The conservation value of small, isolated fragments of lowland tropical rain forest

Deforestation is occurring at an alarming rate in the lowland tropics. In many tropical regions, rain forest is restricted to small (<100 ha), isolated fragments. While only the preservation of large areas of tropical rain forest can safeguard the complete biota, recent research has shown that a substantial number of forest species can persist for decades in fragmented forest, though large vertebrates are susceptible to habitat fragmentation. Inevitably, small fragments will become the last refuges of many rainforest species that are on the brink of extinction. In areas with little rain forest remaining, fragments can be the 'seeds' from which to re-establish extensive forest.     

The reproductive biology of two understory plants in the Atlantic rain forest, Brazil

Outcrossing and sexual reproduction of most flowering plants depends on pollinators. Plant traits likely to be involved in pollinator attraction include flower color, shape, and size. Furthermore, plant or flower density and the temporal flowering pattern may have an effect on reproduction. In this study, we examine the pollination ecology, breeding system, female reproductive output, and germination of two tropical understory species, Stenostephanus lobeliiformis (Acanthaceae) and Besleria melancholica (Gesneriaceae), which differ in these traits. Pollinator observations revealed that the dense flowering S. lobeliiformis with pinkish flowers received a higher diversity of pollinators, but visitor frequency measured as visits per flower per hour was much less (0.1 h^?1) than that to B. melancholica, which has a smaller floral display of dull-colored flowers (1.5 h^?1). Pollination experiments revealed that S. lobeliiformis but not B. melancholica is pollen-limited. In addition, both species are partially self-incompatible and depend on pollinators for outcrossing. Natural fruit set of open-pollinated unmanipulated flowers (control treatment) in both species is 22–26 %. Germination studies indicated inbreeding depression in S. lobeliiformis. We conclude that the pollination ecology of these species is influenced by a broad set of traits and that very different combinations of these traits can be successful in terms of reproduction.     

The vertical distribution of small flying insects in the lowland rain forest of Zaire

To monitor the vertical distribution of flying insects in the semi-deciduous rain forest of Zaire, two types of trap were hung at four vertical levels. Large insects were excluded. The entire catch was analysed. There was a marked concentration of flying insects within and above the canopy, over a wide range of orders. The most abundant taxa showed the greatest tendency to occur at these upper levels. Within the size range collected, biomass in general reflected abundance, but was influenced by the relatively high proportion of small insects in and above the canopy. There was a strong similarity in the relative abundance of orders between trap types and sites, but total numbers varied greatly. This variation and the biases inherent in these trapping methods are discussed and we conclude that the bulk of the small flying insects of the rain forest are concentrated in the upper canopy.     

Interception, pH and solid content of rainfall in a Nigerian lowland rain forest

Rainfall interception by forest trees, pH, alkalinity, total suspended and dissolved solids of incident rainfall, stemflow and throughfall and the effect of tree species in these parameters were investigated in three open sites and a secondary rain forest at Ile-Ife, Nigeria, in 1994 and 1995. The tree species Blighia sapida , Holarrhena floribunda and Piptadeniastrum africanum intercepted different proportions of incident rainfall, 1.6, 39.4, and 7.4%, respectively. The pH of stemflow was higher than that of throughfall and the pH of both was always higher than that of incident rainfall. The total suspended solids were higher at the beginning and towards the end of the rainy season. The total dissolved solids concentration in all rainfall fractions was highest at the early rains and during the heavy rain months, especially in throughfall and stemflow. The total suspended and dissolved solids concentration of stemflow was higher than that of throughfall and those of both were higher than that of the incident rain. Total alkalinity of incident rainfall and throughfall decreased, while that of stemflow increased with increase in rainfall. There were significant differences in the alkalinity of stemflow and throughfall under the crowns of the tree species.     

