Abstract: Chilling injury is one of the main climatic problems affecting the cultivation and production of Morchella. However, there are few reports about the mechanism of chilling injury, meteorological index and climate risk zoning of Morchella, and there is lack of necessary technical support to carry out the weather services for Morchella chilling injury. It provides scientific basis for the production planning of Morchella in the study area, the dynamic assessment of the risk of chilling injury and the meteorological service of disaster prevention and reduction, and facilitates the development of agricultural industry in mountainous areas. Taking the upper and middle reaches of the Qu River below 600m above sea level as the study area, DEM data of this area and climatic data of 21 stations in and around the basin from 1991 to 2020, and experimental data of Morchella production from 2018 to 2019 were used, based on the chilling injury types and disaster-causing factors of Morchella, extreme minimum air temperature and accumulated cold were selected as zoning indices to analyze the relationship between air temperature and ground temperature from February and March in the study area, to determine the threshold of extreme minimum air temperature; to statistically analyze the temporal and spatial distributions of extreme minimum air temperature, cold accumulation, chilling injury frequency and its lasting days. The spatial distribution data of index factors were standardized by establishing the spatial distribution model of chilling damage index. Analytic hierarchy process and natural breakpoint method were used to determine the influence weight and risk level thresholds of chilling injury indexes respectively. Based on the principle of comprehensive meteorological disaster risk assessment, ArcGIS10.1 was used to make a classification in Morchella chilling risk. The results showed that: (1) the average difference between air and ground temperature from February and March was about 1.0℃(0.7~1.4℃) in the study area, smaller in the south and larger in the north. The risk index of chilling injury of Morchella was the daily minimum temperature that was less than or equal to 2.0℃, and the basic index of early-warning of chilling injury risk was daily average temperature that was less than 6.0℃. (2) The chilling injury frequency of Morchella was more than 7 times in 10 years, mainly occurred from early February to early March, and the occurrence frequency and intensity decreased every 10 days, among which 70% occurred in early and middle February. The duration of chilling injury process was 1−3 days, accounting for 82%−89% of the total number of processes, the longest duration was 6−8 days, and the maximum accumulated cold was 3.64℃·d. (3) The risk levels of chilling injury of Morchella increased from south to north and from low altitude to high altitude, mainly in the middle and low risk areas. The middle and low risk areas are mainly distributed in the shallow hills and valleys below 520m above sea level in the middle and upper reaches of the Qu River, accounting for about 2/3 of the total area. The secondary high and high risk areas were scattered, mainly distributed in the low-mountain valley area with an altitude of 520−600m in the central and northern part, accounting for about 1/3 of the area. (4) After controlling the differentiation stage of Morchella to late February, the chilling injury frequency was reduced to about 2 times in 3 years, the chilling injury intensity was significantly reduced, and the harm was significantly reduced. (5) The planting site selection and the establishment of greenhouses had different effects on the chilling injury of Morchella. the influence of local topography on microclimate can be judged comprehensively according to the altitude and whether it is conducive to the southward cold air flow and aggregation, the cultivation facilities built with black sunshade net can reduce the environmental minimum temperature by about 0.3℃ and aggravate the chilling damage to Morchella. In the study area, the suitable season cultivation of Morchella should be controlled below 520m above sea level. According to the weather conditions, the primary basal differentiation period should be adjusted after late February. Attention should be paid to the adverse effects of local microclimate and black hollowed-out greenhouse in the process of chilling injury, so as to avoid or reduce the risk and harm of chilling injury.

Key words: Morchella, Chilling injury, Climate risk, The middle and upper reaches of the Qu River