Long-term dynamics of pine and hardwood litter in contrasting environments: toward a global model of decomposition

We analysed data on mass loss after five years of decomposition in the field from both fine root and leaf litters from two highly contrasting trees, Drypetes glauca, a tropical hardwood tree from Puerto Rico, and pine species from North America as part of the Long‐Term Intersite Decomposition Experiment (LIDET). LIDET is a reciprocal litterbag study involving the transplanting of litter from 27 species across 28 sites in North and Central America reflecting a wide variety of natural and managed ecosystems and climates, from Arctic tundra to tropical rainforest. After 5 years, estimated k‐values ranged from 0.032 to 3.734, lengths of Phase I (to 20% mass remaining) from 0.49 to 47.92 years, and fractional mass remaining from 0 to 0.81. Pine litter decomposed more slowly than Drypetes litter, supporting the notion of strong control of substrate quality over decomposition rates. Climate exerted strong and consistent effects on decomposition. Neither mean annual temperature or precipitation alone explained the global pattern of decomposition; variables including both moisture availability and temperature (i.e. actual evapotranspiration and DEFAC from the CENTURY model) were generally more robust than single variables. Across the LIDET range, decomposition of fine roots exhibited a Q₁₀ of 2 and was more predictable than that of leaves, which had a higher Q₁₀ and greater variability. Roots generally decomposed more slowly than leaves, regardless of genus, but the ratio of above‐ to belowground decomposition rates differed sharply across ecosystem types. Finally, Drypetes litter decomposed much more rapidly than pine litter in ‘broadleaved habitats’ than in ‘conifer habitats’, evidence for a ‘home‐field advantage’ for this litter. These results collectively suggest that relatively simple models can predict decomposition based on litter quality and regional climate, but that ecosystem‐specific problems may add complications.     

菌根真菌对土壤呼吸以及凋落物分解的影响

土壤呼吸是植物固定的碳由陆地生态系统进入大气的主要途径之一; 凋落物分解是养分循环的重要环节。陆地植物的90%以上可同菌根真菌形成共生关系, 菌根真菌对于植物获取环境中的养分具有重要的作用。然而, 其对土壤呼吸和凋落物分解的影响却经常在生态系统对环境变化的响应研究中被忽视。本文系统地综述了国内外相关研究进展, 对菌根真菌如何影响土壤呼吸和凋落物分解这两个过程及这种影响如何受到环境变化的制约做了全面的分析, 并对以往研究中存在的问题以及未来的研究方向提出了展望。     

Succession of microfungi during Pistacia lentiscus litter decomposition in a Sardinian Mediterranean maquis

Abstract

Changes in the microfungal community developing on Pistacia lentiscus L. leaf litter were monitored from February 2001 (senescent leaves) to December 2002 using litter bags. The Principal component analysis of the 16 samples showed a microfungal succession related to the progressive decomposition of the substratum. The Correspondence analysis of fungal colonizers with Rf > 10 revealed three main groups succeeding during the study period. The co-occurrence relationships (on the same leaf) among the major colonizers were analysed. The specialized saprotrophs on P. lentiscus litter: Asterostomella sp. 1 and Endophragmiella boewei were identified as principal colonizers in the mature community.     

Effect of ectomycorrhizal fungi on nitrogen mineralisation and the growth of Scots pine seedlings in natural peat

The aim of this study was to investigate the potential of different isolates of ectomycorrhizal (EM) fungi to enhance the growth of Pinus sylvestris seedlings in five natural peat substrates with different nitrogen concentrations, and the effect of the Scots pine seedlings and fungal inoculum on the formation of dissolved inorganic and organic nitrogen in peat. Utilization of different organic nitrogen compounds by microbial community in the peat was also investigated using Biolog MT MicroPlates. Inoculation of the seedlings with EM fungi enhanced seedling growth. Piloderma croceum increased root growth especially, whereas Lactarius rufus increased needle growth and Suillus variegatus I, II and III improved both root and needle growth. All the EM fungi also significantly affected stem growth. Nitrogen concentration of the peat did not affect seedling growth as much as the EM fungi. At the lowest peat N concentration (1.17%) NH ₄ ⁺ mineralisation was lower and DON (dissolved organic nitrogen) accumulation higher than at higher peat N concentrations. The EM fungal isolates had different effects on NH ₄ ⁺ and DON accumulation/degradation in peat. The EM fungal isolates significantly increased NH ₄ ⁺ formation in the peat, whereas L. rufus and P. croceum had an opposite effect on DON accumulation. S. variegatus I significantly decreased the DON concentrations during peat incubation. The N concentration of the peat slightly affected the utilization of amino acids and polyamines by the microbial community, whereas inoculation with S. variegatus I, II or III had no effect.     

