气生植物的生物学特性及研究展望

气生植物是指不需要土壤,生长所需的水分和营养可以全部来自空气的植物。它既不同于附生植物．也不同于具有气生根的植物。主要包括地衣、苔藓、蕨、凤梨科和兰科植物中的某些附生类群。它们没有根或者根不发达,仅起固定植株的作用。因为气生植物直接从空气中吸收水分和养分,但空气中的水分和养分毕竞是有限的,所以这些植物一般都具有很强的利用水分及养分的能力,很多植物已经成为有效地检测环境变化的“指示生物”和去除环境污染的修复植物。另外,因为这些植物具有忍受恶劣环境条件的生理基础,还可能成为适应空间环境的先锋植物,在空间植物学研究中将具有特殊的意义。     

云南哀牢山地区森林附生维管植物多样性及区系特征

附生植物作为山地森林生态系统中重要的结构性成分,在维持森林生态系统生物多样性格局、水分和养分循环等方面发挥着重要作用。本文通过野外调查、标本查阅并结合相关文献,对云南哀牢山地区附生维管植物物种组成及分布进行了系统研究。结果显示,哀牢山地区附生维管植物共有23科83属218种,其中附生蕨类和兰科植物最丰富。附生蕨类有34属93种,以附生-石生蕨类生活型占优势,其中水龙骨科17属62种,占附生蕨类的66.67%,瓦韦属(Lepisorus)和石韦属(Pyrrosia)分别有13种和10种。附生兰科植物有26属65种,其中石斛属(Dendrobium)和石豆兰属(Bulbophyllum)分别有12种和8种。该地区附生维管植物属的分布具有明显的热带性质并以热带亚洲分布居多。附生植物生长于生境因子变化剧烈、资源有限的林冠,对环境变化敏感,极易遭受破坏且破坏后难以恢复,不少附生植物具有很高的药用、观赏等价值。因此,应加强对附生维管植物这一特殊类群的保护。     

哀牢山常绿阔叶林常见兼性附生植物的化学计量特征

作为山地森林生态系统附生植物区系的重要组分,兼性附生植物是一类既能附生于树皮,又能根植于土壤的特殊植物类群,是同一物种在不同生长基质上的生态型。研究兼性附生植物在不同生境下的化学计量特征及其变化,有助于了解兼性附生植物对生境变化的响应与养分利用策略。以云南哀牢山亚热带山地湿性常绿阔叶林中常见的兼性附生植物长叶粗筒苣苔(Briggsia longifolia)为研究对象,通过对其地生、树干基部和1.3 m树高处不同生境的基质、植株叶片和根系中C、N、P含量及其化学计量比的测试与分析,探讨不同生境下兼性附生植物的化学计量特征及其养分利用策略。研究结果显示：长叶粗筒苣苔的生长基质以及各器官的化学计量特征在不同生境间存在差异。林地土壤C、N、P含量以及C∶N、C∶P和N∶P均低于树干附生基质,树干基部基质的C、N、P化学计量特征介于两者之间。与地生生境相比,在附生生境下长叶粗筒苣苔的N、P含量较高,而C∶N、C∶P和N∶P则较低,说明其养分利用效率较低。在3种生境下长叶粗筒苣苔叶片的N含量与N∶P均低于根系,而C∶N则高于根系。长叶粗筒苣苔叶片中N、P元素以及N∶P比的内稳性指数高于根系,叶片...     

附生植物对全球变化的响应及其生物指示作用

附生植物是一类生活在其他植物体上但不从宿主载体吸收营养和水分的特殊植物,其特有的形态结构和生态习性导致了它们对周围环境变化具有高度的敏感性和脆弱性.研究附生植物对全球变化的响应及其生物指示作用,具有重要的指导意义和应用价值.本文概述了附生植物对大气组成变化、气候变化和土地利用/覆盖方式转变等全球变化事件的响应及其生物指...     

西双版纳热带森林附生维管植物的物种多样性与区系特征

附生植物是山地森林生态系统中重要的结构性成分。因受林冠调查技术限制, 人们对林冠附生植物知之甚少。本文在前人有关西双版纳植物区系研究的基础上, 结合野外调查和标本资料, 对该地区附生植物的物种组成与分布进行了整理。结果表明, 西双版纳热带森林附生维管植物共有29科134属486种, 约占全部维管植物的11%。附生兰科是最丰富的类群(69属293种), 其中以石斛属(Dendrobium) (49种)和石豆兰属(Bulbophyllum) (48种)物种数最多。蕨类是仅次于兰科的附生类群(13科38属97种), 其中水龙骨科(51种)占附生蕨类总数的50%以上。基于生活史和养分来源的划分标准, 该地区48%的附生物种属于兼性附生, 其次是以兰科为主的专性附生(46%), 半附生仅占6%。从区系上看, 西双版纳附生植物属的分布具有明显的热带亚洲性质。附生植物主要分布于资源受限的林冠生境, 对环境变化极为敏感, 在人为干扰日益加剧的背景下, 这类植物正面临严重威胁。因此, 需要加强对西双版纳林冠亚系统的保护。     

