Characteristic Analysis of the Spatio-Temporal Distribution of Key Variables of the Soil Freeze–Thaw Processes over Heilongjiang Province, China

The soil freeze–thaw phenomenon is one of the most outstanding characteristics in Heilongjiang Province. Quantitative analysis changes key variables processes great scientific importance for understanding climate change, as well ecological and hydrological processes. Based on daily surface temperature air data Province past 50 years, spatial–temporal distribution their correlations with latitude process were analyzed using linear regression, Mann–Kendall test, local thin disk smooth spline function interpolation method, correlation analysis; additionally, during are discussed under different vegetation types. results show that there a trend delayed freezing early melting from north to south. From 1971 2019 a, start date (FSD) was at rate 1.66 d/10 end (FED) advanced 3.17 days (FD) shortened 4.79 a; each 1 °C increase temperature, FSD by about 1.6 d, FED 3 FD 4.6 d; 1° latitude, 2.6 2.8 5.6 d. spatial variation same cover closely related altitude, where lower more obvious trend; among them, interannual meadow obvious, which varied 9.65, 16.86, 26.51 respectively. In addition, trends ground types generally consistent, longest period unstable shortest stable freeze coniferous forests, compared meadows. study important our Province, evolution high-latitude permafrost; they also promote further exploration impact agricultural production change.