Density Management Diagram Research Articles

A Density Management Diagram for Pitch Pine to Illustrate Tradeoffs between Carbon and Wildfire Risk

Abstract Pitch pine (Pinus rigida Mill.) can be found across a broad range in eastern North America but assumes local dominance only on poor soils in the northeastern United States. Contemporary management goals in the Northeast for areas dominated by pitch pine are focused on noncommercial benefits of forests, such as carbon density, reduced wildfire risk, habitat for rare species, and water provisioning. We present a density management diagram that empirically articulates the size-density limits of even-aged pitch pine stands. Included in the diagram are wildfire risk and carbon density, which are inversely related for most stand sizes. Maximum possible aboveground live tree carbon begins to decline at a quadratic mean diameter greater than 9 in., while crown fire risk remains high along the size-density limit until a quadratic mean diameter above 12 in. is achieved. Study Implications: Modern silvicultural tools that illustrate forest stand conditions have not been developed for pitch pine, but this species occurs in a region with much public attention on forests. We develop and present a density management diagram to show the interplay of different social goals for the forest and how they relate to the maximum size-density relationship. Pitch pine stands with high levels of aboveground live carbon are at high risk of crown fire, particularly in the smaller size classes.

Is it needed to integrate mixture degree in Stand Density Management Diagram (SDMD)?

Is it needed to integrate mixture degree in Stand Density Management Diagram (SDMD)?

Assessment of the Full Density Curve in Stand Density Management Diagrams for Hinoki (Chamaecyparis obtusa) in Kyushu Island, Japan: Implications for Forest Management

Accurate forest information on tree species, stand age, tree density, and stand volume is required to ensure effective forest management practices. In Japan, forest information is consolidated in forest yield tables and stand density management diagrams (SDMDs) that are specifically designed for major forest plantation species. In this study, we analyzed whether the current full density curve in the SDMD of Hinoki (Chamaecyparis obtusa) plantation stands in Kyushu Island aligns with the characteristics of the existing stands. Data from 18 Hinoki forests were used to measure tree heights, diameters, and densities. Equations were developed to establish relationships between stand factors, and various curves were derived for average height, competition ratio, full density, yield ratio, average diameter, and natural mortality. The results showed that the current full density curve in the SDMD for Hinoki plantation stands did not completely align with the characteristics of the existing Hinoki plantation stands in Kyushu Island. Thus, the full density curve in the SDMD for the Hinoki stands in this region should be significantly adjusted. These results can enhance forest management in Japan and advance SDMD modeling and its application in forest planning and management.

Resource communication: New forestry tools for natural beech forests in northwestern Spain

Aim of study: Although beech (Fagus sylvatica L.) forests in north-western Spain constitute c.a. 40% of the total area occupied by the species in the whole country, no growth or yield studies have been carried out regarding these forests. The specific objective of this study was to elaborate yield tables and stand density management diagrams for the beech forests.
 Area of study: Asturias and León provinces (NW Spain).
 Material and methods: Sample plots (n=112) were established in natural beech forests, and 60 dominant trees were felled for sampling. The Asturias Government Forest Service provided data on another 351 felled trees. Yield tables and stand density management diagrams (SDMDs) were elaborated to estimate tree volume and biomass in the study area for the first time.
 Main results: These forests are more productive than expected. Although they are currently not managed for forestry purposes, they could be managed again in the future and the tools are now available for this purpose.
 Research highlights: The study generates new user-friendly tools to manage beech forests in northwestern Spain. These tools will also enable simulations to be conducted to determine the potential carbon storage or the capacity of the stands to sequester atmospheric carbon.

SIIMADER: Inifap Computer System to Management Stands Density

Density management diagrams (DMD) are tools for diagnose the level of stand competence and for prescribing thinning programs.However, they are perceived as complex, so their acceptance and use is limited. To overcome this idea, DMDs are required to bescaled to an intuitive and interactive level to facilitate their practical use by foresters. The objective was to design and develop anonline computer application (CA) that reproduces DMDs based on the Reineke and Yoda functions to provide operational andinteractive functionality to users in the diagnosis and prescription of thinning as intermediate silvicultural treatments to managementregular forests. The engineering, architecture, components, modules, catalogs and programming language of the CA were designedand defined, for this a participatory process was applied that involved: (1) intellectual part, by expert researchers with specializedknowledge in thinning; (2) users, identified as forestry technicians who conduct operational management when applying forestry;and (3) developers, by expert programmers. The CA developed was called SIIMADER, an acronym for "Inifap Computer System toManagement Stands Density", which through algorithms executes routines to enter, process, store and output information in tabularand graphical form to manage density. The main output are thinning programs. The CA was generated in the Visual Studio® 2019development environment, to program the algorithms the C # language was used, the database management system was Microsoft®SQL Server® Standard version 12.0. AI is operating online with free access and prior registration in a hosting with its own domainon the internet. SIIMADER is a computer science and technological innovation tool that will help to apply quantitative forestry andimprove the growth of stands.

