Tree Height Increment Research Articles

Evaluating dynamic tree-species-shifting and height development caused by ungulate browsing in forest regeneration using a process-based modeling approach

Ungulate browsing can prevent the successful regeneration and development of forest-owner-intended and climate-resilient admixed tree species, compromising the future provision of multiple ecosystem services. A reduction of the height increment of palatable tree species caused by ungulate browsing results in a competition shift in favor of less palatable species. While this key process of losing admixed tree species is well understood, forest growth models have not yet captured its full complexity. Therefore, our objectives were to simulate (i) the loss of susceptible tree species from different browsing regimes and its impact on stand development, (ii) changes in the height increment of saplings and trees, and (iii) the shifts in social status during stand development without pre-defined limits a sapling can resist browsing. To address these objectives, we used the process-based model iLand to simulate the exposure of Norway spruce, Silver fir, and European beech stands to varying browsing densities. We successfully reproduced expected dynamic shifts in species composition and height development 24 years after establishment, depending on ungulate pressure and species-specific competitive strength. Stand composition and growth differences already occur with slight changes in ungulate density. When saplings remained in stand structure, independent of the number being browsed, our results led to more individuals with substantially smaller dimensions. We found that dynamic tree species shifting can be simulated realistically by a process-based modeling approach, which can be used to show the strong impact of ungulates on stand development.

Interaction effect of boron and zinc on growth, yield and quality of guava (Psidium gaujava L.) Cv. ‘Lalit’

The present investigation was carried out at Agricultural Research Farm, Suresh Gyan Vihar University, Jaipur (Rajasthan) to study the effect of foliar application of boron and zinc on growth, yield and quality of guava (Psidium gaujava L.) during the year 2022-23. The various concentrations of boric acid, zinc sulphate and their interactions had significant effect on various vegetative growth, yield and quality parameters and the maximum (22.07 cm) tree height increment, (70.39 cm) annual shoot growth, (215.96) fruits per tree, longest (8.74 cm) fruit length, (7.84 cm) fruit diameter, heaviest (264.20 g) fruit, yield (58.57 kg/tree) and (16.27 t/ha), (15.87%) TSS, (7.60%) total sugar, (268.25 mg/100 g) ascorbic acid and (1.36%) pectin was recorded under Boric acid @ 0.25% + ZnSO4 @ 0.25% (T11).The non-significant effects were observed in application of different combinations of boric acid and zinc sulphate on acidity percentage.

Tree height and stem growth dynamics in a Scots pine dominated boreal forest

Tree growth is a key forest ecosystem service and essential for carbon sequestration and biomass production. However, the intra-seasonal dynamics of tree height and stem diameter growth have been difficult to measure hampering the understanding of the interplay between these processes. Here, we investigated the feasibility of a laser scanning system in monitoring tree height development, aiming to study how tree height and stem diameter growth dynamics vary and interact, and how environmental variables explain the tree growth dynamics within a growing season. The experimental design consisted of 40 boreal trees equipped with dendrometers measuring changes in the stem diameter at 15-minutes intervals while a laser scanner fixed to a 35-meter tower was used to measure tree height near-daily during the monitoring period from May to mid-August 2021. We found that vertical changes in the tree-segmented point clouds enabled monitoring of tree height increment and investigation of the temporal dynamics of changes in tree height and stem diameter, when coupled with dendrometer measurements. The experiments revealed that, on average, height increment occurred ahead of diameter increment and deviated more towards the late season. Norway spruce showed more delayed diameter increment than Scots pine during the late season. Silver birch experienced diameter increment ahead of height increment. Based on the dendrometer measurements, we computed a radial change response function that aimed at characterizing the current state of stem diameter development, whether it was increasing or decreasing from its past state. When these radial change responses were compared against environmental variables, we found that the radial change response was mostly controlled by balance between precipitation and evapotranspiration, soil water content, minimum daily temperature, and vapor pressure deficit. Our findings support the utilization of laser scanning time series for measuring intra-seasonal changes in tree height and increase our understanding of the interactions between tree height and stem diameter growth processes.

