Pollen dispersal and representation in a neotropical rain forest

Results of 3 years of pollen trapping on Barro Colorado Island, Panama, are presented. Minimum pollen dispersal distances are estimated for the most abundant pollen taxa. Dispersal distances for some taxa appear to be as low as 5 m, while for other taxa at least 50% of the trapped pollen had travelled more than 40 m. No consistent pattern of spatial variation was reflected in the pollen rain, however, samples close to large canopy gaps had exceptional abundances of 'disturbance' taxa. A preliminary analysis of the representation of canopy components indicates that as much as 19% of pollen caught in the traps was derived from large tree species.     

海南岛热带山地雨林种类组成的局域分布与垂直分布

对海南岛四大山地雨林区常见植物种类的局域及垂直分布进行了研究,结果表明,海南岛热带山地雨林的种类组成,除了在各林区有一定数量相同的种外,各林区之间种类成分也存在着显著的差异,由于各林区生态因子的差异,使得生态幅度不同的物种在垂直方向上的分布也产生明显的差异,生态幅度较小的物种仅局限于某一地段,生态幅度较广,适应性较强的种类则有较广泛的分布。     

The community ecology of Asian rain forests,in relation to catastrophic events

Although natural catastrophic disturbance of tropical forests in Asia can be caused by volcanism and earthquakes climate-induced catastrophes are most widespread. These are prevalent and most diverse at high tropical latitudes because of the single annual dry and wet monsoon. Comparative studies indicate that periodicity of catastrophes may influence forest physiognomy, structure and species richness but long-term research in sample plots suggests that a variety of other factors are locally influential. The importance of accounting for natural catastrophes in silvicultural protocols is stressed, and research priorities identified.     

Recovery from clearing,cyclone and fire in rain forests of Tonga,South Pacific: Vegetation dynamics 1995–2005

Abstract In late 2001 a category 3 cyclone impacted forest plots that were established in Tonga in 1995, and additionally, one plot was accidentally burned by an escaped land‐clearing fire. Subsequent surveys provide observations of 10 years of forest dynamics in this poorly studied region, and the first reported observations of large interannual variation in juvenile (seedling and sapling) abundance in the western tropical Pacific. The severely disturbed (burned) plot was initially colonized by a non‐native early pioneer, Carica papaya L., but 3.5 years later a native pioneer, Macaranga harveyana (Muell. Arg.) Muell. Arg., was the most abundant tree species. The seedling layer included some long‐lived pioneers and shade‐tolerant species. Two mature forest plots affected only by the cyclone changed very little over a decade. Late‐successional shade‐tolerant species that dominated the overstory were also abundant as seedlings and saplings. This is in contrast with a 30‐ to 40‐year‐old, formerly cultivated, secondary forest plot that still shows no recruitment of late‐successional dominants, in spite of the proximity of remnant forest patches. This study suggests differing pathways of succession following shifting cultivation versus cyclone and fire disturbances in Tonga. Land use legacies appear to have a long‐lasting effect on community composition.     

Phylogenetic tests of community assembly across regional to continental scales in tropical and subtropical rain forests

Aim To measure and quantify community phylogenetic structure to evaluate how evolutionary, ecological and biogeographic processes have shaped the distributions and assemblage of tropical and subtropical rain forest tree species across local, regional and continental scales. Location Australia. Methods We used 596 assemblage‐level samples and 1137 woody species in rain forest vegetation sampled across two latitude regions (tropics and sub‐tropics) and five distinct areas. Based on this dataset, we obtained and analysed species‐level trait values (for leaf size, seed size, wood density and maximum height at maturity), measures of community phylogenetic structure and species turnover across space (beta) and evolutionary time (phylobeta). Results Phylobeta values showed that at continental scales (i.e. across the latitude regions combined) species replacement, as turnover in assemblages through time, was by more phylogenetically distant (i.e. less closely related) taxa. Within latitude regions replacement was by more closely related taxa. Assemblages of species were more phylogenetically clustered across the whole phylogeny (net relatedness index) and with respect to more recent divergences (nearest related taxon index) where the effects of historic disturbance (climatic oscillations) had been greater, and less clustered in long‐term stable (refugial) locations. Local species composition in the stable wet tropics showed significant phylogenetic evenness, but there was no corresponding evenness in distributions of the ecological traits measured. Main conclusions Despite a shared evolutionary and biogeographic history, the two regions diverged from each other before the development of internal divergences. Phylogenetic evenness is more evident in long‐term stable habitats (refugia) where species interact in conserved niches. Phylogenetic clustering is more evident where recolonization of more highly disturbed areas from historically reduced species pools reflects filtering of species into phylogenetically preferred habitats.     

