An algorithm-based approach for tree selection in continuous cover forestry

The main organic carbon stocks in the predominantly boreal forests of Russia are contained in the soil pool. Quantitative estimates of soil pool carbon stocks vary considerably. This is due to the high temporal and spatial variability of the organic carbon content in soils, the lack of empirical data for a number of regions, the difference in approaches to assessing soil carbon and the density of soil horizons, the thickness of the soil layer taken into account, the inclusion of forest litter carbon stocks, the peat layer, etc. In 2020, the 1st cycle of the State Forest Inventory in Russia was completed using a selective statistical method. Forest inventory characteristics, environmental indicators and information on forest growth conditions have been obtained for 69.1 thousand permanent sample plots. The limited availability of field descriptions of soils necessitates the testing of an integrated approach to using the State Forest Inventory data in the software environment of geographic information systems in combination with open-access digital resources to assess carbon stocks in the soil pool. A methodology for quantitative assessment of carbon stocks in the forest soil pool has been developed and experimentally tested. The proposed methodology includes: 1) geo-referencing of sample plots; 2) bringing the initial data of the State Forest Inventory on soil types to a standard classification; 3) using the digital resources of the World Data Center for Soils (SoilGrids) to obtain reference average carbon stocks on the network of sample plots surveyed during the State Forest Inventory; 4) calculating the total carbon stock in the soil pool of forest lands based on the average carbon stocks of SoilGrids and areas of standard soil types based on the data of the State Forest Inventory. The experimental testing has been carried out using the Republic of Karelia as an example. The sample size has been 667 permanent sample plots. According to the results of the study, the predominant complex of soil types – illuvial-ferruginous and illuvial-humus podzols (without division), illuvial low- and high-humus podzols – covers an area of 7.28 mln ha. The total carbon stock in the 0–30 cm soil layer for the forest lands of the Republic of Karelia is estimated at 773.9 Mt C with an average of 79.1 t C/ha.

The province of Ontario holds approximately 70.2 million hectares of forests: about 17% of Canada’s and 2% of the world’s forests. Approximately 21 million hectares are managed as commercial forests, with an annual harvest in the early part of the decade approaching 200 000 ha. Yield tables developed by Walter Plonski in the 1950s provide the basis for most wood supply calculations and growth projections in Ontario. However, due to changes in legislation, policy, and the planning process, they no longer fully meet the needs of resource managers. Furthermore, Plonski`s tables are not appropriate for the range of silvicultural options now practised in Ontario. In October 1999, the Canadian Ecology Centre- Forestry Research Partnership (CEC-FRP) was formed and initiated a series of projects that collectively aimed at characterizing, quantifying and ultimately increasing the economically available wood supply. Comprehensive, defensible, and reliable forecasts of forest growth and yield were identified as key knowledge gaps. The CEC-FRP, with support from the broader science community and forest industry, initiated several new research activities to address these needs, the results of which are outlined briefly in this paper. We describe new stand level models (e.g., benchmark yield curves, FVS Ontario, stand density management diagrams) that were developed using data collected from permanent sample plots and permanent growth plots established and remeasured during the past 5 decades. Similarly, we discuss new height–diameter equations developed for 8 major commercial tree species that specifically account for stand density. As well, we introduce a CEC-FRP-supported project aimed at developing new taper equations for plantation grown jack pine and black spruce trees established at varying densities. Furthermore, we provide an overview of various projects undertaken to explore measures of site productivity. Available growth intercept and site index equations are being evaluated and new equations are being developed for major commercial tree species as needed. We illustrate how these efforts are advancing Ontario’s growth and yield program and supporting the CEC-FRP in achieving its objective of increasing the supply of fibre by 10% in 10 years while maintaining forest sustainability. Key words: permanent sample plots (PSPs), permanent growth plots (PGPs), normal yield tables, sustainable forest management, NEBIE plot network, forest inventory, Forest Vegetation Simulator

