Spatial Variability of Soil Respiration In Row Crops

Using crops or feedstock as a source of cellulosic biofuel has the potential to mitigate harmful environmental consequences like greenhouse gas emissions or deforestation. This has ignited much controversy over the economic and environmental impacts of biofuels, especially greenhouse gas emissions such as carbon dioxide. My project seeks to study one aspect of total carbon dioxide emission—soil respiration—from production of continuous corn, switchgrass, and hybrid poplar trees. Not only has there been controversy in the method used to most precisely measure soil respiration, also known as CO₂ efflux, but we predict there is variation of in-row and between-row measurements due to spatial variability of chamber placement. We are trying to come up with a better measurement protocol that can be used by other researchers to reduce errors. We hypothesize that in-row CO₂ flux is significantly greater than between-row CO₂ efflux, that soil temperature is positively correlated with CO₂ efflux, and there is no significant difference for in-row and between-row switchgrass measurements (used as our control). We used a LI-6400 system weekly to calculate the soil respiration and soil temperature along ten points in one transect of each plot. Additionally, a theta probe measured the soil moisture along the same points. All data analysis was performed using the SAS-JMP statistics package. Essentially, we see a conspicuous trend for in-row soil respiration to be higher than between-row depending on the month and a direct correlation between soil temperature and CO₂ efflux.