Indicator Of Site Quality Research Articles

Predicting carbon storage of mixed broadleaf forests based on the finite mixture model incorporating stand factors, site quality, and aridity index

The diameter distribution function (DDF) is a crucial tool for accurately predicting stand carbon storage (CS). The current key issue, however, is how to construct a high-precision DDF based on stand factors, site quality, and aridity index to predict stand CS in multi-species mixed forests with complex structures. This study used data from 70 survey plots for mixed broadleaf Populus davidiana and Betula platyphylla forests in the Mulan Rangeland State Forest, Hebei Province, China, to construct the DDF based on maximum likelihood estimation and finite mixture model (FMM). Ordinary least squares (OLS), linear seemingly unrelated regression (LSUR), and back propagation neural network (BPNN) were used to investigate the influences of stand factors, site quality, and aridity index on the shape and scale parameters of DDF and predicted stand CS of mixed broadleaf forests. The results showed that FMM accurately described the stand-level diameter distribution of the mixed P. davidiana and B. platyphylla forests; whereas the Weibull function constructed by MLE was more accurate in describing species-level diameter distribution. The combined variable of quadratic mean diameter (Dq), stand basal area (BA), and site quality improved the accuracy of the shape parameter models of FMM; the combined variable of Dq, BA, and De Martonne aridity index improved the accuracy of the scale parameter models. Compared to OLS and LSUR, the BPNN had higher accuracy in the re-parameterization process of FMM. OLS, LSUR, and BPNN overestimated the CS of P. davidiana but underestimated the CS of B. platyphylla in the large diameter classes (DBH ≥18 ​cm). BPNN accurately estimated stand- and species-level CS, but it was more suitable for estimating stand-level CS compared to species-level CS, thereby providing a scientific basis for the optimization of stand structure and assessment of carbon sequestration capacity in mixed broadleaf forests.

A new index integrating forestry and ecology models for quantitatively characterizing forest carbon sequestration potential ability in a subtropical region

Due to the important role of forests in carbon neutrality, it is a big task in accurately calculating and predicting forest carbon storage and carbon sink capacity in recent years. However, considering the factors on the capacity of forest carbon sequestration, ecologists and foresters consider different models to evaluate the forest carbon sink ability at different scales, with foresters focusing more on forest growth models, while ecologists adding more climate and environmental factors, which may result in inconsistent results in carbon storage. Therefore, constructing an integrated model by combining the forestry and ecology models is essential for accurately quantifying and characterizing the forest carbon sink potential at the regional scale. Here, we proposed a new forest carbon sink potential index (FCSPI), which is defined as fractional deficiency of the current forest carbon to its maximum level, based on forest permanent plots, climate, and edaphic data to evaluate the forest sink potential ability from stand level to zonal scale across the northern subtropical zone in Hubei province, China, which coupled the stand growth model and climate-productivity model. The results at stand level showed that the R2 and RMSE of FCSPI were 0.78 and 0.072 respectively, which indicated that the FCSPI is an intuitive, highly practical, straightforward, easy, and rapid to implement methodology for forest carbon sequestration assessment. Moreover, FCSPI can conveniently extended from stand scale to zonal scale based on the site quality index for carbon sink (SIC) and stand age variables, which were derived from the opened climate, edaphic, and topographic data. The results of wall-to-wall FCSPI across the subtropical forest in Hubei province reveal the current and future carbon potential sequestration, which can help managers to focus on forest management for climate-smart actions and planning in forest ecosystem services framework.

