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Using remote-sensing technologies, this study sought to provide an up-to-date map of
C3/C4 distribution representative of temperate grassland in northern China. Several studies
focused on the central grasslands of North America have demonstrated that C4 species coverage
can be discriminated from C3 species by using time-series vegetation index data based on their
phenological differences. Considering that the hydrothermal patterns and C4 percentage of grass
flora in the study area and North America are different, we first examined temporal features of
C3/C4 communities by using multitemporal moderate resolution imaging spectroradiometer normalized
difference vegetation index data throughout the 2010 growing season. It was found that
the asynchronous seasonality exhibited by communities with varied C3/C4 compositions also
existed in our study region. Based on this asynchrony and separation rate, a hierarchical decision
tree was developed to classify four grassland types with varied C3/C4 compositions. As a result,
a classification map of the mixed C3/C4 grassland was generated with an overall accuracy of
87.3% and a kappa coefficient of 0.83. The geographic distribution of C3 and C4 species showed
that the study area was dominated by C3 grasses, but C4-dominated grasslands accounted for
39% of the land cover. Thus C4 species also made an important contribution to grassland
biomass, especially in dry and low-lying saline-alkaline habitats. The results also indicated that
the trajectory-based methods for C3/C4 mapping rooted in asynchronous seasonality worked
effectively in the climate regimes of both northern China and North America.
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