两种落叶分解过程中养分和碳素的行为

利用分解袋法对日本亚高山针叶林的针叶(Abies veitchii Lindl.and A.mariesiMast.)和阔叶(Betulaermanii Cham.and B.corylifolia Regal.et Maxim.)凋落物进行了分解实验研究.结果表明尽管分解初期的两种凋落物的养分以及分解后期凋落物剩余重量差异很大,但两种凋落物养分浓度在分解后期(30个月以后)趋于一致.这种趋同现象在不同养分中有不同的趋同机制.氮元素浓度升高到分解后期浓度差变小,这种现象是由于分解菌的固持作用及受木质素的束缚所致;钾和镁在分解初期浓度急剧下降,进而浓度差变小,是由于淋溶作用所致.在分解过程中这些元素非常容易被淋溶掉,直到和土壤中的浓度达到一致为止.钙是结构元素,它的行踪和有机物组分有密切关系.由于分解后期有机组分木质化和腐殖质化进而浓度趋同,所以钙的浓度也相应趋同.     

雪被覆盖对高山森林凋落物分解过程中水溶性和有机溶性组分含量的影响

季节性雪被可能通过冻结、淋溶以及冻融循环等对高山森林凋落物水溶性和有机溶性组分含量产生影响.本文采用凋落物分解袋法,以川西高山森林典型乔木（四川红杉、岷江冷杉、红桦、方枝柏）和灌木（高山杜鹃、康定柳）凋落物为研究对象,研究了雪被覆盖不同时期（雪被形成期、雪被覆盖期和雪被融化期）和雪被厚度（厚型雪被、中型雪被、薄型雪被和无雪被）下凋落物水溶性和有机溶性组分含量的动态变化特征.结果表明： 在一个冬季的分解过程中,6种凋落物水溶性组分含量在雪被形成期和融化期降低而雪被覆盖期增加,但除高山杜鹃凋落物有机溶性组分含量在雪被覆盖期增加外,其他5种凋落物有机溶性组分含量在整个冬季呈降低趋势.相对于凋落物有机溶性组分含量,不同厚度雪被斑块对凋落物水溶性组分含量变化的影响更大,且主要表现在雪被形成期和雪被覆盖期.相对于其他雪被斑块,薄型雪被斑块更加显著地促进了高山柳和高山杜鹃凋落物水溶性组分含量降低,但显著抑制了方枝柏凋落物水溶性组分含量降低,而其他凋落物水溶性组分含量变化在不同斑块间无显著差异.冬季高山森林雪被对凋落物水溶性和有机溶性组分含量的影响主要受控于凋落物质量.     

不同土壤厚度、水分和种植方式对喀斯特两种草本凋落物分解质量损失和化学计量特征的影响

为了探究生长期间不同土壤厚度、水分及种植方式处理对草本植物凋落物分解质量损失和化学计量特征的的影响,采用分解袋法,在露天分解床上分解经过生长期间2种土壤厚度(对照土壤厚度和浅土处理)、2种水分(正常灌水处理和干旱处理)和2种种植方式(单种和混种)处理的苇状羊茅(Festuca arundinacea Schreb.)和黑麦草(Lolium perenne L.)凋落物,研究生长期间土壤厚度和水分减少及不同的种植方式是否通过改变两物种初始凋落物质量、产量和组分来影响自身凋落物分解。结果发现:(1)与对照组(CK)相比,在干旱组(D)和浅土+干旱组(SD),两物种地上、根系和总的凋落物质量损失率、初始N和P含量均显著增加,凋落物产量、C/N和C/P显著降低,凋落物地上组分比大体上无显著变化;而不同的种植方式处理对各组分质量损失率、元素含量、计量比、凋落物产量和组分比大体上无显著影响;(2)两物种地上、根系和总凋落物的质量损失率分别与地上、根系和总N含量呈显著正相关,与C/N呈显著负相关,与凋落量呈显著负相关,而总凋落物质量损失率与地上凋落物组分比呈显著正相关。结果表明,生长期间干旱和浅土+干旱处理能够通过影响苇状羊茅和黑麦草的初始凋落物质量、产量和组分比来加快地上、根系和总凋落物分解,其中凋落物N含量和C/N是影响两物种凋落物分解快慢的主要原因。     

