Complex Vegetation Research Articles

Metabarcoding of Soil Fungal Communities in Rupestrian Grassland Areas Preserved and Degraded by Mining: Implications for Restoration.

Rupestrian grasslands are vegetation complexes of the Cerrado biome (Brazilian savanna), exhibiting simultaneously great biodiversity and important open-pit mining areas. There is a strong demand for the conservation of remaining areas and restoration of degraded. This study evaluated, using next-generation sequencing, the diversity and ecological aspects of soil fungal communities in ferruginous rupestrian grassland areas preserved and degraded by bauxite mining in Brazil. In the preserved and degraded area, respectively, 565 and 478 amplicon sequence variants (ASVs) were detected. Basidiomycota and Ascomycota comprised nearly 72% of the DNA, but Ascomycota showed greater abundance than Basidiomycota in the degraded area (64% and 10%, respectively). In the preserved area, taxa of different hierarchical levels (Agaromycetes, Agaricales, Mortierelaceae, and Mortierella) associated with symbiosis and decomposition were predominant. However, taxa that colonize environments under extreme conditions and pathogens (Dothideomycetes, Pleoporales, Pleosporaceae, and Curvularia) prevailed in the degraded area. The degradation reduced the diversity, and modified the composition of taxa and predominant ecological functions in the community. The lack of fungi that facilitate plant establishment and development in the degraded area suggests the importance of seeking the restoration of this community to ensure the success of the ecological restoration of the environment. The topsoil of preserved area can be a source of inocula of several groups of fungi important for the restoration process but which occur in low abundance or are absent in the degraded area.

Habitat use, richness, and abundance of native mice in the highlands of the Talamanca mountain range, Costa Rica

The Costa Rican highlands are considered hotspots of diversity and endemism, but studies on rodents are scarce. We compared the richness and abundance of mice between the montane forest and the paramo at the summit of the Talamanca mountain range. We selected two study sites within the Talamanca mountain range: the Cerro de la Muerte Biological Station and the paramo. The former is a montane forest dominated by oaks, and the latter is dominated by an herbaceous layer, and some scattered bushy patches. We captured mice in two different microhabitats within each montane forest and paramo, so we had four different sampling microhabitats: (1) paramo–bush, (2) paramo–Chusquea, (3) montane forest–bush, and (4) montane forest–Chusquea. Mice were marked to identify recaptures. We captured four mouse species and their abundance varied largely between habitats and among microhabitats (Table 1). The most abundant species, representing 85 % of all mouse captures, was Peromyscus nudipes. Mice were more abundant in the montane forest than in the paramo. Within the montane forest, mice were more abundant in the microhabitat containing bushes. The montane forest has a more complex vegetation structure with more diversity of food resources and shelters than the paramo. As well as at the habitat level, we argue that differences in abundance among microhabitats are directly related with the structure of vegetation. A more complex habitat structure may provide rodents with better conditions.

Honeydew associated with four common crop aphid species increases longevity of the parasitoid wasp, Bracon cephi (Hymenoptera: Braconidae)

Abstract The absence of sugar resources can be an important factor in limiting the success of parasitoids as biological control agents. Restoring vegetation complexity within agricultural landscapes has thus become a major focus of conservation biological control efforts, with a traditional emphasis on nectar resources. Aphid honeydew is also an important source of sugars that is infrequently considered. We carried out a laboratory experiment to examine the potential effects of honeydew from six different aphid species by crop species combinations on the longevity of Bracon cephi Gahan (Hymenoptera: Braconidae), the most important biological control of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), a major pest of wheat in the northern Great Plains of North America. The benefits of honeydew for parasitoid longevity varied significantly among different aphid and crop species, illustrating the complexity of these interactions. However, honeydew produced by four aphid species commonly found in wheat, pea, and canola crops significantly increased the longevity (by two- to threefold) of the parasitoid. The study suggests that honeydew provisioning could be an important mechanism underlying the benefits of crop diversification to support biological control that merits further research.

