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Society for Conservation Biology: 2002 Annual Meeting

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Society for Conservation Biology: 2002 Annual Meeting


Society for Conservation Biology 16th Annual Meeting July 14-July 19 2002
co-hosted by DICE and the British Ecological Society


Abstracts for Community Ecology
Session Two

Wednesday 17th July, 15.30 - 17.30, Grimond Lecture Theatre 2

Chair: David King




(BLOCK CAPITALS indicate the presenting author)


15.30 - 15.45
VÁZQUEZ, DIEGO P. Department of Ecology and Evolutionary Biology, University of Tennessee, 569 Dabney Hall, Knoxville, TN 37996-1610, USA, <vazquez@utk.edu>.

INDIRECT EFFECTS OF INTRODUCED UNGULATES ON POLLINATION AND PLANT REPRODUCTION

Herbivores can affect plants not only directly through browsing and trampling, but also indirectly through other species. For example, herbivores could affect the interaction between plants and their pollinators. Because plant population density is known to affect plant-pollinator interactions and thus plant reproductive success, herbivores could affect plant reproduction indirectly by decreasing their population density. I conducted field studies in the temperate forest of the southern Andes, where introduced ungulates are a major source of anthropogenic alteration. I used a combination of large-scale comparisons between grazed and ungrazed sites, detailed spatial studies at smaller scales, and experimental manipulations. For one understory species, the herb, Alstroemeria aurea (Alstroemeriaceae), I show that trampling by ungulates drastically reduces its population density, which results in lower deposition of conspecific pollen and higher deposition of heterospecific pollen in flower stigmas. This reduced pollination quality in turn results in lower reproductive performance. Thus, by directly reducing the population density of A. aurea, introduced ungulates are indirectly affecting its reproduction. To my knowledge, this is the first time that this kind of indirect effect is demonstrated.

15.45 - 16.00
KING, DAVID and Richard M. DeGraaf. USDA Forest Service Northeastern Research Station, University of Massachusetts Amherst, Amherst, MA 01003, USA, <dking@fs.fed.us>.

FACTORS ASSOCIATED WITH THE LOCAL EXTIRPATION OF A DISTURBANCE-DEPENDANT BIRD

Birds requiring periodic disturbance to maintain suitable habitat include some of the most threatened vertebrate taxa in North America. Although previous studies demonstrate that some bird species are restricted to particular seral stages, few studies include analyses of potential mechanisms for these patterns. To investigate the factors restricting these species to early seres, we studied a disturbance-dependant bird, the Chestnut-sided Warbler, Dendroica pensylvanica, in regenerating clearcuts from 1994 to 2002. Both study populations declined over this period, and were virtually extirpated by 2002, although there was no change in arthropod abundance or nesting or fledging success during the study. Chestnut-sided Warblers consistently selected shrubs ca. 1.5 m tall as nest substrates, and the average height of nests did not change; however, the availability of suitable nest-sites (stems 1.5 m tall) decreased and the average height of the vegetation increased over time. Because neither reproductive success nor food abundance changed during the study, we conclude that the observed decline in nest site availability is the most likely cause of extirpation at these sites. The identification of mechanisms restricting organisms to early seres can aid conservation efforts by ensuring that management activities produce the specific conditions otherwise limiting populations of these species.



16.00 - 16.15
MISURELLI, DARCY and Felicia Keesing. Department. of Biology, State University of New York at Albany, NY 12222, USA, <ratgirl@mpala.org> (DM), Dept. of Biology, Bard College, P.O. Box 1266, Annadale-on-Hudson, NY 12504, USA (FK).

LARGE UNGULATE IMPACTS ON BIRD DIVERSITY AND ABUNDANCE IN AN EAST AFRICAN SAVANNA

Effects of experimental manipulation of domestic and wild ungulate densities on bird diversity and abundance in an East African savannah were measured using replicated four hectare treatments from which different combinations of ungulates were excluded. Birds were sampled using a point-count method over a period of one year. There was no significant difference in bird abundance between treatments however; there was a significant difference in bird diversity between treatments. On average, treatments that allowed megaherbivores (elephants and giraffe) had the lowest bird diversity. The treatment which excluded all ungulates had the highest bird diversity. Insects were sampled on all treatments using three methods; aerial sticky traps, pitfall traps, and sweep-netting. One tree species, Acacia mellifera, had significantly more aerial insects than the dominant tree species, Acacia drepanolobium. Plots with more A. mellifera trees had higher levels of bird diversity. The abundance of ground dwelling insects was significantly correlated with bird diversity, but explained only a small percentage of the variation. A savannah ecosystem with minimal impacts by ungulates favours bird diversity. The more ungulate groups (megaherbivores, large ungulates such as zebra and gazelles, and cattle) that are added to the system, the greater the decrease in bird diversity.



16.15 - 16.30
BILA-ISIA, INOGWABINI, Zoological Society of Milwaukee, Field Conservation Director, DRC Program

NEST BUILDING IN GORILLA GORILLA GRAUERI AND PAN TROGLODYTES SCHWEINFURTHI IN KAHUZI-BIEGA NATIONAL PARK AND ADJACENT FORESTS, EASTERN DEMOCRATIC REPUBLIC OF CONGO.

Nests of Gorilla gorilla graueri and Pan troglodytes schweinfurthi were studied in the Kahuzi-Biega National Park and Kasese. Objectives were to document materials used for nesting, plant species, nest heights, site geographical spread, site characteristics, and effects of predation on nest distributions. Gorillas built more woody nests and used 221 plant species. They preferred sites with steep slopes and open canopy in areas neighboring villages and sites on ridge with continuous canopy in the forest core. Nest heights and nesting tree DBHs decreased with increasing distance from major villages. Chimpanzees used 117 plant species. They preferred sites with ridge tops and soft slopes with lightly covered canopy in strata adjacent to villages. Chimpanzee nest heights and nesting tree DBHs also decreased with increased distance from villages. Neither vertical nor horizontal distribution appeared significantly affected by predators other than humans. It is thus suggested that patterns of nest sites are induced by human predation.



