Total Basal Area Research Articles

Structure and Composition of Woody Species in the Kpatawee Tropical Rainforest in Liberia

Studying ecosystem structure and species composition is pivotal, offering critical insights into environmental health and biodiversity. It facilitates the evaluation of environmental changes, like deforestation and climate shifts, and their influence on species dynamics within ecosystems. Our study aimed to assess the woody species composition and structure within Liberia's Kpatawee tropical rainforest. We conducted transect walks, crossing the forest south-north and east-west, establishing six 20 m x 20 m sampling plots. Using the PlantNet plant species identifier tool, we cataloged surviving trees with a DBH ≥ 5 cm, including their scientific names. Results unveiled 71 tree species across 42 families, with Leguminosae displaying the highest diversity. Prominent species included Quararibea asterolepis, Hasseltia floribunda, and Castilla elastica. An intriguing inverted J-shaped pattern in diameter distribution linked to stem-stand shrubs, small-sized trees, and young large trees characterized the first class. The tree layer, mainly species like Garcinia benthamiana, Iramyan therasagotiana, and Eschweilera decolarans, contributed significantly to the total DBH (65.45%). Total basal area (BA) for trees DBH ≥ 5 cm was 16.39 m² ha-1. Notably, eight species accounted for 93% of the basal area, reflecting a concentration of individuals in lower DBH classes in the first category. This trend suggests a gradual decline in numbers in higher DBH classes. Consequently, we recommend implementing sustainable forest management to mitigate the impacts of selective cutting on forest recruitment and regeneration processes. The inverted J-shaped pattern, indicating prolific regeneration but limited recruitment, possibly due to selective cutting, underscores the imperative for prudent forest management.

The effects of tree planting on allergenic pollen production in New York City

Planting low-pollen trees could reduce aeroallergen exposure in cities, but the effects of historical tree planting on contemporary airborne pollen exposure remains largely unexplored. Whether tree selection decisions can effectively reduce airborne pollen will depend in part on which taxa are the most important sources of allergenic pollen and the extent to which they are intentionally planted vs. unplanted (i.e., recruiting naturally). Here, we use airborne pollen measurements to examine which taxa are of allergenic importance in New York City (NYC), and then combine two tree surveys with allometric equations to determine pollen production for several taxa. Future changes in pollen production as a function of growth, mortality, and recruitment are then simulated using i-Tree Eco Forecast. The most important producers of allergenic pollen in NYC are Quercus, Platanus, Morus, and Betula; they comprise 71% of airborne pollen measured and 93% of estimated pollen production (107 quadrillion pollen grains; however, pollen production was not estimated for all taxa). Previous municipal planting decisions have resulted in the high abundance of Platanus × acerifolia; it accounts for 34% of total street tree basal area and has an estimated annual pollen production of 27.7 ± 6.4 quadrillion grains. In contrast, Morus and Betula are generally unplanted, indicating that tree planting decisions will have smaller effects on their future pollen production rates in NYC. Quercus trees produced an estimated 68.2 ± 12.3 quadrillion pollen grains and accounted for almost 25% of airborne pollen collected, but were very abundant in parks and were mostly unplanted, suggesting that planting has not and will not have a major effect on city-wide pollen production. Overall, this study demonstrates that tree planting decisions can have important and long-lasting consequences for city-wide pollen production but only for species that are both primarily planted and large producers of allergenic pollen.

Decentralized Forest Governance and Resource Management: Assessing Community Dependence and Conservation Effectiveness in Broad-Leaved and Coniferous Forest Stands

