@article{cacho_youssef_shi_chescheir_skaggs_tian_leggett_sucre_nettles_arellano_2019, title={Impacts on soil nitrogen availability of converting managed pine plantation into switchgrass monoculture for bioenergy}, volume={654}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2018.11.133}, abstractNote={Biofuels derived from lignocellulosic materials is one of the options in addressing issues on climate change and energy independence. One of the most promising bioenergy crops is switchgrass (Panicum virgatum L.), particularly in North America. Future advancement in large-scale conversion of lignocellulosic feedstocks and relatively more competitive price for biomass and other economic advantages could lead to landowners opting to venture on switchgrass monoculture (SWITCH) in lieu of loblolly pine monoculture (PINE). Therefore, we investigated the conversion of previously managed loblolly pine stand into SWITCH in eastern North Carolina, U.S.A. on soil N availability. Treatments included PINE, SWTICH, and mature loblolly pine stand (REF). Each treatment was replicated three times on 0.8 ha plots drained by open ditches dug 1.0–1.2 m deep and spaced at 100 m. Rates of net N mineralization (Nm) and nitrification (Nn) at the top 20 cm were measured using sequential in-situ techniques in 2011 and 2012 (the 3rd and 4th years of establishment, respectively) along with a one-time laboratory incubation. On average, PINE, SWITCH, and REF can have field net Nm rates up to 0.40, 0.34 and 0.44 mg N·kg soil−1·d−1, respectively, and net Nn rates up to 0.14, 0.08 and 0.10 mg N·kg soil−1·d−1, respectively. Annually, net Nm rates ranged from 136.98 to 167.21, 62.00 to 142.61, and 63.57 to 127.95 kg N·ha−1, and net Nn rates were 56.31–62.98, 16.45–30.45, 31.99–32.94 kg N·ha−1 in PINE, SWITCH, and REF, respectively. Treatment effect was not significant on field Nm rate (p = 0.091). However, SWITCH significantly reduced nitrate-N production (p < 0.01). Overall, results indicated that establishment of SWITCH on poorly drained lands previously under PINE is less likely to significantly impact total soil N availability and potentially has minimum N leaching losses since soil mineral N under this system will be dominated by ammonium-N.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Cacho, Julian F. and Youssef, Mohamed A. and Shi, Wei and Chescheir, George M. and Skaggs, R. Wayne and Tian, Shiying and Leggett, Zakiya H. and Sucre, Eric B. and Nettles, Jami E. and Arellano, Consuelo}, year={2019}, month={Mar}, pages={1326–1336} }
 @article{tian_cacho_youssef_chescheir_fischer_nettles_king_2017, title={Switchgrass growth and pine-switchgrass interactions in established intercropping systems}, volume={9}, ISSN={["1757-1707"]}, DOI={10.1111/gcbb.12381}, abstractNote={Abstract}, number={5}, journal={GLOBAL CHANGE BIOLOGY BIOENERGY}, author={Tian, Shiying and Cacho, Julian F. and Youssef, Mohamed A. and Chescheir, George M. and Fischer, Milan and Nettles, Jami E. and King, John S.}, year={2017}, month={May}, pages={845–857} }
 @article{cacho_youssef_chescheir_skaggs_leggett_sucre_nettles_arellano_2015, title={Impacts of switchgrass-loblolly pine intercropping on soil physical properties of a drained forest}, volume={58}, DOI={10.13031/trans.58.11238}, abstractNote={Intercropping switchgrass ( L.) with managed loblolly pine ( L.) has been proposed as an alternative source of bioenergy feedstock that does not require conversion of agricultural cropland. Different management practices may alter soil physical properties (SPP), which could influence productivity, hydrologic and biogeochemical processes. Therefore, we investigated the effect of switchgrass-loblolly pine intercropping on the SPP of a poorly drained forest soil in eastern North Carolina using three management regimes: young loblolly pine stand (PINE), switchgrass-pine intercropping (PSWITCH), and a 38-year-old loblolly pine stand (REF). Measurements of SPP were conducted before and after the third annual harvesting operation using intact soil cores taken from three points within each of three replicated plots and at three depths: 0-15 cm, 15-30 cm, and 30-45 cm. Pre- and post-harvest values of SPP in PSWITCH were not significantly different. Compared to PINE, changes in bulk density and in both total porosity and saturated hydraulic conductivity in PSWITCH were significant only in the top 30 and 15 cm of soil, respectively. Volume drained and drainable porosity in PSWITCH decreased significantly at water table depths ≤45 cm. Cumulative effects of V-shearing for switchgrass seedbed preparation and the first and second harvest operations may have caused structural changes to the surface soil layer in PSWITCH that subsequently resulted in the measured differences in SPP between PSWITCH and PINE. We suggest that soil disturbance should be minimized during field operations to lessen the adverse effects on SPP, and models used to quantify impacts of management practices and land use change on the hydrology and biogeochemistry of managed forests should consider SPP changes caused by management regimes.}, number={6}, journal={Transactions of the ASABE}, author={Cacho, J. F. and Youssef, M. A. and Chescheir, G. M. and Skaggs, R. W. and Leggett, Zakiya H and Sucre, E. B. and Nettles, J. E. and Arellano, C.}, year={2015}, pages={1573–1583} }
 @article{tian_cacho_youssef_chescheir_nettles_2015, title={Switchgrass growth and morphological changes under established pine-grass agroforestry systems in the lower coastal plain of North Carolina, United States}, volume={83}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2015.10.002}, abstractNote={Switchgrass (Panicum virgatum L.) intercropped with Loblolly pine (Pinus taeda L.) has been proposed as a potential biomass feedstock for biofuel production in the southeastern United States. This study investigated effects of treatments (intercropping vs. grass only) on biomass increment processes and morphological properties of switchgrass at two experimental plots (Lenoir1) located in the coastal plain of North Carolina. We also evaluated effects of trimming lower tree branches of pine trees on switchgrass growth at another watershed-scale site (Carteret7) in the same region. Results showed that biomass yield of intercropped switchgrass was reduced by adjacent trees and negatively affected by relative position of grass to trees at the 6th year after planting at Lenoir1. Relative grass-to-tree position was also found to be a significant (p < 0.001) factor affecting grass growth at Carteret7 site with tree age of 5 years old, which is irrespective to the trimming practice. Trimming lower tree branches did not significantly (p = 0.57) improve biomass yield of switchgrass at Carteret7. We also observed intercropped switchgrass typically had higher specific leaf area and grew taller compared to grass-only plots. Stem-to-leaf ratios of switchgrass were significantly (p = 0.02) affected by trees at Lenoir1, but not by trimming lower branches in Carteret7 and relative position of grass to trees at both study sites. Findings from this study are important for evaluating the viability of producing biofuel feedstocks using this proposed intercropping system in the southeastern United States.}, journal={BIOMASS & BIOENERGY}, author={Tian, Shiying and Cacho, Julian F. and Youssef, Mohamed A. and Chescheir, George M. and Nettles, Jami E.}, year={2015}, month={Dec}, pages={233–244} }