Principles of terrestrial ecosystem ecology.pdf

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Atmosphere Euphotic zone Deep ocean Sediments Terrestrial inputs POC PON Biological pump HCO 3 - Water-column decomposition Benthic decomposition Figure 10.9. Major pools and net fluxes of carbon (C) and nitrogen (N) in the ocean. Phosphorus and other essential nutrients cycle in patterns similar to that shown for nitrogen. CO 2 in the euphotic zone equilibrates with bicarbonate in ocean water and with CO 2 in the atmosphere. CO2 is depleted by photosynthesis by primary producers and is replenished by respiration of organisms and by upwelling and mixing from depth. Grazers consume primary producers and bacteria and are eaten by other animals and lysed by viruses. Each of these organisms releases dissolved and particulate forms of carbon and nitrogen (DOC, DON; POC, PON).Animals and decomposers also release available nitrogen (N avail). tems. The net effect of the biological pump is to move carbon from the atmosphere to the deep waters and to ocean sediments. Carbon accumulation in midocean sediments is slow (about 0.01% of NPP) because most decomposition CO 2 CO 2 Primary producers Grazers, predators, and viruses Decomposers Navail CO2 Carbon (C) fluxes Nutrient (N) fluxes DOC DON Deep-ocean transport N avail Upwelling and mixing Oceans 235 DOC is consumed by bacteria, and available nutrients are absorbed by primary producers. Particulate carbon and nutrients produced by feces and dead organisms sink from the euphotic zone toward the sediments; as they sink, they decompose, releasing CO 2 and available nutrients. Benthic decomposition also releases CO 2 and available nutrients. Bottom waters, which are relatively rich in CO 2 and available nutrients, eventually return to the surface through mixing and upwelling; this augments the supply of available nutrients in the euphotic zone. DOC, dissolved organic carbon; DON, dissolved organic nitrogen; POC, particulate organic carbon; PON, particulate organic nitrogen. occurs in the water column before organic matter reaches the sediments and because these well-oxygenated sediments support decomposition of much of the remaining carbon (Valiela 1995).
236 10. Aquatic Carbon and Nutrient Cycling The biological pump that transports carbon to depth carries with it the nutrients contained in dead organic matter. Decomposition continues as particles sink, so much of the decomposition occurs in the water column rather than in the sediments, particularly in the deep oceans. The rapid (about weekly) turnover of carbon and nutrients in phytoplankton in the euphotic zone (Falkowski et al. 1999) makes these nutrients vulnerable to loss from the ecosystem and contributes to the relatively open nutrient cycles of pelagic ecosystems. The longer-lived and larger primary producers on land can store and internally recycle nutrients for years. This reduces the proportion of nutrients that are annually cycled and contributes to the tightness of terrestrial nutrient cycles. Benthic decomposition is more important on continental shelves than in the deep ocean because the coastal pelagic system is more productive, generating more detritus. In addition, the dead organic matter has less time to decompose before it reaches the sediments. Here oxygen consumption by decomposers depletes the oxygen enough that decomposition becomes oxygen limited, and organic matter accumulates or becomes a carbon source for methanogens and denitrifiers. Lakes Lakes consist of a range of ecosystem types, from pelagic systems to wetlands dominated by vascular plants (Wetzel 2001). The centers of deep lakes are structurally similar to marine ecosystems with discrete pelagic and benthic systems; phytoplankton are the major primary producers, and zooplankton are the major herbivores. The littoral zone of lakes generally experiences less disturbance from wave action and currents than in marine systems.This allows mats of algae to grow directly on lake sediments, even where light is only 0.1% of that present at the surface. The littoral zone of lakes often has rooted vascular plants, whose leaves extend above the water surface and shade the water, reducing the light available to phytoplankton and benthic algae. Floating aquatic plants like water lilies cause a similar reduction in light availability in the water column. Many lakeshore ecosystems and salt marshes, their marine equivalent, are structurally and functionally similar to terrestrial wetland ecosystems. There is therefore a continuum between the structural and functional properties of aquatic and terrestrial ecosystems. The origin of lakes strongly affects their structure and functioning (Lodge 2001). Glacial lakes are abundant in young landscapes at high latitudes and altitudes. They are frequently interconnected with other lakes by short stream segments and have a low degree of endemism. Rivers create lakes in several ways, including isolation of former river channels (oxbow lakes) and periodically inundated swamps and floodplains such as the Pantanal of Bolivia and Brazil. These lakes are generally shallow and occasionally reconnect with adjacent rivers during floods. Tectonic lakes form along faults. They are often large, deep, and isolated from one another, providing an environment for substantial diversification, such as in the rift lakes in eastern Africa and Lake Baikal in Siberia. These large tectonically derived lakes harbor most of the endemic freshwater organisms. Over 80% of the open water animals of Lake Baikal, for example, are endemic (Burgis and Morris 1987). Other lakes form in volcanic craters, by damming of rivers, and other processes. Controls over NPP Photosynthesis in fresh-water ecosystems is seldom carbon limited, just as in the ocean. Groundwater entering fresh-water ecosystems is supersaturated with CO2 derived from root and microbial respiration in soil (Kling et al. 1991). Most streams, rivers, and oligotrophic lakes are net sources of CO2 to the atmosphere because the rates of water and CO2 input from groundwater generally exceed the capacity of primary producers to use the CO2 (Cole et al. 1994, Hope et al. 1994). Eutrophic lakes with their high algal biomass have a greater demand for CO2 to support photosynthesis than do oligotrophic systems, but their organic accumulation and high decomposition rate in sediments provide a large CO2 input to the water column.
