长白山阔叶红松林不同强度择伐后关键树种的竞争关系

天然林择伐改变了林分的树种组成和结构,导致林木竞争关系发生变化,进而影响树木的生长和种群的动态.关键树种在维持群落结构和生态系统功能方面具有至关重要的作用.为了弄清长白山区阔叶红松林典型林型关键树种竞争关系的特点,本研究以红松、紫椴和水曲柳为研究对象,运用Hegyi竞争指数分析了受不同程度采伐干扰后形成的原始林(未受干扰)、轻度择伐林、中度择伐林和重度择伐林的林分结构和竞争关系.结果表明: 与原始林相比,轻度择伐林中关键树种的种群结构没有显著变化;中度择伐林和重度择伐林中3个关键树种大树(胸径DBH≥20 cm)的密度和平均胸径均显著减少,但幼树(2 cm≤DBH<10 cm)的数量增加.所有样地中关键树种的竞争指数均随径级的增加而减小,且二者服从幂函数分布,而林木胸径生长到20 cm后,竞争指数进入稳定状态.在原始林、轻度和中度择伐林中,3个树种的幼树的竞争指数受到非冠层树种的影响最大,而红松小树(10 cm≤DBH<20 cm)和大树主要受红松种内和非冠层树种的影响;水曲柳主要受红松和非冠层树种的影响,紫椴主要受种内和红松的影响.重度择伐林中,白桦是3个树种的主要竞争来源,贡献率均超过50%.根据以上关键树种竞争关系的特点,抚育非冠层树种有利于3个关键种幼树的更新和生长;对于小树来说,还需要根据树种类型来采取相应措施,而大树不需要采用抚育措施.本研究对关键树种培育和天然林择伐后快速恢复具有指导意义.     

落叶松原始林树木生长对氮添加的响应

氮沉降对树木生长的影响是全球变化研究的一个核心问题。该文通过设置4种氮添加水平(对照(0)、低氮(20 kg N·hm^-2·a^-1)、中氮(50 kg N·hm^-2·a^-1)和高氮(100 kg N·hm^-2·a^-1)), 研究了模拟氮沉降对落叶松(Larix gmelinii)原始林树木胸径生长的影响。结果表明: 中氮和高氮添加对落叶松胸径相对生长率有显著影响, 而且这种影响随施氮年限的增加而增强。不同高度的树木对氮添加的响应有很大差异, 较低树木(树高<16.5 m)的生长对氮添加无显著响应, 而较高(树高>16.5 m)的树木在中氮和高氮处理下胸径生长有显著加速(胸径相对生长率增幅>79.5%), 但随着树木高度的进一步增加, 这种加速作用明显下降。研究结果显示氮添加会促进落叶松胸径生长, 这种促进作用主要发生在较高的落叶松个体中。     

长白山阔叶红松林3个常见树种径向生长的影响因素

为探究树木径向生长的影响因子,基于对长白山阔叶红松林25 hm²样地中3个常见树种红松、紫椴、蒙古栎连续5年的生长环监测数据,分析各树种的季节生长变化,比较树种间的生长速率差异,并分析初始径级、邻体树木竞争、土壤、地形因素等对不同树种径向生长的作用.结果表明: 3个树种径向生长的季节变化趋势一致,树木于5月末开始生长,7月是生长旺盛期,8月底生长开始减缓,于10月中下旬停止生长.3个树种的径向相对生长率存在显著差异,蒙古栎相对径向生长率显著高于红松和紫椴,该差异在小、中径级个体中表现更为显著.3个树种径向生长的主要影响因子不同,邻体树木的竞争显著抑制了红松和蒙古栎的径向生长,而紫椴的径向生长主要受初始径级、土壤和地形等因子的影响.     