Globally decentralized forest governance is being promoted to conserve and sustainably manage forest resources along with meeting local livelihoods. In the Central Himalayan region of India, it came into existence in 1931, long before the time when the concept of decentralized forest governance became popular globally, and the aim was to accomplish the subsistence needs of the smallholders in the region. This article discusses whether the species types (broadleaved and coniferous) affect biophysical conditions, species richness, and conservation effectiveness of community-owned forests (locally called Van Panchayat forests), and what could be done to improve their management in the near future. The findings are based on a household survey covering 16 villages as well as a biophysical assessment of 18 community forest stands (9 per forest type) covering an area of 1778 ha and 341 ha in both forest categories. It was found that farmers across the villages are intricately dependent on forest resources to support their livelihoods that are governed by a village institution (Van Panchayat) to maintain equity of benefit-sharing among all stakeholders. Both forest categories exhibited high dependence, however, there was a considerable difference in resource quality, viz. quality of fodder, fuel, and litter in broadleaved forests, therefore the community has more preference for such stands. The broadleaved Banj-oak stands revealed better biophysical status in terms of species diversity, tree density, total basal area, and regeneration than the coniferous Chir-pine stands. Although the local government has taken up selective policy initiatives to encourage decentralized forest governance, more needs to be done to strengthen it on the ground level, particularly in Chir-pine stands. It is suggested that the community management of forests needs to be improved in relation to leadership development, rationale use of bio-resources, and adopting site-specific management strategies. In areas with Chir-pine forests community need to be educated to reduce forest fire and promote the plantation of broad-leaved species. Also, the scope of community forests needs to be broadened by adopting and involving smallholders in various forest enterprise development and climate action programs. For this, developing proper alliances of village institutions with civil society groups and other partner institutions along with virtuous support from local government can lead to enhance social and environmental resilience of communities.

Floristic Composition, Diversity, and Regeneration of Woody Plant Species of Dabal Forest in Southeastern Ethiopia: Implication for Conservation.

Floristic composition, population structure, and regeneration status of woody species of Dabal forest found in East Hararghe zone of Oromia Regional State, Ethiopia, were studied. Vegetation data were obtained from 52 main plots of 20 × 20 m for mature woody species and 5 subplots of 5 × 5 m for seedlings and saplings. Density and dbh of each live woody plant species found in each sample plot were recorded. Frequency, basal area, importance value, and Shannon-Wiener diversity indices were also computed. Totally 59 woody plant species distributed in 33 families were documented. Of these, 45.80, 44.10, and 5.08% were shrubs, trees, and lianas, respectively. Species diversity and evenness indices were 3.56 and 0.87, respectively. Stem count of all woody species was 3379 stems ha-1. Out of this, 44.6, 30.8, and 24.59% were seedlings (dbh <3.5 cm), saplings (dbh between 3.5 and 10 cm), and mature (dbh >10 cm) individuals, respectively. Total basal area of all individuals with dbh ≥3.5 cm was 29.88 m2 ha-1. Juniperus procera, Cupressus lusitanica, Eucalyptus globulus, Afrocarpus falcatus, Eucalyptus camaldulensis, Myrsine africana, Maytenus undata, Hagenia abyssinica, Ekebergia capensis, and Cordia africana were species with top ten IVI. Most of these species were top densest, dominant, and frequent. Analysis of population structure based on pooled densities of all species in each dbh class showed that density of seedling > sapling > mature individuals, signifying healthy population structure with good natural regeneration potential. On individual basis, however, 35.6 and 8.5% of species showed fair and poor regeneration statuses, respectively, that deserve attention for conservation.

Unlocking nature's hidden treasure: Unveiling forest status, biomass and carbon wealth in the Binsar Wildlife Sanctuary, Uttarakhand for climate change mitigation

