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.     

Effects of mixing pine and broadleaved tree/shrub litter on decomposition and N dynamics in laboratory microcosms

This study was carried out to compare the ecological function of exotic pine (Pinus radiata—Pr) and native pine (Pinus tabulaeformis—Pt) in terms of litter decomposition and its related N dynamics and to evaluate if the presence of broad-leaved tree species (Cercidiphyllum japonicum—Cj) or shrub species (Ostryopsis davidiana—Od) litter would promote the decomposition of pine needles and N cycling. Mass remaining, N release of the four single-species litters and mixed-species (Pt + Cj; Pr + Cj; Pt + Od; Pr + Od) litters and soil N dynamics were measured at microcosm scale during an 84-day incubation period. The Pt and Pr litter, with poorer substrate quality, indicated slower decomposition rates than did the Cj and Od litter. Due to their high C/N ratios, the N mass of Pt and Pr litter continuously increased during the early stage of decomposition, which showed that Pt and Pr litter immobilized exogenous N by microbes. No significant differences of soil inorganic, dissolved organic and microbial biomass N were found between the Pt and Pr microcosm at each sampling. The results showed that the exotic Pr performed similar ecological function to the native Pt in terms of litter decomposition and N dynamics during the early stage. The presence of Cj or Od litter increased the decomposition rates of pine needle litter and also dramatically increased soil N availability. So it is feasible for plantation managers to consider the use of Cj as an ameliorative species or to retain Od in pine plantations to promote the decomposition of pine litter and increase nutrient circulation. The results also suggested that different species litters induced different soil dissolved organic nitrogen (DON). As a major soluble N pool in soil, DON developed a different changing tendency over time compared with inorganic N, and should be included into soil N dynamic under the condition of our study.     

沈阳城市和城郊油松凋落叶的分解动态

为了检测分解地点和凋落物类型对分解的影响,采用交互分解实验分析了油松凋落叶在城市林分和城郊林分中分解时不同立地条件(城市和城郊)以及不同油松凋落叶类型(城市油松凋落物和城郊油松凋落物)对凋落物的分解速率以及N、P残留率的相对作用。结果表明:不同的立地条件对油松凋落叶分解速率有显著影响(P<0.05):城郊林分中的油松凋落叶比城市林分中分解快,说明外在环境条件对分解的影响显著;在同一林分里,凋落物类型对凋落叶分解速率也有显著影响(P<0.05):城市凋落物分解快于城郊凋落物,说明凋落物内在特性对分解的影响显著。分解地点对于N、P残留率没有显著的影响,然而凋落物类型对N、P残留率有显著影响:城郊凋落物由于具有较高的C/N以及C/P初始值,比城市凋落物更容易富集N、P。     

黄土高原典型草原优势植物凋落物分解及养分释放对氮添加的响应

利用原位分解袋法研究了黄土高原典型草原优势植物长芒草(Stipa bungeana)和阿尔泰狗娃花(Heteropappus altaicus)凋落物的养分释放过程对氮添加的响应,试验周期为1 a。设置6个氮添加水平,分别为N0(0)、N1(1.15 g N m~(-2)a~(-1))、N2(2.3 g N m~(-2)a~(-1))、N3(4.6 g N m~(-2)a~(-1))、N4(9.2 g N m~(-2)a~(-1))和N5(13.8 g N m~(-2)a~(-1)),氮素类型为尿素((NH_2)_2CO)。结果表明:(1)氮添加处理两年显著改变了长芒草和阿尔泰狗娃花凋落物的初始化学性质。随着氮梯度的增加,凋落物的N(氮)含量逐渐增加,木质素含量先增加后下降,C/N(碳氮比)和木质素/N降低,C(碳)、P(磷)和C/P(碳磷比)没有显著的差异。(2)氮处理对长芒草和阿尔泰狗娃花凋落物的分解速率的影响不显著。长芒草和阿尔泰狗娃花凋落物C含量随分解时间整体为降低过程,N和P含量总体上为增加过程,且整个分解过程中N含量各处理间差异显著。(3)氮处理对长芒草和阿尔泰狗娃花凋落物C和P的分解基本无影响,两种元素都呈现释放过程。氮处理对凋落物的N残留率有显著的影响,在N1—N3(1.15—4.6 g/m~2)处理下的长芒草凋落物N残留率高于其他处理,且呈现富集过程;而阿尔泰狗娃花凋落物中的N呈现富集-释放过程。在土壤养分贫瘠的黄土高原典型草原,适量的氮输入可以促进系统的固氮。     

