阔叶红松林林隙结构与树种多样性关系研究

对阔叶红松林林隙与林下不同层次树种多样性进行比较,探讨林隙大小及发育阶段与树种多样性间的关系.结果表明,林隙与林下树种多样性存在显著差异（P<0.01）.与林下相比,林隙更新层树种多样性、丰富度和均匀度增大,生态优势度减小（P<0.01）;演替层树种多样性、丰富度和均匀度减小,生态优势度增大（P<0.0001）.林隙中不同层次树种多样性随着林隙大小呈现出相反的变化趋势.长白山阔叶红松林林隙演替层树种多样性和丰富度总体上呈单峰形变化,中等大小林隙（100～250 m²）中树种多样性和丰富度较高,生态优势度较小.而更新层树种多样性和均匀度在≥250 m²和<100 m²的林隙中最大,在200～250 m²的林隙中最小;生态优势度在200～250 m²的林隙中达到最大.更新层和演替层树种对林隙面积大小反应不同,有利于更新层幼苗建立的林隙面积并不是演替层幼树发育和成活的最适面积;随林隙年龄的增加,更新层和演替层树种多样性在不同层次上呈互补关系.     

子午岭地区辽东栎和油松林建群种的更新生态位宽度分析

通过实地调查并采用Levins生态位宽度指数对子午岭地区主要树种辽东栎(Quercus liaotungensis)和油松(Pinus tabulaeformis)的幼苗、幼树和成树在不同坡向的辽东栎林、油松 辽东栎混交林和人工油松林3种群落中的生态位宽度进行了分析研究。结果显示:(1)辽东栎和油松的更新生态位宽度在不同群落中各不相同,成树的生态位宽度与群落类型一致;(2)辽东栎幼苗和幼树在阳坡和阴坡人工油松林中的生态位宽度分别是0.951、0.95和0.98、0.94,且生态位宽度显著大于其它2个群落,表明辽东栎幼苗和幼树能很好地适应人工油松林的环境条件;(3)在阳坡,油松幼苗的生态位宽度在辽东栎林最大为0.79,且极显著大于其它2个群落,而阳坡油松幼树的生态位宽度在人工油松林中最大为1.00;在阴坡,油松幼苗的生态位宽度在人工油松林最大为0.63,而阴坡油松幼树的生态位宽度却在油松 辽东栎混交林最大为0.83,且极显著大于其它2个群落;表明油松幼苗适应阳坡的辽东栎林环境和阴坡的人工油松林环境,油松幼树适应阳坡的人工油松林环境和油松 辽东栎林环境。结果表明,人工种植油松林有利于该地区的植被恢复,人工油松林和油松 辽东栎混交林会在该地区存在较长时间,而阳坡的油松 辽东栎混交林存在时间会更长。     

林窗尺度对马尾松人工林林下灌草层优势种生态位的早期影响北大核心CSCD

马尾松作为中国广泛栽植的乡土树种,其人工林群落结构简单和生物多样性低下是普遍存在的生态学问题。探究不同林窗尺度对马尾松人工林林下植被群落的影响,可为马尾松人工林近自然经营提供理论依据。该研究在45 a生马尾松人工林中分别设置A(50 m^(2))、B(100 m^(2))、C(200 m^(2))和D(667 m^(2))4种不同尺度的林窗,以不做任何处理的马尾松人工林作为对照(CK),探究采伐开窗后林窗内自然更新1 a后的灌草层植物组成、优势种生态位宽度和生态位重叠度分布特征。结果显示:(1)除100 m^(2)林窗下灌木层物种数与对照无显著差异外,其余林窗灌草层物种数均显著高于对照(P<0.05),且200 m^(2)林窗下灌草层物种数均最多,分别为35种和20种;4种林窗下灌草层物种丰富度指数较对照均显著增加(P<0.05),最大值均出现在200 m^(2)林窗下,其值分别为对照的1.5倍和2.6倍。(2)林窗增加了灌草层喜光植物种类,且在200 m^(2)林窗下种类最多,灌木层喜光植物有13种,草本层喜光植物有5种。(3)4种林窗下灌草层优势种中,喜光植物生态位宽度均较大,200 m^(2)林窗下灌草层生态位宽度平均值最小,其对资源利用程度低,重要值与生态位宽度之间无显著相关性(P>0.05)。(4)4种林窗下灌草层优势种间生态位重叠度指数均较小。667 m^(2)林窗下,灌草层优势种平均生态位重叠度指数最小,分别为0.029和0.024,200 m^(2)林窗下灌草层优势种高生态位重叠度占总数比例最大,分别为20%和23.8%。研究表明,采伐开窗促进了马尾松人工林林下植被发育,丰富了林下植物多样性,有利于马尾松林稳定持续发展,对精准提升马尾松人工林质量具有重要意义。     

