萌生杉木林空间结构特征研究

利用结构参数角尺度、大小比数、混交度对浙江龙泉萌生杉木林的空间结构进行分析,结果表明:林分的平均角尺度为0.512,林分空间格局为随机分布;杉木树种分布格局为团状分布,木荷树种整体分布格局为随机分布,其它树种的整体分布格局为均匀分布;林分的平均混交度为0.438 4,在弱度混交和中度混交之间;林分中树种以胸径作为比较指标的林木个体的优势排列顺序为:苦槠、马尾松> 杉木> 樟树> 木荷> 枫香、红豆树> 拟赤杨> 榆树。根据萌生杉木林的结构特征提出经营对策, 通过合理择伐和补植乡土树种进行林分结构调整,提高林分质量,优化林分空间结构,以便更好地发挥其功能。     

南京郊区典型人工林分空间结构及间伐响应

采用混交度、大小比数、角尺度等林分空间分布格局参数分析了南京市郊区3种不同人工林的空间结构特征。结果表明,马尾松与杉木的混交林分平均混交度达0.61,接近较强度混交,群落的组成较复杂。而间伐前杉木林和麻栎林的混交度较小,分别为混交度为0.25和0.15,处于较弱度混交以下,群落组成较简单。马尾松与杉木混交林和麻栎林混交的平均角尺度分别为0.50和0.49,处于随机分布状态,而间伐前杉木林的林分平均角尺度为0.55,林内所有树种均属于聚集分布状态。马尾松与杉木混交林、麻栎林和间伐前杉木林的平均大小比数分别为0.61,0.5和0.54。在麻栎林中,麻栎的生长占较优势状态;在间伐前杉木林和马尾松与杉木混交林中,马尾松生长占绝对优势。杉木林间伐2 a后,林分的平均混交度由0.25上升到0.38,达到了较弱度混交以上,而林分的平均角尺度和平均大小比数变化不明显。     

北京八达岭油松人工林结构分析

用传统林分结构因子配合混交度、大小比、角尺度3参数来分析北京八达岭林场油松人工林空间结构特征.结果表明:该林分的树种组成式为8油松1槲树1山梨 暴马丁香,林分密度为1 325 株/hm2.林分的平均角尺度为0.478,林分立木空间分布格局为随机分布.平均混交度为0.433,不同树种间呈现中度混交,种间隔离程度较小.林分平均胸径大小比为0.389,平均树高大小比为0.464,说明处于优势地位的株数较多,林分分化明显,且林分的发展空间还很大.胸径大小比数和树高大小比数在反映各树种参照树与相邻木之间的生长优势方面具有较强的一致性.     

河北省北沟林场针阔混交林空间结构优化技术研究

为了研究针阔混交林空间结构特征,用林分直径分布特征以及空间结构3个参数(角尺度、混交比和大小比数)对河北省北沟林场的华北落叶松、白桦混交林进行了分析。结果表明:该林分直径分布中,白桦的直径分布均匀,落叶松较差;林分平均角尺度为0.352 6,林分基本处于均匀分布状态;林分平均混交度为0.425,处于中度混交;从大小比数来看,林分中白桦处于优势地位,更新树种五角枫被压严重。以林分空间结构3个参数为依据,提出林分结构调整的几种方法,使林分结构更加接近最优状态。     

基于 VBA 的杉阔混交人工林林分择伐空间结构分析

基于VBA建立的林分空间结构分析系统,主要包括林分空间参数自动化计算及林分择伐优化两部分。利用ExcelVBA对混交度、大小比数和角尺度3个空间结构参数的数学模型进行编码,实现林分空间结构自动分析计算,采用第4邻体距离判定法校正边缘效应,提高空间参数计算的准确性;在ExcelVBA编辑器中通过编写宏语言设置择伐参数进行模拟采伐,对比分析林分择伐前后空间结构,在择伐强度满足要求的前提下,对林分空间结构进行多次调整优化。以杉阅混交人工林为例,林分空间结构分析系统在分析现实林分空间结构的基础上,合理确定采伐木,使调整后的杉闹混交人工林分空间结构趋向合理。结果表明：基于ExcelVBA建立的林分择伐空间结构分析系统,其计算过程简化,结果可靠,能为林分近自然经营提供科学依据。     

柳杉纯林改造后林分空间结构变化预测

运用混交度、大小比数、角尺度和开敞度参数对柳杉林间伐前后空间结构的变化进行预测分析.结果表明:间伐后柳杉周围的同种树种相对减少,柳杉的混交度增加;而杉木的混交度变化则相反.柳杉和杉木的大小比数都有所增加,其中杉木最为明显.在角尺度方面,间伐前后林木的分布格局均为均匀分布.开敞度则由于间伐后林木间距的增大而得以提高.由此可见,在人工择伐作业后,单木的优势地位、树种的空间隔离程度,以及所占生存空间的大小都得到了较好的改善;这有利于培育大径级材和乡土树种的侵入.而林木分布格局的调整则明显滞后.     

