Impact of soil mesofauna on the decomposition of two main species litters in a Pinus koraiensis mixed broad-leaved forest of the Changbai Mountains

In most terrestrial ecosystems, the majority of aboveground net primary productivity enters the decomposition system as plant litter. The decomposition of plant litter plays a critical role in regulating build up of the forest soil organic matter, releasing of nutrients for plant growth, and influencing the carbon cycling. Soil fauna are considered to be an important factor in the acceleration litter decomposition and nutrient transformations. Mechanisms of soil faunal contribution to litter decomposition include digestion of substrates, increase of surface area through fragmentation and acceleration of microbial inoculation into litter. The Pinus koraiensis mixed broad-leaved forest is one of the typical forest vegetation types in Changbai Mountain. Previously, major studies carried here were focused on climate, soil and vegetation; however, on litter decomposition and the role of soil fauna in this forest ecosystem were limited. In this paper, we conducted a litter decomposition experiment using litterbag method to explore the contribution of soil fauna on litter decomposition and provide a scientific basis for maintaining a balanced in P. koraiensis mixed broad-leaved forest in Changbai Mountains. During 2009 and 2010, we used litterbags with different mesh sizes to examine the decomposition of two dominant tree species (P. koraiensis, Fraxinus mandshurica) in studied site. The results showed that the process of litter decomposition can be separated into two apparent stages. The initial decomposition process at former six months was slow, while accelerated the final six months. The former six months (from October 2009 to April 2010) was winter and spring. There was low temperature and almost no activity of soil fauna and microbes. The final six months (from June to October 2010), decomposition rates increased. In summer and autumn, both temperature and moisture increases, abundance of soil fauna was much than before and was most active. The remaining mass of P. koraiensis was higher than that of F. mandshurica in two mesh size litterbags after 1 year decomposition, meanwhile litter in 2 mm mesh size litterbag had higher decomposition rate than that of 0.01 mm for two species litter. The Collembola, Acari, Enchytraeidae Lithobiomorpha and Diptera larvae were mainly fauna groups in the litterbags. The composition of soil fauna community was difference between P. koraiensis and F. mandshurica during litter decomposition. 24 different soil fauna groups and 1431 individual were obtained in P. koraiensis litterbags; Isotomidae, Tomoceridae and Oribatida were dominant groups; while 31 different soil fauna groups and 1255 individual were obtained in F. mandshurica litterbags; Isotomidae, Hypogastruridae Oribatida and Mesostigmata were dominant groups. The rate of litter decomposition was positively correlated with the individual and group density of soil fauna. Contribution rate to litter decomposition was 1.70% for P. koraiensis and 4.83% for F. mandshurica. Repeated measures ANOVA showed that litter species, time and soil fauna had a significant impact on the rate of litter decomposition (P < 0.05). Our results suggested that soil fauna could accelerate litter decomposition and, consequently, nutrient cycling in P. koraiensis mixed broad-leaved forest, Changbai Mountains.     

Drivers of litter mass loss and faunal composition of detritus patches change over time

Decomposition of vegetal detritus is one of the most fundamental ecosystem processes. In complex landscapes, the fate of litter of terrestrial plants may depend on whether it ends up decomposing in terrestrial or aquatic conditions. However, (1) to what extent decomposition rates are controlled by environmental conditions or by detritus type, and (2) how important the composition of the detritivorous fauna is in mediating decomposition in different habitats, remain as unanswered questions. We incubated two contrasting detritus types in three distinct habitat types in Coastal Georgia, USA, to test the hypotheses that (1) the litter fauna composition depends on the habitat and the litter type available, and (2) litter mass loss (as a proxy for decomposition) depends on environmental conditions (habitat) and the litter type. We found that the abundance of most taxa of the litter fauna depends primarily on habitat. Litter type became a stronger driver for some taxa over time, but the overall faunal composition was only weakly affected by litter type. Decomposition also depends strongly on habitat, with up to ca. 80% of the initial detrital mass lost over 25 months in the marsh and forest habitats, but less than 50% lost in the creek bank habitat. Mass loss rates of oak versus pine litter differed initially but converged within habitat types within 12 months. We conclude that, although the habitat type is the principle driver of the community composition of the litter fauna, litter type is a significant driver of litter mass loss in the early stages of the decomposition process. With time, however, litter types become more and more similar, and habitat becomes the dominating factor in determining decomposition of older litter. Thus, the major driver of litter mass loss changes over time from being the litter type in the early stages to the habitat (environmental conditions) in later stages.     

