高寒森林溪流对凋落叶分解过程中木质素降解的影响

doi:10.17521/cjpe.2016.0163

摘要/Abstract

摘要：

溪流广泛分布于高寒森林地表, 凋落于其中的林木凋落物的分解是整个森林生态系统物质循环的重要环节, 水体流动过程中的冲刷和淋洗作用及其他独特的环境条件可能显著影响凋落物中木质素的降解。该研究采用凋落袋法对比研究了岷江上游高寒森林4种典型且初始质量差异显著的凋落叶, 即康定柳(Salix paraplesia)、高山杜鹃(Rhododendron lapponicum)、方枝柏(Sabina saltuaria)和四川红杉(Larix mastersiana), 在不同生境(林下、溪流和河岸带)下分解过程中木质素残留质量和浓度(质量百分率)的动态变化特征。经过两年的分解, 发现溪流显著促进了凋落叶中木质素的降解; 同一物种凋落叶在不同生境下木质素残留质量差异显著(p < 0.05), 整体表现为溪流<河岸带<林下; 在凋落叶分解的初期木质素有明显的降解, 其浓度表现为先降低后升高, 但不同物种之间存在显著(p < 0.05)的差异; 在整个分解过程中, 木质素残留质量总体呈现出了降低的趋势。此外, 生境类型、分解时期和区域性环境因子(温度、pH值和营养元素的有效性)能显著影响木质素的降解率。这些结果表明, 传统上认为木质素在凋落叶分解初期相对稳定的观点可能并不准确, 其浓度很可能是先下降后升高, 这也与有关木质素动态的最新研究结果相一致。另一方面, 在不同分解时期和不同生境下, 凋落叶木质素降解率表现出了显著差异, 表明区域性环境因子在凋落叶分解和木质素降解过程中具有重要的作用。

关键词: 碳循环, 林下, 溪流, 河岸带, 降解率, 物种, 环境因子

Abstract:

AimsStreams are widely distributed in alpine forests, and litter decomposition in which is an important component of material cycling across the forest landscape. The leaching and fragmenting effects as well as the unique environmental factors in streams may have significant impacts on lignin degradation during litter decomposition, but studies on this are lacking.
Methods Using litterbag methods, we investigated the dynamics of lignin mass remaining and concentration (percent litter mass, %) during the decomposition of four foliar litters, which varied significantly in the initial litter chemical traits, from the dominant species of Salix paraplesia, Rhododendron lapponicum, Sabina saltuaria, and Larix mastersiana under different habitats (forest floor, stream, and riparian zone) in the upper reaches of the Minjiang River.
Important findings After two year’s incubation, litter lignin mass remaining for a specific litter species varied significantly (p < 0.05) among habitats, with an order of stream < riparian zone < forest floor. Lignin was degraded substantially in the early stage of litter decomposition process, and the lignin concentration first decreased and then increased with the proceeding of litter decomposition, but varied significantly (p < 0.05) among different litter species. Lignin mass showed a general trend of decrease across the 2-year decomposition course. In addition, habitat type, decomposition period and microenvironmental factors (e.g., temperature, pH value and nutrient availability) showed substantial influences on lignin degradation rate. These results suggest that the traditional view that lignin was relatively recalcitrant with an increase of concentration in the early stage of litter decomposition is challenged, but the loss of lignin in the early phrase is in line with recent findings about the fate of lignin during litter decomposition. Moreover, the significant differences of lignin degradation rates among different decomposition period and habitat types indicated that local-scale environmental factors can play a significant role in litter decomposition and lignin degradation processes.

Key words: carbon cycling, forest floor, stream, riparian zone, degradation rate, species, environmental factor

岳楷, 杨万勤, 彭艳, 黄春萍, 张川, 吴福忠. 高寒森林溪流对凋落叶分解过程中木质素降解的影响. 植物生态学报, 2016, 40(9): 893-901. DOI: 10.17521/cjpe.2016.0163

Kai YUE, Wan-Qin YANG, Yan PENG, Chun-Ping HUANG, Chuan ZHANG, Fu-Zhong WU. Effects of streams on lignin degradation during foliar litter decomposition in an alpine forest. Chinese Journal of Plant Ecology, 2016, 40(9): 893-901. DOI: 10.17521/cjpe.2016.0163

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2016.0163

https://www.plant-ecology.com/CN/Y2016/V40/I9/893

图/表 8

表1 不同生境下凋落叶分解过程中环境因子特征(平均值±标准偏差, n = 90)

