西双版纳热带雨林凋落叶分解的生态过程Ⅰ.凋落叶分解动态

doi:10.17521/cjpe.2006.0100

摘要/Abstract

摘要：

通过野外试验和室内模拟相结合,系统研究了西双版纳热带雨林生态系统混合凋落叶分解的生态过程。野外试验采用网袋法,即1 mm和100 μm网眼网袋,分别限制大型土壤动物和螨类的进入,从而分别观测小型土壤动物(螨类)、线虫的分解作用;室内试验则通过控制温、湿度条件,采用灭菌-接种法分别观测微生物和线虫对凋落叶的分解。研究结果表明,凋落叶的分解是一个先快后慢的过程,在这个过程中存在分解“滞留”阶段,分解速率变化发生波动,且波动的程度与食物链的复杂程度有关,食物链越复杂,波动程度越强烈。利用单指数衰减模型 x_t/x₀=exp(-kt)和双指数模型x_t/x₀=a×exp(-k₁t)+b×exp(-k₂t)对凋落叶分解过程进行模拟,后者将凋落叶前欺的快速分解和后期的慢速分解两个过程分别拟合,不但弥补了分解前期单指数衰减模型与观测值之间不能吻合的缺陷,而且消除了单指数模型对长期分解进程的过高预测,因此能更好地反映实际分解进程。利用双指数生物模型研究生物和非生物因子对凋落叶分解速率的贡献表明,土壤动物是影响分解进程的最重要因子,占影响因子总量的78.1%,非生物因素的作用为14.1%,微生物对分解速率的贡献只有7.8%。在热带森林生态系统中,土壤动物是最重要的分解者。

关键词: 西双版纳, 热带雨林, 混合凋落叶, 分解, 模型

Abstract:

Background and Aims Decomposition of mixed leaf litters in Xishuangbanna tropic rain forest was studied both in the field and laboratory. Negative exponential model x_t/x₀=exp(-k_t) and binomial exponential model x_t/x₀=a×exp(-k₁t)+b×exp(-k₂t) were used to simulate the observed decomposition process with. Bio-models were introduced to analysis the contribution of biotic and abiotic factors to the decay rates of leaf litters.

Methods Coarse (with mesh size of 1 mm) and fine (with mesh size of 100 μm) litterbags were used in the field to examine the effects of different components of soil fauna on litter decomposition by restricting access by most soil macrofauna and mites, respectively, i.e. feasible for most mites to coarse mesh and nematodes to fine mesh. In the laboratory, sterilization and inoculation were adopted to investigate the effects of nematodes and microbiota on leaf litters.

Key Results The decomposition process was a course fast incipiently then slowdown with stagnation periods. The decay rate of mixed leaf litters fluctuated over the decomposing period with the magnitude of fluctuation positively related to complexity of food-web. The binomial exponential model simulated the two different courses of leaf litter decomposition whereas the negative exponential model did not simulate the initial stage well and overestimated the long-term decay process. Soil fauna accounted for 78.1% of the decay rates while abiotic factors for 14.1% and microorganisms only for 7.8%.

Conclusions This study suggests that the decomposition of leaf litters was a cascade process and binomial exponential model can describe the process better than the negative exponential model. Soil fauna played a dominating role in litter decomposition in tropic rain forest.

Key words: Xishuangbanna, Tropic rain forest, Mixed leaf litter, Decomposition, Model

张瑞清, 孙振钧, 王冲, 葛源, 李云乐, 乔玉辉, 庞军柱, 张录达. 西双版纳热带雨林凋落叶分解的生态过程Ⅰ.凋落叶分解动态. 植物生态学报, 2006, 30(5): 780-790. DOI: 10.17521/cjpe.2006.0100

ZHANG Rui-Qing, SUN Zhen-Jun, WANG Chong, GE Yuan, LI Yun-Le, QIAO Yu-Hui, PANG Jun-Zhu, ZHANG Lu-Da. ECO-PROCESS OF LEAF LITTER DECOMPOSITION IN TROPICAL RAIN FOREST IN XISHUANGBANNA, CHINA. Ⅰ. DECOMPOSITION DYNAMIC OF MIXED LEAF LITTERS. Chinese Journal of Plant Ecology, 2006, 30(5): 780-790. DOI: 10.17521/cjpe.2006.0100

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2006.0100

https://www.plant-ecology.com/CN/Y2006/V30/I5/780

图/表 11

表1 试验年度(2004年4月~2005年3月)研究地区月平均气温和降雨量

Table 1 Average monthly temperature and amount of monthly precipitation at sampling time (from April 2004 to March 2005) in study site of Xishuangbanna

项目 Item	2004									2005
项目 Item	4月 Apr.	5月 May	6月 June	7月 July	8月 Aug.	9月 Sept.	10月 Oct.	11月 Nov.	12月 Dec.	1月 Jan.	2月 Feb.	3月 Mar.
气温Temperature (℃)	21.5	23.6	24.7	25.5	25.2	25.4	24.2	22.3	19.8	15.0	16.8	19.3
降雨量Precipitation(mm)	263.0	779.0	223.9	79.9	169.0	204.6	160.1	56.8	45.8	0.0	1.5	0.0

表2 研究样地土壤基本理化性质

Table 2 Physio-chemical properties of the top soil (0-2.5 cm) in experiment fields in Xishuangbanna

有机质 Organic matter (g·kg^-1)	全氮 Total nitrogen (g·kg^-1)	C/N	pH	容重 Density (×10⁹ mg·m^-3)
48.30±0.85	2.30±0.04	12.30±1.23	4.75±0.22	1.02±0.10

