小兴安岭典型阔叶红松林不同演替阶段凋落物分解及养分变化

2006年10月—2008年11月,以小兴安岭地区典型阔叶红松林不同演替阶段[白桦次生林、择伐后的阔叶红松林(简称择伐林)、原始阔叶红松林]的混合凋落叶以及阔叶红松林优势树种(枫桦、紫椴和红松)的凋落叶为对象,采用网袋分解法分析阔叶红松林演替阶段中凋落叶的残留率和养分元素的动态变化.结果表明:各种凋落叶的残留率与时间均呈指数关系,凋落叶年分解系数(k)在0.137～0.328,其分解50%和95%的时间分别在2.340～4.989 a和9.360～21.796 a;不同演替阶段凋落叶的k值差异不显著,其中混合凋落叶k值的大小顺序为阔叶红松林择伐林白桦林,而其他凋落叶没有表现出明显的规律;在凋落叶分解过程中,C、P和K不断释放,且形式有所差异,其中C为线性衰减模式,P和K为一元多次方程模式;N虽有不同程度的积累,但无明显规律性.     

高山森林林窗对凋落叶分解的影响

林窗对降水和光照等环境条件的再分配以及分解者群落的影响可能深刻作用于森林凋落物分解过程,但有关高山森林林窗大小对凋落物分解的影响尚无研究报道。采用凋落物分解袋法,研究了川西高山森林不同大小林窗对非生长季节和生长季节红桦(Betula albo-sinensis)和岷江冷杉(Abies faxoniana)凋落叶质量损失的影响。结果显示,经过1a的分解,不同生境下红桦和岷江冷杉凋落叶分别分解了27.25%—30.12%和27.04%—27.96%,其中非生长季节占53.83%—60.18%和50.23%—59.09%。林窗对红桦和岷江冷杉凋落叶质量损失的影响因物种不同而呈现季节差异。总体上,林窗加快了岷江冷杉凋落叶的分解而延缓了红桦凋落叶的分解。与郁闭林下相比,林窗显著增加了2种凋落叶非生长季节的质量损失速率,显著降低了生长季节2种凋落叶的质量损失速率;2种凋落叶质量损失速率在非生长季节随林窗面积增大而加快,在生长季节随林窗面积增大而减慢。林窗显著影响了初冻期、深冻期和融化期岷江冷杉凋落叶的质量损失率,但对红桦凋落叶质量损失率影响不显著。可见,高山森林凋落物分解过程受到林窗的显著影响,并且阔叶和针叶凋落叶在非生长季节和生长季节对林窗的响应具有明显差异。     

原始阔叶红松林下红松、蒙古栎混合凋落叶分解特征及相互作用研究

采用凋落物网袋（litter bag）分解法,模拟红松（Pinus koraiensis）(以下用P表示)和蒙古栎（Quercus mongolica）（以下用M表示）在不同演替阶段可能的组成比例(P、M/P1∶3、M/P1∶1、M/P3∶1、M）进行野外分解实验。分析不同比例的两种凋落叶混合的分解特征、相互作用及机理。结果表明：1.从质量损失率来看,与单种凋落叶分解情况相比,蒙古栎和红松凋落叶混合对凋落物分解具有促进作用,其中蒙古栎和红松（M/P）按1∶3混合分解最快,且随着蒙古栎凋落叶在混合比例中的增加,混合分解速率先减小后增大。2.从C、N元素动态看,C素在各处理的凋落叶主要表现为净释放,而N素在各处理中变现比较复杂,在各处理的红松凋落叶中表现为富集,而在各处理蒙古栎凋落叶中则表现为释放。蒙古栎凋落叶可以促进红松凋落叶C元素释放和N元素的富集,降低红松凋落叶的C/N比,促进红松凋落叶的分解。红松凋落叶能促进蒙古栎凋落物C元素释放,但对蒙古栎凋落叶N元素的释放作用不明显,对蒙古栎凋落叶的C/N比影响也并不一致。     

