Tree Size Diversity Research Articles

Fusion of airborne LiDAR and multispectral sensors reveals synergic capabilities in forest structure characterization

Forest stand structure is an important concept for ecology and planning in sustainable forest management. In this article, we consider that the incorporation of complementary multispectral information from optical sensors to Light Detection and Ranging (LiDAR) may be advantageous, especially through data fusion by back-projecting the LiDAR points onto the multispectral image. A multivariate data set of both LiDAR and multispectral metrics was related with a multivariate data set of stand structural variables measured in a Scots pine forest through canonical correlation analysis (CCA). Four statistically significant pairs of canonical variables were found, which explained 83.0% accumulated variance. The first pair of canonical variables related indicators of stand development, i.e. height and volume, with LiDAR height metrics. CCA also found attributes describing stand density to be related to LiDAR and spectral variables determining canopy coverage. Other canonical variables pertained to Lorenz curve-derived attributes, which are measures of within-stand tree size variability and heterogeneity, able to discriminate even-sized from uneven-sized stands. The most relevant result was to find that metrics derived from the multispectral sensor showed significant explanatory potential for the prediction of these structural attributes. Therefore, we concluded that metrics derived from the optical sensor have potential for complementing the information from the LiDAR sensor in describing structural properties of forest stands. We recommend the use of back-projecting for jointly exploiting the synergies of both sensors using similar types of metrics as they are customary in forestry applications of LiDAR.

Effect of different tree mortality patterns on stand development in the forest model SIBYLA

Abstract Forest mortality critically affects stand structure and the quality of ecosystem services provided by forests. Spruce bark beetle (Ips typographus) generates rather complex infestation and mortality patterns, and implementation of such patterns in forest models is challenging. We present here the procedure, which allows to simulate the bark beetle-related tree mortality in the forest dynamics model Sibyla. We explored how sensitive various production and stand structure indicators are to tree mortality patterns, which can be generated by bark beetles. We compared the simulation outputs for three unmanaged forest stands with 40, 70 and 100% proportion of spruce as affected by the disturbance-related mortality that occurred in a random pattern and in a patchy pattern. The used tree species and age class-specific mortality rates were derived from the disturbance-related mortality records from Slovakia. The proposed algorithm was developed in the SQLite using the Python language, and the algorithm allowed us to define the degree of spatial clustering of dead trees ranging from a random distribution to a completely clustered distribution; a number of trees that died in either mode is set to remain equal. We found significant differences between the long-term developments of the three investigated forest stands, but we found very little effect of the tested mortality modes on stand increment, tree species composition and diversity, and tree size diversity. Hence, our hypothesis that the different pattern of dead trees emergence should affect the competitive interactions between trees and regeneration, and thus affect selected productivity and stand structure indicators was not confirmed.

Assessing the factors influencing natural regeneration patterns in the diverse, multi‐cohort, and managed forests of Maine, USA

AbstractQuestionsWhat are the primary biotic and abiotic factors driving composition and abundance of naturally regenerated tree seedlings across forest landscapes of Maine? Do seedling species richness (SR) and density (SD) decrease with improved growing conditions (climate and soil), but increase with increased diversity of overstorey composition and structure? Does partial harvesting disproportionately favour relative dominance of shade‐intolerant hardwoods (PIHD) over shade‐tolerant softwoods (PTSD)?LocationForest landscapes across the diverse eco‐regions and forest types of Maine, USA.MethodsThis study used USDA Forest Service Forest Inventory Analysis permanent plots (n = 10 842), measured every 5 yr since 1999. The best models for each response variable (SR, SD, PIHD and PTSD) were developed based on AIC and biological interpretability, while considering 35 potential explanatory variables incorporating climate, soil, site productivity, overstorey structure and composition, and past harvesting.ResultsMean annual temperature was the most important abiotic factor, whereas overstorey tree size diversity was the most important biotic factor for SR and SD. Both mean annual temperature and overstorey tree size diversity had a curvilinear relationship with SR and SD. Average overstorey shade tolerance and percentage tolerant softwood basal area in the overstorey were the top predictor variables of PIHD and PTSD, respectively. Partial harvesting favoured PIHD but not PTSD.ConclusionsThis is one of the first studies to comprehensively evaluate a number of factors influencing naturally established tree seedlings at a broad landscape scale in the Northern Forest region of the eastern USA and Canada. Despite limitations associated with relatively small plot size, large seedling size class and lack of direct measurements of light, water and nutrients, this study documents the influence of these factors amid high variability associated with patterns of natural regeneration. The curvilinear relationship between mean annual temperature with SR and SD supports the argument that species richness and abundance usually have unimodal relationships with productivity indicators, whereas the curvilinear relationship between overstorey tree size diversity and SR and SD suggest that moderate overstorey diversity incorporates multiple species as well as higher seedling individuals.

