A.M. Cleef

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.

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.

Successional age and forest structure in a Costa Rican upper montane Quercus forest

Changes in structure of a Costa Rican upper montane Quercus forest were studied in twelve 0.1 ha plots along a chronosequence including 8- to 20-year-old Early Secondary Forest (ESF), 25- to 32-year-old Late Secondary Forest (LSF) and mature Primary Forest (PF). In 1.2 ha 2854 stems ≥ 3.0 cm dbh belonging to 42 tree species were recorded. Tree species richness per 0.1 ha ranged from 15 to 30. Diversity indices did not change significantly during succession. Stem density did not differ significantly among successional phases, while basal area was significantly higher in PF than in ESF and LSF. Maximum canopy height and basal area increased linearly during the first three decades of recovery. Height and dbh showed a significant, logarithmic regression for all forest phases. A period of 84 y was estimated as the theoretically minimum time needed for structural recovery. The maximum canopy height and basal area recovered two to five times slower in upper montane than in lower montane or lowland Neotropical forests.

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.

High altitude C4 grasslands in the northern Andes: relicts from glacial conditions?

The altitudinal vegetation distribution in the northern Andes during glacial time differed from the present-day conditions as a result of temperature and precipitation change. New evidence indicate that as a response to a reduced atmospheric partial CO(2) pressure (pCO(2)), the competitive balance between C(3) and C(4) plants have changed. Effects may have remained virtually undetected in pollen records, but can be observed using a stable carbon isotope analysis. Vegetation dominated by C(4) taxa, belonging to the families Cyperaceae (e.g. Bulbostylis and Cyperus) and Poaceae (e.g. Muhlenbergia, Paspalum and Sporobolus), may have been able to replace for a significant part the modern type C(3) taxa (e.g. species belonging to Carex, Rhynchospora, Aciachne, Agrostis, Calamagrostis, and Chusquea). Impact of reduced glacial atmospheric pCO(2) levels and lower glacial temperatures on the composition and the elevational distribution of the vegetation types is discussed. The present high Andean vegetation communities may differ from the glacial equivalents (non-modern analogue situation). We identified dry Sporobolus lasiophyllus tussock grassland and Arcytophyllum nitidum dwarfshrub paramo as the possible relict communities from glacial time. The effect on previous estimates of paleo-temperatures is estimated to be small.

Altitudinal zonation of montane Quercus forests along two transects in Chirripó National Park, Costa Rica

Abiotic and vegetation data were collected along two altitudinal transects through mature montane Quercus forests on the Pacific and Atlantic slopes of Costa Ricas Chirripó Massif. Between 2000 and 3200 m asl twenty-four 0.05 ha forest plots were selected at altitudinal intervals of 100 m, and eight soil profiles were described at intervals of 200 m. A TWINSPAN classification aided in the determination of eight zonal forest communities on the basis of their floristic composition. They are grouped in two sets of four: (i) the palm-rich lauraceous-fagaceous Lower Montane Mollinedia-Quercus Forests (2000–2600 m asl) and (ii) the bamboo-rich myrsinaceous-fagaceous Upper Montane Schefflera-Quercus Forests (2500–3200 m asl), respectively. Vegetation changes seem correlated with two major climatic gradients: (i) a temperature gradient (altitude), and (ii) a moisture gradient (wet Atlantic vs. moist Pacific slope). Most soils are Andepts, and residual, colluvial or derived from volcanic material. Humus layers are thicker on the wetter Atlantic slope. A total of 431 vascular plant species consisted of 86 pteridophytes, 1 gymnosperm, 296 dicots and 48 monocots. Species richness, canopy height and stem diameter decrease with increasing altitude, while the canopy surface becomes more flattend. A comparison with other studies shows that Chirripós montane Quercus forests fit within the environmental ranges known from altitudinal zonations elsewhere in the Tropics.

