Species Density Research Articles

Biotic and abiotic drivers of harbor seal (Phoca vitulina) fine‐scale densities in the Salish Sea

AbstractUnderstanding relationships between environmental characteristics and variation in species occurrence and density can provide information for managing human activities, protected species, and species of commercial importance in a dynamic system. To identify environmental drivers associated with variation in harbor seal (Phoca vitulina) densities in the Salish Sea, Washington, we analyzed 20 years of boat‐based survey data and environmental covariates using a hierarchical distance sampling model. We included spatial, temporal, and spatiotemporal environmental covariates in our model and produced fine‐scale predictive maps displaying in‐water estimated densities from our model results. We found that spatial covariates were the strongest predictors for harbor seal densities in the Salish Sea. Harbor seals were more abundant closer to major river mouths, near shore, in shallower waters, and in areas with more haul‐out sites. Additionally, harbor seal density varied with shoreline type. Changes in predicted harbor seal spatial use of the Salish Sea varied but with little difference between breeding/molting and nonbreeding/nonmolting seasons. Our results revealed spatiotemporal variation in harbor seal fine‐scale density in the Salish Sea, which are particularly important for conservation planning, as spatiotemporal variation in harbor seal density can exert heterogenous top‐down effects on prey species populations, some of which are threatened.

Relative decline in density of Northern Hemisphere tree species in warm and arid regions of their climate niches

Although climate change is expected to drive tree species toward colder and wetter regions of their distribution, broadscale empirical evidence is lacking. One possibility is that past and present human activities in forests obscure or alter the effects of climate. Here, using data from more than two million monitored trees from 73 widely distributed species, we quantify changes in tree species density within their climatic niches across Northern Hemisphere forests. We observe a reduction in mean density across species, coupled with a tendency toward increasing tree size. However, the direction and magnitude of changes in density exhibit considerable variability between species, influenced by stand development that results from previous stand-level disturbances. Remarkably, when accounting for stand development, our findings show a significant change in density toward cold and wet climatic conditions for 43% of the species, compared to only 14% of species significantly changing their density toward warm and arid conditions in both early- and late-development stands. The observed changes in climate-driven density showed no clear association with species traits related to drought tolerance, recruitment and dispersal capacity, or resource use, nor with the temperature or aridity affiliation of the species, leaving the underlying mechanism uncertain. Forest conservation policies and associated management strategies might want to consider anticipated long-term species range shifts alongside the integration of contemporary within-distribution density changes.

Exploring seed density and limiting similarity to reduce invasive grass performance for grassland restoration purposes

AbstractQuestionsControl of invasive species and seed addition are key steps in grassland restoration. Nevertheless, selecting seed mixes and seed quantities are hard tasks in restoration projects. An interesting idea is to design seed mixes using functional traits and create a community based on limiting similarity to overlap and outcompete the invader. We aimed to test the effect of two sown communities (one created to overlap the invader niche) and three seed sowing densities to reduce the performance of the invasive grass Eragrostis plana.LocationGreenhouse experiment in the Campos Sulinos grasslands region, Southern Brazil.MethodsWe created a bifactorial experiment. The first factor was the sown community, each composed of nine native grasses but with different proportions: (1) Limiting, based on limiting similarity, and (2) Balanced, where all species were sown at the same seed weight. We used leaf functional traits (Specific leaf area, leaf area, leaf dry matter content ) to design the Limiting community. The second factor was the seed density of native species, sowing twice (1) 1 g/m2, (2) 2 g/m2, and (3) 4 g/m2 (i.e., total density was 2, 4, and 8 g/m2). E. plana was sown once at 0.5 g/m2. Above‐ground and below‐ground biomass of all species were collected after nine months to assess the treatment effects.ResultsBiomass production of the invasive species was lower when sown with native species. Nevertheless, both sown communities did not differently affect the invasive biomass production. Higher seed density of native species resulted in lower invasive above‐ground biomass, but not below‐ground biomass. Three native species did not germinate, consequently, the established communities were quite different from those designed.ConclusionsThe low species germination limited our discussion about the use of limiting similarity to design seed mixes. High seed sowing density is a better approach when defining sowing strategies to compete with invasive grasses.

