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Calcium (Ca) is a critical plant nutrient typically applied at the time of planting in intensive Eucalyptus plantations in South America. At two sites in Colombia, we examined (1) calcium source by comparing growth after application of 100 kg ha−1 elemental Ca as lime or as pelletized highly reactive calcium fertilizer (HRCF) compared to a no application control, and (2) Ca rate by applying 0, 100, 200, and 400 kg ha−1 elemental Ca as HRCF with the addition of nitrogen, phosphorus, potassium, sulfur, and boron (NPKSB). We assessed height, diameter, and volume after 12 and 24 months. There were no growth differences from Ca source at the 100 kg ha−1 rate. We found increased volume after 24 months at the “Popayan” site with 200 and 400 kg ha−1 Ca HRCF+NPKSB treatments (112 and 113 m3 ha−1, respectively) compared to control (92 m3 ha−1), a 22% increase. In contrast, volume did not differ after 24 months at the “Darien” site, ranging from 114 m3 ha−1 in the 0 kg ha−1 Ca HRCF+NPKSB treatment to 98 m3 ha−1 in the control. Differences in response are likely due to soil characteristics, such as organic matter, emphasizing the importance of identifying site-specific nutrient deficiencies.

Fine roots serve as the primary interface between trees and the soil, and they are dynamic in their response to environmental conditions. Among many functions, they are principle in gathering nutrients and water, and they constitute a major component of the tree. Their overall contribution to soil carbon flux is not well understood, nor is the effect of site and genotype on their dynamics, and these factors are crucial to understanding nutrient cycles and tree growth under variable conditions. This study evaluated how the fine root dynamics of loblolly pine (Pinus taeda L.) might be different between genotypes and on different sites. Three loblolly pine plantations were established, two in 2009 in North Carolina (NC) and Virginia (VA), and one in 2011 in Brazil (BR). Root biomass was estimated with soil cores across the three sites and between two genotypes in 2020. Seasonal and annual fine mot production was measured at the NC and VA sites over the 12th growing season using ingrowth cores. The trees in BR that were two years younger were much larger than those in NC and VA and had more fine root biomass at initial sampling than those in NC, despite similar levels of fertility. Meanwhile, fine mot production rates decreased with higher rates of aboveground productivity across all measured plots in NC and VA. These results indicate that (1) standing fine root biomass may be related to environmental conditions that are not easily manipulated, which could inform modeling of carbon cycles, and (2) in these intensively managed plots, sufficient resources were available to allow for increased aboveground growth despite lower rates of fine mot production, which supports the employment of these intensive silvicultural practices. Department of Forestry and Environmental Resources at NC State University; Department of Forest Resources and Environmental Conservation at Virginia Tech; Department of Forest Sciences at the Federal University of Lavras; NSF I/UCRC Center for Advanced Forestry Systems [1916552]; Div Of Industrial Innovation & Partnersh; Directorate For Engineering [1916552] Funding Source: National Science Foundation Published version We would like to thank the Forest Productivity Cooperative and personnel of Valor Florestal for their establishment and maintenance of these study sites, and for the COOP members' continued support of this research. We also acknowledge the support of this project from the Department of Forestry and Environmental Resources at NC State University, the Department of Forest Resources and Environmental Conservation at Virginia Tech, and the Department of Forest Sciences at the Federal University of Lavras. We appreciate the hours of selfless assistance from Andrew Laviner, Gerardo Rojas, Kyle Peer and Clay Sawyers at the Reynolds Homestead Forest Resource Research Center, Hans Rohr, Christopher Clark, and Brandon Merritt of the North Carolina Forest Service's Bladen Lakes State Forest, and from Karen Sarsony of the US Forest Service Southern Research Station.This work was supported by NSF I/UCRC Center for Advanced Forestry Systems, award 1916552. Public domain – authored by a U.S. government employee

Rising demand for renewable energy has created a potential market for biomass from short-rotation pine plantations in the southeastern United States. Site preparation, competition control, fertilization, and enhanced seedling genotypes offer the landowner several variables for managing productivity, but their combined effects on financial returns are unclear. This study estimated returns from a hypothetical 10-year biomass harvest in loblolly pine plantation using field studies in the Coastal Plain of North Carolina and the Virginia Piedmont testing combinations of tree genotype, planting density, and silviculture. Although enhanced varietal genotypes could yield more biomass, open-pollinated seedlings at 1,236–1,853 trees ha−1 under operational silviculture had the greatest returns at both sites, with mean whole-tree internal rates of return of 8.3%–9.9% assuming stumpage equal to current pulpwood prices. At a 5% discount rate, break-even whole-tree stumpage at the two sites in the optimal treatments was $8.72–$9.92 Mg−1, and break-even yield was 175–177 Mg ha−1 (roughly 18 Mg ha−1 yr−1 productivity), although stumpage and yield floors were higher if only stem biomass was treated as salable. Dedicated short-rotation loblolly biomass plantations in the region are more likely to be financially attractive when site establishment and maintenance costs are minimized.

Remote sensing offers many advantages to supplement traditional, ground-based forest measurements, such as limiting time in the field and fast spatial coverage. Data from airborne laser scanning (lidar) have provided accurate estimates of forest height, where, and when available. However, lidar is expensive to collect, and wall-to-wall coverage in the United States is lacking. Recent studies have investigated whether point clouds derived from digital aerial photogrammetry (DAP) can supplement lidar data for estimating forest height due to DAP's lower costs and more frequent acquisitions. We estimated forest heights using point clouds derived from the National Agricultural Imagery Program (NAIP) DAP program in the United States to create a predicted height map for managed loblolly pine stands. For 534 plots in Virginia and North Carolina, with stand age ranging from 1 year to 42 years old, field-collected canopy heights were regressed against the 90th percentile of heights derived from NAIP point clouds. Model performance was good, with an R2 of 0.93 and an RMSE of 1.44 m. However, heights in recent heavily thinned stands were consistently underestimated, likely due to between-row shadowing leading to a poor photogrammetric solution. The model was applied to non-thinned evergreen areas in Virginia, North Carolina, and Tennessee to produce a multi-state 5 m x 5 m canopy height map. NAIP-derived point clouds are a viable means of predicting canopy height in southern pine stands that have not been thinned recently. Published version

In 2019, the Forest Productivity Cooperative (FPC) celebrated its 50th anniversary. The mission of the FPC is and has been creating innovative solutions to enhance forest productivity and value through the sustainable management of site resources. This industry-government-university partnership has generated seminal research with sweeping implications for increasing productivity throughout the southeastern United States and Latin America. To commemorate this semicentennial, we highlighted some of the pivotal findings in the southeastern United States from the past 50 years derived from our large, regional experiments: regionwide trials.

