Long‐term seed bank dynamics in a temperate forest under conversion from coppice‐with‐standards to high forest management

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics? Location: An ancient Quercus petraea — Carpinus betulus forest in conversion from coppice‐with‐standards to regular Quercus high forest near Montargis, France. Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid‐successional stages of stands in transition from coppice‐with‐standards (to high forest (16 plots) and early‐ and mid‐successional high forest stands (32 plots). Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres. Conclusions: Abandonment of the coppice‐with‐standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high‐forest cycles may increasingly depend on inflow from seed sources.     

The Nature of Seedling Assemblages in a Fragmented Tropical Landscape: Implications for Forest Regeneration

Whether aging forest fragments are able to recover original assemblages or progressively move toward impoverished successional stages remains as an open question. This study tested the hypothesis that seedling assemblages in forest fragments differ from those across mature forest stands and examined to what extent the uncovered patterns supported the notion that edge‐affected habitats tend to support impoverished tree assemblages dominated by pioneer species. We contrasted a series of small forest remnants (3–91 ha) to old‐growth stands located in the largest (ca 3500 ha) and best preserved forest remnant in northeastern Brazil and found that tree seedling assemblages inhabiting forest fragments exhibited reduced species richness (up to 50%) at different spatial scales in comparison to seedling assemblages in mature forest and adult assemblages in both fragments and mature forest stands. Moreover, ordination analyses clearly segregated fragment seedling assemblages in taxonomic/functional terms and segregation correlated to the richness of pioneer species. Seedlings of pioneer species and those bearing medium‐sized seeds (0.6–1.5 cm) increased in fragments, whereas large‐seeded species (1.5–3.0 cm) were reduced by more than a half. Such a multiple‐scale replacement of the old‐growth flora by pioneers was also confirmed by an indicator species analysis and the resulting pioneer indicator species. Our results suggest that small forest fragments support impoverished and distorted seedling assemblages. This floristic/functional drift implies that forest remnants or edge‐affected habitats tend to be dominated by a small set of pioneer tree species rather than supporting a substantial portion of the old‐growth flora as do mature forest stands.     

Influence of Post‐Clearing Treatment on the Recovery of Herbaceous Plant Communities in Amazonian Secondary Forests

Secondary forests are an increasingly common feature in tropical landscapes worldwide and understanding their regeneration is necessary to design effective restoration strategies. It has previously been shown that the woody species community in secondary forests can follow different successional pathways according to the nature of past human activities in the area, yet little is known about patterns of herbaceous species diversity in secondary forests with different histories of land use. We compared the diversity and abundance of herbaceous plant communities in two types of Central Amazonian secondary forests—those regenerating on pastures created by felling and burning trees and those where trees were felled only. We also tested if plant density and species richness in secondary forests are related to proximity to primary forest. In comparison with primary forest sites, forests regenerating on non‐burned habitats had lower herbaceous plant density and species richness than those on burned ones. However, species composition and abundance in non‐burned stands were more similar to those of primary forest, whereas several secondary forest specialist species were found in burned stands. In both non‐burned and burned forests, distance from the forest edge was not related to herbaceous density and species richness. Overall, our results suggest that the natural regeneration of herbaceous species in secondary tropical forests is dependent on a site's post‐clearing treatment. We recommend evaluating the land history of a site prior to developing and implementing a restoration strategy, as this will influence the biological template on which restoration efforts are overlaid.     

Higher temperatures enhance the effects of invasive sportfish on mountain zooplankton communities

1. Decades of introductions of exotic sportfish to mountain lakes around the world have impoverished them biologically, and this may be exacerbated by global warming. We assessed the current status of invasive salmonids and native zooplankton communities in 34 naturally fishless lakes along an elevational gradient, which served as an environmental proxy for the expected effects of climate change. 2. Our main goal was to explore how climate‐related variables influence the effects of stocked salmonids on the total biomass, species richness and taxonomic composition of zooplankton. We predicted that warmer conditions would dampen the negative predatory effects of exotic brook trout (Salvelinus fontinalis) on zooplankton communities because more temperate lakes contain a greater diversity of potentially tolerant species. 3. Instead, we discovered that the persistence of stocked brook trout in the warmer lakes significantly amplified total zooplankton biomass and species richness. In colder and deeper lakes, zooplankton were relatively unaffected by S. fontinalis, which however persisted better in alpine lakes than at lower elevations after stocking practices were halted over two decades ago. Warmer lake conditions and higher concentrations of dissolved organic carbon (DOC) were significant primary drivers of zooplankton species turnover, both favouring greater species diversity. 4. Our findings of an ecological surprise involving potential synergistic positive effects of climate warming and exotic trout on native zooplankton communities presents a conundrum for managers of certain national mountain parks. Present mandates to eradicate non‐native trout and return the mountain lakes to their naturally fishless state may conflict with efforts to conserve biodiversity under a rapidly changing climate.     