The pivotal role of water potential in phenology and seed germination of Abies spectabilis in the western Himalayan treeline region

Abies spectabilis (East Himalayan Fir), a dominant timber-producing species in the Himalayas, plays a dynamic role in ecological balance and sustains various habitats across temperate to subalpine altitudes. Himalayan montane forests express signs of changes in the growth, regeneration, and population density of forest tree species due to ongoing climate change, including its upper distribution limit. The research was conducted at 30°11´02˝N and 79°39′36˝E, ranging from 3,100 to 3,500 m asl elevation in the treeline ecotone of western Himalaya. The study presents a comprehensive perspective on how water availability and its intricate interactions with climatic and ecological variables shape the dynamics of treeline ecosystems. The study’s phytosociological analysis of treeline sites revealed the complex interplay between species composition, adaptability, and regeneration potential. The eco-physiological aspects of water balance were thoroughly explored, underscoring how plants employ various strategies to cope with changing water availability. The soil moisture content ranged from 32.17 to 73.50%. The dynamic nature of water potential (pre-dawn (ΨPD) and mid-day (ΨMD)) across seasons and years reflects and varies between −0.13 and − 1.25 MPa, the species’ ability to adjust and manage water balance according to environmental shifts. Osmotic potential at full turgor varied from −0.72 to −1.77 MPa, these adjustments are crucial for key life cycle events of vegetative and reproductive phases of species. The strong correlation of water potential (Ψ) and phenophases emphasizes the importance of water status in regulating these vital processes. Furthermore, the study delved into the maturation and germination processes, highlighting the significance of Ψ and moisture content in seed development and germination success. The maximum germination of 46.33% was observed when the seed moisture content was 30.90 ± 3.11%. The observed correlations between cone characteristics and seed parameters indicate the existence of trade-offs that impact seed size, weight, and germination capacity, contributing to the overall fitness of the species.

Land use changes effect by slash and burn cultivation to understory diversity composition and soil degradation

This study contributes to understanding ecological changes in land use following slash-and-burn land clearing. This study aimed to compare the richness and density of plant species and soil fertility in farmland cultivated for one year (1 Y), three years (3 Y), and five years (5 Y) after slash-and-burn, with the conditions in the secondary forest (SF) in Berau Regency of East Kalimantan. Understory plant taxon types, numbers, and soil organic matter were measured in each region using a series of nested plots. The size of each observation plot was 20 x 100 m. Data on understory vegetation composition was collected using 1 x 1 m mini plots at 20 sampling points and divided into five blocks, with a 10 m spacing between sampling points on each property. Understory vegetation species and cover percentage, litter cover percentage, open soil percentage, and soil fertility were measured for each observation plot. The results showed that the land cover percentage increased each year during the 5 years transition from secondary forest to farmland. Furthermore, within the 5 years, there was a change in understory species, particularly the presence of grasses and sedges at 3 and 5 years after the land use change. However, the transition from secondary forest to farmland within 5 years did not alter soil organic matter and total nitrogen.

Estimates of late Early Cretaceous atmospheric CO2 from Mongolia based on stomatal and isotopic analysis of Pseudotorellia.

The Aptian-Albian (121.4-100.5 Ma) was a greenhouse period with global temperatures estimated as 10-15°C warmer than pre-industrial conditions, so it is surprising that the most reliable CO2 estimates from this time are <1400 ppm. This low CO2 during a warm period implies a very high Earth-system sensitivity in the range of 6 to 9°C per CO2 doubling between the Aptian-Albian and today. We applied a well-vetted paleo-CO2 proxy based on leaf gas-exchange principles (Franks model) to two Pseudotorellia species from three stratigraphically similar samples at the Tevshiin Govi lignite mine in central Mongolia (~119.7-100.5 Ma). Our median estimated CO2 concentration from the three respective samples was 2132, 2405, and 2770 ppm. The primary reason for the high estimated CO2 but with relatively large uncertainties is the very low stomatal density in both species, where small variations propagate to large changes in estimated CO2. Indeed, we found that at least 15 leaves are required before the aggregate estimated CO2 approaches that of the full data set. Our three CO2 estimates all exceeded 2000 ppm, translating to an Earth-system sensitivity (~3-5°C/CO2 doubling) that is more in keeping with the current understanding of the long-term climate system. Because of our large sample size, the directly measured inputs did not contribute much to the overall uncertainty in estimated CO2; instead, the inferred inputs were responsible for most of the overall uncertainty and thus should be scrutinized for their value choices.