Fish Assemblages as Ecological Indicators in the Büyük Menderes (Great Meander) River, Turkey

This research describes fish assemblages and associated aquatic ecosystem degradation patterns in the Büyük Menderes River, one of Turkey’s most important Anatolian basins. Using standard electrofishing, 44 river sites were sampled throughout the basin accounting for the distribution and abundance of 20 native and seven non-native species, totaling 13,535 fish specimens. At each sampling site, anthropogenic pressures were assessed, and information was gathered to determine the degree of human-induced degradation that may affect fish and their habitats; each site was scored on the basis of a site quality index (SQI). Using the best-available relatively less-degraded river sites, cluster analyses of the samples defined six fish assemblage river types. Further classification of all fish samples utilizing bipartite network analysis resulted in comparable assemblage groupings. The European Fish Index (EFI+) with minor adaptations was applied for assessing river ecological integrity at all sampled sites in order to explore the utility of this widely used index. The EFI+ index results correlated with scores of the SQI but provided a very narrow assessment range, thus failing to accurately and consistently assess the severity of anthropogenic degradation. We recommend a new multimetric index to be developed for the Western Anatolian Ecoregion, of which this basin is a part. The data and insights gained from this exercise may help continue fish-based indicator development for policy-relevant management and conservation in Turkey’s rivers.

Marketing statistical analysis of the website of the University of Customs and Finance

The aim of the article. Analyze the website of the higher education institution (University of Customs and Finance) in Dnipro in comparison with other educational institutions' websites; on the basis of the conducted research, develop the design of the main page of the site. The results of the analyses. Based on the assessment of university websites for 2023, we can conclude that the largest number of visits to the website of the NTU "Dniprovska Polytechnic", and the least number of visits to the website of the University of Customs and Finance. Dnipro State Agrarian and Economic University (DDAEU) spent the longest time on the site and viewed 12 pages, the least interested was the information posted on the Dnipro State Academy of Construction and Architecture, number of pages viewed – 2, 5, Time of stay on the UMSF website is 5 minutes. 7 p. and an average of 2.7 pages were viewed. This is a low value of the indicator and indicates that the content posted on the website of the Dnipro State Agrarian and Economic University was the most interesting, and the least on the website of the Dnipro State Academy of Construction and Architecture, the percentage of rejections on website of the University of Customs and Finance is 46.45%. Foreign users were most interested in information on the website of the Dnipro National University named after O. Honchar, while foreigners were least interested in the website of the University of Customs and Finance. All the universities we studied use social networks to spread information about their calling. Based on the results of the research, we can conclude that the website of the Dnipro University named after A. Nobel has the best design and navigation, and the website of the Dnipro National University named after O. Honchar has the worst indicators. The website of the studied higher education institution (University of Customs and Finance) has 64 points according to experts. In general, it has convenient navigation, simple design, textual content is accompanied by illustrative content, meaningful information content. A negative indicator is the lack of a site search button on the main page. In addition, contacts for feedback and links to social networks are at the very bottom of the page. Based on the results of the SEO analysis of the site content, we can conclude that the Dnipro National University of Railway Transport website has the largest number of symbols. V. Lazaryan, and the smallest - the Dnipro State Academy of Construction and Architecture. The UMSF website has 14,292 characters. The largest number of unique words on the UMSF website. This means that the text has a higher semantic index. Low semantic index on the PDABA website. The highest "nauseousness" of the text on the website of NTU "Dniprovska Polytechnic", so search engines regard such an article as low-quality. The best content for search engines is the text on the website of the Dnipro State Academy of Construction and Architecture. The content of the website of the University of Customs and Finance is within the norm. "Perfect" website according to the Zipf index of Dniprovska Polytechnic National Technical University. The least naturalness of the text on the page is Dnipro University named after A. Nobel. The text on the UMSF website is considered to be spammed if the quality of the text is 47% according to Zipf's law. The highest site quality index is 440 (Dnieper State Academy of Construction and Architecture), meaning users are satisfied with the site. The lowest level of trust in the portal of the University of Customs and Finance. The results of the calculation of the integral index showed that the Dnipro State Agrarian University has a critical condition in the use of the website, and the satisfactory use of the Internet site has the Dnipro University named after A. Nobel, the state of use of the site of the Dnipro State Academy of Construction and Architecture is assessed as tense. Conclusions and perspectives for further research. To improve the functioning of the website of the University of Customs and Finance, it is necessary to: add an analytics counter to the site, remove duplicates of the main page, improve the site architecture and add internal linking, add a separate postal address for placement on the site, develop a strategy to improve the number and quality of backlinks , improve site security, redirect to the main site address, include keywords in the meta title and meta description, increase the page title tag, add an English version of the site, change the site design. The proposed measures will help to improve the technical characteristics of the site, and, therefore, to occupy better positions in Google's search results. The design change will contribute to better recognition of the university, improvement of the communicative component.