In the context of present climate change concerns, the quantification of forest biomass and the comprehension of carbon stock distribution within protected areas are of paramount importance for exact carbon budgeting and the development of effective forest management strategies. This study conducted comprehensive field assessments with the primary objective of quantifying tree biomass and carbon stocks, as well as assessing structural attributes of forest stands. These assessments involved the meticulous collection of ground-based data encompassing various structural attributes, including circumference at breast height (CBH), stem height, basal area, stem density, frequency, girth class by utilizing a simple random sampling methodology. The results of this study unveiled substantial variations in all tree structural attributes across different forest stands along altitudinal gradients. Notably, species richness, tree density and species diversity exhibited an upward trend with increasing altitude. The maximum tree species richness (25) and tree density (1068 ± 102.2 individuals ha−1) were recorded at stand-IV, situated between 2200 to 2400 m, however, stand-I exhibited the maximum basal area. The highest aboveground, belowground, total biomass, and carbon stock was estimated in the stand-IV, with values of 279.12 ± 17.56 Mg ha−1, 65.58±11.20 Mg ha−1, 344.70 ± 20.66 Mg ha−1, and 163.73 ± 10.33 Mg ha−1, respectively. The study further revealed a positive correlation between elevation and species richness, biomass, and carbon stock. Additionally, it demonstrated positive correlations between total biomass and carbon stock with species richness, total basal area, and tree density. These findings convey immediate significance for the development and implementation of climate change mitigation policies and practices, particularly within the context of protected areas in the Himalayan landscape.

Changes in forest structure over 23 years under disturbances in a warm temperate rain forest on Yakushima Island, Japan

AbstractClarifying the influence of disturbances by biotic and abiotic agents on long‐term changes in forest structure and demographic rates is an important task of forest ecology. Here, we investigated changes in forest structure and demographic rates and the effects of biotic and abiotic factors (sika deer, ambrosia beetle, neighborhood trees, and indices of strong wind and wetness) in a 4‐ha long‐term ecological study plot in a lowland warm temperate rain forest on Yakushima Island, Japan, from 1996 to 2019 for three regeneration groups related to gap dynamics (gap demander: GD, light shade tolerant: LS, and strong shade tolerant: SS). GD had relatively lower recruitment and survival than LS and/or SS. Changes in demographic rates were not significantly correlated with those in the index of strong wind in any regeneration group. The effects of sika deer on demographic rates did not differ among groups. Stems of Fagaceae species belonging to LS attacked by ambrosia beetles recorded in 2013 did not significantly differ in RGR and survival rates. Our results indicate that despite the relatively long monitoring period of 23 years, we did not detect significant effects of strong winds on demographic rates among regeneration groups, and shade‐tolerant species (LS and SS) showed better demographic performance than light‐demanding species (GD) and an increase in total basal area over time. We need longer monitoring of forest dynamics to understand forest responses to disturbances considering several factors, including the time lag of demographic responses to disturbances and the long‐term effects of disturbances.

Population Structure and Regeneration Dynamics of Tree Species in Banj Oak Forests of Tehri Garhwal, Western Himalaya

Forest regeneration is a natural process of forest resource reclamation through production of young ones (saplings and seedlings). Tree species show variable regeneration potential in different associations and response to natural and man-made factors. Banj oak (Quercus leucotrichophora A. Camus), one of the important forest forming tree species in western montane Himalaya, is facing regeneration failure in different locations. The present study attempted to assess the population structure and regeneration of Q. leucotrichophora and associated tree species in five different stands (sites) of a less explored region (Tehri Garhwal, Uttarakhand, Western Himalaya). To investigate the phytosociological attributes, ten sampling quadrats (400 m2) were laid in random sampling manner in each forest stand for surveying tree layer, 2 sub-quadrats (25 m2) for saplings, and 5 sub-quadrats (1 m2) for seedlings in each sampling quadrat. Among the studied forest stands, tree species richness ranged 8 to 11 (8.8±1.3), total stem density (ind/ha) 750 to 950 (846±85.6), and total basal area (m2/ha) 18.68 to 29.18 (24.1±3.9). Based on abundance data the banj oak showed ‘good’ regeneration statuses (density of seedling &gt; saplings &gt; adult trees) in all forests. The distribution of adult tree individuals into different size classes (DBH classes) also indicate ‘good’ regeneration pattern (higher density in lower size classes and gradual decrease in density towards higher classes or forming a reverse J-shaped pattern). However, majority of the banj oak associated species (e.g. Prunus cerasoides, Pyrus pashia, Rhododendron arboreum, etc.) represented ‘fair’ regeneration statuses (seedlings &gt; or ≤ saplings ≤ adult trees). Overall, the results of this study shed light on the positive prospects for Q. leucotrichophora regeneration and the importance of sustainable coexistence between human communities and these vital forest ecosystems.

