植物种群更新限制——从种子生产到幼树建成

更新限制是指种子由于各种原因,不能够萌发并生长成幼树。它作为解释生物多样性的理论,一直受到国内外群落生态学家关注。从种源限制、传播限制和建成限制3个角度,对更新限制机制研究进展进行了综述。从种源限制而言,时空因素是影响植物种群更新限制的重要因素,因为植物结实量存在明显时空变化,造成植物更新个体出现明显的时空规律。从传播限制而言,传播数量、距离和食果动物行为均限制植物种群更新。数量上,缺乏有限传播者势必减少传播数量,但如果种子拥有较高质量,则能逃脱数量限制;距离上,植物更新个体显示出明显的Janzen-Connell格局,但传播距离趋向稳定,形成植物种群的进化稳定对策;食果动物行为上,不同传播者对更新贡献存在差异,捕食者直接降低更新,融入两类动物行为的模型更能反映食果动物对更新的限制。从建成限制而言,环境因子制约植物生长。小尺度下,微生境的好坏对于植物幼苗建成至关重要;大尺度下,植物提供较好的广告效应则能摆脱生境限制。将传播者行为、捕食者行为与幼苗的空间分布格局、种子传播机理模型等结合,建立植物更新限制机理模型应是更新限制未来的研究热点。选择稀有种和古老种为主题的长期更新限制研究,为种群恢复提供指导,也是未来重要研究方向。     

Gene expression in response to multiple nutrient-starvation conditions in Salmonella typhimurium

Abstract In nature, bacteria encounter a variety of environmental conditions, among the most frequent of these is the limitation or starvation of one or more essential nutrients. It is reasonable to assume, therefore, that bacteria have evolved mechanisms to enhance their survival over prolonged periods of nutrient starvation. We have identified eight genetic loci in the enteropathogen Salmonella typhimurium , using Mu d -directed lacZ operon fusion technology, that were induced in response to two or more different starvation conditions (sti) . In simultaneous studies, we also identified genetic loci, using Mu d-lac fusions, which respond to only phosphate-starvation conditions (psi) . We further characterized these loci as to their induction-characteristics, kinetics of induction, expression during growth on different carbon sources, and approximate location on the S. typhimurium genetic map. In concurrent studies, we analyzed whole cell extracts of S. typhimurium grown under a variety of nutrients oxydation conditions as well as under nonlimiting conditions, using two-dimensional polyacrylamide gel electrophoresis. Results from these studies correlated well with our gene fusion studies. In more recent studies, we have demonstrated a complex genetic regulation of a number of these starvation-inducible loci, and have implicated at least four of these loci in the long term starvation-survival of S. typhimurium .     

Seed dispersal and seedling recruitment of trees at different successional stages in a temperate forest in northeastern China

Aims Spatial distribution of adult trees in a forest community is determined by patterns of both seed dispersal and seedling recruitment. The objectives of our study were to understand the processes of seed dispersal and seedling recruitment of dominant tree species in a temperate forest of northeastern China and to identify the factors constraining seed dispersal and seedling establishment at different stages of forest succession.Methods During three summer and autumn sessions between 2006 and 2008, altogether 113080 seeds from 22 different tree species were collected in three large field plots representing different forest types in the Changbai Mountain region of northeastern China. The spatial distribution of seed abundance was analyzed using a Syrjala test. Regeneration success of nine major tree species was assessed using variables defining 'limitations' in 'seeds' and 'seedling establishment'.Important findings We found that seed production fluctuated between years and varied greatly with forest types. Four tree species, Acer spp., Fraxinus mandshurica, Tilia amurensis and Betula spp., had the greatest seed production and the widest range of seed dispersal, whereas Quercus mongolica showed the most sustained seed production pattern. The spatial patterns of seed abundance differed significantly among forest types and years. The tree species investigated in this study differed in the degree of seed limitation, as well as in limitation of seedling establishment. There were both negative and positive correlations between seed density and seedling density, depending on site and parental tree density. Seeds of 16 tree species were found in the Populus davidiana–Betula platyphylla forest (PBF) plot, 11 in the conifer and broad-leaved mixed forest (CBF) plot but only 8 in the broad-leaved-Korean pine mixed forest (BKF) plot. The number of seed-contributing species was not only greater in the secondary forests (CBF and PBF plots) than in the primary forest (BKF plot) but was also more variable during the 3 years of assessment. Results from the correlations between seed density and seedling occurrence and that between parental tree density or seed weight and dispersal limitation confirm our intuitive expectations, i.e. heavy seeds had greater dispersal limitation but higher establishment success than light seeds.     

