Fungal decomposition of Abies needle and Betula leaf litter

The effect of litter type and incubation temperature on the ability of fungi to decompose leaf litter of subalpine trees was examined by a pure-culture test. Mass loss of Abies needle and Betula leaf litter and utilization patterns of lignin and carbohydrates were investigated under two temperature conditions (20 C and 10 C) and compared for 29 species in basidiomycetes, ascomycetes and zygomycetes. The decomposing ability was generally higher in basidiomycetes than in ascomycetes and zygomycetes. Mass loss (% original mass) of litter was higher in Betula than in Abies and higher at 20 C than at 10 C. The 29 fungi were divided into lignocellulose decomposers, cellulose decomposers and sugar fungi based on their substrate utilization in Abies and Betula litter. Mass loss of lignin and carbohydrates by lignocellulose and cellulose decomposers was higher in Betula than in Abies. Mass loss of carbohydrates was higher at 20 C than at 10 C, but the temperature did not influence mass loss of lignin, indicating lignin decomposition by fungi was less sensitive to temperature than carbohydrate decomposition. Lignin/carbohydrate loss ratio (L/C) of Collybia spp. that caused selective delignification was lower at 20 C than at 10 C. These results indicate that the decomposability of litter, lignin and carbohydrate was different between Abies and Betula and that temperature affected not only the rate at which fungi decompose litter but also the ability of fungi to use lignin and carbohydrates.     

Fungal succession and decomposition of <Emphasis Type="Italic">Camellia japonica</Emphasis> leaf litter

Decomposition processes of Camellia japonica leaf litter were investigated over an 18-month period with reference to the role of fungal succession in the decomposition of lignin and holocellulose. Decomposition and fungal succession were studied in bleached and nonbleached portions of litter, which were precolonized by ligninolytic and cellulolytic fungi, respectively. Coccomyces nipponicum and Lophodermium sp. (Rhytismataceae), which can attack lignin selectively, caused mass loss of lignin and were responsible for bleaching during the first 4 months (stage I), whereas cellulolytic fungi caused mass loss of holocellulose in adjacent nonbleached portions. Soluble carbohydrates and polyphenols also decreased rapidly during this stage. Pestalotiopsis guepini, coelomycete sp.1, and the Nigrospora state of Khuskia oryzae caused mass loss of holocellulose between 4 and 14 months (stage II) and Xylaria sp. caused mass loss of both lignin and holocellulose from 14–18 months (stage III). In stages II and III, decomposition was more rapid in bleached portions than in nonbleached portions probably due to the prior delignification of lignified holocellulose in bleached portions. Frequencies of these fungi showed different responses among species to the pattern of changes in lignin and holocellulose contents during decomposition. Total hyphal length increased in both portions over the study period, but mycelia of basidiomycetes accounted for about 2% of total hyphal length, suggesting that their role in fungal succession and decomposition was low. Lignin and nitrogen contents were consistently lower and holocellulose content was higher in bleached portions than in nonbleached portions during decomposition. The succession of ligninolytic and cellulolytic fungi was a major driving factor that promoted decomposition and precolonization by ligninolytic fungi enhanced decomposition.     

Screening of ecologically diverse fungi for their potential to pretreat lignocellulosic bioenergy feedstock

A widespread and hitherto by far underexploited potential among ecologically diverse fungi to pretreat wheat straw and digestate from maize silage in the future perspective of using such lignocellulosic feedstock for fermentative bioenergy production was inferred from a screening of nine freshwater ascomycetes, 76 isolates from constructed wetlands, nine peatland isolates and ten basidiomycetes. Wheat straw pretreatment was most efficient with three ascomycetes belonging to the genera Acephala (peatland isolate) and Stachybotrys (constructed wetland isolates) and two white-rot fungi (Hypholoma fasciculare and Stropharia rugosoannulata) as it increased the amounts of water-extractable total sugars by more than 50 % and sometimes up to 150 % above the untreated control. The ascomycetes delignified wheat straw at rates (lignin losses between about 31 and 40 % of the initial content) coming close to those observed with white-rot fungi (about 40 to 57 % lignin removal). Overall, fungal delignification was indicated as a major process facilitating the digestibility of wheat straw. Digestate was generally more resistant to fungal decomposition than wheat straw. Nevertheless, certain ascomycetes delignified this substrate to extents sometimes even exceeding delignification by basidiomycetes. Total sugar amounts of about 20 to 60 % above the control value were obtained with the most efficient fungi (one ascomycete of the genus Phoma, the unspecific wood-rot basidiomycete Agrocybe aegerita and one unidentified constructed wetland isolate). This was accompanied by lignin losses of about 47 to 56 % of the initial content. Overall, digestate delignification was implied to be less decisive for high yields of fermentable sugars than wheat straw delignification.     