Today, the overgrowth of woody and shrubby vegetation on former agricultural lands is a serious problem. The aim of this research has been to investigate age-related changes in the forest inventory indicators of forest stands on abandoned farmlands. Taking into account the temporal factor when monitoring the carbon budget allows identifying a number of processes in the dynamics of carbon sequestration that cannot be estimated in a single study. To address this issue, data from permanent sample plots have been analyzed in 2011 with repeated measurements in 2023. The sample plots are located on the abandoned farmlands on the border of the Krasnoyarsk forest-steppe area. The dynamics of the process of Today, the overgrowth of woody and shrubby vegetation on former agricultural lands is a serious problem. The aim of this research has been to investigate age-related changes in the forest inventory indicators of forest stands on abandoned farmlands. Taking into account the temporal factor when monitoring the carbon budget allows identifying a number of processes in the dynamics of carbon sequestration that cannot be estimated in a single study. To address this issue, data from permanent sample plots have been analyzed in 2011 with repeated measurements in 2023. The sample plots are located on the abandoned farmlands on the border of the Krasnoyarsk forest-steppe area. The dynamics of the process of overgrowth and development of plantations has shown that as the abandoned farmlands form, in addition to the dominant Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth) and aspen (Populus tremula L.), Siberian larch (Larix sibirica Ledeb.), Siberian spruce (Picea obovata Ledeb.) and goat willow (Salix caprea L.) are also found. The dynamic process of pine abandoned farmlands has been established over a period of 15 to 27 years after land abandonment. The mixed plantations of various successional origins have ranged in age from 10 to 30 years old. Various processes have been observed in the research plots in terms of changes in the density of abandoned farmlands (overgrowth, thinning). The reforestation of abandoned farmlands occurs from the forest border and at a distance of up to 50 m continues after 30 years. The abandoned farmlands are characterized by various forms of overgrowth: clumps, biogroups, complete and by single trees. The average quantitative assessment has shown that that the most intense changes in height, diameter, height to the crown base, height to the largest crown width, and crown diameters have occurred in the test area where the minimum density has been observed, which has been decreasing dynamically. In the plot with the maximum density, morphological indicators have been characterized by an average increase. Minimal changes have been recorded in the sample plot where the density has increased significantly over 12 years. The growth rate of trees of the same diameter in height has been greater in 2023 compared to 2011. It is possible that this has been influenced by a combination of external and internal factors, including climate change. To assess the carbon productivity of forest stands growing on the abandoned farmlands, it is advisable to use regression equations developed for a specific area. The results of the study of the dynamics of carbon sequestration by young forests growing on the abandoned farmlands indicate the feasibility of using postagrarian lands for the implementation of forest climate projects.

Rola zaburzeń w kształtowaniu struktury i dynamiki naturalnych lasów bukowo-jodłowo-świerkowych w Karpatach Zachodnich

It is generally agreed that preservation of forest areas can contribute strongly to the mitigation of global climate change. However, studies have demonstrated that there are still uncertainties for an accurate estimation of carbon stock particularly in the tropical forest. This study aims therefore to develop some allometric equations that can be used to estimate above-ground tree biomass and carbon partitioning between major carbon pools such as tree and litter for IITA secondary forest ecosystem. Ten permanent sample plots of 20 m × 20 m were randomly laid in the forest reserve. Diameter at breast height, total height, crown diameter and wood density were measured. Forty quadrants of 1 m × 1 m for litter fall collection were also randomly laid in four locations in each permanent sample plots. Twenty four tree species present in all the permanent sample plots were selected for destructive sampling. Mean biomass of each sampled plots were pooled together to develop allometric equations to obtain biomass and carbons were also estimated using standard method. A total of nine hundred and forty seven tree species were measured in the study area. These tree species belong to sixteen different families. Allometric equations of family level and whole stand level for estimating above-ground tree biomass were therefore developed. The best fitted allometric equations were used to predict above-ground tree biomass. Model 3 indicated the highest modelling efficiency of 0.954, 0.960 and 0.984. Therefore taking this into consideration, that model 3 was selected as the best model for predicting the above-ground tree biomass with an estimation of 17698.76 g at family level. Allometric equations of whole stand level for above-ground tree biomass indicated good correlation with H, DBH, CD and WD (0.534, 0.597, 0.751, and 0.648). Model 5, 7 and 8 were designated the highest modelling efficiency of 0.898, 0.922 and 0.948. Model 8 is selected as the best models for predicting the above-ground tree biomass with an estimate of 838036.15 g. Therefore, carbon capture per hectare of above-ground tree biomass was 368280.40 g/ha. Carbon capture per hectare of litter had 2663.259 g/ha using standard method. The distributions of the standard residual values and standard error estimate with the fitted values are adequate.

