Site Index Curves Research Articles

Site Index Determination Techniques for Southern Bottomland Hardwoods

Site index is a species-specific indirect measure of forest productivity expressed as the average height of dominant and codominant trees in a stand of a specified base age. It is widely used by forest managers to make informed decisions regarding forest management practices. Unfortunately, forest managers have difficulty in determining site index for southern US bottomland hardwood stands because of a lack of available information for many tree species, outdated information for several techniques, and a lack of knowledge in the application of other techniques for specific site conditions. Techniques to determine site index in bottomland hardwood stands include species trials, site index curves, soil-site equations, soil series, and expert systems. Each technique is reviewed here, including recent advances if available, advantages, disadvantages, and application to bottomland hardwood stands.

Sixty-year effects of deciduous removal on white spruce height growth and site index in the Western Boreal

In the boreal plains of western Canada, white spruce (Picea glauca (Moench) Voss) height−age and site index (SI) curves have been developed and applied to assess site productivity for white spruce without fully considering the competition that usually occurs between the spruce and taller deciduous trees. In this study, we evaluated the effects of deciduous removal on white spruce height growth potential using stem analysis on typical control spruce grown with deciduous neighbours and spruce that were released from deciduous competition ∼60 years prior. Due to the late application of the release treatments (at stand ages of 20–60 years), the observed site index of spruce was not affected by treatment. However, height growth in the 50 years following treatment was increased by 2.1 m. We present a height−age model to specifically estimate the change in SI required to achieve the observed height response following late release. The model indicated that the post-release SI estimate of white spruce would need to be on average 4.2 m higher than control SI to track the height response. This model is useful for estimating the true, competition-free SI for white spruce from the observed SI in natural mixed stands.

A new method for the identification of old-growth trees in National Forest Inventories: application to Pinus halepensis Mill. stands in Spain

Old-growth trees play a very important role in the maintenance of biodiversity in forests. However, no clear definition is yet available to help identify them since tree age is usually not recorded in National Forest Inventories. To develop and test a new method to identify old-growth trees using a species-specific threshold for tree diameter in National Forest Inventories. Different nonlinear mixed models for diameter–age were generated using data from the Spanish Forest Inventory in order to identify the most appropriate one for Aleppo pine in its South-western distribution area. The asymptote of the optimal model indicates the threshold diameter for defining an old-growth tree. Additionally, five site index curves were examined to analyze the influence of site quality on these models. The Hossfled III mixed model was found to be the most appropriate to fit diameter–age curves for Aleppo pine trees. The overall diameter at breast height threshold for old-growth trees was 40.6 cm, although over a range of sites with increasing site quality, the threshold figure was 36.0, 38.0, 40.4, 43.1, and 46.3 cm, respectively. This method allows the identification of old-growth trees and therefore of biodiversity hotspots, thus providing decision makers with a useful tool for management purposes.

No major impact of insertion/deletion polymorphism of the angiotensin-converting enzyme gene on thyroid-associated ophthalmopathy

Difference equations derived on the basis of the McDill-Amateis differential functions and from the integral form of the Bertalanffy, Richards, and Korf growth functions were used to model the dominant height growth of young European aspen (Populus tremula L.) stands on Athos Peninsula (northern Greece). Data from stem analysis were used for fitting. Both numerical and graphical analyses were used to compare alternative models. The cross-validation approach was used to analyze the predictive ability of the models. The algebraic difference form of the differential function proposed by McDill and Amateis resulted in the best compromise between biological and statistical aspects and produced the most adequate site index curves. Therefore, it is recommended for height growth prediction and site classification of European aspen stands on Athos Peninsula. This equation is base-age invariant, so any number of points (A1, H1) on a specific site curve can be used to make predictions for a given age A2 and the predicted height H2 will always be the same.

Ecological Modeling for Half Sib Progenies of Pinus Roxburghii Sarg.