Comparison of litter decomposing ability among diverse fungi in a cool temperate deciduous forest in Japan

The litter decomposing ability of 79 fungal isolates (41 genera, 60 species) was assessed with the pure culture decomposition test. The isolates were collected qualitatively in a cool temperate deciduous forest in Japan during a 21-mo period. Loss of original weight of sterilized litter ranged from 0.1% to 57.6%. Six isolates in the Basidiomycota caused high weight losses ranging from 15.1% to 57.6%. Fourteen isolates in Xylaria and Geniculosporium (the Xylariaceae and its anamorph) also caused high weight losses ranging from 4.0% to 14.4%. Other isolates in the Ascomycota and associated anamorphs and in the Zygomycota caused low weight losses on mean. Six fungi in the Basidiomycota, and all in the Xylariaceae showed a bleaching activity of the litter and caused lignin and carbohydrate decomposition. Mean lignin/weight loss ratios (L/W) and lignin/carbohydrate loss ratios (L/C), were 0.9 and 0.7 for the Basidiomycota and 0.7 and 0.4 for the Xylariaceae, respectively. Significant differences were found in L/W and L/C between the two groups when the result of Xylaria sp. that showed marked delignification was excluded. These differences in lignin and carbohydrate utilization patterns are discussed in relation to the structural and the chemical properties of the decomposed litter and to the implications for organic chemical changes during litter decomposition processes.     

Decomposition of litter in sub-alpine forests of Eucalyptus delegatensis,E. pauciflora and E. dives

The rate of decomposition of summer leaf-fall (abscised leaves), winter leaf-fall (containing some green leaves) and mature green (picked) leaves was assessed in sub-alpine forests of E. delegatensis (R. T. Baker), E. pauciflora (Sieb. ex Spreng) and E. dives (Schau.) in the Brindabella Range, Australian Capital Territory, using litter bag and tethered leaf techniques. The relative contribution of leaching, microbial respiration and grazing by invertebrate macrofauna to loss of leaf weight was determined. The effect of leaching and microbial respiration was assessed in terms of weight loss per unit area of leaf (specific leaf weight), while losses due to macro-faunal grazing were assessed by measuring reductions in leaf area. Litter decomposition constants for litter components (leaf, bark, wood) and total litter were determined from long-term records of litterfall and accumulated litter. Weight losses of abscised leaves during the initial 12 months ranged from 25% for E. pauciflora to 39% for E. delegatensis and were almost entirely due to reduction in specific leaf weight. Losses in the weight of leaves falling in winter ranged from 38 to 49%, while green leaves lost 45 - 59%. Approximately 50% of the total weight loss of green leaves was due to a loss in leaf area caused by skeletonization by litter macrofauna. Thus abscised leaves rather than green leaves must be used for measuring litter decomposition rates since abscised leaves constitute most of the litterfall in eucalypt forests. Leaves placed in the field in autumn decomposed slowly during the first summer, while the rate increased during the second winter and summer. Low litter moisture content appears to limit decomposition in the initial summer period in all communities, after which litterfall provides a mulch which reduces the rate of desiccation of lower litter layers. A simple linear regression model relating decomposition rate to the number of days (D) when litter moisture content exceeded 60% ODW accounted for 63-83% of the variation in decomposition of leaves in the field. Inclusion of mean monthly air temperature (T) and the product of D and T (day degrees when litter was wet) in a multiple linear regression increased the variation in decomposition accounted for to 80 – 90%. The rate of weight loss showed a positive linear relationship with the initial concentration of nitrogen (N) or phosphorus (P) in the leaf. These concentrations are an index of the decomposability of leaf substrates (e.g. degree of sclerophylly or lignification). The rate of loss of specific weight was similar for tethered leaves and for leaves enclosed in mesh bags. Measured loss in specific leaf weight after 70 – 90 weeks was less than that predicted using decomposition constants (k).     