喀斯特峰丛洼地植被演替过程中土壤养分的积累及影响因素

以桂西北环江县典型喀斯特峰丛洼地为对象,利用空间代替时间的方法,于2009年分析了植被演替过程中表层土壤(0～15 em)养分的变化及其主要控制因素.结果表明:随着植被正向演替(草地-灌丛-次生林-原生林),表层土壤的有机碳、全氮和全磷等含量显著增加,分别由演替初期(草地)的29.1、2.48和0.72 g·kg-1增加为演替后期(原生林)的73.9、8.10和1.6g·kg-1.土壤阳离子交换量与有机碳和全氮密切相关,是喀斯特土壤C、N积累的主要控制因素;凋落物中的P含量、C/P和N/P是土壤全磷积累的主要控制因素,较高的凋落物P含量、N/P以及较低的C/P有利于土壤中P的积累;而坡度、坡向和裸岩率等地形因子对土壤养分的影响较小.     

格氏栲天然林与人工林凋落物数量、养分归还及凋落叶分解(英文

通过对中亚热带格氏栲天然林(natural forest of Castanopsis kawakamii。约150年生)、格氏挎和杉木人工林(monoculture plantations of C．kawakamii and Cunninghamia lanceolata,33年生)凋落物数量与季节动态、养分归还及凋落叶分解与其质量的关系为期3a的研究表明。林分年均凋落量及叶所占比例分别为：格氏栲天然林11．01t／hm^1。59．70t／hm^2;格氏栲人工林9．54％。71．98％;杉木人工林5．47t／hm^2。58．29％。格氏栲天然林与人工林凋落量每年只出现1次峰值(4月份)。而杉木林的则出现3次(4或5月份、8月份和11月份)。除杉木林的Ca和格氏栲人工林的Mg年归还量最大外。N、P、K及养分总归还量均以格氏栲天然林的为最大。杉木人工林的最小。分解la后格氏栲天然林中格氏栲叶的干重损失最大(98．16％)。杉木叶的最小(60．78％)。C／N及木质素／N比值与凋落叶分解速率呈显著负相关。而N、水溶性化合物初始浓度与分解速率呈显著正相关。与针叶树人工林相比,天然林的凋落物数量大、养分归还量高、分解快。具有良好自我培肥地力的能力。因此。保护和扩大常绿阔叶林资源已成为南方林区实现森林可持续经营的重要措施之一。     

栲-木荷林凋落叶混合分解对土壤有机碳的影响

用网袋法在20℃条件下将润楠、栲、木荷凋落叶及其混合物(润楠+栲、润楠+木荷、栲+木荷、润楠+栲+木荷)进行室内培养,测定在培养第14、42和84天时凋落叶残留率及其培养下土壤总有机碳(TOC)、可溶性有机碳(DOC)、微生物量碳(MBC),研究其相关性。结果表明:培养到14d,润楠+栲、栲+木荷、润楠+栲+木荷混合凋落叶显著提高了土壤TOC;润楠、栲、木荷、润楠+栲凋落叶显著抑制了土壤DOC;润楠+栲+木荷凋落叶显著增加了土壤MBC,润楠+栲和润楠+木荷凋落叶显著降低了土壤MBC。在培养到42d,仅润楠+木荷、栲+木荷混合凋落叶显著提高了土壤TOC和DOC;仅润楠+栲、润楠+木荷和润楠凋落叶显著减少了土壤MBC。在培养到84天,所有凋落叶都对土壤TOC与DOC无显著影响,栲+木荷、润楠+栲+木荷、木荷、润楠+栲凋落叶显著增加了土壤MBC,栲凋落叶显著减少了土壤MBC;凋落叶分解快慢为栲+木荷>木荷>润楠+栲+木荷>润楠+栲>栲>润楠+木荷>润楠。凋落叶分解率和土壤TOC、DOC及MBC在不同培养时期,具有不同的相关性。结果显示,凋落叶种类和混合对凋落叶分解以及对土壤TOC、DOC和MBC的影响效应包括促进、抑制和无显著影响,这种效应与凋落叶的质量及其分解过程中的养分释放有关。     

