Influence of land use on the dynamics of soil organic carbon in northern Kazakhstan

Figures & data

Figure 1  Climatic condition at each site during CO2 emission monitoring period.

Table 1 Potentially mineralizable organic carbon content and soil organic content at the CO2 monitoring plots

	Dark Chestnut			Southem Chemozem			Ordinary Chernozem
	No. plots	PMC	SOC	No. plots	PMC	SOC	No. plots	PMC	SOC
		(Mg C ha^−1)			(Mg C ha^−1)			(Mg C ha^−1)
2002
Cereal	–	–	–	9	2.65 ± 0.89^†	39.12 ± 10.3	–	–	–
Fallow	–	–	–	–	–	–	–	–	–
Meadow	–	–	–	–	–	–	–	–	–
2004
Cereal	8	1.82 ± 0.41	29.72 ± 5.01	9	2.38 ± 0.67	35.85 ± 4.66	6	1.64 ± 0.17	46.92 ± 5.43
Fallow	2	1.90	30.29	1	3.27	40.85	4	2.21 ± 0.31	45.82 ± 2.71
Meadow	2	2.47	36.92	2	3.61	41.77	2	2.41	60.70
2005
Cereal	11	2.20 ± 0.43	32.65 ± 3.71	17	2.80 ± 0.75	37.23 ± 4.48	10	1.87 ± 0.77	46.48 ± 4.38
Fallow	7	1.86 ± 0.44	29.95 ± 5.24	5	2.32 ± 0.26	34.64 ± 4.59	1	2.70	51.54
Meadow	2	2.47	36.92	4	3.42 ± 0.60	40.99 ± 3.74	2	2.41	60.70
^†Mean ± standard deviation. PMC, potentially mineralizable carbon; SOC, soil organic carbon; –, data not collected.

Figure 2  Daily CO2 emission, soil water content, precipitation, daily mean air temperature and daily precipitation at DC site. Upper figure shows daily CO2 emission. Middle figure shows soil water content. Lower figure shows mean air temperature (solid line) and precipitation (rods).

Figure 3  Daily CO2 emission, soil water content, precipitation, daily mean air temperature, and daily precipitation at SC site. Upper figure shows daily CO2 emission. Middle figure shows soil water content. Lower figure shows mean air temperature (solid line) and precipitation (rods).

Figure 4  Daily CO2 emission, soil water content, precipitation, daily mean air temperature, and daily precipitation at OC site. Upper figure shows daily CO2 emission. Middle figure shows soil water content. Lower figure shows mean air temperature (solid line) and precipitation (rods).

Table 2 Coefficients determined by stepwise multiple regression analysis

Site	Land use	Coefficients							Q10 (10–20°C)	R^2	n
		A	OM	b	W	c	Cumulative days	E
DC	Cereal	23.05**	PMC	0.23*	Precipitation	0.09**	8	42.47**	1.81	0.62**	156
	Fallow	22.87**	–	–	Dryness	0.30**	15	41.42**	1.79	0.49**	60
	Meadow	28.94**	PMC	2.63*	Dryness	0.04	8	62.04**	2.39	0.65**	34
SC	Cereal	25.58**	PMC	0.15	Precipitation	0.19**	15	48.31**	1.97	0.40**	417
	Fallow	27.86**	PMC	0.68*	Dryness	0.08**	9	54.38**	2.14	0.52**	51
	Meadow	29.95**	–	–	Precipitation	0.17**	10	58.81**	2.28	0.65**	57
OC	Cereal	17.34**	PMC	0.33*	Precipitation	0.54**	15	31.34**	1.55	0.83**	148
	Fallow	28.54**	–	–	Precipitation	0.15	15	55.84**	2.19	0.72**	45
	Meadow	40.83**	–	–	Dryness	0.36**	15	82.53**	3.18	0.74**	38
*P < 0.05.
**P < 0.051.
CO2 = AOM^bW^c(–E/RT). CO2, daily CO2 emission (mol C ha^− ^1 day^−l); A, coefficient (mol C ha^1 day^−l); organic matter (OM) is soil organic carbon or potentially mineralizable carbon (PMC) (Mg C ha^−l); W, cumulative precipitation or dryness factor (cumulative days was from 2 to 15 days, selected by the highest R^2; E, activation energy (kJ mol^−1); R, gas constant (8.314 [J mol^−1 kg^−1]); T, soil temperature (K); –.

Table 3 Annual (from April to October) carbon flow and carbon budget of the crop rotation systems

Site	Land use	Year	Carbon input as plant residue	Carbon output	Carbon budget	Average carbon budget (2004 and 2005)	Estimation under different fallow frequencies
							3-year rotation (F–C–C)	4-year rotation (F–C–C–C)	5-year rotation (F–C–C–C–C)
			(Mg C ha^−1)
DC	Cereal	2004	0.75 ± 0.20^†	0.75 ± 0.04	0.00	0.10	−0.51	−0.42	−0.32
		2005	0.99 ± 0.36	0.80 ± 0.03	0.19
	Fallow	2004	0.02	0.72	−0.70	−0.70
		2005	0.02	0.71 ± 0.01	−0.69
	Meadow	2004	1.56	0.61	0.95	0.81
		2005	1.39	0.68	0.66
SC	Cereal	2002	1.82 ± 0.50	1.06 ± 0.07	0.77
		2004	1.37 ± 0.03	1.01 ± 0.06	0.36	0.27	−0.30	−0.03	0.25
		2005	1.32 ± 0.29	1.14 ± 0.07	0.18
	Fallow	2004	0.02	0.92	−0.90	−0.84
		2005	0.02	0.79 ± 0.07	−0.77
	Meadow	2004	2.11	0.66	1.45	1.17
		2005	1.61	0.73 ± l.04	0.88
OC	Cereal	2004	1.31 ± 0.03	0.92 ± 0.03	0.39	0.35	−0.10	0.25	0.60
		2005	1.44 ± 0.79	1.13 ± 0.07	0.31
	Fallow	2004	0.02	0.85 ± 0.04	−0.83	−0.80
		2005	0.02	0.79	−0.77
	Meadow	2004	2.50	1.22	1.28	1.26
		2005	2.57	1.34	1.23
^†Mean ± standard deviation. C, cereal; F, fallow.