北美红杉组培快繁体系的建立与优化

以北美红杉1年生带芽茎段为外植体,通过基本培养基筛选和不同植物生长调节剂水平对比试验得到北美红杉组织培养的不定芽诱导、增殖、生根等生长阶段的优化配比培养基,以期建立北美红杉高效的快繁体系。结果表明:确定最佳消毒方法为75%乙醇消毒30 s,无菌水冲洗2次,再用0.1%氯化汞消毒处理10 min,无菌水冲洗4次;最佳不定芽诱导培养基配方为MS+6-BA 1.0 mg·L^-1+NAA 0.10 mg·L^-1+蔗糖30 g·L^-1+琼脂6 g·L^-1,不定芽诱导效果最好,诱导芽率高达2 153.3%,且芽生长健壮;最佳不定芽增殖培养基配方为MS+6-BA 1.0 mg·L^-1+NAA 0.10 mg·L^-1+蔗糖30 g·L^-1+琼脂6 g·L^-1,增殖系数高达15.8;最佳生根培养基配方为1/2MS+KT 1.5 mg·L^-1+IBA 1.0 mg·L^-1+蔗糖30 g·L^-1+琼脂6 g·L^-1,其生根率达90.0%,根多且粗长,植株高大健壮;最佳移栽基质为V_炉渣∶V_原土∶V_腐殖土=1∶1∶1,植株成活率达91.7%。     

北美红杉扦插生根的影响因素分析

研究了扦插基质,激素种类、浓度与处理时间,采条部位以及基因型对北美红杉扦插成活率的影响。结果表明:基质配比、激素种类、浓度及处理时间、采条部位等对北美红杉扦插成活率均有显著影响。基质配比以珍珠岩∶草炭=7∶3效果最好;激素以1 000 mg/kg ABT速蘸处理效果为佳;枝条顶部插穗好于下部插穗。不同基因型的扦插成活率差异显著。选取合适的基因型,采集顶部插穗,用1 000 mg/kg的ABT速蘸处理,扦插在珍珠岩∶草炭=7∶3的基质上能获得理想的效果。     

北美红杉生态因子的研究状况

北美红杉自然分布范围狭窄 ,通过 10 0多年的努力 ,北美红杉已在 2 0多个国家成功引种。许多学者对北美红杉的生态因子进行了大量的研究。为了解国内外的研究状况 ,从影响北美红杉分布和生长的光、温度、雾、土壤 4个重要的生态因子出发 ,结合该树种自然分布区的生态环境 ,对其研究成果进行了概括和分析     

北美红杉种子育苗试验

对不同种源的北美红杉种子作不同试剂浸种处理和控制不同发芽温度的发芽试验 ,以及开展不同种源种子的播种育苗试验 ,结果表明 :种子发芽率和发芽势最好的方案是用SYA6种源 ,种子经 10 0 0mg/L的KMnO4溶液浸泡 12h ,发芽温度采用 2 0℃。参试的 3种因素中 ,种源因素对种子发芽率和发芽势影响显著 ;北美红杉各个种源苗木生长迅速 ,1年生苗木除苗木侧根数外 ,各种源间苗木的苗高、地径、主根长度、苗木鲜重和苗木干重差异极显著     

Phellinus torulosus on Cupressus sempervirens in Italy

Phellinus torulosus was reported for the first time on Cupressus sempervirens in Tuscany, Italy. This fungus causes white rot in roots and stems and may also invade and kill the cortical tissue. The invasion of trees by the fungus and its subsequent spread is probably facilitated by fire scars.     

北美红杉不同个体间插穗生根能力的研究

对北美红杉不同个体间插穗生根能力的试验研究表明:北美红杉不同个体间插穗生根能力存在着很大的变异性,其中生根率的变异范围在16%~100%,插穗的平均生根时间变异范围在39~110d;生根率与平均生根时间的负相关关系达到了极显著水平(相关系数r=-0.846 6);对31个单株个体插穗的生根类型研究表明,有27个为以愈伤组织生根为主的类型,有4个为中间生根类型;插穗生根率随着生根类型多样性的增加呈现升高的趋势。     

北美红杉在云南的引种成效及其造林展望

北美红杉在云南引种栽培近30年,生长发育正常,与原产地比较相近,保持了速生特性和较强的抗逆性。引进的北美红杉不同种源、不同无性系,在云南不同生态环境生长有显著差异;在幼龄期表现较好的有SYA4s、SYA6s等6个优良种源和无性系,分别适应云南省的纬度范围为北纬22°59′～26°52′,海拔高度为1300～2400m的不同海拔、不同气候带、不同生态环境。还有少数耐寒种源和无性系,在海拔3200～3500m的高寒山地也能生长。该项研究对促进北美红杉在云南发展造林将起到积极推进作用。     

Wildfire Effects on Understory Vegetation,Natural Regeneration,and Forest Floor Fuels in a Sierran Mixed Conifer Stand

Wildfire effects on understory shrubs and herbs, regeneration of the seedling and sapling size classes, and downed and dead fuels were assessed in a mixed conifer stand located in the Lake Tahoe Basin in which California white fir (Abies concolor var. lowiana [Gord.] Lemm.) was most abundant but with Jeffrey pine (Pinus jeffreyi Grev. & Balf.) also prevalent. In burned and unburned stand portions, prefire measurements served as a basis of comparison for the postfire measurements pertinent to each study component. Fire severely suppressed the understory vegetation, which was dominated by shrubs such as bush chinquapin (Chrysolepis sempervirens [Kellogg] Hjelmqvist) and antelope bitterbrush (Purshia tridentata [Pursh] DC.), while a tepid postfire recovery of most of the preexisting species in the burned stand portion was augmented by new ones, including shrubs such as snowbrush (Ceanothus velutinus Douglas ex Hook.) and whitethorn (Ceanothus cordulatus Kellogg) ceanothus and herbs such as Holboell's rockcress (Arabis holboellii Hornem.). Tree seedling abundance was also substantially reduced in the burned portion, but the postfire population was dominated by Jeffrey pine whereas white fir had been most prevalent originally. Sapling regeneration was eliminated from the burned stand portion regardless of species. Downed and dead fuel loading was severely diminished by the fire, especially regarding fine fuels, permitting subsequent sheet erosion to imperil new seedling regeneration. These results contribute to an understanding of the direction and pace of postwildfire succession on sites occupied by Sierra Nevada mixed conifer and similar forest cover types, which is critical in decisions concerning the need for, and extent of, postfire site rehabilitation measures.     

常春油麻藤种子萌发和扦插繁殖试验

[目的]筛选常春油麻藤(Mucuna sempervirens)最佳播种和扦插繁殖技术。[方法]采用磨破种皮和不同温度的热水浸泡种子处理,开展种子发芽试验;采用L9(34)正交试验设计研究插穗年龄、激素种类、激素浓度对常春油麻藤扦插的影响。[结果]种子不经任何处理,发芽率为28.3%,将种皮磨破后播种,种子发芽率为71.6%,明显高于种皮完好的种子发芽率;用热水浸泡种子可提高种子发芽率,但影响不明显;插穗年龄对扦插生根有显著影响,其中1~2年生枝条扦插成活率最高,其次为多年生枝条,当年生嫩枝成活率最低,激素种类和激素浓度对生根率的影响较小。[结论]磨破种皮可明显提高常春油麻藤种子的发芽率,A2B3C2为扦插处理试验最优组合,即1~2年生枝条用200 mg/L的IBA处理,扦插生根率最高。     

Presettlement and modern disturbance regimes in coast redwood forests: Implications for the conservation of old-growth stands

Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.