Broad-leaved Forest Stands Research Articles

Key structural factors and their thresholds for promoting bird diversity in spruce-dominated production forests of central Europe

Many of native forests in Europe have been transformed into even-aged production forests of commercially attractive conifers. In recent decades, a moderate shift back to a more native tree species composition accompanied by the maturation of some close natural stands has been evident in the Czech Republic. We aimed to investigate the effects of increasing age and contribution of native tree species on bird species and to identify the potential critical thresholds of these factors in central European forests. For this purpose, bird monitoring and forest structure measurements were carried out at 120 plots in production forests and 20 forest reserves located on 20 study sites throughout the Czech Republic. These plots covered gradients of native tree species contribution and stand age. Birds were counted during the 2018, 2019 and 2020 breeding seasons using passive acoustic monitoring, followed by subsequent computer analysis of the recordings. We assessed relationships between differences in bird species composition and structural and environmental factors. We also used generalised additive models (GAMs) to investigate the effects of individual structural and environmental factors on birds, taking into account their occurrence frequencies and habitat preferences. Our results convincingly documented, that dissimilarities in bird species composition, especially species turnover, strongly coincided with differences in the share of conifer basal area and stand age. The effect of tree species composition on the bird species turnover reflected the habitat preferences of individual species. In addition, we found that some cavity-nesting species were strictly associated with stands with a low contribution of conifers and high stand age. The presence of forest older than at least 125, but sometimes up to 280 years is a critical factor for rare and old-growth bird species. Conversely, the high contribution of conifers (more than app. 60 % of basal area) inhibited the occurrence of the species-rich communities, especially the birds associated with close natural stands. Therefore, increasing the area of mature close-natural stands would be beneficial for bird diversity, especially for rare species. In central Europe, however, the rotation length of forest stands is usually less than 120 years in order to maximise timber production. Forest management practices should therefore support the maturation of forest stands and the transformation of tree species composition towards more native broadleaved forest stands. These measures are essential for the protection of species-rich bird communities, especially old-growth-associated birds, in central Europe.

Rainfall Physical Partitioning and Chemical Characteristics in Evergreen Coniferous and Deciduous Broadleaved Forest Stands in a High Nitrogen Deposition Region, China

Atmospheric rainfall is one of the major sources of water and nutrient inputs in forest stands. Understanding the atmospheric rainfall partitioning and hydrochemical fluxes of forest stands is critical for forest management and monitoring regional atmospheric pollution, especially in high N deposition regions. In this study, annual rainfall collections were implemented to investigate rainfall partitioning, element concentrations, and element fluxes in an evergreen coniferous forest (ECF) stand, a deciduous broadleaved forest (DBF) stand, and open area field (OAF) in a high N deposition region, China. Rainfall in the ECF and DBF was partitioned into throughfall, stemflow, and interception loss, which accounted for 74.7%, 4.8%, and 20.5% of the gross annual rainfall in the ECF stand, respectively; and 79.8%, 5.8%, and 14.4% of the gross annual rainfall in the DBF stand, respectively. Rainfall physical partitioning chemical characteristics varied with forest stand type. The amount of throughfall and stemflow in the ECF stand was lower than that in the DBF stand; the interception loss in the ECF stand was higher than that in the DBF stand. Element concentrations and element fluxes increased as rainfall passed through forest canopies in the high N deposition region. The stemflow pH in the ECF was lower than that in the DBF stand, the concentrations of NO3−-N, Cl−, and SO42−-S in stemflow in the ECF stand were higher than those in the DBF stand, and the concentrations of K+, Na+, Ca2+, Mg2+ and NH4+-N in stemflow in the ECF stand were lower than those in the DBF stand. The inorganic N deposition was 52.7 kg ha−1 year−1 for the OAF, 110.9 kg ha−1 year−1 for the ECF stand, and 99.6 kg ha−1 year−1 for the DBF stand; stemflow accounted for 15.1% and 19.2% of inorganic N deposition in the ECF stand and the DBF stand, respectively. In the present study, given the similar rainfall characteristics and meteorological conditions, the differences in rainfall partitioning and chemical characteristics between the ECF stand and the DBF stand could largely be attributed to their differences in stand characteristics. The results of the study will facilitate a greater understanding of the atmospheric rainfall partitioning and hydrochemical fluxes of forest stands in a high nitrogen deposition region.