Modelling height growth of temperate mixedwood forests using an age-independent approach and multi-temporal airborne laser scanning data

Forest inventories provide information regarding the status of a range of attributes as well as enabling predictive applications. Growth and yield models are essential tools for sustainable forest management, importantly enabling projections of future forest conditions (such as height growth). To select the most appropriate growth trajectory, site index models are commonly used to quantify the productivity of a given site. However, applying these methods to more complex, multi-species, and multi-age forests can be challenging due to deviations from the assumptions made for even-aged stands. In this study, we provide a comprehensive indicator of site quality for more complex and irregular stand structures by developing age-independent height growth models for various forest types. We used multi-temporal airborne laser scanning (ALS) data from 2005, 2012, and 2018 in the Great Lakes–St. Lawrence forest region in southern Ontario, Canada. The stochastic differential equations approach was used to develop age-independent height models and a height growth rate index as a proxy of site quality from ALS-derived height metrics. We evaluated the sensitivity of the models using two different modelling approaches and found that the model that incorporated data from both periods (i.e., 2005–2012 and 2012–2018) generally provided the lower root mean square error (RMSE) value for most forest types. Overall, our results showed good agreement between the model predictions of top height and observed top height in 2018 from field plots for all forest types. We demonstrated the use of these models by creating a system of height growth curves for each forest type and producing a map of site quality for a mixedwood forest (∼10,000 ha) at a spatial resolution of 25 m. The approach developed herein leverages the accurate, spatially detailed characterization of canopy heights afforded by ALS data and is independent of stand age, which is challenging to measure accurately and is typically not available at a spatial resolution that is commensurate with the ALS data. Additionally, the demonstrated approach can be adapted to other data sources that accurately capture canopy heights (i.e., digital aerial photogrammetric or DAP), thereby increasing the possible geographic extent of height growth estimates.

Litterfall dynamics in Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula) stands in Estonia

Canopy litterfall represents an essential aboveground flux in every forest ecosystem, affecting soil carbon and nutrient dynamics as well as soil fertility. However, despite the important role of the canopy litter flux in ecosysteḿs functioning and carbon sequestration, litterfall dynamics is still poorly studied in hemiboreal forests. The main aim of the current study was to estimate average annual litter fluxes in Scots pine, Norway spruce and birch (Betula pendula and Betula pubescens) stands, as well as to compile regional litter models for estimating the annual litter flux. The annual litter flux from a total of 33 pine, 15 spruce and 21 birch stands, with 85, 43 and 53 datapoints, respectively, was included in the study.Although the annual litter flux depended on site quality index and stand age, no significant relationship was established between stand basal area and litter flux. Average annual canopy litterfall was similar for the studied tree species, being 3.24 ± 0.14 for pine, 3.62 ± 0.16 for spruce and 3.22 ± 0.07 t ha−1 yr−1 for birch across the stands of different ages. For all studied tree species, the relative proportion of needles or leaves in the total annual litter flux declined with stand age, due to the increased share of twigs and other fractions in the litter of older stands. The developed models of the litter flux allow to estimate the annual litter production of the canopy for the studied tree species on the basis of site quality index and stand age.

Analysis of internal factors affecting the health condition of mangrove forests in the coastal area of East Lampung Regency

