Canopy Layer Research Articles

Individual Tree-Crown Detection and Species Identification in Heterogeneous Forests Using Aerial RGB Imagery and Deep Learning

Automatic identification and mapping of tree species is an essential task in forestry and conservation. However, applications that can geolocate individual trees and identify their species in heterogeneous forests on a large scale are lacking. Here, we assessed the potential of the Convolutional Neural Network algorithm, Faster R-CNN, which is an efficient end-to-end object detection approach, combined with open-source aerial RGB imagery for the identification and geolocation of tree species in the upper canopy layer of heterogeneous temperate forests. We studied four tree species, i.e., Norway spruce (Picea abies (L.) H. Karst.), silver fir (Abies alba Mill.), Scots pine (Pinus sylvestris L.), and European beech (Fagus sylvatica L.), growing in heterogeneous temperate forests. To fully explore the potential of the approach for tree species identification, we trained single-species and multi-species models. For the single-species models, the average detection accuracy (F1 score) was 0.76. Picea abies was detected with the highest accuracy, with an average F1 of 0.86, followed by A. alba (F1 = 0.84), F. sylvatica (F1 = 0.75), and Pinus sylvestris (F1 = 0.59). Detection accuracy increased in multi-species models for Pinus sylvestris (F1 = 0.92), while it remained the same or decreased slightly for the other species. Model performance was more influenced by site conditions, such as forest stand structure, and less by illumination. Moreover, the misidentification of tree species decreased as the number of species included in the models increased. In conclusion, the presented method can accurately map the location of four individual tree species in heterogeneous forests and may serve as a basis for future inventories and targeted management actions to support more resilient forests.

Dynamic variation of non-structural carbohydrates in branches and leaves of temperate broad-leaved tree species over a complete life history

The composition of non-structural carbohydrates (NSC), one of the photosynthetic products of plants, reflects the survival strategy of a plant. Although several studies have investigated variation of NSC content in woody plants over a set time scale, few studies have considered the dynamic variation of NSC over a continuous life history. In this study, the leaves, new twigs, and old branches of seven temperate broad-leaved tree species (diffuse-porous species:Betula platyphylla,Betula costata,Tilia amurensis,Acer pictumsubsp.mono; ring-porous species:Ulmus davidianavar.japonica,Ulmus laciniata,Fraxinus mandshurica) were observed at three life history stages (seedling, sapling, and mature tree) to measure the dynamic changes of NSC and its influencing factors throughout the entire life cycles of these species. The results showed that life history, wood type, and environmental factors (soil nitrogen and phosphorus content, soil pH) significantly affected the NSC content in leaves and branches (including both new twigs and old branches). As plants grew, the NSC content in the leaves and branches generally showed an upward trend, meaning the total non-structural carbohydrate (TNC) content and soluble sugar (SS) content increased significantly, and the starch (ST) content was relatively stable. Lastly, there was no significant difference in NSC content between the canopy layers of mature trees. This indicates that the influence of life stage on NSC content in leaves and branches of plants may be dominated by genetics instead of being regulated by light factors.

How Sensitive Is Thermal Image-Based Orchard Water Status Estimation to Canopy Extraction Quality?

Accurate canopy extraction and temperature calculations are crucial to minimizing inaccuracies in thermal image-based estimation of orchard water status. Currently, no quantitative comparison of canopy extraction methods exists in the context of precision irrigation. The accuracies of four canopy extraction methods were compared, and the effect on water status estimation was explored for these methods: 2-pixel erosion (2PE) where non-canopy pixels were removed by thresholding and morphological erosion; edge detection (ED) where edges were identified and morphologically dilated; vegetation segmentation (VS) using temperature histogram analysis and spatial watershed segmentation; and RGB binary masking (RGB-BM) where a binary canopy layer was statistically extracted from an RGB image for thermal image masking. The field experiments occurred in a four-hectare commercial peach orchard during the primary fruit growth stage (III). The relationship between stem water potential (SWP) and crop water stress index (CWSI) was established in 2018. During 2019, a large dataset of ten thermal infrared and two RGB images was acquired. The canopy extraction methods had different accuracies: on 12 August, the overall accuracy was 83% for the 2PE method, 77% for the ED method, 84% for the VS method, and 90% for the RGB-BM method. Despite the high accuracy of the RGB-BM method, canopy edges and between-row weeds were misidentified as canopy. Canopy temperature and CWSI were calculated using the average of 100% of canopy pixels (CWSI_T100%) and the average of the coolest 33% of canopy pixels (CWSI_T33%). The CWSI_T33% dataset produced similar SWP–CWSI models irrespective of the canopy extraction method used, while the CWSI_T100% yielded different and inferior models. The results highlighted the following: (1) The contribution of the RGB images is not significant for canopy extraction. Canopy pixels can be extracted with high accuracy and reliability solely with thermal images. (2) The T33% approach to canopy temperature calculation is more robust and superior to the simple mean of all canopy pixels. These noteworthy findings are a step forward in implementing thermal imagery in precision irrigation management.

