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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 Landscape Ecology
Session One

Tuesday 16th July, 10.15 - 12.15, Grimond Lecture Theatre 2

Chair: William Laurance




(BLOCK CAPITALS indicate the presenting author)

10.15 - 10.30
NEEL, MAILE, Kevin McGarigal, Sam Cushman. Department of Natural
Resources Conservation, University of Massachusetts, Amherst, Massachusetts
01003 USA. (mailen@forwild.umass.edu)

COMPARISON OF LANSCAPE STRUCTURE METRICS FOR EVALUATING AND QUANTIFYING FRAGMENTATION


Habitat loss and fragmentation strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes, especially effects that are independent of area alone. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 65 metrics in neutral landscapes across a 31 step gradient in aggregation and a 21 step gradient in area using a full factorial design with 100 replicates in each factor to assess how well metrics reflected changes in landscape structure due to fragmentation. Metrics could be grouped into 3 major behavioral classes: strongly related to area (n=10), strongly related to configuration (n=7), and confounded by area and configuration (n=48). The confounded metrics exhibited widely varying, often non-linear behavior that renders interpretation difficult. Of the metrics strongly related to configuration, only two were relatively straightforward: the clumpiness index and perimeter area fractal dimension. While these metrics are valuable, they describe only limited aspects of landscape structure. Ultimately, comprehensive characterization of landscapes undergoing habitat loss and fragmentation will require using several metrics distributed across behavioral groups.

10.30 - 10.45
LAURANCE, WILLIAM F. Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Republic of Panamá; and Biological Dynamics of Forest Fragments Project, National Institute for Amazonian Research, Manaus, Brazil, <laurancew@tivoli.si.edu>.

RAPID EROSION OF PLANT BIODIVERSITY IN AMAZONIAN FOREST FRAGMENTS

At a landscape scale, the remarkable biodiversity of tropical forests results not only from high species richness at any individual site (alpha diversity), but also from large variation in species composition among different sites (beta diversity). I demonstrate that in central Amazonian rainforests, habitat fragmentation causes a far more rapid erosion of beta diversity than alpha diversity. Results were derived from a 22-year study of highly diverse tree communities in 34 one hectare plots in fragmented and intact forests, that were repeatedly sampled before and after fragment isolation. For each plot, trajectories of change in floristic composition were assessed using ordination analyses for >1100 individual tree species. Rapid change in plant composition was driven by dramatically accelerated tree mortality within 100-300 m of fragment margins, causing large-scale declines in many old-growth taxa and increases in some disturbance-tolerant species. Although declines of tree species richness in fragment plots were limited, rates of species turnover accelerated substantially. Because beta diversity declined much more sharply than alpha diversity, forest fragments appear to be converging in floristic composition, and may eventually support a biased and depauperate subset of the originally hyper-diverse biota.



10.45 - 11.00
MARINI, MIGUEL ., Fabiane Sebaio, and Érica Braga. Departamento de Zoologia, Universidade de Brasília, 70910-900, Brasília, DF, Brazil, <marini@unb.br> (MM), Pós-graduação em Ecologia, Conservação e Manejo de Vida Silvestre, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 30.161-970, Belo Horizonte, MG, Brazil (FS), Departamento de Parasitologia, Universidade Federal de Minas Gerais, 30.161-970, Belo Horizonte, MG, Brazil (EB).

PARASITISM AND BODY CONDITION OF BIRDS IN FRAGMENTED AND CONTINUOUS AREAS OF THE ATLANTIC FOREST, BRAZIL

The health of birds in fragmented forests may be worse than in more protected areas. However, this line of research has been largely neglected in spite of its strong relevance to wildlife conservation. Here, we evaluated the prevalence of blood (Trypanosoma, Plasmodium and Haemoproteus) and ecto parasites [ticks (Acari) and chewing lice (Phthiraptera)], and the incidence of pathologies in the tarsus and flight feathers of birds from six small (< 20 ha) forest fragments close to six large (> 1.000 ha) Atlantic Forest patches from southeast Brazil. Overall, 1146 birds were sampled, with a mean of 95.5 birds sampled per area. Forest fragmentation does not seem to affect any of the variables measured, since all statistical results were non significant (P > 0.10). Most of these variables ranged widely (ex. chewing lice prevalence in fragmented forests: from 14.4 to 57.7 %). Differences in parasitism and pathology levels varied considerably between, as well as within, landscapes. Apparently protected forests might host birds with high levels of parasitism, whereas apparently disturbed forests might host birds free of parasites. Local unknown factors such as abundance of other wild or domestic animals, historical events, and chance might be generating these random variations.



