Population genetics of Ryparosa kurrangii (Achariaceae), a rare lowland rainforest tree

Ryparosa kurrangii B.L. Webber (Achariaceae) is a rare lowland rainforest tree found in dense, discrete populations between the Daintree River and Cape Tribulation in Far North Queensland, Australia. It is one of many Australian rainforest trees thought to rely on the Southern Cassowary (Casuarius casuarius johnsonii) for long-distance seed dispersal. A survey of chloroplast non-coding DNA found no genetic variation at any of four non-coding chloroplast loci. Seedlings of three populations separated by a mountain range were then examined for amplified fragment length polymorphisms. High levels of genetic diversity were found within each population. Only two percent of the variation in this study was explained by separation due to the mountain range. This finding of high genetic diversity but minimal distinction between populations accords with general expectations for outcrossing, large-fruited, animal-dispersed trees. Either continuing or historical long-distance gene flow (mediated by cassowaries) could explain these results.     

Bottom-up and top-down regulation of decomposition in a tropical forest

The soil nutrients, microbes, and arthropods of tropical forests are patchy at multiple scales. We asked how these three factors interact to generate patterns of decomposition in 450 100 cm² litterbags arrayed along a 50 m ridge top in a Panama rainforest. We tested top-down (via grazing by microbivores like collembola and diplopods) and bottom-up (via added N and P) effects on the decomposition of cellulose. By using a 1,000-fold gradient in mesh size we generated a two-fold gradient in arthropod grazing. Microbivore grazing first retarded then ultimately enhanced decomposition rates. Micropulses of N and P (simulating concentrated urine) enhanced neither decomposition rates nor microbivores but increased the abundance of predacious ants. Decomposition rates also varied across the ridge, and were lowest in a plot with the deepest litter and highest soil moisture. These data generate the working hypothesis that N and P cascade upward at grains of 100 cm² to enhance a major predator in the litter; predators then absorb any increases in microbivores attracted to the extra fungal growth. These population interactions are in turn embedded in mesoscale variability generated by individual tree canopies that drive changes in litter quality and soil moisture. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Microclimate of daytime den sites in a tropical possum: implications for the conservation of tropical arboreal marsupials

Tree cavities are an important shelter site for a variety of vertebrate species, including birds, reptiles and mammals. Studies indicate that in most taxa favoured tree hollows are those in larger trees and higher from the ground, generally thought to be related to decreased predation risk and a more optimal thermal environment. However, neither of these ideas has been tested definitively. Here, we investigate the microclimate of daytime den sites in tree hollows of common brushtail possums in tropical northern Australia. We compare tree and hollow characteristics of dens known to be used by possums, and those not known to be used, to determine whether possums choose trees with microhabitats with a more favourable daytime microclimate. Possums chose to den in tree hollows which were on average 1.6 °C cooler during the day, and were more buffered from temperature extremes, than other potential den locations. Important factors explaining daytime temperatures between hollows included height of the hollow, entrance width and tree diameter. Tropical arboreal marsupials have been identified as being particularly vulnerable to climate change and there are calls to identify and preserve natural refuges, such as tree hollows, which could buffer them from extreme temperatures. Our results highlight the value of older, larger hollow-bearing trees as refuges from extreme temperature, the importance of which may become critical for some temperature-sensitive species under the combined effects of continuing habitat loss and climate change.     

Testing target‐specific bait delivery for controlling feral pigs in a tropical rainforest

Mitigation of feral pig (Sus scrofa) impacts in Australia’s Wet Tropics World Heritage Area has been impeded by the lack of a target‐specific method for delivering toxic baits in the region. This study evaluated methods to reduce bait‐take by susceptible nontarget species without inhibiting bait‐take by pigs, to enable more effective pig management. We predicted that dingoes would not select an unprocessed corn bait and that other potential nontarget bait consumers would be unable to access the same bait presented under a lightweight cover. Neither of these methods was expected to reduce bait selection or access by pigs. We tested these predictions by monitoring animal interactions with covered and uncovered corn baits, and covered corn and manufactured baits. Use of corn as a bait substrate effectively prevented bait‐take by dingoes. Covering baits substantially reduced bait‐take by other nontarget species and completely prevented nontarget bait‐take when uncovered feed was provided simultaneously. The corn bait preparation was highly acceptable and accessible to feral pigs. We conclude that the methods evaluated here could enable the consideration of poison baiting as a viable method for controlling feral pigs in the World Heritage Area, where it has previously been unavailable.     

