Tree Basal Area Research Articles

Effects of soil compaction on above- and belowground interactions during the early stage of forest development

Forested green spaces in urban and peri-urban areas are expected to serve multiple roles, including providing ecosystem services and maintaining species diversity and soil health, both of which are particularly important for human health. However, soil compaction is a major cause of soil degradation in urban areas and brownfields (abandoned, previously developed land). We examined the effects of compaction on soil physicochemical properties, tree species richness, tree basal area, and the functional diversity of microbial communities in an immature volcanic soil through a long-term (14-year) field experiment. Our experimental results showed that soil compaction reduced not only both tree species richness and biomass but also the multifunctionality of soil microbial communities. Furthermore, tree species richness was significantly positively related to soil microbial decomposition activity. These findings provide evidence of above- and belowground interactions and underscore their importance in the design of urban forests using ecosystem-based solutions.

Seasonal vertical accretion in different hydro-geomorphic environments of Indian Sundarban: Assessing the role of mangroves in mitigating sea level rise impacts

The Indian Sundarban, renowned for its unique hydro-geomorphic diversity, faces rising threats from sea level rise, necessitating an examination of the spatio-temporal variation of vertical accretion and the role played by mangroves in mitigating these impacts. As such, fifteen transects were chosen across buffer and transition zones of Indian Sundarban, each equipped with 4–6 sedimentation pins, to gauge accretion rates in premonsoon, monsoon, and postmonsoon season during period March 2020 to March 2022, considering diverse hydro-geomorphic attributes. The vertical accretion rate exhibits a curvilinear pattern, ascending from the lower seafront zone towards the middle of the estuarine region, reaching a peak, and subsequently declining towards the upper estuarine zones. Specifically, in the seafront zone, the yearly mean accretion (focusing solely on accretion and excluding subsidence) ranges between 5 and 10 mm/year, while in the middle estuarine region, it increases to an average of 38.1 ± 9.44 mm/year. However, in the upper zone, the yearly mean accretion decreases slightly to approximately 17.71 ± 9.54 mm/year. Similar patterns are observed when considering the distance from the riverfront to the interior of the mangrove zones. Seasonal analysis demonstrates that the postmonsoon period exhibits the highest accretion, followed by the premonsoon season, while the monsoon tends to be erosional in nature. Mangrove zonation, and subsequent distribution of root height, root diameter, root density, tree density, tree basal area, inundation frequency, current speed, variation in suspended sediment concentration were identified as influential factors affecting vertical accretion rates. Based on multiple regression analysis, root density, inundation frequency, and tree density demonstrated moderate-positive correlations with vertical accretion, whereas distance from the riverfront, root height, and root diameter displayed negative correlations. This study enhances our understanding of the intricate processes behind vertical accretion in the Sundarban, offering valuable insights for future research and advancing discussions on the broader implications of climate change in coastal regions.

Does It Matter Whether to Use Circular or Square Plots in Forest Inventories? A Multivariate Comparison

The design of a sampling unit, whether a simple plot or a subplot within a clustered structure, including shape and size, has received little attention in inferential forestry research. The use of auxiliary variables from remote sensing impacts the precision of estimators from both model-assisted and model-based inference perspectives. In both cases, model parameters are estimated from a sample of field plots and information from pixels corresponding to these units. In studies assisted by remote sensing, the shape of the plot used to fit regression models (typically circular) often differs from the shape of the population elements for prediction, where the area of interest is divided into equal tessellated parts. This raises interest in understanding the effect of the sampling unit shape on the mean of variables in forest stands of interest. Therefore, the objective of this study was to evaluate the effect of circular and square subplots, concentrically overlapped and arranged in an inverted Y cluster structure, over tree density, basal area, and aboveground biomass in a managed temperate forest in central Mexico. We used a Multivariate Generalised Linear Mixed Model, which considers the Gamma distribution of the variables and accounts for spatial correlation between Secondary Sampling Units nested within the Primary Sampling Unit. The main findings of this study indicate that the type of secondary sampling unit of the same area and centroid, whether circular or square, does not significantly affect the mean tree density (trees), basal area (m2), and aerial biomass.