Short-term effects of retention forestry on the diversity of root-associated ectomycorrhizal fungi in Sakhalin fir plantations, Hokkaido, Japan

We have examined the effects of dispersed and aggregated retention on the diversity of root-associated ectomycorrhizal fungi (EcMf) in Sakhalin fir (Abies sachalinensis) plantations, 4 years after logging. Roots of Sakhalin fir seedlings and the adjacent broadleaved or Sakhalin fir trees were sampled in broadleaved dispersed retention sites (10, 50, or 100 trees/ha), conifer aggregated retention sites (a single 60 × 60 m square patch of Sakhalin fir trees per site), clear-cut sites, unharvested Sakhalin fir plantations, and natural broadleaved forest stands. The EcMf on the roots were grouped into operational taxonomic units based on the similarity of the internal transcribed spacer sequences within the nuclear ribosomal DNA. Clear-cutting significantly reduced the species richness and diversity of the EcMf and altered the species composition when compared with the unharvested Sakhalin fir plantations and natural broadleaved forests. In contrast, both the aggregated and dispersed retention sites maintained higher levels of EcMf diversity, as well as different EcMf communities when compared with the clear-cut sites. Aggregated retention was effective at conserving EcMf diversity at the unharvested Sakhalin fir plantations, but the effects were limited within retained patches. Broadleaved dispersed retention did not retain the EcMf communities that were present prior to logging even at high retention levels, but they could retain unique EcMf communities, which differed between the Sakhalin fir plantations, natural broadleaved forests, and clear-cut sites. The species richness and diversity values for some of the dispersed retention sites were comparable to the values for the unharvested Sakhalin fir plantations and tended to be greater than the values for the aggregated retention sites. The results indicate that dispersed retention could be an effective strategy by which to preserve a larger number of EcMf species and unique EcMf communities in logged conifer plantations, although the positive effects were likely limited spatially within the rooting zones of the retained broadleaved trees. Finally, naturally regenerating Sakhalin fir seedlings were found to share a large amount of their EcMf with adjacent broadleaved retention trees, indicating that multi-host EcMf of retained trees largely contribute to ectomycorrhizal colonization of the surrounding regenerated seedlings in the logged areas. Our findings demonstrated that both dispersed and aggregated retention methods could be used to mitigate the impacts of logging on EcMf diversity in Sakhalin fir plantations, in Japan, and that there were large differences in the effects among the different retention methods.

STRUCTURAL ATTRIBUTES, DIVERSITY AND MANAGEMENT OF SOME VAN PANCHAYAT FOREST STANDS OF GARHWAL HIMALAYA

Oak (Quercus oblongata) is an important component of mid-altitude ecosystem of the Central Himalaya which are exposed to over-exploitation making conditions favourable for the invasion by light-demanding conifers such as chirpine (Pinus roxburghii). The present study provides information on woody vegetation structure, composition, regeneration and management of four broadleaved forest stands of Garhwal Himalaya managed by Village Panchayat. Quercus oblongata was the most important and dominant species in all the stands. Although dominance was shared by a number of species, no single species was found to complete with this climax species. The presence of Alnus nepalensis (a nitrogen-fixing species) depicts the poor nitrogen status of these forest stands. High density values and low basal cover suggest that these community forest stands are younger than the natural oak reserve forests of the Central Himalaya. The richness index shows that the seedling strata are ecologically richer than the tree, sapling and/or shrub strata. High richness in the seedling strata is attributed to the low magnitude of biotic interferences in these communities based conserved forest stands. The regeneration potential of Quercus oblongata is much higher than the natural oak forests of Central Himalaya managed by the forest department. This supports the view that moderate disturbance regimes are more conducive to satisfactory regeneration of this species. Since the management of these forest stands is looked after by the Village Panchayat, they are introducing some conifers for their vested interests. This may add an additional competition of the broadleaved climax species with conifers as has been witnessed in most of the broadleaved oak forests of this altitudinal range.

