藏西北地区气候变化及其对草地畜牧业的影响

近40 a（1971-2010年）藏西北地区气温明显升高，尤其是旱季气温显著增高；大部分地区降水量增多，蒸发量减少。从地区分布来看，藏西北中东部各地气温明显升高、降水增多、蒸发减小，气候呈暖湿化趋势；西部的狮泉河等地气温升高、降水减少、蒸发量增大，气候呈现暖干化趋势。近40 a藏西北地区牧草生长季、青草期提前，结束期推迟，持续日数增多，期间积温和降水量也呈显著增多趋势；大部分地区牲畜抓膘期日数显著增多〔倾向率为2.7 d•(10a)^-1〕，掉膘期日数显著减少〔倾向率为6.1 d•(10a)^-1〕，气候变化趋势对藏北草地畜牧业十分有利。合理调整畜种结构，有效控制牲畜数量，尤其是山羊数量，对遏制藏西北地区草地退化具有重要意义。

Climate Change and Its Effect on Steppe Animal Husbandry in Northwest Tibet

Temperature in northwest Tibet was increased significantly, especially in dry season, precipitation was increased in most areas, but the potential evaporation was decreased during the period from 1971 to 2010. Regionally, temperature was increased significantly, precipitation was increased, potential evaporation was decreased in the central and eastern parts of northwest Tibet, and climate trended a warming wetting pattern. However, temperature was increased, precipitation was decreased, potential evaporation was increased, and climate trended a warming drying pattern in the western regions including Shiquanhe. The beginning time of pasture growing and green grass seasons became earlier, their end time was postponed, the durations were extended significantly, and the cumulative temperature and precipitation were increased significantly in these seasons. The fatten duration of livestock were extended significantly in most places 〔the tendency rate was 2.7 d•(10a) ^-1〕, and the fat loss duration was in a significant reduction 〔the tendency rate was 6.1 d•(10a)^-1〕 in northwest Tibet in recent 35 years. Climate change was in a favorable trend for steppe animal husbandry in the northwest Tibet. It is of significance for controlling steppe degeneration to rationally regulate the livestock structure and limit the number of livestock, especially goats in northwest Tibet.