Ecosystems and Spatial Patterns - Ecological Systems - page 106

Interactions Among Spatial Processes
Spatial processes within ecosystems interact with each other directly as well as with
the spatial legacies of previous, historical processes. In this way, spatial patterns
and processes are connected through a dynamic and persistent feedback loop [ 32 ].
Spatial legacies can be thought of as a form of spatiotemporal connectivity among
disjunct spatial processes or events that are mediated by forest succession and
aging. The legacies of historical processes as represented by contemporary patterns
can have long-lasting and significant impacts on biodiversity [ 16 , 35 ] and efforts to
sustainably manage forest ecosystems [ 23 , 36 ].
Spatial legacies can be defined at different scales and describe persisting features
within a stand, landscape, or ecosystem. The term “legacy” can refer to fine-scale
structural complexity following windthrow [ 37 ], landscape level forest age struc-
ture [ 18 , 38 ], disturbance-mediated seed availability [ 39 ], and residual forest
structure following fire [ 39 , 40 ]. Because patterns of historical land use can
influence contemporary ecosystem composition, configuration, and ecosystem pro-
cess dynamics long after the actual event [ 41 ], a better understanding of spatial
legacies and their influence on ecosystem dynamics and landscape change over
time is needed and requires novel spatial and temporal methods of investigation
and analysis.
From the perspective of sustainability, spatial disturbance legacies, including
those created through human activities, represent future ecosystem patterns and
future challenges for sustainable management. Gustafson et al. [ 42 ] showed that
new forest harvest goals are not easy to achieve due to existing conditions when
examining shifting forest management rules. Wallin et al. [ 38 ] demonstrated that
shifts from a dispersed to an aggregated harvest pattern did not immediately result
in a change in forest attributes such as patch size and edge density. Instead, new
harvest rules had to work around the legacies of previous patterns, and original
patterns were enforced. Similarly, Gustafson and Rasmussen [ 43 ] found that when
varying parameters in a harvest simulation model, the persistent legacies of previ-
ous harvest patterns resulted in timber harvest shortfalls. Using a simulation
approach, James et al. [ 18 ] demonstrated that legacies in forest age structure created
through forest management can persist for over 100 years. Ecologically, the
consequences of these legacies interacting with new disturbances can result in
greater system variability and gradual ecosystem degradation [ 43 - 45 ] or alternative
stable states [ 21 , 46 ].
Multiple Spatial Scales
Inferring the characteristics of spatial processes through analysis of spatial pattern
is a central goal of most ecological studies as it is often very difficult to analyze the
processes of interest directly. This can be particularly challenging when several
types of pattern ( Fig. 7.1 ) and underlying processes are present ( Fig. 7.2 ). The