Vegetation Structural Complexity Research Articles

A taxonomic, functional, and phylogenetic perspective on the community assembly of passerine birds along an elevational gradient in southwest China.

Integrating multiple facets of biodiversity to describe spatial and temporal distribution patterns is one way of revealing the mechanisms driving community assembly. We assessed the species, functional, and phylogenetic composition and structure of passerine bird communities along an elevational gradient both in wintering and breeding seasons in the Ailao Mountains, southwest China, in order to identify the dominant ecological processes structuring the communities and how these processes change with elevation and season. Our research confirms that the highest taxonomic diversity, and distinct community composition, was found in the moist evergreen broadleaf forest at high elevation in both seasons. Environmental filtering was the dominant force at high elevations with relatively cold and wet climatic conditions, while the observed value of mean pairwise functional and phylogenetic distances of low elevation was constantly higher than expectation in two seasons, suggested interspecific competition could play the key role at low elevations, perhaps because of relative rich resource result from complex vegetation structure and human‐induced disturbance. Across all elevations, there was a trend of decreasing intensity of environmental filtering whereas increasing interspecific competition from wintering season to breeding season. This was likely due to the increased resource availability but reproduction‐associated competition in the summer months. In general, there is a clear justification for conservation efforts to protect entire elevational gradients in the Ailao Mountains, given the distinct taxonomic, functional, and phylogenetic compositions and also elevational migration pattern in passerine bird communities.

Epigeal spider assemblage responses to vegetation structure under contrasting grazing management in upland calcareous grasslands

Abstract Calcareous grassland is one of the most species rich and diverse habitats within Europe, but has faced decline due to agricultural intensification and abandonment. In recent years, conservation organisations have altered grazing practices in an attempt to maintain floristic components. However, there has been little consideration of the effects of changes in grazing practices on invertebrates. This study determines the impacts of commonly used grazing practices in upland calcareous grasslands on spiders in relation to vegetation structural complexity. Typical grazing management regimes were examined in three regions of upland calcareous grassland in Britain. Spiders were sampled from April to August 2014 and vegetation structural complexity was recorded in 2 × 2 m quadrats paired with pitfall traps sequentially throughout the sample period. There were three distinct spider assemblages among the grazing regimes; ungrazed, heavy sheep grazed and one shared between cattle and light sheep (which had a comparable grazing intensity). The distinct spider assemblages among grazing regimes can be attributed to the interaction of grazing and habitat structure. Increased vegetation structural complexity in ungrazed regimes resulted in an assemblage dominated by ‘sheet web weavers’ (dominated by Linyphiidae). In contrast, reduced vegetation structural complexity and homogeneity in heavy sheep grazing resulted in an assemblage dominated by ‘other hunters’ (including Oedothorax and Erigone genera). Grazing regime alters vegetation structural complexity and is important in supporting distinct spider assemblages. This research indicates that low intensity conservation grazing regimes, in addition to no grazing, should be promoted across upland calcareous grassland landscapes to maintain heterogeneity.

Does habitat structural complexity influence the frequency of extra-pair paternity in birds?

Several studies have suggested that vegetation structural complexity can influence the frequency of extra-pair copulations, especially by reducing mating-guarding efficiency. Here we investigate if habitat structural complexity affects broad patterns of extra-pair paternity (EPP) and extra-pair broods (proportion of nests presenting at least one extra-pair young—EPB), specifically testing the prediction that species living in habitats with denser vegetation would have a higher frequency of EPP or EPB. We reviewed studies reporting EPP and EPB levels and categorized structural complexity of vegetation for the study population into five habitat categories. Using both phylogenetic ANOVA and phylogenetic generalized least squares (PGLS), we found no significant effects in either EPP or EPB rates. Under the mating-guarding point of view, possible explanations for the lack of support are (i) trade-offs between the possibilities for females to escape from male surveillance and the difficulty to encounter neighbor extra-pair males by visual orientation in areas with dense vegetation; (ii) the predominance of passerine birds in most categories of vegetation complexity, which are small and agile, such that even less vegetated areas may allow extra-pair copulation to be concealed; (iii) environmental components other than vegetation, such as rocks and cliffs, also could provide concealment opportunities for extra-pair copulation; and (iv) the performance of predawn forays, when habitat complexity may play a weak role on guarding effectiveness. A macroecological understanding of EPP and EPB is a continuing challenge for understanding variation in avian mating systems. Our results contribute to improving the knowledge of the impact of habitat in sexual selection. Although a vast literature on avian extra-pair paternity (EPP) and its causes exists, the influence of a number of environmental parameters remains poorly addressed. One such parameter is habitat structural complexity. Scattered pieces of evidence from single-species studies have supported the idea that in more complex habitats, i.e., dense vegetation, extra-pair copulation (EPC) is facilitated by concealment opportunities. Here we provide a broad review on studies reporting EPP and EPB (proportion of nests presenting at least one extra-pair young) levels, and we classified study sites into five habitat categories, which were then compared. After controlling for phylogenetic effect, we found no significant effect. Possible explanations for the nonsignificance under a mating-guard perspective can involve trade-offs between the possibilities for females to escape from social surveillance and the difficulty to encounter neighbor extra-pair mates, the availability of habitat components other than vegetation providing concealment for EPC, and the use of strategies such as predawn forays to avoid mate-guarding consequences. Our results further expand the role of habitat in avian sexual selection.

