Short-term effects of fire intensity on soil organic matter and nutrient release after slash-and-burn in Eastern Province, Zambia

Figures & data

Table 1 Characteristics of burned trees and burned spots in 2008–2010

	Height of trees (m)	DBH^† of trees (cm)	Tree biomass (Mg ha^–1)	Burned area per total cleared area (%)	Burned biomass per area burned (Mg ha^–1)
Bur L^¶	18.9 ± 1.0	43.1 ± 1.3	29.3 ± 4.8	6.9 ± 0.5	209.4 ± 20.1
Bur S^¶	3.5 ± 0.1	3.1 ± 0.2	9.0 ± 1.4	7.5 ± 1.1	84.5 ± 13.4

Values are mean ± standard error (n = 9).

^†DBH is diameter of breast height.

The tree biomass (Y) was estimated by the allometric equation of Chidumayo (1997).

The equation for Bur L was Y = 13.67 × DBH + 7.48 × length–193.2 and Bur S was Y = 0.99 × DBH–0.61.

^¶Bur L is the area burned with large tree piles (DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Table 2 Maximum soil temperature during burning measured by Thermo-crayon in 2008

	Maximum soil temperature (°C)
Depth (cm)	Bur L^¶	Bur S^¶
0	460–600	460
5	300–460	50–100
10	100–200	50
15	50	50

Values shows the temperature of Thermo-crayon-melting point (n = 3).

^¶ Bur L is the area burned with large tree piles (diameter at breast height, DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Figure 1 Soil temperature during burning at depths of 1, 3, 5, 10 and 15 cm in spots burned with (a) piles of large trees (Bur L) and (b) in spots burned with small trees (Bur S) in 2010 (n = 3).

Table 3 Physicochemical properties of soil and ash in burned and unburned spots

Treatment	Depth (cm)	Bulk density (g cm^–3)	Total C*(Mg ha^–1)	Total N* (Mg ha^–1)	pH	Total P*(kg ha^–1)	Total Ca*(kg ha^–1)	Total Mg*(kg ha^–1)	Total K*(kg ha^–1)	Total Na* (kg ha^–1)
Bur S^¶	ash	–	1.48 ± 0.13 a	0.03 ± 0.00 a	–	36 ± 5 a	2,120 ± 256 a	239 ± 31 a	681 ± 122	17 ± 2 a
Bur L^¶	ash	–	4.14 ± 0.42 b	0.01 ± 0.00 b	–	132 ± 18 b	6,395 ± 792 b	612 ± 137 b	2,186 ± 427	39 ± 7 b
						Available P (kg ha^–1)	Exchangeable Ca (kg ha^–1)	Exchangeable Mg (kg ha^–1)	Exchangeable K (kg ha^–1)	Exchangeable Na (kg ha^–1)
Unburned	0–15	1.26 ± 0.01 a	18.35 ± 0.47 a	1.27 ± 0.02 a	6.8 ± 0.1 a	107 ± 7 a	1381 ± 40 a	254 ± 13 a	305 ± 15 a	29 ± 11 a
Bur S^¶	0–15	1.18 ± 0.04 a	15.64 ± 0.59 b	1.15 ± 0.06 a	7.6 ± 0.2 b	338 ± 47 b	1354 ± 21 a	263 ± 19 a	372 ± 27 ab	30 ± 11 a
Bur L^¶	0–15	1.16 ± 0.03 a	13.73 ± 0.53 b	1.08 ± 0.05 b	8.1 ± 0.1 b	920 ± 49 c	2151 ± 280 b	252 ± 22 a	408 ± 27 b	16 ± 5 a
Bur S^¶	0–5	1.15 ± 0.05 a	6.73 ± 0.68 a	0.49 ± 0.04 a	8.0 ± 0.4 a	230 ± 7 a	687 ± 27 a	109 ± 9 a	167 ± 17 a	10 ± 4 a
Bur L^¶	0–5	1.14 ± 0.03 a	5.08 ± 0.21 b	0.39 ± 0.03 a	8.5 ± 0.2 a	450 ± 45 b	1240 ± 137 b	116 ± 8 a	184 ± 17 a	4 ± 2 a
Bur S^¶	5–10	1.17 ± 0.03 a	5.13 ± 0.34 a	0.37 ± 0.03 a	7.0 ± 0.1 a	71 ± 29 a	378 ± 25 a	80 ± 7 a	103 ± 6 a	12 ± 4 a
Bur L^¶	5–10	1.18 ± 0.02 a	4.66 ± 0.39 a	0.37 ± 0.03 a	7.5 ± 0.2 a	394 ± 18 b	530 ± 95 a	69 ± 7 a	114 ± 8 a	6 ± 3 a
Bur S^¶	10–15	1.23 ± 0.02 a	3.78 ± 0.20 a	0.29 ± 0.02 a	7.3 ± 0.1 a	38 ± 13 a	289 ± 6 a	73 ± 8 a	102 ± 7 a	9 ± 3 a
Bur L^¶	10–15	1.23 ± 0.01 a	3.99 ± 0.17 a	0.32 ± 0.02 a	7.2 ± 0.2 a	76 ± 11 a	381 ± 54 a	67 ± 24 a	110 ± 5 a	6 ± 2 a

Values are mean ± standard error (n = 3). *C, N, P, Ca, Mg, K and Na represent carbon, nitrogen, calcium, magnesium, potassium and sodium, respectively.

Different letters vertically indicate that the means are significantly different (P < 0.05) at each depth.

^¶ Bur L is the area burned with large tree piles (diameter at breast height, DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Unburned and Bur S samples were collected in October 2008 and Bur L samples were collected in October 2009.

