Comparison of seed removal by ants in vegetation on fertile and infertile soils

Plants which have seeds adapted for dispersal by ants (myrmecochores) are more common in some vegetation types than others. In Australia, myrmecochores are common in sclerophyll shrublands which are associated with infertile soils but not in forests on fertile soils. One hypothesis to explain this difference is that ants are less abundant or less active in seed removal on fertile soils. A test of this hypothesis was carried out on four sites in the Royal National Park, south of Sydney, by measuring the number of myrmecochorous seeds removed by ants in a 24 h period. It was found that the removal rates of seeds were slightly higher on fertile sites although this difference was not significant. The hypothesis that a lower removal rate on fertile soils could account for the lower percentage myrmecochory was therefore rejected. Apart from the gross removal rate of seeds by ants, other differences in ant behaviour might be important. It is possible that a greater proportion of ant species unfertile soils are seed predators or ineffective seed dispersers, and evidence obtained indicates that this is worthy of further research.     

Suburban development and change in vegetation nutritional status

In a study of species presence/absence and soil properties in bushland around northern Sydney, Clements (1983) found that species groupings were related to total soil phosphorus. This report presents analysis of foliage nutrient concentrations in species within these groupings. The highest concentrations of phosphorus, calcium, magnesium and potassium occurred in the suburban/disturbed group. The lowest overall concentrations were found in foliage from species in the dry sclerophyll communities. Mean foliage phosphorus was 0.099%, 0.125% and 0.042% for wet sclerophyll, disturbed and dry sclerophyll groups, respectively. Exotic species, particularly in disturbed environments, had the highest foliage nutrient concentrations. Results presented here showed that foliage nutrient concentrations are consistent with definitions of these groups on the basis of total soil phosphorus. These changes are considered to be important for management and conservation of bushland areas around Sydney.     

Effects of Clearfell Harvesting on Lucanid Beetles (Coleoptera: Lucanidae) in Wet and Dry Sclerophyll Forests in Tasmania

The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota.     

Structural variables drive the distribution of the sensitive lichen Lobaria pulmonaria in Mediterranean old-growth forests

We tested the hypothesis that structural variables related to old-growth features affect the distribution of Lobaria pulmonaria in a Mediterranean National Park of Italy. A total of 36 plots, with old-growth characteristics and representing overall three forest types (beech- oak- and mixed- forests) were studied. The lichen was absent in about half of the sites, suggesting that the selection of old-growth forests based solely on structural features is not sufficient to predict the presence of this species, which therefore proves to be rather sensitive and selective. Its abundance was related to high tree circumference and basal area, and to availability of deadwood, confirming the relevant effect of substrate and stand continuity in the conservation of this species and emphasizing its role of indicator species of undisturbed forest ecosystems with long ecological continuity.     

Rare plant species occurrence patterns are associated not with soil properties,but with frequent fire in a southeast Australian dry sclerophyll forest

Question

Soil properties can play a crucial role in influencing the abundance and distribution of plant species. Fire regimes can also have substantial impacts on plant community composition. However, few studies have examined the effects of both fire regimes and soil properties on the occurrence of rare plant species. Here, we asked if rare species have specific soil and fire regime associations relative to common species, and if soil properties may explain potential fire effects.

Location

Booderee National Park, southeastern Australia.

Methods

We collected soil cores and completed vegetation surveys on 42 sites in Sydney Coastal Dry Sclerophyll Forest vegetation. We tested for associations between the number of rare species and common species present in relation to three soil chemical properties (available phosphorus, ammonium and organic carbon), fire frequency, and time since fire.

Results

We found that rare and common species were not associated with any of the examined soil properties. However, rare species were associated with sites with a high fire frequency, while common species were negatively associated with time since fire.

Conclusions

Our results indicate that rare species’ occurrence patterns may be influenced by the direct effects of fire or mediated by multiple factors, rather than shaped solely by soil properties in our study area. Future work to understand the factors that underpin rare species’ occurrence patterns in response to fire is critical to develop fire management protocols that effectively conserve rare species in dry sclerophyll forests.     