高浓度O3对城市蒙古栎凋落叶分解和养分释放的影响

采用开顶箱(OTCs)模拟法和分解袋法,以O₃自然浓度(40 nmol·mol^-1)为对照,研究高浓度O₃(约120 nmol·mol^-1)对城市自然环境下生长的10年生蒙古栎凋落叶分解和养分释放的影响,分解时长达150 d.结果表明：高浓度O₃未对蒙古栎凋落叶的分解产生显著影响.高浓度O₃抑制了蒙古栎凋落叶C、K释放,分解150 d,高浓度O₃处理K残留率为23.9%,显著高于对照(17.1%).高浓度O₃在分解前期(0～60 d)抑制了凋落叶N、木质素的释放,在分解后期(60～150 d)起促进作用.高浓度O₃处理与对照木质素/N变化趋势一致且无显著差异.除分解中期(60 d)外,对照P残留率始终高于高浓度O₃处理.C/P变化趋势与P相反,在整个分解过程中,高浓度O₃处理C/P高于对照,而且C、N、K残留率以及C/N与凋落叶干质量剩余率呈显著正相关.因此,高浓度O₃将对蒙古栎林的营养循环产生一定影响.     

关帝山华北落叶松林凋落物分解过程及其养分动态

采用野外凋落物收集器法和埋置凋落物分解袋法,对关帝山林区华北落叶松林凋落物的数量和组成、年凋落过程、不同埋置层凋落叶分解速率和营养元素动态进行了分析.结果表明:华北落叶松林年凋落物总量为19.15 t · hm-2 · a-1,其中树叶占35.7%,树枝占54.4%,花果占6.7%,树皮和杂物占3.1%.凋落物逐月动态变化为单峰型,10月为年凋落量高峰期,但各成分的凋落进程不同.华北落叶松林凋落物残留量均值为9.803t/hm2,凋落物分解常数为1.95;凋落叶在不同埋置层的分解失重率有明显差异,凋落叶的周年平均失重率29.82%,分解半衰期1.5～2a,分解95%需7～9a;凋落叶分解过程中,氮磷钾元素含量表现出不同的动态过程,其中氮素的年动态变化总体上属于富集过程,到后期开始出现下降,磷素的年动态变化表现为7月份前下降,之后出现快速富集,到生长季末期富集过程变缓,钾素的年动态变化表现为持续下降过程,不出现富集过程.     

小兴安岭不同林龄天然次生白桦林凋落物分解及养分变化

在2009年5月到2010年10月。以小兴安岭地区3种林龄的天然白桦次生林（20a,36a,82a)为研究对象,采用网袋分解法研究不同林龄的白桦林凋落物分解过程中的残留量和养分动态变化。结果表明：不同林龄白桦林在分解过程分为两个阶段：快速分解阶段(0~150 d)和缓慢分解阶段(150~540 d)。凋落物残留量随时间呈指数变化趋势。年分解常数k值在0.584～0.657,凋落物分解50%和95%所用的时间分别为1.06～1.19 a和4.56～5.13 a。3种林龄白桦天然次生林分解速率从大到小依次为82 a>36 a>20 a。在凋落物分解过程中,C和K元素浓度不断释放,而N和P元素浓度先上升后下降,最终N元素为富集,P元素为释放模式。     

