Even-aged Forest Research Articles

Modeling Tree Characteristics of Individual Black Pine (Pinus nigra Arn.) Trees for Use in Remote Sensing-Based Inventory

The main aim was to develop models for predicting diameter at breast height (DBH), merchantable tree volume (V), and aboveground biomass (AGB) of individual black pine (Pinus nigra Arn.) trees grown in Sub-Mediterranean Croatian pure even-aged forests, which will be suitable for remote sensing based forest inventories. In total, eight variables obtained from field measurement, existing database, and digital terrain model were candidates for independent variables in regression analysis. DBH, V, and AGB were modeled as linear function of each of the independent variables, and all possible linear combinations thereof. Goodness of fit of every model was then evaluated using R2 statistic. Comparison between selected models showed that the variability of all dependent variables are explained best by models which include both crown diameter and tree height as independent variables with coefficients of determination of 0.83, 0.89, 0.82 for DBH, V, and AGB, respectively. Consequently, these models may be recommended as the most suited for DBH, V and AGB estimation of black pine trees grown in pure Sub-Mediterranean forest stands using high-resolution aerial images or high-density airborne laser scanning data. This assumption should be further validated by conducting remote sensing inventory and comparing the obtained results with field measurement results.

A combined economic analysis of optimal planting density, thinning and rotation for an even-aged forest stand

A planting and timber harvest scheduling model for even-aged forest stands was developed by combining and extending the dynamic thinning approach and existing work on planting density. A net present value maximum solution for planted volume, thinning regime and rotation schedule was determined simultaneously. The influence of the planting density on the optimal stand volume path, thinning schedule and rotation length was analyzed, emphasizing the importance of optimal stand establishment. The results and dependencies are discussed in detail and compared to findings presented in the literature.

Dead before detection: addressing the effects of left truncation on survival estimation and ecological inference for neonates

SummaryNeonate survival is a key life history trait, yet remains challenging to measure in wild populations because neonates can be difficult to capture at birth. Estimates of survival from neonates that are opportunistically captured might be inaccurate because some individuals die before sampling, resulting in data that are left truncated. The resulting overestimation of survival rates can further affect ecological inference through biased estimates of covariate effects in survival models, yet is not addressed in most studies of animal survival. Here, we quantify the effects of left truncation on survival estimates and subsequent ecological inference.Vaginal implant transmitters (VITs) enable capture of ungulates at birth, yielding data without left truncation. The effects of left truncation on survival estimation were quantified using age‐dependent survival models for VIT and opportunistically captured neonatal deer. Differences in daily survival rates (DSRs) and cumulative survival probability were calculated for the first 70 days of life. In addition, left truncation was simulated by removing fawns that died during the first 1 or 2 days of life from the VIT‐caught sample, isolating the effect of left truncation.Cumulative probability of survival during the first 70 days of life was overestimated by 7–23% for fawns caught opportunistically compared with those caught by VIT, depending on model design. Differences in DSRs were large at age 1 day, but had converged by age 30 days. Simulated left truncation resulted in overestimates of survival of up to 31%. Model selection and covariate coefficients were strongly affected by left truncation, producing spurious ecological inference, including changes to sign and/or magnitude of inferred effects of all covariates.We recommend (i) every effort be made to capture neonates; (ii) consistent capture methods, using at least in part non‐truncating techniques, be implemented across years and study areas; and (iii) exclusion of left‐truncated data from survival estimates until DSRs converge with those calculated from non‐truncated data. This work emphasizes the importance of accounting for left truncation in survival estimation for any species with strong age‐dependent survival in order to prevent biased conclusions produced by sampling method rather than true ecological effects.

Thinnings as Unequal Harvest Ages in Even-Aged Forest Stands

Thinnings as Unequal Harvest Ages in Even-Aged Forest Stands

Differential responses of herbivores and herbivory to management in temperate European beech.