Decomposition and nitrogen release from the foliage litter of fir (Abies sachalinensis) and oak (Quercus crispula) under different forest canopies in Hokkaido, Japan

When two tree species co-occur, decomposition and nitrogen (N) release from the foliage litter depend on two factors: the forest floor conditions under each canopy type and the species composition of the litter. We conducted an experiment using fir and oak to answer several questions regarding decomposition beneath canopies of the two species and the effects of litter species composition on decomposition. We compared the rates of decomposition and N release from three different litters (fir needle, oak leaf, and a mixture of the two) in 1-mm-mesh litterbags on the forest floor under three different canopies (a 40-year-old fir plantation, large oak trees, and mixed fir and oak trees) in Hokkaido, Japan, over a 2-year period. Beneath each of these canopy types, the litter decomposition rate and percentage of N remaining in the litterbags containing a mixture of fir and oak litter were not significantly different from the expected values calculated for litterbags containing litter from a single tree species. Oak leaf litter decomposed significantly faster than fir needle litter beneath each canopy type. The litter decomposition rate was significantly higher beneath the fir canopy than under the oak canopy, and was intermediate under the mixed canopy of fir and oak. No net N release, that is, a decrease in the total N compared to the original amount, was detected from fir litter under each canopy type or from oak leaf litter beneath the oak canopy. N increased over the original amount in the fir litter beneath the oak canopy and the mixed canopy of fir and oak, but N was released from the oak litter under the fir canopy and the mixed canopy of fir and oak. These results suggest that oak leaf litter blown onto fir forest floor enhances nutrient cycling, and this might be a positive effect of a mixed stand of conifer and broad-leaved trees.     

川西高山林线交错带凋落叶分解速率与初始质量的关系

对我国川西高山林线交错带14种代表性植物凋落叶分解速率与初始质量的关系进行研究.结果表明: 高山林线交错带植物凋落叶分解速率（k）为0.16～1.70,乔木和苔藓凋落叶分解较慢,灌木凋落叶次之,草本凋落叶分解最快.凋落叶分解速率与N、木质素、酚类物质、C/N、C/P、木质素/N均具有显著的线性回归关系.通径分析得出,木质素/N和半纤维素含量可以解释k变异的78.4%,其中木质素/N可以解释k变异的69.5%,木质素/N对k的直接通径系数为-0.913.主成分分析表明,第1排序轴k、分解时间（t）的贡献率达99.2%,木质素/N、木质素含量、C/N、C/P与第1排序轴呈显著正相关,其中木质素/N与第1排序轴的相关关系最强(r=0.923).木质素/N是影响川西高山林线交错带植物凋落叶分解速率的关键质量指标,且凋落叶初始木质素/N越高,分解速率越低.     

Litter decomposition of a pine plantation is affected by species evenness and soil nitrogen availability

Background and aims

Litter decomposition is a key process controlling flows of energy and nutrients in ecosystems. Altered biodiversity and nutrient availability may affect litter decomposition. However, little is known about the response of litter decomposition to co-occurring changes in species evenness and soil nutrient availability.

Methods

We used a microcosm experiment to evaluate the simultaneous effects of species evenness (two levels), identity of the dominant species (three species) and soil N availability (control and N addition) on litter decomposition in a Mongolian pine (Pinus sylvestris var. mongolica) plantation in Northeast China. Mongolian pine needles and senesced aboveground materials of two dominant understory species (Setaria viridis and Artemisia scoparia) were used for incubation.

Results

Litter evenness, dominant species identity and N addition significantly affected species interaction and litter decomposition. Higher level of species evenness increased the decomposition rate of litter mixtures and decreased the incidence of antagonistic effects. A. scoparia-dominated litter mixtures decomposed faster than P. sylvestris var. mongolica- and S. viridis-dominated litter mixtures. Notably, N addition increased decomposition rate of both single-species litters and litter mixtures, and meanwhile altered the incidence and direction of non-additive effects during decomposition of litter mixtures. The presence of understory species litters stimulated the decomposition rate of pine litters irrespective of N addition, whereas the presence of pine litters suppressed the mass loss of A. scoparia litters. Moreover, N addition weakened the promoting effects of understory species litters on decomposition of pine litters.

Conclusions

Pine litter retarded the decomposition of understory species litters whereas its own decomposition was accelerated in mixtures. Nitrogen addition and understory species evenness altered species interaction through species-specific responses in litter mixtures and thus affected litter decomposition in Mongolian pine forests, which could produce a potential influence on ecosystem C budget and nutrient cycling.     

