Tree Flora Research Articles

Distributional modelling and parsimony analysis of endemicity of Senecio in the Mediterranean‐type climate area of Central Chile

AbstractAim Floristic blocks and areas of endemism resulting from a parsimony analysis of endemicity (PAE) using raw floristic data versus data generated from distributional modelling for 130 species in the genus Senecio Tourn. ex L. distributed in the Mediterranean‐type climate area of Central Chile were compared, and the results were used to identify conservation priorities for the flora of the region.Location Central Chile, between 30° and 38° S.Methods Using herbarium records, a species × area matrix consisting of presence/absence data was constructed from a 0.5° × 0.5° grid. Distributional modelling techniques incorporating vegetation formations, elevation and the contagion index were used to interpolate floristic composition of poorly known areas. Parsimony analysis of endemicity was used to identify floristic blocks and areas of endemism.Results Using the number of most parsimonious trees as an index, distributional modelling greatly optimized the results of the PAE analysis. Three floristic blocks and four areas of endemism were suggested based on the PAE results using potential distribution data not incorporating the contagion index, while four blocks and two areas of endemism were suggested from the PAE results using potential distribution data incorporating the contagion index. Floristic blocks for the northern coast, southern Andes, and northern/central Andes were found, with some blocks showing divisions within them representing distinct geographic subunits. Major breaks between and within floristic blocks were identified at 32.5°–33° S and 34.5°–35° S.Main conclusions The floristic blocks identified with the distributional modelling and PAE correspond well to results from some previous studies and support hypothesized biogeographic divisions within Central Chile. The results were similar to those obtained from parallel analysis of the entire tree flora of Central Chile. The vegetative formation‐based distributional modelling produced robust and reproducible results when used along with PAE, especially when the contagion index was incorporated, and is a useful technique for area classification. The results demonstrate the utility of Senecio as an indicator genus for biogeography and conservation in southern South America.

The role of Ulmus laevis in German floodplain landscapes

In the past, the spread of modern civilisation has heavily reduced the occurrence of natural woodlands in floodplain landscapes and the numbers of elms have also been reduced on a large scale. At the time of the outbreak of Dutch elm disease (DED), the elm populations may have already been reduced by an estimated 90%. At that time, Ulmus minor was the most common elm species in the riparian forests of lowland Central Europe. Eighty years later, the numbers of U. minor had decreased significantly. Data from three rivers in Saxony, Germany suggest that a further 90% of the trees have succumbed to DED. The survivors have mostly been reduced to shrubs and small trees. Ulmus laevis has taken over the role of the typical and well established elm species in floodplain landscapes. Being less susceptible to DED, the trees dominate parts of floodplain meadow landscapes and riparian forests. However, the overall number is low when compared with other tree species. Most U. laevis trees find only restricted habitats within agricultural landscapes and in many cases the elm itself is the only reminder of the existence of a former riparian wildwood. Also, some individuals show a high degree of crown transparency without having been infected with DED. If elms are to constitute an important part of the floodplain tree flora in the future, it is crucial to protect and enhance the existing U. laevis populations. Controlled provenances can help in the process of re-establishing floodplain forests.

Three New Species, Two New Subspecies and Five New Combinations at the Subspecific Level in Aglaia Lour. (Meliaceae)

The genus Aglaia (Meliaceae) is well represented in Borneo, with 60 species now recognised for the island. Twelve of these are endemic, of which three are described in this paper. Most of the remainder are also found in Peninsular Malaysia and Sumatra. Pannell's monographic revision of Aglaia was confined to treatment at the species level; no subspecies were recognised. For a regional flora, however, it is desirable to describe infraspecific variation in more detail. Seven subspecies for Borneo are recognised here, two of which require new names. All but one of these subspecies are included in the account of Aglaia submitted to the editors of the 'Tree Flora of Sabah and Sarawak'.

