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1.
Sofía Solórzano Guillermo Ibarra-Manríquez Ken Oyama 《Biodiversity and Conservation》2002,11(2):197-212
We describe liana diversity and variation in morphology of flowers and diaspores in two tropical forests in Mexico: a seasonally deciduous forest at Chamela, Jalisco and a lowland rain forest at Chajul, Chiapas. Flowers were classified as inconspicuous (1 cm in length and white or pale green flowers) or conspicuous (> 1 cm and brightly colored flowers). Dispersal syndrome was classified as anemochory, barochory, and zoochory. We recorded a higher number of lianas species in Chajul (128 spp.) than in Chamela (71 spp.). In both sites, families with the highest number of species were Bignoniaceae, Leguminosae, Sapindaceae, and Malphigiaceae, and almost half of the liana species had inconspicuous flowers. Most of the species had an abiotic syndrome of dispersal with 40 (56.3%) and 71 (55.5%) wind-dispersed species in Chamela and Chajul, respectively. Zoochory was significantly associated with inconspicuous flowers and anemochory with conspicuous flowers. Our results suggest that (1) flower morphology and dispersal type are not related with the amount of rainfall and (2) lianas are more prone to be wind-dispersed. 相似文献
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Patrick Addo‐Fordjour Zakaria B. Rahmad Joycelyn Amui Chareles Pinto Mavis Dwomoh 《African Journal of Ecology》2013,51(2):217-227
Most studies have concluded that liana diversity and structure increase with disturbance. However, a contradictory pattern has emerged recently calling for more research in the area. Liana diversity and structure were investigated in three forest types that differ in disturbance intensity (nondisturbed, moderately disturbed and heavily disturbed forest: NDF, MDF and HDF, respectively) in the Atewa Range Forest Reserve, Ghana. In each forest type, 10 square plots of 0.25 ha were demarcated. Lianas with diameter ≥1 cm located on trees with diameter ≥10 cm were enumerated. A total of 429 individuals representing 40 species, 29 genera and seventeen families were identified in the study. Shannon diversity and species richness of lianas were significantly lower in the HDF (P < 0.05). Liana density and basal area differed significantly across all forest types (P < 0.0001). The importance value index (IVI) of most liana species varied greatly across the forest types. The current study has provided evidence to support the pattern of decreasing liana diversity and structure with disturbance in some tropical forests. Further studies are recommended to gain more understanding of the factors that are responsible for the divergent liana responses to disturbance in tropical forests. 相似文献
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Chris M. Smith-Martin Robert Muscarella William M. Hammond Steven Jansen Timothy J. Brodribb Brendan Choat Daniel M. Johnson German Vargas-G María Uriarte 《Ecology letters》2023,26(11):1829-1839
Tropical rainforest woody plants have been thought to have uniformly low resistance to hydraulic failure and to function near the edge of their hydraulic safety margin (HSM), making these ecosystems vulnerable to drought; however, this may not be the case. Using data collected at 30 tropical forest sites for three key traits associated with drought tolerance, we show that site-level hydraulic diversity of leaf turgor loss point, resistance to embolism (P50), and HSMs is high across tropical forests and largely independent of water availability. Species with high HSMs (>1 MPa) and low P50 values (< −2 MPa) are common across the wet and dry tropics. This high site-level hydraulic diversity, largely decoupled from water stress, could influence which species are favoured and become dominant under a drying climate. High hydraulic diversity could also make these ecosystems more resilient to variable rainfall regimes. 相似文献