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。     

Changes in leaf litter decomposition of primary Korean pine forests after degradation succession into secondary broad‐leaved forests

Forest degradation succession often leads to changes in forest ecosystem functioning. Exactly how the decomposition of leaf litter is affected in a disturbed forest remains unknown. Therefore, in our study, we selected a primary Korean pine forest (PK) and a secondary broad‐leaved forest (SF) affected by clear‐cutting degradation, both in Northeast China. The aim was to explore the response to changes in the leaf litter decomposition converting PK to SF. The mixed litters of PK and SF were decomposed in situ (1 year). The proportion of remaining litter mass, main chemistry, and soil biotic and abiotic factors were assessed during decomposition, and then, we made an in‐depth analysis of the changes in the leaf litter decomposition. According to our results, leaf litter decomposition rate was significantly higher in the PK than that in the SF. Overall, the remaining percent mass of leaf litter''s main chemical quality in SF was higher than in PK, indicating that leaf litter chemical turnover in PK was relatively faster. PK had a significantly higher amount of total phospholipid fatty acids (PLFAs) than SF during decomposition. Based on multivariate regression trees, the forest type influenced the soil habitat factors related to leaf litter decomposition more than decomposition time. Structural equation modeling revealed that litter N was strongly and positively affecting litter decomposition, and the changes in actinomycetes PLFA biomass played a more important role among all the functional groups. Selected soil abiotic factors were indirectly driving litter decomposition through coupling with actinomycetes. This study provides evidence for the complex interactions between leaf litter substrate and soil physical–chemical properties in affecting litter decomposition via soil microorganisms.     

Neighbour identity hardly affects litter-mixture effects on decomposition rates of New Zealand forest species

The mass loss of litter mixtures is often different than expected based on the mass loss of the component species. We investigated if the identity of neighbour species affects these litter-mixing effects. To achieve this, we compared decomposition rates in monoculture and in all possible two-species combinations of eight tree species, widely differing in litter chemistry, set out in two contrasting New Zealand forest types. Litter from the mixed-species litter bags was separated into its component species, which allowed us to quantify the importance of litter-mixing effects and neighbour identity, relative to the effects of species identity, litter chemistry and litter incubation environment. Controlling factors on litter decomposition rate decreased in importance in the order: species identity (litter quality) >> forest type >> neighbour species. Species identity had the strongest influence on decomposition rate. Interspecific differences in initial litter lignin concentration explained a large proportion of the interspecific differences in litter decomposition rate. Litter mass loss was higher and litter-mixture effects were stronger on the younger, more fertile alluvial soils than on the older, less-fertile marine terrace soils. Litter-mixture effects only shifted percentage mass loss within the range of 1.5%. There was no evidence that certain litter mixtures consistently showed interactive effects. Contrary to common theory, adding a relatively fast-decomposing species generally slowed down the decomposition of the slower decomposing species in the mixture. This study shows that: (1) species identity, litter chemistry and forest type are quantitatively the most important drivers of litter decomposition in a New Zealand rain forest; (2) litter-mixture effects—although statistically significant—are far less important and hardly depend on the identity and the chemical characteristics of the neighbour species; (3) additive effects predominate in this ecosystem, so that mass dynamics of the mixtures can be predicted from the monocultures.     

粤北地区溪流中的树叶分解及大型底栖动物功能摄食群

利用2种孔径(5mm的塑料网袋和0.1mm的布袋)的分解网袋对2种树叶在广东北部的横石水河的3级溪流中,进行了为期101d的树叶分解研究.结果表明:人面子树叶在网袋和布袋中的分解速率分别为0.0247d-1和0.0151d-1;而蒲桃树叶的分解速率则分别为0.0108d-1和0.0095d-1.说明2种树叶在布袋中的分解速率均比网袋慢,且人面子树叶的分解速率比蒲桃树叶快.定殖在2种树叶网袋中的功能摄食群以刮食者的比例最高(36%),其次是集食者(33%)和捕食者(25%),撕食者的比例最低(6%).在实验中后期,人面子树叶上的底栖动物个体总数、优势类群数和密度显著高于蒲桃树叶.说明在亚热带地区的中等级别的溪流中,由于撕食者种类减少,刮食者的类群数及密度对树叶分解速率具有显著影响.对微生物活动的抑制作用和对底栖动物取食的驱避作用使富含单宁成分的蒲桃树叶的分解速率下降.     

