Joost F. Duivenvoorden

An analysis of the floristic composition and diversity of Amazonian forests including those of the Guiana Shield.

A large number of newly published and unpublished hectare plots in Amazonia and the Guiana Shield area allow an analysis of family composition and testing of hypotheses concerning alpha-diversity in the south American rain forest. Using data from 94 plots the family-level floristic patterns in wet tropical South America are described. To test diversity patterns, 268 plots are used in this large area. Contrary to a widely held belief, western Amazonian plots are not necessarily the most diverse. Several central Amazonian plots have equal or even higher tree diversity. Annual rainfall is not a good estimator for tree diversity in the Amazonia area and Guiana shield. Plots in the Guiana Shield area (and eastern Amazonia) usually have lower diversity than those in central or western Amazonia. It is argued that this is not because of low rainfall or low nutrient status of the soil but because of the small area of the relatively isolated rain forest area in eastern Amazonia and the Guiana Shield. The low diversity on nutrient-poor white sand soils in the

Distribution and Ecology of Parent Taxa of Pollen Lodged Within the Latin American Pollen Database.

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.

Different floristic patterns of woody understorey and canopy plants in Colombian Amazonia

Distribution patterns of vascular plants with diameter at breast height (dbh) ≥ 2.5 cm were studied on the basis of compositional data from 30 small plots located in a rain-forest area in Colombian Amazonia. The research questions were: How are distribution patterns of species in relation to local abundance in plots? Do understorey species (defined as species with individuals that never attained dbh ≥ 10 cm anywhere) show better correlations with soils and environment than canopy species (defined as species with individuals that attained dbh ≥ 10 cm)? Are patterns found in the entire range of landscape units comparable to those found in well-drained uplands alone? Species that occurred in more than one plot showed higher local abundances. This pattern was consistent among environmental generalists and specialists. Locally rare species (with only one individual in a plot) occurred mostly in well-drained uplands. Considering all landscape units, Mantel tests showed substantial correlations between environmental data (soil chemical data, drainage and flooding) and species composition. Canopy species were only slightly less correlated with environmental data than understorey species. Elimination of the spatial component in the data did not reduce these correlations. In well-drained uplands, understorey species were better correlated with soils than canopy species. Here, however, the spatial configuration of the plots became more important in explaining species patterns.

Distribution and ecology of parent taxa of pollen lodged within the Latin American Pollen Database

The cornerstone of palaeoecological research, concerned with vegetation dynamics over the recent geological past, is a good understanding of the present-day ecology and distribution of the taxa. This is particularly necessary in areas of high floral diversity such as Latin America. Vegetation reconstructions, based on numerous pollen records, now exist with respect to all major vegetation associations from Latin America. With this ever-increasing number of sedimentary records becoming available, there is a need to collate this information and to provide information concerning ecology and distribution of the taxa concerned. The existing Latin American Pollen Database (LAPD) meets the first of these needs. Information concerning the ecology and distribution of the parent taxa responsible for producing the pollen, presently lodged within the LAPD, is the focus of this paper. The ‘dictionary’ describes the ecology and distribution of the parent taxa responsible for producing pollen identified within sedimentary records. These descriptions are based on a wide range of literature and extensive discussions with members of the palaeoecological community working in different parts of Latin America investigating a range of different vegetation types.

Mid- to Late-Holocene pollen-based biome reconstructions for Colombia

Abstract The assignment of Colombian pollen data to biomes allows the data to be synthesised at 10 ‘time windows’ from the present-day to 6000 radiocarbon years before present (BP). The modern reconstructed biomes are compared to a map of modern potential vegetation to check the applicability of the method and the a priori assignment of pollen taxa to plant functional types and ultimately biomes. The reconstructed modern biomes are successful in describing the composition and distribution of modern vegetation. In particular, altitudinal variations in vegetation within the northern Andean Cordilleras are well described. At 6000 BP the biomes are mainly characteristic of warmer environmental conditions relative to those of the present-day. This trend continues until between 4000 and 3000 BP when there is a shift to more mesic vegetation that is thought to equate to an increase in precipitation levels. The period between 2500 and 1000 BP represents little or no change in biome assignment and is interpreted as a period of environmental stability. The influence attributed to human-induced impact on the vegetation is recorded from 5000 BP, but is particularly important from 2000 BP. The extent of this impact increases over the Late-Holocene period, and is recorded at increasingly high altitudes. Despite these changes, a number of sites do not change their biome assignment throughout the analysis. This asynchronous vegetation response is discussed within the context of site location, non-linear response of vegetation to Late-Holocene environmental change, regionally differential signals, localised human impact and methodological artefacts.

Vascular plant species counts in the rain forest of the Middle Caqueta area, Colombian Amazonia

More than 1200 vascular plant species, distributed over 369 genera and 112 families were encountered in ten plots of 0.1 ha in the humid evergreen rain forests of the middle Caquetá area in eastern Colombia. The total number of vascular plant species in the two most diverse plots ranged from 310 to 313 species 0.1 ha-1. These values indicate that high levels of vascular plant species densities may be encountered all over NW Amazonia, including the Colombian Amazon. The floodplain plots contained fewer vascular plant species and families than the well-drained upland plots. The high species density in the well-drained upland plots was mostly due to comparatively large numbers of species found among the very slender trees of diameter at breast (DBH)≤2.5 cm. Small and slender treelets (DBH < 10 cm) are by far the most species rich habit group. About 50% of the total number of vascular plant species in the plots was exclusively collected with a diameter of less than 2.5 cm. Shrubs, (hemi)epiphytes, and climbers were present with relatively few species. Many of the most species-rich families were tree families. The highest species richness was principally found among tree genera, as well. In this respect the floristic sample from the ten species count plots combined shows much affinity to the local florula around Manaus.