草地利用方式对土壤呼吸和凋落物分解的影响

草地利用方式影响植被群落结构和土壤微环境, 制约草地生态系统碳循环。该文通过测定温带草原在放牧、割草、围封3种利用方式下湿润年(2012年)和干旱年(2011年)的凋落物产量、质量及其分解速率和土壤碳通量, 分析了草地利用方式对土壤呼吸和凋落物的影响, 探讨了凋落物对土壤呼吸的贡献机制。结果表明: 在干旱年份, 放牧样地土壤呼吸最大, 分别达到割草和围封样地的1.5倍和1.29倍; 在湿润年份, 割草样地土壤呼吸最大, 为309 g C∙m^-2∙a^-1, 明显高于放牧样地和围封样地。不论干旱年还是湿润年, 围封样地凋落物产量都大于放牧样地和割草样地。3种利用方式下湿润年土壤呼吸和凋落物分解均比干旱年增强。因此, 水分是温带草原植物生长和生态系统碳循环的主要限制因子, 草地利用方式则显著影响凋落物生产和分解。进一步分析表明, 经过两年的分解, 同一样地内凋落物质量C:N下降, N含量和木质素:N升高, 土壤呼吸与凋落物产量、凋落物分解速率以及木质素:N正相关, 而与凋落物C:N负相关。     

Extracellular Enzyme Activities and Carbon Chemistry as Drivers of Tropical Plant Litter Decomposition

Litter quality parameters such as nitrogen and lignin content correlate with decomposition rates at coarse scales, but fine‐scale mechanisms driving litter decomposition have proven more difficult to generalize. One potentially important driver of decomposition is the activity of extracellular enzymes that catalyze the degradation of complex compounds present in litter. To address the importance of this mechanism, we collected 15 Hawaiian plant litter types and decomposed them in fertilized and control plots for up to two years. We measured litter nutrient content and carbon chemistry prior to decomposition, as well as extracellular enzyme activities, mass loss, and litter nutrient content over time. We found that water‐soluble carbon content, cellobiohydrolase activities, and polyphenol oxidase activities were significantly correlated with mass loss. Enzyme activities and decomposition rate constants both varied significantly by litter type, and fertilization increased mass loss rates in five litter types. Some litter types that decayed faster under fertilization also showed time‐dependent increases in carbon‐degrading enzyme activities, but others decayed faster independent of enzyme changes. These results suggest that extracellular enzyme activities partially determine litter decomposition rates, but high soluble carbon content may circumvent the requirement for enzyme‐catalyzed decomposition.     

Comparison of Leaf Litter Decomposition Rates in Restored and Mature Riparian Forests on the Sacramento River, California

One of the largest riparian restoration projects in the United States is currently taking place in California on the Sacramento River. Nearly 2,000 ha of land adjacent to the river channel have been revegetated with native riparian species in an effort to reestablish riparian forests. The objective of this study was to compare leaf litter decomposition rates in restored riparian forests to those in mature, naturally established riparian forests, in order to monitor the development of this ecosystem function in restored forests. Leaf litter decomposition rates were measured over 1 year in six restored riparian forests (4, 7, and 9 years old) and two mature remnant riparian forests (>50 years old), in order to test two hypotheses: (1) decomposition rates of restored and mature forests are significantly different and (2) decomposition rates in the chronosequence of restored forests are moving along a trajectory, approaching the decomposition rates characteristic of mature forests as they age. Statistical analyses revealed no significant differences in annual decay rates among the four different forest ages and no trajectory among leaf litter decomposition rates in restored forests. These results suggest that a functionally equivalent process of leaf litter decomposition occurs in both restored and naturally established forests and show promise for the efficiency of nutrient cycling processes in these restored forests.     