Relevance of Broad-Leaved Forest Stands for Maintaining Epiphytic Bryophyte Species and Functional Trait Diversity in Forest Landscape in Latvia

AbstractBroad-leaved trees play an important role in supporting epiphyte richness in deciduous forests. In this study we tested which broad-leaved forest stands in terms of tree composition best predicted biodiversity in regard to bryophyte species number and their functional traits. The bryoflora was surveyed in 70 stands differing in dominant broad-leaved tree species. One circular plot with diameter 30 meters was established in each stand situated in different parts of Latvia. Fifty-three of the plots were located in stands identified as protected habitats of the European Union. In total, 82 bryophyte species were recorded. At plot level the total number of species ranged between 6 and 38 species. Using principal component analysis (PCA), the ordination axes explained 41% of the variation in composition of bryophytes. The PCA axes were related to tree species composition. The presence of broad-leaved trees, especially ash, lime, and oak, was connected with higher species richness. Generalised linear models confirmed that epiphyte richness, both at the total and indicator species levels, was higher in ash stands. From the functional traits, all expected life-strategy and life-form categories were recorded. The most represented life-forms were smooth mats, tall turfs, and rough mats, while the dominant life-strategy was perennial stayers, followed by competitive perennials and long-lived shuttles. Functional trait richness was highest in Fraxinus excelsior, Tilia cordata, and Quercus robur forest stands.

Adjustment of leaf anatomical and hydraulic traits across vertical canopy profiles of young broadleaved forest stands

Adjustment of leaf anatomical and hydraulic traits across vertical canopy profiles of young broadleaved forest stands

The capacity of ion adsorption and purification for coniferous forests is stronger than that of broad-leaved forests

In the past few decades, industrialization has caused a large number of pollutants to be released into the atmosphere. Forest ecosystems play an important function in regulating the biogeochemistry and the circulation of metal ions pollutants. Forest ecosystems affect the absorption of pollutants and dissolution of nutrients from the atmosphere and vegetation canopy, thereby influencing the content and composition of forest floor leachate and soil solution. This study examined changes in acid anions (NO3−, SO42−, Cl−) and metal cations (K+, Ca2+, Na2+, Mg2+, Fe3+, Pb2+, Cu2+, Cd2+) in rainfall, throughfall, stemflow, and forest floor leachate for five different forests (Larix principis-rupprechtii, Picea wilsonii, Picea crassifolia, Betula platyphylla and Rhododendron communities). The results showed that the enrichment capacity of acid anions and metal cations in the vegetation canopy of the coniferous forests (L. principis-rupprechtii, P. wilsonii, P. crassifolia) was stronger than that of the broad-leaved forests (B. platyphylla and Rhododendron communities). The content of acid anions and metal cations in stemflow of coniferous forests were 3.7–5.6 times and 0–9.3 times higher than those of broad-leaved forests, respectively. Corresponding values in throughfall were 1–1.4 times and 0.3–2.4 times, respectively. The contents of NO3−, Cl−, K+, Mg2+, Fe3+, Pb2+, Cu2+, and Cd2+ in leachate filtered from the soil layers that are deepening gradually showed consistent decreasing trend for all the forest stands. In addition, NO3−, Cl−, K+, Mg2+, Fe3+, and Pb2+ were also concentrated in the topsoil, except for Cu2+ and Cd2+. Nevertheless, SO42− and Na+ were concentrated in the subsoil, whereas Ca2+ was concentrated in the upper soil layers. Soil organic carbon (SOC) and total nitrogen (TN) contents in coniferous forest stands were 20–37% and 34–63% higher than those in broad-leaved forest stands, respectively. This results also shown that the contents of OC and TN has a strong correlation with the content of partial metal cations in soil and litter, indicating that coniferous forest stands had stronger ion scavenging and adsorption capacity in soil layer and litter layer than broad-leaved forest stands. Therefore, L. principis-rupprechtii, P. wilsonii, P. crassifolia had higher air pollutant adsorption and soil pollution remediation capacities than the other two forests. Thus, we recommend planting coniferous tree species (L. principis-rupprechtii, P. wilsonii and P. crassifolia) for eco-rehabilitation and water purification to improve the ecological service function of forest ecosystems.

Tree diversity and carbon stock in a subtropical broadleaved forest are greater than a subtropical pine forest occurring in similar elevation of Meghalaya, north-eastern India

