Understanding the links between biodiversity and biogeochemistry in a spatial context within tropical forest plant communities is an unresolved problem. High plant diversity -- phylogenetic, functional, and genetic -- often characteristic of tropical forests, is poorly understood in the context of soils. I collected and georeferenced a large sample of surface soil cores (n=625, 6.25 cm diameter x 10 cm depth) from the Barro Colorado Island (BCI) 50 ha (0.5 km2) Forest Dynamics Plot (FDP), Republic of Panama (9.15 N, 79.8 W) -- described in Chapter One. In Chapter Two, I tested a commonly made assumption in research on plot scales in tropical forests, that abiotic controls entirely explain plot scale soil heterogeneity. To do this, I analyzed a high spatial resolution and multiple spatial scale (multiscale) set of topography features from airborne light detection and ranging (LiDAR), a bedrock map, and the geospatial soil chemical observations to test if abiotic controls (erosion, hydrology, bedrock) were sufficient to explain soil heterogeneity in the BCI tree community. In Chapter Three, I evaluate whether spatial variation in soil organic matter (SOM) and patterns of correlation with rock-derived nutrients are consistent with plants changing soils through litterfall. In Chapter Four, I document the first use of high-throughput DNA sequencing data for observing plant species roots in a tropical forest rhizosphere. The main findings of my dissertation are that at the plot scale in a tropical forest soil chemical heterogeneity was weakly related to abiotic controls and rock-derived macronutrients vary in association strength with soil organic matter in a manner consistent with plants exerting strong biotic controls on the spatial heterogeneity of soil calcium. Furthermore, that research is needed to understand plant nutrient cycling within the context of tropical forest plant communities.