Species relative abundance Most species rare:few common Lower likelihood of sampling rare species-so underrepresented by dominance-diversity curves Species-area relationship:#species increases with greater area sampled S=cAZ or log S=logc+z log A (S=species:A=area:c.z=constants) z=slope=0.2 to 0.35 (less in continental areas than islands) What expains this relationship? Larger areas give large samples Sample more types of habitats Larger islandsare bigger target for immigrants Populations large enough to prevent Community characteristics Physiognomy:Architecture,life forms,cover,LAI ete Species comp:Keystone sp.rare sp,relative importance Species patterns:Spatial,niche breadth and overlap Species diversity:Richness.evenness Nutrient cycling:Nutrient demand,storage,uptake rate Change over time:Succession,stability Productivity:Biomass,annual net productivity. Creation and control over a microenvironment:temperature,R.H.,light etc. Life form (reflects the summation of all biotic and abiotic factors that surrounds and Discussion organization(twenty minutes) What controls abundance within each trophie level? Top-down control(=predation) Bottom-up control (=nutrients,plant productivity.plant defense) Trophic cascade:ripple effects from top level through multiple trophic levels Indirect effects on lower levels;abundance alternates at each trophic level