We examined crown architecture and within crown leaf area distribution effects on Pinus taeda L. growth in North Carolina (NC), Virginia (VA), and Brazil (BR) to better understand why P. taeda can grow much better in Brazil than in the southeastern United States. The NC, VA, and BR sites were planted in 2009, 2009, and 2011, respectively. At all sites, we planted the same two genetic entries at 618, 1236, and 1854 trees ha(-1). In 2013, when trees were still open grown, the VA and NC sites had greater branch diameter (24%), branch number (14%), live crown length (44%), foliage mass (82%), and branch mass (91%), than the BR site. However, in 2017, after crown closure and when there was no significant difference in tree size, site did not significantly affect these crown variables. In 2013, site significantly affected absolute leaf area distribution, likely due to differences in live crown length and leaf area, such that there was more foliage at a given level in the crown at the VA and NC sites than at the BR site. In 2017, site was still a significant factor explaining leaf area distribution, although at this point, with crown closure and similar sized trees, there was more foliage at the BR site at a given level in the crown compared to the VA and NC sites. In 2013 and 2017, when including site, genetic entry, stand density, and leaf area distribution parameters as independent variables, site significantly affected individual tree growth efficiency, indicating that something other than leaf area distribution was influencing the site effect. Better BR P. taeda growth is likely due to a combination of factors, including leaf area distribution, crown architecture, and other factors that have been identified as influencing the site effect (heat sum), indicating that future work should include a modeling analysis to examine all known contributing factors. Public domain – authored by a U.S. government employee

Summary • Availability of growth limiting resources may alter root dynamics in forest ecosystems, possibly affecting the land–atmosphere exchange of carbon. This was evaluated for a commercially important southern timber species by installing a factorial experiment of fertilization and irrigation treatments in an 8-yr-old loblolly pine (Pinus taeda) plantation. • After 3 yr of growth, production and turnover of fine, coarse and mycorrhizal root length was observed using minirhizotrons, and compared with stem growth and foliage development. • Fertilization increased net production of fine roots and mycorrhizal roots, but did not affect coarse roots. Fine roots had average lifespans of 166 d, coarse roots 294 d and mycorrhizal roots 507 d. Foliage growth rate peaked in late spring and declined over the remainder of the growing season, whereas fine roots experienced multiple growth flushes in the spring, summer and fall. • We conclude that increased nutrient availability might increase carbon input to soils through enhanced fine root turnover. However, this will depend on the extent to which mycorrhizal root formation is affected, as these mycorrhizal roots have much longer average lifespans than fine and coarse roots.

Vegetation indices calculated from remotely sensed satellite imagery are commonly used within empirically derived models to estimate leaf area index in loblolly pine plantations in the southeastern United States. The data used to parameterize the models typically come with observation errors, resulting in biased parameters. The objective of this study was to quantify and reduce the effects of observation errors on a leaf area index (LAI) estimation model using imagery from Landsat 5 TM and 7 ETM+ and over 1500 multitemporal measurements from a Li-Cor 2000 Plant Canopy Analyzer. Study data comes from a 16 quarter 1 ha plot with 1667 trees per hectare (2 m × 3 m spacing) fertilization and irrigation research site with re-measurements taken between 1992 and 2004. Using error-in-variable methods, we evaluated multiple vegetation indices, calculated errors associated with their observations, and corrected for them in the modeling process. We found that the normalized difference moisture index provided the best correlation with below canopy LAI measurements (76.4%). A nonlinear model that accounts for the nutritional status of the stand was found to provide the best estimates of LAI, with a root mean square error of 0.418. The analysis in this research provides a more extensive evaluation of common vegetation indices used to estimate LAI in loblolly pine plantations and a modeling framework that extends beyond the typical linear model. The proposed model provides a simple to use form allowing forest practitioners to evaluate LAI development and its uncertainty in historic pine plantations in a spatial and temporal context. Published version

Evolving bioenergy markets requires consideration of marginal lands for woody biomass production worldwide. Growing short rotation woody crops for bioenergy (SRWCs) on marginal land minimizes concerns about using croplands for agricultural production and reinforces sustainability of wood supply. Evaluation of the profitability of marginal land that may have SRWCs potential as sources of biomass for energy production has been rarely reported. This study attempts to account for investments uncertainties on SRWCs production considering Eucalyptus globulus managed under contrasting silvicultural intensities on marginal land by comparing four environments and four levels of initial planting density. Our study consider biomass yields over this gradient of productivity and biomass market prices and costs from local contractors. We estimated mean annual aboveground dry biomass increments (MAIs) and evaluated the economic feasibility of various cycles of harvest (2–6 years) using Monte Carlo simulation to examine how uncertainty over the input variables affects NPV of SRWCs. MAIs that ranged 3.91–18.07 Mg ha−1 yr−1 increased with stand density and harvesting age. Rotation length affected economic outcomes although the returns were poor due to high establishment and maintenance costs, low productivities and low biomass prices. Under an average scenario, current market price of biomass, absence of subsidies and current costs, SRWC are not profitable when productivities are lower than 351 m3 ha−1 of green biomass.