Mapping gradual landscape-scale floristic changes in Amazonian primary rain forests by combining ordination and remote sensing

Aim We present a new method to economically map gradual changes in plant species composition in lowland rain forests using field data and satellite images. Such a method will be a useful tool in planning the sustainable use and conservation of Amazonian rain forests. Location The study covered an area of c. 700 km² of primary rain forest in Amazonian Ecuador. Methods We field inventoried the species composition of pteridophytes and Melastomataceae in 340 inventory plots (5 m × 50 m), described the prevailing topography and analysed soil cation concentration and texture. We used non‐metric multidimensional scaling (NMDS) to summarize the floristic variation among the inventory plots in three ordination dimensions. The scores of the three ordination axes were predicted to non‐visited places using a Landsat TM (thematic mapper) satellite image and the k nearest neighbours (knn) estimation method. To avoid extrapolation, we excluded from the analysis those pixel windows whose spectral values were not represented in the areas covered by field sampling. The accuracy of the predictions was evaluated by cross‐validation and by comparing the predictions based on spectrally nearest neighbours to the predictions based on random neighbours. Results The floristic gradients presented by NMDS ordination were interpretable in terms of topography, drainage and soil cation content. Thirteen percent of the cloud‐free pixels were excluded from the knn analysis to avoid extrapolation. The estimates of the floristic ordination scores based on spectrally nearest neighbours were always more accurate than estimates based on random neighbours. Main conclusions The presented method needs a relatively small input of work and resources, is mechanistic and produces maps that give relevant information on floristic variation over forest areas that are traditionally considered essentially homogeneous. Therefore, the method appears to have a great potential for use in mapping large areas of Amazonian rain forests.     

银合欢成功入侵热带雨林先锋群落的关键因素

由于生长速率高, 耐旱性强, 银合欢(Leucaena leucocephala)被广泛应用于世界各地退化热带亚热带森林的修复, 但它也是一种全球性的外来入侵植物。已经有研究发现高生长速率可以帮助银合欢成功入侵亚热带森林, 但是目前还不清楚高生长速率和强耐旱性是否能帮助银合欢成功入侵热带森林。该研究以位于中国三亚抱坡岭被银合欢入侵的热带雨林先锋群落为研究对象, 通过t检验比较干季和湿季银合欢和8个热带雨林先锋群落的本地优势种与快速生长(光合速率、气孔导度和蒸腾速率)和耐旱性(叶片膨压丧失点)紧密相关的功能性状的差异, 并利用主成分分析(PCA)研究这些功能性状是否能很好地区分银合欢和其他8个本地优势种。结果表明: 银合欢在干湿季均能快速地生长(比本地物种显著更高的光合速率、气孔导度和蒸腾速率), 且在干季拥有更强的耐旱性(比本地物种显著更低的叶片膨压丧失点)。PCA结果表明这些功能性状能够显著区分银合欢和其他8个本地优势种。因此干湿季的稳定的快速生长和干季的强耐旱性使银合欢成功入侵热带雨林先锋群落。未来可利用这些功能性状筛选合适的本地物种对入侵其他热带森林的银合欢进行有效的生物防治。     