Wildland Fire: Understanding and Maintaining an Ecological Baseline

The goal was to synthesize the literature on wildland fires, how they create resilient landscape mosaics that affect ecosystem function and maintenance of biodiversity, and how the fires themselves are affected by wilderness edge effects and climate change. The emphasis is on cold-temperate and boreal forests. The interactions of fires with landforms create large-magnitude spatial and temporal heterogeneity in fire severity that cannot be seen in smaller natural areas. Patterns of live and dead biomass and characteristic syndromes of fire-species interactions determine future successional trajectories and spatial-temporal dynamics of landscape mosaics. Therefore, wildlands with freely occurring fires provide a scientific baseline for complexity of vegetation structure and maintenance of biodiversity and ecosystem processes on time scales from years to centuries and millennia. Although wildlands are impacted by climate change, they may have considerable resilience, partly due to fire occurrence, and may still serve as a moving baseline. Thus, the patterns observed in wildlands can be used as blueprints for restoration of landscape structure, biodiversity, and ecosystem function in human-dominated ecosystems. Wildland fires play an important role in maintenance of ecological function and biodiversity, even on landscapes where fire is considered to be rare. At time scales of centuries, fires in large wilderness areas maintain a balance among successional stages, and although early and late-successional stages are rarely absent, their occurrences change in space and time, possibly leading to metapopulation dynamics for species that depend on certain successional stages. Over thousands of years, fires influence the trajectory of ecosystem retrogression, and in cold climates, fires can prevent ecosystem acidification that reduces forest productivity. Fire regimes within large wildlands are subject to change caused by fragmentation effects at large spatial extents; this can result in increased or reduced fire frequencies (disturbance dilution effect) within wildlands. Wildland managers need to think about how changes in the surrounding landscape influence the integrity of the natural disturbance baseline, while forest managers need to think about how harvesting compares to the baseline with respect to maintenance of productivity and biodiversity.

Interacting effects of fire severity, time since fire and topography on vegetation structure after wildfire

Fire is an important disturbance in forest ecosystems globally. Many of the effects of fire on forest processes are mediated through effects on vegetation structure. Understanding how fire properties, fire regimes and environmental variation interact to affect structure is required in the face of predictions of increasing size and severity of fires – “megafires”. Here, we investigated the influence of topographic position, fire severity, and time since last fire on vegetation structure in foothill eucalypt forests, two years after a large wildfire in south-eastern Australia. We found that forest gullies had significantly greater structural complexity than forest slopes; but that fire severity and time since last fire influenced the structure of vegetation in gullies and slopes in similar ways. Two years after wildfire, severely burnt gullies and slopes (tree crowns scorched or consumed) had a reduced canopy cover, but a denser cover of eucalypt saplings up to 4m tall, than gullies and slopes that had not been burnt. Compared with severe fire, understorey fire had much less influence on the structure of vegetation, with a significant effect only on slopes. There was little effect of the time since last fire prior to 2009 (≤3years vs. ≥20years) on subsequent vegetation structure after wildfire in either gullies or slopes. Finally, we found that fire did not homogenise the structure of gullies and slopes: vegetation structure in paired gullies and slopes did not become more similar following understorey or severe fire. Two years after a large wildfire, heterogeneity in the structural complexity of forest vegetation was evident at both the site and landscape scale. At the landscape scale, fire-induced heterogeneity in vegetation structure, arising from spatial variation in fire severity, provides habitat structures of differing quality for plants and animals. At a finer scale, the rapid return of distinct vegetation structure between adjacent gullies and slopes is important for the persistence of species that depend on a complex vegetation structure or require fine-scale heterogeneity in vegetation.

