Table 3 - uploaded by David W. Hann
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Descriptive statistics of the data used to model merchantable cubic foot volume above breast height in southwest Oregon.
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The equations used in ORGANON for predicting the various elements of tree volume and taper were published in the 1980s: bark thickness equations (Larsen and Hann 1985), stump diameter at 1.0-feet above the ground equations (Walters et al. 1985), total stem cubic foot volume above breast height equations (Walters et al. 1985, Hann et al. 1987), merc...
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... Tree volume was estimated using the available allometric taper and volume equations. Total tree-level volume of red spruce and balsam fir were estimated by using the taper equations of Li et al. (2012), while for Douglas-fir and loblolly pine trees were estimated by using the equations of Hann (2011) and Tasissa et al. (1997), respectively. The required height and height to crown base of all trees, which were partly missing in the datasets for Douglas-fir, balsam fir, and red spruce, were estimated from species-specific DBH-height relationships determined from the data, while considering the associated plot within site-specific random effects using the nonlinear mixed effect modelling approach described by Kuehne et al. (2016). ...
Thinning is commonly applied to increase the tree growth in forest stands by improving the availability of water, light, and nutrients. However, thinning also can increase soil evaporation and intensify wind penetration into residual stands, potentially increasing moisture stress and wind damage. To strengthen our understanding of tree-level responses to thinning, we used long-term measurements from three controlled, replicated thinning experiments for four commercially important softwood species in North America, including the shade-intolerant loblolly pine (Pinus taeda L.), moderately shade-tolerant Douglas-fir (Pseudotsuga menziesii Mirbel), and shade-tolerant red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea L.). The objectives of this study were to assess the long-term (13-24 years) pattern of individual-tree growth and survival after a variety of commercial thinning treatments. Our results showed that on average tree volume growth was 31% higher in thinned stands relative to unthinned stands irrespective of species and tree size. However, the rate of growth decreased over time following thinning for loblolly pine and Douglas-fir, while a curvilinear relationship was observed for red spruce and balsam fir. Tree size was important only for loblolly pine where growth increased linearly with the size of residual trees. Tree survival was also higher in thinned stands than unthinned stands across all species in the long-term, but a significant initial decrease in survival was found in balsam fir and red spruce immediately after thinning due primarily to windthrow and breakage. Stand relative age and total basal area at time of thinning were negatively related with growth for all tree species, which may indicate that the trees examined in this study had reached their maximum growth potential or had a period of suppression prior to thinning. The relatively minor influence (i.e., 5% of total R 2) of thinning intensity on growth may suggest that the timing of thinning (i.e., age of trees when thinned) and stand characteristics (species, tree age, and stand basal area) were more important in promoting individual-tree growth. However, a heavier intensity of thinning increased survival of loblolly pine and Douglas-fir trees. Overall, our results indicated that thinning can increase tree growth and survival across species of varying shade tolerance. To ensure the maximum benefits of thinning, the timing and intensity of the treatment needs to be adjusted for species characteristics, stand structure, and tree age.
... The tree-ring measurements covered the period from 1997 to 2015. Basal area increments (BAI) (mm 2 year À1 ) over the same period were estimated assuming the crosssection of the tree conformed to a circle at the beginning and end of each annual growth period, and that diameter inside bark at breast height in 2015 (DIB 15 ) was the following function of DBH in 2015 (Hann, 2011 ...
