Abstract:

Based on daily temperature data from 1990 to 2019 in the Xinjiang cotton region and cotton yield data for each county (city, district), the Mann−Kendall trend test and Sen’s slope method were used to analyze the spatiotemporal variation characteristics of cotton yield and low−temperature cold damage during the cotton growing season (including seedling stage and flowering−boll stage cold damage). The copula function was employed to assess the impact of low−temperature cold damage on cotton yield. This study aimed to reveal the historical evolution of both cotton yield and low−temperature cold damage, and to quantify the impact of low−temperature cold damage on the probability of yield reduction, helping cotton farmers mitigate production risks. The results showed that, from 1990 to 2019, cotton yield exhibited a highly significant increasing trend (P<0.01) in 86.3% of the Xinjiang region, with an average annual increase of 30.22 kg·ha⁻¹. The high−value cotton production areas were mainly concentrated near the Tianshan mountains, while the yield stability showed a gradual increase from west to east. During the period from 1990 to 2019, significant changes in low−temperature cold damage occurred in the cotton−growing regions of Xinjiang. In 27.4% of the cotton-producing counties (districts and cities), the number of cumulative days of low−temperature stress during the seedling stage (LST) showed a highly significant decrease. Moreover, 37.0% of the counties experienced a highly significant decreasing trend (P<0.01) in cumulative low−temperature stress days during the flowering−boll stage (LTB). As the cumulative number of LST days increased, the probability of cotton meteorological yield loss increased by 19.1 percentage points in southern Xinjiang and by 19.0 percentage points in northern Xinjiang. Similarly, as cumulative LTB days increased, the probability of yield reduction increased by 18.6 percentage points in southern Xinjiang and by 20.5 percentage points in northern Xinjiang. In conclusion, over the past 30 years, cotton yield in Xinjiang has significantly increased, the frequency of low−temperature cold damage has generally decreased, and as the duration of low−temperature cold damage increased, the probability of cotton yield reduction rose, with the impact being more significant in northern Xinjiang than in southern Xinjiang.

Key words: Climate change, Cold damage in seedling stage, Cold damage in flowering?boll stage, Meteorological yield, Risk analysis, Xinjiang