Forest Species Composition Research Articles

Light availability and phorophyte identity drive epiphyte species richness and composition in mountain temperate forests

Bryophytes and lichens are the most species-rich groups of epiphytes in temperate forests. They colonise different tree species that create a wide variety of microhabitats, and conditions in these microhabitats are modulated by different factors. We assessed drivers that create and maintain epiphyte species richness and diversity of bryophytes and lichens along tree species composition gradients. We hypothesised that tree species composition influences the diversity of lichens and bryophytes. The study was conducted on 31 plots along the Kudowski Potok River (SW Poland). Each plot was a 500 m2 circle (r = 12.62 m), along the banks of the stream. These sites are among the best-preserved remnants of a mountain landscape with a high diversity of forest types, representing a transition from the planted Picea abies secondary communities to broadleaved forests (potential natural vegetation). We analysed the tree species composition gradient using PCA, and we measured diffuse light availability. We assessed differences in epiphyte species richness among tree species using generalized linear mixed-effects models and species composition gradients of epiphytes using redundancy analysis. We found that tree species composition and light availability affected the composition of both bryophyte and lichen species. Moreover, lichen and bryophyte species richness were positively correlated. Broadleaved trees such as Acer pseudoplatanus and Fraxinus excelsior clearly increase the number of epiphytic bryophytes and lichen species in spruce stands. Deciduous trees left in management forests serve as a reservoir for epiphytic bryophytes and lichens. Our results indicate the importance of refuges composed of diverse deciduous trees that increase the biodiversity in commercial forests.

Impacts of forest fire frequency on structure and composition of tropical moist deciduous forest communities of Bandhavgarh Tiger Reserve, Central India

Forest fire is one of the prominent factors especially in tropical seasonal forests that have a variety of consequences on ecosystem composition, structure and function depending upon the type of fire, fire intensity, and fire frequency. Forest fire incidences have been increasing in the last few decades especially in tropical moist forests, raising the concerns for forest restoration and management since the inhabiting plants in these forest communities largely lack adaptive strategies. The present study was carried out in tropical moist deciduous forests to (A) understand the patterns of forest fire frequency by delineating the fire affected areas and (B) evaluate the impacts of forest fire frequency on species composition, diversity and regeneration of a moist deciduous forest of Central India. A fire frequency map was prepared using Landsat satellite images from 2005 to 2021 for the study purpose. Vegetation data were collected from field surveys for each fire frequency class separately. Results of the present study showed that 25.12 % area was affected by low frequent fires, 2.92 % by moderate frequent fires and 0.099 % by high frequent fires, whereas 71.85 % area remained unaffected by fire. The diversity of the tree layer was highest in the low fire frequency class whereas, for the sapling layer, it was highest in unburned areas. Overall, the negative impact of fire frequency on species diversity was observed for the tree and sapling layers. Favorable effects of fire on young current year recruitments were observed as a result of the removal of seed dormancy. Results indicate that moderate fire frequency in moist deciduous forests helps to increase tree density. Contrary to this, unburned areas are suitable for species diversity of seedlings and saplings which consequently decides the composition of mature vegetation. Overall, a negative impact of fire frequency on density was observed for the sapling and seedling layers. Our study concludes that higher fire frequency is detrimental to both the density and diversity of tree, sapling and seedling layers, particularly in tropical moist deciduous forest communities of Central India. It is expected that fire incidences are likely to increase with the increasing temperatures as a result of climate change. In this context, the present study would be highly valuable for forest policy development as information on the impact of fire in tropical moist forests is lacking especially from Central Indian region.