降水强度变化对天山云杉地表凋落物和细根分解的影响

为了探明不同降水条件下干旱区山地森林主要优势树种凋落物分解特征,采用野外模拟试验,通过设计3种降水强度处理[ZP（去除降水）、CK（自然降水,对照）、DP（双倍降水）],研究了降水强度变化对天山云杉地表凋落物（叶和枝）和细根分解的影响。研究结果表明：分解24个月后对照凋落叶、凋落枝和细根干重损失率比去除降水损失率分别高24.79%、2.54%和23.09%,比双倍降水损失率低7.04%、0.68%和10.70%,去除降水对凋落叶和细根分解的抑制作用显著,对凋落枝抑制作用较微弱,双倍降水对分解具有促进作用,但仅对细根分解的促进作用显著。对照和双倍降水处理下凋落叶和细根月平均分解率均表现为双峰型曲线,凋落枝为单峰曲线,去除降水处理下地表凋落物和细根月平均分解率相对平缓。木质素和纤维素残留率也表现为去除降水 > 对照 > 双倍降水。不同降水处理下分解过程中N元素释放模式不同,但C释放模式基本一致。相关分析表明,凋落物月分解率与0~10 cm土层温度的相关性不显著（P>0.05）,但与土壤含水量间为线性极显著正相关（P<0.05）。我们研究结果发现云杉凋落物与根系分解对降水强度变化存在明显差异,未来气候变化对土壤碳周转影响应该充分考虑这种器官间差异。     

凋落物多样性及组成对凋落物分解和土壤微生物群落的影响

凋落物分解是生态系统营养物质循环的核心过程,而土壤微生物群落在凋落物分解过程中扮演着极其重要且不可替代的角色。随着生物多样性的丧失日益严峻,探讨凋落物多样性及组成对凋落物分解和土壤微生物群落的影响,不仅有助于了解凋落物分解的内在机制,而且可为退化草原生态系统的恢复提供参考。以内蒙古呼伦贝尔草原退化恢复群落中的草本植物为研究对象,依据植物多度、盖度、频度和物种的重要值及其在群落中的恢复程度筛选出排序前4的羊草（Leymus chinensis）、茵陈蒿（Artemisia capillaris）、麻花头（Serratula centauroides）、二裂委陵菜（Potentilla bifurca）的凋落物为实验材料,通过设置3种凋落物多样性水平（1,2,4）,包括11种凋落物组合（单物种凋落物共4种,两物种凋落物混合共6种,四物种凋落物混合共1种）,利用磷脂脂肪酸（PLFA）方法来研究分解60 d后凋落物多样性及组成对凋落物分解和土壤微生物群落的影响。结果表明：（1）凋落物物种多样性仅对C残余率具有显著影响,表现在两物种混合凋落物C残余率显著低于单物种凋落物,而凋落物组成对所观测的4个凋落物分解参数（质量、C、N残余率以及C/N）均具有显著影响;（2）凋落物物种多样性对细菌（B）含量具有显著影响,而凋落物组成对真菌（F）含量具有显著影响,两者对F/B以及微生物总量均无显著影响;（3）冗余分析结果表明凋落物组成与凋落物分解相关指标（凋落物质量、C、N残余率及C/N）和土壤微生物（真菌、细菌含量）的相关关系高于凋落物多样性。（4）进一步建立结构方程模型（Structural Equation Model,SEM）发现,凋落物初始C含量对凋落物质量、C、N残余率及C/N有显著正的直接影响;凋落物木质素含量对凋落物质量、C、N残余率有显著正的直接影响;凋落物初始N含量对N残余率有显著正的直接影响,而对C残余率及C/N有显著负的直接影响;凋落物初始C/N对凋落物质量、N残余率有显著正的直接影响,而对C/N有显著负的直接影响。此外,凋落物初始C、N、木质素含量及C/N均对真菌含量具有显著正影响,并可通过真菌对凋落物质量分解产生显著负的间接影响。以上结果表明该退化恢复区域优势种凋落物分解以初始C、木质素为主导,主要通过土壤真菌影响凋落物的分解进程,这将减缓凋落物的分解速率进而减慢草原生态系统的进程。这些结果为凋落物多样性及组成对自身分解和土壤微生物群落的影响提供了实验依据,也为进一步分析凋落物分解内在机制以及草原生态系统的恢复提供了数据参考。     