Influence of Structure from Motion Algorithm Parameters on Metrics for Individual Tree Detection Accuracy and Precision

Uncrewed aerial system (UAS) structure from motion (SfM) monitoring strategies for individual trees has rapidly expanded in the early 21st century. It has become common for studies to report accuracies for individual tree heights and DBH, along with stand density metrics. This study evaluates individual tree detection and stand basal area accuracy and precision in five ponderosa pine sites against the range of SfM parameters in the Agisoft Metashape, Pix4DMapper, and OpenDroneMap algorithms. The study is designed to frame UAS-SfM individual tree monitoring accuracy in the context of data processing and storage demands as a function of SfM algorithm parameter levels. Results show that when SfM algorithms are properly tuned, differences between software types are negligible, with Metashape providing a median F-score improvement over OpenDroneMap of 0.02 and PIX4DMapper of 0.06. However, tree extraction performance varied greatly across algorithm parameters, with the greatest extraction rates typically coming from parameters causing increased density in dense point clouds and minimal point cloud filtering. Transferring UAS-SfM forest monitoring into management will require tradeoffs between accuracy and efficiency. Our analysis shows that a one-step reduction in dense point cloud quality saves 77–86% in point cloud processing time without decreasing tree extraction (F-score) or basal area precision using Metashape and PIX4DMapper but the same parameter change for OpenDroneMap caused a ~5% loss in precision. Providing reproducible processing strategies is a vital step in successfully transferring these technologies into usage as management tools.

Assessing Carbon Stocks and Ecosystem Functioning in Char (Buchanania lanzan) Forests of Central India

The present study assessment of plant community structure, carbon stock and CO2 sequestration of char (Buchanania lanzan) dominant forest sites in Central India during 2020-22. The forest vegetation was analysed using 20 quadrats (each 10 x 10 m in size for tree layers, 5 x 5 m in size for sapling layers and 1 x 1 m size for seedling layers) within the representative one-hectare plot on each site. The biomass, carbon stock, and carbon dioxide sequestration from three district (Mahasamund, Gariaband, and Kabirdham) char dominated forest sites of dry deciduous forests in Central India were estimated using the non-destructive allometric equation approach. The results revealed that the density of tree, sapling and seedling were ranged from 430-605 stems ha-1, 120-600 stems ha-1 and 28000-34500 stems ha-1, respectively. The basal area of tree and sapling layers were varied from 18.15-29.68 m2 ha-1 and 0.33-1.04 m2 ha-1, respectively. The diversity indices of tree layer viz; Shannon index, Simpson index, Evenness, species richness and beta diversity were ranged from 2.40-2.72, 0.17-0.22, 1.08-1.18, 2.26-3.11 and 5.0-6.0, respectively on different forest site in Central India. The total biomass, carbon stock and CO2 sequestration potential of tree layers were varied from 105.72-216.96 Mg ha-1, 50.22-103.06 Mg ha-1 and 184.29-378.22 Mg ha-1, respectively on char dominant various forest sites in Central India. The correlation coefficients were statistically significant performed between basal area and biomass, carbon stock and CO2 sequestration potential with R2 values of 0.988 at p<0.01 levels. After doing this study, it can be concluded that estimating the biomass and carbon stock in Central India will be useful for managing forests sustainably.