长白山阔叶红松林凋落物组成及其季节动态

为了解群落尺度上凋落物组成及其时空变化,对长白山阔叶红松林25 hm² 样地内2008年度收集的凋落物进行统计分析.结果表明: 一年间,150个收集器内收集的凋落叶分属35种树木,占样地内胸径≥1 cm树种数(52种)的67.3%;凋落物总量为29.39 kg,折合3918.4 kg·hm^-2,其中,阔叶、杂物、针叶和枝条凋落量分别占凋落物总量的61.7%、18.0%、11.7%和 8.6%;紫椴、水曲柳、蒙古栎、色木槭和春榆5个树种的叶凋落量占阔叶总凋落量的83.8%;不同树种的凋落量季节差异很大,61.9%的凋落物产生于9月13日至10月10日.其中,红松和紫椴叶凋落高峰出现在9月13-26日,蒙古栎、春榆和色木槭叶凋落高峰出现在9月27日-10月10日.收集器间凋落物量差异较大,其中68个收集器的年凋落量在150～200 g,1个收集器大于500 g;单个收集器全年最多可收集到18个树种的凋落叶,凋落叶种数为12种的收集器最多(32个).叶凋落量与样地内该树种的胸高断面积总和成正比.样地内凋落叶的分布存在明显的空间异质性,且收集器内凋落物的收集量与其所处的位置有关.     

温带红松阔叶混交林凋落叶与主要大型土壤动物热值的季节变化

对温带红松阔叶混交林不同种类凋落叶、混合凋落叶和主要大型土壤动物的干质量热值及季节变化规律进行了研究.结果表明：不同种类凋落叶和3种大型土壤动物的干质量热值不同,且其季节变化规律存在一定的差异.红松凋落叶的干质量热值平均值最高(19.71 kJ·g^-1),枫桦(18.22 kJ·g^-1)、紫椴(18.13 kJ·g^-1)、混合凋落叶(17.91 kJ·g^-1)居中,水曲柳(16.94 kJ·g^-1)和色木槭(16.25 kJ·g^-1)最低.红松和色木槭凋落叶干质量热值随凋落叶分解进行呈逐渐降低趋势,水曲柳凋落叶干质量热值季节变化较小,而紫椴、枫桦和混合凋落叶干质量热值次年有上升的趋势.大型土壤动物中,蜈蚣(22.07 kJ·g^-1)的干质量热值最高,蚯蚓(16.72 kJ·g^-1) 次之,马陆(13.28 kJ·g^-1)最低.蚯蚓和马陆干质量热值的季节变化规律一致,蜈蚣干质量热值的季节变化规律则有所不同.凋落叶和3种大型土壤动物干质量热值的季节变化之间没有明显的相关性.     

鼎湖山季风常绿阔叶林凋落叶分解与土壤动物群落动态和多样性

2001年12月~2002年12月,采用不同孔径分解凋落叶样袋法,对鼎湖山季风常绿阔叶林3类凋落叶的分解进行了研究,并对落叶分解过程中凋落叶袋内和袋下土样中的土壤动物群落和多样性进行了调查。结果表明,3种孔径袋内凋落叶的分解速率为大孔>中孔>微孔;混合凋落叶的分解速率大于单种凋落叶;蜱螨目在凋落叶分解的整个过程中相对数量都较高,弹尾目在凋落叶的分解过程中在凋落叶袋和土壤间移动,数量变化较大。凋落叶袋内大、中型土壤动物的个体数量在分解前期较多,中、小型土壤动物在分解的中期数量剧增;凋落叶袋内土壤动物的个体数量、密度以及多样性指数都随着落叶的分解而增加,9月最高;土壤样内则在分解的前期较高,以后逐渐降低。凋落叶的分解和土壤动物群落动态及多样性受凋落叶基质质量以及样地温度、降雨量等综合因素的影响。     