Habitat associations of opossums and rodents in a lowland forest in French Guiana

Opossums and rodents were sampled by live-trapping at Paracou, French Guiana to study habitat use. Tomahawk and Sherman traps were placed on the ground and at various heights in the subcanopy and canopy. We captured 10 species of opossums and seven species of rodents. We measured 14 microhabitat variables at each of 485 sampling stations. Presence or absence at a trap station of the three most abundant species of opossums (Didelphis albiventris, Didelphis marsupialis, and Micoureus demerarae) and two rodents (Oecomys rutilus and Proechimys cuvieri) were related by logistic regression analysis to the microhabitat variables. All five species were associated with at least one habitat variable. Linear analysis of categorical data was used to determine the degree of arboreality. Didelphis marsupialis and P. cuvieri were more commonly captured on the ground, D. albiventris was equitably distributed between ground and arboreal traps, and the remaining species were mostly arboreal. Linear analysis was used to compare the distribution of arboreal captures among two substrate types, two heights, and two substrate diameters. Oecomys rutilus was more commonly captured on lianas, D. albiventris and O. rutilus were more commonly captured at lower heights, and D. marsupialis demonstrated a preference for larger arboreal substrates.     

Hunting in lowland,tropical rain forest: Towards a model of non-agricultural subsistence

It has recently been argued that hunter-gatherers do not, did not, and could not live in tropical rain forest without some access to agricultural produce. This opinion challenges models of past non-agricultural subsistence patterns that are based in analogies derived from modern rain forest dwelling groups. In this paper, the socio-ecological bases of the hunting system of the Kubo people of lowland Papua New Guinea are described. It is argued that this system lacks necessary dependence upon the agricultural system with which it co-occurs and, in fact, can be connected with a system of carbohydrate procurement that is not agricultural. The hypothesized connection provides the basis of a model of non-agricultural subsistence in lowland tropical rain forest.     

Pollination biology in a lowland dipterocarp forest inSarawak, Malaysia. I. Characteristics of the plant-pollinator communityin a lowland dipterocarp forest

Flowerings and flower visitors were observed continuously in alowland dipterocarp forest in Sarawak, Malaysia, for 53 mo in1992-1996. Flower visitors of 270 plant species were observed orcollected, and pollinators were assessed by observing body contact tostigmas and anthers. We recognized 12 categories of pollination systems.Among them, plants pollinated by social bees included the largest numberof species (32%) and were followed by beetle-pollinated species(20%). Pollination systems were significantly related with somefloral characters (flowering time of day, reward, and floral shape), butnot with floral color. Based on the relationships between pollinatorsand floral characters, we described pollination syndromes found in alowland dipterocarp forest. The dominance of social bees and beetlesamong pollinators is discussed in relation to the general floweringobserved in dipterocarp forests of West Malesia. In spite of high plantspecies diversity and consequent low population densities of lowlanddipterocarp forests, long-distance-specific pollinators were uncommoncompared with theNeotropics.     

Diversity and vertical distribution of epiphytic macrolichens in lowland rain forest and lowland cloud forest of French Guiana

Recent work on bryophyte diversity in lowland forests of northern South America has suggested the existence of a new type of cloud forest, the “tropical lowland cloud forest” (LCF). LCF occurs in river valleys with high air humidity and radiation fog, and is rich in epiphytes. We explored the lichenological characteristics of putative LCF in a lowland area (200–400 m a.s.l.) near Saül, central French Guiana, using macrolichens (including large crustose species) as indicator taxa. We analyzed macrolichen diversity on 16 trees in two 1 ha plots, in LCF and in lowland rain forest without fog (LRF). Sampling efficiency was ca. 80% in both forest types. Canopies of both LRF and LCF were richer in lichen species than understory trunks. Species richness of macrolichens was rather similar in the two forest types but species composition was significantly different. Cyanolichen richness in LCF was ca. 2.5 times higher than in LRF; in contrast, LRF had 4 times more species of green-algal Parmeliaceae. Our study suggests that cyanolichens except for Coccocarpiaceae serve as indicators of LCF. We explain the detected diversity patterns by differences in water availability due to fog precipitation and higher humidity. This is indicated by the higher relative air humidity in the lowland cloud forest, which was >6% higher than in the rain forest.     

Abundance and stratification of foliage arthropods in a lowland rain forest of Cameroon

Abstract.

• 1 Arthropod densities and apparent leaf damage were compared within the canopy ecotone and the shrub layer of a lowland rain forest in Cameroon, using a branch clipping method.
• 2 Most of the individuals collected consisted of ants (average 44%) and various herbivores (31%). Overall arthropod densities amounted to 17 individuals per sample, which, on average, consisted of 0.85 m² of foliage area. Arthropod densities were lower than on temperate foliage.
• 3 Arthropod densities were about 3 times higher in the canopy than within the shrub layer. In particular, ants and herbivores were significantly more abundant in the canopy than within the shrub layer. Usually, layer effects rather than site effects appeared to cause greater variance in arthropod abundance.
• 4 Arthropod species-richness, as estimated by the number of operational taxonomic units sorted, was higher in canopy samples than in samples obtained from the shrub layer. However, apparent leaf damage was higher within the shrub layer (10.9%) than on the canopy (5.2%).
• 5 Possible factors responsible for the high densities of ants and herbivores on the canopy and for the high leaf damage within the shrub layer are discussed.