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Fog is an important supplemental source of water in regions with heavy fog and little rainfall. In the present study, we used the stable isotope content of xylem water to investigate the dry season water source partition between soil and fog water of two evergreen tree species (Cleistanthus sumatranus and Lasiococca comberi), two deciduous tree species (Mayodendron igneum and Lagerstroemia tomentosa), two liana species (Acacia pennata and Combretum latifolium) and understory seedlings of three tree species (C. sumatranus, L. comberi and Celtis philippensis) in a tropical karst forest in southern Yunnan, China. The soil gravimetric water content (GWC) and volumetric water content (VWC), pre‐dawn leaf water potential (Ψpre‐dawn) and leaf water absorbance were also measured. There were no significant differences in both GWC and VWC among 10 to 100 cm depths in the dry season. In the dry season 2009, Ψpre‐dawn of the two evergreen tree species and the understory seedlings down to −4.5 to −6.3 MPa, and which were significantly lower than those of a normal dry season. The proportion that fog contributed to xylem water ranged from 15.8% (understory seedling of C. sumatranus) to 41.3% (liana species C. latifolium). After immersing in water for 3 h, leaves of all the studied species absorbed a significant volume of water. Our results reveal that the woody plants in the tropical karst forest of Xishuangbanna use fog water as an important supplement in the dry season, with more fog water being used by lianas than by trees. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Floristic, structural and seed bank diversity of a dry Afromontane forest at Mafai, central Tanzania
Herbert V. Lyaruu Shadrack Eliapenda Ingvar Backéus 《Biodiversity and Conservation》2000,9(2):241-263
Flora, vegetation and seed bank were studied in a dry Afromontane forest in the Kondoa Irangi Hills, Tanzania with the objective to obtain information necessary for the promotion of conservation of this forest, which is rapidly degenerating due to human pressure. A preliminary checklist of 104 vascular plants occurring in the forest is provided. Based on 27 plots, each of 400m2, the forest had the following ecological features: mean tree density 408 stems·ha–1; basal area 66.56m2·ha–1; Shannon and Wiener diversity 2.6406; evenness 0.7585 and species richness 31 tree species per 1.08ha. The seed bank was dominated by woody species, including mature forest tree species, and had several species in common with the standing vegetation. The forest contains species that are phytogeographically linked to Madagascan, Western and Southern African floras and also species disjunctly distributed in this forest and the Eastern Arc Mountains of Tanzania. Correspondence Analysis of tree species based on size classes showed that the timber species had declining populations, indicating the possibility of genetic erosion, while other species showed expanding or interrupted populations. Some DBH-size classes (e.g. 145.0–189.9cm) have disappeared from the forest, presumably due to their selective removal. We recommend detailed integrated floristic and faunistic studies of the forest, targeting the ecologically sensitive indicators of habitat change such as orchids, birds, reptiles and amphibians. Finally, a proposal to conserve the forest under a community-based forest conservation scheme is put forward. 相似文献
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Abstract: On the southeastern Ivory Coast, two coconut plantations were compared with regard to the frequency of the epiphytic fern Platycerium stemaria on coconut trees as influenced by plant collecting for commercial purposes. At each of the two sites, 250 coconut trees were investigated for the presence of P. stemaria and signs of collecting activity. General species richness of vascular epiphytes at the study sites was low, with only three other epiphytic ferns ( Asplenium sp., Microgramma owariensis, Phymatodes scolopendria ) being present. At study site no. 1, which was located directly behind several flower stalls offering P. stemaria for sale, the number of coconuts bearing living P. stemaria was significantly lower than at site no. 2 with no flower stalls in the immediate