海拔和郁闭度对祁连山青海云杉林叶凋落物分解的影响

为了探究海拔和郁闭度对青海云杉林叶凋落物分解的影响,本文选择海拔为2850 m,3050 m,3250 m和3450 m四个梯度和高、中、低三个林分郁闭度,采用分解网袋法,研究青海云杉叶凋落物分解速率及分解过程中N、P元素变化。结果表明,质量损失率随时间在波动增大。分解速率先减小后增大,不同海拔下分解速率为K₃₄₅₀ > K₃₀₅₀ > K₃₂₅₀ > K₂₈₅₀,不同郁闭度下分解速率为K_低 > K_中 > K_高,青海云杉叶枯落物分解50%和95%所需时间约为5.3 a和22.7 a。枯落物分解过程中,N、P含量和累积系数在不同海拔和郁闭度下的变化不同,与季节变化有关。研究结果为祁连山森林生态系统地球化学循环奠定基础。     

Litter decay controlled by temperature,not soil properties,affecting future soil carbon

Widespread global changes, including rising atmospheric CO₂ concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon‐cycle feedbacks on atmospheric CO₂ levels, climate warming and biodiversity. But predicting litter decomposition is difficult because of many interacting factors related to the chemical, physical and biological properties of soil, as well as to climate and agricultural management practices. We applied ¹³C‐labelled plant litter to soil at ten sites spanning a 3500‐km transect across the agricultural regions of Canada and measured its decomposition over five years. Despite large differences in soil type and climatic conditions, we found that the kinetics of litter decomposition were similar once the effect of temperature had been removed, indicating no measurable effect of soil properties. A two‐pool exponential decay model expressing undecomposed carbon simply as a function of thermal time accurately described kinetics of decomposition. (R² = 0.94; RMSE = 0.0508). Soil properties such as texture, cation exchange capacity, pH and moisture, although very different among sites, had minimal discernible influence on decomposition kinetics. Using this kinetic model under different climate change scenarios, we projected that the time required to decompose 50% of the litter (i.e. the labile fractions) would be reduced by 1–4 months, whereas time required to decompose 90% of the litter (including recalcitrant fractions) would be reduced by 1 year in cooler sites to as much as 2 years in warmer sites. These findings confirm quantitatively the sensitivity of litter decomposition to temperature increases and demonstrate how climate change may constrain future soil carbon storage, an effect apparently not influenced by soil properties.     

Soil microbial activities and litter decomposition related to altitude

Summary On a southern slope in the Austrian Central Alps (Hohe Tauern Mountains) at altitudes of 2550 m, 1920 m and 1650 m above sea level, respectively, microbial activities were investigated by measuring the decomposition of litter, the cellulase and xylanase activities, CO₂-evolution and the cell counts of viable non differentiated and cellulolytic bacteria. After one year 46% of litter exposed was decomposed at an altitude of 2550 m, 76% at 1920 m and 86% at 1560 m. Investigations with litter bags of different mesh sizes (25 μm and 1000 μm) revealed that small soil animals (<1 mm) did not significantly influence the decomposition of litter at different altitudes and in different vegetation types. The enzymatic activities and the CO₂-evolution of soils decreased with increasing altitude. Plate counts of bacteria from soils at the alpine zone (2550 m) and the tall grass meadow (1650 m) indicated that in some cases the lower metabolic activities caused by bad climatic conditions were compensated by an increase in cell numbers. This work was supported by the Austrian MaB-Hochgebirgsprogramm, Alpine ?kosysteme     