Long-term dynamics of forests with Pinus sibirica in the upper reaches of the River Kolva (Northern Pre-Urals, Russia) from 1938 to 2023

Forest ecosystems have been impacted by human activity over several millennia in a variety of ways. Previous land use activity has not only changed the ratio of various terrestrial ecosystems, but also influenced the distribution of tree species. The insight into the forest species composition, dynamics and revealing how it differs from the modern one should be of decisive importance for the identification and conservation of the most valuable forests, as well as the restoration of ones previously disturbed. The density and distribution of some species continues to decline rapidly due to the anthropogenic activity. This problem is most urgent in boreal forests, formed by a limited set of tree species. Studies of the long-lived tree species dynamics and their ability to restore after various types of disturbances deserve special attention. Based on analysis of forest management materials from 1938 and 2023, this paper was aimed to analyse the dynamics of forests with the participation of Pinus sibirica in the Northern Pre-Urals (Permsky Krai, Russia), on the western border of the species' natural range. In 1938, the forests with Pinus sibirica occupied 16.6% of all forests in the research area. In 1938, most forests with Pinus sibirica (64%) were forests, in which P. sibirica was represented by only 1–5% of the stock. Pinus sibirica-dominated forests were almost absent, with only one site with 60% dominance of P. sibirica, and five sites with 40% dominance of P. sibirica. Over the next 85 years, the area of forests with Pinus sibirica participation in the research area has decreased by 2.5 times due to the impact of clear cuttings and forest fires. By 2023, the ratio of forest areas with various proportions of Pinus sibirica participation had changed considerably. The highest changes were found in forests with Pinus sibirica participation of 1%, 5% and 20% of the stock. Analysis of the typological structure of forests showed that at present Pinus sibirica has survived only in natural dark-coniferous forests, which have not been affected previously by forestry activities and fires. Due to the exceptionally slow regeneration following fires and logging activities, Pinus sibirica is absent in the forests formed over the studied period. The current federal legal restrictions prove ineffective as they target the preservation of forest stands containing over 30% of Pinus sibirica, while the majority of forests in the study area contain less proportion of this species. We believe that it is necessary to develop uniform measures to preserve existing and restore the lost Pinus sibirica populations in the Komi Republic and the Permsky Krai, including the prohibitions on the logging of forests with any proportion of Pinus sibirica as well as the creation of P. sibirica forest plantations.

Drivers of tree regeneration in coniferous monocultures during conversion to mixed forests in Central Europe – Implications for forest restoration management

In Central Europe, anthropogenic coniferous monocultures have been subject to conversion to more diverse mixed forests since the 1990s, however, they are still abundant across many forest landscapes. Artificial and natural tree regeneration both play a key role during conversion by determining the species composition and structure of the future forests. Many abiotic and biotic factors can potentially influence the regeneration process and its specific combinations or interactions may be different among tree species and its developmental stages. Here, we aimed to identify and quantify the effect of the most important drivers on the density of the most abundant regenerating tree species (i.e., Norway spruce and European beech), as well as on species and structural diversity of the tree regeneration. We studied tree regeneration in four former monospecific coniferous stand types (i.e., Norway spruce, Scots pine, European larch, and Douglas fir) in Southwest Germany that have been under conversion to mixed forests since the 1990s. We sampled tree regeneration in four growth height classes together with a variety of potentially influencing factors on 108 sampling plots and applied multivariate analyses. We identified light availability in the understorey, stand structural attributes, browsing pressure, and diaspore source abundance as the most important factors for the density and diversity of tree regeneration. Particularly, we revealed species-specific differences in drivers of regeneration density. While spruce profited from increasing light availability and decreasing stand basal area, beech benefited either from a minor reduction or more strikingly from an increase in overstorey density. Increasing diaspore source abundance positively and a high browsing pressure negatively affected both species equally. Our results suggest that humus and topsoil properties were modified during conversion, probably due to changes in tree species composition and silvicultural activities. The species and structural diversity of the tree regeneration benefitted from increasing light availability, decreasing stand basal area, and a low to moderate browsing pressure. We conclude that forest managers may carefully equilibrate among the regulation of overstorey cover, stand basal area, and browsing pressure to fulfil the objectives of forest conversion, i.e., establishing and safeguarding a diverse tree regeneration to promote the development of mature mixed forests in the future.