Xylem anatomical and hydraulic traits vary within crown but not respond to water and nitrogen addition in Populus tomentosa

Nitrogen (N) and water availability are the two crucial factors confining tree growth and forest productivity. Irrigation, fertilization, and combined fertigation are commonly applied to plantation forests for improving productivity. However, how xylem vasculature responds to these management practices remains poorly understood. Here we investigated the responses of tree growth, xylem anatomical structure, and hydraulics of the upper, middle, and lower canopy branches in a 6-year-old Populus tomentosa plantation subjected to four years of irrigation and fertigation treatments. The results showed that an improvement in tree growth only occurred in the irrigation treatment while the addition of N in fertigation treatments did not have a cumulative effect on tree growth. Most of the xylem anatomical traits, including vessel hydraulic diameter (Dh), vessel density (VD), vessel fraction (VF), double vessel wall thickness (t), potential specific sapwood hydraulic conductivity (Kp), fiber wall to lumen ratio (Tf/Df), vessel wall reinforcement (t/b)2, and wood density (WD) all showed conserved plasticity to long-term irrigation and fertigation, despite different tree growth rate, implying that aboveground biomass accumulation may have decoupled from the branch-level xylem traits. Besides, the alterations of other factors, including stomatal regulation strategy and crown structure with soil water and N availabilities, might better explain the variation in tree growth. In contrast, greater variations in branch xylem traits were detected across canopy layers. The upper canopy showed greater hydraulic safety characterized by narrower and denser vessels, higher cell wall to lumen ratio, and higher wood density compared to the lower canopy, while hydraulic efficiency (Kp) remained constant across the crown, thus highlighting the priority of hydraulic safety over efficiency in the construction of branch xylem. Overall, our study revealed the response pattern of P. tomentosa xylem structure to long-term water and N management, which facilitates a comprehensive understanding on the mechanisms underpinning the influence of water and nutrients regulation on the performance of fast-growing tree species’ plantations.

Computational wind engineering: 30 years of research progress in building structures and environment

The paper reviews the evolution of computational wind engineering from environmental and structural perspectives, since the inaugural conference of computational wind engineering held in Tokyo 30 years ago (CWE 92). The progress in computational methodologies and important aspects for accurate analysis are discussed. As a groundwork for the application of computational fluid dynamics (CFD) to various environmental issues, the importance of accurate modeling of atmospheric boundary layer, urban boundary layer, and urban canopy layer is pronounced. Environmental applications refer to urban micro-climate, pedestrian level wind, near-field pollutant dispersion, natural and urban ventilation, urban wind energy and snow/sand erosion and accumulation. Structural applications refer to wind loading on low- and high-rise buildings, including wind directionality. The most seminal contributions are examined, and their results are presented. It becomes clear that the engineering community has gained more benefits from environmental than structural computational wind engineering applications, mainly due to the usually less demanding computational needs for the former. Future challenges in CFD applications are thoroughly discussed and the need to bridge the gap between environmental and structural applications is highlighted.

