西藏植被净初级生产力对气候变化的响应

Responses of Net Primary Production to Climatic Changes over Tibet Plateau from 1971 to 2005

根据1971-2005年年平均气温、降水量资料．采用Thornthwaite Memorial模型计算了西藏植被净初级生产力（net primary production，NPP），分析了NPP的空间分布、年际和年代际变化特征，以及未来气候变化对NPP的影响。结果表明，西藏NPP有自东南向西北递减的分布规律。近35a阿里地区西南部、聂拉木、江孜NPP为减少趋势，减幅为11．9～314．2kg·hm^-2·（10a）^-1，以普兰减幅最大；其他各地呈不同程度的增加趋势，增幅为26．8～459．8kg·hm^-2·（10a）^-1，其中拉萨增幅最明显；林芝地区、昌都地区北部、那曲地区NPP呈明显的逐年代增加趋势，阿里地区西南部、聂拉木NPP表现为逐年代减少趋势。就西藏平均而言，20世纪70年代气候“冷干”，NPP偏低；90年代气候“暖湿”，NPP偏高。从设定的气候变化情景来看，“暖湿型”气候对西藏NPP有利，平均增产6％～13％；“冷干型”气候对西藏NPP不利，平均减产6％-14％。未来西藏以“暖湿型”气候为主，到2050年NPP将增加11％～26％。

Based on the annual mean temperature and precipitation data at the 38 meteorological stations over Tibet from 1971 to 2005, the net primary production （NPP） is computed by Thornthwaite Memoriai Model. The spatial distributions, interannual and interdecadal variations of the NPP are analyzed, and the influences of climate changes on NPP are discussed. The results show that the distribution of NPP is characterized by a remarkable regional feature, i. e. decreasing from the southeastern to the northwestern of Tibet. During last 35 years, the reduction of NPP was insignificant in southwestern Ngari district and Nyalam county,and it ranged from 11.9 to 314.2 kg · hm^-2 · （ 10 a）^ -1 ,with the largest in Purang county. In other districts of Tibet, NPP has increased and the increment ranged from 26.8 to 459.8 kg · hm^-2 · （10 a） ^-1 ,with the largest in Lhasa. Also,the results show that NPP has increased interdecadally in Nyingri district, northern Chamdo district and Nakchu district, but decreased in southwestern, Nyalam county and Gyantse county. On an average over the whole Tibet, the NPP changed interdecadally. When the cold and dry climate occurred in the 1970s,the NPP was lower;and when the warm and wet climate appeared in the 1990s ,the NPP was higher. Under climate change scenarios,the warm and wet climate would benefit the NPP with an average increment of yield by 6% to 13% over Tibet,while the cold and dry climate would have an adverse impact on NPP with an average reduction of yield by 6% to 14%. The future climate over Tibet would become warm and moist, and the NPP would also increase by 11% to 26% in 2050.