Effects of warming and nitrogen and phosphorus addition on dissolved organic carbon biodegradability of litter in a subtropical forest

doi:10.17521/cjpe.2023.0272

Abstract

Abstract:

Aims The biodegradability of dissolved organic carbon (DOC) is crucial to affect the amount of soil organic carbon in forest ecosystems as litter-derived DOC is one of the important sources of soil DOC. To further understand the formation and stability of forest soil organic carbon under climate change scenarios, it is essential to focus on the effects of climate warming and nutrient addition on the biodegradability of DOC (BDOC).

Methods Based on a manipulative soil warming experiment in a subtropical evergreen broadleaf forest, we took leaf litter of Castanopsis kawakamii with 0-day decomposition (undecomposed stage) and 180-day decomposition (middle-late stage of decomposition) as research materials. We experimentally quantified the effects of warming and nitrogen and phosphorus addition and their interactions on the BDOC of litter and the corresponding variation in ultraviolet-visible spectral index (ΔDOC spectral index) at different decomposition stages.

Important findings The results showed that: (1) the BDOC decreased gradually with litter decomposition, with a 22.6% reduction at the middle-late stage of decomposition compared to the undecomposed stage. (2) Warming significantly enhanced the BDOC at undecomposed stage while had no significant effects at the middle-late stage. Similarly, warming significantly increased the ΔDOC spectral index of undecomposed litter, but not at the milled-late stage. (3) Nitrogen addition significantly decreased BDOC at undecomposed stage but increased it at the middle-late stage. However, nitrogen addition did not change ΔDOC spectrum index at both decomposition stages. (4) Phosphorus addition significantly enhanced BDOC and ΔDOC spectrum index at both decomposition stages. (5) The interaction between warming and nutrient addition also had significant effects on increasing BDOC and ΔDOC spectrum index. Overall, both warming and phosphorus addition accelerated the degradation of DOC derived from undecomposed litter, while the degradation of DOC derived from middle-late decomposed litter was mainly regulated by nutrient contents.

Key words: warming, nitrogen addition, phosphorus addition, subtropical forest, litter, dissolved organic carbon biodegradability, Castanopsis kawakamii

RAN Jia-Xin, ZHANG Yu-Hui, WANG Yun, YANG Zhi-Jie, MAO Chao. Effects of warming and nitrogen and phosphorus addition on dissolved organic carbon biodegradability of litter in a subtropical forest[J]. Chin J Plant Ecol, 2024, 48(9): 1232-1242.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2023.0272

https://www.plant-ecology.com/EN/Y2024/V48/I9/1232

Figures/Tables 7

Table 1 Soil microbial properties of the warming (CK) and control (W) plots in the Castanopsis kawakamii forest (mean ± SE)

因子 Factor	对照 CK	增温 W
MBC (mg·kg^-1)	181.05 ± 9.05^a	148.38 ± 6.32^b
MBN (mg·kg^-1)	79.99 ± 6.63^a	53.17 ± 2.97^b
MBC/MBN	2.30 ± 0.16^b	2.82 ± 0.17^a
βG (nmol·h^-1·g^-1)	19.47 ± 0.87^b	24.93 ± 1.00^a
CBH (nmol·h^-1·g^-1)	0.61 ± 0.04^b	1.23 ± 0.05^a
PPO (nmol·h^-1·g^-1)	0.68 ± 0.04^b	0.97 ± 0.07^a
Px (nmol·h^-1·g^-1)	5.00 ± 0.50^b	7.20 ± 0.35^a

Fig. 1 Effects of warming and decomposition time on dissolved organic carbon (DOC) content of litter in a subtropical forest (mean ± SE). CK, control treatment; t, decomposition time; W, warming. Different lowercase letters indicate significant differences (p < 0.05) between warming and control treatment.

