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森林生态系统中,凋落分解对土壤养分周转、能量流动、碳循环等方面发挥着重要的作用[1-2]。森林生态系统一般都是多种植物的复合系统,凋落物主要以混合状态而非孤立的形式存在[3]。这种混合状态可以改变凋落物的分解环境[4]、异质凋落物间的养分互补[5-6],以及微生物群落和土壤动物的栖息生境[7-8],进而改变凋落物分解和养分循环的速率。近年来,混合凋落物的研究逐渐受到重视,混合凋落物分解和养分释放产生的混合效应并无一致的结论,主要表现为正效应[9]、负效应[10]和加和效应[11]。综合30项研究结果发现,70%混合凋落物叶分解表现出混合效应(正效应或负效应)[12],即混合凋落物的实际分解速率偏离于期望分解速率。混合凋落物的分解过程不仅和各物种的特异性质有关,还受其物理、化学性质组分的差异的影响,甚至改变混合凋落物分解的最终结果[13]。因此,在同一生态系统中深入了解凋落物混合分解的效应,对认识不同物种间的相互作用和关系具有重要意义。竹林作为我国一种主要的森林类型,具有分布广、面积大、生长快等特点,高效的固碳能力对调节大气CO2浓度具有重要作用[14]。在亚热带毛竹林中往往伴生一些林下植被[15],这些林下植被的存在对毛竹林凋落物的分解和养分动态的影响如何,以及林下植被本身凋落物的分解动态情况又如何,目前,关于竹林和林下植被复合模式下凋落物分解和养分动态的研究还未见报道。本研究以四川省长宁县典型竹林——毛竹(Phyllostachys edulis (Carr.) H.de Lehaie)和林下植被优势种芒箕(Dicranopteris pedata (Houtt.) Nakaike)为研究对象,对比毛竹和芒箕凋落物的化学特征,分析两种植被单独以及混合凋落分解和养分动态的变化特征,探讨毛竹和芒箕凋落物之间相互作用的潜在机制,为毛竹林林下植被的合理经营管理提供理论参考。
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毛竹和林下植被芒箕的凋落物叶初始化学组分有着明显差异(表 1)。其中C、N、P 3种元素含量在芒箕凋落物中均显著高于毛竹林凋落物(P < 0.05);C:N和C:P比为毛竹凋落物显著高于芒箕凋落物(P < 0.05),而N:P比无显著差异性。
表 1 凋落物的初始化学组成
Table 1. Initial chemical composition of litter
凋落物类型Litter type C/(g·kg-1) N/(g·kg-1) P/(g·kg-1) C:N C:P N:P 毛竹P. edulis 415.78±0.15b 17.55±0.04b 0.204±0.001b 23.69±0.06a 2 042.40±8.08a 86.21±0.48a 芒箕D. pedata 421.64±0.29a 35.33±0.19a 0.404±0.001a 11.93±0.06b 1 044.06±2.13b 87.49±0.42a 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8.毛竹和芒箕凋落物叶初始有机碳化学结构研究结果显示,两者有机碳化学结构格局不同,毛竹中氧烷基碳最高(62.39%±0.75%),羟基碳最低(7.49%±0.13%),而芒箕中羟基碳最高(52.81%±0.95%),芳香碳最低(9.82%±0.30%);毛竹中烷基碳、氧烷基碳和芳香碳均显著高于芒箕(P < 0.05),而羟基碳及烷基碳/氧烷基碳比显著低于芒箕(P < 0.05)(表 2)。
表 2 凋落物的初始有机碳化学结构相对含量
Table 2. Proportions of the components of initial organic carbon functional group of litter
% 凋落物类型
Litter type烷基碳
Alkyl氧烷基碳
O-alkyl芳香碳
Aromatic羟基碳
Carbonyl烷基碳/氧烷基碳
Alkyl/o-alkyl毛竹P. edulis 15.02±0.12a 62.39±0.75a 15.11±0.21a 7.49±0.13b 24±0.27b 芒箕D. pedata 12.55±0.28b 24.81±0.44b 9.82±0.30b 52.81±0.95a 51±0.43a 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8. -
毛竹和芒箕凋落物干质量剩余率随分解进程均呈逐渐下降的趋势,且凋落物分解总体表现为初始阶段分解最快,后期分解逐渐减慢(图 1A)。分解1年后,毛竹和芒箕凋落物干质量剩余率分别为56.10%和48.03%,差异性显著(P < 0.05)(表 3)。从表 3可以看出芒箕凋落物年分解速率(0.73±0.02)明显高于毛竹(0.58±0.03)(P < 0.05),Olson的指数方程能够很好模拟两种植被凋落物的分解过程,毛竹和芒箕相关系数(R2)分别为0.999和0.984。
图 1 单一凋落物分解过程中干质量和养分含量的变化(*表示种间差异显著(P < 0.05))
