No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Evaluation of forest site productivity
... It is assessed by several methods that can be broadly grouped into two: geocentric and phytocentric. The geocentric methods are mostly based on site indicators of climate, topography and soil, whereas the phytocentric methods are vegetation related, made up of tree-or plantbased indicators (Hägglund, 1981;Skovsgaard and Vanclay, 2008). The two methods have been widely applied in studies on forest site productivity assessment for several tree species across biomes (e.g. ...
... However, expressing SI in terms of the potential average volume yield produced over the stand rotation is desired since timber volume is a key parameter in economic and ecological analyses of forest resources. Hence, for even-aged forest stands, the relation between SI and maximum mean annual volume increment (hereafter, referred to as yield capacity) can directly be used to describe the potential amount of wood volume that can be obtained per year on a site for a given species (Hägglund, 1981;Hägglund and Lundmark, 1982;Elfving and Nyström, 1996) and for further classification of forest lands as productive and unproductive units. ...
... On the methods of yield capacity estimation, existing growth functions were used to simulate the yield capacities from NFI data collected using temporary sample plots in the early 1980s (Hägglund, 1981;Hägglund and Lundmark, 1982;Ekö, 1985). The Swedish NFI is a statistically distributed sample and so therefore covers a wider amplitude of stand variation (Fridman et al., 2014). ...
Information on forest site productivity is a key component to assess the carbon sequestration potential of boreal forests. While site index (SI) is commonly used to indicate forest site productivity, expressions of SI in the form of yield capacity (potential maximum mean annual volume increment) is desirable since volume yield is central to the economic and ecological analyses of a given species and site. This paper assessed the functional relationship between SI and yield capacity on the basis of yield plot data from long-term experiments measured over several decades for Norway spruce (Picea abies), Scots pine (Pinus sylvestris), Lodgepole pine (Pinus contorta) and Larch (Larix decidua and Larix sibirica) in Sweden. Component models of total basal area and volume yield were also developed. SI was determined by existing height development functions using top height and age, whereas functions for stand-level (m 2 ha − 1) basal area development were constructed based on age, SI and initial stand density using difference equations and nonlinear mixed-effects models. The relation between volume yield (m 3 ha − 1) and top height was adjusted with total basal area production through nonlinear mixed-effects models. Species-specific parametric regression models were used to construct functional relationships between SI and yield capacity. The root mean square errors of the species-specific models ranged from 2 to 6% and 10-18% of the average values for the basal area and volume equations, respectively. For the yield capacity functions, the explained variations (R 2) were within 80-96%. We compared our yield capacity functions to earlier functions of the species and significant differences were observed in both lower and higher SI classes, especially, for Scots pine and Norway spruce. The new functions give better prediction of yield capacity in current growing conditions ; hence, they could later be used for comparing tree species' production under similar site and management regimes in Sweden.
... Accurate and reliable predictions of the future development of forest site productivity are crucial for the effective management of forest stands. In the context of the management of forests for wood production forest site productivity is defined as a quantitative measure of the potential of a specific forest stand on a specific site type to produce wood (Hägglund, 1981). In forestry the most widespread indicator of forest site productivity is site index (Skovsgaard and Vanclay, 2008). ...
... In forestry the most widespread indicator of forest site productivity is site index (Skovsgaard and Vanclay, 2008). Site index is usually defined as the mean (or dominant) stand height of a specific tree species at a predefined reference age (Assmann, 1970;Hägglund, 1981). Since site index is highly sensitive to site potential but (almost) insensitive to stand density it is the most commonly used measure of forest site productivity. ...
Accurate and reliable predictions of the future development of forest site productivity are crucial forthe effective management of forest stands. Static models which simply extrapolate productivity intothe future are inappropriate under conditions of environmental change since they lack a close linkbetween fundamental environmental drivers and forest growth processes. Here we present a dynamicenvironment-sensitive site index model formulated in the framework of a nonlinear state space approachbased on longitudinal data from long-term experimental plots. Estimation of the model parameters wascarried out using the prediction error minimization method. Our aim was to identify dynamic relation-ships between site index and environmental variables and to make conditional predictions of the futuredevelopment of site index under climate change scenarios. Nonlinear, interactive, as well as accumula-tive effects of environmental factors (climate/weather and nitrogen influx) on the growth response wereconsidered in the model. In the study, we estimated the dynamic environment-sensitive site index modelusing data from 604 Norway spruce (Picea abies [L.] Karst.) long-term experimental plots in southwestGermany with measurement data covering a period of more than 100 years from the end of the 19thcentury until today. We used the calibrated model to project future site index changes under increas-ing growing season temperature scenarios. Conventional climate change impact studies usually utilizea gradient approach and apply space-for-time substitution for the parameterization of models that arecalibrated using spatial variability in the data. In contrast, the approach presented here utilizes the longi-tudinal data structure of multiple real growth time series to simultaneously exploit spatial and temporalvariation in the data to provide more reliable and robust projections. Limitations of the space-for-timesubstitution approach in forest growth modelling are discussed.
... (Bravo and Montero 2001; Carmean 1975; Fontes et al. 2003; Hagglund 1981). However, 31 it has been difficult to quantify site quality from soil properties in forested ecosystem 32 because of the complex relationship between soils and stand productivity (Dye et al. 33 2004; Landsberg et al. 2003). ...
... Soil-site studies often used regression techniques to 34 predict SI from the edaphic and topographic properties of a site (Baker and Broadfoot 35 1979; Beaulieu et al. 2011; Carmean 1975; Wang 1995). These soil-site studies used 36 ordinary least square methods of multiple linear regression where SI was used as a 37 response variable and soil variables were used as the regressors (Carmean 1975; Fontes 38 et al. 2003; Hagglund 1981). However, in soil site studies multicollinearity can be a 39 serious problem when multiple linear regression methods are used (Fontes et al. 2003; 40 Kayahara et al. 1995). ...
Data from 15 sites with loblolly pine (Pinus taeda L.) plantations located in the southeastern United States were used to predict site index (SI) from soil physical and chemical properties from the top 15 cm of the mineral soil. Two modeling approaches were used to predict SI from soil properties. First, the ordinary least-squares method of multiple linear regression was used, which selected calcium, potassium, AND sand percentage as the significant predictor variables. Second, partial least-squares regression was used, which selected total nitrogen, carbon, calcium, magnesium, AND sand percentage as the significant predictor variables. The partial least-squares regression approach addressed multicollinearity in the data and produced a better model to predict SI. The partial least-squares regression model explained 77% of the variation in SI.
... Estimates of site productivity must be accurate as any bias may propagate through growth, mortality and recruitment functions to affect all modelling results. In even-aged stands of a single species, one alternative to estimate the site productivity is through site index (Hágglund, 1981;Vanclay, 1994). In Nothofagus forest (Provinces of Tierra del Fuego and Santa Cruz) the average height of dominant and codominant trees is often used as the measure of stand productivity. ...
Nofhofagus pumilio is tre most important timber native species in Patagonian forest. Since there is not any site index equation for lenga forest, we set as our aim to provide such an equation. One hundred trees were selected (along ten sites) for stem analysis and the data obtained were used in the nonlinear regression analysis. The constrained Weibull-type site index model was selected, because it showed the best statistics; it also has the property of H=S at index age. Base age at 60 years was selected, and a range Sl,, of 9.8 to 23.22 m of total height was obtained. The use of this equation provides some of the information required for different management regimes and silvicultural situations on lenga forests.
... Method 1 uses the height and age of the dominant trees (i.e., the 100 largest trees in diameter per hectare) to estimate the expected height at a reference age (e.g. 100 years for Scots pine-Pinus sylvestris L. and Norway spruce-Picea abies (L.) H. Karst, and 50 years for birch-Betula pendula Roth. and Betula pubescens Ehrh.) 10,14,15 . This method of estimating site index is denoted as SIH. ...
Forest growth varies across landscapes due to the intricate relationships between various environmental drivers and forest management. In this study, we analysed the variation of tree growth potential across a landscape scale and its relation to soil moisture. We hypothesised that soil moisture conditions drive landscape-level variation in site quality and that intermediate soil moisture conditions demonstrate the highest potential forest production. We used an age-independent difference model to estimate site quality in terms of maximum achievable tree height by measuring the relative change in Lorey’s mean height for a five year period across 337 plots within a 68 km² boreal landscape. We achieved wall-to-wall estimates of site quality by extrapolating the modelled relationship using repeated airborne laser scanning data collected in connection to the field surveys. We found a clear decrease in site quality under the highest soil moisture conditions. However, intermediate soil moisture conditions did not demonstrate clear site quality differences; this is most likely a result of the nature of the modelled soil moisture conditions and limitations connected to the site quality estimation. There was considerable unexplained variation in the modelled site quality both on the plot and landscape levels. We successfully demonstrated that there is a significant relationship between soil moisture conditions and site quality despite limitations associated with a short study period in a low productive region and the precision of airborne laser scanning measurements of mean height.
... En Carmean (1975) se puede encontrar una pormenorizada revisión del tema en relación a bosques templados, con énfasis en aspectos metodológicos y conceptuales. También para este tipo de bosques y para el período posterior a 1973, Hägglund (1981) actualiza aquel trabajo. Por su parte, Vanclay (1992) revisa las principales diferencias y particularidades que este concepto presenta en el marco de la silvicultura de los bosques tropicales. ...
