RESUMO
Drought disaster space agglomeration assessment is one of the important components of meteorological disaster prevention and mitigation. Agriculture affected by drought disaster is not only a serious threat to world food security, but also an obstacle to sustainable development. Additionally, China is an important agricultural import and export country in the world. Therefore, we used the global Moran's I and the local indicators of spatial autocorrelation (LISA) to reveal the spatial agglomeration of agricultural drought disaster in China from1978 to 2016, respectively. The results showed that China's agricultural drought disaster presents local spatial autocorrelation of geographical agglomeration at national level during the study period. The spatial agglomeration regions of China's agricultural drought disaster were in Inner Mongolia, Jilin province, Heilongjiang province, Liaoning province, Shanxi province, Hebei province, Shandong province, Shaanxi province and Henan province, indicating that agricultural drought disaster mainly distributed in North and Northwest China, especially occurred in the Yellow River Basin and its north areas. We also found that the overall movement direction of agricultural drought disaster agglomeration regions was northwest, and the maximum moving distance was 722.16 km. Our results might provide insight in early warning and prevention for drought disaster.
RESUMO
We estimated grassland NPP using CASA model in the Loess Plateau during 2000-2015 and further analyzed the spatiotemporal dynamics, stability and persistence of grassland NPP. The driving factors of grassland NPP were analyzed from four aspects, i.e., vegetation types, topographic factors, climate change, and human activities. The results showed that the average NPP was 202.93 g C·m-2·a-1. The grassland NPP showed an increasing trend with an average increase rate of 2.43 g C·m-2·a-1. The distribution of NPP in grassland had obvious spatial heterogeneity, which was generally high in the south and low in the north. 91.2% of the total grassland area showed an increasing trend, mainly distributed in most areas of Shaanxi Province, Longdong and Longzhong areas of Gansu Province, and most parts of Qinghai Province. The regions with a stable growth condition of grassland NPP mainly located in the south of Ordos, northern Shaanxi, and Gansu. The future change trend of grassland NPP would be consistent with that of the past in most areas. The grassland NPP would continue to increase in most areas of Shaanxi Province, Longzhong and Longdong areas in Gansu Province. The average NPP of slope grassland was 703.37 g C·m-2·a-1, while that of alpine and subalpine grassland was 57.28 g C·m-2·a-1. The grassland NPP was higher in high altitude area and relative low in plain and hilly area. The increased precipitation promoted the increase of grassland NPP during the study period. Human activities such as improvement of overgrazing and returning cropland to grassland also played an important role in the increase of grassland NPP in the Loess Plateau.