Ecological preferences of the Swiss pine (Pinus cembra L.) forests in the Gorgany Nature Reserve

Swiss pine (Pinus cembra L.) is a montane Carpathian (Alpine-Carpathian) species. The modern distribution of the Swiss pine is disjunct, the two isolated areas are located in western and central Europe (Alps) and the middle and high mountains of the Carpathians. The largest areas of Swiss pine in Ukraine are preserved in the Gorgany region at the altitude of 1250‒1450 m above sea level, where it forms the upper forest line. In the Gorgany Nature Reserve, P. cembra grows in the altitude range from 1070 to 1475 m ASL. The lower boundary, in the form of individual trees, descends to 1000 m ASL, and the upper boundary rises to 1585 m ASL. To define the ecological preferences of the Swiss pine, a series of route surveys were conducted and research sites (permanent forest monitoring plots, stationary research profiles, and stationary areas for the counting of natural forest regeneration) were established. The study of the plant communities with P. cembra on the southwestern slopes of the Dzhurdzhi tract showed the dependence of the forest species composition on the altitude above sea level. The forest stands quantitative composition and productivity are also significantly influenced by slope exposure. The proportion of P. cembra in the forests on steep slopes (30‒55°) of west and north-west exposure is relatively high (from 17.1% to 49.0%). Under other conditions, the proportion of P. cembra in the stand composition gradually decreases. Swiss pine is almost completely absent on the slopes of eastern and northern exposures except for rare single trees in Pinus mugo Turra scrub on northern slopes. The forests with P. cembra are typical of sunny slopes where the available sum of active temperatures ranges between 1000° and 1400° and the average ambient temperatures from -12.2°С to +16°С. The optimal environmental conditions for the relict species P. cembra in the Dovbushanski Gorgany region are on the western slopes with a steepness of 17‒55° and southwestern and northwestern slopes with a steepness of 35°‒42°. In terms of soil fertility, oligotrophic edaphotopes with moderate moisture are optimal for the growth of Swiss pine.

Streamflow responses to forest and climate change in the boreal Da Hinggan Mountains, Northeastern China

AbstractBoreal forests cover vast stretches of land across all continents and represent a principal source area of clean water in the northern hemisphere. Increasingly, studies are conducted on the impact of changes in boreal forest cover on water yield; however, much remains unknown concerning the effects of forest structure changes on stream discharge over the course of multi‐decadal forest harvest cycles. In this study, we analysed long‐term hydrometeorological and forest dynamics data spanning from 1990 to 2016 from a typical boreal forest watershed in the Da Hinggan Mountains in northern China. Our objective was to quantify how changes in forest age and tree species composition affect mean annual streamflow and flow regimes in the context of a changing climate. To distinguish the effects of forest and climate changes on annual streamflow from one another, we employed a combination of a sensitivity‐based method and a temporal trend analysis. Further, we evaluated the impact of forest changes on flow regimes using four indicators: magnitude, duration, frequency, and variability. The results indicated that mean annual streamflow increased by 55.8 mm, with forest changes contributing +61.4 mm compared to −5.6 mm due to climate change (negative effect). This increase occurred when approximately 20% of mature coniferous forests transitioned to mid‐age broad‐leaved forests, accompanied by a 10% increase in total stock volume during the later period. Finally, the effect of changes in forest structure on flow regime were not significant. Our results underscore that variations in forest structure affect streamflow differently depending on stand age and species proportions. Therefore, dynamic forest structure management can benefit not only carbon sequestration but also water supply capacity in boreal forested watersheds.

