Abstract
In recent years, with the constant change in the global climate, the effect of climate factors on net primary productivity (NPP) has become a hot research topic. However, two opposing views have been presented in this research area: global NPP increases with global warming, and global NPP decreases with global warming. The main reasons for these two opposite results are the tremendous differences among seasonal and annual climate variables, and the growth of plants in accordance with these climate variables. Therefore, it will fail to fully clarify the relation between vegetation growth and climate changes by research that relies solely on annual data. With seasonal climate variables, we may clarify the relation between vegetation growth and climate changes more accurately. Our research examined the arid and semiarid areas in China (ASAC), which account for one quarter of the total area of China. The ecological environment of these areas is fragile and easily affected by human activities. We analyzed the influence of climate changes, especially the changes in seasonal climate variables, on NPP, with Climatic Research Unit (CRU) climatic data and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite remote data, for the years 2000–2010. The results indicate that: for annual climatic data, the percentage of the ASAC in which NPP is positively correlated with temperature is 66.11%, and 91.47% of the ASAC demonstrates a positive correlation between NPP and precipitation. Precipitation is more positively correlated with NPP than temperature in the ASAC. For seasonal climatic data, the correlation between NPP and spring temperature shows significant regional differences. Positive correlation areas are concentrated in the eastern portion of the ASAC, while the western section of the ASAC generally shows a negative correlation. However, in summer, most areas in the ASAC show a negative correlation between NPP and temperature. In autumn, precipitation is less important in the west, as opposed to the east, in which it is critically important. Temperatures in winter are a limiting factor for NPP throughout the region. The findings of this research not only underline the importance of seasonal climate variables for vegetation growth, but also suggest that the effects of seasonal climate variables on NPP should be explored further in related research in the future.
Highlights
Terrestrial net primary productivity (NPP) is the primary factor involved in identifying ecosystem carbon sources and carbon sequestration, and is one of the main sources of human food resources, wood products and fuel (Knapp and Smith, 2001; Zhou et al, 2002)
The NPP in the ASAC has increased in recent years; vegetation conditions in this area have improved substantially
Based on the analysis of Climatic Research Unit (CRU) climatic data, we found that both annual temperature and annual precipitation in ASAC increased from 2000 to 2010
Summary
Terrestrial net primary productivity (NPP) is the primary factor involved in identifying ecosystem carbon sources and carbon sequestration, and is one of the main sources of human food resources, wood products and fuel (Knapp and Smith, 2001; Zhou et al, 2002). The Intergovernmental Panel on Climate Change (IPCC) report indicates that the global average temperature has risen by 0.74°C over the past 100 years (1906–2005), with a warming rate of 0.13°C/decade in the most recent 50 years (IPCC, 2007). An emerging body of literature suggests that climate change has a pronounced impact on global terrestrial NPP (Houghton et al, 1999; Houghton, 2002; Nemani et al, 2002). A precise understanding of the driving mechanisms of climate change on NPP variability has important theoretical and practical implications for evaluating the environmental quality of terrestrial ecosystems, regulating the ecological process, and estimating the terrestrial carbon sink (Friend et al, 2014)
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