Естественное возобновление на валежной древесине в реликтовом лесу Янь Республики Сербской

The paper investigates the natural regeneration of downed deadwood in the Janj primeval forest. The old-growth forest is located in the southwestern part of the Republic of Srpska, which is dominated by dolomite geological base on which cambial soils were formed. The climate is perhumid and mountainous and the plantation belongs to the Piceo-Abieti-Fagetum community. The hectare contains 517 live trees with a total basal area of 53.0 m2/ha and a volume of 876 m3/ha. Twenty six downed deadwoods classified into three different degrees of decay were included in the study, where fir and spruce seedlings were found to be predominant and beech seedlings were rarely represented. The first degree of decay includes 7 (26.9 %), the second 8 (30.7 %), and the third 11 (42.3 %). The total volume of deadwood is 110.82 m3/ha with an average volume per tree of 4.2 m3/ha. The total number of seedlings on fallen dead trees is 836 seedlings (Abies alba – 89.59 %, Picea abies – 10.17 %, Fagus silvatica – 0.24 %). Fir seedlings are found on 25 fallen trees, spruce on 18 fallen trees, and beech on 2 fallen trees. Regarding quality, on average fir seedlings are better than spruce seedlings, but both species show a lot of senescence and very small size of current height increment. Most seedlings belong to the third quality class (fir – 46.2 %, spruce – 61.1 %), followed by second class (fir – 34.6 %, spruce – 22.2 %) and third class (fir – 19.2 %, spruce – 16.7 %). The total number of seedlings was found to have a statistically significant difference in the amount of downed deadwood depending on the degree of decay, and the number of seedlings depended on the degree of tree decay. The number of seedlings increased with increasing volume and length of rotten trees. For citation: Govedar Z., Prokhorova N., Babić V., Dukić V., Kanjevac B., Bilić S. Natural Regeneration on Deadwood in the Primeval Forest Janj. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 90–102. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-90-102

Differential effects of fire regime and site conditions on bark beetles (Coleoptera: Curculionidae) in a longleaf pine (Pinus palustris Mill.) ecosystem

Longleaf pine (Pinus palustris Mill.) ecosystems in the southeastern U.S. are fire-driven. Frequent prescribed fire or lack thereof through shifts in fire regimes may have consequences for tree health and associated herbivorous subcortical beetles (Coleoptera: Curculionidae). Yet, interactions between these ecologically and economically important beetles and prescribed fire in the southeastern U.S. are not well documented. We assessed the effects of various fire regimes, specifically of frequent fire, fire exclusion, and fire reintroduction, on bark and root-feeding beetles in mature longleaf pine stands in two edaphic types (mesic and xeric) in southwestern Georgia. We employed an information theoretic statistical approach to determine the effects of site conditions, as defined by both soil properties and stand structure, and prescribed burning on trap catches of subcortical beetles by species. We trapped a total of 141,611 beetles, indicating that subcortical beetles are abundant in this ecosystem. While the highest trap catches for three Ips beetle species were in the xeric fire-exclusion treatment, catches of I. grandicollis (Eichhoff) were similar at both sites for the fire-exclusion treatment. For the fire-exclusion treatment, I. avulsus (Eichhoff) and I. calligraphus (Germar) catches were 2–10 times higher at the xeric than mesic sites. Orthotomicus caelatus (Eichhoff) and Dendroctonus terebrans (Olivier) catches were 1.1–2.4 times higher in frequent-fire than fire-exclusion treatments. Root-feeding weevils, Pachylobius picivorus (Germar) and Hylobius pales (Herbst), exhibited opposite trends with catches higher and lower in burned treatments, respectively. Ips calligraphus were positively associated with percent basal area of understory trees, indicating this species may benefit from fire exclusion. Ips avulsus catches were negatively correlated with total basal area, suggesting this species may benefit from more open habitats like those facilitated by frequent fire. We conclude that both soil properties and stand conditions interact with the fire regime to differentially affect the catches of southeastern bark and root-feeding beetle species in a longleaf pine ecosystem.

