全氮含量从大到小依次是人工岸坡、陡坡、缓坡、江心洲,其值分别为:3.12、2.33、1.56、1.32 g/kg;土壤全氮与土壤有机质呈显著正相关。江心洲和缓坡有效磷含量远远大于人工岸坡和陡坡,原因是漓江水长期受人为洗漱影响,导致受江水干扰大的立地类型有效磷含量高。(3)根长密度、比根长、根系生物量与有机质、全氮含量呈正相关,与有效磷含量呈负相关,说明土壤根系越丰富,越有利于增加土壤有机质和全氮含量,但遏制了土壤有效磷。细根长度、生物量与根长密度在0.01水平(双侧)上显著正相关,与根系生物量密度呈负相关。     

间伐对黄龙山油松中龄林细根空间分布和形态特征的影响

为探究油松细根生长与抚育间伐的关系,以黄龙山林区4种不同间伐强度(对照,轻度,中度,强度)下的油松人工中龄林为研究对象,采用根钻法,分3层(0—20,20—40,40—60cm)获取细根样品,研究了间伐强度对油松细根生物量和形态特征的影响。结果表明:油松细根生物量主要分布在0—20 cm土层,不同间伐强度下细根生物量差异显著(P0.05),随间伐强度的增大,细根生物量先升高后降低,强度间伐下0—20 cm土层细根生物量显著降低(P0.05),20—40 cm土层和40—60 cm土层细根生物量所占比例随间伐强度的增大而增大。细根根长密度和根表面积密度在不同间伐强度和不同土层间均差异显著(P0.05),且变化规律与生物量基本一致。细根比根长和比表面积随间伐强度的增加而增大,且强度间伐与其他强度呈显著性差异(P0.05)。轻度和中度间伐对小径级细根(0—1.0 mm)有显著影响,对较大径级细根(1.0—2.0 mm)的影响则不显著(P0.05),强度间伐对0—2.0mm的细根均有显著影响(P0.05)。中度间伐(保留郁闭度0.7)条件下,油松林地细根总生物量达到最大1022.43 g/m2,此条件下细根的根长密度和根表面积密度也达到最大,能充分利用林地的立地资源,最有利于保留木的生长。     

不同林龄红锥人工林细根垂直分布和衰老生理特征

以广西桂东和桂南地区3种林龄(7、14和25 a)红锥人工林细根为对象,在红锥生长旺季,采用根钻法,分表层(0～20 cm)和亚表层土壤(20～40 cm)获取细根,研究不同林龄红锥人工林细根在不同土层的形态、生物量以及衰老生理生化指标变化特征,以期深入认识红锥生长发育机制及林分生产力,为红锥人工林可持续经营提供依据。结果表明:在相同土层中,随林龄增加,红锥细根根长密度、根表面积密度、生物量、比表面积、细根活力、可溶性糖和可溶性蛋白含量均显著增加,而比根长、游离脯氨酸和丙二醛(MDA)含量显著减少;在相同林龄下,随土壤深度增加,红椎细根比根长、比表面积、细根活力、各渗透调节物质含量均显著增加,而根长密度、表面积密度、生物量、MDA含量显著减少;林龄和土层的交互作用对细根生物量、可溶性糖、可溶性蛋白和MDA含量有显著影响。细根根长密度、根表面积密度和生物量与各土壤因子间呈显著正相关;细根游离脯氨酸含量与各土壤因子间呈显著负相关;细根活力、可溶性糖和可溶性蛋白仅与土壤含水率、速效氮呈显著正相关。因此,7 a红锥细根易衰老,更新快,14 a林次之,25 a林细根更新慢;表层土(0～20cm)的红锥细根代谢旺盛,周转速率快,寿命较短。     