The degree of space occupancy with woody plants has a certain limit associated with their biological characteristics and the level of soil fertility. The value of relative density in our country serves as a criterion for determining the intensity of thinning, while abroad the “index of forest density is used”. The purpose of the study is to substantiate the limit line “average diameter – average distance between trees” in stands of the main forest-forming species according to the data of long-term observations on permanent sample plots. The materials for the study were measurement data on permanent sample plots in the Forest experimental station of the Russian State Agrarian University – Moscow Timiryazev Agricultural Academy. Sample plots were selected where the sums of the cross-sectional areas reached the maximum values once during the life of the stand, as well as where the sums of the cross-sectional areas reached the maximum twice. To verify the validity of the regression line passing through the origin, a program for calculating the equation of a straight line with a free term was used. The hypothesis of direct proportionality of the average diameter of forest stands to the average distance between trees is confirmed, while the dependence of the proportionality coefficient on the initial number of trees is not observed. In stands with maximum sums of cross-sectional areas, the ratio of the maximum average diameter to the average distance between trees is close to the constant. It serves as a good indicator of the degree of space occupancy and can be used in production and technical calculations.

Prediction of stand attributes of even-aged teak stands using multilevel models

Modelling top height growth and site index using repeated laser scanning data

Pathways of forest compositional dynamics over five decades (1953–2005) were reconstructed using measurements from permanent sample plots in a long-term silviculture experiment in a central Maine mixedwood forest. The objective of this study was to elucidate the dynamics of tree species composition at the sample plot level in relation to the initial composition when the experiment was established (1953–1957) and harvest disturbance history following a wide range of even-aged and uneven-aged silvicultural treatments. Cluster analysis revealed three groupings of sample plots based on pretreatment composition and harvest disturbance history, or nine subclusters (i.e., three harvest disturbance histories nested within each pretreatment composition). From 1953 to 2005, the silvicultural treatments generated an array of compositional outcomes at the plot level. Hardwood dominance increased following a history of heavy and infrequent harvests, while northern conifer dominance was maintained where harvests were lighter and more frequent. The importance of balsam fir ( Abies balsamea (L.) Mill.) changed little across a range of harvest intensities. A ubiquitous decline in northern white-cedar ( Thuja occidentalis L.) was found among silvicultural treatments, suggesting that additional intervention may be needed to promote cedar recruitment. Plot-level compositional dynamics indicated that neighborhood-scale stand dynamics were associated with variability in harvest disturbance overlain on plot-to-plot variability in tree species composition at the time the experiment was established.

In 1972-1973, large-scale drainage of peat lands for the purposes of effective forestry was carried out on the territory of the West Dvina Peatland-Forest Station of the Institute of Forest Science of the Russian Academy of Sciences in the Tver Region [Biogeocenological ..., 1982]. Here, in the conditions of the subtaiga of European Russia, swamp forests, bog moss forest and swamps are common, formed on different types of peat − from eutrophic to oligotrophic. In 1974, a permanent sample plot was laid in the Pinetum andromedo-eriophoroso-sphagnosum on the oligotrophic bog. Repeated surveys of this sample plot were conducted in 1983 and 2023. The sample plot (SP) has the number 5-74, has an area of 0.36 ha and a rectangular shape of 36×100 m2 (Fig. 1). The long side of the SP is located parallel to the drainage ditches 35 m from them. The distance between the ditches is 106 m. The depth of the peat is about 4 m. The drainage regime corresponding to the location of SP 5-74 in the middle of the 106-meter channel is considered extensive. The peat soil was characterized by the constancy of the botanical composition of peat-forming agents up to 3.5 m and was represented by the upper magellanicum peat (Sphagnum magellanicum Brid.) with a degree of decomposition of 5-25%, deeper − sphagnum transition (Sph. girgensonii Russ.) with a decomposition rate of up to 30%. The carbon content in peat is 48-50%, the pH does not exceed 3.0, the ash content is 2-5%. High peat soil is characterized by a low volume mass (density): from 0.046 in the upper layers to 0.090 g/cm3 in the lower ones [Glukhova, 1990]. In 1974 SP 5-74 was laid in the Pinetum andromedo-eriophoroso-sphagnosum, which was characterized by Vb class of productivity and V class of age. In 1983, a more productive pine forest of the same V class of age was formed at this place, but still belonging to the Vb class of productivity: compare table 1 for 1983 M = 24.4 m3/ha, and for 1974 M =14.3 m3/ha. In 2023, the Pinetum ledoso-sphagnosum drained of the Va class of productivity and V class of age with M=50.0 m3/ha was already described at this site. The taxational characteristics of the stand by year and layer are given in table 1. Extensive drainage of Pinetum andromedo-eriophoroso-sphagnosum with Vb productivity class showed that 10 years after drainage, a more productive pine forest was formed, and 50 years later – Pinetum ledoso-sphagnosum drained with Va productivity class. Based on the taxation data, the stock of stand was calculated for three years of observations (1974, 1983, 2023), which amounted to 14.3, 24.4 and 50.0 m3/ha, respectively. To convert stand stocks into carbon stocks in the phytomass of a stand (trunk, branches, foliage, roots), a conversion coefficient was used, which, in accordance with the methodological guidelines [On approval ..., 2022] turned out to be 0.314. The analysis of carbon stocks showed that it increased 1.7 times in 10 years, and 3.5 times in 50 years. Regression analysis of these data showed a linear dependence of the carbon stock (C) on the age of extensive drainage (Adrain) over a 50-year period (Fig. 2): C = 0.2322 × Adrain + 5.0116, t/ha, where R2 = 0.99; p-value (F) = 0.064 for α = 0.05. The coefficient of determination (R2) of the regression linear equation is high, but the equation is not reliable (p-value (F) α). In the future, these data can be replenished by analyzing the increments of model trees or mathematical modeling. Over the 50-year drainage period, the average annual increase in the stock of the stand was 0.71 m3/ha and the average annual increase in the carbon stock of the phytomass of the stand was 0.24 t/ha. An analysis of the literature on drained bog pine forests of the V-Vb bonitet showed that the stock of stands, depending on the age of drainage, may generally increase, less often decrease.