长白山北坡主要森林群落凋落物现存量月动态

以长白山北坡4种主要森林群落类型为研究对象,于2006年群落生长季节(5-10月)每月初采用直接收获法对森林凋落物现存量进行连续定位调查研究。结果表明:各群落内凋落物现存量大小依次为阔叶红松林(6.43 t/hm²)>白桦林(6.02 t/hm²)>云冷杉林(5.51 t/hm²)>山杨林(5.50 t/hm²);凋落叶和枝现存量占现存凋落物总量的比例最大,达50%以上,其次为半分解物(>35%),花果皮等所占比例较少,各占总量的10%和5%以下。凋落物现存量月动态阔叶红松林、白桦林和山杨林呈双峰型变化,峰值出现在5月和7月;云冷杉林则呈单峰型变化,峰值仅出现在7月。位于相近海拔高度的阔叶红松林、白桦林和山杨林,凋落物各组分现存量月动态变化趋势相似,其中白桦林和山杨林变化趋势基本相同,凋落枝、皮及半分解物现存量5月和7月较高,凋落叶则呈现下降趋势,而阔叶红松林凋落叶和枝现存量5月和7月较高,而位于较高海拔的云冷杉林,则与前者呈现不同变化趋势,8月前波动较大,从5月开始明显上升,7月达到峰值,8月后曲线渐趋平缓或略有下降。进一步对阔叶红松林和云冷杉林内凋落叶现存量月动态进行比较得出,阔叶红松林7月份凋落叶现存量高不完全取决于红松叶现存量,主要由色木槭、紫椴和水曲柳等阔叶树种叶凋落物现存量变化决定,而云冷杉林则取决于红松和云冷落叶的凋落物的量。     

长白山四种森林类型凋落物分解动态

2003年5月—2004年9月在长白山自然保护区北坡4个森林类型阔叶红松林、红松云冷杉林、岳桦云冷杉林和岳桦林内,利用凋落物原位减少法对4种森林类型的凋落物分解动态进行了研究。结果表明,凋落物现存量最大的为红松云冷杉林,依次为阔叶红松林、岳桦云冷杉林、岳桦林;凋落物分解速率与时间均呈指数关系,凋落物年分解常数为0.25～0.47,分解95%所需时间为18～39年,其中阔叶红松林凋落物年分解常数最大,依次为岳桦林、红松云冷杉林、岳桦云冷杉林。同一类型森林中,不同植物组分的年分解系数不同,一般是阔叶最大,针叶最小。     

蚯蚓对不同阔叶落叶的摄食作用

采取室内试验,研究蚯蚓对红松阔叶混交林中几种不同阔叶的摄食量及影响因素、蚯蚓在不同阔叶中的生长状况和对有机碳和全氮的影响,探讨蚯蚓在东北红松阔叶混交林阔叶分解中的作用。蚯蚓喜食枫桦、紫椴和色木槭分解落叶,不喜食水曲柳分解落叶。试验表明,温度、凋落叶种类和凋落叶的分解时间等因素影响蚯蚓摄食量的大小。蚯蚓对3种喜食分解落叶摄食量平均值为:枫桦>色木槭>紫椴。不同温度条件下蚯蚓摄食量平均值为:20℃>25℃>15℃。凋落叶分解时间越长,蚯蚓越喜食,其摄食量也越大。分解落叶的C/N比新鲜凋落叶低。蚯蚓在3种凋落叶中的日增重倍数和日排粪量随着温度的升高而增加。不同温度下蚯蚓日增重倍数的平均值为25℃>20℃>15℃。蚯蚓在紫椴凋落叶中日增重倍数高于枫桦和色木槭分解落叶,在色木槭分解落叶的摄食过程中日排粪平均值高于紫椴和枫桦凋落叶。微生物对落叶中有机碳分解40d的作用小于蚯蚓对落叶摄食20d。蚯蚓摄食20d对增加凋落叶中的全氮含量的作用大于微生物单独分解40d。在凉水国家级自然保护区,蚯蚓对阔叶凋落叶的分解占年平均凋落叶量的10.3%左右。蚯蚓在红松阔叶混交林中阔叶分解中的作用不可忽视。     

