华北地区冬小麦干旱风险区划

灾害风险评估与区划是是实现灾害应急管理向风险管理转变的关键。综合考虑了影响灾害风险大小的自然属性和社会属性,从多角度选取了干旱灾害强度、基于冬小麦干旱指数的干旱频率、基于灾损的干旱频率、灾年减产率变异系数、区域农业经济发展水平、抗灾性能指数等6个风险评估指标。通过引入CCA排序方法,揭示了不同风险评估指标之间的相关关系以及评估指标与相对气象产量的关系;并以确定的风险评估指标和相对气象产量之间的关系为基础,构建了不考虑抗灾和考虑抗灾2种风险指数。对比两种风险指数分析结果,表明在抗灾和不抗灾2种条件下,华北地区冬小麦干旱风险格局发生了明显改变。说明在当前农业生产水平下,人类的减灾抗灾和风险管理水平对冬小麦生产起着至关重要的作用。最后,以模糊聚类分析为手段,以考虑抗灾能力的风险指数和灾年减产率为分类标准进行聚类,实现了华北地区冬小麦干旱风险综合区划。

The drought risk zoning of winter wheat in North China

With its wheat production accounting for about 60 percent of the national total, North China is one of the most important grain-producing areas in China. The wheat production in this region directly determines the import and export of wheat of China and is potentially associated with the overall development of agriculture in China. However, suffering the longest and the most severe drought almost every year due to the interannual variability of monsoon climate, this region possesses the largest drought-hit area in China. Therefore, drought risk classification over this region is of particular significance. Generally, disaster risk assessment and zoning play a key role in risk management and disaster emergency response. In North China, drought is one of the most serious agro-meteorological disasters that constrain the winter wheat yield. Considering both natural and social attributes of the natural disaster risk, six indices are selected for the risk assessment in this research. They include the intensity of drought, the frequency of drought occurrences based on wheat drought index anomaly, the frequency of drought occurrences based on yield losses, disaster variation coefficient of yield losses, regional agricultural production level of winter wheat, and the index of disaster resistance. It is well known that in multivariate analysis, ordination is a complementary method in data clustering and is used mainly in exploratory data analysis. By using the most common Canonical Correspondence Analysis (CCA) ordination method, it is found that there are relationships between different risk assessment indices and they are correlated with the relative meteorological yields. Based on the findings, two risk indices are constructed for two situations with and without defensive responses to drought. Comparison results obtained from these two indices indicate that both the temporal and spatial distributions of the drought risk with defensive responses to drought is quite different from that without defensive responses to drought in the North China Plains, suggesting that the level of the disaster mitigation and risk management plays a great role in the winter wheat production under the current farming practice conditions. Finally, an integrated regionalization for the drought risk of the winter wheat in the North China Plains is successfully carried out using the fuzzy clustering method through the analysis of the decreasing rate of the crop yields in the famine year and risk indices involving disaster resistance as the clustering standards.