模拟干旱和磷添加对热带低地雨林氮矿化过程的影响

土壤氮矿化作为氮转化的主要过程决定土壤供氮能力。热带森林生态系统往往受磷限制, 氮矿化过程对干旱的响应是否受磷限制的调控值得探讨。该研究以海南三亚甘什岭自然保护区热带低地雨林为研究对象, 利用2019年建立的林内穿透雨减少(50%)及磷添加双因素交互实验平台, 通过野外树脂芯原位培养法研究模拟干旱及磷添加对土壤无机氮(包括铵态氮和硝态氮)含量和氮矿化过程的影响。结果表明: 1)减雨处理显著降低了5和15 cm深度土壤的水分含量, 而对土壤温度没有显著影响。2)减雨处理和减雨与磷添加共同处理无论在旱季还是湿季对0-10 cm土壤无机氮含量均没有产生显著影响, 但磷添加处理在旱季显著降低了土壤硝态氮含量, 表明磷添加处理对氮有效性的影响主要体现在旱季, 而非湿季。3)干旱处理在旱季和湿季均显著降低了土壤净氨化速率和净氮矿化速率, 而磷添加处理和减雨与磷添加共同处理无论在旱季还是湿季对净氨化速率、净硝化速率和净氮矿化速率均没有产生显著影响, 结果表明了干旱能够显著降低土壤净氮矿化速率。4)土壤水分含量与土壤净氨化速率和净氮矿化速率呈显著正相关关系, 同时减雨处理显著影响了土壤净氨化速率与铵态氮含量的关系, 并且在铵态氮含量相等的情况, 随着干旱的影响净氨化速率下降得更快。这表明土壤水分含量变化是影响该研究样地土壤氮矿化的主要因素。上述研究结果说明, 降水变化对热带低地雨林中土壤氮矿化有重要影响, 短期磷添加没有显著影响, 减雨与磷添加对土壤氮矿化过程并没有交互效应。     

热带与亚热带森林分子生态学研究

当前 ,植物学家会有更多的方法和手段来从事植物学的研究 ,如分子生物学方法、遗传学的方法、植物生理学的方法、分类学方法等。其中分子生物学方法直接研究植物遗传物质ＤＮＡ ,从根本上揭示了生物体内涵 ,有着极其重要的作用[4 7] 。因此用分子生物学手段进行生态学的研究有着广泛应用前景和重要意义。分子生物学方法既节省时间和资金 ,又比传统方法解决了更多的问题[6 1] 。例如在动物学研究中 ,用少许的毛发就可以分析高山土拨鼠 (ＭａｒｍｏｔａｍａｒｍｏｔａＳｃｉｕｒｉｄａｅ)的交配系统[30 ] ;粪便所带的肠道粘膜细胞ＤＮＡ也可以…     

西双版纳热带季节雨林的树种组成和群落结构动态

研究了西双版纳热带季节雨林1 hm2(hectare)动态监测样地1993年与2007年之间树种组成和群落结构的变化。对样地中胸径≥5 cm的乔木进行了每木调查。目前其树种组成的热带分布科、属所占比例分别为91%和94%,具有较高比例的热带植物区系性质。在1993年与2007年两次调查之间,树种数量由145种增至179种,仅有1到2个个体的稀有树种所占比例从54%降为51.1%。从森林的垂直结构来看,A、B、C三层的个体死亡率分别为12.8%、12.9%和19.0%,各层树木的增长率分别为-8.5%、-1.4%和44.8%。与此相对应,C层小径级的树木所占比例有较大提高。虽然小径级的树木在种类和数量上比例增大,但个体数量和种类组成相对稳定的A、B层优势树种变化不大,维持了群落结构的稳定性。14 a间,群落中新增加的具有先锋性质的树种不超过5个。1993年时,A、B两层尚有先锋树种存在,2007年已经从A、B两层中退出。因此,从14 a间树种组成和群落结构的变化来看,虽然具有树木的死亡和增补,但其物种成分和群落结构的总体格局没有明显的变化,处于动态平衡过程中。     

Woody plants diversity,floristic composition and land use history in the Amazonian rain forests of Madidi National Park,Bolivia