控雪处理下红松和蒙古栎凋落叶分解动态

气候变化导致的冬季雪被格局变化将改变地表水热环境及分解者活性, 从而显著影响高寒地区森林凋落物分解过程。2014-2016年采用凋落物分解袋法, 研究了帽儿山森林生态站人工林控雪模拟试验下红松(Pinus koraiensis)和蒙古栎(Quercus mongolica)的凋落叶于雪被期和无雪期不同阶段的分解动态。控雪试验包括增雪、除雪和对照3个处理。结果发现: 树种、控雪处理、分解阶段以及环境因子(凋落物层平均温度、冻融循环次数、有机层全氮、全磷含量等)均影响着凋落叶分解率。分解试验的两年内, 不同控雪处理下红松凋落叶的分解率为52.1%-54.5%, 蒙古栎为53.9%-59.1%。两种凋落叶的分解系数均以增雪处理最大, 除雪处理最小。此外, 控雪处理改变了两种凋落叶雪被期或无雪期对分解总量的贡献率。与对照相比, 增雪处理使红松和蒙古栎凋落叶雪被期的分解贡献率分别提高9.1%和10.4%; 而除雪处理使两种凋落叶无雪期的分解贡献率分别提高10.4%和12.7%。因此, 由气候变化带来的冬季雪被改变不但会显著影响温带森林凋落叶的分解过程, 而且会改变雪被期和无雪期的分解量对年分解总量的贡献率。     

Early stage of single and mixed leaf-litter decomposition in semiarid forest pine-oak: the role of rainfall and microsite

It is well known that inherent characteristics of forest species constitute the main control of litter decomposition. In mixed forest, chemical interactions occurring through precipitation turn mechanisms of litter decomposition very uncertain and difficult to predict. Early-stage leaf litter decomposition of Quercus potosina and Pinus cembroides and their controls were examined based on Ostrofsky’s decomposition mechanisms. From June 2007 to May 2008, litterbags with pure and mixed leaf-litter of Q. potosina and P. cembroides were incubated in situ in monospecific and mixed tree stands, respectively. Sampling was carried out 3, 6, 9, and 12?months after incubation. After 12?months, two phases of decomposition of pure and mixed litter were identified; an early phase with a greater rate of mass loss of the labile litter fraction (k _L ; soluble compounds) and a later phase with a lower rate of mass loss of the recalcitrant litter fraction (k _R; lignin). The labile fraction lost was observed at three and 6?months of incubation, which coincided with the months of highest rainfall likely triggering a rapid release of soluble carbon compounds from leaf litter. Results also indicate that leaf-litter from Q. potosina had higher concentration of soluble compounds and lower lignin concentration than leaf litter from P. cembroides. Observed facilitative and inhibitory mechanisms for mass loss in Q. potosina and P. cembroides were controlled by interaction between physico-chemical litter characteristics and rainfall.     

Leaf litter decomposition of 12 tree species in a subtropical forest in Japan

The leaf litter decomposition of 12 tree species was examined for three years in a subtropical forest in Japan to follow the pattern of changes in organic chemical constituents and nitrogen (N) and the relationship between these components. The remaining mass of the leaf litter reached 7–53% of the original mass at the end of the field incubation, and the decomposition constants (k) ranged from 0.37 to 2.39 year^?1. The decomposition constant was significantly negatively correlated with the initial content of acid-unhydrolyzable residue (AUR) for all 12 tree species. A net increase of AUR that lasted for the first 3 to 6 months was noted for leaf litter of four tree species. The absolute amount of total N increased initially and then decreased thereafter in leaf litter of five tree species, whereas total N mass decreased throughout the study period in leaf litter of the other species. Contents of AUR and total N in leaf litter generally increased linearly with the accumulated mass loss of litter during decomposition, resulting in positive slopes of linear regressions. Lignocellulose index and AUR to N ratio of the litter showed convergent trends for 12 tree species as the decomposition progressed. When compared with datasets for an Asian climatic gradient, the decomposition rates in the subtropical forest was intermediate between the rates in tropical and temperate forests, and AUR and N contents in decomposing litter were consistently lower than those in temperate forests, indicating faster loss of AUR and N.     