Environment-induced growth changes in forests of Finland revisited - a follow-up using an extended data set from the 1960s to the 2020s

After a rising trend for 1971 – 2013, during which the annual volume growth of the forests of Finland increased by more than 70 %, a recent reduction has been observed. We analyzed the development of annual growth in the forest of Finland, focusing on the component not explainable by changes in growing stock. The data originate from nine consecutive Finnish National Forest Inventories. In the data, diameter increments were measured from increment cores and tree height increments from standing sample trees in the field. We developed models predicting periodic (5 years) annual volume increment per hectare with properties of the trees and stands as predictor variables. Deviations from model-predicted values were interpreted to be induced by environmental variation. The development was analyzed for all tree species combined and separately for three species groups: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.) and broadleaves. We observed a rising growth trend not solely explainable by increased growing stock. The species groups produced rather a similar pattern in different parts of Finland: from the 1960s to the mid-1990s, the observed volume increment was mainly below the model-predicted level, thereafter above it. During the current century, the difference between observed and predicted annual volume increment has shown a downward trend for Scots pine. For Norway spruce, the difference has continued to increase in southern Finland, but shows little change in the north. For broadleaved species, the difference between measured and predicted increment shows a recent increase as well, though not as large as for Norway spruce. The geographical pattern of the environment-induced increment component was described in more detail via maps using a 75 km × 75 km grid. The changing environment has enhanced forest productivity in Finland over a period of nearly six decades, but recent years have not been favorable for Scots pine, which represents 50 % of the growing stock volume of the forests of Finland.

Individual Tree Height Increment Model for Quercus mongolica Secondary Forest in the Northeastern China Using Generalized Nonlinear Two-Level Mixed-Effects Model

(1) Background: Mongolian oak secondary forest is widely distributed in the northeast of China, and most of these forests are formed after the overcutting of broad-leaved Pinus koraiensis mixed forest. Most of the forest productivity is low and the ecological function is degraded, due to insufficient understanding of Mongolian oak and lack of scientific management. Deepening the research on exploring reasonable management measures of Mongolian oak secondary forest to an improved stand status is the basis for improving its quality and promoting its forward succession process. (2) Methods: Twelve permanent plots with an area of 1 ha were established in the Mongolian oak secondary forest on Tazigou forest farm in Wangqing, Jilin Province of northeastern China. The response of tree height increment of Mongolian oak secondary forest is studied based on the survey data of 2013 and 2018. Two-level nonlinear mixed-effects models were constructed to predict the height of a single tree using sample plots and tree species as random effects, combined with a variety of tree size factors, site factors, and competitive factors as independent variables. (3) Results: The significant factors related to the height increment of Mongolian oak secondary forest are the initial diameter at breast height as the size of the tree itself (DBH), height (H), crown height ratio (CR), and site productivity index reflecting site quality (SPI). The distance-dependent and distance-independent competition indexes have no significant effect on tree height increment. The fitting accuracy of the two-level mixed-effects model that introduces plots and tree species as random effects has been greatly improved (coefficient of determination R2 increased by 51.8%). The prediction results show that the two trees with the largest DBH have the strongest prediction ability. (4) Conclusions: The generalized nonlinear two-level mixed-effects model constructed in this study can describe the height increment of an individual tree in the Mongolian oak secondary forest. Two sample trees, namely the two largest trees in each sub-plot, were applied for estimating the random effects when both measurement cost and potential errors of prediction were balanced.