Regional mapping of vegetation structure for biodiversity monitoring using airborne lidar data

Vegetation structure is identified as an important biodiversity indicator providing the physical environment that generates, supports, and maintains forest biodiversity. Airborne lidar systems (light detection and ranging) have the capacity to accurately measure three-dimensional vegetation structure, and have been widely used in wildlife habitat mapping and species distribution modeling. Large–area structural inventories using lidar-derived variables that characterize generic habitat structure have rarely been done, yet would be helpful for guiding biodiversity monitoring and conservation assessments of species at regional levels. This study provides a novel approach for processing regional-scale lidar data into categorical classes representing natural groupings of habitat structure. We applied cluster analysis on six lidar-derived habitat-related variables to classify vegetation structure into eight classes for the forested areas of ten natural subregions in boreal and foothill forests in Alberta, Canada. Structure classes were compared across different natural subregions and under anthropogenic/non-anthropogenic disturbance regimes. We found that the Lower Foothills Natural Subregions had the most complex vegetation structure, and wildfire was the most prevalent disturbance agent for all classes except for the rarest class (i.e. stands with high standard deviations of height and low canopy cover) which was more heavily altered by timber harvesting. This data product provides continuous, regional mapping of vegetation structure directly measured from lidar, with a spatial resolution (30m) relatively finer than what was provided by polygon-based forest inventories. This vegetation structure classification and its associated spatial distribution address the fundamental issue of habitat structure in biodiversity monitoring. It can serve as a base layer used together with species and land cover data for forest resources planning, species distribution and animal movement modeling, as well as prioritization of conservation efforts on critical habitat structures.

Contribution of Vegetation Structure on Carbon Assimilation Capacity of Mangrove Ecosystem: A Case Study from Negombo Estuary, Sri Lanka

Mangrove ecosystems perform number of important ecological functions and provide a wide range of services at the local or national level and provide a unique combination of both organic matter production and sequestration, which is different from other coastal ecosystems. Mangroves are extensively used to extract twigs and branches for the construction of “Brush piles”, the predominant fishing devices in the Negombo estuary, Sri Lanka, believed to have one major impact on the vegetation structure followed by the changes in primary productivity and carbon assimilation capacity of the ecosystem. Present study was conducted with an objective of quantify and relationships between the vegetation structure and Gross Primary Productivity (GPP) of disturbed and natural mangrove stands in the Negombo estuary. Vegetation structural parameters were gathered according to the standard procedures and the measurement of Photosynthetically Active Radiation (PAR) used to calculate the Leaf Area Index (LAI) followed by the GPP. Highest values of vegetation structural parameters, LAI and GPP were recorded from estuarine waterfront and decreased with landwards, which indicated more active vegetation is near by the estuarine waterfront. Comparatively, vegetation structural/structural complexity (CI) and GPP/carbon assimilation capacity were superior in undisturbed/ natural mangrove stands (31.86-36.65 Mg ha -1 y -1 ) than that was recorded in disturbed/ replanted mangrove areas (26.42-35.25 Mg ha -1 y -1 ) at Negombo estuary. Statistically significant liner relationships (P<0.01) were revealed between vegetation structural complexity and GPP (CI=.0.498 GPP +28.208); structural complexity and Leaf Area Index (CI=0.0956 LAI +5.3551).

The importance of canopy complexity in shaping seasonal spider and beetle assemblages in saltmarsh habitats

