Shifts in timing of local growing season in China during 1961–2012

The warming rates in China determined by daily minimum temperature (T min ) are considerably large than those based on daily mean temperature (T mean ); therefore, the thermal growing season indices defined from T min are expected to show more pronounced changes than those from T mean . In this study, we investigate changing rates in the local growing season (LGS) defined using the climatological annual mean T min and T mean as temperature thresholds throughout China for the period 1961–2012. Changes in the thermal growing season indices based on fixed-temperature thresholds such as 0 °C, 5 °C, and 10 °C are analyzed for comparison. Results show that the T min -based LGS-lengthening rate (3.0 days per decade) is at least 1.2 times that of the T mean -based result (2.5 days per decade). It is also suggested that the growing season defined via a fixed-temperature threshold should only be applicable when determining the validity of a particular station in relation to its location. For example, the 0 °C-, 5 °C-, and 10 °C-based growing season definitions are applicable in regions to the north of 36° N, 32° N, and 26° N, respectively, based on T mean in eastern China and to the north of 33° N, 27° N, and 24° N, respectively, based on T min . To the north of 35° N in China, the average T min -based growing season lengthening rates are about 1.3, 1.4, and 1.7 times of those T mean -based rates in case of using the fixed-temperature thresholds of 0 °C, 5 °C, and 10 °C, respectively. Therefore, the changes of the growth of some plant species that are more directly correlated with changes in T min should be much more pronounced than those of other species.