The surrounding community widely uses mangrove forests as a fulfillment of life. This requires an efforts to preserve the mangrove forest so that no damage occurs. This study aimed to determine the internal factors that affect the health condition of mangrove forests. The research method used to obtain internal factor data is by measuring the ecological indicators of forest health using the Forest Health Monitoring (FHM) method, then the data is processed by the Multiple Regression Analysis method using SPSS 20 through data on internal factors of mangrove forest health which are analyzed for their effect on health conditions of the mangrove forest. The results showed that the significant value of the regression was 0.008 ((α = 0.05) > 0.008), this means that simultaneously the independent variables (tree damage, crown damage, Cation Exchange Capacity-CEC, and biodiversity have an effect on the dependent variable (mangrove forest health) at the level of = 5%. Furthermore, through individual regression coefficients from internal factor data, it is found that the internal factors of biodiversity indicators in measurements 1 and 2 and crown conditions in the second measurement do not affect forest health conditions. Therefore, this research concludes that the internal factors that affect the level of forest health in the first measurement are vitality indicators (tree damage/cluster Plot Index-CLI and crown condition) and site quality indicators (CEC). Meanwhile, in the second measurement, there was a change in the crown condition parameters, which did not significantly affect forest health.

Estimating the effects of fish quality and size on the economic value of fishing in Oklahoma streams and rivers: A revealed preference and contingent behavior approach

Fishing in Oklahoma’s rivers and streams provides a unique experience for anglers in the state. Despite its popularity, information on total demand and economic benefits associated with stream fishing is limited in the state. Research on the role of site quality indicators, such as fish size and quantity, on recreational fishing has shown mixed results. Whether fish size or quantity plays an important role in determining fishing demand and economic value may have important management implications. We estimated the demand and economic value of fishing under varying scenarios by using anglers’ responses to hypothetical behavioral questions related to fishing in Ozark Highland streams and rivers in Oklahoma. We asked how intended number of trips might change in the future given hypothetical increases in catch rates of fish, catch rates of trophy-sized fish, and catch rates of preferred fish species, in combination with anglers’ trip-related data. Under current conditions, we estimated consumer surplus per person per trip to be $55 and aggregate value across all stream anglers in Oklahoma to be $68.51 million. Changes in marginal benefits varied among hypothetical scenarios of fish size and abundance but was maximized with a 25% increase in catch rates of trophy-sized fish. The study findings contribute to the understanding of the economic benefit of fishing in streams and suggest that fish size, rather than fish quantity, is more important to stream anglers in the area.

A Dynamic Stand Growth Model System for Loblolly Pine Responding to Mid-Rotation Treatments

Intensive loblolly pine (Pinus taeda L.) plantation management in the southeastern United States includes mid-rotation silvicultural practices (MRSP) like thinning, fertilization, competitive vegetation control, and their combinations. Consistent and well-designed long-term studies considering interactions of MRSP are required to produce accurate projections and evaluate management decisions. Here we use longitudinal data from the regional Mid-Rotation Treatment study established by the Plantation Management Research Cooperative (PMRC) at the University of Georgia across the southeast U.S. to fit and validate a new dynamic model system rooted in theoretical and biological principles. A Weibull pdf was used as a modifier function coupled with the basal area growth model. The growth model system and error projection functions were estimated simultaneously. The new formulation results in a compatible and consistent growth and yield system and provides temporal responses to treatment. The results indicated that the model projections reproduce the observed behavior of stand characteristics. The model has high predictive accuracy (the cross-validation variance explained was 96.2%, 99.7%, and 98.6%; and the prediction root mean square distance was 0.704 m, 19.1 trees ha−1, and 1.03 m2ha−1 for dominant height (DH), trees per hectare (N), and basal area (BA), respectively), and can be used to project the current stand attributes following combinations of MRSP and with different thinning intensities. Simulations across southern physiographic regions allow us to conclude that the most overall ranking of MRSP after thinning is fertilization + competitive vegetation control (Fert + CVC) > fertilization only (Fert) > competitive vegetation control only (CVC), and Fert + CVC show less than additive effect. Because of the model structure, the response to treatment changes with location, age of application, and dominant height growth as indicators of site quality. Therefore, the proposed model adequately represents regional growth conditions.

