Response of plant-pollinator communities to fire: changes in diversity, abundance and floral reward structure

Globally, plant-pollinator communities are subject to a diverse array of perturbations and in many temperate and semi-arid systems fire is a dominant structuring force. We present a novel and highly integrated approach, which quantifies, in parallel, the response to fire of pollinator communities, floral communities and floral reward structure. Mt Carmel, Israel is a recognised bee-flower biodiversity hotspot, and using a chronosequence of habitats with differing post-fire ages, we follow the changes in plant-pollinator community organisation from immediately following a burn until full regeneration of vegetation. Initially, fire has a catastrophic effect on these communities, however, recovery is rapid with a peak in diversity of both flowers and bees in the first 2 years post-fire, followed by a steady decline over the next 50 years. The regeneration of floral communities is closely matched by that of their principal pollinators. At the community level we quantify, per unit area of habitat, key parameters of nectar and pollen forage known to be of importance in structuring pollinator communities. Nectar Volume, nectar water content, nectar concentration and the diversity of nectar foraging niches are all greatest immediately following fire with a steady decrease as regeneration proceeds. Temporal changes in energy availability for nectar, pollen, total energy (nectar + pollen) and relative importance of pollen to nectar energy show a similar general decline with site age, however, the pattern is less clear owing to the highly patchy distribution of floral resources. Changes in floral reward structure reflect the general shift from annuals (generally low-reward open access flowers) to perennials (mostly high-reward and restricted access flowers) as post-fire regeneration ensues. The impact of fire on floral communities and their associated rewards have clear implications for pollinator community structure and we discuss this and the role of other disturbance factors on these systems.

Recent patterns of change in vegetation structure and tree composition of British broadleaved woodland: evidence from large-scale surveys

Evidence is presented of widespread changes in structure and species composition between the 1980s and 2003–2004 from surveys of 249 British broadleaved woodlands. Structural components examined include canopy cover, vertical vegetation profiles, field-layer cover and deadwood abundance. Woods were located in 13 geographical localities and the patterns of change were examined for each locality as well as across all woods. Changes were not uniform throughout the localities; overall, there were significant decreases in canopy cover and increases in sub-canopy (2–10 m) cover. Changes in 0.5–2 m vegetation cover showed strong geographic patterns, increasing in western localities, but declining or showing no change in eastern localities. There were significant increases in canopy ash Fraxinus excelsior and decreases in oak Quercus robur/petraea. Shrub layer ash and honeysuckle Lonicera periclymenum increased while birch Betula spp. hawthorn Crataegus monogyna and hazel Corylus avellana declined. Within the field layer, both bracken Pteridium aquilinum and herbs increased. Overall, deadwood generally increased. Changes were consistent with reductions in active woodland management and changes in grazing and browsing pressure. These findings have important implications for sustainable active management of British broadleaved woodlands to meet silvicultural and biodiversity objectives.

Non-uniform bird assemblages in urban environments : the influence of streetscape vegetation

The urban landscape encompasses a broad spectrum of variable environments ranging from remnant patches to highly modified streetscapes. Despite the expansion of urban environments, few studies have examined the influence of urbanization on faunal diversity, particularly in the Southern Hemisphere. In this study, four broad habitat types were recognized in the urban environment, representing a continuum of modification ranging from parks with remnant vegetation to streetscapes dominated by native vegetation and those dominated by exotic vegetation to recently developed streetscapes. Bird censuses were conducted at 36 sites throughout urban Melbourne, with nine sites surveyed in each habitat type. The four habitat types supported significantly different bird communities based on species richness, abundance and composition suggesting that bird assemblages of urban environments are non-uniform. Parks and native streetscapes generally supported fewer introduced species than exotic and recently developed streetscapes. Overall abundance and richness of species were lower in the exotic and recently developed streetscapes than in parks and native streetscapes. Significant differences were also observed in foraging guilds within the four habitat types, with parks having the most foraging guilds and recently developed streetscapes having the fewest. The transition from native to exotic streetscapes saw the progressive loss of insectivorous and nectarivorous species reflecting a reliance by these species on structurally diverse and/or native vegetation for both shelter and food resources. The implementation of effective strategies and incentives which encourage the planting of structurally diverse native vegetation in streetscapes and gardens should be paramount if avian biodiversity is to be retained and enhanced in urban environments. It is also critical to encourage the maintenance of the existing remnant vegetation in the urban environment.