The Growing Dynamic of Pure Scots Pine Stands Using Different Thinning Regimes in Lithuania

The aim of this study is to relate initial stand density and thinning intensity to tree diameter, height, and volume increment based on continuous 30-year observations in thinning experimental stands of Scots pine (Pinus sylvestris L.). The thinning experiments on Scots pine were established in 1990 and 1992, and the experimental model in each trial comprised five density variants: control and four plots with tree densities up to 3.0–4.4, 2.0–2.4, 1.0–1.2, and 0.5–0.6 thousand trees per hectare after the initial thinning. Since the establishment, only the dead trees were removed in control plots, and other initial density plots were thinned according to predefined thinning treatment plans. Our study shows that the lowest increment in diameter was found in control plots and the highest in the most intensive thinning plots, in which the diameter increment was 1.5 times higher. However, the intensification of thinning and the signs of growth stabilization in the control stands cannot guarantee them the position of highest productivity and cumulative volume in the future.

Assessment of the effect of stand density on the height growth of Scots pine using repeated ALS data

• Repeated ALS allows detecting the height increment variation influenced by stand density. • Higher stand density stimulate height growth, particularly on most productive sites. • Repeated ALS data allows developing density-dependent top height growth models. The spread of remote sensing technologies allows for continuous and precise mapping of forest ecosystem attributes over large areas. One of the most important attributes of a forest ecosystem is site productivity, an essential determinant of resource availability. Knowledge of site productivity is crucial for sustainable forest management because it is the basis for predictions of future forest growth and is fundamental to long-term planning in forestry. Models of forest dynamics allow us to better understand the functioning of forest ecosystems and to assess the provision of ecosystem services. However, discussions on the factors affecting forest growth are ongoing. Previous research has not clarified the influence of stand density on the height increment of trees. Consequently, this uncertainty leads to inconsistent predictions for stand growth and nonoptimal forest-management decisions. We aimed to analyse the effect of stand density on top height (TH) growth and the development of the TH growth model for Scots pine based on bitemporal ALS measurements. We applied repeated ALS observations from two acquisitions (2011, 2019) to fit a density-sensitive TH growth model. We found that stand density affected the TH growth of Scots pine. A higher stand density stimulated TH growth, particularly in productive sites showing a TH increment of about 10%. We demonstrated the usefulness of bitemporal ALS measurements for developing a TH growth model for Scots pine considering stand density. We found that the predictive accuracy of the TH increment increased when stand density was considered.

PINUS SYLVESTRIS L. REGENERATION FROM SEED TREES IN VACCINIOSA AND MYRTILLOSA

Scots pine (Pinus sylvestris L.) is an economically important tree species in temperate forests, including Latvia. Purposeful selection work has resulted in the provision of faster-growing planting material for forest planting. Natural restoration initially requires less investment, it has several disadvantages. When using this method, it must be considered that the forest stands will have an uneven species composition, the age and height of the trees will differ. The study was carried out in young naturally regenerated stands in Vacciniosa and Myrtillosa forest site type and compared with planted stands The aim of the study was to evaluate the natural regeneration and last 5 year tree height increment of Scots pine regenerated from the seed trees in the Vacciniosa and Myrtillosa, compared to planted stands, as well as to assess the impact of tree health on pine height increment. In total 10 young stands were surveyed, 66 sample plots were established and 704 trees were measured. The area of the temporary sample plot was 25 m2 with a radius of 2.82 m. Comparing the annual height increases of Scots pine, both in naturally regenerated and planted young stands in Vacciniosa and Myrtillosa, it was found that there are statistically significant differences between forest types, stand origin type, as well as in existing stands in the last 5 years by years (p <0.05). The most significant damage to young pine stands is caused by needle cast, ungulates, and large pine weevil.

