Diameter At Breast Height Growth Research Articles

Individual-Tree Diameter Growth Models for Mixed Nothofagus Second Growth Forests in Southern Chile

Second growth forests of Nothofagus obliqua (roble), N. alpina (raulí), and N. dombeyi (coihue), known locally as RORACO, are among the most important native mixed forests in Chile. To improve the sustainable management of these forests, managers need adequate information and models regarding not only existing forest conditions, but their future states with varying alternative silvicultural activities. In this study, an individual-tree diameter growth model was developed for the full geographical distribution of the RORACO forest type. This was achieved by fitting a complete model by comparing two variable selection procedures: cross-validation (CV), and least absolute shrinkage and selection operator (LASSO) regression. A small set of predictors successfully explained a large portion of the annual increment in diameter at breast height (DBH) growth, particularly variables associated with competition at both the tree- and stand-level. Goodness-of-fit statistics for this final model showed an empirical coefficient of correlation (R2emp) of 0.56, relative root mean square error of 44.49% and relative bias of −1.96% for annual DBH growth predictions, and R2emp of 0.98 and 0.97 for DBH projection at 6 and 12 years, respectively. This model constitutes a simple and useful tool to support management plans for these forest ecosystems.

Genetic variation of wood tracheid traits and their relationships with growth and wood density in clones of Pinus tabuliformis

To improve wood quality for pulpwood industries, it is important to examine not only wood density but also its components, especially tracheid characteristics. We studied genetic variations in the following tracheid traits by earlywood (EW) and latewood (LW): tracheid length (TL), double wall thickness (WT), radial lumen diameter (R_D1), tangential lumen diameter (T_D1), radial central diameter (R_D2), and tangential central diameter (T_D2). We also studied the relationship with the following growth traits: diameter at breast height (DBH), height (H), crown breadth south-north axis (NSC), crown breadth east–west axis (EWC), ring width (RW), latewood percentage (LWP), and wood density (WD). All sample materials were collected from a 33-year old clonal seed orchard of Pinus tabuliformis Carr. Genetic variation among clones was moderate for all tracheid traits, 9.49–26.03%. Clones significantly affected WT, R_D1, R_D2, T_D1, T_D2, and the two ratios WT/R_D1 and TL/T_D2 in EW but had no effects in LW. Clones significantly affected TL in LW but had no effects in EW. $$ H\frac{2}{C} $$ was higher in LW (0.50) than in EW (0.20) for TL, while $$ H\frac{2}{C} $$ was higher in EW (0.27–0.46) for other tracheid traits and the two ratios (TL/T_D2 and WT/R_D1) than in EW (0.06–0.22). WD and TL were significantly positively correlated, but WT and TL were negatively correlated both at individual and clone levels; all tracheid diameters and the four ratio values (EW_WT/R_D1, LW_WT/R_D1, EW_TL/T_D2 and LW_TL/T_D2), were strongly positively correlated with DBH, H, NSC, WEC and RW, and strongly negatively correlated with WD both at individual and clone levels. The most important variables for predicting WD were LW_TL, EW_WT and R_D1 in both EW and LW (r2 = 0.22). Selecting the top 10% of the clones by DBH would improve DBH growth by 12.19% (wood density was reduced by 0.14%) and produced similar responses between EW and LW for all tracheid traits: a reduction of 0.94 and 3.69% in tracheid length and increases in tracheid diameters (from 0.36 to 5.24%) and double wall thickness (0.07 and 0.87%). The two ratios WT/R_D1 and TL/T_D2 across tissues (EW and LW) declined 0.59 and 4.56%, respectively. The decreased tracheid length and the ratio between tracheid length and diameter is disadvantageous for pulp production. The unfavorable relationship of tracheid traits with wood density indicate that multiple trait selection using optimal economic weights and optimal breeding strategies are recommended for the current long-term breeding program for P. tabuliformis.

