Changes in organic carbon in soil of natural grassland converted to <i>Pinus taeda</i> plantations at three ages

Cassol, Paulo Cezar; Fachini, Leandra; Mafra, Álvaro Luiz; Brand, Martha Andréia; Simonete, Marcia; Coimbra, Jefferson Luís Meirelles

doi:10.5902/198050986301

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Artigos • Ciênc. Florest. 29 (2) • Apr-Jun 2019 • https://doi.org/10.5902/198050986301 copy

Changes in organic carbon in soil of natural grassland converted to Pinus taeda plantations at three ages

Alterações no carbono orgânico do solo de campo natural submetido ao plantio de Pinus taeda em três idades

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Pine plantations on former natural grassland (NG) areas can change the forms and stocks of organic carbon (OC) in the soil. To quantify these changes, the contents and stocks of the total OC (TOC), consisting of particulate OC (POC) and the mineral-associated OC (MAC) fractions, were determined in five layers, at depths between 0.0 and 0.40 m, in soil under NG and pine plantations aged five (P5), 16 (P16) and 21 (P21) years. The study was carried out in areas of Cambissolo Húmico, dystrophic, on the southern plateau of Santa Catarina state. The TOC content in the different layers and under different land uses ranged from 15.0 to 44.5 g kg^-1 and the TOC stock, in all layers together, from 86 to 144 Mg ha^-1. The POC content varied from 2.1 to 23.2 g kg^-1 and the POC stock from 7.4 to 21.8 Mg ha^-1, while the MAC content varied between 12.2 and 23.7 g kg^-1 and MAC stock between 79 and 122 Mg ha^-1. In general, the TOC stocks and contents and MAC and POC fractions in the soil increase with the age of the pine plantations up to 21 years. The TOC and POC contents and POC stock usually decrease with depth under NG, P5 and P21, whereas the MAC content and MAC and TOC stocks generally remain unchanged in layers to a depth of 0.40 m.

Keywords:
Organic matter; Carbon sequestration; Planted forests

Table 1 Mean* clay, silt and sand contents in five layers (0.00-0.05; 0.05-0.10; 0.10-0.20; 0.20-0.30; and 0.30-0.40 m) of a Cambissolo Húmico, dystrophic, on the southern highland of Santa Catarina state under natural grassland (NG) and Pinus taeda plantations in the second rotation, aged five (P5), 16 (P16) and 21 (P21) years.

Particle-size fraction	Land use
Particle-size fraction	NG	P5	P16	P21
	g kg^-1
Clay	319 B	284 B	382 A	178 C
Silt	220 C	272 B	291 B	323 A
Sand	461 A	444 A	327 B	499 A

Table 2 Pearson’s correlation coefficient between the contents of total organic carbon (TOC), particulate organic carbon (POC) and mineral-associated organic carbon (MAC), and the contents of soil particle size fractions (sand, clay and silt) in the 0.00–0.40 m soil layer of a Cambissolo Húmico, dystrophic, on the southern highland of Santa Catarina under grassland (NG), and Pinus taeda plantations in the second rotation, aged five (P5), 16 (P16) and 21 (P21) years.

Particle-size fraction	Organic carbon fraction
Particle-size fraction	TOC	POC	MAC
Sand	0.15^ns	0.08^ns	0.21^ns
Clay	-0.53^**	-0.48^**	-0.44^**
Silt	0.60^**	0.65^**	0.33^*

Table 3 Soil bulk density of a Cambissolo Húmico, dystrophic, on the southern highland of Santa Catarina state under grassland (NG) and Pinus taeda plantations in the second rotation, aged five (P5), 16 (P16) and 21 (P21) years.

Layers (m)	Land use
Layers (m)	NG	P5	P16	P21
	g dm^-3
0.00 - 0.05	1.2 b A	0.9 b B	1.0 c B	0.8 b C
0.05 a 0.10	1.4 a A	1.4 a A	1.1 b B	0.9 a C
0.10 a 0.20	1.5 a A	1.4 a A	1.2 a B	0.9 a C
0.20 a 0.30	1.4 a A	1.4 a A	1.2 ab B	0.9 a C
0.30 a 0.40	1.4 a A	1.4 a A	1.2 ab A	1.0 a B

Table 4 Content of total organic carbon (TOC), particulate organic carbon (POC) and mineral-associated organic carbon (MAC) in five layers of a Cambissolo Húmico, dystrophic, on the southern highland of Santa Catarina under natural grassland (NG) and Pinus taeda plantations in the second rotation, aged five (P5), 16 (P16) and 21 (P21) years.