Intensive management of forest plantations has evolved significantly in recent decades because of advances in our understanding of environmental and silvicultural effects on forest productivity combined with improvements in information technologies. Our paper summarizes concepts that provide a basis for making strategic and operational silvicultural decisions that insure sustainability when applying intensive management of forest plantations. In addition, we include new information in areas where there are knowledge gaps in forest plantation management. Intensive management of forest plantations increasingly incorporates large-scale precision silviculture to estimate silvicultural, biotic, and abiotic effects on site-specific forest productivity. Remote sensing measurements combined with strategically located ground information provide spatial modeling tools needed for this type of silviculture. Long-term field experiments, which are a part of this methodology, provide a mechanistic understanding of environmental and silvicultural effects on forest production that is required for the models driving silvicultural decisions. The focus on maximizing production will challenge scientific efforts to alleviate concerns about intensive land use and to provide solutions for water use conflicts while maintaining long-term productivity and sustainability. Future work will need to develop a better understanding of genetic × environment × silvicultural (G × E × S) interactions to improve productivity and simultaneously provide improved ecosystem services. New silviculture technology combines remote sensing information with ground data to model resource availability and limitations to forest productivity. Understanding G × E × S permits successful implementation of these new silvicultural technologies. An improved understanding of G × E × S will provide practical tools that may be incorporated into our scientific and technical models while providing robust economic sustainability.

Accurate estimations of stem volume and tree component biomass are of paramount importance for the study and management of forests. In Chile, the most important commercial tree species are Pinus radiata, Eucalyptus globulus and Eucalyptus nitens, which are successfully planted in other parts of the world. Available individual-tree allometric models are typically local models which do not include age or stand scale covariates and rely solely on stem diameter outside bark at breast height (DBH) and, in some cases, total tree height (H). We used data from 1571 trees across the distribution of the three species in Chile to develop general individual-tree equations for stem volume inside and outside bark, and biomass components (dead branch, live branch, foliage, bark and stem wood inside and outside bark). Our models include DBH or DBH and H as predicting variables, as well as stand-level variables like age, basal area and stand density. General allometric models that include stand-level variables have not been previously reported for P. radiata, E. globulus and E. nitens. Given the broad area of inference in our data, the models are applicable over a large geographical area and a variety of stand ages and characteristics and can be used to support management decisions or integrated in stand-level productivity models to enhance the accuracy and precision of model outputs. The collective effort behind this study is a remarkable example of cooperation across researchers and practitioners in order to address complex questions in a transdisciplinary world.

We quantified the response duration to one-time applications of 112, 224, and 336 kg ha−1 of elemental nitrogen (112 N, 224 N, and 336 N, respectively) combined with 28 or 56 kg ha−1 of elemental phosphorus in mid-rotation Pinus taeda L. stands. Post-application measurements continued for 10 years at 32 sites in the southeastern United States and one site in Argentina, and we fit a Ricker model to data from each treatment in the event that a zero growth response was not observed in our measured data. The response duration was eight (measured), 14 (modeled), and 16 (modeled) years after treatment for the respective 112 N, 224 N, and 336 N treatments. The corresponding growth response per unit of applied nitrogen estimated from fertilization to when the growth response was not different from zero (whether measured or modeled) was 0.20, 0.16, and 0.13 m3 kg−1 for the 112 N, 224 N, and 336 N treatments, respectively. We hypothesized that the mechanism controlling the response duration was related to the amount of fertilizer nitrogen remaining in the foliage over time after treatment; previous studies found that nitrogen application had large impacts on the foliage amount and foliar nitrogen content. Based on retranslocation rate estimates from the literature of 67% of fertilizer nitrogen per year, our results suggest that a good correlation exists between the growth response and the amount of fertilizer nitrogen remaining in the foliage.

We installed a thinning and fertilization study at five sites in mid-rotation Pinus taeda L. stands in the southeastern United States to examine treatment effects on diameter growth, basal area production, and volume increment. The treatments were four levels of post-thinning stand density (247, 494, 741 and 1235 stems ha −1 ) and two levels of fertilization (none and 224 and 28 kg ha −1 of elemental nitrogen and phosphorus, respectively), applied in four replications at each site using either a randomized complete block (3 sites) or a split plot (2 sites) design. Six years after treatment, thinning significantly increased diameter and diameter increment as the residual density level decreased and increased stand basal area, stand basal area increment, stand volume and stand volume increment as residual density level increased at all sites. Fertilizer significantly increased diameter and stand basal area increments at two sites and stand volume increment at one site; these sites had low initial leaf area index, a metric commonly used to assess the potential for response to fertilization. Diameter increment increased as initial diameter class increased. Larger trees grew faster than smaller trees at all sites and for all treatments. Diameter growth decreased as initial stand basal area increased, and fertilization significantly increased diameter growth for a given level of initial stand basal area at sites where fertilization affected diameter growth. Stand volume increment increased as diameter increment increased for crop trees (largest 247 stems ha −1 ), whereas stand volume increment decreased as diameter increment increased for all trees. The stand-scale ‘cost’ for greater individual-tree diameter growth was a reduction in stand volume increment in the 247 stems ha −1 treatment; this reduction was 13 m 3 ha −1 yr −1 across all sites compared with the 1235 stems ha −1 treatment, whereas the individual tree diameter growth ‘benefit’ was 0.9 cm yr −1 when comparing these same treatments. Trade-offs were quantified between individual tree size and stand growth across the thinning and fertilization levels imposed in this study, which will be useful in empirical and process-based modeling efforts for predicting thinning and fertilization responses of P. taeda .

Predicting how forest carbon cycling will change in response to climate change and management depends on the collective knowledge from measurements across environmental gradients, ecosystem manipulations of global change factors, and mathematical models. Formally integrating these sources of knowledge through data assimilation, or model–data fusion, allows the use of past observations to constrain model parameters and estimate prediction uncertainty. Data assimilation (DA) focused on the regional scale has the opportunity to integrate data from both environmental gradients and experimental studies to constrain model parameters. Here, we introduce a hierarchical Bayesian DA approach (Data Assimilation to Predict Productivity for Ecosystems and Regions, DAPPER) that uses observations of carbon stocks, carbon fluxes, water fluxes, and vegetation dynamics from loblolly pine plantation ecosystems across the southeastern US to constrain parameters in a modified version of the Physiological Principles Predicting Growth (3-PG) forest growth model. The observations included major experiments that manipulated atmospheric carbon dioxide (CO2) concentration, water, and nutrients, along with nonexperimental surveys that spanned environmental gradients across an 8.6 × 105 km2 region. We optimized regionally representative posterior distributions for model parameters, which dependably predicted data from plots withheld from the data assimilation. While the mean bias in predictions of nutrient fertilization experiments, irrigation experiments, and CO2 enrichment experiments was low, future work needs to focus modifications to model structures that decrease the bias in predictions of drought experiments. Predictions of how growth responded to elevated CO2 strongly depended on whether ecosystem experiments were assimilated and whether the assimilated field plots in the CO2 study were allowed to have different mortality parameters than the other field plots in the region. We present predictions of stem biomass productivity under elevated CO2, decreased precipitation, and increased nutrient availability that include estimates of uncertainty for the southeastern US. Overall, we (1) demonstrated how three decades of research in southeastern US planted pine forests can be used to develop DA techniques that use multiple locations, multiple data streams, and multiple ecosystem experiment types to optimize parameters and (2) developed a tool for the development of future predictions of forest productivity for natural resource managers that leverage a rich dataset of integrated ecosystem observations across a region.

Increasing forest productivity is important to meet future demand for forest products, and to improve resilience in the face of climate change. Forest productivity depends on many things, but the timing of leaf development (hereafter: “plant phenology”) is especially important. However, our understanding of how plant phenology affects the productivity of managed forests, and how silviculture may in turn affect phenology, has been limited because of the spatial scale mismatch between phenological data and field experimental observations. In this study, we take advantage of a new 30 m satellite land surface phenology dataset and stand growth measurements from long-term experimental pine plantation sites in the southeastern United States to investigate the question: is stand growth related to remotely sensed phenology metrics? Multiple linear regression and random forest models were fitted to quantify the effect of phenology and silvicultural treatments on stand growth. We found that 1) Greater wood volume growth was associated with longer green up periods; 2) Fertilization elevated EVI2 measurement values during the whole growing season, especially in the winter; 3) Competing vegetation could affect remotely sensed observations and complicates interpretation of remotely sensed phenology metrics.

Pine plantations in the southern US are among the most intensively managed forests in the world and their productivity has tripled over natural pine forests through application of intensive pine plantation establishment and management practices. As we are trying to increase carbon (C) sequestration through further enhancing pine plantation productivity by refinement of silvicultural regimes, whether a maximum productivity or the maximum potential C sequestration exists remains unclear. Our analysis of six long-term field trials indicated that a maximum productivity and a maximum response to silvicultural practices for loblolly pine (Pinus taeda L.) exist across the species geographic range in the southern US. The maximum response was inversely proportional to the base site quality, and silvicultural treatments never increased productivity above that maximum. Further analysis of loblolly pine culture and density studies demonstrated that the effects of planting density and cultural treatment intensity on biomass production strongly interacted with site quality in that lower quality sites responded more to silvicultural intensity than higher quality sites. The results highlight that we can optimize silvicultural prescriptions for specific sites by changing silvicultural intensity depending on the site quality.

Pinus taeda plantations in subtropical areas of South America are extremely productive and commonly established on well-drained red clay sites. In the past, land with more poorly-drained soil was avoided due to concern over the factors limiting site productivity. Establishment of intensively managed plantations on poorly-drained soils usually includes soil preparation by subsoiling and/or bedding, weed control, and fertilization. However, forest managers lack information about the efficacy of early silvicultural practices to ameliorate environmental limitations and if these intensive practices generate long-term improvements in productivity in this area. Consequently, we established studies in northeastern Argentina on two sites differing by drainage class and soil texture as a full factorial design with site preparation (S; disking and disking + subsoiling (red clay) or bedding (wet loam)), fertilization (F; none or 78 kg ha−1 elemental phosphorus at planting), and weed control (W; none or two-year banded). Seven years after planting, the red clay and wet loam sites were equally productive, with maximum treatment means of 218 m3 ha−1 and 264 m3 ha−1 respectively. At the red clay site, only weed control significantly increased volume. At the wet loam site, both weed control and site preparation significantly increased volume, mainly due to increased survival. The combination of weed control and bedding yielded a non-additive volume response as indicated by a significant W*S interaction. Our results do not support the common practice of subsoiling on red clay soils. In addition, fertilization with P alone appears counterproductive or unneeded at both sites.

Mid-rotation fertilization presents an opportunity to increase the economic return of plantation forests in the southeastern United States (SEUS). For this reason, the Forest Productivity Cooperative established a series of mid-rotation fertilization trials in Pinus taeda L. plantations across the SEUS between 1984 and 1987. These trials identified site-specific responses to nitrogen (N) and phosphorus (P) fertilizers, resulting in increased stand production for 6&ndash, 10 years after fertilization. There are successful volume response models that allow users to quantify the gain in stand productivity resulting from fertilization. However, all the current models depend on empirical relationships that are not bounded by biological response, meaning that greater fertilizer additions continue to create more volume gains, regardless of physiological limits. To address this shortcoming, we developed a bounded response model that evaluates relative volume response gain to fertilizer addition. Site index and relative spacing are included as model parameters to help provide realistic estimates. The model is useful for evaluating productivity gain in Pinus taeda stands that are fertilized with N and P in mid-rotation.

