南亚热带杉木人工林材种结构长期立地与密度效应

[目的]揭示南亚热带杉木人工林材种发育的长期立地和密度动态效应规律。[方法]以广西大青山A(1667株·hm^-2)、B(3333株·hm^-2)、C(5000株·hm^-2)、D(6667株·hm^-2)、E(10000株·hm^-2株)5种初植密度、36 a生杉木(Ctmninghamia lanceolata)密度试验林为研究对象,分析密度和立地影响下材种株数与材种材积分布的动态变化规律。[结果]杉木林分小径材株数和材积比率在初期随林龄增长而递增,达峰值后随林龄增长而减少,初植密度越小、立地指数级越高,减少速度越快;中、大径材株数和材积比率随林龄增长而增加,初植密度越小、立地指数级越高,增速越快。18立地指数级D及以下密度林分28 a生前中径材材积比例约50%;36 a生时A密度林分大径材材积比例约50%。16立地指数级中低初植密度林分中径材材积比例均超过45%,且以C密度林分最高、约48%;36 a生时A密度林分大径材材积比例超过26%。14立地指数级,A密度林分中径材材积比例24 a生时达44%,A、B、D密度林分小径材材积分别于12、18、24 a生时达83%、76%、69%o 10立地指数级C、E密度林分36 a生时小径材材积比例分别达71%、61%。[结论]杉木林材种形成与立地、密度和林龄关系密切,立地质量具决定性作用,而培育高规格材种时初植密度亦可成为关键限制因素。初植密度越低、立地指数越高,越利于中、大径材形成。在杉木南带产区,10指数级立地短周期经营时只适宜培育小径材及小条木。14指数级立地适宜培育中、小径材,若以中径材为第一培育材种时初植密度宜低。16指数级立地适宜培育中径材,长周期经营时也可培育大径材,但初植密度不宜超1667株·hm^-2。18指数级立地中径材生产潜力很大,但更宜培育大径材,且初植密度宜控制在A密度,轮伐期不宜低于36 a。     

西南桦人工林的林分密度研究

采用"典型抽样"方法,2011年春和2012年春,在德宏州调查了78块20 m×20 m的西南桦人工林样地。通过相关分析,认为林分密度与林分年龄、平均胸径、蓄积量、年平均蓄积生长量显著相关,而与林分平均树高相关不显著。林分密度与林龄等相关指标的回归,以双曲线方程拟合最好。78块西南桦人工林样地的林分密度-林龄回归方程为y-1=0.014 2-0.009 6 x-1,相关系数r=0.336 8。10年生同龄林分18块样地林分密度-平均胸径的相关系数r=0.627 0,其回归方程为y-1=0.082 5-0.851 6 x-1;林分密度-蓄积量的相关系数r=0.663 5,其回归方程为y-1=0.058 3+2.846 6 x-1;林分密度与年平均蓄积生长量的相关系数与蓄积量同值,其回归方程为y-1=0.582 9+28.465 7 x-1。从林分密度随林龄增长的变化规律及与林分平均胸径的相关变化提出,(1)西南桦人工林应提早在3～5年生时进行抚育间伐;(2)采用"低密粗径"的育林方针,以提高西南桦大中径材产出。到20年生主伐时,抚育间伐后的密度则以900～1 050株/hm2最佳;(3)西南桦造林初植密度降到1 665～1 335株/hm2(株行距2 m×3 m～2.5 m×3 m)为宜。     

杨树林分密度对材积生长量的影响

对杨树进行窄宽行 (3m× 2m与 3m× 8m交替 )、3m× 6m和 3m× 5m 3种营林密度对比试验 ,从第 1年到第 4年林龄的生长量调查和试验分析表明 ,3种林分密度单位面积年平均材积生长量的比值分别为 198∶116∶10 0 ,杨树利润比值为 2 33∶1 13∶1。证明窄宽行的林分密度能产生最佳的经济效益 ,为营造杨树速生丰产林提供科学的林分密度。     