1. Habitat structure, including vegetation structural complexity, largely determines invertebrate assemblages in semi‐natural grasslands. The importance of structural complexity to the saltmarsh invertebrate community, where the interplay between vegetation characteristics and tidal inundation is key, is less well known.2. It was hypothesised that canopy complexity would be a more important predictor of spider and beetle assemblages than simple vegetation attributes (e.g. height, community type) and environmental variables (e.g. elevation) alone, measured in two saltmarsh regions, south‐east (Essex) and north‐west (Morecambe Bay) U.K. Canopy complexity (number of non‐vegetated ‘gaps’ in canopy ≥ 1 mm wide) was assessed using side‐on photography. Over 1500 spiders and beetles were sampled via suction sampling, winter and summer combined.3. In summer, saltmarshes with abundant spider and beetle populations were characterised by high scores for canopy complexity often associated with tussocky grass or shrub cover. Simple vegetation attributes (plant cover, height) accounted for 26% of variation in spider abundance and 14% in spider diversity, rising to 46% and 41%, respectively, with the addition of canopy complexity score. Overwintering spider assemblages were associated with elevation and vegetation biomass. Summer beetle abundance, in particular the predatory and zoophagous group, and diversity were best explained by elevation and plant species richness.4. Summer canopy complexity was identified as a positive habitat feature for saltmarsh spider communities (ground‐running hunters and sheet weavers) with significant ‘added value’ over more commonly measured attributes of vegetation structure.

Meta-analysis of field scale spatial variability of grassland soil CO2 efflux: Interaction of biotic and abiotic drivers

In this study eight temperate grassland sites were monitored for soil CO2 efflux (Rs) and the spatial covariate soil water content (SWC) and soil temperature (Ts) at fine scale in over 77 measurement campaigns. The goals of this multisite study were to explore the correlations between environmental gradients and spatial patterns of Rs, SWC and Ts, which are not site-specific and to quantify the relevance of biotic and abiotic controls over spatial patterns along increasing vegetation structural complexity. These patterns in water-limited ecosystems in East-Central Europe are likely to be influenced by summer droughts caused by the changing climate.A consistent experimental setup was applied at the study sites including 75 sampling locations along 15m circular transects. Spatial data processing was mainly based on variography. Two proxy variables were introduced to relate the site characteristics in terms of soils, water status and vegetation. Normalised SWC (SWCn) reconciled site-specific soil water regimes while normalised day of year integrated temperature and vegetation phenology.A principal component analysis revealed that the progressing closure of vegetation in combination with large Rs and SWCn values, as well as low Ts and Rs variability support the detectability of spatial patterns found in both the abiotic and biotic variables. Our results showed that apart from SWC the pattern of soil temperature also had an effect on spatial structures. We detected that when the spatially structured variability of Ts was low, a strong negative correlation existed between SWCn and the spatial autocorrelation length of Rs with r=0.66 (p<0.001). However, for high spatially structured variability of Ts, occurring presumably at low Ts in spring and autumn, the correlation did not exist and it was difficult to quantify the spatial autocorrelation of Rs. Our results are indicative of a potential shift from homogeneity and dominance of biotic processes to an increased heterogeneity and abiotic regulation in drought prone ecosystems under conditions of decreasing soil moisture.

To what extent does vegetation composition and structure influence beetle communities and species richness in private gardens in New Zealand?

Private gardens comprise a large proportion of urban green space and can contain diverse and structurally complex vegetation, typically dominated by exotic species, but potentially providing resources for a diverse invertebrate fauna. We determined how much beetle diversity and community structure were influenced by vegetation composition and structure, native vegetation, garden land covers, and proximity and extent of neighbourhood green spaces in 55 gardens in Dunedin, New Zealand. We recorded 164 species from 29 families after 10 days of pitfall trapping; 68% native, 15% exotic. Beetle diversity exceeded that reported in other less modified New Zealand habitats, possibly due to high habitat heterogeneity at the scale of the garden but also the variety of habitats present at a larger scale but separated by relatively short distances within this small city and across a short altitudinal gradient, from sea level to sub-alpine environments. Number of shrubs (2–5m), woody plant density, and area of lawn and hedge influenced beetle richness, diversity and community structure, but explained <30% of variation between gardens. We found no effect of mean diversity of herbaceous vegetation in bed use, mowing and composting on diversity or community structure. Proximity to green space, woody plant diversity and vegetation structural complexity influenced beetle community composition, but correlations were weak. Although only 17% of all woody plants were native, most beetle species were native. With the exception of gardens that had very little vegetation, landscaping choices appeared to have little effect on beetle diversity and assemblage composition.