Introduced birds in urban remnant vegetation : does remnant size really matter?

Introduced birds are a pervasive and dominant element of urban ecosystems. We examined the richness and relative abundance of introduced bird species in small (1–5 ha) medium (6–15 ha) and large (>15 ha) remnants of native vegetation within an urban matrix. Transects were surveyed during breeding and non-breeding seasons. There was a significant relationship between introduced species richness and remnant size with larger remnants supporting more introduced species. There was no significant difference in relative abundance of introduced species in remnants of different sizes. Introduced species, as a proportion of the relative abundance of the total avifauna (native and introduced species), did not vary significantly between remnants of differing sizes. There were significant differences in the composition of introduced bird species between the different remnant sizes, with large remnants supporting significantly different assemblages than medium and small remnants. Other variables also have substantial effects on the abundance of introduced bird species. The lack of significant differences in abundance between remnant sizes suggests they were all equally susceptible to invasion. No patches in the urban matrix are likely to be unaffected by introduced species. The effective long-term control of introduced bird species is difficult and resources may be better spent managing habitat in a way which renders it less suitable for introduced species (e.g. reducing areas of disturbed ground and weed dominated areas).

Distribution and abundance of the white-faced storm petrel (Pelagodroma marina) in Victoria

Habitat loss and modification is a major factor driving reductions of seabird populations. The white-faced storm petrel (Pelagodroma marina) is restricted to three breeding colonies within Victoria: Mud Islands and South Channel Fort in Port Phillip Bay, and Tullaberga Island off Mallacoota. The numbers of storm petrels breeding on Mud Islands and South Channel Fort have declined considerably, possibly a result of the significant vegetation changes, together with increases in local populations of other species of birds, most notably, silver gulls (Larus novaehollandiae). On Mud Islands the breeding area available to the storm petrels appears to be limited by the recent arrival of the Australian white ibis (Threskoirnis molucca), and straw-necked ibis (T. spinicollis) which now breed on the islands in large numbers (approximately 15,000 pairs). The impact of these changes on the storm petrels is poorly understood. The current status of storm petrels at Tullaberga Island is unknown. This study estimated the size of the breeding population at all three sites by determining burrow densities, and a burrow-scope was used to determine occupancy. Burrow density was found to be related to vegetation type and other habitat factors. This study has highlighted important information on the breeding habitat of the white-faced storm petrel and the implications for management are discussed.

Plant pathogens causing vegetation dieback: a serious threat to the conservation of small mammals in Australia

The soil-borne plant pathogen Phytophthora cinnamomi occurs in most Australian states. It is pathogenic to many Australian species, particularly the Proteaceae, Fabaceae, Dillineaceae and Epacridaceae. In Western Australia, c. 2000 of the 9000 endemic plant species are directly affected by the disease. The epidemic of plant deaths caused by P. cinnamomi is recognised as one of 11 Key Threatening Processes to the Australian Environment, and is now also acknowledged as a potential threat fauna in a range of communities. The implications of landscape modification due to the effects of P. cinnamomi dieback prompted our research, designed to measure the distribution and abundance of small mammals in disease-affected ecosystems. This study was in the Jarrah (Eucalyptus marginata) forests in the Darling Range, Western Australia and measured the distribution and abundance of one small mammal species, the Mardo (Antechinus flavipes) by Elliott trapping in forests with (1) high, (2) mixed and (3) no evidence of Phytophthora dieback. Trap success was highest in sites with no effect of Phytophthora (7.3 animals per 100 trap nights), whereas the lowest trap success was recorded at the high impact sites (0.67 animals per 100 trap night). There was a significant difference in trap success of Mardos in Elliott trapping over 1800 trap nights (x²= 23.19, d.f = 5, p < 0.001). An examination of the distribution of individuals and sexes suggests that Phytophthora-affected sites act as sinks for Mardos, while source areas are healthy, unaffected Jarrah forest.