亚热带森林附生植物叶片气孔特征及其可塑性对光照变化的响应

附生植物是热带亚热带森林生态系统中物种多样性极高且极其脆弱敏感的生物类群之一。光照被认为是促进附生植物由陆生类群演化而来并决定其生长和分布的关键因素。然而,由于接近林冠和规范性采样的限制,附生植物与光照的关系仍亟待阐述。为揭示附生植物对光强变化的响应和适应策略,该研究以亚热带常绿阔叶林6种附生植物(林冠层木本:鼠李叶花楸、毛棉杜鹃;林冠层草本:狭瓣贝母兰、毛唇独蒜兰;树干区草本:点花黄精、距药姜)为对象,对其在4个光处理梯度下生长的叶片气孔特征及其可塑性进行了对比分析。结果表明:(1) 2种附生小乔木的气孔面积(SA)、气孔密度(SD)、潜在气孔导度指数(PCI)和表皮细胞密度(ECD)均对光强改变显著响应。2种附生兰科植物的SA最大,而SD最小;附生乔木叶片SD和ECD的光响应趋势与陆生植物更相似,而附生草本则出现种间差异。(2) 6种附生植物的气孔、表皮细胞特性及其表型可塑性,在草本-木本、常绿-落叶植物、林冠-树干区之间,均无明显差别。(3)附生植物气孔特性和表皮细胞平均可塑性指数均低于陆生植物。综上结果表明,亚热带常绿阔叶林中附生植物对于光环境变化的适应性相对较弱。不同的附生植物可以通过不同程度地增加叶片SD和ECD来适应高光强生境,并通过对SD和SA的双重调节以增大潜在光合能力从而应对低光胁迫。     

林冠附生植物生态学研究进展

林冠附生植物及其枯死存留物是构成山地湿性森林生态系统中生物区系、结构和功能的重要组分。由于在林冠攀爬技术上的限制,过去对林冠附生植物在生态系统结构和功能过程中的作用未能引起足够的重视。近20年来,随着对林冠生物多样性及其在生态系统功能过程影响的认识和研究技术上的提高,对林冠附生生物的研究已逐步从个体水平转移到系统水平上。有关林冠附生植物多样性、生物量及其生态学效应已成为近年来国际上新兴研究领域——“林冠学”的研究热点之一。许多研究表明,林冠附生植物在生态系统水平上的交互作用比它们的解剖、形态和生理特征更为重要。国外大量的研究结果表明,林冠是一个适合于许多生物种类生存的场所,其数量比想象的更为丰富。在全球范围内估计有29 500余种附生植物,其中维管束附生植物的种类高达24 000种,约占总维管束植物种类的10%。林冠附生物的生物量在世界各地森林中存在较大的差异,其范围在105~44 000 kg·hm^-2之间,其中在一些热带和温带天然老龄林中林冠附生物的生物量超过了宿主林木的叶生物量。林冠附生植物还具有较大的叶面积指数(LAI)。林冠附生物丰富的物种组成、较高的生物量、独特的生理形态特征以及它们分布于森林与大气相互作用的关键界面,使得它们在生态系统物种多样性形成及其维持机制、养分和水分循环、指示环境质量等方面具有重要的作用。林冠附生植物及其枯死残留物具有较强的能力吸收雨水和空气中的营养物质,在林冠层中形成一个潮湿的环境促进氮固定,林冠附生植物群落还能为生存于林冠的其它生物(如鸟类、哺乳动物、两栖动物、爬行动物和昆虫等)提供食物和栖息场所。林冠附生植物的生长发育与分布格局除与宿主有关外,还受到环境因素(气候、地形、微生境条件等)和人为干扰的影响。由于世界各地森林类型多样和环境条件各异,目前国际上有关附生物的研究仍十分活跃,建立了林冠研究网络,研究不同类型森林中附生植物及其枯死残留物的动态及其与群落特征、环境因子的数量关系,探讨、交流和发展有效的标准测量方法和技术是该领域研究的主要内容。国内对林冠附生植物生态学的研究刚刚起步,有待于今后加强该领域的研究。     