Effects of site productive capacity and stand density management on the maximum density line for Eucalyptus pilularis (blackbutt)

ABSTRACT Data were available from two measurements of each stand of a set of stands in native regrowth and plantation forests of Eucalyptus pilularis (blackbutt) in subtropical New South Wales and Queensland. Measurements were made after competition-induced mortality had started in each stand. Most of the regrowth forest had been thinned some time before the measurements. Based on the Reineke model that relates stand stocking density to quadratic mean diameter, a maximum density line was determined for each stand based on methods developed by Vanclay and Sands. It was found that the intercept of the maximum density line increased both with increasing stand site productive capacity and in the thinned regrowth stands. The latter finding does not seem to have been reported for forests before; it is hypothesised to be a result of the delayed redevelopment of inter-tree competitive processes following the major reduction in stand density resulting from thinning. Both effects will have consequences for the structure of density management diagrams commonly used to assist in forest management practice.

Croplanner: A Stand Density Management Decision-Support Software Suite for Addressing Volumetric Yield, End-Product and Ecosystem Service Objectives When Managing Boreal Conifers

The objectives of this study were to develop a stand density management decision-support software suite for boreal conifers and demonstrate its potential utility in crop planning using practical deployment exemplifications. Denoted CPDSS (CroPlanner Decision-support Software Suite), the program was developed by transcribing algorithmic analogues of structural stand density management diagrams previously developed for even-aged black spruce (Picea mariana (Mill) BSP.) and jack pine (Pinus banksiana Lamb.) stand-types into an integrated software platform with shared commonalities with respect to computational structure, input requirements and generated numerical and graphical outputs. The suite included 6 stand-type-specific model variants (natural-origin monospecific upland black spruce and jack pine stands, mixed upland black spruce and jack pine stands, and monospecific lowland black spruce stands, and plantation-origin monospecific upland black spruce and jack pine stands), and 4 climate-sensitive stand-type-specific model variants (monospecific upland black spruce and jack pine natural-origin and planted stands). The underlying models which were equivalent in terms of their modular structure, parameterization analytics and geographic applicability, were enabled to address a diversity of crop planning scenarios when integrated within the software suite (e.g., basic, extensive, intensive and elite silvicultural regimes). Algorithmically, the Windows® (Microsoft Corporation, Redmond, WA, USA) based suite was developed by recoding the Fortran-based algorithmic model variants into a collection of VisualBasic.Net® (Microsoft Corporation, Redmond, WA, USA) equivalents and augmenting them with intuitive graphical user interfaces (GUIs), optional computer-intensive optimization applications for automated crop plan selection, and interactive tabular and charting reporting tools inclusive of static and dynamic stand visualization capabilities. In order to address a wide range of requirements from the end-user community and facilitate potential deployment within provincially regulated forest management planning systems, a participatory approach was used to guide software design. As exemplified, the resultant CPDSS can be used as an (1) automated crop planning searching tool in which computer-intensive methods are used to find the most appropriate precommercial thinning, commercial thinning and (or) initial espacement (spacing) regime, according to a weighted multivariate scoring metric reflective of attained mean tree size, operability status, volumetric productivity, and economic viability, and a set of treatment-related constraints (e.g., thresholds regarding intensity and timing of thinning events, and residual stocking levels), as specified by the end-user, or (2) iterative gaming-like crop planning tool where end-users simultaneously contrast density management regimes using detailed annual and rotational volumetric yield, end-product and ecological output measures, and (or) an abbreviated set of rotational-based performance metrics, from which they determine the most applicable crop plan required for attaining their specified stand-level objective(s). The participatory approach, modular computational structure and software platform used in the formulation of the CPDSS along with its exemplified utility, collectively provides the prerequisite foundation for its potential deployment in boreal crop planning.