Vegetation and Soil Dynamics : Insights from Prosopis juliflora- Intruded Areas in Hastinapur Wildlife Sanctuary

Ecological study on plant diversity and soil characteristics of two contrasting sites (Prosopis juliflora-invaded and non-invaded) in Hastinapur Wildlife Sanctuary was undertaken to understand the structure of vegetation and soils and implication of exotic dominance in a dry tropical region of India. Seasonal floristic composition was recorded for one year through monthly visits. Phytosociological study of the two sites in each of three seasons was carried out by sampling a total of 120 quadrats (each 1mx1m, n= 20×3×2). Plant species density and abundance was estimated for both sites in each season. Seasonal surface soil (0–10 cm) samples were analyzed for soil pH, moisture content, organic C, and total N. Species occurrences and their relative abundance data were used to estimate alpha and beta diversity. A total of 76 plant species from 29 families were recorded (Malvaceae, Fabaceae and Asteraceae being top dominants). Maximum flora was recorded in rainy season at both sites, higher at non-invaded sites in all seasons. Beta diversity followed similar trend, higher in rainy season and at non-invaded than invaded sites, highest being 13.2 at non-invaded site in rainy season. Dominants changed with site and season. Vegetation patches were distinct in drier seasons compared to rainy months. Soil organic carbon, total nitrogen and C : N ratios were high at invaded sites compared to non-invaded sites except in summer season. While higher diversity and higher similarity amongst different sites in rainy season indicated a homogenization impact in Indian dry tropical regions, higher diversity at non-invaded site suggested implication of diversity-reducing impact of tree invader Prosopis juliflora.

Mangrove Diversity as An Indicator of Ecosystem Health on Ambon Island, Indonesia

The research aims to determine the species richness, diversity and distribution of mangrove populations in forest areas, which is one of the parameters of forest health in the Passo Village’s mangrove forest. It was conducted from July to August 2023 on Ambon Island using the Forest Health Monitoring Field Methods Guide. The research covered 2 hectares of mangrove forest with 3 clusters of 12 observation plots. It was found that seven species of mangroves were found in the area, namely Sonneratia alba, Rhizophorastylosa, Avicennia marina, Aegiceras corniculatum, Bruguiera gymnorrhyza and Bruguiera parviflora. Cluster 1 had 260 trees. Cluster 2 had 321 trees, and Cluster 3 had 193 trees. The highest value of mangrove species richness was at the sapling level of 1,003. Meanwhile, the species diversity was classified as low at only 0.701 at the seedling level. The highest density of the Sonneratia alba species was 4,290, the species dominance of the Sonneratia alba was 22,240, and the highest importance index occupied by the Sonneratia alba was 160.95. Considering the low level of mangrove forest biodiversity on Ambon Island, rehabilitation and reforestation efforts are needed to maintain the quality and health of the ecosystem, especially in facing the impact of climate change on small islands.

Effects of exclosures on mountain grassland floristic composition in Sidama, Ethiopia

This study was conducted to assess the effects of exclosure on mountain grassland’s species composition, richness, diversity and dominance in Sidama, Southern Ethiopia. Locally established exclosures aged between 10 and 12 years old were compared against adjacent open-grazed areas in Mollona-Meno Kebele for this study. The study was replicated at four sites. An exclosure was paired with adjacent open-grazed lands having a similar land area and slope. Both in the exclosures and adjacent open-grazed lands, 87 and 86 plant species were recorded, representing 20 families, respectively. A significantly higher difference was observed between exclosures and adjacent open-grazed lands in terms of herbaceous species abundance, diversity, evenness and density. Higher herbaceous species’ important value index (IVI) was recorded inside exclosures than in the open-grazed lands. The results suggested that the establishment of exclosures on degraded lands could support the restoration of degraded native herbaceous species which consequently enhanced ecosystem services.

