Dr. Zhengguo Li Institute of Agricultural Resources and Regional Planning (IARRP)Chinese Academy of Agricultural Sciences (CAAS)16 Zhongguancun South Street, Haidian, Beijing, 100081, ChinaEmail Zhenguoli@caas.net.cn

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

Part I

Background Information Data and methods Result Analysis Discussion and

Conclusion

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.

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 .

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.

Part II

Background information Data and methods Result Analysis Discussion and

Conclusion

I Data source

Location of maize phenological stations

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.

II Data pre-processing

Preparation of time-series NDVI dataExtraction of phenological parameters based on smoothing NDVI seriesTimesat 3.0 for analyzing time-series remote-sensing data

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III Extraction of phenological parameters

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Number of ten-days

IV Meanings of phenological parameters

Phenological parameters Definition Maize phenological

characteristicsRelevant agricultural thermal conditions

Onset-of-growth date

Date when the NDVI fitting curve grew to a certain level (20% of the overall increase)

Seedling stage Average temperature in May

End-of-growth date

Date when NDVI fitting curve was reduced to a certain level (20% of the overall decrease)

Maturity stage Average temperature in Sep.

Length of growing season

Duration from the onset-of-growth date to the end-of-growth date

Length of growth period Length of temperature-allowing growth period

Part III

Background Information Data and Methods Result Analysis Discussion and

Conclusion

I-1 Rising trend of temperature conditions

Average temperature in May (T5)

Average temperature in September(T9)

Temperature-allowing growth period

• 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.

I-2 Spatial pattern of temperature rise

Annual tendency rate of T9Annual tendency rate of T5

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.

II-1 Temporal trend of maize phenophases

Maize maturity stage

Maize growing seasonMaize seedling 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.

II-2 Spatial variation of maize phenophasesMaize seedling stage

Maize maturity stage

Maize growing season

• 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.

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.

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.

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.

Part IV

Background information Data and methods Preliminary

Analysis Discussion and

Conclusion

I Conclusion

In the context of global climate change, phenophase change notonly represents the passive adaption of crops, but also reflectsactive adaption by adjusting crop varieties in agriculturalproduction.In response to the rising trend of T5, advancing of the maizeseedling stage occurred, which was most significant in the northof Songnen Plain, the middle and the east of Jilin.Corresponding to the rising trend of T9, the maize maturitystage showed a postponement trend, which was more significantin the middle and east of Jilin.In response to the extending trend of the temperature-allowingperiod, the maize growth period showed an overall significantextending trend.

II Discussion

Climate warming had resulted in changing phenophases of maize in Northeast China.

Further investigationFluctuation 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.

Thank you very much for your attention!