Size of sampling unit strongly influences detection of seedling limitation in a wet tropical forest

Seedling limitation could structure communities, but often is evaluated with sampling units that are orders of magnitude smaller than mature plants. We censused seedlings for 5.5 years in five 1 × 200-m transects in a wet Neotropical forest. For 106 common species (≥ 10 seedlings in a transect), we calculated prevalence (occurrence of ≥ 1 newly emerged seedlings per sampling unit) at 1 m² and at 1 m × mature crown diameter units by aggregating adjacent quadrats. For most species, prevalence was 2–25% at 1 m², but 20–92% at mature crown scales. Increased prevalence arose from broadly distributed seedlings within transects, with unoccupied segments generally shorter than crown diameters. At the landscape scale, 69% of 301 species were locally rare (< 10 seedlings) and only 16% were represented in all transects (maximally separated by 2.4 km). Nonetheless, for more common species, much lower estimates of seedling limitation at mature crown scales suggest weaker influence of seedling limitation on community dynamics than previously assumed.     

Impacts of cyclone Larry on the vegetation structure of timber plantations,restoration plantings and rainforest on the Atherton Tableland,Australia

Abstract We examined the impact of severe cyclone ‘Larry’ on the vegetation structure of monoculture and mixed species timber plantations, restoration plantings and reference sites in upland rainforests on the Atherton Tableland, north Queensland, Australia. Sites were initially assessed in 2000 and resurveyed in 2006, 6–8 months after the cyclone traversed the region. In both surveys, timber plantations had a relatively open canopy, grassy understorey and few shrubs or small‐sized trees; whereas restoration plantings had a relatively closed canopy, an understorey of bare ground, leaf litter and rainforest seedlings, a high density of small‐diameter trees and a moderate representation of special life forms characteristic of rainforest. Cyclone damage varied with tree size, site type, proximity to the cyclone and stem density. First, the proportion of trees that were severely damaged by the cyclone (major branches broken, stem snapped or pushed over) increased with the diameter of trees across all site types. Second, damage to larger‐sized trees (>10 cm d.b.h., >20 cm d.b.h.) was proportionally highest in monoculture plantations, intermediate in mixed species plantations and rainforest, and lowest in restoration plantings. Third, within site types, damage levels decreased with distance from the cyclone track and with stem density. There was no evidence that topographical position influenced damage levels, at least for timber plantations. We tentatively attribute the high levels of damage experienced by timber plantations to their relatively open structure and the large size of stems in plantations. Restoration plantings generally escaped severe damage by the cyclone, but their continued development towards rainforest conditions may require a coordinated monitoring and maintenance programme to address the potential threat of weed invasion.     

Beetle species’ responses suggest that microclimate mediates fragmentation effects in tropical Australian rainforest

Abstract Despite the enormous contribution of invertebrates to global biodiversity and ecosystem function, the patterns and causes of insect responses to tropical rainforest destruction and fragmentation remain poorly understood. We studied the responses of beetles to these factors in a fragmented upland rainforest landscape in north‐east Queensland, Australia. Beetles were sampled using flight interception traps from six replicate sites in rainforest interior, rainforest edge, small rainforest remnants and pasture, interspersed across about 600 km². Beetles from 10 family/subfamily groups were sorted to species. There were three major findings. First, converting rainforest into pasture has a very strong negative effect on beetle diversity and species composition. Very few beetle species were present in pasture and none of the most abundant species was more abundant in pasture than rainforest. Second, beetle assemblages appeared to respond to climate. Beetle species composition in drier rainforest habitats was different from that of moister rainforest and there were species unique to each rainforest type. Third, beetle species composition differed between small remnants and interior rainforest: drier‐associated species were more abundant in small remnants, whereas wetter‐associated species were more abundant in interiors. Edges tended to be intermediate. We argue that this pattern can be attributed to a fragmentation effect mediated by differences in microclimate rather than by floristic, structural, or area and isolation effects.     

