Relationships Among Soil Properties and Soil CO2 Efflux in a Loblolly Pine-Switchgrass Intercropped System

Abstract

The components of soil CO2 efflux are affected by many soil properties including temperature, moisture, microbial abundance and activity, and other soil physical and chemical properties. Changes in these factors can result in high spatial and temporal variability of total soil CO2 efflux. Low molecular weight organic acids (LMWOAs), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), microbial biomass and activity were measured to evaluate the impact of intercropping switchgrass (Panicum virgatum L.) in a loblolly pine (Pinus taeda L.) plantation. Surface soil samples (0-15 cm) were collected on the bed (PSG-B), interbed (PSG-I) and edge (PSG-E) of pine-switchgrass intercropped treatments, as well as pine only (P-B) and switchgrass only (SG-I) treatments. Differences in most soil properties and processes of intercropped treatments were sporadic and most did not show clear trends. However, significant correlations between DOC, soil temperature, oxalic and acetic acids and soil CO2 efflux were present. In an multiple regression model these factors explained 57% of the variance in total soil CO2 efflux. Therefore we think that LMWOAs, as a labile component of DOC, are influencing total CO2 efflux because they are being consumed by microbial community, increasing heterotrophic respiration and as a result overall total CO2 efflux. The amount and distribution of labile C controls microbial community dynamics, heterotrophic respiration as well as the stabilization of soil C.