Inheritance and expression stability of exogenous genes in insect-resistant transgenic poplar

To understand the genetic and expression stability of transgenic insect-resistant poplar 741, this study compared the experimental plantations of transgenic insect-resistant poplar 741 lines (pb1, pb6, pb11, pb17, and pb29) with non-transgenic poplar 741, P. tomentosa Carr.f.yixianensis (poplar 84 K) and transgenic hybrid progeny lines cultured from immature embryos. The insect resistance and growth stability of transgenic poplar 741 were investigated by detecting exogenous genes by polymerase chain reaction (PCR), measuring the diameter at breast height (DBH) and volume growth, and performing insect-resistance tests against Clostera anachoreta and Hyphantria cunea. The inheritance and expression of the exogenous gene was also examined in transgenic hybrid progeny lines. The results revealed that the exogenous gene was stable, remaining stable in 8–10-year-old transgenic poplar 741 trees. No significant difference was found between the height of 10-year-old transgenic poplar 741 and non-transgenic poplar 741 in the experimental plantations in Baoding, China. The DBH and volume growth of pb17 was significantly greater than that of pb29 and pb11. The 8-year-old transgenic poplar 741 pb29 grown in Zhuozhou showed no significant difference from poplar 741 in terms of height growth, DBH, and volume. From 1999 to 2013, pb29-fed larvae (C. anachoreta larvae and H. cunea) exhibited stable mortality rates >79%. Likewise, pb11-fed larvae showed stable mortality rates (C. anachoreta larvae had mortality rates >75%, and H. cunea larvae exhibited rates >80%). pb17 conferred low insect-resistant stability, showing mortality rates that varied from 28.2 to 99.27% in C. anachoreta and H. cunea larvae. Among the hybrid progeny lines acquired by hybridization of pb1, pb29, and pb11 with 84 K poplar, the ratios of PCR-positive to PCR-negative lines for the BtCry1Ac gene were 1.31, 1.15, and 0.86, respectively. X 2 tests showed that the ratio was consistent with the Mendelian law of 1:1 segregation controlled by an allele pair. The hybrid progeny of pb6 × 84 K had a segregation ratio of 3:1. The nptII gene followed the same segregation rule as Cry1Ac. The transgenic hybrid progeny that contained Cry1Ac gene exhibited the same insect resistance as the parent plants.

Growth of Stone pine (Pinus pinea L.) European provenances in central Chile

Abstract: Pinus pinea is characterized by phenotypic plasticity, tolerance to harsh soils and climates, but low differentiation in growth parameters and low genetic variability. Growth and cone production of six European stone pine provenances (two from Italy, three from Spain and one from Slovenia) were analyzed in a field trial experiment established in central Chile. The study evaluated height, diameter at breast height (DBH) and crown diameter growth of 147 nineteen-year-old trees per provenance, as well as fruiting variables (i.e., number of cones per tree and cone weight). Survival over the first 7 years was also evaluated. Provenances significantly differed in cone number per tree, cone weight, height and DBH growth, and crown diameter growth. Provenances were grouped according to growth and production variables: one group included the Italian and Slovenian provenances, the second group Andalucia and Sierra Morena (Spain), and the third included Meseta Castellana (Spain). Individual cone production was positively correlated with cone weight and other growth variables. Meseta Castellana provenance showed the highest growth and productivity. Our results provide useful information for the selection of P. pinea provenances to be used in new plantations in central Chile.

A Meta-analysis on the Effect of Forest Thinning on Diameter Growth and Carbon Stocks in Korea

With results from previous Korean studies on forest thinning, we conducted a meta-analysis on the effect of thinning on diameter at breast height (DBH) growth and carbon (C) stocks (tree, litter layer, coarse woody debris (CWD), and soils) in Korean forests. Thinning increased the DBH growth and the C stocks in soils by 39.2% and 12.8%, respectively, while it decreased the C stocks in tree by 30.9%. In contrast, thinning had no significant effect on the C stocks in litter layer and CWD. The DBH growth and the C stocks in tree showed significant correlations with thinning intensity and recovery time. The C stocks in litter layer correlated with recovery time while those in CWD and soils did not show significant correlation neither with thinning intensity nor with recovery time. Regression models of the DBH growth and the C stocks in tree were developed to quantify the effect of thinning intensity and recovery time. An integration of the regression model of the tree C stock into forest carbon models is expected to be essential to quantify the effect of thinning on the C stocks in litter layer, CWD, and soils. We also suggested expansion of study species, long-term and frequent monitoring, and investigation on understory vegetation in order to elucidate changes in Korean forests following thinning practices.

