Also to know is, can you use fresh wood chips as mulch?
For sure, nitrogen depletion will be a temporary problem when fresh wood chips are incorporated into the soil, which is why we should only use fresh chips as a surface mulch. Because of this, and the general coarseness of wood chips, they probably are best not used around vegetables and in annual flower beds.
Also, is mulch good for plants? Mulch may make a garden look tidy, but the work it does to improve the growing conditions for plants is what makes it most appealing. Those layers of bark or pine straw also improve soil texture, suppress weeds, and conserve water.
Subsequently, question is, can mulch kill plants?
Mulch packed up against the trunks of woody plants can rot bark and possibly kill plants.
Do you have to remove old mulch before applying new mulch?
For an annual bed, remove old mulch before you till the soil and add compost. If you‘re applying mulch to a perennial bed, you might be tempted to just add a new layer of mulch on top, but this can cause rot, nutrient starvation, and plant death. Remove as much of the old layers as possible before you add more.