Parasitoid guild of the citrus leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Tunisian citrus orchards and a new report of Cirrospilus ingenuus Gahan (Hymenoptera: Eulophidae)

A survey of the parasitoid species of the citrus leafminer (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), a cosmopolitan pest of citrus, was carried out in 2019 and 2020 in the major citrus production area of Tunisia. Four different Eulophidae species were found: Citrostichus phyllocnistoides (Narayanan), representing 81.82% of the identified parasitoids, Semielacher petiolatus (Girault) (9.40%) and the native species Pnigalio pectinicornis (L.) (2.82%). Cirrospilus ingenuus Gahan (Hymenoptera: Eulophidae) is a new report for the parasitoid entomofauna of P. citrella in the country, representing 5.96% of the identified parasitoids. It has probably spread naturally from other Mediterranean regions. Predation by generalist predators is the main mortality factor of CLM (up to 59.11% of the mortality was caused by natural enemies), followed by parasitism (oviposition) (22.47%) and host-feeding (18.42%). Second and third instar larvae of the CLM were the preferred stages for parasitism. Host-feeding and generalist predators’ attacks were most common on first and second instars. Data highlighting the ability for C. phyllocnistoides to develop and disperse clearly predominates in Tunisian citrus orchards. Citrostichus phyllocnistoides may compete with S. petiolatus, exerting a complementary action to that of C. phyllocnistoides, particularly earlier in the season when the densities of the latter species are low. Further studies focusing on inter-specific relationships between these two exotic parasitoids are needed in order to test whether the observed field results could have been estimated from laboratory assays. This will be helpful in critically evaluating the results of the classical biological control programme developed against CLM in Tunisia.

Naturally diverse plant communities do not resist invasion by the strong competitor, Microstegium vimineum.

Theory predicts and empirical studies have shown that ecologically manipulated communities with high species diversity are resistant to invasion, but do these predictions and results hold true when applied to highly competitive invaders in natural communities? Few studies of diversity-mediated invasion resistance have measured both invasion resistance and invader impact in the same study. We used a two-year field experiment to test: (1) diversity-mediated competitive resistance to patch expansion by the grass, Microstegium vimineum; and (2) the competitive effect of M. vimineum on resident plant diversity. We examined responses of M. vimineum to two native plant density-reduction treatments that had opposite effects on species diversity: (1) reducing species richness via the removal of rare species; and (2) reducing dominance by reducing the density of the dominant resident species. We examined the effects of M. vimineum reduction by pre-emergent herbicide on resident diversity in the second year of the study. Neither rare species removal nor dominant species reduction significantly increased M. vimineum density (relative growth rate). The pre-emergent herbicide dramatically reduced M. vimineum in year 2 of the study, but not most resident plants, which were perennials and indirectly benefited from the herbicide at a more productive site, presumably due to reduced competition from M. vimineum. Diversity-mediated resistance did not effectively deter invasion by a highly competitive invader. In the case of M. vimineum and at more productive sites, it would appear that nearly complete removal of this invader is necessary to preserve plant species diversity.

Indeks Ekologi dan Kepadatan Komunitas Cerithidea Spp. di Perairan Pengudang dan Dompak

Macrozoobenthos is a group of benthic organisms measuring more than 1 mm that plays a crucial role in the process of decomposition and mineralization of organic material in aquatic ecosystems. The purpose of this observation was to determine the ecological index and density of macrozoobenthos in Pengudang and Dompak Waters. This observation was conducted from May 26-27, 2024 in the waters of Pengudang and Dompak using the survey method. Determination of sampling points is done by random sampling of 20 points each line transect. Macrozoobenthos measurements using 1x1m quadrant transect. The results showed that Pengudang waters had a higher species density with an average value of 13 (medium) compared to Dompak with an average of 0.03 (low). The diversity index ranged from 0.36-1.05, with Pengudang showing higher values. The uniformity index in Pengudang was 0.50 (medium), and in Dompak 0.17 (low). The dominance index was higher in Dompak (0.84) than Pengudang (0.40). Water quality parameters showed that temperature, salinity and pH were within safe limits, but TSS values in Dompak exceeded quality standards, indicating higher sedimentation levels.

