近50年气候变化对青藏高原牧草生产潜力及物候期的影响

基于青藏高原及周边107个气象站点1965—2013年逐月气温、降水及日照时数等气象数据,分析了1965年以来青藏高原区的气候变化趋势,并采用MODIS数据、Thornthwaite Memorial模型及GIS技术分析了近50 a青藏高原牧草气候生产潜力及其时空变化特征;利用连续22 a的青藏高原牧草生育期观测数据,探讨了牧草生育期的时空变化特征及气象因子与牧草主要发育期的关系。结果表明:1)近50 a青藏高原平均气温呈上升趋势,升温幅度达0.53℃?(10a)?1,降水量总体呈现上升趋势,但增加幅度较小,其倾向率为7.81 mm?(10a)?1;而日照时数呈下降趋势,其下降幅度为16.94 h?(10a)?1。2)1965—2013年青藏高原牧草气候生产潜力总体呈增加趋势,在空间上,由西北向东南依次增加,青海省北部及南部部分地区气候生产潜力上升幅度较大,而西藏东部上升幅度较小,且南北部地区差异较大。3)牧草返青期、抽穗期及开花期均呈提前趋势,而黄枯期呈现推迟趋势,从而延长了牧草物候期;由东南向西北牧草返青期逐渐推迟,而黄枯期主要出现在一年中的第257~289 d,其空间整体差异不如返青期明显。4)温度和降水均与牧草物候期呈显著正相关,而日照时数与其呈显著负相关,且温度是影响牧草物候期变化的主要因子。利用青藏高原牧草生产潜力及物候期与气候因子的响应规律,可为提高该区牧草的实际产量和保护青藏高原草地生态系统提供借鉴和依据。

Impact of climate change on potential productivity and phenological phase of forage in the Qinghai-Tibet Plateau in the past 50 years

The Qinghai-Tibet Plateau is considered to be ideal region for studying the response of natural ecosystems toclimatechangebecauseits’mountainousenvironmentsisoneofthemostfragileoftheglobalecosystems.Theimpactsofthechangesintemperatureandprecipitationonthephenologyvariedamongdifferentgrasslands.Afterexperiencingadistinctwarming in recent decades, some studies noted that remarkable variations in vegetation in the Qinghai-Tibet Plateau werepotentiallyduetoclimatechange.Inordertodeterminetheimpactsofclimatechangeonvegetationphenologyandpotentialproductivity,thispaperusedmeteorologicaldataduring1965–2013intheQinghai-TibetPlateau(e.g.,monthlytemperature,precipitation and sunshine duration) of 107 meteorological stations, and extracted vegetation phenological indices usingMODIS-derivednormalizeddifferencevegetationindexdataduring2000–2013,andusedtheThornthwaiteMemorialmodeland GIS techniques to analyze the spatial and temporal trends of potential climate-driven forage productivity in theQinghai-Tibet Plateau. Then by analyzing 22 years of continuous observation data of growth stages of forage in theQinghai-Tibet Plateau, the relationship between meteorological factors and major growth stages of forage was determined.Also the driving factors of the dynamics of potential climate productivity in the Qinghai-Tibet Plateau were determined.Furthermore, the relationship between temperature or precipitation and sunshine duration during forage growth period wasdetermined based on regression analysis. The results showed that the potential climate productivity of forage in theQinghai-Tibet Plateau was consistently varied with geographical region and spatial temperature distribution. AveragetemperatureintheQinghai-TibetPlateauroseduringthenearly50-yearperiod,increasingby0.53 ℃?(10a)-1.Precipitationgenerallyincreasedattherateof7.81 mm?(10a)-1, whilesunshinedurationdecreasedby16.94h?(10a)-1.PotentialclimateproductivityofforageintheQinghai-TibetPlateaupresentedanincreasingtrendfrom1965to2013,andspatialchangesoftheproductivity,inturn, increasedfromnorthwesttosoutheast. Then potential climate productivity of forage in the north andsouthintheplateausignificantlyincreasedandtherewaslessvariationintheeastoftheplateau.Furthermore,theregreening,heading and blossoming of forages advanced, while yellowing and withering delayed year after year, which extended theforagesphenologicalphases.Regreeningstageofforagedelayedfromsoutheasttonorthwest,althoughwitheringstageshowednoobviouschange.Underdrierandwarmerconditions,phenologicalperiodsofgrasslandvegetationintheregionbecameclosely related to climate change. Then precipitation and sunshine duration were negatively correlated with phenologicalperiodofthegrasslandvegetation.Temperaturewasthedominantconstraintonphenologicalphasesofgrasslandvegetationinthe study area. The study formed a relevant reference and basis for the protection of grassland ecosystems and enhancingpotentialclimateproductivityinQinghai-TibetPlateau.