Mixed leaf litter effects on decomposition rates and soil microarthropod communities in an oak–pine stand in Japan

Rates of decomposition, and soil faunal abundance and diversity associated with single-species and mixed-species litters were studied in a litter bag experiment in an oak–pine forest. We used two canopy species of leaf litter, pine and oak, and one shrub species, Sasa, and compared decomposition rates, and soil microarthropod abundance and community structure of oribatid mites in the litter bags. Mass loss of single species decreased in the order: oak > pine > Sasa. While the total mass loss rates of mixed litter were intermediate between those of the constituent species, enhancement of mass loss from the three-species mixture and from mixed slow-decomposing litters (pine and Sasa) was observed. Faunal abundance in litter bags was higher in mixed-species litter than in those with single-species litter, and species richness of oribatid mites was also higher in the three-species mixed litter. Faunal abundance in single-species litter bags was not correlated with mass loss, although enhancement of mass loss in mixed litter bags corresponded with higher microarthropod abundance. Habitat heterogeneity in mixed litter bags seemed to be responsible for the more abundant soil microarthropod community.     

Mixing Effects of Understory Plant Litter on Decomposition and Nutrient Release of Tree Litter in Two Plantations in Northeast China

Understory vegetation plays a crucial role in carbon and nutrient cycling in forest ecosystems; however, it is not clear how understory species affect tree litter decomposition and nutrient dynamics. In this study, we examined the impacts of understory litter on the decomposition and nutrient release of tree litter both in a pine (Pinus sylvestris var. mongolica) and a poplar (Populus × xiaozhuanica) plantation in Northeast China. Leaf litter of tree species, and senesced aboveground materials from two dominant understory species, Artemisia scoparia and Setaria viridis in the pine stand and Elymus villifer and A. sieversiana in the poplar stand, were collected. Mass loss and N and P fluxes of single-species litter and three-species mixtures in each of the two forests were quantified. Data from single-species litterbags were used to generate predicted mass loss and N and P fluxes for the mixed-species litterbags. In the mixture from the pine stand, the observed mass loss and N release did not differ from the predicted value, whereas the observed P release was greater than the predicted value. However, the presence of understory litter decelerated the mass loss and did not affect N and P releases from the pine litter. In the poplar stand, litter mixture presented a positive non-additive effect on litter mass loss and P release, but an addition effect on N release. The presence of understory species accelerated only N release of poplar litter. Moreover, the responses of mass loss and N and P releases of understory litter in the mixtures varied with species in both pine and poplar plantations. Our results suggest that the effects of understory species on tree litter decomposition vary with tree species, and also highlight the importance of understory species in litter decomposition and nutrient cycles in forest ecosystems.     

Litter decomposition rate is dependent on litter Mn concentrations

A statistically significant linear relationship was found between annual mass loss of foliar litter in the late stages of decomposition and Mn concentration in the litter. We used existing decomposition data on needle and leaf decomposition of Scots pine (Pinus sylvestris L.), lodgepole pine (Pinus contorta var. contorta), Norway spruce (Picea abies (L.) Karst.), silver birch (Betula pendula L.), and grey alder (Alnus incana L.) from Sweden and Aleppo pine (Pinus halepensis Mill.) from Libya, to represent boreal, temperate, and Mediterranean climates. The later the decomposition stage as indicated by higher sulfuric-acid lignin concentrations, the better were the linear relationships between litter mass loss and Mn concentrations. We conclude that Mn concentrations in litter have an influence on litter mass-loss rates in very late decomposition stages (up to 5 years), provided that the litter has high enough Mn concentration. The relationship may be dependent on species as the relationship is stronger with species that take up high enough amounts of Mn.     