Dynamics of aboveground biomass accumulation in monospecific and mixed-species plantations of Eucalyptus and Acacia on a Brazilian sandy soil

In this study, we hypothesized that a positive impact of Acacia trees when grown in mixed stands with Eucalyptus trees in N-deficient soil, leads to a higher biomass production in mixed stands relative to the monocultures. A randomized block design experiment was set up in a Brazilian Planosol to assess the dynamics of aboveground accumulation of monospecific Eucalyptus urograndis (Eucalyptus urophylla S. T. Blake×Eucalyptus grandis W. Hill ex Maiden), with or without nitrogen fertilization (E100+N and E100, respectively), and Acacia mangium (A100) stands, and two arrangements of both species in mixed plantations (E50A50 and E100A100). The height (H), diameter at breast height (DBH), litterfall, and aboveground biomass production were measured over a full rotation. Our results partially confirm the initial hypothesis. Acacia showed limited competitive ability against Eucalyptus, which resulted in a stratified canopy in the mixed stands, with Eucalyptus dominating the top layer, especially in the E100A100 arrangement. The E100A100 stand showed greater overall productivity compared with the E100 stand and similar productivity relative to the E100+N stand. The E50A50 arrangement produced taller Eucalyptus trees with a larger diameter than the monoculture, although the smaller population of Eucalyptus trees in this mixed stand resulted in an overall biomass production that was equal to or less than that of the monocultures E100 and E100+N, respectively. However, the DBH growth rate of Eucalyptus trees in E50A50 showed no signs of stagnation up to 60months, which is different from the other treatments. Consequently, the harvesting age of such stands can be extended, which allows for the production of Eucalyptus logs with greater value for the lumber market.

Impact of thinning intensity on the diameter and height growth of Larix kaempferi stands in central Korea

The objective of this study was to examine the effect of thinning intensity on the diameter at breast height (DBH) and height growth of Japanese larch (Larix kaempferi) stands located in the Yangpyeong-gun region of central Korea. In addition, a growth model was developed from the thinning practice. Four sample plots were prepared separately and thinned at different intensities (0%, 10%, 20%, and 40% cutting based on the number of trees, respectively) in 1997. DBH and height of individual trees were measured independently in 1997 and 2009. The mean DBH for LT00, LT01, LT02, and LT03 increased from 12.0, 12.1, 12.0, and 12.7 cm in 1997 to 15.3, 16.1, 16.2, and 17.1 cm in 2009, respectively. In addition, the mean height for each plot increased from 11.9, 13.5, 13.6, and 12.0 m in 1997 to 17.0, 17.0, 17.1, and 18.1 m in 2009, respectively. Thinning intensity was found to have a significant positive effect on DBH growth (P < 0.05), whereas there was no definite effect on height growth (P > 0.05). This result can be attributed to the fact that thinning promotes DBH growth by reducing horizontal-spacing competition between neighboring trees for securing sunlight and growing space. The developed growth model with our results showed a high degree of reliability (R2 = 0.86) and could generalize the thinning intensity based on DBH growth.

Effect of first thinning and pruning on the individual growth of Pinus patula tree species

The effect of first thinning and pruning on height, diameter at breast height (DBH), and volume growth was studied in individual trees of Pinus patula Schiede and Deppe in Chongoni Plantation, using four plots for thinning trials. Each of the plots was 0.5 ha and subjected to one of the following silvicultural treatments: first thinning and pruning, first thinning and no pruning, pruning and no thinning, and control (no pruning and no thinning). The silvicultural treatments were randomized in four replicates. Fourteen years after planting, the following parameters were measured including total height, DBH, and volume. The highest DBH and volume growth was observed in thinning and pruning, while the highest growth in height was observed where there was pruning and no thinning. Clearly, both thinning and pruning are an important management option in pine species plantations in Malawi to maximize the increase in volume productivity.