Higher temperature reduces the effects of litter quality on decomposition by aquatic fungi

1. We investigated the effects of riparian plant diversity (species number and identity) and temperature on microbially mediated leaf decomposition by assessing fungal biodiversity, fungal reproduction and leaf mass loss. 2. Leaves of five riparian plant species were first immersed in a stream to allow microbial colonisation and were then exposed, alone or in all possible combinations, at 16 or 24 °C in laboratory microcosms. 3. Fungal biodiversity was reduced by temperature but was not affected by litter diversity. Temperature altered fungal community composition with species of warmer climate, such as Lunulospora curvula, becoming dominant. 4. Fungal reproduction was affected by litter diversity, but not by temperature. Fungal reproduction in leaf mixtures did not differ or was lower than that expected from the weighted sum of fungal sporulation on individual leaf species. At the higher temperature, the negative effect of litter diversity on fungal reproduction decreased with the number of leaf species. 5. Leaf mass loss was affected by the identity of leaf mixtures (i.e. litter quality), but not by leaf species number. This was mainly explained by the negative correlation between leaf decomposition and initial lignin concentration of leaves. 6. At 24 °C, the negative effects of lignin on microbially mediated leaf decomposition diminished, suggesting that higher temperatures may weaken the effects of litter quality on plant litter decomposition in streams. 7. The reduction in the negative effects of lignin at the higher temperature resulted in an increased microbially mediated litter decomposition, which may favour invertebrate‐mediated litter decomposition leading to a depletion of litter stocks in streams.     

Interaction between embryogenic cultures of Scots pine and ectomycorrhizal fungi

 Embryogenic cell masses of three Scots pine (Pinus sylvestris) cell lines K779, K884 and K1009 were cultivated with the ectomycorrhizal (ECM) fungi Laccaria bicolor, L. proxima, Pisolithus tinctorius, Paxillus involutus and two strains of Suillus variegatus. The average growth ratio of the slowly proliferating cell line K1009 was improved by L. proxima and S. variegatus strain H, while of the rapidly proliferating lines K779 and K884 the non-mycorrhizal controls grew best. The fungi caused two distinct reactions in embryogenic cultures. In the positive reaction, the shape and light yellow colour of the cultures resembled the controls, while in the negative reaction the embryogenic cells became brown and necrotic and the fungi grew aggressively over them. These reactions to the fungi did not correlate completely with effects on the growth ratio. All the cell lines enhanced the radial growth of S. variegatus H and of P. tinctorius, while the Laccaria species and S. variegatus strain 1 thrived better alone. This study shows that early-stage embryogenic cells of Scots pine and ECM fungi are able to interact. As some fungi produced a positive reaction or even increased proliferation, they could be used to enhance somatic embryogenesis of Scots pine. Specific fungi might be used to induce the growth of slowly proliferating cell lines, and knowledge of positive cell line-fungus interactions could be useful in work with later stages of somatic embryogenesis, such as rooting. Accepted: 16 July 1998     

Life in leaf litter: novel insights into community dynamics of bacteria and fungi during litter decomposition

Microorganisms play a crucial role in the biological decomposition of plant litter in terrestrial ecosystems. Due to the permanently changing litter quality during decomposition, studies of both fungi and bacteria at a fine taxonomic resolution are required during the whole process. Here we investigated microbial community succession in decomposing leaf litter of temperate beech forest using pyrotag sequencing of the bacterial 16S and the fungal internal transcribed spacer (ITS) rRNA genes. Our results reveal that both communities underwent rapid changes. Proteobacteria, Actinobacteria and Bacteroidetes dominated over the entire study period, but their taxonomic composition and abundances changed markedly among sampling dates. The fungal community also changed dynamically as decomposition progressed, with ascomycete fungi being increasingly replaced by basidiomycetes. We found a consistent and highly significant correlation between bacterial richness and fungal richness (R = 0.76, P < 0.001) and community structure (R_Mantel = 0.85, P < 0.001), providing evidence of coupled dynamics in the fungal and bacterial communities. A network analysis highlighted nonrandom co‐occurrences among bacterial and fungal taxa as well as a shift in the cross‐kingdom co‐occurrence pattern of their communities from the early to the later stages of decomposition. During this process, macronutrients, micronutrients, C:N ratio and pH were significantly correlated with the fungal and bacterial communities, while bacterial richness positively correlated with three hydrolytic enzymes important for C, N and P acquisition. Overall, we provide evidence that the complex litter decay is the result of a dynamic cross‐kingdom functional succession.     