Resumen
No obstante los avances en el conocimiento del manejo de los bosques de Austrocedrus chilensis (D. Don) Florin et Boutleje (ciprés de la cordillera), aún se carecen de modelos de producción y para desarrollarlos es esencial la correcta evaluación de la calidad de sitio. En este trabajo se presenta el desarrollo y ajuste de tres variantes de un modelo predictivo del crecimiento en altura dominante que permiten generar funciones de índice de sitio para esta especie. Empleando el método de la ecuación de la diferencia se desarrollaron tres expresiones diferentes del modelo de Chapman-Richards que resultaron invariantes a la edad de referencia. Dos expresiones resultaron polimórficas con asíntota común, mientras que la restante fue anamórfica con asíntota variable. Para generar los datos altura-edad, un total de 23 árboles de sitio, tomados de 10 parcelas, fueron apeados para realizarles el análisis de fuste y reconstruir su crecimiento pasado en altura. En las pruebas convencionales de bondad de ajuste los tres modelos presentaron resultados satisfactorios y ninguno se demostró superior. Considerando criterios e indicadores específicos para las funciones de sitio, el comportamiento predictivo de los tres modelos resultó aceptable, aunque todos mostraron sesgo e imprecisión para edades juveniles. En el rango de edades de mayor importancia práctica la precisión es razonable y el sesgo desaparece, siendo la formulación anamórfica la de mejor desempeño. Para mejorar el comportamiento predictivo, los resultados obtenidos sugieren el uso de la edad a la altura del pecho y el desarrollo de una variante polimórfica con asíntota variable de ese modelo.
... Site index is by far the most common expression of forest site productivity. In the Swedish forest site classification system, site index based on height development curves (denoted as SIH) at a predetermined age (e.g., 100 years for Pinus sylvestris -Scots pine and Picea abies -Norway spruce) is the most preferred method in homogenous stands (Hägglund, 1981;Mensah et al., 2022). The curves show the development of mean heights of the dominant (top) trees (e.g., the 100 largest trees in diameter per hectare) over age. ...
Recent advancements in remote sensing of forests have demonstrated the capabilities of three-dimensional data acquired by airborne laser scanning (ALS) and, consequently, have become an integral part of enhanced forest inventories in Northern Europe. In Sweden, the first national laser scanning revolutionised forest management planning through low-cost production of large-scale and spatially explicit maps of forest attributes such as basal area, volume, and biomass, compared to the earlier practice based on field survey data. A second scanning at the national level was launched in 2019, and it provides conditions for the estimation of height growth and site index. Accurate and up-to-date information about site productivity is relevant for planning silvicultural treatments and for the prognosis of forest status and development over time. In this study, we explored the potential of bi-temporal ALS data and other auxiliary information to predict and map site productivity by site index according to site properties (SIS) of Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.) in even-aged stands in Sweden. We linked ground survey data of SIS from more than 11,500 plots of the Swedish National Forest Inventory (NFI) to bi-temporal ALS data to predict and map site index using an area-based method and two regression modelling strategies: (1) a multiple linear regression (MLR) model with an ordinary least-squares parameter estimation method, and (2) a non-parametric random forests (RF) model optimised for hyper-parameter tuning. For model development, permanent plots were used, whereas the validation was done on the temporary plots of the Swedish NFI and an independent stand-level dataset. Species-specific models were developed, and the root mean square error (RMSE) metric was used to quantify the residual variability around model predictions. For both species, the MLR model gave precise and accurate estimates of SIS. The RMSE for SIS predictions was in the range of 1.96 – 2.11 m, and the relative RMSE was less than 10 % (7.68 – 9.49 %) of the reference mean value. Final predictors of site index include metrics of 90th percentile height and annual increment in the 95th percentile height, altitude, distance to coast, and soil moisture. Country-wide maps of SIS and the corresponding pixel-level prediction errors at a spatial resolution of 12.5 m grid cells were produced for the two species. Independent validations show the site index maps are suitable for use in operational forest management planning in Sweden.
... For a given tree species, a site index (SI) model (or top height growth models) is the most commonly used tool to estimate the potential site productivity, which is defined as the expected average height of dominant trees at the selected reference age [6,7]. Dominant height growth models, also known as SI models, are commonly used to estimate the potential productivity of forest stands. ...
An accurate estimate of the site index is essential for informing decision-making in forestry. In this study, we developed site index (SI) models using stem analysis data to estimate the site index and the dominant height growth for Larix gmelinii var. principis-rupprechtii in northern China. The data included 5122 height–age pairs from 75 dominant trees in 29 temporary sample plots (TSPs). Nine commonly used growth functions were parameterized using the modeling method, which accounts for heterogeneous variance and autocorrelation in the time-series data and introduces sample plot-level random effects in the model. The results show that the Duplat and Tran-Ha I model with random effects described the largest proportion of the dominant height variation. This model accurately evaluated the site quality and predicted the dominant tree height growth in natural Larix forests in the Guandi Mountain region. As an important supplement in improving methods for site quality evaluation, the model may serve as a fundamental tool in the scientific management of larch forests. The research results can inform an accurate evaluation of the site quality and predict the growth of the dominant height in a larch forest in the Guandi Mountain forest area as well as provide a theoretical basis for forest site quality evaluation at similar sites.
... La capacité d'une station à produire du bois dépend de multiples facteurs biogéoclimatiques. Plusieurs variables climatiques, topographiques et édaphiques influencent, de façon directe ou indirecte, la croissance des arbres (Zon 1913, Cajander 1926, Hägglund 1981. Depuis longtemps, les forestiers utilisent l'indice de qualité de station (iQs, défini comme la hauteur des arbres dominants et codominants à un âge de référence donné) pour quantifier le potentiel de croissance des peuplements forestiers. ...
Les projets de modélisation de la croissance et du rendement menés par la Direction de la recherche forestière sont essentiels à un aménagement efficace des ressources
forestières du Québec. L’identification des facteurs biogéoclimatiques cartographiables qui influencent le potentiel de croissance en diamètre des dix espèces d’arbres les mieux représentées au Québec, de même que celui de quatre groupes d’espèces moins abondantes, pourrait permettre d’améliorer la qualité prédictive des modèles de croissance, pour mieux cibler les sites les plus favorables
à la croissance de chaque espèce ou groupe d’espèces.
... In forestry practices, the site index (SI) is the most widely used measure of site productivity, and it is estimated for a given species based on the stand height at a specific base age (Sugawara & Nikaido, 2014;Joan DeYoung, 2016). It is mostly determined by phytocentric methods (Hägglund B, 1981;Skovsgaard & Vanclay, 2008b). However, phytocentric methods are only appropriate for even-aged, undisturbed, and monoculture stands (Carmean & Lenthall, 1989;Huang & Titus, 1993;Skovsgaard & Vanclay, 2008b;Pokharel & Dech, 2011;West, 2015;Fu et al., 2018;. ...
The site index (SI) is the most commonly used and representative measure of the phytocentric approach; it evaluates the site productivity based on the stand height and age. In the case of mixed stands with complex structures, phytocentric methods are very limited, while in non-forest areas, they are not applicable. In situations where the applicability of phytocentric methods is limited, the site productivity is determined by geocentric methods. Geocentric methods allow direct modelling of site productivity, expressed by SI predicted from various environmental variables. The aim of this study was to develop a geocentric model for oak. Site productivity expressed by SI was described by the environmental variables and stand characteristics. To develop the SI model, we used the data from 2490 NFI plots with dominant oak species (Quercus sessilis and Quercus robur). A generalized additive model was used in modelling site productivity. We documented a significant relationship between SI and the environmental variables, age of stands and stand density. Furthermore, the site productivity for oak is shaped by climate factors, soil type, geology, and altitude. The model developed based on the geocentric method, explained 55.1% of the variation of SI.
... For a given tree species, a site index (SI) model (or top height growth models) is the most commonly used tool to estimate the potential site productivity, which is defined as the expected average height of dominant trees at the selected reference age [6,7]. Dominant height growth models, also known as SI models, are commonly used to estimate the potential productivity of forest stands. ...
An accurate estimate of the site index is essential for informing decision-making in forestry. In this study, we developed site index (SI) models using stem analysis data to estimate the site index and the dominant height growth for Larix gmelinii var. principis-rupprechtii in northern China. The data included 5122 height–age pairs from 75 dominant trees in 29 temporary sample plots (TSPs). Nine commonly used growth functions were parameterized using the modeling method, which accounts for heterogeneous variance and autocorrelation in the time-series data and introduces sample plot-level random effects in the model. The results show that the Duplat and Tran-Ha I model with random effects described the largest proportion of the dominant height variation. This model accurately evaluated the site quality and predicted the dominant tree height growth in natural Larix forests in the Guandi Mountain region. As an important supplement in improving methods for site quality evaluation, the model may serve as a fundamental tool in the scientific management of larch forests. The research results can inform an accurate evaluation of the site quality and predict the growth of the dominant height in a larch forest in the Guandi Mountain forest area as well as provide a theoretical basis for forest site quality evaluation at similar sites.