岷江上游4个栽培树种细根功能性状垂直分布的差异性

细根(直径≤2 mm)功能性状及垂直分布格局是反映植物对土壤资源吸收策略和影响森林地下生态过程的关键。本研究以岷江上游4个人工林树种连香树(Cercidiphyllum japonicum)、白桦(Betula platyphylla)、华山松(Pinus armandii)和油松(P.tabuliformis)为对象,调查不同海拔树木细根功能性状及其在不同土层间的垂直分布格局,并分析细根功能性状分布与构型之间的相关关系。结果表明:阔叶树种比针叶树种有更大的根长密度、生物量、比根长和比表面积,而直径反之;4个树种细根集中在0~20 cm土层,根长密度和生物量在较高海拔地段均显著大于较低海拔,且均随土壤深度增加而减少,但比根长、比表面积和直径无显著的海拔差异,随土层加深也无明显的垂直变化规律;针阔树种间的细根构型差异显著,但不受海拔差异的影响,阔叶树的细根分支强度与一级根数量显著大于针叶树种;一级根数和根尖密度与比根长以及分根比与根长密度和生物量均呈显著正相关,而分叉与几个细根功能参数均呈负相关;随着土层深度增加,细根总生长量明显减少,但细根资源利用效率和策略不变;5个细根功能性状的垂直分布格局差异明显,且受树种特性影响显著,细根分支构型对其垂直分布及资源获取策略具有显著影响。     

岷江上游4个栽培树种细根功能性状垂直分布的差异性

细根(直径≤2 mm)功能性状及垂直分布格局是反映植物对土壤资源吸收策略和影响森林地下生态过程的关键。本研究以岷江上游4个人工林树种连香树(Cercidiphyllum japonicum)、白桦(Betula platyphylla)、华山松(Pinus armandii)和油松(P. tabuliformis)为对象,调查不同海拔树木细根功能性状及其在不同土层间的垂直分布格局,并分析细根功能性状分布与构型之间的相关关系。结果表明:阔叶树种比针叶树种有更大的根长密度、生物量、比根长和比表面积,而直径反之; 4个树种细根集中在0～20 cm土层,根长密度和生物量在较高海拔地段均显著大于较低海拔,且均随土壤深度增加而减少,但比根长、比表面积和直径无显著的海拔差异,随土层加深也无明显的垂直变化规律;针阔树种间的细根构型差异显著,但不受海拔差异的影响,阔叶树的细根分支强度与一级根数量显著大于针叶树种;一级根数和根尖密度与比根长以及分根比与根长密度和生物量均呈显著正相关,而分叉与几个细根功能参数均呈负相关;随着土层深度增加,细根总生长量明显减少,但细根资源利用效率和策略不变; 5个细根功能性状的垂直分布格局差异明显,且受树种特性影响显著,细根分支构型对其垂直分布及资源获取策略具有显著影响。     

Responses of the fine root morphology and vertical distribution of Populus × euramericana ‘Guariento’ to the coupled effect of water and nitrogen

Aims Irrigation and fertilization have great potentials to enhance yield in forest plantations. The integrated effect of water and nitrogen management on fine roots morphology and distribution of Populus × euramericana ‘Guariento’, however, remains unclear. The objective of this study was to evaluate the effect of water and nitrogen addition on fine root morphology and distribution in poplar plantations for developing the best water and nitrogen strategy for promoting fine root. Methods The soil core method was used to quantify the morphology and distribution of fine roots in the 0–60 cm in a poplar plantation with surface dripping irrigation and fertilization technologies. The experiment included nine treatments, which were a combination of three irrigation treatments where dripping irrigation was applied when soil water potential (ψ_soil) reached –75, –50, or –25 kPa, and three fertilization treatments at nitrogen additions of 150, 300, or 450 g·tree–1·a–1, respectively). A control plot with non-irrigation and non-fertilizationtreatment in growing season (CK) was also included in the study. Important findings The fine roots biomass density, fine root surface area density, average root diameter in all treatments were mainly found at 0–10 cm and 10–20 cm depths, with root biomass density in the 10–20 cm of 1.03 to 1.21 times of that in the 0–10 cm, 1.25 to 1.80 times of that in the 20–30 cm, 1.62 to 22.10 times of that in the 30–40 cm, 2.77 to 54.35 times of that in the 40–50 cm, and 6.48 to 293.09 times of that in the 50–60 cm. The root biomass density in the 10–20 cm accounted for 27%–37% of the total biomass density in the top 60 cm. For root biomass density and average diameter, there were no significant differences between 0–10 cm and 10–20 cm depths, and between 40–50 cm and 50–60 cm depths. Fine roots in the irrigation and fertilization treatments were significantly higher than that of the CK, except the D1F1 treatment (i.e., with low water and low nitrogen level). Additionally, fine roots in the D2F3 treatment (i.e., with intermedia irrigation and high nitrogen level) and the D3F3 treatment (i.e., with high water and high nitrogen level) were significantly higher than those in other treatments, but not significantly different between D2F3 and D3F3. Compared with the CK, the fine roots biomass density in six soil layers were significantly enhanced at 359%, 388%, 328%, 3823%, 4774% and 2866%, respectively, for the treatment with high water and high nitrogen levels. The vertical distributions of fine roots appeared not affected by the interaction of irrigation and nitrogen addition. However, the surface dripping irrigation and fertilization treatments increased fine roots significantly. Finally, we found that the response of fine root growth and distribution was stronger to fertilization than to the irrigation in this poplar plantation.     

