ABSTRACT
Soil and forest structure in the Colombian Amazon. Forests structural differences could result of environmental variations at different scales. Because soils are an important component of plant’s environment, it is possible that edaphic and structural variables are associated and that, in consequence, spatial autocorrelation occurs. This paper aims to answer two questions: (1) are structural and edaphic variables associated at local scale in a terra firme forest of Colombian Amazonia? and (2) are these variables regionalized at the scale of work? To answer these questions we analyzed the data of a 6ha plot established in a terra firme forest of the Amacayacu National Park. Structural variables included basal area and density of large trees (diameter≥10cm) (Gdos and Ndos), basal area and density of understory individuals (diameter<10cm) (Gsot and Nsot) and number of species of large trees (sp). Edaphic variables included were pH, organic matter, P, Mg, Ca, K, Al, sand, silt and clay. Structural and edaphic variables were reduced through a principal component analysis (PCA); then, the association between edaphic and structural components from PCA was evaluated by multiple regressions. The existence of regionalization of these variables was studied through isotropic variograms, and autocorrelated variables were spatially mapped. PCA found two significant components for structure, corresponding to the structure of large trees (G, Gdos, Ndos and sp) and of small trees (N, Nsot and Gsot), which explained 43.9% and 36.2% of total variance, respectively. Four components were identified for edaphic variables, which globally explained 81.9% of total variance and basically represent drainage and soil fertility. Regression analyses were significant (p<0.05) and showed that the structure of both large and small trees is associated with greater sand contents and low soil fertility, though they explained a low proportion of total variability (R² was 4.9% and 16.5% for the structure of large trees and small tress, respectively). variables with spatial autocorrelation were the structure of small trees, Al, silt, and sand. Among them, Nsot and sand content showed similar patterns of spatial distribution inside the plot. Rev. Biol. Trop. 59 (3): 1307-1322. Epub 2011 September 01.
Las diferencias estructurales del bosque pueden ser el producto de variaciones ambientales a diferentes escalas, entre ellas los suelos. Para evaluar tal asociación, se usaron los datos de estructura del bosque y de suelos de una parcela de 6ha establecida en un bosque de tierra firme de la Amazonía colombiana. Las variables edáficas y estructurales se redujeron con un análisis de componentes principales (ACP) y un análisis de regresión múltiple verificó si existía asociación entre los componentes edáficos y estructurales del ACP. La regionalización de las variables de estudio se verificó con variogramas isotrópicos; además, se construyeron mapas de distribución espacial. El ACP de las variables estructurales identificó dos componentes: dosel y sotobosque, los cuales explicaron el 43.9 y 36.2% de la varianza total, respectivamente; para las variables edáficas los cuatro primeros componentes explicaron globalmente el 81.9% de la varianza total. Los análisis de regresión mostraron que tanto el dosel como el sotobosque se asocian con mayores contenidos de arena y baja fertilidad del suelo (p<0.05), pero explicaron una proporción baja de la variabilidad total (R²=4.9% para dosel y 16.5% para sotobosque). Las tres variables de la estructura del sotobosque, Al, limo y arena presentaron autocorrelación espacial.
Subject(s)
Soil/chemistry , Trees/classification , Colombia , Principal Component AnalysisABSTRACT
A análise exploratória de dados espaciais, empregada para identificação de arranjos urbano-regionais entre os municípios brasileiros, mostrou-se adequada a estudos de conjuntos amplos de unidades observacionais (áreas), possibilitando resultados reveladores de dinâmicas territoriais e de padrões de correlações espaciais entre municípios. Associada a informações de centralidade (rede de cidades), conectividade (sistema viário principal) e densidade dos movimentos pendulares da população, evidenciou conjuntos mais amplos do que as aglomerações urbanas apontadas em estudos precedentes. Tais conjuntos correspondem a morfologias que transcendem as tradicionais aglomerações definidas por manchas contínuas de ocupação entre mais de um município, constituindo-se em categorias espaciais ainda mais complexas do ponto de vista de concentração populacional, econômica e funcional e densidade de deslocamentos de pessoas. Este artigo coloca em discussão o uso dessa técnica de análise, suas possibilidades e limitações.
El análisis exploratorio de datos espaciales, empleado para la identificación de ordenamientos urbano-regionales entre municipios brasileños, se mostró adecuado para estudios de conjuntos amplios de unidades observacionales (áreas), posibilitando resultados reveladores de dinámicas territoriales y patrones de correlaciones espaciales entre municipios. Asociado a informaciones sobre centralidad (red de ciudades), conectividad (sistema vial principal) y densidad de los movimientos pendulares de población, evidenció conjuntos más amplios que las aglomeraciones urbanas apuntadas en estudios precedentes. Tales conjuntos corresponden a morfologías que transcienden las tradicionales aglomeraciones definidas por manchas continuas de ocupación de más de un municipio, constituyéndose en categorías espaciales todavía más complejas desde el punto de vista de la concentración poblacional, económica y funcional, y de densidad de desplazamientos de personas. Este artículo pone en tela de juicio el uso de esa técnica de análisis, sus posibilidades y limitaciones.
Exploratory analysis of spatial data, carried out to identify different regional urban arrangements between Brazilian municipalities, proved to be useful for studies on various areas of observation. This makes it possible to arrive at important findings related to territorial dynamics and patterns of spatial correlations between municipalities. This analysis, associated with information on centrality (networks of cities), connectivity (general street and highway systems) and density of pendular movements of the population, showed groupings that extend beyond the large urban agglomerations found in earlier studies. These newer types of groupings correspond to morphologies that transcend traditional agglomerations defined by continuous urban sprawls that involve more than one municipality. They consist of spatial categories that are even more complex from the point of view of demographic, economic and functional concentrations and in terms of the density of human displacements. This article brings up the discussion of the use of this analysis technique, together with its possibilities and limitations.