Executive Function and IQ Predict Mathematical and Attention Problems in Very Preterm Children

Objective of this study was to examine the impact of executive function (EF) on mathematical and attention problems in very preterm (gestational age ≤ 30 weeks) children. Participants were 200 very preterm (mean age 8.2 ± 2.5 years) and 230 term children (mean age 8.3 ± 2.3 years) without severe disabilities, born between 1996 and 2004. EFs assessed included verbal fluency, verbal working memory, visuospatial span, planning, and impulse control. Mathematics was assessed with the Dutch Pupil Monitoring System and parents and teachers rated attention problems using standardized behavior questionnaires. The impact of EF was calculated over and above processing speed indices and IQ. Interactions with group (very preterm versus term birth status) were examined. Analyses were conducted separately for two subsamples: children in preschool and children in primary school. Very preterm children performed poorer on tests for mathematics and had more parent and teacher rated attention problems than term controls (ß_s>.11, P_s<.01). IQ contributed unique variance to mathematics in preschool and in primary school (ß_s>.16, P_s<.007). A significant interaction of group with IQ (ß = −. 24, P = .02) showed that IQ contributed unique variance to attention problems as rated by teachers, but that effects were stronger for very preterm than for term infants. Over and above IQ, EF contributed unique variance to mathematics in primary school (ß = .13, P<.001), to parent rated inattention in preschool and in primary school (ß_s>−.16, P_s<.04), and to teacher rated inattention in primary school (ß = −.19; ß = .19, P_s<.009). In conclusion, impaired EF is, over and above impaired IQ, an important predictor for poor mathematics and attention problems following very preterm birth.     

Successional Position of Dry Andean Dwarf Forest Species as a Basis for Restoration Trials

The successional affinity of nine woody species was inferred from the structure, diversity and disturbance history of the vegetation where these occurred. This was done in order to obtain a basis for a restoration experiment, currently in execution, in the dry Andean dwarf forest zone on the edge of the High Plain of Bogotá (Colombia), at 2600–2950 m.a.s.l. We laid out 101 relevees in grassland and shrubland types in different stages of recovery, and in relatively little disturbed endemic Condalia thomasiana dwarf forest. The disturbance history of sites over the last ~60 years was inferred from aerial photograph series (1941–1991). CCA and logistic regression were applied to relate species composition to diversity, environment and disturbance history. All species showed a preference for certain structural groups. Also, a clear relation between species occurrence and vegetation diversity was found. Baccharis macrantha, and Dalea coerulea appeared relatively tolerant to grazing, while the remaining seven species reacted negatively. Soil clay content, base availability and organic carbon content was also an important factor for occurrence of each species. Invasion of grasslands by woody species is pioneered by Baccharis macrantha and followed by Dodonaea viscosa. Dalea coerulea was predominantly found on truncated clayey soils, which will probably not support Condalia dwarf forest. The hypothesized classification of the nine planted species to either pioneers or late-successional was fine-tuned. This exploratory study will be of use in the set-up of future succession-based restoration experiments, and for converting exotics afforestations to natural vegetation.     

Fine litter input to terrestrial humus forms in Colombian Amazonia

A comparative litter fall study was made in five rain forest stands along a gradient of humus form development and soils in the Amazon lowlands of eastern Colombia. The total fine litter fall was highest in a plot on a well drained soil of the flood plain of the Caquetá River (1.07 kg · m^-2 · y^-1), lower in three plots on well drained upland soils (0.86, 0.69, and 0.68 kg · m^-2 · y^-1), and lowest in a plot on a poorly drained, upland podzolised soil (0.62 kg · m^-2 · y^-1). In the four upland plots, leaf litter fall patterns were highly associated, which points at climatic regulation. Litter resource quality, as represented by nutrient concentrations and area/weight ratio of the leaf litter fall, was comparatively high in the flood plain plot. In the upland plots, concentrations and fluxes of Ca, Mg, K, and P were as low as in oligotrophic central Amazonian upland forests. This questions generalisations that the western peripheral region of the Amazon basin should be less oligotrophic than central Amazonia. The upland plot on the podzolised soil showed the lowest concentrations and fluxes of N. Mean residence times of organic matter and nutrients in the L horizons hardly differed between the five plots, suggesting that edaphic properties and litter resource quality are of little importance in the first step of decomposition. Mean residence time of organic matter in all ectorganic horizons combined (estimated on the basis of litter input and necromass on the forest floor, and uncorrected for dead fine root input) varied from 1.0 y in the flood plain forest, 1.1–3.3 y in the well drained upland forests, and 10.2 y in the forest on the podzolised soil.     

