The Vulnerability And Risk Assessment Of Spring Wheat Production In Semi-arid Region Under Climate Change

The global climate change shows the main characteristics about temperature rising significantly and precipitation distributing unevenly. And it has already become the important limiting factor for the sustainable development of dryland agriculture in semi-arid region. The Inner Mongolia Autonomous Region has the largest area ratio of semi-arid region in China. It’s also the most representative region of semi-arid region as its climate characteristics and dryland agriculture production. Spring wheat is one of the major grain crops in this region. In recent years, with the negative impacts of climate change, the spring wheat production is suffering serious threat. In order to reduce the threat, we explored the method of vulnerability and risk assessment basing on the pinpointing of climate change characteristics in this region. And we quantitatively evaluated the impacts of climate change on spring wheat production by this method. Based on this, we could put forward the quantitative adaptive countermeasures.The main research results are as follows:(1) The exploration of method of vulnerability and risk assessment.Vulnerability and risk assessment is made up of the three core parts, namely vulnerability assessment, impact threshold assessment and risk assessment. The impacts of climate change can be highlighted by the basic period and study period. The different function status of farmland ecosystem can be reflected by choosing the yield as the main evaluation indicator. The regression equations between climatic yield and climatic factors, and between trend yield and adaptive factors can be built by the Logistic function to separate the crop climatic yield and trend yield. Based on the regression equations, the sensitive yield and adaptive yield can be quantified to complete the vulnerability assessment. By the mathematical analysis of the regression equations, the optimal threshold and stressed thresholds can be achieved. By comparing the difference between the average value of factors in the study period and the impact thresholds, the impact threshold assessment can be completed. Using the anomaly percentage of crop yield, the loss degree of agricultural yield can be quantified. Through the concept of climate change effect accumulated frequency (CCEAF), the probability of occurrence of different loss degree can be calculated to complete the risk assessment.(2) The temporal-spatial characteristics of climatic resources in Inner Mongolia.The average temperature and precipitation of spring wheat growth period are 16.5℃ and 224mm respectively from 1961 to 2012. The northeastern area of this region has the lower temperature and more precipitation. The eastern area has the higher temperature and more precipitation. And the southwestern area has the higher temperature and less precipitation. In the recent 52 years, the average temperature of spring wheat growth period increased significantly with the average rate 0.3℃/10a. The precipitation decreased fluctuatingly with the average rate 4.3mm/10a. This region shows a warming and drying trend.(3) The vulnerability assessment of spring wheat production in Inner Mongolia.In the study period (from 1996 to 2012), the spring wheat vulnerabilities of eastern, central and southwestern areas are higher. And the spring wheat vulnerabilities of northeastern are relatively less. Assuming the adaptative capacity is stable, under historical climate change trend scenarios, the temperature unit vulnerability will increase 50%,117% and 350% respectively by 2030,2050 and 2100 comparing with the average unit vulnerability in the study period. The precipitation unit vulnerability will increase 50%,50% and 150%, respectively. And the comprehensive unit vulnerability will increase 29%,86% and 271%, respectively. Under the RCP4.5 scenarios, temperature unit vulnerability will increase 52%,112% and 337%, respectively. The precipitation unit vulnerability will decrease 6%,27% and 72%, respectively. And the comprehensive unit vulnerability will increase 24%,64% and 227%, respectively. Under the RCP8.5 scenarios, temperature unit vulnerability will increase 115%,290% and 1027%, respectively. The precipitation unit vulnerability will decrease 52%,103% and 154%, respectively. And the comprehensive unit vulnerability will increase 60%,181% and 736%, respectively.(4) The impact threshold assessment of spring wheat production in Inner Mongolia.From 1961 to 2012 the optimal impact thresholds of average temperature, precipitation, fertilization level and moisture supply level are 15.6℃,333mm,319.5kg/ha and 743.7mm, respectively. Compared with the average status in the study period, the maximum fertilization level and moisture supply level can be increased 162.2kg/ha and 406.5mm respectively to improve the adaptative yield.(5) The risk assessment of spring wheat production in Inner Mongolia. The risk of adverse impacts of temperature rising for spring wheat production in Inner Mongolia in the study period is 11.1%. The risk of adverse impacts of precipitation reducing is 9.3%. And the risk of adverse impacts of comprehensive action is 10.3%. The whole region shows the higher risk of temperature and comprehensive action. Especially the northern, eastern and central areas are the higher risk areas under climate change impacts.(6) The proposal of adaptive countermeasures.By adjusting the planting structure in some areas of central and southwest regions to reduce the spring wheat planting proportion, the exposure degree and regional vulnerability can be reduced. On the basis of the optimal thresholds of moisture supply level and fertilization level, the maximum moisture supply level and fertilization level can be increased 441.4mm and 229.9kg/ha respectively to increase the adaptive yield in the northeastern area which has the higher risk and lower vulnerability. In the eastern area which has the higher risk and higher vulnerability, the maximum moisture supply level and fertilization level can be increased 464.3mm and 142.2kg/ha respectively. In the central area which has the higher risk and higher vulnerability, the maximum moisture supply level and fertilization level can be increased 513.7mm and 242.2kg/ha respectively. In the southwestern area which has the lower risk and higher vulnerability, the maximum moisture supply level and fertilization level can be increased 201.7mm and 41.4kg/ha respectively.