陕北黄土高原辽东栎(Quercus liaotungensis)群落类型划分及其生态位特征

根据陕北黄龙林区辽东栎群落30个样地资料,通过聚类对该群落进行了类型划分,共划分为6个群丛,分别为A.辽东栎(Quercus liaotungensis）-土庄绣线菊(Spiraea pubescens)、B.辽东栎-虎榛子(Ostryopsis davidiana)、C.辽东栎-胡枝子（Lespedeza bicolor）、D.辽东栎-水栒子(Cotoneasten multtflorus)、E.辽东栎-白刺花（Sophora viciifolia）、F.辽东栎-黄蔷薇(Rosa hugonis)。另外,对各类型辽东栎林和不同坡向辽东栎群落的生物多样性进行了计算,结果表明各群落Whittaker多样性指数存在明显的差异,并与其所处的生境条件密切相关,其中与坡向关系较大,即北坡>西北坡>东南坡>西南坡>南坡。最后,对辽东栎林乔木层和灌木层组成种类生态位和生态位重叠进行了计算分析,结果表明,乔木层,辽东栎、油松、白桦不仅生态位宽度较大（LB值1.2~1.5）,而且三者之间的生态位重叠值也较大（Oik值0.7~0.9）;在现演替阶段它们之间存在着较为激烈的资源利用性竞争;灌木层,土庄绣线菊、榛子、铁杆蒿、黄蔷薇生态位宽度较大（LB>1）,而葱皮忍冬、南蛇藤、鼠李、鞘柄菝葜较小（LB为0.4~0.45）;生态位重叠值>0.8的种对仅占灌木计算种对的2.8%,而<0.6的种对占87.4%。     

山西太岳山辽东栎群落优势种生态位研究

采用样方法对山西太岳山七里峪林区辽东栎群落进行群落调查, 利用生态位宽度、生态位相似性比例和生态位重叠公式对其10 种乔木, 10 种灌木和11 种草本的种群生态位特征进行研究。结果表明: 1)Levins 和Hurlbert 两种公式在乔、灌、草各层中的总体趋势基本保持一致。群落中辽东栎、土庄绣线菊和披针叶苔草在各层中的重要值和生态位宽度值最大, 对资源环境有较强的适应能力, 在群落中具有重要的地位。而棘皮桦、接骨木、水金凤等种群数量相对较少, 生态位宽度较小, 对资源的利用能力较弱; 2)从乔、灌、草整体的生态位相似性分配格局和重叠格局看, 辽东栎林各种群间生态位相似性比例和重叠程度较小, 群落内种间竞争不激烈, 有利于群落实现长期稳定共存; 3)从对辽东栎群落物种频度、重要值、生态位宽度和平均生态位重叠值的相关性分析可知, 除重要值和平均生态位重叠值相关性不显著外, 其余的都呈显著性正相关。研究发现七里峪辽东栎林是七里峪地区的地带性顶极群落, 多数优势种的生态位重叠值较小, 但仍有少数优势种重叠值较大, 表明在辽东栎群落发展过程中种群间对环境资源的利用性竞争不可避免, 所以维持群落的物种多样性使群落处于动态的稳定状态有利于辽东栎群落的保护和发展。     

长苞铁杉林林隙主要树种生态位初步研究

以林隙前、中、后期3个发育阶段的各个林隙为一维资源位状态,利用Shannon-wiener指数、Levins指数及生态位重叠公式,计算林隙不同发育阶段主要树种生态位特征。结果表明,前期生态位宽度从大到小的顺序为:长苞铁杉、米槠、木荷、甜槠、深山含笑、香桂、青冈、猴头杜鹃、山矾、细叶青冈;中期的为:米槠、木荷、长苞铁杉、香桂、深山含笑、山矾、甜槠、猴头杜鹃、青冈、细叶青冈;后期的为:米槠、木荷、长苞铁杉、青冈、山矾、香桂、深山含笑、细叶青冈、甜槠、猴头杜鹃;林隙发育的不同时期主要树种生态位重叠值均较大,但随着林隙的不断发育,主要树种间生态位重叠值有减小的趋势;长苞铁杉在林隙发育的不同阶段与生态位宽度较大的物种有较小的生态位重叠值,而与生态位宽度较小的物种有较大的生态位重叠值。     