Humid tropical rain forest has expanded into eucalypt forest and savanna over the last 50 years

Tropical rain forest expansion and savanna woody vegetation thickening appear to be a global trend, but there remains uncertainty about whether there is a common set of global drivers. Using geographic information techniques, we analyzed aerial photography of five areas in the humid tropics of northeastern Queensland, Australia, taken in the 1950s and 2008, to determine if changes in rain forest extent match those reported for the Australian monsoon tropics using similar techniques. Mapping of the 1950s aerial photography showed that of the combined study area (64,430 ha), 63% was classified as eucalypt forests/woodland and 37% as rain forest. Our mapping revealed that although most boundaries remained stable, there was a net increase of 732 ha of the original rain forest area over the study period, and negligible conversion of rain forest to eucalypt forest/woodland. Statistical modeling, controlling for spatial autocorrelation, indicated distance from preexisting rain forest as the strongest determinant of rain forest expansion. Margin extension had a mean rate across the five sites of 0.6 m per decade. Expansion was greater in tall open forest types but also occurred in shorter, more flammable woodland vegetation types. No correlations were detected with other local variables (aspect, elevation, geology, topography, drainage). Using a geographically weighted mean rate of rain forest margin extension across the whole region, we predict that over 25% of tall open forest (a forest type of high conservation significance) would still remain after 2000 years of rain forest expansion. This slow replacement is due to the convoluted nature of the rain forest boundary and the irregular shape of the tall open forest patches. Our analyses point to the increased concentration of atmospheric CO(2) as the most likely global driver of indiscriminate rain forest expansion occurring in northeastern Australia, by increasing tree growth and thereby overriding the effects of fire disturbance.     

Resistance and resilience: quantifying relative extinction risk in a diverse assemblage of Australian tropical rainforest vertebrates

Aim Assessing the relative vulnerability of species within an assemblage to extinction is crucial for conservation planning at the regional scale. Here, we quantify relative vulnerability to extinction, in terms of both resistance and resilience to environmental change, in an assemblage of tropical rainforest vertebrates. Location Wet Tropics Bioregion, north Queensland, Australia. Methods We collated data on 163 vertebrates that occur in the Australian Wet Tropics, including 24 frogs, 33 reptiles, 19 mammals and 87 birds. We used the ‘seven forms of rarity’ model to assess relative vulnerability or resistance to environmental change. We then develop a new analogous eight‐celled model to assess relative resilience, or potential to recover from environmental perturbation, based on reproductive output, potential for dispersal and climatic niche marginality. Results In the rarity model, our assemblage had more species very vulnerable and very resistant than expected by chance. There was a more even distribution of species over the categories in the resilience model. The three traits included in each model were not independent of each other; species that were widespread were also habitat generalists, while species with narrow geographical ranges tended to be locally abundant. In the resilience model, species with low reproductive output had a narrow climatic niche and also a low capacity to disperse. Frogs were the most vulnerable taxonomic group overall. The model categories were compared to current IUCN category of listed species, and the product of the two models was best correlated with IUCN listings. Main conclusions The models presented here offer an objective way to predict the resistance of a species to environmental change, and its capacity to recover from disturbance. The new resilience model has similar advantages to the rarity model, in that it uses simple information and is therefore useful for examining patterns in assemblages with many poorly known species.     