Potential of Agroforestry Practices on Woody Species Diversity and Composition: Implication for Conservation of Indigenous Trees in Selected Districts of Tigray, Northern Ethiopia

Human activities such as expanding farmland, producing charcoal, and harvesting construction materials and fuel wood are major contributors to forest degradation and biodiversity loss in Northern Ethiopia. This study aimed to assess woody species' diversity, composition, and threat levels in different agroforestry practices to prioritize their conservation. As the result three potential Agroforestry practices were purposively identified and selected for the study. A total of 45 sample plots, 15 plots from each agroforestry practices such as Woodlot agroforestry (WLAF) (10m x 10m), Homegarden Agroforestry (HGAF) (20m x 10m), and Parkland agroforestry (PLAF) (50m x 100m). Data on woody species were analyzed using Past version 2.17c and SPSS version 20. The results identified 36, 26, and 21 woody plant species from 31, 23, and 19 genera, as well aswell as 22, 16, and 15 families in HGAF, PLAF, and WLAF, respectively. Significant differences (p < 0.001) were found among the agroforestry practices in terms of tree density, species richness, species abundance, and Shannon diversity, though species evenness did not vary. The Importance Value Index (IVI) highlighted the top species in HGAF as A. etbaica (75.2), F. albida (33.1), and A. seyal (30.6). Species with low IVI values, such as B. polystachya (1.56), R. vulgaris (1.57), G. ferruginea (1.62), and C. aurantiifolia (0.90), require significant conservation efforts. In PLAF, the key species were F. albida (131.03), A. seyal (59.33), and C. africana (26.21). In WLAF, E. globulus (61.8), A. seyal (8.83), and C. edulis (31.4) were the most abundant, frequent, and dominant. Trees and shrubs in HGAF and WLAF had smaller stem diameters compared to those in PLAF. However, WLAF had greater tree height and basal area (BA, m²) than both HGAF and PLAF, with HGAF also showing a higher BA than PLAF (p ≤ 0.05). The study concluded that HGAF and PLAF are vital for sustaining local livelihoods, providing food, and conserving biodiversity. These agroforestry systems enhance natural forests and help prevent the extinction of woody species. Therefore, developing and enhancing HGAF, and PLAF in densely populated landscapes should be integral to biodiversity conservation strategies.

Tree Species Diversity and Carbon Stock of Tropical and Sub-Tropical Forests of Mizoram, Northeast India

The present study was conducted in tropical and sub-tropical forests of Mizoram, Northeast India. A total of 49 species belonging to 40 genera and 26 families were recorded in the tropical forest (TF). Whereas, in the subtropical forest (STF), 47 species belonging to 42 genera and 28 families were recorded. As per Importance Value Index (IVI), the most dominant species in TF were : Castanopsis tribuloides (47.67), Schima wallichii (40.71), Aporosa octandra (20.96) and Wendlandia budleioides (17.79). Whereas, the species such as Ilex godajam (41.42), Saprosma ternatum (32.74) and Diospyros racemosa (31.34) were the most dominant species in STF. The total tree density and basal area were 1610 individuals ha-1 and 25.016 m2 ha-1 in TF and 1380 individuals ha-1 and 24.20 m2 ha-1 respectively in STF. The diversity indices such as Shannon’s diversity index (H′), Simpson’s dominance index (CD), Margalef richness index (d), and Pielou’s evenness index (J) ranged from 2.93-3.16, 0.91-0.94, 7.82-8.15, 0.76-0.81 in both the forests. The total tree biomass was 178 Mg ha-1 in TF and 144 Mg ha-1 in STF. Similarly, the total carbon stock in TF was 85 Mg C ha-1 and 68 Mg C ha-1 in STF. Such information on these forests can serve as a valuable tool for improving our capacity to enhance biodiversity conservation efforts and management of tropical forests for their sustainable use in the future.

Unveiling urbanization effects on trees outside forests along the urban-rural gradient in megacity Bengaluru