树轮分析用于森林干扰强度推测的实例研究

树木年轮生长释放一直广泛应用于重建森林干扰,但没有直接的研究证明利用树木年轮分析建立的干扰强度的可靠程度,本文试图通过一个取自青海省互助国家森林公园(1987年经历过择伐)的样方进行验证.在40m×50m的青扦林样方内取胸径≥5cm的树木(124株)树轮芯样并测定胸径、树高和择伐后山杨(PopulusdavilianaDode)树桩(55个)的基径以及树木与树桩的距离.分析结果表明1987和1988年树木生长释放百分率为38.7%,与该林分的准确干扰强度37.7%(树桩基部断面积与该断面积加树木胸高断面积之和的比值)相接近.1980～1989年10a间树木生长释放百分率为62.9%,该10a间的平均干扰强度为37.0%(生长释放百分率62.9%/生长释放平均次数1.7),也接近于该林分的准确干扰强度,因而用树轮资料重建森林干扰强度是可行和可靠的.     

闽北不同立地类型的邓恩桉生长特性调查

通过标准地调查法,分析邓恩桉9 a生林分在闽北不同立地类型中胸径和树高的生长表现。结果表明,山地林1邓恩桉林分平均胸径和树高分别为11.6 cm、11.5 m,山地林2邓恩桉林分平均胸径和树高分别为13.0 cm、13.1 m,河岸林邓恩桉林分平均胸径和树高分别为21.3 cm、17.0 m。虽然各林分之间生长差异明显,但均超过本地乡土树种马尾松、杉木的速生丰产指标,且这些差异主要是由各林分中出现部分林木向高生长方向分化造成的,是邓恩桉在引种区适应生长的表现。     

大兴安岭林区南、北部天然樟子松生长对气候变化的响应差异

利用树木年代学方法,建立大兴安岭林区南、北部樟子松(Pinus sylvestris var.mongolica)年轮宽度年表,探讨樟子松径向生长对气候变化的响应差异。结果表明,南部(阿尔山、海拉尔)树轮宽度主要与当年4—9月的平均标准化降水蒸散指数SPEI(Standardized Precipitation Evapotranspiration Index)极显著正相关(r=0.639,P0.01),而北部(漠河、塔河)树轮宽度主要与同时期的平均最低温极显著正相关(r=0.488,P0.01)。说明南部樟子松径向生长主要受当年4—9月的水分限制,北部主要受同期平均最低温调控。两个地区树木生长对降水的响应一致,对当年4—9月(6月除外)的温度响应相反。近几十年来随着温度显著升高(P0.01),南部树木生长对4—9月平均最高温的负响应不断增强,而北部树木对同时段平均最低温的正响应更加明显。同时,南部樟子松生长量快速下降(r=0.612,P0.001),而北部生长量显著增加(r=0.474,P0.001)。研究发现,高温加剧干旱胁迫是南部樟子松生长量下降的主要原因,而北部樟子松生长量增加是受到4—9月平均最低温和降水量的相互作用。如果持续变暖,未来樟子松分布区可能北移。     

阈值温度和积温对川西高原林线岷江冷杉径向生长的影响

高山林线的形成机理一直是高山生态学讨论的一个焦点问题,其中林线树木生长的阈值温度一直是研究热点。利用川西高原九寨沟弓杠岭林线岷江冷杉(Abies faxoniana)树木径向生长数据,通过树轮宽度-气候因子关系分析,探讨阈值温度和积温对林线岷江冷杉径向生长的影响。结果表明:林线岷江冷杉径向生长主要受到温度限制,其中林线岷江冷杉径向生长与当年生长季(7、8和9月)、冬季(12、1和2)及上一年9、10月温度显著正相关(P0.05),但与降水的相关性较弱。林线岷江冷杉径向生长与不同起始温度的初日负相关,与不同起始温度的终日正相关,且与9.5℃阈值温度的初日负相关最强(P0.05),与6.5℃阈值温度的终日正相关最强(P0.05)。林线岷江冷杉径向生长还与7—9.5℃的积温及9.5℃持续天数显著正相关(P0.05),说明7—9.5℃可能是形成层活动的阈值温度,尤其7℃可能是林线岷江冷杉生长的起始温度。林线岷江冷杉生长期从4月中旬开始到10月初结束,随着1980年后温度的显著升高,生长期活动积温开始增加,生长期初日提前(4.6d/10a,r~2=0.19,P=0.01),生长期终日延后(1.8 d/10a),使得生长期延长(6.4 d/10a),进而对林线岷江冷杉径向生长有显著的促进作用。未来气候变暖可能会使川西林线树木生长增加,林线可能会上移。     