Figure 1. Single litter decomposition rates and nutrient dynamics duiring decomposition (*denote significant difference at P < 0.05 between two species)
表 3 凋落物干质量剩余率与时间的回归分析
Table 3. Regression analysis between dry weight residue of litter and time
类型
Type回归方程
Equation相关系数
R2年残留率
Remaining rate/%分解常数
k半衰期
t0.5/a周转期
t0.95/a毛竹P. edulis y = 0.790 3e-0.341t 0.999 56.10±1.77a 0.58±0.03b 1.21±0.07a 5.25±0.30a 芒箕D. pedata y = 0.630 6e-0.262t 0.984 48.03±0.87b 0.73±0.02a 0.95±0.02b 4.10±0.10b 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8.毛竹和芒箕凋落物C、N、P剩余率全年整体均呈下降趋势(图 1B,C,D),表现为净释放状态。毛竹和芒箕间元素释放格局表现不同,两者C元素释放速率只在分解初期的前3个月有显著差异,表现为芒箕显著高于毛竹(图 1B)(P < 0.05),全年芒箕N元素释放速率显著高于毛竹(图 1C)(P < 0.05),前9个月芒箕P元素释放速率显著高于毛竹(图 1D)(P < 0.05)。
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凋落物混合干质量剩余率实测值与期望值对比结果表明,毛竹和芒箕凋落物的混合分解无显著混合效应(正效应或负效应)(图 2A)。凋落物混合对分解过程中C、N、P元素释放的影响格局不同(图 2B,C,D)。在整个1年的分解过程中,实测C剩余率只在9个月时与期望值有显著差异(P < 0.05);而混合分解对N元素的释放影响全年表现为负效应,实测N剩余率比期望值平均高15.82%(P < 0.05);混合分解对P元素的释放的前9个月有显著的负效应(P < 0.05)。这说明毛竹和芒箕凋落物混合对C、N、P元素释放整体表现为负效应。
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在整个凋落物分解过程中,毛竹和芒箕间C、N、P含量整体变化趋势一致(图 3A,B,C),其中C含量整体呈下降趋势,N含量有小幅度的上升趋势,P含量有微弱的下降趋势,毛竹和芒箕凋落物在全年的分解过程中C、N、P含量均差异显著(P < 0.05),分解1年后,毛竹和芒箕C含量分别为291.33 g·kg-1和333.40 g·kg-1,N含量分别为25.11 g·kg-1和38.56 g·kg-1,P含量分别为0.17 g·kg-1和0.32 g·kg-1;毛竹和芒箕间C、N、P化学计量比的特征整体变化趋势一致(图 3D,E,F),C:N比呈整体下降的趋势,C:P比呈波动性变化,而N:P表现出小幅的上升,分解1年后,毛竹和芒箕间N:P由初始的无差异,在末期表现出显著性差异(P < 0.05),N:P比值分别为151.85和125.32。
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相关分析表明,凋落物叶的干质量损失率与土壤温度呈显著正相关(P < 0.01),与土壤含水量无显著相关性;凋落物叶的干质量损失率与与初始凋落物叶的N、P含量呈显著正相关(P < 0.05),与初始凋落物叶的C:N和C:P呈极显著负相关(P < 0.01)(表 4)。
表 4 凋落物干质量损失量与土壤含水量、温度及初始凋落物质量的Pearson相关系数
Table 4. Pearson correlation coefficient between dry mass loss of litter and soil water content and temperature, the initial quality
类型
Type土壤含水量
Soil water content土壤温度
Soil temperatureC N P C:N C:P N:P 毛竹P. edulis -0.247 0.783** 0.154 0.572* 0.521** -0.411* -0.552* 0.178 芒箕D. pedata -0.311 0.809** 0.123 0.504* 0.373* -0.394* -0.379* 0.172 毛竹和芒箕P. edulis&D. pedata -0.290 0.751* 0.253 0.634** 0.437* -0.517* -0.430* 0.204 注:*表示显著水平P < 0.05;**表示显著水平P < 0.01.
Note: *mean sinificant difference(P < 0.05),**mean sinificant difference(P < 0.01).