Tree height is more responsive to family and within family selection than dbh. Kaldu P5 (30), Charet Mansu P4 (34) and Dohar PT1 (109) were found best performer. Site index curves were developed for Pinus roxburghii Sarg. (Chir pine) based on data from half sib progenies of Pinus roxburghii Sarg. established at UHF, Nauni, Solan (H.P.) Different models were employed to express height as a function of age. The model LnH = a+b/A 0.4 was found to be the best and was used to construct site index curves. Site index of 16.70 m, 15.90 m and 15.80 m at reference age 27 was obtained.

Yield models of pure fir (Abies nordmanniana S. subsp. bornmülleriana (Mattf.)) stands (Western Black Sea region).

Yield models are important tools in forest management planning because they can simulate stand development and production under various management alternatives. Yield of forest stands is determined using tables containing values of height, diameter, number of trees, volume, etc., for different site and age classes. These tables have been created by using basically mathematical equations with statistical analyses. Some species are of low economic importance, but all of them are of high ecological importance for the ecosystems. Abies nordmanniana subsp. bornmulleriana Mattf. is one of the both-way important tree species in Turkey. Hence, site index curves and yield tables for natural fir stands in the Western Black Sea region were developed. Data were collected from a total of 20 sample plots and 15 sample trees. Site index curves were used to classify into site classes of I, II and III, in order of decreasing productivity. The yield models can be calibrated on Turkish Forest Management Planning Department field plot data and tested against independent long-term growth and yield records.

Site Index Model for a Sugi Plantation (Cryptomeria japonica) in Zenlen Area, Taiwan

Assessing potential site productivity is important for forest planning and predicting forest growth and yield. The most common measure of site productivity is the site index (SI), defined as the average height of dominant and co-dominant trees (top height) at a specified (index) age. Two types of SI curves were investigated in this study to build up a SI curve for a Sugi plantation in Zenlen area, Taiwan. Several models were used to compare the performance among models. Pairs of height-age observations were obtained through a stem analysis. Based on the mean square error criterion, the base-age-specific SI model proposed by Payandeh and Wang (1994) was ranked the best one with an average bias in percentage of -0.36. Despite the advantage of being invariant with the base age used, this study showed a large loss of accuracy and precision caused by base-age-invariant models, especially for those trees younger than 10 yr. Moreover, the accuracy of the SI models varied considerably depending on the choice of predictor age for estimating the SI value at the base age. This study showed a tendency that the closer the predictor age was the base age, the higher the accuracy was that was obtained.

Site Index Curves for Young Hybrid Larch Growing on Former Farmland in Sweden

Site index (SI) curves for H20 (dominant height at 20 years total age) were constructed for hybrid larch (Larix × eurolepis Henry) growing in 26 stands on former farmland in southern and central Sweden (Latitude 56–60° N.). The mean total age of the stands was 23 ± 10 (range 17–49) years; the mean diameter at breast height (ob) was 16 (7–34) cm; the mean height was 14 (8–29) m; and the stands had a mean density of 993 (266–2195) stems ha−1. A model derived by Cieszewski (2001) performed best for the data. The model explained 99% of the observed variation in height development. No apparent bias across the range of predicted site indices was found. SI was examined in relation to soil types. Multiple samples were available for three soil types: light clay, medium clay and till. There were no significant differences between these soil types with respect to the choice of SI curve.

Aplicação da função hiperbólica na construção de curvas de índice de local

Neste estudo foi avaliada a eficiência da função hiperbólica, para geração de curvas anamórficas e polimórficas de índices de local. As curvas de índice de local foram construídas utilizando os métodos: da curva-guia, da equação das diferenças, da predição de parâmetros, de Hammer e dos índices de local definidos preliminarmente. Para aplicação desses métodos foram utilizados dados de parcelas permanentes de povoamentos de eucalipto. A eficiência foi confirmada, sendo a função indicada para descrever tendências polimórficas e anamórficas, podendo ser utilizada na classificação da capacidade produtiva de povoamentos de eucalipto.

