Chapter 10 Ecosystems in a Heterogeneous World © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

2 Figure 10.1 Examples of spatial heterogeneity relevant to ecosystem science. Although these figures represent medium to coarse scales, spatial heterogeneity can exist on any scale, from intervals of millimeters to continental scope. (a) A treefall gap contrasting with the closed canopy of an old growth hemlock-oak forest on the grounds of Montgomery Place on the banks of the Hudson River. (b) A model of the surface elevation of the Dead Run watershed in metropolitan Baltimore, MD, based on LiDAR imagery. Both natural and modified surface features, such as roadbeds, leveled areas for large buildings and parking lots, culverts, and channelized drainages, are shown. Blue represents low elevations, and red represents higher elevations. (c) A mountainous landscape in Bhutan, showing cultivated and grazed fields, farmhouses, fallow field shrubland, and patches of intact and lightly managed forest ranging from lower-elevation pine, through oak, to coniferous dominance higher on the slopes of the Himalayan front range. (d) A vacant lot in an old rowhouse neighborhood in Baltimore, MD, that has been converted to a tidy lawn and flower garden by neighboring residents. (Photos (a), (c), and (d) copyright S.T.A. Pickett. Photo (b) copyright Dr. Andrew Miller, University of Maryland, Baltimore County. All used by permission.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

3 Figure 10.2 Differentiation of the elements of heterogeneity within patches, illustrated by coarse land cover types (left) present in human settlements. In this urban example, which is based on the aerial photograph on the right, the elements of terrestrial patchiness are dominant kinds of vegetation, including grass or woody, surfaces including bare or paved, and buildings. Water is also mapped. Patches can be discriminated either by computer algorithm or manually based on the clustering of the different kinds of elements in space, and the abruptness of shifts in distribution of the three kinds of elements. Principles of urban patch classification are described in Cadenasso et al. (2007). (Image copyright M.L. Cadenasso and K. Schwarz, and used by permission.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

4 Figure 10.3 A landscape ecology perspective on ecosystem heterogeneity. This landscape in Dutchess County, New York, combines terrestrial and aquatic patches; wild, cultivated, and built patches; and a transportation network. The landscape ecology perspective invites ecologists interested in populations, communities, and ecosystems to understand how patch composition, patch structure, patch adjacency, and the fluxes among patches, both above and below the surface, determine landscape and ecosystem function. (Image copyright S.T.A. Pickett, and used by permission.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

5 Figure 10.4 A fire mosaic in coniferous forest in the Denali National Park and Reserve, and adjacent areas of Alaska from 1950 through Ages of stands postfire are shown in decadal classes. In addition, whether a fire was set by people or ignited by natural forces is indicated. (Image in the public domain.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

6 Figure 10.5 A pit dug by a foraging animal in Australian arid landscape. Such pits are common features in desert landscapes where animals dig to find the underground storage organs of perennial plants. Seeds, organic matter, and sediment accumulate in such pits, and the disruption of the microphytic soil crust permits enhanced water infiltration during rainfall events that are large enough to generate overland flow. Hence, pits are resource and regeneration hotspots. (Photo copyright S.T.A. Pickett.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

7 Figure 10.6 An arid landscape near Adelaide, Australia, showing the contrast between shrub-dominated patches and the mosaic dominated by microphytic soil crust. Shade, sediment, seeds, and leaf litter are among the factors that differ beneath the shrub-dominated patches compared to the crusted areas among shrubs. (Photo copyright S.T.A. Pickett.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

8 Figure 10.7 Spatial complexity in a small stream ecosystem (Black Creek in the Hudson Valley of New York state). In the background is an open canopy area above the stream, in which sunlight and temperature would be higher than elsewhere, while leaf litter input would be less. In the middle ground are two contrasting habitats, a pool of flowing water and a gravel bar through which subsurface or hyporheic flow would pass. In the foreground are downed logs, behind the submerged portions of which sediment and organic matter would accumulate. Each of these habitats will have different dynamics of material processing. (Photo copyright S.T.A. Pickett.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

9 Figure 10.8 Input of atmospheric nutrients and pollutants at a forest-field edge; DIN=dissolved inorganic nitrogen. Bulk water input in the open field represents the ambient nutrient flux from the atmosphere to the terrestrial ecosystem. Intact forest edge experiences higher inputs of sulfate, nitrate, and ammonium than do the forest interior or the open field. (Data from Weathers et al ) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

10 Figure 10.9 Cattle corrals in Tanzania, East Africa. The corrals are the circular and irregular forms outlined by shrubs and small trees. Active corrals contain structures as well. An abandoned corral with a degenerating woody boundary appears near the center of the photograph. These systems are similar to those investigated by Porensky (2011). (Photo copyright S.T.A. Pickett.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

11 Figure Generalized trends in phosphorus (P), a limiting nutrient over primary successions spanning millions of years. The total amount of P, an element with a geologic rather than a gaseous source (see Chapter 8), declines in the system over time. Labile P available to plants is a small and declining fraction of the total. Plant content is always low compared to insoluble or occluded P and that bound in soil organic matter is low, but peaks in middle ranges of the long succession. Trends redrawn from Vitousek (2004), who confirmed the applicability of this model to ancient volcanic succession across the Hawaiian Islands. © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

12 Figure Diagrammatic representation of the contrast between pulse and press events. Pulse events, whatever the form of their onset, are relatively quick to appear as well as quick to dissipate, though they may have persistent effects. Press events, in contrast, represent persistent changes in the driving factors or structure of an ecological system. Pulse events are exemplified by fires, hurricanes, and floods. Press events include such things as climate shifts, persistent environmental stressors, the exposure of new surfaces by Earth movements, or the invasion of new dominant organisms into a region. © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

13 Figure A conceptual alphabet illustrating the complexity of ecological events not represented by the simple pulse–press contrast. For each graph, the x-axis represents time and the y-axis represents the intensity of the event or of the effect. The top row shows different forms of onset, duration, or release of an ecological event, such as disturbance or imposition of stress. Specific real events can be described by combining the appropriate forms of onset, duration, and release. The bottom row indicates aspects of complexity in the responses to ecological events. Effects can be rapidly emerging, slowly emerging, short persistence, long persistence, gradually declining, or quickly declining. In the lower right panel, the existence of a peaked form of effect is shown by combining rapid emergence, no persistence, and rapid decline. This panel further illustrates the difference between immediately felt and lagged effects. The immediate effect arises directly after the event, and lagged effects are illustrated by the dashed line connecting the event with the right, delayed peak. Lags may exist for effects possessing any of the other combinations of emergence, duration, and decline as well. (Figure courtesy of the Baltimore Ecosystem Study, Long-Term Ecological Research Project.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

14 Figure Contrast in water movement between nonurban and urbanized watersheds. Flow paths and magnitudes of flows across different flow paths are modified by development of human settlements. For example, gutters and curbs impose new headwater structures, storm drains redirect flow below surface layers and efficiently connect stream channels with rainfall, and alteration of vegetation type and cover changes infiltration and evapotranspiration rates. (Diagram from the Maryland Department of Environment and in the public domain.) © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).

15 Figure The general ecosystem heterogeneity framework introduced in Chapter 1, with the addition of interactions representing both internal and external sources of heterogeneity to reflect patterns and processes emphasized in this chapter. Bowties represent controls, and arrows represent flows. © 2013 Elsevier, Inc. All rights reserved. From Fundamentals of Ecosystem Science, Weathers, Strayer, and Likens (eds).