A climate-spatial matrix growth model for major tree species in Lesser Khingan Mountains and responses of forest dynamics change to different representative concentration path scenarios

IntroductionClimate change affects forest distribution, species composition, structure, and yield due to the sensitivity of forests to temperature, precipitation, and CO2. Therefore, for forest management decisions regarding climate change, it is crucial to explore the response of forest growth, mortality, and recruitment to future climate. We aimed to establish tree species’ responses by introducing variables such as climate, stand spatial structure parameters, and diversity indices.MethodsWe produced fixed parameter transition matrix model (FM), climate-sensitive matrix growth model (CM) and climate-spatial matrix growth model (SCM) using data from 786 plots collected during the 7th (2010), and 8th (2015), Chinese National Forest Inventories in Heilongjiang Province, and long-term predictive performance of CM, SCM, and FM were compared using same data. The models were compared using tenfold cross-validation and long-term predictive performance analysis. To predict the response of major tree species in the Lesser Khingan Mountains to three future climate change scenarios (RCP2.6, RCP4.5, RCP8.5).Results and discussionThe cross-validation results show small significant differences among the three models for short-term prediction (5 years), with the FM performing slightly better than the CM and the SCM. In contrast, for long-term projections (85 years), SCM outperformed FM and CM under three different RCPs, and SCM and CM under three representative concentration paths (RCPs), i.e., RCP2.6, RCP4.5, and RCP8.5, suggesting that rather different dynamics are more reliable, since climatic factors are taken into account which may significantly affect forest dynamics, while changes in stand spatial structure also affect the sensitivity of trees to climate, especially in long-term prediction interval, the results of this paper may provide a theoretical basis for optimizing forest management strategies under climate change.

Patterns of liana diversity and host interaction networks in selectively logged and unlogged forests of Uppangala, Western Ghats, India

AbstractLianas shape tropical forest species composition, structure, and dynamics. Increasing climate fluctuation and anthropogenic disturbances increase liana abundance. Despite the increasing number of liana studies in India, only a few have examined the distribution and association of hosts with lianas, or liana–host interaction networks to determine their functional significance and conservational value. Therefore, our objective was to fill the knowledge gap about the diversity, abundance, and network structure of liana–host interactions in response to logging disturbance in a wet evergreen forest of Uppangala in central Western Ghats, India. We sampled lianas ≥1 cm in diameter at 1.3 m from the base and their host trees in thirty 20 m × 20 m plots in selectively logged and unlogged forest management regimes. We evaluated liana–host tree interactions in logged and unlogged forests and retrieved community‐level measures (nestedness, connectance, modularity, and network specialization index) and species‐level indicators (species specialization index). Diversity and abundance of liana species were considerably greater in the selectively logged forest site. The logged forest site had compartmentalization, anti‐nestedness, and network specialization, while unlogged forests were not showing any significant network structure. Most species of lianas and hosts were peripherals, but others were structurally important (connectors, module hubs, and network hubs) in the two forest sites. Forest management regimes had distinct structurally significant species.

Community structure and species composition of typical Quercus variabilis natural secondary forest at the northern foothills of the Qinling Mountains, China

We investigated species composition and community structure of a typical Quercus variabilis natural secondary forest in the northern foothills of the Qinling Mountains, within the dynamic monitoring plot of deciduous broad-leaved forest at the Louguantai experimental forest farm in Zhouzhi County, Shaanxi Province. The results showed that there were 3162 individual woody plants with diameter at breast height ≥1 cm in the plot, which were belonged to 42 species, 36 genera, and 25 families. The community genus's areal type was dominated by the temperate component, which accounted for 44.4%, and followed by the tropical component. The community was dominated by several tree species. The top three species with respect to importance value were Q. variabilis, Pinus tabuliformis, and Quercus aliena, with the sum of their importance value being 64.7%. The average DBH of all woody plants was 7.58 cm. The distribution of all individuals and dominant species in the tree layer was approximately normal, with more medium-size individuals. The community structure was stable. The community was poorly renewed, with a trend of population decline. Biodiversity indices varied considerably among different plots, being lower than those of subtropical broad-leaved evergreen forests. There was a significant correlation between community species distribution and environmental factors. Soil and topography explained 42.4% of the variation in community distribution. Altitude and soil alkali hydrolysable nitrogen had a significant effect on community distribution. Altitude, soil total phosphorus, and organic matter content significantly affected the species diversity of Q. variabilis communities. The stronger adaptability of Q. variabilis populations allowed them to become dominant in low-nutrient environments, which limited species diversity in the community.

