Carbohydrates are utilized as an energy source during plant metabolism. Additionally,they are the primary photosynthates,and are important in other metabolic processes in plants. Plant carbohydrates are classified as either structural carbohydrates( SCs) or non-structural carbohydrates( NSCs). SCs,such as lignin and cellulose,are primarily used for the construction of plant morphology. NSCs,such as glucose and starch,are mainly used in metabolic processes.The NSC contents in leaves represent not only the supply of carbon,but also,to some extent,the adaptation mechanisms of plant species in response to the environmental changes. Leaf NSCs are mainly composed of soluble sugars and starch. The soluble sugars in leaves are primarily glucose,sucrose,and fructose,and play important roles in plant physical adaptation mechanisms. In contrast,starch is used for long-term energy storage.We used the anthrone colorimetric method to determine the NSC levels( soluble sugar + starch) in the leaves of 242 plant species that are commonly found in three forest ecosystems in northeast China( Huzhong, Liangshui, andChangbaishan). We assessed the variations in NSC contents at the species,plant life form,and community levels. We also analyzed the changing trends in the leaf NSC content and its components with temperature. The frequency distributions for leaf NSC and its components were highly skewed,and the content levels of leaf NSCs and their components were medium to low in most plant species. The average concentrations of soluble sugars,starch,and NSCs in 242 plant species were 63.31,65. 66,and 128. 96 mg / g,respectively. These values varied significantly across plant life forms. The leaf soluble sugar content in trees was 76. 87 mg / g,which was significantly higher than that in shrubs and herbs. The leaf starch content in herbs was 71. 92 mg / g,which was significantly higher than that in trees and shrubs. The NSC content in trees was 133. 82 mg / g,and was higher than that in shrubs and herbs. Furthermore,leaf soluble sugars,starch,and NSC in trees increased from north to south in the three forest ecosystems. The average soluble sugars content in trees in Huzhong,Liangshui,and Changbaishan were 58. 60,65. 91,and 99. 96 mg / g,respectively,the average starch contents in trees in Huzhong,Liangshui,and Changbaishan were 55. 83,65. 07,and 75. 93 mg / g,respectively,and the average NSC contents in trees in Huzhong,Liangshui,and Changbaishan were 111. 14,121. 32,and 153. 72 mg / g,respectively. The leaf starch contents were higher in deciduous trees than in evergreen trees,but there were no apparent differences between the leaves of deciduous and evergreen trees in terms of soluble sugar.In conclusion,these data support the carbon limitation hypothesis,which states that NSC contents decline with decreasing temperature from south to north owing to reduced carbon assimilation. Our findings provide basic data on carbon metabolism and the adaptation strategies of plant species in a typical forest ecosystem in northeast China,and provide new insights into the underlying mechanisms and responses of plant species to future climate changes.