子午岭三种生境下辽东栎幼苗定居限制

辽东栎(Quercus wutaishanica)是子午岭地区的乡土乔木树种,也是该地区气候顶极群落的建群种,其幼苗的补充更新影响着森林群落的结构及物种组成。在3种典型生境(辽东栎林、人工油松林、灌草丛)中,设置3因素(种子、干扰、遮荫)两水平的野外播种实验(随机区组设计),记录辽东栎幼苗出苗量,并监测幼苗同生群在3种生境中3a间的生长状况,以确定种子及微生境在辽东栎幼苗补充过程中的限制作用。播种实验样方大小30cm×30cm,共计216个样方。结果显示,在辽东栎林及油松林内,增加种子和干扰强度(去除枯落物),能引起出苗量和幼苗补充量的显著增加,且2种处理方式间存在交互作用,表明在郁闭林冠下,辽东栎幼苗的补充受到了种子和微生境的双重限制,枯落物是导致微生境限制的主要因素之一。在灌草丛生境,各种处理方式均不能增加幼苗的补充量,表明辽东栎无法在开阔生境(强光照、干旱)中完成实生幼苗的补充更新。3种生境中的幼苗同生群生存分析表明,辽东栎幼苗在森林群落中存活率显著高于灌草丛群落。根据幼苗生长指标判断,在3种生境中,人工油松林是辽东栎幼苗定居的最佳场所。与实验预期相反,灌木对辽东栎幼苗的补充无显著影响。     

Effects of light and microcrustacean prey on growth and investment in carnivory in Utricularia vulgaris

SUMMARY 1. In a 5-week enclosure experiment, we studied the effects of light (ambient light, low light) and prey availability (no prey, prey added) on growth and investment in carnivory in Utricularia vulgaris .
2. Investment in carnivory, measured as the proportion of biomass allocated to bladders, was strongly affected by our manipulations of light intensity and prey density. In the treatment with high prey density the light reduction decreased the investment in bladders from 25% to zero. The effect of prey density on investment in bladders was negative. Because prey addition increased the concentration of nutrients, especially phosphorus, we propose that the effect of the prey treatment on investment reflected altered nutrient concentrations.
3. Availability of prey increased growth and apical biomass of Utricularia . As Utricularia had very few bladders in some treatments we suggest that the effect was due to a combination of live prey trapped and increased nutrient availability from dead prey.
4. Abundance of periphyton on Utricularia and on the enclosure walls was highest in the treatments with high prey density where nutrient concentrations were highest. Thus we interpret the response of periphyton as primarily reflecting nutrient availability.     

Effect of Food Quantity and Quality on Population Growth Rate and Digestive Activity in the Euryhaline Rotifer Brachionus plicatilis Müller