Characterizing primate home‐ranges in Amazonia: Using ferns and lycophytes as indicators of site quality

AbstractThe habitats present in research sites across Amazonia have usually been characterized only very broadly, for example, as inundated or non‐inundated (terra firma) forests. However, within each of these categories there is considerable variation in soil properties and floristic composition. This variation is likely to determine habitat quality for animal populations through its effects on primary productivity and food availability, thereby affecting carrying capacity. Therefore, comparison of edaphic properties across sites could provide new insight into which factors affect animal foraging patterns, population densities, and home‐range sizes. We provide an example from Estación Biológica Quebrada Blanco in Peruvian Amazonia, where behavioral studies on primates (especially tamarins) have been conducted for more than three decades but little is known about the edaphic or floristic characteristics of the forest they occupy. We used indicator plant species to estimate and map soil base cation concentration and its variability at Estación Biológica Quebrada Blanco. We found that soils in the study area are relatively cation‐poor in a western Amazonian context, which probably translates into low primary productivity. Some differences in soils among the home‐ranges of three tamarin groups were also observed, illustrating the usefulness of the method for detailed habitat mapping.Abstract in Spanish is available with online material.

Self-thinning tree mortality models that account for vertical stand structure, species mixing and climate

Self-thinning dynamics are often considered when managing stand density in forests and are used to constrain forest growth models. However, self-thinning relationships are often quantified using only data at a conceptualised self-thinning line, even though self-thinning can begin before the stand actually reaches a self-thinning line. Also, few self-thinning relationships account for the effects of species composition in mixed-species forests, and stand structure such as relative height of species (in mixtures), and/or size or age cohorts in uneven-aged forests. Such considerations may be important given the effects of global climate change and interest in mixed-species and uneven-aged forests.The objective of this study was to develop self-thinning relationships based on changes in the tree density relative to mean tree diameter, instead of focusing only on data for state variables (e.g. tree density) at the self-thinning line. This was done while also considering how the change in tree density is influenced by site quality and stand structure (species composition and relative height).The relationships were modelled using data from temperate Australian Eucalyptus plantations (436 plots), subtropical forests in China (88 plots), and temperate forests in Switzerland (1055 plots). Zero-inflated and hurdle generalized linear models with Poisson and negative binomial distributions were fit for several species, as well as for all-species equations.The intercepts and slopes of the self-thinning lines were higher than many published studies which may have resulted from both the less restrictive equation form and data selection. The rates of self-thinning often decreased as the proportion of the object species increased, as relative height increased (species or size cohort became more dominant), and as site (quality) index increased. The effects of aridity varied between species, with self-thinning increasing with aridity index for Abies alba, Pinus sylvestris, Quercus petraea and Quercus robur, but decreasing with aridity index for Eucalyptus nitens, Fagus sylvatica and Picea abies as sites became wetter and cooler. Self-thinning model parameters were not correlated with species traits, including specific leaf area, wood basic density or crown diameter – stem diameter allometry. All-species self-thinning relationships based on all data could be adjusted using a correction factor for rarer species where there were insufficient data to develop species-specific equations.The approach and equations developed could be used in forest growth models to calculate how the tree density declines as mean tree size increases, as height changes relative to other cohorts or species, as species proportions change, and as climatic and edaphic conditions change.

Level of damage on sengon stand based on tree vitality indicators at sengon community forest in Serang District, Banten Province

Sengon plantation is the primary commodity of the community forests, which produces timber with high economic value, especially in Java Island. However, now the condition of sengon stands in Java Island, pests and diseases have attacked most. The information about the health and the severity of the stands due to pests and diseases is beneficial for determining stand productivity and investment security. The purpose of this activity is to determine the level of damage on sengon stands at various locations in Serang Regency, Banten, based on indicators of tree vitality. The method used to determine stand health is Forest Health Monitoring (FHM), which includes using tree vitality indicators and site quality indicators as a basis for assessment. The observation plot was carried out at 3 locations determined purposively based on the flat distance from the beach, which is ≤ 2 km; 2> X≤ 4 km; 4> X ≤6 km. The results showed that the average percentage of healthy sengon trees was still quite high (82.7%), but the level of damage to stands was moderate. The most common type of damage is gummosis (distance ≤ 2 km and > 4-6 km) and boktor (> 2-4 km). Many tree damage occurs in the main branch location found in the live canopy section (code 6), especially in plots that are 2> X≤ 4 km from the coastline and lower stem (distance ≤ 2 km). However, no damage was found at the root location (code 1), shoots (code 8) and leaves (code 9). The damage of the stem causes a decrease in wood production because the damaged at part of the stem cannot be used anymore. Visual Crown Ratio of sengon trees tends to be low due to young trees so that the canopy is not maximal. Maintenance activities, as well as mixed planting techniques with intercropping plants and other woody plants, can prevent sengon plants from attacking pests and diseases.