Managing open habitats by wild ungulate browsing and grazing: A case‐study in North‐Eastern Germany

Question: Can wild ungulates efficiently maintain and restore open habitats? Location: Brandenburg, NE Germany. Methods: The effect of wild ungulate grazing and browsing was studied in three successional stages: (1) Corynephorus canescens‐dominated grassland; (2) ruderal tall forb vegetation dominated by Tanacetum vulgare; and (3) Pinus sylvestris‐pioneer forest. The study was conducted over 3 yr. In each successional stage, six paired 4 m²‐monitoring plots of permanently grazed versus ungrazed plots were arranged in three random blocks. Removal of grazing was introduced de novo for the study. In each plot, percentage cover of each plant and lichen species and total cover of woody plants was recorded. Results: Wild ungulates considerably affected successional pathways and species composition in open habitats but this influence became evident in alteration of abundances of only a few species. Grazing effects differed considerably between successional stages: species richness was higher in grazed versus ungrazed ruderal and pioneer forest plots, but not in the Corynephorus sites. Herbivory affected woody plant cover only in the Pioneer forest sites. Although the study period was too short to observe drastic changes in species richness and woody plant cover, notable changes in species composition were still detected in all successional stages. Conclusion: Wild ungulate browsing is a useful tool to inhibit encroachment of woody vegetation and to conserve a species‐rich, open landscape.     

Regional‐scale directional changes in abundance of tree species along a temperature gradient in Japan

Climate changes are assumed to shift the ranges of tree species and forest biomes. Such range shifts result from changes in abundances of tree species or functional types. Owing to global warming, the abundance of a tree species or functional type is expected to increase near the colder edge of its range and decrease near the warmer edge. This study examined directional changes in abundance and demographic parameters of forest trees along a temperature gradient, as well as a successional gradient, in Japan. Changes in the relative abundance of each of four functional types (evergreen broad‐leaved, deciduous broad‐leaved, evergreen temperate conifer, and evergreen boreal conifer) and the demography of each species (recruitment rate, mortality, and population growth rate) were analyzed in 39 permanent forest plots across the Japanese archipelago. Directional changes in the relative abundance of functional types were detected along the temperature gradient. Relative abundance of evergreen broad‐leaved trees increased near their colder range boundaries, especially in secondary forests, coinciding with the decrease in deciduous broad‐leaved trees. Similarly, relative abundance of deciduous broad‐leaved trees increased near their colder range boundaries, coinciding with the decrease in boreal conifers. These functional‐type‐level changes were mainly due to higher recruitment rates and partly to the lower mortality of individual species at colder sites. This is the first report to show that tree species abundances in temperate forests are changing directionally along a temperature gradient, which might be due to current or past climate changes as well as recovery from past disturbances.     

Influence of rocky landscape features and fire regime on vegetation dynamics in Appalachian Quercus forests

Question : How do interactions between rocky landscape features and fire regime influence vegetation dynamics? Location : Continental Eastern USA. Methods : We measured vegetation, disturbance and site characteristics in 40 pairs of rocky and non‐rocky plots: 20 in recently burned stands, and 20 in stands with no evidence of recent fire (‘unburned’ stands). Two‐way analysis of variance (ANOVA) was used to assess the main and interaction effects of fire and rock cover on plant community composition. Results : In burned stands, rock cover had a strong influence on vegetation. Non‐rocky ‘matrix’ forests were dominated by Quercus, and had abundant ground cover and advance regeneration of early and mid‐successional tree species. Burned rocky patches supported greater density of fire‐sensitive species such as Acer rubrum, Sassafras albidum and Nyssa sylvatica and had little advance regeneration or ground cover. Quercus had fewer fire scars and catfaces (open, basal wounds) on rocky patches, suggesting that rocky features mitigate fire severity. In unburned stands, differences between rocky and non‐rocky patches were less distinct, with both patch types having sparse ground cover, little tree regeneration, and high understorey densities of relatively shade tolerant A. rubrum, N. sylvatica and Betula lenta. Conclusion : Under a sustained fire regime, heterogeneity in rock cover created a mosaic where fire‐adapted species such as Quercus dominate the landscape, but where fire‐sensitive species persisted in isolated pockets of lower fire severity. Without fire, species and landscape richness may decline as early‐mid successional species are replaced by more shade tolerant competitors.     

