华西雨屏区亮叶桦凋落叶分解对模拟氮沉降的响应

doi:10.3724/SP.J.1258.2012.00099

摘要/Abstract

摘要：

从2008年1月至2009年2月, 对华西雨屏区亮叶桦(Betula luminifera)人工林进行了模拟氮(N)沉降试验, N沉降水平分别为对照(CK, 0 g N·m^-2·a^-1)、低N (5 g N·m^-2·a^-1)、中N (15 g N·m^-2·a^-1)和高N (30 g N·m^-2·a^-1)。利用凋落袋法对亮叶桦凋落叶进行原位分解试验, 并在每月下旬定量地对各处理施N (NH₄NO₃)。结果表明, 虽然华西雨屏区大气N沉降量较高, 但模拟N沉降试验表明: 在N沉降继续增加的情况下, 凋落叶分解这一碳(C)循环和养分循环过程仍会受到显著影响。在1年的分解试验中, 模拟N沉降显著抑制了亮叶桦凋落叶的分解, N沉降处理使得凋落叶质量损失95%的时间在2.65年的基础上增加了1.14-1.96年。N沉降抑制凋落叶分解的原因在于无机N的富集对木质素和纤维素的分解造成阻碍。N沉降处理也导致C、N、磷、钾和镁元素在凋落物中的残留量增加, 但N沉降加速了钙元素的释放。凋落物基质化学特性在很大程度上决定了凋落物分解对N沉降的响应方向, 以及凋落物分解过程中各元素的动态变化。

关键词: 亮叶桦, 凋落叶分解, 氮沉降, 养分动态, 华西雨屏区

Abstract:

Aims Our objective was to determine the effect of simulated increased nitrogen (N) deposition on decomposition of Betula luminifera leaf litter, under a high wet-nitrogen deposition background.
Methods From January 2008 to February 2009, a field experiment of simulated N deposition was conducted in a B. luminifera plantation in the Rainy Area of West China. The levels of nitrogen deposition were control (CK), low, medium and high N (0, 5, 15 and 30 g N·m^-2·a^-1, respectively). A field experiment using the litterbag method was conducted on the decomposition of leaf litter of B. luminifera. In the end of each month, NH₄NO₃ was added into N-treated plots.
Important findings Despite the high background N deposition, there were significant effects of simulated increased N deposition on B. luminifera leaf litter. N treatments significantly slowed the decomposition of B. luminifera leaf litter through inhibiting the decay of lignin and cellulose. The time of 95% mass loss (T_95%) of B. luminifera leaf litter was increased by 1.14-1.96 a from 2.65 a (T_95%of CK) caused by simulated N deposition. Simulated N deposition significantly increased the remaining amount of carbon, N, phosphorus, potassium, and magnesium after one year of decomposition. However, calcium release rate was stimulated by simulated N deposition in all three N treatments. The initial chemical characteristics of litter determined the response direction of litter decomposition to simulated N deposition, as well as the nutrient release pattern during litter decomposition.

Key words: Betula luminifera, leaf litter decomposition, nitrogen deposition, nutrient dynamics, Rainy Area of West China

涂利华, 胡红玲, 胡庭兴, 张健, 雒守华, 戴洪忠. 华西雨屏区亮叶桦凋落叶分解对模拟氮沉降的响应. 植物生态学报, 2012, 36(2): 99-108. DOI: 10.3724/SP.J.1258.2012.00099

TU Li-Hua, HU Hong-Ling, HU Ting-Xing, ZHANG Jian, LUO Shou-Hua, DAI Hong-Zhong. Response of Betula luminifera leaf litter decomposition to simulated nitrogen deposition in the Rainy Area of West China. Chinese Journal of Plant Ecology, 2012, 36(2): 99-108. DOI: 10.3724/SP.J.1258.2012.00099

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https://www.plant-ecology.com/CN/Y2012/V36/I2/99

图/表 7

表1 0-10 cm土层基本理化性质(平均值±标准误差)

Table 1 Basic physical and chemical properties of 0-10 cm soil layer (mean ± SE)

容重 Bulk density (g·cm^-3)	最大持水量 Full water capacity (%)	总孔隙度 Total porosity (% )	有机碳 Organic carbon (g·kg^-1)	全氮 Total nitrogen (g·kg^-1)	有效氮 Available nitrogen (mg·kg^-1)	有效磷 Available phosphorus (mg·kg^-1)	速效钾 Available potassium (mg·kg^-1)	pH
1.29 ± 0.05	39.06 ± 4.01	50.29 ± 6.01	9.18 ± 1.53	1.54 ± 0.21	69.88 ± 6.53	14.11 ± 0.85	2.64 ± 0.18	4.88 ± 0.15

表2 亮叶桦凋落叶初始化学性质(平均值±标准误差)

Table 2 Initial chemical properties of Betula luminifera leaf litter (mean ± SE)

木质素 Lignin (mg·g^-1)	纤维素 Cellulose (mg·g^-1)	C (mg·g^-1)	N (mg·g^-1)	P (mg·g^-1)	K (mg·g^-1)	Ca (mg·g^-1)	Mg (mg·g^-1)	C/N	N/P	Lignin/N
336.7 ± 3.8	240.7 ± 9.3	440.3 ± 6.6	9.11 ± 0.10	0.27 ± 0.01	7.15 ± 0.25	0.58 ± 0.01	1.90 ± 0.09	48.3 ± 0.8	33.7 ± 0.5	37.0 ± 1.5

