Individual Tree Selection Research Articles

Potential for domestication of Borassus aethiopum Mart., a wild multipurpose palm species in Sub-Saharan Africa

Borassus aethiopum Mart. is a multipurpose palm native to mainland Africa. Fruits and hypocotyls are the most exploited parts which collection/harvest threats the species. As a pre-requisite for its domestication, this study assessed the (1) environmental-induced diversity in morphological traits of fruits and (2) differences in growth and weight of hypocotyls from one-seeded, two-seeded, and three-seeded fruits from three provenances in the three climatic regions of Benin. 5400 fruits collected from 180 trees in six populations were measured for fruits and tree morphological traits. A randomized complete block design with three replicates was used for the experimentation in each region. Variation in fruit morphological traits was not influenced by climatic regions. The greatest variation (65–94%) in fruit morphological traits was located at tree level, highlighting that selection of many fruits and individual trees within a few populations would capture large variation of fruit traits. Tree diameter at breast height (18.5–52 cm), total (6.4–19.6 m) and bole (4.8–17.6 m) height, and fruit length (7.00–20.50 cm), dry weight (98–2552 g), shape index (0.59–2.80), and number of seed (1–3) were the most discriminative traits of studied populations. Clustering of the trees resulted into five morphotypes based on discriminating traits. Morphotypes 1 and 2 showed high performances for fruits and seeds production. These morphotypes are good candidates for selection and breeding programs. Irrespective of the provenances, best performances of hypocotyls were observed in the humid region. This study provides important baseline information for the domestication of B. aethiopum.

Successful hard pine regeneration and survival through repeated burning: An applied historical ecology approach

Forest inventories commonly report fire-adapted pine populations severely reduced from pre-EuroAmerican times due to the combined effects of past land uses and altered fire regimes. Relatively little information exists about the fire ecology and management of hard pine ecosystems in the northeastern U.S. The objective of this study was to determine what burning frequencies best promote regeneration and recruitment of three hard pine species native to the northeastern U.S. We used data from dendrochronological fire history studies to derive historical fire years, pine regeneration years, and individual tree survival information. For all tree species, pith calendar years ranged from 1530 to 1932 with the majority of regeneration occurring prior to 1754 (the earliest dates of EuroAmerican settlement). The number of years from fire occurrence at a site to regeneration (pith year) ranged from 0 (i.e., regeneration occurred in year of fire, n = 9) to 130 with a median of 8 years. Frequency distributions of regeneration following fire were similarly shaped across species, all being strongly negatively skewed (i.e., most regeneration occurred soon after fires) and increasing abruptly (>100% increase) from 0 to 1 year since fire and then declining following a negative exponential curve. The number of years from regeneration to the next fire ranged from 0 to 172 years with a median of 14 years. Frequency distributions of hard pine survival were negatively skewed, with the exception of red pine. Overall, these data suggest that these species exhibit relatively high regeneration in the years immediately following fire events and a subsequent decrease with time since fire. Although other factors may affect the regeneration of pine following fire, it appears that significant statistical relationships can be established and used to develop effective fire frequency guidelines for successful hard pine regeneration.

Estimation of mortality and survival of individual trees after harvesting wood using artificial neural networks in the amazon rain forest

Modeling individual trees in tropical rain forests in the Amazon allows for the safe use of scarce resources in a sustainable way. Unfortunately, in the Brazilian Amazon, rain forest growth and production models are not yet used to estimate future forest stock. Thus, forest management plans do not present technical-scientific support that guarantees sustainable production of wood throughout the cutting cycle. Therefore, this work aims to estimate the survival and mortality of individual trees in a selectively harvested forest using Artificial Neural Networks (ANN) to support silvicultural decisions in forest management in the Amazon rain forest. In 1979, a selective harvest was carried out, with 72.5 m3 ha-1 in an area of 64 ha in Floresta Nacional do Tapajós, in the state of Pará, Brazil. In 1981, 36 permanent plots were installed at random and inventoried. Nine successive measurements were carried from 1982 to 2012. In the modeling, classification, survival, and mortality, training and ANN testing were performed, using input variables such as: different semi-distance-independent competition indices (DSICI), diameter measured (dbh), forest class (FC), trunk identification class (TIC), competition index (CI), growth groups (GG), liana infestation intensity (liana); and crown lighting (CL); Damage to tree (D) and tree rotting (R). The categorical output variables (Classification) were Dead or Surviving tree. Overall efficiency of the classification was above 89% in training and above 90% in the test for all ANNs. Survival classification hit rate was above 99% in the test and training for all ANNs but the mortality score was low, with hit rates below 6%. The overall Kappa coefficient was below 8% for all ANNs (ranked “poor”) but all ANNs were above 55% in the survival classification (ranked “good”). ANN estimates the individual survival of trees more accurately but this does not occur with mortality, which is a rarer event than survival.