SELEKSI POHON PLUS PADA UJI KETURUNAN Shorea leprosulaDI KALIMANTAN TENGAH

he progeny trial of Shorea leprosula was established in Central Kalimantan under the IUPHHK-HA management of PT. Erna Djuliawati by planting 30 families to examine the genetic superiority of trees asplywood raw material. The trial was laid-out using 8 blocks, 4 tree-plots and a spacing of 6 x 3 m. The aim of the study was to practice the plus trees selection in the progeny trial. The study was conducted using a survey method on phenotypically superior trees based on a diameter at breast height (dbh) baseline of ≥ 30 cm. The data collected and analyzed for the plus trees and comparison trees were total tree height (m), dbh (cm), and dbh increment (cm/yr). The results of the initial selection showed that 110 trees from 29 families were selected as candidate plus trees in the progeny trial. Futhermore, the honest significant difference test (BNJ) and scoring showed that there were 15 trees from 9 families that can be designated as plus trees

Diameter, height and volume increment single tree models for improved Sitka spruce in Great Britain

Abstract The British forestry sector lacks reliable dynamic growth models for stands of improved Sitka spruce, the most important commercial forest type in Great Britain. The aim of this study is to fill this gap by trialling a new modelling framework and to lay the foundations of a future dynamic growth simulator for that forest type. First, we present single tree diameter and height increment models that are climate sensitive and include explicit competition effects. The predictions from the increment models are pooled to project diameter and height at a given age. These projections are then used as inputs to an integrated taper model from which stochastic tree volume predictions are obtained. Retrospective data from over 1400 trees collected in two extensive genetic trials in Scotland and Wales were used for the purposes of this study. Diameter increment and height increment predictions were highly accurate and diameter and height projections proved consistent. The predicted volume at the time of harvesting also exhibited a high degree of accuracy, which shows the robustness of our approach. Further data will be needed in the future to recalibrate the present models and extend their range of validity to the whole of Great Britain.

Simulating tree growth response to climate change in structurally diverse oak and beech forests

This study aimed to simulate oak and beech forest growth under various scenarios of climate change and to evaluate how the forest response depends on site properties and particularly on stand characteristics using the individual process-based model HETEROFOR. First, this model was evaluated on a wide range of site conditions. We used data from 36 long-term forest monitoring plots to initialize, calibrate, and evaluate HETEROFOR. This evaluation showed that HETEROFOR predicts individual tree radial growth and height increment reasonably well under different growing conditions when evaluated on independent sites.In our simulations under constant CO2 concentration ([CO2]cst) for the 2071-2100 period, climate change induced a moderate net primary production (NPP) gain in continental and mountainous zones and no change in the oceanic zone. The NPP changes were negatively affected by air temperature during the vegetation period and by the annual rainfall decrease. To a lower extent, they were influenced by soil extractable water reserve and stand characteristics. These NPP changes were positively affected by longer vegetation periods and negatively by drought for beech and larger autotrophic respiration costs for oak. For both species, the NPP gain was much larger with rising CO2 concentration ([CO2]var) mainly due to the CO2 fertilisation effect. Even if the species composition and structure had a limited influence on the forest response to climate change, they explained a large part of the NPP variability (44% and 34% for [CO2]cst and [CO2]var, respectively) compared to the climate change scenario (5% and 29%) and the inter-annual climate variability (20% and 16%). This gives the forester the possibility to act on the productivity of broadleaved forests and prepare them for possible adverse effects of climate change by reinforcing their resilience.

Weather-sensitive height growth modelling of Norway spruce using repeated airborne laser scanning data

Fluctuations in weather conditions, particularly precipitation and water availability, may strongly affect growth rate patterns and lead to interannual height growth variation. Consequently, height growth models developed using airborne laser scanning (ALS) data collected at short time intervals may over- or underestimate long-term height growth trends and finally result in different growth forecasts. The objective of this study was to develop height growth models for Norway spruce, including the effect of weather conditions. We used ALS-derived top height (TH) estimates and meteorological data from the research area collected for 2007-2012 and 2013-2018 to develop a weather-sensitive height growth model. The top height (TH) growth of Norway spruce was affected by the mean annual precipitation sum (APS) in the studied periods, and a higher APS resulted in faster TH growth. This study demonstrates the high potential of repeated ALS for detecting short-term variation in the tree height increment and the development of weather-sensitive height growth models.

Predawn leaf conductance depends on previous day irradiance but is not related to growth in aspen saplings grown under artificially manipulated air humidity.

