Response of spring wheat yield to snow cover in the black soil region: A perspective from the regulation of freezing and thawing processes of seasonally frozen soil

Seasonal snow and seasonally frozen soil are sensitive to climate change in middle-high latitude regions. Changes in seasonal snow associated with climate change could alter the freezing and thawing processes of seasonally frozen soil. Thus, these modifications may have important consequences on agricultural production by affecting the soil environment (e.g., moisture, temperature, and nutrients). However, the effects of seasonal snow on seasonally frozen soil and their association with food production remain unknown, especially in assessing the impacts of climate change on sustainable agricultural development and food security in the black soil region. This study was designed to explore how seasonally frozen soil regulates spring wheat yield in response to snow cover in an agroecosystem. To achieve this goal, we conducted a snow manipulation experiment in spring wheat fields, composed of snow cover treatment and snow free treatment. Immediately after each snowfall, we manually removed snow using shovels to maintain a snow-free condition in the snow free treatment plots, whereas snow was left undisturbed in the snow cover treatment plots. We measured spring wheat yield, soil temperature dynamics, and soil moisture dynamics in the 0−100 cm soil profile during the soil freezing and thawing periods. Soil freeze-thaw cycle frequency was determined by using soil temperature data. The results showed that spring wheat yield increased with soil moisture at a depth of 10 cm at the spring wheat sowing to seedling stage, and soil freeze-thaw cycle frequency at a depth of 10 cm during the soil thawing period. In contrast, the spring wheat yield decreased with soil moisture at a depth of 20 cm at the spring wheat seedling to four-leaf stage, and soil freeze-thaw cycle frequency at a depth of 10 cm during the soil freezing period. Furthermore, the soil moisture parameters (soil moisture at a depth of 10 cm at the spring wheat sowing to seedling stage and at a depth of 20 cm at the spring wheat seedling to four-leaf stage during the soil thawing period) and soil freeze-thaw cycle frequency parameters (soil freeze-thaw cycle frequency at a depth of 10 cm during the soil freezing/thawing period) explained 74.3%−77.6% and 77.8%−78.7% of the variance in the spring wheat yield in both the snow free and snow cover treatments, respectively. However, spring wheat yield was not related to soil temperature in the 0−100 cm soil profile, soil freezing duration, or soil thawing duration. Thus, the spring wheat yield was regulated by the above-mentioned soil moisture parameters and soil freeze-thaw cycle frequency parameters of seasonally frozen soil, and it did not respond to snow cover in the dry year. Therefore, the response of spring wheat yield in the dry year to snow cover was not significant in the black soil region. These results might provide insight into the potential role of seasonally frozen soil (development of soil freezing and thawing processes, soil temperature, and soil moisture regime) in regulating spring wheat yield in response to snow cover and improve the understanding of the relationship between seasonal snow-seasonally frozen soil and food production in the black soil region of Northeast China during climate change.