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
Part I Background Data and methods Result Analysis Discussion and Information 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 criticalrole in the national food supplyand agricultural production. Northeast China is one regionsubjected to high temperatureincreases .
III Shortcomings of current researchCurrent research on phenophases in Northeast China isconcerned with natural vegetation types, with little analysis ofcrop phenophases.Studies on regional crop phenophases thus far have beenmostly based on agroclimatic conditions, however, actualagricultural production has been confounded by otherenvironmental factors.Application of actual phenophase records in analyzing thetrend of maize phenophases is a good supplement to studiesbased on meteorological data alone.Such response mechanisms of regional maize phenophases toagroclimatic condition changes have yet to be examined.
Part II Background Data and methods Result Analysis Discussion and information Conclusion
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
II Data pre-processing Preparation of time-series NDVI data Extraction of phenological parameters based on smoothing NDVI series Timesat 3.0 for analyzing time-series remote-sensing data
III Extraction of phenological parameters a b c Number of ten-days
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
Part III Background Data and Methods Result Analysis Discussion and Information Conclusion
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.
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.
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.
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.
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 Data and methods Preliminary Discussion and information Analysis Conclusion
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.
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.