Ecology and diversity of leaf litter fungi during early-stage decomposition in a seasonally dry tropical forest

Leaf litter samples of 12 dicotyledonous tree species (belonging to eight families) growing in a dry tropical forest and in early stages of decomposition were studied for the presence of litter fungi. Equal-sized segments of the leaves incubated in moist chambers were observed every day for 30 d for the presence of fungi. Invariably, the fungal assemblage on the litter of each tree species was dominated by a given fungal species. The diversity of fungi present in the litter varied with the tree species although many species of fungi occurred in the litter of all 12 species. A Pestalotiopsis species dominated the litter fungal assemblage of five trees and was common in the litter of all tree species. The present study and earlier studies from our lab indicate that fungi have evolved traits such as thermotolerant spores, ability to utilize toxic furaldehydes, ability to produce cell wall destructuring enzymes and an endophyte-litter fungus life style to survive and establish themselves in fire-prone forests such as the one studied here. This study shows that in the dry tropical forest, the leaf litter fungal assemblage is governed more by the environment than by the plant species.     

红松伐根分解过程中土壤动物动态

为了分析在红松伐根分解的过程中土壤动物的动态变化,以阔叶红松林建群树种红松的伐根为研究对象,选取14a跨度的红松伐根分解的残留物,分离出其中的大型土壤动物、中小型土壤动物,鉴定种类,统计计数。结果表明随分解时间增加,土壤动物的类群和个体数逐渐增加,在伐根分解10年时达到峰值,随后减少;在伐根的地上部分,土壤动物的类群和个体数最多,随伐根深度的增加,土壤动物的类群和个体数逐渐减少,在伐根的最深部分很少有土壤动物活动。     

亚热带森林凋落叶分解过程土壤节肢动物群落的变化特征

土壤动物群落结构和多样性可能随凋落物分解进程和基质质量的变化不断改变。为了解亚热带森林凋落叶分解过程中土壤节肢动物群落变化特征,以四川盆地亚热带森林麻栎（Quercus acutissima）和柳杉（Cryptomeria fortunei）凋落叶为对象,于2011-2015年采用分解袋法研究了2种凋落叶分解过程中土壤节肢动物组成、结构和多样性动态变化。整个研究期间,柳杉和麻栎凋落叶分解袋中共捕获土壤节肢动物3855只,分属于16目51科,且均以等节跳科和棘跳科为优势类群;麻栎凋落叶中土壤节肢动物的个体密度随分解进程呈现增加趋势,在分解的1079天达最高值后降低,而柳杉凋落叶则在分解的156天急剧增加后快速降低,2种凋落叶中土壤节肢动物类群数量具有相似的动态变化过程;2种凋落叶中土壤节肢动物总体以菌食性数量比例最高,腐食性最低,且随凋落叶分解进程,植食性土壤节肢动物占比明显下降,菌食性则上升;非度量多维尺度（NMDS）分析显示,2种凋落叶中土壤节肢动物群落组成具有显著差异,聚类分析表明,2种凋落叶土壤节肢动物群落结构相似性随分解进程不断降低。亚热带森林凋落叶分解过程中土壤节肢动物群落组成、结构和多样性受凋落叶类型影响。     

