不同外援营养液对白灵菇生长的影响

以白灵菇菌株TN01为试材,选取香菇、杏鲍菇、白玉菇3种食用菌菇根为原料配制外援营养液,测定各营养液主要成分含量,并研究了不同类型与浓度营养液对白灵菇菌丝及子实体生长的影响,以期为白灵菇的高产栽培技术提供参考依据。结果表明:与常规PDA培养基相比,适量加入白玉菇菇根提取液可提高白灵菇菌丝生长速度;添加外援营养液对子实体的农艺性状影响不大,对产量有一定的促进作用,其中施用香菇菇根提取液的白灵菇子实体产量最高,小区总产量与对照相比提高了54.6%。施用香菇菇根提取液后对白灵菇子实体中的硝酸盐含量及蛋白质含量有提升的效果,但对亚硝酸盐及粗纤维含量无促增长的效果。     

黑沙蒿根系抗拉特性及其与化学成分的关联性

[目的] 探讨根系抗拉特性与主要化学成分含量的关联性，以期充实根系固土力学特性研究以及提供矿区生态恢复和植物保护的理论支持。[方法] 以神东矿区广泛分布的多年生灌木黑沙蒿（Artemisia ordosica）为研究对象，利用TY8000伺服式强力机，研究1~4 mm径级直根段、含侧根分支处根段抗拉材料的力学特性并测定各径级的纤维素、半纤维素和木质素，研究根系材料力学及其与化学成分的关联性。[结果] ①随着根系直径增加，黑沙蒿直根段、含侧根分支处根段抗拉力增加，而抗拉强度和杨氏模量减小，且抗拉力、抗拉强度和杨氏模量都与根系直径呈幂函数关系。②直根段、含侧根分支处根段化学成分含量差异显著（p<0.05），平均化学成分含量为：半纤维素（31.69%，32.18%） > 木质素（28.42%，25.30%） > 纤维素（15.50%，15.35%）。③随着根系直径增加，直根段纤维素含量减小，半纤维素和木质素含量增加，而含侧根分支处根段纤维素含量减小，半纤维素和木质素含量无变化。④直根段抗拉强度、杨氏模量与纤维素极显著正相关（p<0.01），与半纤维素、木质素极显著负相关（p<0.01）。含侧根分支处根段抗拉强度、杨氏模量与纤维素极显著正相关（p<0.01），与半纤维素、木质素无相关性。[结论] 黑沙蒿根系抗拉特性与化学成分表现出一定的相关性，且纤维素是影响灌木根系材料力学特性的主要化学组分。     

耕作方式与秸秆覆盖对夏玉米根系分布及产量的影响

为探究夏玉米根系分布及水分利用效率对不同耕作结合秸秆覆盖模式的动态响应,于2017年和2018年在河套灌区开展不同耕作模式田间试验。试验设置,常规(CK)、秸秆表覆(BF)、深翻结合秸秆深埋(SM)和深翻结合秸秆深埋与表覆(BFSM)4种处理。结果表明,BF处理显著提高水平向根长密度,较CK处理高24.7%,SM、BFSM处理显著提高深层根长密度,较CK处理高23.8%;2017年夏玉米根长密度与标准化根深呈显著的三阶多项式函数关系,用2018年实测值率定效果较好,可较好描述不同耕作模式根长密度分布。BF、SM、BFSM处理较CK处理根冠比显著提高3.8%、20.8%、26.4%(P<0.05),较CK处理夏玉米产量及水分利用效率分别显著提高8.6%、19.5%、19.7%和13.6%、32.3%、34.8%(P<0.05),SM与BFSM处理差异不显著。该研究为河套灌区农业耕作模式提供一定借鉴。     

黄土高原陡坡土坎植被根-土复合体抗剪强度研究

以黄土高原陡坡土坎6种典型植物群落类型为研究对象，在分析植被根系密度指标的基础上，通过直剪试验，探讨不同植物群落的根-土复合体抗剪强度以及根系对提高抗剪强度的作用。结果表明:1）6种群落的根系密度指标值均具有显著性差异，白刺花-铁杆蒿群落的根重密度、根长密度和根表面积密度在所有群落类型中均为最高，分别为2 757.07 g/m³、17 886.22 m/m³和16.96 m²/m³；2）6种群落之间的根-土复合体的抗剪强度均显著高于素土抗剪强度，其中白刺花-铁杆蒿群落相对于素土的抗剪强度增加值最大，为32.98 kPa，且抗剪强度增加值随土层深度增加而降低；3）根-土复合体抗剪强度相对于素土抗剪强度的增加值与根系密度指标值呈对数函数关系，随根系含量增加而升高。     

退化高寒草甸斑块根—土复合体特征研究

高寒草甸斑块的根-土复合体对局部水土流失过程具有调控作用,为研究其特征及抗侵蚀效应,本研究选取三江源区达日县境内典型中度退化草甸的植被斑块为研究对象,调查草甸斑块中心与边缘植物群落特征,测定斑块边缘0～10 cm土层和斑块中心0～20 cm土层的容重、含水率、毛管孔隙度等土壤物理性质,并开展单根拉伸和根-土复合体直剪试验。结果表明：受优势种矮嵩草的分布影响,地上生物量主要分布在斑块中心,根系主要分布在0～10 cm土层;斑块中心区域土壤抗剪强度、内摩擦角和粘聚力均随土层深度的增加而减小;斑块边缘区域土壤粘聚力,抗剪强度明显高于斑块中心区域,草甸斑块植物根系是土壤抗剪强度的主要影响因素。草甸斑块根-土复合体能明显增加退化草甸土壤的抗侵蚀能力,研究结果可为深入研究高寒草甸根系固土功能及水土流失调控提供科学依据。     

