Composition of the litter and physical rates of

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Unformatted text preview: er, and physical rates of determinance (macro and micro climates) are the factors that control the rate of decomposition. sugar cellulose lignin bacteria decomposers decomposers *********basidiomycetes (white rot fungus) – lignin decomposers Importance of moisture Fig. 19.5 See also Figs. 19.8 and 19.9 Importance of substrate characteristics Fig. 19.7 See also Figs. 19.6 and 19.11 Importance of nutrient content Fig. 19.12 Fig. 19.13 Nutrient – any substance necessary for life Nutrient cycles: Gaseous Sedimentary Relatively fast Relatively slow Examples: C, N, H2O Examples: P, Na, Ca Hybrid: S Nitrogen is the most limiting nutrient in terrestrial ecosystems Examples of a gaseous cycle Fig. 19.3 Atmosphere (N2, N2O) Nitrogen Fixation Soil (NH3) NH4 Plants Nitrification NO2NO3Denitrifcation *********The N cycle is a microbially mediated cycle Denitrofication is anaerobic process Example of a sedimentary cycle – the phosphorus cycle Fig. 19.2 Phosphorus is as limiting in aquatic ecosystems as nitrogen is in terrestrial Can organisms alter nutrient cycles? - nitrogen fixers - “musseling” phosphorus - nutrient spiraling - man’s effects? The weathering of rock is the only source for phosphorus Myrica adds nitrogen to the soil and changes ecological succession it adds more nitrogen than normally found in this ecosystem and changes ecological succession in the Hawaiian islands Geukenzia demissa- keystone species for recycling Phosphorus organic waste (phosphorus) and plants need inorganic coverted to inorganic phosphates that ar taken up by plants BUT MAJORITY of inorganic phosphorus is in particulate organic matter (detritus) found in deep Pete in ecosystems or in shallow water they filter feed from water column that has particulate organic matter and they excrete inorganic for plants Fig. 19.14 nutrients are carried downstream, the cycles move downstream Called nutrient spiraling Benthic organisms enhance nutrient spiraling Organisms are critical to nutrient cycle More organisms, the tighter the cycle (the fewer, the further it will flow downstream) S(spiraling length, length of stream for an atome to complete in cycle)=vt V=velocity of nutrient t= time for nutrient cycle Downstream flows means nutrients don’t flow in cycle Fig. 19.21 Fig. 19.2 Example of a sedimentary cycle Fig. 19.2 Can organisms alter nutrient cycles? Organisms are important for maintain the nutrient within the cycle - nitrogen fixers – ex: - “musseling” phosphorus converts organic phosphorus to inorganic phosphorus - nutrient spiraling - man’s effects? Myrica adds nitrogen to the soil and changes ecological succession Fig. 19.21 Fig. 19.22 In a tropical rain forest 80% of the nutrients are tied up in plant matter The ribbed mussel is a keystone species for recycling P Ribbed Mussel Geukenzia demissa Plants Organic waste Plants Organic phosphates Organic particulates Norganic phosphates Deep Shallow RIBBED MUSSEL Fig. 19.14 Benthos enhance nutrient spiraling in streams The length of stream for an atom to complete a cycle Downstream flow means nutrients do not cycle in place Benthos shorten the cycle by repeatedly reusing the nutrient The shorter the cycle the longer the nutrient is retained within the ecosystem Diversity leads to nutrient retention which leads to high productivity S=VT V=velocity T=time to complete a cycle ****Read pages 476-478 Look at Fig. 19.23 Shows impact of man on en...
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This document was uploaded on 02/23/2014 for the course CHEM 107 at VCU.

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