We investigated the nutritional effects of both food quantity and quality on Brachionus plicatilis. Decomposition of particulate and dissolved organic matter by rotifer digestive enzymes play a crucial role in rotifer nutrition. Among other enzymes, rotifers produce phosphatases, non‐specific enzymes that allow for the release of orthophosphate from a variety of organic phosphorus compounds. Phosphatase saturation was measured in B. plicatilis homogenates using the spectrofluorimetric method. We examined population growth rate, reproduction and phosphatase activity in the homogenate of rotifers (PA_RH) fed by nutrient‐replete algal food supplied at different quantities. Population growth rate, number of eggs per individual and PA_RH were affected by food quantity. Growth rate and number of eggs per individual significantly increased in rotifers fed by food supplied at the highest quantity. The highest population growth rate was reached by rotifers fed by nutrient‐replete food, while it did not significantly differ between rotifers fed on nitrogen (N)‐depleted and phosphorus (P)‐depleted food. The number of eggs per individual was more affected by N than P supply. PA_RH and rotifer RNA content were not influenced by different food quality. The results indicate that B. plicatilis is not able to regulate its digestive apparatus in terms of efficiently getting access to essential nutrients when scarce, but do this when nutrient‐replete food is available in different quantity. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

植物光合作用限制因素与植被生产力研究进展

随着全球气候变化的加剧,陆地生态系统中植物光合作用限制影响程度的增加已成为降低全球植被净初级生产力的主要因素。系统了解植物光合作用限制因素是科学评估植被生产力的重要前提,也是缓解植物光合作用限制,增加植物光合碳同化能力的先决条件。对植物光合作用限制因素进行了系统解析,分析了光合作用三种限制因素生化限制(Biochemical limitation,l_b)、气孔限制(Stomatal limitation,l_s)、叶肉限制(Mesophyll limitation,l_m)的环境响应,重点讨论了叶肉限制及其影响机理,述评了光合作用限制定量分析方法及改善措施,最后以提高植被生产力为驱使目标,对未来植物光合作用限制因素研究提出以下内容：(1)基因工程技术与系统生物学数据相结合提高植被生产力;(2)气孔响应速度对植物光合作用的影响机制;(3)水通道蛋白(Aquaporin, AQPs)和碳酸酐酶(Carbonic anhydrase, CAs)感知环境信号变化的驱动基因。以期为未来气候变化背景下,深入认识和降低植物光合作用限制,提...     

重症心力衰竭患者运动病理生理学特征的临床研究*

目的: 通过症状限制性极限运动心肺运动试验（CPET）,从整体整合角度研究慢性心力衰竭患者（CHF）的运动病理生理学特征。方法: 选2016年10月至2017年10月就诊于中国医学科学院阜外医院签署知情同意书后的CHF 83例,并选同期12例正常人作为对照。在严格定标、规范化操作下按照美国加州大学洛杉矶分校医学中心标准完成连续递增功率方案的症状限制性CPET,并检测运动中呼吸循环代谢等功能指标。结果: CHF病人CPET核心指标中峰值摄氧量为（14.33±2.69） ml/（min·kg）, （44.25±14.74）%pred显著低于正常对照组（29.42±5.46） ml/（min·kg）, （83.88±6.28）%pred。此外,CHF组患者的无氧阈（AT）、峰值氧脉搏、摄氧通气效率峰值平台（OUEP）、二氧化碳通气当量最小值（Lowest VE/VCO₂）、二氧化碳通气当量斜率（VE/VCO₂ Slope）均与正常对照组有显著统计学差异（P<0.01）;CHF肺功能核心指标一秒用力呼气容积（FEV₁）、用力肺活量（FVC）、一秒率（FEV₁/FVC）、肺一氧化碳弥散量（DLCO）百分预计值均显著低于正常对照组（P<0.01）。CHF组收缩压的5个功能状态均显著低于正常对照组（P<0.05）,舒张压无统计学差异,心率在无氧阈、峰值和恢复2 min时均显著低于正常对照组（P<0.01）。分钟通气量、潮气量和呼吸频率在静息和热身状态下显著高于正常对照组（P<0.05）,在运动极限时显著低于正常对照组（P<0.05）,潮气量在恢复期显著高于正常对照组（P<0.05）。摄氧量在无氧阈、峰值和恢复2 min显著高于正常对照组（P<0.01）;氧脉搏在无氧阈、峰值显著高于正常对照组（P<0.01）;脉搏氧饱和在5个功能状态均显著低于正常对照组（P<0.01）。结论: 心源性疾病导致的CHF患者整体功能下降主要源于循环受限,同时呼吸和代谢也有受限。     