Non‐symbiotic nitrogen fixation during leaf litter decomposition in an old‐growth temperate rain forest of Chiloé Island,southern Chile: Effects of single versus mixed species litter

Heterotrophic nitrogen fixation is a key ecosystem process in unpolluted, temperate old‐growth forests of southern South America as a source of new nitrogen to ecosystems. Decomposing leaf litter is an energy‐rich substrate that favours the occurrence of this energy demanding process. Following the niche ‘complementarity hypothesis’, we expected that decomposing leaf litter of a single tree species would support lower rates of non‐symbiotic N fixation than mixed species litter taken from the forest floor. To test this hypothesis we measured acetylene reduction activity in the decomposing monospecific litter of three evergreen tree species (litter C/N ratios, 50–79) in an old‐growth rain forest of Chiloé Island, southern Chile. Results showed a significant effect of species and month (anova , Tukey's test, P < 0.05) on decomposition and acetylene reduction rates (ARR), and a species effect on C/N ratios and initial % N of decomposing leaf litter. The lowest litter quality was that of Nothofagus nitida (C/N ratio = 78.7, lignin % = 59.27 ± 4.09), which resulted in higher rates of acetylene reduction activity (mean = 34.09 ± SE = 10.34 nmol h^?1 g^?1) and a higher decomposition rate (k = 0.47) than Podocarpus nubigena (C/N = 54.4, lignin % = 40.31 ± 6.86, Mean ARR = 4.11 ± 0.71 nmol h^?1 g^?1, k = 0.29), and Drimys winteri (C/N = 50.6, lignin % = 45.49 ± 6.28, ARR = 10.2 ± 4.01 nmol h^?1 g^?1, k = 0.29), and mixed species litter (C/N = 60.7, ARR = 8.89 ± 2.13 nmol h^?1g^?1). We interpret these results as follows: in N‐poor litter and high lignin content of leaves (e.g. N. nitida) free‐living N fixers would be at competitive advantage over non‐fixers, thereby becoming more active. Lower ARR in mixed litter can be a consequence of a lower litter C/N ratio compared with single species litter. We also found a strong coupling between in situ acetylene reduction and net N mineralization in surface soils, suggesting that as soon N is fixed by diazotroph bacteria it may be immediately incorporated into mineral soil by N mineralizers, thus reducing N immobilization.     

三峡库区森林凋落叶化学计量学性状变化及与分解速率的关系

凋落物分解是森林生态系统生物元素循环和能量流动的重要环节,其过程是植物与土壤获得养分的主要途径。为了量化凋落叶化学计量学性状变化过程对分解的影响及对凋落物-土壤生物化学连续体的深层理解,用凋落物分解袋法研究了不同林型各自凋落叶化学计量学性状变化及与分解速率关系,结果表明:林下各自凋落叶分解速率是马尾松林栓皮栎林马尾松-栓皮栎混交林,马尾松林、栓皮栎林、马尾松-栓皮栎混交林凋落叶分解50%和95%的时间分别是2.11 a和9.15 a,1.93 a和8.45 a,1.76 a和7.77 a;凋落叶分解过程中,化学计量学性状变化明显,分解450 d后马尾松-栓皮栎混交林碳释放最快,栓皮栎林最慢;3种凋落叶起始N含量是栓皮栎林最高,马尾松林最低,分解450 d后马尾松林、栓皮栎林和马尾松-栓皮栎混交林N含量分别增加了66.67%、44.91%和44.52%,而P含量分别释放了30.80%、38.89%和42.29%。凋落物不同化学计量学性状与分解速率关系不同,3种林型凋落叶分解速率均与N含量呈正相关(P0.01),与C含量(P0.01)、C/N比(P0.01)呈负相关,与N/P比呈负二次函数关系(P0.01),而P含量与3种林型关系不同,与栓皮栎林(P0.01)和马尾松林(P0.05)呈负线性关系,与马尾松-栓皮栎混交林呈负二次函数关系(P0.05)。研究表明,不同林型凋落叶分解中的养分动态趋向利于分解变化,N、P养分动态是生态系统碳平衡和凋落物分解速率的主要因素,混交林中混合凋落物的养分迁移是分解相对较快的原因。     