Spatial diversity of forest regeneration after catastrophic wind in northeastern Poland

Abstract: We examined the spatial diversity of young growth established after the catastrophic windthrow occurred in 2002 in the northeastern part of Poland. Our observations and measurements were conducted on permanent circular measurement plots located in the Szast Protected Forest (continental lowland temperate forests) that were established 3 years after the windstorm and left to natural succession. We evaluated the spatial indices characterizing the four main aspects of stand structure: the spatial arrangement of seedlings and saplings, species mingling, tree size diversity at the local spatial scale and the overall structural complexity index. The calculations were conducted in parts of the forest with differing severity of disturbance. The obtained results indicated the prevalence of a random arrangement of young growth. Clumps of regeneration were observed to a lesser degree in all parts of the forest. The species diversity was moderate and was the highest in the slightly or severely disturbed stands. Scots pine formed homogenous groups of regeneration and oaks were intermingled among other tree species. The height of the natural regeneration was moderately or highly differentiated in all stands. The overall structural diversity index showed that stand regeneration in the slightly or moderately disturbed stands was more differentiated than the young growth in the severely disturbed stands. The size differentiation of young growth is a long-lasting process and thus should be considered in practices aimed at the re-growing of areas after a natural disturbance. This process might be used to the replace monocultures with more diversified forests even in poor forest site types.

Determinants of stem form: Application to Tectona grandis (Linn. F) stands

ABSTRACTStem form information can enhance rapid estimation of stem volume. Studies on important determinants of stem form in pure stands are scanty. This study aimed at identifying determinants of stem form using Tectona grandis stands in Omo Forest Reserve, Nigeria. Twenty 0.04 ha square plots were randomly selected across four stand ages. Crown diameter, total and merchantable heights (MH), diameters at breast height (DBH), at 5.27 m tree height and at midpoint from breast height to tip of tree were measured in each plot. Measured trees were classified into four canopy layers (CL)—dominant, codominant, intermediate, and suppressed. Merchantable volume, basal area (BA), form factor (Ff), normal form quotient (Qn), Girard form class (QG), absolute form quotient (Qa), ratio of diameter at merchantable limit to diameter at the base (Dt/Db), and tree slenderness coefficient were derived from the data. Analysis of variance, correlation, and regression analyses were used to analyze the data. Significant differences were observed in stem form and tree size variables under different canopy layers. The DBH, BA, MHT, and CL were identified as important variables associated with stem form. Inclusion of Qa improved most the predictive ability of the selected stem volume equation.

Inter-annual variability in Prosopis caldenia pod production in the Argentinean semiarid pampas: A modelling approach

The driest part of the Argentinean pampas is occupied by semiarid woodlands dominates by Prosopis caldenia Burkart (Calden). Calden pods are a highly valuable fodder supplement for livestock but its production is highly variable. Our objective was to analyze and model the temporal pattern in inter-annual variability of Calden pod production. Our key hypothesis is that weather conditions are the main determinant of the pod masting behaviour. Tree size and climatic variables were evaluated as explanatory covariates using a zero-inflated log-normal modelling approach. The proposed final model structure incorporated 25 parameters, including four variance components, two intercepts for both the logistic and the log-normal parts of the model, and nineteen parameters associated with fixed effects. Climate had a strong influence on the flowering-fruiting Calden process and on the inter-annual variability of the final pod production at the tree level. Temperatures during bud breaking, flowering and fruit shedding, together with the precipitation from the final month of fruit shedding and the total amount of the prior vegetative cycle, were the main weather covariates that affect the processes.