Invertebrate communities in a tropical rain forest canopy in Puerto Rico following Hurricane Hugo

1. Canopy invertebrate responses to Hurricane Hugo, tree species, and recovery time were examined at the Luquillo Experimental Forest in Puerto Rico during 1991–92 and 1994–95. Six tree species representing early and late successional stages were examined in paired plots representing severe hurricane disturbance (most trees toppled) and light hurricane disturbance (all trees standing and most branches intact). 2. Hurricane disturbance affected invertebrate abundances significantly. Sap-suckers and molluscs were more abundant, and defoliators, detritivores, and emergent aquatic insects were less abundant in recovering tree-fall gaps than in intact forest during this 5-year period. These changes in functional organisation are consistent with comparable studies of arthropod responses to canopy removal during harvest in temperate forests. 3. Tree species also affected invertebrate abundances significantly, but invertebrate communities did not differ significantly between the three early successional and three later successional tree species. 4. Most taxa showed significant annual variation in abundances, but only two Homoptera species showed a significant linear decline in abundance through time, perhaps reflecting long-term trends during recovery. 5. Leaf area missing, an indicator of herbivore effect on canopy processes, showed significant seasonal and annual trends, as well as differences among tree species and hurricane treatments. Generally, leaf area missing peaked during the wet season each year, but reached its highest levels during an extended drought in 1994. Leaf area missing also tended to be higher on the more abundant tree species in each disturbance treatment. 6. Herbivore abundances and leaf area missing were not related to concentrations of nitrogen, phosphorous, potassium, or calcium in the foliage. 7. This study demonstrated that invertebrate community structure and herbivory are dynamic processes that reflect the influences of host species and variable environmental conditions.     

Diet and dietary selectivity of Cane Toads (Rhinella marina) in restoration sites: a case study in Far North Queensland,Australia

Cane Toads (Rhinella marina, formerly Bufo marinus) in restoration sites on the Atherton Tableland in NE Australia consumed invertebrates belonging to 11 different taxa with ants being the most abundant prey item. Principal component analyses showed that the composition of invertebrates in Cane Toad diet is largely a reflection of invertebrates found in pitfall and leaf litter samples suggesting that the species is an indiscriminant feeder. However, pitfall samples contained more Collembola and Isopoda than were found in Cane Toad stomachs. The Cane Toad may benefit from restoration management practices by utilizing food resources enhanced by mulching and providing microhabitats (e.g. rock piles, logs) as shelter. While further studies would be needed to test this practitioners working in areas where the Cane Toad is problematic may consider trade‐offs between attracting invertebrates and Cane Toads by monitoring provided microhabitat features.     

Cyclone damage to tropical rain forests: Species‐ and community‐level impacts

Abstract Severe Tropical Cyclone ‘Larry’ caused damage to 10 long‐term 0.5 ha monitoring plots in the rain forests of Queensland's Wet Tropics on 20 March 2006. We assessed the community‐level damage and the impact of the cyclone on the most abundant tree species in each plot. Damage was positively correlated with distance from the cyclone eye, though some plots received less damage than predicted owing to topographic shielding. Damage was patchy within plots, which is reflected in the range of damage‐classes recorded for each species, but there are broad trends in the type of response shown by different species. At the plot level, some species were either more susceptible or less susceptible to damage than the rest of the community. Species tended to show similar patterns of damage between plots with different community damage ratings. We discuss these response types in terms of adaptive tolerance to particular wind speeds and the trade‐off between frequently losing canopy volume in light winds, or rarely suffering substantial damage. We suggest that increased frequency of intense cyclones may affect the distribution of some species in the future, with those species most susceptible to high levels of damage at lower wind speeds becoming restricted to leeward‐facing slopes and upland areas away from the coast, and an increased abundance of resilient species in lowland coastal areas.     