Decomposition of organic chemical components in relation to nitrogen dynamics in leaf litter of 14 tree species in a cool temperate forest

Decomposition of lignin, holocellulose, polyphenols and soluble carbohydrates was investigated in relation to nitrogen (N) dynamics in leaf litter of 14 tree species. The influence of organic chemical components and N on litter mass loss rate was then evaluated for 14 litter types. The study was carried out over a 3-year period on upper and lower parts of a forest slope in a cool temperate forest in Japan. The decomposition processes were divided into early and late phases based on N immobilization and mobilization. Mass loss rate of whole litter and organic chemical components was similar for the upper and lower sites. Litter mass loss was faster in the immobilization phase than in the mobilization phase in each of 14 litter types, which was ascribed to the decreased mass loss of holocellulose, polyphenols and soluble carbohydrates in the mobilization phase as compared to the immobilization phase. Mass loss rate of lignin was not different between the phases. Litter mass loss rate in the immobilization and mobilization phases was negatively correlated to lignin content and positively correlated to contents of polyphenols and soluble carbohydrates at the start of these phases, but was not correlated to holocellulose and N contents in either phase.     

Does Atmospheric NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> Deposition Alter the Abundance and Activity of Ligninolytic Fungi in Forest Soils?

Although field studies have demonstrated an ecosystem-specific effect of experimental atmospheric nitrogen (N) deposition on litter decomposition, a mechanistic understanding of how ligninolytic microbial communities respond to atmospheric deposition is lacking. Because high levels of inorganic N suppress lignin decomposition by some basidiomycetes, it is plausible that the abundance and activity of these key microorganisms underlies differential ecosystem responses of decomposition to atmospheric N deposition. We hypothesize that: (a) atmospheric N deposition will cause an ecosystem-specific reduction in basidiomycete activity and abundance with greatest decreases in ecosystems with lignin-rich forest litter and (b) the abundance of lignin degrading basidiomycetes will be positively correlated with ligninolytic enzyme activity. To test these hypotheses, we measured the effects of experimental N deposition on the potential activity of phenol oxidase enzymes, and the abundance of basidiomycete genes encoding laccase, a primary phenol oxidase enzyme, in three hardwood forests spanning a range of leaf litter lignin content. The black oak-white oak (BOWO) contains high lignin litter, the sugar maple-basswood (SMBW) has low lignin litter, and the sugar maple-red oak (SMRO) is intermediate. An ecosystem by N deposition interaction significantly influenced phenol oxidase activity in the surface soil (P = 0.05), where phenol oxidase activity decreased with increasing experimental N deposition in the BOWO ecosystem. No consistent response to N deposition was evident for surface soil phenol oxidase activity within either the SMRO or SMBW ecosystem. This interaction did not influence laccase gene abundance. Instead, basidiomycete laccase gene abundance was reduced by experimental N deposition (main effect) in surface soil. There was only a weak correlation between basidiomycete laccase gene abundance and potential phenol oxidase enzyme activity, suggesting that the abundance of organisms possessing laccase genes may not control phenol oxidase activity in soil. Our results suggest that the regulation of laccase gene expression may mediate the decomposition response to atmospheric N deposition.     

Litter decomposition rates in Canadian forests

The effect of litter quality and climate on the rate of decomposition of plant tissues was examined by the measurement of mass remaining after 3 years’ exposure of 11 litter types placed at 18 forest sites across Canada. Amongst sites, mass remaining was strongly related to mean annual temperature and precipitation and amongst litter types the ratio of Klason lignin to nitrogen in the initial tissue was the most important litter quality variable. When combined into a multiple regression, mean annual temperature, mean annual precipitation and Klason lignin:nitrogen ratio explained 73% of the variance in mass remaining for all sites and tissues. Using three doubled CO₂ GCM climate change scenarios for four Canadian regions, these relationships were used to predict increases in decomposition rate of 4–7% of contemporary rates (based on mass remaining after 3 years), because of increased temperature and precipitation. This increase may be partially offset by evidence that plants growing under elevated atmospheric CO₂ concentrations produce litter with high lignin:nitrogen ratios which slows the rate of decomposition, but this change will be small compared to the increased rate of decomposition derived from climatic changes.     

