降雨变化对高寒草甸不同植物功能群凋落物质量及其分解的影响

doi:10.17521/cjpe.2021.0211

摘要/Abstract

摘要：

凋落物分解是生态系统物质循环的重要过程, 探究降雨变化对高寒草甸不同植物功能群凋落物分解的影响, 有助于了解高寒草甸物质循环对降雨变化的响应规律和机制。该研究设置减雨90% (Pr-90)、减雨50% (Pr-50)、减雨30% (Pr-30)、自然降雨(CK)和增雨50% (Pr+50) 5个降雨处理, 采用网袋分解法, 对青藏高原东部高寒草甸的3种植物功能群(禾本科、莎草科、杂类草)及群落凋落物的化学性质、质量损失和养分释放动态进行研究。结果表明: 1)减雨处理(Pr-90、Pr-50和Pr-30)显著增加禾本科凋落物的初始氮(N)含量, 显著降低碳氮比(C:N)和木质素氮比(木质素:N); 增雨处理(Pr+50)显著增加各类型凋落物初始磷(P)含量。2)根据Olson负指数模型拟合, 不同降雨处理下, 杂类草凋落物分解最快, 分解95%的时间为3.49-7.45年; 群落和莎草科次之, 分别为4.07-8.05和4.65-7.74年; 禾本科分解最慢, 为5.84-11.18年。3)极端减雨(Pr-90)抑制各类型凋落物分解, 适度降雨变化(Pr-50、Pr-30和Pr+50)抑制禾本科分解而对莎草科、杂类草和群落无显著影响, 仅增雨(Pr+50)明显促进杂类草分解。4)各类型凋落物C释放在减雨(Pr-90和Pr-30)下受到抑制, 增雨或减雨均促进禾本科N和P释放, 对于莎草科、杂类草和群落凋落物而言, Pr-30促进N释放, Pr-90抑制P释放, Pr+50促进P释放。5)结构方程模型(SEM)表明, 质量和养分残留率受降雨量的直接负效应, 也受凋落物初始C、N、P和木质素、纤维素、半纤维素含量的间接影响。综上所述, 高寒草甸凋落物质量损失及养分释放受凋落物类型和降雨量的共同影响。考虑到禾本科分解最慢且对降雨变化的响应最为敏感, 未来应关注气候变化尤其是极端减雨下禾本科的质量损失及养分释放对高寒草甸有机质输入及C、N、P循环的影响。

关键词: 凋落物分解, 降雨量, 养分释放, 高寒草甸

Abstract:

Aims Litter decomposition plays a vital role in material cycling of ecosystems. However, the responses of litter decomposition to changing precipitation in alpine meadows and the mechanisms underlying these responses are still not clear. Thus this study was designed to address the effect of changing precipitation on litter decomposition of different plant functional groups in alpine meadows.

Methods We used the litter bag method to investigate changes of initial nutrient content, mass loss and nutrient release in the litter of three plant functional groups (grass, sedge and forb) and in communities in an alpine meadow of Eastern Qingzang Plateau, in response to five precipitation treatments, including 90%, 50% and 30% decrease (Pr-90, Pr-50, Pr-30), ambient control (CK) and 50% increase (Pr+50).

Important findings The results showed that: 1) Precipitation decrease (Pr-90, Pr-50, Pr-30) significantly increased the initial nitrogen (N) content, carbon (C):N and lignin:N ratios of grass litters, while precipitation increase (Pr+50) significantly increased the initial phosphorus (P) content of all litter types. 2) According to the Olson negative exponential model, under different precipitation, the forbs decomposed the fastest, with the 95% decomposition time of 3.49-7.45 a; the decomposition of the communities and of the sedge species were the second fastest, with the 95% decomposition time of 4.07-8.05 and 4.65-7.74 a, respectively; grasses decomposed most slowly, 5.84-11.18 a. 3) Extreme precipitation decrease (Pr-90) inhibited the decomposition of all litter types, while moderate precipitation change (Pr-50, Pr-30, Pr+50) inhibited the decomposition of grass litter, but had no significant effects on sedge, forb and community litter, only precipitation increase (Pr+50) promoted the decomposition of forb litter. 4) C release was inhibited under precipitation decrease (Pr-90, Pr-30) in all litter types. N and P release of grass litters were promoted under both precipitation increase and decrease. Pr-30 promoted N release, Pr-90 inhibited P release and Pr+50 promoted P release in sedge, forb and community litters. 5) Structural equation models (SEM) showed that the mass and nutrient remaining rate were directly negatively affected by precipitation, and indirectly affected by litter types through initial C, N, P, lignin, cellulose and hemicellulose content. In conclusion, both litter types and precipitation can affect the mass loss and nutrient release of litters in an alpine meadow. Decomposition was slower and the response to precipitation was more sensitive in grass than that in other litter types. In the future, we should pay attention to the effects of mass loss and nutrient release of grass litter under climate change, especially extreme precipitation decrease, on organic matter input and C, N and P cycling in an alpine meadow.