Recovery and succession of epiphytes in upper Amazonian fallows

The species richness, number of plants, biomass, and species composition of holo- and hemi-epiphytes were recorded in fifty-six 0.04-ha plots, distributed over forest fallows of 2-30 y old and mature forests in lowland Amazonia (Amacayacu National Park, Colombia). A total of 9190 epiphytic plants representing 162 species were recorded on 4277 phorophytes. Seventy species were classified as holo-epiphyte and 85 as hemi-epiphyte. Aroids were most diverse (58 species) and represented 76% of the total recorded biomass. Anemochory was more dominant among holo-epiphytes and zoochory among hemi-epiphytes. The species richness, density and biomass of both holo and hemi-epiphytes increased significantly from young fallows to old fallows and mature forests. Hemi-epiphytes had greater density and biomass than holo-epiphytes. In canonical ordination, forest age did not relate to the species composition of holo-epiphytes. However, for hemi-epiphytes, the age effect was significant, suggesting that species turnover takes place in the ageing fallows.

Response of pollen diversity to the climate-driven altitudinal shift of vegetation in the Colombian Andes

Change in diversity of fossil pollen through time is used as a surrogate for biodiversity history. However, there have been few studies to explore the sensitivity of the measured pollen diversity to vegetation changes and the relationship between pollen diversity and plant diversity. This paper presents results of a study to assess the relationship between pollen diversity and relative abundance of pollen from different altitudinal vegetation belts (subandean forest, Andean forest, subparamo and grassparamo) in three records from the tropical Andes in Colombia. The results indicated that plant diversity in the vegetation declined with altitude and pollen diversity is positively correlated to the abundance of pollen from lower altitude vegetation belts and negatively correlated to that from the grassparamo. These results, therefore, suggest that pollen diversity coarsely reflects the diversity of the surrounding vegetation. Using this interpretation, we were able to predict changes in plant diversity over the past 430 000 years in the Colombian Andes. Results indicated that under warmer climatic conditions, more species-diverse vegetation of low elevation moved upslope to contribute more pollen diversity to the study sites, and under colder conditions, species-poor grassparamo moved downslope and observed pollen diversity was lower. This study concludes that fossil pollen diversity may provide an important proxy to reconstruct the temporal changes in plant diversity.

Regional patterns of well drained upland soil differentiation in the middle Caqueta basin of Colombian Amazonia

Abstract As part of a land-ecological survey of the middle Caqueta basin in Colombian Amazonia, a total of 41 well drained upland soil profiles under primary rain forest was studied. Two soil groups were recognised on the basis of principal components analysis (PCA). Soils pertaining to the first group cover about 45–60% of the well drained uplands and classify as Afsols and Acrisols. They are characterised by fine textured, reddish B horizons, and are low in exchangeable bases, but high in exchangeable Al. Furthermore, they contain relatively high total nutrient reserves. Soils pertaining to the second group cover about 35–50% of the well drained uplands and classify as Acrisols and Ferralsols. These soils are characterised by medium textured, yellowish B horizons within 100 cm depth, are low in exchangeable bases and Al, and show very low total nutrient reserves. The soils of the Ali-Acrisol group are mostly developed in Andean-origin deposits of the low terraces of the Caqueta River and the Tertiary Pebas formation. The soils of the Acri-Ferralsol group are mostly developed on shield-derived medium to coarse textured Tertiary deposits and are also found on Palaeozoic sandstone outcrops. The differences between the soils of the two groups are, therefore, principally related to variation in the parent materials and reflect the principal geological structure of the middle Caqueta area. A similar kind of well drained upland soil differentiation is found in the Colombian Amazon area as a whole, including footslope areas near the Andes, and probably also in adjacent parts of Peru and Brazil. The presence of the soils of the Acri-Ferralsol group in the middle Caqueta area and in NW Amazonia is in conflict with general statements that well drained upland soils in upper Amazonia would be less weathered than those from central or eastern Amazonia. The reddish or yellowish colour of the B horizon within a depth of 100 cm provides a practical field characteristic to distinguish the two groups of soils. The colour of the B horizons seems mainly related to dynamics of the soil organic matter. In sandy profiles of the soils from the Acri-Ferralsol group a slight degree of podzolisation may occur in the topsoil. Current international soil classification systems do not adequately separate the two well drained upland soil groups in the middle Caqueta area beacuse total nutrient reserves are not sufficiently incorporated and too much emphasis is laind on th presence of a clay increase.

Strong effects of a plantation with Pinus patula on Andean subpáramo vegetation: a case study from Colombia

Abstract The effect of a pine plantation on a native subparamo system in the Andes of Colombia (3100 m above sea level) was studied. The vegetation of an 8 year-old plantation with Pinus patula was compared to that of the surrounding native subparamo. 59 plots made in the subparamo vegetation contained 121 vascular plant species. These plots were classified into three subparamo communities and one Andean scrub community. Sixty-four plots made in the pine plantation contained 76 vascular plant species and were subdivided into four classes of pine cover. With increasing pine cover, pine plantation plots tended to become less similar to the subparamo communities. Habitat-specific subparamo species tended to disappear with increasing pine cover. After controlling for the effects of environmental variables in a partial canonical correspondence analysis, pine cover had a significant impact on plant species patterns. It is concluded that afforestation with Pinus patula resulted in strong negative effects on diversity and composition of the subparamo vegetation at the study site.