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F. Stuart Chapin III Pamela A. Mats
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Preface Human activities are affect
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Contents Preface . . . . . . . . .
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Contents ix Changes in Storage . .
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Contents xi Root Uptake Properties
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Contents xiii Disturbance . . . . .
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1 The Ecosystem Concept Ecosystem e
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Figure 1.1. Examples of ecosystems
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Community ecology Population ecolog
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ing from biotically driven changes
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The pool sizes and rates of cycling
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and alters patterns of vegetation d
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Figure 1.5. Direct and indirect eff
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many aspects of ecology, hydrology,
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Energy (W m -2 ) 1 1 0 1 0 1 0 1 Ab
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The Atmospheric System Atmospheric
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ecular O2 to form O3. The absorptio
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Hadley cell Hadley cell Ferrell cel
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early sailors as the doldrums. Subs
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phere, extends to depths of 75 to 2
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tures in Great Britain and western
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when the water vapor condenses to f
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Solar flux 1.4 1.2 1.0 0.8 0.6 0.4
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Figure 2.16. Time course of the ave
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Radiative forcing (W m -2 ) Warming
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January September Sun March pattern
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access to light compete effectively
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the top? How does each of these atm
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(Dokuchaev 1879, Jenny 1941, Amunds
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Organic carbon (%) Erosion likely g
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erosion dominating on steep hillslo
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conductivity of soils. Groundwater
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chemical weathering through their c
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Although most of the transfers in s
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leached material from above, it is
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opment, so these soils have weak de
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y roots and bacteria are important
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Table 3.4. Sequence of H + - consum
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new chemical conditions cause them
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72 4. Terrestrial Water and Energy
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98 5. Carbon Input to Terrestrial E
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100 5. Carbon Input to Terrestrial
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124 6. Terrestrial Production Proce
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152 7. Terrestrial Decomposition So
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154 7. Terrestrial Decomposition su
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156 7. Terrestrial Decomposition a
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158 7. Terrestrial Decomposition Ma
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160 7. Terrestrial Decomposition Re
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162 7. Terrestrial Decomposition cy
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164 7. Terrestrial Decomposition Ma
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166 7. Terrestrial Decomposition li
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168 7. Terrestrial Decomposition ar
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170 7. Terrestrial Decomposition R
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172 7. Terrestrial Decomposition LO
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174 7. Terrestrial Decomposition Me
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8 Terrestrial Plant Nutrient Use In
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178 8. Terrestrial Plant Nutrient U
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Page 251 and 252: 11 Trophic Dynamics Introduction Al
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288 13. Temporal Dynamics successio
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290 13. Temporal Dynamics Stage Lif
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292 13. Temporal Dynamics that redu
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294 13. Temporal Dynamics Soil carb
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296 13. Temporal Dynamics Nutrient
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298 13. Temporal Dynamics are aband
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300 13. Temporal Dynamics leaf area
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302 13. Temporal Dynamics account f
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304 13. Temporal Dynamics 6. How do
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306 14. Landscape Heterogeneity and
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15 Global Biogeochemical Cycles The
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tion of surface waters. On daily to
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Crowley 1995). An improved understa
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therefore limits the long-term rate
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important for understanding the rec
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Terrestrial N fixation (Tg yr -1 )
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The addition of limiting nutrients
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has a significant atmospheric compo
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cled. Evaporation and precipitation
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Figure 15.11. Trends in (A) world p
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which cycles are soil pools and flu
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Our use, mismanagement, and uninten
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mycorrhizal or nitrogen-fixing mutu
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Major human impacts on the natural
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promote long-term sustainability of
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Coral reef ecosystems have recently
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Table 16.3. Examples of services pr
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anthropogenic change and to sustain
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Abbreviations an nutrient productiv
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Abbreviations 373 NEE net ecosystem
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Glossary A horizon. Uppermost miner
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Biomass. Quantity of living materia
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Coriolis effect. Tendency, due to E
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Exoenzyme. Enzyme that is secreted
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Inceptisol. Soil order characterize
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Microbial loop. Microbial food web
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Phototroph. Nitrogen-fixing microor
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simply to the greater number of spe
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Sun leaf. Leaf that is acclimated t
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Color Plate I monthly averages of t
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Plate 3. The global pattern of net
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