Positivity-preserving discontinuous spectral element methods for compressible multi-species flows

We introduce a novel positivity-preserving numerical stabilisation approach for high-order discontinuous spectral element approximations of compressible multi-species flows. The underlying stabilisation method is the adaptive entropy filtering approach (Dzanic and Witherden, J. Comput. Phys., 468, 2022), which is extended to the conservative formulation of the multi-species flow equations. We show that the straightforward enforcement of entropy constraints in the filter yields poor results around species interfaces and propose an adaptive switch for the entropy bounds based on the convergence properties of the pressure field which drastically improves its performance for multi-species flows. The proposed approach is shown in a variety of numerical experiments applied to the multi-species Euler and Navier–Stokes equations computed on unstructured grids, ranging from shock-fluid interaction problems to three-dimensional viscous flow instabilities. We demonstrate that the approach can retain the high-order accuracy of the underlying numerical scheme even at smooth extrema, ensure the positivity of the species density and pressure in the vicinity of shocks and contact discontinuities, and accurately predict small-scale flow features with minimal numerical dissipation.

Deer exclusion is necessary to promote post‐fire herbaceous regeneration in the understorey of a Mediterranean forest

The frequency of severe wildfires is on the rise in the Mediterranean Basin as a result of climate change and land abandonment. Recurrent wildfires may retard or impede ecosystem recovery, frequently requiring the implementation of restoration practices. In that context, a post‐fire deer exclusion experiment was conducted in a Mediterranean mixed forest ecosystem with high population densities of deer species (Fallow deer and Red deer). A deer exclusion area was established as a form of restoration intervention to promote post‐fire vegetation recovery. We surveyed plant species during the second and third springs after fire in both deer‐excluded and deer‐allowed areas in order to detect changes in the community. We analyzed the plant species composition, species diversity, and structure of herbaceous and woody plant communities. We also compared the frequency of annual and perennial herb species, functional groups, and post‐fire plant regeneration strategies. The main differences were due to differences between springs rather than of deer‐excluded and deer‐allowed plots. Deer consumed both woody and herbaceous species, favoring the assemblage of herbaceous over woody species. Deer favored the establishment of annual forbs, including unpalatable and/or exotic species, while limiting the abundance of graminoids. Observed deer impacts could have been magnified during the second spring by a drought. Our study demonstrates that deer exclusion can be an effective restoration practice for promoting post‐fire herbaceous regeneration in forests with significant densities of wild ungulates, although seasonal effects may override restoration practice effects.

Does weed infestation alter the population density of harmful leafhopper species in second crop maize?

Weed-insect interaction has been studied for decades to determine the role of weeds in insect infestation. This study investigated the impact of weed density on the population density of important leafhopper species (Cicadellidae: Hemiptera) and their egg parasitoid Anagrus atomus (L.) (Hymenoptera: Chalcidoidea) in maize (Zea mays L.) planted as second crop in Şanlıurfa province, Türkiye during 2022 and 2023. Population densities of harmful leafhopper species, i.e., Zyginidia sohrab (Zachvatkin), Empoasca decipiens (Paoli), Asymmetrasca decedens (Paoli), Psammotettix striatus (Linnaeus), and their parasitoid, i.e. A. atomus were monitored by yellow sticky traps (RAL-1016) under weedy and weed-free conditions. Three traps were hung in each experimental unit and the densities of target species were recorded weekly. The population densities of leafhopper species feeding on Sorghum halepense (L.) (Johnsongrass) and the effect of A. atomus on their population density were also determined in weedy treatment. A total 15 maize leaves were taken from both weedy and weed-free treatments, and S. halepense leaf tissues containing leafhopper eggs parasitized by A. atomus were counted weekly. Weed density had non-significant effect on the population density of Z. sohrab during both years. Contrastingly, increasing weed density increased the population density of E. decipiens &amp;amp; A. decedens complex in 2022. Nevertheless, weed density had non-significant effect on the population density of E. decipiens &amp;amp; A. decedens complex during 2023. Weedy treatment recorded higher population density of P. striatus (140 and 100 adults, respectively); however, both weedy and weed-free treatments recorded similar density (125 and 97 adults) during 2023. Weed density proved a significant factor in increasing A. atomus density. A total of 2935 parasitized eggs were recorded from the weedy treatment, whereas 1609 parasitized eggs were recorded from weed-free treatment. Although direct relationship between leafhoppers and weed density remains uncertain, integrated pest management strategies must consider phytophagous insects feeding on weeds at field edges and within fields and the natural enemy complex.