毛竹和林下植被芒箕凋落物分解特征研究
Decomposition Characteristics of Litter of Phyllostachys edulis and Dicranopteris pedata
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摘要:
目的 探讨竹林与其林下植被凋落物叶之间相互影响的潜在机制,为合理经营管理毛竹林林下植被提供理论参考。 方法 采用原位分解袋法研究了四川长宁毛竹与林下植被芒箕凋落物叶分解和养分释放过程。 结果 (1)芒箕凋落物叶初始C、N、P含量和羟基碳高于毛竹(P < 0.05),而C:N、C:P、烷基碳、氧烷基碳和芳香碳低于毛竹(P < 0.05)。(2)凋落物叶分解和养分释放速率芒箕整体高于毛竹,芒箕和毛竹分解常数(k)分别为0.58±0.03和0.73±0.02,C、N、P养分释放均表现为净释放。(3)凋落物叶混合对分解速率没有显著影响,但抑制了N、P元素整个分解周期和C元素中后期的释放。(4)凋落物叶分解过程中元素含量变化格局表现为C含量和C:N比整体呈下降趋势,N含量和N:P比有小幅上升,P含量有微弱的下降趋势,C:P比呈波动性变化。(5)凋落物叶分解速率与土壤温度、初始凋落物叶N和P含量呈显著正相关(P < 0.01),与初始凋落物叶的C:N和C:P呈极显著负相关(P < 0.01),与土壤含水量相关不显著。 结论 单独分解过程中,毛竹凋落物叶分解速率低于林下植被芒箕,养分释放特征均表现为直接释放;混合分解过程中,毛竹和芒箕凋落物叶分解速率无显著混和效应,但养分释放的混合效应表现出一定负效应和不同阶段性。 Abstract:Objective To explore the potential mechanisms of interaction and function between bamboo forest and its understory vegetation's leaf litter, and provide a theoretical reference for the rational management of understory vegetation in Phyllostachys edulis forest. Method The litter in situ decomposition and nutrient release process of Ph. edulis and understory vegetation (Dicranopteris pedata) in Changning of Sichuan Province were investigated using litter bag. Result (1) The initial C, N, P contents and Carbonyl C of D. pedata were higher than those of Ph. edulis (P < 0.05), while C:N, C:P and Alkyl C, O-alkyl C and Aromatic C of D. pedata were all lower than those of P. edulis (P < 0.05). (2) The rate of litter decomposition and nutrient releasing of D. pedata were higher than that of Ph. edulis. The decomposition coefficient of Ph. edulis and D. pedata were 0.58±0.03 and 0.73±0.02, respectively. C, N and P nutrient release all showed net release. (3) The litter mixture of Ph. edulis and D. pedata had no significant effect on the decomposition rate, however, it significantly inhibited the release of N and P elements throughout the decomposition cycle and C elements in the late. (4) The change pattern of element content in litter decomposition process of Ph. edulis and D. pedata showed that C content and C:N ratio turned out a downward trend, and N content and N:P ratio increased slightly. P content showed a slight downward trend, and C:P ratio fluctuated. (5) Litter decomposition rate was positively correlated with soil temperature, initial litter N and P content (P < 0.01), and negatively correlated with C:N and C:P of initial litter (P < 0.01), but had no significant correlation with soil water content. Conclusion There was no significant mixed effect of decomposition rate, but the mixed effect of nutrient release showed certain negative effects and different periodic features. -
Key words:
- Phyllostachys edulis
- / Dicranopteris pedata
- / litter decomposition
- / nutrient release
- / mixing effects
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表 1 凋落物的初始化学组成
Table 1. Initial chemical composition of litter
凋落物类型Litter type C/(g·kg-1) N/(g·kg-1) P/(g·kg-1) C:N C:P N:P 毛竹P. edulis 415.78±0.15b 17.55±0.04b 0.204±0.001b 23.69±0.06a 2 042.40±8.08a 86.21±0.48a 芒箕D. pedata 421.64±0.29a 35.33±0.19a 0.404±0.001a 11.93±0.06b 1 044.06±2.13b 87.49±0.42a 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8.表 2 凋落物的初始有机碳化学结构相对含量
Table 2. Proportions of the components of initial organic carbon functional group of litter
% 凋落物类型
Litter type烷基碳