Critical foliage concentrations of nitrogen and phosphorus as a guide to the nutrient status of araucaria underplanted to pinus

Summary The growth ofAraucaria cunninghamii Ait. planted in lateritic podzolic soils on dry sclerophyll forest sites in southern Queensland is known to be limited primarily by lack of nitrogen; phosphorus is a secondary deficiency. However, Araucaria can be grown without fertilizers on these sites by underplanting to Pinus.A factorial fertilizer trial was used to establish critical levels of foliage nitrogen and phosphorus in Araucaria. The critical level of nitrogen depends     

Diversity,composition, and structure of tropical dry forests in Central America

Tropical dry forests have been reduced to less than 0.1% of their original expanse on the Pacific side of Central America and are considered by some to be the most endangered ecosystem in the lowland tropics. Plots 1000 m² were established in seven tropical dry forests in Costa Rica and Nicaragua in order to compare levels of species richness to other Neotropical dry forest sites and to identify environmental variables associated with species richness and abundance. A total of 204 species and 1484 individuals 2.5 cm were encountered. Santa Rosa National Park was the richest site with the highest family (33), genera (69), and species (75) diversity of all sites. Species richness and forest structure were significantly different between sites. Fabaceae was the dominant tree and shrub family at most sites, but no species was repeatably dominant based on number of stems in all fragments of tropical dry forest. Central American dry forests had similar species richness when compared to other Neotropical forests. There was no correlation between forest cover within reserves, or precipitation and plant species richness. There was a significant correlation between anthropogenic disturbance (intensity and frequency of fire, wood collection, grazing) and total species richness, tree and shrub species richness, and liana abundance. These results suggest controlling levels on anthropogenic disturbance within reserves should be a high priority for resource managers in Central America. Further research in forest fragments which examine individual and a combination of disturbance agents would help clarify the importance of anthropogenic disturbance on species richness and abundance.     

The conservation significance of the proposed Mbaéré-Bodingué national park,Central African Republic,with special emphasis on its primate community

The proposed Mbaéré-Bodingué National Park (872km²) is located in the southwestern part of the Central African Republic and consists of terra firma rain forests and seasonally flooded forests. We assessed the conservation significance of this site using data on wildlife and habitat conditions collected during a comprehensive primate survey. Scores were attributed to a system of variables and sub-variables to assess the conservation value of the proposed park at the national level. We identified a total of 10 diurnal primate species (eight monkeys, two apes) and flooded forests were considered as a key habitat for primates as they hold a greater number of species than terra firma forests. We recorded the presence of 12 mammal species listed under the 2000 IUCN Red List of Threatened Species, including four classified as Endangered (two Primates, one Proboscidae and one Insectivora). We found that the conservation value of the proposed park ranked second out of the 15 existing protected areas of the country. Primate abundance was found to be generally higher than in the nearby Dzanga-Ndoki National Park (the sole other park located in the same vegetation unit), in particular for the species occurring in flooded forests. This highlights the fact that the proposed Mbaéré-Bodingué National Park is an important area for the conservation of species associated with flooded forests, a habitat which is currently under-represented in the national protected area system. Poaching pressure was identified as the main current threat to the integrity of the proposed park.     

Comparing aye-aye (Daubentonia madagascariensis) presence and distribution between degraded and non-degraded forest within Ranomafana National Park, Madagascar

The aye-aye is considered the most widely distributed lemur in Madagascar; however, the effect of forest quality on aye-aye abundance is unknown. We compared aye-aye presence across degraded and non-degraded forest at Ranomafana National Park, Madagascar. We used secondary signs (feeding sites, high activity sites) as indirect cues of aye-aye presence and Canarium trees as an indicator of resource availability. All 3 measured variables indicated higher aye-aye abundance within non-degraded forest; however, the differences across forest type were not significant. Both degraded and non-degraded forests showed a positive correlation between feeding sites and high activity sites. We found that Canarium, an important aye-aye food source, was rare and had limited dispersal, particularly across degraded forest. This preliminary study provides baseline data for aye-aye activity and resource utilization across degraded and non-degraded forests.     