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Monitoring migrating raptors is among the most cost-effective and simple methods for forecasting shift in the ecosystem and environment. The Western Marsh Harrier Circus aeruginosus (Linnaeus, 1758) (Accipitriformes, Accipitridae) represents a widely wintering, on-passage raptor over Iraq's southern Mesopotamian marshlands. However, recent information related to this species’ population trend, as well as its spatial and temporal migration patterns, is not fully known. From October 2021–June 2022, nine ornithological field surveys were undertaken in the Central Marshes (UNESCO Site, RAMSAR Site, and Iraq's National Park). Three transect lines were chosen, and the surveying plot covered 40,000 hectares (400 Km2). Our recent surveys recorded a total of 64 harriers passing over the Central Marshes. The species density was determined using a distance sampling method; perpendicular distances were gauged using a digital range finder. During our surveys, the Central Marshes hosted a migratory population of ≈3,508-21,499 harriers. In addition, we assessed the breeding status of this bird species in the surveyed area; however, no confirmed breeding was found. Furthermore, illegal hunting/trapping were identified as the main threat facing the species in Iraq.

Reclamation of an eroded lakeshore slope using small vegetation islands and terraces

Bioengineering approaches to slope stabilization involve biological and mechanical methods with low impact on the environment and landscape. Slope stabilization using vegetation patches or islands can greatly decrease runoff and soil erosion on an eroded lake shore. While vegetation islands showed promise for forest and grassland reclamation, they have rarely been used on eroded lake shores. A study was conducted to determine whether bioengineering using native vegetation islands and terraces could successfully revegetate and stabilize a severely eroded lake shore slope in the central aspen parkland, Alberta, Canada. Three gullies and three slopes were terraced using pressure treated planks, then transplanted with non-dormant (mid-August) and dormant (mid-October) 20 cm diameter vegetation islands in a soil amended with 25% (by volume) compost. Volumetric water content was significantly less in lower slope positions than upper slope positions, and sediment transport to lower slope positions was much reduced. After one year, both non-dormant and dormant transplanted islands survived and established on the terraced slope, under relatively inhospitable growing conditions. Although non-dormant islands had significantly lower vegetation mortality (10% or less) than dormant islands on both slopes and gullies, no differences in health and vigour were found by the end of the study. Overall plant species number on the site increased during the study. Graminoid species densities increased, while those of forbs, shrub and tree species declined in the transplanted vegetation islands. Non-dormant islands had greater graminoid density than dormant islands, where Poa pratensis was the dominant species in the islands. Bioengineering with vegetation islands and terraces can assist in trapping runoff and sediment, and accelerate establishment of a diversity of plant species and groups relative to traditional revegetation methods.

Post-fire resurveys reveal predictability of long-term conifer recruitment in severely burned California dry forests

