Rumor has it that mulching garden beds or trees and shrubs could starve plants.[…] it becomes available to plants once those microorganisms have used up enough soil carbon, “breathing” it out of the ground as carbon dioxide. […] this scenario – plants being starved of nitrogen – holds true when you mix a load of high-carbon, organic material into the soil. […] that rumor that plants will suffer from high-carbon mulches keeps going around, despite the field experience of agricultural researchers and many gardeners.
A garden, like any biological system, represents a complex interaction of energies, so sweeping generalizations don’t always hold.
Via: Home and Gardening