... The traditional way of determining the SI in the field is by collecting core samples from dominant trees to determine the age at breast height, and then measuring the height of the same trees (Carmean, 1975;Hagglund et al., 1981). The SI can then be predicted using empirical models with age and Hdom as predictors. ...
Site index (SI) indicates the magnitude of timber production that can be realized
at a given site and is a crucial variable in forest planning. In Norwegian
forest management inventories, SI is commonly quantified with large uncertainty
by means of aerial image interpretation, field assessment and information from
previous inventories. Airborne laser scanning (ALS) and digital aerial photogrammetry
(DAP) have revolutionized the field of forest inventory in recent decades,
however operational practices for SI estimation have remained unchanged since
the 1970s. The main objective of this thesis was to develop practical methods of
SI estimation using bitemporal tree height data derived from ALS and DAP.
The first study presented two practical methods of SI estimation; (i) the direct
method, in which models are applied for direct prediction of SI from bitemporal
ALS metrics, and (ii) the indirect method in which the SI is derived indirectly
from estimates of canopy height development over time. Both methods provided
reliable SI estimates, however the direct method was most accurate. Operational
application of the methods requires undisturbed forest growth. Hence, the second
study assessed the use of bitemporal ALS data for classification of various types
of changes in forest structure, and showed that such changes can be classified with
high accuracy at plot level. In the third study, a practical method for predicting
and mapping SI in repeated ALS-based forest inventories was demonstrated. The
method included a forest disturbance classification, and the direct method was
then applied to forest areas classified as undisturbed. The last study compared
the economic utility of six methods of ALS- and DAP-based SI estimation and
conventional practices in a cost-plus-loss analysis, by which the economic losses
due to sub-optimal treatment decisions were added to the inventory costs. The
study showed that SI can be estimated from bitemporal combinations of ALS and
DAP data with unprecedented accuracy and at a lower cost than conventional
methods.
This thesis shows that bitemporal ALS and DAP data are highly suitable for the
estimation of SI. The methods presented here can be used to predict, estimate and
map SI at sub-stand level automatically over large areas of forest. They are practically
applicable and cost-efficient, and can be adopted to replace conventional
practices of SI estimation in repeated forest management inventories.
... Unlike diameter at breast height, mean height and volume, dominant height usually does not show sensitivity to silvicultural treatments and variations in the stand density (Curtis & Reukema, 1970;Hogg & Nester, 1991). The dominant height, due to close relationship with volume, is considered as a good site productivity index (Carmean, 1975;Hagglund, 1981;Clutter et al., 1983). A further important characteristic of dominant height is that its variability within sample plots which are used in site index studies is relatively low, but it shows high variability between sample plots; this latter component of variability is that which is expected to be linked to variations in the productivity of sites (Herrera et al., 1999). ...
Description of the subject. This study evaluates the application of Boosted Regression Trees (BRT) for predicting beech dominant height in the Hyrcanian forests of Iran, inscribed as a UNESCO’s World Heritage due to its remarkable biodiversity.
Objectives. It is widely accepted that tree growth can be influenced by a wide variety of factors such as climate, topography, soil conditions and competition for resources. The early dominant height of trees modelling studies used the multiple linear regression. The development of more advanced non-parametric and machine learning methods provided opportunities to overcome the nonlinear relationships in forest ecosystems.
Method. In this study, boosted regression trees was evaluated to model the dominant height of Fagus orientalis as the most important tree species in the Hyrcanian forest, Iran. Dominant height was related to soil and topographical variables, which are available for 190 sample plots covering all importance environmental gradients in the research area.
Results. The results indicated BRT were found to outperform for modelling beech dominant height. This technique showed that phosphorus, percentage nitrogen, magnesium and percentage sand were among the most important variables.
Conclusions. This study demonstrates the ability of BRT to accurately model the dominant height of oriental beech in relation to environmental predictors, and encourages its use in forest ecology.
... Die erste und am häufigsten verwendete Methode basiert auf der Ansprache der Standortsproduktivität mittels bestimmter Pflanzen, denen ein ökologischer Zeigerwert zugewiesen werden kann; die zweite basiert auf der Verwendung physiognomischer Merkmale der Pflanzen, wie beispielsweise der Blattgröße oder der Pflanzenhöhe. Die beiden Ansätze schließen sich keineswegs gegenseitig aus, sondern können auch gemeinsam zur Anwendung kommen (Hagglund, 1981). ...
... Our analyses showed that AGB was best explained by CWM_Hmax, 506 which indicates that dominant height is the most important trait for high productivity. This has 507 sense, because the dominat height attained by a forest stand at a specified age (known as site 508 index), is the most widely used indicator of potential productivity in forest ecosystems 509 (Hägglund, 1981;Vanclay, 1994). 510 ...
Background: Studies on the relationships between biodiversity and ecosystem productivity have suggested that species richness and functional diversity are the main drivers of ecosystem processes. There is no general pattern regarding the relationship found in various studies, and positive, unimodal, negative, and neutral relationships keep the issue controversial. In this study, taxonomic diversity vs functional diversity as drivers of above-ground biomass were compared, and the mechanisms that influence biomass production were investigated by testing the complementarity and the mass-ratio hypoteses.
Methods: Using data from 414 permanent sampling plots, covering 23% of temperate forests in the Sierra Madre Occiental (Mexico), we estimated the above-ground biomass (AGB) for trees ≥7.5 cm d.b.h. in managed and unmanaged stands. We evaluated AGB-diversity relationships (species richness, Shannon-Wiener and Simpson indices), AGB-weighted mean community values (CWM) of tree species functional traits (maximum height, leaf size, and wood density) and five measures of functional diversity (functional dispersion, functional richness, functional uniformity, functional diversity, and RaoQ index).
Results: We reveal a consistent hump-shaped relationship between aboveground biomass and species richness in managen and unmanaged forest. CWM_Hmax was the most important predictor of AGB in both managed and unmanaged stands, which suggests that the mechanism that explains the above-ground biomass in these ecosystems is dominated by certain highly productive species in accordance of the mass-ratio hypothesis. There were no significant relationships between taxonomic diversity metrics (Shannon-Wiener and Simpson indices) or measures of functional diversity with AGB. The results support the mass-ratio hypothesis to explain the AGB variations.
Conclusions: We concluded that diversity does not influence biomass production in the temperate mixed-species and uneven-aged forests of northern Mexico. These forests showed the classic hump-shaped productivity-species richness relationship, with biomass accumulation increasing at low to intermediate levels of species plant diversity and decreasing at high species richness. Functional diversity explains better forest productivity than classical diversity metrics.
... The most common measure of forest site quality is the dominant height of a stand at a specified reference age. This measure, or index, has the advantage of being independent of stand density (Carmean, 1975;García, 2005;Hägglund, 1981;Skovsgaard and Vanclay, 2008;Tesch, 1980), and is widely known as "site index" (Skovsgaard and Vanclay, 2008;van Laar and Akça, 2007;Weiskittel et al., 2011), although other indices had received the same name. Henceforth, I refer to it as a "traditional site index" or simply TSI. ...
Understanding the height growth of trees is a fundamental component for scientific knowledge and management of forest ecosystems. The height of dominant trees at a reference-age, commonly known as the site-index, is the most widely used forest productivity indicator globally. Yet, it has been criticized for its restricted applicability to monospecific and even-aged forests, making it unreliable for natural forests or mixed-species where there is not a single meaningful age. Here, I develop a mathematical perspective for using height growth-rate at a reference-height as a new type of site index. I provide the mathematical basis for the proposed index and illustrate its application by fitting a nonlinear mixed-effects differential equation model to tree height growth data of three Nothofagus species in southern Chile. The proposed index allows us to foresee and analyze growth patterns, not only by representing growth-rates as a function of time but also of size. In doing so, the proposed index makes tree growth and productivity analyses accessible to a broader community of researchers.
... Betrachtet man die Produktionsfunktionen der Wälder, ist forstliche Standortproduktivität im engeren Sinne definiert als quantitatives Maß für die Fähigkeit eines Waldstandorts, pflanzliche Biomasse zu produzieren. Die forstliche Standortproduktivität hängt sowohl von natürlichen, dem Standort und Bestand innewohnenden Faktoren, als auch von Bewirtschaftungsfaktoren ab (ASS-MANN 1970;DYCK et al. 1994;HÄGGLUND 1981). Häufig wird der Begriff 'Standortqualität' (engl. ...
... Site index is defined as the average total height of dominant and co-dominant trees (site trees) at a specified reference or base age, which is commonly selected to lie close to the rotation age [1]. The top height is the arithmetic mean height of the 100 trees ha −1 with the greatest diameters [2]. However, the most common objective of site index is to determine the height development pattern that a stand is expected to follow throughout rotation [1]. ...