Stand density management diagrams: modelling approaches, variants, and exemplification of their potential utility in crop planning

The evolving shift in forest management objectives towards the collective consideration of volumetric yield, end-product quality and value, and ecosystem service outcomes, while accounting for the impacts of anthropogenic climate change, has resulted in innovative advancements in decision-support models used in stand density management. This review provides a synopsis of these efforts with respect to static, dynamic, and structural stand density management diagrams (SDMDs). More precisely, the scope of this review includes an ecology-based perspective of stand density management, summarization of the foundational quantitative relationships along with their utilization within the analytical structure of the SDMD, examination of SDMD compliance with underlying ecological constructs and empirical prediction expectations, exemplification of a climate-sensitive structural SDMD variant in boreal crop planning, and identification of outstanding analytical challenges and plausible future research directions for advancing the SDMD modelling approach and its utility in stand-level management planning. Collectively, this account of the conceptual basis, historical analytical evolution, ecological integrity, predictive ability, application diversity, and demonstrated utility of the various SDMD variants solidifies the prerequisite evidentiary foundation for the continued development and deployment of SDMD-based crop planning decision-support models.

DENSITY MANAGEMENT DIAGRAM FOR Eucalyptus grandis W. Hill. ex Maiden STANDS CONTROLLED BY DOMINANT HEIGHT

Density management diagram for eucalyptus stands controlled by dominant height. The present study aimed to elaborate Density Management Diagrams (DMD) for Eucalyptus grandis W. Hill. ex Maiden stands including the dominant height. Data were obtained from permanent plots installed in the Centro Oriental Riograndense region and the Porto Alegre Metropolitan area, both located in the state of Rio Grande do Sul. The models to describe the relationships between average volume, number of trees per hectare, mean diameter, and dominant height were assessed by the statistical criteria of coefficient of determination (R²), standard error of the estimate in percentage (Syx%), and graphical analysis of residuals. The developed DMD allows for a better control of stocks in the management of stands due to the strong relationship of dominant height with stand development site and forest yield.Keywords: Growth, Site index, Forest regulation, Yield.

Improved Equations for the Density Management Diagram Isolines of Ponderosa Pine Stands

AbstractThis study was conducted to improve estimation of concomitant variables for implementation of a stand density management diagram (SDMD) for ponderosa pine (Pinus ponderosa Laws.) in northern California and Oregon. In traditional SDMD, isolines for variables such as stand volume are presented in such a way that uncertainty with estimation is not available. We developed the new top height and stand volume equations, as well as aboveground biomass and percent canopy cover, for building isolines in the SDMD using high-quality data collected from well-managed even-aged stands. The data were selected from the USDA Forest Service’s Pacific Southwest Research Station database. A total of 829 observations (from 113 plots across 15 sites in Oregon and California) were used for model construction. In addition, covariance-variance structures of all of the estimated parameters were provided so that users can evaluate the uncertainty associated with predictions. The model validation results indicated that the predictions made from fixed-effects model forms performed better than the current volume equation of SDMD, as well as those from mixed-effects model forms using the population average effect. The proposed equations provide enhanced predictions and additional useful information about managed ponderosa pine stands, including their uncertainty.

Aspectos metodológicos para generar diagramas de manejo de la densidad de rodales con base en el índice de Reineke

La densidad indica el grado de aglutinamiento de los árboles en un rodal, sus cambios afectan el rendimiento maderable y el tamaño de los individuos. El modelo de Reineke y su índice de densidad del rodal (IDR) se usan en la construcción de diagramas para manejar la densidad (DMD), el IDR define el límite superior del autoaclareo y el punto mínimo de ocupación total del sitio. A pesar de su importancia, en la construcción de un DMD es común que exista desconocimiento o poca claridad sobre aspectos metodológicos relevantes. El objetivo es presentar elementos teóricos básicos que el responsable del manejo forestal debe considerar para construir un DMD. Bajo el enfoque clásico de modelación de la función de Reineke, se abordan conceptos sobre densidad, el tipo y características de la fuente de información dasométrica por utilizar, la selección de sitios en alta densidad, el ajuste estadístico de la función, criterios metodológicos para desplazar y delimitar la línea de autoaclareo, y juicios para determinar las zonas de crecimiento de Langsater. Se resalta que la línea de autoaclareo puede delimitarse a partir de sitios de muestreo para inventario maderable, y los de densidad alta se seleccionan aplicando el enfoque del IDR máximo (IDRmáx); el método de mínimos cuadrados ordinarios lineales para ajustar la función de Reineke es robusto y corrige la heterocedasticidad. Para el crecimiento máximo en volumen, los rodales es factible manejarlos entre 35 y 65 % con respecto al IDRmáx. Los niveles óptimos de densidad deben determinarse por especie.

