Forest cover change and its carbon dynamic of the karst area in Bulusaraung, South Sulawesi, Indonesia

Figures & data

Figure 1. Study area and the karst distribution

Table 1. Biomass and carbon stock of karst plain and karst tower

No	Level	Karst plain			Karst tower
		Biomass		Carbon	Biomass		Carbon
		ton/ha	%	ton/ha	ton/ha	%	ton/ha
A	Vegetation
1	Herb	0.92	0.55	0.43	0.71	0.44	0.33
2	Sapling	13.13	7.83	6.17	12.09	7.49	5.68
3	Pole	23.44	13.97	11.02	22.58	13.98	10.61
4	Tree	128.70	76.72	60.49	125.27	77.57	58.88
	Total 1	166.20	99.07	78.11	160.65	99.47	75.51
B	Necromass
5	Litter	1.55	0.92	0.730	0.8500	0.52	0.4000
6	Standing dead wood	0.011	0.01	0.005	0.0009	0.00	0.0004
7	Fallen dead wood	0.002	0.00	0.001	0.0013	0.00	0.0006
	Total 2	1.56	0.93	0.735	0.848	0.53	0.399
8	Soil			870.20			1,040.39
	Grand Total	167.76	100	949.05	161.50	100	1,116.29
	Median			76.80			62.86
	Average			78.85ns			75.90ns
	Std deviation			38.17			38.53

Table 2. Carbon sequestration of each type of area.

No	Type of area	Carbon sequestration (ton CO2)
		Herb	Sapling	Pole	Tree	Total
1	Karst plain Maros	1.58	22.64	40.39	221.80	286.41
2	Karst tower Pangkep	1.22	20.84	38.91	215.89	276.85

Note: all values between karst plain and karst tower are not significantly different according to T-test analysis

Figure 2. Map of land cover changes 2011 – 2021

Table 3. The result of accuracy test

Land cover		Field Check
		SDR	St	MA	DA	MDA	GL	PF	Sh	FP	OW	Total	User accuracy
Interpreation	SDR	43	–	–	–	–	–	–	–	–	–	43	100
	St	–	1	–	–	–	–	–	–	–	–	1	100
	MA	–	–	1	–	–	–	–	–	–	–	1	100
	DA	–	–	–	2	–	–	–	–	–	–	2	100
	MDA	1	–	–	–	11	–	–	1	–	–	13	84.6
	GL	–	–	–	–	–	1	–	–	–	–	1	100
	PF	–	–	–	–	–	–	1	–	–	–	1	100
	Sh	1	–	–	–	–	–	–	16	–	–	17	94.1
	FP	–	–	–	–	–	–	–	–	1	–	1	100
	OW	–	–	–	–	–	–	–	–	–	1	1	100
	Total	45	1	1	2	11	1	1	17	1	1	81
	Producer accuracy	95.6	100	100	100	100	100	100	94.1	100	100
	Kappa index	94.2
	Overall accuracy	96.3

Remarks: SDR = Secondary dryland forest; St = Settlement; MA = Mining area; DA = Dryland agriculture; MDA = Mixed dryland agriculture; GL = Grassland; PF = Paddy field; Sh = Shrub; FP = Fishpond; OW = Open water

Figure 3. Validation results of land cover projection in 2021

Figure 4. Land cover map projections of 2026 and 2031

Figure 5. The dynamic area of each land cover type

Appendix 1. Two types of karst at the Maros – Pangkep area. a. Plain karst; b. Tower karst.

Table 4. Actual and projection of land cover at the karst area of Bulusaraung FMU