Enzyme activities of fungi associated with Picea abies needles

Decomposition of Picea abies needles and production of extracellular enzymes involved in decomposition of lignin, cellulose, hemicelluloses and other organic compounds were studied in fungal strains of interior needle colonizers isolated from needles in different stages of decomposition (attached to trees, and early and late decomposition stages in the litter horizon). In total, 12 strains of ascomycetes (members of Helotiales, Hypocreales, Dothideales, Diaporthales and Eurotiales) and four basidiomycetes (Polyporales, Agaricales and Russulales) were tested. Significant decomposition of needles was recorded for all fungal isolates. All isolates produced cellobiohydrolase, β-glucosidase, β-xylosidase, N-acetylglucosaminidase, α-glucosidase, phosphatase and arylsulfatase and most fungi also produced endocellulase, endoxylanase and laccase in needle litter. In addition, other hemicellulases were produced by all strains. Mn-peroxidase was only produced by two basidiomycetes. Although enzyme activities varied, fungi associated with needles on fallen trees exhibited enzyme production comparable with later litter colonizers, and there was no significant difference in enzyme production between ascomycete and basidiomycete strains.     

Lignin and nitrogen in the decomposition of leaf litter in a sub-tropical forest ecosystem at Shiroy hills in north-eastern India

The effect of the initial lignin and nitrogen contents of the leaves of five tree species, on their decomposition dynamics, was studied in the sub-tropical forest ecosystem existing at Shiroy hills. The decomposition dynamics of litter materials are described by inverse linear relationships between the percentage of the original biomass remaining and the nitrogen concentration in the residual material. Initial lignin and nitrogen were highly correlated with remaining biomass (r=0.94 and 0.77). The rate constants (K), for the annual leaf mass loss, ranged from −0.18 to −0.56. The values for initial lignin (%), initial nitrogen (%), the ratio between initial lignin, initial nitrogen and the annual decomposition rate constants were compared with similar results from other studies in various climatic zones of the world.     

Fungal colonization and decomposition of Castanopsis sieboldii leaves in a subtropical forest

Fungi play a crucial role in the decomposition of lignin in fallen leaves but few studies have examined the functional roles of ligninolytic fungi associated with the decomposition of fallen leaves on tropical forest soils. This study examined fungal populations responsible for lignin decomposition in Castanopsis sieboldii leaves in a subtropical evergreen broad-leaved forest in southern Japan. Fallen leaves of C. sieboldii are characterized by the occurrence of bleached portions attributable to fungal colonization of leaf tissues and decomposition of lignin. The bleached area accounted for 29.7%, on average, of the total area of C. sieboldii fallen leaves in the study site. Leaf mass per unit area (LMA) and lignin content were lower in the bleached area than in the surrounding nonbleached area of the same leaves, indicating that removal of lignin enhanced mass loss from leaf tissues and created small-scale heterogeneity of decomposition within single leaves. An unidentified species of Lachnocladiaceae (Basidiomycetes) was isolated frequently from the bleached area and caused selective decomposition of lignin in leaves under pure culture conditions, indicating that this fungus was responsible for the bleaching. The greater hyphal length of basidiomycetes in the bleached area than in the nonbleached area supported the finding that this Lachnocladiaceae sp. was associated with the bleaching. The relatively rapid decomposition of C. sieboldii leaves on the subtropical forest soil is partly attributable to colonization of the litter by this Lachnocladiaceae sp.     

Mass loss and nitrogen dynamics in decomposing acid forest litter in the Netherlands at increased nitrogen deposition

Litterbag experiments were carried out in five forest ecosystems in the Netherlands to study weight loss and nitrogen dynamics during the first two years of decomposition of leaf and needle litter. All forests were characterized by a relatively high atmospheric nitrogen input by throughfall, ranging from 22–55 kg N ha^–1 yr^–1.Correlation analysis of all seven leaf and needle litters revealed no significant relation between the measured litter quality indices (nitrogen and lignin concentration, lignin-to-nitrogen ratio) and the decomposition rate. A significant linear relation was found between initial lignin-to-nitrogen ratio and critical nitrogen concentration, suggesting an effect of litter quality on nitrogen dynamics.Comparison of the decomposition of oak leaves in a nitrogen-limited and a nitrogen-saturated forest suggested an increased nitrogen availability. The differences in capacities to retain atmospheric nitrogen inputs between these two sites could be explained by differences in net nitrogen immobilization in first year decomposing oak leaves: in the nitrogen-limited oak forest a major part (55%) of the nitrogen input by throughfall was immobilized in the first year oak leaf litter.The three coniferous forests consisted of two monocultures of Douglas fir and a mixed stand of Douglas fir and Scots pine. Despite comparable litter quality in the Douglas fir needles in all sites, completely different nitrogen dynamics were found.     

