2. Peat swamp forests

Natural peat swamps in SE Asia have been recognized as important reservoirs of biodiversity. In particular they contain a large number of endemic tree species, many owing significant commercial value. Peat swamp forests are the last refugees for several rare and endangered animals, including orang-utan, while streams and rivers draining from peatlands are important fish habitats. See also http://en.wikipedia.org/wiki/Tropical_peat

Peat swamp forest floor in Riau

Peat swamp forest floor in Riau

Peat swamp forests (PSF) are rain water fed ecosystems, and thus the nutrient input to this ecosystem comes only from rain water and trough dry deposition from the atmosphere. The concentrations of nutrients in peat profile under the upmost surface peat remain low (Könönen et al., 2015; Lampela et al., 2014). Excess amount of water in the forest floor causes intermittent lack of oxygen that inhibits the litter decomposition and thus creates favorable conditions for accumulation of organic matter i.e. peat. Incompletely decomposed organic matter from the dense rain forest vegetation accumulates into peat and over several millennia lasted peat increment has formed dome-shaped peat massifs between rivers.

Outline of peat swamp forest types after Whitmore (1984).

Outline of peat swamp forest types after Whitmore (1984).

As in boreal raised bogs, in PSF the direction of the water runoff is from the elevated center towards the margins. The main biomass forming flora in PSF comprises almost solely of trees and the peat is thus woody. The trees of PSF have often extensive supportive root systems with buttress or stilt roots as well as air conducting pneumatophores as adaptations to wet environment. Distinct forest types with typical floral communities and forest structure can be found in different parts of the peat dome. Forest floor small scale features (microtopography) consists of elevated surfaces, hummocks, and often wet depressions, hollows (Lampela et al., 2016). The yearly fluctuation in the water table at the forest floor can exceed 1 meter, which creates flooded conditions during the wet season and increasingly drained surface peat profile towards the end of dry season (Lampela et al., 2016). In comparison to the peat in boreal and temperate peatlands, the peat in tropical PSF has rather heterogenic physical structure. Remains of wood in varying size and degree of decomposition are often mixed with well decomposed substrate. Many of the basic ecological characteristics of PSF are usually described, at best, in very general terms in the literature. Lampela et al. (2014) studied in detail forest floor characteristics in surface peat (peat structure and nutrient composition) and in litter at differing microtopographical conditions and with the typical long-term water table position.

Close-up of the peat swamp forest floor during dry season in Central Kalimantan (Photo: J. Jauhiainen)

Close-up of the peat swamp forest floor during dry season in Central Kalimantan (Photo: J. Jauhiainen)

Forestry, by selective removal of commercial species of appropriate size, and non-timber tree species could form the most feasible options providing a regular, sustainable and financially rewarding return for investment (Vasander et al. 2014). However, illegal logging with methods destroying peat hydrology and forest structure undermines this.

Poorly planned timber felling can cause severe damage in forest (photo J. Jauhiainen)

Poorly planned timber felling can cause severe damage in forest (photo J. Jauhiainen)

Timber extraction canals dug into forest floor damage tree root systems, disturb ecosystem hydrology by increasing water outflow from the forest, and increase peat decomposition due to increased depth of oxic peat layer.

Timber extraction canals dug into forest floor damage tree root systems, disturb ecosystem hydrology by increasing water outflow from the forest, and increase peat decomposition due to increased depth of oxic peat layer.

Key words in finnish: suosademetsä, laittomat hakkuut, hydrologia, vesitase, kestävä käyttö, biodiversiteetti


Further information will be provided by Jyrki Jauhiainen and Harri Vasander