Capacidade produtiva local de Tectona grandis em Monte Dourado, Estado do Pará, Brasil

O trabalho teve como objetivo determinar a capacidade produtiva local da teca em Monte Dourado, Estado do Pará, Brasil, por meio da análise de curvas de índice de sítio. Os dados foram obtidos pela análise de tronco de dez árvores dominantes de um povoamento com 26 anos de idade. Foram ajustados dez modelos de regressão e o critério de seleção obedeceu ao menor erro padrão da estimativa, ao maior coeficiente de determinação ajustado, à significância do teste F e dos coeficientes de regressão e à análise gráfica dos resíduos. As curvas de índice de sítio foram confeccionadas pelo método da curva-guia. O modelo de Spillman apresenta o melhor ajuste, por meio do qual foram geradas três curvas de índice de sítio de 16m a 24m na idade-índice de 26 anos. A região de Monte Dourado, PA, apresenta potencial produtivo para o desenvolvimento da teca.

Site index curves for young Populus tremula stands on Athos Peninsula (northern Greece)

Difference equations derived on the basis of the McDill-Amateis differential functions and from the integral form of the Bertalanffy, Richards, and Korf growth functions were used to model the dominant height growth of young European aspen (Populus tremula L.) stands on Athos Peninsula (northern Greece). Data from stem analysis were used for fitting. Both numerical and graphical analyses were used to compare alternative models. The cross-validation approach was used to analyze the predictive ability of the models. The algebraic difference form of the differential function proposed by McDill and Amateis resulted in the best compromise between biological and statistical aspects and produced the most adequate site index curves. Therefore, it is recommended for height growth prediction and site classification of European aspen stands on Athos Peninsula. This equation is base-age invariant, so any number of points (A_1, H_1) on a specific site curve can be used to make predictions for a given age A_2 and the predicted height H_2 will always be the same.

Development of site index curves for Pinus kesiya in the Philippines

This study was conducted to develop a height–age growth model and site index curves for site quality evaluation of old secondary-growth stands of Pinus kesiya in the northern Philippines. The Chapman-Richards growth function was used in the guide curve method to generate anamorphic site index curves for this species. In order to evaluate the developed model, coefficient of determination (R 2 ), root mean square error (RMSE), bias (Ē), absolute mean difference (AMD) and mean percent bias (MPB) were used as statistical criteria. The Chapman-Richards model explained about 96.84% of the total variation of the dominant height. The value of Ē was −0.004 m, AMD was 2.566 m, MPB was 3.88% and RMSE was 3.331. The site index curves developed as a result of this study are significant for forest managers in predicting the growth patterns and classification of site productivities for Pinus kesiya stands.

Modeling Dominant Height Growth in PlantedPinus pineaStands in Northwest of Tunisia

Six generalized algebraic difference equations (GADAs) derived from the base models of log-logistic, Bertalanffy-Richards, and Lundqvist-Korf were used to develop site index model forPinus pineaplantations in north-west of Tunisia. To assure the base-age invariance of the model parameter estimates, a dummy variable approach was used. Data from stem analysis, corrected with Carmean's method, were used for modelling. To take into account the inherent autocorrelation of the longitudinal data, a second-order continuous-time autoregressive error structure was used, which allows the models to be applied to irregularly spaced, unbalanced data. Both a qualitative analysis based on the biological realism of the models and numerical and graphical analyses based on the accuracy of the models as well were used to evaluate the performance of candidate models. The relative error in site index predictions was used to select 30 years as the best reference age. Based on the analysis, a generalized algebraic difference equation (GADA) derived from the base model of Lundqvist-Korf realized the best compromise between biological and statistical constraints, producing the most adequate site index curves. It is a polymorphic model with site-dependent asymptotes. This model is therefore recommended for height growth prediction and site classification ofPinus pineaplantations in north-west of Tunisia.