Flora of Ceará, Brazil: Lythraceae

Abstract This study aimed to carry out a floristic-taxonomic survey of the Lythraceae representatives, as part of the project “Flora do Ceará: knowing to conserve”. The data were obtained via the morphologicals analysis of samples collected in the field, and collections in herbaria as well as in specialized bibliographies. In the state of Ceará, Lythraceae is represented by 15 species belonging to four genera: Ammannia (2); Cuphea (9), Lafoensia (3) and Pleurophora (1). The species were recorded in different phytophysiognomies, but they occur preferentially in the Steppic Savanna (Caatinga and/or Carrasco), in the Dense Ombrophilous Forest (Wet Forest) and in the Vegetation Complex of the Coastal Zone (Dunes and Lowland Semideciduous Forests). The taxon with the highest number of records was Cuphea campestris, which ocurrs in 26 municipalities. Eight species were recorded in ten conservation units in Ceará. Four species are endemic to the northeastern region: Cuphea campestris, C. laricoides, C. loefgrenii and Lafoensia glyptocarpa. Lafoensia glyptocarpa and L. pacari are new records for Ceará. The identification key, morphological descriptions, comments on distribution, ecology, phenology, uses, maps, and species illustrations are presented.

Effects of land use change on the functional diversity and composition of mixed species avian flocks in the high tropical Andes of southern Ecuador

One of the greatest threats to biodiversity is land use change. Habitat alteration can have strong impacts on functional diversity, i.e., the range of biological traits within a suite of organisms. Mixed species avian flocks are integral to maintaining both taxonomic and functional diversity in tropical forests as they provide participants with greater foraging efficiency, reduced predation risks, and increased resiliency of species and ecosystems to environmental change. Our aim for this study was to determine the effects of land use change on the taxonomic and functional structures of mixed species avian flocks in and around Cajas National Park, Azuay Province in the tropical Andes of southern Ecuador by comparing non-native vegetation in agricultural plots and forest regenerating from historical use as pastureland to the largest intact primary forest in the region. We found no changes in species richness and diversity or functional richness of flocks across habitats, but we did find significant differences in species composition. Surprisingly, we found higher functional diversity and uniqueness of flocks in regenerating forest with more diverse and structurally complex vegetation, but native and non-native forests were functionally similar. We did, however, find significant differences in the community weighted means of four of five functional traits in different habitat types. Overall, the taxonomic and functional structures of mixed species flocks in this region seem relatively unaffected by land use change, indicating flocking as a beneficial strategy for species with higher sensitivities to disturbance in areas with anthropogenic activities. It is critical to maintain functional diversity in ecosystems, as a greater variety of functional traits and functional redundancy implies an efficient and more resilient ecosystem in the face of environmental change. Mixed species flocks provide membership benefits that may mitigate impacts of disturbance via land use change and thus can be considered essential units for conserving avian biodiversity.

Satellite-Detected Contrasting Responses of Canopy Structure and Leaf Physiology to Drought

Disentangling drought impacts on plant photosynthesis is crucial for projecting future terrestrial carbon dynamics. We examined the separate responses of canopy structure and leaf physiology to an extreme summer drought that occurred in 2011 over Southwest China, where the weather was humid and radiation was the main growth-limiting factor. Canopy structure and leaf physiology were, respectively, represented by near-infrared reflectance of vegetation (NIRv) derived from MODIS data and leaf scale fluorescence yield (Φ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_f</i> ) derived from both Continuous SIF (CSIF) and global OCO-2 SIF (GOSIF). We detected contrasting responses of canopy structure and leaf physiology to drought with a 14.0% increase in NIRv, compared with 12.6 or 19.3% decreases in Φ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_f</i> from CSIF and GOSIF, respectively. The increase in structure resulted in a slight carbon change, due to water deficit-induced physiological constraints. The net ecosystem effect was a 7.5% (CSIF), 1.2% (GOSIF) and -2.96% (EC-LUE GPP) change in photosynthesis. Our study improves understanding of complex vegetation responses of plant photosynthesis to drought and may contribute to the reconciliation of contrasting observed directions in plant responses to drought in cloudy regions via remote sensing.