A nutrient dose and application frequency study was installed in Eucalyptus grandis stands at six sites in the Colombian Andes to examine three hypotheses: (1) individual sites have different treatment responses (there is a significant site effect); (2) the relationship between volume growth response and applied nitrogen is not linear (there is an optimal amount of applied nitrogen beyond which growth improvements would be small); and (3) application frequency does not affect response if the cumulative dose applied is equivalent (there is no frequency effect). Nitrogen, phosphorus and boron were applied at a 1.0:0.1:0.005 ratio, where nitrogen rates ranged from 0 to 250 kg ha−1 and application frequency was 6, 12, 24 or 36 months. Fertilization began when trees were 11–24 months old and we examined volume growth response three years after study initiation when the maximum cumulative nitrogen application reached 720 kg ha−1. There was a significant site effect: two sites were responsive and four were non-responsive to treatment. At the two responsive sites, the relationship between volume growth response and applied nitrogen was not linear. Three years after treatment initiation, the maximum absolute response was 142 m3 ha−1 (91% increase) and 116 m3 ha−1 (56% increase) for Sites 1 and 4, respectively. Sites 1 and 4 reached maximum volume response at cumulative nitrogen doses of 360 and 480 kg ha−1, respectively. Tests that compared different nitrogen application rates and frequencies to achieve the same cumulative dose were not significantly different except for one test at Site 4 where the volume growth response to three applications of 180 kg nitrogen ha−1 was 58% greater than the response to six applications of 90 kg ha−1.

Short rotation Eucalyptus plantations offer great potential for increasing wood-fiber production in the southern United States. Eucalyptus plantations can be highly productive (>35 m(3) ha(-1) year but they may use more water than intensively managed pine (primarily Pinus taeda L) plantations. This has raised concern about how expansion of Eucalyptus plantations will affect water resources. We compared tree water use, stem growth, and WUE (kg wood per m(3) water transpired) in adjacent nine-year-old Eucalyptus benthamii and P. taeda plantations with similar stand density and leaf area. Sap flux (F-d, g cm(-2) s(-1)) was measured continuously over one year using thermal dissipation probes. Stem biomass, stem growth, tree water use (E-t, L day(-1)), canopy transpiration per unit leaf area (E-1, mmol m(-2) s(-1)), and canopy stomatal conductance (G(s), mmol m(2) s(-1)) were quantified. Eucalyptus had higher daily Fd (196.6 g cm(-2) day(-1)) and mean daily E-t (24.6 L day(-1)) than pine (105.8 g cm(-2) day(-1), 15.2 L day(-1)). Eucalyptus exhibited a seasonally bimodal pattern in daily E-t that did not occur in pine. Monthly E-t was23-51% higher in Eucalyptus and differences between species were greatest in the spring and fall. Annual E-t was 32% higher in Eucalyptus (9.13 m(3) H2O year(-1)) than pine (5.79 m(3) H2O year(-1)). Annual stem biomass increment was greater in Eucalyptus (Eucalyptus: 22.9; pine: 11.8 kg tree(-1) year(-1)), and Eucalyptus had greater WUE (Eucalyptus: 2.86; pine 1.72 kg biomass m(-3) H2O year(-1)). Pine exhibited a lower seasonal minimum and higher seasonal maximum leaf area index (LAI). At low LAI, there was no significant difference between species in E-l or G(s); however, at maximum LAI, pine E-l and G(s) were 46 and 43%, respectively of rates observed in Eucalyptus. The species differed in G(5) response to vapor pressure deficit (D). At a similar reference G(s) (G(s),(ref) at D =1 kPa), pine exhibited greater stomatal sensitivity to D. These results suggest that (1) Eucalyptus trees had higher sap flux and total water use than pine, (2) Eucalyptus had greater stem growth and WUE, and (3) species differences in water use were driven primarily by differences in E-l and G(s). Published by Elsevier B.V. Public domain – authored by a U.S. government employee

Predicting how forest carbon cycling will change in response to climate change and management depends on the collective knowledge from measurements across environmental gradients, ecosystem manipulations of global change factors, and mathematical models. Formally integrating these sources of knowledge through data assimilation, or model-data fusion, allows the use of past observations to constrain model parameters and estimate prediction uncertainty. However, the influence of different experimental treatments on those predictions depends on the exact methods and techniques used for data assimilation. Here, we introduce a hierarchical Bayesian DA approach (Data Assimilation of Pine Plantation Ecosystem Research, DAPPER) that uses observations of carbon stocks, carbon fluxes, water fluxes, and vegetation dynamics from loblolly pine plantation ecosystems across the Southeastern U.S. to constrain parameters in a modified version of the 3-PG forest growth model. The observations included major experiments that manipulated atmospheric carbon dioxide (CO2) concentration, water, and nutrients, along with non-experimental studies that spanned environmental gradients across an 8.6 × 105 km2 region. We optimized regionally representative posterior distributions for the most sensitive model parameters, which dependably predicted data from plots withheld from the data assimilation. The posterior distributions of parameters associated with ecosystem responses to CO2, precipitation, and nutrient addition, along with the corresponding regional changes in production associated with nutrient fertilization and drought, depended on how the experimental data were assimilated. In particular, assimilating nutrient addition experiments reduced the predicted sensitivity to nutrient fertilization while assimilated water manipulation experiments increased the sensitivity to drought. Further, it was necessary to assimilate data from the CO2 experimental enrichment site before other studies to constrain the parameters associated with the influence of CO2 on canopy photosynthesis. The ambient CO2 plots were numerous and had a large contribution to the cost function compared to the low number of elevated CO2 plots (289 ambient vs. 5 elevated plots). Overall, we demonstrated how three decades of research in southeastern U.S. planted pine forests can be used to develop data assimilation techniques that use multiple locations, multiple data streams, and multiple ecosystem experiment types to optimize parameters. This approach allows for future predictions to be consistent with a rich history of ecosystem research across a region.

