The balance between various elements of the ecosystem has been the focus of research related to the ecology of global change and biogeochemical cycles.Ecological stoichiometry is the study of the balance of energy and elements in biological systems and based on the general laws of physics,chemistry and biology.Ecological stoichiometry provides an integrated approach to investigating the stoichiometric relationships and rules in biogeochemical cycling and ecological processes.The primary nutrient elements,carbon(C),nitrogen(N)and phosphorus(P),play an important role in plant growth and regulating various botanic physiological functions.The cycling of N and P are tightly coupled to C cycling in ecosystems,primarily through aspects related to ecosystem carbon primary production. Leaf C,N and P stoichiometry varies throughout many aspects of plant biology.The ratios of C∶N,C∶P and N∶ P may reflect the balance between the plant demand in relation to N and P availability and may constrain various processes.Carbon,nitrogen,and phosphorus stoichiometry of plants reflect the utilization efficiency of plants with regard to soil nutrient elements.After a long period of evolution,plants had form and their own unique ecophysiology and ecological stoichiometry in karst landscapes.Carbon,nitrogen,phosphorus stoichiometry of plant leaves can reveal the regularity of nutrient cycling within karst ecosystems.Three quadrats,sized 20m*20m,in a secondary forest in the karst area of Maocun,Guilin were selected.A total of 186samples of 12plant types were collected.The ecological stoichiometry of carbon,nitrogen,and phosphorus were analyzed using multivariate statistical analysis to study the relationship between them and explored ecological indicating functions of carbon,nitrogen,and phosphorus stoichiometry in karst ecosystems.The results were as follows:Firstly,C,N,and P values in the samples'plant leaves were(456.192.16)mg·g~(-1),(7.710.26)mg·g~(-1),and(0.890.02)mg·g~(-1),respectively.Carbon, nitrogen,and phosphorus values were all lower than China's and global averages.Although the higher contents of N and P in the karst limestone soil because of their low availability and their slow uptake and utilization efficiencies,nitrogen and phosphorus still presented as common limitations to plant growth within the karst area.Secondly,in this study,C∶N,C∶P,and N∶P in the plant leaves of the samples were 80.866.74,639.6553.79,and 10.42 0.89,respectively.Because the contents of N and P in plant leaves in the karst area were significantly lower,it resulted in higher C∶N and C∶P values.Thirdly,the rules of N∶P was less than 14,indicating nitrogen limits;N ∶P was more than 16,indicating nitrogen limits;and N∶P between 14and 16showed that nitrogen and phosphorus limits were not entirely suitable for determining the limiting nutrient elements within the karst area.Lastly,correlation analysis between elements showed that there was a significant negative correlation between leaf C and N(P<0. 01),and a significantly negative correlation between C and P(P<0.05),while there was a significant positive correlation between N and P(P<0.01).This correlation reflected the change of the relative consistency of nutrient elements of plants.The results contributed to the understanding of plant adaptive mechanisms and ecological geochemical process,providing the theory basis for ecological control of the karst area.