Table 1 Characteristics of environmental conditions of different habitats during the process of foliar litter decomposition (mean ± SD, n = 90)

生境 Habitat	AT (℃)	C (g·kg^-1)	N (g·kg^-1)	P (g·kg^-1)	pH
林下 Forest floor	2.0 ± 5.2	126 ± 26	5.8 ± 1.1	1.2 ± 0.2	6.6 ± 0.02
生境 Habitat	AT (°C)	HCO₃^- (mg·L^-1)	NH₄⁺ (mg·L^-1)	NO₃^-(mg·L^-1)	PO₄^3- (μg·L^-1)	pH	FV (m·s^-1)
溪流 Stream	5.1 ± 2.6	13.9 ± 1.96	0.10 ± 0.05	0.29 ± 0.07	7.85 ± 0.38	6.6 ± 0.4	0.53 ± 0.15
河岸带 Riparian zone	4.8 ± 3.4	19.7 ± 1.33	0.04 ± 0.02	0.34 ± 0.08	7.84 ± 0.41	6.9 ± 0.3	0.05 ± 0.01

表2 康定柳、高山杜鹃、方枝柏和四川红杉凋落叶初始质量特征(平均数±标准偏差, n = 9)

Table 2 Initial chemical properties of Salix paraplesia, Rhododendron lapponicum, Sabina saltuaria, and Larix mastersiana foliar litters (mean ± SD, n = 9)

物种 Species	C (%)	N (%)	P (%)	木质素 Lignin (%)	C:N	C:P	N:P	Lignin:N
康定柳 S. paraplesia	34.8 ± 0.9^c	2.64 ± 0.15^a	0.17 ± 0.01^a	24.7 ± 1.3^d	13.2 ± 0.8^d	207 ± 19.7^c	15.7 ± 1.7^a	9.38 ± 0.8^c
高山杜鹃 R. lapponicum	38.6 ± 1.1^b	0.69 ± 0.10^d	0.10 ± 0.02^d	29.8 ± 0.8^b	57.2 ± 10.2^a	375 ± 53.6^a	6.75 ± 1.5^c	44.3 ± 8.3^a
方枝柏 S. saltuaria	46.9 ± 1.8^a	1.05 ± 0.06^c	0.15 ± 0.01^b	28.1 ± 0.8^c	45.1 ± 3.9^b	304 ± 12.6^b	6.79 ± 0.7^c	26.9 ± 1.8^b
四川红杉 L. mastersiana	37.5 ± 0.5^b	1.59 ± 0.11^b	0.12 ± 0.01^c	37.8 ± 1.0^a	23.6 ± 1.8^c	320 ± 24.6^b	13.6 ± 0.8^b	30.1 ± 2.1^b

图1 不同生境下康定柳(A)、高山杜鹃(B)、方枝柏(C)、四川红杉(D)凋落叶分解过程中木质素残留质量(g)的动态特征(平均值±标准偏差, n = 9)。不同小写字母表示同一分解时期同一物种在不同生境下木质素残留质量差异显著(p < 0.05)。

Fig. 1 Dynamics of lignin mass remaining (g) in the decomposing foliar litter of Salix paraplesia (A), Rhododendron lapponicum (B), Sabina saltuaria (C), and Larix mastersiana (D) under different habitat conditions (mean ± SD, n = 9). Different lowercase letters indicate significant (p < 0.05) differences of lignin mass remaining for a given litter species in a specific decomposition period under different habitat conditions.

图2 不同生境下康定柳(A)、高山杜鹃(B)、方枝柏(C)、四川红杉(D)凋落叶分解过程中木质素浓度(质量百分率, %)的动态特征(平均值±标准偏差, n = 9)。不同小写字母表示同一物种凋落叶在同一生境的不同分解时期木质素浓度差异显著(p < 0.05)。FP, 冻结期; GS, 生长季节; IV, 初始值; LGS, 生长季节后期; PP, 冻结初期; TP, 融化期; 1, 第一年; 2, 第二年。

Fig. 2 Dynamics of lignin concentration (percent litter mass, %) during Salix paraplesia (A), Rhododendron lapponicum (B), Sabina saltuaria (C), and Larix mastersiana (D) foliar litter decomposition (p < 0.05) under different habitat conditions (mean ± SD, n = 9). Different lowercase letters indicate significant (p < 0.05) differences of lignin concentration among different decomposition periods for a given litter species incubated in a specific type of habitat. FP, freezing period; GS, growing season; IV, initial value; LGS, late growing season; PP, pre-freezing period; TP, thawing period; 1, first year; 2, second year.