Dynamic Structural Stand Density Management Diagrams for even-aged natural stands and plantations

A forest stand model that is able to account for individual stand characteristics and uses this information for state prediction, growth and yield projection and for management decisions at individual-stand level can be expected to possess the best properties and be of the highest utility. The aim of our study was to combine the advantages of the graphically presented whole-stand models called Stand Density Management Diagrams (SDMDs) with those of the state-space models to develop an improved, stand-specific density management model and to examine its performance with data from even-aged natural stands and plantations.A dynamic, structural Stand Density Management Diagram (DSSDMD) consisting of a whole-stand model and distribution sub-models was developed. The whole-stand model is composed of a state vector and transition functions and is presented diagrammatically by four sets of isolines on a density-total volume/biomass chart. The state, developmental scenarios and thinning schedules of any stand are simulated on its individual DSSDMD and are characterized by three principal local model parameters, two of which are stand-specific and the third is common to a range of stands of the species under the same environmental conditions.Dynamic Structural Stand Density Management Diagrams (DSSDMDs) were constructed for plantations of two pine species (Pinus radiata D. Don and P. sylvestris L.) and for natural even-aged stands of Quercus robur L. and Betula pubescens Ehrh. The goodness-of-fit tests revealed that, in most cases, regression equations explained more than 95% of the variation in the modelled variable and yielded a Root Mean Square Error <15% and bias <2% from the mean experimental variable values. When used for predicting or projecting total stand volume or biomass, the models performed acceptably well, in terms of the critical error estimate, within the observed range of ages and projection intervals. Management alternatives, according to specified objective, can be optimized for any particular stand using its DSSDMD, and the model can be incorporated into a simulator to ensure its most efficient usage.

STAND DENSITY MANAGEMENT DIAGRAMS OF Eucalyptus viminalis: PREDICTING STEM VOLUME, BIOMASS AND CANOPY COVER FOR DIFFERENT PRODUCTION PURPOSES

ABSTRACT Stand density management diagrams (SDMD) provide a guide for forest density management taking into account stands attributes such as trees´ diameter or volume. One of the most common species planted in Pampean plains of Argentina is Eucalyptus viminalis for multiple objectives: solid wood use or firewood in local markets, pulp for cellulose industry and to provide services for agriculture and cattle raising (windbreaks or cattle refuge). The objective of this study was to gather the available production information /inventory data and to develop a first SDMD for estimating standing volume, biomass and canopy cover of E. viminalis as a tool for forest managers aiming at different plantation purposes. Data to develop the SDMD were obtained from 161 plots, distributed along a climate and soil gradient. We also generated two predictive equations capable of estimating dominant height from the diameter of the trees as well as canopy cover from stand basal area. As an example of application, the SDMD was used to estimate the wood production of three alternative systems: a) an unmanaged plantation (simulating a common practice in the region), b) a mixed production system such as an agroforestry system, and c) a plantation that maximizes wood biomass or volume production.

Development and application of density management diagram for Pinus massoniana plantation

Development and application of density management diagram for Pinus massoniana plantation

Diagrama para manejo de la densidad en rodales de Pinus patula Schiede ex Schltdl. &amp; Cham. en Puebla, México