高山森林林窗位置和附生植物去除对倒木总酚和缩合单宁含量的影响

倒木分解是森林生态系统中重要的养分循环过程,倒木中的难分解物质对土壤有机质积累具有积极作用。但关于森林林窗和附生植物对倒木难分解物质含量的影响还不清晰。为了理解林窗更新及附生植物生长对倒木总酚和缩合单宁含量的影响,2013年8月在川西高山原始森林进行样地布置,在进行3年附生植物去除处理后,2016年8月在不同林窗位置（林窗、林缘和林下）下两种处理（附生植物去除和保留）不同腐解等级（I-V）进行岷江冷杉（Abies faxoniana）倒木不同结构（心材、边材和树皮）样品采集,分析其总酚和缩合单宁含量。结果表明：树皮总酚和缩合单宁含量显著高于心材和边材,树皮总酚和缩合单宁含量随腐解等级变化差异不显著;森林林窗对Ⅲ-V腐解等级心材和边材总酚含量具有显著影响,但对心材和边材缩合单宁影响差异不显著,林窗对倒木树皮总酚和缩合单宁含量影响差异极显著且两者含量特征均表现为林窗 > 林缘 > 林下;附生植物去除处理降低了心材缩合单宁和边材总酚含量,增加了倒木边材缩合单宁含量。附生植物去除处理对树皮影响和林窗位置存在交互作用,林缘和林下的倒木附生植物去除显著降低了树皮总酚和缩合单宁含量。此外,不同林窗位置的温度差异是导致树皮总酚和缩合单宁含量变化的主要原因,附生植物去除对倒木pH的影响也可能是影响倒木总酚和缩合单宁含量的原因之一。由此可见,高山森林林窗更新及附生植物生长会显著影响倒木难分解物质含量变化特征,为进一步了解倒木分解过程在养分循环及对环境的响应提供了新的角度。     

林冠附生植物观测方法概述

林冠的物种多样性极为丰富,在整个森林生态系统中具有非常重要的作用。但由于乔木树体高大,冠层难以接近,在很大程度上限制了林冠植物多样性的研究。在过去30年中,各种技术不断应用于林冠附生植物的采样,林冠取样方法的研究成为林冠附生植物的多样性、生物量及其生态学效应等方面研究的重要基础。文中以附生植物多样性、生物量和附生植物群落的生态功能等为基础,结合作者已开展的工作,综述了林冠附生植物的观测调查及取样方法,并且分析了不同方法的特点及在林冠研究中的应用,对进一步深入研究附生植物提出了一些建议。     

西双版纳地区附生与非附生植物叶片角质层对水分的透性研究

为了探讨雾水对西双版纳地区不同类型植物的生态学效应,干季于20℃及30℃下用自制的设备测定了西双版纳地区4种附生和4种非附生植物叶片上表皮水分进出角质层的透性,比较研究了不同类型植物叶片通过角质层蒸腾失水速率(P_T)、叶片通过角质层吸水速率(P_A)以及吸水与失水速率的比值(R=P_A/P_T)高低,及其与生活方式的关系。结果表明,附生植物的R值都高于非附生植物且大于1,说明附生植物通过叶片吸收的水分大于蒸腾失水,雾水对于附生植物具有更重要的生态学意义;P_T和P_A在不同植物间有显著差异,这可能与不同植物的角质层化学成分和物理结构不同有关,对其适应各自生活方式及多雾环境有重要意义。除附生植物贝母兰(Coelogyne occultata)和掌唇兰(Staurochilus dawsonianus)以及非附生植物大叶藤黄(Garcinia xanthochymus)外,30℃下其余植物的P_T和P_A都显著高于20℃的,说明温...     

西双版纳地区附生与非附生植物叶片对雾水的吸收

采用蒸馏水喷雾(模拟雾)法,测定了西双版纳地区干季中10种附生植物和非附生植物叶片水势(Φ)、相对含水量(RWC)和吸水量的变化,探讨了不同类型植物叶片的吸收雾水的能力.结果表明,随喷雾时间的延长,植物叶片Φ、RWC和吸水量均升高,说明附生植物和非附生植物叶片都能吸收雾水,但附生植物叶片吸水后Φ升高明显快于非附生植物.附生植物附着实蕨和爬树龙叶片吸水快、RWC变化大,表明其叶片吸收雾水的能力强;贝母兰和掌唇兰叶片吸水能力低于非附生植物中的穿鞘花和野靛稞,但高于其它4种非附生植物.傍晚雾生之前附生植物叶片Φ显著低于清晨,表明夜间附生植物叶片吸收了雾水;而非附生植物傍晚叶片Φ与清晨水势差异不显著,夜间几乎不吸收雾水.除贝母兰外,附生植物叶生物量分数高于非附生植物,利于其吸收雾水.由于西双版纳地区干季多雾,该区植物叶片最低水势均在-0.8 MPa以上,水分胁迫不严重.     