Microtopographic Variation in Biomass and Diversity of Living and Dead Wood in a Forest in Dongling Mountains, China

Habitat heterogeneity caused by topographic variations at the local scale is the environmental basis for the establishment and evolution of biodiversity and biomass patterns. The similarities and distinctions between the effects of microtopographic variables on living wood (LWD) and dead wood (CWD) remain unknown. In the present study, the response mechanisms of biomass and species diversity patterns of living wood (LWD) and coarse woody debris (CWD) to microtopographic parameters were quantified in a warm temperate secondary forest located in Dongling Mountain, China. This quantification was achieved using a generalized additive model on a completely mapped 20-hectare permanent plot. The evaluation of biomass and species diversity of woody plants was carried out by utilizing the total basal area of all individuals and the species richness within each 20 m × 20 m quadrat as a standard. The results indicate that there are notable disparities in the influence of microtopographic elements on the LWD and CWD. In the case of LWD, microtopography accounts for 22.90% of the variation in total basal area, with convexity making a greater relative contribution than elevation, slope, and aspect. Additionally, microtopography explains 46.20% of the variation in species richness, with aspect making a greater relative contribution than elevation, convexity, and slope. Nevertheless, the influence of microtopography on CWD may only account for a deviation of 10.20% in the total basal area and 4.95% in the species richness; aspect and slope have been identified as the primary drivers in this regard. The inclusion of microtopographic factors in the model resulted in a 23.10% increase in the explanatory deviations of LWD biomass and an 8.70% increase in the explanatory deviations of CWD biomass. The findings suggest that topographic considerations have a greater impact on the biomass distribution of LWD compared to that of CWD. Conversely, the biomass of CWD is more influenced by the species richness. The presence of microtopography plays a vital role in determining the spatial distribution of species and biomass at local scales, reflecting the multiple response mechanisms and growth strategies of vegetation in response to redistribution in water, soil, and light.

DINAMIKA PERTUMBUHAN POHON DI HUTAN RESTORASI BODOGOL TAMAN NASIONAL GUNUNG GEDE PANGRANGO, JAWA BARAT

The Restored Forest (RF) in Bodogol, Gunung Gede Pangrango National Park (GGPNP) is located in the degraded lowland forest area. The Bodogol RF constituted the area of the ecosystem restoration program, where the initial tree planting was carried out by Mrs. Megawati Soekarnoputri the 5th President of the Republic of Indonesia. In that restored forest area, a study was conducted by establishing one hektare plots. We recorded 26 tree species and 16 families, including 14 tree species that were used in the restoration, four cultivated species, and eight species that naturally enter the site as new arrival (recruitment). The total basal area was 7.47 m2/Ha and tree density was 256 trees/Ha. The mean diameter growth was 1.78 cm/year, and the highest diameter growth was Hibiscus tilliaceus (2.42 cm/year). The mean total height growth was 0.52 m/year, and the highest was Paraserianthes falcataria (0.85 m/year). The density of Toona sureni was very high (61 trees/Ha) and in the future it ay dominate the forest will, therefore other tree species native to Mt. Gede-Pangrango should be planted to enrich the present restored forest so as to encourage the development of mixed lowland or montane forests similar to the original climax forests with high species diversity. Structurally, about 50 % of the RF has been achieved, but species composition still needs further enrichment either by active intervention of planting native TNGGP species if deemed necessary or by allowing succession to take place naturally, although it will take a very long time.