Dynamics of the relationship between NDVI and SWIR32 vegetation indices in southern Africa: implications for retrieval of fractional cover from MODIS data

ABSTRACTFractional cover of photosynthetic vegetation (FPV), non-photosynthetic vegetation (FNPV), and bare soil (FBS) has been retrieved for Australian tropical savannah based on linear unmixing of the two-dimensional response envelope of the normalized difference vegetation index (NDVI) and short wave infrared ratio (SWIR)32 vegetation indices (VI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data. The approach assumes that cover fractions are made up of a simple mixture of green leaves, senescent leaves, and bare soil. In this study, we examine retrieval of fractional cover using this approach for a study area in southern Africa with a more complex vegetation structure. Region-specific end-members were defined using Hyperion images from different locations and times of the season. These end-members were applied to a 10-year time series of MODIS-derived NDVI and SWIR32 (from 2002 to 2011) to unmix FPV, FNPV, and FBS. Results of validation with classified high-resolution imagery indicated major bias in estimation of FNPV and FBS, with regression coefficients for predicted versus observed data substantially less than 1.0 and relatively large intercept values. Examination with Hyperion images of the inverse relationship between the MODIS-equivalent SWIR32 index and the Hyperion-derived cellulose absorption index (CAI) to which it nominally approximates revealed: (1) non-compliant positive regression coefficients for certain vegetation types; and (2) shifts in slope and intercept of compliant regression curves related to day of year and geographical location. The results suggest that the NDVI–SWIR32 response cannot be used to approximate the NDVI–CAI response in complex savannah systems like southern Africa that cannot be described as simple mixtures of green leaves, dry herbaceous material high in cellulose, and bare soil. Methods that use a complete set of multispectral channels at higher spatial resolution may be needed for accurate retrieval of fractional cover in Africa.

Spectral Unmixing of Forest Crown Components at Close Range, Airborne and Simulated Sentinel-2 and EnMAP Spectral Imaging Scale

Forest biochemical and biophysical variables and their spatial and temporal distribution are essential inputs to process-orientated ecosystem models. To provide this information, imaging spectroscopy appears to be a promising tool. In this context, the present study investigates the potential of spectral unmixing to derive sub-pixel crown component fractions in a temperate deciduous forest ecosystem. However, the high proportion of foliage in this complex vegetation structure leads to the problem of saturation effects, when applying broadband vegetation indices. This study illustrates that multiple endmember spectral mixture analysis (MESMA) can contribute to overcoming this challenge. Reference fractional abundances, as well as spectral measurements of the canopy components, could be precisely determined from a crane measurement platform situated in a deciduous forest in North-East Germany. In contrast to most other studies, which only use leaf and soil endmembers, this experimental setup allowed for the inclusion of a bark endmember for the unmixing of components within the canopy. This study demonstrates that the inclusion of additional endmembers markedly improves the accuracy. A mean absolute error of 7.9% could be achieved for the fractional occurrence of the leaf endmember and 5.9% for the bark endmember. In order to evaluate the results of this field-based study for airborne and satellite-based remote sensing applications, a transfer to Airborne Imaging Spectrometer for Applications (AISA) and simulated Environmental Mapping and Analysis Program (EnMAP) and Sentinel-2 imagery was carried out. All sensors were capable of unmixing crown components with a mean absolute error ranging between 3% and 21%.

Vulnerability of a riparian zone towards invasion by alien plants depends on its structure

AbstractRiparian zones support high biodiversity and are among the most vulnerable parts of the landscape. Their degradation facilitates the spread of invasive alien plant species. Our aim was to investigate the relationship between environmental characteristics of riparian zones and distribution and abundance of invasive alien plant taxa (IAT) along three rivers in Slovenia. In 100-m reaches of riparian zone we determined environmental characteristics and the presence and abundance of IAT. Canonical correspondence analysis was used to assess the relationship between IAT and environmental factors. The numbers and abundances of IAT in specific reaches were correlated with environmental factors using Spearman coefficient. These results revealed that the number and abundance of IAT in riparian zone were strongly positively correlated to the distance from river source, while they were negatively correlated with altitude, vegetation structure complexity, completeness of riparian zone and current velocity. Environmental factors that explained the distribution and abundance of IAT significantly were: the altitude, flow dynamics, distance from source, width of riparian zone, land-use, bank and channel structure, water depth and velocity. The research has pointed out the need for proper management of riparian zones to prevent invasion by IAT and also to strengthen other services provided by riparian zone as buffering anthropogenic impacts to water body, stabilising bank structure and increasing biodiversity.