Studies on relationship between tree diversity and carbon stock has not been consistent. The present study was undertaken to quantify and compare the plant diversity and carbon stock in a subtropical broadleaved and a subtropical pine forest of Meghalaya, northeast India. Biomass-based carbon estimation was undertaken in two subtropical broadleaved forest stands viz., Mawnai (MBF) and Nongkrem (NBF) and adjacent Pinus kesiya dominated forest stands (MPF and NPF), occurring in similar topography, climatic conditions and soil type. The aboveground and belowground tree biomass was estimated using existing allometric models. Carbon was estimated as 47.4% of the total biomass. Tree species richness was greater in the subtropical broadleaved forest stands at MBF and NBF (117 and 21 species) than in the adjacent pine forests, MPF and NPF (15 and 16 species). The density values were 1294 and 1127 individuals ha−1 in the broadleaved forest stands, and 894 and 1032 individuals ha−1 in the adjacent pine forest stands, respectively. The broadleaved forest stands, MBF and NBF had tree biomass carbon stock of 140.4 Mg C ha−1 and 133.6 Mg C ha−1, respectively, which were significantly greater (F = 26.6; P 66 cm) to the total biomass carbon was greatest in MBF, while the lower diameter trees belonging to 5–15 cm and 16–25 cm were the major contributors to the total biomass carbon in the pine dominated stands.

The relationship between soil properties, enzyme activity and land use

Abstract The aim of this study was to assess the effects of different types of land use (forest, tillage and pasture) on soil properties, especially enzyme activity. Our investigation was carried out on 53 research plots with 11 plots in broadleaved forest stands, 12 plots in mixed broadleaved stands, 10 plots in mixed coniferous stands, 9 plots on tillage and 11 plots on pasture. The soil samples were collected from a depth of 0–15 cm after removing the organic horizon. Contents of organic carbon and nitrogen, pH and soil texture were investigated. Furthermore, dehydrogenase and urease activity were determined. Significant differences in the enzyme activity between forest and agricultural soils were observed, thus demonstrating that enzyme activity is influenced by the organic matter content of the soil. The highest enzyme activity was recorded in the forest soil within broadleaved stands, whilst the lowest activity was found in tillage soil, because tillage soil contained significantly less organic matter. High enzymatic activity of pasture soils is the combined result of vegetation type and the lack of plowing.

How much water do Chilean forests use? A review of interception losses in forest plot studies

AbstractAfter several years of decreased annual rainfall and water shortages, the Chilean society is demanding that forest plantations take accountability of their role in consuming scarce water resources. Evidence has shown that interception losses are considerable when determining water production in watersheds. The aim of this study was to determine if site and stand variables explain interception losses by Chilean forests for the development of an empirical model that could predict the potential impacts of forest management practices and land‐use change. A total of 127 data from annual water balance plot studies in Chile were compiled to derive relationships between interception and precipitation, species composition, plantation age and other stand and site variables. The reviewed data indicated that annual interception losses are mainly explained by annual rainfall and basal area of the forest stands, with a clear difference between the northern (dryer) and southern (wetter) regions of Chile. For a wide latitudinal gradient, forest composition and age, annual interception accounted for approximately 21% of incoming precipitations. Broadleaved forest stands (including native broadleaved and eucalypt forests) generally presented higher interception losses than conifers. Interception was higher in northern zones, indicating that forests have greater impacts on water resources in dryer regions. Our results were compiled in empirical models, which can be used to estimate forest interception in a latitudinal gradient in Chile and to support policy making. These results are also proposed as an approximate analogue of the changes in forest interception losses, which may occur as vegetation belts shift latitudinally as a result of the impact of climate change. Copyright © 2016 John Wiley & Sons, Ltd.

Relationship between Soil Bacterial Population and Various Physico- Chemical Properties at Two Broadleaved Forest Stands of Meghalaya Differing in Altitudes

Although soil bacterial communities are one of the important biotic components that influence decomposition and nutrient mineralization in the terrestrial ecosystems, factors driving this biotic community in the broadleaved forest stands of Meghalaya are not well studied. The present study examined the importance of physico-chemical properties in driving soil bacterial communities in the broadleaved forest stands of Meghalaya differing in altitudes. Soils were collected at two different (0-10 cm and 10-20 cm) depths monthly for a period of two years. Results showed that bacterial CFU was higher in the high altitude forest stand at 0-10 cm depth as compared to the low altitude forest stand at 10-20 cm depth. It also showed significant positive correlation with organic carbon and total nitrogen in both the two forest stands indicating that these two constitute the major driving factors of bacterial communities in the broad leaved forest stand of Meghalaya.