Evaluation of Methods for Modeling Individual Tree Survival

Evaluation of Methods for Modeling Individual Tree Survival

Coexistence, association and competitive ability of Quercus petraea and Quercus robur seedlings in naturally regenerated mixed stands

In most mixed-species forestry systems, regeneration is a critical step for individual tree survival and species coexistence. Species coexistence is driven by the fine-scale spatial patterns and competitive abilities of species. In naturally regenerated mixed oak (Quercus petraea and Quercus robur: QP and QR, respectively) stands, species coexistence was assessed by analysing the spatial distribution of both species and their growth responses to intra- and interspecific competition.Four sites located in North Eastern France with an established (1.4–2.8-m-high) mixed QP and QR regeneration were selected for the study. In a first step, individual seedling location was recorded along line transects to analyse the spatial distribution of the two species. Univariate pair correlation functions were used to test for spatial aggregation for each species and bivariate pair correlation functions were used to test for spatial associations between the two species. In a second step, seedlings were measured in small plots to analyse their response to local competition. Mixed linear models were used to estimate the combined effects of density, mixture, seedling size and seedling status on seedling growth.QP and QR were both highly aggregated in monospecific patches, and the two species were strongly segregated at a decametric scale. Transition zones between monospecific patches were reduced to a few meters. For both species, mixture had no effect on seedling growth. In all sites, the two species showed very similar diameter and height growth rates in response to density, mixture, seedling size and seedling status, and similar intra- and interspecific competitive abilities.Highly patchy patterns of QP and QR regeneration strongly reduce interactions between the two species and, in transition zones between monospecific patches where the two species are mixed, no species is expected to outcompete its companion species. For each species, long-term persistence at the stand scale is determined by intraspecific competition rather than by interspecific competition. At this developmental stage, the QP-QR mixture appears to be very stable and no specific silvicultural treatment is required to maintain the mixture.

Examining growth relationships in Quercus stands: An application of individual-tree models developed from long-term thinning experiments

This manuscript seeks to further the understanding of growth patterns in Quercus forests, thereby informing the development of appropriate thinning practice. The author leveraged a network of thinning experiments established by the US Forest Service more than 50years ago. Individual-tree diameter growth and survival models were developed along with a simulation framework to evaluate the relationship between stand stocking and 20-year basal area and volume growth. Models predicting five-year diameter growth and survival of individual trees included variables representing tree size, competitive position, stand density, and/or site quality. Model evaluation focused on the collective accuracy and cumulative error propagation of the individual-tree models through four, five-year growth cycles. Through a series of stand density simulations in white oak (Quercus alba L.) dominated forest structures representing four mid-rotation age conditions, it was found that stand basal area and total volume growth followed a unimodal pattern culminating at 50–60% stocking. Sawtimber volume growth was more sensitive to initial stand age, and the stocking level where it peaked increased with increasing age. The study not only helps to define relationships for Quercus stands of the Central Hardwood Forest Region, USA, but it also adds to the limited body of research quantifying individual-tree and stand growth relationships within mixed species broadleaf forest types.

Second-Log Branching in Multiaged Redwood and Douglas-Fir: Influence of Stand, Site, and Silviculture

We studied branching in Sequoia sempervirens (Lamb. ex D. Don) Endl. (coast redwood) and Pseudotsuga menziesii (Mirb.) Franco var. menziesii (coast Douglas-fir) because of their commercial value to coastal northern California. We focused on branching in the second log, which constitutes an important part of a tree’s wood volume and potential value. We quantified branch size and branch growth of overstory trees in multiaged stands in Mendocino County, California, in response to topographic, silvicultural, and stand- and tree-related variables. Higher stand density—a measure of competition averaged across the sample plot—did not correlate with size of the largest second-log branch measured but was associated with a smaller average diameter of the largest branches measured on all sides of the study tree. The largest branch measured was smaller when in closer proximity to branches of its immediate neighbor tree. Redwood had larger branches than Douglas-fir but their size was more sensitive to an ecological gradient of soil-moisture deficit. Branches responded differently to individual tree selection harvest of conifers versus herbicide control of hardwoods. Residual conifer branches in harvested plots responded almost immediately with increased growth, but this release was short-lived. Branches in herbicide-treated plots exhibited a delayed release, giving more consistent branch growth throughout two five-year measurement periods after treatment.