Un diagrama para el manejo de la densidad (DMD) es una herramienta técnica para aplicar silvicultura cuantitativa, la que contribuye a mejorar el manejo técnico de los bosques. El objetivo fue generar un diagrama para manejar la densidad con base en el índice de densidad de rodal de Reineke en bosques coetáneos de Pinus patula en Puebla, México. Se procesó una muestra compuesta por 252 sitios de muestreo para inventario seleccionados en condiciones de máxima densidad, que cubrió todas las condiciones de crecimiento y del intervalo de edades. La información de densidad y diámetro cuadrático se procesó mediante regresión estadística ajustando la relación funcional tamaño-densidad de Reineke. Se comparó la técnica de mínimos cuadrados ordinarios contra la de regresión frontera estocástica en sus modalidades de modelo semi-normal, normal truncado y normal exponencial. Una evaluación de la calidad de ajuste estadístico y gráfico evidenció que la técnica de regresión frontera estocástica en su modalidad semi-normal fue superior, por lo que se seleccionó para determinar la línea de autoaclareo. El índice de densidad máximo fue de 1 078 árboles ha-1 para un Dq de referencia de 20 cm. El DMD se generó con la definición de las diferentes zonas de crecimiento de Langsaeter. El DMD es útil para gestionar y prescribir la intensidad de aclareos como tratamientos silvícolas intermedios, en términos del número de árboles en una hectárea por remover y su equivalente en área basal por hectárea para rodales coetáneos.

A Nonlinear Mixed-Effects Height-to-Diameter Ratio Model for Several Tree Species Based on Czech National Forest Inventory Data

Height-to-diameter at breast height (DBH) ratio (HDR) is an important tree and stand stability measure. Several factors such as stand dynamics, natural and anthropogenic disturbances, and silvicultural tending significantly affect HDR, and, therefore, in-depth investigation of HDR is essential for better understanding of ecological processes in a forest. A nonlinear mixed-effects HDR model applicable to several tree species was developed using the Czech national forest inventory data comprising 13,875 sample plots and 348,980 trees. The predictive performance of this model was evaluated using the independent dataset which was originated from 25,146 trees on 220 research sample plots. Among various tree- and stand-level variables describing tree size, site quality, stand development stage, stand density, inter-tree spacing, and competition evaluated, dominant height (HDOM), dominant diameter (DDOM), relative spacing index (RS), and DBH-to-quadratic mean DBH ratio (dq) were identified as the most important predictors of HDR variations. A random component describing sample plot-specific HDR variations was included through mixed-effects modelling, and dummy variables describing species-specific HDR variations and canopy layer-specific HDR variations were also included into the HDR model through dummy variable modelling. The mixed-effects HDR model explained 79% of HDR variations without any significant trends in the residuals. Simulation results showed that HDR for each canopy layer increased with increasing site quality and stand development stage (increased HDOM) and increasing competition (increased RS, decreased DDOM and dq). Testing the HDR model on the independent data revealed that more than 85% of HDR variations were described for each individual species (Norway spruce, Scots pine, European larch, and European beech) and group of species (fir species, oak species, birch and alder species) without significant trends in the prediction errors. The HDR can be predicted with a higher accuracy using the calibrated mixed-effects HDR model from measurements of its predictors that can be obtained from routine forest inventories. To improve the prediction accuracy, a model needs to be calibrated with the random effects estimated using one to four randomly selected trees of a particular species or group of species depending on the availability of their numbers per sample plot. The HDR model can be applied for stand stability assessment and stand density regulation. The HDR information is also useful for designing a stand density management diagram. Brief implications of the HDR model for designing silviculture strategies and forest management planning are presented in the article.

Can an Exponential Function Be Applied to the Asymptotic Density–Size Relationship? Two New Stand-Density Indices in Mixed-Species Forests

This study presents two stand-density indices (SDIs) based on exponential density decline as a function of quadratic mean diameter for all species combined in mixed-species forests with 22 species mix grouped in four species groups. The exponential-based density–diameter relationship, as well the density index corresponding to the slope or instantaneous mortality rate parameters, was compared with those based on power-law density–diameter relationship. A dataset of 202 fully stocked circular plots at maximum density was used for fitting the models, and a dataset of 122 circular plots was used for validation stand density index for all species combined of mixed-species stands. The dataset for validation was independent of dataset for model development. The first stand-density index showed a density management graphic (DMG) with a variable intercept and common instantaneous mortality rate, and the second index showed a DMG with common intercept and variable mortality rate. Additionally, the value of the initial density of the fitted line was more realistic than those generated by the potential model for all species combined. Moreover, the density management diagrams showed a curvilinear trend based on the maximum stand density index in graphical log–log scale. The DMGs could be interpreted as forest scenarios based on variable initial density and common management objectives or the same density and different management objectives for forest-rotation periods involving all species combined in mixed-species stands. The fitting of exponential and potential equations for species or species groups showed that the density–size relationships in mixed-species forests should be modeled for all species combined because the disaggregation of mixture species represented a weak tendency for each species or species group and the resultant fitted equations were unrealistic.

