杜仲雄花主要活性成分含量的多样性

【目的】研究不同种质杜仲雄花主要活性成分含量的遗传变异规律,比较并评价杜仲雄花主要活性成分含量的多样性,为雄花用杜仲优良资源选育和开发利用提供科学依据和材料。【方法】以193份不同种质杜仲雄花为材料,采用AlCl_3比色法测定杜仲雄花中总黄酮含量,全自动氨基酸分析仪测定氨基酸含量,HPLC法测定桃叶珊瑚苷、京尼平苷酸、绿原酸、京尼平苷、异槲皮苷、紫云英苷6种活性成分含量,并对8种活性成分含量进行变异分析、相关性分析、主成分分析和聚类分析。【结果】不同种质杜仲雄花8种活性成分含量和多样性指数均以氨基酸最高,分别为206.23 mg·g~(-1)和2.05;变异系数以京尼平苷最高,达112.00%,氨基酸最低,仅为12.52%。相关性分析结果显示:桃叶珊瑚苷、京尼平苷酸、绿原酸、京尼平苷及异槲皮苷5种活性成分间均呈极显著正相关,氨基酸除与总黄酮呈极显著正相关外,与其他活性成分相关性不显著。通过主成分分析,前4个主成分的累计贡献率达87.040%,可以用于杜仲雄花资源前期的评价选择。基于8种活性成分,将193份杜仲种质划分为5个类群,各类群8种活性成分含量之间均存在显著性差异。第Ⅰ类群种质8种活性成分含量均较低;第Ⅱ类群种质氨基酸含量最高;第Ⅲ类群种质黄酮类化合物及其组分含量最高;第Ⅳ类群种质环烯醚萜类化合物组分含量最高;第Ⅴ类群种质绿原酸和京尼平苷酸含量最高。初步明确杜仲种质雄花的不同类型。【结论】杜仲种质雄花8种活性成分含量较高,开发利用价值大,而且表现出丰富的多样性和变异,很有选择潜力和改良潜力。     

不同种源多穗柯主要生物活性成分与矿质元素含量变异分析

【目的】阐明多穗柯主要药用活性成分与矿质元素的种源遗传变异规律。【方法】对设置在江西省分宜县多穗柯全分布区的5个种源试验林植株叶部根皮苷、三叶苷、总黄酮、有机碳、氮、磷和钾元素含量进行测定、分析。【结果】不同种源多穗柯叶部根皮苷、三叶苷、总黄酮、有机碳、全氮、全磷含量差异均存在极显著差异(P <0.01)。不同种源根皮苷含量变异范围为16.03~64.35 mg·g-1,三叶苷含量变异范围分别为4.76~29.97 mg·g-1,根皮苷含量变异范围为61.59~81.05 mg·g-1,其中重庆北碚为根皮苷、有机碳、全磷和全氮含量高的种源,与其他种源相比根皮苷含量最高,四川米易三叶苷含量最高,江西分宜总黄酮含量最高。多穗柯根皮苷含量随日照时数增加呈显著降低趋势(P <0.05),三叶苷含量随无霜期增加呈显著降低趋势,总黄酮含量随经度增加呈极显著增加的趋势,随降水量增加呈显著增加的趋势;根皮苷与全氮含量呈极显著正相关关系,有机碳与全钾含量呈显著负相关关系;聚类分析表明,5个多穗柯种源可划分为2个类群,高根皮苷、高总黄酮、低三叶苷类群和低根皮苷、低总黄酮和高三叶苷类群。【结论】多穗柯根皮苷、三叶苷、总黄酮和主要矿质元素含量具明显种源变异,重庆北碚、四川米易和江西分宜的多穗柯为优良种源。     