surroundings. At site no. 1, the frequency of P. stemaria was lowest in the neighbourhood of the flower stalls and increased with distance. Within a distance of less than 50 m from the flower stalls, ca. 70 % of the coconuts showed signs of P. stemaria collecting activity. Compared with site no. 1, the number of palm trees with living P. stemaria at site no. 2 was considerably higher ( ca. 20 %) and only three coconut trees showed signs of Platycerium collection. Over much of the Ivorian rain forest region where the forest has been cut or converted into agricultural land, plantation trees are important phorophytes (in particular cocoa trees). In many West African regions plantation trees form the last remaining sites for vascular epiphytes, which often occur with considerable abundance. In the Ivory Coast, the collecting of P. stemaria in coconut plantations causes locally a drastic decline in the population size. However, much more threatening to the long-term maintenance of epiphyte communities in plantations is their conversion into non-tree plantations (e.g., pineapples, bananas) or their replacement by urban structures and tourist facilities. 相似文献
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Tropical dry forests occupy more area and are more endangered than rainforests, yet their regeneration ecology has received less study and is consequently poorly understood. We recorded the flowering and fruiting phenology of a tropical dry forest in Jamaica over a period of 26 mo within ten 15 × 15‐m plots. Community‐wide recruitment reached a maximum in the wet season, whereas no recruitment occurred during the dry season. We observed a unimodal peak in rainfall and fruit production, and the periodicity and intensity of seed production were significantly correlated with rainfall seasonality (the optimal time for germination). Flowering at the community and system levels lagged behind a significant increase and subsequent decrease in rainfall by 7 and 3 mo, respectively, indicating that the dominant factor controlling flowering periodicity is the passage of the major (4‐mo long) rainy season and changes in soil moisture conditions. Fruiting lagged behind flowering by 2 mo and a significant increase in fruiting occurred 2 mo prior to a significant increase in rainfall. At the population level, a correspondence analysis identified a major dichotomy in the patterns of flowering and fruiting between species and indicated two broad species groups based on their time of peak fruiting and the number of times they were in fruit. These were either individuals which were usually in peak fruit 1–2 mo prior to the start of the major rainy season or those that were in fruit more or less continuously throughout the year with no peak fruiting time. This study supports the view that seasonal variation in rainfall and hence soil water availability constitutes both the proximate and the ultimate cause of flowering periodicity in tropical dry forests. 相似文献
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Evan M. Gora Phillip M. Bitzer Jeffrey C. Burchfield Stefan A. Schnitzer Stephen P. Yanoviak 《Ecology and evolution》2017,7(20):8523-8534
The effects of lightning on trees range from catastrophic death to the absence of observable damage. Such differences may be predictable among tree species, and more generally among plant life history strategies and growth forms. We used field‐collected electrical resistivity data in temperate and tropical forests to model how the distribution of power from a lightning discharge varies with tree size and identity, and with the presence of lianas. Estimated heating density (heat generated per volume of tree tissue) and maximum power (maximum rate of heating) from a standardized lightning discharge differed 300% among tree species. Tree size and morphology also were important; the heating density of a hypothetical 10 m tall Alseis blackiana was 49 times greater than for a 30 m tall conspecific, and 127 times greater than for a 30 m tall Dipteryx panamensis. Lianas may protect trees from lightning by conducting electric current; estimated heating and maximum power were reduced by 60% (±7.1%) for trees with one liana and by 87% (±4.0%) for trees with three lianas. This study provides the first quantitative mechanism describing how differences among trees can influence lightning–tree interactions, and how lianas can serve as natural lightning rods for trees. 相似文献