11.00 - 11.15
GALE, GEORGE, Puntipa Pattanakaew, J. F. Maxwell, Rebecca Scott and Stephen Elliott. King Mongkut's University of Technology Thonburi, School of Bioresources and Technology, Bangmod, Thungkru, Bangkok 10140, Thailand, <george.and@kmutt.ac.th> (GG, PP, RS), Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand (JFM, SE).

DO BIRD PERCHES INCREASE SEEDLING RECRUITMENT IN DEFORESTED TROPICAL LANDSCAPES?

Artificial perches have been shown to greatly increase input of bird-dispersed seeds into deforested lands, but their affect on seedling recruitment in tropical systems has been unclear. Here we report on a relatively large-scale study using a total of 96 perches and 96 control points divided among eight plots undergoing various stages of natural and assisted regeneration in northern Thailand. Early successional vegetation was also removed at selected perches and control points to assess its effect on seedling recruitment. After 31 months, seedfall beneath perches (299 seeds m-2 yr-1) was 22 times greater than in sites without perches. Although highly variable, density of bird-dispersed plants was significantly higher beneath the perches (7.7 plants m-2) than in the control points (2.2 m-2) and in seven out of eight plots, total number of seedlings was greater beneath perches. Selective weeding had no significant effect on the number seedling recruits, while preliminary germination trials indicated that germination rates were generally low. Our results suggested that perches can accelerate seedling recruitment at least until regenerating woody vegetation reaches a height similar to the perches. Recruitment limitation appeared to be due to factors influencing germination rate, rather than from competition from weedy species.



11.15 - 11.30
HAUGHLAND, DIANE L., Karl W. Larsen. Department of Biology, University of Victoria, Victoria, British Columbia, V8W 3N5, Canada, <dianeh@uvic.ca> (DLH), Department of Forestry and Natural Resource Sciences, University College of the Cariboo, Kamloops, British Columbia, V2C 5N3, Canada (KWL).

QUASI-DISPERSIVE MOVEMENT BY JUVENILE NORTH AMERICAN RED SQUIRRELS (TAMIASCIURUS HUDSONICUS)

Few studies examine dispersal tactics employed by juveniles, despite the importance of natal dispersal to fitness, population ecology, and conservation of dispersive species. North American red squirrels are ideal animals for studying dispersal search patterns in relation to habitat because juveniles make exploratory forays prior to settlement; individuals from ‘sub-optimal’ habitat may search habitat randomly, or bias searching towards either familiar habitat ('imprinting') or towards high-quality habitat. I conducted 8-hour focal observation periods on 30 unrelated juvenile squirrels originating from either side of an intact/commercially thinned forest transition over a two-year period. Fifty percent of the resultant movement pathways differed significantly from correlated random walk pathways; further analyses utilizing net squared displacement confirmed that all non-random pathways were significantly circular in nature. Non-random movement does not appear to be associated with habitat of origin, sex, or collaring date. Regardless of pre-dispersal movement patterns, all juveniles collared in 2001 were philopatric, settling on or beside their natal territory. This suggests that larger scale phenomena such as weather and cone crop may override other dispersal cues, a result with important implications for managers and conservationists predicting the impact of habitat alteration on a species in any given year.



11.30 - 11.45
AKÇAKAYA, H. RESIT, Volker C. Radeloff, David J. Mladenoff and Hong S. He. Applied Biomathematics, Setauket, NY 11733, USA, <resit@ramas.com> (HRA), Department of Forest Ecology and Management, University of Wisconsin, Madison, Wisconsin, USA (VCR, DJM), School of Natural Resources, University of Missouri-Columbia, Columbia, MO 65211, USA (HSH).