CURVAS ANAMÓRFICAS DE ÍNDICE DE SITIO PARA PLANTACIONES DE Pinus caribaea Morelet var. caribaea Barret y Golfari DE LA EMPRESA FORESTAL INTEGRAL MACURIJE (EFI) EN LA PROVINCIA DE PINAR DEL RÍO, CUBA

In this work we selected the best model for obtaining anamorphic site index curves for Pinus caribaea Morelet var. caribaea Barret and Golfari stands belonging to the Macurije Integral Forest Company, located in the municipalities of Guane and Mantua in the province of Pinar del Rio, Cuba. We used data recorded from 14 permanent plots established in the year 2006 with four consecutive measurements taken throughout the different Basic Forest Production Units, 256 temporary lots randomly distributed throughout the enterprise area and the forest inventory carried out by the company in 2002-2003. The anamorphic-based site index curve system was constructed using the nested regression method applied by Bailey and Clutter (1976) and described by Alder (1980) as a method of hierarchical regression with a common slope estimator. The model fitted dominant height (Ho)-age data, and six site indices were derived for 13, 16, 19, 22, 25 and 28 m at 35 years old. In addition, the equation for determining the site index was obtained.

USO DE MODELOS ESTATÍSTICOS PARA CLASSIFICAÇÃO DE SÍTIOS EM POVOAMENTOS DE Pinus taeda NA REGIÃO DE CAÇADOR – SC

Este trabalho teve como objetivo testar diferentes modelos estatísticos para ajuste de curvas de índice de sítio e verificar se as curvas anamórficas geradas foram satisfatórias para classificação de sítios em povoamentos de Pinus taeda L. na região de Caçador, SC. Os dados de altura dominante (hdom) utilizados nesta pesquisa foram obtidos de parcelas permanentes de área fixa e formato retangular, com áreas de 500 e 625 m². As parcelas foram distribuídas de forma aleatória nos povoamentos, a fim de abranger a maior variabilidade possível de produtividade. A seleção do melhor modelo estatístico ajustado foi feita por meio das seguintes estatísticas de ajuste e precisão: coeficiente de determinação ajustado (R²aj), erro padrão da estimativa (Syx), erro padrão da estimativa em porcentagem (Syx%) e distribuição de resíduos em porcentagem. O modelo monomolecular apresentou os melhores resultados para os critérios de seleção, portanto foi escolhido para a construção das curvas de índice de sítio pelo método da curva guia. Depois de se proceder à classificação de sítios, foram realizados testes de anamorfismo, os quais indicaram o padrão anamórfico das curvas geradas pelo modelo estatístico ajustado para classificação de sítios dos povoamentos de Pinus taeda na região de Caçador, SC.Palavras-chave: Modelos estatísticos; teste de anamorfismo; curvas de índice de sítio; altura dominante. AbstractUse of statistical modells for site classification of Pinus taeda plantation in the region of Caçador, Santa Catarina State, Brazil. This study aimed to test different statistical models for fitting site index curves and check if the anamorphic curves generated were satisfactory to classify the loblolly pine (Pinus taeda L.) plantations in the region of Caçador, Santa Catarina State, Brazil. The data of dominant height (hdom) used in this study were obtained from permanent plots of fixed area and rectangular shape, with areas of 500 and 625 square meters. The plots were distributed randomly in the stands to cover the largest possible variability of productivity. The selection of the best equation was made by the following fitting and precision statistics: adjusted coefficient of determination (R²aj), standard error of estimation (Syx), standard error of estimate in percentage (Syx%) and graphical distribution of the residuals in percentage. The monomolecular model showed the best performance, so it was chosen for the construction of the site index curves by guide curve method. After construction of the site index curves, the stability of the curves was also tested, which indicated the anamorphic pattern of the curves generated by the equation for site classification of loblolly pine plantations in the region of Caçador, Santa Catarina State, Brazil.Keywords: Statistical models; test of anamorphism; site index curves; dominant height.