Wheat root biomass and nitrogen dynamics—effects of daily irrigation and fertilization

Root biomass, root nitrogen content, and root distribution down to 50 cm depth in winter wheat were determined by soil coring on five dates in four different treatments: control (C), drought (D), daily irrigation (I), and daily irrigation and fertilization (IF). The first three treatments received the N fertilizer application as a single dose in spring, whereas in IF daily doses of N were supplied in the irrigation water using a drip-tube system, according to the estimated nutrient demand of the crop. All treatments received 20 g N m⁻² year⁻¹. The maximum root biomass (104 g m⁻²) was reached earliest in IF. On 6 June, root samples were taken down to a depth of 100 cm, and the proportion of deep roots (50–100 cm) was least in I, indicating that it had the shaklowest root system. The root biomass as a fraction of the total plant mass decreased during crop development in all treatments down to about 4% at harvest. The decrease was more rapid in I and C than in D and IF. The higher proportion of roots during spring in D and IF coincided with a low nitrogen concentration in the roots, which was attributed to the restricted water supply and to the relative shortage of nitrogen during early crop development in D and IF, respectively. The dynamics of mass and nitrogen in macroscopic organic debris in the soil suggested that root turnover rates were high. ei]{gnB E}{fnClothier}     

Development of root biomass in an Eucalyptus globulus plantation under different water and nutrient regimes

The distribution along the soil profile of Eucalyptus globulus root biomass was followed in a plantation in central Portugal at 1, 2 and 6 years after planting, using an excavation technique. The experimental design consisted of a control (C) and 3 treatments: application of solid fertilizers twice a year (F), irrigation without the application of fertilizers (I) and irrigation combined with liquid fertilizers (IL). Below- and above-ground biomass decreased as follows: IL>I>F>C. So, water stress limited growth more severely than nutrient stress. The roots rapidly colonized the top soil volume (0–20 cm depth) during the first year after planting. Fine root biomass 6 years after planting was 2.2, 1.8 and 1.6 times higher in IL treatment than it was respectively in control, and in F and I treatments. The distribution of fine roots along the soil profile 6 years after planting was more even in IL compared to the other treatments. However, fine roots in the top soil were more concentrated along the tree rows in the irrigated treatments than in the others. The proportion of below-ground biomass relative to the total tree biomass and the root/shoot ratio were higher in C than in the treatments at early growth stages. This pattern was not so clear 6 years after planting, due to the increased proportion of the tap root relative to total biomass, especially in the IL treatment.     