We quantified biomass and nutrient accumulation of Acacia dealbata Link and Eucalyptus globulus Labill. planted at stem densities of 5000 and 15000 ha(-1) in a bioenergy plantation in Chile. We tested the hypotheses that species and stocking will not affect biomass or nutrient accumulation. Species and stocking did not affect biomass accumulation after five years; however, species and stocking did influence nutrient mass. A. dealbata had higher nitrogen mass than E. globulus for total (397 kg ha(-1) more, i.e., 126% higher), foliage (188 kg ha(-1), 218%), branch (55 kg ha(-1), 95%), stem (120 kg ha(-1), 86%), and root (34 kg ha (-1), 109%) components, likely because A. dealbata fixes nitrogen. A. dealbata had lower calcium mass than E. globulus for branch (111 kg ha(-1), 60%) and stem (69 kg ha(-1), 39%) components. Root nitrogen and phosphorus masses and foliage, branch and root boron masses were significantly lower with a stocking density of 5000 ha(-1). Low stocking produced the same amount of total biomass as high stocking for both species and would be less expensive to plant. A. dealbata had higher nitrogen mass and likely increased soil nitrogen. E. globulus had high calcium mass in the stem and branches; off-site losses could be mitigated with stem-only harvests and debarking of stems in the field. Given the rainfall patterns and water availability constraints in Chile, additional criteria including water use efficiency would be required to determine the best species for bioenergy plantations in Chile. (C) 2017 Elsevier Ltd. All rights reserved. Department of Forest Resources and Environmental Conservation at Virginia Polytechnic Institute and State University; Departamento de Silvicultura, Facultad de Ciencias Forestales, Universidad de Concepcion; Department of Forestry and Environmental Resources at North Carolina State University; Virginia Agricultural Experiment Station; McIntire-Stennis Program of the National Institute of Food and Agriculture, United States Department of Agriculture; Chilean National Commission for Scientific and Technological Research; FONDECYTComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1140482] We gratefully acknowledge the support provided by the Forest Productivity Cooperative and especially Masisa S.A. for their role in providing the study site. We appreciate the support of the Department of Forest Resources and Environmental Conservation at Virginia Polytechnic Institute and State University, the Departamento de Silvicultura, Facultad de Ciencias Forestales, Universidad de Concepcion and the Department of Forestry and Environmental Resources at North Carolina State University. Funding for this work was provided in part by the Virginia Agricultural Experiment Station and the McIntire-Stennis Program of the National Institute of Food and Agriculture, United States Department of Agriculture. This work was supported by the Chilean National Commission for Scientific and Technological Research with FONDECYT Project Grant #1140482. We thank all those who helped complete the field work and to process the biomass samples especially Leonardo Munoz, Juan Espinoza, Yuri Burgos, Marco Yanez, Viviana Munoz and Pablo Mena. The use of trade names in this paper does not imply endorsement by the associated agencies of the products named, nor criticism of similar ones not mentioned. Public domain – authored by a U.S. government employee

There is an increasing interest in estimating biomass for loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm. var. elliottii), two of the most ecologically and commercially important tree species in North America. The majority of the available individual-tree allometric models are local, relying on stem diameter outside bark at breast height (dbh) and, in some cases, total tree height (H): only a few include stand age or other covariates. Using a large dataset collected from five forestry research institutions in the southeastern U.S., consisting of biomass measurements from 744 loblolly pine and 259 slash pine trees, we developed a set of individual-tree equations to predict total tree above-stump biomass, stem biomass outside bark, live branch biomass and live foliage biomass, as well as functions to determine stem bark fraction in order to calculate stem wood biomass inside bark and stem bark biomass from stem biomass outside bark determinations. Local and general models are presented for each tree attribute. Local models included dbh or dbh and H as predicting variables. General models included stand-level variables such as age, quadratic mean diameter, basal area and stand density. This paper reports the first set of local and general allometric equations reported for loblolly and slash pine trees. The models can be applied to trees growing over a large geographical area and across a wide range of ages and stand characteristics. These sets of equations provide a valuable alternative to available models and are intended as a tool to support present and future management decisions for the species, allowing for a variety of ecological, silvicultural and economic applications, as regional assessments of stand biomass or estimating ecosystem C balance. 2014 Elsevier B.V. All rights reserved.

There is growing interest in using switchgrass (Panicum virgatum L.) as a biofuel intercrop in forestry systems. However, there are limited data on the longevity of intercropped bioenergy crops, particularly with respect to light availability as the overstory tree canopy matures. Therefore, we conducted a greenhouse study to determine the effects of shading on switchgrass growth. Four treatments, each with different photosynthetically active radiation (PAR) levels, were investigated inside the greenhouse: control (no shade cloth, 49 % of full sunlight), low (under 36 % shade cloth), medium (under 52 % shade cloth), and heavy shade (under 78 % shade cloth). We determined the effect of shading from March to October 2011 on individually potted, multi-tillered switchgrass transplants cut to a stubble height of 10 cm. In the greenhouse, there was a reduction in tiller number, tiller height, gas exchange rates (photosynthesis and stomatal conductance), leaf area, above- and belowground biomass and light-use efficiency with increasing shade. Total (above- and belowground) biomass in the control measured 374 ± 22 compared to 9 ± 2 g pot−1 under heavy shade (11 % of full sunlight). Corresponding light-use efficiencies were 3.7 ± 0.2 and 1.4 ± 0.2 g MJ−1, respectively. We also compared PAR levels and associated aboveground switchgrass biomass from inside the greenhouse to PAR levels in the inter-row regions of a range of loblolly pine (Pinus taeda L.) stands from across the southeastern United States (U.S.) to estimate when light may limit the growth of intercropped species under field conditions. Results from the light environment of loblolly pine plantations in the field suggest that switchgrass biomass will be significantly reduced at a loblolly pine leaf area index between 1.95 and 2.25, which occurs on average between ages 6 and 8 years across the U.S. Southeast in intensively managed pine plantations. These leaf area indices correspond to a 60–65 % reduction in PAR from open sky.