Rainforest air-conditioning: the moderating influence of epiphytes on the microclimate in tropical tree crowns

Epiphytes are often assumed to influence the microclimatic conditions of the tree crowns that they inhabit. In order to quantify this notion, we measured the parameters "temperature" (of the substrate surface and the boundary layer of air above it), "evaporative drying rate" and "evapotranspiration" at various locations within tree crowns with differing epiphyte assemblages. The host tree species was Annona glabra, which was either populated by one of three epiphyte species (Dimerandra emarginata, Tillandsia fasciculata, or Vriesea sanguinolenta) or was epiphyte-free. We found that during the hottest and driest time of day, microsites in the immediate proximity of epiphytes had significantly lower temperatures than epiphyte-bare locations within the same tree crown, even though the latter were also shaded by host tree foliage or branches. Moreover, water loss through evaporative drying at microsites adjacent to epiphytes was almost 20% lower than at exposed microsites. We also found that, over the course of several weeks, the evapotranspiration in tree crowns bearing epiphytes was significantly lower than in trees without epiphytes. Although the influence of epiphytes on temperature extremes and evaporation rates is relatively subtle, their mitigating effect could be of importance for small animals like arthropods inhabiting an environment as harsh and extreme as the tropical forest canopy.     

Causes and consequences of high osmotic potentials in epiphytic higher plants

Past reports of the water relations of epiphytes, particularly bromeliads, indicate that tissue osmotic potentials in these tropical and subtropical plants are very high (close to zero) and are similar to values for aquatic plants. This is puzzling because several ecophysiological studies have revealed a high degree of drought stress tolerance in some of these epiphytes. The goal of this study was two-fold: (1) to increase the number of epiphytic taxa sampled for tissue osmotic potentials; and (2) to explain the apparent discrepancy in the significance of the tissue water relations and tolerance of drought stress in epiphytes. Tissue osmotic potentials of 30 species of epiphytic ferns, lycophytes, and orchids were measured in a subtropical rain forest in northeastern Taiwan. Nearly all values were less negative than -1.0 MPa, in line with all previous data for epiphytes. It is argued that such high osmotic potentials, indicative of low solute concentrations, are the result of environmental constraints of the epiphytic habitat on productivity of these plants, and that low rates of photosynthesis and transpiration delay the onset of turgor loss in the tissues of epiphytes such that they appear to be very drought-stress tolerant. Maintenance of photosynthetic activity long into drought periods is ascribed to low rates of transpiration and, hence, delayed tissue desiccation, and hydration of the photosynthetic tissue at the expense of water from the water-storage parenchyma.     

Phytoplankton and Epiphyte Development and Their Shading Effect on Submerged Macrophytes in Lakes of Different Nutrient Status

The annual mean light intensity at the depth limit of the Littorella vegetation was 24–33% of the subsurface light intensity, despite large variations in each attenuation component (lake water, phytoplankton, and epiphytes). In oligotrophic, silicate-poor lakes, the light attenuation above the submerged vegetation was dominated by the water itself, which accounted for 65–72% of the total attenuation. Phytoplankton and epiphytes were equal in importance to each other. In oligotrophic, silicate-rich lakes and lakes receiving a nitrogen supply above background level, the epiphytes were more abundant, accounting for about 50% of the light attenuation. In one lake with a high nutrient supply, the epiphytes were responsible for 86% of the light attenuation. A new method of measuring the effect of shading by the epiphytic community on submerged macrophytes is presented. The light attenuation caused by the phytoplankton and the epiphytes was investigated and related to the depth distribution of the submerged angiosperm, Littorella uniflora. It is shown that the biomass of the epiphytes increased more than the biomass of the phytoplankton in response to an external or internal nutrient loading. Shading by epiphytes is of decisive importance for the depth distribution of Littorella at increasing nutrient supply.     

