Environmental Engineering Reference
In-Depth Information
Succession
Succession
Succession
Disturbance
Processes
Fire
Insects
Harvest
Spatial
Patterns
Large range of
patch sizes
Small range of
patch sizes
Temporal
Patterns
Continuous
(several years)
Discrete
Discrete
Individual
Realizations
Observed Spatial Pattern
Fig. 7.2 Spatial and temporal scales of forest disturbances. Interactions among disturbances are
dependent on the unique successional responses to each disturbance (
row 1
). Historical forest
systems were governed by interactions mainly between fire and insects (
arrows
) although pres-
ently, logging also interacts with these historical processes. Columns show the unique spatial and
temporal attributes of each of the three main boreal forest disturbance agents: fire, insects
(i.e., SBW), and harvesting (i.e., logging). These different spatial features result in different
realization, or spatial signatures, of each disturbance (
row 4
). Interactions among these different
processes produce a single observed spatial realization of spatial structure that contains elements
of each of the different processes (
row 5
). Observed patterns contain elements of all three main
processes; the objective of spatial analyses is to begin to tease apart the relative contributions of
different processes to observed spatial pattern (
row 6
)
ponderosae
), are less discrete and tend to produce more complicated spatial struc-
ture and continue to affect forest structure at a given location for multiple consecu-
tive years [
29
].
Each disturbance also has a unique relationship with forest regeneration pro-
cesses [
30
] such that forest succession is tightly coupled to the type of disturbance
that reinitiates stand development. These relationships determine future forest
structure. Historically, fire and insects were the main disturbances in North Ameri-
can forest systems. Adaptations to disturbance such as serotiny in pine species