Site-specific constraints on foliage development and leaf area duration were investigated in two-year-old Pinus radiata D. Don. plantations established under a factorial combination of soil tillage (shovel vs. subsoil + bedding + shovel), fertilization (B only vs. N, P, K, and B), and weed control (pre-plant vs. pre-plant + two-year banded) at three contrasting textural (sand, clay and ash) and climatic soil-site conditions in the Central Valley of Chile. We examined site effects and five treatments at each site to test hypotheses that soil tillage and nutrient and water limitations, would not influence foliage development or leaf area duration. Site effects were evident for foliage development and leaf area duration. Improved nutrient availability increased fascicle length at the sand and clay sites. Improved water availability increased fascicle length and leaf area duration at the sand site, and increased fascicle number at the sand and clay sites. Soil tillage reduced fascicle length at the ash site. Fascicle length may be influenced by factors including water and nutrient availability and soil and air temperature; however based on our data and indications in the literature that the largest effects on foliage length have been associated with resource availability we hypothesize that tillage may have induced nutrient and or water limitations at the ash site.

Fertilization and irrigation may substantially increase productivity of forests by increasing stand leaf area index and the efficiency of converting intercepted light into wood biomass. This stand-level growth response is the summation of individual tree responses, and these tree-level responses are often non-linear, resulting from shifting in the intensity of competition and dominance. We examined tree-level responses of aboveground net primary production (ANPP), absorbed photosynthetically active radiation (APAR) and (light use efficiency) LUE in relation to tree size class to explore how stand-level outcomes depend on shifting patterns among trees. We evaluated the production ecology of a nine-year-old loblolly pine (Pinus taeda L.) plantation, 2 years after the initiation of treatments: control, irrigation, fertilization and irrigation + fertilization. We measured tree level ANPP, simulated APAR for individual tree crowns using the MAESTRA process-based model and calculated LUE (ANPP/APAR) in relation to tree size to explore the influence of tree dominance on both light capture and light use efficiency. Fertilization and irrigation + fertilization strongly increased both APAR and LUE, in contrast to little effect of irrigation alone. Tree size had a strong influence on APAR and LUE across all treatments; the largest 20% trees showed 3.4 times greater ANPP when compared to the smallest 20% trees, with 66% resulting from higher APAR, and 34% from higher LUE, than the smallest 20% of trees. Fertilization increased the growth of the largest 20% trees 2-fold (8.6 kg tree−1 year−1), with 29% of the increase resulting from higher APAR (13.7 GJ tree−1 year−1), and 71% from higher LUE (0.63 g MJ−1), relative to the largest trees in the control treatment (4.3 kg tree−1 year−1, 11 GJ tree−1 year−1 and 0.39 g MJ−1, respectively). Irrigation and fertilization tripled production (13.2 kg tree−1 year−1) of the largest trees with an even greater proportional contribution from increased LUE (15.1 GJ tree−1 year−1, 85% response contribution; APAR 0.87 g MJ−1, 15% response contribution). Overall, large trees grow faster than smaller trees because of greater light capture, whereas the greater response of large trees to treatments resulted more from increased efficiency of using light.

International audience; We used published data from nine sites where nutrient and water optimization studies had been installed in a 2 × 2 factorial design to determine maximum biomass production in response to a simple set of treatments. We tested for site and treatment effects on the relationships between stem, aboveground (stem, branches, foliage) and total (aboveground + roots) biomass production versus intercepted light (light use efficiency, LUE). We also estimated the additional carbon stored as a result of treatment. The sites were located in Australia (Pinus radiata), Brazil (Eucalyptus grandis × urophylla), France (Pinus pinaster), the United States in Georgia and North Carolina (Pinus taeda) and Hawaii (Eucalyptus saligna), Portugal (Eucalyptus globulus), South Africa (E. grandis), and Sweden (Picea abies). We hypothesized that site, treatment and their interaction would significantly affect LUE; however, we rejected our hypothesis because stem, aboveground and total LUE were not affected by site or treatment. The stem, aboveground and total LUE values were 1.21, 1.51, and 0.85 g MJ−1, respectively. The total LUE value was lower than that for stem and aboveground LUE because a different population was used for the analysis (only five of the nine sites had total production data), and the total LUE relationship had a zero intercept whereas the stem and aboveground LUE relationships had a negative intercept. The average amount of additional carbon that would be stored by the irrigation, fertilization, and fertilization plus irrigation treatments was 3.9, 6.8 and 13.4 Mg CO2 equivalents ha−1 yr−1, respectively. These additional carbon storage estimates, based on these research studies with annual nutrient and water applications, were similar to results obtained in operational settings with less intensive nutrient applications.

We examined environmental factors affecting growth rates of Pinus radiata in Chile. The relationships between annual volume growth and soil, climate, canopy and stand factors were analysed using data from 48 permanent sample plots in P. radiata plantations in central Chile. Water availability (as affected by precipitation, soil water holding capacity and potential evapotranspiration) appeared to be the factor most limiting to leaf area and growth. Maximum growing season temperature also negatively affected growth. Sites with the highest productivities had the lowest annual water deficits. The most productive sites used water and light more efficiently. Growth per unit of potential evapotranspiration ranged from 0.5 to 1.6 kg of wood per m 3 of water and growth per unit of radiation ranged from 0.3 to 0.5 g of wood per MJ of photosynthetically active radiation for low and high productivity sites. The inclusion of simple climatic variables such as maximum temperature and precipitation into Chilean P. radiata growth and yield models should improve their performance.