     

Logging,exotic plant invasions,and native plant reassembly in a lowland tropical rain forest

Habitat modification and biological invasions are key drivers of global environmental change. However, the extent and impact of exotic plant invasions in modified tropical landscapes remain poorly understood. We examined whether logging drives exotic plant invasions and whether their combined influences alter understory plant community composition in lowland rain forests in Borneo. We tested the relationship between understory communities and local‐ and landscape‐scale logging intensity, using leaf area index (LAI) and aboveground biomass (AGB) data from 192 plots across a logging‐intensity gradient from primary to repeatedly logged forests. Overall, we found relatively low levels of exotic plant invasions, despite an intensive logging history. Exotic species were more speciose, had greater cover, and more biomass in sites with more local‐scale canopy loss. Surprisingly, though, exotic species invasion was not related to either landscape‐scale canopy loss or road configuration. Moreover, logging and invasion did not seem to be acting synergistically on native plant composition, except that seedlings of the canopy‐dominant Dipterocarpaceae family were less abundant in areas with higher exotic plant biomass. Current low levels of invasion, and limited association with native understory community change, suggest there is a window of opportunity to manage invasive impacts. We caution about potential lag effects and the possibly severe negative impacts of exotic plant invasions on the long‐term quality of tropical forest, particularly where agricultural plantations function as permanent seed sources for recurrent dispersal along logging roads. We therefore urge prioritization of strategic management plans to counter the growing threat of exotic plant invasions in modified tropical landscapes.     

Environmental and neighbourhood effects on tree fern distributions in a neotropical lowland rain forest

Questions: To what extent are the distributions of tropical rain forest tree ferns (Cyatheaceae) related to environmental variation, and is habitat specialization likely to play a role in their local coexistence? Location: Lowland rain forest at La Selva Biological Station, Costa Rica. Methods: Generalized linear (GLM) and generalized additive (GAM) logistic regression were used to model the incidence of four tree fern species in relation to environmental and neighbourhood variables in 1154 inventory plots regularly distributed across 6 km² of old‐growth forest. Small and large size classes of the two most abundant species were modelled separately to see whether habitat associations change with ontogeny. Results: GLM and GAM model results were similar. All species had significant distributional biases with respect to micro‐habitat. Environmental variables describing soil variation were included in the models most often, followed by topographic and forest structural variables. The distributions of small individuals were more strongly related to environmental variation than those of larger individuals. Significant neighbourhood effects (spatial autocorrelation in intraspecific distributions and non‐random overlaps in the distributions of certain species pairs) were also identified. Overlaps between congeners did not differ from random, but there was a highly significant overlap in the distributions of the two most common species. Conclusions: Our results support the view that habitat specialization is an important determinant of where on the rain forest landscape tree ferns grow, especially for juvenile plants. However, other factors, such as dispersal limitation, may also contribute to their local coexistence.     

啮齿动物对印度栲种子扩散的效率

从2007 年11 月到2009 年11 月,在西双版纳热带雨林中选取三棵母树,在每棵树下每年释放标记印度栲种子200 粒(三年共计1 800 粒),并追踪其命运。通过调查啮齿动物搬运和分散贮藏印度栲种子的比例,以及
查贮藏种子的微生境、贮藏点大小和扩散距离,分析贮藏种子的存活情况,进而评估啮齿动物对印度栲种子扩散的效率。结果表明,啮齿动物搬运了69.3% 的印度栲种子,被搬运的种子中18% 被分散贮藏。所有被分散贮藏的种子均被埋于落叶下或埋于土壤表层,并且大部分贮藏点仅含一粒种子。种子的扩散距离从0.5 m 到43.8 m,平均距离为7.1 m,扩散距离在年间没有显著差异。2007 年(种子密度低,啮齿动物密度高) 没有种能最终存活到实验结束,而2008 和2009 年(种子密度高,啮齿动物密度低)分别有0.3% 和1.5% 的种子存活。研究表明,啮齿动物是印度栲有效的种子扩散者,但其扩散效率很大程度上取决于森林中种子的密度和啮齿动物的丰富度。     

