The fast-growing tree, eastern cottonwood (Populus deltoides), currently is being planted to catalyze native forest restoration on degraded agricultural sites in the southeastern United States. Many of these restoration sites are appropriate for short rotation woody crop (SRWC) culture that addresses climate mitigation objectives, but information needed to optimize climate mitigation objectives through such plantings is limited. Therefore, we established a 10-year experiment on degraded agricultural land located in the Mississippi Alluvial Valley, USA, aiming to quantify the dynamics of aboveground carbon (AGC) accumulation in a cottonwood planting of four replicated spacing levels (3.7 × 3.7 m, 2.7 × 1.8 m, 2.1 × 0.8 m, and (0.8 + 1.8) × 0.8 m) aligned with SRWC systems targeting various ecosystem services. Annual sampling revealed a substantial range in increments of AGC and year 10 carbon stocks among stands of different densities. Mean annual increments for AGC (MAIAGC) were similar for the two tightest spacing levels, peaking higher than for the other two spacings at about 7.5 Mg ha−1 y−1 in year 7. Year 10 AGC ranged between 22.3 Mg ha−1 for stands spaced 3.7 × 3.7 m and 70.1 Mg ha−1 for stands of the two tightest spacings, leading us to conclude that a spacing between 2.1 × 0.8 m and 2.7 × 1.8 m would maximize aboveground carbon stocks through year 10 on sites of similar agricultural degradation. Increments and accumulation of AGC on the degraded site trended lower than values reported from more productive sites but illustrate that quick and substantial transformation of the carbon stock status of degraded agricultural sites can be achieved with the application of SRWCs to restore forests for climate mitigation and other compatible ecosystem services.

Black willow and eastern cottonwood are fast-growing hardwoods native to river bottoms throughout the southeastern United States, e.g., the Lower Mississippi Alluvial Valley (LMAV), that are often grown as short rotation woody crops (SRWCs) because of their potential to provide high biomass yields in short periods of time. This study focused on developing allometric equations to estimate individual tree, coppice, and stand level aboveground biomass (AGB) of these species using data from destructively sampled trees collected through the age of 6 years. Diameter at breast height (dbh), total stem height, and their transformations and combinations were the predictors of individual tree AGB. Coppice models included number of stems in the coppice as an additional predictor variable. The stand level AGB was predicted using planting density, dominant height, and stand age. A logarithmic model that used dbh squared then multiplied by total stem height was the best fitting model (Adj. R2 = 0.982, RMSE = 1.13 kg) for the individual tree AGB estimation for black willow. Whereas a model that used dbh and total stem height as separate predictors was the best fitting model (Adj. R2 = 0.954, RMSE = 2.90 kg) for eastern cottonwood. Using the number of stems as an additional predictor in the coppice models reduced RMSE by 5.67% for black willow and by 4.95% for eastern cottonwood. The stand level models explained 79.5% and 94.1% of the variation in stand AGB for black willow and eastern cottonwood and had RMSEs of 2.38 and 6.59 Mg/ha, respectively. Overall, these models will be useful for forestland owners in the LMAV for estimating available bioenergy feedstock from black willow and eastern cottonwood plantations without requiring destructive sampling.

Modulus of elasticity (MOE), modulus of rupture (MOR), and specific gravity (SG) are important properties for determining the end-use and value of a piece of lumber. This study addressed the variation in MOE, MOR, and SG with physiographic region, tree height, and wood type. Properties were measured from two static bending samples (dimensions 25.4 mm × 25.4 mm × 406.4 mm) representing each wood type (corewood and outerwood) at heights 2.4, 7.3, and 12.2 m from three trees sampled from 135 loblolly pine ( Pinus taeda L.) stands distributed across the natural range of the species. An analysis of variance was conducted to detect the effect of physiographpic region, height, and wood type on each property. Significant regional variation was observed for MOE, MOR, and SG for both wood types with high values in the Gulf and South Atlantic Coastal Plains compared with other regions. A significant height-related trend in MOE, MOR, and SG within a tree was identified; MOE and MOR increased in corewood and decreased in outerwood with height. Maps showing regional variation in MOE and MOR at different heights by wood type were produced and showed significant variation for both properties.