Мониторинг российских сайтов архивных учреждений (интернет-ресурсов) с точки зрения поисковой оптимизации

Sites as virtual representatives of memory institutions on the Internet perform many functions of these institutions. Currently, archival site building is developing quite actively, and the attention of researchers is focused on organization, data layout, and design. One of the most important tasks of a memory institution is to attract users. However, literature has been paying insufficient attention to optimization of the sites’ search engines. Thus, the author has turned to studying the sites of the federal archives in terms of their search engine optimization. Comparative analysis of the sites has been carried out according to such criteria as site quality index, number of external links to the resource, total social activity, as well as adaptability of the site for mobile devices. The PR-CY.ru service has been used as an analysis tool. Site Quality Index (IQS) is a new indicator introduced by Yandex instead of citation index to characterize the site’s usefulness to the user, taking into account a large number of factors and more truthfully reflecting the state of the information resource. According to the study, the State Archive of the Russian Federation (GARF) and the State Archive of Ancient Acts (RGADA) have the highest value of IQS, and are, thus, good sites from the user’s point of view. The majority of sites of federal archives have low IQS and need further improvement. An important indicator in website promotion is number of links to the website. In number of external links, the GARF and the Russian State Archive of the Navy (RGAVMF) are in the lead, while the Russian State Archive of Social and Political History (RGASPI) and the Russian State Archive of Literature and Art (RGALI) number most links from social networks. Sites of the RGAVMF and the Russian State Military Archive (RGVA) are optimized for mobile devices. Few sites have responsive design, which complicates access to their data. The author notes the need for regular site monitoring by means of web analytics. As a free site analysis tool, she recommends the PR-CY.ru service.

The Standard Output of Forest Index ‒ an Indicator of Site Quality

The Standard Output of Forest Index (SOFI) describes the ability of forests to produce financial value from wood production based on the standardized monetary value of the mean annual increment of the potential final harvest relative to a reference forest type. It can be applied on regions where the forests can be classified into major tree species or species groups and into site classes. The potential volume of final wood harvest is estimated through yield tables. Using the share of lowquality and high-quality wood product groups in the final harvest, and their respective standardized price, the output value of the final harvest is expressed and then divided by the rotation age. This standardized output is compared to a reference forest type identified by its tree species and site class, and multiplied by 10 points. The SOFI of the reference forest, therefore, is 10, while higher values represent higher potential output and smaller values represent smaller potential output. With the necessary modifications, the SOFI can be applied to uneven-age forests as well. It can primarily be used to describe and compare the financial output potential of larger forest areas.

Assessing site form as an indicator of site quality in even-aged Pinus radiata D. Don stands in north-western Spain

Key messageSite form and site index have shown similar precision for estimating site quality in even-agedPinus radiataD. Don stands in north-western Spain. Additionally, SF presents the advantage that it does not require stand age information and can therefore be used in a wider set of situations in the forestry practice.ContextEstimation of site quality is essential for characterizing, monitoring and predicting forest resources. Site index (i.e. the dominant height of the stand at a reference age) is ordinarily used to estimate site quality; however, this index is only useful for even-aged stands of known age. By contrast, SF is age-independent as it uses the dominant height of the stand at a reference dominant diameter.AimsThe aim of this study was to compare the performance of SF and SI for site quality estimation in even-aged P. radiata stands.MethodsDynamic equations derived with the Generalized Algebraic Difference Approach (GADA) from the Hossfeld IV base model were fitted to predict site quality with both SI and SF. SF predictions were compared with SI regarding variability within the same plot and consistency in site quality predictions, using the observed maximum mean annual volume increment (MAI) as a direct measure of site quality.ResultsBoth approaches showed good performance in model fitting and provided similar goodness-of-fit statistics and variability in the predictions. However, SI performed slightly stronger when related to MAI.ConclusionSF performed adequately in estimating site quality for even-aged P. radiata stands, with results comparable to those obtained using traditional SI.