Comparing Tree Selection as Performed by Different Professional Figures

The study compared the silvicultural results of individual tree selection as performed by licensed foresters, loggers, and licensed agronomists. The experiment was conducted on two tree marking training sites installed by the Regional Forest administration for Lombardy in the northern Italian mountains. Each site consisted of a 1.2-acre (0.5-ha) forest plot where all trees had been identified with painted numbers. Sixty-four volunteers were extracted from a larger pool representing licensed foresters, loggers, and licensed agronomists. Each volunteer was provided with simple paper forms on which he or she would note the identification number of each tree selected for removal. All volunteers were asked to apply the same silvicultural prescription. Statistical analysis of the results indicated no differences between the different professional groups. Most participants reached the prescribed percent removals and consistently selected the right tree size for two different silvicultural treatments. On the other hand, differences between single individuals were quite substantial, possibly reflecting different practical experience with tree marking. Overall, the study suggests that the quality of tree selection is not determined by the group an individual belongs to. Therefore, one may consider delegating tree selection to a properly trained logger, especially if the silvicultural prescription is relatively straightforward.; ;

The value of information in conservation planning: Selecting retention trees for lichen conservation

Conservation planning studies at small scales such as forest stands and below are uncommon. However, for retention forestry, developed during the last two decades and with current wide and increasing application in boreal and temperate regions, the need for cost-effective selection of individual trees is evident. In retention forestry certain trees are left at final harvest to promote flora and fauna. There is also a scarcity of studies on information costs and how these relate to the cost-effectiveness of conservation. We addressed both of these issues by studying whether decisions about the retention of aspen Populus tremula L. trees can be made more cost-effectively by including information about tree characteristics. We analyzed data from 12 recently harvested stands in middle Sweden containing 131 epiphytic lichen species (a biodiversity proxy) on 360 aspen trees. We related the presence of lichen species to bark and stem attributes and used those relationships to prioritize trees for retention. We estimated the value of using different sets of survey information (lichens, tree characteristics) to select retention trees to achieve various conservation goals. Depending on species or species groups of interest, and the type of tree information being collected, the value of collecting the information is up to 20% of the total value of all potential retention trees, which, given current labor costs, allows up to four hours for planning and selecting the right trees on an average-sized clearcut. The current practice of almost randomly selecting aspen trees to retain at final harvest can be improved by adding easily collected information on tree characteristics, such as black-colored bark, slow tree growth, inclining stems and speckled bark. This can lead to attainment of a given level of a conservation goal (like maximizing the number of lichen species of conservation concern) with fewer retention trees. Inventory of tree information often can be performed quickly, and if part of the gains from using such information to guide tree selection would be spent on additional conservation efforts, this would benefit biodiversity. Studies on more organism groups and tree species are needed to increase the applicability of results.

A Generalized Mixed Logistic Model for Predicting Individual Tree Survival Probability with Unequal Measurement Intervals

A Generalized Mixed Logistic Model for Predicting Individual Tree Survival Probability with Unequal Measurement Intervals

Ethanol Attracts Scolytid Beetles to Phytophthora ramorum Cankers on Coast Live Oak

Ethanol in sapwood was analyzed along vertical transects, through small spot cankers and larger basal cankers, of Phytophthora ramorum-infected stems of Quercus agrifolia at three sites in California. Trees with large basal cankers, known to attract scolytid beetles, had a 4.3 times higher ethanol level than trees with spot cankers that attract fewer beetles. Ethanol concentrations inside cankers, where scolytid beetles preferentially attack, varied by about four orders of magnitude among samples, with a median level of 16.0 μg.g(-1) fresh mass. This concentration was 4.3 and 15.5 times greater, respectively, than the concentrations at 1 cm or 15-30 cm outside the canker boundaries. In the laboratory, we demonstrated that ethanol escaped through the bark of a Q. garryana log just 3 days after it was added to the sapwood. At the three study sites, traps baited with ethanol captured more Xyleborinus saxesenii, Pseudopityophthorus pubipennis, and Monarthrum dentiger (all Coleoptera: Curculionidae: Scolytinae) than traps baited with ethanol plus (-)-α-pinene, or ethanol plus 4-allylanisole (4AA). Logs of Q. agrifolia with a 50 % ethanol solution added to the sapwood were placed at the study sites, with or without additional bark treatments above the ethanol. The number of scolytid beetle gallery holes above the ethanol-infused sapwood was 4.4 times greater than that on the opposite side of the log where no ethanol was added. Attachment of ultra-high release (-)-α-pinene pouches to the bark surface above the 50 % ethanol solution reduced scolytid attacks to a density of 19.1 % that of logs without this treatment. We conclude that ethanol in P. ramorum cankers functions as a primary host attractant for scolytid beetles and is an important link in colonization of these cankers and accelerated mortality of Q. agrifolia. The results of this research shed light on the chemical ecology behind the focused scolytid attacks on P. ramorum-infected coast live oaks, and lay the groundwork for future efforts to prolong the survival of individual trees of this keystone species.