杜仲种质资源果实性状变异及综合评价

[目的 ]分析杜仲种质资源果实性状变异规律并进行综合评价,为杜仲良种选育和开发利用提供理论依据和遗传材料。[方法 ]基于我国18个省(市、区)331份杜仲种质资源,针对杜仲果实19个主要性状,采用相关性分析、聚类分析和主成分分析等方法,分析果实性状变异状况,评价并筛选优良种质。[结果 ]杜仲果实性状变异系数为4.64%～25.79%,平均变异系数为12.65%,变异系数较高的为包裹种仁果皮百粒质量(25.79%)、种仁百粒质量(22.32%)、种仁体积指数(22.02%)、果实体积指数(19.53%),变异系数较小的为亚麻酸(4.64%)、油酸(5.78%)、果型指数(8.04%)。果实性状遗传多样性指数介于1.657 2～2.094 7,平均为2.023 4。果实百粒质量与果实体积指数、种仁百粒质量等性状呈极显著正相关,杜仲橡胶含量与包裹种仁果皮百粒质量、果实侧径均呈极显著正相关,与种仁粗脂肪含量呈显著负相关。聚类分析将杜仲种质资源划分为3个类群,类群Ⅰ为小果型类群,类群Ⅱ为中型果类群,类群Ⅲ为大果型类群,初步明确杜仲种质果实不同类型。通过主成分分析,前7个主成分累积贡献率达85.169%,表明这7个主成分代表了杜仲果实性状的大部分信息,针对油用、橡胶用和综合利用等不同用途进行评价,分别筛选出10份最优种质。[结论 ]杜仲种质资源果实性状表现出丰富的变异,以包裹种仁果皮百粒质量、种仁百粒质量等产量指标变异最大,为杜仲优良种质选育提供了可能,针对不同用途筛选的杜仲最优种质,为我国杜仲良种选育及综合利用提供了优异的种质基础。     

不同种源华重楼主要生物活性成分地理变异及其相关性分析

[目的]阐明华重楼主要药用成分的地理变异规律,为华重楼种质资源利用和原料林基地选址提供科学依据。[方法]以我国8省份10个种源华重楼为材料,对其根茎总酚酸、总黄酮、重楼皂苷Ⅰ、Ⅱ、Ⅵ和Ⅶ含量进行了测定、分析。[结果]不同地理种源间华重楼根茎总酚酸、总黄酮、重楼Ⅰ、Ⅱ、Ⅵ和Ⅶ含量差异均达极显著水平。不同种源华重楼根茎中总酚酸含量变异幅度为1.718～5.436 mg·g~(-1);总黄酮含量变异幅度为0.780～1.457mg·g~(-1);重Ⅰ、Ⅱ、Ⅵ和Ⅶ含量变异幅度为0.008～2.106、 0.000～0.646mg·g~(-1)、 0.000～0.521和0.000～9.170 mg·g~(-1);华重楼根茎中总酚酸含量与原产地海拔、皂苷Ⅱ与1月均温呈中度正相关关系,总黄酮含量与全年日照时数、皂苷Ⅶ与海拔呈中度负相关关系。总皂苷与海拔间呈高度负相关关系,皂苷Ⅱ与年均温、皂苷Ⅵ与7月均温间均呈高度正相关关系;华重楼根茎中总酚酸与总黄酮含量、总黄酮与皂苷Ⅰ含量、皂苷Ⅰ与皂苷Ⅱ含量呈中度正相关关系,总皂苷与皂苷Ⅶ含量呈高度正相关关系。聚类分析表明,10个种源可以划分为3个类群,低酚酸、低黄酮和高皂苷类群,高酚酸、高黄酮、低皂苷类群和中酚酸、中黄酮、中皂苷类群。[结论]广西桂林为高酚酸和高黄酮优良种源,安徽祁门为高皂苷优良种源。     

青钱柳叶片中活性成分含量的年动态变化

以人工栽培的5年生青钱柳Cyclocarya paliurus为研究对象,通过对4-9月不同月份采集的青钱柳叶片中黄酮、多糖、三萜及黄酮类化合物的含量测定,分析叶片中主要活性成分的累积变化规律。结果表明:青钱柳叶片中黄酮含量最高为5月份达4.28%,最低的为6月份为3.16%,5月份的黄酮含量与6,7月间存在极显著差异(P0.01),与4,8月间存在显著差异(P0.05),而与9月间无显著差异;青钱柳叶片中多糖含量以嫩叶期的4月份为最高,且与其它月份间存在极显著差异(P0.01),随着季节变化总体表现出先下降再缓慢上升的变化规律;青钱柳叶片中的总皂甙含量4-9月一直呈现上升趋势,至9月含量最高达16.47%;叶片中的黄酮类化合物异槲皮甙含量远高于槲皮素和山奈酚含量,6个采样期的平均值占总黄酮平均值的14.23%,且与总黄酮表现出相似的变化规律。从青钱柳叶片中主要活性成分的动态变化来看,以黄酮和多糖含量为指标的采收季节应以4,5月为佳,而以皂甙含量为指标的采收季节应以9月为佳。     