	Actual land cover (ha)						Projection (ha)				2011-2031 changes	% ^(*)
	2011	%	2016	%	2021	%	2026	%	2031	%
Secondary dryland forest	4622.7	59.2	4613.1	59.1	4579.2	58.6	4222.2	54.1	3904.4	50.0	718.3	−15.5
Dryland agriculture	166.8	2.1	182.5	2.3	219.6	2.8	418.1	5.4	510.7	6.5	343.9	206.2
Mixed dryland agriculture	1111.8	14.2	1109.8	14.2	1091.1	14.0	1089.7	14.0	1075.9	13.8	35.9	−3.2
Settlement	0.9	<0.1	0.9	<0.1	1.6	<0.1	1.6	<0.1	1.6	<0.1	0.7	72.6
Mining area	47.2	0.6	56.8	0.7	93.8	1.2	277.3	3.6	506.3	6.5	459.0	971.6
Shrub	1805.5	23.1	1788.5	22.9	1751.6	22.4	1629.2	20.9	1534.9	19.7	270.5	−15.0
Grassland	5.9	0.1	6.9	0.1	7.6	0.1	7.4	0.1	7.4	0.1	1.5	24.9
Paddy field	46.4	0.6	48.7	0.6	62.7	0.8	161.9	2.1	266.1	3.4	219.7	473.4
Open water	1.6	<0.1	1.6	<0.1	1.6	<0.1	1.5	<0.1	1.5	<0.1	0.1	−4.8
Fishpond	1.0	<0.1	1.0	<0.1	1.0	<0.1	1.0	<0.1	1.0	<0.1	0.0	4.2
Total	7809.8		7809.8		7809.8		7809.8		7809.8

⁽*⁾a negative number indicates a decrease in area

Table 5. Details of changes in forest cover to/from other land cover

Land cover sources	Decrement (ha)	Increment (ha)	Change (ha)	Change proportion (%)
Dryland agriculture	104.25	0.06	104.19	14.51
Mixed dryland agriculture	83.57	0.91	82.66	11.51
Settlement	0.08	0.02	0.06	< 0.01
Mining area	316.01	0.00	316.01	44.00
Shrub	17.33	7.72	9.61	1.34
Grassland	0.16	0.42	−0.26	< 0.01
Paddy field	206.04	0.00	206.04	28.69
Open water	0.01	0.03	−0.01	< 0.01
Fishpond	0.03	0.05	−0.02	< 0.01
Total	727.48	9.20	718.27	100

Table 6. Dynamic carbon stock prediction based on land cover change prediction

Years	Area of secondary dryland forest (ha)		Carbon stock (ton)
	Karst tower	Karst plain	Karst tower	Karst plain	Total
2011	3075.1	1547.6	5308303.5	2617236.6	7925540.1
2016	3067.6	1545.5	5295254.5	2613785.5	7909040.0
2021	3044.8	1534.4	5255939.7	2594971.5	7850911.2
2026	2805.7	1416.5	4843156.9	2395626.3	7238783.3
2031	2582.4	1322.0	4457771.0	2235734.9	6693505.9

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Carbon	Equal variances assumed	.078	.782	.251	41	.803	2.94178	11.72973	−20.74688	26.63045
	Equal variances not assumed			.251	40.276	.803	2.94178	11.72201	−20.74423	26.62779

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Soil_carbon	Equal variances assumed	.540	.466	−1.301	41	.200	−170.18546	130.80003	−434.34148	93.97056
	Equal variances not assumed			−1.279	35.845	.209	−170.18546	133.06800	−440.10051	99.72960

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Herb_sequestration	Equal variances assumed	2.561	.117	.880	41	.384	.36772	.41775	−.47595	1.21138
	Equal variances not assumed			.855	31.713	.399	.36772	.43019	−.50886	1.24430

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Sapling_sequestration	Equal variances assumed	.432	.515	.248	41	.806	1.79915	7.26354	−12.86987	16.46818
	Equal variances not assumed			.252	40.689	.802	1.79915	7.14640	−12.63663	16.23494

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Pole_sequestration	Equal variances assumed	.406	.527	.109	41	.914	1.48216	13.62045	−26.02490	28.98922
	Equal variances not assumed			.107	35.892	.915	1.48216	13.85456	−26.61913	29.58344

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Tree_sequestration	Equal variances assumed	.602	.442	.133	41	.895	5.90914	44.56361	−84.08890	95.90717
	Equal variances not assumed			.134	40.983	.894	5.90914	44.17605	−83.30732	95.12560

Table

Independent Samples Test
		Levene’s Test for Equality of Variances		t-test for Equality of Means
		F	Sig.	t	df	Sig. (2-tailed)	Mean Difference	Std. Error Difference	95% Confidence Interval of the Difference
									Lower	Upper
Total_sequestration	Equal variances assumed	.019	.895	.047	8	.964	3.82200	81.12738	−183.25808	190.90208
	Equal variances not assumed			.047	7.993	.964	3.82200	81.12738	−183.28612	190.93012