Variations in soil physico-chemical properties, soil stocks, and soil stoichiometry under different soil layers, the major forest region Liupan Mountains of Northwest China

Rahman, M.; Zhang, K.; Wang, Y.; Ahmad, B.; Ahmad, A.; Zhang, Z.; Khan, D.; Muhammad, D.; Ali, A.

doi:10.1590/1519-6984.256565

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Brazilian Journal of Biology

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Original Article • Braz. J. Biol. 84 • 2024 • https://doi.org/10.1590/1519-6984.256565 copy

Variations in soil physico-chemical properties, soil stocks, and soil stoichiometry under different soil layers, the major forest region Liupan Mountains of Northwest China

Variações nas propriedades físico-químicas do solo, estoques e estequiometria do solo sob diferentes camadas de solo, a principal região florestal das montanhas Liupan do noroeste da China

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Liupan Mountains are an important region in China in the context of forest cover and vegetation due to huge afforestation and plantation practices, which brought changes in soil physio-chemical properties, soil stocks, and soil stoichiometries are rarely been understood. The study aims to explore the distribution of soil nutrients at 1-m soil depth in the plantation forest region. The soil samples at five depth increments (0-20, 20-40, 40-60, 60-80, and 80-100 cm) were collected and analyzed for different soil physio-chemical characteristics. The results showed a significant variation in soil bulk density (BD), soil porosity, pH, cation exchange capacity (CEC), and electric conductivity (EC) values. More soil BD (1.41 g cm^-3) and pH (6.97) were noticed in the deep soil layer (80-100 cm), while the highest values of porosity (60.6%), EC (0.09 mS cm^-1), and CEC (32.9 c mol kg^-1) were reflected in the uppermost soil layer (0-20 cm). Similarly, the highest contents of soil organic carbon (SOC), total phosphorus (TP), available phosphorus (AP), total nitrogen (TN), and available potassium (AK) were calculated in the surface soil layer (0-20 cm). With increasing soil depth increment a decreasing trend in the SOC and other nutrient concentration were found, whereas the soil total potassium (TK) produced a negative correlation with soil layer depth. The entire results produced the distribution of SOCs and TNs (stocks) at various soil depths in forestland patterns were 0→20cm > 20→40cm > 40→60cm ≥ 60→80cm ≥ 80→100 cm. Furthermore, the stoichiometric ratios of C, N, and P, the C/P, and N/P ratios showed maximum values (66.49 and 5.46) in 0-20 cm and lowest values (23.78 and 1.91) in 80-100 cm soil layer depth. Though the C/N ratio was statistically similar across the whole soil profile (0-100 cm). These results highlighted that the soil depth increments might largely be attributed to fluctuations in soil physio-chemical properties, soil stocks, and soil stoichiometries. Further study is needed to draw more conclusions on nutrient dynamics, soil stocks, and soil stoichiometry in these forests.

Keywords:
forest soil; physico-chemical properties; soil stocks; soil depth; Liupan Mountain

Sample Plot	longitude	latitude	Altitude (m)	Slope Aspect	Canopy Density (%)	Tree Density (trees/ha)	Avg Tree Height (m)
Jing-01	106.222350	35.516560	2276.6	Southeast	0.75	907	16.19
Jing -02	106.223250	35.513820	2294.7	Southeast	0.72	955	15.97
Jing-03	106.223250	35.513830	2312.6	Southeast	0.74	1035	16.57
Jing-04	106.223250	35.513840	2330.4	Southeast	0.8	786	18.07
Jing-05	106.223250	35.513850	2348.4	Southeast	0.71	770	17.04
Jing-06	106.223250	35.513860	2362.9	Southeast	0.68	572	17.75
Jing-07	106.223250	35.513870	2376.7	Southeast	0.62	674	18.24
Jing-08	106.223250	35.513880	2394.2	Southeast	0.74	815	17.87
Jing-09	106.223250	35.513890	2411.4	Southeast	0.81	933	17.12
Jing-10	106.223250	35.513900	2429.0	Southeast	0.76	719	17.94
Jing-11	106.223250	35.513910	2447.1	Southeast	0.71	831	15.72
Jing-12	106.223670	35.513760	2460.4	Southeast	0.78	746	17.54
Jing-13	106.223950	35.513920	2474.1	Southeast	0.75	870	17.4
Jing-14	106.224170	35.513990	2489.7	Southeast	0.72	854	17.04
Jing-15	106.224240	35.514840	2506.9	Southeast	0.76	749	17.04
Jing-16	106.224280	35.516770	2524.5	Southeast	0.74	942	16.71
Jing-17	106.224430	35.514850	2308.5	Southwest	0.75	/	/
Jing-18	106.224460	35.516230	2323.1	Northeast	0.76	/	/
Jing-19	106.224570	35.515960	2281.0	Northwest	0.85	725	18.3
Jing-20	106.224590	35.514120	2352.0	Northwest	0.45	462	16.1
Jing-21	106.224640	35.514590	2349.0	Northwest	0.49	876	20.1
Jing-22	106.224740	35.513920	2263.0	Northwest	0.85	675	12.2
Jing-23	106.225030	35.513870	2335.0	Southwest	0.75	954	18.9
Jing-24	106.226480	35.514130	2277.0	Southwest	0.78	1221	19.9