图1 亮叶桦凋落叶分解过程中质量残留率变化(平均值± 标准误差, n = 3)。斜体文字表示重复测量方差分析(repeated measures ANOVA)中的时间效应、N效应及其交互效应。各取样时间点上的LN、MN和HN (LN, 低N (5 g N·m-2·a-1); MN, 中N (15 g N·m-2·a-1); HN, 高N (30 g N·m-2·a-1))表示该处理与对照(CK)差异达到显著水平(p < 0.05)。

Fig. 1 Variations of mass remaining of Betula luminifera leaf litter during decomposition (mean ± SE, n = 3). Italic texts indicate that time effect, nitrogen effect and interaction effect are significant in repeated measures ANOVA. LN, MN and HN marked at each sampling date indicate significant differences at p < 0.05 between control and the levels of experimental N inputs (LN, low-N (5 g N·m-2·a-1); MN, medium-N (15 g N·m-2·a-1); HN, high-N (30 g N·m-2·a-1)), respectively.

表3 亮叶桦凋落叶质量残留率(y, %)与时间(x, a)的指数回归方程(y = ae-kx)

Table 3 Models (y = ae-kx) for the relationship between mass remaining (y, %) of Betula luminifera leaf litter and time (x, a)

处理 Treatment	拟合参数 Fitting parameter a	分解系数 Decomposition coefficient k	决定系数 Determination coefficient R²	p	n	分解50%时间 T_50%(a)	分解95%时间 T_95%(a)
对照 Control (0 g N·m^-2·a^-1)	102.4	1.13	0.97	< 0.001	7	0.61	2.65
低氮 Low nitrogen (5 g N·m^-2·a^-1)	94.9	0.79	0.94	< 0.001	7	0.88	3.79
中氮 Medium nitrogen (15 g N·m^-2·a^-1)	96.4	0.70	0.97	< 0.001	7	0.99	4.28
高氮 High nitrogen (30 g N·m^-2·a^-1)	97.6	0.65	0.97	< 0.001	7	1.07	4.61

图2 亮叶桦凋落叶分解过程中木质素和纤维素的残留率变化(平均值±标准误差, n = 3)。斜体文字表示重复测量方差分析(repeated measures ANOVA)中的时间效应、N效应及其交互效应。各取样时间点上的LN、MN和HN (LN, 低N (5 g N·m-2·a-1); MN, 中N (15 g N·m-2·a-1); HN, 高N (30 g N·m-2·a-1))表示该处理与对照(CK)差异达到显著水平(p < 0.05)。

Fig. 2 Variations of mass remaining of lignin and cellulose of Betula luminifera leaf litter during decomposition (mean ± SE, n = 3). Italic texts indicate that time effect, nitrogen effect and interaction effect are significant in repeated measures ANOVA. LN, MN and HN marked at each sampling date indicate significant differences at p < 0.05 between control and the levels of experimental N inputs (LN, low-N (5 g N·m-2·a-1); MN, medium-N (15 g N·m-2·a-1); HN, high-N (30 g N·m-2·a-1)), respectively.

图3 亮叶桦凋落叶分解过程中C、N、P、K、Ca、Mg元素的残留率变化(平均值±标准误差, n = 3)。斜体文字表示重复测量方差分析(repeated measures ANOVA)中的时间效应、N效应及其交互效应。各取样时间点上的LN、MN和HN (LN, 低N (5 g N·m-2·a-1); MN, 中N (15 g N·m-2·a-1); HN, 高N (30 g N·m-2·a-1))表示该处理与对照(CK)差异达到显著水平(p < 0.05)。

Fig. 3 Variations of remaining of C, N, P, K, Ca, and Mg of Betula luminifera leaf litter during decomposition (mean ± SE, n = 3). Italic texts indicate that time effect, nitrogen effect and interaction effect are significant in repeated measures ANOVA. LN, MN and HN marked at each sampling date indicate significant differences at p < 0.05 between control and the levels of experimental N inputs (LN, low-N (5 g N·m-2·a-1); MN, medium-N (15 g N·m-2·a-1); HN, high-N (30 g N·m-2·a-1)), respectively.

表4 华西雨屏区几个树种凋落叶分解对N沉降的响应比较

Table 4 Comparison of effects of simulated N deposition on decomposition of leaf litter from several tree species, in the Rainy Area of West China

树种 Tree species	初始N含量 Initial N concentration (mg·g^-1)	初始C/N Initial C/N	最初2个月N动态 N dynamics in the first two months	N沉降效应 N deposition effect	研究时间 Study time (a)	参考文献 Reference
苦竹 Pleioblastus amarus	3.9	100.0	富集 Enrich	抑制 Inhibition	2	Tu et al., 2011
亮叶桦 Betula luminifera	9.1	48.3	微弱富集 Gently enrich	抑制 Inhibition	1	本研究 This study
巨桉 Eucalyptus grandis	11.6	39.0	微弱富集 Gently enrich	抑制 Inhibition	2	胡红玲等(2011)
撑绿杂交竹 Bambusa pervariabilis × Dendrocala mopsi	13.1	28.6	释放 Release	抑制 Inhibition	2	涂利华等(2011a)
慈竹 Neosinocalamus affinis	22.3	20.5	释放 Release	微弱促进 Gently stimulation	1	李仁洪等(2009, 2010)

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