A floristic inventory of woody plants was carried out to analyse the relationships between floristic similarity and geographical distance, and to compare the effect of land use history on the floristic composition between sites. Three lowland and two submontane sites were studied in Madidi, Bolivia. In one site, there is evidence of an Inca ruin. A total of 877 species and 12,822 individuals of woody plants with a diameter at breast height ≥2.5 cm were recorded in 44 0.1–ha plots. Fisher’s Alpha index values were slightly higher for the lowlands than for the submontane. Floristic similarity was higher within sites than between sites as measured by both Sørensen and Steinhaus indexes. The fact that the 30 most important species per site (totalling 94 species) accounted for 61.7% of total individuals, support the hypothesis that Amazonian plant communities are dominated by a limited set of species, genera and families. On the other hand, 18 out of the 94 species were reported in a single site, suggesting that some species are patchy in distribution and may be environmentally determined. Both the oligarchy and environmental-determinism hypotheses can be complementary in order to understand floristic patterns of this region. The Ruins submontane site is floristically the most distinct, and past human disturbance is likely to be the main reason. Since species diversity (ranging from 53 to 122 species per plot) and density (ranging from 157 to 503 per plot) are highly variable in Madidi, to characterize the diversity of a site, it is necessary to quantify an average of 10 0.1-ha plots in a relatively small geographical area.     

Successional Patterns of Microfungi in Fallen Leaves of Ficus pleurocarpa (Moraceae) in an Australian Tropical Rain Forest1

Successional patterns of microfungi on decaying leaves of Ficus pleurocarpa were assessed as part of a study to enumerate microfungi in tropical rain forest leaf litter. Leaves degraded into fragments over a period of 3 mo. Two methods were applied, a direct observational method and a particle filtration protocol. Using a direct method, 104 species were observed, while 53 sporulating taxa and 100 sterile morphotaxa were isolated by particle filtration. Overall patterns of succession were confirmed by both methods, but the relative abundance of species detected differed between the two methods. Nonmetric Multidimensional Scaling identified at least four successional stages and suggested that microfungal communities increased in similarity with advancing decay. Data collected by the direct method indicated a slow but steady decline of diversity with advancing decay, whereas an increase in diversity was detected by particle filtration. Synecological succession studies provide a useful tool to identify patterns and generate hypotheses. Understanding the underlying causes of successional patterns will require further autecological studies.     

Ecological and biogeographical studies on the tropical rain forest of south Yunnan,SW China with a special reference to its relation with rain forests of tropical Asia

Abstract. Ecological and biogeographic analyses of the tropical rain forest in south Yunnan were made using data from seventeen sample plots and floristic inventories of about 1000 species of seed plants. The rain forest is shown to be a type of true tropical rain forest because it has almost the same profile, physiognomic characteristics, species richness per unit area, numbers of individuals in each tree species and diameter classes of trees as classic lowland tropical rain forests. As the area is at the northern margin of monsoonal tropics, the rain forest differs from equatorial lowland rain forests in having some deciduous trees in the canopy layer, fewer megaphanaerophytes and epiphytes but more species of lianas as well as more species of microphylls. In its floristic composition, about 80% of total families. 94% of total genera and more than 90% of total species are tropical, of which about 38% of genera and 74% of species are tropical Asian. Furthermore, the rain forest has not only almost the same families and genera, but also the same families rank in the top ten both in species richness and in dominance of stems, as lowland forests in southeast Asia. It is indisputable that the flora of the rain forest is part of the tropical Asian flora. However, most of the tropical families and genera have their northern limits in south Yunnan and most have their centre of species diversity in Malesia. More strictly tropical families and genera have relatively lower species richness and importance compared with lowland rain forests in tropical southeast Asia. Thus, the flora also shows characteristics of being at the margin of the tropics. Based mainly on physiognomy and floristic composition the tropical rain forest of Yunnan is classified into two types, i.e. seasonal rain forest and wet seasonal rain forest, the latter is further divided into two subtypes, i.e. mixed rain forest and dipterocarp rain forest. From analysis of geographic elements it is also shown that the tropical rain forest of Yunnan occurs at a geographical nexus with its flora coming mainly from four sources, i.e. Malesia, south Himalayas, Indochina and China.