The variation of the basic density within the juvenile wood of Sitka spruce (Picea sitchensis)

The variation in the basic‐density level of 45 stems of Sitka spruce from two Danish sites has been examined. It is shown that the basic‐density level, i.e. the basic density as a function of ring width, within the juvenile wood decreases with (1) increasing distance from the pith and (2) increasing height in the stem (same ring number from pith provided). Furthermore, the basic‐density level seems to decrease with increasing stand quality, which may affect the pattern of variation in basic‐density level if the stand quality class varies with age. The basic density of the juvenile wood is markedly higher in Sitka spruce than in Norway spruce, whereby the risk of stem cracks probably is reduced.     

Canopy density in stands of Picea abies and Pinus sylvestris after different thinning methods

Altogether 82 plots (261 estimations) of Picea abies (L.) Karst, and 193 plots (360 estimations) of Pinus sylvestris (L.) stands were estimated by a vertical tube. The “crown free projection”, CFP, of stands thinned in three methods with different thinning grades was measured: unthinned, heavily and very heavily thinned, heavily thinned delayed first thinning, extra heavily thinned and thinned from the top. Basal area (m²ha^?1) density (stems ha^?1) and diameter sum (m ha^?1) were plotted against CFP. Basal area was the best practical measure of stand in this study. Generally Scots pine stands have higher CFP and the curves are steeper than in Norway spruce stands. Depending on the grade of thinning, heavily and very heavily thinned spruce stands, delayed first thinning included, have CFP values of 10–15% and stands thinned from the top, 20–40%, compared with 30–80% and 30–60% respectively in pine stands. Extra heavily thinned stands have the highest CFP, 20–80% in spruce and 50–90% in pine stands. The CFP levels after thinning are too high in pine stands for avoidance of sucker and sprout production of aspen and birch. In dense Norway spruce stands thinned from the top or heavily and very heavily thinned, the CFP values are low enough (≤30%) to diminish the production of suckers.     

Cytotoxic, cytoprotective and antioxidant effects of isolated phenolic compounds from fresh ginger

Twenty-nine phenolic compounds were isolated from the root bark of fresh (Yunnan) ginger and their structures fully characterized. Selected compounds were divided into structural categories and twelve compounds subjected to in-vitro assays including DPPH radical scavenging, xanthine-oxidase inhibition, monoamine oxidase inhibition, rat-brain homogenate lipid peroxidation, and rat pheochromocytoma PC12 cell and primary liver cell viability to determine their antioxidant and cytoprotective properties. Isolated compounds were also tested against nine human tumor cell lines to characterize anticancer potency. Several diarylheptanoids and epoxidic diarylheptanoids were effective DPPH radical scavengers and moderately effective at inhibiting xanthine oxidase. An enone–dione analog of 6-shogaol (compound 2) was isolated and identified to be most effective at protecting PC12 cells from H₂O₂-induced damage. Almost all tested compounds inhibited lipid peroxidation. Three compounds, 6-shogaol, 10-gingerol and an enone-diarylheptanoid analog of curcumin (compound 6) were identified to be cytotoxic in cell lines tested, with KB and HL60 cells most susceptible to 6-shogaol and the curcumin analog with IC₅₀ < 10 μM. QSAR analysis revealed cytotoxicity was related to compound lipophilicity and chemical reactivity. In conclusion, we observed distinct compounds in fresh ginger to have biological activities relevant in diseases associated with reactive oxygen species.     

水土保持林的密度调控

在明确水土保持林定义及功能的基础上,分析了水土保持林密度对林分成活率、郁闭度、高生长、直径、单株材积、干材产量、生物量、干材质量、根系等的影响,详细介绍了常见的几种林分密度控制的测算方法。针对山西省的实际情况,提出了在山西省要利用密度调控实现经营目标所需注意的几个问题。     

油松纯林乔木层碳密度影响因子分析

分析了影响中国油松林碳密度的各因子的作用,结果显示,在油松林适生的温度范围内,低温、高降雨量更有利于其积累碳素;随着林龄的增大,气温和降雨量对碳密度的影响作用逐渐减小;天然林和人工林碳密度预测模型分别为：C=-5．107×T＋0．079XR＋1．263XA（R^2=0．895）;C=-3．319×T＋0．010×R＋2．220×A（R^2=0．934）．     