Key words: litter decomposition, precipitation, nutrient release, alpine meadow

杨德春, 胡雷, 宋小艳, 王长庭. 降雨变化对高寒草甸不同植物功能群凋落物质量及其分解的影响. 植物生态学报, 2021, 45(12): 1314-1328. DOI: 10.17521/cjpe.2021.0211

YANG De-Chun, HU Lei, SONG Xiao-Yan, WANG Chang-Ting. Effects of changing precipitation on litter quality and decomposition of different plant functional groups in an alpine meadow. Chinese Journal of Plant Ecology, 2021, 45(12): 1314-1328. DOI: 10.17521/cjpe.2021.0211

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https://www.plant-ecology.com/CN/Y2021/V45/I12/1314

图/表 9

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凋落物类型 Litter type	降雨处理 Precipitation treatment	碳氮比 C:N	碳磷比 C:P	氮磷比 N:P	木质素氮比 Lignin:N
禾本科 Grass	Pr-90	39.89 ± 7.83^b	284.72 ± 5.46^b	7.29 ± 0.66^a	4.63 ± 1.14^b
	Pr-50	40.61 ± 5.20^b	218.11 ± 10.87^bc	5.40 ± 0.21^b	4.35 ± 0.32^b
	Pr-30	34.56 ± 11.61^b	205.99 ± 32.36^bc	5.05 ± 0.62^bc	4.96 ± 0.69^b
	CK	59.29 ± 6.13^a	422.31 ± 31.38^a	7.13 ± 0.39^a	8.78 ± 0.79^a
	Pr+50	58.95 ± 5.53^a	214.73 ± 14.81^c	3.68 ± 0.37^c	7.59 ± 1.19^a
莎草科 Sedge	Pr-90	32.00 ± 7.20^a	187.68 ± 7.32^bc	6.02 ± 0.60^ab	2.10 ± 0.27^b
	Pr-50	29.73 ± 7.44^a	157.00 ± 12.52^cd	5.42 ± 0.61^bc	1.75 ± 0.31^b
	Pr-30	36.08 ± 5.33^a	203.36 ± 4.81^b	5.72 ± 0.55^abc	3.20 ± 0.72^a
	CK	35.10 ± 6.74^a	262.80 ± 15.30^a	7.57 ± 0.38^a	2.01 ± 0.24^b
	Pr+50	37.79 ± 7.89^a	135.70 ± 12.49^d	3.76 ± 0.80^c	2.10 ± 0.39^b
杂类草 Forb	Pr-90	32.51 ± 3.28^ab	196.31 ± 29.32^ab	5.98 ± 0.62^ab	3.76 ± 0.68^abc
	Pr-50	34.20 ± 1.58^ab	184.84 ± 2.23^ab	5.41 ± 0.14^ab	4.04 ± 0.21^ab
	Pr-30	29.63 ± 0.79^b	187.40 ± 3.94^ab	6.32 ± 0.07^a	4.48 ± 0.12^a
	CK	35.53 ± 1.09^a	230.84 ± 8.03^a	6.50 ± 0.23^a	3.61 ± 0.30^bc
	Pr+50	32.69 ± 4.11^ab	153.42 ± 13.25^b	4.79 ± 0.70^b	3.18 ± 0.09^c
群落 Community	Pr-90	38.53 ± 2.91^a	265.60 ± 16.99^a	6.90 ± 0.37^ab	4.12 ± 0.40^a
	Pr-50	29.90 ± 2.54^cd	177.17 ± 10.97^b	5.92 ± 0.21^b	3.16 ± 0.56^b
	Pr-30	26.51 ± 3.14^d	166.29 ± 16.61^bc	6.26 ± 0.29^ab	3.38 ± 0.40^ab
	CK	32.51 ± 1.25^bc	231.13 ± 2.96^a	7.12 ± 0.18^a	3.87 ± 0.16^ab
	Pr+50	34.59 ± 1.49^ab	128.28 ± 19.92^c	3.69 ± 0.51^c	3.94 ± 0.50^ab