植物种群更新的补充限制

补充限制基于生态位理论, 从种子萌发、幼苗存活和生长、繁殖体扩散等生活史阶段的种群统计特征及环境因素(土壤水分、养分、凋落物等)着手, 探讨种群的更新问题。种源限制和微生境限制是补充限制理论研究的核心内容, 但是哪个更为重要并没有统一的结论。种源限制与种子生产、土壤种子库和地下芽库中的繁殖体数量不足有关。其中, 气候的年际波动、土壤种子库寿命和动物的捕食都会影响种子生产在种群更新中的作用; 土壤种子库常被视为种群更新的保险库, 与地上种子雨共同促进种群更新, 但是, 如果土壤里种子具有较高的死亡率和休眠率, 将会降低种子库的作用; 地下芽库及其产生的无性分株对于种群更新的意义更多地体现在干扰后种群更强的恢复能力上。扩散限制是种群更新中的普遍现象, 与种子产量、散布能力、传播媒介、幼苗密度等因素有关。微生境限制主要表现为水分、养分、凋落物等非生物因素以及竞争、捕食等生物因素对种子的活力、萌发性、幼苗的存活力、物质分配等过程的影响, 其重要性随着植物生活史阶段而发生变化。未来需要进行综合的、长期的实验, 并应着重加强种源限制及相关生态过程的进化与生态相结合的机理性研究, 从而更深刻地认识和理解种群更新问题, 建立更为综合、系统的种群更新理论体系。     

Pollen and Resource Limitation in Veratrum nigrum L. （Liliaceae）, an Andromonoecious Herb

Pollen limitation and resource limitation were invoked to account for the pattern that flowering plants produce more flowers and ovules than fruits and seeds. This study aimed to determine their relative importance in Veratrum nigrum, a self-compatible, perennial, andromonoecious herb. In order to determine whether female production was limited by pollen grains on stigmas or by available resources, we performed supplemental hand pollination in three populations, male-flower-bud removal in three other populations, and emasculation of hermaphroditic flowers in still another population, resulting in a total of seven populations experimentally manipulated. Across the three populations, supplemental hand pollination did not significantly increase fruit set, seed number per fruit, and total seed production per individual, nor did emasculation of hermaphroditic flowers. Taken together, our results suggest that pollen grains deposited on stigmas were abundant enough to fertilize all the ovules. Male-flower-bud removal significantly increased the mean size of hermaphroditic flowers in all three populations. Female reproductive success was increased in one population, but not in the other two populations possibly due to heavy flower/seed predation. We concluded that the female reproductive success of V. nigrum was not limited by pollen grains but by available resources, which is consistent with Bateman＇s principle. Furthermore, the female reproduction increase of male-flower-bud removal individuals might suggest a trade-off between male and female sexual functions.     

土壤水分对温室盆栽番茄叶片生理特性的影响及光合下降因子动态

以温室盆栽番茄(Lycopersicon esculentum Mill．)为试验材料,研究了土壤水分对叶水势(LWP)、细胞液浓度(CSC)、气孔导度(Gs)、气孔限制值(Ls)和叶片光合特性的影响,以及引起光合下降的因子动态。结果表明,随着土壤水分胁迫程度的增加,净光合速率(Pn)、蒸腾速率(Tr)、LWP明显下降．Gs具有相同的趋势,而CSC显著升高。土壤水分胁迫和高水分处理的Pn与Tr日变化呈双峰曲线,但在适宜土壤水分下为单峰曲线。随着土壤含水量的增加,光合下降的非气孔限制出现的时间具有滞后现象。本文对非气孔限制出现的临界点动态作了进一步的探讨。     

