Variations in Soil Chemistry and Biological Activity with Tree Cover in an Urban Nature Center

This research examines variations in soil respiration associated with a woodland, versus solitary trees within a savanna, including both an oak and a pine tree, all in an urban nature center.  In addition to soil respiration, soils were analyzed for bulk density and macronutrient content (phosphorus, nitrogen, and potassium).  Soil respiration, the exchange of gases by living organisms in soil, is measured by carbon dioxide emissions over time.  It is expected that the respiration rate in the woodland will be lower than in the vicinity of solitary trees within the savanna.  Single trees may have lower nutrient uptake, leaving more soil nutrients to support other soil organisms.  It is also expected that lower soil respiration rates will correlate with lower concentrations of macronutrients within the soil.  Standard methods of the U.S. Department of Agriculture were used for all the tests.  In the savanna, soil respiration rate, bulk density, and nitrogen, phosphorus, and potassium content were measured at increasing distances from tree bases in order to assess the impact of tree coverage.  The results indicate that the woodland has a lower soil respiration rates compared to areas near solitary trees.  The research allowed for the exploration of the variability in tree coverage and tree species and relationships of these variables to respiration rate and macronutrient concentration.  This research demonstrates variations in soils within two distinct ecosystems, and possibly variations due to different species of trees.