Evaluating and modeling variation in site-level maximum carrying capacity of mixed-species forest stands in the Acadian Region of northeastern North America

Currently no universal approach exists to estimate regional site-level maximum carrying capacity in terms of stand densityindex (SDIMAX) of mixed species stands across contrasting forest ecosystems. Regional research efforts that account forinfluential stand-level variables and species traits are needed to reliably derive SDIMAXunder varying environmental conditions and stand characteristics. This study used regionally comprehensive forest inventory data from various permanentsampling efforts to evaluate the effects of contrasting biotic and abiotic stand- and site-level factors on SDIMAXof multiple-species, structurally heterogeneous stands of the climatically diverse Acadian Forest Region of North America. Specifically,we aimed to i) quantify the stand-level maximum size-density line for an array of forest stands found across the study area,irrespective of stand structure; ii) evaluate the relationship between this stand-specific estimate of SDIMAXand various other stand-level attributes; and, iii) develop a generalized SDIMAXprediction model using SDIMAXestimates from objective i) aswell as potential regional drivers of SDIMAXfrom objective ii). The most influential stand-level factors on SDIMAXwere proportion of total stand basal area in hardwood species, basal area weighted mean specific gravity, range in stem diameter, andspecies diversity. Direct climatic variables were not included in our SDIMAXprediction model due to the limited variationexplained, but relationships with elevation and a site quality index based on these climatic variables were. Overall, we con-clude that i) variation in SDIMAX appears to be mostly driven by the softwood to hardwood ratio of the mixed species,structurally complex stands evaluated in our study and ii) the general approach offers a viable framework for estimating sitemaximum carrying capacity at a regional-scale and effectively managing stand density accordingly.

Species-specific, pan-European diameter increment models based on data of 2.3 million trees

BackgroundOver the last decades, many forest simulators have been developed for the forests of individual European countries. The underlying growth models are usually based on national datasets of varying size, obtained from National Forest Inventories or from long-term research plots. Many of these models include country- and location-specific predictors, such as site quality indices that may aggregate climate, soil properties and topography effects. Consequently, it is not sensible to compare such models among countries, and it is often impossible to apply models outside the region or country they were developed for. However, there is a clear need for more generically applicable but still locally accurate and climate sensitive simulators at the European scale, which requires the development of models that are applicable across the European continent. The purpose of this study is to develop tree diameter increment models that are applicable at the European scale, but still locally accurate. We compiled and used a dataset of diameter increment observations of over 2.3 million trees from 10 National Forest Inventories in Europe and a set of 99 potential explanatory variables covering forest structure, weather, climate, soil and nutrient deposition.ResultsDiameter increment models are presented for 20 species/species groups. Selection of explanatory variables was done using a combination of forward and backward selection methods. The explained variance ranged from 10% to 53% depending on the species. Variables related to forest structure (basal area of the stand and relative size of the tree) contributed most to the explained variance, but environmental variables were important to account for spatial patterns. The type of environmental variables included differed greatly among species.ConclusionsThe presented diameter increment models are the first of their kind that are applicable at the European scale. This is an important step towards the development of a new generation of forest development simulators that can be applied at the European scale, but that are sensitive to variations in growing conditions and applicable to a wider range of management systems than before. This allows European scale but detailed analyses concerning topics like CO2 sequestration, wood mobilisation, long term impact of management, etc.