Review of mixed forest litter decomposition researches

The litter plays an important role in forest ecosystems. Decomposition of mixed leaf litters has recently become an active research area because it mimics the natural state of leaf litters in most of forests. Many studies reported effects of mixing litters on their decomposition, ranging from positive, negative to neutral. In this paper decomposition mechanisms of mixed litters concluded by researchers were summarized. Firstly, plant litter quality had been recognized as an important factor to affect decomposition rate. Some studies showed a positive significant correlation between initial N, P concentration and non-additive effect in litter mixture decomposition. Secondly, it has been suggested that litter mixture could increase abundance and diversity of fauna and microbial decomposers, especially fungi. Thirdly, compared with single litter decomposition, the nutrient exchange between different litter species is often considered as one of main non-additive effects observed in litter mixture. Some results showed that the active transport of nutrients by fungal hyphae derived positive effect on the decomposition of litter mixture. The multiple factors such as, leaf litter species, investigation method and plot, were also analyzed. In conclusion, it is necessary to enhance a further research on factors in mixed litter decomposition and an interaction between various factors due to the complex relationship. We are looking forward to using these theories of mixed litter decomposition to direct practical forest management.     

Review of mixed forest litter decomposition researches

The litter plays an important role in forest ecosystems. Decomposition of mixed leaf litters has recently become an active research area because it mimics the natural state of leaf litters in most of forests. Many studies reported effects of mixing litters on their decomposition, ranging from positive, negative to neutral. In this paper decomposition mechanisms of mixed litters concluded by researchers were summarized. Firstly, plant litter quality had been recognized as an important factor to affect decomposition rate. Some studies showed a positive significant correlation between initial N, P concentration and non-additive effect in litter mixture decomposition. Secondly, it has been suggested that litter mixture could increase abundance and diversity of fauna and microbial decomposers, especially fungi. Thirdly, compared with single litter decomposition, the nutrient exchange between different litter species is often considered as one of main non-additive effects observed in litter mixture. Some results showed that the active transport of nutrients by fungal hyphae derived positive effect on the decomposition of litter mixture. The multiple factors such as, leaf litter species, investigation method and plot, were also analyzed. In conclusion, it is necessary to enhance a further research on factors in mixed litter decomposition and an interaction between various factors due to the complex relationship. We are looking forward to using these theories of mixed litter decomposition to direct practical forest management.     

全球变化对陆地生态系统枯落物分解的影响

了解枯落物分解对大大二氧化碳浓度增高,气候变暖和降水变化的反应,对深入理解陆地生态系统土壤有机物形成和碳的固化能力（Carbonh sequestration)十分重要。通过分析业已发表的文献,实验室根系分解实验和美国西北部针叶林叶片的分解实验,旨在评估大气二氧化碳浓度增高,气候变暖和降水化对陆地生态系统枯落物分解的可能影响,大气二氧化碳浓度增高可通过降低枯落物质量和增加草原生态系统土壤水分间接地影响枯落物分离,根据17项研究结果,大气二氧化碳浓度加倍可导致木本和草本枯落物平均氮含量降低19．6％和9．4％;木质素／氮化值增高36．3％和5．5％,枯落物质地的降低通常导致枯落物分解减慢。气候变暖一般加速枯落物的分解,但是用于表示这种促进作用的Q10随着温度的增高而降低,全球降水变化对陆地生态系统枯落物分解的影响不但取决于现有水分条件而且还以决于降水变的程度。以美国西北部地的针叶林为例,降水改变对森林生态系统枯落物分解的影响将是 多元的,有的增加,有的降低,而有的相对不变,最后,指出了今后 在方该领域有待加强的几个研究方面。     

半干旱草地植物枯落物碳、氮和磷元素释放对放牧和封育管理的响应

在半干旱草地,关于放牧和封育管理对草地植物枯落物分解及其与土壤动物互作关系的研究一直是该区域生态系统物质循环与生态恢复过程研究的重要科学问题。以放牧和封育样地中赖草(Leymus secalinus)、牛枝子(Lespedeza potaninii)及其混合枯落物为研究对象。于2017年9月、2018年5月和9月、2019年5月和9月,采用2种不同孔径(30目和250目)网袋量化中小型土壤动物的作用,调查了宁夏半干旱草地枯落物碳、氮和磷元素分解与土壤动物群落分布及其对放牧和封育样地的响应规律。结果显示：(1)封育样地中,枯落物碳元素最终残留率均表现为3种枯落物处理间无显著差异;但250目网孔中枯落物氮、磷元素最终残留率和30目网孔中氮元素最终残留率均表现为牛枝子显著高于赖草和混合物,而后两者间无显著差异;仅30目网孔中磷元素最终残留率表现为牛枝子和混合物显著高于赖草,而前两者间无显著差异。放牧样地中,250目网孔的碳、磷元素最终残留率和30目网孔中的氮、磷元素最终残留率均表现为牛枝子显著高于混合物,而赖草居中;氮元素最终残留率表现为牛枝子显著高于赖草和混合物,后两者间无显著差异。(2)...     