Phosphorus Fertilization Increases the Abundance and Nitrogenase Activity of the Cyanolichen Pseudocyphellaria crocata in Hawaiian Montane Forests

Nitrogen-fixing epiphytes (especially lichens with a cyanobacterial symbiont—cyanolichens) have the potential to contribute significant amounts of nitrogen (N) to montane tropical forests, which are typically low in N—but the factors controlling the abundance and distribution of epiphytic cyanolichens are poorly understood. In long-term fertilization experiments in montane forests on a 4.l million-yr-old Oxisol on the island of Kauà'i and on a 152-yr-old lava flow on the island of Hawai'i, the epiphytic cyanolichen Pseudocyphellaria crocata increased significantly in abundance in canopies of host trees fertilized with phosphorus (P). There was no response to fertilization with N or other essential elements. Nitrogen-fixation rates were also elevated in lichens in P-fertilized plots at both sites. Phosphorus supply to host trees may be an important factor controlling N inputs to montane tropical forests by N-fixing epiphytes.     

Settlements as a source for the spread of non-native plants into Central European suburban forests

Urbanization is considered as a major driver for biotic homogenization. Urbanization also promotes the dispersal of non-native species. This study examined the roles of suburban settlements and of the surrounding landscape composition for the spread of non-native plant species into adjacent mixed deciduous forests in Southern and Northwestern Switzerland. The number and abundance of native and non-native vascular plant species in both the ground vegetation and shrub layer were recorded in 15 forest sites situated adjacent to settlements and 15 control sites far from settlements. Various site and landscape characteristics were assessed in the surroundings (100 m radius) of the study sites. In both regions we found a higher number and larger abundance of non-native plant species in forest sites adjacent to settlements than in control forest sites. Furthermore, non-native plants were more frequently recorded close to roads and in sites surrounded by a large percentage cover of garden. All these effects were more pronounced in Southern Switzerland, a region with milder winter climate, than in Northwestern Switzerland. Our study showed that settlements are a source for the spread of non-native plant species into Central European suburban forests, and that the composition of the surrounding landscape matrix (e.g. traffic infrastructure, percentage cover of gardens) also affects the establishment of non-native plants.     

Impacts of land use on riparian forest along an urban – rural gradient in southern Manitoba

Extensive landscape modification by humans has led to the fragmentation of riparian forests across North America. We compared the vegetation of extant riparian forest along an urban-rural disturbance gradient. In 1999, twenty-five sites along Assiniboine River in Manitoba, Canada were categorized according to land use: urban, suburban, high intensity rural, low intensity rural, and relatively high quality reference forest. Differences in herbaceous, shrub, and tree species composition and diversity were related to the proportion of surrounding land use, forest patch size, connectivity, and area:perimeter ratio. Urban riparian forests were more disturbed and isolated. They were smaller and characterized by drier, more alkaline soils. Moreover, they had significantly lower native and overall understorey species diversity, and had a higher proportion of exotics including Solanum dulcamara and Hesperis matronalis. Suburban forests were less disturbed, faced greater development pressure, and had sandier soils. Although suburban understorey diversity was similar to that of rural forests, suburban sites had a higher proportion of exotic species, especially escaped horticultural and invasive species including Caragana arborescens and Rhamnus cathartica. Reference sites were relatively large and exhibited greater connectivity, but there was little difference in species composition and diversity among high intensity rural, low intensity rural, and reference sites. These site types were less disturbed than either urban or suburban forests, and reference sites were characterized by hydrophilic species including Scirpus fluviatilis and Carex aquatilis. Our results suggest that landscape measures of disturbance, and related changes in environment, may be confidently used to assess impacts of land use on vegetation along urban-rural gradients. This revised version was published online in June 2006 with corrections to the Cover Date.     

Allosyncarpia-dominated rain forest in monsoonal northern Australia

Following recent classifications of rain forest vegetation in northern Australia this paper examines the biogeo-graphical status and condition of a rain forest type endemic to that region, dominated by the sclerophyll Allosyncarpia ternata (Myrtaceae). These forests are restricted to the Arnhem Land region of the Northern Territory, which includes Kakadu National Park. They cover an area of 1138 km², or 41 % of all rain forest in northern and northwestern Australia. DCA of floristic data from 140 sites illustrates that Allosyncarpia forests occupy a range of sandstone-derived substrates, from moist valley sediments to steep, freely draining, rocky sites. DCA of floristic transect data illustrates that Allosyncarpia is by far the dominant canopy species over this topographic-moisture sequence, but especially on seasonally dry substrates where it provides over 80 % basal area and effectively the entire canopy. DCA of floristic quadrat data from a floristi-cally singular site illustrates major death of the fire-sensitive gymnosperm Callitris intratropica, and, to a lesser extent, Allosyncarpia itself, on the forest-savanna boundary. Biogeographical implications arising from the Gondwanic distributions of Allosyncarpia and its close relatives, Arillas-trum (New Caledonia), Eucalyptopsis (eastern Malesia), and an as yet undescribed taxon (eastern Australia), suggest that taxa ancestral to this group were extensive in the late Cretaceous. Their current restriction is in marked contrast to the success of their near relatives, the eucalypts. Given the tolerance of Allosyncarpia to a wide range of substrate moisture conditions in the present day, it is argued that fire regulates patch margins of this forest type. Although tolerant of light fires, canopy trees at patch margins are susceptible under a regime of frequent, intense late dry-season fires, such as are prevalent in Arnhem Land today. For effective conservation of fire-sensitive communities in this floristically significant region, greater attention must be given to management and monitoring of the fire regime.     