Assessing the Fauna Diversity of Marudu Bay Mangrove Forest, Sabah, Malaysia, for Future Conservation

Mangrove is an evergreen, salt tolerant plant community, which grows in inter-tidal coastal zones of tropical and subtropical regions of the world. They are ecologically important for many fauna species and are rich in food resources and consist of many different vegetation structures. They serve as ideal foraging and nursery grounds for a wide array of species such as birds, mammals, reptiles, fishes and aquatic invertebrates. In spite of their crucial role, around 50% of mangrove habitats have been lost and degraded in the past two decades. The fauna diversity of mangrove habitat at Marudu Bay, Sabah, East Malaysia was examined using various methods: i.e. aquatic invertebrates by swap nets, fish by angling rods and cast nets, reptiles, birds, and mammals through direct sighting. The result showed that Marudu Bay mangrove habitats harbored a diversity of fauna species including 22 aquatic invertebrate species (encompassing 11 crustacean species, six mollusk species and four worm species), 36 fish species, 74 bird species, four reptile species, and four mammal species. The wide array of fauna species could be due to the availability of complex vegetation structures, sheltered beaches and tidal mudflats, which are rich in food resources and also offer safe foraging and breeding grounds for them. These heterogeneous habitats must be protected in a sustainable way in order to ensure the continued presence of aquatic and terrestrial fauna species for future generations.

The diversity and abundance of North American bird assemblages fail to track changing productivity.

Plant biomass or productivity and the species richness of birds are associated across a range of spatial scales. Species-energy theory is generally assumed to explain these correlations. If true, bird richness should also track productivity temporally, and there should be spatial and temporal relationships between productivity and both bird abundance and bird richness. Using the summer normalized difference vegetation index (NDVI) for 1982-2006 and the North American Breeding Bird Survey, we evaluated the response of avian richness and abundance to interannual changes in plant biomass or productivity. We found positive spatial relationships between richness and NDVI for all 25 years. Temporally, however, richness and NDVI were positively associated at 1579 survey sites and negatively associated at 1627 sites (mean r2 = 0.09). Further, total abundance and NDVI were unrelated spatially (r2 values spanning < 0.01 and 0.03) and weakly related temporally (mean r2 = 0.10). We found no evidence that productivity drives bird richness beyond the spatial correlations, and neither prediction arising from species-energy theory was confirmed. Spatial relationships between productivity and bird richness may thus be largely spurious, arising via covariance between plant biomass or productivity and vegetation structural complexity, and the latter may be driving bird communities. This is consistent with the MacArthurs' classic hypothesis that the vertical profile of foliage drives bird species diversity.

Predation drives nesting success in moist highland grasslands: the importance of maintaining vegetation cover for bird conservation

By focusing on process-oriented data rather than inventory-type data, this study provides a robust understanding of the effects of agricultural management on grassland bird reproductive output in the moist highland grasslands (MHGs) of South Africa. Four-hundred and four nests of 12 grassland-breeding bird species were monitored in five different land-use types. Survivorship was modelled using Program MARK to assess the effects of these management practices on reproductive performance. Six of the species were modelled individually to assess speciesspecific responses. Both nest-site selection and nest success were driven by vegetation structure, which in turn is driven by habitat management. There was an increase in nesting success through the season for cup (ground) nesting birds as vegetation structural complexity increased through the breeding season (September to March). Nest success was driven by predation pressure rather than food availability. Analysis of the nesting success of the Yellow-breasted Pipit Anthus chloris indicated that unconserved areas house sink populations, confirmation of which would depend on a measure of adult survival. The generalist African Pipit Anthus cinnamomeus, on the other hand, thrived in disturbed, communally grazed lands. To conserve MHG bird species, managers should maintain a mosaic of burning regimes, with the majority burning biennially or less frequently.

Identifying essential ecological factors underpinning the development of a conservation plan for the Endangered Australian tree Alectryon ramiflorus

AbstractReintroduction of rare and threatened species often fails to yield quantifiable conservation benefits because insufficient attention is focused on the species’ habitat requirements and biology. We demonstrate the value of such data in informing a recovery plan for Alectryon ramiflorus S.Reyn. (Sapindaceae), a tree species endemic to a region on the southern coast of Queensland, Australia. When the species was categorized as Endangered on the IUCN Red List in 1997 the total known population consisted of only 26 adult plants, in five disjunct populations in remnant patches of native vegetation. Analysis of vegetation type, soil chemistry and composition data comparing remnant patches with and without A. ramiflorus revealed that the species is not restricted to a specific soil type but prefers sites with relatively fertile soil and a more complex vegetation structure. The species is cryptically dioecious, displays asynchronous flowering between individuals, and requires insect-vectored pollination. The low rate of seedling production recorded within individual patches was attributed to the scarcity of trees of both genders, asynchronous flowering of individual trees and, in smaller patches, a sparse population of pollinating insect species. Successful reintroduction of A. ramiflorus will require consideration of these aspects of demographic success. The findings highlight the importance to species recovery plans of the knowledge of habitat requirements, interspecific relationships and critical dependencies, as well as species reproductive biology.