Many hectares of intensively managed Douglas-fir (Pseudotsuga menziesii Mirb. Franco) stands in western North America are fertilized with nitrogen (N) to increase growth rates, but only about ⅔ of all stands respond. Understanding the mechanisms of response facilitates prioritization of stands for treatment. The primary objective of this study was to test the hypothesis that the short-term basal area growth response to a single application of 224 kg N ha⁻¹ as urea was associated with reduced stable carbon isotope discrimination (Δ¹³C) and increased intrinsic water use efficiency (iWUE) in a 20-yr-old plantation of Douglas-fir in the Oregon Coast Range, USA. Increment cores were measured to estimate earlywood, latewood, and total basal area increment over a time series from 1997 to 2015. Stable carbon isotope discrimination and iWUE were estimated using earlywood and latewood stable carbon isotope concentrations in tree-ring holocellulose starting seven years before fertilization in early 2009 and ending seven years after treatment. A highly significant (p < 0.01) interaction effect between fertilization treatment and year was found for total basal area growth and earlywood basal area increment. Specifically, fertilized trees showed significant responses (p < 0.05) in total basal area growth and earlywood basal area increment in the first (2009) and second (2010) growing seasons after fertilization in 2009. A marginally significant (p < 0.10) fertilization effect was found for latewood basal area increment only in the first growing season after treatment. A significant treatment × year interaction was also found for Δ¹³C and iWUE in earlywood and latewood. Fertilization significantly reduced earlywood Δ¹³C and increased earlywood iWUE in the first and second growing seasons after fertilization. Only a marginally significant fertilization effect was detected for latewood Δ¹³C and iWUE in the second growing season after treatment. Previous studies of N fertilization of Douglas-fir forests have reported consistently increased growth and iWUE on low productivity sites treated with relatively high fertilization rates. This study suggested that these responses can also be observed on highly productive sites despite their lower frequency and apparently shorter duration. Other key mechanisms driving growth responses appear less important than iWUE, including an increase in LAI and shift from belowground to aboveground carbon allocation.
... Periodic annual ∆V was calculated by: 1. Using the volume equation of Hann (2011) to predict the total stem cubic foot volume of each tree with measured values of D, H, and CR at both the start and end of the growth period. Differences in definitions of HCB used in the SMC data set and the volume equations were ignored. ...
... These results indicate possible illconditioning in the correlation matrix of the predictor variables or in a misspecification of the model forms (Weiskittel et al. 2011). As discussed in Weiskittel et al. (2011), thinning response modifiers, such as Equation (6a) and Equation (6b), can be needed if the thinning: (1) changes the residual population by removing damaged trees that often have reduced height and diameter increments (Hann andHanus 2002a and2002b), (2) increases the probability of damage, such as caused by wind or snow, to the residual trees, (3) causes thinning shock, (4) increases crown density, (5) accelerates differences among crown classes in the dynamics of diameter increment, height increment, and/or crown recession, (6) increases the amount of competing vegetation on the plots which results in increased competition, and/or (7) increases the resources available to the residual trees beyond expectations based on thinning intensity, i.e., level of stand density reduction [for example, as represented BA and BAL in Equation (4)]. If any of these possible consequences of thinning do occur and they are not adequately represented in the thinning response modifier equation, then problems with model misspecification can occur. ...
The Stand Management Cooperative (SMC) was established in 1985 to study the impact of planting density and subsequent silvicultural treatments upon stand and tree development, including growth, yield, and wood quality in plantations located throughout the Pacific Northwest of the US and Canada. The SMC Type I installations (Type I) were created to simulate, through initial respacing of existing plantations, the effect of planting at different densities. The assumption was that stand development after respacing would not deviate substantially from that expected after planting at similar initial densities. This assumption was evaluated in this study by assessing the possible impact of respacing upon the site index of the plots and volume increment (V) of the trees.
The data used in the analysis came from the 30 SMC’s Type I installations that had been established in Douglas-fir sapling stands located in western Washington and Oregon. To simulate the effect of different planting densities, the average number of stems per acre was calculated for all the plots within an installation (ISPA), and a subset of the plots were respaced to retain one half of the initial trees (hereafter called the ISPA/2 plots) or to retain one fourth of the initial trees (hereafter called the ISPA/4 plots). The remaining plots retained the initial spacing (hereafter called the ISPA/1 plots).
The site index analysis found no significant trend in estimated site index across stand age for the ISPA/1 and ISPA/2 plots but a significant trend for the ISPA/4 plots. The site index analysis also found that the average site index for the ISPA/2 and ISPA/4 plots were significantly lower than the ISPA/1 plots, with the difference being greater for the ISPA/4 plots. Possible explanations for these differences were also explored.