A Study of Variation of Growing Traits of Liriodendron and Its Excellent Provenance Selection

In this paper,Liriodendron provenance forest at the age of twenty-two in Qionglai National Forest Farm in Sichuan province was taken as the research object,the main growth traits such as tree height (H), diameter at breast height (DBH),volume (V),height under branch(HB) and crown width(CW) were determined in order to analyze the genetic variation and conduct the selection of its provenance. The results showed that there were statistically significant difference in H,DBH,and V among different provenances,while there were significant difference in HB,and CW. The average H,average DBH,average V, average CW and average HB of 9 provenances were 12.44 m,20.20 cm,0.2182 m3,3.18 m and 8.35 m respectively. The elevation level had a significant influence on the DBH growth of Liriodendron. The hereditabilities of tree height, DBH, volume of tree, CW and HB were 0.856, 0.847, 0.806, 0.576 and 0.547,which indicated that the growth traits were strongly controlled by genetic factors. Three superior provenances Liping Guizhou,Xuyong Sichuan and America A, were selected by synthetic evaluation. The selected provenances' genetic increments of DBH, H and stem volume were 19.56%, 6.60% and 35.36% respectively. Six superior individuals were selected out by comprehensive appraisal,whose average DBH,H and stem volume were 30.4 cm,15.17 m and 0.5230 m3 respectively, and exceeded the population means of 22.09%,14.47% and 66.63% respectively. This study provided the material conditions and theoretical basis for the cultivation and popularization of Liriodendron in Sichuan region.

Shelterwood cutting in a boreal mixedwood stand: 10-year effects of the establishment cut on growth and mortality of merchantable residual trees

We used two-step shelterwood cutting to release conifer advance growth and limit development of trembling aspen (Populus tremuloïdes Michx.) suckers in a stratified mixed aspen – conifer stand, in Quebec, Canada. This study presents the 10-year response of residual trees to the establishment cutting. We examined growth and mortality of merchantable trees (diameter at breast height (DBH)⩾9.1cm) following the application of different cutting intensities (0%, 35%, 50%, 65%, and 100% basal area removal). Initial post-cut densities were 1100, 670, 640, 580 and 150stemsha−1, respectively. Mortality of aspen was highest in the uncut control and 35% cut due to senescence, while mortality of paper birch (Betula papyrifera Marsh.) was highest in the 65% cut due to post-logging decadence. In the species mixture under study, the 50% cut allowed for the harvest of declining aspen without excessively opening the canopy that would be detrimental for residual paper birch. Low mortality, high recruitment and a relatively high DBH growth in this moderate cut resulted in a higher 10-year net increment in total basal area (7.0m2ha−1), compared to the 0%, 35%, 65%, and 100% cuts (2.6–3.7m2ha−1). This result was mostly attributable to balsam fir (Abies balsamea (L.) Mill.) that generated two-thirds of the net increment. Therefore, our growth results support retention of small merchantable conifer stems (DBH 9.1–15.0cm) as a basic strategy to limit hardwood invasion.

Identifying the biological effects of pre-commercial thinning on diameter growth in young Scots pine stands

Data from seven Scots pine (Pinus sylvestris L.) stands in central Sweden that had undergone pre-commercial thinning (PCT) were used to investigate the biological effect of PCT on the diameter at breast height (DBH) growth of the remaining trees. Two treatments were considered: a PCT treatment and a control (C) with no PCT. The DBH of the trees in each stand was measured on up to four occasions over 15 years. We examined mean DBH and DBH growth of the largest 300, 600, 900 and 1200 trees ha−1. Two methods of selecting the trees used to calculate the mean DBH values for each measurement occasion were considered: the actual mean DBH (Dma), which is based on the DBH distribution of the trees on the measurement occasion in question, and the genuine mean DBH (Dmg), which is based on the DBH distribution of the trees on the final measurement occasion of the study and therefore focuses on the same set of trees for all measurement occasions. There was no clear difference between the Dma- and Dmg-based DBH increments, but the Dmg values tended to be somewhat larger both for the C and PCT treatments. Over a 15-year period, the relative mean yearly increments (Dma/Dmg) for different tree size classes ranged from 0.91 to 0.98, with lower values for the C treatment and larger DBH size classes. We found that PCT promotes DBH growth: over a 15-year period, the increased growth amounted to about 2.0 mm year−1 compared to the trees in unthinned plots.