16.30 - 16.45
BARLOW, JOS and Carlos Peres. Centre for Ecology, Evolution and Conservation, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK <J.barlow@uea.ac.uk>.

FORESTS, FLAMES AND FEATHERS: EFFECTS OF EL NIÑO MEDIATED FOREST FIRES ON AMAZONIAN UNDERSTOREY BIRD ASSEMBLAGES

Fire events within Amazonian forests have been rare over the past 7000 years and until recently the high rainfall, moist microclimate, and ability of trees to utilise deep soil water in times of low rainfall have ensured that tropical rainforests remain largely immune to wildfires. However, the synergistic effects of logging and extended El Niño mediated dry seasons have led to understorey wildfires in tropical forests becoming increasingly common. The biotic consequences of these apparently benign fires are examined, focusing upon how the understorey avifauna responds along a gradient of increasing burn intensity (including unburnt, once-burnt and twice-burnt forest). Considering different foraging and dietary guilds, ant-following, dead leaf gleaning and arboreal sallying insectivores were the most affected by fires, whilst frugivores, nectarivores and arboreal granivores displayed unimodal responses. Only arboreal gleaning insectivores increased along the gradient of burnt severity. Species similarity between plots was examined using the Morisita-Horn similarity index. These pairwise comparisons showed that the degree of similarity between plots was related to the difference in burn severity, and that twice-burnt forests were almost entirely dissimilar from unburnt forests. These results demonstrate that the emerging fire regime represents an enormous threat to the future of Amazonian biodiversity.



16.45 - 17.00
OTTERSTROM, SARAH M. and Mark Schwartz. Department Environmental Science and Policy, University of California, Davis, Davis, CA 95616, USA, <sotter@ucdavis.edu>.

IS FIRE A NECESSARY DISTURBANCE IN THE TROPICAL DRY FORESTS OF MESOAMERICA?

Human-ignited wildfires in the mesoamerican tropical dry forests have been considered destructive and conservationists have worked to reduce their incidence. Nevertheless, few controlled studies have examined the effects of fire disturbance on the dry forest. Our research considers the effect of fire within an intact tropical dry forest in the Chococente Wildlife Refuge, Nicaragua. In order to assess community responses to fire, experimental burn treatments were carried out in 15x75 m forest plots during the dry season of the year 2000. Results demonstrate few significant changes to forest structure while tree seedling densities increased significantly relative to shrub and liana densities following burn treatment. The only significant adult mortality was for lianas and understory shrubs. Several threatened or endangered tree species experienced a significant increase in seedling recruitment following fire. Long-term monitoring plots affected by wildfire in 1998 were also studied. Seedling and sapling density was significantly higher in burn areas. This study demonstrates that fire disturbance is not necessarily catastrophic for the dry forest as once believed and that fire likely plays a role in dry forest regeneration. Further research considering the life history of dry forest species as well as the impact of varying fire regimes is merited.



17.00 - 17.15
MORETTI, MARCO. Swiss Federal Research Institute WSL, Sottostazione Sud delle Alpi, PO Box 57, CH-6504 Bellinzona, Switzerland, <marco.moretti@wsl.ch>.

WILDFIRE, FAUNISTIC DIVERSITY AND SPECIES CONSERVATION: COHERENCE OR CONTRADICTION?

In the present study we investigated the post-fire ecological effects on different faunistic indicators like soil and floor habitat dwelling groups, wood-eating and flower visiting insects, as well as invertebrates living on vegetation. As response parameters we used the number of species, the number of individuals, diversity indices, the number of rare and endangered species, the ecological requirements of the species and sinecological patterns. The results show that fast spreading surface winter fires of low to medium intensity which occur often on the southern slope of the Alps are an important factor initiating succession and adaptation processes in plants and animals, enhancing biodiversity and promoting species conservation, but not everywhere. Moreover, our study confirms the importance of an integration of different elements in the analysis which permits a better understanding of the complexity of the forest ecosystem. This is also the best way to develop judicious recommendations for post-fire management activities.



17.15 - 17.30
KREMEN, CLAIRE, Neal M. Williams and Robbin W. Thorp. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA, <ckremen@Princeton.edu> (CK, NMW), Department of Entomology, University of California, Davis, CA 95616, USA (RWT).

BEE DIVERSITY AND POLLINATION SERVICES IN AN AGRO-NATURAL LANDSCAPE

Communities of bees can provide valuable ecosystem services by pollinating crops, providing motivation for the conservation of pollinator habitat within agro-natural landscapes. We investigated how natural habitat distribution and farm management practices influenced diversity and abundance of a native bee community, and how this affected the pollination services they provided to a target row crop, watermelon, Citrullus lanatus. On farms located at different distances (near versus far) from native habitat, using organic versus conventional management, we assessed visitation rates and per-visit pollen deposition to calculate the contributions of the native bee community to watermelon pollination. The native bee community (>30 species) provided sufficient pollination services on farms in the most favorable environment (near-organic-). On farms far from natural habitat, native bees did not consistently meet pollination requirements, due to greatly reduced diversity and abundance; this effect was stronger on conventional than organic farms. Farmers on far-organic and conventional farms usually relied on rented honey bee colonies to make up the pollination shortfall. Native bee communities therefore provide an important ecosystem service and insurance in the event of shortfalls in honey bee availability. Degradation of the agro-natural landscape is likely to destroy or severely reduce this service.