杜仲次生代谢物部位差异性的研究

对同一生态环境下生长的杜仲不同部位次生代谢物含量的测定和分析表明 ,各次生代谢物个体间差异显著 ,同一个体不同部位之间差异也显著。就某一种次生代谢物而言 ,各部位含量高低的顺序为 :绿原酸 :叶 >雄花 >皮 >果 ;桃叶珊瑚甙 :果 >叶 >皮 >雄花 ;总黄酮 :雄花 >叶 >皮 >果 ;杜仲胶 :果 >皮 >叶 >雄花。就某一部位而言 ,各种次生代谢物含量的高低顺序为 :叶 :绿原酸 >总黄酮 >杜仲胶 >桃叶珊瑚甙 ;皮 :杜仲胶 >桃叶珊瑚甙 >绿原酸 >总黄酮 ;雄花 :总黄酮 >桃叶珊瑚甙 >绿原酸 ;果 :杜仲胶 >桃叶珊瑚甙 >总黄酮 >绿原酸。分析结果显示 ,所测定的绿原酸、桃叶珊瑚甙、总黄酮等天然活性物质的含量 ,均是叶部高于皮部 ,这为“以叶代皮”提供了新的科学依据 ;果实中除富含亚麻酸油 (α 亚麻酸含量高达 5 1% )外 ,还富含杜仲胶和桃叶珊瑚甙 ,是亟待开发的新资源 ;杜仲雄花中的黄酮类化合物含量最高 ,绿原酸和桃叶珊瑚甙的含量也较高 ,是杜仲资源开发的又一个新的部位     

花楸树(Sorbus pohuashanensis)营养物质与药用成分探究

[目的]以花楸树为研究对象,探究不同部位物质成分组成和含量差异以及不同生境条件对物质含量的影响。[方法]采用有机溶剂浸提及液相色谱法测定了花楸树不同部位(嫩枝、嫩叶、成熟叶、鲜果和干果)营养和药用物质。[结果]结果表明:花楸树不同部位含有丰富的营养和药用物质,其中成熟叶片中维生素C、类胡萝卜素和黄酮类物质含量较高,干果中蛋白质、可溶性糖、总酚、花色苷和单宁含量较高;与北京花楸相比,花楸树不同部位蛋白质、花色苷、黄酮类物质和总酚含量均较高,其中果实中花色苷和类胡萝卜素含量分别约为北京花楸的3倍和5倍,成熟叶片中的黄酮类物质和总酚含量约为2倍;花楸树新鲜果实中黄酮类和酚类物质种类丰富,其中槲皮素和表儿茶素的含量最高,且分别约为北京花楸的1.5倍和3倍。[结论]与北京花楸相比,花楸树的营养物质和药用成分的含量更高,值得加强其果实和叶片中黄酮和果实酚类物质资源的开发利用。     

三球悬铃木树皮的酚类化学成分研究

研究了三球悬铃木树皮的酚类化学成分.采用SephadexLH-20柱色谱及薄层色谱等方法进行分离,从其70%丙酮提取物乙酸乙酯溶性部分中分到11种化合物,经波谱分析及理化性质化合物分别鉴定为:儿茶素、表儿茶素、没食子儿茶素、表没食子儿茶素、山奈酚、槲皮素、阿福豆苷、异槲皮苷、紫云英苷-6″-没食子酸酯、异槲皮苷-6″-没食子酸酯和酪醇.11种化合物均首次从该树种中分得.     

锦叶栾黄酮含量及叶绿素荧光参数动态分析

以锦叶栾新鲜叶片为试材,采用L9(34)正交试验确定锦叶栾叶片内总黄酮的最佳提取方案,即以60%丙酮为提取剂,新鲜叶片与丙酮料液比1∶20,60℃下回流提取2 h。后通过分光光度法探究锦叶栾叶片内总黄酮含量的季节性变化规律,结果表明:在其旺盛生长阶段,叶片中均具有较高的黄酮含量,总黄酮含量在5月底达到峰值(36.72 mg·g-1),6月底之后含量逐渐降低到平均值(22.06 mg·g-1)以下。利用Handy PEA测定锦叶栾叶片叶绿素荧光参数以分析其黄酮含量在7月之后下降的主要原因,发现锦叶栾不完全适应北京地区的夏季高温,由此引起光合作用效率下降,次生代谢产物黄酮积累减少。     