A floristic analysis of the lowland dipterocarp forests of Borneo

AbstractAim To (1) identify floristic regions in the lowland (below 500 m a.s.l.) tropical dipterocarp rain forest of Borneo based on tree genera, (2) determine the characteristic taxa of these regions, (3) study tree diversity patterns within Borneo, and (4) relate the floristic and diversity patterns to abiotic factors such as mean annual rainfall and geographical distance between plots.Location Lowland tropical dipterocarp rain forest of Borneo.Methods We used tree (diameter at breast height ≥ 9.8 cm) inventory data from 28 lowland dipterocarp rain forest locations throughout Borneo. From each location six samples of 640 individuals were drawn randomly. With these data we calculated a Sørensen and Steinhaus similarity matrix for the locations. These matrices were then used in an UPGMA clustering algorithm to determine the floristic relations between the locations (dendrogram). Principal coordinate analysis was used to ordinate the locations. Characteristic taxa for the identified floristic clusters were determined with the use of the INDVAL method of Dufrene & Legendre (1997). Finally, Mantel analysis was applied to determine the influence of mean annual rainfall and geographical distance between plots on floristic composition.Results A total of 77 families and 363 genera were included in the analysis. On average a random sample of 640 trees from a lowland dipterocarp forest in Borneo contains 41.6 ± 3.8 families and 103.0 ± 12.7 genera. Diversity varied strongly on local scales. On a regional scale, diversity was found to be highest in south‐east Borneo and central Sarawak. The most common families were Dipterocarpaceae (21.9% of trees) and Euphorbiaceae (12.2% of trees). The most common genera were Shorea (12.3% of trees) and Syzygium (5.0% of trees). The 28 locations were clustered in geographically distinct floristic regions. This was related to the fact that floristic similarity depended strongly on the geographical distance between plots and similarity in mean annual rainfall.Conclusions We identified five main floristic regions within the lowland dipterocarp rain forests of Borneo, each of which had its own set of characteristic genera. Mean annual rainfall is an important factor in explaining differences in floristic composition between locations. The influence of geographical distance on floristic similarity between locations is probably related to the fact that abiotic factors change with distance between plots. Borneo's central mountain range generally forms an effective dispersal barrier for the lowland tree flora. Diversity patterns in Borneo are influenced by the mid‐domain effect, habitat size and the influence of past climatic changes (ice ages during the Pleistocene).

Broad‐scale biodiversity pattern of the endemic tree flora of the Western Ghats (India) using canonical correlation analysis of herbarium records

A crucial step in understanding the origin and maintenance of biological diversity is the assessment of its distribution over space and time and across environmental gradients. At the regional scale, two important attributes of species can be assessed that provide insight into speciation processes: species geographical and environmental ranges. The endemic tree flora of the Western Ghats is an interesting case for analyzing broad‐scale biodiversity patterns because of the steep environmental gradients that characterize this tropical region of India. We analysed species geographical and environmental ranges by Canonical Correlation Analysis of point data from herbarium collections. We performed partial analyses to discriminate spatial and environmental correlates of species distribution, and evaluate the contribution of higher taxonomic ranks to these ranges. We identified different levels of organization in the distribution of endemism: 1) general features, such as the concentration of endemic species in the southern part of the Western Ghats, and the decrease in endemic species richness along the altitudinal and the dry season length gradients, and 2) patterns specific to genera or families, such as species niche separation along the environmental gradients. Our analyses enabled us to formulate hypotheses about the diversification of the endemic tree flora of the Western Ghats. They also confirm the value of Canonical Correlation Analysis as the suitable method for collection data analysis.

Deterministic Plio‐Pleistocene extinctions in the European cool‐temperate tree flora

AbstractExtinctions have been important in the shaping of modern phytogeographic patterns. A classic example is the heavy Plio‐Pleistocene losses that have caused Europe to have a depauperate temperate tree flora compared to eastern North America and eastern Asia. To investigate the mechanisms involved in this extinction event, I test the hypothesis that the present European status (extinct, relictual, or widespread) of cool‐temperate tree genera found in Pliocene Europe is predictable from their modern climatic requirements. As a prerequisite for this analysis, I test for genus‐level conservatism in climatic requirements by comparing congeneric values across Europe, eastern Asia and North America, and find strong evidence hereof. I find a high degree of ecological determinism in the fate of European Pliocene tree genera, still widespread taxa being more tolerant of cold growing season and winter temperatures than extinct and relictual taxa, and relictual taxa being more drought tolerant than extinct taxa.