长白山阔叶红松林主要树种凋落叶分解速率及其与叶性状的关系

阔叶红松林是我国东北地区地带性顶级森林群落,对维持区域生态系统稳定性具有重要作用。对阔叶红松林内主要树种凋落叶分解过程及影响因素进行研究,有助于增加长白山阔叶红松林生态系统的基础数据,为明确阔叶红松林的养分循环和物质流动提供依据。选取了长白山阔叶红松林内30个常见乔灌树种和16个凋落叶性状,采用野外分解袋法和室内样品分析等方法研究了长白山阔叶红松林内主要树种凋落叶分解速率及其与凋落叶性状的关系。1年的野外分解实验表明,30个树种的凋落叶重量损失率表现出较大差异。不同树种凋落叶的重量损失率在20.56%—92.11%之间,以红松(Pinus koraiensis)质量损失率最低,东北山梅花(Philadelphus schrenkii)质量损失率最高。不同生活型树种的凋落叶在质量损失率上存在显著差异,以灌木树种凋落叶的质量损失率最高,小乔木次之,乔木树种质量损失率最低。Olson模型拟合结果表明,不同树种凋落叶的分解速率k以红松最低,瘤枝卫矛(Euonymus verrucosus)最高,分别为0.24和1.64。不同树种分解50%和95%所需的时间分别在0.43—2.86年,1.83—...     

Fractionated extraction and speciation of macronutrients from Scots pine and Norway spruce needles of different ages

Summary The relationship between proteins and the macroelements potassium, magnesium, calcium, sulphur and phosphorus was studied in homogenates of needles of different ages from Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.]. Complete extractions by acid digestion, protein extractions by a buffer-detergent and non-protein extractions by a buffer alone showed that most of the potassium and magnesium of the needles was soluble independent of the proteins. Only a minor part (50–60 ppm, dry weight) of the magnesium could be referred to the chlorophyll content of the needles. Both potassium and magnesium appeared independent of the protein gel filtration. This was also valid for the minor fraction of the total calcium content, which was extractable in a buffer. Heterogeneous calcium deposits are also suggested by extraction using a chelator (EGTA). Part of the buffer-soluble sulphur and phosphorus compounds occurred independently of solubilized proteins, and had complex distribution patterns after gel filtration, even outside the high molecular separation range. It is suggested that further analyses along the present lines, compared with conventional analyses on total extracts, may extend the usefulness of mineral nutrient analyses in plants.     

Purification and properties of glutamate dehydrogenase in Scots pine (Pinus sylvestris) needles

NADH-dependent glutamate dehydrogenase (GDH. EC 1. 4. 1.2) was isolated from the needles of Scots pine (Pinus sylverstris L.) grown on a rural and on a heavily polluted industrial area, and it was purified about 500 fold. The purification procedure included salt I'ractionation, ion exchange and affinity chromatography. Miehaelis constants for 2-oxoglularale (1.7 mM). for ammonium sultate (19 mM ) and for NADH (42.5 resp. 53 μM) the pH optimum (8.5) the requirements for Ca²⁺ ions, the temperature dependence ofl the enzyme activity (incubation from 0 to 82°C). and the relation between forest region and electrophoretie isoenzyme pattern were determined. The possible role of GDH in the adaptation of plants to ammonia assimilation (detoxification) under stress conditions, particularly with respect to air pollution, is discussed.     

三种乔木落叶分解过程中跳虫群落结构的演替

1993到1995年,用落叶袋法研究跳虫群落在青冈Cyclobalanopsis glauca、马尾松Pinus massoniana和麻栎Quercus acutissima 3种乔木落叶分解过程中的演替变化。青冈落叶分解经淋洗、养分固定和养分活化3个阶段,马尾松和麻栎没有出现阶段性变化。青冈落叶中跳虫个体数和多样性指数均高于马尾松和麻栎落叶中的相应值。跳虫在落叶分解过程中的集聚型分为3组：A组为落叶分解前期集聚的种类,B组为后期的种类,C组为中期或全过程的种类。3种乔木在A组中共有的种类为鳞Tomocerus sp.、等节Isotoma sp. 和杭州刺齿Homidia hangzhouensis;B组共有种类为八眼符Folsomia octoculata、拟裸长角Pseudosinella sp. 和类符Folsomina onychiurina;C组没有共有种类。     

Changes in fungal community of Scots pine (Pinus sylvestris) needles along a latitudinal gradient in Sweden

Conifer needles are typically long lived and can host a diverse community of fungal species with various effects on their host tree. The purpose of this study was to analyse shifts in the fungal community of Scots pine (Pinus sylvestris) needles on different spatial scales using 454 pyrosequencing. The fungal community composition changed gradually along a north-south gradient through Sweden, representing boreal to temperate vegetation zones. OTU richness and Shannon's diversity index increased with increasing latitude, but only in naturally regenerated forests. On the tree level, needles with symptoms of disease hosted a more diverse mycobiota compared to healthy needles, presumably supporting more pathogenic or saprotrophic species. This study provides a better insight into the patterns of fungal communities of Scots pine needles and highlights the need for further experimental research to identify specific environmental factors shaping the abundance of different fungal species.     