凋落物类型 Litter type	降雨处理 Precipitation treatment	碳氮比 C:N	碳磷比 C:P	氮磷比 N:P	木质素氮比 Lignin:N
禾本科 Grass	Pr-90	39.89 ± 7.83^b	284.72 ± 5.46^b	7.29 ± 0.66^a	4.63 ± 1.14^b
	Pr-50	40.61 ± 5.20^b	218.11 ± 10.87^bc	5.40 ± 0.21^b	4.35 ± 0.32^b
	Pr-30	34.56 ± 11.61^b	205.99 ± 32.36^bc	5.05 ± 0.62^bc	4.96 ± 0.69^b
	CK	59.29 ± 6.13^a	422.31 ± 31.38^a	7.13 ± 0.39^a	8.78 ± 0.79^a
	Pr+50	58.95 ± 5.53^a	214.73 ± 14.81^c	3.68 ± 0.37^c	7.59 ± 1.19^a
莎草科 Sedge	Pr-90	32.00 ± 7.20^a	187.68 ± 7.32^bc	6.02 ± 0.60^ab	2.10 ± 0.27^b
	Pr-50	29.73 ± 7.44^a	157.00 ± 12.52^cd	5.42 ± 0.61^bc	1.75 ± 0.31^b
	Pr-30	36.08 ± 5.33^a	203.36 ± 4.81^b	5.72 ± 0.55^abc	3.20 ± 0.72^a
	CK	35.10 ± 6.74^a	262.80 ± 15.30^a	7.57 ± 0.38^a	2.01 ± 0.24^b
	Pr+50	37.79 ± 7.89^a	135.70 ± 12.49^d	3.76 ± 0.80^c	2.10 ± 0.39^b
杂类草 Forb	Pr-90	32.51 ± 3.28^ab	196.31 ± 29.32^ab	5.98 ± 0.62^ab	3.76 ± 0.68^abc
	Pr-50	34.20 ± 1.58^ab	184.84 ± 2.23^ab	5.41 ± 0.14^ab	4.04 ± 0.21^ab
	Pr-30	29.63 ± 0.79^b	187.40 ± 3.94^ab	6.32 ± 0.07^a	4.48 ± 0.12^a
	CK	35.53 ± 1.09^a	230.84 ± 8.03^a	6.50 ± 0.23^a	3.61 ± 0.30^bc
	Pr+50	32.69 ± 4.11^ab	153.42 ± 13.25^b	4.79 ± 0.70^b	3.18 ± 0.09^c
群落 Community	Pr-90	38.53 ± 2.91^a	265.60 ± 16.99^a	6.90 ± 0.37^ab	4.12 ± 0.40^a
	Pr-50	29.90 ± 2.54^cd	177.17 ± 10.97^b	5.92 ± 0.21^b	3.16 ± 0.56^b
	Pr-30	26.51 ± 3.14^d	166.29 ± 16.61^bc	6.26 ± 0.29^ab	3.38 ± 0.40^ab
	CK	32.51 ± 1.25^bc	231.13 ± 2.96^a	7.12 ± 0.18^a	3.87 ± 0.16^ab
	Pr+50	34.59 ± 1.49^ab	128.28 ± 19.92^c	3.69 ± 0.51^c	3.94 ± 0.50^ab

凋落物化学性质 Litter property	L		Pr		L × Pr
凋落物化学性质 Litter property	F	p	F	p	F	p
碳含量 Carbon (C) content	6.758	0.001	1.391	0.255	1.444	0.187
氮含量 Nitrogen (N) content	20.094	<0.001	6.986	<0.001	2.287	0.025
磷含量 Phosphorus (P) content	6.708	0.001	19.042	<0.001	1.767	0.088
木质素含量 Lignin content	86.889	<0.001	6.828	<0.001	3.747	0.001
纤维素含量 Cellulose content	289.576	<0.001	1.483	0.225	3.227	0.003
半纤维素含量 Hemicellulose content	575.796	<0.001	1.922	0.126	2.282	0.025
碳氮比 C:N	23.248	<0.001	6.978	<0.001	3.426	0.002
碳磷比 C:P	28.676	<0.001	38.313	<0.001	5.335	<0.001
氮磷比 N:P	0.372	0.773	25.016	<0.001	1.391	0.210
木质素氮比 Lignin:N	6.648	0.001	1.119	0.361	1.604	0.130

凋落物化学性质 Litter property	L		Pr		L × Pr
凋落物化学性质 Litter property	F	p	F	p	F	p
碳含量 Carbon (C) content	6.758	0.001	1.391	0.255	1.444	0.187
氮含量 Nitrogen (N) content	20.094	<0.001	6.986	<0.001	2.287	0.025
磷含量 Phosphorus (P) content	6.708	0.001	19.042	<0.001	1.767	0.088
木质素含量 Lignin content	86.889	<0.001	6.828	<0.001	3.747	0.001
纤维素含量 Cellulose content	289.576	<0.001	1.483	0.225	3.227	0.003
半纤维素含量 Hemicellulose content	575.796	<0.001	1.922	0.126	2.282	0.025
碳氮比 C:N	23.248	<0.001	6.978	<0.001	3.426	0.002
碳磷比 C:P	28.676	<0.001	38.313	<0.001	5.335	<0.001
氮磷比 N:P	0.372	0.773	25.016	<0.001	1.391	0.210
木质素氮比 Lignin:N	6.648	0.001	1.119	0.361	1.604	0.130

差异来源 Source of variation	MR (%)		R_C(%)		R_N(%)		R_P(%)
差异来源 Source of variation	F	p	F	p	F	p	F	p
L	51.072	<0.001	23.966	0.001	138.895	<0.001	73.247	<0.001
T	334.324	<0.001	284.117	<0.001	49.010	0.002	239.147	<0.001
Pr	34.481	<0.001	60.966	<0.001	104.726	<0.001	158.340	<0.001
L × T	3.550	0.029	3.529	0.030	3.489	0.031	6.871	0.002
L × Pr	3.632	0.003	1.924	0.083	14.058	<0.001	27.063	<0.001
T × Pr	7.714	<0.001	6.350	0.001	9.822	<0.001	73.057	<0.001
L × T × Pr	3.077	<0.001	1.855	0.034	3.762	<0.001	5.484	<0.001