Modelos arquitectónicos en la flora arbórea de la Península de Yucatán

Los modelos arquitectónicos ayudan a describir el desarrollo y la organización de las copas de los árboles. Este conocimiento es indispensable para entender el desarrollo de los árboles en el bosque y puede ayudar a entender la relación evolutiva entre taxa. En esta contribución se presenta una lista de 108 especies de la flora arbórea de la Península de Yucatán, que representa el 25% del total de las especies y el 68% de las familias presentes en la flora peninsular. En total se reconocieron 15 modelos arquitectónicos diferentes. Los datos provienen tanto de trabajo de campo como de una revisión de la literatura.

A COMPARISON OF TREE SPECIES DIVERSITY IN TWO UPPER AMAZONIAN FORESTS

We inventoried two Amazonian tree communities separated by ;1400 km of continuous lowland tropical forest, in an effort to understand why one was more diverse than the other. YasuniNational Park, near the equator in eastern Ecuador, has one of the most diverse tree communities in the world. Manu National Park, at 128 S in Peru's Madre de Dios region, is only moderately diverse by upper Amazonian standards. Following the field inventories, a database of morphological, ecological, and other traits was compiled from the taxonomic literature for 1039 species from the plots. Our goals were (1) to describe how terra firme tree communities at the two sites differed in composition, diversity, and structure; (2) to characterize the ''extra'' species responsible for the higher diversity at Yasuni ´; and (3) to assess, in the light of those observations, some explanations for why forests near the equator are so diverse. Yasunihas ;1.4 times as many tree species as Manu at all three spatial scales we examined: local (1 ha), landscape (,10 000 km 2 ), and regional (,100 000 km 2 ). Yasuni ´ samples contain more families and genera, more individual trees per unit area, and a larger proportion of small trees. Tree species at Yasunihave smaller stature, larger leaves, larger seeds, and smaller geographic and altitudinal ranges than those at Manu, and dispropor- tionate increases in species diversity are observed within the Myrtaceae, Lauraceae, Me- lastomataceae, and several other families. Community structures were strikingly similar, with the same species (Iriartea deltoidea, a palm) dominating both sites at identical den- sities. Common species at Yasunioccur at the same densities as equally ranked species at Manu, but there are substantially more very rare species at Yasuni ´. The poorer tree flora is not a nested subset of the richer tree flora, though a majority of species in each inventory do occur at the other site. Several models that offer explanations for geographic variation in tropical tree species diversity are assessed in light of these data. Most do a poor job of accounting for the patterns revealed by the inventories. We speculate that the most important factor in pro- ducing the higher diversity in Yasuniis its rainier, aseasonal climate, and we discuss two specific rainfall-related mechanisms that appear to be supported by the data: (1) year-round water availability allowing more species to persist in the understory at Yasuniand (2) a newly described ''mixing effect'' related to the higher stem density there.

VEGETATION CLASSIFICATION AND FLORISTICS OF THE SAVANNAS AND ASSOCIATED WETLANDS OF THE RIO BRAVO CONSERVATION AND MANAGEMENT AREA, BELIZE

A floristic inventory and preliminary vegetation classification were made for the tracts of savanna and associated wetland vegetation in the Rio Bravo Conservation and Management Area (RBCMA) in Belize. A total of 258 species were recorded, representing c.7% of the Belizean flora. Of these, 148 species are characteristic of the drier savanna systems, while 47 show a preference for hydrologic savanna and wetland areas. Only 57 species (22% of RBCMA savanna flora) are woody, with the savanna tree flora comprising 15 species. The flora of the RBCMA was found to be fairly typical of the savannas of the Central American and Caribbean region. Savanna systems are generally poorly represented in conservation areas in Central America, and due to the diverse range of structural and ecological formations of this vegetation type found within the RBCMA, and its relatively diverse flora, this reserve constitutes an important protected area.

Propagating framework tree species to restore seasonally dry tropical forest: implications of seasonal seed dispersal and dormancy

One effective approach to forest restoration in degraded tropical forestland is the so-called ‘framework species method’ which involves planting 20–30 indigenous forest tree species to re-establish a basic forest structure that catalyses the recovery of biodiversity. For the seasonally dry tropical forests of Doi Suthep-Pui National Park in northern Thailand, a provisional list of 36 potential framework species was compiled, from 19 different families representing a broad spectrum of the tree flora. This paper examines the seed germination characteristics of these species when grown as a nursery ‘crop’ for planting to restore degraded sites, focussing on germination phenology and dormancy. It considers how such characteristics affect the first stage of nursery production from seed collection to pricking out seedlings in the nursery. Twenty-nine species had a germination percentage of 60% or greater, which is acceptable for nursery production. The median length of dormancy (MLD) ranged from 7 days in the case of Erythrina subumbrans to 219 days for Lithocarpus garrettianus. Germination was defined as rapid if the MLD occurred within 3 weeks, and slow if occurring after 12 weeks. Twelve species germinated rapidly and eight germinated slowly, the remainder being intermediate. Seedling emergence ranged over a period of 7 days in the case of Erythrina stricta and E. subumbrans to 322 days in the case of L. garrettianus.