Aerobic cellulolytic bacterial flora associated with decomposing Phragmites leaf litter in a seawater lake

A litter bag experiment was carried out in a eutrophic seawater lake from autumn to summer in order to determine which bacterial genera play an important role in decomposition of Phragmites communis leaf litter. The count of cellulolytic bacteria and decomposition rate of litter cellulose increased rapidly during the initial month. In contrast, the count of cellulolytic fungi was lowest in this period. Pseudomonas accounted for 65–90% of total isolates of cellulolytic bacteria up to 5 months. These results suggest that Pseudomonas plays an important role in at least the initial decomposition stage of the litter.     

Fate of leaf litter in restored Kandelia obovata (S. L.) mangrove forests with different ages in Jiulong River Estuary,China

Ecological processing of leaf litter plays important roles in carbon dynamics of mangrove forests. Fate of leaf litter, that is, removal by crabs, microbial decomposition, and tidal export was quantified in two restored Kandelia obovata forests with ages of 24 years and 48 years, respectively, from December 2009 to November 2010. Crab abundance was also investigated to test the role of crabs in leaf litter processing. Daily leaf litter production was 1.064 ± 0.108 g C m^?2 day^?1 at the 24‐year forest and was 0.689 ± 0.040 g C m^?2 day^?1 at the 48‐year forest. Annual mean removal of leaf litter by crabs was lower at the 24‐year forest than at the 48‐year forest (0.177 ± 0.046 g C m^?2 day^?1 vs. 0.220 ± 0.050 g C m^?2 day^?1), due to a higher crab abundance at the older forest. Microbial decomposition and change in standing stock of leaf litter on the forest floor made a negligible contribution to the annual leaf litter production. Tidal exports of leaf litter were estimated as 0.875 ± 0.090 g C m^?2 day^?1 and 0.458 ± 0.086 g C m^?2 day^?1 at the 24‐year and 48‐year forests, respectively, accounting for 82.2% and 66.5% of their daily leaf litter production. Turnover rate of leaf litter was higher at the younger forest (1.7 ± 0.4 day^?1) than the older forest (1.2 ± 0.3 day^?1). Removal of leaf litter by crabs was higher in warm months while tidal export of leaf litter showed a much less apparent seasonal pattern. Spatial variations of crab removal and tidal export of leaf litter with forest zones were observed within each forest, while microbial decomposition of leaf litter was comparable among the different zones. These indicated that the ecosystem functions of restored mangrove forest could not reach a level equivalent to those of a mature forest even 24 years after restoration.     

青海云杉林凋落物分解早期微生物生物量时空动态变化

凋落物分解过程中的微生物生物量动态对于深入了解森林生态系统凋落物分解机理具有重要意义。为了解高寒山地森林典型树种凋落物分解过程中的微生物生物量动态特征,采用凋落物袋野外原位分解法,研究了海拔2850 m、2950 m、3050 m、3150 m和3250 m树冠中心(CC)与树冠边缘(CE)青海云杉(Picea crassifolia)叶凋落物分解过程中凋落物和土壤中的微生物生物量碳(MBC)、微生物生物量氮(MBN)和微生物生物量磷(MBP)时空动态变化。时间尺度上,不同海拔CC与CE凋落物中的MBC、MBN和MBP在生长季节初期上升,生长季节后期下降;但土壤中的MBC、MBN和MBP却在生长季节初期下降,生长季节后期上升。然而,3050 m海拔CE和3250 m海拔土壤中的MBP含量呈“先下降-后上升-再下降”的倒“N”型变化格局。空间尺度上,凋落物中的MBC和MBN含量高于土壤中的,但MBP出现相反情况;CE处的MBC、MBN和MBP含量均显著(P<0.05)高于CC;总体而言,MBC、MBN和MBP含量以中海拔显著最高(P<0.05),其次为低海拔,高海拔显著最低(...     