Forest management not only affects biodiversity but also might alter ecosystem processes mediated by the organisms, i.e. herbivory the removal of plant biomass by plant-eating insects and other arthropod groups. Aiming at revealing general relationships between forest management and herbivory we investigated aboveground arthropod herbivory in 105 plots dominated by European beech in three different regions in Germany in the sun-exposed canopy of mature beech trees and on beech saplings in the understorey. We separately assessed damage by different guilds of herbivores, i.e. chewing, sucking and scraping herbivores, gall-forming insects and mites, and leaf-mining insects. We asked whether herbivory differs among different forest management regimes (unmanaged, uneven-aged managed, even-aged managed) and among age-classes within even-aged forests. We further tested for consistency of relationships between regions, strata and herbivore guilds. On average, almost 80% of beech leaves showed herbivory damage, and about 6% of leaf area was consumed. Chewing damage was most common, whereas leaf sucking and scraping damage were very rare. Damage was generally greater in the canopy than in the understorey, in particular for chewing and scraping damage, and the occurrence of mines. There was little difference in herbivory among differently managed forests and the effects of management on damage differed among regions, strata and damage types. Covariates such as wood volume, tree density and plant diversity weakly influenced herbivory, and effects differed between herbivory types. We conclude that despite of the relatively low number of species attacking beech; arthropod herbivory on beech is generally high. We further conclude that responses of herbivory to forest management are multifaceted and environmental factors such as forest structure variables affecting in particular microclimatic conditions are more likely to explain the variability in herbivory among beech forest plots.

An Approach for Projecting Mixed-Species Forest Growth and Mortality

Mixed-species forests are common throughout the United States and growth and yield models are needed which rc/[cct cOmplex intcrrclatioriships. A stand-table projection approach \Vith upgrO\Jth and mortality components is presented for modeling growth and development in such forests. The mCthod involves concepts previously used to model mixed-species (liamctcr growth, in the upgrowth component ofthc projection system. Tentative equation forms arc presented to help clarify the general approach. Decisions regarding timber harvesting and ~tand density are of prime concern to forest managers. Harvesting directly influences both the profitability and the environmental impacts of forestry operations. Analyses of intermediate and final harvest alternatives require reliable means of projecting growth and yield, including responses to harvesting and other ~ultural practices. Models of growth and yield which recognize the mixedMspecies nature of most forest types are particularly needed for considering harvesting options. Only when such models are available can detailed management alternatives be evaluated for vast numbers 1 of existing mixedMspecies stands. 1 Stand-table projection is a growth and yield technique which can reflect differential growth and responses to harvesting. A stand-table projection method is presented for modeling growth and structural changes in even-aged forests of mixed-species. The general approach to modeling mixed-species forest types is emphasized, rather than a specific, empirically estimated model. Following an . outline of notation, a general discussion of the approach is presented, including tentative equation forms. Relative advantages and disadvantages of the proposed method are also discussed.

A simple theory to link bole surface area, stem density and average tree dimensions in a forest stand

A geometrical model of a forest stand has been analyzed. A forest stand has been modeled as a population of cones which was described by the change of total bole surface area with density $$\hat{S}(N)$$ , relation between density and a horizontal dimension (radius r) r(N), and the relation between vertical dimension (generatrix l) and radius l(r). It has been shown that there are close relationships between $$\hat{S}(N)$$ , l(r) and r(N). In case of $$\hat{S}(N) = const$$ , power exponent of l(r) can be predicted from the power exponent of r(N) and vice versa. A comparison of the model analysis with the data available on Scots pine (Pinus sylvestris L.) stands has been performed. In spite of the model simplicity, its inferences proved to be workable in many cases where the data can be interpreted as a dynamics of an even-aged forest stand. In particular, if the estimation of total bole surface area is constant, the power exponent in the relation of diameter and stand density DBH(SD) can be calculated on the basis of the power exponent in the relation of height and diameter H(DBH) and vice versa. Possible limitations and the meaning of the analysis are discussed.