Response of tree growth to nitrogen addition in a Larix gmelinii primitive forest

 氮沉降对树木生长的影响是全球变化研究的一个核心问题。该文通过设置4种氮添加水平(对照(0)、低氮(20 kg N·hm^-2·a^-1)、中氮(50 kg N·hm^-2·a^-1)和高氮(100 kg N·hm^-2·a^-1)), 研究了模拟氮沉降对落叶松(Larix gmelinii)原始林树木胸径生长的影响。结果表明: 中氮和高氮添加对落叶松胸径相对生长率有显著影响, 而且这种影响随施氮年限的增加而增强。不同高度的树木对氮添加的响应有很大差异, 较低树木(树高<16.5 m)的生长对氮添加无显著响应, 而较高(树高>16.5 m)的树木在中氮和高氮处理下胸径生长有显著加速(胸径相对生长率增幅>79.5%), 但随着树木高度的进一步增加, 这种加速作用明显下降。研究结果显示氮添加会促进落叶松胸径生长, 这种促进作用主要发生在较高的落叶松个体中。     

黄连木雌雄植株径向生长的影响因子

采用树木年轮学方法,研究了性别、树木大小及气候因子(温度和降水)对雌雄异株树种黄连木径向生长的影响。结果表明:性别对黄连木径向生长无显著影响(P0.05),树木大小对黄连木径向生长影响显著(P0.05),且不同径级黄连木雌雄植株径向生长速率不同,径级10～15cm黄连木雌树径向生长速率显著大于雄树。与气候因子的相关分析表明,黄连木雌雄植株径向生长与气候因子的关系有一定共性,即均与当年3月的月均最低温度,当年11月的平均温度、月均最高温度和当年5月的月降水量呈显著正相关,而与当年5月的平均温度、月均最高温呈显著负相关;黄连木雌雄植株径向生长对气候因子的响应也存在一定的差异性,其中,雌株径向生长与当年1月平均温度呈显著负相关;黄连木雄树径向生长与当年4月的月均最低温度呈显著正相关,与当年7月的平均温度、月均最高温度呈显著负相关。     

海南中部山区天然林群落结构与多样性变化

为了解海南中部山区天然林群落结构与多样性变化规律,对五指山山地雨林原始林、尖峰岭低地雨林、吊罗山山地雨林、霸王岭云雾林次生林内建成的各1600 m²样地进行常年监测,基于2012—2020年监测数据,从群落结构、树木生长、树木死亡、物种多样性等方面分析群落近8年动态特征。结果表明：2012—2020年,(1)五指山山地雨林、尖峰岭低地雨林的径级结构与树高结构均呈倒“J”型,吊罗山山地雨林、霸王岭云雾林的径级结构呈倒“J”型,树高结构呈近“L”型;随着时间的推移,群落结构更加复杂。(2)小径级个体树高生长速率较快,随胸径增加树高生长速率降低,胸径生长速率升高;死亡个体数量随胸径的增加而减少,表现出小径级个体对阳光等资源的强烈竞争。(3)翻白叶(Pterospermum heterophyllum)、岭南山竹子(Garcinia oblongifolia)、四蕊三角瓣花(Prismatomeris tetrandra)、海南山矾(Symplocos hainanensis)种群变化率分别为-6.07%、+7.10%、+12.52%、+14.29%,种群变化率均大于5%...     