Effects of thinning-induced changes in structural heterogeneity on growth, ingrowth, and mortality in secondary coastal Douglas-fir forests

Thinning is believed to accelerate the development of late-successional attributes, thereby enhancing stand structural heterogeneity in young, secondary forests. By making use of a large-scale experiment implemented in 40- to 60-year-old coastal Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) forests, we addressed the following objectives: (i) determine the effect of three thinning treatments on the temporal dynamics (first 11 years after thinning) of key forest structure measures, (ii) evaluate the relationships between spatially explicit structural diversity measures and spatially nonexplicit stand metrics, and (iii) test the relationships between stand structure and observed periodic stand volume growth, ingrowth, and mortality. Treatments consisted of high-density, moderate-density, and variable-density thinnings-from-below, as well as a control. Differences in stand structural heterogeneity between treatments were mostly nonsignificant. However, our results suggest that variable-density stands displayed structural enrichment as tree size and tree species diversity increased throughout the study period as a result of continuous ingrowth of species other than Douglas-fir. Simple spatially nonexplicit metrics could not be used to reliably model spatially explicit structural diversity measures. The inclusion of structural and species diversity measures only rarely improved accuracy of sample plot level growth, ingrowth, and mortality prediction models. Despite the short-term nature of this study, we conclude that variable-density thinning shows promise in increasing structural heterogeneity in young even-aged stands. The inclusion of structural diversity measures in growth and mortality models may be beneficial, but further work is needed to clarify the underlying relationships, particularly at the individual-tree level.

Assessing visual green effects of individual urban trees using airborne Lidar data

Urban trees benefit people's daily life in terms of air quality, local climate, recreation and aesthetics. Among these functions, a growing number of studies have been conducted to understand the relationship between residents' preference towards local environments and visual green effects of urban greenery. However, except for on-site photography, there are few quantitative methods to calculate green visibility, especially tree green visibility, from viewers' perspectives.To fill this research gap, a case study was conducted in the city of Cambridge, which has a diversity of tree species, sizes and shapes. Firstly, a photograph-based survey was conducted to approximate the actual value of visual green effects of individual urban trees. In addition, small footprint airborne Lidar (Light detection and ranging) data was employed to measure the size and shape of individual trees. Next, correlations between visual tree green effects and tree structural parameters were examined. Through experiments and gradual refinement, a regression model with satisfactory R2 and limited large errors is proposed. Considering the diversity of sample trees and the result of cross-validation, this model has the potential to be applied to other study sites. This research provides urban planners and decision makers with an innovative method to analyse and evaluate landscape patterns in terms of tree greenness.

Stand and landscape scale variability in the amount and diversity of coarse woody debris in primeval European boreal forests

Factors influencing natural variability in coarse woody debris (CWD) as an indicator of ecosystem services in boreal forests need to be better defined. We analysed the CWD characteristics in 194 dynamic primeval boreal forest stands and 3 landscapes under different disturbance regimes. The volume of CWD in the spruce dominated forests linearly increased with increasing annual temperature. The CWD amount and species diversity were higher in spruce than in pine dominated stands. The CWD volume increased in relationship to the types of forest stand dynamics in the order: ‘even-aged’, ‘cohort’, ‘fine-scale gap’. The CWD volumes were 52.3; 207.0 and 146.8m3ha−1 and the dead:live wood volume ratios were 29%, 102% and 60% in the landscapes with disturbance regimes driven by periodic surface fires, cohort-replacing windthrow, and fine-scale gap dynamics, respectively. Mean dead:live wood volume ratios exceeded 100% in spruce stands with even-aged and cohort dynamics and in pine stands with even-aged and fine-scale gap dynamics. The CWD decay class diversity was higher in pine than in spruce dominated stands. The CWD volume distribution by decay class was the most even in forest stands driven by fine-scale gap dynamics in both spruce and pine dominated stands. The CWD position diversity was higher in spruce than in pine dominated forests. Fallen logs dominated among other CWD position types in the spruce dominated stands with cohort and fine-scale gap dynamics and in pine stands with cohort and even-aged dynamics. Pine forests with fine-scale gap dynamics stored the greatest volume of snags. In the spruce dominated stands, the proportion of leaning logs decreased and the proportion of snags and stumps increased among forest dynamic types in the following order: even-aged, cohort, fine-scale gap. The CWD diameter distribution had peaks in small-sized CWD in even-aged spruce stands and pine stands with fine-scale gap dynamics. Mid-sized CWD dominated in spruce stands driven by cohort and fine-scale gap dynamics and pine stands with even-aged and cohort dynamics. The large quantity of CWD that encompassed a wide range of variation in tree species, decay class, position type and size creates a diversity of CWD habitats for saproxylic organisms and ensures functional resilience in boreal forest ecosystems. Our results stress that mean annual temperatures and natural site-specific disturbance regimes should be taken into account when setting targets for CWD volumes and dead:live wood volume ratios for management and restoration of CWD in boreal forests.