The home range and multi-scale habitat selection of the threatened maned three-toed sloth (Bradypus torquatus)

Habitat selection is a scale-dependent process of paramount importance to the understanding of how species deal with environmental variation. This process has practical implications for wildlife conservation, aiding in the identification of key resources for animals and in the definition of scales relevant to the proposal of practical conservation actions. In this study, we investigated in different spatial scales the habitat selection of the maned three-toed sloth (Bradypus torquatus), a threatened and endemic arboreal folivore of the Atlantic rainforest (vulnerable, sensu IUCN). We radio-tracked and monitored seven sloths for 18 months in landscapes of Southern Bahia, Brazil, the current core region of the species’ distribution. The average values of the home-range estimates were low, but varied considerably among individuals regardless of the estimator (from 0.95 to 27.8ha, MCP method, and from 0.39 to 21.52ha, fixed kernel method). At the landscape scale, the maned sloths preferred early secondary forest and shade cacao plantations, avoided open areas, and occupied late secondary forest as expected compared to its availability. At the home range scale, however, the sloths did not show preference for any forest category, though, again, avoided open areas. At smaller spatial scales, the sloths were highly selective towards forest patches characterized by complex vegetation structures (i.e., areas with a high density of trees, closed and dense canopies), and selected large trees with lianas and bromeliads and also with connected crowns. The high selectivity observed at finer scales appeared to be the result of limited spatial perception and experience due to the species’ characteristic slow mobility. Our results support the notion that maned sloths can effectively occupy (and even select for) disturbed forested habitats. However, we do not know whether sloth populations are viable in landscapes containing only disturbed habitats or low proportions of undisturbed habitats.

Risks in extrapolating habitat preferences over the geographical range of threatened taxa: a case study of the quokka (Setonix brachyurus) in the southern forests of Western Australia

Context Extrapolation of knowledge for threatened taxa between parts of their range that are disconnected and/or ecologically diverse can result in significant sources of error that undermine the effectiveness of conservation efforts. Aims We investigated the risks associated with extrapolation of ecological information across environmental gradients, using the quokka (Setonix brachyurus) as a case study. Information documented in the northern part of its range is currently used to manage this species across its range in south-western Australia. We examined the suitability of this approach by developing a habitat suitability model (HSM) for the quokka in the southernmost areas of its range and comparing this with existing knowledge for the species. Methods We surveyed 327 sites, representative of a range of ecotypes, for presence/absence of quokkas. Occupancy models were applied to select a subset of habitat variables that best predicted occupancy patterns. Key results Occupancy patterns were influenced by complex vegetation structure, low levels of woody debris and habitat patchiness. HSMs developed for quokkas in the north could not predict occupancy patterns in the south. Significant fragmentation of subpopulations was observed due to patchiness in the availability of suitable habitat. Conclusions The choice of predictor variables in HSMs that are not transferrable between regions could contribute to inappropriate management of habitat for quokkas and an increased risk of local extinctions. In addition, failure to consider processes that affect preferred habitat variables could contribute to the segregation of habitat patches and intervening distances that are too great for successful dispersal, immigration and recolonisation processes. Implications The extrapolation of HSMs between geographical areas can increase the risk of outcomes that are detrimental to the conservation of threatened species. Where such extrapolation is necessary, actions guided by the HSMs should be implemented in a management framework that can detect adverse effects, allow for inclusion of new ecological information and explicitly consider the limitations and assumptions of this approach. In addition, perceptions of habitat fragmentation need to include processes such as fire regimes and feral animals that affect the availability and connectivity of habitat and have the potential to adversely affect population viability.