猴耳环嫩枝和叶组织的代谢物分析

对猴耳环Pithecellobium clypearia主要药用部分嫩枝和叶中的代谢物成分及其含量差异进行分析,从猴耳环的嫩枝和叶中共鉴定出712种代谢物成分,主要为氨基酸类、有机酸类、酚酸类、脂质类和黄酮类等化合物。猴耳环嫩枝和叶组织部位之间代谢物成分含量差异显著,其中槲皮素、表儿茶素苷和表没食子儿茶素没食子酸酯等猴耳环药用特征标志物在嫩枝中的含量显著高于叶组织,而表儿茶素、槲皮苷和杨梅苷等特征标志物则在叶组织中含量更高。综合表明猴耳环嫩枝和叶组织均富含多种高生物活性物质,大部分药用特征代谢物在嫩枝和叶中的含量差异显著。     

Tree biomass estimation in regenerating areas of tropical dry vegetation in northeast Brazil

Allometric equations have been developed for various different vegetation types but have rarely been validated in the field and never for dry tropical forest such as caatinga. In three areas of semi-arid Brazil, with regenerating caatinga vegetation, we measured and weighed twelve hundred individuals of four tree species and used the data to validate equations previously determined in mature caatinga. They and several other equations developed for tropical vegetations overestimate the biomass (B) of trees from the regeneration areas by more than 20%, possibly because these trees have reduced crowns, with lower branch masses. We then determined new allometric equations for them, validating equations for one site against data of the others and pooling the data if they were cross-validated. The best equations were power ones, based on diameter at breast height (D), with little improvement by including height, crown area and/or wood density (Caesalpinia pyramidalis, B = 0.3129D^1.8838; Croton sonderianus, B = 0.4171D^1.5601; Mimosa ophthalmocentra, B = 0.4369D^1.8493; and Mimosa tenuiflora, B = 0.3344D^1.9648 and 0.4138D^1.7718).     

Alkaloid patterns in some varieties of Datura stramonium

A comparative GC-MS investigation of the alkaloid patterns of three varieties of Datura stramonium vars. stramonium, tatula and godronii, was carried out. Twenty-five tropane alkaloids were identified in the plant organs. Alkaloid patterns of the roots, leaves and seeds of the varieties grown at equal conditions in Bulgaria were very similar. In contrast, alkaloid pattern of D. stramonium var. stramonium, grown in Egypt, showed significant differences indicating that it is influenced more strongly by the environmental factors than genetic ones.     

Effects of prescribed fire and season of burn on direct and indirect levels of tree mortality in Ponderosa and Jeffrey Pine Forests in California,USA

Many forests that historically experienced frequent low-intensity wildfires have undergone extensive alterations during the past century. Prescribed fire is now commonly used to restore these fire-adapted forest ecosystems. In this study, we examined the influence of prescribed burn season on levels of tree mortality attributed to prescribed fire effects (direct mortality) and bark beetles (Coleoptera: Curculionidae, Scolytinae) (indirect mortality) in ponderosa pine, Pinusponderosa Dougl. ex Laws., and Jeffrey pine, Pinusjeffreyi Grev. and Balf., forests in California, USA. A total of 816 trees (9.9% of all trees) died during this 3-yr study. Significantly higher levels of tree mortality (all sources) occurred following early and late season burns compared to the untreated control, but no significant difference was observed between burn treatments. The majority (461 trees) of tree deaths were attributed to direct mortality from prescribed burns and was strongly concentrated (391 trees) in the smallest diameter class (<20.2 cm diameter at breast height, dbh). For the largest trees (>50.7 cm dbh), significantly higher levels of tree mortality occurred on early season burns than the untreated control, most of which resulted from indirect mortality attributed to bark beetle attacks, specifically western pine beetle, Dendroctonus brevicomis LeConte, and mountain pine beetle, D. ponderosae Hopkins. Red turpentine beetle, D. valens LeConte, was the most common bark beetle species found colonizing trees, but tree mortality was not attributed to this species. A total of 355 trees (4.3% of all trees) were killed by bark beetles. Dendroctonus brevicomis (67 trees, 18.9%) and D. ponderosae (56 trees, 15.8%), were found colonizing P. ponderosa; and Jeffrey pine beetle, D. jeffreyi Hopkins, was found colonizing P. jeffreyi (seven trees, 2.0%). We also found pine engraver, Ips pini (Say) (137 trees, 38.6%), and, to a much lesser extent, Orthotomicus (=Ips) latidens (LeConte) (85 trees, 23.9%) and emarginate ips, I. emarginatus (LeConte) (3 trees, 0.8%) colonizing P. ponderosa and P. jeffreyi. Few meaningful differences in levels of indirect tree mortality attributed to bark beetle attack were observed between early and late season burns. The incidence of root and root collar pathogens (Leptographium and Sporothrix spp.), including species known to be vectored by bark beetles, was low (18% of trees sampled). The implications of these and other results to management of P. ponderosa and P. jeffreyi forests are discussed in detail.     