Layers (m)	NG	P5	P16	P21
	TOC g kg^-1
0.00 - 0.05	27.2 a B	23.8 a B	23.7 a B	44.5 a A
0.05 - 0.10	24.3 a B	17.9 b C	24.0 a B	44.2 a A
0.10 - 0.20	20.2 b B	15.1 b C	22.2 a B	40.0 b A
0.20 - 0.30	18.3 b BC	15.0 b C	21.3 a B	40.9 b A
0.30 - 0.40	15.2 c C	16.2 b C	20.8 a B	34.0 c A
Mean* (0.00 - 0.40)	19.86 BC	16.78 C	22.03 B	39.81 A
	POC g kg^-1
0.0 - 0.05	9.1 a B	10.7 a B	9.2 a B	23.2 a A
0.05 - 0.10	6.2 b B	4.8 b B	7.6 ab B	20.5 b A
0.10 - 0.20	3.8 c B	2.9 b B	6.0 b B	19.6 b A
0.20 - 0.30	2.6 c C	2.3 b C	6.5 ab B	17.5 c A
0.30 - 0.40	2.1 c B	2.1 b B	5.0 b B	13.0 d A
Mean* (0.00 - 0.40)	4.03 C	3.76 C	6.47 B	17.98 A
	MAC g kg^-1
0.0 - 0.05	18.2 a A	13.1 a B	14.5 a B	21.3 ab A
0.05 - 0.10	18.0 a B	13.1 a C	16.3 a BC	23.7 a A
0.10 - 0.20	16.4 ab B	12.2 a C	16.3 a B	20.4 b A
0.20 - 0.30	15.8 ab B	12.7 a B	14.9 a B	23.4 ab A
0.30 - 0.40	13.1 b B	14.1 a B	15.8 a B	21.0 ab A
Mean* (0.00 - 0.40)	15.85 B	13.02 B	15.6 B	21.82 A

Table 5 Stocks of total organic carbon (TOC), particulate organic carbon (POC) and mineral-associated carbon (MAC) in five layers of a Cambissolo Húmico in the Southern highlands of Santa Catarina under native grassland (NG), and Pinus taeda plantations with five (P05), 16 (P16) and 21 y ears (P21), in the second rotation. Means of seven samples.

Layers (m)	NG	P05	P16	P21
	TOC Mg ha^-1
0.00 - 0.05	16.0 a	10.2 b	11.4 b	16.6 a
0.05 - 0.10	17.1 b	12.6 c	13.1 c	19.9 a
0.10 - 0.20	29.4 b	20.9 c	27.6 b	36.5 a
0.20 - 0.30	26.0 b	20.8 c	26.2 b	38.4 a
0.30 - 0.40	20.5 c	21.9 bc	25.4 b	32.7 a
Sum 0.0 - 0.40	109.0 b	86.4 c	103.7 b	144.1 a
	POC Mg ha^-1
0.00 - 0.05	2.0 b	2.0 b	1.3 c	3.0 a
0.05 - 0.10	1.5 b	1.5 b	1.2 b	3.2 a
0.10 - 0.20	1.9 b	1.7 b	2.2 b	6.2 a
0.20 - 0.30	1.2 c	1.4 c	2.4 b	5.3 a
0.30 - 0.40	0.8 c	1.2 bc	1.8 b	4.1 a
Sum 0.0 - 0.40	7.4 b	7.8 b	8.9 b	21.8 a
	MAC Mg ha^-1
0.00 - 0.05	14.1 a	8.3 b	10.2 b	TTT13.8 a
0.05 - 0.10	15.6 a	11.0 b	11.8 b	16.3 a
0.10 - 0.20	27.4 ab	19.2 c	25.4 b	30.4 a
0.20 - 0.30	24.8 b	19.4 c	23.8 b	33.1 a
0.30 - 0.40	19.7 b	20.7 b	23.7 b	28.6 a
Sum 0.00 - 0.40	101.6 b	78.6 c	94.9 bc	122.2 a

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[TFN1] Means followed by different letters in the row differ from each other by the Least Significant Difference (LSD) test at 5% probability.

[TFN6] * Weighted average, considering four layers with a thickness of 0.10 m, where the two uppermost layers were computed by their mean content.