The potential of sago palm forplantation on rewetted drainageimpacted peatland
Yukako Monda
Kyoto University, JapanDrained-based Land use of Peatlands causes many problems

Problem can be solved byraising the water level
Zoningbased on scientific results and social consensus

Major degradation

Minor degradation
Wichtmann et al.2016

Forest Rehabilitation

PaludiculturePaludiculture
The sustainable production of biomass (agricultural orsilvicultural ) on wet peatlands(Wichtmann et al. 2016).
Re-wetted peatlands also OK.

This include the revival of traditional land use throughmodified land-use schemes.

Sago palm (Metroxylon sagu)
・Traditional cultivated tropical wetland plant
・Submerged condition = OK・Starch accumulation in the pith・Cultivated by methods based on semi-traditional cultivation

Smallholder’s plantations by semi-traditional method(Indigenous knowledge)

Sago's root suckers
for transplantation

Manual slashing trees/shrubs/weeds
To make planting row (partial field preparation)
After transplanting: about twice a year

No fertilization and No sucker control

Flower bud
Change infrond length

The owners decide harvest timing by flower bud formation→Little or no maintenance is carried out after planting

Sago Cultivation in Tebing Tinggi Island, Riau

History of sago cultivation in research site
1980s Sago cultivation was started

2005 Small canal was built
2009 Large canal was built and connected→Peatland was drained

Productivity of sago palm in the village had declined significantly(lower yields, increased mortality,and reduced growth rates ofjuvenile individuals: Sasaoka 2015)2014 Massive Fire
Due to the fire extinguishingactivities by villagers, sago
cultivation is continuing.
Peatland with ferns growing after drainage and peat fireHistory of sago cultivation in research site
2015 Canal Blocking
Water level is kept highDid sago palm productivity recover after re-wetted?

Methods

Owners of Small Holder’s Sago Plantation(Plots location and Canal)
The average peat depth → 5.85 m, up to 8.70 m (Nasrul et al. 2020).
Peat depth → Thicker on the upper reaches of the canal (KLHK 2015).
E
EC=0.9 – 1.1 mS/cm

ENSeNAIAM

NSWWNCanalC

Methods

Sago Census

Trunk Phase (Trunk Height >2m)
→ Trunk height and dbh

Large Rosette Phase(Trunk Height < 2m) →Count

Trunk Phase

Field Work
Nov. 2016, Nov. 2017, Mar. 2020

Large Rosette Phase

Stem heightMethods

Measurement of harvest size

4 palms : Suitable size for harvest(decided the harvest timing by Owner )Methods

Annual sago yield comparisons

Jong FS. 2001. Sago production in Tebing Tinggi subdistrict, Riau, Indonesia. Sago Palm 9:9-15.
→Before drainage (August 1999) by social economic surveys.

Annual harvested number of trunks(27 smallholder sago farmers)
Trunk height at harvest(5 groups of sago harvesting workers)

Results

Relationship between estimate maximum trunkheight and environmental condition
According to villagers,
Harvest trunk height → Generally 7-10 m,
up to 12 m,
The most upstream 5-6m

(Monda et al. submitting)

Shallower

Ticker

The thicker the peat thickness, the smaller the maximum trunk heightResults

Comparison of harvest size

2016-2020(current)

1999(before drainage)(Monda et al. submitting)

Sago palm cultivation recover harvest size by re-wetting

Results

Comparison of sago yieldNo. ofsurvey
plots

Annual harvested trunks(max-min)2016-2020

1626.8 (7.2-67.5)

1999

2726.0 (5.6-53)(Monda et al. submitting)

Sago palm cultivation recover annual sago yield by re-wetting.
Large variation in the annual trunk yields

Forest structure of sago palm cultivation(Monda et al. submitting)Results

Type 1

Type 2Type 3201620172020(Monda et al. submitting)Results
14N

13
15

12428316

76111591017181920(Monda et al. submitting)Discussion

Sago productivity recovering?

→Yes
Harvest size and number of harvested palms has recovered tothe same level as before drainage.

→Yield varies from year to year
Characteristic of smallholder’s plantation.

To assess forest dynamics of sago palm, long-term surveys andplots that cover a variety of forest structures are important.

Discussion

Annual yields

Variations in the number of harvested palms, andlow number of harvested palms can be improvedby proper management (Jong 2001 and Yanagidate et al 2009).
High number of harvesting is difficult achievealternate year harvesting (Sato 1986).

The choice of feasible management is importantAcknowledgement
Professor Emeritus Shigeo Kobayashi
People in Sungai Tohor village
Professor Kosuke Mizuno
This research was supported by JASTIP, and ResearchInstitute for Humanity and Nature (RIHN : a constituent
member of NIHU) Project No. 14200117