Antimicrobial activity of some endemic plants growing in the Eastern Black Sea Region, Turkey

The Eastern Black Sea Region has an extensive flora because of ample rainfall lasting all year. In this study, antimicrobial effects of 74 crude extracts of 22 endemic plants were investigated. Among the 30 active crude extracts, water-insoluble crude extracts from Betula medwediewii, Heracleum platytaenium, Primula longipes, Anthemis cretica ssp. argaea and Centaurea helenioides were the prominent ones with their MIC values.     

Response of bark beetles and their natural enemies to fire and fire surrogate treatments in mixed-conifer forests in western Montana

Four treatments (control, burn-only, thin-only, and thin-and-burn) were evaluated for their effects on bark beetle-caused mortality in both the short-term (one to four years) and the long-term (seven years) in mixed-conifer forests in western Montana, USA. In addition to assessing bark beetle responses to these treatments, we also measured natural enemy landing rates and resin flow of ponderosa pine (Pinus ponderosa) the season fire treatments were implemented. All bark beetles were present at low population levels (non-outbreak) for the duration of the study. Post-treatment mortality of trees due to bark beetles was lowest in the thin-only and control units and highest in the units receiving burns. Three tree-killing bark beetle species responded positively to fire treatments: Douglas-fir beetle (Dendroctonus pseudotsugae), pine engraver (Ips pini), and western pine beetle (Dendroctonus brevicomis). Red turpentine beetle (Dendroctonus valens) responded positively to fire treatments, but never caused mortality. Three fire damage variables tested (height of crown scorch, percent circumference of the tree bole scorched, or degree of ground char) were significant factors in predicting beetle attack on trees. Douglas-fir beetle and pine engraver responded rapidly to increased availability of resources (fire-damaged trees); however, successful attacks dropped rapidly once these resources were depleted. Movement to green trees by pine engraver was not observed in plots receiving fire treatments, or in thinned plots where slash supported substantial reproduction by this beetle. The fourth tree-killing beetle present at the site, the mountain pine beetle, did not exhibit responses to any treatment. Natural enemies generally arrived at trees the same time as host bark beetles. However, the landing rates of only one, Medetera spp., was affected by treatment. This predator responded positively to thinning treatments. This insect was present in very high numbers indicating a regulatory effect on beetles, at least in the short-term, in thinned stands. Resin flow decreased from June to August. However, resin flow was significantly higher in trees in August than in June in fire treatments. Increased flow in burned trees later in the season did not affect beetle attack success. Overall, responses by beetles to treatments were short-term and limited to fire-damaged trees. Expansions into green trees did not occur. This lack of spread was likely due to a combination of high tree vigor in residual stands and low background populations of bark beetles.     

Ungulate herbivory of regenerating conifers in relation to foliar nutrition and terpenoid production

Ungulate browsing greatly influences regeneration dynamics of some forest ecosystems, yet the relationship between browse susceptibility and foliar chemistry of forest tree seedlings is not well understood. We applied field fertilization (15N-9P-10K controlled-release fertilizer at 0, 20, 40, and 60 g per seedling) and investigated how subsequent changes in terpenoid production and foliar nutrition influence ungulate browse preference for Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla Raf. Sarg.), and western redcedar (Thujaplicata Donn ex D. Don) seedlings across four sites in northwestern Oregon, USA. Fertilization increased foliar N concentration of all three species, but above-ground growth of only Douglas-fir and western hemlock. Foliar monoterpene concentrations for western hemlock and western redcedar also increased at higher fertilization rates, while Douglas-fir monoterpene production was not affected by fertilization. Regardless of monoterpene levels, ungulate browse preference was greater for fertilized western hemlock seedlings. The opposite response, however, was observed for western redcedar at two of the four study sites where the likelihood of browse was greater for non-fertilized than fertilized seedlings. Differences in browse preference among species may depend on the type and amount of individual monoterpenes manufactured in response to fertilization. Western redcedar produce α- and β-thujone, oxygenated monoterpenes known to promote gastroenteritis and possibly inhibit microbial rumen activity, which were absent from Douglas-fir or western hemlock. Higher concentrations of α- and β-thujone associated with increasing fertilizer rate provide a plausible explanation as to why ungulates preferred non-fertilized western redcedar. Our results illustrate species-specific adaptation in browse avoidance and selective ungulate browsing behavior of individual trees as linked to foliar chemistry.     