间伐对马尾松天然次生林林下植物多样性的影响

选择12和14地位指数的2种立地的林分,分别设置6种和5种保留密度,对间伐4年后的23年生马尾松天然次生林林下植物多样性进行研究。结果表明:马尾松天然次生林林下植物种数随着林分保留密度的增大,12和14地位指数的林分均表现为由逐渐增加至一个峰值后逐渐减少;适宜的保留密度有利于提高林下植物的多样性,12和14地位指数林分的植物多样性分别以保留密度130株/667 m2和100株/667 m2的样地为最优;随着林分密度与冠层郁闭度的增大,林下植物类型有由阳性植物为主向中性与荫性变化的趋势,而形成阳性、中性及荫性共存的多态性植物群落;适宜的保留密度有利于提高林下植物的生物量和植被总盖度,12和14地位指数林分的林下植物生物量和植被总盖度分别以保留密度130株/667 m2和90株/667 m2的样地为最佳;2种地位指数不同保留密度林分的林下枯落物自然风干重、枯落物层厚及腐殖质层厚差异均不显著,而林下地被物鲜重和植被总盖度则均表现为差异极显著。     

蔗糖密度梯度法定量口蹄疫完整病毒粒子（146S）的特异性研究

为验证蔗糖密度梯度法检测口蹄疫完整病毒粒子（146S）的特异性,选择pH值6．0、5．0、4．0PBS酸解处理3批提纯后的146S灭活抗原液,并将酸解后样品进行146S检测,发现8至11级份OD259峰值消失,146S含量由酸解前的1．77、6．60、3．67μg／mL至酸解后完全不能检测到。同时对3批不含病毒的细胞液按抗原纯化灭活工艺处理后进行146S检测,结果显示3批细胞液在8至11级份均没有明显吸收峰,而且其OD259值与PBS空白对照OD259值基本平行一致,说明不含病毒的细胞液对检测结果没有明显干扰。试验证明,蔗糖密度梯度法定量FMD病毒液中146S含量具有很好的特异性。     

鹅掌楸种源试验研究

笔者以湖北省京山县鹅掌楸属种源试验林2个树种鹅掌楸与北美鹅掌楸共20个种源为对象,进行了14 a时的生长和主要木材性状的研究。结果表明:北美鹅掌楸的生长优于鹅掌楸,而木材性状则不及鹅掌楸。在胸径、树高、材积、基本密度和纤维长度5个测试性状中,各种源之间存在显著或者极显著差异,为优良种源的选择奠定了基础。相同试验材料不同试验点的结果存在较大分歧表明:鹅掌楸受到较强的环境因素影响,因此在进行种源选择时必须加以考虑。     

福安市马尾松林分密度效应的研究

运用随机抽样法抽取马尾松成熟林分50个小班,调查胸径、树高、单位蓄积量及密度等测树因子,运用回归分析法进行测树因子相关性分析,结果表明,林分蓄积量对于密度、胸径、树高之间存在显著线性关系,其相关性数学模型可用三元线性回归方程y=b0+b1x1+b2x2+b3x3表示,其中,密度是影响林分蓄积量的主导因素。相关性变化趋势分析表明,在兼顾林分产量和林木径级的情况下,合理保留密度每667 m2为105株。     

不同栽植密度和施肥量对艳椒425产量的影响

以单生朝天椒新品种艳椒425为试材,采用复式裂区试验设计,研究了3种不同栽植密度（主处理）和3种不同施肥量（副处理）对其产量的影响。结果表明,栽植密度和肥料施用量：是影响艳椒425产量的主要因素,其中在中等肥力的土壤中,较低密度（2200株／667m^2）和中等施肥量（50kg／667m^2三元复合肥＋2500kg／667m^2腐熟人畜粪）处理下的艳椒425产量最高,达2084．38kg／667m^2,与其他处理差异达显著或极显著水平。