Climate and litter quality differently modulate the effects of soil fauna on litter decomposition across biomes

Climate and litter quality have been identified as major drivers of litter decomposition at large spatial scales. However, the role played by soil fauna remains largely unknown, despite its importance for litter fragmentation and microbial activity. We synthesised litterbag studies to quantify the effect sizes of soil fauna on litter decomposition rates at the global and biome scales, and to assess how climate, litter quality and soil fauna interact to determine such rates. Soil fauna consistently enhanced litter decomposition at both global and biome scales (average increment ~ 27%). However, climate and litter quality differently modulated the effects of soil fauna on decomposition rates between biomes, from climate‐driven biomes to those where climate effects were mediated by changes in litter quality. Our results advocate for the inclusion of biome‐specific soil fauna effects on litter decomposition as a mean to reduce the unexplained variation in large‐scale decomposition models.     

Fungal succession on pine needles in Germany

The mycofloral succession on the needles ofPinus sylvestris was investigated in Tübingen, southwest Germany. Dead needles attached to the branches (D-type), those caught on branches (C-type) and three types of fallen needles, i.e., freshly fallen (L-type), slightly discolored (OL-type) and almost black needles (F-type) were examined for their fungal flora. Common primary saprophytes were rich on the dead needles on the tree, and on the L-type needles. They were replaced by successive species that contained the well-known species preferring pine needles as their substratum, such asVerticicladium trifidum orSympodiella acicola. Their ecological niches in pine leaf litter and their distribution patterns from a biogeographical viewpoint were discussed.     

四川盆地亚热带常绿阔叶林不同物候期凋落物分解与土壤动物群落结构的关系

为了解植物生长不同物候时期凋落物分解过程中土壤动物群落结构动态及其与凋落物分解的关系,以四川盆地亚热带常绿阔叶林典型人工林树种马尾松和柳杉,次生林树种香樟和麻栎凋落物为研究对象,采用凋落物分解袋试验研究,凋落物分解过程中土壤动物的群落特征。4种凋落物分解袋共获得土壤动物8047只,其中,柳杉(2341只)>香樟(2105只)>马尾松(2046只)>麻栎(1555只)。其中,秋末落叶期、萌动期和展叶期,马尾松凋落物袋中主要以捕食性土壤动物为优势类群,而后以菌食性土壤动物为主;香樟凋落物袋中除秋末落叶期和叶衰期以菌食性土壤动物为主要优势类群外,其他各时期均以捕食性土壤动物为主要优势类群;柳杉凋落物分解各时期均以菌食性土壤动物为主要优势类群;麻栎凋落物分解在前3个时期以菌食性为主,而后以植食性土壤动物为主要优势类群。相关分析表明,在秋末落叶期和萌动期土壤动物的个体密度主要和氮、磷含量及其格局密切相关,叶衰期主要和难分解组分木质素显著相关。除在秋末落叶期土壤动物对凋落物分解的贡献率与土壤动物的个体密度显著相关外,其余主要物候关键时期均与土壤动物的类群密度及其食性显著相关。     

石灰和EM处理条件下土壤动物群落在落叶分解中的变化

2003年6月至2005年10月,用石灰和EM处理改变土壤微酸性特性和微生物活性,采用网袋分解法对大兴安岭地区土壤动物群落结构在落叶分解过程中的动态变化进行了研究。结果如下:(1) 土壤动物群落个体数、类群数和DG指数仍表现为季节波动性,气候因子是影响研究区土壤动物群落长期动态变化的重要因素,石灰和EM处理未改变这种规律。(2)处理条件下土壤动物在落叶分解过程中仍具有阶段性特征,且各类群集聚时间有所差异。(3) CCA排序分析表明,土壤pH值和有机质是影响土壤动物群落动态变化的重要因素,中气门亚目、前气门亚目、节跳虫科、甲螨亚目、绫跳虫科、山跳虫科、棘跳虫科、鳞跳虫科和石蜈蚣目对土壤pH值和有机质变化具有较强的适应能力。