The leaf carbon isotope ratio (C-13) is a useful parameter for predicting a plant's water use efficiency, as an indicator for plant classification, and even in the reconstruction of paleoclimatic environments. In this study, we investigated the spatial pattern of leaf C-13 values and its relationship with plant functional groups and environmental factors throughout China. The high leaf C-13 in the database appeared in central and western China, and the averaged leaf C-13 was -27.15, with a range from -21.05 to -31.5. The order of the averaged C-13 for plant life forms from most positive to most negative was subshrubs>herbs=shrubs>trees>subtrees. Leaf C-13 is also influenced by some environmental factors, such as mean annual precipitation, relative humidity, mean annual temperature, solar hours, and altitude, although the overall influences are still relatively weak, in particular the influence of MAT and altitude. And we further found that plant functional types are dominant factors that regulate the magnitude of leaf C-13 for an individual site, whereas environmental conditions are key to understanding spatial patterns of leaf C-13 when we consider China as a whole. Ultimately, we conducted a multiple regression model of leaf C-13 with environmental factors and mapped the spatial distribution of leaf C-13 in China by using this model. However, this partial least squares model overestimated leaf C-13 for most life forms, especially for deciduous trees, evergreen shrubs, and subtrees, and thus need more improvement in the future.

The leaf carbon isotope ratio (C-13) is a useful parameter for predicting a plant's water use efficiency, as an indicator for plant classification, and even in the reconstruction of paleoclimatic environments. In this study, we investigated the spatial pattern of leaf C-13 values and its relationship with plant functional groups and environmental factors throughout China. The high leaf C-13 in the database appeared in central and western China, and the averaged leaf C-13 was -27.15, with a range from -21.05 to -31.5. The order of the averaged C-13 for plant life forms from most positive to most negative was subshrubs>herbs=shrubs>trees>subtrees. Leaf C-13 is also influenced by some environmental factors, such as mean annual precipitation, relative humidity, mean annual temperature, solar hours, and altitude, although the overall influences are still relatively weak, in particular the influence of MAT and altitude. And we further found that plant functional types are dominant factors that regulate the magnitude of leaf C-13 for an individual site, whereas environmental conditions are key to understanding spatial patterns of leaf C-13 when we consider China as a whole. Ultimately, we conducted a multiple regression model of leaf C-13 with environmental factors and mapped the spatial distribution of leaf C-13 in China by using this model. However, this partial least squares model overestimated leaf C-13 for most life forms, especially for deciduous trees, evergreen shrubs, and subtrees, and thus need more improvement in the future.