This study aims to develop site index for Teak (Tectona grandis) in Kanya Forest Plantation, Nigeria. Site index is defined as the total height of the dominant or co-dominant trees at an arbitrary index age, it is a method used for quantifying site quality for pure even-aged stands which is essential in growth and yield modelling. The data used in this study were obtained from six different age classes. Five sample plots each were selected across all age classes in which a total of 712 trees were measured, variables measured include total height, diameter at the base, middle, top, and diameter at the breast height were taken from 30 temporary sampled plots of 25x25m approximately from the centre, 180 dominant trees were selected from 712 trees. Basal area and volume of sampled trees were computed. Yield values obtained from the dominant trees are (B = 249.312 m3/ha, D = 196.128 m3/ha, F = 134.976 m3/ha, C = 119.328 m3/ha, E = 100.320 m3/ ha and A = 86.976 m3/ha). The results showed that B was the best and A was the poorest. Seventeen models were generated and paired sampled t-test was used for model validation, comparing the actual and predicted height. Two out of 17 were rejected (significant P<0.05). The first model Hd=12075.346-354.809(Age)+3.448(Age)2-135193.126(1/Age) is the recommended height estimation of Teak in Kanya Forest plantation for its best performance.
... When the physical, chemical and biological properties of the soil are used, site productivity/site quality is generally better estimated (Subedi and Fox, 2016). Numerous soil-site studies attempted to associate the measured soil properties with the site index (SI) (Carmean 1975, Hagglund 1981, Bravo and Montero 2001, Fontes et al. 2003) Nevertheless, it is quite difficult to measure the site productivity/site quality from soil properties in forest ecosystems due to the complex correlations between stand productivity and soil properties. The site quality and stand productivity can be approached from a different perspective, and site factors can be considered as a function of geoclimatic variables (Pokharel and Froese 2009;Bontemps and Bouriaud 2014). ...
Oriental Beech grows naturally in the Eastern Caucasus, Northern Iran and Crimea, from the west of the Balkans towards Anatolia. Akkuş Region of Turkey is one of the moist ecosystems where this tree species spread optimally. In this spread area, the change of local site factors affect the site productivity. In this study, the correlations between the height growth of pure Oriental beech forests between 1200-1500 m altitudes in Akkuş region and some soil characteristics and location factors were investigated. 40 sample plots were taken from normally covered Oriental beech stands. In the sample plots, soil profiles were dug and soil sampling was performed according to genetic soil horizons. The location factors of the sample plots in the field were determined, and d0.30 diameter, d0.30 age and upper height were measured in 4-6 trees with upper stand height. The site productivity (site index) was determined based on the correlation between standard age and upper stand height. Physical and chemical soil analyses were performed in the soil samples taken. The correlations between the productivity indexes (site index) of the sample plots and the local ecological characteristics of the site were tested by correlation analysis. Positive correlations were determined between site index and the land slope degree and altitude. There are negative correlations between soil properties of average amount of clay, average amount of silt, field capacity, fine soil weight, soil reaction, and site index, while there are positive correlations between horizon Ah's organic matter, average amount of sand, physiological soil depth, skeleton weight and site index.
... Paterson showed that the forest productivity of a site is mainly determined by climatic factors, e.g., solar radiation, favorable temperature, precipitation and number of vegetation active months in any regions, where the climate has had enough time to develop soils (Nabuurs 1998). The CVP index was designed to predict the maximum growth potential in terms of volume production (Hägglund 1981). The index has been widely used by forest managers in Spain (Benavides et al. 2009), Australia (Howden and Gorman 1999), Pakistan (Champion et al. 1965), Bangladesh and so on with acceptable results at regional scales (Vanclay 1992). ...
Climate warming is expected to influence forest growth, composition and distribution. However, accurately estimating and predicting forest biomass, potential productivity or forest growth is still a challenge for forest managers dealing with land-use at the stand to regional levels. In the present study, we predicted the potential productivity (PP) of forest under current and future climate scenarios (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) in Jilin province, northeastern China by using Paterson’s Climate Vegetation and Productivity (CVP) index model. The PP was validated by comparing it with the mean and maximum net primary production calculated from light energy utilization (GLM_PEM). Our results indicated that using the CVP index model is partially valid for predicting the potential forest productivity in northeastern China. PP exhibited obvious spatial heterogeneity varying from 4.6 to 8.9 m3 ha−1 year−1 with an increasing tendency from northwest to southeast driven by the precipitation across the region. The number of vegetation-active months, precipitation and insolation coefficient were identified as the primary factors affecting PP, but no significant relationship was found for warmest temperature or temperature fluctuation. Under future climate scenarios, PP across the Jilin Province is expected to increase from 1.38% (RCP2.6 in 2050) to 15.30% (RCP8.5 in 2070), especially in the eastern Songnen Plain (SE) for the RCP8.5 scenarios.
... The lowered WT then reduces total evapotranspiration and transpiration by surface vegetation, thereby increasing summer base flow (Sirin et al., 1991). The main factor causing studies to reach conflicting conclusions on peatland runoff characteristics after drainage and restoration is the variation in infiltration capacity and hydraulic conductivity of peat soils in different regions, which forces them to react differently to drainage and restoration and complicates the runoff process (Gessel, 1986). ...
Potential benefits of peatland restoration by rewetting include carbon sequestration, restored biodiversity, and improved hydrological functions. There is great uncertainty about how catchment hydrological processes change after restoration, with a particular lack of well‐documented catchment runoff data. This study compared five formerly Disturbed (now Restored) and two undisturbed peatlands. In total, 455 and 728 hydrological events were selected for the analysis, using a three‐event selection technique. Mean event runoff coefficient (RC) values varied greatly between conditions and hydrological events. RC in Disturbed conditions was slightly higher than in undisturbed conditions, but RC in Restored conditions was higher than under other conditions. Mean transit time revealed that event rainfall water reached the outlet faster in Disturbed conditions. Mean event peak flow in Disturbed conditions was higher and peaked faster than under other conditions. However, the base flow showed no noticeable difference between treatments. Significantly higher watertable (WT) rise per rainfall input (0.36‐0.85 cm/mm) was observed in Disturbed conditions, due to lower specific yield (Sy) values (0.13‐0.24) than under Restored and undisturbed conditions (Sy 0.25‐0.50). Shallow WT showed significant positive correlations with runoff and storage properties, and was a key component of the runoff generation mechanisms in peatlands. Storage‐related parameters (Sy, WT rise per rainfall input) and catchment response time parameters revealed disturbance‐related hydrological changes in peatlands more clearly than other runoff parameters tested (e.g., RC). Overall, with restoration, WT and storage properties recovered to the levels at undisturbed sites, but increased runoff was observed occasionally due to wetter antecedent moisture conditions.
... Measuring site index, which is most widely and commonly used for productivity evaluation in forestry (e.g., Davis and Johnson, 1987;Hägglund, 1981;Monserud et al., 1990;Takeshita et al.,1960;Wang, 1995), is challenging and causes problems in developing site index prediction models (Mitsuda et al., 2007;Mitsuda, 2014). Site index is defined as the dominant tree height at a reference age (Davis and Johnson, 1987) (40 years is commonly used in Japan); field measurement of dominant tree height in stands of the reference age or stem analysis are limited ways for accurately measuring the site index (e.g., Kayahara et al., 1998;Mitsuda et al., 2001;2007;Monserud et al.,1990;Wang, 1995). ...
This study aimed to compare three methods for developing site index prediction model for specific species for a given site using environmental factors as explanatory variables. The following methods were compared in this study: (1) guide curve based method, (2) difference equation based method, and (3) combined site index prediction and height growth curve models method. The site index models were parameterized by the three methods with a permanent plot data and then evaluated for accuracy and practicability in model prediction using the stem analysis data. Root mean squared error and Spearman's rank correlation coefficient were used as statistics representing model accuracy and practicability; values obtained for the model derived from combined method were 4.468 and 0.754, respectively, which indicated that it was the best among the three models.
... In this context, site index (SI) equate with the overall potential of site environmental parameters to sustain tree growth. Forest productivity is supposed to correlate well with tree height growth (Hägglund, 1981) for a wide range of stand density (Eichhorn, 1904). Thus SI is generally derived from the height of individual trees in unevenaged stands, or from the mean or dominant height of evenaged stands, at a given reference age; it is then defined as "age-height SI" (Skovsgaard et al., 2004). ...
Aleppo pine (Pinus halepensis Mill.) is one of the dominant conifer species in the Mediterranean area. Many studies have investigated the role of climate variables (precipitations, temperature) in its occurrence and growth, but few have taken the effect of local site conditions into account, nor their interaction with climate. This study aimed at thoroughly assessing forest sites potential for Aleppo pine in France, and designing a
practical tool to help forest managers implementing these results. The study is based on a network of 512 plots laid out in the French Mediterranean area, where 2158 trees were measured. A site index was computed using a height growth model calibrated on these plots. Using neural networks and partial least square regression models (PLS), we disentangled the effects of climatic factors and local site conditions in Aleppo pine presence and growth.
Local water balance (assessed through topography, soil, geology and legacies of past human activities) was the main factor driving Aleppo pine productivity in the study area. Climate played a significant role as a whole but more important at the species distribution margins, frost and snow limiting Aleppo pine range northwards and in elevation. Based on these results, a practical tool was designed for two different types of mother rocks to
help assessing forest site potential for Aleppo pine. As the span of climate conditions in south-eastern France includes most of those found in Aleppo pine distribution
area, except the driest and hottest ones found in its southernmost locations, this study could easily be used or adapted in most other concerned countries. Because of the ongoing climate change and increasing drought in the Mediterranean area, the balance between local and climate factors may change in time and space. Our results show that without an accurate knowledge of local conditions, the impact of climate change cannot be predicted.