Seasonal dynamics of forage for red deer in temperate forests: importance of the habitat properties, stand development stage and overstorey dynamics

The recent increase of red deer Cervus elaphus population and consequent damage caused by their herbivory impact increasingly concern foresters and farmers in Slovakia as well as in other European countries. Thus, the topic of vegetation—deer interactions with focus on forage production is especially relevant for developing adequate management guidelines. Using data from 320 sampling plots, we estimated the overall availability of all forage items seasonally consumed by red deer in commercial temperate forests and identified the main factors affecting forage availability in summer and winter. We found that cutblocks were the most productive habitats throughout the year irrespective of the site quality. Summer forage biomass peaked at ≈8 years and winter forage biomass at ≈10 years following felling, then slowly declined as the cutblocks aged and the canopy increased. Understorey vegetation production in mature forests was determined primarily by light availability, as the major driving factor of vegetation growth in the closed‐canopy forest ecosystems, and to a lesser extent by a site quality. We suggest that the site quality index that is traditionally used in forestry is not an efficient predictor of the forage availability for red deer, and estimations of the forage potential of hunting grounds should incorporate more complex models to evaluate carrying capacity of the landscape.

Modelling crown width–diameter relationship for Scots pine in the central Europe

Crown width–diameter relationship, which is significantly influenced by various characteristics, was modelled using tree and stand measures, and plot-level random effect parameters. A proposed model precisely predicts crown width of Scots pine. Crown size is significantly correlated with growth and biomass of other parts of a tree, and therefore crown measures are used as predictors to develop tree growth and biomass models. We modelled crown width–diameter at breast height (DBH) allometry using data from permanent sample plots located in both monospecific and mixed species stands of Scots pine (Pinus sylvestris L.) in various parts of the Czech Republic. Among various predictors evaluated, dominant height (HDOM), height-to-DBH ratio (HDR—also known as a tree slenderness coefficient), height to live crown base (HCB), relative spacing index (RS), and basal area proportion of a species of interest (BAPOR) significantly contributed to the variations in the crown width–DBH allometry. The sample plot-level random effect parameters, which account for stand heterogeneity and randomness caused by various stochastic factors, were included through the mixed-effects modelling approach. Heteroskedasticity in the residuals was reduced through the integration of a power variance function with DBH as an independent variable. Both mixed-effects model and ordinary least square (OLS) model described more than two-thirds of the total variations in the crown width–DBH allometry with no significant trend in the residuals. The model showed that crown width increased with increasing site quality (increasing HDOM) and relative spacing index (increasing RS), and decreasing species mixture per sample plot (increasing BAPOR). However, crown width decreased with increasing tree slenderness coefficient (increasing HDR) and height to live crown base (increasing HCB). Model validation by splitting data also confirmed a high precision of the model, because it described most of the variations in the crown width–DBH allometry with no significant trend in the prediction errors. Because of more attractive fit statistics and higher prediction accuracy than that of the OLS model, the mixed-effects model with the random effect parameters estimated from crown width measurements of a sub-sample of four randomly selected Scots pine trees per sample plot is suggested for application. Application of the crown width model may have various implications that are briefly mentioned in the article.

Constructing site quality curves and productivity assessment for uneven-aged and mixed stands of oriental beech (Fagus oriental Lipsky) in Hyrcanian forest, Iran

ABSTRACTIn the domain of sustainable forest management, site productivity assessment is a major forestry topic. The reliable estimates of site quality are crucial for improved predictions of timber yields and for meaningful simulation studies. Site quality curves were constructed and assessed for beech forests in a Hyrcanian forest, located in the north of Iran. A measure of the site quality concept known as site form (i.e. the expected mean height at 75 cm diameter at breast height) was used. One hundred and twenty seven 0.1 ha circular sample plots were established covering soil and topographic variations in Tarbiat Modares University Experimental Forest. Site productivity curves were constructed using a difference equation approach in the context of the Chapman-Richards model and the Edminster el al. (1991) method. After estimating site form for each plot, they were divided into three categories (poor, medium, and good). Ordinal logistic regression model of site form on soil and topographic variables were fitted using the free statistical programming language ‘R’. The results showed that only the percentage of clay, altitude, and phosphorous were significant at 0.05 significance level (Nagelkerke pseudo-R-squared = 51.58%). The results of this study suggest that site form appears to be a potentially useful indicator of site quality in mixed and uneven-aged forests.