Multi-scale variability in tropical soil nutrients following land-cover change

The effects of land-cover change on soil properties have reached regional proportions in the southwestern Amazon, and can be detected in their patterns at the scale of hundreds of thousands of square kilometers. Spatial analysis of an extensive soil profile database revealed four nested spatial scales at which different patterns in soil properties occur: <3, <10, <68, and >68 km. The shortest scales account for the majority of the spatial variability in the biogeochemically important properties (phosphorus, nitrogen, organic carbon), while the longest scales explain the most for pedologic properties (pH, aluminum, percent clay and sand). The magnitude and sign of correlations among soil properties changed with scale, indicating major shifts in distribution and soil dynamics depending on the scale of observation and analysis. Precipitation, substrate composition, topography, and biological influences vary over large areas, leading to variable distribution of soil properties, and complicating the evaluation of the effect of deforestation on biogeochemical cycling. We modeled the relationships among scale-specific patterns in soil properties and the soil forming state factors to tease out the relative impact of changing land cover. Soil property short-scale variability corresponded with the distribution of land cover and terrain attributes, medium scale variation with geology and state soil map classifications, and long scale with geology and precipitation. The strength of these relationships may be partially attributable to the resolution of the maps used as proxies for the soil forming factors. Land-cover change has already left a discernable imprint on broad-scale soil nutrient patterns, although it is still not the dominant process.     

Response of soil respiration to simulated N deposition in a disturbed and a rehabilitated tropical forest in southern China

Responses of soil respiration (CO₂ emission) to simulated N deposition were studied in a disturbed (reforested forest with previous understory and litter harvesting) and a rehabilitated (reforested forest with no understory and litter harvesting) tropical forest in southern China from October 2005 to September 2006. The objectives of the study were to test the following hypotheses: (1) soil respiration is higher in rehabilitated forest than in disturbed forest; (2) soil respiration in both rehabilitated and disturbed tropical forests is stimulated by N additions; and (3) soil respiration is more sensitive to N addition in disturbed forest than in rehabilitated forest due to relatively low soil nutrient status in the former, resulting from different previous human disturbance. Static chamber and gas chromatography techniques were employed to quantify the soil respiration, following different N treatments (Control, no N addition; Low-N, 5 g N m⁻² year⁻¹; Medium-N, 10 g N m⁻² year⁻¹), which had been applied continuously for 26 months before the respiration measurement. Results showed that soil respiration exhibited a strong seasonal pattern, with the highest rates observed in the hot and wet growing season (April–September) and the lowest rates in winter (December–February) in both rehabilitated and disturbed forests. Soil respiration rates exhibited significant positive exponential relationship with soil temperature and significant positive linear relationship with soil moisture. Soil respiration was also significantly higher in the rehabilitated forest than in the disturbed forest. Annual mean soil respiration rate in the rehabilitated forest was 20% lower in low-N plots (71 ± 4 mg CO₂-C m⁻² h⁻¹) and 10% lower in medium-N plots (80 ± 4 mg CO₂-C m⁻² h⁻¹) than in the control plots (89 ± 5 mg CO₂-C m⁻² h⁻¹), and the differences between the control and low-N or medium-N treatments were statistically significant. In disturbed forest, annual mean soil respiration rate was 5% lower in low-N plots (63 ± 3 mg CO₂-C m⁻² h⁻¹) and 8% lower in medium-N plots (61 ± 3 mg CO₂-C m⁻² h⁻¹) than in the control plots (66 ± 4 mg CO₂-C m⁻² h⁻¹), but the differences among treatments were not significant. The depressed effects of experimental N deposition occurred mostly in the hot and wet growing season. Our results suggest that response of soil respiration to elevated N deposition in the reforested tropical forests may vary depending on the status of human disturbance. Responsible Editor: Hans Lambers.     

