中文摘要：

通过比较不同自然降水年份（极端干旱和极端湿润）19年生疏林草地樟子松的针叶δ13C、比叶面积和干物质含量,结合土壤含水量和地下水埋深,探讨了极端降水对樟子松水分利用的影响.结果表明：干旱年份（2009）樟子松林土壤含水量显著低于湿润年份（2010）,但樟子松当年生针叶的δ13C在两年间没有显著差异,且两年相同月份间亦无显著差异;干旱年份当年生针叶的比叶面积显著低于湿润年份,而不同年份间干物质含量的差异不显著.在两种极端降水条件下,樟子松的水分利用效率没有明显变化,主要通过改变当年生针叶的比叶面积来适应降水量的变化.对于地下水埋深高于3.0m的疏林草地樟子松人工林生态系统,极端干旱不会严重影响樟子松的存活和生长.

英文摘要：

A comparative study was conducted on the needles stable carbon isotope composition （ δ13 C）, specific leaf area （ SLA）, and dry matter content （ DMC ） of 19-year-old Pinus sylvestris vat. mongolica trees in a sparse wood grassland in the south edge of Keerqin Sandy Land under the conditions of extreme drought and extreme wetness, aimed to understand the water use of Pinus syl- vestris under the conditions of extreme precipitation. The soil water content and groundwater level were also measured. In the dry year （2009）, the soil water content in the grassland was significantly lower than that in the wet year （2010）, but the δ3C values of the current year-old needles had no significant difference between the two years and between the same months of the two years. The SLA of the current year-old needles was significantly lower in the dry year than in the wet year, but the DMC had no significant difference between the two years. Under the conditions of the two extreme precipitations, the water use efficiency of the trees did not vary remarkably, and the trees Could change their needles SLA to adapt the variations of precipitation. For the test ecosystem with a groundwater level more than 3.0 m, extreme drought could have no serious impact on the growth and survival of the trees.