Recolonisation of powerline corridor vegetation by small mammals : timing and the influence of vegetation management

Powerline corridors through forested ecosystems have been criticised due their potential to fragment the landscape and facilitate the intrusion of undesirable species into natural areas. This study investigates the effects of vegetation management (slashing), on: (1) timing of small mammal recolonisation; (2) vegetation characteristics that drive small mammal responses; and (3) the point where corridor resources are sufficient to provide functional habitat for native species. Small mammal trapping was undertaken within Bunyip State Park, Australia, across three sites, once a month from January 2001 to May 2002 and every 2 months thereafter until January 2004. Changes in vegetation around each trap station were assessed annually in the forest and bi-annually in the corridor. Principal components analysis on the vegetation structural complexity values produced factors for use in species abundance models. Native small mammal species recolonised the corridor 1.5–3.5 years after management and the corridor supported a breeding population of small mammals around 2.5 years post-management. Males however, generally recolonised the corridor first, resulting in a sex-biased population in these areas. Species corridor habitat models for five native and one introduced species suggested cover and shelter were more important in determining corridor use than plant species per se. Powerline corridors have the potential to create a mixture of different successional stages, enhancing habitat availability for many species. However, the intensity of current management needs to be reduced and an integrated approach to management needs to be undertaken if powerline corridors are to continuously provide habitat for native small mammal species.

Effects of vegetation, fire and other disturbance factors on small mammal ecology and conservation

The relationship of vegetation and disturbance factors to the distribution, abundance and diversity of small mammals in the eastern Otway region, Victoria were investigated. Antechinus stuartii, Rattus fuscipes and Rattus lutreolus were widely distributed and occurred in the majority of the eleven floristic vegetation groups identified. Antechinus minimus, Antechinus swainsonnii and Pseudomys novaehollandiae had restricted distributions and were recorded in only two or three vegetation groups. New information on the distribution of the rare species P. novaehollandiae, was obtained and two floristically rich vegetation groups that it preferred were identified. Species-rich small mammal communities occurred in vegetation communities with high numbers of sclerophyll plant species and high structural diversity. Maximum food resources were considered to be provided in these communities. Local habitat diversity was also correlated with species-richness. Small mammal abundance was maximum in non-sclerophyllous canmunities, where high plant productivity was considered to be important. For the first time, the presence of the plant pathogen Phytophthora cinnamomi was shown to affect small mammals. It was associated with small mammal communities of low species richness and abundance, Recovery of small mammal populations after wildfire was slow until the fourth year. Mus musculus reached peak abundance from 2-3 years and then declined rapidly. P. novaehollandiae was the only native species that achieved maximum abundance early in the succession. A. stuartii, R. fuscipes and R. lutreolus approached maximum abundance in mid-succession, while Isoodon obesulus was a mid- to late-successional species. A. minimus survived the fire, but did not persist after one year. The pattern of succession was influenced by attributes of species, such as survival after fire, their ability to disperse and reproduce.

Ageing mallee eucalypt vegetation after fire : insights for successional trajectories in semi-arid mallee ecosystems