Composition and Structure of Mangrove Species in Sekurau Bawah Hamlet, East Kutai Regency, East Kalimantan

The aim of this research is to explore the species composition and structure of mangrove forests in Sekurau Bawah Hamlet, Sekerat Village, Bengalon District, East Kutai Regency, East Kalimantan Province. Although the mangrove vegetation in Sekurau Bawah Hamlet is thick, there is still a lack of information on the composition and structure of the species. Therefore, research is needed to explore the biological resources around the mangrove forest area. The collection of vegetation data was done by combining the path method and compartmentalizing it. The plot areas for each growth stage are seedling, sapling and tree levels. The point of observation is determined purposively. The results of the study showed the highest Important Value Index (IVI) for growth for both seedling and sapling growth was of the Bruguiera parviflora species, while the tree level was of the Avicennia marina specie based on the representative condition of the mangrove vegetation studied.

Status, Diversity, and Feeding Guilds of Avifauna in the Mining Area

Birds contribute to the ecosystem by delivering a variety of ecological services. Birds help the ecology by performing a number of ecological functions. Specific habitats determine bird distribution and community structure. The variety and feeding guilds of birds in various land covers were studied at PT. Vale Indonesia’s mining concession. We studied birds’ variety, status, and feeding guilds in three distinct land covers using the point count methods: i) primary dryland forest; ii) secondary dryland forest; and iii) shrubs. Data were obtained from January 20th to February 24th, 2020. There were 38 species from 24 families reported. We discovered 11 Sulawesi endemic species, and 1 vulnerable species. Secondary dryland forest species composition was more similar to primary dryland forest than to shrubs. Carnivores, frugivores, granivores, insectivores, nectarivores, and piscivores make up the fowl. The insectivore bird composition was the highest, while the piscivore bird composition was the lowest. The availability of food supplies and vegetation characteristics may be critical to the diversity of birds in any ecosystem. As a result, this study indicates that land-cover alteration and modification may have an impact on bird diversity structure. Maintaining vegetation as a source of food and habitat for birds is crucial for bird conservation.

Protecting our streams by defining measurable targets for riparian management in a forestry context

Abstract Generally, governments and industry have implemented some degree of protection to reduce the impacts of forestry on aquatic ecosystems. Here, we consider the widespread application of streamside management in terms of riparian buffer retention to protect freshwaters from forestry practices across three jurisdictions with large and intensive forestry sectors (British Columbia, Finland and Sweden). This perspective was developed by working with researchers, practitioners and policymakers on mitigation measures to decrease the impacts of forestry on streams. We demonstrate that it is exceedingly rare for policies and guidelines to specify concrete objectives and measurable targets that can be assessed against riparian buffer management outcomes. Most often, policy objectives for riparian management prescribe ‘to prevent or mitigate impacts’, and this vagueness is insufficient to protect our waters. We argue that we should be clearer about the targets (outcomes) for riparian management and go beyond the simple idea that buffer presence, without further specification of its conditions, is always a successful protection strategy. One cannot measure the effectiveness of rules and guidelines without quantitative targets. Policy implications: In this paper, we suggest that locally developed and adjusted targets for riparian buffers must include quantifiable, measurable goals that specify what is supposed to be achieved and protected with respect to ecological functions, biological communities or other values. It should be relatively simple to move from current vague objectives such as ‘protect and prevent’ to a defined range of values for ecological parameters that buffers are supposed to provide. For example, these can include region‐specific shading levels and microclimate targets, large wood volumes, or riparian forest species composition. We stress that these targets must be developed through an open dialogue between agencies, practitioners, land owners and scientists. We acknowledge that there are trade‐offs between being too prescriptive and too vague. However, when excessively broad goals are the norm, we lose the capacity to effectively implement, monitor or evaluate the outcomes of protection measures.

Simulation and prediction of changes in tree species composition in subtropical forests of China using a nonlinear difference equation system model.