降水量变化对蒙古栎落叶分解过程的间接影响

分析了在4种不同降水量条件下蒙古栎叶凋落物基质质量的变化,并应用分解袋法研究其凋落物在蒙古栎次生林内的分解过程.结果表明：与对照相比,降水量减少条件下,蒙古栎叶凋落物的初始N、P、K浓度显著升高,初始木质素浓度显著降低,凋落物分解速率大,N、P、K矿化率高,N和P固持时间缩短;降水量增加情况下,其凋落物初始N浓度显著降低、木质素浓度显著升高,N、P、K矿化率低,N和P固持时间延长.4种类型叶片凋落物的质量损失过程均符合指数降解模型,分解速率可以由凋落物木质素/N来预测.相关性分析显示,木质素浓度高、N浓度低的两种凋落物的分解速率与N浓度相关性最大;而木质素浓度低、N浓度高的两种凋落物的分解速率与木质素浓度相关性最大.说明降水量的变化显著地改变了蒙古栎叶凋落物的基质质量,进而间接地改变了凋落物的分解过程.     

陆地生态系统混合凋落物分解研究进展

凋落物分解在陆地生态系统养分循环与能量流动中具有重要作用,是碳、氮及其他重要矿质养分在生态系统生命组分间循环与平衡的核心生态过程。自然生态系统中,植物群落大多具有较高的物种丰富度和多样性,其混合凋落物在分解过程中也更有可能发生养分传递、化学抑制等种间互作,形成多样化的分解生境,多样性较高的分解者类群以及复杂的级联效应分解,这些因素和过程均对研究混合凋落物分解过程、揭示其内在机制形成了极大的挑战。从构成混合凋落物物种丰富度和多样性对分解生境、分解者多样性及其营养级联效应的影响等方面,综合阐述混合凋落物对陆地生态系统凋落物分解的影响,探讨生物多样性在凋落物分解中的作用。通过综述近些年的研究发现,有超过60%的混合凋落物对其分解速率的影响存在正向或负向的效应。养分含量有差异的凋落物混合分解过程中,分解者优先利用高质量凋落物,使低质量的凋落物反而具有了较高的养分有效性,引起低质量凋落物分解加快并最终使混合凋落物整体分解速率加快;而凋落物物种丰富度对土壤动物群落总多度有轻微的影响或几乎没有影响,但是对线虫和大型土壤动物的群落组成和多样性有显著影响,并随着分解阶段呈现一定动态变化;混合凋落物改变土壤微生物生存的理化环境,为微生物提供更多丰富的分解底物和养分,优化微生物种群数量和群落结构及其分泌酶的活性,并进一步促进了混合凋落物的分解。这些基于植物-土壤-分解者系统的动态分解过程的研究,表明混合凋落物分解作用不只是经由凋落物自身质量的改变,更会通过逐级影响分解者多样性水平而进一步改变分解速率和养分释放动态,说明生物多样性确实在一定程度上调控凋落物分解及其养分释放过程。     

长白山次生针阔混交林叶凋落物中有机物分解与碳、氮和磷释放的关系

采用分解袋法,研究了长白山次生针阔混交林内9种树种叶凋落物34个月的分解过程.结果表明:在次生针阔混交林中,不同树种叶凋落物的初始N和P浓度存在很大差异,叶凋落物分解速率(k)与初始N浓度和C/N显著相关.有机物剩余百分率与C剩余百分率呈显著的线性正相关关系,与N和P剩余百分率之间呈显著的二项式回归关系. N和P剩余百分率在初期阶段随有机物分解而增加,达到峰值后逐渐降低. 随着有机物剩余百分率的下降,C/N和C/P均呈逐渐降低趋势,各种叶凋落物之间C/N和C/P的差异逐渐减小,分解末期分别趋近于23和350. 随有机物剩余百分率的降低, N/P变化不明显,当有机物剩余百分率低于25%时,不同树种叶凋落物之间N/P差异显著下降. 有机物剩余百分率可用来预测C、N和P的剩余百分率. 