Diversity of Arthropods in an Oil Palm Plantation in Sabah

Malaysia is one of the largest palm oil-producing countries in the world. Located in the Southeast Asia region, this country is also known as one of the mega biodiversity-rich countries which contains numerous species. In this study, arthropods were sampled using sticky traps at three sites within an oil palm dominated landscape. We examined how vegetation structure affects arthropod community distribution within an oil palm plantation. The number of arthropod species was significantly greater at higher vegetation complexity structures. The findings also showed that the number of arthropod species that had been recorded for the three sites had nearly reached asymptote. This study suggests that maintaining vegetation complexity through sustainable agriculture practice as recommended by the Malaysian Sustainable Palm Oil (MSPO) may be useful in supporting arthropod species within oil palm plantations.&#x0D;

Agricultural Robot under Solar Panels for Sowing, Pruning, and Harvesting in a Synecoculture Environment

Currently, an agricultural method called SynecocultureTM has been receiving attention as a means for multiple crop production and recovering from environmental degradation; it helps in regreening the environment and establishing an augmented ecosystem with high biodiversity. In this method, several types of plants are grown densely, and their management relies mainly on manual labor, since conventional agricultural machines and robots cannot be applied in complex vegetation. To improve work efficiency and boost regreening by scaling-up Synecoculture, we developed a robot that can sow, prune, and harvest in dense and diverse vegetation that grows under solar panels, towards the achievement of compatibility between food and energy production on a large scale. We adopted a four-wheel mechanism with sufficient ability to move on uneven terrain, and a two orthogonal axes mechanism with adjusted tool positioning while performing management tasks. In the field experiment, the robot could move straight on shelving slopes and overcome obstacles, such as small steps and weeds, and succeeded in harvesting and weeding with human operation, using the tool maneuver mechanism based on the recognition of the field situation through camera image.

Vegetation complexity and nesting resource availability predict bee diversity and functional traits in community gardens.

Urban gardens can support diverse bee communities through resource provision in resource poor environments. Yet the effects of local habitat and landscape factors on wild bee communities in cities is still insufficiently understood, nor is how this information could be applied to urban wildlife conservation. Here we investigate how taxonomic and functional diversity of wild bees and their traits in urban community gardens are related to garden factors and surrounding landscape factors (e.g., plant diversity, amount of bare ground, amount of nesting resources, amount of landscape imperviousness). Using active and passive methods in 18 community gardens in Berlin, Germany, we documented 26 genera and 102 species of bees. We found that higher plant species richness and plant diversity as well as higher amounts of deadwood in gardens leads to higher numbers of wild bee species and bee (functional) diversity. Furthermore, higher landscape imperviousness surrounding gardens correlates with more cavity nesting bees, whereas a higher amount of bare ground correlates with more ground-nesting bees. Pollen specialization was positively associated with plant diversity, but no factors strongly predicted the proportion of endangered bees. Our results suggest that, aside from foraging resources, nesting resources should be implemented in management for more pollinator-friendly gardens. If designed and managed using such evidence-based strategies, urban gardens can create valuable foraging and nesting habitats for taxonomically and functionally diverse bee communities in cities.