Diagrama de manejo de la densidad para los bosques mezclados de la región de El Salto, Durango

Introduction: Density management diagrams (DMDs) are useful tools for characterizing andmanaging stand density. Objective: To develop a DMD to schedule thinnings in the natural mixed-species forests of theEl Salto region, Durango. Materials and methods: The data were collected in 441 temporary sampling plots in 263 mixed-species stands with mainly species of the Pinus and Quercus genus. The DMD was based on theHart-Becking index and a relationship of two allometric equations: 1) the quadratic meandiameter (dg, cm) with the density (N, trees·ha−1) and dominant height (Hd, m), and 2) the volume(V, m3·ha−1) with the dg, Hd and N. In fitting equations, the ordinary Nonlinear Least Squares(NLS) method was used simultaneously. The maximum density limit was estimated by potentialquantile regression that related N to Hd. Results and discussion: Efficient goodness-of-fit statistics were reported in the fitted models, interms of Root Mean Square Error (2.29) and coefficient of determination (0.86). The DMDsuggests applying thinnings below the maximum density line to avoid mortality. Through theDMD it is possible to evaluate different silvicultural alternatives, schedule thinnings, maximizegrowth space, promote tree growth and improve forest products. Conclusion: The DMD developed is useful for thinning scheduling to obtain saw-timber atrotation age

Diagrama de manejo de densidad para el género Pinus en el ejido Pueblo Nuevo, Durango

Se desarrolló un diagrama de manejo de densidad (DMD) para el género Pinus en un predio bajo manejo del ejido Pueblo Nuevo, Durango, cuyo objetivo es la producción de madera para aserrío. Los datos se obtuvieron del inventario forestal de la Umafor 1008, en El Salto, Durango y consta de 196 sitios de muestreo, de los cuales se estimó el número de árboles por hectárea N, la altura dominante H0, el diámetro medio cuadrático dg y el volumen V. El diagrama se desarrolló con dos ecuaciones base, en las que se representó el diámetro medio cuadrático y el volumen. El Índice de espaciamiento de Hart-Becking IH, se calculó como referencia en la planeación de cortas; las ecuaciones base fueron ajustadas a través de la regresión no lineal de la función nls en el software estadístico R project 3.4.0. Rstudio 1.0.143, a través de un proceso iterativo; el ajuste simultáneo de las ecuaciones se realizó por el método de FIML (full information maximum likelihood). El sistema de ecuaciones fue ajustado simultáneamente mediante el procedimiento MODEL del sistema estadístico SAS/ETS®. La bondad de ajuste de los estadísticos arrojó un coeficiente de determinación R2 = 0.7074 y un error medio cuadrático RMSE = 2.7563 para la ecuación de dg y de R2 = 0.9947 y RMSE = 7.9114 para el volumen. Las isolíneas del Índice de Hart adquirieron valores mínimos y máximos en porcentaje de la densidad de 16 de 56, respectivamente. Se planteó un esquema de cortas de acuerdo al objetivo de producción: madera con dimensiones para aserrío.

Climate-sensitive self-thinning trajectories of Chinese fir plantations in south China

The self-thinning rule is fundamental in regulating maximum stocking and constructing stand density management diagrams. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) is the most important tree species and widely distributed across subtropical China. Yet, our understanding of how the self-thinning line of Chinese fir relates to climate is limited. Longitudinal data from 48 plots distributed in Fujian, Jiangxi, Guangxi, and Sichuan provinces were used to describe self-thinning for Chinese fir in relation to climate through first-order autoregressive (AR(1)) and nonlinear mixed effects (NLME) models. Results showed that self-thinning lines had steeper slopes for Chinese fir growing in areas with larger annual precipitation and summer mean maximum temperature but flatter slopes with higher mean annual temperature, degree-days below 0 °C, and winter mean minimum temperature. Winter mean minimum temperature was the dominant climatic factor in shaping self-thinning lines, which suggests that temperature was the key climate driver that affects self-thinning of Chinese fir. In addition, differences of slopes for any two of the four sites were significant, except between the Guangxi and Sichuan sites. Our results will be useful for both the silvicultural practices and mitigation strategies of Chinese fir under climate change in south China.