Using sex ratios to estimate what limits reproduction in parasitoids

The reproductive success of a foraging parasitoid may be limited by the number of eggs that she produces and/or the number of hosts that she can locate. Despite the significance for population dynamics and numerous areas of behavioural ecology, the relative importance of these factors remains an issue of contention. Attempts to resolve this controversy have been hindered because estimating the importance of factors limiting reproduction in the field can be extremely laborious and time consuming. We show how sex ratio data can be used as a relatively easy method to indirectly estimate the relative importance of the factors limiting reproduction. Sex ratio data from 48 samples of eight species suggest that: (a) the extent of host or egg limitation in a species varies between site collected and time of year; and (b) on average, species are at an intermediate position on the egg/host limitation continuum, with a bias towards host limitation.     

Migration of herbaceous woodland flora into post-agricultural black alder woods planted on wet and fertile habitats in south western Poland

Because post-agricultural black alder woods have not been the subject of studies on forest recovery, the aim of the research was to investigate the process of colonization of their herb layer by woodland flora. Migration rates of 51 forest plant species in the herb layer of alder woods planted on abandoned meadows, bordering meso- and eutrophic forests, were studied. Mean migration rates calculated for typical wet alderwoods reached 1.20–1.60 m yr⁻¹, for oak-hornbeam forests 1.17–1.63 m yr⁻¹, and for alder-ash carrs 0.79–1.26 m yr⁻¹, exceeding those reported in studies conducted in less fertile, drier sites. Although migration rates for many species exceeded 2 or 3 m, there was a group of slow colonizing species, mainly ancient woodland indicators. Species migration patterns fitted either the model based on the establishment of isolated individuals, or the model of a wave front. The age of the recent forests and the presence of Urtica dioica in their herb layer are the main factors explaining the species composition in post-agricultural black alder woods.     

The interplay of pollination,costs of reproduction and plant size in maternal fertility limitation in perennial <Emphasis Type="Italic">Paeonia officinalis</Emphasis>

Although several factors can limit female fertility in perennial plants, rarely have they been jointly studied in a single species over several years. In this study we experimentally manipulate seed production and simultaneously analyse the potential contribution of pollen limitation, costs of reproduction and plant size to variation in seed output over a 3-year period in the perennial herb Paeonia officinalis, in southern France. Since this rare species is threatened by forest closure in many sites we also examine the causes of female fertility variation in relation to habitat closure (open habitat vs. woodland). P. officinalis has a partial self-incompatibility system and only very low ability for autonomous self pollination in the absence of pollinators. However, supplementary pollination of individual plants in three consecutive years did not significantly increase seed production above natural levels. Forest closure was associated with a decline in ovule and seed production, which again was not due to pollen limitation since supplementary pollination had no significant effect on seed set in the woodland habitat. Comparison of the maternal fertility of plants which were previously excluded from reproduction with those which were hand pollinated to maximise seed set in two previous years produced no evidence that seed production in year three is limited by costs associated with prior reproduction. Likewise, flowering probability was not related to prior seed production but was however positively related to plant size. The absence of any influence of pollen limitation or prior reproduction on seed production suggests that sub-maximal seed production in long-lived perennial herbs may be part of a size-dependent strategy that maximises life-time seed production and fitness without compromising survival.     

子午岭马兰林区辽东栎幼苗定居限制的初步研究

在子午岭马兰林区选择油松林、辽东栎林、灌丛、草地等四种群落,通过播种实验及3 a的跟踪调查,研究四种不同生境下辽东栎幼苗在定居过程中的生长规律.结果显示:在四种生境中,人为增加辽东栎种子密度,均能明显提高出苗量,幼苗生长三年后大量死亡,死亡高峰出现在第三年.郁闭生境下(油松林和辽东栎林),辽东栎出苗率及存活率高于开阔生...     

