Peatland rehabilitation aims to repair ecosystem processes, productivity and services of the former peatland, but does not imply the reestablishment of the pre-existing biotic integrity in terms of species composition, community structure and ecosystem functions (Clarke and Rieley, 2010). Peatland restoration, i.e. the process of assisting the recovery of peatland that has been degraded or damaged to its original natural condition, goes one step further. Unlike the well-established studies of ecological restoration of temperate peatlands (Kozulin et al., 2010), knowledge of tropical peatland restoration is still in the early stage (Jauhianen et al., 2016; Jaenicke et al., 2010; Page et al., 2009).
In practice tropical peatland restoration trials have included activities on restoration of hydrology and restoration of vegetation (Jauhianen et al., 2016; Lampela et al., 2017).

Restoration of hydrology
Rizema et al. (2014) lists the first efforts to restore the hydrology in degraded peatlands:

Central Kalimantan Block A of the former MRP where Wetlands International built 20 dams in deep peat (>3 m). These dams have a width up to 30 m and consist of two rows of poles alongside bags filled with sand in the core (Suryadiputra, 2005). The dams were built by a local contractor in co-operation with the local community using building materials from outside the area (such as concrete and sand).

The same type of damswere built byWWF-Indonesia to block illegally dug canals in the Sebangau National Park; since 2005 more than 176 canal sections have been blocked (Maya, 2009).

Cooperation between University of Helsinki and Centre for International Cooperation in Sustainable Management of Tropical Peatland (CIMTROP) in KEYTROP project, which was joined later by EU-funded RESTORPEAT build and maintained series of 6 wide dams for research purposes in Ex-MRP area, Central Kalimantan. The overall objective was to investigate how peatland hydrology can be restored by blocking drainage canals. Peat and canal hydrology monitoring and greenhouse gas emission monitoring are reported, for example in Rizema et al. 2014 (hydrology) and Jauhiainen et al. 2008 (GHGs).

The Australian government-funded Kalimantan Forests and Climate Partnership (KFCP) is one of the earliest large-scale REDD+ demonstration activities in Indonesia (active 2009 – 2013). One of the four components of this project aimed to demonstrate effective approaches and techniques to rehabilitate peatland at scale and preserve threatened peat swamp areas in Block-A at the Ex-MRP area.

Restoration of vegetation
Another major challenge for tropical peat restoration is establishment of vegetation. In the case of peat swamp forests where most of the vegetation is trees this means reforestation. When the trees are cut and burnt, there are very limited possibilities for natural regeneration (Graham & Page 2012, Blackham et al. 2013, 2014). Instead, there is a need for active reforestation.
Harsh conditions in the open degraded peatlands set several prerequisite for reforestation success. Firstly, when the sheltering canopy cover of a natural peat swamp forest is lost, the open degraded peatland becomes very hot in the daytime. Secondly, without regulating vegetation both flooding and drought are also more pronounced. Thirdly, most of the nutrients from the soil are lost when the fertilizing litter of a living canopy is removed, and soil surface layers containing most of the available nutrients for vegetation are first burnt and then leached with heavy rain to the watercourses. Lastly, wild fires form the main obstacle in successful return of trees on degraded peatlands.

The requirements for successful reforestation are:

Seedlings or seeds of species that can survive in open and hot environment with high tolerance for flooding and drought. Even though most of the peat swamp species need shelter from closed canopy, there are pioneer species such as Combretocarpus rotundatus, Shorea balangeran and Cratoxylon arborescens that tolerate more open conditions even in early stages.

Appropriate hydrological conditions for seedlings growth through water table regulation. Some species tolerate heavy flooding even at early stages but in most cases long prevailing high water table kills seedlings. This can be avoided by planting seedlings on elevated surfaces, for example on constructed mounds.

Securing the nutrient supply for the seedlings. This can be either done by selecting species with very modest nutrient requirements (for example nitrogen binding species) or enhancing the nutrient status by fertilizing

The area must be secured from fires and logging for several years/decades. During the dry season when dry peat surface burns easily and wild fires spread unexpectedly, constant monitoring and sufficient firefighting equipment and personnel have to be organized. To avoid logging or other unwanted activities in the reforestation areas, the land-tenure rights have to be clear and well implemented. This requires sufficient and long-term communication with the local communities and authorities.

Experimental demonstration plots on tropical peat reforestation have been made by scientists (CIMTROP, Saito et al. 2005, Morrogh-Bernard et al. 2011, Graham et al. 2013), and practical reforestation programs by governmental organizations and NGOs (Wetlands International, Indonesian government, Australian government KFCP, WWF, The Borneo Orangutan Survival Foundation). There is very little published information on the success of these experiments and programs. Many of the areas have been destroyed by fires and there is still very little information on tree species survival and growth potential that could be used in reforestation planning. Until now, there are more studies on natural regeneration conducted on degraded peat areas (Blackham et al. 2013, 2014) than active reforestation experimenting (Lampela et al. 2017).
Approaches for reforestation can include everything from small scale demonstration plots to seed sowing from helicopter to wide areas. One of the more systematic approaches, i.e. Buy a Living Tree System (BLTS), was implemented by CIMTROP.

STEM-reforestation demonstrations
During our STEM –project a practical reforestation experimenting was started in areas near the provincial capital (Palangka Raya) of Central Kalimantan. These areas were monitored until the wide-spread wild fires destroyed the site in 2015. Results from these experiments are in publication phase or published (i.e. Lampela et al. 2017) .

Aim of the study was to find suitable tree species for tropical peat swamp restoration. The first study site was clear-felled, drained and several times burnt deep peat area in the Kalampangan zone and the other was degraded shallow peat flooding area in the Natural laboratory area in the Sabangau National park.

We chose species which had potential for restoration purposes or importance for local communities. Seeds were collected from local sources and seedlings were grown in a field nursery for 6-11 months. The seedlings were planted in three blocks representing differing wetness conditions typical for the area. For species with already known potential for restoration, we performed management practices such as fertilizing, mounding and weeding to further study the possible practices for restoration. Mortality, diameter and height growth of the seedlings was monitored several times of the year. Environmental variables such as ground water table, soil temperature and chemistry were also monitored.

Further information on restoration of tropical peat hydrology will be provided by
Jyrki Jauhiainen and Harri Vasander and information on tropical peat reforestation by Maija Lampela