酚酸和氮素交互作用下欧美杨107细根形态特征

树木细根生长与根际过程的关系十分密切。该研究仿生欧美杨107 (Populus × euramericana ‘Neva’)人工林根际土壤酚酸沉降与氮素有效性变化, 通过设置3种酚酸梯度(0X、0.5X、1.0X, X为田间土壤酚酸含量)与3种氮素水平(缺氮0 mmol·L^-1、正常氮10 mmol·L^-1、高氮20 mmol·L^-1), 探究酚酸和氮素对欧美杨107细根形态的影响, 以期为阐明树木根系生长对根-土界面过程的响应奠定基础。结果表明: (1)在无酚酸(0X)环境中, 缺氮和高氮均可抑制欧美杨107细根生长, 尤其对1-3级细根的影响更为显著。比根长随氮素水平升高逐渐减小, 但其他细根特征并未呈现与氮素水平的线性关系。(2) 0.5X和1.0X酚酸梯度相比, 欧美杨107的1-2级细根直径和体积随酚酸浓度增加而显著增大(p < 0.05)。酚酸和氮素对杨树细根的影响存在交互作用, 1-2级细根直径、体积受酚酸的影响显著, 而4-5级细根长度、表面积受氮素影响显著。双因素方差分析结果表明, 酚酸和氮素对细根形态建成具有协同或拮抗效应。(3)主成分分析(PCA)和冗余分析(RDA)结果表明, 在酚酸和氮素交互效应下, 杨树1-3级、 4级、 5级细根之间具有显著的形态差异。第一主成分主要体现细根觅食性状特征, 可解释细根形态变异的60.9%的信息; 第二主成分主要体现细根形态构建特征, 可解释25.3%的信息。杨树细根形态变化与根序高度相关, N素影响杨树细根形态的主效应较酚酸更强。因此, 根际环境中酚酸累积和氮素有效性变化会影响杨树细根的形态构建和细根对水分、养分的吸收, 而氮素有效性是影响杨树细根生长的重要因素, 开展杨树人工林土壤养分管理是林分生产力长期维持的关键。     

Interactive effects of phenolic acid and nitrogen on morphological traits of poplar (Populus × euramericana ‘Neva’) fine roots

Aims The relationship between rhizosphere process and fine root growth is very close but still obscure. In poplar plantation, phenolic acid rhizodeposition and soil nutrient availability were considered as two dominant factors of forest productivity decline. It is very hard to separate them in the field and they might show an interactive effect on fine root growth. The objective of this study is to examine the influence of phenolic acids and nitrogen on branch orders of poplar fine roots and to give a deeper insight into how the ecological process on root-soil interface affected fine root growth as well as plantation productivity. Methods The cuttings of health annual poplar seedlings (I-107, Populus × euramericana ‘Neva’) serve as experiment materials, and were cultivated under nine conditions, including three concentration of phenolic acids at 0X, 0.5X, 1.0X (here, X represented the contents of phenolic acids in the soil of poplar plantation) and three concentration of nitrogen at 0 mmol·L^-1, 10 mmol·L^-1, 20 mmol·L^-1, based on Hoagland solution. The roots were all separated from poplar seedlings after 35 days, and 30 percent of total fine roots of every treatment were taken as fine root samples. These fine roots were grouped according to 1 to 5 branch orders, and then the morphological traits of each group of fine roots were scanned via root analyzer system (WinRHIZO, Regent Instruments Company, Quebec, Canada) including total length, surface area, volume and average diameter. Meanwhile, the dry mass of fine root samples of every order was measured to calculate specific root length (SRL), root tissue density (RTD). All data were analyzed via SPSS 17.0 software, and interactive effect of phenolic acids and nitrogen on roots was analyzed through univariate process module. Principal component analysis (PCA) and redundancy analysis (RDA) were conducted via Canoco 4.5 software. Important findings Under the conditions without phenolic acids application, the fine roots growth was significantly inhibited in deficiency and higher nitrogen treatments, especially for 1-3 order roots. Only specific root length appeared decreased with nitrogen level, and other traits of fine roots did not demonstrate linear relationship with nitrogen concentrations. Compared to 0.5X phenolic acids treatment, 1.0X phenolic acids significantly promoted the diameter and volume of 1-2 order roots (p < 0.05). Both phenolic acids and nitrogen demonstrated influence on poplar fine root traits. However, the diameter and volume of 1-2 order roots were significantly affected by phenolic acids, while the total length and surface area of 4-5 order roots was affected by nitrogen. Two way ANOVA showed that phenolic acids and nitrogen made a synergistic or antagonistic effect on morphological building of fine roots. Furthermore, PCA and RDA indicated that the interactive effects of phenolic acids and nitrogen led to significant differences among 1-3 order, 4th order and 5th order of poplar fine roots. The PC1 explained about 60.9 percent of root morphological variance, which was related to foraging traits of roots. The PC2 explained 25.3 percent of variance, which was related to root building properties. The response of poplar roots to phenolic acids and nitrogen was closely related to root order, and nitrogen played more influence on poplar roots than phenolic acids. Thus, phenolic acids and nitrogen level would affect many properties of root morphology and foraging in rhizosphere soil of poplar plantation. But nitrogen availability would serve as a dominant factor influencing root growth, and soil nutrient management should be critical to productivity maintenance of poplar plantation.     