Scale dependence of disease impacts on quaking aspen (Populus tremuloides) mortality in the southwestern United States.

Depending on how disease impacts tree exposure to risk, both the prevalence of disease and disease effects on survival may contribute to patterns of mortality risk across a species' range. Disease may accelerate tree species' declines in response to global change factors, such as drought, biotic interactions, such as competition, or functional traits, such as allometry. To assess the role of disease in mediating mortality risk in quaking aspen (Populus tremuloides), we developed hierarchical Bayesian models for both disease prevalence in live aspen stems and the resulting survival rates of healthy and diseased aspen near the species' southern range limit using 5088 individual trees on 281 United States Forest Service Forest Inventory and Analysis plots in the southwestern United States. We found that disease prevalence depended primarily on tree size, tree allometry, and spatial variation in precipitation, while mortality depended on tree size, allometry, competition, spatial variation in summer temperature, and both temporal and spatial variation in summer precipitation. Disease prevalence was highest in large trees with low slenderness found on dry sites. For healthy trees, mortality decreased with diameter, slenderness, and temporal variation in summer precipitation, but increased with competition and spatial variation in summer temperature. Mortality of diseased trees decreased with diameter and aspen relative basal area and increased with mean summer temperature and precipitation. Disease infection increased aspen mortality, especially in trees of intermediate size and trees on plots at climatic extremes (i.e., cool, wet and warm, dry climates). By examining variation in disease prevalence, mortality of healthy trees, and mortality of diseased trees, we showed that the role of disease in aspen tree mortality depended on the scale of inference. For variation among individuals in diameter, disease tended to expose intermediate-size trees experiencing moderate risk to greater risk. For spatial variation in summer temperature, disease exposed lower risk populations to greater mortality probabilities, but the magnitude of this exposure depended on summer precipitation. Furthermore, the importance of diameter and slenderness in mediating responses to climate supports the increasing emphasis on trait variation in studies of ecological responses to global change.

Reconciling Biodiversity Conservation and Timber Production in Mixed Uneven-Aged Mountain Forests: Identification of Ecological Intensification Pathways.

Mixed uneven-aged forests are considered favorable to the provision of multiple ecosystem services and to the conciliation of timber production and biodiversity conservation. However, some forest managers now plan to increase the intensity of thinning and harvesting operations in these forests. Retention measures or gap creation are considered to compensate potential negative impacts on biodiversity. Our objectives were to assess the effect of these management practices on timber production and biodiversity conservation and identify potential compensating effects between these practices, using the concept of ecological intensification as a framework. We performed a simulation study coupling Samsara2, a simulation model designed for spruce-fir uneven-aged mountain forests, an uneven-aged silviculture algorithm, and biodiversity models. We analyzed the effect of parameters related to uneven-aged management practices on timber production, biodiversity, and sustainability indicators. Our study confirmed that the indicators responded differently to management practices, leading to trade-offs situations. Increasing management intensity had negative impacts on several biodiversity indicators, which could be partly compensated by the positive effect of retention measures targeting large trees, non-dominant species, and deadwood. The impact of gap creation was more mitigated, with a positive effect on the diversity of tree sizes and deadwood but a negative impact on the spruce-fir mixing balance and on the diversity of the understory layer. Through the analysis of compensating effects, we finally revealed the existence of possible ecological intensification pathways, i.e., the possibility to increase management intensity while maintaining biodiversity through the promotion of nature-based management principles (gap creation and retention measures).

