294
30
G.A. Bradshaw et al.
log (m)
-0.20
Figure 14.11. Wavelet cross-covariance calculated between hemlock seedling and
downed log distributions. The x-axis refers to the lag at which correlation between
the two variables occurs; the y- axis refers to the scale at which correlation occurs
(meters). Overstory canopy gap and hemlock seedling distribution are correl ated
on average at 5 m and 25 m in this old growth Douglas-fir stand described in
Figure 14.10.
From the geomorphic perspective, landforms processes influence ecosystem heterogeneity in several ways, by (1) modulating resource quality
and availability (e.g. , elevational modulation of temperature, nutrient
distribution); (b) controlling flow of energy and material through the
landscape (e.g., water movement) ; and (c) affecting the timing, frequency ,
and distribution of disturbances (e.g., wildfire, erosion, and wind; Grant
et al., 1990; Swanson , Kratz, Caine , & Woodmansee, 1988). The timing
distribution, and spatial arrangement of land movement and disturbance
in general relates to the " range of natural variability ," that is, a set of
conditions or states that an ecosystem may have occupied prior to
influence of European settlers (Swanson et al., 1994). Successional patterns and forest stand mosaics vary with disturbance intensity, location,
and extent reflecting local and regional controls of climate, geology,
vegetation dynamics (Delcourt, Delcourt, & Webb , 1983). It is instructive
30
G.A. Bradshaw et al.
log (m)
-0.20
Figure 14.11. Wavelet cross-covariance calculated between hemlock seedling and
downed log distributions. The x-axis refers to the lag at which correlation between
the two variables occurs; the y- axis refers to the scale at which correlation occurs
(meters). Overstory canopy gap and hemlock seedling distribution are correl ated
on average at 5 m and 25 m in this old growth Douglas-fir stand described in
Figure 14.10.
From the geomorphic perspective, landforms processes influence ecosystem heterogeneity in several ways, by (1) modulating resource quality
and availability (e.g. , elevational modulation of temperature, nutrient
distribution); (b) controlling flow of energy and material through the
landscape (e.g., water movement) ; and (c) affecting the timing, frequency ,
and distribution of disturbances (e.g., wildfire, erosion, and wind; Grant
et al., 1990; Swanson , Kratz, Caine , & Woodmansee, 1988). The timing
distribution, and spatial arrangement of land movement and disturbance
in general relates to the " range of natural variability ," that is, a set of
conditions or states that an ecosystem may have occupied prior to
influence of European settlers (Swanson et al., 1994). Successional patterns and forest stand mosaics vary with disturbance intensity, location,
and extent reflecting local and regional controls of climate, geology,
vegetation dynamics (Delcourt, Delcourt, & Webb , 1983). It is instructive