Depth (cm)	BD (g cm^-3)	Porosity (%)	pH	EC (mS cm^-1)	CEC (c mol kg^-1)
0-20	0.88 ± 0.09^e	60.68 ± 2.41^a	6.35 ± 0.40^c	0.85 ± 0.23^a	32.90 ± 8.04^a
20-40	0.99 ± 0.08^d	56.78 ± 2.06^b	6.51 ± 0.48^bc	0.65 ± 0.10^b	27.98 ± 4.20^b
40-60	1.12 ± 0.12^c	51.92 ± 4.32^c	6.74 ± 0.51^ab	0.55 ± 0.12^c	22.57 ± 4.40^c
60-80	1.28 ± 0.12^b	47.94 ± 4.96^d	6.85 ± 0.58^a	0.48 ± 0.011^c	18.88 ± 4.55^d
80-100	1.41 ± 0.16^a	43.56 ± 5.96^e	6.97 ± 0.62^a	0.52 ± 0.10^c	17.34 ± 3.94^d
Mean	1.14 ± 0.12	52.18 ± 3.95	6.69 ± 0.52	0.62 ± 0.14	23.94 ± 5.03

Depth (cm)	SOC (g kg^-1)	TN (g kg^-1)	TP (g kg^-1)	TK (g kg^-1)	AP (mg kg^-1)	AK (mg kg^-1)
0-20	54.72 ± 11.12^a	4.66 ± 1.32^a	0.85 ± 0.183^a	19.98 ± 1.94^b	11.4 ± 4.27^a	227.3 ± 51.06^a
20-40	41.48 ± 9.86^b	3.58 ± 0.84^b	0.81 ± 0.157^ab	20.51 ± 1.71^ab	5.22 ± 1.38^b	120.4 ± 36.56^b
40-60	26.75 ± 11.28^c	2.41 ± 0.84^c	0.72 ± 0.198^bc	20.62 ± 1.74^ab	2.91 ± 0.95^c	72.03 ± 18.05^c
60-80	18.23 ± 9.21^d	1.49 ± 0.78^d	0.62 ± 0.199^cd	21.00 ± 1.98^ab	2.28 ± 1.27^c	64.90 ± 12.68^c
80-100	14.75 ± 7.52^d	1.18 ± 0.64^d	0.60 ± 0.174^d	21.18 ± 2.27^a	2.04 ± 1.28^c	64.99 ± 14.07^c
Mean	31.19 ± 10.40	2.58 ± 0.97	0.73 ± 0.18	20.66 ± 1.93	4.78 ± 1.83	109.9 ± 26.49

Depth (cm)	SOCs (Mg ha^-1)	TNs (Mg ha^-1)	TPs (Mg ha^-1)
0-20	95.95 ± 25.77^a	8.20 ± 2.65^a	1.50 ± 0.38^a
20-40	83.60 ± 21.32^b	6.66 ± 2.19^b	1.62 ± 0.38^a
40-60	59.37 ± 24.72^c	4.82 ± 2.16^c	1.61 ± 0.46^a
60-80	45.09 ± 20.12^cd	3.60 ± 1.75^d	1.58 ± 0.45^a
80-100	39.85 ± 16.83^d	3.18 ± 1.41^d	1.67 ± 0.39^a
Mean	64.77 ± 21.76	5.30 ± 2.03	1.60 ± 0.41

