| The temporal and spatial changes of global NPP from 1901 to 2005 were studied by using the net primary production?NPP?simulated by six earth system models.The temporal and spatial changes of carbon flux of vegetation in China from 1901 to 2005were studied using the net primary production?NPP?of 7 earth system models.In addition,the spatiotemporal changes of NHx and NOy in nitrogen deposition fluxes over China from 1901 to 2005 were further studied,and the relationship between the changes of NHx and NOy and temperature,precipitation and NPP was analyzed.The main conclusions are drawn as follows:?1?Global NPP shows an upward trend at centennial scale,and the trend coefficient of the model ensemble mean is 0.88,which passed the 99.9%confidence level of the statistical test.The trend is more pronounced in the northern hemisphere than the southern hemisphere.From 1901 to 2005,the high value of NPP above 800 gC m-2year-11 mainly distributed in the equatorial region of South America,equatorial Africa,Indo-China peninsula and the tropical rain forests around Indonesia.The low value mainly distributed in the high latitude areas of the northern hemisphere,the northern Africa,the arid and semi-arid areas of the Asian continent and the northwest of the Qinghai-Tibet plateau.?2?Global NPP is mainly positively correlated with the centennial evolution of temperature in most regions,and negatively correlated only in South America,Africa and India near the equator,mainly because radiation in these regions is the limiting factor of NPP.On the centennial time scale,the global NPP and precipitation are mainly positively correlated in most regions,and negatively correlated in the arid and semi-arid regions from northern Africa to west Asia and central Asia.In most of the 21 regions across the globe,the NPP of the 6 earth system models is consistent with the change of temperature and precipitation.The NPP change of the six models in western Africa is inconsistent,which shows the NPP simulation is of large uncertainty,followed by the Mediterranean region.?3?In recent 100 years,NPP in China shows an upward trend,and the trend coefficient of the model enseble mean is 0.88,which has passed the 99.9%confidence test.In the past 100 years,the nitogen depostion of NHx and NOy in China showed an upward trend,in which the trend coefficients were 0.98 and 0.98,respectively,and passed the 99.9%confidence level of statistical test.The distribution trend of NPP is generally characterized by a gradual increase from northwest to southeast.In general,NHx and NOy show a characteristic of low in the north and high in the south,and a gradual increase from northwest to southeast.?4?In each model,NPP in most regions of China is positively correlated with temperature,precipitation,long-wave radiation and short-wave radiation,and the average correlation coefficient of the model ensemble is 0.88,0.73,0.91 and 0.67,respectively.The spatial distribution of correlation coefficients between NHx and NOy and air temperature is generally similar,but the values are slightly different.The spatial distribution of correlation coefficient between NHx and NOy and air temperature is positive,negative and positive interval from east to west.The spatial distribution of the correlation coefficient between NHx and NOy and precipitation is also roughly similar,but the spatial distribution of the precipitation correlation coefficient is relatively complex.In the monsoon regions,the positive,negative and positive wave series are distributed from north to south,and the negative,positive and negative distribution is shown in the non-monsoon region from east to west.The spatial distribution of correlation coefficients between NHx and NOy and NPP is generally consistent,in which the trend coefficient of the model ensemble mean is positive in the northeast and southwest regions,while other regions are positive and negative alternately.The distribution of the relationships between carbon and nitrogen fluxes is relatively complex. |
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