Effects of Anthropogenic Habitat Fragmentation on the Genetic Connectivity of the Threatened and Endemic Campylorhynchus yucatanicus (Aves, Trogloditydae) in the Yucatan Peninsula, Mexico

Identifying connectivity patterns among remnant bird populations and their relationships with land use practices and adjacent habitat fragments is key to implementing appropriate long-term management strategies for species conservation. The coastal scrub and dune vegetation complex of the northern Yucatan Peninsula is rich in endemisms and has been affected by human development, which threatens the survival of the Yucatan Wren (Campylorhynchus yucatanicus) population, an endemic bird species. To identify possible anthropogenic barriers to the connectivity of C. yucatanicus along 14 localities in the Yucatan (Mexico) coastal north, we explored the relationship between the species population’s genetic variability at each sampled site and landscape structure using regression models, in addition to the relationship between genetic distance and landscape resistance. Seven nuclear microsatellite loci were used as genetic markers. Four genetic populations were highlighted by the clustering method implemented in the Geneland program. Human settlement and availability of adequate habitat were significantly related to genetic distance (Fst), suggesting limited connectivity among sites due to ongoing land use changes. We suggest changing the IUCN threat category of C. yucatanicus to endangered as we found a significant loss of genetic variability in addition to restricted distribution, small population, habitat degradation, and loss of connectivity.

Community structure of medium-large mammals across a tree plantation cycle in natural grasslands of Uruguay

In temperate South America, the conversion of natural grasslands into crops and exotic tree plantations, such as with Eucalyptus sp., has reached outstanding levels, especially in the Río de la Plata Grasslands. The cycle of Eucalyptus plantations for pulp production is a very dynamic phenomenon; however, most of the studies on the impacts on biodiversity have been static and focused on the mature stage of the plantation. We studied the mammal assemblage in a grassland afforestation landscape of Uruguay to address how mammals respond to habitat complexity variation across the plantation cycle and landscape characteristics. We installed 26 camera traps for two years in four different age stages of Eucalyptus plantations and native habitats to assess mammals’ richness, composition, and intensity of habitat use. We registered 16 mammal species, 13 native and three exotics, with a sampling effort of 19,136 camera-nights. Of these species, 11 were found in the Eucalyptus plantations but with significant variability during the production cycle. Only one species was recorded at the beginning (0–2 years) of the cycle and four species at the end (8–10 years). But at intermediate ages (2–4 years), when vegetation complexity resembles a native forest structure, species richness was maximum (11 species) in the plantations and relatively close to forest richness (14 species). Species composition was also determined by habitat structure, but it was further modulated by landscape features, particularly the proximity to native forests and landscape heterogeneity. Our results demonstrated that asynchronous plantations promote spatial heterogeneity that favors mammal diversity in afforested landscapes, but for grassland mammals, additional conservation management measures are needed.

A novel seed cone of Pinus from the Miocene of coastal Southeast China indicates kinship with Southeast Asian pines

Pinus is an economically and ecologically important genus whose members are dominant components globally in low-latitude mountainous and mid-latitude temperate forests. Pinus species richness is currently concentrated in subtropical mid-low latitudes of the Northern Hemisphere, differing from the latitudinal diversity gradient mostly recognized in woody angiosperms. How the present pattern was developing in Earth's past is still poorly studied, particularly in eastern Asia. Here, a new fossil species, Pinus shengxianica sp. nov. is described based on a fossil seed cone from the Late Miocene Shengxian Formation in Zhejiang, southeast China. A co-occurring cone is recognized as a known fossil species, Pinus speciosa Li. Extensive comparison of extant and fossil members of Pinus suggests P. shengxianica shares a striking cone similarity to Pinus merkusii and Pinus latteri (subsection Pinus) from tropical Southeast Asia in having annular bulges around the umbo on the apophysis. The morphological resemblance indicates these two extant low-latitude pines probably possess a close affinity with the present newly-discovered P. shengxianica and originated from East Asian mid-low latitude ancestors during this generic re-diversification in the Miocene. This scenario is consistent with the evolutionary trajectory reflected by the pine fossil history and molecular data, marking the Miocene as a key period for the origin and evolution of most extant pines globally. The co-occurrences of diverse conifers and broadleaved angiosperms preferring diverse niches demonstrate Late Miocene eastern Zhejiang was one of the hot spots for coniferophyte diversity and hosted a needled-broadleaved mixed forest with complex vegetation structure and an altitudinal zonation.