Five different analysis techniques were explored for examining the possible impact of respacing upon annual tree volume increment. Two of the techniques used simultaneous methods and the remaining three techniques used a sequential modeling method found in Weiskittel et al. (2011). The results of this comparison indicated that the two simultaneous methods suffered from possible ill-conditioning in the correlation matrix of the predictor variables or in a misspecification of the model form. Therefore, a three step sequential modeling method was used to evaluate the impact of respacing upon the annual volume increment of Douglas-fir trees.
The results of the volume increment analysis showed a significant increase in annual volume increment following respacing, with the greatest increase occurring for the trees on the ISPA/4 plots. The annual volume increment was predicted to increase to a peak and then decline as time since respacing increased. Similar effects have been previously reported for trees that had been thinned.
The results of this analysis indicate that the assumption that respacing would have no impact other than that expected from planting at different densities is probably not true. Instead, respacing has modified the top height population in a manner that affected the estimates of site index on the respaced plots, and the respaced plots are behaving like they had been precommercially thinned due to the enhanced growth of individual trees on respaced plots.
... Also, basal area growth of survivors provided the same trend as would be expected for change in quadratic mean diameter. Tree volumes for each inventory were estimated from taper equations developed by Walters and Hann (1986) . If the verified 2004 height measurement was less than the Y1991 measurement , the tree was assumed to have had negligible height growth, and the 2004 height was assigned to both measurement dates. ...
Complex management objectives for many publicly owned Douglas-fir forests have prompted renewed interest in silvicultural systems other than clearcutting. The College of Forestry Integrated Research Project at Oregon State University was implemented to test for differences in economic, biological, and human responses to group selection and two-story silvicultural systems. Three separate blocks were established and treated between 1989 and 1991. Trees were measured immediately after the harvest treatments (1991 or 1992) and after the 2004 growing season. Responses of residual overstory trees to initial group selection and two-story treatments were tested relative to untreated controls units in terms of (1) gross basal area and stem volume growth of all residual trees and of the 10 largest trees per acre; (2) gross basal area and stem volume growth conditional on initial basal area and stem volume, respectively, of all residual trees and of the 10 largest trees per acre; and (3) mortality of all overstory trees. Basal area and volume growth were greatest in the control and least in the two-story treatment, but volume growth conditional on initial volume did not differ significantly among treatments. Mortality was significantly greater in the two-story treatment. Overstory growth release in residual Douglas-fir may require 10 years or more to appear after regeneration cuts on some sites, and the possibility of increased overstory mortality complicates attainment of desired long-term structure under two-story silvicultural systems.
Nitrogen (N) fertilizer is a commonly applied silvicultural treatment intended to promote growth of intensively managed coast Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii] plantations in the Pacific Northwest region of the US (PNW) and adjacent areas of Canada. Because responses have been geographically variable, fertilization trials were established in the Coast Range of northwestern Oregon to enhance general understanding of Douglas-fir growth response and test the economic viability of operational N applications in this subregion. Twenty-three operational stands comprising the trials were dominated by Douglas-fir, had an initial total age of 16–24 years, had been pre-commercially thinned 7–10 years prior to establishment of the fertilization trials, and started with 387–1260 trees ha⁻¹. Nitrogen fertilizer was applied aerially as pelletized urea (46% N) at a rate of 224 kg N ha⁻¹ to half of each stand during the dormant season of 2009–2010. In the dormant season of 2016–2017, seven growing seasons following fertilizer application, forty sample trees were felled in ten randomly selected stands to assess the influence of N-fertilization on stem form. A variable exponent taper model was developed using a nonlinear mixed-effects modelling approach. A tree-level random effect and a first-order continuous autoregressive [CAR(1)] error process were incorporated into the model to facilitate accurate tests of significance on model parameter estimates. The variable exponent taper model captured significant variation in stem form resulting from fertilization based on interaction with a crown variable, suggesting that the N-fertilization influence on stem form was mediated by initial crown length of trees with given diameter and height. Volume predictions from the resulting taper model were compared to those from the regional growth model ORGANON, which assumes no influence of fertilization on stem form. The regional growth model ORGANON significantly (p < 0.01) under-predicted fertilized tree volume by 3.6%. Results are being incorporated into individual-tree growth models to improve site-specific predictions of growth response. Improved understanding and modeling of mechanistic responses of foliage, growth, and stem form to fertilization may help discriminate between sites with high and low growth response potential. Mechanistic insights coupled with better site characterization should help improve the understanding of economic and environmental performance of fertilized Douglas-fir stands.