模拟氮沉降对华西雨屏区慈竹林凋落物分解的影响

试验设对照(CK,0 kg·hm^-2·a^-1)、低氮(LN,50 kg·hm^-2·a^-1)、中氮(MN,150 kg·hm^-2·a^-1)和高氮(HN,300 kg·hm^-2·a^-1)4个施氮水平,通过原位试验,研究了模拟N沉降对华西雨屏区慈竹(Neosinocalamus affinis)林凋落物分解的影响.结果表明：不同组分凋落物分解过程中,慈竹叶片分解速率最快,其次是箨,枝最慢,分解15个月时,叶片、箨、枝的质量残留率分别为26.38%、46.18%和54.54%,三者差异极显著(P<0.01);叶片在凋落后第1～2月和7～10月分解较快,而箨和枝则在第5～8月分解较快;凋落叶片分解95%需要的时间(2.573年)分别比箨和枝短1.686年和3.319年.凋落叶分解15个月时,各N沉降处理间分解率差异不显著;凋落箨分解95%需要2.679～4.259年,其中MN分解率最高,CK最低;凋落枝经过15个月的分解,各处理分解率大小顺序为MN>HN>LN>CK,MN与LN处理间差异达显著水平(P<0.05).说明N沉降对3种凋落物分解均有明显的促进作用,且对凋落箨促进作用最强;但随着N沉降浓度的增加和时间的延长,其促进作用减缓.     

Stronger effects of litter origin on the processing of conifer than broadleaf leaves: A test of home‐field advantage of stream litter breakdown

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根系在凋落物层中的生长及其对凋落物分解的影响

凋落物分解是生态系统养分循环的重要过程, 直接影响着生态系统功能。植物根系作为重要的生物因子调控着凋落物分解过程, 然而这一重要作用却在凋落物分解的研究中长期被忽视。凋落物中下层养分充足、保水能力强, 为根系生长提供了良好环境; 同时, 生长进入凋落物层的根系通过激发效应、共生真菌、N吸收等方式对分解过程产生了重要影响。该文针对根系生长及其影响因素、根系对凋落物分解的影响及其内在机制等关键方面进行了综述, 并提出了根系生长与凋落物分解之间关系的概念模型, 以期引起大家对这个领域的关注, 并为根系与凋落物分解之间关系的研究提供良好的借鉴。     

The Vertical Pattern of Rooting and Nutrient Uptake at Different Altitudes of a South Ecuadorian Montane Forest

The vertical pattern of root length densities (RLD) of fine roots (<2 mm in diameter) and nitrogen (N) uptake potential were determined at different altitudes (1,900, 2,400, and 3,000 m a.s.l.) of a tropical montane forest in order to improve our knowledge about the depth distribution of nutrient uptake in this ecosystem. At higher altitudes, precipitation rate and frequency of fog were higher than at lower altitudes while mean annual air temperature decreased with increasing altitude. Soils were always very acid with significantly lower pH at a depth of 0.0–0.3 m in mineral soil at 3,000 m (2.8–2.9) than at 1,900 and 2,400 m (3.1–3.5). The vertical distribution of RLD was very similar both during the dry and the rainy season. During the dry season the percentage of root length in the organic layer increased from 51% at 1,900 m to 61% at 2,400 m and 76% at 3,000 m. At 3,000 m, RLD was markedly higher in the upper 0.05 m than in the remaining organic layer, whereas at 1,900 m and 2,400 m RLD were similar in all depths of the organic layer. In mineral soil, RLD decreased to a greater degree with increasing soil depth at the upper two study sites than at 1,900 m. The relative N uptake potential from different soil layers (RNUP) was determined by ¹⁵N enrichment of leaves after application of ¹⁵N enriched ammonium sulphate at various soil depths. RNUP closely followed fine root distribution confirming the shallower pattern of nutrient uptake at higher altitudes. RNUP was very similar for trees, shrubs and herbs, but shallower for saplings which obtained N only from the organic layer at both altitudes. Liming and fertilizing (N, P, K, Mg) of small patches in mineral soil had no significant impact on fine root growth. We conclude that the more superficial nutrient uptake ability at higher altitudes may be partly related to increased nutrient input from canopy by leaching. However, the specific constraints for root growth in the mineral soil of tropical montane forests warrant further investigations.     

