What happens to the carbon stored in the plants when they die?

Know what happens? P.S. If it doesn't help sorry Answer-Because when fossil fuels are burned,the fossil fuels are running out more and more and so sientists are trying to figure out a way for fossil fuels to become more of a renewable resources then a nonrenewable resource so that we have more of a likely cause that we will have a future use of all the fossil fuel that are about to run out just like an extinct species. Your welcome if it worked!

i think the answer is Released as CO2 by the action of decomposers such as bacteria and fungi. 

C. a mature ovule of a plant.