Application of progeny test breeding values to forecast yield gains at rotation-age in genetically improved stands remains a very challenging yet crucial task for breeders of Douglas-fir and other long-rotation timber species such as western hemlock, white spruce, Norway spruce, and Scots pine. Evaluation of the economic returns on genetic improvement requires reliable estimates of yield gains at rotation age. Large-plot realized gain trials should provide more accurate estimates of yield gain than inferences from progeny tests, but are most dependable when they reach rotation age or at least approach rotation age.
A set of coastal Douglas-fir realized genetic gain trials in western Oregon, based on a first-generation breeding program, was measured most recently at plantation ages ranging between 17 and 21 years. The trial was established on five sites at a spacing wide enough (3.6 × 3.6 m) to assume that the trees could be grown to rotation age with no further silvicultural intervention. A growth model, CIPSANON v. 4.0, projected the current tree lists from these trials to plantation age 60 years to facilitate estimation of yield gains at various rotation ages up to 60 years. The following two simulation approaches were explored: (1) apply genetic-gain multipliers developed from a previous study for diameter and height growth, and (2) assume that genetic gain differences were fully represented by plot-level site index expressed at the most recent measurement. The two approaches resulted in similar estimates of realized yield gain at plantation ages up to 60 years. Relative gain decreased over time, but absolute gain (in cubic meters or board feet) increased over time. Relative stand volume gain simulated to the average current rotation age of 50 years was about 30% of the relative realized gain measured at plantation age 10/12 years (birth age 13/15 years) and about 38% of the relative realized gain measured at plantation age 17–21 years (birth age 20–24 years).
Several validation needs were identified including magnitude of genetic-gain multipliers, duration of annual multiplier application over the duration of a simulation, adjustment of multipliers as the stand ages, and most appropriate multiplier resolution (tree versus stand). A potentially critical knowledge gap remains about any genetic improvement effects on yield gains associated specifically with increased carrying capacity that would be consistent with the crop ideotype concept.
Korean larch (Larix olgensis) is one of the main tree species for afforestation and timber production in northeast China. However, its timber quality and growth ability are largely influenced by crown size, structure and shape. The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots, but crown dynamic models has seldom been constructed. Therefore, this study aimed to develop height to crown base (HCB) and crown length (CL) dynamic models using the branch mortality technique for a Korean larch plantation. The nonlinear mixed-effects model with random effects, variance functions and correlation structures, was used to build HCB and CL dynamic models. The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China. The results showed that HCB progressively increases as tree age, tree height growth (HT growth) and diameter at breast height growth (DBH growth). The CL was increased with tree age in 20 years ago, and subsequently stabilized. HT growth, DBH growth stand basal area (BAS) and crown competition factor (CCF) significantly influenced HCB and CL. The HCB was positively correlated with BAS, HT growth and DBH growth, but negatively correlated with CCF. The CL was positively correlated with BAS and CCF, but negatively correlated with DBH growth. Model fitting and validation confirmed that the mixed-effects model considering the stand and tree level random effects was accurate and reliable for predicting the HCB and CL dynamics. However, the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation, and the fitting precision of the models was reduced. Therefore, from the point of view of application, we should take care to avoid setting up over-complex models. The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China.
