(1) Leaf production period: This occurred normally from
Julian day 115 to 140. The commencement of this
period was somewhat early in 2000 (Julian day 112)
and somewhat late in 1997 (Julian day 117). The most
obvious characteristic of this period is the rapidly
increasing LAI from 0.0 to near maximum values. The
daily rates of LAI increase during this period were
similar across the years (0.22 day1), leading to the
similar developing pattern during this period across
years;
(2) Period of constant leaf area: From Julian day 141 to
270, LAI remained constant near the maximum values
of each year during this period. The Fourier transformed
LAI curves, however, showed a slight LAI
depression around Julian day 200;
(3) Period of leaf senescence: From Julian day 271 to the
end of the year, LAI dropped from the maximum to
almost zero at a relatively slower rate compared with
rate of leaf production. Moreover, the interannual
variation of the rate of LAI decrease was quite large.
The most rapid rate of decrease was in the year 1996 at
0.13 day1, while the lowest rate of decrease was only
0.067 day1 in 1997. For the other years, the rates of
LAI decrease were 0.090 (1999), 0.111 (2000), and
0.103 day1 (2001). These variations may account for
the different patterns of LAI within even the same time
periods in the different years