气候变暖对新疆不同秋眠级紫花苜蓿种植适宜性的影响

基于新疆102个气象台站1961?2019年逐日平均气温、最低气温资料，采用统计学方法以及ArcGIS的空间插值技术，在对影响新疆紫花苜蓿种植的主要气候因子 ≥ 5 ℃积温、冬季最低气温时空变化特征分析的基础上，以80%保证率 ≥ 5 ℃积温和90%保证率冬季最低气温作为指标因子，研究了气候变暖背景下，新疆不同秋眠级紫花苜蓿种植气候适宜性的变化。结果表明：新疆80%保证率 ≥ 5 ℃积温和90%保证率冬季最低气温的空间分布总体呈现“南疆多(高)，北疆少(低)；平原多(高)，山区少(低)”的格局。受上述两指标要素空间分异的综合影响，秋眠级4～6级紫花苜蓿适宜种植区主要分布在南疆的塔里木盆地以及东疆的吐鲁番盆地和哈密盆地；秋眠级2～3级紫花苜蓿适宜种植区分布在塔里木盆地、吐鲁番盆地和哈密盆地周边山前倾斜平原，伊犁河谷以及准噶尔盆地西部和东部的低平原地带；秋眠级1～2级紫花苜蓿适宜种植区分布在北疆北部、西部，准噶尔盆地腹地以及天山和昆仑山中、低山带；阿尔泰山、天山和昆仑山区大部为紫花苜蓿不适宜种植区。影响不同秋眠级紫花苜蓿种植的主导因子不同，秋眠级4～6级紫花苜蓿适宜种植区以及紫花苜蓿不宜种植区主要受80%保证率 ≥ 5 ℃积温的影响；秋眠级1～2级和2～3级紫花苜蓿适宜种植区主要受90%保证率冬季最低气温的影响。在全球变暖背景下，近59年新疆 ≥ 5 ℃积温和冬季最低气温分别以65.52 (℃·d)·10 a?1和0.63 ℃·10 a?1的倾向率呈极显著(P < 0.001)上升趋势，80%保证率 ≥ 5 ℃积温和90%保证率冬季最低气温也总体增多或升高，但其变化具有阶段性差异，时段Ⅰ (1961–1980年) 80%保证率 ≥ 5 ℃积温和90%保证率冬季最低气温为近59年最低时期；时段Ⅱ(1981?2000年)较时段Ⅰ的90%保证率冬季最低气温升高2.9 ℃，但80%保证率 ≥ 5 ℃积温变化不大；时段Ⅲ(2001?2019年)较时段Ⅱ的90%保证率冬季最低气温不升反降0.8 ℃，而80%保证率 ≥ 5 ℃积温增加147.0 ℃·d。受上述气候要素变化的影响，近59年新疆秋眠级4～6级和2～3级紫花苜蓿适宜种植区呈扩大趋势，而秋眠级1～2级紫花苜蓿适宜种植区及紫花苜蓿不宜种植区呈减小趋势。这表明气候变暖对新疆紫花苜蓿种植的发展总体趋于有利。

Impact of climate warming on planting suitability of alfalfa with different fall dormancy grades in Xinjiang

Using the data of daily mean temperature, the minimum temperature from 102 meteorological stations in Xinjiang during 1961–2019, based on statistical method and ArcGIS, the fundamental spatial-temporal change characteristic of key climatic factors affecting alfalfa planting, such as ≥ 5 ℃ accumulated temperature (\begin{document}$\sum $\end{document}Tmean ≥ 5 ℃), and the minimum temperature in winter (Tmin) were analyzed. Taking 80% guarantee rate ≥ 5 ℃ accumulated temperature (\begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate) and 90% guarantee rate minimum temperature (Tmin of 90% guarantee rate) as the index factors, the climate suitability changes of different fall dormancy grades in alfalfa planting were studied under the background of climate warming in Xinjiang. The results showed that spatial distribution of \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate and Tmin of 90% guarantee rate had very obvious differences from place to place in Xinjiang. Generally, they were more in the south than in the north and more in the plain than in the mountainous regions. Under their comprehensive influence, the suitable planting areas for alfalfa off all dormancy grades 4 ~ 6 was mainly in the Tarim, Turpan, and Hami Basins. The suitable areas for fall dormancy grades 2 ~ 3 was in the sloping plains around the Tarim Basin, Turpan Basin, Hami Basin, the Yili Valley, and the low plains in the west and east of the Junggar Basin. Areas for fall dormancy grades 1 ~ 2 was in the north and west of northern Xinjiang, the hinterland of Junggar Basin, and the middle and low mountain belts of Tianshan mountain and Kunlun mountains. Alfalfa was not suitable for planting in the Altai, Tianshan, and Kunlun mountains. The dominant factors affecting the distribution of suitable planting areas for alfalfa of different fall dormancy grades were different. Generally, the suitable planting areas of fall dormancy grades 4 ~ 6 and 2 ~ 3 were mainly affected by \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate, but the areas of suitable planting for alfalfa of fall dormancy grades 1 ~ 2 and unsuitable for alfalfa planting were mainly affected by Tmin of 90% guarantee rate. In the background of global warming, \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ and Tmin significantly (P < 0.001) increased at the rate of 65.52 (℃·d)·10 a?1 and 0.63 ℃·10 a?1 respectively, during 1961–2019 in Xinjiang. \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate and Tmin of 90% guarantee rate were increased too, but the changes were different in different periods during 1961–2019. During period Ⅰ (1961–1980), \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate and Tmin of 90% guarantee rate were the lowest in nearly 59 years. In period Ⅱ (1981–2000), the Tmin of 90% guarantee rate was 2.9 ℃ higher than that of period Ⅰ, but the \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate had no obvious change. In period Ⅲ (2001–2019), the Tmin of 90% guarantee rate was 0.8 ℃ lower than that of period Ⅱ while the \begin{document}$\sum $\end{document}Tmean ≥ 5 ℃ of 80% guarantee rate increased by 147.0 ℃·d. Under their influence, the suitable planting areas for 4 ~ 6 and 2 ~ 3 grades of fall dormancy alfalfa showed an expanding trend, whereas the suitable planting areas of 1 ~ 2 grades and the unsuitable planting areas of alfalfa showed a decreasing trend in Xinjiang. These results showed that climate warming was beneficial to the development of alfalfa planting in Xinjiang.