Table 2 Effects of warming and nutrient addition on 0-day decomposition and 180-day decomposition litter-derived dissolved organic carbon (DOC) in a subtropical forest

处理 Treatment	分解0天 0-day decomposition		分解180天 180-day decomposition
处理 Treatment	F	p	F	p
W	21.18	<0.01	0.01	0.91
N	5.57	<0.05	5.90	<0.05
P	167.92	<0.01	144.70	<0.01
N × P	50.94	<0.01	4.87	<0.05
W × N	3.05	0.09	0.74	0.40
W × P	21.11	<0.01	4.77	<0.05
W × N × P	5.29	<0.05	3.44	0.07

Fig. 2 Effects of warming and nitrogen and phosphorus addition on the biodegradability of litter-derived dissolved oganic carbon (BDOC) at 0-day decomposition (A) and 180-day decomposition (B) stage in a subtropical forest (mean ± SE). CK, control treatment; N, nitrogen addition; NP, interaction between nitrogen and phosphorus addition; P, phosphorus addition; W, warming; WN, interaction between warming and nitrogen addition; WNP, interactions among warming, nitrogen and phosphorus addition; WP, interaction between warming and phosphorus addition.

Table 3 Effects of warming and nitrogen and phosphorus addition on the variation in dissolved organic carbon (ΔDOC) spectral index of littex at 0-day decomposition and 180-day decomposition stages in a subtropical forest.

分解时间 Decomposition time	处理 Treatment	ΔSUVA₂₅₄		ΔSUVA₂₆₀		ΔSUVA₂₈₀		Δa₃₀₀
分解时间 Decomposition time	处理 Treatment	F	p	F	p	F	p	F	p
分解0天 0-day decomposition	W	4.23	<0.05	6.82	<0.05	11.92	<0.01	0.45	0.51
	N	6.23	<0.05	0.27	0.61	0.40	0.53	8.34	<0.01
	P	55.52	<0.01	34.63	<0.01	51.21	<0.01	31.14	<0.01
	N × P	20.35	<0.01	9.52	<0.01	6.65	<0.05	11.88	<0.01
	W × N	2.85	0.10	6.22	<0.05	0.45	0.51	0.17	0.68
	W × P	7.04	<0.05	6.51	<0.05	4.31	<0.05	0.32	0.57
	W × N × P	1.92	0.18	0.02	0.89	2.93	0.10	0.25	0.62
分解180天 180-day decomposition	W	0.69	0.41	1.01	0.32	0.46	0.50	0.02	0.89
	N	2.04	0.16	2.54	0.12	2.84	0.10	0.54	0.47
	P	30.57	<0.01	49.27	<0.01	21.43	<0.01	49.74	<0.01
	N × P	<0.01	0.99	1.28	0.27	5.93	<0.05	0.03	0.86
	W × N	<0.01	1.00	0.02	0.88	0.03	0.87	5.74	<0.05
	W × P	2.35	0.14	6.99	<0.05	5.99	<0.05	0.03	0.86
	W × N × P	0.03	0.86	0.61	0.44	2.47	0.13	5.68	<0.05

Fig. 3 Effects of warming and nitrogen and phosphorus addition on the variations in dissolved organic carbon (ΔDOC) spectral index of litter with 0-day decomposition and 180-day decomposition in a subtropical forest (mean ± SE). ΔSUVA254, ΔSUVA260, ΔSUVA280 and Δa300 represented the aromaticity, hydrophobicity, high molecular weight and chromophoric dissolved oganic matter composition of leaf litter, respectively after 28-day incubation. CK, control treatment; N, nitrogen addition; NP, interaction between nitrogen and phosphorus addition; P, phosphorus addition; W, warming; WN, interaction between warming and nitrogen addition; WNP, interactions among warming, nitrogen and phosphorus addition; WP, interaction between warming and phosphorus addition.

Fig. 4 Variations of dissolved organic carbon biodegradability (BDOC) and corresponding the variations in dissolved organic carbon (ΔDOC) with initial dissolved organic carbon (DOC) during litter incubation. SUVA254, SUVA260, SUVA280 and a300 represented the aromaticity, hydrophobicity, high molecular weight and chromophoric dissolved organic matter (DOM) composition of leaf litter, respectively. ΔSUVA254, ΔSUVA260, ΔSUVA280 and Δa300 denoted the aromaticity, hydrophobicity, molecular weight and chromophoric DOM composition of leaf litter, respectively during 28-day incubation.

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