Soil dynamics in tropical forest transition: a case study from Borneo, Indonesia

THINKING beyond the canopy

Soil dynamics in tropical forest transition: a case study from Borneo, Indonesia

[Imam Basuki and Yves Laumonier][July, 22nd 2014 – Cairns, Australia]


Few studies had been conducted in

SEA on deforestation’s impact on soils.

The research hypothesized that

deforestation and forest degradation

have decreased performance of soil

function such as fertility, water

regulation and sequestration of GHG.

Introduction

Presenter

Presentation Notes

Photo: Traditional tree cutting – Kapuas Hulu Women collecting Piliostigma reticulatum pods for animal feed.


Concept of local LUC


Methods Site selection considered: slope ≥ 40%, slope position (up,

mid, bottom), and distance to primary forests 33 sites. Soil samples were collected from 5 LUs, i.e., the primary

forest and the adjacent logged over forests, rice field, fallow, and rubber garden. Lab. analyses on soil physical and chemical properties.


Research site


Results

Presenter

Presentation Notes

Photo: tree in Primary forest, Kapuas Hulu


Status of soil surface characteristics by land types

-------------------------------- Land type (N) -----------------------------------

Soil characteristics

Primary Forest (12)

Logged Forest (8)

Upland rice (5)

Fallow (4)

Rubber (4)

CEC (me/100g) L - M VL - L L VL VLBase Saturation (%) VL VL VL - L L LP2O5 (ppm) VL - M VL VL VL VL

K2O (ppm) M - VH L - VH M - VH VH M - VHC (%) L - VH VL - M VL - H VL - H VL - LN (%) L - M VL - L VL - M VL - M VL - LC/N M - H M M M L - MK+ (me/100g) VL - L VL - L VL - M L - M VL - LNa+ (me/100g) VL - L VL - L VL - L VL - L VLMg2+ (me/100g) VL VL VL - L VL VLCa2+ (me/100g) VL VL VL VL VLAl3+ (me/100g) VL VL VL VL VL


Stock changes on mean carbon and exchangeable cations in the soil surface

Land-use Soil layer

Change in stocks of soil carbon and exchangeable cations (kg/ha)

C N P2O5 Ca2+ Mg2+ K+ Na+ Al3+

Primary forest (PF)

1 *45422.88 *3370.96 *9.06 *101.51 *44.74 *72.95 *30.94 *668.45

2 *15560.84 *1266.95 *4.26 *121.39 *35.83 *32.45 *26.70 *448.93

Logged over forest (LF) 1 -18884.48 -1300.42 -2.74 +20.40 -1.20 -14.33 +4.46 -104.84

2 +1606.46 +100.98 +1.11 +31.61 +0.51 +2.79 -0.88 +87.50Upland rice (UR)

1 -6000.09 -186.54 -1.70 +66.83 +15.22 +22.75 +9.04 -111.912 +898.69 +130.13 -0.11 +63.05 +12.87 +19.91 +5.19 -121.46

Fallow (FL)

1 -20256.88 -1035.46 -6.02 +27.36 +9.91 +26.11 +6.37 -381.692 +6828.16 +760.55 -1.71 +10.20 +9.72 +31.32 -10.43 -265.36

Rubber (RB)

1 -29969.38 -1910.96 -5.97 +69.57 +12.44 -2.98 -13.99 -405.332 +13550.66 +1353.55 -1.96 +79.68 +11.39 +37.34 -6.92 -130.29

(*) : original stock (-) : lost stock; (+) : gained stock


Soil fertility and water availability

Logging activities and forest conversion to agriculture land decreased soil fertility in the research area.

Forest conversion into upland rice, fallow and rubber garden had increased the infiltration rate of surface soil and percentage of macro pores.

Logging activities had increased soil bulk density and decreased the soil macro porosity as well as infiltration rate.


Carbon and Nitrogen loss

Soil organic carbon stock had decreased from primary to logged over forests, upland rice, fallow and rubber garden by -18.8 Mg/ha (-42%), -6.0 Mg/ha (-13%), -20.3 Mg/ha (-54%) and -30.0 Mg/ha (-66%) respectively.

Soil nitrogen had also decreased by -1.3 Mg/ha (-39%) in LF, -0.2 Mg/ha (-6%) in UR, -1.0 Mg/ha (-31%) in FL and -1.9 Mg/ha (-57%) in RB.


Deforestation deplete soil-Al3+

Al3+

(cm

ol/k

g)

a. Clay (%) b. P2O5 (ppm)


Conclusion

Logging activities and forest conversion to agriculture-land decrease soil fertility in the research area.

Moreover, those activities can increase runoff, soil erosion and further released the carbon and nitrogen stocks from soils.

Logging should be totally banned on the steep slopes and soil conservation techniques are needed to sustain a more productive and responsible agriculture.


Acknowledgement

Authors would like to express gratitude to research partners particularly Riak Bumi foundation that provided logistical and technical supports during the research.

We appreciate all the helps and trusts from local people in Keluin longhouse and local government in Kapuas Hulu District, West Kalimantan, Indonesia.

We also express sincere thanks to the Europian Union for funding this research, and to CIFOR CRP-6 Component 3 for financial supports.


www.cifor.cgiar.orgThank you!

Soil dynamics in tropical forest transition: a case study from Borneo, Indonesia

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