Habitat highs and lows: Using terrestrial and UAV LiDAR for modelling avian species richness and abundance in a restored woodland

Vegetation structure influences landscape use and habitat quality for many bird species. Owing to the difficulties associated with collecting structural data from traditional field measurements, numerous studies have investigated the utility of Light detection and ranging (LiDAR) for providing landscape-scale structural information that may be useful for exploring animal-habitat associations. Notably, almost all of these studies have involved the use of LiDAR from airborne rather than terrestrial platforms. However, vegetation metrics that might be important for explaining bird species occurrence and diversity, such as understory vegetation complexity and overall vegetation volume, may be partially obscured from airborne sensors by tree canopy cover. These challenges might be overcome by terrestrial and UAV LiDAR sensors that can provide detailed information of understory forest strata. For the first time, we collected terrestrial LiDAR (TLS) and unoccupied aerial vehicle LiDAR (ULS) data in a woodland landscape to compare the ability of both sensors to identify relationships among vegetation structural metrics and bird species richness and abundance. Overall, TLS and ULS models provided similar results based on the sampling methodology we used for LiDAR data collection in an open woodland landscape. Canopy roughness, ground vegetation vertical complexity, total vegetation volume and canopy height derived from these sensors were among the most common significant variables in explaining avian diversity and individual species abundance. Individual species abundance models provided better prediction power (up to R2 = 0.82 (TLS) and R2 = 0.83 (ULS)) than bird community abundance by functional guilds (up to R2 = 0.40 (TLS), R2 = 0.41 (ULS)) and overall bird abundance (R2 = 0.10 (TLS), R2 = 0.16 (ULS)), species richness (R2 = 0.14 (TLS), R2 = 0.14 (ULS)) and diversity (R2 = 0.17 (TLS), R2 = 0.16 (ULS)). Additionally, we found that several vulnerable bird species are strongly associated with LiDAR structural variables, which may assist with habitat assessment and conservation management.

Tangled in a Web: Management Type and Vegetation Shape the Occurrence of Web-Building Spiders in Protected Areas.

Land management of parks and vegetation complexity can affect arthropod diversity and subsequently alter trophic interactions between predators and their prey. In this study, we examined spiders in five parks with varying management histories and intensities to determine whether certain spider species were associated with particular plants. We also determined whether web architecture influenced spider occurrence. Our results showed that humpbacked orb-weavers (Eustala anastera) were associated with an invasive plant, Chinese privet (Ligustrum sinense). This study revealed how invasive plants can potentially influence certain spider communities, as evidenced by this native spider species only occurring on invasive plants. Knowing more about spider populations-including species makeup and plants they populate-will give insights into how spider populations are dealing with various ecosystem changes. While we did not assess the effect of invasive plants on the behavior of spiders, it is possible that invasive species may not always be harmful to ecosystems; in the case of spiders, invasive plants may serve as a useful environment to live in. More studies are needed to ascertain whether invasive plants can have adverse effects on spider ecology in the long term.

Population Density and Stability of Breeding Birds in English Oak Woodland Over a 32-Year Period in Relation to Habitat Structure and Edges