模拟氮沉降对华西雨屏区天然常绿阔叶林凋落物木质素和纤维素降解的影响

从2013年11月至2014年11月,采用尼龙网袋法对华西雨屏区天然常绿阔叶林凋落物进行原位分解试验,模拟N(NH₄NO₃)沉降水平分别为对照(0 g N·m^-2·a^-1)、低氮沉降(5 g N·m^-2·a^-1)、中氮沉降(15 g N·m^-2·a^-1)和高氮沉降(30 g N·m^-2·a^-1),研究了N沉降对常绿阔叶林凋落物分解及其木质素和纤维素降解的影响.结果表明:华西雨屏区天然常绿阔叶林凋落物在夏季分解较快,明显快于其他季节.N沉降显著抑制了阔叶林凋落物的分解,抑制作用随N沉降量的增加而加强.N沉降使凋落物质量损失95%的时间与对照(4.81年)相比增加了0.53～1.88年.经过1 年的分解,中氮沉降和高氮沉降处理木质素和纤维素残留率显著高于对照,表明N沉降显著抑制了凋落物木质素和纤维素的降解.凋落物质量残留率与木质素和纤维素残留率呈显著正相关.N沉降抑制凋落物分解的原因可能是无机N的添加对木质素和纤维素的降解造成了阻碍.     

Ascomycetes with cellulolytic,amylolytic, pectinolytic,and mannanolytic activities inhabiting dead beech (<Emphasis Type="Italic">Fagus crenata</Emphasis>) trees

It is generally accepted that dead tree decomposition is performed mainly by delignifying basidiomycetes. While ascomycetes have been reported to inhabit dead tree bark, their contribution to dead tree decomposition is still unclear. Here, we isolated five bark-inhabiting ascomycetes possessing cellulolytic activity from dead beech tree and assessed their polysaccharolytic activities. When cultivated in a medium containing filter paper as a sole carbon source, three strains degraded >40 % of the filter paper in a 4-week cultivation and the others degraded 15–30 % of the paper. The degraders possessed amylolytic, pectinolytic, and mannanolytic activities as well as cellulolytic activity, implying that they play an important role in dead tree decomposition after delignification by basidiomycetes. Phylogenetic analysis based on large subunit ribosomal DNA (lsu-DNA) sequences implied that the isolates belonged to Penicillium or Amorphotheca.     

Palo Podrido: Model for Extensive Delignification of Wood by Ganoderma applanatum

Chemical and micromorphological analysis revealed that South Chilean “palo podrido” results from a white-rot fungus that causes highly selective and extensive delignification. Palo podrido samples from 10 different hardwood trunks (Eucryphia cordifolia, Drimys winteri, and Nothofagus dombeyi) decayed by Ganoderma applanatum were analyzed. Of 14 samples, 11 had extremely low Klason lignin values, ranging from 6.1 to 0.4% (dry weight). The most remarkable and unusual feature was that delignification and defibration were not restricted to small pockets but extended throughout large areas in the interior of trunks subjected to undisturbed rotting over long periods of time. Comparative analysis of water content, swelling capacity, and lignin content led to the conclusion that besides lignin degradation, suppression of the cellulolytic activity of the rotting organisms plays a decisive role. Among various nutrients added to a palo podrido sample (3% residual Klason lignin), the nitrogen source was the only one leading to almost complete cellulose degradation. We suggest that the extremely low nitrogen content (0.037 to 0.073% [dry weight]) of the investigated wood species was the primary cause for the extensive delignification as well as the concomitant suppression of cellulose breakdown. The low temperatures, high humidity, and microaerobic conditions maintained within the decaying trunks are discussed as additional ecological factors favoring delignification in South Chilean rain forests.     

Effects of streams on lignin degradation during foliar litter decomposition in an alpine forest

AimsStreams are widely distributed in alpine forests, and litter decomposition in which is an important component of material cycling across the forest landscape. The leaching and fragmenting effects as well as the unique environmental factors in streams may have significant impacts on lignin degradation during litter decomposition, but studies on this are lacking.
Methods Using litterbag methods, we investigated the dynamics of lignin mass remaining and concentration (percent litter mass, %) during the decomposition of four foliar litters, which varied significantly in the initial litter chemical traits, from the dominant species of Salix paraplesia, Rhododendron lapponicum, Sabina saltuaria, and Larix mastersiana under different habitats (forest floor, stream, and riparian zone) in the upper reaches of the Minjiang River.
Important findings After two year’s incubation, litter lignin mass remaining for a specific litter species varied significantly (p < 0.05) among habitats, with an order of stream < riparian zone < forest floor. Lignin was degraded substantially in the early stage of litter decomposition process, and the lignin concentration first decreased and then increased with the proceeding of litter decomposition, but varied significantly (p < 0.05) among different litter species. Lignin mass showed a general trend of decrease across the 2-year decomposition course. In addition, habitat type, decomposition period and microenvironmental factors (e.g., temperature, pH value and nutrient availability) showed substantial influences on lignin degradation rate. These results suggest that the traditional view that lignin was relatively recalcitrant with an increase of concentration in the early stage of litter decomposition is challenged, but the loss of lignin in the early phrase is in line with recent findings about the fate of lignin during litter decomposition. Moreover, the significant differences of lignin degradation rates among different decomposition period and habitat types indicated that local-scale environmental factors can play a significant role in litter decomposition and lignin degradation processes.     