林窗对格氏栲天然林更新层物种生态位的影响

采用改进更新生态位宽度和更新生态位重叠模型分析林窗干扰对福建三明市格氏栲天然林更新层物种生态位的影响。结果表明:林窗中格氏栲更新生态宽度值大于林下,林窗在促进格氏栲更新过程中具有重要作用。林窗和林下更新生态位宽度最大的为桂北木姜子,其与格氏栲更新生态位重叠值也较大。林窗中的格氏栲与其它物种更新生态位重叠值低于0.6,林窗微生境的异质性导致格氏栲与其它树种间对资源的利用存在明显的共享趋势,促进了物种间共存。林下的格氏栲与木荷、木荚红豆和短尾越桔的更新生态位重叠值均高于0.6,格氏栲与这些物种相互争夺资源与空间,种间竞争较强。格氏栲天然林未来树种组成中,主要由桂北木姜子、木荷、矩圆叶鼠刺与格氏栲等组成的混交群落,整个群落正向物种组成多样化的方向演变。     

河南省栓皮栎林主要种群的生态位研究

对河南省栓皮栎林主要树种的生态位宽度与重叠进行分析。结果表明栓皮栎种群的生态位宽度较大,尤其是在土壤厚度空间资源上利用的优势明显;栓皮栎与麻栎、小叶青冈栎的生态位重叠较大,但在总资源轴上具分异性与互补性,生态位重叠随资源轴数增加而减小,从而使得栓皮栎林具有一定的稳定性。指出今后研究应注重栓皮栎对土壤利用的功能及机理。     

陕北黄土高原辽东栎(Quercus liaotungensis)群落类型划分及其生态位特征

根据陕北黄龙林区辽东栎群落30个样地资料,通过聚类对该群落进行了类型划分,共划分为6个群丛,分别为A．辽东栎（Quercus liaotungensis）-土庄绣线菊（Spiraea pubescens）、B．辽东栎-虎榛子（Ostryopsis davidiana）、c．辽东栎-胡枝子（Lespedeza bicolor）、D．辽东栎．水枸子（Cotoneasten multtflorus）、E．辽东栎-白刺花（Sophora viciifolia）、F．辽东栎-黄蔷薇（Rosa hugonis）。另外,对各类型辽东栎林和不同坡向辽东栎群落的生物多样性进行了计算,结果表明各群落Whittaker多样性指数存在明显的差异,并与其所处的生境条件密切相关,其中与坡向关系较大,即北坡〉西北坡〉东南坡〉西南坡〉南坡。最后,对辽东栎林乔木层和灌木层组成种类生态位和生态位重叠进行了计算分析,结果表明,乔木层,辽东栎、油松、白桦不仅生态位宽度较大（LB值1．2—1．5）,而且三者之间的生态位重叠值也较大（0ik值0．7—0．9）;在现演替阶段它们之间存在着较为激烈的资源利用性竞争;灌木层,土庄绣线菊、榛子、铁杆蒿、黄蔷薇生态位宽度较大（LB〉1）,而葱皮忍冬、南蛇藤、鼠李、鞘柄菝葜较小（LB为0．4—0．45）;生态位重叠值〉0．8的种对仅占灌木计算种对的2．8％,而〈0．6的种对占87．4％。     

辽东栎林林隙特征及其对群落更新的影响

通过对黄土高原马栏林区辽东栎(Ouercus liaotungensis)林林隙的定量研究,发现其林隙大小以20～40和40～60 m2的中小林隙居多,林隙的年龄结构以中期和后期数量居多,林隙形成方式以枯立和干基折断占总数的70.31%,林隙形成木多为1～3个,说明该地区辽东栎林隙多为自然干扰形成,林隙边缘木中辽东栎的株数占绝大多数.在林隙中,不同生活史阶段的辽东栎多度对林隙环境因子的响应不同.幼苗多度与林隙面积和边缘木高度间存在极显著相关关系(R2=0.429,P＜0.01),幼树多度与散射光的强度有极显著相关关系(R2=0.286,P＜0.01),而成树多度与林隙环境因子的关系并不明显,但与林隙内幼树的多度有显著的相关关系(R2=0.175,P＜0.05).     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.     

我国葫芦科植物离体培养研究进展

葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义。综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望。