Ecology and phenology of the Dysderidae (Araneae) in the Djurdjura National Park (Algeria)

The ecology and phenology of the Dysderidae (Araneae) were investigated in two different sites (Tala-Guilef and Tikjda), located at opposite slopes of the Djurdjura National Park in Algeria. The following questions were investigated: Are there any endemic species in the studied area? Do the slopes' orientation influence the abundance, richness and diversity of these spider communities? Are the activity and the vital cycle of the three most abundant species different in the two different plant physiognomies (cedar forests and alpine grasslands)? The Dysderidae were collected monthly for 2 years using pitfall traps. In total, 1532 specimens were collected: 333 males, 389 females and 381 juveniles in Tala-Guilef and 230 males, 66 females and 133 juveniles in Tikjda. Among the total of 10 species sampled, three species belonging to three genera in Tala-Guilef, 10 species belonging to four genera in Tikdja and four endemic species was recorded. The slope orientation influence the abundance and the species richness. The activity and the vital cycle of the three most abundant species were not different in the cedar forests and alpine grasslands. For these species, no relationship was found between the activity cycle and the vegetation physiognomy.     

Patterns of ecological,chorological and taxonomic diversity at both sides of the Strait of Gibraltar

Abstract. Diversity relations in Mediterranean heathlands and the understorey of oak woodlands on sandstone-derived substrates were studied at both sides of the Strait of Gibraltar. Trends in species composition and cover were analysed by Detrended Correspondence Analysis; the first axis, assumed to reflect a main environmental gradient, was used to analyse the patterns of three aspects of community diversity. Species richness, i.e. number of species along a 100-m transect, shows a humpbacked trend along the gradient, with the highest values in the understorey of evergreen Quercus suber woodlands, associated with soils of intermediate fertility and moisture status. The number of endemic species is highest in open heathlands, associated with more extreme conditions of acid, infertile soils on exposed ridges. The taxonomic singularity, as measured by the inverse of the average number of species per genus at each site, is highest at the most fertile and moist sites occupied by semideciduous Q. canariensis woodlands. A comparison between northern (Spanish) and southern (Moroccan) sides of the Strait of Gibraltar shows a general concordance of the trends of woody plant communities along the main environmental gradient. However, significant differences of the southern samples are: (1) lack of some differential, habitat-specific species and greater abundance of widespread generalists; and (2) a general reduction in species diversity, number of endemics and taxonomic singularity. We interpret these differences as affected partly by the smaller extent and fragmentation of sandstone areas in the south, and partly by the higher impact of slashing and grazing there.     

Habitat factors affecting site occupancy and relative abundance of four-horned antelope

The four-horned antelope is endemic to the Indian sub-continent. It was formerly distributed widely in deciduous forests throughout its range, but the current distributional patterns of this low-density species are largely unknown and conservation efforts are hampered by the lack of information on species–habitat relationships. We investigated the habitat factors influencing four-horned antelope occurrence and abundance in Bandipur National Park, an important four-horned antelope conservation site in India. Detection/non-detection data, collected under a systematic sampling framework, were used to test a priori hypotheses incorporating covariates believed to influence occurrence and abundance. The best fitting models for four-horned antelope occurrence and relative abundance reveal that the tree-savanna deciduous habitat sub-type, characterized by relatively open habitats with a lower tree density and a high degree of deciduousness, is most preferred by the species. Four-horned antelope conservation efforts in Bandipur National Park and other reserves should be focused on areas typified by tree-savanna habitats. Four-horned antelope occurrence was negatively related to the alien weed Lantana camara . The prolific spread of this weed in Indian deciduous forests is a likely threat.     