图3 不同生境下康定柳(A)、高山杜鹃(B)、方枝柏(C)、四川红杉(D)凋落叶分解过程中木质素降解率(%/月)的动态特征(平均值±标准偏差, n = 9)。不同小写字母表示同一物种凋落叶在同一生境下不同分解时期木质素降解率差异显著(p < 0.05)。FP, 冻结期; IV, 初始值; GS, 生长季节; LGS, 生长季节后期; PP, 冻结初期; TP, 融化期; 1, 第一年; 2, 第二年。

Fig. 3 Dynamics of lignin degradation rate (%/month) during Salix paraplesia (A), Rhododendron lapponicum (B), Sabina saltuaria (C), and Larix mastersiana (D) foliar litter decomposition (p < 0.05) under different habitat conditions (mean ± SD, n = 9). Different lowercase letters indicate significant (p < 0.05) differences of lignin degradation rate among different decomposition periods for a given litter species incubated in a specific type of habitat. FP, freezing period; GS, growing season; IV, initial value; LGS, late growing season; PP, pre-freezing period; TP, thawing period; 1, first year; 2, second year.

表3 凋落叶分解过程中木质素降解率与物种、生境和分解时期的重复测量方差分析

Table 3 Repeated-measure ANOVA analysis on the effects of litter species, habitat type, and decomposition period on lignin degradation rate during litter decomposition process

影响因子 Influence factor	自由度 Degree of freedom	F	p
物种 Species	3	165.753	< 0.001
生境 Habitat	2	75.197	< 0.001
时期 Period	9	504.141	< 0.001
物种×生境 Species × habitat	6	40.353	< 0.001
物种×时期 Species × period	27	17.003	< 0.001
生境×时期 Habitat × period	18	18.317	< 0.001
物种×生境×时期 Species × habitat × period	54	12.020	< 0.001

表4 凋落叶木质素两年总降解率(%/月)与初始质量的逐步回归分析

Table 4 Stepwise regression analysis between lignin degradation rate (%/month) of the 2 years and foliar litter initial chemical properties

生境 Habitat	回归式 Regression model
	a₀	a₁X₁	a₂X₂	a₃X₃	a₄X₄
林下 Forest floor	ŷ = 0.424	-0.017 C:N (0.353)	+0.042 C (0.607)
溪流 Stream	ŷ = 1.602	-0.031 Lignin:N (0.785)	+13.231 P (0.874)
河岸带 Riparian zone	ŷ = -7.311	+0.032 Lignin (0.783)	+20.108 P (0.888)	+0.164 N:P (0.932)	+0.090 C (0.940)

表5 不同生境下凋落叶分解过程中木质素降解率(%/月)与环境因子回归分析的F值

Table 5 F-value for the regression analysis between lignin degradation rate (%/month) and environmental factors under different habitats during foliar litter decomposition

林下 Forest floor	AT	C	N	P	pH
康定柳 Salix paraplesia	26.925^***	35.094^***	1.987	0.340	6.194^*
高山杜鹃 Rhododendron lapponicum	16.022^***	0.064	5.700^*	17.816^***	2.431
方枝柏 Sabina saltuaria	10.134^**	1.037	23.348^***	23.681^***	8.314^**
四川红杉 Larix mastersiana	30.336^***	7.748^**	32.560^***	10.076^**	13.489^***
溪流 Stream	AT	HCO₃^-	NH₄⁺	NO₃^-	PO₄^3-	pH	FV
康定柳 Salix paraplesia	0.001	0.572	2.692	13.248***	0.522	6.208*	0.385
高山杜鹃 Rhododendron lapponicum	1.286	1.722	6.088^*	8.832^**	1.612	1.652	1.590
方枝柏 Sabinasaltuaria	1.245	4.809^*	7.579^**	8.964^**	0.001	6.454^*	0.103
四川红杉 Larix mastersiana	2.815	2.179	4.681^*	11.866^**	0.063	5.594^*	0.053
河岸带 Riparian zone	AT	HCO3-	NH4+	NO3-	PO43-	pH	FV
康定柳 Salix paraplesia	35.148***	5.748*	12.267**	0.256	1.305	16.431***	2.540
高山杜鹃 Rhododendron lapponicum	3.702	2.822	2.029	1.369	0.001	7.300^**	5.752^*
方枝柏 Sabina saltuaria	1.564	4.024^*	6.775^*	4.609^*	0.115	3.545	6.232^*
四川红杉 Larix mastersiana	36.978^***	15.189^***	19.985^***	4.305^*	0.055	0.371	11.602^**

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