气候变化严重影响农业生产，危及粮食安全。中国是世界第二大玉米生产国，也是最大的玉米消费国。分析气候变化对玉米单产的影响可以为国家和国际经济和政治提供有效的指导。面板模型无法确定数据集的组间异方差、截面相关和组内自相关，因此我们采用广义最小二乘模型（FGLS）来评估1979-2016年气候变化对中国玉米单产的影响。得到以下结果：（1）在1979-2016年期间，温度升高对中国玉米单产产生了负面影响。温度每升高1℃，玉米单产减少5.19 kg 667 m^-2（1.7％）。在此期间，降水仅略有增加，因此其对玉米单产的影响可以忽略不计。降水量每增加1 mm，玉米单产将增加0.043 kg 667 m^-2（0.014％），这是微不足道的。（2）气候变化对玉米单产的影响在空间上有所不同，在中国南部地区受到的影响更大。在该地区，温度每升高1℃，玉米单产下降7.49 kg 667 m^-2，而温度对中国北方玉米单产的影响不明显。降水量每增加1 mm，华南玉米单产增加0.013 kg 667 m^-2，而华北玉米增加0.066 kg 667 m^-2。（3）玉米作物对气候变化的适应力强，1990-2016年期间的中国南北部温度的边际效应均小于1979-2016年期间。

Received  25 July, 2017    Accepted  19 February, 2018
 

The spatial-temporal patterns of grain production and consumption have an important influence on the effective national grain supply on condition of tight balance in the total grain amount in China. In this paper, we analyze the spatial-temporal patterns of grain production, consumption and the driving mechanism for their evolution processes in China. The results indicate that both gravity centers of grain production and consumption in China moved toward the northern and eastern regions, almost in the same direction. The coordination of grain production and consumption increased slightly from 1995 to 2007 but decreased from 2000 to 2007. There is a spatial difference between the major districts of output increase and the strong growth potential in grain consumption, which indicates an increasing difficulty in improving the regional coordination of grain production and consumption. The movement of the gravity center of grain production is significantly correlated with regional differences in grain production policy, different economic development models, and spatial disparity of land and water resource use. For grain consumption, the main driving factors include rapid urbanization, the upgrade of food consumption structure, and distribution of food industries.

The paper studies the relationship, adjustment ability, path, efficiency and intensity of price transmission in the swine industry chain in China, which consists of the prices of corn, compound feed for fattening pig, piglet, pig and pork. Monthly prices covering a period of 18 yr (1994-2011) are analyzed using a Market-Chain Cooperated Model (MCM). The empirical results show that there exists a stable long-term cointegration and short-term dynamic relationship in the price system. First, the adjustment speed of each price series is very slow and the transmission path is top-down and one-way significantly. Second, the price from upstream to downstream lags about 2 mon, while there is no lag in price transmission from midstream to downstream. Third, in terms of price transmission intensity, the price of pig impacted greatly on pork price, not only in the current period but also through the whole period. Besides, the price of corn has the largest lagged effects on pork price. According to the above empirical results, we suggest that government should strengthen monitoring and early warning of the swine industry chain, especially the upstream and midstream, attach great importance to the timely adjustment of feed prices and perfect the measures of price subsidy.