A critical requirement in the ecological management of fire is knowledge of the age-class distribution of the vegetation. Such knowledge is important because it underpins the distribution of ecological features important to plants and animals including retreat sites, food sources and foraging microhabitats. However, in many regions, knowledge of the age-class distribution of vegetation is severely constrained by the limited data available on fire history. Much fire-history mapping is restricted to post-1972 fires, following satellite imagery becoming widely available. To investigate fire history in the semi-arid Murray Mallee region in southern Australia, we developed regression models for six species of mallee eucalypt (Eucalyptus oleosa F.Muell. ex. Miq. subsp. oleosa, E. leptophylla F.Muell. ex. Miq., E. dumosa J. Oxley, E. costata subsp. murrayana L. A. S. Johnson & K. D. Hill, E. gracilis F.Muell. and E. socialis F.Muell. ex. Miq.) to quantify the relationship between mean stem diameter and stem age (indicated by fire-year) at sites of known time since fire. We then used these models to predict mean stem age, and thus infer fire-year, for sites where the time since fire was not known. Validation of the models with independent data revealed a highly significant correlation between the actual and predicted time since fire (r = 0.71, P < 0.001, n = 88), confirming the utility of this method for ageing stands of mallee eucalypt vegetation. Validation data suggest the models provide a conservative estimate of the age of a site (i.e. they may under-estimate the minimum age of sites >35 years since fire). Nevertheless, this approach enables examination of post-fire chronosequences in semi-arid mallee ecosystems to be extended from 35 years post-fire to over 100 years. The predicted ages identified for mallee stands imply a need for redefining what is meant by ‘old-growth’ mallee, and challenges current perceptions of an over-abundance of ‘long-unburnt’ mallee vegetation. Given the strong influence of fire on semi-arid mallee vegetation, this approach offers the potential for a better understanding of long-term successional dynamics and the status of biota in an ecosystem that encompasses more than 250 000 km² of southern Australia.

When more is less : urban remnants support high bird abundance but diversity varies

Urban remnant vegetation, especially where it occurs in public parks, allows for relatively easy access for ongoing biodiversity monitoring. However, relatively little baseline information on bird species distribution and abundance across a range of identifiable urban remnants appears in the published literature. We surveyed the relative abundance and distribution of birds across urban and suburban remnant vegetation in Melbourne, Australia. One hundred and six species were recorded, of which 98 were indigenous. Red wattlebirds had the highest mean relative abundance with 2.94 birds/ha, followed by rainbow lorikeets (2.51), noisy miners (1.93), brown thornbills (1.75) and spotted doves (0.96). There was no obvious trend between overall relative abundance and the size of the remnant, in contrast to species richness which was positively correlated with remnant size. The data revealed that some species were either totally restricted to, or more abundant in, larger remnants and generally absent from smaller remnants. Some of the more common birds (crimson rosella, superb fairy-wren, spotted pardalote and black-faced cuckoo-shrike) recorded during this study were detected at similar densities to those found in comparable vegetation to the east of Melbourne within a largely forested landscape. Other species occurred at much lower densities (e.g., white-browed scrubwren, brown thornbill, eastern yellow robin and grey fantail) or had habitat requirements or ecological characteristics that could place them at risk of further decline or local extinction in the urban area. We identify a suite of bird species of potential conservation concern within Melbourne’s urban landscape. The establishment of repeatable, fixed-point, and long-term monitoring sites will allow for repeat surveying over time and provide an early warning of population declines, or conversely an indication of population increase for other species.

Nurse plant effects of a dominant shrub (Duma florulenta) on understorey vegetation in a large, semi-arid wetland in relation to flood frequency and drying

 Questions: Do nurse plant interactions significantly influence understorey vegetation diversity in a large, semi-arid, shrub-dominated wetland? How do the modes and net effects of nurse plant interactions vary spatially along a flood frequency gradient, and temporally in response to drying? Location: Narran Lakes Ramsar site, New South Wales, Australia. Methods: Microhabitat characteristics, understorey vegetation and germinable soil seed banks were investigated in shrub and open habitats across a flood frequency gradient in a large, semi-arid wetland dominated by open shrubland under productive conditions following floodwater recession and again following 6 mo of drought. Split-plot ANOVA and multivariate analyses were used to determine the effects of shrubs on microhabitat character, understorey vegetation cover, species diversity, richness and composition and germinable soil seed banks. Results: Microhabitat characteristics, including canopy cover, litter cover and soil character, all differed between shrub and open habitats, especially in the most frequently flooded sites. Under productive conditions following flooding, lignum shrubs suppressed understorey vegetation cover but increased species richness at the site scale across the flood frequency gradient and, in the most frequently flooded sites, supported higher species density at a microhabitat scale. Under dry conditions, lignum shrubs had a positive effect on understorey vegetation cover, species richness and species density across the flood frequency gradient, but particularly in frequently flooded sites. A significant difference in soil seed bank composition between shrub and open habitats was only observed in frequently flooded sites. Conclusions: Nurse plant interactions appear to play an important role in determining understorey vegetation diversity in the lignum shrubland of the Narran Lakes wetland system. The modes and net effects of these nurse plant interactions vary in space and time in relation to flood history and drying. Positive interactions, probably involving microhabitat amelioration, appear to be particularly important to plant diversity and abundance under dry conditions. Under more favourable wetter conditions, lignum shrubs also contribute to understorey vegetation diversity by facilitating the establishment of different species than those dominating open habitats. Our findings have implications for the management of perennial shrubs and hydrological regimes in such wetlands.