Table 4 Daily rate of carbon (C) mineralization in burned and unburned spots

		Rate of carbon mineralization (mg C kg^–1 day^–1)
Treatment	Depth (cm)	0–56 days		0–3 days
Unburned	0–15	9.6 ± 0.5		31.3 ± 4.0
Bur S^¶	0–5	19.7 ± 0.6	a *	130.2 ± 4.2	a *
Bur L^¶	0–5	17.3 ± 0.3	a *	134.6 ± 3.0	a *
Bur S^¶	5–10	7.7 ± 1.9	a	36.6 ± 13.3	b
Bur L^¶	5–10	16.3 ± 2.0	b *	127.4 ± 16.8	a *
Bur S^¶	10–15	3.6 ± 0.3	a	13.5 ± 1.1	b
Bur L^¶	10–15	9.6 ± 0.9	b	72.3 ± 10.6	a *

Values are mean ± standard error (n = 3).

Different letters vertically indicate that the means are significantly different (P < 0.05) between Bur L and Bur S at each depth.

* represents significant difference compared with Unburned (P < 0.05).

^¶ Bur L is the area burned with large tree piles (diameter at breast height, DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Unburned and Bur S samples were collected in October 2008 and Bur L samples were collected in October 2009.

Figure 2 Cumulative carbon (C) mineralization at a depth of 0–15 cm during the incubation experiment. Samples from unburned and spots burned with small trees (Bur S) were collected in October 2008 and samples from spots burned with piles of large trees (Bur L) were collected in October 2009. Bars indicate standard error (n = 3).

Figure 3 Net nitrogen (N) mineralization at a depth of 0–15 cm during the incubation experiment. Samples from unburned and spots burned with small trees (Bur S) were collected in October 2008 and samples from spots burned with piles of large trees (Bur L) were collected in October 2009. Bars indicate standard error (n = 3).

Table 5 Inorganic nitrogen (N) at 0 day incubation and daily rate of N mineralization and immobilization in burned and unburned spots

			Rate of nitrogen mineralization or immobilization^†(mg N kg^–1 day^–1)
Treatment	Depth (cm)	In–N0^‡(mg N kg^‒1)	0–56 days	0–3 day
Unburned	0–15cm	2.54 ± 0.1	0.33 ± 0.03	1.32 ± 0.07
Bur S^¶	0–5cm	31.29 ± 3.6 a *	0.52 ± 0.25 a	1.87 ± 1.18 a
Bur L^¶	0–5cm	43.08 ± 2.9 a *	–0.21 ± 0.17 a	–2.48 ± 0.80b *
Bur S^¶	5–10cm	11.66 ± 5.2 b *	0.21 ± 0.09 a	3.08 ± 0.22 a
Bur L^¶	5–10cm	44.70 ± 11.1 a *	0.31 ± 0.10 a	2.24 ± 0.63 a
Bur S^¶	10–15cm	7.77 ± 5.0 b	0.11 ± 0.07 a	2.04 ± 0.16 a
Bur L^¶	10–15cm	25.46 ± 8.0 a *	0.32 ± 0.04 a	2.06 ± 0.51 a

Values are mean ± standard error (n = 3).

Different letters vertically indicate that the means are significantly different between Bur L and Bur S at each depth (P < 0.05).

* represents significant difference compared with Unburned (P < 0.05).

^† Positive value indicates N mineralization and negative value indicates N immobilization.

^‡ In–N₀ indicates inorganic N at 0 day of incubation.

^¶ Bur L is the area burned with large tree piles (DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Unburned and Bur S samples were collected in October 2008 and Bur L samples were collected in October 2009.

Figure 4 The amounts of (a) ammonium nitrogen (NH₄-N) and (b) nitrate nitrogen (NO₃-N) at a depth of 0–15 cm during the incubation experiment. Samples from unburned and spots burned with small trees (Bur S) were collected in October 2008 and samples from spots burned with piles of large trees (Bur L) were collected in October 2009. Bars indicate standard error (n = 3).

Table 6 Aboveground biomass of weed and maize in burned and unburned spots

	Herbaceous weed (Mg ha^–1)	Woody weed (Mg ha^–1)	Maize* stover (Mg ha^–1)	Maize grain (Mg ha^–1)
2008/2009
Unburned	0.94 ± 0.01 a	0.93 ± 0.01 a	1.06 ± 0.10 a	0.65 ± 0.09 a
Bur S^¶	0.19 ± 0.01 b	0.34 ± 0.02 a	4.75 ± 0.42 b	2.27 ± 0.26 b
Bur L^¶	0.02 ± 0.00 b	0.00 ± 0.00 b	6.58 ± 0.47 b	3.17 ± 0.34 c
2009/2010
Unburned	0.26 ± 0.04 a	0.39 ± 0.17 a	3.37 ± 0.23 a	1.18 ± 0.19 a
Bur S^¶	0.16 ± 0.05 b	0.18 ± 0.04 a	7.71 ± 0.63 b	2.51 ± 0.43 b
Bur L^¶	0.10 ± 0.05 b	0.00 ± 0.00 b	8.25 ± 0.72 b	3.85 ± 0.38 c

Values are mean ±standard error (n = 3). * Maize was Zea mays L.

Different letters vertically indicate that the means are significantly different (P < 0.05) in each year.

^¶ Bur L is the area burned with large tree piles (DBH > 27 cm) and Bur S is the area burned with small tree piles (DBH < 27 cm).

Chidumayo EN 1997: Miombo Ecology and Management an Introduction, Intermediate Technology Publications, London.

 Google Scholar