Rapid urbanization has caused significant changes along the urban-rural gradient, leading to a variety of landscapes that are mainly shaped by human activities. This dynamic interplay also influences the distribution and characteristics of trees outside forests (TOF). Understanding the pattern of these trees will support informed decision-making in urban planning, in conservation strategies, and altogether in sustainable land management practices in the urban context. In this study, we employed a deep learning-based object detection model and high resolution satellite imagery to identify 1.3 million trees with bounding boxes within a 250 ​km2 research transect spanning the urban-rural gradient of Bengaluru, a megacity in Southern India. Additionally, we developed an allometric equation to estimate diameter at breast height (DBH) from the tree crown diameter (CD) derived from the detected bounding boxes. Our study focused on analyzing variations in tree density and tree size along this gradient. The findings revealed distinct patterns: the urban domain displayed larger tree crown diameters (mean: 8.87 ​m) and DBH (mean: 43.78 ​cm) but having relatively low tree density (32 trees per hectare). Furthermore, with increasing distance from the city center, tree density increased, while the mean tree crown diameter and mean tree basal area decreased, showing clear differences of tree density and size between the urban and rural domains in Bengaluru. This study offers an efficient methodology that helps generating instructive insights into the dynamics of TOF along the urban-rural gradient. This may inform urban planning and management strategies for enhancing green infrastructure and biodiversity conservation in rapidly urbanizing cities like Bengaluru.

Influence of wildfires severity on tree composition and structure in Aberdare Afromontane Forest Ranges, Kenya

Wildfires strongly impacts on the forest ecosystems, with poorly understood consequences on the composition, diversity and structure within Afromontane forests of Eastern Africa. The impacts of wildfire on vegetation were investigated one year after the fire occurrence season. The burn severity was evaluated using Sentinel-2 satellite derived spectral index known as dNBR (difference Normalized Burn Ratio). This was used to delineate wildfire into low and high severity classes. We investigated the effects of wildfires using 36 plots of 15m radius distributed in high and low burn severities while others were laid in unburnt areas. Our findings indicated that tree height, basal area and density were significantly different along severity classes (p = 0.003, p=0.007 and p<0.000 respectively). However, diameter at breast Height was not significant along severity classes (p=0.185). The most ecologically important species based on Important Value Index (IVI) within the fire affected areas were Juniperus procera, Nuxia congesta, Olea europaea subsp. cuspidata, Protea kilimandscharicum and Scurtia myrtina. Among the five dominant tree species, the density of Protea kilimandscharicum and Olea europaea subsp. cuspidata were significant along the fire severities (p<0.05). Interaction of vegetation zones and wildfire severity indicated that only height was significant (p= 0.000) while all the other tree variables and species diversity index were insignificant; DBH (p=0.053), basal area (p=0.606), tree density (p=0.389), Shannon Weiner diversity index (p=0.843), Simpson dominance index (p=0.490) and Pielou's evenness index (p=0.248). Whereas this study was on a short-term post-fire effects on vegetation, it has shown remarkable findings which can guide restoration and management of fire affected landscapes. The study recommends evaluation of long-term regeneration and recovery to guide integrated fire management within Afromontane Forest Ecosystems.

Vegetation Structure, Composition and Plant Community types in Tropical Dry Deciduous Forests of Jaipur, Rajasthan, India

The research was carried out in the Aravalli Forests of Nahargarh (NWLS) and Jamwa Ramgarh Wildlife Sanctuaries (JRWLS) of Jaipur, Rajasthan, India. The vegetation structure, composition, biodiversity and plant community types were assessed across the five forest stands viz Nahargarh biological park (S1), Nahargarh Sanctuary (S2) in NWLS and Ramgarh (S3), Raisar (S4), and Digota (S5) of JRWLS, respectively. A total of 164 qaudrats of 20*20 m2 were laid to assess the vegetation data including frequency, basal area, density, importance value index (IVI), biodiversity indices (Shannon-weiner, Simpson, Pielou and Margalef’s) and plant community types. The tree basal area ranged between 18.56 -34.36 m2/ha while stand density was 923-1433 tree/ha. Our study indicated the dominance of family Fabaceae with 20 species and 11 genera with Anogeissus pendula showing the maximum frequency, density, mean basal area and IVI. Further, the agglomerative hierarchal clustering showed five types of plant communities with Anogeissus-Adhatoda as the most widely spread community in these forests. Among the two sanctuaries, species diversity was higher for JRWLS (2.83) than NWLS (2.80). The current study provides important baseline data for forthcoming research on monitoring and preserving these forest’s biological diversity. The significance of present study will provide insight into the structure and variety of tree species in tropical dry deciduous forests.