华北落叶松林细根生物量对土壤水分、氮营养空间异质性改变的响应

在华北落叶松(Larix principis-rupprechtii)林选取采伐干扰样地和未采伐干扰样地进行对比研究, 分析采伐干扰造成林下土壤水分和氮营养空间异质性的改变对细根生物量空间变异的影响。采用空间格局分析的小支撑、多样点的设计原则, 对每个样点的土壤分3层取样(0-10 cm、10-20 cm、20-30 cm)。进行细根(≤1 mm和1-2 mm)生物量与土壤含水量、全氮、硝态氮、铵态氮和土壤pH的偏相关分析, 以及细根生物量变异函数值和土壤各因子变异函数值的线性回归分析。研究结果表明, 在不同样地, 细根生物量与土壤各因子均表现为正相关关系, 不同土层相关性强弱表现各异, 其中土壤含水量与细根生物量的相关性显著。受采伐干扰后, 细根生物量与土壤含水量、全氮、土壤硝态氮空间变异的关联性更趋于明显。多元线性回归分析结果表明, 采伐干扰样地细根生物量的空间变异更多地受到土壤多因子的综合影响, 而未采伐干扰样地的细根生物量受土壤水分、全氮和硝态氮单独效应的影响更大。     

杨树人工林细根数量和形态特征的季节动态及代际差异

采集欧美杨107Ⅰ代和Ⅱ代人工林细根样品,分析杨树不同根序细根数量特征(根长度、表面积和生物量)和形态特征(比根长、根长密度、根组织密度)对季节波动的响应及其代际差异.结果表明： 杨树各根序细根数量特征(根长度、表面积和生物量)均呈明显的季节变化,且具有明显的根序差异性.低级根序细根数量特征季节差异显著,细根生物量在生长季显著增加而生长季后显著下降.高级根序细根比根长季节波动显著,而根长密度和根组织密度等形态特征波动较小.连作导致人工林杨树1～2级细根长度、生物量、比根长和根长密度在生长季显著增大.1级细根数量特征与土壤温湿度呈显著正相关,与土壤有机质和速效氮含量呈显著负相关;而2级细根数量特征仅与土壤养分显著相关.杨树人工林细根特征的季节动态及代际差异体现了杨树对细根的碳投入变化,因连作引发的土壤养分匮乏可能引发植株对根系的碳投入增加,这种碳分配格局与人工林地上部分生产力形成密切相关.     

Fine root growth and element concentrations of Norway spruce as affected by wood ash and liquid fertilisation

A field experiment to test various management practices of sustainable forestry was conducted in a Swiss spruce forest for two growing seasons. Treatments were a control (C), yearly application of 4000 kg ha^–1 wood ash (A), daily irrigation with a steady state fertilisation as `optimal nutrition` (F) and irrigation with a water control (W). Samples were taken on a 5 × 5 m grid once a year with a soil corer to determine fine root biomass ( 2 mm) and soil pH of the topsoil. A subset of the fine root samples was further analysed for its nutrient composition by CN and ICP-AES analyses. The dynamics of root growth were observed with the aid of ingrowth-cores after 1, 1.5, and 2 years of treatment and the growth pattern was analysed in terms of biomass, tips, forks, length and root diameter of the samples. The A, F and also the W treatment resulted in a significant increase of soil pH in the topsoil. The fine root density increased over the two growing seasons, irrespective of the treatment. The root growth was only slightly different between the treatments with a initially faster growth under the A treatment. The W treatment reduced the number of root tips and forks, and the root length, while the A treatment increased the number of root tips, forks and the root length, but reduced the diameter. The differences between the three harvesting times (March 1999, October 1999, March 2000) of the ingrowth-cores stressed seasonal differences in root growth and the development of quasi `steady state' root dynamics. The root turnover was not changed by the treatments. The elements in the fine roots were strongly affected by the treatments A and F and sometimes by W. Fine root N increased with the F treatment, while C concentrations decreased under the A, F and W treatments. The Ca and Mg concentrations were strongly enhanced by A but also by the F treatment. The K and P concentrations in the fine roots were improved by all three applications. Due to the pH increase Al, Fe and Mn concentrations in the fine roots were decreased by the A and F treatments. S and Zn concentrations showed inconsistent changes over the growing seasons. The results of this study were comparable with those of other studies in Europe and confirm the abilities of the fine roots as indicators of forest nutrition, to some extent more sensitive than the commonly used foliar analysis.     