冀北山地杨桦次生林林分空间结构研究

在木兰林管局桃山林场选取面积为100 m×100 m的杨桦次生林样地,以每株林木树高、胸径和坐标为基础数据,运用混交度、大小比数和角尺度等林分空间结构参数分析了杨桦次生林的空间结构特征。结果表明:(1)该林分中山杨Populus davidiana和白桦Betula platyphylla在株数和断面积比例上占优势,为林分内优势树种;(2)林分各混交类型的比例相差不大,林分整体呈中度混交状态;(3)林分优势木和亚优势木相对较多,基于胸径、树高得到的平均大小比数结果基本一致,均能客观反映林分的分化规律;(4)林分平均角尺度为0.504,属于随机分布,林下伴生树种以集聚分布为主,但优势树种的随机分布趋势起决定作用。     

福寿林场杉木人工林林分空间结构的研究

以福寿林场杉木人工林为研究对象,用角尺度、大小比和混交度3个空间结构参数分析了其空间结构特征。结果表明:林分平均混交度是0.138,为零度混交和弱度混交过渡类型。说明树种的空间隔离程度较小,林分的稳定状态差。平均角尺度为0.533,分布格局为聚集分布。大小比数为0.478,林木大小比数分布均匀,表明林分内林木个体胸径差异不大,林木分化不严重。     

湿地松枫香混交林林分空间结构特征研究

于湖南省杜家冲林场湿地松枫香混交林内设置4块具有代表性的样地进行调查,利用混交度、大小比数、角尺度3种结构参数,分析其林分空间结构特征。结果表明:该林分的平均混交度为0.678,属于中度偏强混交,说明该森林群落较为复杂与稳定;林分平均角尺度为0.475,林木空间分布格局为均匀到随机分布;样地平均胸径大小比数的取值范围在0.27~0.87之间,且湿地松(0.27)枫香(0.47)香樟(0.59)木荷(0.87),说明各树种在样地中分化较严重,湿地松和枫香在样地中较占优势。     

大兴安岭林区典型针叶林林分空间结构特征

文章以大兴安岭针叶林林分为研究对象,利用角尺度、混交度及大小比数3个空间结构参数,分析了针叶林林分的空间结构特征。研究发现:针叶林样地内各树种径级分布呈倒“J”型;林分的平均角尺度为0.489,林分整体水平空间分布格局为随机分布;林分的平均混交度为0.436,林分整体上处于中弱度混交状态;林分的平均大小比数为0.455,林分整体上偏中庸状态。     

Antibacterial activity of plant extracts from Brazilian southeast region

A screening was conducted with 26 plants collected in the Brazilian southeast region, to identify plant extracts with antibacterial properties against Aeromonas hydrophila, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus. Initially, the agar diffusion method was employed. Then, those extracts presenting activity were submitted to a broth microdilution assay to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). It was observed that 13 of the tested extracts showed antibacterial activity. The best results were obtained with those from Lantana lilacina and Phyllanthus tenellus.     

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.     

Anti-HBV activities of Streblus asper and constituents of its roots

The extracts from leaves, heartwood, barks and roots of the Streblus asper were investigated for anti-HBV activities, separately. The results suggested that the MeOH extracts of the heartwood, barks, and roots exhibited good anti-HBV activities. Further investigations displayed that ethyl acetate and n-butanol soluble parts of their MeOH extracts showed more significant anti-HBV activities. Moreover, a new lignan, together with 11 known compounds, was isolated from n-butanol-soluble part of MeOH extract of the roots of S. asper. The structures were elucidated by spectroscopic methods, including 1D NMR ((1)H NMR, (13)C NMR), 2D NMR (HMQC, HMBC) and HR-EI-MS experiments. Compounds 1-3 were evaluated for their anti-HBV activities. Honokiol showed significant anti-HBV activity with IC(50) values of 3.14μM and 4.74μM for HBsAg and HBeAg with no cytotoxicity respectively, while lamivudine (3TC, positive control) exhibited weak anti-HBV activity with IC(50) values of 11.81μM and 25.80μM for HBsAg and HBeAg respectively.     

