Crop yields impacted by ENSO episodes on the North China Plain: 1956–2006

Yuan LIU            Xiaoguang YANGIEDA, CAAS        CAU7th Nov 2011 IEDA,CAAS CAU CSIRO

Outline

• Background

• Data and Methods

• Results

• Summery

Background

• ENSO (El Niño - Southern Oscillation) is the most prominent driver for inter-annual variability of climate around the world, which affects regional cropproduction through its impacts on regional climate.

• Climate anomalies: drought, flooding and hurricanes

• Agriculture worldwide: Plants, Fishing, Agricultural economics

• The North China Plain (NCP) (350,000 km2) is one of the largest agriculturalproduction areas in China. There is still lack of detailed studies on therelationship among ENSO, regional climate and crop production in the NCP.

• Well, the linkage of ENSO and crop yield in the NCP will potentially providethe insight to climate change impact on the food security subject in China.

Objectives

• Case study: winter wheat and summer maize

• to analyse the relationships between ENSO and regional climateanomalies

• to ascertain whether the grain yield of the two main crops in the NCP, isaffected by the different phases of ENSO

What is ENSO• ENSO is a planetary scale

phenomenon, involving thecoupling of the ocean and theatmosphere.

• SOI and SST have been used asindicator to describe ENSO events.

• The rainfall region is different in ElNiño and La Niña years near theequator.

ENSO and climate in China

• ENSO is a significant climatic signal to the summer precipitation fluctuation in the NCP;

• Rainfall tends to be low in El Nino years in the region, the reverse pattern is occur in LaNina years

• Temperature response is not as strong as rainfall

Is it completely opposite conditions in the El Niño and La Niña years?

The correlation between the summer rain fall in China and the SST in the eastern equatorial Pacific

in the developing stage of ENSO. Shaded areas indicate the coefficient of correlation above 0.4.

(Huang RH and Wu YF, 1989)

Enso precipitation anomalies in relative percentage distribution in ENSO year

(Liu YQ and Ding YH, 1995)

Relationship between ENSO and summer precipitation in China

ENSO and yield in the world

• ENSO also negatively or positively impacted the crop yield in the world:

• Negative: maize in Zimbabwe, rice in the Philippines and Indonesia, cereals production in Indian…

• Positive: corn in U.S., sorghum and soybean in Argentina…

Study Sites

Nanyang : 33.0oN, 112.6oE, 80.0mZhengzhou : 34.8oN, 113.7oE, 129.2mLuancheng : 37.9oN, 114.6oE, 52.5m

Weather and Crop Data

Item Nanyang Zhengzhou Luancheng

WeatherData

Daily temperature1956—2006Daily sunshine hour

Daily precipitationCrop Data Grain yield 1956—2006

All data were obtained from China Meteorological Agency and China Statistics Press.

Categorization of ENSOWarm event years

(El Niño) Neutral years Cold event years(La Niña)

1957 1958 1984 1956

1963 1959 1985 1964

1965 1960 1989 1967

1969 1961 1990 1970

1972 1962 1992 1971

1976 1966 1993 1973

1982 1968 1994 1975

1986 1974 1995 1988

1987 1977 1996 1998

1991 1978 2000 1999

1997 1979 2001

2002 1980 2003

2006 1981 2004

1983 2005

Based on Japan Meteorological Agency (JMA).

Statistical Analysis1. Trend analysis:

• using Student’s t-test to examine the slope confidence (statistically significant at 95%and 99% levels)

• using Kolmogorov–Smirnov (KS) test to examine the contrasting distributions

2. Data Standardization:• removing such non-climate-related influences as improved varieties, better

management, more irrigation, and higher doses of fertilizers introduced since 1956.