Recent studies have suggested that predawn stomatal opening may enhance early-morning photosynthesis (A) and improve the relative growth rate of trees. However, the causality between night-time stomatal conductance, A, and tree growth is disputable because stomatal opening in darkness can be mediated by previous day photosynthate loads and might be a consequence of growth-related processes like dark respiration (R). To identify linkages between night-time leaf conductance (gl_night), A, R, and tree growth, we conducted an experiment in hybrid aspen saplings grown under different air relative humidity (RH) conditions and previous day irradiance level (IR_pday). Predawn leaf conductance (gl_predawn) depended on RH, IR_pday and R (P < 0.05), whereas early-morning gross A (Agross_PAR500) depended on IR_pday and gl_predawn (P < 0.001). Daytime net A was positively related to Agross_PAR500 and leaf [N] (P < 0.05). Tree diameter and height increment correlated positively with gl at the beginning and middle of the night (P < 0.05) but not before dawn. Although our results demonstrate that gl_night was related to tree growth, the relationship was not determined by R. The linkage between gl_predawn and Agross_PAR500 was modified by IR_pday, indicating that daily CO2 assimilation probably provides feedback for stomatal opening before dawn.

Height increment of Cycas micronesica informs conservation decisions

ABSTRACT Growth dynamics of pachycaulous stems of arborescent cycad plants are not well understood, and most observations have been made in cultivated garden plants. We studied Cycas micronesica plants in Guam, Tinian, and Yap to understand the influences of geography, plant size, sex, and herbivory on stem growth. We also determined the changes in demography of Guam’s population after 15 years of damage by non-native insect herbivores. The height increment (HI) was similar for plants within the height range from 100 cm to more than 600 cm, so the relative growth rate declined with height. Female tree HI was 68% of male tree HI, and Yap tree HI was 87% of Guam tree HI. Chronic herbivory by non-native insect herbivores caused a mean 44% decline in HI. Plants in managed gardens grew more rapidly than plants in a wild habitat. The HI was used to estimate that Guam has experienced a complete loss of ≈70 y of demographic depth resulting from the selective mortality of small plants since 2005. When future conservation interventions successfully mitigate the ubiquitous biological threats, our HI may be useful for empirically quantifying recovery of plant health.

Modeling the number of the first- and second-order branches within the live tree crown of Korean larch plantations in Northeast China

Modeling the number of branches in a tree is fundamental for simulating other branch characteristics and crown structure. In this study, a total of 77 Korean larch (Larix olgensis Henry) trees were destructively sampled from plantations in Northeast China. The number of first- and second-order branches was modeled using seven count data models, namely Poisson, negative binomial (i.e., NB, including NB-1, NB-2, and NB-P), and generalized Poisson (i.e., GP, including GP-1, GP-2, and GP-P) regression models. Generalized linear mixed models (GLMMs) were then applied to those models using the sampled trees as the random effects. The results showed that (i) the Poisson regression was preferred for modeling the number of first-order branches; (ii) the GP-1 regression was considered the optimal model for the number of second-order branches; (iii) the significant predictor variables included tree height increment, branch position, relative tree size, mean dominant height, and tree age; (iv) the GLMMs significantly improved both model fit and prediction performance; (v) the prediction accuracy of the GLMMs increased gradually with increasing sample size; and (vi) a relatively small sample size with an appropriate sampling strategy would be adequate to provide a good estimation at a specific crown section.