Sustainability of forest management under changing climatic conditions in the southern United States: Adaptation strategies, economic rents and carbon sequestration

The impacts of climate change on profitability and carbon storage in even-aged forest stands of two dominant commercial pine species, loblolly and slash pine, in the southern United States were assessed under alternative assumptions about the impact of climate change on forest productivity and catastrophic disturbance rates. Potential adaptation strategies to reduce losses from disturbance included: 1) alternative planting densities, and 2) planting slash pine instead of loblolly pine. In addition, the amount of sequestered carbon was used to develop an index of economic efficiency for carbon sequestration, which further helps rank the suitability of alternative adaptation strategies. Our results indicate that greater economic rents from forests occur with lower planting densities and the substitution of slash pine for high density loblolly pine. However, less carbon is sequestered by low density loblolly pine compared to slash pine and high density loblolly pine. Both adaptation strategies are economically more effective in terms of carbon sequestration compared to the baseline since they generate more economic revenues per Mg of sequestered carbon.

Regulation of even-aged forests with inclusion of environmental constraints

This study aimed to propose alternative methods of inclusion of environmental constraints in forest regulation models. Models were constructed for an experimental rural estate with a total planted area of 3.491 ha which was divided into 135 management units. The formulation of the regulation models included integer constraints for all management units. Genetic algorithm metaheuristic was used for solving the models. For comparison purposes, the classical model of forest regulation (model I) was used, and the model with adjacency constraints. The proposed formulations proved to be environmentally more effective than the imposition of adjacency constraints.

Analisi storica e modellizzazione della dinamica del carbonio in foresta attraverso il Carbon Budget Model: un esempio per la Provincia Autonoma di Trento

Historical analysis and modeling of the forest carbon dynamics using the Carbon Budget Model: an example for the Trento Province (NE, Italy). The Carbon Budget Model (CBM-CFS3) developed by the Canadian Forest Service was applied to data collected by the last Italian National Forest Inventory (INFC) for the Trento Province (NE, Italy). CBM was modified and adapted to the different management types (i.e., even-aged high forests, uneven-aged high forests and coppices) and silvicultural systems (including clear cuts, single tree selection systems and thinning) applied in this province. The aim of this study was to provide an example of down-scaling of this model from a national to a regional scale, providing (i) an historical analysis, from 1995 to 2011, and (ii) a projection, from 2012 to 2020, of the forest biomass and the carbon stock evolution. The analysis was based on the harvest rate reported by the Italian National Institute of Statistics (from 1995 to 2011), corrected according to the last INFC data and distinguished between timber and fuel woods and between conifers and broadleaves. Since 2012, we applied a constant harvest rate, equal to about 1300 Mm3 yr-1, estimated from the average harvest rate for the period 2006-2011. Model results were consistent with similar data reported in the literature. The average biomass C stock was 90 Mg C ha-1 and the biomass C stock change was 0.97 Mg C ha-1 yr-1 and 0.87 Mg C ha-1 yr-1, for the period 1995 -2011 and 2012-2020, respectively. The C stock cumulated by the timber products since 1995 was 96 Gg C yr-1, i.e., about 28% of the average annual C stock change of the forests, equal to 345 Gg C yr-1. CBM also provided estimates on the evolution of the age class distribution of the even-aged forests and on the C stock of the DOM forest pools (litter, dead wood and soil). This study demonstrates the utility of CBM to provide estimates at a regional or local scale, using not only the data provided by the forest inventories, but also by forest management plans.

Relation between selected indicators of forest stand diversity and quality of timber production in young stands aged up to 40 years

The present study examines the relationships between the indicators of tree species and structural diversity and the quality of timber production in young even-aged forest stands with the average age below 40 years. The study is based on the forest inventory data from University Forest Enterprise Kostelec nad Černými lesy, Czech Republic, performed from 2009 to 2011. The examined young stands were recorded in 256 sample plots representing 21.2% of the enterprise area. On each sample plot, we quantified 171 partial biodiversity indicators. In total, we analysed 16,416 different variants of the relationship between the diversity indicator and the quality of timber production. The analysis revealed that similarity indicators such as the range of tree heights, Canberra distance, Bray and Curtis index, and index of species evenness and heterogeneity were the most frequent basic indicators occurring in significant correlations. The results indicate a positive relationship between the proportions of assortments in quality classes I to IV and stand diversity expressed by the number of tree species and Canberra distance.

