There are numerous benefits to using mulch around plant beds, shrubs and trees.
Mulch can help plants grow that are located in shady areas, and will increase the temperature of soil in winter and decrease it in summer.
A cubic yard of mulch will typically weigh between 400 and 800 pounds (181 to 363 kg).
The weight of mulch will depend upon its moisture content.
Compost is usually heavier and a cubic yard will typically weigh between 1000 and 1600 pounds (454 to 726 kilograms).
Soil blends are even heavier with a cubic yard typically weighing between 2200 and 2700 pounds (998 to 1225 kilograms).
Mulch will minimize the amount of water that an established plant requires.
Mulch can inhibit weed germination when it is fresh.
A layer of mulch can prevent certain diseases in plants.
Mulch looks good in planting beds and will make them appear more uniform.
~ Fun Fact ~
Mulch does not have to be organic to be effective. As long as the substance will biodegrade and it is not toxic it can be used.
Resources
http://mulchstoremn.com/faq.html