Up-Scaling Fuel Hazard Metrics Derived from Terrestrial Laser Scanning Using a Machine Learning Model

The characterisation of fuel distribution across heterogeneous landscapes is important for wildfire mitigation, validating fuel models, and evaluating fuel treatment outcomes. However, efficient fuel mapping at a landscape scale is challenging. Fuel hazard metrics were obtained using Terrestrial Laser Scanning (TLS) and the current operational approach (visual fuel assessment) for seven sites across south-eastern Australia. These point-based metrics were then up-scaled to a continuous fuel map, an area relevant to fire management using random forest modelling, with predictor variables derived from Airborne Laser Scanning (ALS), Sentinel 2A images, and climate and soil data. The model trained and validated with TLS observations (R2 = 0.51 for near-surface fuel cover and 0.31 for elevated fuel cover) was found to have higher predictive power than the model trained with visual fuel assessments (R2 = −0.1 for the cover of both fuel layers). Models for height derived from TLS observations exhibited low-to-moderate performance for the near-surface (R2 = 0.23) and canopy layers (R2 = 0.25). The results from this study provide practical guidance for the selection of training data sources and can be utilised by fire managers to accurately generate fuel maps across an area relevant to operational fire management decisions.

Selecting maize cultivars to regulate canopy structure and light interception for high yield

AbstractUnder climate change background, long shady days during the summer maize growing season reduce the yield potential of this crop in the North China Plain. Optimizing the canopy structure can increase light interception to mitigate the negative effects of climate change. The spatial arrangement of each leaf along the stem affects the light interception that was influenced by cultivar characteristics. Field studies were carried out to select cultivars to optimize canopy structure in maize (Zea mays L.). Results indicated that the middle‐upper canopy above the ear and two leaves below the ear position play a more important role than that of the lower canopy below the ear in deciding the final grain yield. The middle‐upper canopy layer had larger leaf photosynthetic potential decided by the larger net photosynthesis rate and leaf area, as compared with the lower canopy. Larger FIPAR (the fraction of the photosynthetically active radiation) and less PAR (the photosynthetically active radiation) observed below the ear position were beneficial for yield improvement. Therefore, optimizing the middle‐upper canopy structure by selecting cultivars to construct an ideotype plant in maize should be adopted for higher grain production.

Evaluating Threatened Bird Occurrence in the Tropics by Using L-Band SAR Remote Sensing Data

The biodiversity loss in Southeast Asia indicates an urgent need for long-term monitoring, which is lacking. Much attention is being directed toward bird diversity monitoring using remote sensing, based on relation to forest structure. However, few studies have utilized space-borne active microwave remote sensing, which has considerable advantages in terms of repetitive observations over tropical areas. Here, we evaluate threatened bird occurrence from L-band satellite data explaining forest structure in Sumatra, Indonesia. First, we identified L-band parameters with strong correlations with the forest layer structure, defined as forest floor, understory, and canopy layers. Then, we analyzed the correlation between threatened bird occurrence and L-band parameters identified as explaining forest structure. The results reveal that several parameters can represent the layers of forest floor, understory, and canopy. Subsequent statistical analysis elucidated that forest-dependent and threatened bird species exhibit significant positive correlations with the selected L-band parameters explaining forest floor and understory. Our results highlight the potential of applying microwave satellite remote sensing to evaluate bird diversity through forest structure estimation, although a more comprehensive study is needed to strengthen our findings.

A Global Synthesis of Multi‐Factors Affecting Water Storage Capacity in Forest Canopy, Litter and Soil Layers

AbstractWater storage capacity in the layers of canopy, litter, and soil of forest ecosystems has not yet been thoroughly investigated on a global scale. We estimated the global pattern of water storage capacity of forest ecosystems related to water regulation services (WSCFE) in the above three layers based on 1,288 observations and analyzed their 22 controlling environmental factors. The results show that the global mean WSCFE per unit area is 456.7 mm, and the total volume of WSCFE is 22,662.5 km3. Climatic variables are the leading factors contributing to the variations of WSCFE, followed by forest attributes, terrain factors, soil properties, and litter characteristics. This study advances the understanding of the large‐scale variation mechanisms of WSCFE in different forest types and climate zones and provides scientific evidence for ecological protection according to local conditions.