模拟氮沉降对中亚热带杉木幼树根系生物量的影响

植物根系是全球陆地生态系统碳储量的重要组成部分,在全球生态系统碳循环中起着重要作用,日益加剧的氮沉降会影响根系生物量在空间和不同径级的分配,进而影响森林生态系统的生产力和土壤养分循环。以杉木幼树为研究对象,通过野外氮沉降模拟实验,研究氮沉降四年后对不同土层、不同径级根系生物量的影响。结果发现：（1）低氮和高氮处理总细根生物量较对照均无显著差异（P > 0.05）,高氮处理粗根生物量及总根系生物量较对照分别增加45%和40%（P < 0.05）;（2）与对照相比,施氮处理显著增加20-40 cm与40-60 cm土层细根和粗根生物量,且在低氮处理下,20-40 cm土层细根、粗根在总土层细根与粗根生物量的占比显著提高。（3）与对照相比,高氮处理显著增加了2-5 mm、5-10 mm及10-20 mm径级的根系生物量,低氮处理显著增加2-5 mm、5-10 mm径级根系生物量,且显著降低20-50 mm径级根系生物量。综上所述表明：氮沉降后杉木幼树通过增加较粗径级根系来增加对养分及水分的输送,同时通过增加深层根系生物量及其比例的策略来维持杉木幼树的快速生长;而根系生物量的增加,在一定程度上会增加根系碳源的输入,影响土壤碳循环过程。     

指数施肥对楸树无性系生物量分配和根系形态的影响

为探求楸树不同无性系生物量分配和根系形态的差异,2011年3-8月在甘肃省天水市小陇山林科所,以2年生楸树无性系1-4、7080和015-1组培苗为试验材料,设置了CK、6、10、14 g尿素/株4个处理,研究指数施肥对楸树无性系生物量分配和根系形态的影响.结果表明:(1)同一无性系中,10 g尿素/株的根、茎、叶生物量及总生物量、根长、根表面积、根体积和根平均直径均高于其它处理.无性系015-1的生物量和根系形态参数整体上高于无性系1-4和7080.无性系015-1在10 g尿素/株的根、茎、叶生物量及总生物量分别为89.44 g、61.30 g、79.97 g、230.71 g,是CK的1.48、1.52、2.09、1.66倍;根长、根表面积和根体积为22667 cm、6260 cm2、578.14 cm3,是CK的1.94、1.54、2.43倍.(2)指数施肥和无性系的遗传差异明显影响楸树不同无性系生物量的分配格局.适量施氮明显促进3个楸树无性系生物量的积累,而氮素缺乏或过量均不利于生物量的积累.8月同一无性系的根冠比均随施氮量的增加而降低;同一处理下无性系7080的根冠比高于无性系1-4和015-l.无性系1-4和7080的生物量主要向叶和茎分配,而无性系015-1主要向叶分配.(3)指数施肥在6月和7月主要促进细根根长和根表面积的增加;指数施肥在8月主要促进细根、中等根和粗根体积的急剧增加,分别比7月高达36.88％、124.96％、154.79％.这利于根系在中后期吸收更多养分,从而引起生物量分配格局的变化.(4)生物量参数和根系形态参数关系密切.根生物量、地上生物量、总生物量分别和根长、根表面积、根体积、根平均直径极显著正相关;根冠比和根长、根表面积、根体积、根平均直径极显著负相关;比根长和地上生物量、总生物量显著正相关,和根冠比极显著负相关.