The structure of termite communities in the Australian tropics

The distributions of 50 species of termites across five habitat types in Kakadu National Park are described. Open forests are richest in species and monsoon forests are species-poor. The greatest diversity of termites is associated with infertile soils and is probably related to the enhanced role of termites in these nutrientimpoverished sites. Only the richness of livewood feeders is associated with disturbance in the form of water buffalo impact. Few relationships with physical characteristics of the soil were apparent. Comparisons between continents suggest that lower termites are richer in Australia than on other continents. There are fewer species of soil-feeding termites, but only two of the four subfamilies of the higher termites (Termitidae) are present in Australia. There appears to be a complementary distribution of areas of high diversity of termites and native herbivorous mammals. This may be due to the ability of termites and other invertebrate groups to exploit low fertility systems and has profound implications for the size structure of the vertebrate community.     

Biological Invasions in the Amazonian Tropical Rain Forest: The Case of Drosophilidae (Insecta,Diptera) in Ecuador,South America

There have been few reports of invasions in continental rain forests, especially for exotic animals. This study provides original data concerning the potential of exotic drosophilid species to colonize the Amazonian tropical rain forest. To investigate if the structure of drosophilid assemblages differed in response to anthropogenic disturbance, we performed a taxonomic survey at six sites within the Yasuni National Park in Ecuadorian Amazonia along a disturbance gradient from pristine to clearcut artificial forest. A total of 7425 individuals from 34 species were collected of which seven species were exotic. There was significant variation in the assemblage composition along this disturbance gradient; 31 percent of which was explained by the presence of exotic species, particularly at the most disturbed sites, through nonmetric multidimensional scaling and SIMPER analyses. These results confirm the susceptibility of continental rain forests to invasion by exotic species. There is an urgent need to develop and implement monitoring systems, for example, based on drosophilid assemblage surveys, to detect exotic invasions in continental tropical forests.     

Priority sites for conservation of land snails in Gabon: testing the umbrella species concept

In order to assess the potential for molluscan conservation of a protected area considered representative of regional megafauna, we sampled molluscs inside and outside Lopé National Park in Gabon. In the northern part of Lopé National Park, 116 stations were surveyed and 71 species collected. Outside the park, 37 stations yielded 96 species, including 71 in Lastoursville, a small limestone area where molluscs are significantly more abundant than in other collecting sites. Lastoursville is among the richest sites known for molluscs in Africa. Overlap between sampling areas was limited, with 20.0% of the species found only in Lopé National Park, and 40.8% of the species found only outside. This suggests that Lopé National Park does not protect the whole molluscan diversity of central Gabon. Given the high levels of allopatric diversity of tropical land snails, conservation strategies cannot be the same for snails and for wide-ranging vertebrates. Protecting small areas with a high abundance and diversity of molluscs would be less expensive and as efficient for molluscan conservation as protecting large tracts of rainforest. Despite limited general knowledge of central African molluscs, robust estimates of site-specific diversity can be produced. Limestone areas harbour a remarkable biodiversity: sites such as Lastoursville would be ideal candidates for small protected areas dedicated to the conservation of land snails, and would complement the role of large protected areas.     

不同生态保护地植物特征和土壤性质的对比研究——以黑河中游湿地为例

选择黑河中游张掖国家湿地公园和张掖黑河湿地国家级自然保护区为研究对象,对比分析了植物组成、物种多样性、植物生长状态、土壤养分、土壤理化性质及植物土壤间关系。结果显示:湿地公园的植物高度和土壤养分含量(有机碳、全氮、速效氮、全磷、速效钾)显著高于自然保护区,土壤理化性质含量(容重、pH)显著低于自然保护区,表明湿地公园有利于植物生长发育、土壤养分固存、改善土壤质地;自然保护区的植物科属种、多度、物种多样性(多样性指数、丰富度指数、均匀度指数)显著高于湿地公园,表明自然保护区有利于维持植物多样性;两种保护地中影响植物多样性的土壤因子不同,湿地公园物种多样性与土壤全磷和速效磷显著正相关,而自然保护区物种多样性与土壤盐分显著负相关。