High‐frequency fire alters C : N : P stoichiometry in forest litter

Fire is a major driver of ecosystem change and can disproportionately affect the cycling of different nutrients. Thus, a stoichiometric approach to investigate the relationships between nutrient availability and microbial resource use during decomposition is likely to provide insight into the effects of fire on ecosystem functioning. We conducted a field litter bag experiment to investigate the long‐term impact of repeated fire on the stoichiometry of leaf litter C, N and P pools, and nutrient‐acquiring enzyme activities during decomposition in a wet sclerophyll eucalypt forest in Queensland, Australia. Fire frequency treatments have been maintained since 1972, including burning every 2 years (2yrB), burning every 4 years (4yrB) and no burning (NB). C : N ratios in freshly fallen litter were 29–42% higher and C : P ratios were 6–25% lower for 2yrB than NB during decomposition, with correspondingly lower 2yrB N : P ratios (27–32) than for NB (34–49). Trends in litter soluble and microbial N : P ratios were similar to the overall litter N : P ratios across fire treatments. Consistent with these, the ratio of activities for N‐acquiring to P‐acquiring enzymes in litter was higher for 2yrB than NB, whereas 4yrB was generally intermediate between 2yrB and NB. Decomposition rates of freshly fallen litter were significantly lower for 2yrB (72 ± 2% mass remaining at the end of experiment) than for 4yrB (59 ± 3%) and NB (62 ± 3%), a difference that may be related to effects of N limitation, lower moisture content, and/or litter C quality. Results for older mixed‐age litter were similar to those for freshly fallen litter although treatment differences were less pronounced. Overall, these findings show that frequent fire (2yrB) decoupled N and P cycling, as manifested in litter C : N : P stoichiometry and in microbial biomass N : P ratio and enzymatic activities. Furthermore, these data indicate that fire induced a transient shift to N‐limited ecosystem conditions during the postfire recovery phase.     

Litter dynamics recover faster than arthropod biodiversity during tropical forest succession

Litterfall and litter decomposition are key elements of nutrient cycling in tropical forests, a process in which decomposer communities such as macro-arthropods play a critical role. Understanding the rate and extent to which ecosystem function and biodiversity recover during succession is useful to managing the growing area of tropical successional forest globally. Using a replicated chronosequence of forest succession (5–15, 15–30, 30–45 years, and primary forest) on abandoned pastures in lowland tropical wet forest, we examined litterfall, litter chemistry, and effects of macro-arthropod exclusion on decomposition of two litter types (primary and 5- to 15-years-old secondary forest). Further, we assessed macro-arthropod diversity and community composition across the chronosequence. Overstory cover, litterfall, and litter nutrients reached levels similar to primary forest within 15–30 years. Young secondary forest litter (5–15 years) had lower initial N and P content, higher C:N, and decayed 60 percent faster than primary forest litter. The presence of macro-arthropods strongly mediated decomposition and nutrient release rates, increasing litter mass loss by 35–44 percent, N released by 53 percent, and P release by 84 percent. Forest age had no effect on soil nutrients, rates of litter decomposition, nutrient release, or macro-arthropod influence. In contrast, abundance and community composition of macro-arthropods remained significantly lower and distinct in all ages of secondary compared with primary forest. Order richness was lower in 5–15 years of secondary compared with primary forest. Our results suggest that in highly productive tropical wet forest, functional recovery of litter dynamics precedes recovery of decomposer community structure and biodiversity.     