... In this context, site index (SI) equate with the overall potential of site environmental parameters to sustain tree growth. Forest productivity is supposed to correlate well with tree height growth (Hägglund, 1981) for a wide range of stand density (Eichhorn, 1904). Thus SI is generally derived from the height of individual trees in unevenaged stands, or from the mean or dominant height of evenaged stands, at a given reference age; it is then defined as "age-height SI" (Skovsgaard and Jeffery, 2004). ...
Aleppo pine (Pinus halepensis Mill.) is one of the dominant conifer species in the Mediterranean area. Many studies have investigated the role of climate variables (precipitations, temperature) in its occurrence and growth, but few have taken the effect of local site conditions into account, nor their interaction with climate.
This study aimed at thoroughly assessing forest sites potential for Aleppo pine in France, and designing a practical tool to help forest managers implementing these results. The study is based on a network of 512 plots laid out in the French Mediterranean area, where 2158 trees were measured. A site index was computed using a height growth model calibrated on these plots. Using neural networks and partial least square regression models (PLS), we disentangled the effects of climatic factors and local site conditions in Aleppo pine presence and growth.
Local water balance (assessed through topography, soil, geology and legacies of past human activities) was the main factor driving Aleppo pine productivity in the study area. Climate played a significant role as a whole but more important at the species distribution margins, frost and snow limiting Aleppo pine range northwards and in elevation. Based on these results, a practical tool was designed for two different types of mother rocks to help assessing forest site potential for Aleppo pine.
As the span of climate conditions in south-eastern France includes most of those found in Aleppo pine distribution area, except the driest and hottest ones found in its southernmost locations, this study could easily be used or adapted in most other concerned countries. Because of the ongoing climate change and increasing drought in the Mediterranean area, the balance between local and climate factors may change in time and space. Our results show that without an accurate knowledge of local conditions, the impact of climate change cannot be predicted.
... SA deduces past height growth from growth ring observations made on dissected sample trees. Generally, PSPs are considered to be the best sources of data for development of site index models (Hägglund, 1981;Raulier et al., 2003); however, PSPs require repeated measurements over the course of several years to obtain usable datasets (Perin et al., 2013). PSPs are generally established for experimental purposes or in the context of national forest inventories that cover different periods of time (Elfving and Kiviste, 1997;Raulier et al., 2003;Sharma et al., 2011;Weiskittel et al., 2009). ...
Abstract
Forest site productivity, which is a quantitative estimate of the potential of a site to produce plant biomass, remains a fundamental variable in forestry. The most commonly used and widely accepted method of evaluating site productivity is the site index. Therefore, the construction of site index models describing top height (TH) growth with age remains a fundamental task for site productivity differentiation. Three main data sources have been used for site index model development to date: (1) repeated measurements on permanent sample plots (PSP); (2) temporary sample plot (TSP) data from periodic inventories; and (3) stem analysis (SA) data. Our study is practical application of change detection using airborne laser scanners for the development of top height growth models. We demonstrated how wall-to-wall airborne laser scanner (ALS) data obtained for large forest areas can be used in developing top height growth models for Norway spruce that appropriately reflect site-specific growth trajectories. Site specific growth trajectories were successfully captured by repeated height measurements using ALS data from notably short 5-year period, which indicates that such a period between subsequent ALS observations is sufficient and surmounts the noise and other uncertainties connected with ALS systems and interannual TH growth variations. Height increment obtained by change detection using repeated airborne laser scanning (ALS) may be recognized as a new, fully valuable data source for TH growth and site index modelling. Repeated ALS observations can be a substitute for height growth data used in site index modelling and collected to-date from SA, PSP or TSP. It could be expected that improving ALS technologies, decreasing costs of laser scanning acquisition and increasing data availability will result in improving the accuracy of forest height growth estimates. Therefore, in the near future, both utility and increased predictive validity will lead to substantial increases in the importance of change detection using airborne laser scanners in forest growth modelling using the data from repeated ALS measurements.
... When the plantation was 25 years old, the total height of 9 largest (diameter) trees (the 100 largest trees per hectare, according to Hägglund (1981)) was used to calculate the site productivity (SP) for each plot (Table 1). At the same age (25 years old), 35 trees were randomly selected for each planting density, according to the randomized block design (4 treatments x 3 replicates), but outside plots marked for dendrometric measurements (to avoid affecting tree-density). ...
Aim of study: We built biomass expansion factors (BCEFs) from Douglas-fir felled trees planted with different planting densities to evaluate the differences according tree size and planting density.
Area of study: The Douglas-fir plantation under study is located on the northern coastal chain of Calabria (Tyrrhenian side) south Italy.
Materials and methods: We derived tree level BCEFs, relative to crown (BCEFc), to stem (BCEFst = basic density, BD) and total above-ground (BCEFt) from destructive measurements carried out in a Douglas-fir plantation where four study plots were selected according to different planting densities (from 833 to 2500 trees per hectare). The measured BCEFs were regressed against diameter at breast height and total height, planting density, site productivity (SP) and their interactions to test the variation of BCEFs. Analysis of variance (ANOVA) and the post hoc Tukey comparison test were used to test differences in BCEFt, BCEFc and in BD between plots with different planting density.
Main results: BCEFs decreased with increasing total height and DBH, but large dispersion measures were obtained for any of the compartments in the analysis. An increasing trend with planting density was found for all the analyzed BCEFs, but together with planting density, BCEFs also resulted dependent upon site productivity. BCEFt average values ranged between 1.40 Mg m-3 in planting density with 833 trees/ha (PD833) to 2.09 Mg m-3 in planting density with 2500 trees/ha (PD2500), which are in the range of IPCC prescribed values for Douglas-fir trees.
Research highlights: Our results showed that the application of BCEF to estimate forest biomass in stands with different planting densities should explicitly account for the effect of planting density and site productivity.
... The most commonly used and widely accepted method of evaluating site productivity is the site index (Johansson, 1999;Raulier et al., 2003;Skovsgaard & Vanclay, 2008) determined on the basis of the height of a stand at a certain age using species-specific site index models, which are also the primary modules in the growth models of trees and stands (Hägglund, 1981;Pretzsch et al., 2002;Pretzsch, 2009;Bruchwald & Zasada, 2010). ...
The strength and temporal rigidity of climate signals are important characteristics of proxy data
used to reconstruct climate variability over pre-instrumental periods. Here, we assess the performance of
different tree-ring proxies, including ring width, maximum latewood density, δ13C, and δ18O, during exceptional
cold (1800–1850) and warm periods (1946–2000). The analysis was conducted at a spruce (Picea
abies) timberline site in the Swiss Alps in proximity to long homogenized instrumental records to support
calibration tests against early temperature and precipitation data. In this cold environment, tree-ring width,
maximum latewood density, and δ18O are mainly controlled by temperature variations. δ13C is influenced
by various factors including temperature, precipitation, sunshine, and relative humidity. When comparing
the response patterns during cold and warm periods, ring width and maximum latewood density revealed
temporally stable temperature signals. In contrast, the association between the stable isotopes and climate
changed considerably between the early 19th and late 20th centuries. The temperature signal in δ18O was
stronger during the recent warm period, whereas the opposite is true for δ13C. In δ13C, the temperature
signal weakened from the early 19th to the late 20th centuries, but an (inverse) precipitation signal evolved
indicating that soil moisture conditions additionally limited recent carbon isotope ratios. An attempt to
combine the tree-ring proxies in a multiple regression model did not substantially improve the strength of
the dominating temperature signal retained in the latewood density data as this proxy already explained
a significant fraction of summer temperature variability. Our findings underscore the importance of split
calibration/verification approaches including cold and warm periods, and challenge transfer models based
on only late 20th century observational data.
... , 2014), which can make spruce growth and productivity very hardly predictable. Substantial differences in productivity drivers along climatic gradients also highlight the limits to the use of regional productivity models (Bošel'a et al., 2013a;Hägglund, 1981;Socha, 2008), which do not consider such differential responses. Relative to our results, results of ecophysiological studies (e.g., Ditmarová et al., 2010;Ježík et al., 2015) and dendroecological studies (e.g., Zang et al., 2014), which better control for inter-plot variability, indicated a strong response of spruce to both observed and simulated drought. ...
Climate is an important driver of forest health, productivity, and carbon cycle, but our understanding of these effects is limited for many regions and ecosystems. We present here a large-scale evaluation of climate effects on the productivity of three temperate tree species. We determine whether the National Forest Inventory data (NFI) collected in the Czech Republic (14,000 plots) and Slovakia (1,180 plots) contains sufficient information to be used for designing the regional climate-productivity models. Neural network-based models were used to determine which among 13 tested climate variables best predict the tree species-specific site index (SI). We also explored the differences in climate-productivity interactions between the drier and the moister part of the distribution of the investigated species. We found a strong climatic signal in spruce SI (R 0.45-0.62) but weaker signals in fir and beech (R 0.22-0.46 and 0.00-0.49, respectively). We identified the most influential climate predictors for spruce and fir, and found a distinct unimodal response of SI to some of these predictors. The dominance of water availability-related drivers in the dry-warm part of a species’ range, and vice versa, was not confirmed. Based on our findings, we suggest that (i) the NFI-based SI is quite responsive to climate, particularly for conifers; (ii) climate-productivity models should consider the differences in productivity drivers along ecological gradients, and models should not be based on a mixture of dry and moist sites; and (iii) future studies might consider the subset of influential climate variables identified here as productivity predictors in climate-productivity models.