云南石林喀斯特地区半湿润常绿阔叶林附生植物的初步研究

对云南石林喀斯特山地原生植被——半湿润常绿阔叶林中附生植物的组成、生物量以及附生植物持水量等进行研究,结果表明该区森林林木附生植物种类相对较少,只有8科9种附生维管束植物和5种苔藓植物,而林内岩石表面则有石附生维管束植物16科17种,苔藓植物3种,两种不同生境附生植物的相似性系数为0.5。相同取样面积(400cm2)条件下,岩石表面附生植物平均生物量(11.7g)比林木表面(4.9g)的高。附生植物一次持水量为自身干重的5.5~9.7倍。     

Regeneration of drought-stressed gametophytes of the epiphytic fern, Pyrrosia pilosellodes (L.) Price

The epiphytic habitat represents a highly dynamic environment, and water deficit is one of the common factors that affects growth and development of epiphytes. Gametophytes of the epiphytic fern, Pyrrosia piloselloides (L.) Price, were able to tolerate up to 50 days of drought. Upon rehydration, cells that recovered from water stress were capable of forming new gametophytes. The ability of gametophytes to recover from desiccation plays an important role in the survival and growth of the fern species under natural conditions. Received: 20 May 1998 / Revision received: 5 August 1998 / Accepted: 21 August 1998     

Association between rainfall seasonality and the flowering of epiphytic plants in a Neotropical montane forest

The association between the reproductive phenology of epiphytic communities with environmental and ecological factors remains largely unexplored. Because epiphytes depend on environmental moisture, seasonal changes in moisture conditions likely act as the primary determinants of their reproductive timing. We examined whether water limitation or pollinator competition structures the flowering phenologies of an epiphytic community in a seasonal mountain forest in Costa Rica. Additionally, we addressed the environmental factors that might trigger floral induction. Using a 24‐month dataset of bimonthly flowering records from 104 species, we found high seasonality of flowering at the species level but somewhat lower seasonality at the community level. The flowering mid‐dates of most epiphytes, particularly from monocotyledonous species, occurred during the wettest months, as predicted if water limitation structures flowering. The increased moisture and nutrient availability during the rainy season give epiphytes the resources needed to complete floral development and anthesis, and later fruit and seed maturation. The observed flowering pattern of epiphytes coincides with reproductive patterns of terrestrial herbs and shrubs from seasonal tropical ecosystems, and suggests shared constraints to sexual reproduction in both ecological guilds under similar climatic conditions. In contrast, flowering patterns of congeneric epiphytes in the same pollination guild mostly did not follow the expectations of a pollinator competition scenario. Finally, we discuss the possible combined effect of precipitation, temperature, and daily insolation on floral induction of epiphytic plants.     

Water relations of epiphytic and terrestrially-rooted strangler figs in a Venezuelan palm savanna

Water use patterns of two species of strangler fig, Ficus pertusa and F. trigonata, growing in a Venezuelan palm savanna were contrasted in terms of growth phase (epiphyte and tree) and season (dry and wet). The study was motivated by the question of how C3 hemiepiphytes accommodate the marked change in rooting environment associated with a life history of epiphytic establishment followed by substantial root development in the soil. During the dry season, stomatal opening in epiphytic plants occurred only during the early morning, maximum stomatal conductances were 5 to 10-fold lower, and midday leaf water potentials were 0.5–0.8 MPa higher (less negative) than in conspecific trees. Watering epiphytes of F. pertusa during the dry season led to stomatal conductances comparable to those exhibited by conspecific trees, but midday leaf water potentials were unchanged. During the rainy season, epiphytes had lower stomatal conductances than conspecific trees, but leaf water potentials were similar between the two growth phases. There were no differences in ¹³C between the two growth phases for leaves produced in either season. Substrate water availability differed between growth phases; tree roots extended down to the permanent water table, while roots of epiphytic plants were restricted to material accumulated behind the persistent leaf bases of their host palm tree, Copernicia tectorum. Epiphytic substrate moisture contents were variable during both seasons, indicating both the availability of some moisture during the dry season and the possibility of intermittent depletion during the rainy season. Epiphytic strangler figs appear to rely on a combination of strong stomatal control, maintenance of high leaf water potentials, and perhaps some degree of stem water storage to cope with the fluctuating water regime of the epiphytic environment.     

Factors affecting the initiation and growth of aboveground adventitious roots in a tropical cloud forest tree: an experimental approach

Some of the proximate factors that would induce aboveground stems to produce adventitious roots were investigated experimentally on Senecio cooperi, a tropical cloud forest tree. Stem segments were air-layered with different treatments to promote root formation, and the number of roots initiated and rates of root growth were monitored for 20 weeks. Treatments were the application of wet epiphytes or dry epiphytes plus associated humus, sponges wetted with either water or nutrient solutions, or dry sponges. Controls (stem segments with nothing applied) were also monitored. Numbers of adventitious roots formed and rates of subsequent root growth differed among treatments. Wet epiphyte/humus and nutrient solutions were most effective in producing roots, which suggests that epiphytes and the nutrients they intercept and retain within the canopy may cue adjacent host tissue to exploit this resource.