Site index curves for poplar growing on former farmland in Sweden

Site index (SI) curves for H 20 (dominant height at 20 years total age) were constructed using growth data from 64 hybrid poplars (Populus spp.) growing in 33 stands planted on farmland in Sweden (Lat. 55–60°N). The mean age of the stands was 24 years (range 14–45), the mean density 993 stems ha−l (155–3493), and the mean diameter at breast height (outside bark) 24 cm (10–45). SI curves fitted for H 20 at total age were well in accordance with the SI curves presented by other studies. A number of dynamic equations for modeling top-height growth from total age were assessed. A generalized algebraic difference approach (ADA) model derived by Cieszewski performed best. The model explained 98% of the observed variation in height development and exhibited no apparent bias across the range of predicted site indices. SI was also examined in relation to soil type. Multiple samples were available for three types of soil: light clay, medium clay, and till. There were no significant differences between the soil types.

Predicting the dominance of planted and invading trees using site index curves

Predicting the dominance of planted and invading trees using site index curves

Site-specific height growth models for six common tree species in Denmark

Site-specific height growth models were developed for European beech, pedunculate and sessile oak, Norway spruce, Sitka spruce, European silver fir and Douglas fir in Denmark. The models were derived based on base-age invariant methods to fit the three-dimensional surface of stand age, stand top height and site index in a manner that directly estimated site indices as parameters from the fitting procedure. The estimated base-age invariant models represented the observed age–height patterns well across the range of site conditions. For all species the model explained more than 98% of the observed variation in stand height development and exhibited no apparent bias across the range of predicted site indices. Compared to historical site index curves, the growth patterns expressed by the site-specific height growth models were considerably different, indicating that the historical site index curves were biased. The pattern of deviation depended on tree species and site conditions.

Ring width, latewood proportion and dry density in stems of Pinus brutia Ten.

This study examined basic characteristics of stem wood produced in Pinus brutia Ten. reforestations in Northeastern Greece. Sixteen dominant trees growing at good and medium site qualities were felled at 14–22 years. Site quality classification was based on site quality surrogates and confirmed by using site index curves that were created for a neighbouring area. Discs were taken at three stem positions (base, middle, top) to study variations in ring width, latewood proportion and dry density. Generally, at both good and medium sites, ring width was found to increase towards the top of the stems while latewood proportion and dry density showed a negative relationship with stem height. Radial variability trends were similar at all heights, and at both sites, revealing a rapid increase for ring width in the first 3–6 annual rings followed by a decrease towards the bark, a gradual increase for latewood proportion and no specific change for dry density. Comparisons between wood material produced during the same growth period (2005–2001) showed statistically significant differences among sampling heights in all cases except for dry density in medium sites. At the base of the stems, mean ring width and dry density were significantly (P ≤0.05) higher at good sites (3.6 mm and 0.53 g/cm3) than at medium sites (3.0 mm and 0.50 g/cm3). However, the differences between the sites are of small magnitude and therefore have limited practical impact on wood processing. The availability of such data is useful in utilising small-dimension timber of brutia pine.

Estimation of height growth patterns and site index curves for Pinus radiata plantations in New South Wales, Australia

The objective of this study was to estimate the mean top height growth patterns and site index curves (base index age 20 years) for Pinus radiata stands grown in New South Wales, Australia. Garcia's stochastic differential equation version of the Bertalanffy-Richards equation was selected for stand height prediction using data from permanent growth and long-term experimental plots. This technique uses simultaneous maximum likelihood methods to estimate the global and local model parameters. Three regional base age invariant site index curves were created based on this height estimation methodology. These models may be used for modelling stand height growth as a component of a stand growth model and can also provide an indication of the productivity of the site quality of Pinus radiata stands planted in New South Wales, Australia.