Temperature Sensitivity and Basal Rate of Soil Respiration and Their Determinants in Temperate Forests of North China

The basal respiration rate at 10°C (R10) and the temperature sensitivity of soil respiration (Q10) are two premier parameters in predicting the instantaneous rate of soil respiration at a given temperature. However, the mechanisms underlying the spatial variations in R10 and Q10 are not quite clear. R10 and Q10 were calculated using an exponential function with measured soil respiration and soil temperature for 11 mixed conifer-broadleaved forest stands and nine broadleaved forest stands at a catchment scale. The mean values of R10 were 1.83 µmol CO2 m−2 s−1 and 2.01 µmol CO2 m−2 s−1, the mean values of Q10 were 3.40 and 3.79, respectively, for mixed and broadleaved forest types. Forest type did not influence the two model parameters, but determinants of R10 and Q10 varied between the two forest types. In mixed forest stands, R10 decreased greatly with the ratio of coniferous to broadleaved tree species; whereas it sharply increased with the soil temperature range and the variations in soil organic carbon (SOC), and soil total nitrogen (TN). Q10 was positively correlated with the spatial variances of herb-layer carbon stock and soil bulk density, and negatively with soil C/N ratio. In broadleaved forest stands, R10 was markedly affected by basal area and the variations in shrub carbon stock and soil phosphorus (P) content; the value of Q10 largely depended on soil pH and the variations of SOC and TN. 51% of variations in both R10 and Q10 can be accounted for jointly by five biophysical variables, of which the variation in soil bulk density played an overwhelming role in determining the amplitude of variations in soil basal respiration rates in temperate forests. Overall, it was concluded that soil respiration of temperate forests was largely dependent on soil physical properties when temperature kept quite low.

Nitrogen in soils beneath 18–65 year old stands of subtropical evergreen broad-leaved forests in Laoshan Mountains in Eastern China

Monitoring of soil nitrogen (N) cycling is useful to assess soil quality and to gauge the sustainability of management practices. We studied net N mineralization, nitrification, and soil N availability in the 0–10 cm and 11–30 cm soil horizons in east China during 2006–2007 using an in situ incubation method in four subtropical evergreen broad-leaved forest stands aged 18-, 36-, 48-, and 65-years. The properties of surface soil and forest floor varied between stand age classes. C:N ratios of surface soil and forest floor decreased, whereas soil total N and total organic C, available P, and soil microbial biomass N increased with stand age. The mineral N pool was small for the young stand and large for the older stands. NO3−-N was less than 30% in all stands. Net rates of N mineralization and nitrification were higher in old stands than in younger stands, and higher in the 0–10 cm than in the 11–30 cm horizon. The differences were significant between old and young stands (p < 0.031) and between soil horizons (p < 0.005). Relative nitrification was somewhat low in all forest stands and declined with stand age. N transformation seemed to be controlled by soil moisture, soil microbial biomass N, and forest floor C:N ratio. Our results demonstrate that analyses of N cycling can provide insight into the effects of management disturbances on forest ecosystems.

Root Growth and Recovery in Temperate Broad-Leaved Forest Stands Differing in Tree Species Diversity

In contrast to studies on aboveground processes, the effect of species diversity on belowground productivity and fine-root regrowth after disturbance is still poorly studied in forests. In 12 old-growth broad-leaved forest stands, we tested the hypotheses that (i) the productivity and recovery rate (regrowth per standing biomass) of the fine-root system (root diameter < 2 mm) increase with increasing tree species diversity, and that (ii) the seasonality of fine-root biomass and necromass is more pronounced in pure than in tree species-rich stands as a consequence of non-synchronous root biomass peaks of the different species. We investigated stands with 1, 3, and 5 dominant tree species growing under similar soil and climate conditions for changes in fine-root biomass and necromass during a 12-month period and estimated fine-root productivity with two independent approaches (ingrowth cores, sequential coring). According to the analysis of 360 ingrowth cores, fine-root growth into the root-free soil increased with tree species diversity from 72 g m−2 y−1 in the monospecific plots to 166 g m−2 y−1 in the 5-species plots, indicating an enhanced recovery rate of the root system after soil disturbance with increasing species diversity (0.26, 0.34, and 0.51 y−1 in 1-, 3-, and 5-species plots, respectively). Fine-root productivity as approximated by the sequential coring data also indicated a roughly threefold increase from the monospecific to the 5-species stand. We found no indication of a more pronounced seasonality of fine-root mass in species-poor as compared to species-rich stands. We conclude that species identification on the fine root level, as conducted here, may open new perspectives on tree species effects on root system dynamics. Our study produced first evidence in support of the hypothesis that the fine-root systems of more diverse forest stands are more productive and recover more rapidly after soil disturbance than that of species-poor forests.