Economic performance of uneven-aged forests analysed with annuities

For this study, 18 permanent research plots in Switzerland with an area between 0.5 and 2.5 ha that have been installed between 1905 and 1931 were analysed using annuities. The plots cover a wide range of uneven-aged forest-types from pure Norway spruce to classical single-tree selection (plenter) forests dominated by Silver fir in different elevations (575–1810 m a.s.l). The areas have been managed according to an uneven-aged silvicultural system and growth and yield characteristics have been assessed on a single-tree basis every 5–11 years. Net revenues of timber harvesting were computed as a time series from the installation of the plots until today and transformed into net present values and subsequently into annuities for each assessment interval. Three types of annuities: (1) for cutting cycles; (2) forward; (3) backward for the whole assessment period were calculated together with internal rates of return. The results display that annuities were usually positive with an interest of 2 per cent. High elevation (>1400 m) Norway spruce dominated forests as well as heavily overstocked (>900–1000 m3 ha−1) plots showed the lowest or even negative annuities. The reduction of overstocks lead in the mid-term to an increase, but resulted in a short-term decrease of the annuities. For many of the research plots, especially those in higher elevations, there is a trend towards an increase of the annuities over time. The highest annuities were found in Silver fir dominated selection forests with a growing stock close to or slightly above an equilibrium structure. The backward calculation of the annuities improved for some plots the problem of the strong influence of the value of the initial growing stock. Implications for uneven-aged silviculture as well as for the analysis of the economic performance of uneven-aged and even-aged forests and the application of annuities are discussed in the paper.

On the way to continuous cover forest at middle elevations - the question of forest structure and specific site characteristics

The transformation process of even-aged forest stands to irregular forest stands on waterlogged sites after 20 years effort was analysed. Data from two 1-ha PRP was analysed with special focus on structural (Shannon Evenness Index, Simpson Index and Gini Index) and species (Shannon Evenness Index and Simpson Index) diversity. Different development on study plots confirmed that the highest structural diversity is not often compatible with the concept of species diversity. On PRP 1 high diameter differentiation has led to lower values of species diversity, while on PRP 2 rather moderate diameter differentiation supported higher species diversity in lower DBH classes. The Gini Index was confirmed to be the best indicator for monitoring the diameter differentiation in the course of stand transformation.

Evaluating competitive interactions between trees in mixed forests in the Western Carpathians: Comparison between long-term experiments and SIBYLA simulations

The competition interactions between trees and species have already been thoroughly studied, but most often for mono-species and even-aged forests. Several recent studies have been undertaken, prompted by changes in forest management objectives, which now favour mixed-species forests to increase biodiversity. However, there have been no studies focused on the competition interactions for the mixed-species forests in the Western Carpathians. Recently, the single tree-based growth simulator SIBYLA has been developed for use in the forests of this area. The development of this model was based upon the growth simulator SILVA. Since there were no data available from long-term experiments for the Western Carpathian forests, SIBYLA was only calibrated using large-scale data from the Slovakian forest monitoring network. The aim of this study was (i) to define the potential maximum radial growth of silver fir (Abies alba L.), European beech (Fagus sylvatica L.) and Norway spruce (Picea abies L. Karst.) in mixed forests, (ii) to test the above-ground competition effects on the radial increment of these species using a competition index based on competition light cone, and (iii) to evaluate the simulator SIBYLA using seven long-term experimental plots established in the 1960s, in the mixed-species uneven-aged forests of the Western Carpathians. These plots were repeatedly measured between five to eight times at intervals of 5–16years, from 1967 to 2010. Long-term climatic records were obtained to allow simulation of tree growth in real climatic conditions. The results showed the differences in potential maximum radial growth between the species. The results also suggested that the competition effect on radial increment predicted by the SIBYLA is an overestimate compared to the real observed effect on silver fir, Norway spruce, and European beech. This, together with other factors, is suggested to be the cause of the observed bias between measurements and SIBYLA simulations, which ranged from −2.2% to −11% for silver fir, −0.2 to −3.7% for Norway spruce, and 0.9% to 13.9% for European beech (average bias for the measurement periods).