Resource limitation,competition and the influence of life history in a freshwater snail community

Summary Previous work on a snail community occurring throughout lakes in southwestern Michigan showed that predation by molluscivorous sunfish had large impacts on only the rarest snail species. Thus, competition might play a major role in population limitation because dominant members of the snail community are relatively immune to predation. The present experiments were conducted to determine the extent to which the snail community depleted the abundance of food resources (epiphytes) and the extent to which epiphyte abundances limited snail production. An experimental gradient in snail densities showed that removal of snails increased epiphyte biomass by approximately 3-fold relative to that observed at natural snail densities. Enrichment of the environment with phosphorus fertilizer increased epiphyte biomass by approximately 20-fold and provided a test of food limitation in the snail community. All snail taxa exhibited positive numerical or growth responses to enrichment. The observations that snails depleted resources and that resources limited snail production demonstrated that snails competed exploitatively for epiphytes. The response of each snail species to increased food abundance differed depending on the timing of fertilization relative to the snails' life histories. Snails hatched before the experiment began were larger in fertilized treatments, due to increased growth, but their densities were similar among treatments. On the other hand, densities of snails born during the experiment were up to 15-fold greater in fertilized treatments, due in part to increased survival of newborn snails. Comparison of the responses of snails to food addition and to predator removals (based on prior experiments) suggested that food availability limits snail production more than predators do. Additionally, the large responses by algae and snails to fertilization demonstrated that both the producers and herbivores in this simplified food chain were strongly resource limited.     

Effect of pollen and resource limitation on reproduction of Zygophyllum xanthoxylum in fragmented habitats

Limitations on pollen and resources may significantly affect plant reproduction in fragmented habitats. In this study, phenology and pollinator frequency and activity were investigated to estimate the role of pollinators in Zygophyllum xanthoxylum reproduction, and this species is ecologically important in northwest China. In addition, the relative impact of restrictive amounts of pollen and resources on the seed set per flower was evaluated. It was found that adding pollen boosted the size of the seed set per flower, but had no significant effect on the number of flowers. By contrast, the addition of resources increased flower numbers as well as had a slight impact on the seed set per flower. These results indicate the amount of available pollen is a limiting factor for reproductive success. Moreover, Apis mellifera was identified as the most effective pollinator of Z. xanthoxylum, and there were more overall pollinators and visitations in the control than in the fragmented habitats. Furthermore, the limitations in pollen were more restrictive in the fragmented area than in the control. This was due to increased pollinator visitations in the control that could ameliorate the effects of lower pollen levels. When there is a limited availability of suitable pollinators, self‐pollination is critical in fragmented habitats. Z. xanthoxylum has reproductive strategies that aid in adapting to harsh environments, including protogyny and delayed selfing.     

氮添加诱导的磷限制改变了亚热带黄山松林土壤微生物群落结构

土壤微生物在陆地生态系统的生物地球化学循环中起着重要作用。然而目前尚不清楚氮(N)添加量及其持续时间如何影响土壤微生物群落结构,以及微生物群落结构变化与微生物相对养分限制状况是否存在关联。本研究在亚热带黄山松林开展了N添加试验以模拟N沉降,并设置3个处理:对照(CK, 0 kg N·hm^-2·a^-1)、低N(LN, 40 kg N·hm^-2·a^-1)和高N(HN, 80 kg N·hm^-2·a^-1)。在N添加满1年和3年时测定土壤基本理化性质、磷脂脂肪酸含量和碳(C)、N、磷(P)获取酶活性,并通过生态酶化学计量分析土壤微生物的相对养分限制状况。结果表明: 1年N添加对土壤微生物群落结构无显著影响,3年LN处理显著提高了革兰氏阳性菌(G⁺)、革兰氏阴性菌(G^-)、放线菌(ACT)和总磷脂脂肪酸(TPLFA)含量,而3年HN处理对微生物的影响不显著,表明细菌和ACT对N添加可能更为敏感。N添加加剧了微生物C和P限制,而P限制是土壤微生物群落结构变化的最佳解释因子。这表明,N添加诱导的P限制可能更有利于部分贫营养菌(如G⁺)和参与P循环的微生物(如ACT)的生长,从而改变亚热带黄山松林土壤微生物群落结构。