At what spatial scales does resource selection vary? A case study of koalas in a semi‐arid region

AbstractThe conservation of any species requires understanding and predicting the distribution of its habitat and resource use, including the effects of scale‐dependent variation in habitat and resource quality. Consequently, testing for resource selection at the appropriate scales is critical. We investigated how the resource selection process varies across scales, using koalas in a semi‐arid landscape of eastern Australia as a case study. We asked: at what scales does tree selection by koalas vary across regions? We tested the importance of the variation of our ecological predictors at the following scales: (i) the site‐scale (a stand of trees representing an individual koala's perception of local habitat); (ii) the landscape‐scale (10 × 10 km area representing a space within which a population of koalas exists); and (iii) a combination of these scales. We used a mixed‐modelling approach to quantify variation in selection of individual trees by koalas among sites and landscapes within a 1600 km2 study area. We found that tree species, and tree height, were the most important factors influencing tree selection, and that their effect did not vary across scales. In contrast, preferences for trees of different condition, which is the state of tree canopy health, did vary across landscapes, indicating spatial variation in the selection of trees with respect to tree condition at the landscape‐scale, but not at the site‐scale. We conclude that resource selection processes can depend on the quality of those resources at different scales and their heterogeneous nature across landscapes, highlighting the consequence of scale‐dependent ecological processes. Designing studies that capture the heterogeneity in habitat and resources used by species that have an extensive distribution is an important prerequisite for effective conservation planning and management.

An Annual Tree Survival and Diameter Growth Model for Loblolly and Slash Pine Plantations in East Texas

An annual growth model that predicts individual tree survival and diameter growth was developed for loblolly pine (Pinus taeda) and slash pine (Pinus elliottii) trees in East Texas as a function of individual-tree diameter, plantation age, basal area per acre, dominant height, quadratic mean diameter, and presence of fusiform rust (Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme). Data from 104,035 loblolly pine and 37,515 slash pine individual tree observations collected on a 3-year cycle from 174 loblolly pine and 80 slash pine permanent plots located in plantations throughout East Texas were used in this study. The survival equation assumes that mortality is constant across the projection length, whereas the diameter growth equation incorporates whole-stand predictions to update stand-level independent variables on an annual basis. Predictions were evaluated in terms of bias and precision, with independent observations for projection lengths from 3 to 24 years. For both survival and diameter growth, bias was lowest and precision highest for 3-year projection lengths. For survival, bias increased and precision decreased as projection length increased through 24 years. For diameter growth, bias was constant (<1 in.) across all projection lengths, whereas precision decreased from <1 in. for the 3-year projection length to <2 in. for the 6—24-year projection lengths. A numerical example is provided that describes how to use the new model to project individual tree survival and diameter growth on an annual basis.

Prediction of annual tree growth and survival for thinned and unthinned even-aged maritime pine stands in Portugal from data with different time measurement intervals