Effects of microsite, water, weeding, and direct seeding on the regeneration of native and alien species within a Hawaiian dry forest preserve

Tropical dry forests are among the most endangered ecosystems in the world in general and in Hawaii in particular. To investigate the regeneration ecology of native and alien dry forest species on the island of Hawaii, we used a factorial experiment with microsite (sub-canopy vs. inter-canopy), water (supplemental vs. ambient), and weeding (alien species removed vs. not removed) treatments, and also seeded six native woody species into each plot at the start of the experiment. At the end of the 21-month study, the biomass of the volunteer native and alien species (i.e. unplanted species consisting mainly of relatively fast-growing shrubs) was nearly three and 13 times that of the seeded species, respectively. The biomass of the native volunteers was greater in the inter-canopy plots, greater for the seeded species in the sub-canopy plots, and did not differ significantly within this treatment for the alien species. Few species survived in the ambient water plots, resulting in greater biomass in the watered plots for all species. There were no significant differences in the biomass of the native species within the weeded vs. non-weeded plots; on the contrary, we found consistently positive correlations between the abundance of the seeded species and the volunteer native and alien species. Thus it may be possible to restore Hawaii's degraded dry forests by manipulating these naturally recruiting species to create microsites favorable for the eventual re-establishment of the endangered native canopy tree flora.

Heterogeneity and differentiation of the tree flora in three major land uses in Guangzhou City, China

The tree flora of humid-tropical Guangzhou city in south China was studied to understand its composition and variations. Aerial photographs identified three major urban-forest types in three land uses: institutional, park and roadside. Data on 115 064 trees in 246 species were statistically analyzed. Park and roadside areas have lower species richness than institutional forest. Park habitat has re- latively more rooms for species, biomass and floral enrichment. Roadside leads in tree density with full utilization of plantable space, whereas institutional forest has the highest species density index and the most rare natives. Commonality of species amongst forests li- mits to 91 species, with park and institutional sharing 68 species, and road sharing merely 8 and 1 species respectively with institutional and park. Institutional forest has distinct composition and character, with less domination by popular species and more solitary or rare species. Native species exceed exotics at roadside; institutional and park have a reverse trend. Practical implications for urban-forest ma- nagement are discussed.

Biogeographical analysis of the tree flora of the Yucatan Peninsula

AimThe purpose of this study was to examine the biogeographical relationships of the tree flora of the Yucatan Peninsula (YP2). To this aim we: (1) evaluated the affinities of political entities of tropical America with the Yucatan Peninsula, considering the distribution of tree species occurring in the latter region; (2) assessed floristic affinities between political entities of the Yucatan Peninsula based on endemic species; (3) defined biogeographical districts for the Mexican portion of the Yucatan Peninsula; and (4) evaluated the conservation status of endemic species in the area.LocationThe Yucatan Peninsula is a biogeographical area comprising the entire territory of the Mexican states Campeche, Quintana Roo, and Yucatan, adjacent small portions of Tabasco and Chiapas, the El Petén department in Guatemala, and the northern half of Belize. Because of heterogeneous data availability some analyses were restricted to the first three above listed Mexican states (YP1), which comprise the core of the Yucatan Peninsula.MethodsDistributional data of 434 tree species were obtained from three sources: inspection of 7640 herbarium specimens, specialist advice regarding the taxonomic status of the tree species, and an extensive review of taxonomic and floristic literature. We based the various analyses of phytogeographical affinities on Jaccard's Index. Information on individual species distributions was subjected to a multivariate analysis. Occurrence of endemic species in five existing protected areas in the Yucatan Peninsula was analysed by examining floristic checklists available for them.ResultsAffinities of the tree flora of YP1 with twenty‐four political entities of tropical America generally decreased as geographical distances from this region increased. Distributional patterns of the seventy‐two tree species endemic to YP2 showed the strongest affinities to exist between Campeche, Quintana Roo and Yucatan, and in turn these entities displayed a large similarity with Belize and Guatemala. Regionalization of YP1, based on the distributions of both all species and the endemic ones, led to the distinction of two districts: a smaller one in the north‐western corner, and a larger one comprising the remaining areas. Although the distributions of numerous species in the two groups matched the limits of these districts, ubiquitous species of panpeninsular distribution also occurred. For YP1 we identified nineteen endemic trees, indicating a percent endemism of 4.4 for this area. Of the sixty‐four species endemic to YP2 which occur in YP1, fifty‐two (81.2%) have been recorded in at least one of the five protected areas of this territory (three occurred in the five preserves and nineteen did so in a single one), whereas twelve (18.8%) were not found in any protected area.Main conclusionsThe definition of the Yucatan Peninsula as a biogeographical province was confirmed. The strongest floristic affinities of YP1 were with Mesoamerican entities, whereas affinities with the Antilles were much weaker. The distinction of two biogeographical districts corresponds closely to the peninsula's climatic and vegetational zonation. This regionalization agrees partially with schemes proposed for other animal and plant groups. Further inventory work in protected areas is needed to adequately assess the conservation status of the Yucatan Peninsula's tree endemics.