Lack of tree layer control on herb layer characteristics in a subtropical forest,China

Question: Knowledge of the interaction between understorey herb and overstorey tree layer diversity is mostly restricted to temperate forests. How do tree layer diversity and environmental variables affect herb layer attributes in subtropical forests and do these relationships change in the course of succession? Do abundance and diversity of woody saplings within the herb layer shift during succession? Location: Subtropical broad‐leaved forests in southeast China (29°8′18″‐29°17′29″N, 118°2′14″118°11′12″E). Methods: A full inventory of the herb layer including all plants below 1‐m height was done in 27 plots (10 × 10 m) from five successional stages (<20, <40, <60, <80 and ≥80 yr). We quantified the contribution of different life forms (herbaceous, woody and climber species) to herb layer diversity and productivity and analysed effects of environmental variables and tree layer diversity on these attributes. Results: Herb layer composition followed a successional gradient, as revealed by non‐metric multidimensional scaling (NMDS), but diversity was not correlated to the successional gradient. There was no correlation of diversity across layers. Herb layer productivity was neither affected by tree layer diversity nor by herb layer diversity. Although abundance of woody species in the herb layer decreased significantly during succession, woody species contributed extraordinarily to herb layer species diversity in all successional stages. All environmental factors considered had little impact on herb layer attributes. Conclusions: The subtropical forest investigated displays an immense richness of woody species in the herb layer while herbaceous species are less prominent. Species composition of the herb layer shows a clear successional pattern, however, the presence or absence of certain species appears to be random.     

Effects of Previous Land-Use on Plant Species Composition and Diversity in Mediterranean Forests

At some point in their history, most forests in the Mediterranean Basin have been subjected to intensive management or converted to agriculture land. Knowing how forest plant communities recovered after the abandonment of forest-management or agricultural practices (including livestock grazing) provides a basis for investigating how previous land management have affected plant species diversity and composition in forest ecosystems. Our study investigated the consequences of historical “land management” practices on present-day Mediterranean forests by comparing species assemblages and the diversity of (i) all plant species and (ii) each ecological group defined by species’ habitat preferences and successional status (i.e., early-, mid-, and late-successional species). We compared forest stands that differed both in land-use history and in successional stage. In addition, we evaluated the value of those stands for biodiversity conservation. The study revealed significant compositional differentiation among stands that was due to among-stand variations in the diversity (namely, species richness and evenness) of early-, intermediate-, and late-successional species. Historical land management has led to an increase in compositional divergences among forest stands and the loss of late-successional forest species.     

Diversity and community composition of herbaceous plants in different habitat types in south‐east Cameroon

The composition of herbaceous vegetation was evaluated with the aim of characterizing forests at various ages of stand development. Herb stems were sampled in 250 4‐m² square plots distributed within six habitat types. A total of 36 herb species belonging to 15 families were recorded. Species richness did not significantly differ between habitat types. Most herb species occurred in all habitat types and were therefore generalists. However, a few indicator herb species were detected, and the results roughly suggested that herb species of the families Poaceae and Araceae were indicative of late successional forests; Zingiberaceae are indicative of early successional forests; and Commelinaceae, Costaceae, Cyperaceae and Marantaceae are indicators of flooded habitats. Species diversity and stem density of herbaceous plants did not change with forest succession as a decrease in abundance and frequency of occurrence of pioneer species in late successional forests was counterbalanced by the presence of generalist and late successional species. However, increasing proportions of dwarf stems in late successional forests translated to changes in the vertical structure of herbaceous plant communities. Herbivory pressure by gorillas did not have a notable effect on herbaceous plant community development. This study contributes to the definition of herbaceous ecological indicators of forest succession in different settings.     

