The anticipated negative impacts of climate change coupled with rising gasoline prices have prompted the search for alternatives to fossil fuels. Utilizing forest biomass for biofuel production has emerged as a promising approach. However, very little research has focused on how to simultaneously grow biomass for biofuel production while still managing for high quality wood products. Furthermore, the potential effect that this could have on long-term soil productivity is critical for the viability of such an intensive management system. As a result of this gap in scientific knowledge, a long term study has been established in a recently harvested 35 year old loblolly pine (Pinus taeda L.) plantation that investigates the effects of intercropping and biomass management on site productivity and sustainability. The study consists of the following treatments with and without logging residuals for a total of six treatments replicated four times: 1) traditional loblolly pine plantation, 2) loblolly pine with switchgrass (intercropped) between beds, and 3) loblolly pine establishment with flat-planted pine trees between crop tree beds. Pure stands of switchgrass were also established to help elucidate the effects of converting a forest ecosystem to a grassland ecosystem. The site preparation for each of these treatments varied in intensity and number of entries. The impacts of these non-traditional land management approaches on soil sustainability and productivity were evaluated. A first step in evaluating the conversion of monoculture plantations to a dual-crop system was to evaluate the potential impacts associated with land clearing for establishing switchgrass and the removal of coarse woody debris on the ‘without logging residuals’ treatments. Soil compaction measurements were obtained using a soil penetrometer to a depth of 30 cm at 2.5 cm intervals before and after treatment installation
Results/Conclusions
There were no significant differences in soil compaction before and after treatment installation. The average reading across all treatments at the soil surface was 201 kPa which increased to 1539 kPa and 1923 kPa at 15cm and 30cm depths, respectively. Clearing and site preparation treatments did not adversely affect soil tilth. The conversion of monoculture plantations into a dual-crop system consisting of switchgrass and loblolly pine is a feasible and sustainable practice at this time.