A meta-analysis on the impacts of partial cutting on forest structure and carbon storage

Abstract. Partial cutting, which removes some individual trees from a forest, is one of the major and widespread forest management practices that can significantly alter both forest structure and carbon (C) storage. Using 748 observations from 81 studies published between 1973 and 2011, we synthesized the impacts of partial cutting on three variables associated with forest structure (mean annual growth of diameter at breast height (DBH), stand basal area, and volume) and four variables related to various C stock components (aboveground biomass C (AGBC), understory C, forest floor C, and mineral soil C). Results show that the growth of DBH increased by 111.9% after partial cutting, compared to the uncut control, with a 95% bootstrapped confidence interval ranging from 92.2 to 135.9%, while stand basal area and volume decreased immediately by 34.2% ([−37.4%, −31.2%]) and 28.4% ([−32.0%, −25.1%]), respectively. On average, partial cutting reduced AGBC by 43.4% ([−47.7%, −39.3%]), increased understory C storage by 391.5% ([220.0%, 603.8%]), but did not show significant effects on C stocks on forest floor and in mineral soil. All the effects, if significant (i.e., on DBH growth, stand basal area, volume, and AGBC), intensified linearly with cutting intensity and decreased linearly over time. Overall, cutting intensity had more strong impacts than the length of recovery time on the responses of those variables to partial cutting. Besides the significant influence of cutting intensity and recovery time, other factors such as climate zone and forest type also affected forest responses to partial cutting. For example, a large fraction of the changes in DBH growth remains unexplained, suggesting the factors not included in the analysis may play a major role. The data assembled in this synthesis were not sufficient to determine how long it would take for a complete recovery after cutting because long-term experiments were scarce. Future efforts should be tailored to increase the duration of the experiments and balance geographic locations of field studies.

Effect of genotype by spacing interaction on radiata pine genetic parameters for height and diameter growth

Effect of genotype by spacing interaction on radiata pine (Pinus radiata D. Don) height and diameter at breast height (DBH) growth was studied using three spacings (1×1m, 1×2m and 2×3m) and 55 half-sib families in a long-term progeny trial. Examined were the effect of spacing and family on early tree height and diameter growth up to 10years, and on annual ring width (RW) and accumulated DBH of the surviving trees up to age 28years. The effects of spacing on heritability, and age–age genetic correlations were also studied using multiple-year measurements. Spacing had little or limited impact on tree height growth, but a highly significant effect on diameter growth. Spacing also had no significant effect on heritability for tree height, but a very significant effect on the patterns and values of heritability for diameter and DBH growth. Closer spacing was found to depress heritability estimates for DBH. Spacing was also observed to have a significant impact on age–age genetic correlation, and the higher competition level at closer spacing treatment distorted the age–age genetic correlation patterns for DBH due to higher mortality. The spacing effect on heritability was more apparent from early growth measurements due to relatively small mortality compared with the late age measurements. Our current study for the first time revealed significant and useful genotype by spacing interactions in radiata pine for DBH growth. The significant genotype by spacing interactions were mainly caused by a few well-performing families reacting more to spacing changes. Therefore, matching genotype with spacing has the potential to increase productivity of radiata pine plantations.

Relationships of tree height and diameter at breast height revisited: analyses of stem growth using 20-year data of an even-aged Chamaecyparis obtusa stand

Stem diameter at breast height (DBH) and tree height (H) are commonly used measures of tree growth. We examined patterns of height growth and diameter growth along a stem using a 20-year record of an even-aged hinoki cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl.) stand. In the region of the stem below the crown (except for the butt swell), diameter growth rates (ΔD) at different heights tended to increase slightly from breast height upwards. This increasing trend was pronounced in suppressed trees, but not as much as the variation in ΔD among individual trees. Hence, ΔD below the crown can be regarded as generally being represented by the DBH growth rate (ΔDBH) of a tree. Accordingly, the growth rate of the stem cross-sectional area increased along the stem upwards in suppressed trees, but decreased in dominant trees. The stem diameter just below the crown base (DCB), the square of which is an index of the amount of leaves on a tree, was an important factor affecting ΔDBH. DCB also had a strong positive relationship with crown length. Hence, long-term changes in the DCB of a tree were associated with long-term changes in crown length, determined by the balance between the height growth rate (ΔH) and the rising rate of the crown base (ΔHCB). Within the crown, ΔD's were generally greater than the rates below the crown. Even dying trees (ΔD ≈ 0 below the crown) maintained ΔD > 0 within the crown and ΔH > 0 until about 5 years before death. This growth within the crown may be related to the need to produce new leaves to compensate for leaves lost owing to the longevity of the lower crown. These results explain the different time trajectories in DBH–H relationships among individual trees, and also the long-term changes in the DBH–H relationships. The view that a rise in the crown base is strongly related to leaf turnover helps to interpret DBH–H relationships.