Harvesting intensity affects forest structure and composition in an upland Amazonian forest

Forest structure and floristic composition were studied in a series of 0.5 ha natural forest plots at four sites near Porto Trombetas in Pará State, Brazil, 11–12 years after being subjected to differing levels of above-ground biomass harvest and removal. In addition to undisturbed control plots, experimental treatments included: removal of most trees ≥45 cm DBH (low intensity harvest); removal of trees <20 and ≥60 cm DBH (moderate intensity harvest); clear-cutting (100% above-ground biomass removal). Post-harvest basal area growth generally increased with harvest intensity, and total basal areas for trees ≥5 cm DBH were, at the time of our study, 60% (in the clear-cut) to about 80% of those in the control plots. Biomass harvests stimulated recruitment and growth of residual trees, particularly in the smaller diameter classes, but had little effect on species richness for small trees, seedlings, vine, herbs, and grasses. Species richness for trees ≥15 cm DBH was greater in the control and low-intensity (74–75 species) than in the moderate intensity (47 species) and clear-cut (26 species) treatment plots. While the tree flora within all harvest treatments was broadly similar to the undisturbed (control) plots and included similar numbers of species of the major plant families typical of the surrounding forests, the more intensive harvest treatments, especially the clear-cut, were dominated by a higher proportion of short-lived, early successional tree species.

Seed dispersal by a diurnal primate community in the Dja Reserve, Cameroon

Multiple species of primate disperse seeds and differentially contribute to the seed rain in tropical forests. The goal of this study was to examine seed dispersal by a primate community of five monkey and two ape species in the Dja Reserve, Cameroon. The density of primates in the reserve was calculated to be 77 individuals km-2. Analysis of 5789 faecal clumps demonstrated that 40% of monkey and 74% of ape faecal clumps possessed whole seeds. Six of the seven focal species acted as seed dispersers; faecal clumps passed by the black-and-white colobus (Colobus guereza) did not contain any whole seeds during the study. Seed passage trials on four captive monkey species showed monkeys to have an average seed passage time of 22 hours and defecation rate of five times per day. From the above results, the primate community was estimated to defecate 1129 seeds km-2 d-1. Seeds passed by the primate community came from 125 species of trees, lianas and shrubs, equivalent to at least 34% of the known tree flora. Rarefaction curves indicated that additional collection effort would identify more seed species passed by primates. Germination studies demonstrated that primate-passed seeds are viable. The number of seeds and plant species dispersed suggests that the primate community plays an important role in the maintenance of forest structure.