Raw (Grey dots) and smoothed (black line) time series (a) and the detrended residual (b) of wheat yield around whole China, 1954-2008

Manager Report

Soil pH

Environmentalsection

Ecologicalsection

Crop

Crop A

Crop B

￤￤

Surface residue

Soil water

Soil N

Soil P

Soil erosion

Meteorological data

ENGINE

Pasture

3. APSIM modelAPSIM = (Agricultural Production Systems Simulator)Structure: Processes represented as modules

Model CalibrationYucheng, 2000-2001 Treatment1,Beijing, 2004-2005

NRMSE: 36% NRMSE: 28%

(Li Yan, 2006)

Model ValidationYucheng, 2000-2001 Treatment1,Beijing, 2004-2005

Yield

NRMSE: 21%

(Li Yan, 2006)

APSIM model can be applied under the monsoon climate

conditions in the NCP to simulate the crop growth dynamics

and grain yields of wheat and maize.

Simulated Scenario

• The validated APSIM model was used to simulate the growth andgrain yield of wheat and maize crops using historical climate data(1956-2006)

• One variety of wheat and maize (from 1981) was used for thesimulations during the whole period to eliminate impact of varietalchanges

• Potential/Rain-fed yields simulated (different of irrigation regimes)were conducted under conditions of fully water and fertilizer supplyto eliminate impact of water and nutrient stresses

Climatic Background

Red nodes are for El Niño event, blue nodes are for La Nina event, black for normal year.

Annual precipitation had slightly declined over the past 50yr without significant.

Warming trends were occurred , especially significant increase in minimum temperature after 1980.

Sunshine hour had decreased significantly at three sites.

Climate Trends on ENSO phasesClimatic 

Parameters PhasesNanyang Zhengzhou Luancheng

Trend Trend Trend

P

El Niño ‐22 ‐22 ‐8

Neutral 8 6 11

La Niña ‐57* ‐47 ‐53

SH

El Niño 1.4 3.1 5.3

Neutral ‐0.9 ‐1.3 ‐1.3

La Niña 6.9 5.5 7.1

T_avg

El Niño 2.6 3.0 2.1

Neutral ‐1.3 ‐1.2* ‐1.4

La Niña 6.6* 7.5* 9.7

T_max

El Niño 2.3 2.8 0.6

Neutral ‐1.3 ‐1.3* ‐1.2

La Niña 9.4* 10.3 10.9

T_min

El Niño 1.6 3.7 5.9

Neutral ‐1.2 ‐1.1 ‐1.4

La Niña 1.0 2.1 4.6

%/decadee.g. Precipitation

The 5 climatic variables had the sametrend in both El Nino and La Nino year.

Precipitation had declined in both Ell Nino and La Nina year and increased in Neutral year.

Probability of Climatic parameters on ENSO yearsP

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bilit

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exc

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nce

Probability exceedance of precipitation in La Niña years are higher than the El Nino phases, the Neutral years had the similar trends with total years.

Probability of potential yields on ENSO years

Under full of water regime in crop growth, there was no significant difference in both El Niño and La Niña years and even Neutral years,

Probability of rainfed yields on ENSO years

Under no irrigation regime in the crop growth, for wheat the probability is lower in La Niña years than that in El Niño years at Nanyang and Zhengzhou sites.

For maize, the probability in El Niño years is lower than other phases at Luancheng and Zhengzhou.

Probability of statistical yields on ENSO years

At the provincial level, thecategories had little impact onactual yields in well-managedfields.Maize production was morevulnerable in El Nino and LaNina years than wheatproduction was.

Summary• With all the years together over the past 50 years, no significant

trend in annual climatic variables at three sites.

• But there seems to be a trend of decrease in annualprecipitation in both El Niño and La Niña years, while a trend ofincrease in neutral years. In general, the probability ofexceeding certain amount of rainfall was higher in La Niñayears than in El Niño years

• ENSO events affect maize yield more than wheat yield,particularly under conditions of insufficient irrigation watersupply.

• The yield was lower in El Nino and La Nina years because oflower precipitation and higher in the Neutral year because oflonger sunshine hours and additional irrigation.

Thank you for your attention!

IEDA, CAAS

Yuan LIU

Email: Liuyuan@ieda.org.cn