Changes in tree species composition are one of the key aspects of forest succession. In recent decades, significant changes have occurred in the tree species composition of subtropical forests in China, with a decrease in coniferous trees and an increase in broad-leaved trees. This study focuses on Zhejiang Province, located in the subtropical region of China, and utilizes seven inventories from the National Continuous Forest Inventory (NCFI) System spanning 30 years (1989-2019) for modeling and analysis. We categorized tree species into three groups: pine, fir, and broadleaf. We used the proportion of biomass in a sample plot as a measure of the relative abundance of each tree species group. A novel nonlinear difference equation system (NDES) model was proposed. A NDES model was established based on two consecutive survey datasets. A total of six models were established in this study. The results indicated that during the first two re-examination periods (1989-1994, 1994-1999), there was significant fluctuation in the trend of tree species abundance, with no consistent pattern of change. During the latter four re-examination periods (1999-2004, 2004-2009, 2009-2014, 2014-2019), a consistent trend was observed, whereby the abundance of the pine group and the fir group decreased while the abundance of the broad-leaved group increased. Moreover, over time, this pattern became increasingly stable. Although the abundances of the pine group and the fir group have been steadily declining, neither group is expected to become extinct. The NDES model not only facilitates short-term, medium-term, and even long-term predictions but also employs limit analysis to reveal currently obscure changing trends in tree species composition.

Relationship between Maling bamboo (Yushania maling) invasion and decrease of plant species diversity in the Eastern Himalayan temperate forest

Temperate forests of the Eastern Himalayan region are undergoing a noticeable transformation due to invasion and over-dominance by indigenous Yushania maling, Maling bamboo. In the present study, the impact of invasion of Maling bamboo on forest species composition in the Senchal Wildlife Sanctuary located in Darjeeling district of West Bengal, India was investigated, using a comparative approach. Ten plots each from Maling and non-Maling habitats at 10 sites were sampled using the nested quadrat method. Maling-infested plots showed lower species richness and diversity compared to non-Maling plots. The Maling-infested plots harboured 119 species compared to 165 species in non‑Maling plots. Across habitat and vegetation strata, diversity indices such as Shannon-Weiner, Menhinick, Simpson, and evenness consistently indicated lower diversity in Maling-dominated habitats accompanied by higher dominance scores. Significantly lower shrub and herb species diversity were observed in Maling plots, along with elevated shrub density and moderately lower tree density as compared to non‑Maling plots. The sapling species diversity and density were significantly lower in Maling plots, along with moderately reduced seedling density. The average Maling culm density was 1232.8 per 0.04 ha. These results underscore the adverse impact of Maling bamboo over-dominance on species composition of shrub, herbs, sapling and seedlings, and the density of trees, shrubs, saplings and seedlings within the temperate forests. Potential management strategies for the native species are discussed.

Variability in forest tree species composition and diversity in different aged cocoa agroforests of Ghana

Variability in forest tree species composition and diversity in different aged cocoa agroforests of Ghana

Disparities in soil and water conservation functions among different forest types and implications for afforestation on the Loess Plateau