Stem stiffness functionality in a submerged canopy patch under oscillatory flow

Seagrass canopies are coastal ecosystems that are able to modify the abiotic environment through their architectural structure. They have different structural parameters, such as plant stem stiffness, patch length and canopy density, all of which determine their overall functionality in modifying the seafloor hydrodynamics within coastal areas. To determine the interaction between hydrodynamics and the canopy structure, a set of laboratory experiments were carried out with both rigid and flexible stems for different canopy densities, patch lengths and wave frequencies. In the upper part of the canopy, flexible plants move with the flow without generating drag or producing turbulent kinetic energy, while rigid plants generate drag and produce turbulent kinetic energy. In the inner canopy layer, both types of plants behave like rigid stems and produce turbulent kinetic energy. A non-dimensional model based on the turbulent kinetic energy, the wave velocity and the plant characteristics is presented to describe the behaviour of flexible and rigid plants under an oscillating flow. Flexible plants behave in a stiffer manner under high wave frequencies than under low wave frequencies, thus making their behaviour closer to that of rigid plant stems. This difference between both canopy structures can explain their distribution in the environment, with rigid canopies being more extended in more sheltered regions while flexible plants are characteristic of more exposed regions with high flow energy.

Efficiency of Fungicide Application an Using an Unmanned Aerial Vehicle and Pneumatic Sprayer for Control of Hemileia vastatrix and Cercospora coffeicola in Mountain Coffee Crops

Coffee production and marketing is one of the main global commercial activities, but crop yields depend on several factors, among which plant health. The objective of this study was to evaluate the efficiency of spray droplet deposition in coffee crops grown in a mountain region, associated to the efficacy of the control of fungal diseases. The application efficiency, using an unmanned aerial vehicle (UAV), and the efficacy of the products applied were tested. Water-sensitive paper tags were used to analyze the application efficiency; agronomic efficiency, vegetative vigor, yield, and physiological parameters were used to determine the fungicide efficacy. Droplet coverage in the upper canopy layer using a pneumatic sprayer (28.70%) was 4.11-fold higher than that found in the same layer for application using a UAV (6.98%) at the rate of 15 L ha−1. The highest droplet depositions by using a UAV were found for the rate of 15 L ha−1: 1.60, 1.04, and 0.43 µL cm−2 in the upper, middle, and lower layers, respectively; the deposition in the upper layer with application using a pneumatic sprayer was 42.67 µL cm−2, and therefore, a 26.7-fold higher deposition. The results denote that the control of fungal diseases through fungicide applications using a UAV is efficient for mountain coffee crops.

A systematic literature review on the forest health biomonitoring technique: A decade of practice, progress, and challenge

The approach for monitoring forest health such as canopy layer, air quality, soil texture has evolved in tandem with the advancement of new technology such as lab analysis, remote sensing etc. The application of biomonitoring techniques for example species diversity and morphological observation, on the other hand, has been positive and has made its own contribution to forest management. Many studies have been conducted in the last decade (2011–2021), which use the biomonitoring techniques in assessing the forest health status. Therefore, this study aims to systematically review the forest health biomonitoring techniques in the last decade. This study used the PRISMA guidelines as the protocol to search and analyze all the papers. This study selected 72 out of 538 papers for a thematic analysis which eventually identified four main biomonitoring techniques, namely: 1) diversity distribution, 2) morphological observations, 3) trace elements, minerals and physiological measurements, and 4) behavioral observations. The biomonitoring techniques applied to monitor forest health has evolved with numerous ways that can support existing technologies, as well as help educate people on the necessity of protecting and safeguarding the natural forest environment. This also will give more options to the authority in monitoring the forest health and not only focusing on technology.