Ungulate browsing shapes climate change impacts on forest biodiversity in Hungary

Climate change can result in a slow disappearance of forests dominated by less drought-tolerant native European beech (Fagus sylvatica) and oak species (Quercus spp.) and further area expansion of more drought-tolerant non-native black locust (Robinia pseudoacacia) against those species in Hungary. We assumed that the shift in plant species composition was modified by selective ungulate browsing. Thus, we investigated which woody species are selected by browsing game. We have collected data on the species composition of the understory and the browsing impact on it in five different Hungarian even-aged forests between 2003 and 2005. Based on these investigations the non-native Robinia pseudoacacia living under more favourable climatic conditions was generally preferred (Jacobs’ selectivity index: D = 0.04 ± 0.77), while the native Fagus sylvatica and Quercus spp. (Q. petraea, Q. robur), both more vulnerable to increasing aridity, were avoided (D = −0.37 ± 0.11; −0.79 ± 0.56; −0.9 ± 0.16; respectively) among target tree species. However, economically less or not relevant species, e.g. elderberry (Sambucus spp.), blackberry (Rubus spp.) or common dogwood (Cornus sanguinea) were the most preferred species (D = 0.01 ± 0.71; −0.12 ± 0.58; −0.2 ± 0.78, respectively). Our results imply that biodiversity conservation, i.e. maintaining or establishing a multi-species understory layer, can be a good solution to reduce the additional negative game impact on native target tree species suffering from drought. Due to preference for Robinia pseudoacacia selective browsing can decelerate the penetration of this species into native forest habitats. We have to consider the herbivorous pressure of ungulates and their feeding preferences in planning our future multifunctional forests in the light of climate change impacts.

A density management diagram for Norway spruce in the temperate European montane region

Norway spruce is one of the most important conifer tree species in Europe, paramount for timber pro- vision, habitat, recreation, and protection of mountain roads and settlements from natural hazards. Although natural Norway spruce forests exhibit diverse structures, even-aged stands can arise after disturbance or as the result of common silvicultural practice, including off-site afforestation. Many even-aged Norway spruce forests face issues such as senescence, insufficient regeneration, mechanical stability, sensitivity to biotic disturbances, and restoration. We pro- pose the use of Density Management Diagrams (DMD), stand-scale graphical models designed to project growth and yield of even-aged forests, as a heuristic tool for assessing the structure and development of even-aged Norway spruce stands. DMDs are predicated on basic tree allometry and the assumption that self-thinning occurs predictably in forest stands. We designed a DMD for Nor- way spruce in temperate Europe based on wide-ranging forest inventory data. Quantitative relationships between tree- and stand-level variables that describe resistance to selected natural disturbances were superimposed on the DMD. These susceptibility zones were used to demonstrate assessment and possible management actions related to, for example, windfirmness and effectiveness of the protective function against rockfall or avalanches. The Norway spruce DMD provides forest managers and silviculturists a simple, easy-to-use, tool for evaluating stand dynamics and sched- uling needed density management actions.