Transforming growth factors and control of neoplastic cell growth

Transforming growth factors (TGFs) are peptides that affect the growth and phenotype of cultured cells and bring about in nonmalignant fibroblastic cells phenotypic properties that resemble those of malignant cells. Two types of TGFs have been well characterized. One of these, TGF alpha, is related to epidermal growth factor (EGF) and binds to the EGF receptor, whereas the other, TGF beta, is not structurally or functionally related to TGF alpha or EGF and mediates its effects via distinct receptors. TGF beta is produced by a variety of normal and malignant cells. Depending upon the assay system employed, TGF beta has both growth-inhibitory and growth-stimulating properties. Many of the mitogenic effects of TGF beta are probably an indirect result of the activation of certain growth factor genes in the target cell. The ubiquitous nature of the TGF beta receptor and the production of TGF beta in a latent form by most cultured cells suggests that the differing cellular responses to TGF beta are regulated either by events involved in the activation of the factor or by postreceptor mechanisms. The combined effects of TGF beta with other growth factors or inhibitors evidently play a central role in the control of normal and malignant cellular growth as well as in cell differentiation and morphogenesis. Since transforming growth factor as a concept has partially proven misleading and insufficient, there is a need to find a new nomenclature for these regulators of cellular growth and differentiation.     

From growth arrest to growth suppression.

Since the introduction of the cell cycle concept two approaches to study growth regulation of cells have been proposed. One claims that cells are naturally quiescent, requiring a stimulatory encouter with growth factors for induction of cell division. The other considers cellular multiplication as the natural steady-state; cessation of multiplication is thus a restriction imposed on the system. In the latter case emphasis is mainly on the signals involved in arrest of multiplication. This Prospect focuses on specific events occurring in mammalian cells at growth arrest, senescence, and terminal differentiation, specifically emphasizing the growth inhibitory factors, tumor suppressor genes, and other signals for growth suppression.     

Effect of recombinant growth hormone on expression of growth hormone receptor,insulin-like growth factor mRNA and serum level of leptin in growing pigs

Sixteen Large White × Landrace castrated male pigs were allotted into treatment and control group. The treatment group was injected intramuscularly with recombinant porcine growth hormone (rpGH, 4 mg d⁻¹) and the control group with vehicle for 28 days. Animals were slaughtered 4 h after final injection for liver, longissimus dorsi (LD) muscle and blood sampling. Serum concentration of insulin-like growth factor 1 (IGF-I) and leptin were determined by RIA. The total RNA was extracted from tissues to measure the abundance of growth hormone receptor (GHR), IGF-I mRNA by RT-PCR with 18S rRNA internal standard. Results showed that rpGH enhanced the average daily weight gain by 26.1% (P < 0.05), the serum IGF-I concentration by 70.94% (P < 0.01), decreased serum leptin by 34.8% (P < 0.01). The relative abundance of GHR and IGF-I mRNA in liver were increased by 24.45% (P < 0.05) and 45.30% (P < 0.01), respectively, but no difference of GHR (P > 0.05) and IGF-I mRNA (P > 0.05) in LD between GH treated and control group was found. These results suggest that rpGH can up-regulate hepatic GHR and IGF-I gene expression and improve animal growth. However the effect of rpGH on GHR and IGF-I gene expression are tissue-specific.     

Effect of recombinant growth hormone on expression of growth hormone receptor, insulin-like growth factor mRNA and serum level of leptin in growing pigs

Growth hormone (GH) plays an important role in regulation of animal growth, metabolism and lactation[1]. Numerous studies have shown that exogenous somatotropin (ST) can increase average daily weight gain, improve feed efficiency, stimulate protein deposition and muscle growth and decrease lipid accretion rate[1]. The original somatomedin hypothesis suggested that the effect of GH on postnatal growth was mediated by insulin-like growth hormone factor 1 (IGF-I) which was thought to be deriv…     

Simulation of biological growth

Researchers concerned with the growth of biological tissue often use models that predict the growth as a function of a mechanical stimulus such as stress, strain or elastic energy. However, a general theory for bulk growth should consider that the mechanical stimulus may only be one of many factors contributing to growth. Another important factor could be time, as living tissues can be assumed to have a pre-programmed directional biological growth that is independent of mechanical stimuli. This paper has two objectives: the first is to introduce the concept of directional biological growth within a well developed growth theory, the second is to present the computational methods by which three-dimensional growth that encompasses time and stress effects can be simulated using commercially available finite element analysis software.     