... Paterson showed that the forest productivity of a site is mainly determined by climatic factors, e.g., solar radiation, favorable temperature, precipitation and number of vegetation active months in any regions, where the climate has had enough time to develop soils (Nabuurs 1998). The CVP index was designed to predict the maximum growth potential in terms of volume production (Hägglund 1981). The index has been widely used by forest managers in Spain (Benavides et al. 2009), Australia (Howden and Gorman 1999), Pakistan (Champion et al. 1965), Bangladesh and so on with acceptable results at regional scales (Vanclay 1992). ...
In order to predict the impact of climate change on the distribution of Quercus variabilis, one of the most widely distributed species in East Asia, the maximum entropy model (Maxent) was used to analyze the potential distribution under past (Mid Holocene, 6000 years ago), current (1950—2000) and future (2050) climate conditions. The jackknife method was used to reveal the contribution of the dominant climatic factors of Q. variabilis. The results showed that the potential distribution of Q. variabilis under the current climate conditions centered on the south of East Asia, comprising up to 21.88% of the total studied area. The distribution range was mostly located in central and south of China, as well as south of the Korean peninsula, and central to south of Japan. Suitable habitats, comprising 5.69% of the studied area, were mainly centered on Qinling, Daba, Funiu, Luoxiao, Nanling, and Wuyi Mountains, the Yunnan-Guizhou Plateau, and Taiwan. The climate change scenarios showed that the areas of the suitable habitats have changed slightly, while significantly for the distribution range. With changes in global climate volatility, the distribution centers of Q. variabilis are gradually concentrating in the regions of Qinling and Daba Mountains and Yunnan-Guizhou Plateau, and the areas of suitable habitats are gradually expanding. Minimum air temperature of the coldest month (Bio6), mean air temperature of the coldest quarter (Bio11), and annual precipitation (Bio12) were found to be dominant in influencing the geographic distribution of Q. variabilis, with contribution rates of 48.6%, 21.4%, and 14.2%, respectively.
... C'est par exemple le cas de l'accroissement périodique en volume. Il existe néanmoins des solutions plus simples pour estimer le potentiel de production d'un peuplement équienne dès lors que l'on connaît son âge et sa hauteur dominante (Hägglund, 1981 ;Sharma et al., 2002). La hauteur dominante (Hdom), définie comme la hauteur moyenne des 100 plus gros arbres par hectare (Rondeux, 1999), présente un intérêt tout particulier pour les gestionnaires forestiers car son évolution au cours du temps est, d'une part, fortement corrélée avec le potentiel de production des peuplements purs équiennes et, d'autre part, peu influencée par les opérations sylvicoles. ...
In forestry, top height is a common parameter used as indicator of the stand development stage. It can be used to estimate the potential production of monospecific even-aged stands. However, accurate field estimation of top height is time-consuming and expensive. Since the last two decades, LiDAR has proven to be very useful in estimating forest heights. In Wallonia, a low density LiDAR dataset (0.8 points /m2 on ground-level) is available for the whole territory. This paper outlines a tool, based on a predictive model of top height from airborne LiDAR data, to help forest management decision-making. The estimations provided by the model are associated with top height growth models to update top height over time and then estimate Site Index. The model has been validated for Norway spruce (Picea abies (L.) H. Karst.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stands in the entire Wallonia area (Belgium). In order to facilitate access to these models, the process has been implemented as a plugin of the open source GIS software QGIS. Free and user-friendly, it is aimed to be used by forest managers and scientists.
... In addition, among the several indicators, stand height seems to be the most widely used, accepted and versatile site productivity indicator for even-aged forests (Hägglund, 1981;Kramer, 1988;Wenk et al., 1990;Vanclay, 1994;Pretzsch, 2001Pretzsch, , 2002Avery and Burkhart, 2002;Burger, 2004;Skovsgaard, 2004). Further, the site index, which is defined as the height of the dominant trees in the stand at a reference base age, gives an idea how a particular tree species performs over different sites. ...
ABSTRACT
Khaya (Khaya senegalensis) being a new introduction, recommended for forest plantation establishment in the Dry and
Intermediate Zones of Sri Lanka, assessment of site quality at growing localities is vital. Variables, i.e. tree height and tree
diameter were measured non-destructively, at identified age classes of Khaya in Anuradhapura and Kurunegala divisions as
representatives of Dry and Intermediate Zones, respectively. Khaya in Kurunegala has achieved 39.98 cm of dbh and 18.31 m of
height by the age of 18-20, whereas in Anuradhapura they were 22.21 cm and 12.41 m. The dbh and tree height showed a strong
degree of correlation in both divisions. Among the height-diameter models regressed, parabolic model (h = ß 0 + ß 1.d + ß 2.d2
)
and the model, h – 1.3 = ß 1.d + ß 2.d2
showed the best fit with the available data in Anuradhapura and Kurunegala divisions,
respectively. As per height-diameter relation, site quality of the beat Polpithigama in Kurunegala is superior to the beats
Ullukkulama and Rathmale in Anuradhapura, while the beat Mihintale in Anuradhapura is superior to the beats Ranawarawa
and Ambanpola in the Kurunegala division. Khaya has attained average top heights of 14.2 m and 20.8 m at the base age of 18-
20 years in Anuradhapura and Kurunegala divisions, respectively. Elevated top heights demonstrated the richness of site quality
in Kurunegala division. Top height being the site index, it can be concluded that the beats Rathmale, Elayapattuwa and Punewa
in Anuradhapura and the beats Ranawarawa and Ambanpola in Kurunegala division are inferior, while the beat Mihintale in
Anuradhapura and the beats Kuliyapitiya, Nikaweratiya, Nakkawatta and Polpitigama in Kurunegala division are superior in
site quality. This confirms that Khaya performs well in the Intermediate Zone than in the Dry Zone of Sri Lanka. Further, it
identified the inferior sites for the growth of Khaya. These findings can direct the decision making process on future forest
plantation establishment in Sri Lanka with possible refining of present recommendations.
Key words: Top height, Height-diameter relation, Khaya senegalensis, Site quality
... Most existing lodgepole pine stands in Sweden were planted with an initial density of ∼2500 seedlings ha −1 , thus the effect of density is not likely to affect height development. Liziniewicz et al. (2012) found small differences in the mean and top height in 23-year-old lodgepole pine planted in spacings from 1.65 × 1.65 m up to 4.0 × 4.0 m Data from long-term experimental plots are considered superior to stem analysis data for constructing SI models if a large representative sample is available (Hägglund 1981a(Hägglund , 1981bClutter et al. 1983). The superiority of permanent plots is due to measurements done constantly on thickest trees (Garcia 2005). ...
A model was developed for predicting site index values and top height growth of lodgepole pine in northern Sweden. Data on 169 experimental plots from 61 experiments were used for model construction. Six dynamic site equations derived using the generalised algebraic difference approach (GADA) were tested. All of the equations estimate height and site index values on the basis of a known height and total age, and are base-age invariant. Unbiased parameter estimates were obtained by non-linear modelling without accounting for autocorrelation of residuals. The special formulation of the Hossfeld model and the GADA-transformed logistic function produced the most reliable site index curves The Hossfeld model is recommended as it did not produced extreme outlying estimates for young stands. The developed model is polymorphic with variable asymptotes and can predict site index and dominant height growth for lodgepole pine between 20 and 50-years-old.
... Height is commonly used to index site productivity (HÄGGLUND, 1981). However, variance analyses (Table 4 and 5), a graphical examination of cumulative growth, and comparison of means ( Table 3) all indicate that diameter was highly variable among provenances (sites), and may be a more reliable indicator of productivity than height because of the vulnerability of the latter to typhoons. ...
Cunninghamia konishii is the island race of the species complex C. lanceolata, and is native to Taiwan. It is a valuable timber species. A comprehensive provenance-family test was established in 1973. Height and diameter were measured periodically until age 26, which was close to the species' harvest age of about 30. These data offered an opportunity to examine the species' growth characteristics by fitting asymptotic growth functions. We adopted the concept of repeated measures data analyses, i.e., a combination of variance component analysis and growth curve fitting, the latter involved fitting the individual tree height and diameter data to a Weibull-based function. A severe typhoon in 1996 caused serious damage to the plantation, mostly to tree heights. To prevent this damage from influencing our results, we limited the analyses to those trees judged relatively free of typhoon damage, and focused on the diameter growth data. Fitting a Weibull function with parameters a, b, and c was statistically successful (e.g. the mean R(2) for diameter was 0.98). Both analyses indicate substantial variation among provenances and families, and thus opportunities for genetic selection and breeding. We particularly expound on the practical applications of growth curve fitting as an analytical tool for elucidating the mechanistic process of tree growth to assist decisions on the age for selection, even retrospectively, and modeling the response of tree growth to future climate.