Distance-Dependent Competition Measures for Individual Tree Growth on a Taiwania Plantation in the Liuguei Area

Competition among trees within a stand occurs when resource availability is insufficient to meet the total requirements of a tree population for optimal growth. Six distance-dependent competition measures that incorporate tree sizes and distances from neighbors, evaluated over varying competition zones, were used to assess the competition stress among trees. A reduction in the mean square error relative to the no-competition index involved was used to judge the performance of each competition index for 3 growth components (i.e., diameter at breast height (DBH), basal area, and volume). The results showed that except for Martin-Ek, the other competition indices investigated were significantly correlated with periodic growth in the 3 growth components (p ＜ 0.0001). The performance of the competition indices in predicting 5-yr growth indicated that the inclusion of competition indices in the growth-prediction model reduced the mean square error from 14% for volume growth to 17% for DBH growth. Moreover, expanding the search zones in the Hegyi competition index was found to have slightly improved the ability to estimate competition effects.

Fertilization during the establishment of a Eucalyptus camaldulensis plantation in the northern Brazilian Amazon.

Forestry plantations should be regarded as an alternative sustainable land-use system in degraded savannah areas. They contribute to the maintenance of productive processes in degraded soils that are of economic importance for local inhabitants; in addition, in the ecological sense, timber and non-timber products from planted forests reduce the exploitation pressure on native forests. Eucalyptus plantations on degraded savannahs in the northern Brazilian Amazon may help to reduce exploitation pressure on native forests. However, there is no information regarding the nutrients rates that would allow faster eucalyptus growth in that region. A trial was installed in an Yellow Latosol (Oxisol) soil type adopting a one-half-type fractional factorial design with four ates of N, P, and K. Functions were adjusted for the dependent variables height, diameter at breast height (DBH), leaf tissue nutrient content, and soil-chemical attributes. Interaction N versus K was observed on tree height with a maximum of 7.8 m recorded at 200 kg ha-1 of N and 50 kg ha-1 of K. Phosphorus fertilization promoted greater DBH growth with maximum value at 120 kg ha-1 of P; however, the highest gain was obtained at 30 kg ha-1 of P. The NPK rates that maximized Eucalyptus camaldulensis growth were 200, 30, and 50 kg ha-1, respectively.

Performance differences among ex situ native-provenance collections of Pinus radiata D. Don. 1: potential for infusion into breeding populations in Australia and New Zealand

Growth and form traits from a series of three provenance trials of Pinus radiata D. Don planted in New Zealand and Australia were analysed at age 9 years from planting. The trials included selections from three mainland California natural populations—Ano Nuevo, Monterey and Cambria. Monterey and Cambria performed better than Ano Nuevo at two New Zealand sites, but Monterey and Ano Nuevo were almost identical in growth, whereas Cambria grew less vigorously at the Australian site. We detected significant provenance differences for diameter at breast height (DBH) growth and stem straightness across countries (p < 0.001). Estimated heritability for DBH ranged from 0.19 to 0.26 within sites, while heritability estimates for stem straightness and branching frequency ranged from 0.10 to 0.24. Estimated type B genetic correlations for DBH were always higher between the two trials in New Zealand trials than between pairs of trials in New Zealand and the Australian site. The genetic coefficient of variation (CVA) for DBH was around 8–10% compared to ca. 5% for the current breeding population. These results suggested that there is appreciable genetic variation in the native populations, and infusion of these materials would increase the genetic variation in current breeding populations. Ten unrelated parents ranked above control seedlots from the older open-pollinated seed orchard stock for DBH growth and would be potential candidates for infusion. The promising performance of the Cambria material is an important result because the genetic base of the present Australian and New Zealand plantations is principally derived from Ano Nuevo and Monterey.