Numerical Investigation of Flow and Dispersion over Two-Dimensional Semi-Open Street Canyon

A semi-open street canyon is able to protect pedestrians from unpleasant situations such as direct sunlight and rain. However, the protruding elements of the two opposite building facades that form the semi-open configuration can affect the air quality of the urban canopy layer (UCL). Therefore, this paper investigated the influence of the eave structures on the flow and pollutant dispersion over an idealized 2D street canyon with a unity aspect ratio. The length of the eaves was varied into 0.25H and 0.5H (H is the building height) and placed either on the leeward wall, the windward wall, or on both building facades located at the same elevation as the street canyon. Numerical simulations were performed using the steady-state Reynolds-averaged Navier-Stokes (RANS) equations in conjunction with Re-Normalization Group (RNG) k-ε as the turbulence closure model. The pollutant was released from a line source in the center of the bottom of the target canyon with uniform flow rate. Six different eave configurations were simulated in the wind direction perpendicular to the canyon axis, representing the worst condition of canyon ventilation. The evolution of the primary vortex, which occupied the entire canyon with the characteristic of skimming flow, showed less dependence on the length and position of the eave, except for the longest eave on the windward wall. However, the position of the vortex center depicted opposite results. The pollutant concentration is always higher near the leeward wall, but for the eave that protrudes from the windward wall with a length of 0.5H, the pollutant accumulates near the windward region. The ratio of pollutant concentration showed higher concentration in the semi-open configurations compared to the fully open layout as a result of limited penetration of shear flow into the canyon, which leads to deterioration of pollutant removal.

Plant–atmosphere heat exchange during wind machine operation for frost protection

To mitigate spring frost damage, fruit farmers use wind machines to mix warm overlying air down to the vegetation. Up to this point, studies on wind machine efficiency have focused on air temperatures. The temperature of different plant organs during operation remains unknown, while critical for the actual degree of frost damage. With Distributed Temperature Sensing we measured vertical in-canopy air temperature profiles in a pear orchard in the Netherlands and thermistors were installed to determine the plant tissue temperatures. We found that to optimize wind machine operation, it is important to consider two effects of a wind machine: (1) mixing of stratified air above and into the canopy layer and (2) erosion of the leaf boundary layer to facilitate plant–air heat exchange. We show how foliage reduces plume penetration to the ground with distance to the wind machine. Due to this blocking at least 15 rotations (∼ 75 min) are needed for optimal mixing. Leaf temperatures lag behind air temperatures, due to strong radiative cooling. We found that over the rotation cycle of a wind machine the temperature difference between leaf and air is variable as convective warming repeatedly dominates over radiative cooling. This is different for flowers and shoots due to different heat capacities. Thin flower petals store little heat and are almost in direct equilibrium with air temperature changes. Shoots, with their higher heat capacity and lower surface/volume ratio, store more heat during the day that is slowly released at night. This discrepancy between plant and air temperature should be considered for frost damage prediction.

Spatial and temporal dynamics of the urban heat island effect in a small Brazilian city

AbstractThis study examined the spatial and temporal patterns of the canopy layer urban heat islands (UHIUCL) in a small city in southeastern Brazil using the local climate zone (LCZ) system. We analysed the influence of weather conditions, LCZs characteristics, and local surface relief on the UHIUCL magnitudes. Mobile traverses were used to measure air temperatures during representative nights of wet and dry seasons. Daily maximum magnitudes were observed in compact classes (LCZs 3 and 7) under ideal weather conditions (dry, clear skies, and calm) and higher anthropogenic heat release (weekdays). Seasonal effects on LCZ thermal differences were negligible. The peripheral landscapes were warmer than the city centre in both seasons. Among the warmer areas in the city, magnitudes in compact LCZs 3 and 7 were consistently higher than in LCZ 6. In general, representative sites of the main ‘built’ LCZs in the study area exhibit similar inter‐zone temperature patterns to those reported for cities of different sizes from tropical and midlatitude regions. Thermal contrasts of ΔTLCZ 3 − D in the study area reveal significant evidence that small cities can have as strong heat islands as bigger cities. These findings highlight the importance of the LCZ system to identify the main controlling factors driving such thermal differences and the need to extend the application of this approach in other South American cities to yield systematic data of UHIUCL for urban planning given the coming challenges of climate change over the region.

