黑土表层有效养分含量和酶活性对雪被去除的季节性响应

为探究黑土养分和土壤酶活性对极端积雪覆盖情况的季节性响应，该研究采用雪被去除的方法，设置了2个试验组（积雪覆盖试验组和雪被去除对照组），并进行了土壤温湿度、有机质含量、碱解氮含量、速效磷含量以及脲酶活性和转化酶活性动态变化的分析。结果表明，雪被去除显著降低了土壤温度和土壤水分（P<0.05），使土壤冻结和融化时间提前，显著增加了冻融循环次数。同时，雪被去除显著增加了早冬和深冬时期的土壤有机质、碱解氮和速效磷的含量，并显著降低了冬末三者的含量。而在雪被去除处理下，土壤酶活性显著降低，与对照组相比，雪被去除使土壤转化酶和脲酶活性降低了25.0%和16.3%以上。此外，除了在深冬时期，两种酶活性的主要控制因素均为土壤有效养分含量外，在早冬和冬末两个阶段，控制两种土壤酶活性大小的因素也存在差异。研究揭示了未来气候变化所引起的积雪减少将导致土壤有效养分积累与释放过程发生转变，表现为土壤养分在冬季早期迅速释放，冬季末期逐渐累积，进而造成一定养分流失。研究结果可为未来气候变暖的土壤生物化学演化机制研究提供理论支撑。

Seasonal response of available nutrient content and enzyme activity in black soil surface to snow removal

Abstract: Snow cover patterns from climate change have profoundly dominated the soil physical structure and biochemical processes in farmland, as global warming is becoming much more serious in recent years. The resulting nutrient loss has posed a great threat to the black soil, a precious soil resource in China. Particularly, most black soils are distributed in seasonally frozen soil areas that are covered by snow all the year round. The snow cover has also some impacts on the black soils in these areas. Similarly, the soil nutrients and enzyme activities have a profound impact on the cycle process of soil materials in the growth and development of crops and grain yields. This study aims to further explore the seasonal response of the available nutrient content and enzyme activity in the black soil to the snow cover removal. Two experimental groups were divided in the study area, including the artificial snow cover removal, and the normal snow cover control group. A seven-month long-term field experiment was carried out to measure the soil temperature, moisture, organic matter content, available nitrogen content, available phosphorus content, invertase activity, and urease activity. The seasonal dynamics were then determined using the measured data. The results showed that the artificial snow removal led to a significant decrease in the soil temperature and soil moisture (P<0.05). At the same time, the artificial snow removal could greatly contribute to making the soil freezing and thawing time earlier, and significantly increased the number of soil freezing and thawing cycles, compared with the normal snow cover control group. In addition, the removal of artificial snow significantly increased the soil organic matter content, soil available nitrogen content, and soil available phosphorus content in early and late winter. However, the contents of soil organic matter, available nitrogen and phosphorus decreased significantly in late winter and early spring. There was also a significant decrease in the two soil enzyme activities of invertase and urease during most of the winter. The snow removal treatment decreased the activities of soil invertase and urease by more than 25.0% and 16.3%, respectively, compared with the normal snow cover control group. In addition, there were some differences in the controlling factors of soil invertase and urease activity in the whole winter and early spring. However, the soil''s available nutrient content was the main controlling factor for the activities of two enzymes during most of the winter. In the future, global warming can lead to the reduction of snow cover in the middle and high latitudes of the world, some of which can have no snow cover, resulting in the different accumulation and release of soil available nutrients. The specific mechanism can be that the reduction of snow cover can cause the rapid accumulation of soil available nutrients in the early winter, and then gradually accumulate in the late winter, resulting in the loss of certain nutrients. This finding can also provide some theoretical support to the soil biochemical evolution under the condition of future climate warming.