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Human Resource Use Human Values & Attitudes (Socio-political) Human Land Use Practices 1) Agriculture 2) Suburban Development Let’s pick on Indiana: • • 97% of land in state = privatelyowned In central Indiana, • 70+% of land in row crop • <10% in forest • Urban sprawl intensifying Human Impacts Ecosystem simplification: elimination of species from food webs via human alterations to land Example: vertebrate communities in ag. landscapes Intensive Agriculture & Clean Farming Timber Extraction & Fragmentation Formation of Terrestrial “Islands” Oceanic Island = Terrestrial Island ????? Species-Area Relationship S = cAz S = # of species A = island area • Positive correlation between island size & number of species • Applies to terrestrial “islands” also Island Biogeography • equilibrium model suggesting that the number of species occurring on an island represents a balance between immigration (in) and extinction (out) • Robert MacArthur & E.O. Wilson Habitat Fragmentation • Process of breaking contiguous unit into smaller pieces; area & distance components • Leads to: < remnant patch size > edge:interior ratios > patch isolation < connectivity • Community & Ecosystem processes altered Formation of Terrestrial “Islands” #patches Patch isolation Patch size Edge What about aquatic systems? What about aquatic systems? Con.Bio 12(6) Increased Edge Habitat Increased Edge Habitat Habitat Fragmentation • First-Order Effects: fragmentation leads to change in a species’ abundance and/or distribution • Higher-Order Effects: fragmentation indirectly leads to change in a species abundance and/or distribution via altered species interactions Habitat Fragmentation • area-sensitive species: species that require minimum patch size for daily life requirements • Edge effects: influence of factors from outside of a patch Edge Effects • Habitat surrounding a patch can: - change abiotic conditions; e.g., temp. - change biotic interactions, e.g., predation Example of nest predation = edge effect of approximately 50 m into forest patch But can extend 100’s of meters….maybe km’s Edge Effects • How does patch size (in a landscape) & shape affect amount of edge? • Groups – give me a mathematical example with forested landscapes that have timber extraction via clearcutting Exponential vs. Logistic dN N rN 1 dt K dN rN dt No DD All populations same DD All populations same No Spatial component Incorporating Space Metapopulation: a population of subpopulations linked by dispersal of organisms • subpopulations separated by unsuitable habitat • subpopulations differ in population size & distance between Metapopulation Model dp cp1 p ep dt p = habitat patch (subpopulation) c = colonization e = extinction Another Population Model Source-sink Dynamics: grouping of multiple subpopulations, some are sinks & some are sources Source Population = births > deaths = net exporter Sink Population = births < deaths Source-sink Dynamics >1 <1 <1 Source-sink Dynamics Corridors Who Cares? Why bother discussing these models? Metapopulations & Source-sink Populatons highlight the importance of: • habitat & landscape fragmentation • connectivity between isolated populations • genetic diversity Vancouver Island marmot (Marmota vancouverensis) ~100 left Isolated from hoary and Olympic marmots Vancouver Island marmot (Marmota vancouverensis) Natural tree succession Vancouver Island marmot (Marmota vancouverensis) • Logging – disjunct patches - max. dispersal = 7 km • Climate • Prey-Predator Dynamics Differential Sensitivities to Habitat Alteration • Niche breadth (diet & habitat) – inverse relation • Range periphery = more sensitive (W & N) • Body size = mobility (allometric relation) • Social and territorial behavior (limited K) Swihart et al. 2003 Ways to Manage 1) Featured Species Mgt – single species – particular purpose – e.g., white-tailed deer – could also include “umbrella species” and “flagship species” or “sensitive species” Ways to Manage 2) Species Richness Mgt – maintain diversity and certain # of each species (follow MVP concept) 3) Indicator Species Mgt – use a species (or group of species) to monitor environmental conditions – not necessarily managing for these spp. – bioindicators, biosentinels, “canary in coal mine” Ways to Manage 4) Guild Mgt or Life-Form Mgt – grouping of species based on use of same type of resources (e.g., foraging guilds)
