in
al
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
a
300
_ LOS «279.4381 - 1.6362 x Latitude
| RÉ-0.1402
280 - A
260 -
9. i
8240 -
a i
220 -
200 -
"atitude (dj 2 2
b
LIG = 279.6161 — 9.4874 x Latitude
160 - R* - 0.9713
= 140 —
= 120 -
o
ge " ‘Éatitude edi m 2
Figure 7: Latitudinal gradients of vegetation phenol-
ogy along the transect (a) LOS; (b) LIG. The equations
show the phenological metrics as a function of latitude.
The vertical lines are the temporal standard deviations
of these latitudinal gradients.
T T
12 14
Y Y
1 18
Latitude
Figure 8: Spatial distributions and interannual variation
of MinG breakpoints. Small points are interannual vari-
ations of annual minimum EVI along the latitude, large
points are interannual variations of breakpoints. The
north and south boundaries of these breakpoints are in-
dicated by two vertical lines. The numbers give the ac-
tual latitudes of north and south boundary.
From an evolutionary point of view, the vegetation phe-
nology is the result of biological adaption to historical
climate. However, it is hard to study the variations of
vegetation phenology in the time dimension over a short
period. The assumption of using sub-continental scale
transects to study global change problems is that the spa-
tial variation can be used as a surrogate of the temporal
variations (Koch et al., 1995). So that even if it is dif-
ficult to predict vegetation phenology in future, we do
have the possibilities to derive the vegetation phenology
under different climate change scenarios through the in-
vestigation in the spatial dimensions, which is more fea-
sible (Cook and Heerdegen, 2001).
The southward decreasing trends of vegetation produc-
tivity (annual integral EVI) can be attributed to both in-
ternal and external factors. Internally, tree species rich-
ness are decreasing southward along NATT (Williams
et al., 1996). Previous studies suggested that decreasing
of woody richness always associates with decreasing of
vegetation productivity (Waring et al., 2006, MacArthur,
1969). Externally, environmental factors , including pre-
cipitation and soil water content, also have significant
north-south decreasing trend in this area (Williams et
al., 1996).
In the temporal scale, large interannual variations of veg-
etation phenology may suggest that the environmental
factors, which control vegetation growth, should have
corresponding interannual variations in this area. In the
NATT, both precipitation amount and precipitation pat-
tern have significant interannual variations (Cook and
Heerdegen, 2001).
In this study we used annual minimum EVI, which is
considered as an indicator of evergreen component, to
investigate the spatial distribution of a biogeographical
boundary in the NATT area. However, in addition to
annual minimum EVI, we still have seven other pheno-
logical metrics available. This study suggested the po-
tential to define the biogeographical boundary from a
vegetation phenology perspective. Future research will
attempt to identify this boundary using other phenolog-
ical metrics.
In conclusion, this study characterized eight vegetation
phenological metrics for a sub-continental tropical tran-
sect spanning the past 11 years. Our results showed that
these metrics had significant spatial patterns as well as
considerable interannual variations. However, the en-
vironmental control on these phenological patterns re-
mains unclear, which requiring further investigations with
the collaboration efforts from both remote sensing and
climatological perspectives.
ACKNOWLEDGEMENTS
This research was partially support by ARC-(DP1115479)
grant entitled “Integrating remote sensing, landscape flux
measurements, and phenology to understand the impacts
of climate change on Australian landscapes" (Huete, CI).
The first author appreciates the financial support from
Chinese Scholarship Council, which enables the first au-
thor to study abroad and focus on his research.
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