Suchergebnisse

As southern pine forests (both planted and naturally regenerated) are more heavily used to provide biomass for the developing energy sectors and carbon sequestration, a better understanding of models used to characterize regional biomass estimates is needed. We harvested loblolly pines (Pinus taeda L.) between 0.5 and 15 cm dbh from several plantations and naturally regenerated stands in southeastern Arkansas to evaluate allometric relationships based on stand origin. In this process, each pine was separated into stemwood, branches + foliage, and taproot biomass components. Although the differences changed with dbh, loblolly pines from planted stands generally had greater percentages of biomass allocated to foliage + branches and taproots, whereas those from natural-origin stands had greater amounts in stemwood, aboveground, and total biomass. National Biomass Estimator (NBE) high-specific gravity pine equations predicted natural-origin aboveground biomass reasonably well. However, the same NBE model underpredicted aboveground biomass for small (similar to 5 cm) diameter planted pine and overpredicted planted pines between 7 and 15 cm dbh. When scaled to stand-level estimates, the NBE models resulted in estimates for average stand diameters of 5, 10, and 15 cm that ranged from -18.6 to 2.1% for natural stands and from -21.9 to 62.8% for planted stands. ; Agriculture and Food Research Initiative Competitive Grant from the USDA National Institute of Food and Agriculture [2009-35103-05356]; Southern Research Station of the USDA Forest Service; Arkansas Forest Resources Center ; We thank the following individuals for their contributions: Kirby Sneed and Rick Stagg (USDA Forest Service); Jonathan Hartley (University of Arkansas-Monticello); and Conner Fristoe (Weyerhaeuser Company). This research was supported by Agriculture and Food Research Initiative Competitive Grant 2009-35103-05356 from the USDA National Institute of Food and Agriculture, the Southern Research Station of the USDA Forest Service, and the Arkansas Forest Resources Center. ; Public domain authored by a U.S. government employee

Net primary productivity (NPP) and net ecosystem production (NEP) are often used interchangeably, as their difference, heterotrophic respiration (soil heterotrophic CO2 efflux, R-SH = NPP-NEP), is assumed a near-fixed fraction of NPP. Here, we show, using a range-wide replicated experimental study in loblolly pine (Pinus taeda) plantations that R-SH responds differently than NPP to fertilization and drought treatments, leading to the divergent responses of NPP and NEP. Across the natural range of the species, the moderate responses of NPP (+11%) and R-SH (-7%) to fertilization combined such that NEP increased nearly threefold in ambient control and 43% under drought treatment. A 13% decline in R-SH under drought led to a 26% increase in NEP while NPP was unaltered. Such drought benefit for carbon sequestration was nearly twofold in control, but disappeared under fertilization. Carbon sequestration efficiency, NEP:NPP, varied twofold among sites, and increased up to threefold under both drought and fertilization. ; USDA National Institute of Food and AgricultureUnited States Department of Agriculture (USDA) [2011-68002-30185]; US Forest Service Eastern Forest Environmental Threat Assessment Center [08-JV-11330147-038]; McIntire-Stennis Project [121209 94160] ; Published version ; This study was conducted as part of The Pine Integrated Network: Education, Mitigation, and Adaptation Project (PINEMAP) that was a Coordinated Agricultural Project funded by the USDA National Institute of Food and Agriculture, Award #2011-68002-30185. The authors thank Foley Timber and Land Company (Florida), Ed Hurliman (Oklahoma), and the Virginia Department of Forestry, Appomattox-Buckingham State Forest (Virginia) for providing property access to install the experiments. Partial support was provided by US Forest Service Eastern Forest Environmental Threat Assessment Center Grant 08-JV-11330147-038, and McIntire-Stennis Project 121209 94160. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ; Public domain authored by a U.S. government employee