Trees in shifting and continuous cultivation farms in Ibadan area, southwestern Nigeria

This study compares the types and density of tree species in continuous cultivation farms at the fringe of Ibadan city, Nigeria, with shifting cultivation farms in a rural district near the city. Both categories of farm are used for cultivating field crops of maize, cassava and yams that are intercropped. Tree density is much higher in continuously farmed plots at the city outskirts, where tree density averaged 511 trees/ha compared to 143 trees/ha in shifting cultivation farms in the countryside. In spite of the general similarity in tree flora between the two categories of farmlands, certain tree species are more abundant in one than the other. Gliricidia sepium, an exotic tree legume that improves soil fertility, is more abundant on the continuous cultivation farms while the oil palm, Elaeis guineensis, is more abundant on the shifting cultivation farms. Certain tree species such as Myrianthus arboreus, Alchornea laxiflora and Blaghia sapida were restricted to the shifting cultivation farms and Trema guineensis to the continuously cultivated plots. It seems that the farmers at the urban fringe, having eliminated the bush fallow period, depend mainly on trees on the farmland, especially G. sepium, for the maintenance of soil fertility, as they do not apply fertilizers, while the shifting cultivators retain mainly trees of economic and utilitarian importance on their farms. It is advocated that the shifting cultivators should preserve more trees as farmers at the urban fringe do. This will not only facilitate tree regeneration, on which restoration of soil fertility during the fallow period largely depends, but also help to conserve soil fertility during cropping and to augment farmers’ fuelwood supplies.

Regulation of water flux through tropical forest canopy trees: do universal rules apply?

Tropical moist forests are notable for their richness in tree species. The presence of such a diverse tree flora presents potential problems for scaling up estimates of water use from individual trees to entire stands and for drawing generalizations about physiological regulation of water use in tropical trees. We measured sapwood area or sap flow, or both, in 27 co-occurring canopy species in a Panamanian forest to determine the extent to which relationships between tree size, sapwood area and sap flow were species-specific, or whether they were constrained by universal functional relationships between tree size, conducting xylem area, and water use. For the 24 species in which active xylem area was estimated over a range of size classes, diameter at breast height (DBH) accounted for 98% of the variation in sapwood area and 67% of the variation in sapwood depth when data for all species were combined. The DBH alone also accounted for > or = 90% of the variation in both maximum and total daily sap flux density in the outermost 2 cm of sapwood for all species taken together. Maximum sap flux density measured near the base of the tree occurred at about 1,400 h in the largest trees and 1,130 h in the smallest trees studied, and DBH accounted for 93% of the variation in the time of day at which maximum sap flow occurred. The shared relationship between tree size and time of maximum sap flow at the base of the tree suggests that a common relationship between diurnal stem water storage capacity and tree size existed. These results are consistent with a recent hypothesis that allometric scaling of plant vascular systems, and therefore water use, is universal.

Patterns of Floristic Differentiation among Atlantic Forests in Southeastern Brazil and the Influence of Climate1

ABSTRACTThe tree flora of southeastern Brazilian Atlantic forests was investigated according to two main aspects: (a) the variations in floristic composition of bodi rain and semi‐deciduous forests were analyzed in terms of geographic and climatic variables by performing multivariate analyses on 125 existing floristic checklists; and (b) the links of both rain and semi‐deciduous forests to Amazonian forests and Cerrados (woody savanna) were assessed. All analyses were performed at the species, genus, and family levels. The information obtained for the 125 forest areas was organized into an environmental database containing geographic and climatic records, and a floristic database containing binary presence records for 2532 species, 520 genera, and 106 families. Canonical correspondence analyses (CCA) were utilized to assess the relationship between geographic and climatic variables, and tree flora composition. Venn diagrams and cluster analyses were used to assess the floristic links to Amazonian forests and Cerrados. The following patterns were detected at all three taxonomic levels: (a) the differentiation between rain and semi‐deciduous forests is floristically consistent and strongly correlated with rainfall regime, although transitions may be abrupt to gradual; (b) a north–south differentiation exists for both rain and semi‐deciduous forests, probably caused by variations in both temperature and rainfall regime; (c) The flora of semi‐deciduous forests also changes with increasing distance from the ocean and the associated increasing rainfall seasonality; and (d) elevation and associated temperatures are strongly correlated with the internal differentiation of both rain and semi‐deciduous forests. To a considerable extent, the tree flora of semi‐deciduous forests is a subset of the rain forest flora, probably extracting species that are able to cope with a longer dry season. There is greater floristic similarity at the species level between Atlantic rain and semi‐deciduous forests than between any of these and either Amazonian rain forests or Cerrados. Nevertheless, semi‐deciduous forests and Cerrados show stronger links, particularly at the generic and familial levels. Therefore, rhere is little floristic ground for viewing Atlantic rain forests as being closer to their Amazonian counterparts than to the adjacent semi‐deciduous forests. The most appropriate view of rain and semi‐deciduous forests in southeastern Brazil is that of a continuum in tree species distribution. We suggest that the definition of Atlantic forests should be as comprehensive as that of Amazonian forests.

