Chapter 11 Controls on Ecosystem Structure and Function © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer,

Chapter 11Chapter 11

Controls on Ecosystem Structure and Controls on Ecosystem Structure and FunctionFunction

© 2013 Elsevier, Inc. All rights reserved.From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

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Figure 11.1 Biotic control of an aquatic ecosystem from the top of the food web. The trophic cascade hypothesis proposes that top predators may control the abundance of organisms lower in the food chain. By reducing the abundance of their prey (planktivorous fish), this in turn may allow an increase in the abundance or size of organisms among the prey’s food source (zooplankton), which can lead to grazing down phytoplankton populations and increase water clarity and concentrations of dissolved nutrients (Trophic cascade available at: http://biology-forums.com/index.php?action=gallery;sa=view;id=2029.)


http://biology-forums.com/index.php?action=gallery;sa=view;id=2029

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Figure 11.2 Autogenic (a, b, c) and allogenic (d, e, f) ecosystem engineering. (a) Oak (Quercus rubra) forest near Millbrook, NY, changes microclimate and affects soil biogeochemistry and understory species. (b) Smooth cordgrass, Spartina alterniflora, in a tidal marsh in the La Plata estuary near Playa Peninos, Uruguay. The marsh attenuates storm surges, increases sedimentation, and retains organic matter affecting biogeochemistry and creating protected habitat for other species. (c) Reefs of tube-building polychaetes, Ficopomatus enigmaticus, an exotic species in Mar Chiquita coastal lagoon, Argentina. The reef in the foreground is ca. 3 meters across, and it alters hydrodynamics and increases sedimentation, providing shelter for many invertebrates. (d) Riparian forest area transformed by the dam-building activity of beaver, Castor canadensis, in Tierra del Fuego, Chile, where it is an exotic species. The dam alters hydrology, sedimentation, and light levels and so affects biogeochemistry and species habitats. (e) Mound made by leaf-cutting ant, Atta sexdens, in the “blanqueal” area near Fray Bentos, Uruguay; ants bring saline soil from depth to the surface, eliminating most vegetation on the mound. (f) The Southwestern Atlantic burrowing crab, Neohelice (Chasmagnathus) granulata, in Mar Chiquita coastal lagoon, Argentina, buries litter in excavation mounds and prevents litter export as a nutrient subsidy to adjacent estuary. (Photos: (a) Jorge Gutiérrez; (b) Cesar Fagúndez; (c) Martín Bruschetti; (d), (e) Clive Jones; (f) Pablo Ribeiro. From Gutiérrez and Jones 2008.)


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Figure 11.3 Cause-and-effect relationships representing a physically engineered ecosystem. The solid arrow for autogenic engineering is the physical manifestation of organismal structure inserted into the abiotic milieu. The dashed arrow for allogenic engineering represents the action of the engineer on other living or nonliving structures. (From Jones et al. 2010.)


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Figure 11.4 Biotic (vegetation structure) and abiotic (wind speed, cloud frequency, cloud liquid water content) factors interact to affect fog water capture. For a given elevation and climatic region, greater vegetation height and surface area will increase the fog capture.


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Figure 11.5 Control on ecosystems can come from (a) outside or (b) inside the ecosystem.


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Figure 11.6 Examples of different kinds of functional relationships between controlling variables and ecosystem characteristics.


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Figure 11.6 cont’d. Examples of different kinds of functional relationships between controlling variables and ecosystem characteristics.


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Figure 11.7 Both positive and negative feedbacks to climate, via atmospheric carbon dioxide, are possible with warming of a tallgrass prairie. An enhancement of root and soil respiration and a positive feedback to climate could result from stimulation of soil microbial activity associated with higher temperatures. This positive feedback would be weakened if there is acclimatization such that soil (root-plus-microbial) respiration does not continue to increase with increased warming. In contrast, if greater microbial activity leads to enhanced nutrient availability and plant growth, this could result in greater carbon sequestration in plants and soil—and a negative feedback to carbon dioxide concentrations in the atmosphere. (From Luo et al. 2001.)


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Chapter 11 Controls on Ecosystem Structure and Function © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer,