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Unformatted text preview: rease nutrients, productivity increases Positive relationship between nutrients and primary productivity (in aquatic and tesstrial—ex: tundra) Increased primary production across coastal regions, because of waste drainage Also see Figs. 18.4-18.9 Consumers can control rates of primary production of ecosystems Importance of animal utilization: Fig. 18.15 – Wildebeests - Intermediate levels of disturbance can increase primary productivity Grazing increases growth rates of many grass species due to compensatory growth Lower rates of respiration in the grass b/c lower biomass If you have lower biomass you have reduced self shading of the grasses Lower biomass also leads to improved water balance due to reduced leaf area At low levels of grazing—insufficient to promote increased production Medium intensity have the highest primary production High intensity grazing is also associated with low production Wound responsebottom up control -refer to influence of temp and nutrients on the productivity of ecosystems of top down control- looking at influence of consumers on ecosystems o Fig. 18.11 Trophic cascade Hypothesis – when something happens to one level another level is affected o If you remove consumers the planktivorous fish will increase and zoo and phytoplankton go up Figure 18.12 The trophic cascade model predicts that manipulating piscivore biomass will lead to changes in biomass and production of planktivores, herbivores, and phytoplankton. Ecosystems rely on a constant source of energy, the sun Sun fuels primary productivity Which then makes it available to all other organisms of ecosystem All which will die and form Detritus—energy and nutrients are locked up in this organic matter and decomposer organisms break it down Decomposers mobilize the nutrients that are bound in organic material and make them available to plants other nutrients are lost via leaching and are soaked up by plants RULE #6: energy flows unidirectional through and ecosystem while nutrients cycle Rule #6: Energy must flow but nutrients cycle. E0 E0 SC Detritus E0 PC Decomposers E0 PP Available Nutrients E0 = Energy Loss = Heat Tax 4-24-06 Rule #6: Energy must flow but nutrients cycle. E0 E0 SC Detritus E0 PC Decomposers E0 PP Available Nutrients EO – energy output PP – primary productivity PC – primary consumption SC – secondary consumption Detritus – dead organic material Nurient Cycling (19) Importance of decomposition Gas vs sedimentary cycles Importance of Importance of Decomposition The final release of energy Nutrient mobilization C-compounds + O2 Two forms: Biological CO2 + H2O Fire Controlling factors: Moisture, temperature, pH, O2, substrate characteristics, and nutrient content Decomposition of organic matter is a universal process in ALL ecosystems ****Rates of decomposition influence soil fertility, nutrient cycling, organic matter accumulation, and are a forcing factor controlling ecosystem structure and function General trends in litter as it starts to decompose Phase 1 Regulated by nutrient level and readily available carbon (the labile fraction of the litter is lost completely) Phase 2 Regulated by lignin decomposition rate (the more lignin the slower it decomposes) Phase 3 Final stages Labile VS Refractory compounds (refractory=tough components) 2 Major Phases of Decomposition Rapid Phase (days to months) Slow Phase (months, years, centuries) % mass remaining Time Decomposing organisms, chemical composition of the litt...
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This document was uploaded on 02/23/2014 for the course CHEM 107 at VCU.

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