Heaviest forest
Jedediah Smith Redwoods State Park, Redwood National Park, Humboldt Redwoods State Park
4,000 tonne(s)/metric ton(s)
United States ()

The world’s heaviest forests (based on aboveground biomass comprising all live and dead plant material) are found in the northern portion of the range of coast redwoods (Sequoia sempervirens) in Del Norte and Humboldt Counties in northern California, USA. Four long-term, permanent research plots - located in Jedediah Smith Redwoods State Park, Redwood National Park and Humboldt Redwoods State Park - have each recorded in excess of 4,000 tonnes (4,409 US tons) of trees per hectare .

One of these plots included >800 tonnes (>880 US tons) per hectare of dead wood, which is also a global record for a closed-canopy forest.

Redwood forests are also invaluable carbon sinks. One study, published in the journal Forest Ecology and Management in Sep 2016, estimated that they store 2,600 tonnes (2,866 US tons) of carbon per hectare (2.4 acres) - more than double the absorption rate of the Pacific Northwest’s conifer trees or Australia’s eucalyptus forests.

Not surprisingly given that forest mass is determined by the size of the trees, California is also home to the tallest forest in terms of tall trees per hectare. Rockefeller Forest (which lies within Humboldt Redwoods State Park) occupies an area of only 344 hectares (850 acres), yet contains 130 trees that are >107 m (>351 ft) tall, including 30 trees that stand taller than 110 m (360 ft 10.7 in). This equates to a density of one >107 m (>351 ft) tree for every 2.6 hectares (6.4 acres), or 0.37 trees per hectare.

The world 's largest individual tree (by volume and mass) is a giant sequoia (Sequoiadendron giganteum) named General Sherman, located in Sequoia National Park in the Sierra Nevada Mountains of California, USA. The tree is 83.6 m (274 ft 3.3 in) tall and has an aboveground dry mass of 582 tonnes (642 US tons). The bark alone has a dry mass of 48 tonnes (53 US tons), and the tree supports 1.68 tonnes (1.85 US tons) dry mass of leaves. As of 2013, total volume of wood and bark was 1,591 m3 (56,186 cu ft) – 1,389 m3 (49,052 cu ft) of which is in the main trunk. General Sherman is estimated to contain the equivalent of almost 675,000 board feet of timber, enough to make in excess of 5 billion matchsticks.