东北黑土区降水特征及其对土壤水分的影响

水分是东北黑土区农业生产的主要限制因子，为了探讨东北黑土区可持续的土壤水分管理方式，该研究以中国科学院海伦农田生态系统野外科学观测研究站内为基础，利用SPI（standard precipitation index）值（标准降水指数）研究了该地区1952－2008年的大气降水情况，同时分析了土壤水分对大气降水（1999－2008年）的响应。1952－2008年平均年降水量为540 mm，标准差为121 mm，生长季内平均降水量为473 mm，占年平均降水量的87.60%。利用标准降水指数（SPI）将1952－2008年大气降水划分为7个不同的干/湿状态，分别是极端干旱，严重干旱、中等干旱、平常年份、中等湿润、非常湿润和极端湿润。分析近10 a（1999－2008）大气降水的SPI值发现极端干旱的年份有增加的趋势，同时对生长季末期土壤含水量的影响表现为湿润的年份（2003年，SPI值=1.5）能够显著增加土壤含水量（639.70 mm），而在极端干旱的年份（2004年，SPI=-2.6）土壤含水量达到了最低值（512.21 mm）。年际间降水量的差异也影响了土壤的供水特征特，同时肥料的施用增加了作物对土壤中水分的消耗。根据降水合理地管理东北黑土区的土壤水分对农业的可持续发展具有重要意义。

Characteristics of precipitation in black soil region and response of soil moisture dynamics in Northeast China

Water is one of mainly limiting factors influencing agricultural productivity in black soil region of Northeast China which is rain-fed agriculture. In order to improve the sustainable soil water management, Standard precipitation index (SPI) was used to analysis precipitation conditions from 1952 to 2008, and the response of soil moisture to precipitation during 1999 to 2008 were considered based on long-term experiment in National Observation Station of Hailun Agroecology System, Chinese Academy of Sciences (CAS). Mean annual precipitation of 540 mm was observed in study site, with standard deviation of 121 mm and 473 mm occurring in growing season which accounted for 87.6% of mean annual precipitation. Seven dry/wet states were distinguished based on SPI(standard precipitation index), they are extremely dry state, severely dry state, moderately dry state, normal state, moderately wet state, very wet state and extremely wet state. Extremely dry state had a increasing trend during recent decade (1999-2008). Soil moisture at the end of growing season was increased remarkably in moderately wet year (2003, SPI=1.5), whereas, was in low level (512.2 mm) in extremely dry year (2004, SPI=-2.6), variation in annual precipitation also impacted the characteristics of soil water supply. More water stored in soil profile was consumed when chemical fertilizer and organic matter were applied, compared with no fertilizer. Therefore, there is great significance for the sustainable development of agricultural production to regulate the soil water according to the precipitation conditions.