Moran's I statistic measures the spatial autocorrelation in a random variable measured at discrete locations in space. Permutation procedures test the null hypothesis that the observed Moran's I value is no greater than that expected by chance. The spatial autocorrelation of gross basal area increment is analyzed for undisturbed, naturally regenerated stands in three Georgia forest types: loblolly, shortleaf, and slash pine. The analysis uses 0.4-ha permanent sample plots from a forest inventory that included two remeasurement intervals (1961-1972 and 1972-1982). We present a new statistic for exploratory spatial analyses, and this statistic revealed an anomalous cluster of unusually slow-growing shortleaf pine plots occurred in the mountains 100 km north of Atlanta. A regression model was used to predict gross basal area increment as a function of variables that describe local stand conditions, and no significant spatial autocorrelations existed in the regression residuals. This result suggests that the anomalous cluster of slow-growing plots can be explained by the spatial distribution of local stand conditions rather than spatial patterns of other possible causes such as air pollution, although alternative interpretations are possible. For. Sci. 40(2):314-328.

Summary Permanent sample plots (PSPs), measured at 5- to 10-year intervals, are presently used to monitor stand development in boreal forests in Canada. These data cannot easily be used to study inter-annual variability in stand development processes nor can they monitor the effects of transient factors affecting stands annually because of their coarse temporal resolution. It also takes a considerable period of time to obtain time series of data for regions without PSPs. Long re-measurement intervals are necessary because instruments like diameter tapes, calipers and clinometers cannot discern annual growth in these slow-growing forests. Dendrochronological stand reconstruction techniques are a method that can be used to obtain annual data on forest growth and stand development. We show that these techniques can provide annual information on stand development patterns while periodic measurements of PSPs cannot, and that these data can be obtained in a short period of time, relative to waiting to obtain data from PSPs established today. Detailed, annual data will become more important in the future, as climate change will affect both forest growth and stand dynamics. Annual resolution data on these processes will be required to describe and account for these effects.

Forest tree ingrowth is a highly variable and largely stochastic process. Consequently, predicting occurrence, frequency, and composition of ingrowth is a challenging task but of great importance in long-term forest growth and yield model projections. However, ingrowth data often require different statistical techniques other than traditional Gaussian regression, because these data are often bounded, skewed, and non-normal and commonly contain a large fraction of zeros. This study presents a set of regression models based on discrete Poisson and negative binomial probability distributions for ingrowth data collected from permanent sample plots in the Acadian Forest Region of North America. Models considered here include regular Poisson, zero-inflated Poisson (ZIP), zero-altered Poisson (ZAP; hurdle Poisson), regular negative binomial (NB), zero-inflated negative binomial (ZINB), and zero-altered negative binomial (ZANB; hurdle NB). Plot-level random effects were incorporated into each of these models. The ZINB model with random effects was found to provide the best fit statistics for modeling annualized occurrence and frequency of ingrowth. The key explanatory variables were stand basal area per hectare, percentage of hardwood basal area, number of trees per hectare, a measure of site quality, and the minimum measured diameter at breast height of each plot. A similar model was developed to predict species composition. All models showed logical behavior despite the high variability observed in the original data.