Changes in Mediterranean plant succession: old-fields revisited

Abstract. Old-field plots used for a study of succession in Mediterranean France were revisited after 12–14 yr. Our aims were: (1) to verify if predicted patterns of species richness, turnover and composition are confirmed; (2) to compare the development in disturbed plots with that in undisturbed ones; (3) to discuss the impact of management changes. In undisturbed plots species richness and turnover decreased with successional age. Floristic composition changed in a way consistent with the predicted successional development in most plots. Therophytes decreased and phanerophytes increased; anemochorous species decreased and endozoochorous species increased, as expected. In plots disturbed since the first analysis richness decreased with successional age, but generally remained higher than in undisturbed plots. Floristic composition, species turnover and an increase in therophytes indicated changes towards younger successional stages. Thus, disturbance changed succession but not much. This is probably linked with the regeneration abilities typical of mediterranean species, e.g. resprouting. At the landscape scale, richness did not change and species turnover was low. The plots studied were situated in two distinct locations. One had not been disturbed between the two observation periods, while the other is a mosaic of undisturbed and disturbed sites. Observations fitted predictions much more closely at the undisturbed location. We conclude that permanent plot studies are powerful in identifying successional trends and can also provide additional insights into the effects of disturbance some of the mechanisms underlying the dynamics of diversity.     

Long‐term directional changes in upland Quercus forests throughout Oklahoma,USA

Questions: (1) How have the composition and structure of undisturbed upland Quercus forests changed over 50 years across a large region and moisture gradient; (2) What factors are associated with long‐term and broad‐scale changes in these forests? Location: Oklahoma, USA. Methods: We re‐sampled 30 forest stands originally sampled in the 1950s across a large geographical area and compared basal area, tree density, and sapling density between the sampling periods using paired t‐tests, CCA, and DCA. We examined vegetation dynamics in the context of drought indices compiled for the sample period. Results: Total and Quercus stellata basal area and tree density increased, but Q. stellata and Q. marilandica sapling density decreased. Juniperus virginiana and woody species richness increased for all measures. DCA indicated that re‐sampled stands generally changed from Q. stellata–Q. marilandica‐dominated forests to forests with greater woody species richness and more J. virginiana. Q. stellata remained a dominant tree species; otherwise, composition shifted towards mesophytic and invasive woody species. Measurements taken in the 1950s immediately followed a major drought; whereas subsequent decades were significantly moister. Conclusions: Fire exclusion and drought may have played an important role in driving changes towards lower dominance by Quercus, increased importance of mesophytic and invasive species, and greater woody species richness. These phenomena are similar to those found in Quercus‐dominated forests throughout the northern hemisphere.     

Biodiversity Promotes Tree Growth during Succession in Subtropical Forest

Losses of plant species diversity can affect ecosystem functioning, with decreased primary productivity being the most frequently reported effect in experimental plant assemblages, including tree plantations. Less is known about the role of biodiversity in natural ecosystems, including forests, despite their importance for global biogeochemical cycling and climate. In general, experimental manipulations of tree diversity will take decades to yield final results. To date, biodiversity effects in natural forests therefore have only been reported from sample surveys or meta-analyses with plots not initially selected for diversity. We studied biomass and growth of subtropical forests stands in southeastern China. Taking advantage of variation in species recruitment during secondary succession, we adopted a comparative study design selecting forest plots to span a gradient in species richness. We repeatedly censored the stem diameter of two tree size cohorts, comprising 93 species belonging to 57 genera and 33 families. Tree size and growth were analyzed in dependence of species richness, the functional diversity of growth-related traits, and phylogenetic diversity, using both general linear and structural equation modeling. Successional age covaried with diversity, but differently so in the two size cohorts. Plot-level stem basal area and growth were positively related with species richness, while growth was negatively related to successional age. The productivity increase in species-rich, functionally and phylogenetically diverse plots was driven by both larger mean sizes and larger numbers of trees. The biodiversity effects we report exceed those from experimental studies, sample surveys and meta-analyses, suggesting that subtropical tree diversity is an important driver of forest productivity and re-growth after disturbance that supports the provision of ecological services by these ecosystems.     