中国温带和亚热带8个树种叶和吸收根协同分解

叶和细根(2mm)是森林生态系统的分解主体,二者是否协同分解,将极大影响所属植物在生态系统碳(C)循环中的物种效应。已有研究显示,叶和细根的分解关系具有极大的不确定性,认为很大程度上归因于细根内部具有高度的异质性,导致叶和细根在功能上不相似。为此,使用末梢1级根和细根根枝作为研究对象,它们在功能上同叶类似,称为吸收根。通过分解包法,分别在黑龙江帽儿山和广东鹤山,研究了2个阔叶树种和2个针叶树种(共8个树种)的叶和吸收根持续2a多的分解。结果发现,分解速率k(a~(-1),负指数模型)在8个树种整体分析时具有正相关关系(P0.05),在相同气候带或植物生活型水平上是否相关,受叶的分解环境及吸收根类型的影响;N剩余量整体上并不相关,亚热带树种的叶和细根根枝的N剩余量在分解1a后高度显著正相关,温带树种的叶和1级根的N剩余量在分解2a后显著高度正相关。本研究中,根-叶分解过程是否受控于相同或相关的凋落物性质是决定根-叶分解是否相关的重要原因,其中分解速率与酸溶组分正相关、与酸不溶组分负相关。比较已有研究,总结发现,根-叶分解关系受物种影响较大,暗示气候变化导致物种组成的改变将极大影响地上-地下关系,也因此影响生态系统C循环。     

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。     

Effects of competition and mowing on growth and reproduction of the invasive plant Erigeron annuus at two contrasting altitudes

Invasive plants are often abundant at frequently disturbed sites such as roadsides, because they benefit from reduced competition or increased nutrient availability. In Switzerland, roadsides are subjected to regular mowing, and to persist in these sites, plants must be able to compensate for the biomass removal. However, the ability to tolerate competition and mowing might decline under less favourable growth conditions, such as those at higher altitudes. I investigated how competition and mowing affect growth and reproduction of Erigeron annuus (L.) Pers., an invasive plant common on Swiss roadsides, and how these effects change with altitude. The experiment was replicated in common gardens at altitudes of 400 m and 1,000 m asl, representing growth conditions in the main distribution area of E. annuus and at its altitudinal limit, respectively. Vegetative growth was negatively affected by competition at both sites, but especially at 1,000 m. The number of capitula was not affected by competition at 400 m, but was reduced at 1,000 m. Plants regrew vigorously after mowing in both gardens. The effects of mowing on reproductive output were positive at 400 m, but negative at 1,000 m. These results imply that E. annuus is able to tolerate competition and mowing at low altitudes, but both of these factors hinder its reproduction at higher altitudes.