Impacts of Spatial Variability on Aboveground Biomass Estimation from L-Band Radar in a Temperate Forest

Estimation of forest aboveground biomass (AGB) has become one of the main challenges of remote sensing science for global observation of carbon storage and changes in the past few decades. We examine the impact of plot size at different spatial resolutions, incidence angles, and polarizations on the forest biomass estimation using L-band polarimetric Synthetic Aperture Radar data acquired by NASA’s Unmanned Aerial Vehicle Synthetic Aperture Radar (UAVSAR) airborne system. Field inventory data from 32 1.0 ha plots (AGB < 200 Mg ha−1) in approximately even-aged forests in a temperate to boreal transitional region in the state of Maine were divided into subplots at four different spatial scales (0.0625 ha, 0.25 ha, 0.5 ha, and 1.0 ha) to quantify aboveground biomass variations. The results showed a large variability in aboveground biomass at smaller plot size (0.0625 ha). The variability decreased substantially at larger plot sizes (>0.5 ha), suggesting a stability of field-estimated biomass at scales of about 1.0 ha. UAVSAR backscatter was linked to the field estimates of aboveground biomass to develop parametric equations based on polarized returns to accurately map biomass over the entire radar image. Radar backscatter values at all three polarizations (HH, VV, HV) were positively correlated with field aboveground biomass at all four spatial scales, with the highest correlation at the 1.0 ha scale. Among polarizations, the cross-polarized HV had the highest sensitivity to field estimated aboveground biomass (R2 = 0.68). Algorithms were developed that combined three radar backscatter polarizations (HH, HV, and VV) to estimate aboveground biomass at the four spatial scales. The predicted aboveground biomass from these algorithms resulted in decreasing estimation error as the pixel size increased, with the best results at the 1 ha scale with an R2 of 0.67 (p < 0.0001), and an overall RMSE of 44 Mg·ha−1. For AGB < 150 Mg·ha−1, the error reduced to 23 Mg·ha−1 (±15%), suggesting an improved AGB prediction below the L-band sensitivity range to biomass. Results also showed larger bias in aboveground biomass estimation from radar at smaller scales that improved at larger spatial scales of 1.0 ha with underestimation of −3.62 Mg·ha−1 over the entire biomass range.

Optimal Solution of Forest Management Under Risk

This paper investigate the idea and the field of stochastic phenomena in forestry. The text covers forestry decisions and optimal solution of forest management that are based on stochastic phenomena. Optimal decisions in the presence of stochastic timber prices are discussed. Optimal decisions of forest management under risk in even-aged forests and uneven-aged forests are disused and formulated. Stochastic dynamic programming technique is a reliable method for modeling optimization problems in uneven-aged forest that involve risk and uncertainty.

Optimum structures of Black Sea Region fir forests.

It is known that fir, being a shade-tolerant tree species, form selection forests which have naturally self-specific increment and growth laws. Because of that they are managed as even-aged forests or in the direction of allowable cut formulas which are not suitable to its natural structure, their optimum structures and ecosystems of these forests being spoiled. With the applied management form contrary to the concept of today’s sustainable forestry, these fir forests are managed at a level of very small increment. Whereas, if they are managed as selection forest, both its ecosystem improvement and sustainability will be provided and a contribution will be made to the economy of the country, running them with an increment potential equal to or more than 13 m 3 /ha. In this paper, the information about increment and growth laws which provide posibilities to manage the Black Sea Region fir forests as selection forests will be given.

Regulation of even-aged forest with adjacency constraints

The objective of this work is to present a model of forest regulation to include adjacency constraints and present an evaluation index that fits the characteristics of even-aged forest in Brazil. The models were constructed for a model farm with an area of effective planting of 3491ha, divided into 135 management units. The regulation models were formulated as model I, including integer constraints for the management units. We used meta-heuristic genetic algorithm for solving the models. For comparison we formulated a classical model of forest regulation. The purpose was maximizing the Net Present Value (NPV). The application of the technique of genetic algorithm is efficient for solving models, built with constraints and objectives of socioeconomic and environmental character. A comparison of volume variation is discussed to satisfy the demand of production imposed on all models. The inclusion of the adjacency constraint has reduced the overall NPV at 8% compared to the classical model. The IHA has shown to be feasible and efficient for evaluating the environmental influences of forest management even-aged.