Depth (cm)	C:N-ratios	C:P-ratios	N:P-ratios
0-20	11.86 ± 0.83^a	66.48 ± 15.39^a	5.46 ± 0.96^a
20-40	11.87 ± 1.00^a	51.15 ± 10.20^b	4.20 ± 1.14^b
40-60	11.41 ± 4.65^a	36.37 ± 12.43^c	3.01 ± 1.11^c
60-80	12.69 ± 4.58^a	28.20 ± 9.96^d	2.30 ± 0.94^d
80-100	12.79 ± 2.98^a	23.78 ± 9.31^d	1.91 ± 0.81^d
Mean	12.12 ± 2.81	41.20 ± 11.46	3.38 ± 0.99

Depth	Component	SOC	TN	TP	TK	AP
0-20 cm	TN	0.95^ . Correlation was evaluated at significance level 0.01 (P < 0.01).	1
	TP	0.72**	0.76**	1
	TK	-0.70**	-0.60**	-0.44^* * . The correlation was tested at a significance level of 0.05 (P ≤ 0.05).	1
	AP	0.78**	0.75**	.34	-0.64**	1
	AK	0.372	0.38	0.32	-0.029	0.173
20-40 cm	TN	0.95**	1
	TP	0.57**	0.60**	1
	TK	-0.28	-0.26	-0.11	1
	AP	0.62**	0.54**	0.11	-0.01	1
	AK	0.22	0.08	0.44*	0.32	0.08
40-60 cm	TN	0.71**	1
	TP	0.75**	0.54**	1
	TK	-0.24	-0.17	-0.02	1
	AP	0.71**	0.53**	0.43*	0.10	1
	AK	0.48*	0.22	0.62**	0.37	0.52**
60-80 cm	TN	0.88**	1
	TP	0.77**	0.62**	1
	TK	0.03	-0.08	0.16	1
	AP	0.56**	0.59**	0.46*	0.39	1
	AK	0.40	0.31	0.47*	0.63**	0.58**
80-100 cm	TN	0.93**	1
	TP	0.68**	.59**	1
	TK	-0.02	-.12	0.27	1
	AP	0.50*	0.37	0.51*	0.18	1
	AK	0.29	0.13	0.42*	0.65**	0.66**

Depth	Component	SOCs	TNs	TPs	C:N	C:P
0-20 cm	TNs	0.95^ . Correlation was evaluated at significance level 0.01 (P < 0.01).	1
	TPs	0.74**	0.79**	1
	C:N	-0.41*	-0.64**	-0.68**	1
	C:P	0.50^* * . The correlation was tested at a significance level of 0.05 (P ≤ 0.05).	0.52**	-0.08	-0.14	1
	N:P	0.54**	0.54**	-0.05	-0.13	0.96**
20-40 cm	TNs	0.56**	1
	TPs	0.63**	0.22	1
	C:N	0.22	-0.62**	0.10	1
	C:P	0.53**	0.44*	-0.29	0.18	1
	N:P	0.20	0.75**	-0.43*	-0.51*	0.73**
40-60 cm	TNs	0.66**	1
	TPs	0.72**	0.35	1
	C:N	0.62**	-0.08	0.57**	1
	C:P	0.75**	0.62**	0.11	0.39	1
	N:P	0.46*	0.84**	-0.10	-0.16	0.79**
60-80 cm	TNs	0.89**	1
	TPs	0.53**	0.39	1
	C:N	0.24	-0.20	0.36	1
	C:P	0.84**	0.81**	0.03	0.04	1
	N:P	0.72**	0.86**	-0.08	-0.32	0.92**
80-100 cm	TNs	0.71**	1
	TPs	0.71**	0.33	1
	C:N	0.36	-0.38	0.50*	1
	C:P	0.78**	0.72**	0.12	0.05	1
	N:P	0.53**	0.86**	-0.09	-0.45*	0.85**

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