Differentiating mixed- and high-severity fire regimes in mixed-conifer forests of the Canadian Cordillera

Mixed-severity fire regimes are important drivers of forest dynamics, stand structural attributes, and regional and local landscape heterogeneity, but they remain poorly understood. We reconstructed site-level fire histories using fire scars and even-aged cohorts at 20 sites in two contiguous watersheds in southeastern British Columbia, Canada, a region that is particularly understudied. We compared stand composition and structural attributes (i.e., snag and veteran tree densities, tree size variability, and maximum tree size) at sites found to be mixed-severity, as well as those found to be high-severity after recent (<150years) and older (⩾150years) stand-replacing fires. We developed two forest indices capturing age-structure complexity and continuity to refine these comparisons.Eleven of 20 sites displayed mixed-severity fire histories and were located at elevations 600m higher than previously described for this landscape. Tree species composition varied with disturbance history. Mixed-severity sites were dominated by Douglas-fir and western larch that regenerated after frequent low- to moderate-intensity fires, which created fire scars. Periodic moderate-severity fires generated some even-aged cohorts with surviving veteran trees. At higher-elevations, intense fires generated cohorts dominated by lodgepole pine. Subalpine fir dominated high-severity sites that last burned>250years ago.Age structures at mixed- and older high-severity sites were of similar complexity, but could be differentiated using our index of age structure continuity. We found western larch to be a strong indicator of historical mixed-severity fire regimes. Western larch trees and stumps were only found at mixed-severity sites, and 84% of these individuals established within 15years of antecedent fire scars. Snag densities were greatest at high-severity sites that burned>150years ago, in contrast to expectations that mixed-severity sites would be more structurally complex. Tree size attributes were indistinguishable between mixed- and high-severity sites, although, subcanopy densities were particularly high (upwards of 5600ha−1) having persisted since the last fire at most sites. Selective harvesting and fire suppression during the 20th century have homogenized contemporary forest structures in mid-elevation forests. An improved understanding of mixed-severity fire regimes is vital to determining whether forest resilience is compromised and where ecological restoration is warranted.

Optimizing management of goats and oak trees for sustainability and community's welfare: a case study from Zagros, Iran

A deterministic dynamic bio-economic model was used to analyse different management options for goats and charcoal production in a forest in Zagros, Iran. The study sought optimal management options from a local community point of view considering net present value (NPV) of income from sale of goats and charcoal under different restrictions on forest harvest imposed by the state. The model was run under six model scenarios: (1) business as usual (BAU), (2) no state intervention, (3) no forest harvesting, (4) strict quota, (5) medium quota and (6) loose quota on charcoal production. The scenarios' results were compared based on four numeric criteria (NPV of income from goats and charcoal, development of standing volume and tree size diversity in forest, interaction between goat population and oak forests) and one subjective criterion (state budget for managing forest). The results indicated that two main challenges exist in forest management in Zagros; (1) to determine the balance between local communities' welfare and biological stability of the forest and (2) to choose between a cheap management regime prohibiting wood harvest but implicitly accepting some illegal charcoal production and a more expensive, but legal, harvest regulation through charcoal production quota. We conclude that the BAU scenario, where forest harvesting was prohibited de jure, but some illegal charcoal production was still undertaken, was the only viable management, which also is practically acceptable by both state and local communities.

Надземна фітомаса дерев ялини європейської в природних лісостанах

The article promotes to use tree social classes method for the selections of model trees while evaluate biomass in mature natural forest stands because of tree size variability. Average aboveground biomass of Norway spruce model trees calculated to be 542 ± 42 kg, which accumulate every year 6,1 ± 0,4 kg of dry matter and sequester 2,9 ± 0,2 kg of carbon from the atmosphere. We found a significant effect (α = 0,05) of a tree canopy position on a volume of accumulated biomass. Key words: natural stands, mature phase, Cheremosh watershed, Norway spruce, social class, tree size variability, aboveground biomass, mean annual increments, aboveground biomass components, sequestered carbon.

Modelo linear misto para o incremento em área basal de árvores individuais de cedro (&lt;i&gt;Cedrela odorata&lt;/i&gt; L.) na Amazônia ocidental, Brasil