Long-term breeding bird censuses in Białowieża National Park (BNP), north-east Poland, have revealed rather low densities of birds and high community stability which may be features of near-natural forest conditions. This paper reports on a long-term census of breeding birds in 50 ha of oak woodland in central England which contained both managed and undisturbed areas. New information is provided on breeding bird density and its spatial variation within English mature broadleaved woodland to address two questions: Under what circumstances are English woods likely to support higher densities than those occurring in BNP? Is there evidence that population and community stability is lower in English woodland? The overall bird density was lower than in the BNP oak-hornbeam stands, at the scale of both the whole study area and the undisturbed stands. Densities of three of the five dominant species (Cyanistes caeruleus, Parus major, Troglodytes troglodytes) were lower in BNP, Fringilla coelebs was higher, while Erithacus rubecula was similar. Within the undisturbed stands, densities of seven of 12 species, including T. troglodytes, were similar to those in BNP, two were considerably higher (C. caeruleus, P. major) and one much lower (F. coelebs). Selection of the external woodland edge by several species resulted in relatively high overall densities in the edge zone. The broad composition of the bird community remained fairly stable with the exception of declines in tropical migrants and increases in shrub layer nesters. Temporal abundance patterns of species showed much individuality. Trends of several species appeared to be driven by changes in habitat structure. However, the same species remained numerically dominant or characteristic of the wood throughout the study period. This suggests there was a core of resilient species, much as proposed for BNP. Although caution is needed in drawing conclusions from a single site, with the exception of a small number of species, in recent decades there is unlikely to have been a general pattern of higher densities of birds in English woodland than in BNP. However, some English woods with highly complex vegetation structures, or a high proportion of edge habitat, do have exceptionally high densities (> 100 territories/10 ha).

Pollen metabarcoding reveals the floral resources and niche overlap of honeybees in forest areas

AbstractWe investigated the floral resources of the honeybee (Apis mellifera) by pollen DNA metabarcoding as the first step in honeybee conservation. We attempted to identify as many floral resources and as wide resource availability as possible in areas and compared the richness of floral resources between forests and national parks. We found that both forest and national parks can sufficiently support honeybee floral resources; however, national parks were more stable habitats with more complex vegetation structure than those of forests. Also, honeybee's preferences for floral resources were determined using niche breadth, niche overlap, and network analysis among the floral resources in forest areas. Quercus and Actinidia were the most frequently detected taxa of pollen resources in both forests and national parks by pollen metabarcoding. Even though we anticipated that more various pollen resource taxa would be found in national parks than forests, no differences in the number pollen resource taxa were detected between them. According to the niche overlap analysis result, the honeybee preferred the pollen resources in both forests and national parks, and the co‐occurrence pattern analysis of pollen resource taxa in both forests and national parks showed a simple network. Altogether, our findings suggested that DNA metabarcoding of pollen collected by the honeybee can provide useful information on the flowering plants in a given area. As the use of floral pollen resources varies spatially and temporally, periodic monitoring of pollen resources can identify which pollen is required to maintain the health of honeybee colonies.

Three-dimensional numerical modelling of floods in river corridor with complex vegetation quantified using airborne LiDAR imagery

Excessive flood flow over the historic diversion weir in the vegetated Asahi River in Okayama Prefecture, Japan, was recently recorded for the first time after its renovation work. Fluvial researchers analysed the diversion discharge for flood mitigation measures through laboratory studies and conventional two-dimensional (2-D) depth-averaged simulations. The existing model was insufficient for simulation of certain phenomena such as flow resistance caused by vegetation branches and leaves and vertical flow distribution around the river corridor. Therefore, we developed a three-dimensional (3-D) vegetation resistance porous model by estimating topography, land cover, and vegetation distribution from airborne light detection and ranging (LiDAR) topo-bathymetry (ALB) data. Results show that the water level and flow regime were more reproducible than by referenced 2-D calculations when compared to space-time image velocimetry (STIV) data and field measurements. The diversion discharge designed using the proposed model is feasible with the current riverbed and vegetation conditions.