马尾松与乡土阔叶树种凋落叶混合分解过程中全碳释放的动态变化

为了调整低山丘陵区低效林林分结构,探明马尾松（Pinus massoniana Lamb.）与乡土阔叶树种凋落叶混合分解过程中的全碳（C）释放规律。本研究以华南广泛分布的马尾松、檫木（Sassafras tzumu（Hemsl.） Hemsl）、香樟（Cinnamomum camphora（Linn） Presl）以及香椿（Toona sinensis（A. Juss.） Roem.）凋落叶为研究对象,将这4个树种凋落叶按照不同树种搭配以及混合比例组合为35个处理后进行野外分解实验,探讨C释放最佳的凋落叶树种组合以及混合比例。研究发现：4个单一树种凋落叶之间,香椿凋落叶的C释放最快,檫木和香樟凋落叶次之,马尾松凋落叶最慢。31个混合凋落叶中,C释放的非加和效应随着分解时间的延长表现出先升增强后减弱的趋势,且相对于其他季节,凋落叶在秋季的非加和效应有所减弱。一针一阔树种组合中,香樟凋落叶占比≥30%的处理：PC73和PC64的协同效应较强;一针两阔和一针三阔组合中,阔叶占比≥30%且含有香椿凋落叶的处理：PST613和712、PCT631和613、PSCT7111和6121的协同效应较强。     

Chemical Composition and Decomposition of Silver Birch Leaf Litter Produced under Elevated CO2 and O3

Two field-growing silver birch (Betula pendula Roth) clones (clone 4 and 80) were exposed to elevated CO₂ and O₃ over three growing seasons (1999–2001). In each year, the nutrients and cell wall chemistry of naturally abscised leaf litter were analyzed in order to determine the possible CO₂- and O₃-induced changes in the litter quality. Also CO₂ and O₃ effects on the early leaf litter decomposition dynamics (i.e. decomposition before the lignin decay has started) were studied with litter-bag experiments (Incubation 1 with 1999 leaf litter, Incubation 2 with 2000 leaf litter, and Incubation 3 with 2001 leaf litter) in a nearby silver birch forest. Elevated CO₂ decreased N, S, C:P and α-cellulose concentrations, but increased P, hemicellulose and lignin+polyphenolic concentrations, C:N and lignin+polyphenolic:N in both clones. CO₂ enrichment decreased the subsequent decomposition of leaves of clone 4 transiently (in Incubations 1 and 2), whereas elevated CO₂ effects on the subsequent leaf decomposition of clone 80 were inconsistent. In contrast to CO₂, O₃ decreased P concentrations and increased C:P, but both of these trends were visible in elevated O₃ treatment only. O₃-induced decreases in Mn, Zn and B concentrations were observed also, but O₃ effects on the cell wall chemistry of leaf litter were minor. Some O₃-induced changes either became more consistent in leaf litter collected during 2001 (decrease in B concentrations) or appeared only in this litter lot (decrease in N concentrations, decrease in decomposition at the end of Incubation 3). In conclusion, in northern birch forests elevated CO₂ and O₃ levels have the potential to affect leaf litter quality, but consistent CO₂ and O₃ effects on the decomposition process remain to be validated.     

Leaf Litter Decomposition and Substrate Chemistry of Early Successional Species on Landslides in Puerto Rico1

Decomposition is a critical process for nutrient release and accumulation of soil organic matter in disturbed soils, such as those found on landslides. I conducted a decomposition experiment on five landslides in the Luquillo Mountains of Puerto Rico as part of an investigation of the successional roles of two of the most common plant colonists to landslides, Cecropia schreberiana Miq. (Cecropiaceae) a pioneer tree species, and Cyathea arborea (L.) Sm. (Cyatheaceae) a pioneer tree fern. I compared leaf litter decomposition over one year and the initial and 1‐yr chemistry for both species. Initial litter chemistry differed between the two species, as Cecropia had slightly higher nitrogen (9.2 mg/g) than Cyathea (8.2 mg/g) and higher lignin (28.6%) than Cyathea (26.0%), but water‐soluble carbon and nonpolar extractable carbon (fats and oils, waxes, chlorophylls) were higher in Cyathea than Cecropia. Total carbon, acid‐soluble carbon, total phosphorus, and pH did not differ significantly between leaf litter species. Across all five landslides, Cyathea (k= 0.93 ± 0.06) leaves decomposed significantly faster than Cecropia (k= 0.68 ± 0.06). The differences in these species leaf litter decomposition rates and chemical composition could potentially influence organic matter dynamics and nutrient cycling rates in these early successional systems.     