Community structure, species diversity and biomass of trees in Tranum Forest Reserve, Raub, Pahang

This study was conducted at the Tranum Forest Reserve, Raub, Pahang to determine the community structure, species diversity and biomass of trees in the area. Four study plots, each measuring 25 m × 20 m, were established at the study site, which covered a total area of 0.2 ha. All trees with diameter at breast height (DBH) of 5 cm and above were measured and recorded. A total of 175 trees was enumerated in the study plots, comprising 106 species and 79 genera from 40 families. The largest family was Lauraceae, represented by 11 species from six genera, followed by Myrtaceae with eight species from one genus. Tree species diversity of the study area was high, as reflected by a Shannon Diversity Index (H’) value of 4.49 (Hmax = 4.66). Margalef Richness Index (R’) and Shannon Evenness Index (E) showed values of 20.33 and 0.84, respectively. The most important family, based on the highest Family Important Value Index (FIVi), was Dipterocarpaceae, with a value 17.31%. Shorea platyclados was the most important species with Important Value Index (IVi) of 17.04%. The tree density of the study area was 875 indidivuals per hectare (ind/ha), with Lauraceae being the densest family at 85 ind/ha. Vitex gamosepala was the densest species at 40 ind/ha. The total basal area of trees was 66.23 m2/ha, with Dipterocarpaceae showed the highest basal area of 31.69 m2/ha and Shorea platyclados had the highest basal area of 31.69 m2/ha at species level. The total biomass of trees was estimated at 1,307.56 t/ha, of which the above ground biomass and the below ground biomass were 1,091.33 t/ha and 216.23 t/ha, respectively. Dipterocarpaceae contributed the highest biomass with an estimate of 743.83 t/ha and Shorea platyclados showed the highest biomass at species level with 743.83 t/ha.

Dynamics of resin yield in Pinus brutia: A quantitative analysis using bark streak tapping

The sustainable harvesting of resin yield from forests plays a crucial role in providing valuable renewable resources. Specifically, Pinus brutia forests in Türkiye are significant for their oleoresin, utilized in various industries. Yet, understanding how dendrometric and meteorological factors influence resin yield is essential for optimizing production while ensuring forest sustainability. This study aimed to estimate oleoresin yield in Pinus brutia plantations using dendrometric parameters (such as diameter at breast height and tree height, basal area, volume and canopy closure) and meteorological parameters (including monthly; minimum, maximum, and average temperature, precipitation, humidity, vapor pressure, and wind speed), to identify the key factors affecting resin production. Resin was collected from 389 Pinus brutia trees of varying diameters across 27 different plots using the bark streak tapping method, with data recorded every 15 days over a year. Weighted Leased Square regression analysis was conducted to explore the relationship between resin yield and the aforementioned dendrometric and meteorological parameters. The analysis revealed that diameter at breast height, monthly average temperature, wind speed, and precipitation significantly influence resin yield. The study underscores the intricate interplay between these factors and resin production, indicating that larger diameters and specific meteorological conditions—especially average temperature, wind speed, and precipitation—are positively correlated with increased resin output. The findings suggest that sustainable resin extraction practices in Pinus brutia forests should account for not only the physical characteristics of the trees but also the local meteorological conditions to maximize yield without compromising forest health. This research contributes to the development of more effective guidelines for oleoresin harvesting, ensuring both economic viability and ecological preservation.