Afforestation is widely acknowledged as an effective approach for enhancing ecological conditions. Considering the challenging ecological environment on the Loess Plateau, prioritizing soil and water conservation functions in stands is crucial. The study aimed to ascertain the future development direction of forestry on the Loess Plateau by examining two representative forest types: planted forest (Robinia pseudoacacia pure forest and Pinus tabulaeformis pure forest), and natural secondary forest (a mixed forest of Quercus liaotungensis and Populus davidiana). The assessment centered on the soil and water conservation functions of the two forest types, encompassing the water conservation function (rainfall distribution and changes in multi-year soil moisture storage (0–200 cm)), soil conservation function (soil physicochemical properties), and understory plant diversity and stability. The results indicated that natural secondary forests outperformed planted forests in terms of water conservation function by effectively converting more precipitation into soil moisture, reducing runoff, and maintaining higher soil moisture storage. Additionally, natural secondary forests exhibited superior soil conservation functions compared to planted forests, characterized by higher soil porosity and nutrient properties. The variation in community structure between the shrub and herbaceous layers was more significant among different forests than within each forest (P < 0.05). Natural secondary forests exhibited higher understory shrub and herb biodiversity and interspecific repeatability compared to planted forests. Therefore, natural secondary forests are a more suitable forest type considering the natural conditions and silvicultural objectives of the Loess Plateau. To enhance the quality of afforestation, it is recommended to adopt near-natural planting patterns that replicate the environmental conditions of natural forests. For instance, actively creating mixed forests that emulate the tree species composition of natural forests and gradually reducing dependence on a single dominant tree species. Furthermore, the arborous and litter layers had a more direct and substantial influence on soil and water conservation functions compared to the shrub and herb layers. Foresters should prioritize regulating stand structure, such as increasing canopy variability, to enhance the water conservation function of stands. Additionally, they should actively protect the understory litter to fulfill its role in enhancing soil quality. This study provides a theoretical foundation and practical guidance for the implementation of vegetation restoration in ecologically vulnerable areas, such as the Loess Plateau.

Seed rain composition responds to climate change in a subtropical forest

Recent climate change has been shown to alter aspects of forest plant demography, such as growth and mortality, but less attention has been focused on how climate change alters the reproduction of plant populations through time. We hypothesized that the plant seed production would respond to climate change, and that the response would differ according to plant life form and functional traits. We tested this hypothesis by examining climate change from 2005 to 2020 and by determining the temporal trends of seed rain and seed production from plants with different life forms (e.g., herbs, vines, trees, palms) and of tree species with different statures as well as leaf, seed and wood traits during 2014-2020. We also tested the correlation between meteorological variables and time series of seed rain using cross correlation analysis. We found increasing wetness (lower vapor pressure deficit) through time but with decreasing minimum relative humidity, which is a pattern consistent with trends seen in many other parts of the world. During the study period, seed production of shrubs and relative contribution of woody vines to total seed rain decreased, while relative contribution of palms to total seed rain and tree species with more conservative leaf traits increased their contribution to total seed rain. Overall, these trends were well explained by the trends of meteorological variables and the responses of these life forms to climate change in previous studies. Additionally, the increasingly conservative leaf traits were also consistent with shifts in traits following recovery from disturbance. Our results suggest that a trait-based approach may help to unveil trends that are not readily apparent by examining seed counts alone. The compositional change found in the seed rain may indicate future shifts in forest species composition and should be incorporated into future studies of forest modelling and projections under climate change.

Assessing future climate trends and implications for managed forests across Canadian ecozones

Climate change interacts with ecological processes leading to changes in tree and forest growth rate, biome shifts and species composition, all of which are influenced by disturbances. This study explores future overarching climate trends of eight of Canada's ecozones containing managed forests. For the 2071 to 2100 period, climate projections indicate a warming trend of up to an additional 5.5 °C and an overall increase in annual precipitation. Future trends suggest marked contrast between coastal and interior forests and polarization between western and eastern forests. Warmer temperatures, accumulating degree-days above 5 °C and frost-free days suggest longer and drier growing seasons and greater risk of drought particularly in moisture-limited areas such as montane cordillera, taiga shield and boreal shield ecozones. Warmer temperatures and rising precipitation combined with less snow suggest shorter and wetter future winters. This indicates greater risk of rain-on-snow and freeze-thaw events, flooding and landslides particularly in coastal ecozones. We discuss how these projections are likely to result in shifts in dominant species and abundance, which when coupled with the cumulative effects of future disturbances, is likely to alter future forest dynamics and impact harvestable wood volumes for Canada's forestry industry.