... We reviewed this area of research in a previous report to MAF (Svavarsdóttir et al. 1999). The most widely used approach in forest site classification is the site index method, which is usually applied to productivity of even-aged stands (Hägglund 1981). An ecosystem-based approach to ecological site classification will need to define management units that are relevant to a much wider range of forest values than just productivity, and a wider range of stand structural types than even-aged stands. ...
... De Perthuis in 1788 derived tree height-age curves that were site dependent (Batho and García 2006). From these curves, the height at a reference age, called site index, can be determined for pure, even-aged stands (Curtis 1964;Hägglund 1981;Vanclay 1994). Site index has long been known to be intimately related to forest productivity (e.g., Eichhorn 1902). ...
... Site index (SI), a universal and standard measuring procedure in forestry operations for measuring tree growth performance (Tesch, 1981;Hunter and Gibson, 1984;Eyles, 1986), is defined as the mean height at age 20 years of the 100 largest diameter trees per hectare (Hagglund, 1981). While there are some drawbacks with site index, its relative insensitivity to management practices, compared with basal area or volume, make it a good measure of site quality (Richardson et al. 1999). ...
Digital terrain modelling and sampled plot productivity data is used to generate a predictive surface of site productivity across a heterogeneous landscape of 35,000 ha of plantation forestry. The productivity surface is generated from terrain and topographic attributes, specifically slope, elevation and a solar radiation index, using map algebra functions in a Geographic Information System. The quantitative surface is able to explain 41% of the variation in site productivity across the landscape. The within-compartment variation in site productivity was related to the variation predicted by the model surface. This technique makes it possible to model site productivity from terrain characteristics, reducing the need to collect detailed soil or other environmental data. This approach is relatively low cost, directly links the terrain to forest productivity and provides a useful tool for planning and optimising stand management units in the forestry enterprise with respect to the environmental variability of sites across the landscape.
... Site index has been a readily accepted indicator of forest productivity for its ease of measurement and robustness. For most species, site index is relatively independent of stand density (Hagglund 1981, Green et al. 1989. Green et al. (1989) defined 4 factors that govern site index evaluation: the stand should be dominated by the species for which productivity is being assessed, the stand should be even-aged with a closed canopy, free of damage and stand age should be between a given age range. ...
Both the coastal and interior varieties of Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco; Pseudotsuga menziesii var. glauca ) are found throughout a wide range of environmental conditions across British Columbia. The species is long-lived and can grow rapidly to standing volumes that approach the highest recorded among temperate conifers. Understanding the growth of the species across British Columbia, and its site index (defined as individual tree height at 50 m) is important for forest managers for both production and conservation objectives. To date, predictions of site index have traditionally been derived from forest inventory using estimates of species, height and age combined with the appropriate height-age model. More recently, process-based modelling has offered a viable alternative approach due to increased computing power, model simplifications and availability of input data. In this paper we applied a physiological forest growth model, 3-PG (Physiological Principles Predicting Growth) to predict and map site index of Douglas-fir across British Columbia at 1-km cell resolution. Our model predictions were scaled-up and compared to independent estimates of average site index for subzones from the British Columbia Biogeoclimatic Ecosystem Classification (BEC) system. Results indicated the 3-PG predictions closely matched those summarized by the BEC sub-zones (r = 0.86, p< 0.001, SE = 3.0m). Predicted environmental limitations of growth suggest that the coastal variety of the species is most severely affected by temperature and frost constraints, and in some locations, soil water stress, whereas the interior variety is principally restricted by soil water availability. The proposed modelling approach complements ecological classifications and offers the potential to identify the most favourable sites for management of other native tree species under current and projected climates.
Установлено, что индексы CVP и ГТК, определяющие потенциальную продуктивность растительного покрова, в том числе и лесов, на изучаемой территории имеют высокую годичную изменчивость для всех рассмотренных районов. Средние коэффициенты вариации индексов CVP и ГТК равны 38,5 и 48,4%, соответственно. Изучение изменений индексов по годам показало наличие линейной тенденции (тренда) к их увеличению за изучаемый период. Более выражена тенденция к увеличению индекса CVP. Графики изменений индексов показали наличие значительных случайных колебаний (отклонений) индексов от трендов. Случайный характер колебаний проверен с помощью медианного теста. Для расчетов потенциального прироста древесной растительности на основе литературных данных получено уравнение связи величины прироста и индекса CVP с высоким коэффициентом детерминации, равным 94,5%. С помощью этого уравнения проведены расчеты потенциального прироста древесной растительности для всех районов на изучаемой территории. Расчеты показали, что в результате высокой изменчивости индексов CVP и ГТК по годам изучаемого периода (1995-2021 гг.) потенциальная продуктивность лесов на изучаемой территории составляет в среднем 0,7 м3/га-год. В благоприятные годы максимальные значения прироста могут достигать 1,5 м3/га-год, а в неблагоприятные прирост может падать до нуля, ставя таким образом древесную растительность на грань выживания. Установлена прямая пропорциональная связь между величинами индексов CVP и ГТК с коэффициентом детерминации 86,0% для изучаемой территории, что позволяет использовать один индекс вместо другого в случае такой необходимости. В целом, гидротермические условия для роста лесов в районе г. Эрбиль следует оценить как неблагоприятные.
It was found that the CVP and HTC indices, which determine the potential productivity of vegetation cover, including forests, in the studied area, have high annual variability for all the considered districts. The average coefficients of variation of the CVP and HTC indices are 38.5 and 48.4%, respectively. The study of changes in indices over the years showed the presence of a linear trend towards their increase over the period under study. The tendency to increase the CVP index is more pronounced. The graphs of index changes showed the presence of significant random fluctuations (deviations) of indices from trends. The random nature of the fluctuations was verified using a median test. To calculate the potential growth of forests based on the literature data, an equation was obtained for the relationship between the growth rate and the CVP index with a high coefficient of determination equal to 94.5%. Using this equation, calculations of the potential growth of wood volume for all areas in the study area were carried out. Calculations have shown that as a result of the high variability of the CVP and HTC indices over the years of the studied period (1995-2021), the potential productivity of forests in the studied area is on average 0.7 m3/ha-year. In favorable years, the maximum growth values can reach 1.5 m3/ha-year, and in unfavorable years, the increase can fall to zero, thus putting woody vegetation on the brink of survival. A direct proportional relationship has been established between the values of the CVP and HTC indices with a determination coefficient of 86.0% for the studied territory, which allows using one index instead of the other if necessary. In general, the hydrothermal conditions for forest growth in the Erbil region area should be assessed as unfavorable.
[Objective] Considering stand density, diameter structure and tree species structure, the optimal model for stand mean height and mean DBH relationship was constructed using algebraic difference approach. It may provide a theoretical basis for site productivity estimation and sustainable management of natural mixed forests. [Method] Base algebraic difference approaches were modeled with 4 different data structure types, i.e. typeC, typeD, typeE and typeF based on Richards model using 4 inventory data of
permanent sample plots in natural Quercus spp. broadleaved mixed stands. The 4 different base algebraic difference approaches were comparatively analyzed to get the optimal data structure type. Algebraic difference approach of diversity indices was constructed based on the optimal data structure type using 5 different stand density indices, including tree number (N), stand basal area (BA), stand density index (SDIr),
additive stand density index (SDIa) and canopy density (CD), and the 5 different diameter diversity indices including Shannon evenness index (ShaI), Simpson index (SimI), McIntosh evenness index (MceI), Gini coefficient (GinI) and Berger-Parker index (BerI), and the 4 different species diversity indices including ShaI, SimI, MceI and BerI. The algebraic difference approach of diversity indices was comparatively analyzed to obtain the optimize algebraic difference approaches, i.e. the optimize stand mean height and mean DBH relationship. [Result] Model fitting effects of calibration data in different data
structure types were sorted from best to worst, and the ranking was: typeD > typeC > typeF > typeE. Except for typeC, model coefficients b and r of the other three data structure types were significant (P < 0.01), indicating that the model fitting effects of typeD were the best. Model fitting effects of SDIr were the best. Model coefficients b0, r and cSD were significant (P < 0.01), regardless of which stand density index was
used, indicating that model fitting effects of the 5 different stand density indices were reasonable. Model fitting effect of ShaI was the best. Except for GinI, model coefficients b0, r, cSDIr and cDI of the other 4 diameter diversity indices were significant (P < 0.01), indicating that model fitting effects of ShaI, SimI, MceI and BerI were reasonable. Model fitting and validation effects had little difference among the 4 species diversity indices. Model coefficients b0, r, cSDIr, cShaI and cSP of BerI were significant (P < 0.01),
indicating that BerI was reasonable. However, model coefficients b0, r, cSDIr, cShaI and cSP of ShaI, SimI and MceI were not significant at the level of 0.05, indicating that ShaI, SimI and MceI were not reasonable. [Conclusion] TypeD is the best data structure type, stand density, diameter diversity and species diversity were significant for algebraic difference approach. Moreover, the model fitting effects of algebraic difference approach within SDIr, ShaI and BerI are the best, which is served as the optimize stand mean
height and mean DBH relationship in natural Quercus spp. broadleaved mixed stands.
