Secondary forest

Secondary forestation is common in areas where forests have been degraded or destroyed by agriculture or timber harvesting; this includes abandoned pastures or fields that were once forests. While many definitions of secondary forests limit the cause of degradation to human activities, other definitions include forests that experienced similar degradation under natural phenomena like fires or landslides. It typically takes a secondary forest 40 to 100 years to begin to resemble the original old-growth forest; however, in some cases a secondary forest will not succeed, due to erosion or soil nutrient loss in certain tropical forests. Depending on the forest, the development of primary characteristics that mark a successful secondary forest may take anywhere from a century to several millennia. Hardwood forests of the eastern United States, for example, can develop primary characteristics in one or two generations of trees, or 150–500 years. Today, most of the forests of the United States – especially those in the eastern part of the country – as well as forests of Europe consist of secondary forest. == Characteristics ==

. This mixed conifer and broadleaf woodland is located in West Sussex, United Kingdom. Secondary forests tend to have trees closer spaced than primary forests and contain less undergrowth than primary forests. Usually, secondary forests have only one canopy layer, whereas primary forests have several. These secondary disturbances can clear the canopies to encourage lower canopy growth as well as provide habitats for small organisms such as insects, bacteria and fungi which may feed on the decaying plant material. Additionally, forest restoration techniques such as agroforestry and intentionally planting/seeding native species can be combined with natural regeneration to restore biodiversity more effectively. Land-use conversions from secondary forests to rubber plantations in Asia are expected to rise by millions of hectares by 2050; as such, the carbon stored within the biomass and soil of secondary forests is anticipated to be released into the atmosphere. Recommendations from the Intergovernmental Panel on Climate Change (IPCC), Convention on Biological Diversity, and REDD+ have led to efforts to reduce and combat deforestation in places like Panama and Indonesia. Natural and human-assisted growth of secondary forests can offset carbon emissions and help countries meet climate targets. == Biomes ==

Rainforests canopy on Ko Mak island in Thailand In the case of semi-tropical rainforests, where soil nutrient levels are characteristically low, the soil quality may be significantly diminished following the removal of primary forest. In addition to soil nutrient levels, two areas of concern with tropical secondary forest restoration are plant biodiversity and carbon storage; it has been suggested that it takes longer for a tropical secondary forest to recover its biodiversity levels than its carbon pools. However, due to the diminished quality of soil, among other factors, the presence of a significant majority of primary forest species fail to recover in these second-growth forests. == See also ==

• CIFOR Secondary Forest • FAO Forestry • World Resource Institute == External links ==