Реконструкция истории древостоев и оценка воздействия инвазивного короеда в пихтовых лесах с помощью анализа пространственной структуры

The most devastating insect invasion of forest ecosystems in Russia is the recent mass reproduction of the four-eyed fir bark beetle (Polygraphus proximus Blandf.) in southern Siberian fir (Abies sibirica Ledeb.) forests. The objective of our research was to study the spatial structure of fir forests and their change under the impact of the four-eyed fir bark beetle in its secondary (invasive) distribution range. We selected two fir stands located near the villages of Itatka and Malinovka in the Tomsk region. Both stands represent natural ripe succession forests on sites that previously experienced logging activities, which were triggered by settlement activities in the second half of the nineteenth century. We used Field-Map technology for gathering non-spatial and spatial stand data. The analysis showed that height, diameter and radial increment of fir trees, killed or severely weakened by attacks of the four-eyed fir bark beetle, were significantly lower than that of healthy individuals. The social status of fir trees, seriously attacked or already killed by Polygraphus proximus was indicated by the Ui index as moderately suppressed. In contrast to the distribution pattern of living firs, the pattern of dead or severally weakened firs killed by the four-eyed fir bark beetle was significantly clumped over short distances (sample plots (SP) Itatka and Malinovka). This finding coincides with visual observations in other stands, that dead trees are grouped to some extent. However, the hypothesis of spatial independence of the tree positions of living and dead firs was accepted for both plots.Funding: The research was funded by the Russian Foundation for Basic Research and the government of Tomsk region, grant No. 16-44-700782, and carried out as part of a state assignment of the Center for Forest Ecology and Productivity of the Russian Academy of Sciences (No. АААА-А18-118052400130-7).For citation: Debkov N.M., Gradel A., Aleinikov A.A. Reconstruction of Stand History and Impact Evaluation of an Invasive Bark Beetle in Siberian Fir Forests with the Help of Spatial Structure Analysis. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 3, pp. 24–41. DOI: 10.37482/0536-1036-2020-3-24-41

Modeling Height–Diameter Relationship for Poplar Plantations Using Combined-Optimization Multiple Hidden Layer Back Propagation Neural Network

Relationship of total height and diameter at breast height (hereafter diameter) of the trees is generally nonlinear, and therefore has complex characteristics, which can be accurately described by the height-diameter model developed using the back propagation (BP) neural network approach. The multiple hidden layered-BP neural network has several hidden layers and neurons, and is therefore considered more appropriate modeling approach compared to the single hidden layered-BP neural network approach. However, the former approach is not widely applied for tree height prediction due to absence of the effective optimization method, but it can be done using the BP neural network modeling approach. The poplar (Populus spp. L.) plantation data acquired from Guangdong province of China were used for evaluating the BP neural network modeling approach and compared its results with those obtained from the traditional regression modeling and mixed-effects modeling approaches. We determined the best BP neural network structure with two hidden layers and five neurons in each layer, and logistic sigmoid transfer functions. Relative to the Mitscherlich height-diameter model that had the highest fitting precision among the six traditional height-diameter models evaluated, coefficient of determination (R2) of the neural network height-diameter model increased by 10.3%, root mean squares error (RMSE) and mean absolute error (MAE) decreased by 12% and 13.5%, respectively. The BP neural network height-diameter model also appeared more accurate than the mixed-effects height-diameter model. Our study proposes the method of determining the optimal numbers of hidden layers, neurons of each layer, and transfer functions in the BP neural network structure. This method can be useful for other modeling studies of similar or different types, such as tree crown modeling, height, and diameter increments modeling, and so on.

Coppicing improves the growth response of short-rotation hybrid aspen to elevated atmospheric humidity