暖温带落叶阔叶林辽东栎枝条分解过程中有机物质的变化

应用网袋法对暖温带地区广泛分布的乔木树种辽东栎（ＱｕｅｒｃｕｓｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｄｚ．）枝条分解进行了连续５年时间的观察,并测定了凋落物在分解过程中有机质（纤维素、木质素、蛋白质）的变化。用Ｏｌｓｏｎ的指数方程对分解枝条重量的减少进行了模拟,并预测暖温带地区辽东栎枝条完全（９５％）分解需要约２１年的时间。在各有机成分含量的变化上,表现出明显不同的分异。蛋白质的含量随着分解过程的不断进行,从３．５％增加至５．５％,半纤维素则从１６．０％下降至８．０％,而粗纤维和木质素的含量出现了上下波动的情形。经过拟合,凋落物的丢失速率符合Ｏｌｓｏｎ的指数降解曲线,含量较大的粗纤维和木质素的减少也较好地符合Ｏｌｓｏｎ的指数降解曲线,半纤维素也可以用Ｏｌｓｏｎ指数方程拟合,但蛋白质的拟合效果较差。     

高寒森林溪流对凋落叶分解过程中木质素降解的影响

溪流广泛分布于高寒森林地表, 凋落于其中的林木凋落物的分解是整个森林生态系统物质循环的重要环节, 水体流动过程中的冲刷和淋洗作用及其他独特的环境条件可能显著影响凋落物中木质素的降解。该研究采用凋落袋法对比研究了岷江上游高寒森林4种典型且初始质量差异显著的凋落叶, 即康定柳(Salix paraplesia)、高山杜鹃(Rhododendron lapponicum)、方枝柏(Sabina saltuaria)和四川红杉(Larix mastersiana), 在不同生境(林下、溪流和河岸带)下分解过程中木质素残留质量和浓度(质量百分率)的动态变化特征。经过两年的分解, 发现溪流显著促进了凋落叶中木质素的降解; 同一物种凋落叶在不同生境下木质素残留质量差异显著(p < 0.05), 整体表现为溪流<河岸带<林下; 在凋落叶分解的初期木质素有明显的降解, 其浓度表现为先降低后升高, 但不同物种之间存在显著(p < 0.05)的差异; 在整个分解过程中, 木质素残留质量总体呈现出了降低的趋势。此外, 生境类型、分解时期和区域性环境因子(温度、pH值和营养元素的有效性)能显著影响木质素的降解率。这些结果表明, 传统上认为木质素在凋落叶分解初期相对稳定的观点可能并不准确, 其浓度很可能是先下降后升高, 这也与有关木质素动态的最新研究结果相一致。另一方面, 在不同分解时期和不同生境下, 凋落叶木质素降解率表现出了显著差异, 表明区域性环境因子在凋落叶分解和木质素降解过程中具有重要的作用。     

Change of Organic Matter in the Decomposing Oak Twigs in the Temperate Forest Ecosystems

Litter bag method was used in this study on the twig decomposition of an oak ( Quercus liaotungensis Koidz. ) which is dominant in the warm temperate deciduous forests. A consecutive five-year investigation was carded out to measure the changes of organic components in the twig litter. The decomposition of oak twigs based on rates of the mass loss during the first five years was simulated using the Olson exponential equation. The simulated data fit well with the observed values. Oak twigs were predicted to reach 95% decomposition within 21 years. During the first five years, the concentration of protein in the remaining litter increased from 3.5 % to 5.5 %, while the concentration of semicellulose decreased from 16.0% to 8.0%. However, there was no obvious change in the concentrations of lignin and cellulose. The loss of lignin, crude-cellulose, cellulose and semicellulose could be well simulated using the Olson exponential equation. However, this was not so effective for protein.