Sr. Herwitz et al., CO-REGISTERED AERIAL STEREOPAIRS FROM LOW-FLYING AIRCRAFT FOR THE ANALYSIS OF LONG-TERM TROPICAL RAIN-FOREST CANOPY DYNAMICS, Photogrammetric engineering and remote sensing, 64(5), 1998, pp. 397-405
Ground-based censusing of tagged trees in permanent plots has been the
standard research method for monitoring the long-term dynamics of tro
pical rainforest tree populations. This paper describes a method for q
uantifying the turnover and crown growth rates of tropical rainforest
canopy trees over an 18-year period using a temporal sequence of large
-scale aerial stereopairs. The stereopairs were co-registered using an
array of control points that consisted of surveyed aerial targets and
primary branch bifurcation points (BIPs) having the same persisent ge
ometry and spatial coordinates in the crowns of selected canopy trees.
Six crown size classes were distinguished, and critical late stages i
n the life history of mature canopy trees were identified. The smalles
t crown size classes (<20 and 20 to 40 m(2)) experienced, more than 75
percent of the canopy tree mortality over the 18-year period; Of the
canopy trees that survived, the mid-range 60- to 80-m(2) crown size cl
ass was identified as a critical late stage, having both the highest m
ean crown growth rate (2.42 m(2) yr(-1) among those trees that exhibit
ed positive growth as well as the highest proportion of trees (47 perc
ent) experiencing a reduction in crown size. The results demonstrate t
hat high resolution, aerial stereophotography from low-flying aircraft
can serve as a valuable tool for demographic research in tropical rai
nforest ecosystems.