Tidal Freshwater Forested Wetlands in the Mobile-Tensaw River Delta along the Northern Gulf of Mexico

Tidal freshwater forested wetlands (TFFWs) typically occur at the interface between upriver non-tidal forests and downstream tidal marshes. Due to their location, these forests are susceptible to estuarine and riverine influences, notably periodic saltwater intrusion events. The Mobile-Tensaw (MT) River Delta, one of the largest river deltas in the United States, features TFFWs that are understudied but threatened by sea level rise and human impacts. We surveyed 47 TFFW stands across a tidal gradient previously determined using nine stations to collect continuous water level and salinity data. Forest data were collected from 400 m2 circular plots of canopy and midstory species composition, canopy tree diameter and basal area, stem density, and tree condition. Multivariate hierarchical clustering identified five distinct canopy communities (p = 0.001): Mixed Forest, Swamp Tupelo, Water Tupelo, Bald Cypress, and Bald Cypress and Mixed Tupelo. Environmental factors, such as river distance (p = 0.001) and plot elevation (p = 0.06), were related to community composition. Similar to other TFFWs along the northern Gulf of Mexico, forests closest to Mobile Bay exhibited lower basal areas, species density, diversity, and a higher proportion of visually stressed individual canopy trees compared to those in the upper tidal reach. Results indicate a strong tidal influence on forest composition, structure, and community-level responses.

A first look into moss living tardigrades in boreal peatlands.

Tardigrades (Tardigrada) are a phylum of micrometazoans found in all biomes on Earth, but their ecology and habitat preferences remain vastly understudied. Boreal peatlands include a diversity of habitat types and high structural heterogeneity that represents an interesting system to study some of the poorly known habitat preferences of tardigrades. Here, we investigate for the first time tardigrade communities in peatland mosses and the latter's potential associations with key environmental variables. We collected 116 moss samples from 13 sites representing different peatland types and management histories. We found that tardigrades are common and diverse in boreal peatlands, as tardigrades were present in 72% of the collected samples and we identified 14 tardigrade genera. Tardigrade abundance seemed to increase alongside the increasing tree basal area and the density was higher in the microtopographic level further from the water table level, that is, hummocks (mean 117/moss gram) than in lawns/hollows (mean 84/moss gram). Furthermore, the highest tardigrade density was found in the moss taxa that are associated with forested peatland types (i.e., feather mosses) (321 mean/moss gram). Finally, we found interesting patterns regarding tardigrade functional diversity, as carnivorous tardigrades were found only in peatlands with tree basal area > 20 m2 and mostly in hummocks. Our study demonstrates that the habitat heterogeneity of peatlands (e.g., variation in moisture and vegetation cover) represents an interesting system to study tardigrade ecology and habitat preferences. However, since we found variation in tardigrade abundance and communities across peatland types and microhabitats within peatlands, our results highlight that such studies should be conducted with numerous replicate samples and a systematic study design that properly addresses the habitat heterogeneity between and within different peatland types.

Tree cavity density is a limiting factor for a secondary cavity nester in second-growth Andean temperate rainforests

Abstract Cavity-nesting bird populations are most frequently limited by the number of tree cavities available in second-growth forests. However, this possible limitation of a key resource is less clear in old-growth forests. We compared forest attributes (i.e., basal area, density of larger trees, density of dead trees, and tree cavity density) in second-growth and old-growth stands in Andean temperate rainforests in southern Chile. To examine the role of nest-site availability in limiting the populations of Aphrastura spinicauda (Thorn-Tailed Rayadito), a secondary cavity-nesting bird species, we conducted an experiment in which nest boxes were added and removed in old-growth and second-growth forests during a 5-yr period (2008–2013). In old-growth forests, as compared to second-growth forests, we found a more than double basal area (99.6 vs. 43.7 m2 ha–1), a three times higher density of larger trees (88.2 vs. 36.4 trees ha–1), and a 1.5 times higher number of small cavities (25.9 vs. 10.3 cavities ha–1). The density of cavities also strongly increased with tree diameter and basal area. In second-growth forests, A. spinicauda showed a strong response to the addition and removal of nest boxes, with population abundance increasing by 13% and then decreasing by 50%, respectively. In contrast, we found no impact in old-growth stands. Our experiment emphasizes the importance of maintaining large and dead trees in second-growth, disturbed, and managed forests. These trees provide suitable cavities for A. spinicauda, and likely many other secondary cavity nesters, increasing their abundances in a Globally significant Biodiversity Hotspot in southern South America.