LINKING LANDSCAPE AND METAPOPULATION MODELS: SHARP-TAILED GROUSE IN A DYNAMIC LANDSCAPE

We analyse the effect of forest management options on the viability of the Sharp-tailed Grouse, Tympanuchus phasianellus, in the Pine Barrens region of northwestern Wisconsin, using a model that integrates landscape and metapopulation modelling approaches. Our model simulates metapopulations in dynamic and fragmented habitats; it allows population viability analyses based on temporal changes in the habitat patch structure, brought about by processes such as succession, disturbances, and silviculture. Both the landscape and metapopulation components are spatially dynamic models. The landscape component (LANDIS) predicts landscape dynamics in the form of a time series of maps that describe the tree species composition and age distribution at each decade. These maps are then combined into a time series of patch structures, which form the dynamic spatial structure of the metapopulation component (RAMAS). The results indicate that the viability of the Sharp-tailed Grouse in the Pine Barrens depends both on landscape dynamics and on demographic variables such as fecundity and mortality. Ignoring the landscape dynamics gave overly optimistic results, and results based only on landscape dynamics (ignoring demography) led to a different ranking of the management options than the ranking based on the more realistic model that incorporated both landscape and demographic dynamics.



11.45 - 12.00
LAPIN, MARC. Cornell University, Ithaca, New York. Mailing Address: Ecosystem Science and Conservation, 239 Cider Mill Road, Cornwall, VT 05753 USA (mlapin@shoreham.net)

A FRAMEWORK FOR UNDERSTANDING AND CONSERVING NATURE IN A HIGHLY-FRAGMENTED LANDSCAPE: THE CHAMPLAIN VALLEY CLAY PLAIN, VERMONT, USA

To begin understanding ecological structure and function in a highly fragmented landscape, a biophysical ecosystem classification (based on geology, soils, physiography) was developed and applied in conjunction with the patch-corridor-matrix model. Analyses of vegetation and soils, spatial arrangement of landscape elements, and proportional representation of landscape ecosystem types were conducted. The study area, a post-glacial, clay-soil lake plain, has been used for intensive agriculture for 200 years. The vegetation of the clay-soil forests is plant-species rich and includes numerous species at northeastern range peripheries; the vegetation type does not occur on other landforms in Vermont or neighboring states/provinces. The pattern of fragmentation resembles landscape pattern in many agricultural regions in the Eastern and Midwestern U.S. Mean patch size is 12 ha on the lowest level lake plain and 20 ha in the entire biophysical subregion. A disproportionate amount (75%) of remaining forest occurs on the less extensive, agriculturally non-productive soils. Application of conservation science and landscape ecology principles indicates the need to conserve fragments of clay-soil forest that are relatively large and occur in clusters, and conserve connectivity. Forest fragments are not evenly distributed across the landscape and maintaining fragments scattered throughout is likely beneficial to overall nature conservation.



12.00 - 12.15
FISCHER, JOERN and David B. Lindenmayer. Centre for Resource and Environmental Studies, The Australian National University, Canberra ACT 0200, Australia, <joern@cres.anu.edu.au>.

ISOLATED PATCHES OR HABITAT CONTINUUM? – BIRDS IN AN AUSTRALIAN GRAZING LANDSCAPE

We present findings from two studies on birds within the Nanangroe landscape in southeastern Australia. Our aims were: 1) to provide an Australian perspective of some pressing conservation issues, and 2) to outline some future challenges for conservation biologists working in similar environments. The Nanangroe landscape is a grazing landscape throughout which over 100 remnant woodland patches and hundreds of scattered trees have been retained throughout the pastures. We surveyed birds in 70 sites comprised of scattered trees, and 105 remnant patches (1-16 ha). Of 91 species recorded, 74 species were detected in patches smaller than 1 ha, and more than 30 species used scattered trees. Data on the flight direction of birds suggested that scattered trees were used as stepping stones by birds. Our findings emphasise that the traditional classification of landscapes into patches may be inappropriate in some locations. For many birds, the Nanangroe landscape functioned as a complex and well-connected habitat continuum, and small habitat features were important components of this continuum. Appropriate conceptualisation of landscape function is necessary to suggest conservation strategies. For example, it may be more important to enable natural regeneration in the pastures than to enhance the size of small woodland patches.