Stable Isotopes Reveal the Effect of Canopy and Litter Layer Interception on Water Recharge in a Subtropical Manmade Forest of Southwest China

In areas completely covered by vegetation, the rainwater that passes through the canopy layer and litter layer is the source supplying surface runoff and seeping into the soil layer. To reveal the influence mechanisms of the canopy and litter layer on water supply in forest areas, this study conducted event-scale water sampling and hydrogen and oxygen isotopic comparison for the rainfall, canopy throughfall and litter layer throughfall in a manmade forest. The results show that canopy interception will lead to a more concentrated distribution and lower isotopic variability. The d-excess and the intercept and slope of the δD-δ18O regression line of the canopy throughfall are slightly higher than those of rainfall, reflecting that the evaporation fractionation caused by canopy interception is weak, and the selection process may play a leading role. Compared with the canopy throughfall, the distribution of the δ18O, δD and d-excess in the litter layer throughfall is more dispersed, and the slope and intercept of the δD-δ18O regression line are higher, indicating the strong influence of non-equilibrium fractionation on the water input caused by litter layer interception. The isotopic differences between the litter layer throughfall and canopy throughfall indicate that the water components of small-scale precipitation events (precipitation amount lower than 5 mm) and the early stage of large-scale precipitation events (precipitation amount higher than 25 mm) may be dissipated by litter layer interception, while that of the latter stage of large-size events is slightly affected. The findings of this study will be helpful to deeply understand the mechanisms of the water cycle in the forest ecosystem under the background of climate change and provide insights for the sustainable utilization of water resources.

Heterogenous Canopy in a Lagrangian-Stochastic Dispersion Model for Particulate Matter from Multiple Sources over the Haifa Bay Area

The Haifa Bay area (HBA) is a major metropolitan area in Israel, which consists of high volume transportation routes, major industrial complexes, and the largest international seaport in Israel. These, which lie relatively near densely populated residential areas, result in a multitude of air pollution sources, many of whose emissions are in the form of particulate matter (PM). Previous studies have associated exposure to such PM with adverse health effects. This potential consequence serves as the motivation for this study whose aim is to provide a realistic and detailed three-dimensional concentration field of PM, originating simultaneously from multiple sources. The IIBR in-house Lagrangian stochastic pollutant dispersion model (LSM) is suitable for this endeavor, as it describes the dispersion of a scalar by solving the velocity fluctuations in high Reynolds number flows. Moreover, the LSM was validated in urban field experiments, including in the HBA. However, due to the fact that the multiple urban sources reside within the canopy layer, it was necessary to integrate into the LSM a realistic canopy layer model that depicts the actual effect of the roughness elements’ drag on the flow and turbulent exchange of the urban morphology. This was achieved by an approach which treats the canopy as patches of porous media. The LSM was used to calculate the three-dimensional fields of PM10 and PM2.5 concentrations during the typical conditions of the two workday rush-hour periods. These were compared to three air quality monitoring stations located downstream of the PM sources in the HBA. The LSM predictions for PM2.5 satisfy all acceptance criteria. Regarding the PM10 predictions, the LSM results comply with three out of four acceptance criteria. The analysis of the calculated concentration fields has shown that the PM concentrations up to 105 m AGL exhibit a spatial pattern similar to the ground level. However, it decreases by a factor of two at 45 m AGL, while, at 105 m, the concentration values are close to the background concentrations.

Biometric-Based Net Primary Production (NPP) and the Effects of a Masting Event on Production Allocation in a Secondary Lucidophyllous Forest in Central Japan

Lucidophyllous (evergreen broad-leaved) forests are the dominant forests in human-dominated subtropical/warm-temperate regions in East Asia. Biometric-based estimates of net primary production (NPP) were conducted in a secondary lucidophyllous forest on Mt. Kinka (35°26′ N, 136°47′ E) near the northern limit of their distribution in central Japan for three years, including the masting event. The forest stand mainly consists of Castanopsis cuspidata (Thunb.) Schottky and Cleyera japonica Thunb. in the canopy and subtree layers, respectively. In 2018, the total NPP of the masting year was 14.53 ± 2.03 ton ha−1 yr−1, including woody NPP (above: 2.63 ± 0.35 ton ha−1 yr−1; below: 0.57 ± 0.08 ton ha−1 yr−1), foliage NPP (4.07 ± 0.23 ton ha−1 yr−1), reproductive NPP (4.81 ± 0.77 ton ha−1 yr−1), and fine root production (Pfr) (2.46 ± 1.84 ton ha−1 yr−1). Pfr and belowground production comprised 16.9% and 20.9%, respectively, of the total NPP. The nut production of C. cuspidata in 2018 (4.31 ± 0.75 ton ha−1 yr−1) was significantly higher than that in 2017 (0.77 ± 0.13 ton ha−1 yr−1) and 2019 (0.23 ± 0.06 ton ha−1 yr−1). No significant change was observed for the three years of foliage NPP and total NPP without Pfr. However, the woody NPP in 2018 (3.20 ± 0.43) was lower than in 2017 (5.37 ± 0.33 ton ha−1 yr−1) and 2019 (4.71 ± 0.38 ton ha−1 yr−1). This suggests that nut production in the masting years compensated by decreasing woody production in the Castanopsis forest.