表3 试验用材料(混合凋落叶)基本理化性质a

Table 3 Physio-chemical properties of materials (mixed leaf litters) used in study

全碳 Total C(%)	全氮 Total N(%)	碳氮比 C/N-ratio	灰分 Ash(%)	纤维素 Cellulose (%)	木质素 Lignin (%)
49.10±0.22	1.11±0.01	44.30±0.16	7.41±0.02	41.29±0.06	28.26±0.04

图1 野外试验不同处理凋落叶分解动态(残留率和分解速率) 平均值±标准差 Mean±SD (n=4) C: 大网眼网袋 Coarse mesh F: 小网眼网袋 Fine mesh

Fig.1 Dynamics of decomposition of leaf litters in field experiments (Ash-free dry mass (AFDM) remaining ratio and decay rate)

图2 室内模拟试验不同处理凋落叶分解动态(残留率和分解速率) 平均值±标准差 Mean±SD (n=3) M: 接种微生物 Incubated microbiota only MN: 接种微生物+线虫 Incubated microbiota and nematodes

Fig.2 Dynamics of decomposition of leaf litters in simulated study indoors (Ash-free dry mass (AFDM) remaining ratio and decay rate)

图3 单指数衰减模型模拟各影响因子在凋落叶分解过程中的单独作用和协同作用(图示分解进程)

Fig.3 Single exponential models for individual and collected effects of influencing factors on leaf litter decay rate (curves displayed decomposing process)

图4 野外试验和室内模拟试验不同处理凋落叶分解动态模拟 ▲:观测值 The observed ——:双指数模拟曲线 Binomial exponential curve ----:单指数模拟曲线 Single exponential curve C: 野外大网眼 Coarse mesh in field F: 野外小网眼 Fine mesh in field M: 室内接种微生物(未接种线虫) Without nematode in simulated MN: 室内接种微生物+线虫 With nematode in simulated

Fig.4 Simulation of leaf litter decomposition process for different treatment in field and simulated studies

图5 不同处理凋落叶分解双指数模拟曲线及其主、附指数曲线 C, F, MN, M: 同图4 See Fig.4

Fig.5 Binomial exponential curve and its main-exponent and sub-exponent for leaf litter decomposition process with different treatment in field and simulated studies

表4 凋落叶分解进程的双指数模拟方程

Table 4 Formula of binomial exponential model to simulate decomposition process

处理 Treatment	因子 Factor				F值 F value
处理 Treatment	a	k₁	b	k₂
C	0.886 2	0.003 52	0.108 3	0.049 8	<0.000 2
F	0.685 5	0.001 75	0.304 4	0.017 4	<0.000 1
MN	0.794 7	0.001 27	0.205 0	0.063 0	<0.000 1
M	0.737 8	0.000 28	0.261 2	0.046 9	<0.000 1

表5 单指数和双指数模型对凋落叶年分解速率及分解50%和95%所需时间的预测

Table 5 Prediction values of decay rate and time for 50% and 95% decomposition by single and binomial exponential models

处理 Treatment	指数模型 Model	分解速率 Mass loss rate		分解50%和95%所需要的时间 Time for 50% and 95% decomposition
处理 Treatment	指数模型 Model	d^-1	a^-1	a (t_0.5)	a (t_0.95)
C	1	0.003 96	1.45	0.48	2.08
	2	0.003 52	1.28	0.52	2.26
F	1	0.003 15	1.15	0.60	2.61
	2	0.001 75	0.64	0.96	4.15
M	1	0.002 33	0.85	0.81	3.53
	2	0.000 28	0.10	6.11	26.5
MN	1	0.002 79	1.02	0.68	2.95
	2	0.001 27	0.46	1.39	6.04

表6 不同因子对有机残体分解速率的影响

Table 6 Effects of different factors on decay rates of litter

分解材料 Litter type	分解速率 Decay constants (a^-1)			环境和微生物的作用 Effect without fauna (k_a+k_m)/k_total	土壤动物的作用 Faunal effect k_f/k_total
分解材料 Litter type	环境和微生物 Without fauna (k_a+k_m)	土壤动物 Faunal component (k_f)	总因子 Total factor (k_total)	环境和微生物的作用 Effect without fauna (k_a+k_m)/k_total	土壤动物的作用 Faunal effect k_f/k_total
混合凋落叶Mixed leaf litter^*	0.28	1.00	1.28	21.9	78.1
混合凋落叶Mixed leaf litter^**	0.98	0.47	1.45	67.6	32.4
山茱萸叶Macrocarpium officinalis foliage	0.69	0.13	0.82	84.1	15.9
栗树叶Chestnut oak foliage	0.48	0.02	0.50	96.0	4.0
混合凋落叶Mixed deciduous foliage	0.40	0.30	0.70	57.1	42.9
白栎树叶Quercus albus foliage	0.60	0.32	0.92	65.2	34.8
山毛榉树叶Fagus longipetiolata foliage	0.41	0.09	0.50	82.0	18.0
板栗树叶Castanea mollissima foliage	0.27	0.01	0.28	96.4	3.6
橡树叶Shinnery oak foliage	0.22	0.21	0.43	51.2	48.8
森林冻原草Mixed tundra grasses	0.22	0.10	0.32	68.8	31.3
莎草Cyperus sp.	0.30	0.06	0.36	83.3	16.7
格兰马草Bouteloua gracilis	0.14	0.31	0.45	31.1	68.9
牧草Mixed pasture grasses	1.15	0.09	1.24	92.7	7.3
桉树叶Eucalyptus pauciflora foliage^*	0.45	0.28	0.73	61.6	38.4
桉树叶Eucalyptus pauciflora foliage^**	0.69	0.04	0.73	94.5	5.5

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