南亚热带杉木林分蓄积量生长立地与密度效应

[目的]揭示南亚热带不同密度和立地条件下杉木人工林蓄积量发育规律。[方法]以广西大青山36 a生杉木密度试验林为研究对象,分析A(1 667株·hm~(-2))、B(3 333株·hm~(-2))、C(5 000株·hm~(-2))、D(6 667株·hm~(-2))、E(10 000株·hm~(-2))5种初植密度杉木人工林总蓄积、活立木蓄积动态变化。[结果]初植密度与立地对林分活立木蓄积生长的影响与总蓄积一致。中幼龄阶段林分总蓄积与初植密度和立地正相关,初植密度愈高,立地指数愈大,林分蓄积生长量愈大;但15 a后中等密度林分总蓄积最大。林分蓄积连年生长高峰随密度增大而愈早;平均生长达高峰后下降,密度越大下降越早、下降趋势越明显;林分蓄积连年生长量、平均生长量大多分别在10、14 a达到高峰,林分蓄积生长率降到3%时林龄为19～25 a。[结论]随初植密度增大,立地指数对林分总蓄积的影响程度减弱。若以蓄积生长量最大为培育目标,16指数级以C密度为最适宜造林密度。南亚热带杉木林首次间伐、最后间伐、主伐时间分别为10、14、25 a;主伐林龄不宜早于19 a,且初植密度愈低主伐林龄更晚,A、B密度林分的主伐林龄可推迟到25 a。     

人工用材林木材产量经营模拟研究

以长白落叶松人工用材林为代表,分别对7个立地等级和3种初植密度(分别为2500株/hm2、3300株/hm2和4400株/hm2)的人工用材林木材产量进行经营模拟。根据立地指数曲线确定不同类型林分在不同林龄阶段的平均树高,利用相关模型推算相应林龄阶段的林分平均胸径和林分平均单株材积。建立林分密度定量管理模型,确定不同立地等级不同初植密度林分在理想状态下的间伐时间、间伐强度及相应的木材收获量,为营林生产和科研提供参考和借鉴。     

杉木人工林材种结构的立地及密度效应研究

采用30年生未间伐的杉木人工林连续观测数据,研究了不同林龄立地质量、林分密度对林分材种结构的影响。结果表明:初植密度相同时,立地质量越好各材种出现时间及达到最大出材率的时间越早,22立地指数初植密度1 667株·hm^-2的小径材最大出材率出现时间较16立地指数初植密度1 667株·hm^-2早4 a,中径材最大出材率出现的时间早6 a;立地指数相同时,随初植密度增加小径材出材率的峰度及峰值均减小,20立地指数样地中,初植密度为1 667株·hm^-2的小径材出材率峰值较初植密度为10 000株·hm^-2的高17%,而初植密度对中径材、大径材影响不大;在林分发展的不同时期,林分密度对材种出材率的影响不同,30年生时林分蓄积相近的但初植密度不同的样地,初植密度越大小径材出材率越高,大径材出材率越低。     

西双版纳普文实验林场西南桦人工林的生长研究

对11~13年生西南桦纯林(初植密度包括2 m×2 m,2 m×3 m,2 m×4 m,2 m×5 m,2 m×6 m,3 m×3 m和2 m×3 m×7 m)、12年生西南桦与高阿丁枫(初植密度2 m×3m)和11年生西南桦(初植密度3 m×3 m)与山桂花(初植密度3 m×1.5 m)混交林的生长分析显示,西南桦造林后迅速进入速生期。7年生前尤为速生,速生期可延续至10年生林分,在速生期内,平均木的胸径、树高和木材年平均生长量分别为1.17~2.50 cm.yr-1、1.20~3.60 m.yr-1和0.000 11~0.018 04 m3.yr-1,其连年生长量分别为0.50~2.65 cm.yr-1、0.5~4.0 m.yr-1和0.000 11~0.018 68 m3.yr-1。西南桦纯林中,2 m×5 m和2 m×4 m的初植密度较为有利于林木生长和木材生产,其13年生林分生长量分别达:(1)年平均胸径1.42 cm.yr-1和1.72 cm.yr-1,年平均树高1.77 m.yr-1和1.72 m.yr-1;(2)单位面积材积为209.807 1 m3.hm-2和208.933 8 m3.hm-2,并且胸径>16 cm的林木分别占80.00%和60.00%。混交林的木材产量:(1)12年生西南桦与高阿丁枫混交林单位面积木材产量是同林龄西南桦纯林(初植密度2 m×3 m×7 m)的1.845倍(172.363 7 m3.hm-2比94.978 9 m3.hm-2);(2)11年生西南桦与山桂花混交林单位面积木材产量是同林龄西南桦纯林的2.774倍(158.742 0m3.hm-2比57.219 0 m3.hm-2)。在西南桦与高阿丁枫混交林中,1行西南桦与2行高阿丁枫混交模式能提高西南桦高生长和木材产量。高阿丁枫和山桂花是可以同西南桦相匹配营造混交林的两个云南热带乡土树种。     