Phytogeography of Talamanca Montane Quercus Forests, Costa Rica

Phytogeographical patterns of the vascular generic flora of the montane Quercus forests in the Cordillera de Talamanca, Costa Rice, have been studied. With the exception of orchids and bromeliads, 114 families and 253 genera have been recorded, of which eighty are trees, seventy-seven shrubs, forty-four herbs, twenty-one climbers and thirty-one ferns. About 75% of all genera are tropical in distribution. The remaining 25% is made up of temperate (17%) and cosmopolitan (8%) genera. The neotropical element is best represented and contributes to almost half of the genera (46%), whereas the tropical afroamerican element is worst represented (3%). This overall spectrum does not differ much from the spectrum of woody genera alone. Only the percentage of cosmopolitan genera is significantly reduced among the woody genera since most cosmopolitan genera are herbs (14%) and ferns (29%). Tree genera are mainly neotropical, tropical malayo-american and pantropical in distribution, while shrub genera are principally neotropical (over 60%, mostly Andean-centered), pantropical and northern or southern temperate. Herb genera are basically neotropical, pantropical and wide-temperate, climber genera mainly neotropical and pantropical, while fern genera expose fundamentally cosmopolitan, pantropical and neotropical distributions respectively. The Talamanca woody spectrum has been compared to spectra available from Mexican and Colombian montane Quercus forests. Analysis reveals a greater phytogeographical affinity with the Northern Andes than with the Mexican Neovolcanic Belt. This is probably due to the Nicaraguan depression, which separates mountain ranges on the Central American landbridge and thus serves as a mayor barrier to dispersal of montane plant taxa in the Neotropics. Also the drier climatic conditions prevailing in Mexican montane forests may play an important role in floristic (dis)similarity trends.

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.

Pollen representation and successional vegetation change on the sandstone plateau of Araracuara, Colombian Amazonia

The floral composition of the vegetation on the sandstone plateaus near Araracuara (Colombian Amazonas) was studied on the basis of 92 vegetation relevees. We compared the vegetation data with samples of the modern pollen rain in the 18 relevees that had non-barren pollen samples. By using the association index of Davis [Rev. Palaeobot. Palynol. 40 (1984) 295–315] and correspondence analysis, we evaluated to which degree pollen spectra reflect the actual vegetation. Rain forest taxa appeared overrepresented in the pollen rain on the sandstone plateau. Poaceae, Xyris, Cyperaceae, and Melastomataceae showed highest correspondence between pollen rain and measured vegetation cover, whereas Bonnetia, Bromeliaceae, and Ochnaceae showed an intermediate level of accuracy. Pollen analysis of a 25-cm sediment core, reflecting vegetation changes on the Araracuara sandstone plateau during the latest Holocene cm, showed a transition from open Rapateaceae-dominated vegetation to a Bonnetia martiana-dominated scrub. Successional stages in the pollen record were interpreted as discrete vegetation communities in the field, all occurring at present day as part of a mosaic-like vegetation. The pollen record included a substantial number of genera and families in which C4 and CAM physiological pathways are common.

Tree architecture and secondary tropical rain forest development: A case study in Araracuara, Colombian Amazonia

Summary Four successional forests, the oldest 30 years old, and a mature forest on the low terrace of the Caqueta river (Colombian Amazonia), were analysed architecturally. The architecture of these secondary forests was largely determined by species of Vismia , Miconia and Inga reaching their maximal crown expansion during the first 30 years of secondary forest development. Forest profiles were drawn to scale, indicating the development phase of every tree (Dbh > 5 cm). Three development phases were distinguished according to crown architecture, i.e. potential trees, trees of the present and trees of the past. These development phases were used to determine the dynamics of the species within the secondary forest A first approximation of the secondary forest development in Araracuara is as follows: 1. Within seven years a set of trees of the present (Vismia glaziovii and Miconia minutiflora) develop a low ( 2. Between seven and eleven years Vismia japurensis and Vismia macrophylla develop a higher (10–15 m) canopy of trees of the present making survival of the previous set of the present impossible. Again potential trees of other species are present, some of them emerging. 3. Around 20 years Miconia poeppigii, Miconia myriantha, Jacaranda copaia and several Inga species form a still higher (c. 20 m) canopy of trees of the present, making survival of the Vismia set almost impossible. Most potential trees in this development phase are lower than the trees of the present, some are still emerging, i.e. Cecropia spp. A lower (ca. 10m) set of the present is formed by several Miconia species already present from the initiation of the succession ( Miconia prasina, Miconia pilgeriana, Miconia punctata, Miconia splendens ) and Piper arboreum 4. Around 30 years the canopy of Miconia and Inga species starts to degenerate. Potential trees grow into the gaps. 5. In the mature forest the formation of gaps by trees of the past is the most important factor in the regeneration From every tree species encountered in the transects documented by profiles, the basic branching pattern, i.e. architectural model (sensu HALLE et al. 1978), was determined. For every transect an architectural spectrum was made. These spectra show the numbers of individuals and species having the same architectural models. By approximation, the results are broadly in agreement with earlier research from French Guyana. Young secondary forests have many individuals with Rauhs model, together with many individuals with Rouxs model, and few individuals with Trolls and Massarts model, and certainly few species with those models. In mature forest there is a large number and great variety of Trolls model, Massarts model and often Aubrevilles model, and still quite a number of individulas with Rauhs model. Rouxs model is found in the understorey of the mature forest