Lee Kong Chian Natural History Museum

Secondary Forest

Photo credit: Wang Luan Keng

Description

A secondary forest consists of vegetation which have developed after the destruction of the original 'primary' vegetation. Secondary forests usually possess a much lower diversity of plants and animals compared to the original forest. This might be due to the limited dispersal of plants and animals from a primary source as well as the simplified forest structure not being able to support primary forest species.

In Singapore, much of its original primary forests have been cleared, used and subsequently abandoned, thus allowing secondary forests to form. In the 19th and early 20th century, land was cleared and cultivated until the soils were compacted and depleted of nutrients and organic matter. Only a restricted number of pioneer plant species were able to re-colonise these lands, particularly the dominant shrub Adinandra dumosa (tiup-tiup), thus giving rise to secondary forest and shrub known locally as 'Adinandra belukar'. In other less degraded areas, however, other fast-growing pioneers become the dominant species, including those from the genera Macaranga and Trema. As these pioneer species are not shade tolerant, their own seedlings eventually fail to propogate and they will be succeeded by other more tolerant species, forming taller, more species-rich forests. Though some secondary forests have existed for a century in Singapore, they have a more even-aged structure with lower diversity compared to primary forests and they still lack emergents such as dipterocarps.

Though supporting less diversity than primary forests, tall secondary forests in Singapore can be important as they cover a much larger area than Singapore's remnant primary forests and are often also utilised by most remaining primary forest vertebrates. Young secondary forests, on the other hand, supports much less biodiversity due to its smaller patch size, simpler forest structure, and greater isolation from source areas. These young forests have also been observed to be very susceptible to invasion by non-native species of plants and animals. This has been especially true in the past 30 years.

Keywords

Secondary Forest

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