http://dx.doi.org/10.5902/1980509810557Dados confiáveis de crescimento de árvores são importantes para o manejo florestal. Características da árvore como o tamanho, arquitetura da copa e índices de competição, associados aos dados de crescimento da árvore são utilizados com freqüência como variáveis preditoras. Entretanto, a efetividade desse tipo de variáveis na modelagem do crescimento de árvores tropicais é pouco conhecida. Nesta pesquisa, reconstruímos o incremento periódico em área basal (IPG) de árvores individuais deCedrela odorata,amostradas na floresta Amazônica, para desenvolver um modelo de crescimento utilizando preditores potenciais como: (1) tamanho da árvore; (2) dados morfométricos; (3) competição; (4) posição sociológica e infestação de lianas na copa. Apesar da alta variação no tamanho da árvore e no crescimento, observamos que estas variáveis descrevem muito bem o IPG em nível de árvore individual. O modelo misto ajustado apresentou alta eficiência (R2=92.7 %) e estimou para três anos o IPG com casca em árvores com diâmetro a altura do peito variando desde 10 a 110 cm. A altura total, grau de esbelteza e formal de copa demonstraram elevada influência no crescimento em área basal e explicaram a maior parte da variação no crescimento (R2 parcial=87.2%). Variáveis de competição apresentaram influência negativa no IPG, entretanto, explicaram cerca de 7% da variação total. A introdução do parâmetro aleatório no modelo de regressão (modelo misto) conduziu a uma melhor aproximação aos dados observados (acurácia) com predição mais realística quando comparado ao modelo fixo.

Analysing tree species and size diversity patterns in multi-species uneven-aged forests of Northern China

The diversity of complex multi-species uneven-aged forests is not easy to describe efficiently and meaningful. In the past, most importance has been assigned to species diversity and there is a wide range of approaches to quantifying this aspect of diversity. In woodlands, size diversity is another important dimension of biodiversity, as trees can be small or large and depending on their size play different ecological roles. Traditionally size diversity has often been neglected in diversity surveys of woody vegetation or considered as difficult to handle. We investigated the size and species diversity of two multi-species uneven-aged forests from monsoon- and subtropical/warm-temperate climate zones in northern China using non-spatial and spatially explicit forestry and diversity characteristics. We found that the analysis of both species and size diversity provided a much better understanding of diversity patterns in complex multi-species forests. Interestingly the relationship between size- and individual-based relative abundances follows a saturation curve. The analysis using non-spatial forestry and biodiversity characteristics led to approximately similar results in all four plots despite the very different woodland communities involved. However, with spatial measures we gained a deeper insight concerning the deviation from random distributions of species and size as well as interaction ranges of trees. We also found an aggregation of similar species and sizes at small inter-tree distances in the monsoon influenced climate and an aggregation of different sizes in the subtropical/warm-temperate climate zone. The use of second-order characteristics was instrumental in elaborating the subtle differences between the diversity of the two study areas and thus made an important contribution to this study.

Rest-site selection by fishers (Martes pennanti) in the eastern deciduous forest

Information on fisher (Martes pennanti) resource selection in deciduous forests of eastern North America is limited. We studied resting habitat selection in a fisher population that recolonized predominantly deciduous forest in Pennsylvania, USA, during 2006–2007. We quantified selection by comparing used and randomly selected available sites at 2 spatial scales: the rest structure and at the rest site (area surrounding rest structures). We identified 79 rest structures used by 15 fishers. The most common rest sites were live trees with cavities or broken tops (69%), with black cherry (Prunus serotina), American beech (Fagus grandifolia), and sugar maple (Acer saccharum) accounting for nearly 65% of tree use. Standing dead trees with cavities or broken tops accounted for 17% of rest structures. Ground-level structures (including burrows, rock piles, and root balls) comprised 14% of observations. Trees selected as rest structures were larger in diameter at breast height (55.3 cm ± 14.9 cm) than were trees at the center of random sites (28.8 cm ± 6.8 cm). Relative to random sites, important components of forest surrounding rest structures included structurally complex forest floors (based on coarse woody debris and rocky ground cover), canopy complexity, and diversity of tree condition class. Maintaining resting habitat for fishers in the eastern deciduous forest can be accomplished through management practices that encourage structurally diverse forests, including retention of coarse woody debris, and variation in tree size and condition. © 2013 The Wildlife Society.