Micropattern-immobilization of heparin to regulate cell growth with fibroblast growth factor

Heparin was immobilized on a polystyrene plate in a specificpattern by photolithography. Heparin was coupled with azidoaniline. Thederivatized heparin was cast on the polystyrene plate from aqueoussolution. After drying, the plate was photo-irradiated in the presence of aphotomask. The micropatterning was confirmed by staining with a dye,ethydium bromide. Since heparin has negative charges, the cationic dyewas adsorbed on the regions where heparin was immobilized. In thepresence fibroblast growth factor (FGF), the growth of mouse fibroblastSTO cells was enhanced only on the heparin-immobilized regions. Thisresult indicated that micropattern-immobilized heparin activated FGF forcell growth activity.     

Milk-derived growth factors as serum supplements for the growth of fibroblast and epithelial cells

Summary We have investigated the response of several epithelial and fibroblastic cells to a mitogenic extract of bovine milk. Cation exchange chromatography was used to produce a mitogen-rich fraction from an industrial whey source that, although comprising only 0.5% of total whey protein, contained the bulk of the growth factor activity. This fraction was a source of potent growth promoting activity for all mesodermal-derived cells tested, including human skin and embryonic lung fibroblasts, Balb/c 3T3 fibroblasts, and rat L6 myoblasts. Maximal growth of all these cell types exceeded that observed in 10% fetal bovine serum. Feline kidney and baby hamster fibroblasts and Chinese hamster ovary cells were less responsive, achieving a maximal growth response of 50–75% that observed in 10% fetal bovine serum. Maximal growth achieved in whey-extract-supplemented cultures of Balb/c 3T3 and human skin fibroblasts, and L6 myoblast cultures exceeded that seen in response to recombinant acidic or basic fibroblast growth factor, platelet-derived growth factor, insulin-like growth factor, or epidermal growth factor. Importantly, addition of low concentrations of fetal bovine serum to the whey-derived mitogenic fraction produced an additive response. However, concentrated milk-derived factors were found to be inhibitory to the growth of all epithelial lines tested, including rat intestinal epithelial cells, canine kidney epithelial cells, and mink lung cells. It is concluded that industrial whey extracted in this form constitutes an important source of potent growth-promoting agents for the supplementation of mesodermal-derived cell cultures.     

Osteopontin contributes to hepatocyte growth factor-induced tumor growth and metastasis formation

The cytokine hepatocyte growth factor (HGF)/scatter factor-1 and its cognate receptor, Met, are involved in the etiology and progression of many types of cancer. Despite recent advances in understanding the signal transduction pathways activated by HGF, the mechanism by which HGF exerts its tumorigenic effect is not well understood. To identify proteins that may be involved in mediating HGF-induced cell motility, invasiveness, and tumorigenesis, we used two separate differential display screening methods to identify changes in gene expression that are initiated by HGF in an epithelial cell culture system. Among several known and unknown genes whose expression was modified, osteopontin (OPN), a protein previously associated with tumorigenesis, was found to be upregulated within 6 h following HGF stimulation. OPN expression was dependent on activation of the PI-3 kinase pathway. Autocrine secretion of HGF resulted in sustained expression of OPN. Downregulation of opn expression by stable antisense transfection attenuated OPN expression and repressed HGF-induced invasiveness in vitro and decreased HGF-mediated tumor growth and metastasis formation in vivo. Constitutive expression of OPN in itself exerted partial invasiveness in vitro, but its expression itself was not sufficient to initiate tumor growth or metastasis formation in vivo. Thus, together with other molecules, OPN activity contributes to HGF-induced tumor growth and invasiveness.