High severity fire is far outpacing post-fire reforestation capacity across the American West, highlighting the need to better understand when and where natural regeneration is sufficient to meet short- and long-term reforestation goals. The vast majority of available post-fire data represents regeneration in the first few years following a fire, raising the question of how well recovery trajectories can be predicted from early post-fire snapshots. We utilize a unique dataset from seven wildfires and 78 plots surveyed twice following stand-replacing fire in two California ecoregions, the northern Sierra Nevada and Klamath Mountains, to ask (1) how are post-fire vegetation and conifer densities changing over time and (2) how well do relatively early post-fire sampling efforts and biophysical factors (availability of seed source, shrub competition, and microclimate) explain longer-term (12–23 year) conifer recovery in California dry forests. Change in conifer seedling density between survey periods was highly variable. Overall, densities of all conifer species during the first decade after fire provided reliable estimates of longer-term conifer recovery in northern California dry forests, though in different ways for different species. Early post-fire seedling density readily explained longer-term densities for less shade-tolerant species, yellow pine (Pinus ponderosa and Pinus jeffreyi) and Douglas-fir (Pseudotsuga menziesii). In contrast, early seedling density was a poor predictor for shade-tolerant species, predominantly white fir (Abies concolor), with site conditions better explaining longer-term density. In general, the probability of a site experiencing net seedling mortality between surveys was highest in sites with high shrub cover and the probability of net recruitment increased with decreasing heat load, suggesting a continued role of microclimate and competition in forest recovery long after the initial post-fire period. Our results lend support to the use of relatively early post-fire surveys to infer longer-term forest recovery trajectories for forest management planning and can help refine reforestation prioritization tools.

High resolution remote sensing for biodiversity assessment and monitoring: A case study of dominant tree species in an old-growth forest

Biodiversity assessment and monitoring in old-growth forests (OGFs) is crucial for their effective management and conservation amongst various natural and human-induced challenges. In the present study, the spatial and temporal species diversity were assessed in the mixed stands of Białowieża Forest (BF), a renowned UNESCO world heritage site recognized as an OGF. The BF has encountered challenges due to pest outbreaks peaking in 2016–2017 with adverse impacts on species composition. Utilizing airborne laser scanning (ALS) and color infrared (CIR) datasets from 2015 and 2019 (prior and following the peak, respectively), 30 variables were extracted and employed as input for the Random Forest algorithm to identify 14 species of broadleaved and coniferous individuals at plot levels (458 plots) within the BF. We calculated biodiversity indices (including α, β, and γ diversity), Importance Value Index (IVI), bivariate scale-dependent density of species, and temporal β diversity indices independently for data acquired from both field observation (FO) and species maps obtained through remote sensing analysis (RSA). The study found no significant differences in α diversity indices between the FO and RSA across the BF, however, notable discrepancies existed in species richness. Limited species detection was attributed to low species frequency and therefore, insufficient reference individuals. Average β and γ diversities from both datasets showed no significant differences. The RSA accurately identified top species and their changes in terms of IVI. Additionally, the RSA explored scale-dependent density changes of broadleaved individuals around conifers. Consistency was observed between FO and RSA in identifying dominance shifts from losses to gains within the BF communities. The comparison of diversity indices obtained from FO and RSA suggests that the RSA provided comparable results to FO in capturing the diversity of dominant tree species within the BF, providing a promising approach for advancing our understanding of forest biodiversity in OGFs.

Impacts and status of Invasion by Lantana camara in natural forests of an Indo-Burma biodiversity hotspot region- A case study in Mizoram, India

Invasion by Lantana camara represent a major threat for biodiversity and ecosystems functioning on a global scale. In this study, we investigated the ecological impact of Lantana camara invasion in natural forests of Mizoram. The sampling plots were implemented within six sites spread across the state and Lantana camara invasion were investigated along altitudinal gradient. In addition to the associated floristic inventory, we gathered the socio-economic utilization data. The results revealed that Lantana camara invasion cause adverse effects where it may result into suppression of various native plant species of invaded communities. The floristic and phytosociological assessment from Lantana camara invaded natural forests revealed a total of 74 species belonging to 68 genera and 30 families. Herbs were the dominant habit (60%) followed by shrubs (26.67%) and climbers (13.33%). The most dominant family was represented by Asteraceae with 18 species belonging to 16 genera. The general plant species diversity, density, richness and importance value index were reduced by the invasion of Lantana camara. Hence, based on the associated species present in the invaded study areas, forest management activities may be followed for the sustainable control measures to eliminate the spread of the invasive Lantana camara. This study recommends the imperative nature of effective Lantana camara management, particularly during the initial stages of invasion.