Elevated Ozone Negatively Affects the Community Characteristics and Productivity of Subtropical Grassland in India

Tropospheric ozone (O 3 ) is found to be a severe threat to agriculture and natural vegetation. The present study was conducted to investigate the structural and functional changes in an intact seminatural grassland community when exposed to elevated O 3 (EO 3 ; ambient + 20 parts per billion) compared to ambient O 3 (AO 3 ) for 3 years using open-top chambers. Parameters such as species richness (SR), evenness ( E ), Shannon index ( H ′), β-diversity (BD), concentration of dominance (Cd), similarity index (SI), biomass in canopy layers, and community productivity were evaluated. Species like Cynodon dactylon , Dichanthium annulatum , Parthenium hysterophorus , Digitaria sanguinalis , Cyperus killinga , Oplismenus burmannii , and Commelina benghalensis showed higher importance value index (IVI), whereas Trifolium resupinatum , Desmodium triflorum , Melilotus officinalis , Oxalis corniculata , Eleusine indica , Cyperus rotundus , Malvestrum coromandelianum , and Lindernia anagallis showed lower IVI under EO 3 treatment compared to AO 3 . EO 3 enhanced BD and Cd, whereas SR, E , and H ′ in the community reduced. Biomass accumulation reduced maximally in top layer compared to bottom and middle canopy layers in both forbs and grasses fraction under EO 3 treatment. Higher reduction in total biomass compared to aboveground biomass indicates less carbon allocation toward root system. The results of the present study clearly indicates that 3 years of exposure at EO 3 level caused deleterious impact on grassland community by increasing O 3 -tolerant and decreasing sensitive species, thus resulting in a shift in species composition and community productivity.

Differences in bird community structure between riparian and upland zones in a New Guinean rainforest

Riparian forests serve as important habitats that enhance diversity of bird species and perform crucial ecosystem functions in tropical forest landscapes. We compared the community structure (represented by functional trait composition) and diversity (represented by Shannon index) of birds in riparian and upland zones in a semi-continuous primary rainforest in Papua New Guinea. Distance sampling was applied to provide unbiased abundance estimates. Bird community structure was examined by principal coordinate analysis of neighbour matrices (PCNM) in the Canoco 5 program. Analysis of diversity was performed using mixed-effects linear models in R 3.5.1. Species diversity was marginally higher in riparian zones (P = 0.065). Community structure differed significantly in riparian and upland zones (P = 0.008). Invertivorous and omnivorous birds preferred riparian habitats but frugivorous and nectivorous birds avoided riparian zones. Birds in riparian zones were characterised by preferences for high-density forest interior but birds in upland areas mostly occupied exposed canopy layers. Beak dimensions were greater in riparian zones but body mass, and lengths of wing and tarsus were greater in upland zones. Species found in riparian zones had greater geographical ranges than those in upland zones. Our results highlight the adaptability of a rainforest bird community to natural disturbances characterised by localised river flooding and riverbank erosion. For example, small invertivorous and omnivorous birds can navigate disturbed vegetation and exploit river-associated invertebrate food supply while moving to alternative food sources during intensive flooding. On the other hand, large frugivorous and nectarivorous birds are mostly sedentary and require an intact canopy layer for foraging, responding poorly to changes in vegetation structure. By moving beyond species-level relationships when examining bird community structure, we were able to better interpret and connect our findings with other studies on bird communities in tropical rainforest.