Application of the 3PG forest growth model to a Eucalyptus globulus plantation in Northwest Spain

This paper presents an assessment of the ability of the 3PG process-based model to simulate height (h) and diameter at breast height (DBH) growth in three plots located in a Eucalyptus globulus plantation on the Atlantic coast of Galicia (Northwest Spain). The obtained results show how this model estimates adequately height (h) and DBH growth, and determination coefficients (R 2) between observed data and data predicted by the model are always higher than 0.97, root mean square error (RMSE) of 0.45–1.05 cm in DBH and 0.46–0.85 in h, and a model efficiency (EF) close to 1 (0.98–0.99). In order to improve the results predicted by the model, we propose modifying the nS and fullCanAge parameter values given by default so as to adjust growth rates in the plantation to the weather conditions in the site. The ability of the model to discriminate growth rates in the three plots must be noted, even when plots are located in the same plantation and they only show differences in aspects related to site factors. Given the obtained results in the three plots used in this study, its simplicity and the small number of parameters needed as input data, the 3PG model stands out as a very useful tool for forest plantation management.

Growth process and diameter structure of Pinus tabulaeformis forest for soil and water conservation in the hilly loess region of China

Using stem analysis method, the biomass, growing process and diameter structure of 21-year shady and sunny slope Pinus tabulaeformis forest were investigated in hilly loess-gully region. Results showed that there were distinct difference in the indexes, tree height, diameter at breast height (DBH) and timber volume between shady and sunny slope forest. The biomass, growth status and its diameter structure of shady slope forest were greater than those in sunny slope forest. The fast-growing period of tree was from 9 to 13 years. After 13 years, the annual increment of shady slope forest was greater than that of the sunny slope forest (the annual increment of shady slope forest reached 0.26 m.a(-1), while it was about 0.1 m.a(-1) in sunny slope forest in the 21st year). The DBH growth increment of 2 forests were reduced greatly after 13 years, but the declining degree of shady slope forest was less than the sunny slope forest. The current annual increment of shady slope forest was greater than the sunny slope forest after 17 years. There was little difference in the increment of 2 timber production before 13 years. But the increment of shady forest was greater than the sunny forest after 13 years (in the 21st year, the annual increment was 0.0023 m(3) in shady slope, but in sunny slope it was only 0.0015 m(3)). The summit of DBH distribution curve was both partial to left, while the skewness (SK was 0.75) of shady forest was lower than that of the sunny forest (SK was 1.03) and kurtosis (K was 1.05) of shady forest was higher than that of sunny forest (K was 0.94). The results indicated the density structure of sunny slope forest was greater than shady slope forest.

Short-term changes in Pinus strobus sapling height/diameter ratios following partial release: testing the acclimative stem-form development hypothesis

Following release, mature trees can acclimatively shift aboveground growth allocation from height to diameter at breast height (DBH) growth to adjust their stem form (reducing height/diameter ratio (HDR)) to better withstand increased wind stress. The purpose of this study was to determine if, over a 6-year period, 7- to 12-year-old eastern white pines ( Pinus strobus L.) also responded to different levels of partial release with (i) stem-form adjustments (reduced HDR) through growth-allocation shifts from height to DBH growth and (ii) lower HDR values (shorter heights) than for unreleased trees of the same DBH (“acclimative stem-form development hypothesis”). Over the 6-year postrelease period, juvenile white pine seedlings exhibited unsynchronized height and DBH growth response patterns that depended on their prerelease height growth. Height growth of faster growing white pines was temporarily reduced. Concurrently, DBH growth was enhanced with increasing release intensity. HDR reductions followed a fairly narrow and predictable trajectory, but HDR values of released trees were not lower than those of unreleased trees of the same DBH after 6 years. Juvenile white pine seedlings appear to maintain a balance among aboveground tree parts to enhance future tree stability, which may be an adaptive trait for moderately shade-tolerant species.