Tree species composition and rain forest-environment relationships in the middle Caquetá area,Colombia, NW Amazonia

As part of an integrated forest vegetation and soil survey, tree species composition (DBH 10 cm) was recorded in 95 plots of 0.1 ha, distributed over the principal physiographic units in the middle Caquetá area, Colombian Amazonia. A total of 1077 tree species was found, classified into 271 genera and 60 families. Leguminosae and Sapotaceae show high familial importance values in all physiographic units. Lauraceae, Chrysobalanaceae, Moraceae, and Lecythidaceae are more important on well drained (flood plain or upland) soils, while Palmae, Guttiferae, Bombacaceae, and Apocynaceae are more important in swamps and on podzolised (white sand'rs) soils. Plots on well drained soils show a lower degree of dominance than plots in swamps or on podzolised (white sand) soils. The composition of the most dominant species in the plots changes continuously. Most species (59%) are only recorded in one plot. Individual plot pairs generally show a low overlap of about 2–5 tree species, resulting in Jaccard coefficients below 20%.complementary to a previous forest classification based on TWINSPAN analyses, detrended and canonical correspondence analyses were carried out, using CANOCO 3.1. Despite of a low amount of tree species variance explained (only 6.2% by the first two canonical axes), meaningful patterns of tree species composition were recognised. These are most strongly related to drainage, flooding, humus forms, and soil nutrient status. Forest types are well separated in the CCA ordination diagram. The most frequently found tree species are listed according to their preference with respect to drainage, flooding, and soil nutrient status.Tree species composition in the well drained upland forests was analysed separately. In view of the model explaining high NW Amazonian tree species diversity on the basis of dense community packing and high beta diversity along soil gradients, the canonical analysis here focused on the effect of soils. By means of partial canonical ordination it was found that patterns of tree species composition depended significantly on soil properties, even though the edaphic component explains only a small fraction of the tree species variance. The results show that the well drained uplands of the middle Caquetá area are covered by a complex of two intergrading tree species assemblages. The first assemblage (community of Goupia glabra-Clathrotropis macrocarpa) is associated to some-what less poor, clayey soils developed in Andean origin deposits or Tertiary sediments from the Pebas formation. The second assemblage (community of Swartzia schomburgkii-Clathrotropis macrocarpa) shows affinities to very poor, loamy soils developed in parent materials derived from the Guiana shield. This simple dichotomous pattern of geology, soils, and forest types is incompatible with concepts of high soil heterogeneity and associated beta diversity controlling tree species diversity in well drained uplands of NW Amazonia. The gradient length of tree species in the detrended correspondence analysis was low (3.7 SD), also suggesting a low beta diversity.     

Vascular plant species counts in the rain forests of the middle Caquetá 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.     

Recent Changes in Patch Characteristics and Plant Communities in the Jalca Grasslands of the Peruvian Andes

Habitat loss and fragmentation are considered major threats to biodiversity, especially in tropical mountain ecosystems. Most studies focus on the relationships between biodiversity and patch characteristics such as patch size, connectivity or degree of contrast with the surrounding matrix, but leave the rate of change within these variables little explored. We analyzed the importance of changes in patch characteristics over time on species diversity and species composition in the paramo of northern Peru, a tropical grassland ecosystem, locally known as jalca. We obtained land use/cover maps for 1987 and 2007 spanning an area of 6300 km², and quantified land use change, jalca patch characteristics and their proportional changes over 20 yr. In 2009, 371 vascular plant species were recorded in 92 plots, each plot representative of single patches. Between 1987 and 2007, jalca cover decreased from 47 to 35 percent due to encroaching agriculture. This activity showed an upward shift probably favored by climate change. The number of jalca patches increased, mean patch size decreased, and the patches showed a higher contrast with the surrounding matrix. Multiple linear regression failed to show that species diversity relates to changes in patch characteristics. Canonical correspondence analysis indicated that species composition relates to the degree of contrast between the patch and its surrounding matrix and its changes through time. We concluded that changes in patch characteristics are important only for species composition. This study highlights the importance of considering matrix management with a long term perspective for conservation efforts.     

Patterns of plant species composition on Amazonian sandstone outcrops in Colombia

Vascular plant species compositional patterns of the low forest, scrub, and herbaceous vegetation on white sand soils and sandstone substrates were studied at six sandstone plateaus in Colombian Amazonia, by means of a field survey according to the Braun‐Blanquet relevé method. Canonical Correspondence Analysis (CCA) was applied to separate effects of habitat and spatial configurations of the plateaus on species patterns. Also, information on dispersal ability and phytogeographic affinity of species was used to test explanations for between plateau differences. Low trees, shrubs and herbs were the main species recorded in 212 relevés. The main gradients in the species patterns were linked to the spatial configuration of the plateaus. Spatially controlled species patterns were mainly related to soil depth and soil organic matter. The association between phytogeographic affinity and the habitat controlled spatial link of species pointed at insufficient sampling at one plateau. Dispersal ability did not explain the habitat controlled spatially distributed occurrences of plant species. This might indicate a low frequency of local extinctions at the sandstone plateaus, especially of the poorly dispersed species, possibly because plant populations survive fire or drought disturbances in local sheltered places. Space and habitat controlled species patterns at one plateau were quite distinct from patterns at the other plateaus. This might be due to unmeasured habitat factors (e.g. unrecorded soil variation or human disturbance history) or the preferential, surveyor biased sampling procedure.