The recovery of ground ant diversity in secondary Lacandon tropical forests

Ants in tropical forests participate in a wide variety of processes, but human activity can disturb their communities and cause the loss of key species. In this study, we evaluated the effects of human disturbance on the alpha and beta diversity of ant assemblages in a successional gradient of secondary forests growing in abandoned maize fields of the Lacandon region, previously covered by tropical rain forest. Our results show that the alpha diversity of ant species and genera increases with the age of the secondary forests; however, deforestation could cause the loss of certain genera. The turnover of ant species is low along the successional gradient and it is regulated by ecological filters. Secondary forests serve as a refuge for certain ant species and as their successional age increases, they tend to recover the species richness of the mature forest.     

Long-Term Impacts of Forest Ditching on Non-Aquatic Biodiversity: Conservation Perspectives for a Novel Ecosystem

Artificial drainage (ditching) is widely used to increase timber yield in northern forests. When the drainage systems are maintained, their environmental impacts are likely to accumulate over time and along accompanying management, notably after logging when new forest develops on decayed peat. Our study provides the first comprehensive documentation of long-term ditching impacts on terrestrial and arboreal biodiversity by comparing natural alder swamps and second-generation drained forests that have evolved from such swamps in Estonia. We explored species composition of four potentially drainage-sensitive taxonomic groups (vascular plants, bryophytes, lichens, and snails), abundance of species of conservation concern, and their relationships with stand structure in two-ha plots representing four management types (ranging from old growth to clearcut). We found that drainage affected plot-scale species richness only weakly but it profoundly changed assemblage composition. Bryophytes and lichens were the taxonomic groups that were most sensitive both to drainage and timber-harvesting; in closed stands they responded to changed microhabitat structure, notably impoverished tree diversity and dead-wood supply. As a result, natural old-growth plots were the most species-rich and hosted several specific species of conservation concern. Because the most influential structural changes are slow, drainage impacts may be long hidden. The results also indicated that even very old drained stands do not provide quality habitats for old-growth species of drier forest types. However, drained forests hosted many threatened species that were less site type specific, including early-successional vascular plants and snails on clearcuts and retention cuts, and bryophytes and lichens of successional and old forests. We conclude that three types of specific science-based management tools are needed to mitigate ditching effects on forest biodiversity: (i) silvicultural techniques to maintain stand structural complexity; (ii) context-dependent spatial analysis and planning of drained landscapes; and (iii) lists of focal species to monitor and guide ditching practices.     

Do lianas shape ant communities in an early successional tropical forest?

Almost half of lowland tropical forests are at various stages of regeneration following deforestation or fragmentation. Changes in tree communities along successional gradients have predictable bottom‐up effects on consumers. Liana (woody vine) assemblages also change with succession, but their effects on animal succession remain unexplored. Here we used a large‐scale liana removal experiment across a forest successional chronosequence (7–31 years) to determine the importance of lianas to ant community structure. We conducted 1,088 surveys of ants foraging on and living in trees using tree trunk baiting and hand‐collecting techniques at 34 paired forest plots, half of which had all lianas removed. Ant species composition, β‐diversity, and species richness were not affected by liana removal; however, ant species co‐occurrence (the coexistence of two or more species in a single tree) was more frequent in control plots, where lianas were present, versus removal plots. Forest stand age had a larger effect on ant community structure than the presence of lianas. Mean ant species richness in a forest plot increased by ca. 10% with increasing forest age across the 31‐year chronosequence. Ant surveys from forest >20 years old included more canopy specialists and fewer ground‐nesting ant species versus those from forests <20 years old. Consequently, lianas had a minimal effect on arboreal ant communities in this early successional forest, where rapidly changing tree community structure was more important to ant species richness and composition.     

Properties of native plant communities do not determine exotic success during early forest succession