Long-term permanent plot observations of vegetation dynamics in Budongo, a Ugandan rain forest

Species composition and turnover that have occurred in a series of permanent sample plots established during the 1930s and 1940s in Budongo, a semi-deciduous Ugandan forest, are reported. The plots were established as part of a sequence first used to describe forest succession, five of which have been maintained and which were last measured in 1992-1993. One plot (plot 7) provides 53 y of data from old-growth pristine forest. Plot 15 was established in wooded grassland at the forest edge and is now closed high forest. Evaluation of the remaining three plots is complicated by silvicultural interventions carried out in the 1950s. Forty species have been added since the first evaluations and a total of 188 tree species (over 80% of Budongo's forest tree flora, and including two exotics) has now been recorded from within the plots. The pattern of shade-tolerance in the original plot series conforms to patterns expected for succession with an increasing proportion of shade-tolerant species with development, and large stems appearing to ‘lag behind’ smaller stems in this respect. The time series data are less consistent, and while plot 7 increased in the proportion of shade-tolerant stems through time, the proportion of shade-tolerant species actually declines. Stem-turnover (the mean of mortality and recruitment) slowed with implied successional stage. Most species have a higher recruitment than mortality rate and stem numbers have thus increased in all plots. This is most pronounced in the putatively ‘early successional’ plot. Stem size structure has changed within the plots, with an increased proportion of smaller stems. Species show different rates of turnover and these vary from plot to plot and period to period. In plot 7, the overall mortality rate decreased with initial stem size. Estimates imply that some tree species may easily live longer than 500 y after reaching 10 cm DBH, and that 1000 y is possible. The importance of large trees in determining forest dynamics is illustrated by the finding that death of only seven stems in plot 7 contributed over 60% of net basal area losses recorded over the 53-y observation period. Many of the observed patterns were not predicted and could only have been found by long-term studies.

Patterns of Floristic Differentiation among Atlantic Forests in Southeastern Brazil and the Influence of Climate1

The tree flora of southeastern Brazilian Atlantic forests was investigated according to two main aspects: (a) the variations in floristic composition of both rain and semi-deciduous forests were analyzed in terms of geographic and climatic variables by performing multivariate analyses on 125 existing floristic checklists; and (b) the links of both rain and semi-deciduous forests to Amazonian forests and Cerrados (woody savanna) were assessed. All analyses were performed at the species, genus, and family levels. The information obtained for the 125 forest areas was organized into an environmental database containing geographic and climatic records, and a floristic database containing binary presence records for 2532 species, 520 genera, and 106 families. Canonical correspondence analyses (CCA) were utilized to assess the relationship between geographic and climatic variables, and tree flora composition. Venn diagrams and cluster analyses were used to assess the floristic links to Amazonian forests and Cerrados. The following patterns were detected at all three taxonomic levels: (a) the differentiation between rain and semi-deciduous forests is floristically consistent and strongly correlated with rainfall regime, although transitions may be abrupt to gradual; (b) a north–south differentiation exists for both rain and semi-deciduous forests, probably caused by variations in both temperature and rainfall regime; (c) The flora of semi-deciduous forests also changes with increasing distance from the ocean and the associated increasing rainfall seasonality; and (d) elevation and associated temperatures are strongly correlated with the internal differentiation of both rain and semi-deciduous forests. To a considerable extent, the tree flora of semi-deciduous forests is a subset of the rain forest flora, probably extracting species that are able to cope with a longer dry season. There is greater floristic similarity at the species level between Atlantic rain and semi-deciduous forests than between any of these and either Amazonian rain forests or Cerrados. Nevertheless, semi-deciduous forests and Cerrados show stronger links, particularly at the generic and familial levels. Therefore, there is little floristic ground for viewing Atlantic rain forests as being closer to their Amazonian counterparts than to the adjacent semi-deciduous forests. The most appropriate view of rain and semi-deciduous forests in southeastern Brazil is that of a continuum in tree species distribution. We suggest that the definition of Atlantic forests should be as comprehensive as that of Amazonian forests.