Fluctuation of agroclimatic zones and its impact on agricultural production in China

Abstract

Accumulated temperature above 100°C (Σt) and minimum annual temperature (Tm) are the major indexes for demarcating agroclimatic thermal zones. The paper calculated the return period (τ) of Σt andTm, and the shift of Σt-andTm-isopleths with τ. The results show: (1) According to the magnitude of shift of Σt-and Tm-isopleths, in Northeast China, Inner Mongolia and northern Xinjiang the fluctuation of thermal resources in growing season from year to year is the greatest and strongly impacts the yield of annual thermophilous crops, but in the Changjiang River basin the fluctuation of the low temperature in winter is the greatest and seriously injures the perennial subtropical tree crops. (2) In the anomalous cool summer year with τ=30, the northern boundaries of the southern subtropical, northern subtropical and warm temperate zones and the southern boundary of the frigid temperate zone in China could be expected to shift southward 150, 220, 250 and 300 km from their normal positions, respectively. (3) In the anomalous cold winter year with τ=30, the northern boundaries of the tropical, southern subtropical, northern subtropical and warm temperate zones, and the southern boundary of the frigid temperate zone in China could be expected to shift southward 270, 150, 450, 290 and 350 km from their normal positions, respectively. The extremely low temperature seriously injures not only the subtropical tree crops in the Changjiang River basin, but also the tropical tree crops in South China and even in southern Yunnan.