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Drought stress in tropical dry forests is thought to result in greater asexual regeneration via vegetative sprouting ( e.g ., basal, root, and branch layering) than occurs in moister tropical forests. We tested this hypothesis by examining the prevalence of tree sprouting and seeding in tropical forests located along a rainfall gradient on the island of Hawai'i. Additionally, we examined the potential for novel disturbance, feral pig Sus scrofa rooting and trampling, to alter patterns in tree regeneration mode. We found greater sprouting (in terms of relative density and basal area) in dry forests than in mesic and wet forests, supporting the hypothesis. We also found that feral pig disturbance is negatively correlated with the relative density and basal area of seedlings in wet forests, but is positively correlated with the relative importance of sprouting, and the richness and diversity of sprouting species. Our results suggest rainfall regimes may be an important factor controlling broad-scale patterns in tree regeneration mode, and that exotic ungulates can significantly modify such patterns with potential consequences for the structure and dynamics of tree populations and communities. 相似文献
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Susanne Jahns 《Vegetation History and Archaeobotany》1996,5(3):207-213
Palynological investigation of the marine core, GeoB 1008-3, from near the mouth of the Congo river (6°35.6S/10°19.1E), provides information about the changes in vegetation and climate in West Equatorial Africa during the last 190 ka. The pollen diagram is divided into zones 1–6 which are considered to correspond in time with the marine isotope stages 1–6. Oscillations in temperature and moisture are indicated during the cold stage 6. During stage 5, two cooler periods (5d and 5b) can be shown with an expansion of Podocarpus forests to lower elevations on the expense of lowland rain forest. Extended mangrove swamps existed along the coast in times of high sea level (stages 5 and 1). 相似文献
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蛟河阔叶红松林林冠干扰及林隙更新研究 总被引：8，自引：0，他引：8
研究了吉林蛟河实验林场阔叶红松林的林冠干扰状况及林隙更新的基本规律。结果表明,扩展林隙（ＥＧ）和冠空隙（ＣＧ）在阔叶红松林中所占的面积比例分别是１８．０９％和１２．５１％,林冠干扰的返回间隔期为７００ａ左右;ＣＧ的大小平均为ＥＧ的６９％,ＥＧ的面积变化在１７—２８４ｍ２之间,平均为７５．４９ｍ２,而ＣＧ的面积变化在１０—２３４ｍ２之间,平均为５１．９８ｍ２,大多数林隙的平均直径仅为主林层树高的２０—６０％;大多数的林隙是由单株形成木形成的,形成林隙最重的方式是干基折断和掘根风倒;林隙形成木主要是由红松、沙松、枫桦和鱼鳞松四个树种组成,林隙形成木的胸径大都在４０—８０ｃｍ之间,树高在２５—３０ｍ之间;林隙的空间分布格局是均匀型的。不同树种在林隙内外的数量特征不同,随着林隙与非林隙的交替变化,不同树种的优势地位亦发生相应的变化,根据不同树种在林隙内外重要值位序差值的大小,可将蛟河阔叶红松林内树种对林隙的更新反应划分为三种类型。林隙及非林隙林分的物种多样性特征不同 相似文献
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Pavla Hejcmanová Michal Hejcman Abdoul Aziz Camara Markéta Antonínová 《African Journal of Ecology》2010,48(2):408-417
Sahelian savannah faces increasing pressure from human activities, leading to its degradation. The aim of this study was to investigate the possibility of restoration of dryland savannah vegetation by the elimination of disturbance factors on the ecosystem. Is degraded dryland savannah vegetation able to be restored by means of natural succession? What is the timescale for its recovery? The study took place in the Bandia Reserve, 65 km south‐east of Dakar (Senegal), a unique site with two successional stages due to the elimination of uncontrolled exploitation. The vegetation structure of 15 years (15YRS) and 5 years (5YRS) after fencing was compared with vegetation exposed to continuous livestock grazing and wood collection outside the fenced area. Calculated by redundancy analysis, a significant effect of selected areas on the cover of all species was revealed and successional stage explained more than 45% of data variability. Perennial forbs, annual forbs and perennial grasses achieved the highest cover in 5YRS, woody species in 15YRS and annual grasses in the area outside of the fenced reserve. The dominant woody species Acacia seyal, A. ataxacantha, A. nilotica subsp. adstringens and Balanites aegyptiaca reconstituted the dense formation of Acacia bushland by means of natural succession in the 15YRS area. 相似文献