Forest composition shapes seed‐rodent interactions in a gradient of broadleaves and conifers

Abstract Non‐native tree species and mixed forests have been increasingly employed in forestry practice as a safeguard against climate change and as a tool to foster biodiversity while providing economic benefits. Though these changes in forest composition may affect animal communities and ecosystem processes, they are seldom studied through a plant–animal interaction perspective. Here we investigated how forests with varying proportions of a native broadleaf (Fagus sylvatica) and two conifers (introduced Pseudotsuga menziesii and native Picea abies) affect rodents and their interactions with seeds. We surveyed terrestrial small mammal communities, estimated species' densities, assessed seed preference by rodents, collected data on environmental variables (understory density and tree basal area), measured Fagus sylvatica seed production and tracked 1200 seeds of Fagus sylvatica in 20 different forest plots in northern Germany in a mast and non‐mast year for Fagus sylvatica. Forest composition influenced the interactions between rodents and seeds. In forests with a lower proportion of broadleaves, beech seeds were harvested faster and in greater quantities, had diminished survival and were less often cached. These results are in agreement with three other findings: (a) seed fate responded to the proportion of broadleaves and conifers irrespective of conifer tree identity, (b) rodents preferred nutritious beech seeds over small conifer seeds, and (c) higher proportions of seeds were harvested during the period when beech seeds were scarce (non‐mast year). Synthesis and applications: This work provides evidence of how forest composition can affect plant–animal interactions without necessarily altering animal communities or population densities. Specifically, we found no differences between forests with native and non‐native conifer trees regarding small mammal community, seed‐rodent interactions or seed fate. Furthermore, rodents may provide a service in mixed forests by primarily preying upon seeds of Fagus sylvatica, a superior‐competitive species, and thus mitigate beech dominance over conifer species.

Old-growth forests are critical to safeguard tropical birds in complex landscape mosaics exposed to slash-and-burn agriculture

ContextSlash-and-burn agriculture generates landscape mosaics composed of different land uses. Ecological theory postulates that in these mosaics, the structure of species assemblages depends on both local- and landscape-scale factors, but their relative role remains poorly known.ObjectivesUnderstanding the relative importance of local and landscape variables for bird assemblages in landscape mosaics of the Mayan tropical forest, Mexico.MethodsWe evaluated the effect of two local variables (land use type and tree basal area) and two landscape variables (old-growth forest cover and human proximity) on bird abundance and diversity, separately assessing forest and non-forest birds. As species extirpation may accelerate when forest loss exceeds certain limits (extinction thresholds), we assessed forest loss effects with linear and nonlinear models.ResultsWe recorded 1867 birds from 118 species in four land-use types (old-growth forest, secondary forest, burned lands, and agricultural lands). Land-use type and surrounding old-growth forest cover better predicted bird abundance and diversity than tree basal area and human proximity. Agricultural lands showed the lowest abundance and diversity of forest species, but the highest abundance and diversity of non-forest species. We found no support for the extinction threshold hypothesis. Yet, independently of the land use, old-growth forest loss decreased the diversity of forest species and increased the abundance and diversity of non-forest species. Human proximity also decreased total bird abundance, especially because of the loss of forest species.ConclusionsOur findings highlight the key role played by old-growth forests for preserving bird assemblages in landscape mosaics exposed to slash-and-burn agriculture.