An annual individual tree survival and growth model was developed for pure even-aged stands of maritime pine in Portugal, using a large data set containing irregularly time-spaced measurements and considering thinning effects. The model is distance-independent and is based on a function for diameter growth, a function for height growth and a survival function. Two approaches are compared for modeling annual tree growth. The first approach directly estimates a future diameter or height using well-known growth functions formulated in difference form. The second approach estimates diameter or height using a function in differential form estimating the increment over a year period. In both approaches, the function parameters were related to tree and stand variables reflecting the competition status of the tree as well as of a thinning response factor. Variable growth and survival rates were assumed in the modeling approaches. An iterative method was used to continuously update tree and stand attributes using a cut-off to convert the survival probability for a living or a dead tree. The individual tree diameter growth model and the survival probability model were fitted simultaneously using seemingly unrelated regression (SUR). Parameters of the height function were obtained separately as the number of observations for height was much lower than the number of observations for diameter, which may affect the statistical inference and the estimation of contemporaneous cross-equation error correlation inherent to the system of equations. PRESS residuals were used to evaluate the predictive performance of the diameter and the height growth functions. Additional statistics based in the log likelihood function and also in the survival probability were computed to evaluate the survival function. The second modeling approach, which integrates components of growth expansion and decline, performed slightly better than the first approach. A variable accounting for the thinning response that was tested proved to be significant for predicting diameter growth, even if the model already included competition-related explanatory variables, namely the basal area of trees larger than the subject tree. However, this thinning response factor was not significant for predicting height growth.

Partial harvesting of dry Douglas-fir forests: stand structure, range habitats and maintenance of biodiversity using small mammal indicators

Summary Our study used ‘ stand structures ’ and ‘ ecological indicators ’ as inferences to managing dry Douglas-fi r ( Pseudotsuga menziesii (Mirbel) Franco) forests for timber, biodiversity and range habitat attributes at 10 – 12 years after partial harvesting. Forest structures included densities and sizes of Douglas-fi r and species and structural diversity of total conifers. Ecological indicators included cattle forage species in the understor e y vegetation and three small mammal species: a closed-canopy specialist, the southern red-backed vole ( Myodes gapperi Vigors) and two early successional species, the long-tailed vole ( Microtus longicaudus Merriam) and heather vole ( Phenacomys intermedius Merriam). Harvesting treatments were across a gradient of historical cut, individual tree selection and patch cut sites in the upper Interior Douglas-fi r (IDF dk ) biogeoclimatic zone near Summerland, British Columbia, Canada. Small mammal populations were sampled from 2006 to 2008. Closed-canopy forest structure seemed to maintain populations of red-backed voles in the harvested sites. Development of understor e y vegetation in harvest-origin openings was similar across the levels of partial cutting and provided at least fi ve plant species for cattle forage. Patches of grassland and shrubland in all treatment sites maintained viable populations of long-tailed voles and heather voles. These three small mammal indicators represent both late and early successional conditions in these IDF forests, which need to be managed for multiple objectives. Long-term monitoring of indicators will verify relationships with the components of biodiversity that they represent.

Conforto térmico propiciado por algumas espécies arbóreas: avaliação do raio de influência através de diferentes índices de conforto

As características termorreguladoras das árvores podem ser mais bem aproveitadas quando há um conhecimento sobre o conforto térmico proporcionado por um indivíduo arbóreo isolado em seu raio de influência. Vários índices de avaliação de conforto térmico têm sido utilizados, mas poucos são, de fato, adaptados à realidade brasileira. O objetivo deste trabalho é comparar os resultados de três índices de conforto térmico em ambientes externos, a Carta Bioclimática Tridimensional para clima Tropical de Altitude, o PET e o PMV, para a avaliação do comportamento de três diferentes espécies arbóreas no microclima urbano: ipê-amarelo, jambolão e mangueira. A pesquisa foi dividida em três etapas: (a) seleção dos locais de medição apropriados e os indivíduos arbóreos; (b) coleta dos parâmetros ambientais: radiação solar, temperatura do ar e de globo, velocidade do vento e umidade relativa do ar; e (c) comparação de índices por meio do parâmetro Unidade de Hora Confortável. Os resultados mostram que o conforto térmico propiciado pelas diferentes espécies ao longo do ano, independentemente dos índices utilizados na análise, dependem da arquitetura da copa. O ipê-amarelo é a espécie que proporciona melhor sensação de conforto térmico, enquanto as espécies perenes, como o jambolão e a mangueira, têm maior influência sobre a sensação térmica no entorno imediato no período de verão do que no inverno, com condições mais confortáveis encontradas à sombra da copa da árvore.