Diversity and regeneration status of tree species in Binsar Wildlife Sanctuary, Uttarakhand, India

We assessed tree species diversity and regeneration status in the Binsar wildlife sanctuary, Uttarakhand. Six major forest sites were selected for sampling ranging from 1600-2400m asl in north and south aspects. In each forest stand a 100 x 100m plot was laid and trees, saplings and seedlings were recorded following standard ecological methods.The overall tree density ranged from 663 to 1066 individuals ha-1 among the identified forest communities and total basal area from 40.24-71.20 m2 ha-1. Good regeneration was observed in higher altitudinal community.

Effects of the Dominate Plant Families on Elevation Gradient Pattern of Community Structure in a Subtropical Forest

Dominant groups and rare groups often coexist in forests. Dominate plant families generally have more species diversity and occupy most of the biomass. However, their effects on community construction and species diversity maintenance remain to be studied. This study aims to investigate this question by using the two dominant plant families in a Chinese subtropical forest (Lauraceae and Fagaceae). In this study, 22 forest dynamic plots were established in the forest distribution area of Daming Mountain Nature Reserve at an elevation of 300–1400 m. We explored the elevational change in the community structure and its relationship with Lauraceae and Fagaceae using generalized additive models (GAM) and a regression analysis. Then we used a correlation analysis to describe the relationship between environmental factors and the community structure. Our results showed the species diversity index showed a hump-shape trend along the elevation, and the total basal area showed no significant change along the elevation. The richness of Lauraceae and Fagaceae showed a positive correlation with the species diversity, but only the richness of Fagaceae showed a positive correlated with the total basal area. Species diversity was positively correlated with soil total nitrogen and soil organic matter. Species diversity and the total basal area were negatively correlated with the soil pH. In summary, Lauraceae and Fagaceae are correlated for community structure, and this correlation is not affected by elevation. Fagaceae has played a more important role than Lauranceae. This study highlights the impact of dominant plant families on the forest community assembly along the elevational transect.

ARTICLE WOODY SPECIES STRUCTURE AND REGENERATION STATUS IN MEHAL WONZ - ZEGO FOREST, N/ SHEWA ZONE, AMHARA REGIONAL STATE, ETHIOPIA

This study was conducted on Mehalwonze- Zego forest in North Shewa zone, Amhara Regional State, Ethiopia, A Transect sampling method was used to collect vegetation data. Sixty seven(67) plots of 20m × 20m were laied each at 300m intervals and five subplots of 2m × 2m, one in the center and four in the corner of the main plots, were laid for seedling and sapling inventory. Vegetation parameters such as DBH &gt;2.5cm, H ≥2.5m of as well as seedling and sapling density with five sub plots of 2m × 2m. A total of 55 woody species belonging to 51 genera and 38 families were identified. The density of seedlings, saplings and matured woody plants in all of the plots were 1302, 1517 and 905 individuals, respectively. Importance Value Index (IVI) of each species were calculated, based on this value the conservation priority classes was done which indicated that there are woody species that require urgent conservation. The total basal area of the forest was 67.96 m2/ha. DBH and height class distribution of woody spcies confirms that the forest is under a secondary stage of development. Based on the results of regeneration assessment, conservation priority should be given for species with poor regeneration status.

Forest Restoration in an Abandoned Seasonally Dry Tropical Forest in the Mae Klong Watershed, Western Thailand

Deforestation for the development of agricultural land is a critical driver of biodiversity loss. We examined the relationships between tree species and environments after the abandonment of a plot of land at the Mae Klong Watershed Research Station, Western Thailand. Vegetation monitoring was conducted every two years on a 16-ha permanent plot established in 2011 until 2019. All trees with diameter at breast height (DBH)≤1 cm were measured. Canonical correspondence analysis (CCA) was performed to investigate the relationships between tree species and environments. We found a total of 199 tree species in the plot, which comprised both pioneer and climax species. The high tree density and low basal area were 1,280 stem/ha and 7.30 m2/ha, respectively. During 2011-2019, the species richness and total tree density were decreased by nine species (from 206 to 197 species) and 83 stem/ha (from 1,120 to 1,037 stem/ha). In contrast, the total basal area increased from 6.41 to 7.26 stem/ha. According to the measured environmental variables, mixed deciduous species such as Pterocarpus macrocarpus and Xylia xylocarpa var. kerrii preferred higher elevations and drier sites compared to dry evergreen species such as Dipterocarpus alatus. Early colonizing species such as Trema orientalis and Ficus species exhibited rapid population decreases, whereas climax species such as Lagerstroemia tomentosa exhibited highly successful regeneration under natural conditions. Artificial reforestation efforts may be required in areas with large disturbance, including the planting of mixed tree species to promote natural regeneration and reduce the recovery period.