川西高山林线交错带凋落叶分解初期转化酶特征

胞外酶对于有机质的降解具有重要的作用。在凋落物分解过程中,酶活性不仅受到凋落物种类或基质质量的影响,还受到环境因素的影响。转化酶催化蔗糖水解为葡萄糖和果糖,因此在凋落物分解早期,转化酶比降解难分解物质的酶具有更重要的作用。以川西高山林线交错带12种代表性凋落叶为研究对象,对林线交错带不同植被类型下的凋落叶转化酶活性以及物种和环境因子对转化酶活性的影响进行了研究。结果表明:同一植被类型下,12个物种转化酶活性具有极显著差异(P0.01)。物种、环境因子及其交互作用对转化酶活性有极显著的影响(P0.01)。初始纤维素含量与转化酶活性极显著正相关(P0.01)。初始木质素和总酚含量与转化酶活性极显著负相关(P0.01),能够共同解释转化酶活性变异的50.8%。不同植物生活型中,禾草类转化酶活性均为最高,这可能与禾草类较高的初始纤维素含量、较低的木质素和总酚含量有关。多元线性回归分析表明,凋落叶含水量能单独解释转化酶活性变量的62.1%,是环境因子中最重要的变量。从植被类型来看,大多数物种的转化酶活性在针叶林中均极显著高于高山草甸和灌丛(P0.01),这可能与针叶林中凋落叶的含水量最高且雪被最厚有关。历经一个雪被期分解后,凋落叶初始质量与环境因子的综合作用能够解释转化酶活性变异的79.1%,表明川西高山林线交错带凋落叶分解前期转化酶活性主要受初始木质素含量、总酚含量和含水量的调控。在全球气候变化情景下,凋落物水分含量的变化将会强烈的影响凋落叶分解前期的转化酶活性。     

Effects of the Tropical Freshwater Shrimp Caridina weberi (Atyidae) on Leaf Litter Decomposition1

Effects of feeding by atyid shrimp, Caridina weberi, on the rate of decomposition of leaf litter were studied in the Opunohu River, Moorea, French Polynesia. In a laboratory feeding experiment shrimp consumed microbially conditioned Hibiscus leaves, but in a field study shrimp did not affect the rate of decomposition of leaf litter. In this system, the rate of decomposition was influenced more by water discharge or by microbial activity than by shrimp.     

The Effect of Phosphorus Availability on Decomposition Dynamics in a Seasonal Lowland Amazonian Forest

Once the weathering of parent material ceases to supply significant inputs of phosphorus (P), vegetation depends largely on the decomposition of litter and soil organic matter and the associated mineralization of organic P forms to provide an adequate supply of this essential nutrient. At the same time, the decomposition of litter is often characterized by the immobilization of nutrients, suggesting that nutrient availability is a limiting factor for this process. Immobilization temporally decouples nutrient mineralization from decomposition and may play an important role in nutrient retention in low-nutrient ecosystems. In this study, we used a common substrate to study the effects of native soil P availability as well as artificially elevated P availability on litter decomposition rates in a lowland Amazonian rain forest on highly weathered soils. Although both available and total soil P pools varied almost three fold across treatments, there was no significant difference in decomposition rates among treatments. Decomposition was rapid in all treatments, with approximately 50% of the mass lost over the 11-month study period. Carbon (C) and nitrogen (N) remaining and C:N ratios were the most effective predictors of amount of mass remaining at each time point in all treatments. Fertilized treatments showed significant amounts of P immobilization (P < 0.001). By the final collection point, the remaining litter contained a quantity equivalent to two-thirds of the initial P and N, even though only half of the original mass remained. In these soils, immobilization of nutrients in the microbial biomass, late in the decomposition process, effectively prevents the loss of essential nutrients through leaching or occlusion in the mineral soil.     

辽东栎叶片凋落物在不同气候带下的分解及其主要元素释放的比较

辽东栎叶片凋落物在不同气候带下的分解及其主要元素释放的比较 王立新 王 瑾 黄建辉