Effects of Temperature and Precipitation Variation on Vegetation Net Primary Productivity in the Northern and Southern Regions of the Qinling Mountains from 1960 to 2011

Based on climatic observational data of monthly average temperature and precipitation in Northern and Southern Regions of the Qinling Mountains in 1960～2011,the net primary productivity(NPP) of natural vegetation in the northern and southern regions of the Qinling Mountains was computed by using Zhou Guangsheng-Zhang Xinshi Model,climate trend rate and Spline interpolation method.The variation of temperature and precipitation and its effect on NPP(Net Primary Productivity) were analyzed.The results are as follow:(1)The average annual temperature of the research area was higher in southern part and lower in northern part.1993 was the turning point of temperature.The cooling trend in southern area before 1993 was more obvious,since then the temperature of most stations increased.The temperature of 98% stations increased during last 52 years.(2)The annual precipitation decreased from south to north.1985 was the turning point of precipitation.The precipitation showed a decreasing trend before 1985,while 70% stations increased since 1985.The northern part was becoming dry while the southern slope was becoming wet.There was not significant change in other parts.(3)The mean error between simulated NPP and measured NPP is 11.1%,which is relatively small,and this model is suitable to simulate NPP in Northern and Southern Regions of the Qinling Mountains.NPP was lower in northern part and higher in southern part.According to the size,the order was Ba-Wu Valley,Han River Basin,the southern slope and northern region of Qinling Mountains.The ratio between maximum and minimum values was small which ranging between 1.34 and 1.89.(4)NPP increased over 14.8% under the condition that temperature and precipitation improved together,the northern region of Qinling Mountains had more obvious increasing trend compared with the southern region.Temperate zone deciduous broadleaved showed biggest increasing range,while temperate hassock was the smallest one;Temperature increasing but precipitation decreasing(scenario b) was not good for the accumulation of NPP,thus most stations would decrease instead.Subtropical and tropical broadleaved and deciduous forest showed biggest increasing rate,while temperate zone deciduous broadleaved was the smallest one;NPP increased obviously in scenario c(temperature increasing but precipitation no change),which was smaller than scenario a,NPP of northern region of Qinling Mountains increased more obviously than that of southern region.Different vegetation types showed same changing trend as scenario a,which was smaller than scenario a.