BIOTA 



The biota of forest ecosystems can be classified according to the role of 

 organisms in the transfer of energy through the ecosystem. Four basic 

 functional groups, or trophic levels, exist: 



1. The primary producers, green plants: trees, wood shrubs, nonwoody 

 higher plants, ferns, and mosses. 



2. The decomposers: fungi, bacteria, and microorganisms (smaller soil 

 insects, worm phyla, and other small invertebrates) 



3. The primary consumers, herbivores: many insects and plant-eating 

 vertebrates and invertebrates. 



4. The secondary consumers, the carnivores and insectivores : many 

 insects and vertebrates. 



Energy flow from one level to another is shown in figure 9-4. Sunlight is 

 converted to plant tissue (carbohydrates, fats, and protein) by green plants. 

 This constitutes primary production which then is consumed by herbivores 

 (primary consumers) or falls to the forest floor, where it is utilized by 

 decomposers and other primary consumers. Primary consumers and decomposers 

 then become food for higher level consumers (insectivores and carnivores). 

 The increase in animal tissue as a result of growth or reproduction is termed 

 secondary production. A more detailed discussion of the various trophic 

 levels follows. 



HIGHER LEVEL CONSUMERS PREDATORS 



BIRDS MAMMALS iNvE HT£ BRATtS 



PRIM&Rr CONSUMERS: HERBIVORES 



INSECTS MICE SQUIRRELS DEER haRF 



PRIMARY PRODUCERS 



iJRtEN PLANTS 



SECONDARY CONSUMERS PREDATORS 



INSECTS AND OTHER INVERTEBRATES 

 BIRDS MAMMALS REPTILES AMPMI81ANS 



\ \ 



\ \ 



\ \ 



\ \ 



d*«a am ma IS 



\ 'eces 1 



^ \ 



\ \ I 



DECOMPOSERS 



BACTERIA FUNGI 



/ 



' / / 

 / / ' 



SOIL INVERTEBRATES 



Figure 9-4. Generalized trophic structure of a forest system showing 



major pathways of energy transfer (solid lines are "grazing" 

 pathways, broken lines are "decomposer" pathways). 



9-12 