Summary The composition of Monks Wood, a 157 ha nature reserve in eastern England, in 1964–66 was compared with that in 1996 using data from 36 temporary sample plots distributed systematically across the wood and from a 70 × 35 m permanent sample plot. The overall composition of the wood changed little, but declines in the abundance of Betula pendula, and locally of other species such as Populus tremula had occurred. Both the density of tree stems and of shrub stools declined significantly between 1966 and 1996: for trees from 1469 to 611 stems per hectare, for shrubs from 235 to 177 stools per hectare. Stem basal area also increased. There were substantial changes in the ground flora: reductions in frequency of Mercurialis perennis, increases in Brachypodium sylvaticum, Carex pendula, Glechoma hederacea, Poa trivialis and Urtica dioica. The changes in the tree and shrub layer appear to be mainly a consequence of ‘internal’ factors, stand growth and self-thinning. The ground flora changes reflect a new ‘external’ factor affecting the wood, increases in deer browsing. The die-back of oak Quercus robur recorded over the last six years appears to be a recent phenomenon that needs further monitoring.

Aim Structure and floristic composition of forest regeneration (trees between 1 and 10 cm diameter at breast height (d.b.h), ≥ 1 m growth height) was described in three forest types of Amazonian white‐water forests (várzea), in order to analyse whether floristic composition of saplings is related to the successional stage of the forests, whether it differs in comparision with the mature flora, and if there exists a zonation of sapling species along the gradients of flooding and irradiation.Location Mamirauá Sustainable Development Reserve, Western Brazilian Amazon.Methods The investigated forests were of the low and the high várzea type, on an annual average flooded around 4 and 1 months, respectively. The two low‐várzea forests belonged to the secondary and to the late‐successional stage, the high‐várzea forest also to the late‐successional stage. A total of 24 circular sample plots covering 1885 m2 were installed. They were nested within three rectangular 1 ha permanent sample plots where individuals ≥ 10 cm d.b.h. were formerly inventoried. Average inundation and radiation [relative photosynthetically active radiation (rPAR)] at the forest floor was recorded in all inventoried plots. The Mean spatial Distribution Center (MDC; Ebdon, 1998) for all sapling species was calculated. Sapling species were grouped into associations with respect to their light‐demand and their location along the flood‐level gradient.Results Average flood height and average rPAR at the forest floor was highest in the secondary stage of the low várzea and lowest in the high‐várzea forest. Overall average density and basal area of the saplings averaged 2250 individuals and 2.3 m2 ha−1 in the secondary stage, 2330 individuals and 2.6 m2 ha−1 in the late‐successional stage of the low várzea and 5000 individuals and 4.8 m2 ha−1 in the high várzea. In all forest types, species richness of saplings was lower than species richness of trees ≥ 10 cm d.b.h., and amounted to 25 species in the secondary stage, to 35 species in the late‐successional stage of the low várzea and to 88 species in the high‐várzea forest. The amount of ‘immigrants’ (Bazzaz, 1991) at the sapling level increased with proceeding forest succession and amounted to 24 and 29% in the low várzea and to 31% in the high várzea. Sapling species distribution, species richness and individual density was linked to both, the gradient of flooding and the gradient of irradiation. Species richness and individual density was highest in the high várzea and decreased with increasing influence of flooding. The high várzea was predominated by pronounced shade‐tolerant sapling species, whereas in the low várzea occured both, light demanding and shade‐tolerant species groups.Main conclusions Influence of flooding seems to be the main factor triggering species composition and structure of sapling communities in várzea forests. Proceeding forest succession reduces the impact of flooding because of the biogenical induced silting up of the forested sites. However, forest succession also alters forest architecture of the overstory and such the light conditions at the sapling level. Therefore, radiation is an important factor influencing species composition of sapling communities in várzea forests.