A shifting algorithm to simulate thinnings from below and above

Thinning is a silvicultural practice to improve tree growth and health. Thinning from below for the even-aged silviculture and thinning from above for the uneven-aged silviculture are the two mainly applied thinning practices. In forest management simulations, algorithms that describe which individual trees to be removed from a forest have developed in five growth simulators ( Söderbergh and Ledermann, 2003). We have developed a shifting algorithm that determines the proportion of trees to be thinned from different diameter classes to complement the individual tree selection algorithms. Sampled (or mapped) tree diameters are grouped into diameter classes. Given the target thinning volume, the algorithm automatically computes the thinning rate in each of the diameter classes using the three-parameter Weibull distribution. The thinning rate is obtained by shifting the location parameter of an estimated Weibull distribution either to the right or to the left for thinnings from below and above, respectively. A modified bisection method is used to search for the new location parameter that yields the desired thinning volume. The proposed algorithm is demonstrated in examples by using experimental forest datasets. A stand-alone program called Weibull_thinning is downloadable at http://www.it.abo.fi/suswood/weibull_thinning/.

Effects of altitude and competition on growth and mortality of the conifer Abies sachalinensis

AbstractAltitudinal gradients are convenient subjects to investigate plant responses to air temperature. Plant growth and mortality are also affected by competition at any altitude. This study investigated the effects of altitude and competition on absolute diameter growth rate (ADGR) and mortality of the conifer Abies sachalinensis by using 13‐year data. This study was done at two altitudes (200 and 1,000 m a.s.l.) in northern Japan. Local crowding by conifers and broad‐leaved trees reduced ADGR of target trees. ADGR was lower in high altitude than low altitude at any DBH and any degree of local crowding because of the short growing season. Observed size‐dependent mortality was a U‐shaped pattern against DBH at the two altitudes. Smaller and larger trees tended to die of suppression (standing‐dead) and disturbances (stem‐broken and uprooting), respectively. Mortality of standing‐dead trees was negatively correlated with ADGR, irrespective of altitude, i.e., ADGR was a good predictor of mortality. Thus, mortality of standing‐dead trees was estimated to be greater at high altitude than low altitude at any degree of local crowding because ADGR was lower at high altitude than low altitude. By contrast, mortality due to disturbances was slightly greater at low altitude than high altitude. Thus, this study showed that a short growth period decreases growth and increases mortality due to suppression at high altitude. Although global warming may increase growth and survival of individual trees at high altitude by prolonging the growth period, prediction on mortality due to disturbances needs caution because the mortality is largely affected by frequency and intensity of disturbances.

Effects of Creating Two Forest Structures and Using Prescribed Fire on Coarse Woody Debris in Northeastern California, USA

Little is known about the dynamics of coarse woody debris (CWD) in forests that were originally characterized by frequent, low-moderate intensity fires. We investigated effects of prescribed burning at the Blacks Mountain Experimental Forest in northeastern California following creation of two stand structure conditions: 1) high structural diversity (HiD) that included retaining large, old-growth trees while thinning smaller trees in the understory through whole-tree harvesting, and 2) low structural diversity (LoD) simulating a more traditional approach that removed overstory trees by individual tree selection while thinning the vigorous younger trees and removing the suppressed understory by whole-tree harvesting. Each of the two structures was replicated six times in a randomized block design for a total of 12 approximately 100 ha factorial plots. Each factorial plot was split and prescribed fire applied to one half of each plot. We classified CWD as either: sound or decayed. Coarse woody debris was abundant on all plots regardless of stand structure. Statistically significant differences (α = 0.05) were found in the mass of the CWD between the burned and unburned splits across all experimental units combined for both sound and decayed material. However, when analyzed separately, the difference in the burned and unburned splits was statistically significant for LoD condition but not for HiD condition, likely due to greater heterogeneity of burn in the HiD condition. Coarse woody debris mass declined even in unburned units following treatments (p ≤ 0.1).

Estimating Tree Survival: A Study Based on the Estonian Forest Research Plots Network

Tree survival, as affected by tree and stand variables, was studied using the Estonian database of permanent forest research plots. The tree survival was examined on the basis of remeasurements during the period 1995–2004, covering the most common forest types and all age groups. In this study, the infl uence of 35 tree and stand variables on tree survival probability was analyzed using the data of 31 097 trees from 236 research plots. For estimating individual tree survival probability, a logistic model using the logit-transformation was applied. Tree relative height had the greatest effect on tree survival. However, different factors were included into the logistic model for different development stages: tree relative height, tree relative diameter, relative basal area of larger trees and relative sparsity of a stand for young stands; tree relative height, relative basal area of larger trees and stand density for middle-aged and maturing stands; and tree relative height and stand density for mature and overmature stands. The models can be used as preliminary sub-components for elaboration of a new individual tree based growth simulator.