We estimated net carbon emission and sequestration directly attributable to common forest fertil- ization practices for pine plantations in the southeast United States. We used data from the literature to estimate the carbon emissions associated with the production, transportation, and application of fertilizers used for mid-rotation and early rotation applications as well as the stem wood growth response to these applications. These data were scaled to a regional basis with data from the literature and newly acquired fertilizer application information. Product disposition projections were completed through 125 years (five 25-year rotations). On average, application of nitrogen with 28 kg of elemental phosphorus ha 1 to mid-rotation stands sequestered 19.2 Mg ha 1 carbon dioxide (CO2) equivalents as additional stem growth per CO2 equivalent of emissions associated with the fertilizer application. Maximum combined emissions from forest fertilization were 0.34 Tg year 1 CO2 equivalents in 2002, whereas maximum sequestration was 8.70 Tg year 1 CO2 equivalents in 2007. Sequestration lagged emissions because of the long (up to rotation length) stem wood growth response period. After 100 years, approximately 38% of the CO 2 equivalent sequestration attributed to mid-rotation fertilization would still be in use or in a landfill, whereas 26% would have been emitted without capturing energy and 36% would have been used as an energy source. Carbon sequestration associated with forest fertilization was related to the area fertilized annually, which may have fluctuated with fertilizer material and wood product prices. Capturing economic value from the sequestered carbon would likely increase forest fertilization and conse- quently increase carbon sequestration. FOR .S CI. 58(5):419-429.

Intra-annual nutrient (nitrogen, phosphorus, potassium, calcium and magnesium) flux was quantified for Pinus taeda L. at a nutrient-poor, well-drained sandy site in Scotland County, NC, USA where a 2 × 2 factorial of irrigation and nutrition was applied in four replications in a 10-year-old stand with 1200 stems ha(-1). Treatments were applied with the goal of providing optimum nutrition (no nutritional deficiencies) and water availability. Component (foliage, branch, stem and root) nutrient content was estimated monthly for 2 years using nutrient concentration and phenology assessments combined with destructive harvests. Positive flux values indicated nutrient accumulation in the trees while negative values indicated nutrient loss from the trees. Fertilization significantly increased nitrogen, phosphorus, potassium, calcium and magnesium flux 140%, on average, over non-fertilized. Irrigation significantly increased calcium flux 28% while there was no significant irrigation effect on nitrogen, phosphorus, potassium or magnesium. Maximum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were 0.36 and 1.05 for nitrogen, 0.042 and 0.095 for phosphorus, 0.13 and 0.51 for potassium, 0.27 and 0.42 for calcium, and 0.04 and 0.12 for magnesium, respectively. Maximum flux was coincident with ephemeral tissue (foliage and fine root) development and likely would be higher in stands with more foliage than those observed in this study (projected leaf area indices were 1.5 and 3.0 for the non-fertilized and fertilized stands). Minimum nutrient fluxes (kg ha(-1) day(-1)) for non-fertilized and fertilized stands were -0.18 and -0.42 for nitrogen, -0.029 and -0.070 for phosphorus, -0.05 and -0.18 for potassium, -0.04 and -0.05 for calcium, and -0.02 and -0.03 for magnesium, respectively. Minimum fluxes were typically observed in the dormant season and were linked to foliage senescence and branch death. Foliage and branch component nutrient contents were out of phase for nitrogen, phosphorus, potassium and magnesium, indicating nutrient retranslocation and storage in branches prior to foliage development and after foliage senescence. In contrast to current operational fertilizer programs which often target winter application these data suggest the best application times would be during foliage development.

1Facultad de Ciencias Forestales Universidad de Concepcion, Cooperativa de Productividad Forestal, Casilla 160-C, Correo 3, Concepcion, Chile 2Department of Forestry and Environmental Resources, North Carolina State University, Jordan Hall 3108, Box 8008, Raleigh, NC 27695-8008, USA 3Department of Forest Resources and Environmental Conservation, Virginia Polytechnic Institute and State University, 228 Cheatham Hall, Blacksburg, VA 24060, USA

There is little understanding of how silvicultural treatments, during the early stages of tree development, affect allometric relationships. We developed and compared stem, branch, foliage, coarse and fine root biomass, and leaf area estimation equations, for four-year-old genetically improved radiata pine trees grown on three contrasting soil-site conditions. At each site, selected trees were destructively sampled from a control (shovel planted, no weed control, fertilized with 2 g of boron), a shovel planted + weed control (2 first years) + complete fertilization (nitrogen + phosphorus + boron 2 first years + potassium 2nd year), and a soil tillage (subsoil at 60 cm) + weed control (first 2 years) + complete fertilization treatment. Tissues were separated into foliage, branch, stem, fine and coarse roots (>2 mm). Regression equations for each tree biomass tissue versus leaf area were fit for each site and compared among treatments and sites with the same genetic material. Our results indicated that individual tree biomasses for young plantations are affected by silvicultural treatment and site growing conditions. Higher variability in estimates was found for foliage and branches due to the ephemeral nature of these components. Stem biomass equations vary less, but differences in biomass equations were found among sites and treatments. Coarse root biomass estimates were variable but less than expected, considering the gradient among sites. Similar to stem biomass, a simple positive general linear relationship between root collar diameter, or diameter at breast height with coarse roots biomass was developed across sites and treatments.

Exotic Pinus taeda L. plantations may be more productive than native ones. Several hypotheses may explain this difference; however, process models with a light-interception-driving variable cannot test these hypotheses without foliage display first being quantified in native and exotic trees. We quantified leaf area duration in North Carolina, USA (natural), and Gobernador Virasoro, Argentina (exotic), with no additional nutrients and optimum fertilizer treatments. More (60%–100%) foliage was displayed but for a shorter (∼86 fewer days) time per fascicle in the exotics than in the naturals. Study inference was limited, with only one native and one exotic site. However, while the sites were markedly different in soils, climate, resource availability, and genetics, and we observed significant differences in fascicle display and longevity, most fascicles at both sites survived two growing seasons: the one in which they were produced and the subsequent one. This robust finding indicates it would be reasonable to use two growing seasons for fascicle longevity in process modeling to test hypotheses explaining growth differences in native and exotic loblolly. Fertilization had no effect on any exotic tree parameter, but it increased natural tree fascicle number (24%) and length (30%).