Food web expansion and contraction in responseto changing environmental conditions

摘要

Macroscopic ecosystem properties, such as major material pathways and community biomassstructure, underlie the ecosystem services on which humans rely. While ecologists have longsought to identify the determinants of the trophic height of food webs (food chain length),it is somewhat surprising how little research effort is invested in understanding changesamong other food web properties across environmental conditions. Here we theoretically andempirically show how a suite of fundamental macroscopic food web structures respond, inconcert, to changes in habitat accessibility using post-glacial lakes as model ecosystems. Weargue that as resource accessibility increases in coupled food webs, food chain length contracts(that is, reduced predator trophic position), habitat coupling expands (that is, increasinglycoupled macrohabitats) and biomass pyramid structure becomes more top heavy. our resultsfurther support an emerging theoretical view of flexible food webs that provides a foundationfor generally understanding ecosystem responses to changing environmental conditions.