Tropical Forests Stand Recovery 30-year After Selectively Logged in Peninsular Malaysia

This article analysed the 25–30 years of growth of dipterocarps forests that were logged under the Selective Management System (SMS) at three sites in Peninsular Malaysia to understand how management regimes affected forest stem density and basal area. The management regimes were (1) unlogged, (2) moderately logged forests that logged all dipterocarps ≥ 65 cm diameter at breast height (dbh) and all non-dipterocarps ≥ 60 cm dbh, and (3) intensely logged forests that logged all dipterocarps ≥ 50 cm dbh and non-dipterocarps ≥ 45 cm dbh. The intensely logged regime is similar to the SMS practices in Peninsular Malaysia. This result showed that one-year post-logging, there was no difference in the total stem density and basal area between forests logged according to the two management regimes. Forest stem density decreased over time in all management regimes, significantly greater in unlogged forests (-15.1 stems/ha/yr, confidence interval (CI): -16.9 to -13.3). This decline in stem density reflected that mortality exceeded recruitment in all management regimes. Despite the consistent decline of forest stem density, the basal area increased over time, and the rate of increase in the intensely logged forest (0.22 m2 /ha/yr, CI: 0.19 to 0.25) was significantly greater than the other management regimes. Our study showed that 30 years post-logging, the effect of selective logging remained evident. Both logged forest stem density and the basal area did not recover to that of unlogged forests, indicating the importance of enrichment planting and extending the cutting cycles beyond 30 years for the sustainability of dipterocarps forests.

Broadleaved trees enhance biodiversity of the understorey vegetation in boreal forests

Understorey vegetation constitutes a remarkable part of the total biodiversity of boreal forests. Mixing broadleaved trees in coniferous forests has been shown to enhance vascular plant abundance and species richness, while high stand density has a counteracting effect. However, more information is needed on how environmental factors modify these biodiversity responses.We investigated how the proportion of broadleaved trees of total basal area, tree species richness, stand density, and shrub cover were reflected in the number of vascular plant species and percentage cover of herbs and bilberry (Vaccinium myrtillus). We also studied the response of site fertility indicators, i.e. C:N ratio and extractable calcium concentration in the soil organic layer, to broadleaved species in mixed-forests.The study was based on the data of understorey vegetation, soil, and stand properties in forests on mineral soil, inventoried on a systematic sample plot network in Finland in 2006. We used a subset of 307 plots in the hemi-southern and middle boreal zones and divided the plots either to xeric or mesic types. We used generalized additive models in analysing the data.Birches (Betula sp.) were the main broadleaved species. Vascular species richness and herb cover generally increased with increasing proportions of broadleaved trees and tree species number both on mesic and xeric sites but decreased with increasing stand density on mesic sites. An increase in proportion of broadleaved trees and stand density resulted in decreased bilberry cover in the southern boreal zone, probably due to stand shading, but in increased cover in the middle boreal zone. Vegetation responses to increasing shrub cover often showed unimodal shape. As increase of proportion of broadleaved trees correlated positively with calcium and negatively with C:N of the organic layer, we suggest that nutrient input from easily decomposable birch leaf litter promotes species richness and herb cover via improved nutrient availability in the soil.Our results indicate that many stand characteristics determining understorey biodiversity can be directed by forest management regimes. Generally, slight increase of broadleaved trees benefitted the understory plant richness, given that stand density is not too high. Because site type and zone controlled many responses, we suggest that it would be beneficial to have habitat and zone-specific instructions in forest management practices that conserve understorey vegetation and its multi-purpose ecosystem services.

