Kaleka Agroforest in Central Kalimantan (Indonesia): Soil Quality, Hydrological Protection of Adjacent Peatlands, and Sustainability

Abstract

Increased agricultural use of tropical peatlands has negative environmental effects. Drainage leads to landscape-wide degradation and fire risks. Livelihood strategies in peatland ecosystems have traditionally focused on transitions from riverbanks to peatland forests. Riparian ‘Kaleka’ agroforests with more than 100 years of history persist in the peatlands of Central Kalimantan (Indonesia), where large-scale open-field agricultural projects have dramatically failed. Our field study in a Dayak Ngaju village on the Kahayan river in the Pulang Pisau district involved characterizing land uses, surveying vegetation, measuring soil characteristics, and monitoring groundwater during a period of 16 months. We focused on how local practices and farmer knowledge compare with standard soil fertility (physical, chemical, biological) measurements to make meaningful assessments of risks and opportunities for sustainable land use within site-specific constraints. The Kaleka agroforests around a former settlement and sacred historical meaning are species-rich agroforests dominated by local fruit trees and rubber close to the riverbank. They function well with high wet-season groundwater tables (up to −15 cm) compatible with peatland restoration targets. Existing soil quality indices rate the soils, with low soil pH and high Alexch, as having low suitability for most annual crops, but active tree regeneration in Kaleka shows sustainability.

Can We Simultaneously Restore Peatlands and Improve Livelihoods? Exploring Community Home Yard Innovations in Utilizing Degraded Peatland

“…Peatland in its natural state functions as a large store of carbon [4,5] and water [6,7]. After being drained, they can be developed for agriculture, forestry, and energy [8][9][10], however, this can also result in loss of ecosystem services such as regulation of the hydrological cycle [4,9,10], hosting a rich biodiversity [11][12][13], carbon sequestration [14,15], and provision of livelihoods for the local people [16,17]. There continues to be new peatland development in many areas, including drainage and establishment of new oil palm plantations.…”

“…Repeated peat fires cause peatland degradation due to loss of peat soil as well as changes in its chemical and physical properties [19,20]. In addition, the choice of prospective species on peatland is limited [19] due to low fertility, high acidity, and poor drainage [10]. Another challenge is the suitability of existing agricultural technology on peatlands.…”

“…Due to its fragility, and to avoid degradation of land function, careful and prudent management is required. For this reason, appropriate technological innovations are needed so that peatlands can be used sustainably [10]. Thus, the challenge is how to utilize degraded peatland for cultivation while at the same time reducing or avoiding its negative impact.…”

Flooding tolerance of four tropical peatland tree species in a nursery trial

“…As reported earlier, some agroforestry systems located in peatlands in Central Kalimantan have deep water levels. For instance, the ground water level in an agroforest that includes N. lappaceum and Dyera polyphylla tree species in Tumbang Nusa village of Central Kalimantan province in 2014 fluctuated from between -20 to -140 cm [28], whereas the ground water level in another agroforest farm that included fruit tree species in Henda village, Central Kalimantan, ranged from -8 to -60 cm in 2019 [44]. However, flooding in the area was not reported.…”

“…In addition, a range of fruit tree species, including Nephelium lappaceum [28,42] (and Durio zibethinus [37,43,44], have also been planted as part of peatland restoration initiatives, particularly in agroforestry systems, where they are planted together with other tree species.…”