Studies on epiphytic flora of a tropical rain forest in Southwestern Nigeria

A survey of epiphytes in Gambari Forest Reserve in Southwestern Nigeria was undertaken. A total of 26 epiphytes were recorded. These include five pteridophytes and 21 angiosperm species belonging to the following families; Acanthaceae, Araceae, Asteraceae, Commelinaceae, Moraceae, Orchidaceae, Palmae, Urticaceae Piperaceae, and Portulacaceae. The smooth-barked phorophytes had only one or two epiphytes on them because they are unable to accumulated dust, debris and moisture for germination and growth of the epiphytes. The palm trees with rough barks had points at which they can collect soil, nutrients and moisture for epiphytic growth, hence all the epiphytic species recorded on the site were present on palm trees. Presence of many of the epiphytes is thought to be due to the availability of propagules from reproducing adults in the surrounding vegetation. Also, epiphytes appear to have a dressing effect on the palm trees.     

Studies on epiphytic flora of a tropical rain forest in Southwestern Nigeria

Bark microflora of 12 rainforest trees were examined. Crustose, foliose, and fruticose forms of lichens were observed. Bacillus sp., Erwinia sp., Micrococcus sp., Proteus sp., and Pseudomonas sp. were the five genera of bacteria recorded while three genera of Cyanobacteria; Entophysalis, Gleocapsa and Stigonema were observed. In the algal division, three genera of Chlorophyta found are Chlorococcum, Pleurococcus and Physolinum. Only one diatom, Cocconeis sp. was present on just one tree. Most of the epiphytic microflora found are mainly terrestrial and their spores might have been deposited on the barks by air, or dust-currents. While moisture is regarded as the most critical factor in growth of bark microflora, other factors like texture of the bark, insolation and especially chemical characteristics of the barks may play a key role in occurrence and distribution of micro-organisms on them.     

Diversity of climbing seed plants and their reproductive habit in a karst seasonal rain forest in Nonggang,Guangxi, China

Aims Diversity of climbing seed plants and their reproductive habits and characteristics are central for the understanding of community structure and dynamics of forests and hence are important for forest protection. However, little is known about the climbing seed plants in northern tropical karst seasonal rain forests. Here, using the data of the species diversity and reproductive habits of climbing seed plants in Nonggang, Guangxi, China, we aim to 1) explore the species diversity and distribution of climbing seed plants in northern tropical karst seasonal rain forests, 2) study the flowering and fruiting phenology and 3) the associations of reproductive characteristics to the environment. Methods Species composition, preferred habitat, flowering time, fruiting time and fruit types of climbing seed plants were surveyed. The seasonality of flowering and fruiting were analyzed by concentration ratio and circular distribution. Climbing seed plants were divided into three groups according to their growth forms and places in spatial forest structure: bush ropes, herbaceous vines and lianas. Monthly flowering ratios, fruiting ratios, fruit types and their ratios in different groups were determined. These relationships of flowering ratio, fruiting ratio, fruit type and its ratio to meteorological factors were investigated using Pearson correlation analysis. Important findings There were a total of 333 species of climbing seed plants in Nonggang karst seasonal rain forest, belonging to 145 genera and 56 families. Bush ropes, herbaceous vines and lianas contained 119, 88 and 126 species, respectively. At species level, herbaceous vines were more abundance in valleys, while bush ropes and lianas were more abundance on slopes. Flowering and fruiting of climbing seed plants occurred seasonally, with flowering peaking in April to September, while fruiting peaking in July to December. The seasonality of flowering and fruiting in bush ropes was weaker than in herbaceous vines and lianas. Flowering ratio was significantly positively correlated with rainfall and air temperature, which suggest that flowering peaks in monsoon season. Peak time for fruiting was about three months later than the peak time of flowering, around the end of monsoon season. The ratio of samara species to all fruiting species in lianas was significantly positively correlated with wind speed, but negatively correlated with rainfall and air temperature. It showed that samara in lianas tended to occur in dry season with high wind speed. In conclusion, species diversity and the seasonal features of reproduction of climbing seed plants in Nonggang karst seasonal rain forest were closely related to the spatial and temporal variations of habitat resources.