Fire exclusion vs. a fire-free interval following repeated prescribed fire: Consequences for forest stand structure and species composition in an upland oak forest

In the Central Appalachian forest region, oaks (Quercus L.) and other disturbance-dependent tree species are experiencing widespread regeneration failure after decades of fire suppression. Managers use prescribed fire to decrease basal area with the aim of facilitating oak regeneration and shifting species composition toward pyrophytic species that dominate the overstory. Although fire may set the stage for improved oak regeneration, a fire-free period is necessary for oak seedlings to develop into fire-resistant stems. The effects of prescribed fire have been amply investigated across the region, but few studies have examined changes to stand structure and oak regeneration after cessation of burning. We followed the effects of three treatments, fire-excluded, 3x-burned, and 4x-burned, for 20 years. After a fire-free interval of approximately ten years, burned treatments had significantly lower total basal area and greater relative density of oaks in the subcanopy (10–20 cm DBH) than the fire-excluded treatment. The 4x-burned, which had the greatest reduction in basal area, also had greater relative density of midstory oaks (2–10 cm DBH), and higher stem density of oak regeneration (<2 cm DBH) than the fire-excluded. Despite these trends towards increased regeneration of oaks and other pyrophytes, red maple (Acer rubrum L.) stem density also increased in the midstory of burned treatments, suggesting a legacy effect of decades of fire suppression and the concomitant mesophication that has occurred. We also examined the effects of continued fire exclusion on the fire-excluded reference treatment. Additional evidence of mesophication on this treatment was demonstrated by increased overstory (≥20 cm DBH) and subcanopy red maple stem density as well as midstory (2–10 cm DBH) eastern white pine (Pinus strobus L.) stem density, a prominent mesophyte on these sites. This study supports the idea that repeated prescribed burning followed by a 10-year fire-free interval can alter stand structure and lead to improved oak regeneration by increasing canopy openness. However, the results were variable across burned treatments (3x vs. 4x) and the ingrowth of red maple and other mesophytes after only 10 years of fire exclusion will require additional control measures. Successful maintenance of oak-dominated forests on upland sites in the Central Appalachian hardwoods region may be contingent on a subsequent canopy disturbance that further increases light availability followed by a fire-free interval. Importantly, in the absence of burning or other disturbance, red maple and other mesophytic species will continue to increase in relative stem density.

Sensitive tree species remain at risk despite improved air quality benefits to US forests.

Atmospheric nitrogen (N) and sulfur (S) deposition can significantly affect forest biodiversity and production by altering the growth and survival of trees. Three decades of air quality regulations in the United States (U.S.) have led to large reductions in oxides of N (44-81%) and S (50-99%) emissions and associated deposition. Here, we evaluated the magnitude and extent of effects over 20 years from atmospheric N and S deposition on the growth and survival of 94 tree species - representing 96.4 billion trees and an average of 88% of forest basal area across the contiguous U.S. (CONUS). Overall, species' growth and survival rates have responded positively to declining deposition, but we find that decreases of at least 2.5 kg N ha-1 yr-1 are needed across 19.8% (growth) and 59.5% (survival) of the CONUS to prevent detrimental effects to sensitive species. Reduced forms of N (NHx = NH3 + NH4 +) are now the dominant form of N deposition in 45.4% of the CONUS - notably in agricultural regions - and exclusively need to be reduced by ≥ 5.0 kg N ha-1 yr-1 in some areas. Further S deposition decreases of ≥ 1.0 kg S ha-1 yr-1 are needed in 50.4% (growth) and 56.2% (survival) of the CONUS to protect sensitive species and notably, evergreen trees. Total basal area is increasing in much of the country (85.2%) because of N fertilizing effects, but these growth increases could result in biodiversity loss. Our findings can be used to evaluate past successes of air quality policies and the future benefits of air pollution reductions to terrestrial ecosystems.

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.