Resilience of arboreal folivores to habitat damage by a severe tropical cyclone

Abstract Severe tropical cyclones greatly modify habitat of arboreal folivores by destroying forest canopy, reducing structure and complexity and defoliating remaining trees. We hypothesized that forest modification following severe Cyclone Larry would stress arboreal folivores of the Family Pseudocheiridae and be reflected in increased home ranges and a decrease in body condition. We conducted 19 pre‐cyclone and 24 post‐cyclone spotlighting surveys at a site with severe cyclone damage, and 18 post‐cyclone surveys at a site with minor damage. We detected a greater number of lemuroid, Hemibelideus lemuroides and green, Pseudochirops archeri, ringtail possums as these possums remained in the severely damaged canopy and forest edge. In contrast, Herbert River ringtail possums, Pseudochirulus herbertensis, were detected in smaller numbers. We radio‐tracked eight P. herbertensis before the cyclone, following two of these and nine new animals after the category 4 cyclone. No significant post‐cyclone alteration in home range area or span was recorded in data pooled across the two sites or in limited post‐cyclone data at the severely disturbed site, but a greater variability in home range was observed after cyclone (pooled across sites: 1.72 ± 0.77 ha; 197 ± 47 m) than before the cyclone (1.35 ± 0.30 ha; 196 ± 23 m). In contrast, pooled pre‐ and post‐cyclone home range areas and spans were larger at the severely‐disturbed site (2.08 ± 0.56 ha; 231 ± 32 m) than at the site with minor damage (0.68 ± 0.11 ha; 114 ± 25 m), suggesting resources were more widely spread at the former site. Post‐cyclone home ranges were also larger at the severely damaged site (severe: 3.33 ± 1.36 ha, n = 3; minor: 0.52 ± 0.07 ha, n = 4). Condition of P. herbertensis (mass/tail length) did not differ significantly pre‐ and post‐cyclone or between less and severely disturbed sites. These results and observations of breeding after cyclone suggest that possum populations may be resilient to severe cyclone damage under the relatively wet conditions experienced post‐Cyclone Larry.     

Mechanisms of rainforest persistence and recruitment in frequently burnt wet tropical eucalypt forests

The role of fire in governing rainforest–eucalypt forest ecotone dynamics is of theoretical interest and has conservation management implications. Several eucalypt forests in the Wet Tropics of Australia have an endangered status due to extensive conversion to rainforest. Rainforest plants are known to survive occasional low intensity fires in the eucalypt forest ecotone. However, the ability of rainforest plants to survive frequent fires remains untested. The timing of rainforest expansion is also a subject of interest, and is generally considered to be delayed until fire has been absent for several years. We used 14 years of data collected across 13 plots in the Wet Tropics of north‐eastern Australia to test predictions regarding rainforest seedling recruitment and post‐fire regenerative capacity. The 13 plots received different numbers of fires, between zero and five, over the 14‐year study. The recruitment of new rainforest plants in the ecotone was most abundant in the initial year after fire. If this post‐fire pulse of recruitment is left undisturbed, it can facilitate the subsequent germination of additional rainforest species. The removal of grass cover, whether temporarily in the immediate post‐fire environment or once a developing rainforest mid strata shades out grasses, appears crucial to abundant rainforest recruitment. A variety of tropical rainforest species can persist under a frequent fire regime through resprouting. The difference in the mode of resprouting, between ground‐level coppicing rainforest plants and canopy resprouting eucalypt forest trees, is the critical mechanism that causes regular fire to maintain an open structure in eucalypt forests. The inability of rainforest species to maintain their height when fires fully scorch their crowns, temporarily resets the forest's open structure and delays the rainforest's ability to dominate through shading out grasses to transform the ecosystem into a closed forest.     

Australian Assassins, Part III: A review of the Assassin Spiders (Araneae, Archaeidae) of tropical north-eastern Queensland

The assassin spiders of the family Archaeidae from tropical north-eastern Queensland are revised, with eight new species described from rainforest habitats of the Wet Tropics bioregion and Mackay-Whitsundays Hinterland: Austrarchaea griswoldi sp. n., Austrarchaea hoskini sp. n., Austrarchaea karenae sp. n., Austrarchaea tealei sp. n., Austrarchaea thompsoni sp. n., Austrarchaea wallacei sp. n., Austrarchaea westi sp. n. and Austrarchaea woodae sp. n. Specimens of the only previously described species, Austrarchaea daviesae Forster & Platnick, 1984, are redescribed from the southern Atherton Tableland. The rainforests of tropical eastern Queensland are found to be a potential hotspot of archaeid diversity and endemism, with the region likely to be home to numerous additional short-range endemic taxa. A key to species complements the taxonomy, with maps, natural history information and conservation assessments provided for all species.     