Field Measurement and Prediction of Drag in a Planted Rhizophora Mangrove Forest

AbstractDrag effects of mangrove forests with complex root systems modulate flow and substance transport and promote sedimentation, all of which are linked to mangroves' ecosystem services (e.g., coastal protection, trapping of suspended organic carbon) and resilience (e.g., vertical accretion relative to sea‐level rise). Previous flume studies proposed a predictive model of drag by Rhizophora mangrove forests based on the quadratic drag law using two parameters‐drag coefficient (CD) and vegetation projected area density (a). However, its general applicability to mangrove forests in the field has not been tested. To fill this knowledge gap, this study quantified drag in a 17‐year‐old planted Rhizophora mangrove forest using comprehensive measurements of hydrodynamics and vegetation morphology. The site showed a much higher value for a than the conditions assumed in previous flume studies, mainly due to root branching and high tree density. We found that despite the much higher vegetation complexity, the derived CD was 1.0 ± 0.2 for tide‐driven currents, consistent with previous flume studies. By using the mean value of derived CD (1.0), we confirmed that the quadratic drag model expresses well the field‐measured drag. We also showed that the value of parameter a can be predicted by only two vegetation parameters (stem diameter and tree density) using an empirical Rhizophora root model, and confirmed the successful prediction of drag from these vegetation parameters and the derived CD. This provides insights into effectively implementing the drag model in hydrodynamic models for better representation of flow, transport, and geomorphic dynamics in mangrove forests.

Research on spatiotemporal variation characteristics of soundscapes in a newly established suburban forest park

Passive acoustic monitoring has developed rapidly as a tool for ecological assessments, and the use of acoustic indices to assess biodiversity in urban forests promises to be a low-cost and efficient analytical approach. However, the accuracy of using acoustic indices to characterize biodiversity may be compromised by excessive human interference. The acoustic complexity index (ACI) and normalized difference soundscape index (NDSI) were chosen to determine their application value, and explore the spatiotemporal patterns of change in the soundscape of a newly established suburban forest park in China. To understand the influence of drivers such as different sound source types, road distance, and vegetation structure on the soundscape, the Eastern Suburb Forest Park was selected as the study area, and 55 recording points (200 m intervals, 5 × 11 grids) were set up using a systematic grid. Passive acoustic monitoring was performed for four consecutive days in each season, and the spatiotemporal variation of the soundscape was visualized based on indices interpolation. The results showed that when using ACI and NDSI to rapidly assess biodiversity in urban forest environments, attention needs to be paid to the implications of seasonal fluctuations on indices. The temporal variation of the soundscape was closely related to the natural rhythms and vocal activity intensity of organisms. Distance to a nearby main road, distance to water, and structural complexity of vegetation were key factors influencing spatial variation. The findings support the use of acoustic methods to assess the characteristics of soundscapes in human-built urban forests. Soundscape mapping visualizes hotspots and moments of ecoacoustic activity, and has great potential for development in the conservation and management of suburban forest soundscapes.

Capability of Phenology-Based Sentinel-2 Composites for Rubber Plantation Mapping in a Large Area with Complex Vegetation Landscapes

Mapping rubber plantations in a large area is still challenging in high-cloud-cover and complex-vegetation landscapes. Existing studies were often confined to the discrimination of rubber trees from natural forests and rarely concerned other tropical tree species. The Sentinel-2 constellation, with improved spatial, spectral, and temporal resolution, offers new opportunities to improve previous efforts. In this paper, four Hainan Sentinel-2 composites were generated based on the detailed phenological stages delineation of rubber trees. The random forest classifier with different phenological stage combinations was utilized to discuss the capability of Sentinel-2 composites to map rubber plantations. The optimal resultant rubber plantation map had a producer’s accuracy, user’s accuracy, and F1 score of 81%, 84.4%, and 0.83, respectively. According to the rubber plantation map in 2020, there was a total of 5473 km2 rubber plantations in Hainan, which was 2.93% higher than the statistical data from the Hainan Statistical Yearbook. According to the Hainan Statistical Yearbook, the area-weighted accuracy at the county level was 82.47%. The mean decrease in accuracy (MDA) was used to assess the feature importance of the four phenological stages. Results showed that the recovery growth stage played the most important role, and the resting stage was the least important. Moreover, in terms of the combinations of phenological stages, any dataset group with two phenological stages was sufficient for rubber tree discrimination. These findings were instrumental in facilitating the rubber plantation mapping annually. This study has demonstrated the potential of Sentinel-2 data, with the phenology-based image-compositing technique, for mapping rubber plantations in large areas with complex vegetation landscapes.