雪被厚度和积雪周期对土壤氮素动态影响的初步研究

Preliminary study on the effect of snow depth and snow duration on soil N dynamics

在高山地区和高海拔地区，氮素是植物生命活动的主要限制因素之一。冬季，这类地区的土壤通常被雪被长时间覆盖。以往的研究证实，雪下土壤氮素动态在维持年际氮循环中起着重要作用。气候变化将改变生物地球化学循环，导致雪被覆盖状况发生改变，从而对冬季土壤氮素动态产生重要影响。然而，迄今为止，对气候变化极其敏感的青藏高原东缘雪下土壤物质转化过程的研究却很少。为了了解不同雪况下土壤矿质氮库水平和净氮矿化变化动态，2010年11-2011年4月在青藏高原东缘用PVC管原位培养土壤，通过人工控制雪被厚度和雪被持续时间的方法，设置不同积雪厚度和积雪周期的9个处理，分别测定其无机氮（NH4＋-N和NO3--N）含量，并计算净氮矿化率。结果表明，雪被持续时间可对土壤温度的变化产生明显的影响；随着土壤覆雪厚度和雪被覆盖时间的增加，土壤含水量呈现增长的趋势。土壤无机氮以 NH4＋-N 为主，占总无机氮的69%-86%，而NO3--N含量只占土壤总无机氮的14%-31%。深雪（100 cm和50 cm的积雪覆盖）降低了铵态氮含量，而净氮矿化率无明显变化。不同的积雪覆盖时间（60 d，90 d，150 d）并没有引起土壤氮库的显著变化，说明较早的降雪虽然使土壤有较高的温度和较少的冻融循环，但并不会改变土壤氮库的积累和释放。

Nitrogen is one of the most limiting elements for plants in alpine and high latitude areas which are covered by snow in winter for a long period. The mineralization of soil nitrogen under snow cover is a major component in annual nitrogen circle of soil. And climate change will have an important influence on soil nitrogen dynamics in winter by changing biogeochemical cycle and snow regime. However, so far, little work has been done on the eastern Tibetan Plateau. The effects of snow depth and duration of snow cover on soil N content and net N dynamics were explored byin situ PVC culture tubes method in the alpine belt of the eastern Tibetan Plateau from November 2010 to April 2011. 9 treatments （different snow depth and snow duration） were set by artificially to determine the inorganic N content （NH4＋-N and NO3--N） and calculate net N mineralization. The results showed that snow duration had a significant impact on soil temperature.. Soil water content increased with the increase of snow depth and snow duration. NH4＋-N is the main, accounting for 69%-86% of the soil inorganic N, while NO3-N accounting for only 14%-31%. Deeper snow-cover （100 cm and 50 cm snow cover） reduced soil NH4＋-N concentration, whereas did not change net N mineralization rate. No differences in soil N pools was found under the different duration of snow cover （60 d, 90 d, 150 d）, showing that accumulation and release in soil N pools were not significantly changed by earlier continuous snow cover, although higher temperature and less freeze-thaw cycles were found.