城市公园生境类型对鸟类群落的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 城市公园生境类型对鸟类群落的影响 DOI: 10.5846/stxb201309112250 作者: 作者单位: 华东师范大学，上海市城市化过程与恢复重点实验室,华东师范大学，上海市城市化过程与恢复重点实验室,华东师范大学，上海市城市化过程与恢复重点实验室,华东师范大学，上海市城市化过程与恢复重点实验室,上海市浦东新区林业站,上海市浦东新区林业站,华东师范大学,上海市野生动植物保护管理站,上海科技馆,华东师范大学，上海市城市化过程与恢复重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 上海市绿化和市容管理局专项基金、浦东新区科技发展基金(PKJ2011-N020) The influence of habitat types on bird community in urban parks Author: Affiliation: East China Normal University，Shanghai Key Laboratory of Urbanization and Ecological Restoration,,,,,,,,,East China Normal University，Shanghai Key Laboratory of Urbanization and Ecological Restoration Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:2011 年12 月-2012 年11 月,在上海世纪公园和滨江森林公园对鸟类群落和植物群落进行调查,通过对12 个植被变量进行主成分分析,将两个公园分为8 种不同的生境类型。结果表明:2 个公园生境构成存在显著差异,滨江森林公园灌木层植物发达的生境(Habitat with developed shrub layer, S型)以及灌木层和地被层植物都发达的生境(Habitat with developed tree layer and shrub layer, T+S型)数量显著多于世纪公园,世纪公园地被层发达的生境(Habitat with developed ground cover layer, G型)以及乔木层和地被层植物都发达的生境(Habitat with developed tree layer and ground cover layer, T+G型)数量显著多于滨江森林公园。世纪公园不同生境中鸟种数差异显著,而滨江森林公园中差异不显著。2 个公园有24 种共有鸟种,对共有鸟种生境利用率的配对t检验结果表明,滨江森林公园鸟类生境利用率显著高于世纪公园。对2 个公园共有生境类型中鸟种数进行分析,发现滨江森林公园鹟科(Muscicapidae)鸟类种数显著大于世纪公园。根据以上结果,上海城市公园不同生境类型对鸟类群落结构存在显著影响。因此,建议在规划和建设大型城市公园时,应构建植被分层结构复杂的生境,多样化种植各类乔木,林下多样化搭配灌木。在保留供游客休憩草坪区域的同时种植各类草本植物,以此提高鸟类生境利用率,增加城市公园的鸟类多样性。 Abstract:The bird communities and vegetation communities in Shanghai Century Park and Bingjiang Forest Park were respectively surveyed from December 2011 to November 2012. In accordance with the result of principal components analysis of 12 vegetation variables, the vegetation in the two parks was grouped into 8 types including T type (habitat with developed tree layer), S type (habitat with developed shrub layer), G type (habitat with developed ground cover layer), T+S type (habitat with developed tree layer and shrub layer), T+G type (habitat with developed tree layer and ground cover layer), S+G type (habitat with developed shrub layer and ground cover layer), T+S+G type (habitat with complex vegetation structure), D type (disturbed habitat). Chi-square test suggested that the S type and T+S type habitat in Binjiang Forest Park was significantly more abundant than those in Century Park while G type and T+G type habitat in Century Park was significantly more abundant than those in Binjiang Forest Park. Developed tree layer habitat was abundant both in the two parks and More than 70% of the bird richness and bird abundance were recorded in these habitat. Bird richness was significantly different in habitat types in Century Park, but the richness difference was not significant in Binjiang Forest Park. There were 24 common bird species in the two parks, which were indicated to have performed higher utility rate in Binjiang Park than those in Century Park in accordance with paired sample t test result. Analysis of the bird richness in common habitat types of the two parks showed that the richness of Muscicapidae in Binjiang Park was significantly higher than that of their counterparts in Century Park. Due to the forgoing, we concluded that (1) trees were one of the most important vegetation components that enhanced the bird species richness and diversity in urban green spaces; (2) shrubs were usually treated as being as important as trees for birds living in urban areas, where they provided some forest birds with nesting sites; (3) ground cover layer provided the ground foraging groups with feeding resources. Our research emphasized that habitat types significantly influenced the structure of bird communities in the urban parks in Shanghai. Therefore, we suggest that hierarchical vegetation types should be adopted while planning and constructing large-scale urban parks so that the bird diversity will be improved. Furthermore, in order to perform higher utility rate of urban birds, diversified shrubs and different kinds of herbaceous plant should be planted under the tree layer. 参考文献 相似文献 引证文献