Alkyl氧烷基碳
O-alkyl芳香碳
Aromatic羟基碳
Carbonyl烷基碳/氧烷基碳
Alkyl/o-alkyl毛竹P. edulis 15.02±0.12a 62.39±0.75a 15.11±0.21a 7.49±0.13b 24±0.27b 芒箕D. pedata 12.55±0.28b 24.81±0.44b 9.82±0.30b 52.81±0.95a 51±0.43a 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8.表 3 凋落物干质量剩余率与时间的回归分析
Table 3. Regression analysis between dry weight residue of litter and time
类型
Type回归方程
Equation相关系数
R2年残留率
Remaining rate/%分解常数
k半衰期
t0.5/a周转期
t0.95/a毛竹P. edulis y = 0.790 3e-0.341t 0.999 56.10±1.77a 0.58±0.03b 1.21±0.07a 5.25±0.30a 芒箕D. pedata y = 0.630 6e-0.262t 0.984 48.03±0.87b 0.73±0.02a 0.95±0.02b 4.10±0.10b 注:同列不同字母表示差异显著(P < 0.05),n=8。
Note: Values followed with the different letters within a column mean sinificant difference(P < 0.05),n=8.表 4 凋落物干质量损失量与土壤含水量、温度及初始凋落物质量的Pearson相关系数
Table 4. Pearson correlation coefficient between dry mass loss of litter and soil water content and temperature, the initial quality
类型
Type土壤含水量
Soil water content土壤温度
Soil temperatureC N P C:N C:P N:P 毛竹P. edulis -0.247 0.783** 0.154 0.572* 0.521** -0.411* -0.552* 0.178 芒箕D. pedata -0.311 0.809** 0.123 0.504* 0.373* -0.394* -0.379* 0.172 毛竹和芒箕P. edulis&D. pedata -0.290 0.751* 0.253 0.634** 0.437* -0.517* -0.430* 0.204 注:*表示显著水平P < 0.05;**表示显著水平P < 0.01.
Note: *mean sinificant difference(P < 0.05),**mean sinificant difference(P < 0.01). -
[1] Wardle D A, Hörnberg G, Zackrisson O, et al. Long-term effects of wildfire on ecosystem properties across an island area gradient[J]. Science, 2003, 300(5621):972-975. doi: 10.1126/science.1082709 [2] Wardle D A, Nilsson M C, Zackrisson O, et al. Determinants of litter mixing effects in a Swedish boreal forest[J]. Soil Biology & Biochemistry, 2003, 35(6):827-835. [3] 詹鸿振, 刘传照, 刘吉春, 等.小兴安岭阔叶红松林主要树种凋落物的分解研究[J].东北林业大学学报, 1990, 18(3):1-8. [4] Hättenschwiler S, Tiunov A V, Scheu S. Biodiversity and Litter Decomposition in Terrestrial Ecosystems[J]. Annual Review of Ecology Evolution & Systematics, 2005, 36(36):191-218. [5] Lummer D, Scheu S, Butenschoen O. Connecting litter quality, microbial community and nitrogen transfer mechanisms in decomposing litter mixtures[J]. Oikos, 2012, 121(10):1649-1655. doi: 10.1111/more.2012.121.issue-10 [6] S Linnea Berglund, GÅran I ögren, Alf Ekblad. Carbon and nitrogen transfer in leaf litter mixtures[J]. Soil Biology and Biochemistry, 2013, 57(341):341-348. [7] 胡亚林, 汪思龙, 黄宇, 等.凋落物化学组成对土壤微生物学性状及土壤酶活性的影响[J].生态学报, 2005, 25(10):2662-2668. doi: 10.3321/j.issn:1000-0933.2005.10.030 [8] Kubartová A, Ranger J, Berthelin J, et al. Diversity and decomposing ability of saprophytic fungi from temperate forest litter[J]. Microbial Ecology, 2009, 58(1):98-107. [9] Malosso E, English L, Hopkins D W, et al. Use of 13C-labelled plant materials and ergosterol, PLFA and NLFA analyses to investigate organic matter decomposition in Antarctic soil.[J]. Soil Biology & Biochemistry, 2004, 36(1):165-175. [10] Liu P, Huang J, Han X, et al. Litter Decomposition in Semiarid Grassland of Inner Mongolia, China[J]. Rangeland Ecology & Management, 2009, 62(4):305-313. [11] Tardif A, Shipley B. Using the biomass-ratio and idiosyncratic hypotheses to predict mixed-species litter decomposition[J]. Annals of Botany, 2013, 111(1):135. doi: 10.1093/aob/mcs241 [12] Gartner T B, Cardon Z G. Decomposition dynamics in mixed-species leaf litter[J]. Oikos, 2004, 104(2):230-246. doi: 10.1111/oik.2004.104.issue-2 [13] 李宜浓, 周晓梅, 张乃莉, 等.