Relationship Between Productivity And Climate Change In Inner Mongolia Steppe And Reconstruction Of ANPP From A.D.1-2000

Grassland is an important part of ecosystem, as an important parts of terrestrial ecosystem, Above ground Net Primary Productivity(ANPP) is not only an important parameter in characterizing terrestrial ecological processes, but also plays an important role in global carbon balance.Grassland productivity is strongly dependent on the natural environment and climate change, our current understanding of the long-term productivity in the grass is almost empty.In this paper,using the meteorological data of the past 60 years and the high-precision historical data reconstructed from other studies from A.D. 1 to 2000, based on some assumptions,selecting Hailar, Xilinhot, Bailing Temple as a representative site of meadow steppe, typical steppe and desert steppe,and making use of CENTURY model to reconstruct the sequence of grassland productivity in Inner Mongolia from A.D. 1 to 2000. On the basis of this, the periodic characteristics of ANPP and its relationship with meteorological factors were discussed by using statistical methods such as Pearson correlation, continuous wavelet and cross wavelet.The main conclusions are as follows:1) Using the average annual NDVI and meteorological data of grassland, three representative sites were selected to represent the three grassland -the meadow steppe, typical steppe, desert steppe. ANPP values simulated by CENTURY model has a good consistency with the NDVI in the same period, and passed the 99% confidence level test, which indicates that the CENTURY model can well reflect the changing characteristics of ANPP.2) Nearly 60 years, the climate of meadow steppe, typical steppe and desert steppe showed the trend of warming in Inner Mongolia. The ANPP fluctuates significantly in the three grasslands, which is different from that of the typical steppe has a slight decrease trend, the meadow and desert steppe have a slight increase trend. The typical steppe fluctuates the most, the desert steppe is the second, and the meadow steppe is the smallest; the meadow steppe has the highest productivity, the lowest is desert steppe, and the typical steppe center. There are quasi-3?5a significant periods in the three grasslands, and the quasi-7a and quasi-9a significant periods are also appeared in typical and desert steppe. The ANPP of meadow steppe is mainly controlled by temperature, the higher the temperature,the higher the ANPP, the typical steppe and desert steppe are mainly controlled by precipitation, and the warming is not conducive to the increase of ANPP. It can be used as an example of a change in the productivity of the warm grassland.3) From A.D.l to 2000, the long-term fluctuation of reconstructed ANPP in meadow steppe, typical steppe and desert steppe was similar, among which there was a significant low value stage in the Wei-Jin Dynasties and the Ming-Qing Dynasties. ANPP has significant cycle characteristics from 1 to 2000. The ANPP of meadow steppe has quasi-300a, quasi-150a and quasi-50a significant periods.The ANPP of typical steppe has quasi-280a and quasi-64a significant periods. The ANPP of desert steppe has quasi-256a and 64a significant periods.Precipitation and temperature have a significant effect on grassland productivity,but in different types of grassland effects are different. Typical steppe and desert steppe are mainly controlled by precipitation, and meadow steppe is controlled by precipitation and temperature.4) There are obvious spatial distribution differences of ANPP meanings in the Inner Mongolia grassland area from A.D 1 to 2000, showing an irregular band pattern from east to west. The spatial distribution of ANPP mean from A.D 1 to 2000,ANPP greater than 140gC/m2, greater than 80gC/m2 less than 140gC/m2, less than 80gC/m2 area respectively with corresponding the meadow, typical and desert steppe area.Compared with the ANPP mean distribution, the warm period ANPP showed a general increase of area of more than 140gC/m-, and the cold period was mainly manifested in a significant decrease of area of ANPP more than 80 gC/m2. Warm and humid climate will make the desert grassland into a typical grassland or meadow grassland; dry and cold weather will make the grassland desertification, desert grassland area increased.The above research results will help to understand the global carbon cycle,grassland nomadic tribal livestock economy changes and the rational development and utilization of grassland natural resources to provide theoretical support.