1. International Conference on Climate Change and Food Security 2011
Response of maize phenophases to temperature
changes in Northeast China during the past 20 years
Li Zheng-guo
Institute of Agricultural Resources and Regional Planning (IARRP)
Dr. Zhengguo Li Chinese Academy of Agricultural Sciences (CAAS)
16 Zhongguancun South Street, Haidian, Beijing, 100081, China
Email Zhenguoli@caas.net.cn

2. Part I
Background Data and methods Result Analysis Discussion and
Information Conclusion

3. I Research background
Crop phenophase is the one of key characteristics of
agricultural systems.
Crop phenophase refer to the timings of significant
morphological changes in crops, with seedling, heading and
maturity.
Understanding the dynamic mechanism of crop phenophase
can help formulate and improve policy-making in the face of
climate change.

4. II Study area
Northeast China plays a critical
role in the national food supply
and agricultural production.
Northeast China is one region
subjected to high temperature
increases .

5. III Shortcomings of current research
Current research on phenophases in Northeast China is
concerned with natural vegetation types, with little analysis of
crop phenophases.
Studies on regional crop phenophases thus far have been
mostly based on agroclimatic conditions, however, actual
agricultural production has been confounded by other
environmental factors.
Application of actual phenophase records in analyzing the
trend of maize phenophases is a good supplement to studies
based on meteorological data alone.
Such response mechanisms of regional maize phenophases to
agroclimatic condition changes have yet to be examined.

6. Part II
Background Data and methods Result Analysis Discussion and
information Conclusion

7. I Data source
The remote sensing data used
were the maximum value composites
of the SPOT/VGT NDVI data (VGT-
S10, 1998-2010, 1000 m).
The phenological observation data
used were from 79 agro-
meteorological stations in the
Northeast China .
Specifically, the data included the
number of days of the seedling stage,
heading/tasseling stage, maturity
stage and growth period.
Location of maize phenological stations

8. II Data pre-processing
Preparation of time-series
NDVI data
ƒ—••‹ ˆ
ƒ —…–‘
‹
Extraction of phenological
parameters based on
smoothing NDVI series
Timesat 3.0 for analyzing
time-series remote-sensing
data

9. III Extraction of phenological parameters
a
b
c
Number of ten-days

10. IV Meanings of phenological parameters
Phenological Maize phenological Relevant agricultural
Definition
parameters characteristics thermal conditions
Date when the NDVI fitting
Onset-of-growth Average temperature in
curve grew to a certain level Seedling stage
date May
(20% of the overall increase)
Date when NDVI fitting curve
End-of-growth Average temperature in
was reduced to a certain level Maturity stage
date Sep.
(20% of the overall decrease)
Duration from the onset-of-
Length of Length of temperature-
growth date to the end-of- Length of growth period
growing season allowing growth period
growth date

11. Part III
Background Data and Methods Result Analysis Discussion and
Information Conclusion

12. I-1 Rising trend of temperature conditions
Average temperature in May (T5) Temperature-allowing growth period
Average temperature in September(T9)
• The tendency rate of T5 in Heilongjiang, Jilin and
Liaoning reached 0.072, 0.094 and 0.051°C·y–1.
• The tendency rate of T9 in Heilongjiang, Jilin and
Liaoning reached 0.052, 0.065 and 0.075°C·y–1 .
• The temperature-allowing period for Heilongjiang,
Jilin and Liaoning was extended with tendency rates
of about 0.29, 0.15 and 0.24 d·y–1, respectively.

13. I-2 Spatial pattern of temperature rise
Annual tendency rate of T5 Annual tendency rate of T9
Over the past 20 years, positive trends of average temperature in May and
September, as well as an extended temperature-allowing period, were found
in most areas of the three provinces.

14. II-1 Temporal trend of maize phenophases
Maize seedling stage Maize growing season
Maize maturity stage
• The maize seedling stage in 2000–2009 for
Heilongjiang, Jilin and Liaoning, compared with that in
1990–1999, was advanced by approximately 2, 0.05
and 1 d .
• Compared with 1990–1999, the maize maturity stage
in 2000–2009 was postponed by 1, 2 and 4 d.
• The extension of maize growth season in Liaoning was
about 6 d, followed by that in Jilin and Heilongjiang,
both with 2 d.

15. II-2 Spatial variation of maize phenophases
Maize seedling stage Maize growing season
Maize maturity stage
• The ranges of maize seedling stage, maturity stage
and growing season during 1999–2010 were less than
10 d for most area. Only west part of Songnen Plain
and east part of Sanjiang Plain were more than 20 d.

16. III-1 Responses of maize seedling stage to T5
Correlation coefficients and significance levels between maize seedling stage and T5 (1990–2009)
The negative correlation coefficients in the north of Songnen Plain in Heilongjiang, the
middle and east of Jilin, and the middle of Liaoning were mostly < -0.60 . This indicated
an obvious advanced maize seedling stage in response to the rise of T5.

17. III-2 Responses of maize maturity stage to T9
Correlation coefficients and significance levels between maize maturity stage and T9 (1990–2009)
The correlation analysis showed the correlation coefficients in the middle and east of Jilin
were mostly > 0.60 . This suggested a significant postponement of maize maturity stage in
response to the rise of T9.

18. III-3 Responses of maize growth period
Correlation coefficients and significance levels between the temperature-allowing period and maize growth
period (1990–2009)
For the east and north of Sanjiang Plain in Heilongjiang, middle and east of Jilin, and some
areas of Songnen Plain, the correlation coefficients were mostly > 0.60, which indicated an
obviously advanced maize growth stage in response to the extension of the temperature-
allowing period.

19. Part IV
Background Data and methods Preliminary Discussion and
information Analysis Conclusion

20. I Conclusion
In the context of global climate change, phenophase change not
only represents the passive adaption of crops, but also reflects
active adaption by adjusting crop varieties in agricultural
production.
In response to the rising trend of T5, advancing of the maize
seedling stage occurred, which was most significant in the north
of Songnen Plain, the middle and the east of Jilin.
Corresponding to the rising trend of T9, the maize maturity
stage showed a postponement trend, which was more significant
in the middle and east of Jilin.
In response to the extending trend of the temperature-allowing
period, the maize growth period showed an overall significant
extending trend.

21. II Discussion
Climate warming had resulted in changing phenophases of
maize in Northeast China.
Further investigation
Fluctuation and uncertainty of regional climate change.
Different causes for the changes in maize phenophases.
Crop phenophase observation data does not fully reflect the regional
response of the crop growth to environmental conditions in a timely
manner.

22. Thank you very much for your attention!