Tree diversity and population structure in undisturbed and human-impacted stands of tropical wet evergreen forest in Arunachal Pradesh, Eastern Himalayas, India

Tree species richness, tree density, basal area, population structure and distribution pattern were investigated in undisturbed, mildly disturbed, moderately disturbed and highly disturbed stands of tropical wet evergreen forests of Arunachal Pradesh. The forest stands were selected based on the disturbance index (the basal area of the cut trees measured at ground level expressed as a fraction of the total basal area of all trees including felled ones): (i) undisturbed stand (0% disturbance index), (ii) mildly disturbed (20% disturbance index), (iii) moderately disturbed (40% disturbance index), and (iv) highly disturbed stand (70% disturbance index). Tree species richness varied along the disturbance gradient in different stands. The mildly disturbed stand showed the highest species richness (54 of 51 genera). Species richness was lowest (16 of 16 genera) in the highly disturbed stand. In the undisturbed stand, 47 species of 42 genera were recorded while in the moderately disturbed stand 42 species of 36 genera were found. The Shannon–Wiener diversity index for tree species ranged from 0.7 to 2.02 in all the stands. The highest tree diversity was recorded in the undisturbed stand and the lowest in the highly disturbed stand. The stands differed with respect to the tree species composition at the family and generic level. Fagaceae, Dipterocarpaceae and Clusiaceae dominated over other families and contributed 53% in the undisturbed, 51% in the mildly disturbed, 42% in the moderately disturbed and 49% in the highly disturbed forest stands to the total density of the respective stand. Stand density was highest (5452 stems ha^–1) in the undisturbed stand, followed by the mildly disturbed stand (5014), intermediate (3656) in the moderately disturbed stand and lowest (338) in the highly disturbed stand. Dominance, calculated as the importance value index of different species, varied greatly across the stands. The highest stand density and species richness were represented in the medium girth class (51–110 cm) in all the stands. In the undisturbed stand, the highest density was found in the 111–140 cm girth class, while in the mildly disturbed stand the 51–80 cm girth range recorded the highest density. About 55, 68 and 52% species were found to be regenerating in the undisturbed, mildly disturbed and moderately disturbed stands, respectively. No regeneration was recorded in the highly disturbed stand. Variation in species richness, distribution pattern and regeneration potential is related to human interference and the need for forest conservation is emphasized.     

Any which way will do – the pollination biology of a northern Australian rainforest canopy tree (Syzygium sayeri; Myrtaceae)

The pollination biology of Syzygium sayeri was documented using the special capabilities of the Australian Canopy Crane. Syzygium sayeri is a xenogamous species with poor self-compatibility, moderate levels of natural out-crossing, and the producer of copious amounts nectar throughout the day and night. Of a diverse fauna associated with, and visiting the flowers of S. sayeri , larger vertebrates (blossom bats and honeyeaters) account for approximately half its natural pollination rate, while the balance of pollination is attributable to a host of invertebrate visitors (wasps, flies, thrips, butterflies). Day and night pollinators contributed approximately equally to the successful pollination of S. sayeri ; although the number of individuals visiting flowers was greater during the day, further experimentation might reveal night visitors to be more effective pollinators. The co-occurrence of vertebrates and invertebrates, as well as day and night visitors, suggests that S. sayeri has a generalist pollination system, whereby the absence of a discrete set of faunae could be compensated for by the presence of other pollinators. What is not clear is the contribution of different pollinators to the population success (i.e. gene flow) of this species. Further study is needed to determine the contribution of each pollinator group to the flow of genetic material in populations of S. sayeri . © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 149 , 69–84.