草本植物根系对边坡浅层稳定性影响研究

为研究草本植物根系对边坡浅层稳定性的影响,在假设滑坡体为长方体的条件下,通过对植物根系加固边坡的力学原理进行分析,推导了植物根系对边坡浅层稳定性的安全系数公式,并计算分析了坡度、滑坡体尺寸以及根土面积比对边坡稳定性的影响。结果表明:随着边坡坡度及滑坡体尺寸的增加,边坡的稳定系数将减小。并且,植物护坡的坡体安全系数要大于无防护坡体的安全系数。随着根-土面积比的增大,坡体的稳定系数逐渐增加,说明植物根系能增加边坡的稳定性。     

西双版纳橡胶林细根生物量及其周转

用土钻法研究了西双版纳橡胶Hevea brasiensis林0～20cm土层中≤2mm细根的生物量和生长量,用分解袋法研究了橡胶林细根的分解,结果表明:0～10cm的细根生物量显著高于10～20cm的细根生物量(p<0.01);在0～20cm土层中,橡胶林活细根和死细根现存量分别为2 206 kg·hm~(-2)和345 kg·hm~(-2);活细根现存量的最大值出现在5月份,最小值出现在11月份;死细根现存量的最大值出现在2月份,最小值出现在8月份;年分解量、年死亡量、年生长量和年周转率分别为213 kg·hm~(-2)、733 kg·hm~(-2)、1 801 kg·hm~(-2)和82%。     

Relative contribution of initial root and shoot morphology in predicting field performance of hardwood seedlings

Single and multiple linear regression techniques were used to explain the capacity of initial seedling root volume (Rv) and first-order lateral roots (FOLR) relative to shoot height, diameter, and fresh mass to serve as important indicators of stock quality and predictors of first- and second-year height and diameter on an afforestation site in southern Indiana, USA. This was accomplished for northern red oak (Quercus rubra L.), white oak (Quercus alba L.), and black cherry (Prunus serotina Ehrh) seedlings graded into four Rv categories at establishment. Field survival was high (85–97%) for all species. Initial diameter, height, fresh mass, and Rv provided similar predictive ability of second-year field response for absolute height (R² = 0.59–0.77) and diameter (R² = 0.50–0.73) for both oak species. Initial seedling Rv was a better predictor of field response than FOLR for both oak species, though not for cherry. Multiple-variable models accounted for a greater proportion of the total variation in seedling field height and diameter than did single-variable equations. The high R² (up to 0.95) of regression models suggests field performance of these species can be reliably predicted and confirms the importance of initial seedling morphology in dictating early plantation performance.     

Nitrogen-fixation dynamics in a cut-and-carry silvopastoral system in the subhumid conditions of Guadeloupe, French Antilles

This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system to increase soil fertility and insure sustainability. We analyzed the N₂ fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied. Dinitrogen fixation, as estimated by the ¹⁵N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average, 76% of the N exports from the plot in tree pruning (194 kg [N] ha^–1 yr^–1) originated from N₂ fixation. Grass production averaged 13 Mg ha^–1 yr^–1 and N export in cut grass was 195 kg [N] ha^–1 yr^–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha^–1 yr^–1. Carbon sequestration averaged 1.9 Mg [C] ha^–1 yr^–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha^–1 yr^–1, corresponding to 30% of N₂ fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha^–1 yr^–1) and litter decomposition (40 kg [N] ha^–1 yr^–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground tree biomass than nodules. This revised version was published online in June 2006 with corrections to the Cover Date.     

Configuration and development of root systems of cuttings and seedlings of Eucalyptus globulus

Stem cuttings of Eucalyptus globulus are used within tree improvement programs and for mass deployment. To be successful, cuttings must perform as well or better than seedlings. The root systems of cuttings are fundamentally different from those of seedlings. If these differences influence growth, the differences and their consequences must be identified and the propagation system manipulated to improve performance of the propagules.Cuttings are only a viable alternative to seedlings as planting stock if the method of propagation does not affect their growth and development adversely. Full-sibling cuttings and seedlings of Eucalyptus globulus were compared under controlled environmental conditions to minimise extraneous sources of variation, and to establish whether changes in growth or development were induced by propagation. On three occasions over a period of eight weeks root-collar diameter, shoot height, leaf and stem weight, shoot/root ratios and root system morphology were measured on cuttings and seedlings. Seedlings were taller than cuttings throughout the experiment, but both plant types had similar height growth rates. Diameter growth rates were lower in cuttings than seedlings, and there were differences in both height and diameter growth rates between families. Root system configuration differed between the plant types. Seedlings had strongly gravitropic tap-roots, with two types of primary roots from which secondary roots emerged. Cuttings had no tap roots, and the main structural components of their root systems were adventitious roots formed during propagation. Cuttings did not develop further structural roots during the experiment, whereas seedlings continued to develop primary roots. Individual primary roots of cuttings were longer and had larger mid-point diameters than those of seedlings, but the total length of primary roots was greater in seedlings. Seedlings also had a greater number and total length of secondary roots. Shoot/root ratios, calculated from a range of functional measures, were higher in cuttings than seedlings.