Growth and physiological response of six Australian rainforest tree species to a light gradient

An understanding of growth and photosynthetic potential of subtropical rainforest species to variations in light environment can be useful for determining the sequence of species introductions in rainforest restoration projects and mixed species plantations. We examined the growth and physiology of six Australian subtropical rainforest tree species in a greenhouse consisting of three artificial light environments (10%, 30%, and 60% full sunlight). Morphological responses followed the typical sun-shade dichotomy, with early and late secondary species (Elaeocarpus grandis, Flindersia brayleyana, Flindersia schottiana, and Gmelina leichhardtii) displaying higher relative growth rate (RGR) compared to mature stage species (Cryptocarya erythroxylon and Heritiera trifoliolatum). Growth and photosynthetic performance of most species reached a maximum in 30–60% full sunlight. Physiological responses provided limited evidence of a distinct dichotomy between early and late successional species. E. grandis and F. brayleyana, provided a clear representation of early successional species, with marked increase in A_max in high light and an ability to down regulate photosynthetic machinery in low light conditions. The remaining species (F. schottiana, G. leichhardtii, and H. trifoliolatum) were better represented as falling along a shade-tolerant continuum, with limited ability to adjust physiologically to an increase or decrease in light, maintaining similar A_max across all light environments. Results show that most species belong to a shade-tolerant constituency, with an ability to grow and persist across a wide range of light environments. The species offer a wide range of potential planting scenarios and silvicultural options, with ample potential to achieve rapid canopy closure and rainforest restoration goals.     

Photosynthetic characteristics of Fagus sylvatica and Quercus robur established for stand conversion from Picea abies

Efforts in Europe to convert Norway spruce (Picea abies) plantations to broadleaf or mixed broadleaf-conifer forests could be bolstered by an increased understanding of how artificial regeneration acclimates and functions under a range of Norway spruce stand conditions. We studied foliage characteristics and leaf-level photosynthesis on 7-year-old European beech (Fagus sylvatica) and pedunculate oak (Quercus robur) regeneration established in open patches and shelterwoods of a partially harvested Norway spruce plantation in southwestern Sweden. Both species exhibited morphological plasticity at the leaf level by developing leaf blades in patches with an average mass per unit area (LMA) 54% greater than of those in shelterwoods, and at the plant level by maintaining a leaf area ratio (LAR) in shelterwoods that was 78% greater than in patches. However, we observed interspecific differences in photosynthetic capacity relative to spruce canopy openness. Photosynthetic capacity (A₁₆₀₀, net photosynthesis at a photosynthetic photon flux density of 1600 μmol photons m⁻² s⁻¹) of beech in respect to the canopy gradient was best related to leaf mass, and declined substantially with increasing canopy openness primarily because leaf nitrogen (N) in this species decreased about 0.9 mg g⁻¹ with each 10% rise in canopy openness. In contrast, A₁₆₀₀ of oak showed a weak response to mass-based N, and furthermore the percentage of N remained constant in oak leaf tissues across the canopy gradient. Therefore, oak photosynthetic capacity along the canopy gradient was best related to leaf area, and increased as the spruce canopy thinned primarily because LMA rose 8.6 g m⁻² for each 10% increase in canopy openness. These findings support the premise that spruce stand structure regulates photosynthetic capacity of beech through processes that determine N status of this species; leaf N (mass basis) was greatest under relatively closed spruce canopies where leaves apparently acclimate by enhancing light harvesting mechanisms. Spruce stand structure regulates photosynthetic capacity of oak through processes that control LMA; LMA was greatest under open spruce canopies of high light availability where leaves apparently acclimate by enhancing CO₂ fixation mechanisms.     

利用三种梢栖真菌生物防治落叶松枯梢病的研究

从落叶松梢栖真菌筛选出对落叶松枯梢病病原菌有抑制作用的菌株,对落叶松枯梢病进行生物防治。将自落叶松梢部分离到的11种梢栖真菌与落叶松枯梢病病原菌进行对峙培养,根据被覆盖程度、抑菌率、拮抗系数和防治预试验的结果,综合评价后发现:粪生粪壳、深绿木霉和球毛壳3种梢栖真菌对落叶松枯梢病有良好的拮抗作用。利用这3个菌株在黑龙江省勃利县通天一林场国富沟进行林间防治试验,结果表明:防治效果为粪生粪壳>代森锰锌400倍液>深绿木霉>球毛壳;深绿木霉和粪生粪壳喷洒浓度50%和球毛壳喷洒浓度75%时,真菌多样性最多,梢栖真菌系统较其他浓度更为稳定,与化学防治相比,既达到了防治目的又具有不污染环境的优势。     

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.     

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.     

Screening of antioxidant activity of three Euphorbia species from Turkey

Euphorbia acanthothamnos, E. macroclada and E. rigida were investigated for their antioxidant activity. The antioxidant potential of extracts of E. acanthothamnos, E. macroclada and E. rigida was evaluated using different complementary antioxidant tests.