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通过对海南霸王岭热带山地原始林与伐后林中树木及其攀附木质藤本的调查,研究原始林与伐后林中木质藤本对支持木的选择性。结果表明:1)6科优势树木中附藤率最高的是野牡丹科(Melastomataceae),附藤率最低的科,原始林中是山矾科(Symplocaceae),伐后林中是茜草科(Rubiaceae)。2)原始林中,谷木(Memecylon ligustrifolium)与线枝蒲桃(Syzygiumaraiocladum)的附藤比率和每木藤本数均高于样地平均水平;三角瓣花(Prismatomeris tetrandra)和龟背灰木(Symplocosandenophylla)的附藤比率均低于样地平均水平,而每木藤本数与样地平均水平之间没有显著差异。伐后林中,谷木的附藤比率和每木藤本数高于样地平均水平;九节(Psychotria rubra)的附藤比率和每木藤本数低于样地平均水平。3)杜仲藤(Parabariummicranthum)的主要支持木是谷木,夜花藤(Hypserpa nitida)的主要支持木是线枝蒲桃。研究表明,木质藤本对支持木在科和种水平上都具有选择性,因此木质藤本会对树木造成不对称影响,进而影响森林的结构和动态。 相似文献
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选择海南岛霸王岭天然恢复60 a的次生林样地中形成年限为17和13年的边缘,分别设置4条10 m100 m的样带,研究边缘效应下dbh ≥1 cm树木的攀藤率、被藤本攀附的频度和每木藤本数随距边缘距离的变化。结果表明：在0.8 hm2的样带中,树木的攀藤率分别为44.58%（17年边缘）和32.63%（13年边缘）。2种边缘中,dbh 1—5 cm、5—10 cm树木的攀藤率都随距离发生了变化,17年边缘中dbh ＞20 cm和13年边缘中dbh 10—20 cm树木的攀藤率都没有随距离的变化而变化。树木被藤本攀附的频度随距边缘距离的增加而降低,攀附3株以上藤本的树木最少,在17年边缘中变化趋势较明显;攀附1株藤本的树木最多,在13年边缘中变化明显。17年边缘中每木藤本数随距离增加而降低。在边缘形成初期,边缘形成年限对每木藤本数产生了影响,其在17年边缘中下降程度较大,但总体高于13年边缘中。 相似文献
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K. L. ALVIN T. ANANDA RAO 《Botanical journal of the Linnean Society. Linnean Society of London》1987,95(1):55-60
The leal sclereid pattern is described and interpreted as consisting of two types: fibre–like idiolibrosclereidsi in loose bundles above the veins bill often with branches protruding into the intercostal areas and highly branched idioblaslic sclereids lying in the mesophyll but with branches associated with die veins. The significance of this pattern is discussed in relation to taxonomy and to oilier leal sclereid patterns in angiosperms. 相似文献
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Shin-Ichi Yamamoto 《Ecological Research》1993,8(3):277-285
Gap characteristics and gap regeneration were studied in three mature stands belonging to different community types in a subalpine coniferous forest on Mt Ontake, central Honshu, Japan. Gap disturbance regimes were remarkably similar among stands studied; percentage gap area to surveyed area, gap density and mean gap size were 7.3–8.5%, 17.8–20.0 ha−1 and 40.8–42.5 m2, respectively. The gap size class distributions were also similar and showed a strong positive skewness with a few large and many small gaps; gaps <40m2 were most frequent and gaps >200m2 were rare. Forty-five to 66% of gaps were due to the death of single canopy trees. Canopy trees more often died leaving standing dead wood (40–5.7%) or broken trunks (43–49%). Shade tolerantAbies mariesii andAbies veitchii, frequently, andTsuga diversifolia, less frequently, regenerated in gaps, from advance regenerations recruited before gap formation.Picea jezoensis var.hondoensis may regenerate in gaps, from new individuals recruited after gap formation. The breakage of denseSasa coverage and the mineral soils exposed by the uprooted plants that form gaps might provide regeneration opportunities for shade intolerantBetula. Of the important species limited to the ridge site,Chamaecyparis obtusa, frequently, andThuja standishii, infrequently, regenerated from plants alreadyin situ. Regeneration ofPinus parviflora was not seen. Based on the gap characteristics and gap regeneration behaviour of each species described, stand dynamics in each stand are discussed. 相似文献
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Janet Franklin Riley Andrade Mark L. Daniels Patrick Fairbairn Maria C. Fandino Thomas W. Gillespie Grizelle González Otto Gonzalez Daniel Imbert Valerie Kapos Daniel L. Kelly Humfredo Marcano‐Vega Elvia J. Meléndez‐Ackerman Kurt P. McLaren Morag A. McDonald Julie Ripplinger Julissa Rojas‐Sandoval Michael S. Ross Jorge Ruiz David W. Steadman Edmund V. J. Tanner Inge Terrill Michel Vennetier 《Journal of Biogeography》2018,45(5):1168-1181