Aspens are fast-growing clonal trees with a wide circumboreal distribution range, suitable for the production of pulp and bioenergy. The adaptability of aspen short-rotation coppice systems to climate change has rarely been investigated. For a large part of aspens’ northern range, climate models predict an increase in precipitation and, consequently, in atmospheric humidity. Our aim was to clarify the long-term effect of elevated air humidity on vegetative reproduction capacity and dynamics of above-ground growth and size structure in aspen stands. We analysed tree growth data from two consecutive 6-year rotations (a planted and a coppice generation) in experimental short-rotation hybrid aspen (Populus tremula L. × P. tremuloides Michx.) stands in the Free Air Humidity Manipulation (FAHM) experiment in Estonia. In three plots, mean relative air humidity was elevated by 7% and three plots were controls. Across two rotation periods, the humidification effect on tree height and/or stem basal area increment was year-dependent (p < 0.001): negative in 4 years, positive also in 4 years and non-significant in 3 years. Mean basal area of humidified (11.6 ± 0.8 cm2) and control trees (15.0 ± 1.0 cm2) differed significantly (p = 0.035) at the end of the first but not the second rotation period (9.3 ± 0.9 cm2 and 9.3 ± 1.2 cm2, respectively). Average growth differences levelled out already in the beginning of the second rotation, suggesting that some root-level acclimation must have taken place. The annual size-growth relationships (SGR) indicated a more size-symmetric growth in humidified (SGR = 1.00 ± 0.05) and a size-asymmetric growth (SGR = 1.12 ± 0.04) in control stands, implying a greater role of root-competition in humidified stands. In humidified stands, the growth of re-sprouting trees was more strongly determined by parent tree size, indicating a stronger carry-over of size hierarchy. The tree height diversity fluctuated more in control stands, where mortality was higher, especially after dry years. To summarise, short- and long-term responses of hybrid aspen to elevated air humidity varied, emphasizing the importance of long-term climate manipulations with trees. Generally, hybrid aspen short-rotation coppice forests showed promising acclimation capacity with future more humid climate predicted for northern latitudes.

Tree Height Increment Models for National Forest Inventory Data in the Pacific Northwest, USA

The United States national inventory program measures a subset of tree heights in each plot in the Pacific Northwest. Unmeasured tree heights are predicted by adding the difference between modeled tree heights at two measurements to the height observed at the first measurement. This study compared different approaches for directly modeling 10-year height increment of red alder (RA) and ponderosa pine (PP) in Washington and Oregon using national inventory data from 2001–2015. In addition to the current approach, five models were implemented: nonlinear exponential, log-transformed linear, gamma, quasi-Poisson, and zero-inflated Poisson models using both tree-level (e.g., height, diameter at breast height, and compacted crown ratio) and plot-level (e.g., basal area, elevation, and slope) measurements as predictor variables. To account for negative height increment observations in the modeling process, a constant was added to shift all response values to greater than zero (log-transformed linear and gamma models), the negative increment was set to zero (quasi-Poisson and zero-inflated Poisson models), or a nonlinear model, which allows negative observations, was used. Random plot effects were included to account for the hierarchical data structure of the inventory data. Predictive model performance was examined through cross-validation. Among the implemented models, the gamma model performed best for both species, showing the smallest root mean square error (RSME) of 2.61 and 1.33 m for RA and PP, respectively (current method: RA—3.33 m, PP—1.40 m). Among the models that did not add the constant to the response, the quasi-Poisson model exhibited the smallest RMSE of 2.74 and 1.38 m for RA and PP, respectively. Our study showed that the prediction of tree height increment in Oregon and Washington can be improved by accounting for the negative and zero height increment values that are present in inventory data, and by including random plot effects in the models.

Assessing and modeling total height and diameter increment of ponderosa pine planted in Minnesota, USA

Forest managers are increasingly planting non-native tree species that are adapted to anticipated future conditions such as increased droughts. This work quantified individual tree growth patterns of ponderosa pine (Pinus ponderosa P. & C. Lawson), a western US species, planted outside of its natural range in Minnesota, USA. After 50 years, survival was as high as 69% for some ponderosa pine seed sources, and individuals from the Black Hills, Eastern High Plains, and South and East Montana regions of the western US were some of the tallest and largest diameter trees grown in Minnesota. Predictions of total tree height and diameter increment displayed the lowest bias when equations for ponderosa pine in the western US were used rather than equations for red pine (Pinus resinosa Ait.) in Minnesota, a species that occupies a similar ecological niche. These results indicate that using existing growth and yield equations from a species’ native range may provide a suitable representation of growth and yield patterns if observations from outside the species’ native range are lacking. Historical data from provenance trials such as these can provide a long-term record to quantify the growth potential of non-native species in anticipation of future climate scenarios.