Biol 302 Introduction1 COMMUNITY STRUCTURE (cpt. 20) Biological structure: composition and abundance temporal changes (succession) relationships between species (interactions, dominance, Keystone’s etc.)

Biol 302 Introduction2 COMMUNITY STRUCTURE (cpt. 20) Biological structure determines how the community functions: Productivity Trophic levels Nutrient cycling etc.

Biol 302 Introduction3 VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE: 1.LIFE FORMS 2.HORIZONTAL STRUCTURE 3.VERTICAL STRUCTURE

Biol 302 Introduction4 VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE: 1.LIFE FORMS 2.HORIZONTAL STRUCTURE 3.VERTICAL STRUCTURE

Biol 302 Introduction5 LIFE FORMS In the 1920’s, a Danish botanist, Raunkiaer, provided a classification (1934) based on the position of the perennating tissue (buds, bulbs, seeds etc.). This can be used to characterize a community because certain life forms are dominant in certain environments.

Biol 302 Introduction6 Christen C. Raunkiaer

Biol 302 Introduction7 RAUNKIAER’S LIFE FORMS Phanerophytes (trees) Chamaephytes (shrubs) Hemicryptophytes (perennial herbs) Cryptophytes (bulbs etc.) Therophytes (annuals)

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Biol 302 Introduction13 The great biomes of the world show a remarkable degree of convergence in their “physical appearance”, despite wide variation in the species involved. It is difficult to distinguish between: chaparral of California and Chile nutrient-poor heaths of S. Africa and Australia Arctic and Antarctic fell fields rain forest in Brazil and SE Asia These divergences are vivid testimony of the importance of climatic factors as agents of natural selection.

Biol 302 Introduction14 LIFE FORMS IN DIFFERENT BIOMES

Biol 302 Introduction15 Phanero phytes (trees) Chamae phytes (shrubs) Hemicrypto phytes (perennial herbs) Crypto phytes (bulbs etc.) Thero phytes (annuals) World or Normal LATITUDE Tropical rain forest 9622 Sub tropical forest Warm temperate forest Cold temperature forest Tundra

Biol 302 Introduction16 Phanero phytes (trees) Chamae phytes (shrubs) Hemicrypto phytes (perennial herbs) Crypto phytes (bulbs etc.) Thero phytes (annuals) World or Normal MOISTURE Mesophytic forest Oak woodland Dry grassland Semi-desert Desert

Biol 302 Introduction17 SEVERAL POINTS EMERGE FROM THESE COMPARISONS SEVERAL POINTS EMERGE FROM THESE COMPARISONS: 1.Where there is no unfavorable season, or the less favorable is not too severe, then tree-like plants (phanerophytes) predominate in the flora as a whole. 2.Under ideal growth conditions (constant warmth and moisture) trees are dominant, simply because the competitive spoils go to the tallest individuals. 3.In less equable climates, trees may still be the dominant plants in most communities, but the flora as a whole is made up predominantly of other life forms (hemicryptophytes in northern temperate latitudes)

Biol 302 Introduction18 Where the summer is arid (as in deserts and Mediterranean climates), there is a preponderance of annual plants (which avoid drought by passing the dry period as dormant seeds) and geophytes (which avoid drought by die-back of their above-ground parts and survive by means of underground storage organs). Other desert plants that tolerate drought may appear to be dominant if the vegetation is surveyed during the dry season (xerophytic shrubs and stem succulents) 4.Where the summer is arid (as in deserts and Mediterranean climates), there is a preponderance of annual plants (which avoid drought by passing the dry period as dormant seeds) and geophytes (which avoid drought by die-back of their above-ground parts and survive by means of underground storage organs). Other desert plants that tolerate drought may appear to be dominant if the vegetation is surveyed during the dry season (xerophytic shrubs and stem succulents)

Biol 302 Introduction19 5. Where extreme cold and exposure characterize the unfavorable season, there is a shift towards cushion-forming plants and other species whose buds are held close to the ground surface (chamaephytes). Many Arctic plants have their perennating buds protected by the dead leaf-bases of last year's shoots, because both the exposed aerial environment and the frozen soil are extremely inhospitable conditions for bud survival.

Biol 302 Introduction20 VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE: 1.LIFE FORMS 2.HORIZONTAL STRUCTURE 3.VERTICAL STRUCTURE

Biol 302 Introduction21 HORIZONTAL STRUCTURE HORIZONTAL STRUCTURE: 1.Random Probably never occurs 2.Regular or Systematic Plantations of crops Behavioural interactions 3.Aggregated or Clumped

Biol 302 Introduction22 HORIZONTAL STRUCTURE: 1.Random Probably never occurs 2.Regular or Systematic Plantations of crops Behavioural interactions 3.Aggregated or Clumped

Biol 302 Introduction23 RANDOM ARRANGEMENT

Biol 302 Introduction24 HORIZONTAL STRUCTURE: 1.Random Probably never occurs 2.Regular or Systematic Plantations of crops Behavioural interactions 3.Aggregated or Clumped

Biol 302 Introduction25 REGULAR [OR SYSTEMATIC] ARRANGEMENT ARRANGEMENT

Biol 302 Introduction26 REGULAR, OR SYSTEMATIC, ARRANGEMENT

Biol 302 Introduction27 HORIZONTAL STRUCTURE: 1.Random Probably never occurs 2.Regular or Systematic Plantations of crops Behavioural interactions 3.Aggregated or Clumped

Biol 302 Introduction28 AGGREGATED: ants and termites fish and phytoplankton plants distribution from parent environmental heterogeneity species interactions

Biol 302 Introduction29 AGGREGATED: ants and termites fish and phytoplankton plants distribution from parent environmental heterogeneity species interactions

Biol 302 Introduction30 AGGREGATED: ants and termites fish and phytoplankton plants distribution from parent environmental heterogeneity species interactions

Biol 302 Introduction31 Solidago canadensis Solidago nemoralis

Biol 302 Introduction32 Buttercup (Ranunculus sp.)

Biol 302 Introduction33 Bullrush Cattail

Biol 302 Introduction34 Krebs Fig. 7.9; p94,95,137 Chthamalus Balanus

Biol 302 Introduction35 VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE VARIOUS WAYS TO DESCRIBE COMMUNITY STRUCTURE: 1.LIFE FORMS 2.HORIZONTAL STRUCTURE 3.VERTICAL STRUCTURE

Biol 302 Introduction36 VERTICAL STRUCTURE: Forest (usually associated with light diminution) Warblers in a coniferous forest Aquatic systems Soil layers Root systems

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Biol 302 Introduction38 WARBLERS (Krebs Fig ; p193)

Biol 302 Introduction39 (Krebs Fig ; p193)

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