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Zusammenfassung  Invasive Neophyten kommen an gest?rten Standorten besonders h?ufig vor, da sie dort weniger Konkurrenz oder eine h?here N?hrstoffverfügbarkeit vorfinden. In der Schweiz sind regelm?ssig gem?hte Strassenr?nder wichtige Lebensr?ume und Ausbreitungskorridore für invasive Pflanzen. Offenbar gelingt es den Pflanzen, die Mahdverluste zu kompensieren und sich dennoch zu vermehren. Die F?higkeit von Pflanzen, Konkurrenz oder St?rungen zu ertragen, nimmt in der Regel unter ungünstigen Wachstumsbedingungen ab. Deshalb k?nnte man erwarten, dass invasive Pflanzen mit zunehmender Meeresh?he aufgrund des k?lteren Klimas durch Konkurrenz und Mahd st?rker betroffen werden. Hier wurde untersucht, ob Konkurrenz und Mahd das Wachstum und die Fortpflanzung des einj?hrigen Berufkrauts, Erigeron annuus (L.) Pers., je nach Meeresh?he unterschiedlich beeinflussen. Dazu wurde ein Experiment in zwei G?rten auf 400 und 1,000 m ü.M. angelegt, wobei der obere Garten der heutigen Verbreitungsgrenze von E. annuus entspricht. Konkurrenz reduzierte das vegetative Wachstum an beiden Orten, jedoch st?rker auf 1,000 m. Die Anzahl Blütenk?pfe wurde nur auf 1,000 m durch Konkurrenz reduziert. Nach einer Mahd trieben die Pflanzen in beiden G?rten schnell wieder aus. Die Mahd erh?hte die Anzahl Blütenk?pfe auf 400 m und senkte sie auf 1,000 m. Diese Ergebnisse bedeuten, dass E. annuus in tiefen Lagen Mahd und Konkurrenz ertragen kann, w?hrend in h?heren Lagen beide Faktoren seiner Ausbreitung entgegenwirken.

     

Diversity and Decomposing Ability of Saprophytic Fungi from Temperate Forest Litter

This study was designed to examine saprophytic fungi diversity under different tree species situated in the same ecological context. Further, the link between the diversity and decomposition rate of two broadleaved, two coniferous and two mixed broadleaved-coniferous litter types was targeted. Litter material was decomposed in litter bags for 4 and 24 months to target both early and late stages of the decomposition. Fungal diversity of L and F layers were also investigated as a parallel to the litter bag method. Temperature gradient gel electrophoresis fingerprinting was used to assess fungal diversity in the samples. Mass loss values and organic and nutrient composition of the litter were also measured. The results showed that the species richness was not strongly affected by the change of the tree species. Nevertheless, the community compositions differed within tree species and decomposition stages. The most important shift was found in the mixed litters from the litter bag treatment for both variables. Both mixed litters displayed the highest species richness (13.3 species both) and the most different community composition as compared to pure litters (6.3–10.7 species) after 24 months. The mass loss after 24 months was similar or greater in the mixed litter (70.5% beech–spruce, 76.2% oak–Douglas-fir litter) than in both original pure litter types. This was probably due to higher niche variability and to the synergistic effect of nutrient transfer between litter types. Concerning pure litter, mass loss values were the highest in oak and beech litter (72.8% and 69.8%) compared to spruce and D. fir (59.4% and 66.5%, respectively). That was probably caused by a more favourable microclimate and litter composition in broadleaved than in coniferous plantations. These variables also seemed to be more important to pure litter decomposition rates than were fungal species richness or community structure.     

亚热带森林根系和菌根真菌调控凋落叶分解和主场效应

根系向凋落物层生长是森林生态系统中存在的普遍现象,研究根系和菌根真菌如何调控凋落物分解对理解森林生态系统的养分循环具有重要意义。通过在亚热带楠木(丛枝菌根树种)和格氏栲(外生菌根树种)人工林中进行了2年的凋落物互换和菌根排除实验,研究根系及其共生菌根真菌如何影响森林凋落物的分解速率和主场效应。结果发现:经过720 d的分解,在楠木人工林中,根系的存在促使楠木和格氏栲凋落物的分解速度分别提高了29%和47%,而在格氏栲人工林中,根系存在对格氏栲凋落物分解无显著影响,但增加了楠木凋落物的分解速率。此外,楠木人工林中,有根和无根处理下凋落物分解均无主场效应,而格氏栲人工林凋落物仅在根系存在的情况下显示出负的主场效应。进一步发现格氏栲凋落物的负主场效应归因于楠木人工林凋落物层更大的腐生真菌丰度和更强的磷降解酶活性。结果表明,在亚热带不同菌根类型树种中,菌根真菌与腐生真菌的相互作用(拮抗或促进),很有可能通过影响磷降解酶的活性,进而影响凋落物的分解率和主场效应。