不同林分(地类)虎杖人工栽培生长效果比较

应用随机区组设计在杉木近熟林、天然阔叶林(刺栲、甜槠栲、苦槠栲、青冈栎)近熟林、毛竹丰产林、经济林地(银杏幼林、李果盛产林)以及杉木未成林造林地进行虎杖不同初植密度、不同林分(地类)的人工栽培试验.结果表明:虎杖不同初植密度、不同林分(地类)的人工栽培生长量、生物量具有极显著差异;初植密度的总生物量以株行距0.5 m×0.5 m最高,不同林分(地类)的根、茎、叶累计生物量净增长以经济林地最高.     

不同类型长白落叶松人工林各龄期的木材产量评估

根据立地指数的不同将长白落叶松林地分为7个立地等级(立地Ⅰ~Ⅶ),结合其营林技术规程选择造林密度为2 500株/hm2、3 300株/hm2和4 400株/hm2等不同类型的长白落叶松人工林分作为评估对象。在前人研究的基础上计算该不同类型林分在各林龄阶段的平均树高,利用相关模型推算相应林龄阶段的林分平均胸径和林分平均单株材积。建立长白落叶松人工林分的密度定量管理模型,根据此模型确定不同立地等级不同初植密度长白落叶松人工林分在理想状态下的间伐时间、间伐强度和木材收获量,为其营林生产和科研提供参考。     

湖北高密度杉木人工林生长规律研究

为研究湖北省高密度杉木人工林生长规律,对鄂东南地区高密度杉木人工林进行标准地调查,获取61块样地数据和183株解析木数据,建立了杉木单木树高、胸径和材积生长模型,根据拟合优度及残差指标,高密度杉木单木胸径和树高生长的最优模型选择理查德模型,单木材积最优模型选择考尔夫模型,所选模型检验精度均较高,达到拟合效果;通过绘制杉木胸径、树高和材积的生长曲线图,杉木生长量在初始阶段生长速率较大,单木树高和胸径生长量在第4 a达到最大值后逐渐下降,单木材积连年生长量在第10 a达到最大值;利用多元非线性回归建立关于杉木林分平均胸径、平均树高和林分蓄积与林龄、立地指数和林分密度的林分生长模型,选择的林分生长模型均通过检验;利用林分蓄积量的平均生长量和林分平均直径来确定高密度杉木林分的数量成熟龄和工艺成熟龄,在立地指数16～20 m和林分密度4 000～6 000株/hm~2时,杉木的数量成熟龄和工艺成熟龄分别为10～13 a、10～11 a,与湖北咸宁地区高密度杉木造林小径级采伐年龄相符。     

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.     

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。     

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.     

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.     

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.     

Insecticidal activity of Vitex mollis

Organic extracts from the leaves of Vitex mollis were assessed for their toxic effect on fall armyworm neonate larvae (Spodoptera frugiperda), an important insect pest of corn. The extracts showed insecticidal and insect growth regulatory activity, being CHCl(3)-MeOH (1:1) extract the most active, also found to be toxic in the Artemia salina test.     

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.     

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.     

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.