陆地生态系统混合凋落物分解研究进展[J].生态学报, 2016, 36(16):4977-4987. [14] 江泽慧.世界竹藤[M].沈阳:辽宁科学技术出版社, 2002. [15] 高平珍, 陈双林.毛竹林下植被管理与利用研究综述[J].竹子研究汇刊, 2017, 36(2):44-48. doi: 10.3969/j.issn.1000-6567.2017.02.007 [16] 刘广路, 范少辉, 蔡春菊, 等.撑绿杂交竹和硬头黄竹克隆生长特性比较[J].植物学报, 2013, 48(3):288-294. [17] Olson J S. Energy Storage and the Balance of Producers and Decomposers in Ecological Systems[J]. Ecology, 1963, 44(2):322-331. doi: 10.2307/1932179 [18] 陈瑾, 李扬, 黄建辉.内蒙古典型草原4种优势植物凋落物的混合分解研究[J].植物生态学报, 2011, 35(1):9-16. [19] Jhc C. An experimental comparison of leaf decomposition rates in a wide range of temperate plant species and types.[J]. Journal of Ecology, 1996, 84(4):573-582. doi: 10.2307/2261479 [20] 杨玉盛, 郭剑芬, 陈银秀, 等.福建柏和杉木人工林凋落物分解及养分动态的比较[J].林业科学, 2004, 40(3):19-25. doi: 10.3321/j.issn:1001-7488.2004.03.003 [21] Tian X J, Takahiro T. Relative roles of microorganisms and soil animals on needel litter decomposition in a subalpine coniferous forest J]. Acta Phytoecologica Sinica, 2002, 26(3):257-263. [22] Garcia-Pausas J, Casals P, Romanyà J. Litter decomposition and faunal activity in Mediterranean forest soils:effects of N content and the moss layer[J]. Soil Biology & Biochemistry, 2004, 36(6):989-997. [23] Sanchez F G.Loblolly pine needle decomposition and nutrient dynamics as affected by irrigation, fertilization, and substrate quality[J]. Forest Ecology & Management, 2001, 152(1):85-96. [24] Mendonça E S, Stott D E. Characteristics and decomposition rates of pruning residues from a shaded coffee system in Southeastern Brazil[J]. Agroforestry Systems, 2003, 57(2):117-125. doi: 10.1023/A:1023900822261 [25] 施妍, 陈芳清.大老岭自然保护区日本落叶松林凋落物分解及养分释放研究[J].林业科学研究, 2016, 29(3):430-435. doi: 10.3969/j.issn.1001-1498.2016.03.019 [26] Preston C M, Trofymow J A. Variability in litter quality and its relationship to litter decay in Canadian forests.[J]. Canadian Journal of Botany, 2000, 78(10):1269-1287. doi: 10.1139/b00-101 [27] 杨万勤, 邓仁菊, 张健.森林凋落物分解及其对全球气候变化的响应[J].应用生态学报, 2007, 18(12):2889-2895. [28] Berg B, Mcclaugherty C. Plant Litter. Decomposition, Humus Formation, Carbon Sequestration[M]. Berlin:Springer-Verlag, 2008. [29] 李正才, 徐德应, 杨校生, 等.北亚热带6种森林类型凋落物分解过程中有机碳动态变化[J].林业科学研究, 2008, 21(5):675-680. doi: 10.3321/j.issn:1001-1498.2008.05.015 [30] Einhellig F A, Rasmussen J A, Hejl A M, et al. Effects of root exudate sorgoleone on photosynthesis[J]. Journal of Chemical Ecology, 1993, 19(2):369-375. doi: 10.1007/BF00993702 [31] Knops J M H, Wedin D, Tilman D. Biodiversity and decomposition in experimental grassland ecosystems.[J]. Oecologia, 2001, 126(3):429-433. doi: 10.1007/s004420000537 [32] Rustad L E, Cronan C S. Element loss and retention during litter decay in a red spruce stand i.[J]. Canadian Journal of Forest Research, 1988, 18(7):947-953. doi: 10.1139/x88-144 [33] Hansen R A, Coleman D C. Litter complexity and composition are determinants of the diversity and species composition of oribatid mites (Acari:Oribatida) in litterbags.[J]. Applied Soil Ecology, 1998, 9(1-3):17-23. doi: 10.1016/S0929-1393(98)00048-1 [34] Tlalka M, Bebber D P, Darrah P R, et al. Emergence of self-organised oscillatory domains in fungal mycelia[J]. Fungal Genetics & Biology, 2007, 44(11):1085-1095. [35] 蒋云峰.长白山针阔混交林主要凋落物分解及土壤动物的作用[D].长春: 东北师范大学, 2013.