Intraspecific variability in leaf traits strongly affects alder leaf decomposition in a stream

This study assessed the intraspecific variability of senescent leaves of alder (Alnus glutinosa Gaertn.) and the effects of this variability on leaf decomposition in streams. Leaves were collected at five geographically distant locations in Europe. We analyzed 10 batches of leaf samples for seven quantitative leaf traits as well as leaf decomposition rate in coarse and fine mesh bags exposed in a single stream. The geographic origin of leaf samples largely explained the observed variation in litter quality and decomposition rate. Phosphorus (0.034–0.187%) and lignin (3.9–18.7%) concentrations in leaves varied widely. Together, these two traits accurately predicted leaf decomposition rate (r²=84.1%). Intraspecific variation in leaf decomposition rate was within a range similar to that reported for interspecific variation among co-occurring riparian plant species in Europe. Our study demonstrates extensive intraspecific variability in leaf traits on a continental scale, which can have enormous effects on major ecosystem processes such as leaf decomposition.     

潮虫消耗木本植物凋落物的可选择性试验

近年来,越来越多的学者关注外来植物入侵对土壤生态功能的影响效应及其相应反馈机制的探索与研究,然而本地原生土壤生物群落对不同入侵程度下的外来植物种以及本地原生植物种之间是否存在消耗差异却尚不明了.通过等足目潮虫的选择性喂养试验来测试10个本地种、5个非入侵性外来种和5个强入侵性外来种之间的适口性差异,试图求证外来植物的入侵性是否与植物落叶被消耗率呈现必然联系.数据分析结果显示潮虫对本地种、非入侵性外来种和入侵性外来种的消耗并无显著差异;而潮虫对不同生活型下木本植物的取食却存在显著差异,即灌木消耗率显著高于乔木.其次,通过植物初始性状指标(包括木质素、纤维素、半纤维素、碳、氮含量)与相应消耗率的相关比较,消耗量总体上与植物凋落物的氮含量呈正相关关系(R2 =0.358).由此,研究结论强调植物落叶的降解速率并不一定与植物入侵性或入侵阶段呈绝对相互关连,但是氮含量,抑或各种形式的植物氮元素成分都可能在一定程度上参与并影响着外来植物的入侵进程.     

Species control variation in litter decomposition in a pine forest exposed to elevated CO2

Net primary production and the flux of dry matter and nutrients from vegetation to soils has increased following four years of exposure to elevated CO₂ in a southern pine forest in NC, USA. This has increased the demand for nutrients to support enhanced rates of NPP and altered the conditions for litter decomposition on the forest floor. We quantified the chemistry and decomposition dynamics of leaf litter produced by five of the most abundant tree species in this ecosystem during the third and fourth growing seasons under elevated CO₂. The objectives of this study were to determine (i) if there were systemic or species‐specific changes in leaf litter chemistry associated with a sustained enhancement of plant growth under elevated CO₂; and (ii) whether the process of litter decomposition was altered by increased inputs of energy and nutrients to the forest floor in the plots under elevated CO₂. Leaf litter chemistry, including various C fractions and N concentration, was virtually unchanged by elevated CO₂. With few exceptions, plant litter produced under elevated CO₂ lost mass or N at the same relative rate as that produced under ambient CO₂. The relationship between initial litter chemistry and decomposition was not altered by elevated CO₂. The greater forest floor mass and nutrient content in the plots under elevated CO₂ had no consistent or long‐term effect on litter decomposition. Thus, we found no evidence that plant and microbial processes under elevated CO₂ resulted in systemic changes in mass loss or N dynamics during decomposition. In contrast to the limited effects of elevated CO₂ on litter chemistry and decomposition, there were large differences among species in initial litter chemistry, mass loss and N dynamics during decomposition. If the species composition of this forest community is altered by elevated CO₂, the indirect effect of a change in species composition will exert greater control over the long‐term rate of nutrient cycling than the direct effect of elevated CO₂ on litter chemistry and decomposition dynamics alone.