Stand-level growth responses and plant-level patterns of biomass accumulation and distribution were examined to learn how stand structure influences morphological acclimation and growth of green ash (Fraxinus pennsylvanica Marsh.) advance regeneration following overstory harvesting. Nine, 20-ha plots that received clearcut harvesting (100% basal area removal), partial harvesting (50% basal area removal), or no harvesting (control) were sampled to measure height, root-collar diameter, leaf, stem and root biomass, and leaf mass ratio (LMR), stem mass ratio (SMR) and root mass ratio (RMR) of ash regeneration. Six years after treatment, plot-level analyses indicated that ash growth was greatest in plots receiving clearcut harvesting, and least in control plots. Examination of LMR, SMR and RMR revealed that this growth response was not associated with acclimation that altered plant morphology. Total biomass

The emerging carbon market is an increasingly important source of finance for bottomland hardwood afforestation in the Lower Mississippi River Valley (LMV). Notwithstanding, there is a scarcity of empirical estimates of carbon sequestration specific to the region and we sought to address this outstanding need. We evaluated tree measurements from known-age bottomland hardwood stands from a chronosequence of sites in the LMV, drawing on 540 plot measurements within 67 stands. We derived a model of live tree biomass carbon as a function of stand age. The model explained 83% of the variation in live tree biomass carbon at the stand level, and provides a more accurate projection for application in the LMV than broader regional models currently available. Modeled live tree biomass carbon was greater than the corresponding regional estimate used in the U.S. Department of Energy’s voluntary greenhouse gas reporting program for years 20 through 90 (up to 59% greater at year 50), but trended toward convergence at mature stages.

Postsettlement (1909–2003) fire history of a forested bottomland in the Mississippi Embayment of southern Illinois, USA, was determined using fire-scar analysis. The study area is a forested bottomland hardwood site, with remnant pockets of the dominant presettlement bald cypress – tupelo (Taxodium–Nyssa) vegetation. Ditch drainage was installed in 1919, with agricultural clearing and abandonment varying throughout the early and mid-twentieth century. Commercial agricultural activities ceased after the site became part of a conservation area ca. 1950. The hydrology of the site was further modified in 1957 when it was inundated for waterfowl management. Both drainage and land clearing for agriculture were associated with increased fire frequency. Although drainage was a necessary precursor to agriculture across much of this landscape, land improvement played the stronger role in determining fire frequency. The mean fire interval for the study period (1895–1965) was 1.73 years, with a minimum of 1 year and a maximum of 15 years. This frequency contrasts with the complete fire exclusion that has prevailed in the area since 1965. These results have important implications for the maintenance and restoration of forested wetland ecosystems where the present fire regime differs dramatically from that under which the now-dominant forest vegetation developed.

Forest Inventory and Analysis 1999 survey data for Tennessee were used to compare stem-volume estimates obtained using a previous method, the current method, and newly developed taper models that will be used in the future.Compared to the current method, individual tree volumes were consistently underestimated with the previous method, especially for the hardwoods.The taper models produced estimates very similar to the current method for both hardwoods and softwoods.When expanded to a statewide basis, the previous method differed from the current by -2.128 by 10 9 cubic feet, which represents an 8.16-percent underestimate.Hardwoods again were more severely underestimated than softwoods.Conversely, results from the taper method deviated only 0.230 by 10 9 cubic feet from the current method, or 0.88 percent, which is of little concern.

Steamwood cubic-foot volume inside bark tables are presented for 14 species and 9 species groups based on equations used to estimate timber sale volumes on national forests in the Gulf and Atlantic Coastal Plain. Tables are based on form class measurement data for 2,728 trees sampled in the Gulf and Atlantic Coastal Plain and taper data collected across the South. A series of tables is presented for each species based on diameter at breast height (d.b.h.) in combination with total height and height to a 4-inch diameter outside bark (d.o.b.) top. Volume tables are also presented based on d.b.h. in combination with height to a 7-inch d.o.b. top for softwoods and height to a 9-inch d.o.b. top for hardwoods.

Citation for proceedings: Holley, A. Gordon; Connor, Kristina F.; Haywood, James D., eds. 2015. Proceedings of the 17th biennial southern silvicultural research conference. e–Gen. Tech. Rep. SRS–203. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 551 p. Research Forester, Research Forester, and Supervisory Research Plant Pathologist, respectively, USDA Forest Service, Southern Research Station, Stoneville, MS 38776; and Research Engineer and Project Leader (retired), USDA Forest Service, Southern Research Station, Auburn, AL 36849.