In boreal forests, snow typically covers the forest floor and insulates soil from low and fluctuating air temperature for a large part of the year. Snowpack regimes are currently changing in response to climate warming, and it is uncertain how changing subnivean conditions (i.e. those under the snow cover) will impact soil processes. Here, we experimentally tested in a northern boreal forest how three various types of snow cover changes 1) ice encasement, 2) the absence of snow, and 3) snow compaction influence wintertime soil gas concentrations, growing season microbial respiration and biomass, extracellular enzyme activities (EEAs), and dissolved organic carbon (DOC) and nitrogen (N). The consequences varied drastically among experimental treatments. An initially strong increase in wintertime soil CO₂ accumulation in response to ice encasement weakened during the course of the 3-year experiment, when at the same time, growing season phenol oxidase decreased by 13% and β-glucosidase activity increased by 25%. The absence of snow enhanced β-glucosidase activity by 47% and, by the third year of experiment, increased inorganic soil N concentration. Snow compaction, in turn, enhanced phenol oxidase activity by 27% together with soil microbial respiration and biomass carbon. These findings suggest that consequences of snowpack regime change on the boreal forest soil carbon and nutrient cycling may vary from positive to negative depending on the type of change in the snow cover that becomes dominant.

在北方森林中，一年中的大部分时间里，积雪通常会覆盖森林地面，并使土壤免受低温和多变的空气温度的影响。当前，积雪状况随着气候变暖而变化，不确定亚自然环境的变化（即积雪条件下）如何影响土壤过程。在这里，我们在北部的北方森林中进行了实验，测试了三种不同类型的积雪如何变化：1）冰层包裹，2）没有积雪和3）积雪压实对冬季土壤气体浓度，生长季微生物呼吸和生物量，细胞外酶的影响活性（EEA）以及溶解的有机碳（DOC）和氮（N）。在不同的实验方法中，其后果差异很大。冬季土壤CO ₂的最初强劲增加在为期3年的实验过程中，由于冰包裹而引起的水的积累逐渐减弱，与此同时，生长期的酚氧化酶降低了13％，β-葡萄糖苷酶活性提高了25％。没有积雪可以使β-葡萄糖苷酶活性提高47％，并且到实验的第三年，无机土壤氮的浓度增加。反过来，积雪的压实与土壤微生物的呼吸作用和生物质碳的含量相比，增加了27％的酚氧化酶活性。这些发现表明，积雪状态变化对北方森林土壤碳和养分循环的影响可能从正变负，这取决于占主导地位的积雪变化的类型。