Benchmarking and Calibration of Forest Vegetation Simulator Individual Tree Attribute Predictions Across the Northeastern United States

This study used permanent sample plot data from the USDA Forest Service’s Forest Inventory and Analysis database to benchmark and calibrate three key submodels of the Forest Vegetation Simulator-Northeast variant (FVS-NE). Model predictions for total tree height (ht) and 5-year diameter (dbh5) and height increment (ht5) for the 20 most abundant species did not indicate any serious spatial trends. FVS-NE predictions for total ht performed moderately well, as mean bias averaged 0.9 5.2 ft (mean SD) across all species. FVS-NE dbh5 predictions fell within 15% of observed values between 8.4 and 17.3% of the time and performed best for shade-tolerant species and worst for intermediate shade intolerants. For ht 5 , the number of predictions that fell within 15% of observed values averaged 7.7%. Submodel performance generally improved after calibrating FVS-NE predictions using tree size, site, and climate variables. After employing a calibrated dbh5, 5-year basal area growth continued to be underpredicted across all ecoregions and forest types. Results indicate that (1) an assessment of overall model performance should be conducted if calibrated submodels are used and (2) alternative modeling strategies be explored to better represent the allometry and growth of the important trees species across the northeastern United States.

Modelling tree size diversity from airborne laser scanning using canopy height models with image texture measures

The aim of this study is to investigate the relationships between the plot-level tree size diversity and variables derived from airborne laser scanning (ALS) data, which is a type of LiDAR measurement. We conducted a study using forest stands with a range of managed and near-natural stands with a broad range of species. 33 Plots that represent the forest stand variety in the study area were sampled; within each plot four biophysical variables were measured by ground-based methods, these were height (TH), diameter at breast height (DBH), crown length (CL), and crown width (CW). The resultant tree size diversity was parameterised as Lmoments (t) statistics and compared with both point-based and grid-based laser scanning diversity variables. Point-based measures included the ratios of the Percentile means (P99/P25, P99/P50, P99/75, and P99/P90), Coefficient of variation, Skewness, Kurtosis, and Lmoments (t). The grid-based texture measures derived from the ALS Canopy Height Models (CHMs) included first-order texture, Standard Deviation of Grey Levels (SDGL), and three second-order texture measures, including Contrast, Entropy and Correlation. Furthermore, we tested the influence of scale by analysing the effect of grid cell sizes when generating CHMs from the raw point cloud ALS data. Using linear regression analysis, we show that the grid-based texture measures are superior predictors of tree height diversity than the point-based metrics. Sixty percent of the variance in the tree height diversity and 51% of the variance in the DBH Diversity were explained by the SDGL and Correlation texture measures, respectively (p<0.01). The associations between the texture features and the CL Diversity and CW Diversity were weaker compared to the TH Diversity and DBH Diversity (The highest R2 was 0.46 and 0.45, respectively, p<0.01). While the CHM calculated from a 3×3m grid cell had the strongest correlation with TH Diversity (0.60, p<0.01), the CHMs calculated from 1×1m and 2×2m cell size had the strongest association with DBH Diversity (0.51, p<0.01). Combining selected point- and grid-based variables accounted for up to 85% of the variance of tree height diversity, 68% of the variance of DBH Diversity and 52% of the variance of CL Diversity. Our study shows that the combination of laser-based height percentile ratios and texture measures derived from the ALS–CHM can be used to estimate tree size diversity across forest landscapes.

Multifunctional management of mountain reforestations: thoughts and perspectives from a case study in Central Italy

The conifer reforestations established during the last century in many mountainous areas of Central and Southern Italy allowed the restoration of thousands of hectares of degraded bare lands. During the last sixty years many social and environmental functions were added to such forests and now they require a multifunctional management approach. A 100-years old reforestation with black pine (Pinus nigra Arnold) located in a mountain tourist area and within a Natura 2000 site in Central Italy was taken into consideration as a case study. The stands, although even-aged and dense, have a diversified structure as a consequence of localized wind throws and the growth of an underlayer of hardwoods. The traditional,timber production-oriented management based on strip clear cutting has shown to be inapplicable in such a context. Systemic silviculture grasps this challenge as it assumes as fundamental management goal the search for the functional efficiency of the forest ecosystem. In such a perspective silvicultural practices are guided by an adaptive approach, based on trial and error, rather than on so-called normalisation schemes. Starting from the concept that forest is a complex, self-regulating, dynamically changing system,a management trajectory is proposed to foster the gradual succession of the pine stands towards different types of pure and mixed hardwood forest according to site conditions. The basic silvicultural criterion is to reduce gradually the pine cover by thinning and opening of small gaps in order to increase tree age and size diversity. The public incentives necessary to implement this sort of management are justified by the goal of increasing the functionality and resilience of the forest system: both elements can reduce the risk of damages for the forests. This paper aims to provide general considerations on such issues in the form of a commentary discussion with reference to the considered case study.