The evolution of spatiotemporal patterns and the influencing factors of the multiple cropping index of cultivated land in Southwest China

Based on the multiple cropping index (MCI) and "heat-precipitation" quantitative relation model, this paper analysed the changing trends and pattern evolution oi the MCI from the 1990 to 2015 and its influencing factors. The results indicated that from 1990 to 2015, the MCI values of Yunnan, Guizhou, and Sichuan decreased by 27.04%, 1.67%, and 25.83%, respectively. The average values of MCI values were 147.37%, 239.69%, and 206.05%, respectively. The greatest change in the three provinces occurred from 2006 to 2015. The inter-annual variations in the grain crop MCIs were ranked as follows; Sichuan > Guizhou > Yunnan, with values of -41.01%, -33.55% and -29.60%, respectively. The MCI in the Southwest China as a whole, the spatial pattern was significantly higher in the Eastern Region than that in the Western Region and higher in the Central Region than in the Northern and Southern Regions. In 2010-2015, in Southwest China, the PMCIs in the Eastern and Southern Regions were higher than those in the Central and Northwestern Regions; among them, the PMCI in Eastern Sichuan was the largest. The PIMCI was significantly higher in Yunnan Province than in Guizhou and Sichuan. Guizhou Province had the least potential area for promotion. The interannual variation of the MCI was greatly affected by natural factors and human activities, among which the MCI had a significant positive correlation with the year average temperature, accumulated temperature ▸0°C, population, and gross farm production. The spatial variation in the MCI was closely related to the terrain. Generally, the MCI in the hilly area is lower than that in the plain area; There was a significant positive correlation between the temperature change in the climatic factors and the change in the MCI in the Southwest China (P<0.01), but the temperature change was the key factor affecting the MCI changes.