Long-term effects of single prescribed fires on hardwood regeneration in oak shelterwood stands

One of the arguments against using prescribed fire to regenerate oak (Quercus spp.) forests is that the improvement in species composition of the hardwood regeneration pool is temporary and multiple burns are necessary to achieve and maintain oak dominance. To explore this concern, I re-inventoried a prescribed fire study conducted in the mid-1990s to determine the longevity of the effects of a single prescribed fire on hardwood regeneration. The initial study was conducted in three oak shelterwood stands in central Virginia, USA. In 1994, each stand was divided into four treatments (spring, summer, and winter burns and a control) and the hardwood regeneration was inventoried before the fires. During the burns, fire intensity was measured and categorized in each regeneration sampling plot. Second-year postfire data showed marked differences in species mortality rates, depending on season-of-burn and fire intensity: oak and hickory (Carya spp.) regeneration dominated areas burned by medium- to high-intensity fire during the spring and summer while yellow-poplar (Liriodendron tulipifera) and red maple (Acer rubrum) seedlings dominated unburned areas and all areas treated with low-intensity fire regardless of season-of-burn. The treatments were re-inventoried in 2006 and 2007 to determine whether these fire effects were still present. The new data show that the species distributions by season-of-burn and fire intensity found in 1996 still existed 11 years after the treatments. The fact that fire effects in oak shelterwood stands can last at least a decade has important management implications for resource professionals interested in sustaining oak forests in the eastern United States.     

Differences in soil properties in adjacent stands of Scots pine, Norway spruce and silver birch in SW Sweden

Soil properties were compared in adjacent 50-year-old Norway spruce, Scots pine and silver birch stands growing on similar soils in south-west Sweden. The effects of tree species were most apparent in the humus layer and decreased with soil depth. At 20-30 cm depth in the mineral soil, species differences in soil properties were small and mostly not significant. Soil C, N, K, Ca, Mg, and Na content, pH, base saturation and fine root biomass all significantly differed between humus layers of different species. Since the climate, parent material, land use history and soil type were similar, the differences can be ascribed to tree species. Spruce stands had the largest amounts of carbon stored down to 30 cm depth in mineral soil (7.3 kg C m⁻²), whereas birch stands, with the lowest production, smallest amount of litterfall and lowest C:N ratio in litter and humus, had the smallest carbon pool (4.1 kg C m⁻²), with pine intermediate (4.9 kg C m⁻²). Similarly, soil nitrogen pools amounted to 349, 269, and 240 g N m⁻² for spruce, pine, and birch stands, respectively. The humus layer in birch stands was thin and mixed with mineral soil, and soil pH was highest in the birch stands. Spruce had the thickest humus layer with the lowest pH.     

Investigation of in vitro anthelmintic activities of Pycnanthus angolensis and Sphenocentrum jollyanum

Extracts from Pycnanthus angolensis stem bark, and fruits and seeds of Sphenocentrum jollyanum, when tested in vitro, showed potent anthelmintic activity on the earthworm, Eudrilus eugeniae. Methanolic extract of P. angolensis was more active than its chloroform extract (P<0.001), while fruit ethanolic extract of S. jollyanum was also more potent than the seed extract. When compared with other worms, S. jollyanum fruit extract showed the greatest activity on wireworms when tested at 80 mg/ml.     

Effects of moisture limitation on tree growth in upland and floodplain forest ecosystems in interior Alaska

The objective of this study was to examine the impact of summer throughfall on the growth of trees, at upland and floodplain locations, in the vicinity of Fairbanks, Alaska. Corrugated clear plastic covers were installed under the canopy of floodplain balsam poplar/white spruce stands and upland hardwood/white spruce stands to control soil moisture recharge as a result of summer precipitation. The covers were installed in 1989 and tree growth measurements were conducted through 2005. Soil moisture dynamics were measured using TDR techniques. Tree basal area growth at dbh in the control plots was approximately twice as high on the floodplain compared to the upland. Summer throughfall exclusion significantly decreased white spruce growth on the floodplain sites but not in the upland sites. In upland sites the melting snow pack is a major moisture resource for tree growth although it is not clear if moisture limitation occurs during the summer in the control plots. However in the floodplain stands white spruce growth was highly dependent on seasonal throughfall even though the ground water table was within the rooting zone and the soils were supplied with a spring recharge due to snowmelt. A number of factors were suggested as a foundation for this strong relationship. These include rooting distribution, soil texture, and the electrical conductivity of the ground water.