Simulating the diameter growth responses of Larix gmelini Rupr. and Betula platyphylla Suk. to biotic and abiotic factors in secondary forests in Northeast China

Key messageThe diameter growth of Dahurian larch (Larix gmelini Rupr.) and white birch (Betula platyphylla Suk.) species in secondary forest of Northeast China was not only influenced by biological factors such as tree size and stand characteristics, but also significantly affected by topographic and climatic factors such as temperature and precipitation. It is necessary to consider the abiotic factors in simulating the diameter growth.ContextClimate change, such as global temperature rise, increased frequency of extreme weather events, and rising sea levels, has put forest ecosystems in an unstable state and has an impact on species composition, growth harvest, productivity and other functions of forests. And this impact varies in climate scenarios, regions and forest types.AimsTo gain a comprehensive understanding of the adaptation for key species to their environment in secondary forests in Northeast China, the diameter growth responses of Dahurian larch and white birch to biotic and abiotic factors were simulated to assess the effects of climate on diameter growth.MethodsChina’s National Forest Continuous Inventory (NFCI) data from 2005 to 2015 were used to develop linear mixed-effects diameter growth models with plot-level random effects, and leave-one-out cross-validation was applied to evaluate the developed models. At the beginning of modeling, correlation analysis and best-subset regression were used to analyze the correlation between the diameter increment and the biotic and abiotic factors.Results(i) Sorting the categories of predictors in descending order based on the relative importance of the significant predictors, diameter growth of Dahurian larch was affected by competition, tree size, topographic conditions, stand attributes, diversity index, and climate factors, while the white birch species was affected by competition, tree size, stand attributes, climate factors, diversity index, and topographic conditions; (ii) the plot-level mixed-effects model, which achieved better fit and prediction performance than did basic linear models of individual-tree diameter growth in the cases of prediction calibration, was preferable for modeling individual-tree diameter growth; (iii) the prediction accuracy of the mixed-effects model increased gradually with increasing size of calibration sample, and the best sampling strategy was the use of nine random trees to calibrate and make predictions with the mixed-effects model for the larch and birch species; (iv) Dahurian larch was dominant in terms of interspecific competition, and the growth of this species was enhanced when it was grown with the birch.ConclusionIn addition to biotic factors such as tree size and stand characteristics, the impact of climate on the growth of Dahurian larch and white birch should be considered in future management policies.

Forest structure and biodiversity patterns along elevational gradients in eastern Nepal

This study aimed to assess the forest structure, composition, and diversity pattern at different elevations in Morang District, eastern Nepal, using stratified random vegetation sampling technique in five forests: Bhaunne, Raja-Rani, Murchungi, Adheri, and Sagma. Trees, shrubs and herbs of each forest was sampled through quadrat of 20 × 20 m2, 5 × 5 m2, and 1 × 1 m2 each respectively. A total of 315 plant species belonging to 82 families and 255 genera found by this study. A total of 50 quadrats each for trees, shrubs and herbs sampled during this study. A total 10 quadrats studied for each life form from each forest. This study obtained 5,037 individuals across all forests. The highest number of species (55) was recorded from Raja Rani forest, and the highest tree density (985 ind ha-1) was observed in Adheri forest. The highest density of shrub (24400 ind. ha-1) and herbs (44.1 ind.m-2) were recorded in Sagma forest. The Shannon Wiener index value of herb layer was found to be the highest (3.79) at Bhaunne forest. This value for shrub layer was 2.98 and tree layer was 3.12 at Sagma which was the maximum among forests. The concentrations of dominance value were high for herb and shrub layer in Bhaunne forest, and it was maximum for the tree layer in Adheri forest. The forest species composition were significantly different (p ≤ 0.001) among each other. Total basal area of shrub layer and tree layer recorded were maximum (111.52 m2 ha-1 and 612.08 m2 ha-1) in Sagma and Adheri forest, respectively. The number of trees decreased with increasing elevation, while shrubs increased, and herbs showed a U-shaped trend. The dominant tree species were Senegalia catechu, Shorea robusta, Terminalia alata, and Schima wallichii in Bhaunne, Raja-Rani, Murchungi, and Sagma forest, respectively, with Shorea robusta being dominant in Adheri forest. These findings have important implications for forest management and conservation efforts in the region.