Yes there is relationship between soil nitrogen and leaf nitrogen content but i dont think so with respect to leaf carbon and soil carbon content. Plant can also get C from CO2 through photosynthesis. 

Care !! These relations have to be analyzed as particular cases. I will try to give you some examples. Regarding your question, the carbon is not related, at least in forest plantations. To the nitrogen, if related, but be careful in analyzing this relationship. This relationship can be positive or negative, thereby indicating that you must be careful. More nitrogen in the soil frequently associated with higher leaf nitrogen concentration. It is not always the case. Sometimes the application of nitrogen increases the growth of the plantation, which could result in dilution effect. If this happens, when you analyze the foliar concentration, it will be less. regards

Yes, there is.

You might also want to consider the particular plant species/types of leaves and the soil types.  Coniferous and deciduous trees have different foliage (leaves vs. needles) which impact soil organic matter quality in different ways.  Additionally, the conditions for decomposition in a site would likely impact how much/the rate of incorporation of the foliage.

No studies as such I find on the relationship of leaf carbon and nitrogen concentration to soil carbon and nitrogen concentration. 

@ Rebecca Lever, yes I want to know the carbon and nitrogen concentration in leaves of the particular plant species and  under the soil of these plant species. 

The chemical composition of OM inputs (leaves, braches, roots) is only one of the factors affecting the RELATIVE proportion of C and N in the soil (i.e. the C/N ratio). The other factors are climate, redox conditions, microbial acitivity, soil pH and many others that affect C losses by mineralization, as well as microbial activity, plant uptake, redox conditions and mineralogy (and others) influencing N transformations and losses. The total contents also depends on the amounts of the inputs (ecosystem productivitty). Just think it's a sort of budgets between inputs and losses.

I think this is a complex question. To get you straight answer you would have to more specific in terms of parameters.  I agree with Eleonora's answer above... I attach one case study from Denmark by Vesterdal et al. (2008) that can get you some insight into your problem.... "...Forest floor and litterfall C/N ratios were not related, whereas the C/N ratio of mineral soil (0–30 cm) better indicated N status under deciduous species on rich soil..."

Arshad your question is really articulative. Shall we take  it  this way , whether or not soil C:N ratio affect the leaf  C:N ratio ? . My answer will big affirmative. Any change in concentration of soil C will bring simultaneous change in N status , considering the C:N ratio   of  soil as a constant . Such  soil C:N ratio  will trigger  the better microbial diversity plus the higher buffering capacity of the soil , thereby , maintain the better nutrient supply to above ground plant parts  .