Estimation of fire severity by use of Landsat TM images and its relevance to vegetation and topography in the 2000 Samcheok forest fire

The severity of the 2000 Samcheok forest fire was classified by using Landsat TM images, and the effects of vegetation structures and topographic conditions on fire severity were analyzed. The estimated normalized difference vegetation index differences between the pre and post-fire Landsat TM images were used as the criteria in determining the levels of fire severity–low, moderate, and extreme. According to the results from fire severity estimation, of the 10,600 ha forest stands, 28% was severely damaged by crown fires, 38% was moderately damaged, and the remaining 34% was damaged slightly by surface fires. The overall accuracy of the fire severity classification was 83% (Kappa coefficient = 0.76). The results of χ2-tests showed that fire severity differed significantly with the vegetation and topographic conditions as follows. The coniferous stands, compared with the mixed and broad-leaved, were more vulnerable to fire damage; the higher the slope of fire sites, the greater the fire damage; the south was the most vulnerable aspect; fire severity of coniferous forest stands increased with increasing elevation. However, in the study area it was found that fire severity of broad-leaved forest stands were negatively related to the elevation of the corresponding fire sites and affected more by vegetation conditions rather than by topographic conditions.

Comparative Foraging Success of Insectivorous Birds in Tropical and Temperate Forests: Ecological Implications

Foraging success is the first indicator of food availability which in turn is a major determinant of clutch size, timing and output of reproduction as well as habitat selection, density and survival. Yet it has been rarely investigated among insectivorous birds and never along a latitudinal gradient. To allow a meaningful comparison between a tropical and a temperate guild of small foliage gleaners, the data were recorded in similar conditions and restricted to adult birds actively foraging, in the understory of primary rain forest (French Guiana) and old stands of broad leaved forest (France) during the breeding season. The mean attack rate of tropical species is 4 to 6 times lower than that of their temperate equivalents. The differences are highly significant, consistent over every species, and cannot be attributed to the birds' body size or prey size. The temperate species are more specialized on caterpillars and their foraging success has a lower variance than that of tropical species, suggesting that food resources may be on average higher, richer and more evenly distributed in temperate forests. Foraging speed is significantly higher in temperate than in tropical species and is correlated with attack rate and body size only among the latter. There are no consistent relationships between attack rate and foraging height, capture techniques or substrates used. Tropical species make a greater use of dead leaves and epiphytes than do temperate ones, as well as of the most expensive capture modes (probing, striking, sallying). They also take more prey under the leaf surface and have a larger foraging niche breadth than their temperate counterparts. Contrary to the widely assumed superabundance and stability of food resources in the tropics, it is suggested that a reduced prey availability (density, detectability, distribution, seasonality) may be a major cause of the lower foraging success of rain forest birds. Accordingly this constraint is likely to limit their reproductive rate and would in part explain their very low clutch size.

Yield—Density diagram for natural deciduous broadleaved forest stands

A yield—density diagram for natural deciduous broad-leaved forests in Hokkaido was devised. It consists of Y— N curves, equivalent diameter curves, equivalent mean diameter curves, a B-point curve and a full density curve. The Y— N curve is derived from the relation between cumulative summation ( Y) of individual tree volume from the maximum sized tree to one of a certain given volume, and number ( N) of these trees, and is expressed by the reciprocal equation of two parameters, A and B. The equivalent diameter curve expresses the number of trees whose diameters are larger than a certain size. The equivalent mean diameter curves express the number and volume of trees of selected mean diameters. The B-point curve is a hypothetical trajectory of the B-point of the C— D curved ruler ( C— D rule) which is fitted to each Y— N relation, throughout the course of stand development. The full density curve indicates the upper limit of the number and volume of the standing trees. Utilizing this diagram, we can comprehend numbers, volumes and tree diameters in a stand and among stands. A method is devised of predicting the number and volume of each diameter class of a stand several years after thinning. Thinned trees are assumed to be selected equally from each diameter class so that the Y— N curves are fitted equally to the Y and N data before and after thinning. Volume growth of individual trees is assumed to be proportional to their volumes after thinning. The current volume growth of the stand after crown closure is assumed to be constant irrespective of the stand age. Tree mortality after thinning is assumed to be negligible. With these assumptions, a trajectory of the Y— N curve through thinning is determined, and a yield after n years from thinning is predicted. Comparing the Y— N curve of a thinned stand with that of an unthinned stand after n years from thinning, we can comprehend the thinning effect.