Tree species richness improves soil net nitrogen mineralization rates in a young biodiversity-ecosystem function experiment

Forest ecosystems are facing declining plant species diversity. However, the effects of reduced tree species diversity on soil nutrient supply and tree productivity remain poorly understood. We conducted a biodiversity-ecosystem function experiment with a range of subtropical tree species richness (1, 4, 8, 16, and 32) to investigate the impacts of tree species diversity on soil net nitrogen (N) mineralization rates and its regulation on tree productivity in a young subtropical forest experiment. Our findings indicate a log-linear trend between soil net N mineralization rates and tree species richness, potentially suggesting an improvement in soil N supply capacity with greater species richness. Leaf N content, soil water content and peroxidase enzyme activity were identified as primary positive predictors influencing soil net N mineralization rates. In monoculture forests, soil net N mineralization rates were negatively correlated with litter production and tree basal area, while no such correlation was observed in mixed forests. This implies that soil net N mineralization rates play a critical role in tree productivity for monoculture forests. Together, these results provide strong evidence that the rate of decrease in soil nutrient supply capacity potential accelerates with the loss of tree species diversity in young tree communities, and highlights the importance of increasing tree species diversity to mitigate nutrient limitations. Therefore, preserving tree species diversity is crucial for the future functionality of ecosystems amidst global biodiversity loss.

Stand growth, Biomass and Carbon sequestration potentials of Parkia biglobosa (jacq.) Bench plantation in South-Western Nigeria

This study assessed tree growth variables, above (AGB), below ground biomass (BGB) and total carbon content (TC) sequestered by Parkia biglobosa (Jacq.) Bench. Plantation in Wasangare, Oyo State using non-destructive ground base survey. Tree growth data (Diameter at breast height, Dbh and Tree height, Th) were collected using lacer ace hypsometer and diameter girth tape from 20 temporary sampling plots of size 25 m X 25 m established through systematic transect lines. Diameter size classes (DSC) for the plantation was examined, carbon stock for each DSC was also determine while basal area (m2 ha-1), volume (m3 ha-1), Biomass (Mg ha-1) and Carbon (Mg ha-1) were also estimated. Results showed mean Dbh of 18.7 + 0.25 cm with 8.14 + 0.10 m, 0.033 + 0.00 m2 ha-1 and 0.320 + 0.01 m3 ha-1 for tree height, basal area and volume respectively. AGB and BGB were 10.877 + 0.39 Mgha-1 and 2.175 + 0.08 Mgha-1 respectively while TC was 6.527 + 0.24 Mgha-1. The percentage carbon stock proportion for each DSC revealed class size 25-29-9 cm (19.02%) as the highest while the least proportion was observed in less than 5 cm class with 0.04% of carbon. The DSC showed majority of the tree Dbh in lower Dbh classes with fewer trees in higher classes forming almost a normal bell shape. The study provides information that can help the management in planning silvicultural activities and selective removal from the stand (harvesting schedule). Tree Dbh, height, basal area, volume and biomass are the determinant characteristics for forest carbon assessment. In conclusion, the plantation actively sequesters carbon showing potentials for indigenous trees in climate change mitigation.

Age estimation model for individual tree in natural Larix gmelinii forest based on random forest model

To accurately estimate the age of individual tree and to achieve full-cycle sustainable management of natural Larix gmelinii forest in Great Xing'an Mountains of northeastern China, we constructed individual tree age prediction model using stepwise regression and random forest algorithms based on 44 fixed plots data and 280 stan-dard tree cores obtained from the Pangu Forest Farm. We analyzed the influence of stand structure, site conditions, and competition index on the accuracy of model prediction. The model was evaluated by the coefficient of determination (R2), root mean square error (RMSE), and mean absolute error (MAE). The results showed that the random forest model had the highest prediction accuracy when number of decision trees was 1500 and number of node con-tention variables was 8. The random forest model had better accuracy and prediction ability than the stepwise regression model, with R2, RMSE and MAE of 0.5882, 9.9259 a, 8.1155 a. Diameter at breast height was the most important factor affecting age prediction (83.8%), followed by tree height (34.4%), elevation (17.9%), and basal area per hectare (17.5%). The random forest algorithm exhibited better adaptability and modeling effect on constructing a predictive model for individual tree age. This research contributed to improving the accuracy of growth and harvest estimation for L. gmelinii, and could provide a reference for other scientific studies related to tree age estimation in forests.