Ephemeroptera, Plecoptera and Trichoptera assemblages from riffles in mountain streams of Central Brazil: environmental factors influencing the distribution and abundance of immatures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Composition of the aquatic invertebrate fauna associated to the mangrove vegetation of a coastal river, analyzed through a manipulative experiment.

The present study analyzed the composition of the aquatic fauna associated to the mangrove forest in a southeastern Brazilian river. The composition of the macrofauna in the roots of the marginal vegetation located at three different salinity stretches was analyzed by sampling pieces of the submerged branches of the vegetation (natural substrate) and pieces of sisal rope (artificial substrate), installed close to the natural vegetation and sampled after a period of 14 colonization days. In both types of substrate, twelve taxonomic groups were sampled, representing three phyla (Cnidaria, Annelida and Arthropoda). The crustaceans, corresponding to the most diversified group, were represented by Copepoda, Tanaidacea, Isopoda, Amphipoda and Decapoda. The highest salinity stretch showed the highest abundance, with a progressive decrease from high to low salinity for both substrates. Copepoda and Tanaidacea predominated on both substrates, although the artificial substrate exhibited the highest total abundance and species richness. Considering the relative abundance of the taxonomic groups on both substrates, the majority of groups predominated in the highest salinity range. Significant differences on the longitudinal distribution of abundance were associated to the variation on salinity and with the complexity of the substrate.

Temporal variation in the abundance of two species of thrushes in relation to fruiting phenology in the Atlantic rainforest

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reproductive phenology of coastal plain Atlantic forest vegetation: comparisons from seashore to foothills

The diversity of tropical forest plant phenology has called the attention of researchers for a long time. We continue investigating the factors that drive phenological diversity on a wide scale, but we are unaware of the variation of plant reproductive phenology at a fine spatial scale despite the high spatial variation in species composition and abundance in tropical rainforests. We addressed fine scale variability by investigating the reproductive phenology of three contiguous vegetations across the Atlantic rainforest coastal plain in Southeastern Brazil. We asked whether the vegetations differed in composition and abundance of species, the microenvironmental conditions and the reproductive phenology, and how their phenology is related to regional and local microenvironmental factors. The study was conducted from September 2007 to August 2009 at three contiguous sites: (1) seashore dominated by scrub vegetation, (2) intermediary covered by restinga forest and (3) foothills covered by restinga pre-montane transitional forest. We conducted the microenvironmental, plant and phenological survey within 30 transects of 25 mx4 m (10 per site). We detected significant differences in floristic, microenvironment and reproductive phenology among the three vegetations. The microenvironment determines the spatial diversity observed in the structure and composition of the flora, which in turn determines the distinctive flowering and fruiting peaks of each vegetation (phenological diversity). There was an exchange of species providing flowers and fruits across the vegetation complex. We conclude that plant reproductive patterns as described in most phenological studies (without concern about the microenvironmental variation) may conceal the fine scale temporal phenological diversity of highly diverse tropical vegetation. This phenological diversity should be taken into account when generating sensor-derived phenologies and when trying to understand tropical vegetation responses to environmental changes.