Background
Studies on the relationship between biodiversity and ecosystem productivity have suggested that species richness and functional diversity are the main drivers of ecosystem processes. Several patterns on this relationship have been found, including positive, unimodal, negative, and neutral trends, keeping the issue controversial. In this study, taxonomic diversity and functional diversity as drivers of above-ground biomass (AGB) were compared, and the mechanisms that influence biomass production were investigated by testing the complementarity and the mass-ratio hypotheses.
Methods
Using data from 414 permanent sample plots, covering 23% of temperate forest in the Sierra Madre Oriental (México), we estimated the above-gound biomass (AGB), taxonomic and functional diversity indices, as well as community weighted mean values (CWM) for three functional traits (maximum height, leaf size and wood density) for trees ≥7.5 cm DBH, in managed and unmanaged stands. To compare taxonomic diversity differences between managed and unmanaged stands we carried out a rarefaction analysis. Furthermore, we evaluated the relationship between AGB and taxonomic and functional diversity metrics, as well as CWM traits throught spatial autoregressive models.
Results
We found a hump-shaped relationship between AGB and species richness in managed and unmanaged forests. CMW of maximum height was the most important predictor of AGB in both stands, which suggested that the mechanism underlaying the AGB-diversity relationship is the dominance of some highly productive species, supporting the mass-ratio hypothesis. Above-ground biomass was significantly correlated with three of the five functional diversity metrics, CWM maximum height and species richness. Our results show the importance of taking into account spatial autocorrelation in the construction of predictive models to avoid spurious patterns in the AGB-diversity relationship.
Conclusion
Species richness, maximum height, functional richness, functional dispersion and RaoQ indices relate with above-ground biomass production in temperate mixed-species and uneven-aged forests of northern Mexico. These forests show a hump-shaped AGB-species richness relationship. Functional diversity explains better AGB production than classical taxonomic diversity. Community weighted mean traits provide key information to explain stand biomass in these forests, where maximum tree height seems to be a more suitable trait for understanding the biomass accumulation process in these ecosystems. Although the impact of forest management on biodiversity is still debated, it has not changed the AGB-diversity relationships in the forests of the Sierra Madre Occidental, Mexico.
This study aimed to evaluate the effect of climate change on the potential site productivity of sugi (Cryptomeria japonica)-planted forests in Kyushu Island. In this study, potential site productivity was defined as the simulated 10-year average of net primary production by using the carbon balance-based stand growth model. The spatial unit was a 1-km grid, which had the same as resolution as the climate data, and 15-year-old sugi-planted forests were virtually established in each 1-km grid in the Kyushu Island. Maps of site productivity estimated using current and future climatic data were obtained and compared to generate a map of sugi site productivity change. The average difference between the estimated current and future potential site productivity was −2.61, and the potential site productivity in 87% of the land area of Kyushu Island and of sugi-planted forests was estimated to decrease with future climatic changes. The increase of respiration rate with an increase in temperature was the main factor for the decrease in the potential site productivity of sugi-planted forests.
The objectives of this study were 1) to modify the site index prediction model for sugi (Cryptomeria japonica) planted forests in Miyazaki Prefecture developed in a previous study and 2) to investigate the effects of quality of DEM and the scale of digital terrain analysis on the performances of site index models. The study site was the Tano Forest Science Station, University of Miyazaki. We acquired 18 data sets of site index estimated using stem analysis and global position of each sample site where a sample tree was felled. Three topographic factors,a solar radiation index, a hydrological upslope contributing area index, and a vertical topographic exposure index, were derived from DEMs generated from three data sources (10-m and 50-m interval point data with 3D coordinates and digitized contour map) and at resolutions of 10, 12.5, 25, and 50 m. Several search ranges (100, 250, 500, and 1000 m) were tested. Correlation analysis between site index and topographic factors as well as regression analysis to develop a site index prediction model using topographic factors as explanatory variables revealed that the hydrological upslope contributing area index requires DEMs generated from more informative DEM data sources (10-m interval point data and digitized contour map) and at fine resolution (10 m or 12.5 m); however, these DEMs were unsuitable for solar radiation index. DEMs generated from a less informative DEM data source (50 m interval 3D point data) and at a coarse resolution of 50 m were suitable for the solar radiation index. The effects of search ranges on topographic factors were clear for vertical topographic exposure index but not for the others. The best model developed in this study accepted the solar radiation index derived from the digital contour map based 10-m resolution DEM, the hydrological upslope contributing area index derived from the digital contour map based 12.5-m resolution DEM, and the vertical topographic exposure index derived from the 50-m interval 3D point data based 50-m resolution DEM as the explanatory variables.
Increase in degraded plantation forests in Japan requires an integrated management system that enhances the multiple-use of forests to achieve sustainable forest management. This paper introduces the steps taken in Odai town in Mie Prefecture, Japan, to establish a forest management regime map by evaluating the site suitability for forestry. Site suitability was evaluated from two aspects: the natural site conditions and the relationship among site conditions, growth, and insect damage by Anaglyptus subfasciatus Pic. in Cryptomeria japonica D. Don and Chamaecyparis obtusa Sieb. et Zucc. forests. By analyzing the relationship among site conditions, growth, and insect damage based on field data obtained in plantation forests, a growth evaluation map and insect damage evaluation map were developed. Based on the natural forest investigation, natural site condition maps for C. japonica and C. obtusa were established. Furthermore, by integrating these evaluation maps with the forest road maps showing the accessibility to the forest, the forest management regime for whole of the plantation area of Odai town was established. The forest management regime map indicates sites suitable for long-rotation forestry and short-rotation forestry, and potential sites for short-rotation forestry. Sites more suitable for conversion to broadleaved forests are also identified. Based on the forest management regime map, different forest operations have begun to be implemented at each evaluated area. For sites suitable for long rotation, thinning is implemented for inferior trees and will be repeated as the trees approach the age for cutting (more than 100 years). Thinning is also conducted for the sites suitable for short rotation. However, these will be cut down more rapidly as the trees reach the age for cutting (50 years). At sites evaluated as being more suitable for conversion to broadleaved forests, clear-cutting in a small area is conducted and about 20 broadleaved species are planted in an area of 80–120 m² protected by deer fences. As these measures have just begun, their effect on enhancing sustainable forest management is still being monitored. Notably, the people implementing these measures are proud of their task and work actively, which might be the most important driving force to solve the problem of plantation forest abandonment and to enhance sustainable forest management in Japan.
In the framework of sustainable forest management, measuring site quality and predicting site productivity remain a major forestry topic. Over the past years, it has been fostered by a number of site-growth modelling studies seeking to establish quantitative relationships between site index and explicit biophysical indicators. In addition, comparative modelling studies of site index and site productivity have highlighted limited accordance of their environmental determinism, questioning site index as a reliable indicator of site quality. Lastly, process-based modelling approaches have recently arisen as a means to predict site productivity over large regions. All these investigations have however drawn limited attention in recent syntheses. In this review, we provide an overview of the literature on these site-growth studies. Concepts and vocabulary related to site productivity are introduced. Taking regional studies as a baseline, we first highlight recent progress regarding the geographic areas encompassed, and the major role played by NFI programmes and spatialized environmental information. A trade-off between model accuracy and geographic extent is suggested, pointing out potential deficiencies in the modelling of site-growth associations, insufficient accuracy or resolution in climatic data, or uncontrolled factors in site-growth models that emerge on a higher spatial scale. Inappropriate use of biophysical classifications where environmental factors remain implicit is also emphasized. In a next step, we discuss early and most recent indications on weaknesses of the site index concept when applied over large regions, including its differential response to climate relative to site productivity, regional variations in site index curves, site index dependence on stand density and subsequently on regional silvicultural practices. The role of genetic structure of tree populations and its integration into site-growth studies is also reviewed and discussed. The interests, limits and recent advances of process-based models as an alternative to evaluate site productivity are considered, as they may overcome some of the previous limitations. We last draw challenges and perspectives on the issue. We suggest that the accuracy and the need of site index as a founding concept of forestry science is questioned, by building direct productivityenvironment relationships based on NFI databases as a realistic option at hand. We formulate perspectives regarding the accuracy, resolution and enlargement of environmental indicators currently used, the inclusion of information on genetic structure of tree populations in the context of adaptation to future climate change, as well as the use of site productivity models in forest management.
Assessment of site quality is essential for identifying the productive potential of land and for providing a frame of reference for silvicultural diagnosis and prescription. Site index (average height of the dominant portion of the stand at an arbitrarily chosen age) is the most commonly used indicator of site quality for even-aged, single-species forest stands. This chapter provides a detailed treatment of various methods for computing dominant height, data sources for developing site index curves (temporary plots, permanent plots, tree stem analysis), and commonly-applied alternative methods for empirically fitting site index equations. Methods described for fitting site index functions include the guide curve approach, use of age and height at index age as predictors, segmented models, differential equations approach, difference equations (with extensive attention given to the algebraic difference and generalized algebraic difference approaches), and use of mixed-effects models. The chapter concludes with a discussion of including concomitant information in height-age models and considering the effects of stand density on dominant height development.
ResearchGate has not been able to resolve any references for this publication.