Considerable research has been devoted to understanding how plant invasions are influenced by properties of the native community and to the traits of exotic species that contribute to successful invasion. Studies of invasibility are common in successionally stable grasslands, but rare in recently disturbed or seral forests. We used 16 yr of species richness and abundance data from 1 m² plots in a clearcut and burned forest in the Cascade Range of western Oregon to address the following questions: 1) is invasion success correlated with properties of the native community? Are correlations stronger among pools of functionally similar taxa (i.e. exotic and native annuals)? Do these relationships change over successional time? 2) Does exotic abundance increase with removal of potentially dominant native species? 3) Do the population dynamics of exotic and native species differ, suggesting that exotics are more successful colonists? Exotics were primarily annual and biennial species. Regardless of the measure of success (richness, cover, biomass, or density) or successional stage, most correlations between exotics and natives were non‐significant. Exotic and native annuals showed positive correlations during mid‐succession, but these were attributed to shared associations with bare ground rather than to direct biotic interactions. At peak abundance, neither cover nor density of exotics differed between controls and plots from which native, mid‐successional dominants were removed. Tests comparing nine measures of population performance (representing the pace, magnitude, and duration of population growth) revealed no significant differences between native and exotic species. In this early successional system, local richness and abundance of exotics are not explained by properties of the native community, by the presence of dominant native species, or by superior colonizing ability among exotics species. Instead natives and exotics exhibit individualistic patterns of increase and decline suggesting similar sets of life‐history traits leading to similar successional roles.     

Large‐scale assessment of regeneration and diversity in Mediterranean planted pine forests along ecological gradients

Aim There is increasing concern regarding sustainable management and restoration of planted forests, particularly in the Mediterranean Basin where pine species have been widely used. The aim of this study was to analyse the environmental and structural characteristics of Mediterranean planted pine forests in relation to natural pine forests. Specifically, we assessed recruitment and woody species richness along climatic, structural and perturbation gradients to aid in developing restoration guidelines. Location Continental Spain. Methods We conducted a multivariate comparison of ecological characteristics in planted and natural stands of main Iberian native pine species (Pinus halepensis, Pinus pinea, Pinus pinaster, Pinus nigra and Pinus sylvestris). We fitted species‐specific statistical models of recruitment and woody species richness and analysed the response of natural and planted stands along ecological gradients. Results Planted pine forests occurred on average on poorer soils and experienced higher anthropic disturbance rates (fire frequency and anthropic mortality) than natural pine forests. Planted pine forests had lower regeneration and diversity levels than natural pine forests, and these differences were more pronounced in mountain pine stands. The largest differences in recruitment – chiefly oak seedling abundance – and species richness between planted and natural stands occurred at low‐medium values of annual precipitation, stand tree density, distance to Quercus forests and fire frequency, whereas differences usually disappeared in the upper part of the gradients. Main conclusions Structural characteristics and patterns of recruitment and species richness differ in pine planted forests compared to natural pine ecosystems in the Mediterranean, especially for mountain pines. However, management options exist that would reduce differences between these forest types, where restoration towards more natural conditions is feasible. To increase recruitment and diversity, vertical and horizontal heterogeneity could be promoted by thinning in high‐density and homogeneous stands, while enrichment planting would be desirable in mesic and medium‐density planted forests.     

Structural characteristics and aboveground biomass of old‐growth spruce–fir stands in the eastern Carpathian mountains,Ukraine

Abstract

Temperate old‐growth forests are known to have ecological characteristics distinct from younger forests, but these have been poorly described for the remaining old‐growth Picea abies–Abies alba forests in the eastern Carpathian mountains. In addition, recent studies suggest that old‐growth forests may be more significant carbon sinks than previously recognized. This has stimulated interest in quantifying aboveground carbon stocks in primary forest systems. We investigated the structural attributes and aboveground biomass in two remnant old‐growth spruce–fir stands and compared these against a primary (never logged) mature reference stand. Our sites were located in the Gorgany Nature Reserve in western Ukraine. Overstory data were collected using variable radius plots; coarse woody debris was sampled along line intercept transects. Differences among sites were assessed using non‐parametric statistical analyses. Goodness‐of‐fit tests were used to evaluate the form of diameter distributions. The results strongly supported the hypothesis that old‐growth temperate spruce–fir forests have greater structural complexity compared to mature forests, including higher densities of large trees, more complex horizontal structure, and elevated aboveground biomass. The late‐successional sites we sampled exhibited rotated sigmoid diameter distributions; these may reflect natural disturbance dynamics. Old‐growth Carpathian spruce–fir forests store on average approximately 155–165 Mg ha^?1 of carbon in aboveground tree parts alone. This is approximately 50% higher than mature stands. Given the scarcity of primary spruce–fir forests in the Carpathian region, remaining stands have high conservation value, both as habitat for late‐successional species and as carbon storage reservoirs.